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1

Static dielectric properties of dense ionic fluids  

E-print Network

The static dielectric properties of dense ionic fluids, e.g., room temperature ionic liquids (RTILs) and inorganic fused salts, are investigated on different length scales by means of grandcanonical Monte Carlo simulations. A generally applicable scheme is developed which allows one to approximately decompose the electric susceptibility of dense ionic fluids into the orientation and the distortion polarization contribution. It is shown that at long range the well-known plasma-like perfect screening behavior occurs, which corresponds to a diverging distortion susceptibility, whereas at short range orientation polarization dominates, which coincides with that of a dipolar fluid of attached cation-anion pairs. This observation suggests that the recently debated interpretation of RTILs as dilute electrolyte solutions might not be simply a yes-no-question but it might depend on the considered length scale.

Zarubin, Grigory

2015-01-01

2

Static dielectric properties of dense ionic fluids  

E-print Network

The static dielectric properties of dense ionic fluids, e.g., room temperature ionic liquids (RTILs) and inorganic fused salts, are investigated on different length scales by means of grandcanonical Monte Carlo simulations. A generally applicable scheme is developed which allows one to approximately decompose the electric susceptibility of dense ionic fluids into the orientation and the distortion polarization contribution. It is shown that at long range the well-known plasma-like perfect screening behavior occurs, which corresponds to a diverging distortion susceptibility, whereas at short range orientation polarization dominates, which coincides with that of a dipolar fluid of attached cation-anion pairs. This observation suggests that the recently debated interpretation of RTILs as dilute electrolyte solutions might not be simply a yes-no-question but it might depend on the considered length scale.

Grigory Zarubin; Markus Bier

2015-03-06

3

Static and high frequency magnetic and dielectric properties of ferrite-ferroelectric composite materials  

E-print Network

Static and high frequency magnetic and dielectric properties of ferrite-ferroelectric compositeTM barium strontium titanate BSTO and Trans-Tech nickel zinc ferrite powders. The ferrite loading was varied with a systematic variation in the ferrite loading and to examine the static and high frequency magnetic properties

Patton, Carl

4

Dielectric Properties of Diols and Triols: 2,3-Butanediol  

NASA Astrophysics Data System (ADS)

The results of experimental studies of the dielectric properties of 2,3-butanediol are reported. Static dielectric constant ?s was measured at 1 MHz; dielectric constant ?' and dielectric loss ?'' were determined by the balance method over the frequency range 2-37.5 GHz and the temperature range 293-423 K.

Zhuravlev, V. I.; Lifanova, N. V.; Usacheva, T. M.; Vydrina, E. P.

2008-04-01

5

The Dielectric Properties of 1,4-Butanediol  

NASA Astrophysics Data System (ADS)

The dielectric properties of 1,4-butanediol were studied. The static permittivity ?s was measured at a frequency of 1 MHz. Permittivity ?' and dielectric loss ?? were determined by the balance method over the frequency and temperature ranges 2-37.5 GHz and 293-423 K, respectively.

Zhuravlev, V. I.; Lifanova, N. V.; Usacheva, T. M.; Vydrina, E. P.

2008-03-01

6

The Dielectric Properties of 1,3-Butanediol  

NASA Astrophysics Data System (ADS)

The dielectric properties of 1,3-butanediol were measured over the temperature range 293-423 K. The static permittivity ?s was measured at a frequency of 1 MHz. The permittivity ?' and dielectric loss ?'' were determined by the balance method over the frequency range 2-37.5 GHz.

Zhuravlev, V. I.; Lifanova, N. V.; Usacheva, T. M.; Vydrina, E. P.

2008-02-01

7

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

NASA Astrophysics Data System (ADS)

Static dielectric permittivity measurements on a binary system of 4-cyanophenyl [4' (4''-n-heptylphenyl)] benzoate (referred to as 7CPB) + 4-cyanophenyl 4-nonylbenzoate (referred to as 9.CN) showing both induced smectic Ad and re-entrant nematic phases in a certain concentration range (0.4dielectric permittivity shows a pronounced decrease in the smectic Ad phase due to dipole-dipole correlation. A similar effect is seen in other mixtures but on a reduced scale. Mesogenic molecular dipole moments ? and their inclination angles ? with the molecular long axis have also been determined following the Maier and Meier equations. The effective values of the dipole moments (?eff) in the mixtures are found to be less than those observed in the pure compounds. Moreover, ?eff in the smectic Ad phase is seen to be slightly smaller than that obtained by extrapolation from either the nematic or the re-entrant nematic phases. The lower effective dipole moment in the smectic Ad phase indicates the development of additional anti-parallel ordering of the molecular dipoles in the induced smectic phase.

Prasad, Akhileshwar; Das, Malay Kumar

2011-07-01

8

Dielectric properties of aerogels  

Microsoft Academic Search

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

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

1993-01-01

9

Static Dielectric Permittivity of Ice from First Principles  

NASA Astrophysics Data System (ADS)

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

Bonnet, Nicéphore; Marzari, Nicola

2014-12-01

10

Physical and dielectric properties of pharmaceutical powders  

Microsoft Academic Search

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

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

2003-01-01

11

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...

12

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...

13

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

14

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...

15

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...

16

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

17

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

18

Dielectric properties of cyanoethylated bagasse composites  

Microsoft Academic Search

Bagasse was converted into a thermo-moldable material by cyanoethylation. The effect of reaction conditions employed during the preparation of cyanoethylated bagasse (CE-B) fibers on dielectric properties of hot-pressed composites was studied. Increase in the nitrogen content of the cyanoethylated fiber, i.e., the nitrile groups resulted in an increase in the dielectric constant and a decrease in the dissipation factor (tan ?)

Mohammad L. Hassan

2002-01-01

19

Static and dynamic properties of Fibonacci multilayers  

NASA Astrophysics Data System (ADS)

We theoretically investigate static and dynamic properties of quasiperiodic magnetic multilayers. We considered identical ferromagnetic layers separated by non-magnetic spacers with two different thicknesses chosen based on the Fibonacci sequence. Using parameters for Fe/Cr, the minimum energy was determined and the equilibrium magnetization directions found were used to calculate magnetoresistance curves. Regarding dynamic behavior, ferromagnetic resonance (FMR) curves were calculated using an approximation known from the literature. Our numerical results illustrate the effects of quasiperiodicity on the static and dynamic properties of these structures.

Machado, L. D.; Bezerra, C. G.; Correa, M. A.; Chesman, C.; Pearson, J. E.; Hoffmann, A.

2013-05-01

20

Static Electric Susceptibility and Dielectric Relaxation Time near the Transition Points in NaNO2  

Microsoft Academic Search

The precise temperature dependence of the ralaxation time of the polarization in NaNO2 has been given through a new approach, in which the relaxation time is derived from the imaginary part of the complex dielectric constant in the low frequency region. On the way of this experimental procedure, it was found that the measurement of the static electric susceptibility should

Ichiro Hatta

1970-01-01

21

Static magnetic properties of Maghemite nanoparticles  

NASA Astrophysics Data System (ADS)

We report the static magnetic properties of Maghemite (?-Fe2O3) nanoparticles with an average crystallite size of 14 ± 1.8 nm synthesized via a co-precipitation method. The zero-field-cooled (ZFC) and the field-cooled (FC) magnetization measurements were performed using a physical properties measurements system (PPMS) at temperatures from 5 K to 300 K. The ZFC/FC measurements showed a typical superparamagnetic behavior with a narrow size distribution.

Zulfiqar; Rahman, Muneeb Ur; Usman, M.; Hasanain, Syed Khurshid; Zia-ur-Rahman; Ullah, Amir; Kim, Ill Won

2014-12-01

22

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

23

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 ...

24

Dielectric Properties of Various Nanocomposite Materials  

NASA Astrophysics Data System (ADS)

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

Tuncer, Enis; Polizos, Georgios; Randy James, D.; Sauers, Isidor; Ellis, Alvin R.; More, Karren L.

2010-04-01

25

Evaluation of dielectric properties in polypropylene\\/clay nanocomposites  

Microsoft Academic Search

Effects of nanoflller addition on four typical dielectric properties, namely permittivity ¿¿', dielectric loss factor ¿r¿, space charge accumulation, and partial discharge (PD) resistance were evaluated for polypropylene (PP) and its nanocomposites (NCs) with nanoclay. While ¿r' and ¿¿\\

N. Fuse; T. Tanaka; Y. Ohki

2009-01-01

26

Dielectric properties of aged polymers and nanocomposites  

Microsoft Academic Search

The research presented in this thesis is motivated by two current concerns for electrical wiring insulation materials: i) the aging of polymeric insulation that has been widely used for decades and ii) the development of new dielectric materials with advanced insulating properties, such as polymer-clay nanocomposites.\\u000aThe first part of this thesis investigated the deterioration of insulating function of three

Li Li

2011-01-01

27

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

28

Spacecraft dielectric material properties and spacecraft charging  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

29

Dielectric Properties of PVDF/PZT  

SciTech Connect

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

Zak, A. Khorsand; Chen, Gan Wee; Majid, W. H. Abd. [Low dimensional material research center, Department of physics, Faculty of Science, University of Malaya, Kuala Lumpur 50603 (Malaysia)

2011-03-30

30

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

31

Dielectric properties of cottage cheese and surface treatment using microwaves  

Microsoft Academic Search

This research determines the dielectric properties of cottage cheese and explores the application of microwave treatment to reduce surface spoilage microorganisms, extending the shelf-life of cottage cheese in sealed plastic containers. Dielectric properties of cottage cheese of 0, 2 and 4% fat content were measured at temperatures between 5 and 65 °C. The penetration depths of microwaves of 2450 and

A. G. Herve; J. Tang; L. Luedecke; H. Feng

1998-01-01

32

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

33

Dielectric properties of ultrathin SiO2 slabs  

NASA Astrophysics Data System (ADS)

First-principles total energy calculations have been performed to determine the extent to which surfaces impact the dielectric properties of ultrathin dielectric materials. SiO2 (0001) slabs in ?-quartz phase with various thicknesses were considered in this study, using a new method that allows for the partitioning of the surface and bulk contributions to the total field-induced polarization. It was found that the bulk polarization and the dielectric constant can be determined even from ultrathin films terminated with Si atoms, and that surface effects do not significantly impact the dielectric properties of (0001) ?-quartz slabs.

Shi, N.; Ramprasad, R.

2005-12-01

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

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

36

Dielectric properties of barium titanate supramolecular nanocomposites.  

PubMed

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

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

2014-04-01

37

Automated Monitoring Of Dielectric Properties Of Tree Trunks  

NASA Technical Reports Server (NTRS)

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

Mcdonald, Kyle C.; Chun, William

1996-01-01

38

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

39

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

Microsoft Academic Search

Transformation field method (TFM) is developed to estimate the anisotropic dielectric properties of crystal composites having arbitrary shapes and dielectric properties of crystal inclusions, whose principal dielectric axis are different from those of anisotropic crystal matrix. The complicated boundary-value problem caused by inclusion shapes is circumvented by introducing a transformation electric field into the crystal composites regions, and the effective

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

2010-01-01

40

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

41

Dielectric oxides: How to enhance their beneficial properties  

NASA Astrophysics Data System (ADS)

Dielectric materials are essential for a large number of applications. It is extensively used for electrical energy storage in capacitors and also plays a crucial role in miniaturization of MOSFET's. However, further shrinking of the physical size of such devices with same device capabilities will require the discovery of materials with higher dielectric constants and lower losses than available at present. In fact, in most cases, a combination of several dielectric properties is considered to be optimal, for example, minimal temperature and frequency dependencies of dielectric properties being important in many cases in addition to a large value of the dielectric constant and a low loss. In this talk, I shall discuss two separate series of oxides with useful dielectric properties. In the first example, I shall show that a disorder in the B-site of a family of disordered hexagonal transition metal oxides leads to robust and unusually enhanced dielectric properties, suggesting this to be a general route to prepare oxide materials with such advance properties. In the second example, we start with SrTiO3 which is a well-known dielectric material. We shall then discuss various possibilities to enhance dielectric properties of SrTiO3 by suitable doping. This work is based on collaborative studies involving the following people: Debraj Choudhury, S. V. Bhat, K. T. Delaney, J. Gopalakrishnan, C. Kakarla, Olof Karis, P. Lazor, R. Mathieu, P. Mondal, , P. Nordblad, A. Negi, R.Nirmala, B. Sanyal, N. A. Spaldin, P. Sujatha Devi, A. Sundaresan, A. Venimadhav, U. V. Waghmare and D. D. Sarma

Sarma, D. D.

2010-03-01

42

Texture effects on megahertz dielectric properties of calcite rock samples  

NASA Astrophysics Data System (ADS)

Dielectric measurements have been made from 0.5 to 1300 MHz on Whitestone, a quarried calcite rock, saturated with salty water. Whitestone shows a large increase in dielectric permittivity (dispersion) at the low end of this frequency range. When the conductivity of the water is varied, the dielectric permittivity of Whitestone is found to scale as water conductivity/frequency, i.e., as the complex dielectric constant of water. This is believed to be unique in measurements on insulator-conductor mixtures, and establishes that the dispersion is primarily caused by the geometry of the sample. Two other calcite samples show much lower dielectric dispersion. Micrographs indicate that the variation in dispersion among the three samples is in rough proportion to grain platiness. This is consistent with the platey grain mechanism, one of three mechanisms proposed by Sen to explain dielectric dispersion in water-saturated rocks. A model consisting of water containing insulating spheroids of identical aspect ratio, isotropically distributed in orientation, predicts that increased grain platiness reduces both low-frequency conductivity and high-frequency dielectric permittivity in a closely related way; this is observed experimentally. However, this model does not fit simultaneously all electrical properties of Whitestone; evidently a more complex geometrical model is needed. Dielectric dispersion caused by texture is of practical importance in estimating water content of subsurface rocks from borehole measurements of dielectric permittivity, particularly at high water salinities.

Kenyon, W. E.

1984-04-01

43

Dielectric and magnetic properties of some gadolinium silica nanoceramics  

SciTech Connect

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

Coroiu, I., E-mail: coroiu@phys.utcluj.ro; Pascuta, P., E-mail: coroiu@phys.utcluj.ro; Bosca, M., E-mail: coroiu@phys.utcluj.ro; Culea, E., E-mail: coroiu@phys.utcluj.ro [Technical University, Chemical and Physics Department, 28, Memorandumului, 400114, Cluj-Napoca (Romania)

2013-11-13

44

Electronic properties of defects in polycrystalline dielectric materials  

Microsoft Academic Search

Grain boundaries have been implicated in current leakage and dielectric breakdown of CMOS devices. We calculate the electronic properties of oxygen vacancy defects near grain boundaries in the dielectric insulators MgO and HfO2 using first principles methods. In both materials we find that oxygen vacancies favourably segregate to grain boundaries, in various charge states. Their electronic properties are different from

K. P. McKenna; A. L. Shluger

2009-01-01

45

Modelling of the static and dynamic mechanical properties of human  

E-print Network

Modelling of the static and dynamic mechanical properties of human otoliths DISSERTATION zur of the city of Paris #12;#12;Abstract The aim of this study is a numerical investigation of the static and dynamic prop- erties of the otoliths. The otoliths are a part of the vestibular system, located

Haslwanter, Thomas

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

Recent progress on dielectric properties of protic ionic liquids  

NASA Astrophysics Data System (ADS)

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.

Wojnarowska, Zaneta; Paluch, Marian

2015-02-01

48

Dielectric Properties of Epoxy Nanocomposite System for Packaging Applications  

Microsoft Academic Search

In recent times, there has been an ever-growing need for polymer-based multifunctional materials for electronic packaging applications. In this direction, epoxy-Al2O3 nanocomposites at low filler loadings can provide an excellent material option, especially from the point of view of their dielectric properties. This paper reports the dielectric characteristics for such a system, results of which are observed to be interesting,

Santanu Singha; M. Joy Thomas

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

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

51

The dielectric properties of polymer-water systems  

E-print Network

the dielectric properi;ies are explainable in a satisfactory manner. Another mechanism is possible, however. If ions are present they can move towards the oppositely charged condenser plate. In this manner the charges build up at the interfaces...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...

Lewis, Joe Bill

1976-01-01

52

Triboelectric charging and dielectric properties of pharmaceutically relevant mixtures  

Microsoft Academic Search

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

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

2007-01-01

53

Dielectric and other properties of polyimide aerogels containing fluorinated blocks.  

PubMed

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

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

2014-05-14

54

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

PubMed Central

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

Ji, Zhen; Brace, Christopher L

2011-01-01

55

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

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

56

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

57

Dielectric properties of soils as a function of moisture content  

NASA Technical Reports Server (NTRS)

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

Cihlar, J.; Ulaby, F. T.

1974-01-01

58

Dielectric properties of albumin and yolk of avian egg.  

PubMed

The dielectric properties of albumin and yolk of eggs of hen and duck have been investigated using the time domain reflectometry (TDR) technique in the frequency range 10 MHz to 10 GHz at room temperature. The conductivity and pH values were also measured. It has been found that the values of dielectric constant (epsilon s) is lower, while the values of relaxation time tau(ps) are higher than that of pure water possibly due to the bound water present in the yolk and albumin of the avian egg. The dielectric constant for albumin is more than that for yolk of eggs, while reverse is found with the values of relaxation time. Also albumin shows approximately three times higher conductivity than that of yolk. In the case of relatively older (by 2 days) eggs, the dielectric parameters tend to be slightly increased. PMID:8754629

Lokhande, M P; Arbad, B R; Landge, M G; Mehrotra, S C

1996-04-01

59

Dielectric properties of hypothermic rat artery.  

PubMed

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

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

2013-01-01

60

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

61

The static dielectric constant of SPC and TIP4P water by perturbation theory  

NASA Astrophysics Data System (ADS)

A second-order perturbation theory that was previously applied to hard-sphere-dipolar and Stockmayer fluids is extended to molecules with spherical cores and discrete point charge distribution of arbitrary symmetry. We use a recently published improvement on the Kirkwood superposition approximation for the reference state triplet distribution function, and we apply the theory to obtain the static dielectric constant (?) of SPC and TIP4P water at ˜1 gm cm-3 and a range of temperatures. By comparison with the results of simulations on these models we find that the theory works up to y?3 (where y is the dipolar strength function) but overestimates ? beyond y?3. y?3 is also the range of validity of the theory when applied to a Stockmayer fluid, but for the latter the theory underestimates ? for y?3. We physically interpret our results for the angular correlation parameter (G) by reference to structures that are believed to be important in real water and in dense dipolar fluids.

Goldman, Saul; Joslin, Chris

1993-08-01

62

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

63

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

PubMed

Tunable metal/dielectric composites are promising candidates for a large number of potential applications in electronics, sensor technologies and optical devices. Here we systematically investigate the dielectric properties of Ag-nanoparticles embedded in the highly flexible elastomer poly-dimethylsiloxane (PDMS). As tuning parameter we use uniaxial and biaxial strain applied to the composite. We demonstrate that both static variations of the filling factor and applied strain lead to the same behavior, i.e., the filling factor of the composite can be tuned by application of strain. In this way the effective static permittivity ?eff of the composite can be varied over a very large range. Once the Poisson's ratio of the composite is known, the strain dependent dielectric constant can be accurately described by effective medium theory without any additional free fit parameter up to metal filling factors close to the percolation threshold. It is demonstrated that, starting above the percolation threshold in the metallic phase, applying strain provides the possibility to cross the percolation threshold into the insulating region. The change of regime from conductive phase down to insulating follows the description given by percolation theory and can be actively controlled. PMID:25687891

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

2015-03-14

64

Dielectric Properties of Liquid Pentafluoroethane (HFC125)  

Microsoft Academic Search

This paper reports measurements of the static relative permittivity of HFC-125 in the liquid phase, performed by using the direct capacitance method at 10 kHz, for temperatures from 214 to 304 K and pressures up to 16 MPa. The repeatability of the measurements was found to be of the order of ±0.7×10-3and the uncertainty is estimated to be better than

L. M. Pereira; F. E. de Brito; A. N. Gurova; U. V. Mardolcar; C. A. Nieto de Castro

2001-01-01

65

Effect of dielectric properties of metals on terahertz transmission in subwavelength hole arrays  

E-print Network

Effect of dielectric properties of metals on terahertz transmission in subwavelength hole arrays of dielectric function of metals on the transmission properties of terahertz pulses through periodically metals become highly conductive at terahertz frequencies. Extraordinary terahertz trans- mission

66

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

67

Electrical Conduction and Dielectric Properties of Biodegradable Plastics  

Microsoft Academic Search

We examined the electrical conduction and dielectric properties as well as thermal analysis of polylactic acid (PLA) that is biodegradable plastics. From the results of thermal analyses, it was found that the glass transition temperature (Tg) of PLA was about 60°C and the melting point (Tm) was about 166°C. For the temperature dependence of current density (J), J of PLA

Katsuyoshi Shinyama; Shigetaka Fujita

2005-01-01

68

Mechanical and Dielectric Breakdown Properties of Biodegradable Plastics  

Microsoft Academic Search

The mechanical and dielectric breakdown properties of polylactic acid (PLA), which is a biodegradable plastic, were examined, and a physicochemical analysis was performed. At room temperature, the tensile strength of PLA was about 100 MPa, almost the same as for PP, but at 100°C, even the value for LDPE decreased. The Young's modulus of PLA at room temperature was about

Katsuyoshi Shinyama; Shigetaka Fujita

2006-01-01

69

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...

70

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

71

MICROWAVE DIELECTRIC PROPERTIES OF CEREAL GRAIN AND SEED  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

72

Peculiarities of dielectric properties of nanocrystalline bismuth ferrite  

NASA Astrophysics Data System (ADS)

Results of the single-stage synthesis of nanocrystalline bismuth ferrite are presented. It is shown that the temperature and frequency dependences of dielectric properties of specimens produced by the cold compaction of the obtained powder substantially differ from those of microcrystalline bismuth ferrite produced using traditional ceramic technology.

Palchaev, D. K.; Faradzheva, M. P.; Sadykov, S. A.; Rabadanov, M. Kh.; Murlieva, Zh. Kh.; Kallaev, S. N.; Tabit, A. F. A.; Emirov, R. M.

2014-11-01

73

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

74

Dielectric properties of liquid crystals in polycapillary matrices  

Microsoft Academic Search

This paper reports on the results of investigations into the dielectric properties of liquid crystals embedded in polycapillary matrices and describes a technique for their measurement. It has been revealed that the chemical structure of the rigid core and the length of mobile alkyl groups of liquid-crystal molecules of the alkylcyanobiphenyl group substantially affect the equilibrium configuration of the liquid-crystal

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

2010-01-01

75

Dielectric and pyroelectric properties of ultrathin, monocrystalline lithium tantalate  

NASA Astrophysics Data System (ADS)

Ultrathin, self-supporting lithium tantalate (LiTaO3) wafers have been fabricated out of a single crystal with a minimum thickness of about 0.4 ?m using ion-beam milling. The most decisive parameters (pyroelectric coefficient, relative permittivity, and dielectric loss factor) for their use in pyroelectric radiation detectors were studied in dependence on film thickness and temperature. The potential performance of pyroelectric materials was evaluated using appropriate figures of merit. In addition, the dielectric and pyroelectric properties of stoichiometric LiTaO3 were investigated and compared to congruent LiTaO3 bulk material conventionally used for pyroelectric detectors.

Schossig, Marco; Norkus, Volkmar; Gerlach, Gerald

2014-03-01

76

Electrical, optical and dielectric properties of HCl doped polyaniline nanorods  

NASA Astrophysics Data System (ADS)

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

Chutia, P.; Kumar, A.

2014-03-01

77

Correlation of structure and dielectric properties of silver selenomolybdate glasses  

NASA Astrophysics Data System (ADS)

Structure and dielectric properties of the glasses of compositions yAg2O-(1-y)(xSeO2-(1-x)MoO3) with varying modifier oxide and glass formers ratio have been reported in this paper. Fourier transform infrared (FTIR) spectroscopy has been employed to investigate the effect of SeO2 content on the glass network structure. The existence of different characteristic absorption bands corresponding to the vibration of SeO32- anions, isolated MoO6 units and crystalline molybdate octahedra, has been ascertained from FTIR spectra. It has been observed that the modification of the glass network structure occurs with change of SeO2 content, which reveals the dual role of SeO2 as a network modifier and a network former depending on composition. The dielectric constant as well as dielectric strength increases gradually with the increase of SeO2 content for low modifier oxide content (y), whereas they show a maximum for intermediate and highly modified glasses. The variation of the dielectric parameters correlates directly to the relative proportion of vibration mode of SeO32- ions, which is observed to vary in a similar fashion to dielectric parameters and is, thus in turn, related to the dual behavior of SeO2 as a modifier and a former depending on composition.

Deb, B.; Ghosh, A.

2012-07-01

78

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

79

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

NASA Astrophysics Data System (ADS)

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

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

2001-10-01

80

Technique for Performing Dielectric Property Measurements at Microwave Frequencies  

NASA Technical Reports Server (NTRS)

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

Barmatz, Martin B.; Jackson, Henry W.

2010-01-01

81

Synthesis and dielectric property of polyimide\\/MWNTs nanocomposite films  

Microsoft Academic Search

Multi-wall carbon nanotubes (MWNTs) were acid modified by refluxing with the mixture of H2SO4 and HNO3 under ultrasound, then were attended into the synthesis of polyamic acid (PAA), precursor of polyimide (PI) to form PI\\/MWNTs films via in situ polymerization process. The dispersion situation of MWNTs in the nanocomposites was characterized using scanning electronic microscopy (SEM); dielectric properties of nanoflims

Feng Tian; Mingyan Zhang; Zijian Wu; Xiaoying Zhu; Penghe Diao; Jihua Wang

2009-01-01

82

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

Microsoft Academic Search

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

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

2003-01-01

83

Dielectric properties of liquid crystals in polycapillary matrices  

Microsoft Academic Search

This paper reports on the results of investigations into the dielectric properties of liquid crystals embedded in polycapillary\\u000a matrices and describes a technique for their measurement. It has been revealed that the chemical structure of the rigid core\\u000a and the length of mobile alkyl groups of liquid-crystal molecules of the alkylcyanobiphenyl group substantially affect the\\u000a equilibrium configuration of the liquid-crystal

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

2010-01-01

84

Structure-property relationships in polymers for dielectric capacitors  

NASA Astrophysics Data System (ADS)

Effective energy storage is a key challenge of the 21st century that has fueled research in the area of energy storage devices. In this dissertation, structure-property relationships have been evaluated for polymers that might be suitable for storing energy in high-energy density, high-temperature capacitors. Firstly, hydroxyl-modified polypropylenes (PPOH) were synthesized by copolymerization of the propylene and undecenyloxytrimethylsilane monomers. The presence of H-bonding in PPOH copolymers increased their glass-transition temperature. Steric hindrance by the comonomer reduced the PP crystal growth rate and crystal size, resulting in a melting point depression. The comonomer was restricted outside the crystalline domains leaving the alpha-monoclinic crystal structure of PP unaffected, but increasing the fold-surface free energy. Crystallization was slower for PPOH copolymers than PP, but exhibited a skewed bell curve as a function of hydroxyl concentration. H-bonding persisted even at melt temperatures up to 250°C resulting in a higher elasticity and viscosity for PPOH copolymers. Secondly, sulfonated poly(ether ether ketone) (HSPEEK) was synthesized by sulfonating PEEK with sulfuric acid, and further neutralized with Zn to obtain ZnSPEEK. The thermal and dielectric properties of SPEEK were compared with PEEK. The glass-transition increased and melting point were high enough to enable the use of polymer at 180°C. The incorporation of sulfonic groups in PEEK increased the dielectric constant. HSPEEK had a higher dielectric constant than ZnSPEEK due to higher dipolar mobility, but the dielectric loss was also higher for HSPEEK due to electrode polarization and DC conduction. These results were consistent with our observations from sulfonated polystyrene (HSPS), which was used as a >model&lang' polymer. Lastly, commercial poly(4-methyl-1-pentene) (P4MP) was characterized to check its viability as a high-temperature polymer dielectric. Thermal stability up to 200°C, high melting point (> 225°C) and melting onset at 160 - 190°C indicated that P4MP could be used at 180 - 200°C. Thin free-standing films (~10 mum) with controlled crystal structure and surface morphology were prepared using blade coating and their drying dynamics were measured using a custom-designed solvent-casting platform. These films were further stretched uniaxially or biaxially, and their effect on the dielectric properties of P4MP was studied.

Gupta, Sahil

85

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

86

Bethe-Salpeter amplitudes and static properties of the deuteron  

SciTech Connect

Extended calculations of the deuteron{close_quote}s static properties, based on the numerical solution of the Bethe-Salpeter equation, are presented. A formalism is developed, which provides a comparative analysis of the covariant amplitudes in various representations and nonrelativistic wave functions. The magnetic and quadrupole moments of the deuteron are calculated in the Bethe-Salpeter formalism and the role of relativistic corrections is discussed. {copyright} {ital 1996 The American Physical Society.}

Kaptari, L.P.; Umnikov, A.Y.; Bondarenko, S.G.; Kazakov, K.Y.; Khanna, F.C.; Kaempfer, B. [Research Center Rossendorf, Institute for Nuclear and Hadron Physics, PF 510119, 01314 Dresden (Germany)] [Research Center Rossendorf, Institute for Nuclear and Hadron Physics, PF 510119, 01314 Dresden (Germany); [Bogoliubov Laboratory of Theoretical Physics, JINR, 141980 Dubna, Moscow Region (Russia); [INFN Section Perugia, via A. Pascoli, I-06100 Perugia (Italy); [Far Eastern State University, Vladivostok, 690000 (Russia); [University of Alberta, Edmonton, Alberta T6G 2J1 (Canada); [TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, Canada, V6T 2A3 (CANADA); [Institute for Theoretical Physics, Technical University, 01062 Dresden (Germany)

1996-09-01

87

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

88

Protein dielectrophoresis and the link to dielectric properties.  

PubMed

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

Camacho-Alanis, Fernanda; Ros, Alexandra

2015-02-01

89

Dielectric study of [alcohol]x[water]1-x mixtures and valuation of static permittivity and relaxation time for supercooled water  

Microsoft Academic Search

Results are presented which lead to the characterization of [alcohol]x[water]1-x mixtures between ambient and glass temperature over the whole molar fraction range. Suitable extrapolations to zero alcohol concentration allow one to calculate the dielectric relaxation time and the static permittivity of supercooled water below its homogeneous nucleation temperature. Use is made of a dielectric relaxation spectrometer operating from 1 MHz

G. A. Noyel; L. J. Jorat; J. R. Huck; O. Derriche

1990-01-01

90

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

NASA Astrophysics Data System (ADS)

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

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

2003-03-01

91

A Quarter-Wave Stripline Resonator for the Measurement of the Dielectric Properties of Substrate Materials  

Microsoft Academic Search

In this paper a quarter-wave stripline resonator sensor for the measurement of dielectric sheets is presented. The resonant frequency of the sensor depends linearily on the dielectric constant of the sheet. The sensor can be used for example for the measurement of the dielectric properties of substrate materials at 8 GHz with a spatial resolution of about 6 mm and

Matti Fischer; Pertti Vainikainen; Ebbe Nyfors

1991-01-01

92

Investigating transport properties of nanofiltration membranes by means of a steric, electric and dielectric exclusion model  

Microsoft Academic Search

The transport properties of nanofiltration (NF) membranes are investigated by means of an improved transport model including dielectric exclusion in terms of both Born dielectric effect and image force contribution. The SEDE model (Steric, Electric and Dielectric Exclusion model) can be used to describe transport through pores of cylindrical or slit geometry. The coupling between the various mechanisms involved in

Anthony Szymczyk; Patrick Fievet

2005-01-01

93

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

PubMed

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

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

2015-03-01

94

A blue phase with negative dielectric anisotropy in an electric field. Statics and dynamics  

E-print Network

far are a tetragonal (BPX), a three-dimensional hexagonal (BPH3D) and a two- dimensional hexagonal blue phase (BPH2D) which are stable only in an electric field [1]. For systems with negative dielectric anisotropy BPH3D is the only observed field-induced phase [18, 19]. Additionally, for BPI and BPII

Paris-Sud XI, Université de

95

Dielectric Properties of Generation 3 Pamam Dendrimer Nanocomposites  

NASA Astrophysics Data System (ADS)

Broadband dielectric relaxation spectroscopy (DRS) was employed to study molecular dynamics of blends composed of generation 3 poly(amidoamine) (PAMAM) dendrimers with ethylenediamine core and amino surface groups and four linear polymers: poly(propylene oxide)—PPO, two block copolymers, poly(propylene oxide)/poly(ethylene oxide)—PPO/PEO with different mol ratios (29/6 and 10/31) and poly(ethylene oxide)—PEO. The results were generated over a broad range of frequency. Dielectric spectra of dendrimers in PPO matrix reveal slight shift of normal and segmental processes to higher frequency with increasing concentration of dendrimers. In the 29PPO/6PEO matrix, no effect of concentration on the average relaxation time for normal and segmental processes was observed. In the 10PPO/31PEO matrix the relaxation time of the segmental process increases with increasing dendrimer concentration, while in the PEO matrix, local processes in dendrimers slow down. A detailed analysis of the effect of concentration of dendrimers and morphology of polymer matrix on the dielectric properties of dendrimer nanocomposites will be presented.

Risti?, Sanja; Mijovi?, Jovan

2008-08-01

96

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

97

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

Microsoft Academic Search

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

Thomas Hanemann; Holger Gesswein; Benedikt Schumacher

98

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

99

Effect of Gadolinium Substitution on Dielectric Properties of Bismuth Ferrite  

Microsoft Academic Search

Multiferroic Bi1-xGdxFeO3 (x =0, 0.05, 0.1, 0.15, 0.2) ceramics were prepared by conventional solid state reaction method. X-ray diffraction was carried out to characterize the crystal structure and to detect any possible impurities existing in these ceramics. Frequency dependence of dielectric properties of Bi1-xGdxFeO3 samples at room temperature was measured in a frequency range from 100 Hz to 1 MHz

Chang Fanggao; Song Guilin; Fang Kun; Qin Ping; Zeng Qijun

2006-01-01

100

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

101

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

PubMed

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

Antosiewicz, Tomasz J; Apell, S Peter

2014-01-27

102

The study of dielectric properties of the endohedral fullerenes  

NASA Astrophysics Data System (ADS)

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

Bhusal, Shusil

103

Densities, refractive indices, absolute viscosities, and static dielectric constants of 2-methylpropan-2-ol + hexane, + benzene, + propan-2-ol, + methanol, + ethanol, and + water at 303.2 K  

SciTech Connect

Densities, refractive indices, absolute viscosities, and static dielectric constants have been measured over the entire range of composition for binary mixtures of 2-methylpropan-2-ol with hexane, benzene, propan-2-ol, methanol, ethanol, and water at 303.2 K. Excess molar volumes were fitted to Redlich-Kister equations.

Rived, F.; Roses, M.; Bosch, E. [Universitat de Barcelona (Spain). Departament de Quimica Analitica

1995-09-01

104

Direct measurement of the dielectric polarization properties of DNA.  

PubMed

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

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

2014-09-01

105

Direct measurement of the dielectric polarization properties of DNA  

PubMed Central

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

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

2014-01-01

106

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

107

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

108

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

109

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

110

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

111

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

Microsoft Academic Search

Ferrite nanoparticles of basic composition Ni0.7Mg0.3Fe2-xAlxO4 (0.0<=x<=0.5) were prepared through citrate gel method and characterized using XRD, TEM and dielectric spectroscopy techniques. The dielectric properties were studied as a function of frequency (42 Hz-5 MHz) at room temperature. The average particle size has been found between 8-17 nm. The dispersion in dielectric properties and ac conductivity (sigmaac), with frequency reveals

Razia Nongjai; Khalid Mujasam Batoo; Shakeel Khan

2010-01-01

112

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

113

USEFUL RELATIONSHIPS BETWEEN DIELECTRIC PROPERTIES AND BULK DENSITY OF GRANULAR AND POWDERED MATERIALS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The dielectric properties of cereal grains and oilseeds are used in the determination of moisture content by electrical and electronic moisture meters. The dielectric properties of materials are those electrical characteristics that determine the interaction of the material and electric fields in...

114

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...

115

A STUDY OF THE DIELECTRIC PROPERTIES OF WATER EMULSIONS OBTAINED AFTER A CRYSTALLIZATION/MELTING CYCLE  

E-print Network

825 A STUDY OF THE DIELECTRIC PROPERTIES OF WATER EMULSIONS OBTAINED AFTER A CRYSTALLIZATION paraffine), obtenues après congélation-fusion, sont comparées avec celles des emulsions d'eau avant tout. Abstract. 2014 The dielectric properties of water emulsions (the continuous medium of which is a mixture

Paris-Sud XI, Université de

116

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...

117

Large dielectric permittivity and possible correlation between magnetic and dielectric properties in bulk BaFeO3-?  

NASA Astrophysics Data System (ADS)

We report structural, magnetic, and dielectric properties of oxygen deficient hexagonal BaFeO3-?. A large dielectric permittivity comparable to that of other semiconducting oxides is observed in BaFeO3-?. Magnetization measurements indicate magnetic inhomogeneity and the system shows a paramagnetic to antiferromagnetic transition at ˜160 K. Remarkably, the temperature, at which paramagnetic to antiferromagnetic transition occurs, around this temperature, a huge drop in the dissipation factor takes place and resistivity shoots up; this indicates the possible correlation among magnetic and dielectric properties. First principle simulations reveal that some of these behaviors may be explained in terms of many body electron correlation effect in the presence of oxygen vacancy present in BaFeO3-? indicating its importance in both fundamental science as well as in applications.

Sagdeo, Archna; Gautam, Kamini; Sagdeo, P. R.; Singh, M. N.; Gupta, S. M.; Nigam, A. K.; Rawat, Rajeev; Sinha, A. K.; Ghosh, Haranath; Ganguli, Tapas; Chakrabarti, Aparna

2014-07-01

118

Electro-optical and dielectric properties of a high tilt antiferroelectric liquid crystal mixture (W-193B)  

NASA Astrophysics Data System (ADS)

The electro-optical properties and dielectric relaxation have been investigated for an antiferroelectric liquid crystal mixture W-193B. The material exhibits smectic A*, smectic C* and a wide range of anticlinic smectic C_A^\\ast phases. The high tilt and broad room temperature smectic C_A^\\ast phase make it a good candidate for antiferroelectric display materials. Dielectric studies have been made in a planarly aligned cell in the frequency range 10 Hz-13 MHz. Dielectric spectroscopy reveals the existence of soft mode in the smectic A* phase and Goldstone mode in the smectic C* phase. In the smectic C_A^\\ast phase the dielectric spectrum of the material exhibits two absorption peaks related to the rotational fluctuation around the short axis of the molecules and antiphase azimuthal angle fluctuation, respectively, and are separated by about two orders of frequency. Electro-optical response using a low frequency triangular wave showed a very high quasi-static contrast ratio of 132 : 1, threshold voltage of around 7 V and saturation of 17 V. Surface-stabilized, low thickness cells of this mixture showed a perfect double hysteresis loop with a 1 Hz triangular signal, reaching different transmission levels for different voltage amplitudes. These levels can be stabilized with a single holding voltage, making it possible for the material to be passively multiplexed at video rate.

Nayek, Prasenjit; Ghosh, Sharmistha; Kundu, Sudarshan; Roy, Subir Kr; Pal Majumder, Tapas; Bennis, Noureddine; Otón, Jose Manuel; Dabrowski, Roman

2009-11-01

119

Static and dynamic properties of a reversible gel  

E-print Network

We study a microscopically realistic model of a physical gel and use computer simulations to investigate its static and dynamic properties at thermal equilibrium. The phase diagram comprises a sol phase, a coexistence region ending at a critical point, a gelation line, and an equilibrium gel phase unrelated to phase separation. The global structure of the gel is homogeneous, but the stress is supported by a fractal network. Gelation results in a dramatic slowing down of the dynamics, which can be used to locate the transition, which otherwise shows no structural signatures. Moreover, the equilibrium gel dynamics is highly heterogeneous as a result of the presence of particle families with different mobilities. An analysis of gel dynamics in terms of mobile and arrested particles allows us to elucidate several differences between the dynamics of equilibrium gels and that of glass-formers.

Pablo I. Hurtado; Pinaki Chaudhuri; Ludovic Berthier; Walter Kob

2008-11-10

120

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

121

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 of History Matching with Different Algorithms . . . . . . . . . . . . 39 TIME LAPSE SEISMIC DATA 46 Automatic

Reynolds, Albert C.

122

Dielectric Properties of Vesta's Surface as Constrained by Dawn VIR Observations  

E-print Network

Earth and orbital based radar observations of asteroids provide a unique opportunity to characterize surface roughness and the dielectric properties of their surfaces, as well as potentially explore some of their shallow subsurface physical properties. If the dielectric and topographic properties of asteroid's surfaces are defined, we can constrain their textural characteristics as well as potential subsurface volatile enrichment using the observed radar backscatter. To achieve this objective, we establish the first dielectric model of asteroid Vesta for the case of a dry, volatile-poor regolith -- employing an analogy to the dielectric properties of lunar regolith, and adjusted for the surface densities and temperatures deduced from Dawn's Visible and InfraRed mapping spectrometer (VIR). Our model suggests that the dielectric constant at the surface of Vesta is relatively constant, ranging from 2.0 to 2.1 from the night- to day-side of Vesta, while the loss tangent shows slight variation as a function of diu...

Palmer, Elizabeth M; Capria, Maria Teresa; Tosi, Federico

2015-01-01

123

Cole-Cole Model for Glucose-Dependent Dielectric Properties of Blood Plasma for Continuous Glucose Monitoring  

Microsoft Academic Search

Next generation continuous glucose monitoring systems depends on the accurate relationship between the glucose concentration and the dielectric properties of the blood plasma. In this study, the dielectric properties of 10 blood plasma samples were measured for various glucose levels in the frequency range of 500 MHz to 20 GHz. To relate the glucose concentration with the dielectric properties, first

Tutku Karacolak; Elaine C. Moreland; Erdem Topsakal

124

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

SciTech Connect

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

Abe, H.; Okuda, H.

1994-06-01

125

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

126

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

SciTech Connect

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

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

2000-04-03

127

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...

128

The Huygens principle for a uniaxial dielectric-magnetic medium with gyrotropic-like magnetoelectric properties  

E-print Network

The dyadic Green functions for a uniaxial dielectric-magnetic medium, together with a reversible field transformation, were implemented to derive a formulation of the Huygens principle appropriate to a uniaxial dielectric-magnetic medium with gyrotropic-like magnetoelectric properties.

Mackay, Tom G

2008-01-01

129

Effects of dielectric screening on the optical properties of metallic nanoshells  

Microsoft Academic Search

The time dependent density functional method for the calculation of optical properties of metallic nanoshells is extended to include the combined influence of a dielectric core and a dielectric embedding medium. The coupling between the polarization charges at the inner and outer surfaces of the shell is found to strongly influence the position of the plasmon resonances. The method is

E. Prodan; P. Nordlander; N. J. Halas

2003-01-01

130

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

131

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...

132

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

133

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...

134

Influence of Water Content on RF and Microwave Dielectric Properties of Foods  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dielectric properties of several foods with a wide range of water content are presented graphically at frequencies between 10 MHz and 20 GHz. Their frequency- and temperature-dependent dielectric behavior is discussed with respect to differences in water content and explained by responses of ionic c...

135

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

136

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

137

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 As designers look to lighter-weight, thinner-walled steel castings, knowledge of the location, amount.A., and Beckermann, C., "Simulation of the Mechanical Performance of Cast Steel with Porosity: Static Properties

Beckermann, Christoph

138

Synthesis, characterization and dielectric properties of SnO2 thin films.  

PubMed

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

Y?ld?r?m, M Ali; Y?ld?r?m, Sümeyra Tuna; Sakar, Emine Fedakar; Ate?, Aytunç

2014-12-10

139

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

140

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

NASA Astrophysics Data System (ADS)

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

Francisca, Franco M.; Montoro, Marcos A.

2012-05-01

141

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

NASA Astrophysics Data System (ADS)

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

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

2005-10-01

142

Structural, conductivity and dielectric properties of Li2SO4  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

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

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

145

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

146

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

147

Technique for Performing Dielectric Property Measurements at Microwave Frequencies  

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

148

Effect of sintering on structural and dielectric properties of PLZT ferroelectrics  

NASA Astrophysics Data System (ADS)

Here we report synthesis of (Pb0.93La0.07Zr0.6Ti0.4O3) 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; Mathe, V. L.

2014-04-01

149

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

NASA Astrophysics Data System (ADS)

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

Wang, Yu U.; Tan, Daniel Q.

2011-05-01

150

Correlation between the dielectric properties and biological activities of human ex vivo hepatic tissue  

NASA Astrophysics Data System (ADS)

Dielectric properties are vital biophysical features of biological tissues, and biological activity is an index to ascertain the active state of tissues. This study investigated the potential correlation between the dielectric properties and biological activities of human hepatic tissue with prolonged ex vivo time through correlation and regression analyses. The dielectric properties of 26 cases of normal human hepatic tissue at 10?Hz to 100?MHz were measured from 15?min after isolation to 24?h at 37?°C with 90% humidity. Cell morphologies, including nucleus area (NA) and alteration rate of intercellular area (ICAR), were analyzed as indicators of biological activities. Conductivity, complex resistivity, and NA exhibited opposing changes 1?h after isolation. Relative permittivity and ex vivo time were not closely correlated (p > 0.05). The dielectric properties measured at low frequencies (i.e. <1?MHz) were more sensitive than those measured at high frequencies in reflecting the biological activity of ex vivo tissue. Highly significant correlations were found between conductivity, resistivity and the ex vivo time (p < 0.05) as well as conductivity and the cell morphology (p < 0.05). The findings indicated that establishing the correlation between the dielectric properties and biological activities of human hepatic tissue is of great significance for promoting the role of dielectric properties in biological science, particularly in human biology.

Wang, Hang; He, Yong; Yan, Qingguo; You, Fusheng; Fu, Feng; Dong, Xiuzhen; Shi, Xuetao; Yang, Min

2015-03-01

151

DIELECTRIC PROPERTIES OF MATERIALS AND RELATED AGRICULTURAL APPLICATIONS  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

152

Dielectric Properties of Rare Earth Substituted Cu-Zn Ferrites  

Microsoft Academic Search

Samples with the chemical formula Cu0.5Zn0.5Fe2-xRxO4 (R = La, Nd, Sm and Gd; x = 0 and 0.1) were prepared by the standard ceramic method. The real part of the dielectric constant and the ac electrical conductivity ac are measured and the dielectric loss tangent tan delta is calculated in the frequency range 50-105 Hz and from room temperature up

A. A. Sattar; Samy A. Rahman

2003-01-01

153

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

154

UMBILICS : STATIC PROPERTIES AND SHEAR-INDU CED DISPLACEMENTS  

E-print Network

the structure of umbilical « defects » which should appear under certain conditions in a nematic slab in an electric field. We show that a shear flow can induce a displacement of these defects. LE JOURNAL DE. - A slab contains a nematic monocrystal with a negative dielectric (or magnetic) anisotropy (Fig. 1

Boyer, Edmond

155

Dielectric properties and phase transition of zinc tris(thiourea) sulfate single crystal  

NASA Astrophysics Data System (ADS)

The dielectric properties and the ferroelectric to paraelectric phase transition of zinc tris(thiourea) sulfate (ZTS) single crystal have been investigated in a wide range of temperatures and frequencies. In the lower frequency region the real part of dielectric permittivity of the ZTS crystal shows a sudden increase at 323 K. Prominent first-order ferroelectric to paraelectric phase transition at 323 K has been observed in the plot of dielectric permittivity versus temperature at different frequencies. It has been observed that the phase transition occurs in ZTS crystal with a low degree of disorder. Surprisingly, it has been observed for ZTS that the value of the dielectric permittivity is only about 10 at high frequencies and is found to increase to 50 at low frequencies. Dielectric loss has higher values in the paraelectric region.

Moitra, S.; Bhattacharya, S.; Kar, T.; Ghosh, A.

2008-09-01

156

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

157

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

PubMed

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

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

2009-09-24

158

First-principles study of structural, electronic, vibrational, dielectric and elastic properties of tetragonal Ba{sub 2}YTaO{sub 6}  

SciTech Connect

We report first-principles study of structural, electronic, vibrational, dielectric, and elastic properties of Ba{sub 2}YTaO{sub 6}, a pinning material in high temperature superconductors (HTS), by using density functional theory. By using different exchange-correlation potentials, the accuracy of the calculated lattice constants of Ba{sub 2}YTaO{sub 6} has been achieved with GGA-RPBE, since many important physical quantities crucially depend on change in volume. We have calculated the electronic band structure dispersion, total and partial density of states to study the band gap origin and found that Ba{sub 2}YTaO{sub 6} is an insulator with a direct band gap of 3.50?eV. From Mulliken population and charge density studies, we conclude that Ba{sub 2}YTaO{sub 6} have a mixed ionic-covalent character. Moreover, the vibrational properties, born effective charges, and the dielectric permittivity tensor have been calculated using linear response method. Vibrational spectrum determined through our calculations agrees well with the observed Raman spectrum, and allows assignment of symmetry labels to modes. We perform a detailed analysis of the contribution of the various infrared-active modes to the static dielectric constant to explain its anisotropy, while electronic dielectric tensor of Ba{sub 2}YTaO{sub 6} is nearly isotropic, and found that static dielectric constant is in good agreement with experimental value. The six independent elastic constants were calculated and found that tetragonal Ba{sub 2}YTaO{sub 6} is mechanically stable. Other elastic properties, including bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and elastic anisotropy ratios are also investigated and found that Poisson's ratio and Young's modulus of Ba{sub 2}YTaO{sub 6} are similar to that of other pinning materials in HTS.

Ganeshraj, C.; Santhosh, P. N., E-mail: santhosh@physics.iitm.ac.in [Low Temperature Physics Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai 600 036, Tamil Nadu (India)

2014-10-14

159

Structural Behavior of Alcohol1,4Dioxane Mixtures through Dielectric Properties Using TDR  

Microsoft Academic Search

The values of complex permittivity for alcohol-1,4-dioxane (DX) mixtures with various concentrations have been determined in the frequency range 10 MHz to 20 GHz using the time domain reflectometry (TDR) method. Numbers of hydrogen bonds between alcohol-alcohol and alcohol-dioxane pairs are estimated from the values of the static dielectric constant by using the Luzar model. The model provides a satisfactory

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

2009-01-01

160

Dielectric properties and microstructural characterization of cubic pyrochlored bismuth magnesium niobates  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

161

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

162

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

163

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

PubMed

The dielectric properties, consisting of the dielectric constant (epsilon') and loss factor (epsilon''), were measured with an open-ended coaxial-line probe and impedance analyzer for uncooked broiler breast muscle pectoralis major and pectoralis minor, deboned at 2- and 24-h postmortem, over the frequency range from 10 to 1,800 MHz at temperatures ranging from 5 to 85 degrees C. The dielectric property profiles of chicken breast muscle are dependent upon the radio-wave and microwave frequencies and temperature. Increasing frequency from 10 to 1,800 MHz results in decreasing values of the dielectric constant and loss factor regardless of temperature in this range, chicken breast muscle type, or deboning time. However, the response to temperature varies with the frequency, muscle type, and deboning time. There are no differences in the dielectric constant and loss factor values at frequencies of 26 or 1,800 MHz between samples deboned at 2- and at 24-h postmortem. However, the muscle type significantly affects the average values of the dielectric constant and loss factor, with pectoralis minor having significantly higher average values. Both the deboning time and muscle type significantly affect the average values of the loss tangent (tan delta = dielectric loss factor/dielectric constant) at 26 and 1,800 MHz, with pectoralis minor having higher values than pectoralis major and 2-h samples having higher values than 24-h samples. Our quality measurements also show there are significant differences in chicken meat quality characteristics, including color, pH, drip loss, water holding capacity, and texture (Warner-Bratzler shear force value) between the different muscle types and between different deboning times in the same test. These results suggest that there is a probable potential for using dielectric property measurements to assess the quality of chicken meat. PMID:17954595

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

2007-11-01

164

Structural, optical and dielectric property of Co doped Bi2Fe4O9  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

165

Dielectric Properties of Rare Earth Substituted Cu-Zn Ferrites  

NASA Astrophysics Data System (ADS)

Samples with the chemical formula Cu0.5Zn0.5Fe2-xRxO4 (R = La, Nd, Sm and Gd; x = 0 and 0.1) were prepared by the standard ceramic method. The real part of the dielectric constant and the ac electrical conductivity ac are measured and the dielectric loss tangent tan ? is calculated in the frequency range 50-105 Hz and from room temperature up to 800 K. and tan ? are found to decrease with increasing the frequency while ac is generally increased. On the contrary , ac and tan ? are increased with temperature. No relaxation was detected in tan ?(f) in the investigated frequency range while tan ?(T) showed two maxima. The composition dependence of the dielectric parameters is discussed and the results are explained using Koops's model. (

Sattar, A. A.; Rahman, Samy A.

2003-12-01

166

Structural and dielectric properties of yttrium-substituted hydroxyapatites.  

PubMed

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

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

2015-02-01

167

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

Microsoft Academic Search

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

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

2003-01-01

168

A Comprehensive Study on Nanomechanical Properties of Various SiO2Based Dielectric Films  

Microsoft Academic Search

This paper studies the nanomechanical properties, including hardness and Young's modulus (both in a dry condition and in deionized water), fracture toughness, cohesive strength and scratch resistance of eight commonly used SiO2-based dielectric films, Boron Phosphosilicate Glass (BPSG), BPSG with Rapid Thermal Processing (RTP), Phosphosilicate Glass (PSG), Spin-On Dielectric (SOD), Plasma Enhanced Chemical Vapor Deposition (PECVD) Tetraethyl Orthosilicate (TEOS), high

Guohua Wei; Sony Varghese; Kevin Beaman; Irina Vasilyeva; Tom Mendiola; Andrew Carswell; David Fillmore; Shifeng Lu

2010-01-01

169

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

Microsoft Academic Search

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

Shinong Yan; Yongchang Wang; Tingdun Wen; Jian Zhu

2006-01-01

170

Optical and magneto-optical properties of 1-D dielectric and magnetic photonic crystals  

Microsoft Academic Search

The optical properties of one-dimensional (1-D) photonic crystals (PCs) and magnetic PCs (MPCs), composed of dielectric TiO2 and Al2O3 as well as magnetic Bi:YIG layers deposited on a glass substrate, are investigated in this work. The structure of dielectric 1-D PCs was optimized and a narrow omni -- photonic bandgap (PBG) is found away from the designed wavelength. When a

M. D. Huang; Y. H. Lu; P. J. Kim; S. Y. Park; Y. P. Lee

2006-01-01

171

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

172

Study of dielectric relaxation phenomena and electrical properties of conductive polyaniline based composite films  

Microsoft Academic Search

Composite polyurethane\\/polyaniline and polyamide-6\\/polyaniline films were chemically prepared by oxidative in situ polymerization of aniline inside the previously swelled matrix film. Swelling kinetic studies had shown that for polyurethane and polyamide-6 films the swelling degree of aniline was 25wt.% and 15wt.%, respectively. The dielectric and electrical properties of the composite films were established using dielectric relaxation spectroscopy and four-probe method.

C. Vanga Bouanga; K. Fatyeyeva; P.-Y. Baillif; J.-F. Bardeau; C. Khaokong; J.-F. Pilard; M. Tabellout

2010-01-01

173

First-principles study of dynamical and dielectric properties of tetragonal zirconia  

Microsoft Academic Search

Using the variational density-functional perturbation theory, we investigate the dynamical and dielectric properties of tetragonal zirconia (t-ZrO2). We obtain the phonon frequencies at the center of the Brillouin zone, the Born effective charge tensors, and the dielectric permittivity tensors. For all these quantities, a comparison is made with the related values in the cubic phase. The Born effective charge tensors

G.-M. Rignanese; F. Detraux; X. Gonze; Alfredo Pasquarello

2001-01-01

174

On Artificial Magneto-Dielectric Loading for Improving the Impedance Bandwidth Properties of Microstrip Antennas  

Microsoft Academic Search

In the present paper we discuss the effect of artificial magneto-dielectric substrates on the impedance bandwidth properties of microstrip antennas. The results found in the literature for antenna miniaturization using magnetic or magneto-dielectric substrates are revised, and discussion is addressed to the practically realizable artificial magnetic media operating in the microwave regime. Using a transmission-line model we, first, reproduce the

Pekka Ikonen; Stanislav Maslovski; Constantin Simovski; Sergei Tretyakov

175

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

176

Static and dynamic magnetic properties of Co 2 Z barium ferrite nanoparticle composites  

Microsoft Academic Search

The static, dynamic and attenuation properties of Co2Z barium ferrites and Co2Z composites have been studied. The results showed that both static and dynamic magnetic properties are significantly different for large particles and nanoparticles. As compared to large particles, Co2Z nanoparticles have a small saturation magnetization Ms, large coercivity Hc, small permeability µ'0 and µ''max, but high resonance frequency fR.

Z. W. Li; L. Chen; C. K. Ong; Z. Yang

2005-01-01

177

Factors Influencing the Dielectric Properties of Agricultural Products and Food Materials  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

178

Influence of filler loading on dielectric properties of epoxy-ZnO nanocomposites  

Microsoft Academic Search

Experimental investigations into the dielectric properties of epoxy-ZnO nanocomposites at different filler loadings reveal few unique behaviors (at certain filler loadings) and also advantageous characteristics in contrast to the properties obtained for the corresponding microcomposites. Results demonstrate that in nanocomposites, it is possible to achieve lower values of permittivity and tandelta with respect to unfilled epoxy over a wide frequency

Santanu Singha; M. Joy Thomas

2009-01-01

179

Properties of the growth probability for the dielectric breakdown model in cylinder geometry  

Microsoft Academic Search

We study the properties of the growth probabilities for diffusion limited aggregation and the dielectric breakdown model in the steady state regime of the cylinder geometry. The results show a rather unambiguous picture with the following properties: The projection of the growth probability along the growth direction is exponential, contrary to the Gaussian behavior of the radial case. One can

M. Marsili; L. Pietronero

1991-01-01

180

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

EPA Science Inventory

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

181

Compared optical properties of noble and transition metal-dielectric granular films  

E-print Network

249 Compared optical properties of noble and transition metal-dielectric granular films S. Berthier properties according to the nature of the metallic inclusion : noble or transition. A comparison between Au these proper- ties depend on the nature ofthe metallic inclusion in the compound : noble metal or transition

Paris-Sud XI, Université de

182

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

183

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

184

Effect of clay and salinity on the dielectric properties of rock  

NASA Astrophysics Data System (ADS)

The effect of clay and saline solutions on the complex dielectric properties of geologic formations is not theoretically understood, nor are there satisfactory empirical relations for such complex media. In this work, measurements of the dielectric constant are reported for consolidated sandstone cores containing a fixed percentage of clay with varying salinity and water content. In order to study the effect of varying clay content, the dielectric constants of different sand-clay mixtures were also determined. The measurements were carried out at higher frequencies than previously reported, i.e., in the VHF and microwave range (20 MHz to 1 GHz). The effect of clay increases the real part and decreases the imaginary part of the complex dielectric constant compared to the "clean" sandstone samples. The pronounced frequency dependence on clay, water content, and salinity disappears at our higher frequencies.

Rankin, D.; Singh, R. P.

1985-09-01

185

Microstructure and dielectric properties of pyrochlore Bi2Ti2O7 thin films  

NASA Astrophysics Data System (ADS)

Bi2Ti2O7 thin films were grown by radio-frequency magnetron sputtering on bare and Pt-coated sapphire substrates at low substrate temperatures (˜200 °C). Postdeposition anneals were carried out at different temperatures to crystallize the films. Nearly phase-pure Bi2Ti2O7 thin films with the cubic pyrochlore structure were obtained at annealing temperatures up to 800 °C. Impurity phases, in particular Bi4Ti3O12, formed at higher temperatures. At 1 MHz, the dielectric constants were about 140-150 with a very small tunability and the dielectric loss was about 4×10-3. The dielectric loss increased with frequency. The dielectric properties of Bi2Ti2O7 films are compared to those of pyrochlore bismuth zinc niobate films.

Cagnon, Joël; Boesch, Damien S.; Finstrom, Nicholas H.; Nergiz, Saide Z.; Keane, Sean P.; Stemmer, Susanne

2007-08-01

186

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

PubMed

Molecules in crystals often suffer from severe limitations on their dynamic processes, especially on those involving large structural changes. Crystalline compounds, therefore, usually fail to realize their potential as dielectric materials even when they have large dipole moments. To enable polar molecules to undergo dynamic processes and to provide their crystals with dielectric properties, weakly bound charge-transfer (CT) complex crystals have been exploited as a molecular architecture where the constituent polar molecules have some freedom of dynamic processes, which contribute to the dielectric properties of the crystals. Several CT crystals of polar tetrabromophthalic anhydride (TBPA) molecules were prepared using TBPA as an electron acceptor and aromatic hydrocarbons, such as coronene and perylene, as electron donors. The crystal structures and dielectric properties of the CT crystals as well as the single-component crystal of TBPA were investigated at various temperatures. Molecular reorientation of TBPA molecules did not occur in the single-component crystal, and the crystal did not show a dielectric response due to orientational polarization. We have found that the CT crystal formation provides a simple and versatile method to develop molecular dielectrics, revealing that the molecular dynamics of the TBPA molecules and the dielectric property of their crystals were greatly changed in CT crystals. The TBPA molecules underwent rapid in-plane reorientations in their CT crystals, which exhibited marked dielectric responses arising from the molecular motion. An order-disorder phase transition was observed for one of the CT crystals, which resulted in an abrupt change in the dielectric constant at the transition temperature. PMID:25781627

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

2015-04-01

187

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

188

Dielectric property and conduction mechanism of ultrathin zirconium oxide films  

NASA Astrophysics Data System (ADS)

Stoichiometric, uniform, amorphous ZrO2 films with an equivalent oxide thickness of ˜1.5 nm and a dielectric constant of ˜18 were deposited by an atomic layer controlled deposition process on silicon for potential applications in metal-oxide-semiconductor (MOS) devices. The conduction mechanism is identified as Schottky emission at low electric fields and as Poole-Frenkel emission at high electric fields. The MOS devices showed low leakage current, small hysteresis (<50 mV), and low interface state density (˜2×1011cm-2 eV-1). Microdiffraction and high-resolution transmission electron microscopy showed a localized monoclinic phase of ?-ZrO2 and an amorphous interfacial ZrSixOy layer which has a corresponding dielectric constant of 11.

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

2001-11-01

189

Tailoring the Microwave Dielectric Properties of Alkaline Earth Gehlenite Type Ceramic  

NASA Astrophysics Data System (ADS)

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

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

190

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

PubMed

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

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

2014-07-17

191

Dielectric properties of native and decoated spores of Bacillus megaterium.  

PubMed Central

A general model for use in interpreting dielectric data obtained with bacterial endospores is developed and applied to past results for Bacillus cereus spores and new results for Bacillus megaterium spores. The latter were also subjected to a decoating treatment to yield dormant cells with damaged outer membranes that could be germinated with lysozyme. For both spore types, core ions appeared to be completely immobilized, and decoating of B. megaterium spores did not affect this extreme state of electrostasis in the core. The cortex of B. megaterium appeared to contain a high level of mobile ions, in the cortex of B. cereus. The outer membrane-coat complex of B. megaterium acted dielectrically as an insulating layer around the cortex, so that native dormant spores showed a Maxwell-Wagner dispersion over the frequency range from about 1 to 20 MHz. The decoating treatment resulted in a shift in the dispersion to frequencies below the range of observation. Increases in cell conductivity in response to increases in environmental ionic strength indicated that the coats. of B. megaterium could be penetrated by environmental ions and that they had an inherent fixed charge concentration of about 10 to 20 milliequivalents per liter. In contrast, the dispersion for B. cereus spores was very sensitive to changes in environmental ion concentration, and it appeared that some 40% of the spore volume could be penetrated by environmental ions and that these ions traversed a dielectrically effective layer, either the exosporium or the outer membrane. It appears that dormancy is associated with extreme electrostasis of core ions but not necessarily of ions in enveloping structures and that the coat-outer membrane complex is dielectrically effective but not required for maintenance of extreme electrostasis in the core. PMID:118161

Carstensen, E L; Marquis, R E; Child, S Z; Bender, G R

1979-01-01

192

Dielectric properties of highly concentrated water-in-oil microemulsions  

Microsoft Academic Search

The high-frequency dielectric relaxations of highly concentrated water-in-oil microemulsions have been investigated in the\\u000a frequency range from 1 MHz to 1 GHz, at different temperatures, in the interval from 5 ?C to 60 ?C. In the region of the phase\\u000a diagram studied, the system undergoes a progressive change of its structure, passing from water droplets dispersed in an oil\\u000a matrix

F. Bordi; C. Cametti; P. Codastefano; F. Sciortino; P. Tartaglia; J. Rouch

193

Dielectric properties of wood from 2 to 3 GHz.  

PubMed

Many applications of microwave energy to wooden materials have been developed in the last few decades, both for treatment and for diagnostic purposes. All these applications require a reliable estimation of the permittivity of the wood species of interest, which is the physical parameter of crucial importance in the absorption of electromagnetic energy. This paper presents results obtained in the dielectric characterization of five wood species in the frequency range from 2 to 3 GHz, including the ISM frequency of 2.45 GHz. Permittivity was measured by an open-ended coaxial-line probe of new design on wood samples conditioned at several moisture levels. The influence of the natural variability of wood characteristics on the measured permittivity was also investigated by a suitable experimental setup consisting of a poplar table including both sapwood and heartwood regions. Finally, a theoretical discussion on the meaning of a scalar measurement on anisotropic dielectrics is conducted in terms of an isotropic-equivalent permittivity, which is related to the permittivity tensor of the dielectric material. PMID:11098438

Olmi, R; Bini, M; Ignesti, A; Riminesi, C

2000-01-01

194

Effect of volcanic-ash on the pyroelectric and dielectric properties of Portland cement  

NASA Astrophysics Data System (ADS)

The property of pyroelectric material finds application in infrared detection. A study was conducted to investigate the effect of inclusion of volcanic ash into cement and bonded with polyvinyl alcohol (PVA) giving cement:volcanic-ash systems. The ash used in this experiment is from the eruption of the Soufrière Hill volcano in the island of Montserrat, West Indies. Preliminary results indicate that cement: volcanic ash systems shows pyroelectric effect. Further investigations were carried to determine the effect of temperature and frequency on the variation of dielectric properties. The results show that both dielectric constant and ac conductivity of cement decrease with inclusion of volcanic-ash.

Bhat, Kamala N.; Batra, A. K.; Bhattacharjee, Sudip; Taylor, Robert W.

2010-08-01

195

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

196

Note: Extraction of hydrogen bond thermodynamic properties of water from dielectric constant and relaxation time data  

NASA Astrophysics Data System (ADS)

We recently proposed a theory [Suresh, J. Chem. Phys. 113, 9727 (2000)], 10.1063/1.1320822, based on the principles of statistical mechanics, for describing the temperature variation of static dielectric constant of water and the average number of H-bonds per molecule in the liquid phase. The theoretical model contains three parameters; two of them pertain to the energy and entropy changes accompanying bond-formation, and the third (??) represents the dielectric constant at a frequency that is sufficiently low for atomic and electronic polarization, but sufficiently high for intermolecular relaxation processes involving the movement of permanent dipole moments to be inoperative. In the absence of a consensus in the literature for the value of ?? to be used in dielectric constant calculations, it was arbitrarily set to a commonly accepted value of 1.77 (corresponding to refractive index of 1.33). Values for H-bond parameters were then estimated by best fitting model calculations to experimental data for dielectric constant across temperatures ranging from melting to the critical point of water. It is the purpose of the present Note to eliminate the ambiguity on the choice of ?? and propose refined values for the H-bond parameters.

Rastogi, Abhishek; Yadav, Siddharth; Suresh, S. J.

2011-08-01

197

Fabrication and properties of a glass-lens, static-concentrator mini-module  

Microsoft Academic Search

A glass-lens, static-concentrator mini-module was fabricated by attaching a co-molded glass-lens on a conventional superstrate flat-plate module. Its properties were investigated under simulated and real sunlight conditions. The effect of rear reflection on optical concentration was investigated for the static concentrator mini-modules with white, black and transparent rear Tedlar films. Under a solar simulator condition, optical concentration ratios of 2.05,

K. Yoshioka; T. Nikaido; T. Saitoh; M. Kanai; I. Hide

1997-01-01

198

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

199

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

200

Study of Temperature Dependence of Dielectric Properties of Bound Water in Grain and Seed at Microwave Frequencies  

Technology Transfer Automated Retrieval System (TEKTRAN)

The influence of temperature on dielectric properties of bound water in grain and seed was investigated through measurement of their dielectric properties at microwave frequencies over a wide temperature range between –80 oC and +24 oC. Free–space measurements were performed between 2 and 18 GHz on...

201

3-D Static Elastic Constants and Strength Properties of a Glass/Epoxy Unidirectional Laminate  

E-print Network

3-D Static Elastic Constants and Strength Properties of a Glass/Epoxy Unidirectional Laminate elastic and strength properties for thick unidirectional glass fabric/epoxy laminate and for neat resin Daniel D. Samborsky, John F. Mandell and Pancasatya Agastra Department of Chemical and Biological

202

Synthesis, electrical and dielectric properties of FeVO 4 nanoparticles  

NASA Astrophysics Data System (ADS)

The electrical and dielectric properties of FeVO 4 nanoparticles were studied at different temperatures from ambient to 200 °C. The samples were prepared by simple co-precipitation method using ferric nitrate and ammonium metavanadate as the starting precursors. The powder X-ray diffraction pattern inferred the single phase formation and triclinic structure of FeVO 4. The morphology of the particles was elucidated from SEM studies. Detailed studies on the electrical and dielectric properties of the compound were carried out by using solid state impedance spectroscopy. A maximum dc conductivity of 4.65×10 -5 S cm -1 was observed at the measuring temperature of 200 °C. The calculated activation energy from dc conductivity was found to be 0.28 eV. It was evident that the electrical transport process in the system was due to the hopping mechanism. The detailed dielectric studies were also carried out.

Nithya, V. D.; Kalai Selvan, R.

2011-01-01

203

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

204

Immiscible fluid flow in porous media: dielectric properties  

NASA Astrophysics Data System (ADS)

The movement and retention of immiscible fluids in porous media was determined using a microwave dielectric measuring technique. The technique was used to monitor the composite dielectric constant of columns containing model soil materials to observe the effect of displacement of various saturating fluids by water and determine the retained immiscible components. Various combinations of displacing fluids, both miscible and immiscible, were studied, yielding time-dependent flow characteristics as well as the total retention factor. The flow circumstances were similar to what would be encountered in an accidental spill of chlorocarbons or crude oil. The retention of chlorocarbons and crude oil was determined for model soils consisting of sand or glass spheres. The storage capacity of the sand for immiscible fluids was dependent on the fluid initially saturating the porous medium. For chlorocarbons, it was increased in water-wet compared to dry sands while the inverse was true for crude oil. The retention of crude oil in the sand was dependent on the water flow velocity and was much larger than that for chlorocarbons. The crude oil could be displaced by solvents such as cyclohexane in the sand but the net volume occupied by the two immiscible fluids after water flushing did not change appreciably, i.e. the crude oil component was replaced by the solvent. Application of a miscible fluid-water mixture or surfactants improved the ability of water to displace the immiscible fluid from the sand column.

Alharthi, A.; Lange, J.; Whitaker, E.

1986-02-01

205

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

206

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

207

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

208

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

NASA Astrophysics Data System (ADS)

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

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

1994-09-01

209

Formation and dielectric properties of a novel polymer-metal nanocomposite [for embedded capacitor application  

Microsoft Academic Search

Composites of metal particles within a dielectric medium have attracted a lot of attention because of the interesting properties exhibited by them. The current object of interest is the behavior of such polymer nanocomposites near the percolation loading levels of the metal nanoparticles. This material is particularly suited for a new technology called the Integral Passive technology. Discrete capacitors are

Yi Li; Suresh Pothukuchi; C. P. Wong

2004-01-01

210

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

Microsoft Academic Search

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

Jianqing Wang; Osamu Fujiwara; Soichi Watanabe

2006-01-01

211

Phonons and lattice dielectric properties of zirconia Xinyuan Zhao and David Vanderbilt  

E-print Network

properties of the three low- pressure cubic, tetragonal, and especially monoclinic phases of ZrO2 the energetics of the ZrO2 phases, and the calculated zone-center phonon frequencies yield good agreement partially motivated by the potential for ZrO2 to replace SiO2 as the gate-dielectric material in modern

Vanderbilt, David

212

Structural, electronic, and dielectric properties of amorphous ZrO2 from ab initio molecular dynamics  

E-print Network

Structural, electronic, and dielectric properties of amorphous ZrO2 from ab initio molecular October 2004; published 9 February 2005 Realistic models of amorphous ZrO2 are generated in a "melt semiconductor technology, and may also have implications for HfO2 and for silicates of ZrO2 and HfO2. DOI: 10

Vanderbilt, David

213

Luminescence, structural and dielectric properties of Sm3+ impurities in strontium lithium bismuth borate glasses  

NASA Astrophysics Data System (ADS)

In the present work, different concentrations of Sm3+doped strontium lithium bismuth borate glasses (SLBiB) have been prepared by melt quench technique and investigated their optical, structural and dielectric properties. The amorphous nature of the prepared glass samples was confirmed by X-ray diffraction and SEM analysis. The spectroscopic properties of these glasses were investigated by recording optical absorption, photoluminescence and decay curve analysis. Judd-Ofelt (J-O) theory has been applied for the f ? f transitions of Sm3+ ions to evaluate J-O intensity parameters, ?? (? = 2, 4 and 6). Using the J-O intensity parameters, radiative properties such as transition probabilities (AR), calculated branching ratios (?) and radiative lifetimes (?) are estimated. From the emission spectra, effective bandwidths (??eff) and stimulated emission cross-sections (?p) have been obtained for observed emission levels. From the emission spectra, a strong reddish-orange emission corresponding to the transition, 4G5/2 ? 6H7/2 was observed. The nature of decay curves of 4G5/2 level for different Sm3+concentrations in SLBiB glass has been analyzed. FTIR spectra were recorded to analyze the functional groups present in the glass matrix. From the dielectric properties, variation of dielectric constant, dielectric loss and ac conductivity of Sm3+ doped different glass samples with the variation of frequency was studied.

Rajesh, D.; Balakrishna, A.; Ratnakaram, Y. C.

2012-12-01

214

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...

215

Effect of bismuth oxide dispersivity on the dielectric properties of zinc oxide ceramics  

NASA Astrophysics Data System (ADS)

The dielectrics properties and microstructure of fractured surfaces of ZnO electroceramics samples with different Bi2O3 dispersivity was studied. It is shown that the change of dispersion leads to an insignificant change in the grain structure, but has no effect on character of the dispersion of the permittivity ZnO ceramic.

Malyshkina, O. V.; Ivanova, A. I.; Luzin, R.; Makarenkov, I.; Pugachev, S. I.; Rytov, E.

2015-03-01

216

Coaxial-probe contact-force monitoring for dielectric properties measurements  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

217

Transmission properties and band structure of a segmented dielectric waveguide for the terahertz range  

E-print Network

Transmission properties and band structure of a segmented dielectric waveguide for the terahertz for the terahertz range. The dis- persion curves are obtained using two different methods. The first approach is based on a close relationship between the band structure and narrow resonances in transmission spectra

Ku?el, Petr

218

Far-Infrared Dielectric Properties of Polar Liquids Probed by Femtosecond Terahertz Pulse Spectroscopy  

E-print Network

. These spectra have been measured with femtosecond terahertz pulse transmission spectroscopy. These liquidsFar-Infrared Dielectric Properties of Polar Liquids Probed by Femtosecond Terahertz Pulse by femtosecond terahertz (fs THz) pulses.1 This paper reports the absorption and dispersion spectra of several

219

Optical properties of gold spheroidal particles and nanoshells: Effect of the external dielectric medium  

Microsoft Academic Search

Dependence of optical properties of gold solid nanospheroids and spheroidal nanoshells on the dielectric environment has been studied in comparison with standard spherical models, i.e. with solid spheres and spherical nanoshells, respectively. The extinction and light scattering spectra were calculated using Mie theory, T-matrix, and the separation of variables methods. The sensitivity of plasmon resonance (PR) tuning to variations of

Lyubov A. Trachuk; Stanislav A. Vrublevsky; Boris N. Khlebtsov; Andrei G. Melnikov; Nikolai G. Khlebtsov

2005-01-01

220

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

221

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

E-print Network

Phase transition and dielectric properties of nanograin BaTiO3 ceramic under high pressure Jinlong on the progressive decrease of TC in nano-BTO ceramic under high pressure. Samara,9 Merz,10 and others11­13 have hydrostatic pressure up to 5 GPa. We found that the paraelectric-ferroelectric phase transition temperature TC

Cao, Wenwu

222

Roles of wave impedance and refractive index in photonic crystals with magnetic and dielectric properties  

Microsoft Academic Search

We investigated the roles of wave impedance and refractive index in photonic crystals by means of analytical expressions for edges frequencies of a photonic bandgap (PBG) in a one-dimensional photonic crystal with magnetic and dielectric properties. The analytical expressions were derived when the optical thicknesses of layers are the same. The wave impedance governs the formation of PBG's and the

Chul-Sik Kee; Jae-Eun Kim; Hae Yong Park; H. Lim

1999-01-01

223

Flame retardant and dielectric properties of glass fibre reinforced nylon-66 filled with red phosphorous  

Microsoft Academic Search

Incorporation of red phosphorous into glass fibre reinforced nylon-66 composites not only confers good fire retardancy but also retains good dielectric properties, that makes them suitable for application as electrical insulation components. The limiting oxygen index (LOI) and Underwriter's Laboratory Bulletin 94 (UL-94) flame retardancy rating of the red phosphorous filled nylon-66 composites increase consistently with their red phosphorous contents.

W. S Jou; K. N Chen; D. Y Chao; C. Y Lin; J. T Yeh

2001-01-01

224

TEMPERATURE AND FREQUENCY DEPENDENCE OF THE DIELECTRIC PROPERTIES OF FRESH FRUITS AND VEGETABLES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dielectric properties of tissue from fresh apple, avocado, banana, cantaloupe, carrot, cucumber, grape, orange, and potato were measured with an open-ended coaxial-line probe at frequencies from 10 MHz to 1.8 GHz and at temperatures from 5 to 65 degrees Celsius. Sample results are presented graphi...

225

Optical properties of nanowire dimers with a spatially nonlocal dielectric function  

Microsoft Academic Search

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

Jeffrey M. McMahon; Stephen K. Gray; George C. Schatz

2010-01-01

226

Guidance and leakage properties of a class of open dielectric waveguides. II - New physical effects  

Microsoft Academic Search

The properties of open dielectric waveguide structures which are of importance to the areas of integrated optics and millimeter-wave integrated circuits are discussed with allowance for the coupling between TE and TM modes. The analysis reveals new physical effects caused by TE-TM mode coupling: leakage and sharp resonance or cancellation. Various numerical results are presented for typical waveguide structures which

A. A. Oliner; S.-T. Peng; Ting-Ih Hsu; A. Sanchez

1981-01-01

227

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

228

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 titanate Ba1-xSrxTiO3 BST have emerged as leading candidates for such applications due to their highly

Alpay, S. Pamir

229

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

230

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, delay lines, filters, and phase shifters for steerable antennas.1­3 Barium strontium titanate BaxSr1-x Received 8 April 2008; accepted 13 April 2008; published online 8 May 2008 Compositionally graded barium

Alpay, S. Pamir

231

Effect of UV Curable Polymer on The Dielectric & Electro-Optic Properties of Ferroelectric Liquid Crystal  

Microsoft Academic Search

Results reported on the dielectric properties, spontaneous polarization (Ps) and switching time of a FLC material and a mixture of the FLC material after having doped with a small quantity of optical adhesive polymer. The mixture has been prepared by dissolving NOA65 prepolymer and the FLC compound in chloroform. A homogenous mixture of FLC and polymer formed after chloroform is

Sudarshan Kundu; Taponita Ray; Subir Kumar Roy; Wolfgang Haase; Roman Dabrowski

2003-01-01

232

Properties and applications of periodic dielectric particles as tunable-index materials  

Microsoft Academic Search

In this paper, the properties of cylindrical high-permittivity dielectric particles are studied. The refractive index is calculated with a parameter retrieval method and a Fourier transform method. It is shown that the periodic particles have low losses, while being non-resonant and broadband. Furthermore, the refractive index can be adjustable according to the dimensions of the particles. Application examples are also

Di Bao; Christos Argyropoulos; Efthymios Kallos; Yang Hao

2009-01-01

233

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

234

Dielectric and transport properties of a supercooled symmetrical molten salt.  

PubMed

The liquid-glass transition of the restricted primitive model for a symmetrical molten salt is studied using mode-coupling theory. The transition at high densities is predicted to obey the Lindemann criterion for melting, and the charge-density peak found in neutron-scattering experiments on ionic glass formers is qualitatively reproduced. Frequency-dependent dielectric functions, shear viscosities, and dynamical conductivities of the supercooled liquid are presented. Comparing the latter to the diffusion constant, we find that mode-coupling theory reproduces the Nernst-Einstein relation. The Stokes-Einstein radius is found to be approximately equal to the particle radius only near the high-density glass transition. PMID:11970121

Wilke, S D; Chen, H C; Bosse, J

1999-09-01

235

Dielectric properties and conductivity in CuO and MoO 3 doped borophosphate glasses  

Microsoft Academic Search

A novel set of glasses of the type (B2O3)0.10–(P2O5)0.40–(CuO)0.50?x–(MoO3)x, 0.05?x?0.50, have been investigated for dielectric properties in the frequency range 100Hz–100kHz and temperature range 300–575K. From the total conductivity derived from the dielectric spectrum the frequency exponent, s, and dc and ac components of the conductivity were determined. The temperature dependence of dc and ac conductivities at different frequencies was

B. Vijaya Kumar; T. Sankarappa; Santosh Kumar; M. Prashant Kumar; P. J. Sadashivaiah; R. Ramakrishna Reddy

2009-01-01

236

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

SciTech Connect

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

Nenert, G.; Palstra, T. T. M. [Solid State Chemistry Laboratory, Zernike Institute for Advanced Materials, University of Groningen, Nijenborg 4, 9747 AG Groningen (Netherlands); Bezmaternykh, L. N. [L. V. Kirensky Institute of Physics, Siberian Branch of RAS, Krasnoyarsk 660036 (Russian Federation); Vasiliev, A. N. [Low Temperature Physics Department, Moscow State University, Moscow 119991 (Russian Federation)

2007-10-01

237

Curie temperatures and dielectric properties of doped and undoped KTiOPO4 and isomorphs  

Microsoft Academic Search

The Curie temperatures and dielectric properties of KTiOPO4 (KTP), RbTiOPO4, KTiOAsO4, RbTiOAsO4 , CsTiOAsO4, Ba:KTP, and Ga:KTP were measured with small-signal relative dielectric permittivity (?) analysis, piezoelectric resonance analysis, and optical second harmonic generation. All the isomorphs and the doped KTP exhibit lower Curie temperatures than KTP, ranging from 637°C for CsTiOAsO4 to 955°C for hydrothermally (HT) grown KTP. The

David K. T. Chu; Hui Hsiung; Lap Kin Cheng; John D. Bierlein

1993-01-01

238

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

239

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

240

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

241

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

242

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

243

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

244

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

245

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

246

Changes in the dielectric properties of a plant stem produced by the application of voltage steps  

NASA Astrophysics Data System (ADS)

Time Domain Dielectric Spectroscopy (TDDS) provides a useful method for monitoring the physiological state of a biological system which may be changing with time. A voltage step is applied to a sample and the Fourier Transform of the resulting current yields the variations of the conductance, capacitance and dielectric loss of the sample with frequency (dielectric spectrum). An important question is whether the application of the voltage step itself can produce changes which obscure those of interest. Long term monitoring of the dielectric properties of plant stems requires the use of needle electrodes with relatively large current densities and field strengths at the electrode-stem interface. Steady currents on the order of those used in TDDS have been observed to modify the distribution of plant growth hormones, to produce wounding at electrode sites, and to cause stem collapse. This paper presents the preliminary results of an investigation into the effects of the application of voltage steps on the observed dielectric spectrum of the stem of the plant Coleus.

Hart, F. X.

1983-03-01

247

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

PubMed

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

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

2014-05-01

248

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

NASA Astrophysics Data System (ADS)

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

Sanchez, Luis

249

Static and dynamic Tokunaga stream networks: Statistical properties  

NASA Astrophysics Data System (ADS)

In this study we apply complex-network methods to advance conceptual models of environmental transport on river networks. It is well known that the topology of stream networks is closely approximated by so-called Tokunaga Self-Similar Trees (SSTs). Tokunaga SSTs represent a two-parameter class of trees specified by the parameter pair (a,c); the Shreve river network model is an example of a Tokunaga SST with (a,c)=(1,2). It has been shown that Tokunaga SSTs can describe most real river networks, by using different parameter values, distinct from those of Shreve’s model. Recent studies provide evidence that Tokunaga self-similarity is a characteristic property of general aggregation processes, with a broad range of applications not limited to hydrological settings. This motivates us to analyze here several essential properties of Tokunaga stream networks with a broadly varying range of parameter values. In particular, we relate the statistical description of the width function, including its self-similar properties, to the parameters (a,c). In addition, we further analyze the dynamic tree description of a stream network introduced by Zaliapin et al. (2010) and formulate a related, yet more physically relevant, concept of a dynamic network. The latter concept describes the mixing of fluxes initiated at different sources in a continuous downstream transport. Finally, Boolean delay equations (BDEs) are used to model the downstream transport along real and synthetic river networks.

Zaliapin, I.; Foufoula-Georgiou, E.; Ghil, M.

2010-12-01

250

Dielectric properties of polyaniline-montmorillonite clay hybrids.  

PubMed

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

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

2013-03-01

251

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

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

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

NASA Astrophysics Data System (ADS)

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

Ma, Fengde D.; Wang, Yu U.

2015-03-01

254

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...

255

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

256

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-structured vanadium (V), a bcc metal with a moderately high melting temperature (1910 °C) by high-energy ball milling. Published by Elsevier Ltd. All rights reserved. Keywords: Nano-structured metals; bcc structure; Vanadium

Wei, Qiuming

257

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

PubMed

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

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

2013-09-12

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 isotactic polypropylene and montmorillonite nanocomposites  

Microsoft Academic Search

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

E. Izci; N. Bowler

2010-01-01

260

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

261

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

262

Electrical conductivity and dielectric properties of PMMA/graphite nanoplatelet ensembles  

NASA Astrophysics Data System (ADS)

Poly(methyl methacrylate) (PMMA)/graphite nanoplatelet (GNP) ensembles were prepared by in situ polymerization of MMA in the presence of GNPs with the aid of sonication and heating. Electrical conductivity and dielectric properties of the ensembles were measured using the four-point probe resistivity measurement method and a Network Analyzer. The results showed that the electrical behavior of PMMA/GNP ensembles can be described well by percolation theory. The electrical conductivity of the ensemble was found to exhibit an insulator-conductor transition at a very low percolation threshold for GNPs. The percolation threshold of PMMA/GNP at room temperature was only about 1 wt% filler content, much lower than that of the ensembles filled with conventional graphite particles. Results showed that the difference in filler geometry (high aspect ratio and surface area) has a very significant effect on forming a conducting network in the PMMA matrix and improves both electrical and dielectric properties.

Xu, Ke; Erricolo, Danilo; Dutta, Mitra; Stroscio, Michael A.

2012-05-01

263

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

NASA Astrophysics Data System (ADS)

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

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

264

Modelling of the dielectric properties of trabecular bone samples at microwave frequency  

E-print Network

In this paper the dielectric properties of human trabecular bone are evaluated under physiological condition in the microwave range. Assuming a two components medium, simulation and experimental data are presented and discussed. A special experimental setup is developed in order to deal with inhomogeneous samples. Simulation data are obtained using finite difference time domain from a realistic sample. The bone mineral density of the samples are also measured. The simulation and experimental results of the present study suggest that there is a negative relation between bone volume fraction (BV/TV) and permittivity (conductivity): the higher the BV/TV the lower the permittivity (conductivity). This is in agreement with the recently published in vivo data. Keywords: Bone dielectric properties, Microwave tomography, Finite difference time domain.

Irastorza, Ramiro M; Carlevaro, Carlos M; Vericat, Fernando

2013-01-01

265

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

NASA Astrophysics Data System (ADS)

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

Kumar, Amit; Yadav, K. L.

2011-11-01

266

Synthesis and dielectric properties of zinc oxide nanoparticles using a biotemplate  

NASA Astrophysics Data System (ADS)

Zinc Oxide nanoparticles are synthesized using DNA as capping agent. Zinc oxide nanoparticles are synthesized using DNA as a capping agent. Structural and morphological characterizations are done using SEM, FTIR and XRD. The particle size and lattice parameters are calculated from the diffraction data. The optical properties are studied using UV-Vis absorption spectroscopy and bandgap variation with temperature is determined. The dielectric property of nanoparticles is studied by varying temperature and frequency. The dielectric constant and dispersion parameters are found out. Method of Cole-Cole analysis is used to study the high temperature dispersion of relaxation time. The variation of both AC and DC conductivity are studied and activation energy calculated.

P, Sharmila P.; Tharayil, Nisha J.

2014-10-01

267

Synthesis and dielectric properties of zinc oxide nanoparticles using a biotemplate  

SciTech Connect

Zinc Oxide nanoparticles are synthesized using DNA as capping agent. Zinc oxide nanoparticles are synthesized using DNA as a capping agent. Structural and morphological characterizations are done using SEM, FTIR and XRD. The particle size and lattice parameters are calculated from the diffraction data. The optical properties are studied using UV-Vis absorption spectroscopy and bandgap variation with temperature is determined. The dielectric property of nanoparticles is studied by varying temperature and frequency. The dielectric constant and dispersion parameters are found out. Method of Cole-Cole analysis is used to study the high temperature dispersion of relaxation time. The variation of both AC and DC conductivity are studied and activation energy calculated.

P, Sharmila P, E-mail: sharmilavishram@gmail.com [Sree Narayana College, Kollam, Kerala, India and T.K Madhva Memorial College, Nangiarkulungara, Alapuzha, Kerala (India); Tharayil, Nisha J., E-mail: nishajohntharayil@gmail.com [Sree Narayana College for Women Kollam, Kerala (India)

2014-10-15

268

Dielectric and piezoelectric properties of S001ceramics  

E-print Network

TiO3 ceramics Edward M. Sabolsky,a) Susan Trolier-McKinstry, and Gary L. Messing Materials Research Institute and Department of Materials Science and Engineering, The Pennsylvania State University, University. As previously stated, the enhanced electromechanical properties for the domain engineered materials have been

Messing, Gary L.

269

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...

270

Dielectric Properties of Peanut-hull Pellets at Microwave Frequencies  

Technology Transfer Automated Retrieval System (TEKTRAN)

Peanut-hull pellets are obtained from a waste product, peanut-hulls, which after pelleting can have several uses, namely as a renewable fuel. Rapid and nondestructive characterization of peanut-hull pellets is important for industrial utilization of this resource. Properties such as water content an...

271

Electrical properties of high-quality ultrathin nitride\\/oxide stack dielectrics  

Microsoft Academic Search

The electrical properties of ultrathin nitride\\/oxide (N\\/O) stack dielectrics (2-4 nm), produced by in-situ jet vapor deposition (JVD), have been studied in some detail. Both theoretical calculation and experimental data show that the leakage current in the N\\/O stack is substantially lower than that in the single oxide layer of the same equivalent oxide thickness (EOT). When compared to the

Ying Shi; Xiewen Wang; Tso-Ping Ma

1999-01-01

272

Cryogenic Dielectric and Mechanical Properties of Nanowire-A1203 Filled PBT\\/GF Composites  

Microsoft Academic Search

The cryogenic dielectric and mechanical properties of nanowire-Al 2O3 filled PBT\\/GF (glass fiber) composites are investigated by combing macro-performances testing and microstructures analysis. Compared with PBT\\/GF composites, the PBT\\/GF\\/Al2O 3 ternary systems present improved tensile strength as well as impact strength. The fracture surface shows a typical toughened characteristic under SEM observation, which may be explained by the \\

Demei Yu; Yunchuan Xie; Weitao Wan; Xiusheng Guo; Yingxin Xi; Zhantong Mao; Longbiao Huang

2006-01-01

273

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

274

Dielectric properties of animal tissues in vivo at radio and microwave frequencies: comparison between species  

Microsoft Academic Search

An improved and modified technique with an open-ended coaxial-line sensor was used for measurement of the dielectric properties of animal tissues in vivo. The permittivity of skeletal muscle, brain cortex, spleen and liver of live cats and rats was measured at frequencies between 0.1 and 10 GHz. The results were compared with various published data on in vivo permittivity of

M. A. Stuchly; A. Kraszewski; S. S. Stuchly; A. M. Smith

1982-01-01

275

Electrical conductivity and dielectric properties of SiO 2 nanoparticles dispersed in conducting polymer matrix  

Microsoft Academic Search

Electrical and dielectric properties of conducting polypyrrole–wide band gap silica (PPY–SiO2) nanocomposites have been investigated as a function of temperature and frequency for different concentrations of polypyrrole.\\u000a The average grain size of the nanocomposites is in the range of 40–80 nm. Impedance spectra reveal two distorted semicircles\\u000a corresponding to grain and grain boundary effects. The magnitude of conductivity and its temperature

Kousik Dutta; S. K. De

2007-01-01

276

Microstructure and dielectric properties of PMN–PT ceramics prepared by the molten salts method  

Microsoft Academic Search

The sintering characteristic and dielectric properties of 0.67PMN–0.33PT ceramics prepared by the molten salt synthesis (MSS) method were investigated. PMN–PT particles synthesized by MSS with smaller grain size and good dispersion could lower the sintering temperature of ceramics; PMN–PT ceramics with relative density above 96% could be obtained in the range 1150–1180°C. The molten salts species could significantly affect the

Shixi Zhao; Qiang Li; Yuchuan Feng; Cewen Nan

2009-01-01

277

Influence of core-shell structured grain on dielectric properties of cerium-modified barium titanate  

Microsoft Academic Search

The dielectric properties and chemical inhomogenity of BaTiO3 ceramics sintered with additions of CeO2:1.5TiO2 were investigated using TEM XRD and EDS. Grains had three regions: grain shell severely doped with cerium, grain core BaTiO3 of greater purity, and a concentration gradient region where Curie temperatures were distributed. With decreasing temperatures, the volume fraction of ferroelectric domains in the concentration gradient

Yung Park; Se Ahn Song

1995-01-01

278

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

NASA Astrophysics Data System (ADS)

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

Suherman, Phe Man; Smith, Geoff

2003-02-01

279

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

280

Plasmonic band structures and optical properties of subwavelength metal/dielectric/metal Bragg waveguides.  

PubMed

In this paper, we applied the band structure theory to investigate the plasmonic band (PB) structures and optical properties of subwavelength metal/dielectric/metal Bragg waveguides in the near infrared range with either dielectric or geometric modulation. The Bloch wave vector, density of states, slowdown factor, propagation length and transmittance are calculated and analyzed. Both the modulations are in favor of manipulating surface-plasmon-polariton (SPP) waves. For the dielectric modulation, the PB structure is mainly formed by SPP modes and possesses a "regular pattern" in which the bands and gaps have a relatively even distribution. For the geometric modulation, due to the strong transverse scattering, the contributions of higher modes have to be considered and the gap widths have a significant increase compared to the dielectric modulation. A larger slowdown factor may emerge at the band edge; especially for the geometric modulation, the group velocity can be reduced to 1/100 of light, and negative group velocity is observed as well. While inside the bands, the slowdown factor is smaller and the bands are flat. The contribution of each eigenmode to the PB structure is analyzed. PMID:22453451

Li, Chao; Zhou, Yun-Song; Wang, Huai-Yu

2012-03-26

281

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

282

Dielectric properties of halloysite and halloysite-formamide intercalate  

NASA Astrophysics Data System (ADS)

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.; Rok, M.; Wolny, A.; Orzechowski, K.

2014-01-01

283

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

284

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

PubMed Central

Water is a major component of fluids in the 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

2013-01-01

285

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

PubMed

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

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

2012-08-13

286

Fabrication and Dielectric Properties of AlN Filled Epoxy Nano-composites  

NASA Astrophysics Data System (ADS)

Epoxy resins were materials with excellent mechanical, electrical properties and good chemical stability. Thus, they had been used in various fields, especially in electrical and electronic application. However, because they were brittle material, the fields of application were limited. Adding nano-Aluminum Nitride (AlN) into Epoxy resins could improve the toughness of the composites, the thermal behaviors of composites could also be improved, but the influence on dielectric properties was not very clear. In this research, epoxy resin based composites were fabricated. The relationships between the dielectric properties and the nano-AlN particle content were investigated. The results showed that, both relative permittivity (epsilonr) and dielectric loss tangent (tan?) decreased to be less than that of monolithic epoxy when nano-AlN particle content was no more than certain amount, the DC volume resistivity (?v) and low frequency resistivity decreased with increasing nano-AlN content (in certain range of content). AC breakdown strength (EB) did not have an obvious tendency with nano-AlN content.

Gao, Nai-kui; Yu, Xin; Jin, Hai-yun; He, Bo; Dong, Pu; Gao, Chao

2011-10-01

287

Dielectric properties of barium titanate ceramics doped by B{sub 2}O{sub 3} vapor  

SciTech Connect

The effects of B{sub 2}O{sub 3} vapor doping on the dielectric properties of barium titanate ceramics were studied. After the doping, the Curie point of BaTiO{sub 3} ceramics was increased from 128 deg. C to 130 deg. C and the maximum dielectric constant was considerably increased. X-ray diffraction showed that both the grain lattice parameters and the tetragonality were increased by the boron oxide vapor doping. It was proposed that boron interstitial was introduced into the grain lattice of barium titanate ceramics by B{sub 2}O{sub 3} vapor doping and the dielectric properties were thus obviously changed.

Qi, J.Q.; Chen, W.P.; Wang Yu; Chan, H.L.W.; Li, L.T. [Department of Applied Physics and Materials Research Center, Hong Kong Polytechnic University, Hong Kong (China); Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

2004-12-01

288

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

289

Dielectric properties of some keratinised tissues. Part 2: Human hair.  

PubMed

Some electrical properties of human hair have been investigated to determine whether a significant DC electrical conductance is present in keratinised tissues. The DC conductance was found to be substantial and highly dependent on the moisture level in the hair fibres. At high moisture levels, the conductance was found to be almost frequency independent below 1 kHz. Absorption and desorption profiles were also monitored, revealing different stages of sorption mechanisms in the fibres. Although absorption was found to be a slow process with 'time constants' in the range of hours, desorption was much faster, in the range of a few minutes. PMID:9246848

Martinsen, O G; Grimnes, S; Kongshaug, E S

1997-05-01

290

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

291

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

NASA Astrophysics Data System (ADS)

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

Khalili, L.; Serajzadeh, S.

2014-08-01

292

AGRICULTURAL APPLICATIONS OF DIELECTRIC MEASUREMENTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

A brief historical perspective on dielectric properties of agricultural products is presented, including their use for rapid measurement of moisture content in grain and in considering potential dielectric heating applications. General principles are discussed as they relate to dielectric propertie...

293

Dielectric Properties of Chromium Doped Ba5Ti2O7Cl4  

NASA Astrophysics Data System (ADS)

For the environment protection, lead free materials are needed such as KNbO3, BaTiO3, Ba5Ti2O7Cl4 etc. This paper includes the growth of Ba5Ti2O7Cl4 ferroelectric single crystal. The single crystals of Ba5Ti2O7Cl4 grown by fused method by taking a mixture of BaCO3, TiO2 and BaCl2 in the molar ratio of 1.5:1:1 with an impurity of chromium oxide (CrO3 = 0.005gm). It is orthorhombic at room temperature. The properties of the crystals are strongly affected by the technique of crystal growth as well as by adding external impurities i.e. dopants. In this paper we present the effect of doping on the dielectric studies of Ba5Ti2O7Cl4 single crystals. The dielectric constant and dc conductivity were determined simultaneously from room temperature to Curie temperature. The simultaneous measurement of capacitance (C) and resistance (R) were carried out to determine dielectric constant and conductivity respectively. The slight changes were occurred at room temperature from sample to sample. But at the Curie temperature of about 920 °C, the value of dielectric constant is in the range of 108 to 109. The conductivity at this temperature was found to be equal to 1.85(ohm-cm)-1. The dc conductivity changes with increasing temperature up to 920 °C and then rises to a high value at the Curie temperature of about 920 °C. The temperature at which the dielectric constant and conductivity is high called Curie temperature. The Curie temperature of this crystal is about 920 °C

Patil, Naresh M.; Shamkuwar, S. H.; Pradnyakar, Namrata

2011-11-01

294

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

295

Time domain dielectric spectroscopy of nanosecond pulsed electric field induced changes in dielectric properties of pig whole blood.  

PubMed

The dielectric spectra of fresh pig whole blood in the ?-dispersion range after exposure to 300-nanosecond pulsed electric fields (nsPEFs) with amplitude higher than the supra-electroporation threshold for erythrocytes were recorded by time domain reflectometry dielectric spectroscopy. The implications of the dielectric parameters on the dynamics of post-pulse pore development were discussed in light of the Cole-Cole relaxation model. The temporal development of the Cole-Cole parameters indicates that nsPEFs induced significant poration and swelling of erythrocytes within the first 5min. The results also show that the majority of erythrocytes could not fully recover from supra-electroporation up to 30min. The findings of this study suggest that time domain dielectric spectroscopy is a promising label-free and real-time physiological measuring technique for nsPEF-blood related biomedical applications, capable of following the conformational and morphological changes of cells. PMID:25246350

Zhuang, Jie; Kolb, Juergen F

2015-06-01

296

Tailoring the dipole properties in dielectric polymers to realize high energy density with high breakdown strength and low dielectric loss  

NASA Astrophysics Data System (ADS)

High energy density polymer materials are desirable for a broad range of modern power electronic systems. Here, we report the development of a new class of polymer dielectrics based on polyurea and polythiourea, which possess high thermal stability. By increasing the dipole density, the dielectric constant of meta-phenylene polyurea and methylene polythiourea can be increased to 5.7, compared with aromatic polyurea and aromatic polythiourea, which have a dielectric constant in the range of 4.1-4.3. The random dipoles with high dipolar moment and amorphous structure of these polyurea and polythiourea based polymers provide strong scattering to the charge carriers, resulting in low losses even at high electric fields. Consequently, this new class of polymers exhibit a linear dielectric response to the highest field measured (>700 MV/m) with a high breakdown strength, achieving high energy density (>13 J/cm3) with high efficiency (>90%).

Thakur, Yash; Lin, Minren; Wu, Shan; Cheng, Zhaoxi; Jeong, D.-Y.; Zhang, Q. M.

2015-03-01

297

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

298

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

299

Static and dynamic properties of PbTiO3 at finite temperatures  

NASA Astrophysics Data System (ADS)

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

Mani, Brajesh; Ponomareva, Inna

2013-03-01

300

Microwave dielectric properties of high- Q Mg(Sn x Ti1- x )O3 ceramics  

NASA Astrophysics Data System (ADS)

A series of Sn-doped Mg(Sn x Ti1- x )O3 ceramics were prepared using the conventional solid-state route. The influence of Sn4+ substitution for Ti4+ on the microstructure and microwave dielectric properties of Mg(Sn x Ti1- x )O3 ceramics was systematically investigated. Substitution with a suitable amount of Sn can eliminate the MgTi2O5 phase. The dielectric constants and temperature coefficients of resonant frequency changed slightly with the variation in Sn content in the specimens. However, the quality factors ( Q) dramatically improved and were sensitive to the concentration of Sn4+. The high Q value was attributed to the uniform grain, clean and narrow grain boundary, and elimination of the MgTi2O5 phase. Moreover, the composition-optimized Mg(Sn0.05Ti0.95)O3 ceramics sintered at 1390°C exhibited excellent microwave dielectric properties of ? r = 17.61, Q× f = 328,543 GHz, and ? f = -42 ppm/°C.

Gong, Zhijie; Wang, Zhefei; Wang, Lixi; Fu, Zhenxiao; Han, Wei; Zhang, Qitu

2013-05-01

301

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

302

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

303

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

304

Dielectric properties and conductivity in CuO and MoO 3 doped borophosphate glasses  

NASA Astrophysics Data System (ADS)

A novel set of glasses of the type (B 2O 3) 0.10-(P 2O 5) 0.40-(CuO) 0.50-x-(MoO 3) x, 0.05? x?0.50, have been investigated for dielectric properties in the frequency range 100 Hz-100 kHz and temperature range 300-575 K. From the total conductivity derived from the dielectric spectrum the frequency exponent, s, and dc and ac components of the conductivity were determined. The temperature dependence of dc and ac conductivities at different frequencies was analyzed using Mott's small polaron hopping model, and the high temperature activation energies have been estimated and discussed. The observed initial decrease in conductivity (ac and dc) and increase in activation energy with the addition of MoO 3 have been understood to be due to the hindrance offered by the Mo + ions to the electronic motions. The observed peak-like behavior in conductivity (dip-like behavior in activation energy) in the composition range 0.20-0.50 mol fractions of MoO 3 may be due to mixed transition effect occurring in the present glasses. The temperature dependence of frequency exponent, s, has been analyzed using different theoretical models. It is for the first time that the mixed transition metal ion (TMI) doped borophosphate glasses have been investigated for dielectric properties and conductivity over wide temperature and frequency ranges and the data have been subjected to a thorough analysis.

Vijaya Kumar, B.; Sankarappa, T.; Kumar, Santosh; Prashant Kumar, M.; Sadashivaiah, P. J.; Ramakrishna Reddy, R.

2009-11-01

305

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

306

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

307

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

308

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

309

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

310

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

311

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

312

Piezoelectric and dielectric properties of Pb(Zr ,Ti )O 3 ferroelectric bilayers  

NASA Astrophysics Data System (ADS)

The dielectric and piezoelectric properties of an epitaxial PbZ r0.8T i0.2O3/PbZ r0.6T i0.4O3 ferroelectric bilayer film were studied. Time-resolved synchrotron x-ray microdiffraction provided access to layer-specific structural information during electric-field-induced changes. The observed dielectric and electromechanical responses are consistent with a weak electrostatic polarization coupling and can be described using a thermodynamic model of epitaxial ferroelectric bilayers. The weak electrostatic coupling between ferroelectric layers can enable unusual tail-to-tail and head-to-head polarization configurations. X-ray measurements of the piezoelectric response of the ferroelectric bilayer at a microsecond time scale confirmed a possible tail-to-tail polarization domain configuration.

Grigoriev, Alexei; Yang, Chun; Meisami Azad, Mandana; Causey, Oliver; Walko, Donald A.; Tinberg, Daniel S.; Trolier-McKinstry, Susan

2015-03-01

313

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

314

Study of Structural and Dielectric Properties of Copper Oxide Nanoparticles Prepared by Wet Chemical Precipitation Method  

NASA Astrophysics Data System (ADS)

We report the synthesis of copper oxide (CuO) nanoparticles prepared by wet chemical precipitation method. The structural and dielectric properties are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and complex impedance spectroscopy as a function of frequencies from 40 KHz to 100 KHz in the range of temperatures (308-393K). Maximum value of dielectric constants are found to be in the order of 106 which increases with increase in temperatures. From XRD data it is found that the particle size increases with increase in calcination temperatures. SEM with energy dispersive X-ray fluorescence spectrometer (EDX) results show that only CuO is present in the prepared sample. The selected area electron diffraction (SAED) pattern by TEM shows that uniform size distributions of CuO nanoparticles are present in the sample.

Siddique, Kibriya; Nath, Bhabesh Kumar; Karmakar, Sanjib

2013-01-01

315

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

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

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

PubMed

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

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

2007-09-01

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

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

320

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

321

Measurement of the dielectric properties of high-purity sapphire at 1.865 GHZ from 2-10 Kelvin  

SciTech Connect

A dielectric test cavity was designed and tested to measure the microwave dielectric properties of ultrapure sapphire at cryogenic temperatures. Measurements were performed by placing a large cylindrical crystal of sapphire in a Nb superconducting cavity operating in the TE01 mode at 1.865 GHz. The dielectric constant, heat capacity, and loss tangent were all calculated using experimental data and RF modeling software. The motivation for these measurements was to determine if such a sapphire could be used as a dielectric lens to focus the magnetic field onto a sample wafer in a high field wafer test cavity. The measured properties have been used to finalize the design of the wafer test cavity.

N. Pogue, P. McIntyre, Akhdiyor Sattarov, Charles Reece

2012-06-01

322

Influence of nanogold additives on phase formation, microstructure and dielectric properties of perovskite BaTiO3 ceramics  

NASA Astrophysics Data System (ADS)

The formation of perovskite phase, microstructure and dielectric properties of nanogold-modified barium titanate (BaTiO3) ceramics was examined as a function of gold nanoparticle contents by employing a combination of X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, Archimedes principle and dielectric measurement techniques. These ceramics were fabricated from a simple mixed-oxide method. The amount of gold nanoparticles was found to be one of the key factors controlling densification, grain growth and dielectric response in BaTiO3 ceramics. It was found that under suitable amount of nanogold addition (4 mol%), highly dense perovskite BaTiO3 ceramics with homogeneous microstructures of refined grains (~0.5-3.1 ?m) and excellence dielectric properties can be produced.

Nonkumwong, Jeeranan; Ananta, Supon; Srisombat, Laongnuan

2015-02-01

323

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

324

Vanadium oxide nanotubes VOx-NTs: Hydrothermal synthesis, characterization, electrical study and dielectric properties  

SciTech Connect

Vanadium oxide nanotubes (VOx-NTs) have been synthesized via one-step hydrothermal treatment. The compounds were analyzed through X-ray powder diffraction; scanning electron microscope, UV–Visible spectroscopy, X-ray photoelectron spectroscopy (XPS) and complex impedance spectroscopy. The electrical and dielectric properties dependence on temperature (302–523 K) and on frequency (5 Hz to 13 MHz) of VOx-NTs have been reported. The complex impedance plots exhibits the presence of grain and grain boundaries. Dielectric data were analyzed using complex permittivity and complex electrical modulus for the sample at various temperatures. The presence of non-Debye type of relaxation has been confirmed by the complex modulus analysis. AC conductivity exhibits two conduction mechanisms: at high temperature, a translational motion with a sudden hopping and at low temperature, a localized hopping with a small hopping or reorientational motion. DC conductivity indicated, negative temperature coefficient of resistance (NTCR) type behavior. - Graphical abstract: The imaginary part of dielectric constant decreases with the increase in frequency at all temperatures and the values of ??? exhibit considerable frequency dispersion in the lower frequency range . - Highlights: ?Vanadium oxide nanotubes (VOx-NTs) were synthesized. ?Non-debye type of relaxation has been confirmed. ?AC conductivity exhibits two conduction mechanisms. ?DC conductivity indicated negative temperature coefficient of resistance type behavior.

Nefzi, H. [Laboratoire de Chimie de la Matière Condensée IPEIT, Université de Tunis, 2 rue Jawaher Lel Nehru 1008, B.P. 229 Montfleury, Tunis (Tunisia); Sediri, F., E-mail: sediri68@gmail.com [Laboratoire de Chimie de la Matière Condensée IPEIT, Université de Tunis, 2 rue Jawaher Lel Nehru 1008, B.P. 229 Montfleury, Tunis (Tunisia); Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 El Manar, Tunis (Tunisia)

2013-05-15

325

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

326

Dielectric loss, conductivity relaxation process and magnetic properties of Mg substituted Ni-Cu ferrites  

NASA Astrophysics Data System (ADS)

The dielectric properties, dc and ac electrical resistivities of Mg substituted Ni-Cu ferrites with general formula Ni0.5Cu0.5-xMgxFe2O4 (0.0?x?0.5) have been investigated as a function of frequency, temperature and composition. ac resistivity of all the samples decreases with increase in the frequency exhibiting normal ferrimagnetic behavior. The frequency dependence of dielectric loss tangent showed a maximum in between 10 Hz and 1 kHz in all the ferrites. The conductivity relaxation of the charge carriers was examined using the electrical modulus formulism, and the results indicate the presence of the non-Debye type of relaxation in the prepared ferrites. Similar values of activation energies for dc conduction and for conductivity relaxation reveal that the mechanism of electrical conduction and dielectric polarization is the same in these ferrites. A single 'master curve' for normalized plots of all the modulus isotherms observed for a given composition indicates that the distribution of relaxation time is temperature independent. The saturation magnetization and coercivity as calculated from the hysteresis loop measurement show striking dependence on composition.

Singh, Navneet; Agarwal, Ashish; Sanghi, Sujata; Khasa, Satish

2012-08-01

327

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

328

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

329

Electrical/dielectric properties and conductivity mechanism of epoxy/expanded graphite composites  

NASA Astrophysics Data System (ADS)

In this work the electrical and dielectric properties, as well as the temperature dependence of the electrical conductivity of epoxy/expanded graphite (EG) composites, are studied by employing dielectric relaxation spectroscopy (DRS). For the preparation of the composites EG was sonicated in acetone for 10h and then the appropriate amount of epoxy resin added to the mixture. The sonication was prolonged for another 3 h. The mixture was dried at 60^oC for a few hours and then the appropriate amount of hardener (triethylenetetramine) was added followed by mechanical stirring for 15 min. Finally, the mixture was cast in a glass mould and outgassed overnight at room temperature. Before they were removed from the mould, all samples were post-cured at 127^oC for 10 min in air. Samples with EG weight fractions ranging from 0 to 8 wt.% were produced. Preliminary DRS results at room temperature indicate that electrical percolation threshold (pc) lies between 3-5 wt.% EG. The influence of the EG fillers (for concentrations below pc) on the dielectric relaxation mechanisms of the epoxy matrix, as well as the conductivity mechanism (for concentrations above pc) are investigated.

Kanapitsas, Athanasios; Logakis, Emmanuel; Pandis, Christos; Pissis, Polycarpos; Jovic, Natasa; Djokovic, Vladimir

2009-03-01

330

Electrical properties of atomic layer deposited high-k dielectrics on Indium Nitride  

NASA Astrophysics Data System (ADS)

Indium nitride is a promising channel material for high frequency transistors because of its low effective electron mass (m* = 0.04m0) and high electron velocities. However, realizing practical InN devices has a number of challenges. One of the challenges is the presence of large surface electron accumulation layer. It is caused by InN surface Fermi level pinning above conduction band that results in downward bending of the bands at the surface. It has been reported that chemical surface treatment could un-pin the surface, reducing the electron accumulation density. In this work, hydrochloric acid, ammonium sulfide and trimethylaluminium (TMA) are used for the passivation of InN wafers before dielectric deposition. Metal-oxide-semiconductor capacitor (MOSCAP) structures are fabricated to study the effectiveness of the passivation methods. The current-voltage and capacitance-voltage characteristics are measured on MOSCAPs with atomic layer deposited high-k dielectrics. Current-voltage curves indicate that high-k dielectric layer shows excellent insulating properties with low leakage currents. Measured capacitance-voltage curves demonstrate surface electron accumulation even with passivation. Simulations of device structure are carried out to understand the capacitance-voltage behavior.

Jia, Ye

331

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

332

The dielectric properties of neutron irradiated snake venom and its pathological impact.  

PubMed

The changes in the dielectric properties of a saline solution of Cerastes cerastes snake venom after irradiation with low-level doses of fast neutrons from a Cf-252 source, were investigated. The pathological changes in the internal organs such as liver, kidney spleen, lung and heart of the rats injected with unirradiated and irradiated venom were also studied. The changes in the molecular structure of a diluted saline solution of snake venom were measured through dielectric relaxation studies in the frequency range 0.1-10 MHz at 4 +/- 0.5 degrees C. The absorption spectra of the venom solution were measured in the wavelength range 200 to 600 nm. The results indicated remarkable changes in the molecular radii, shape, relaxation time and dielectric increment of the venom molecules as a result of irradiation. Also, the intensities of the absorption bands of the venom solution decreased as a result of the irradiation process. Furthermore, the pathological examination results indicated that the toxicity of the irradiated venom decreased as compared with that of unirradiated venom, hence increasing the chance of repair of the affected organs. PMID:10495125

Hanafy, M S; Rahmy, N A; Abd El-Khalek, M M

1999-09-01

333

Nonlinear Dielectric Properties of Paraelectric (Ba,Sr)TiO3 Thin Films with Isotropic and Anisotropic Epitaxy  

Microsoft Academic Search

The effects of isotropic and anisotropic epitaxy on the nonlinear dielectric response in (Ba0.6,Sr0.4TiO3) thin films were investigated experimentally. Under isotropic epitaxy, it is shown that the misfit is detrimental to the non-linear response of the films with decreasing film thickness. Nonlinear dielectric properties of films with in-plane compression exhibit more pronounced strain dependence, while the same does not set-in

W. K. Simon; J. A. Bellotti; E. K. Akdogan; A. Safari

2006-01-01

334

Effect of tetra ionic substitution on the dielectric properties of Cu-ferrite  

NASA Astrophysics Data System (ADS)

X-ray diffraction (XRD), of the two systems of mixed ferrites Cu1+xTixFe2-2xO4 (where x = 0.0, 0.1, 0.2, 0.3, and 0.4); indicates that the samples of x = 0 (CuFe2O4) and x = 0.1 of the Cu-Ti system were formed in tetragonal structure and all other samples of the two system were formed in the cubic system.The ac conductivity , dielectric constant , dielectric loss and the loss tangent tan ? were determined against frequency at room temperature for Cu-Ge and Cu-Ti ferrites. The measurements of and tan ? were performed over a wide range of frequency and temperature.The Maxwell-Wagner model was applied to analyze the dielectric properties of the investigated systems, according to which the dielectric parameters such as the relaxation time . A value of 1 = 5 × 10-7 s was found for Cu-Ge ferrite and 2 = 1.85 × 10-6 s for Cu-Ti ferrites. The hopping rate (g) was found to be 2 × 106 s-1 and 5.4 × 105 s-1 for the two systems Cu-Ge and Cu-Ti ferrites, respectively.The conduction of the two-ferrite systems was discussed on the basis of the hopping mechanism. The activation energy for conduction was calculated and found in the range of 0.27-0.39 eV for Cu-Ge ferrite and 0.21-0.30 eV for Cu-Ti ferrite. (

Mazen, S. A.; Zaki, H. M.

2003-09-01

335

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

336

Fabrication and properties of a glass-lens, static-concentrator mini-module  

SciTech Connect

A glass-lens, static-concentrator mini-module was fabricated by attaching a co-molded glass-lens on a conventional superstrate flat-plate module. Its properties were investigated under simulated and real sunlight conditions. The effect of rear reflection on optical concentration was investigated for the static concentrator mini-modules with white, black and transparent rear Tedlar films. Under a solar simulator condition, optical concentration ratios of 2.05, 1.75 and 1.70 were obtained for the white, transparent and black films. From outdoor and also indoor measurements, the mini-module with the white Tedlar showed the highest maximum output power throughout daytime.

Yoshioka, K.; Nikaido, T.; Saitoh, T. [Tokyo A and T Univ., Koganei, Tokyo (Japan); Kanai, M.; Hide, I. [Daido Hoxan Inc., Chitose, Hokkaido (Japan)

1997-12-31

337

Influences of deposition parameters on microstructure and dielectric properties of BST thin film deposited by R.F. magnetron sputtering  

NASA Astrophysics Data System (ADS)

Down graded barium strontium tianate(BST) thin films were prepared on Pt/Ti/SiO2/Si(100) substrate by radio frequency magnetron sputtering. The BST thin films were deposited at various substrate temperatures, then annealed at 700 °C for an hour. The influences of the deposition parameters on the crystallization behavior, microstructure and dielectric properties of BST thin films were investigated by X-ray diffraction, field emission scanning electron microscopy and dielectric frequency spectra. XRD results indicate that the BST thin films deposited at higher temperature have improved crystallization structure.The SEM observations show that the surface of the films is smooth with homogeneous grains.The dielectric properties of the films have been examined and discussed. The experiments show that BST thin films deposited at 650oc, 3.0Pa working pressure exhibits superior dielectric properties: the highest dielectric constant is 448 and lowest dielectric loss is 0.013 at 100 kHz, respectively. These results make BST thin films be a promising candidate for microelectronic device application.

Xiang, Chao; Zhang, Tianjin; Pan, Ruikun; Wang, Jinzhao; Ma, Zhijun; Xia, Min

2009-03-01

338

Dielectric properties of Li3VO4 single crystals grown by the Czochralski method  

NASA Astrophysics Data System (ADS)

We studied dielectric properties of Li3VO4 single crystals grown by the Czochralski method along the a axis at temperatures ranging from room temperature to 800 °C and frequencies ranging from 100 Hz to 15 MHz. We analyzed the impedance data by introducing an equivalent circuit which consists of two parallel combinations of capacitors and resistors in series. The conductivity and the relaxation time of Li3VO4 are found to show the Arrhenius behavior with two different activation energies which crossed over at temperatures around 400 °C. The observed crossover seems to originate from a dissociation of the Li-O bond at high temperatures.

Kim, Dong Jin; Jun, Byeong Eog; Kim, Chung-Sik; Kim, Hyung Kook; Kim, Jung Nam; Hwang, Yoon-Hwae

2003-02-01

339

Vector spherical wavefunctions for orthorhombic dielectric-magnetic material with gyrotropic-like magnetoelectric properties  

E-print Network

Vector spherical wavefunctions were derived in closed-form to represent time-harmonic electromagnetic fields in an orthorhombic dielectric-magnetic material with gyrotropic-like magnetoelectric properties. These wavefunctions were used to formulate the T matrix for scattering by a three-dimensional object composed of the chosen material. Furthermore, a closed-form, coordinate-free expression of the dyadic Green function for the chosen material was derived. Expressions ascertained for the singularity behavior will be useful for formulating volume integral equations for scattering inside the chosen material. A bilinear expansion of the dyadic Green function was obtained in terms of the derived vector spherical wavefunctions.

Lakhtakia, Akhlesh; 10.1007/s12596-012-0084-y

2012-01-01

340

Ferroelectric and Dielectric Properties of Nd-Doped Bi4Ti3O12 Ceramics  

Microsoft Academic Search

Bismuth titanate Bi4-xNdxTi3O12 (x = 0, 0.25, 0.45, 0.65, 0.85) samples were prepared using the solid-state reaction route and their dielectric properties were investigated. Crystal structure was analyzed by X-ray diffraction instrument, which indicated that Bi4-xNdxTi3O12 ceramics were pure phases and no other phases appeared. The split peaks around 47.5° for orthorhombic symmetry were gradually combined into a single peak

Xiaofeng Ruan; Yanxia Li; Xusheng Wang; Xi Yao

2010-01-01

341

Properties of dielectric-barrier-free atmospheric pressure microplasma driven by submicrosecond dc pulse voltage  

NASA Astrophysics Data System (ADS)

Atmospheric pressure microplasma driven by dc pulse is developed. This device has a simple structure comprised of a flowing helium (He) feed gas and dielectric-free metal electrodes without an external current limiting resistor. It is shown that a stable glow mode plasma can be sustained without arc runaway by limiting the voltage pulse width to shorter than 300 ns. The properties of the device are reported in terms of discharge current waveforms, rotational temperature of N2+, and spatiotemporally resolved optical emission characteristics.

Ha, Chang-Seung; Choi, Joon-Young; Kim, Dong-Hyun; Park, Chung-Hoo; Lee, Hae June; Lee, Ho-Jun

2009-08-01

342

Thickness effect on the dielectric, ferroelectric, and piezoelectric properties of ferroelectric lead zirconate titanate thin films  

NASA Astrophysics Data System (ADS)

Lead zirconate titanate (PbZr0.52Ti0.48O3-PZT) thin films with different thicknesses were deposited on Pt(111)/Ti/SiO2/Si substrates by a sol-gel method. Single perovskite phase with (111)-texture was obtained in the thinnest films, whereas with the increase in thickness the films changed to a highly (100)-oriented state. An increase in the mean grain size as the film thickness increased was also observed. Dielectric, ferroelectric, and piezoelectric properties were analyzed as a function of the film thickness and explained based on film orientation, grain size, domain structure, domain wall motion, and nonswitching interface layers. Both serial and parallel capacitor models were used to analyze the influence of the nonswitching interface layer in the dielectric properties and the effect of substrate clamping in the microscopic piezoelectric response as the film thickness decreased. The scanning force microscopy technique was used to study the effect of thickness on the microscopic piezoresponse. Significant differences between the macroscopic and microscopic electrical properties of the films were observed. Those differences can be assigned to changes in the nonswitching film-electrode layer and domain structure.

Pérez de la Cruz, J.; Joanni, E.; Vilarinho, P. M.; Kholkin, A. L.

2010-12-01

343

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

344

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

345

Measurement of insulating and dielectric properties of acrylic elastomer membranes at high electric fields  

NASA Astrophysics Data System (ADS)

This work reports on the investigation of VHB 4910 acrylic elastomer insulating and dielectric properties. This material is widely exploited for the realization of actuators with large deformations, dielectric elastomer actuators (DEA), and belongs to the group of so-called electroactive polymers (EAP). Extensive investigations concerning its mechanical properties are available in literature while its electric behavior at working conditions has not received the same level of attention. In this work, the relative permittivity and the volume resistivity have been measured on VHB 4910 membranes under different fixed stretch conditions (?1, ?2 = 3, 3.6, 4, 5) using circular gold electrodes sputtered onto both sides of the specimens. The measured values of relative permittivity are in fairly good agreement with the results previously published by other groups. The volume resistivity, at field values close to the operational ones, has shown a field-dependent behavior revealing dissipative properties that should be considered in real applications. Further, measurements on circular actuators verify these findings. Consequences for modeling of VHB 4910 are drawn and new material model parameters proposed to account for the value of relative permittivity at high electric fields.

Di Lillo, L.; Schmidt, A.; Carnelli, D. A.; Ermanni, P.; Kovacs, G.; Mazza, E.; Bergamini, A.

2012-01-01

346

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

347

Nonlinear Dielectric Properties of Yeast Cells Cultured in Different Environmental Conditions  

NASA Astrophysics Data System (ADS)

The harmonics of the electric current through yeast suspensions, the nonlinear dielectric properties of yeast cells, have particular patterns according to the biological activity of the cells and the measurement of these patterns is a technique for determining the activity of living cells. The concentration of glucose and oxygen in yeast culture medium influences the manifestation of fermentation or respiration of yeast cells. Measurements were made with yeast cells (Saccharomyces cerevisiae) cultured aerobically and anaerobically in sufficient glucose concentration, aerobic fermentation and anaerobic fermentation, and aerobically in limited glucose concentration, respiration. The results showed that the harmonics were barely apparent for yeast cells in aerobic fermentation and respiratory; however, cells in the anaerobic fermentation displayed substantial third and fifth harmonics. We can say that environmental condition affects the yeast cells' nonlinear properties, from another viewpoint, the measurements of the nonlinear properties are available to determine the activity of yeast cells adjusted to the conditions of their cultivation.

Kawanishi, Gomon; Fukuda, Naoki; Muraji, Masafumi

348

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

349

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

PubMed

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. PMID:25082800

Sasaki, K; Wake, K; Watanabe, S

2014-08-21

350

Control of the Casimir force by the modification of dielectric properties with light  

E-print Network

The experimental demonstration of the modification of the Casimir force between a gold coated sphere and a single-crystal Si membrane by light pulses is performed. The specially designed and fabricated Si membrane was irradiated with 514 nm laser pulses of 5 ms width in high vacuum leading to a change of the charge-carrier density. The difference in the Casimir force in the presence and in the absence of laser radiation was measured by means of an atomic force microscope as a function of separation at different powers of the absorbed light. The total experimental error of the measured force differences at a separation of 100 nm varies from 10 to 20% in different measurements. The experimental results are compared with theoretical computations using the Lifshitz theory at both zero and laboratory temperatures. The total theoretical error determined mostly by the uncertainty in the concentration of charge carriers when the light is incident is found to be about 14% at separations less than 140 nm. The experimental data are consistent with the Lifshitz theory at laboratory temperature, if the static dielectric permittivity of high-resistivity Si in the absence of light is assumed to be finite. If the dc conductivity of high-resistivity Si in the absence of light is included into the model of dielectric response, the Lifshitz theory at nonzero temperature is shown to be experimentally inconsistent at 95% confidence. The demonstrated phenomenon of the modification of the Casimir force through a change of the charge-carrier density is topical for applications of the Lifshitz theory to real materials in fields ranging from nanotechnology and condensed matter physics to the theory of fundamental interactions.

F. Chen; G. L. Klimchitskaya; V. M. Mostepanenko; U. Mohideen

2007-07-30

351

Structural, dielectric and magnetic properties of Nd-doped Co 2Z-type hexaferrites  

Microsoft Academic Search

Z-type hexaferrites doped with Nd3+, Ba3?xNdxCo2Fe24O41 (x=0, 0.05, 0.10, 0.15, and 0.25), were prepared by solid-state reaction. The effect of the Nd3+ ions substitution for Ba2+ ions on the microstructure and electromagnetic properties of the samples was investigated. The results reveal that an important modification of microstructure, complex permeability, complex permittivity, and static magnetic properties can be obtained by introducing

Jijing Xu; Guijuan Ji; Haifeng Zou; Yuan Zhou; Shucai Gan

2011-01-01

352

An analytical, variable resolution, complete description of static molecules and their intermolecular binding properties.  

PubMed

A fully analytical description of molecular shape, as defined by the shrink-wrap isodensity or solvent-excluded surfaces and local properties related to Coulomb, donor/acceptor, and polarizability (dispersion) interactions is described. The molecular surface and four local properties adequate for describing intermolecular interactions (the molecular electrostatic potential and the local ionization energy, electron affinity, and polarizability) are fitted to spherical-harmonic expansions, which provide a compact and information-rich description of the properties of the static molecule. The resolution of the description can be varied from isotropic to near atomistic detail by adjusting the order of the individual spherical-harmonic expansions. Examples are given to illustrate the effect of truncating the different spherical-harmonic approximations. PMID:16045295

Lin, Jr-Hung; Clark, Timothy

2005-01-01

353

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

354

Dielectric properties of organic solvents from non-polarizable molecular dynamics simulation with electronic continuum model and density functional theory.  

PubMed

Dielectric constants of electrolytic organic solvents are calculated employing nonpolarizable Molecular Dynamics simulation with Electronic Continuum (MDEC) model and Density Functional Theory. The molecular polarizabilities are obtained by the B3LYP/6-311++G(d,p) level of theory to estimate high-frequency refractive indices while the densities and dipole moment fluctuations are computed using nonpolarizable MD simulations. The dielectric constants reproduced from these procedures are evaluated to provide a reliable approach for estimating the experimental data. An additional feature, two representative solvents which have similar molecular weights but are different dielectric properties, i.e., ethyl methyl carbonate and propylene carbonate, are compared using MD simulations and the distinctly different dielectric behaviors are observed at short times as well as at long times. PMID:21967704

Lee, Sanghun; Park, Sung Soo

2011-11-01

355

MAPPING OF RESERVOIR PROPERTIES AND FACIES THROUGH INTEGRATION OF STATIC AND DYNAMIC DATA  

SciTech Connect

Knowledge of the distribution of permeability and porosity in a reservoir is necessary for the prediction of future oil production, estimation of the location of bypassed oil, and optimization of reservoir management. But while the volume of data that can potentially provide information on reservoir architecture and fluid distributions has increased enormously in the past decade, it is not yet possible to make use of all the available data in an integrated fashion. While it is relatively easy to generate plausible reservoir models that honor static data such as core, log, and seismic data, it is far more difficult to generate plausible reservoir models that honor dynamic data such as transient pressures, saturations, and flow rates. As a result, the uncertainty in reservoir properties is higher than it could be and reservoir management can not be optimized. The goal of this project is to develop computationally efficient automatic history matching techniques for generating geologically plausible reservoir models which honor both static and dynamic data. Solution of this problem is necessary for the quantification of uncertainty in future reservoir performance predictions and for the optimization of reservoir management. Facies (defined here as regions of relatively uniform petrophysical properties) are common features of all reservoirs. Because the flow properties of the various facies can vary greatly, knowledge of the location of facies boundaries is of utmost importance for the prediction of reservoir performance and for the optimization of reservoir management. When the boundaries between facies are fairly well known, but flow properties are poorly known, the average properties for all facies can be determined using traditional techniques. Traditional history matching honors dynamic data by adjusting petrophysical properties in large areas, but in the process of adjusting the reservoir model ignores the static data and often results in implausible reservoir models. In general, boundary locations, average permeability and porosity, relative permeability curves, and local flow properties may all need to be adjusted to achieve a plausible reservoir model that honors all data. In this project, we will characterize the distribution of geologic facies as an indicator random field, making use of the tools of geostatistics as well as the tools of inverse and probability theory for data integration.

Albert C. Reynolds; Dean S. Oliver; Fengjun Zhang; Yannong Dong; Jan Arild Skjervheim; Ning Liu

2003-01-01

356

Static and Dynamic Properties of Trapped Fermionic Tonks-Girardeau Gases  

E-print Network

We investigate some exact static and dynamic properties of one-dimensional fermionic Tonks-Girardeau gases in tight de Broglie waveguides with attractive p-wave interactions induced by a Feshbach resonance. A closed form solution for the one-body density matrix for harmonic trapping is analyzed in terms of its natural orbitals, with the surprising result that for odd, but not for even, numbers of fermions the maximally occupied natural orbital coincides with the ground harmonic oscillator orbital and has the maximally allowed fermionic occupancy of unity. The exact dynamics of the trapped gas following turnoff of the p-wave interactions are explored.

M. D. Girardeau; E. M. Wright

2005-01-11

357

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

358

Investigation of low field dielectric properties of anisotropic porous Pb(Zr,Ti)O3 ceramics: Experiment and modeling  

NASA Astrophysics Data System (ADS)

Anisotropic porous Pb(Zr,Ti)O3 ceramics with various porosity degrees have been studied in order to determine the role of the pore shape and orientation on the low-field dielectric properties. Ceramic samples with formula Pb(Zr0.52Ti0.48)0.976Nb0.024O3 with different porosity degrees (dense, 10%, 20%, 40% vol.) have been prepared by solid state reaction. Taking into consideration the shape and orientation of the pore inclusions, the dielectric properties of porous ceramics have been described by using adapted mixing rules models. Rigorous bounds, derived on the basis on Variational Principle, were used to frame dielectric properties of porous composites. The finite element method (FEM) was additionally used to simulate the dielectric response of the porous composites under various applied fields. Among the few effective medium approximation models adapted for anisotropic oriented inclusions, the best results were obtained in case of needle-like shape inclusions (which do not correspond to the real shape of microstructure inclusions). The general case of Wiener bounds limited well the dielectric properties of anisotropic porous composites in case of parallel orientation. Among the theoretical approaches, FEM technique allowed to simulate the distribution of potential and electric field inside composites and provided a very good agreement between the computed permittivity values and experimental ones.

Olariu, C. S.; Padurariu, L.; Stanculescu, R.; Baldisserri, C.; Galassi, C.; Mitoseriu, L.

2013-12-01

359

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

360

Measurement of the dielectric properties of dispersive materials over a wide frequency range.  

SciTech Connect

The propagation of electromagnetic waves through dispersive media forms the basis for a wide variety of applications. Rapid advances in materials have produced new products with tailored responses across frequency bands. Many of these new materials, such as radar absorbing material and photonic crystals, are dispersive in nature. This, in turn, has opened up the possibility for the exploitation of these dispersive dielectric properties for a variety of applications. Thus, it is desirable to know the electromagnetic properties of both man-made and natural materials across a wide frequency range. With the advent of transient pulsers with sub-nanosecond risetimes and rates of voltage rise approaching 10**16 V/s, the frequencies of interest in the transient response extend to approximately the 2 GHz range. Although a network analyzer can provide either frequency- or time-domain data (by inverse transform), common TEM cells are only rated to 0.5 to 1.5 GHz--significantly below the maximum frequency of interest. To extend the frequency range to include 2 GHz, a TEM cell was characterized and a deembedding algorithm was applied to account, in part, for the limitations of the cell. The de-embedding technique is described along with such measurement issues such as clear time and sneak around. Measurements of complex permittivity of common drinking water are shown. This frequency extension will lead to more expansive testing of dielectric materials of interest.

Molina, Luis Leroy; Salazar, Robert Austin; Bacon, Larry Donald; Lehr, Jane Marie

2003-06-01

361

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

362

Influence of semiconductor and metal nanoparticles on the dielectric properties of ionic matrix cadmium octanoate  

NASA Astrophysics Data System (ADS)

Dielectric properties of ionic composites consisted of cadmium octanoate matrix and semiconductor or metal nanoparticles have been investigated. The nanoparticles of different nature (semiconductor CdS, metal Au, and metal core-semiconductor shell Au-CdS) were chemically synthesized in the smectic A phase of (Cd+2(C7H15COO)-2, CdC8) that was used as a nanoreactor. These nanocomposites are very stable and well ordered; the size and shape of the nanoparticles (NPs) are well controlled during the synthesis. The main aim of the research was to examine the influence of nanoparticles on the dielectric properties of ionic matrix, which has smectic A ordered structure. Electrical characteristics were investigated at different temperatures, which correspond to different phases of the material. The conductivity of nanocomposites has an activation nature. The electrical conductivity anisotropy confirms the structural anisotropy of the nanocomposites. The conductivity of the nanocomposite along the cation-anion layers is higher by 2 orders of magnitude than that across the cation-anion layers. Basing on the experimental data, we proposed the simple model of the charge carriage process.

Zhulai, Dmytro; Fedorenko, Denys; Kovalchuk, Alexander; Bugaychuk, Svetlana; Klimusheva, Gertruda Vasylivna; Mirnaya, Tetyana Alfredivna

2015-02-01

363

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

SciTech Connect

Diamond thin films with a broad range of microstructures from a ultrananocrystalline diamond (UNCD) form developed at Argonne National Laboratory to a microcrystalline diamond (MCD) form have been grown with different hydrogen percentages in the Ar/CH{sub 4} gas mixture used in the microwave plasma enhanced chemical vapor deposition (CVD) process. The dielectric properties of the CVD diamond thin films have been studied using impedance and dc measurements on metal-diamond-metal test structures. Close correlations have been observed between the hydrogen content in the bulk of the diamond films, measured by elastic recoil detection (ERD), and their electrical conductivity and capacitance-frequency (C-f) behaviors. Addition of hydrogen gas in the Ar/CH{sub 4} gas mixture used to grow the diamond films appears to have two main effects depending on the film microstructure, namely, (a) in the UNCD films, hydrogen incorporates into the atomically abrupt grain boundaries satisfying sp{sup 2} carbon dangling bonds, resulting in increased resistivity, and (b) in MCD, atomic hydrogen produced in the plasma etches preferentially the graphitic phase codepositing with the diamond phase, resulting in the statistical survival and growth of large diamond grains and dominance of the diamond phase, and thus having significant impact on the dielectric properties of these films.

Liu, C.; Xiao, X.; Wang, J.; Shi, B.; Auciello, O.; Carlisle, J. A.; Carpick, R.; Adiga, V.; Univ. of Wisconsin at Madison; Univ. of Pennsylvania

2007-01-01

364

Thermal Stresses in Ferroelectric Thin Films and Their Role on the Dielectric, Pyroelectric, and Electrocaloric Properties  

NASA Astrophysics Data System (ADS)

In-plane strains develop in thin films due to thermal stresses that arise from differences between the thermal expansion coefficients of the film and the substrate upon cooling from a growth temperature (TG) to room temperature (RT). In ferroelectric (FE) films, there is a coupling between strain and polarization through electrostriction. Therefore, thermal strains may have profound effects on the dielectric, pyroelectric, and electrocaloric (EC) responses of FE films. We provide here a quantitative thermodynamic model to investigate the role of in-plane thermal strains on these properties. We show that there is a substantial degradation in the dielectric response and tunability of SrTiO3 films on IC-friendly substrates such as Si and c-sapphire due to tensile thermal in-plane strains. Our analysis on (001)-textured polycrystalline BaxSr1-xO3 (BST) films with different compositions indicates that for BST 60/40 and BST 70/30 films, the pyroelectric response does not display a significant dependence on TG if the FE is in a paraelectric state. Furthermore, we show that for BaTiO3 films on Si, the thermal stresses are sufficient to shift the zero-field Curie temperature to RT, resulting in a strong enhancement of the EC properties as compared to the bulk material.

Zhang, Jialan; Pamir Alpay, S.

2012-02-01

365

Three-Dimensional Microwave Breast Imaging: Dispersive Dielectric Properties Estimation using Patient-Specific Basis Functions  

PubMed Central

Breast imaging via microwave tomography involves estimating the distribution of dielectric properties within the patient's breast on a discrete mesh. The number of unknowns in the discrete mesh can be very large for three-dimensional imaging, and this results in computational challenges. We propose a new approach where the discrete mesh is replaced with a relatively small number of smooth basis functions. The dimension of the tomography problem is reduced by estimating the coefficients of the basis functions instead of the dielectric properties at each element in the discrete mesh. The basis functions are constructed using knowledge of the location of the breast surface. The number of functions used in the basis can be varied to balance resolution and computational complexity. The reduced dimension of the inverse problem enables application of a computationally efficient, multiple-frequency inverse scattering algorithm in 3-D. The efficacy of the proposed approach is verified using two 3-D anatomically realistic numerical breast phantoms. It is shown for the case of single-frequency microwave tomography that the imaging accuracy is comparable to that obtained when the original discrete mesh is used, despite the reduction of the dimension of the inverse problem. Results are also shown for a multiple-frequency algorithm where it is computationally challenging to use the original discrete mesh. PMID:19211350

Winters, David W.; Shea, Jacob D.; Kosmas, Panagiotis; Van Veen, Barry D.; Hagness, Susan C.

2009-01-01

366

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

NASA Astrophysics Data System (ADS)

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

Wakaki, Moriaki; Yokoyama, Eisuke

2011-08-01

367

Trapping-charging ability and electrical properties study of amorphous insulator by dielectric spectroscopy  

SciTech Connect

Usually, the trapping phenomenon in insulating materials is studied by injecting charges using a Scanning Electron Microscope. In this work, we use the dielectric spectroscopy technique for showing a correlation between the dielectric properties and the trapping-charging ability of insulating materials. The evolution of the complex permittivity (real and imaginary parts) as a function of frequency and temperature reveals different types of relaxation according to the trapping ability of the material. We found that the space charge relaxation at low frequencies affects the real part of the complex permittivity ?{sup ?} and the dissipation factor Tan(?). We prove that the evolution of the imaginary part of the complex permittivity against temperature ?{sup ?}=f(T) reflects the phenomenon of charge trapping and detrapping as well as trapped charge evolution Q{sub p}(T). We also use the electric modulus formalism to better identify the space charge relaxation. The investigation of trapping or conductive nature of insulating materials was mainly made by studying the activation energy and conductivity. The conduction and trapping parameters are determined using the Correlated Barrier Hopping (CBH) model in order to confirm the relation between electrical properties and charge trapping ability.

Mekni, Omar, E-mail: omarmekni-lmop@yahoo.fr; Arifa, Hakim; Askri, Besma; Yangui, Béchir [Laboratory of Materials, Organization and Properties LR99ES17, University of Tunis El Manar, Campus Universities El Manar, 2092 Tunis (Tunisia); Raouadi, Khaled, E-mail: khaled-raouadi@yahoo.fr [Laboratory of Materials, Organization and Properties LR99ES17, University of Tunis El Manar, Campus Universities El Manar, 2092 Tunis (Tunisia); Faculty of Sciences of Bizerte, University of Carthage, 7021 Jarzouna (Tunisia); Damamme, Gilles [CEA/Gramat, BP 80200, 46500 Gramat (France)

2014-09-14

368

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

369

Dielectric and piezoelectric properties of hydroxyapatite-BaTiO3 composites  

NASA Astrophysics Data System (ADS)

This letter describes the relationships between the composition and the dielectric and piezoelectric properties of hydroxyapatite-barium titanate composites for polarized bone substitutes. The ac conductivity and permittivity were characterized from 0.1Hzto1MHz, along with measurements of the d33 piezoelectric charge coefficient. The addition of BaTiO3 led to an increase in permittivity and ac conductivity of the material. The increase in both properties was attributed to the presence of the high permittivity ferroelectric phase. The d33 and g33 coefficients decreased rapidly as hydroxyapatite was introduced into BaTiO3 material. Composites below 80% by volume of BaTiO3 exhibited no net piezoelectric effect.

Bowen, C. R.; Gittings, J.; Turner, I. G.; Baxter, F.; Chaudhuri, J. B.

2006-09-01

370

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

371

Study on the relationship between the defect and dielectric properties of ZnO-doped BiNbO 4 ceramic  

Microsoft Academic Search

BiNbO4 ceramic is one kind of potential low-firing microwave dielectric material for microwave applications. ZnO was doped into BiNbO4 ceramics, the dielectric properties of the ceramic as a function of compositional variation, sintering temperature, and sintering atmosphere were studied. By means of the LCR Meter, Network Analyzer and Thermal Environmental Test Chamber, the dielectric properties at various frequencies were tested.

Yong Yang; Shihua Ding; Xi Yao

2004-01-01

372

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

373

Dielectric breakdown properties of hot SF6 gas contaminated by copper at temperatures of 300–3500?K  

NASA Astrophysics Data System (ADS)

The dielectric breakdown properties of hot SF6 gas during the dielectric recovery phase play an important role in understanding gas breakdown occurring in high-voltage circuit breakers. This paper is devoted to the theoretical investigation of dielectric breakdown properties of hot SF6 gas contaminated by copper at temperatures of 300–3500?K and pressures of 0.01–1.6?MPa. The equilibrium compositions of SF6–Cu mixtures are obtained with the consideration of condensed species. The unknown ionization cross sections for CuS, CuF and CuF2 are calculated using a Deutsch–Märk (DM) formalism based on quantum chemistry. The two-term Boltzmann equation is adopted to numerically calculate the electron energy distribution function, collision ionization coefficient and electron attachment coefficient. Then the reduced critical electric field strength is determined when the effective ionization coefficient equals to zero. The influences of the Cu proportion and gas pressure on the dielectric breakdown properties are investigated. It is shown that the existence of copper compounds increases the concentration of high-energy electrons significantly, even for the case with a very low percentage (e.g. 1% Cu). With the increase of copper content, the value of (E/N)cr is reduced remarkably at temperatures below 3000?K, but enhanced slightly above 3000?K. It is also found that the increase of pressure can improve the dielectric breakdown performance of hot SF6–Cu mixtures.

Wang, Xiaohua; Zhong, Linlin; Rong, Mingzhe; Yang, Aijun; Liu, Dingxin; Wu, Yi; Miao, Song

2015-04-01

374

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

375

Electric properties of hemispherical metal nanoparticles: influence of the dielectric substrate  

NASA Astrophysics Data System (ADS)

We calculated surface plasmon resonance position for gold and silver hemispheres placed on a dielectric substrate and covered with a thin dielectric layer. The results are applicable in metal islands film enhanced Raman spectroscopy.

Scherbak, S. A.; Shustova, O. V.; Zhurikhina, V. V.; Lipovskii, A. A.

2014-10-01

376

The Shock Hugoniot Properties of Geological Materials and Relationship to Static Properties  

NASA Astrophysics Data System (ADS)

A series of plate impact experiments was performed using the single stage light gas gun facility at the Cavendish Laboratory, Cambridge University to determine the principal Hugoniot curves of a hypabyssal kimberlite and a siltstone. A reverse impact configuration was employed, over a range of impact velocities 244-927 m/s. VISAR was the main diagnostic and sample geometry allowed for release characteristics to be studied. The release measurements show a significant deviation from the Hugoniot at higher initial shock pressures, though this does not correspond specifically to the HEL. Combined with other data previously reported the resulting Hugoniots are compared to various static data and a good correlation is shown with elastic impedance.

Guest, A. R.; Braithwaite, C. H.; Proud, W. G.; Field, J. E.

2007-12-01

377

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

378

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

SciTech Connect

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

Lakshmi, Mohana; Faisal, Muhammad [Department of Physics, PES Institute of Technology, BSC, Bangalore- 560100 (India)] [Department of Physics, PES Institute of Technology, BSC, Bangalore- 560100 (India); Roy, Aashish S. [Department of Materials Science, Gulbarga University, Gulbarga-585106, Karnataka (India)] [Department of Materials Science, Gulbarga University, Gulbarga-585106, Karnataka (India); Khasim, Syed, E-mail: syed.pes@gmail.com [Department of Physics, PES Institute of Technology, BSC, Bangalore- 560100 (India) [Department of Physics, PES Institute of Technology, BSC, Bangalore- 560100 (India); Department of Physics, University of Tabuk-71491 (Saudi Arabia); Sajjan, K. C. [Department of Physics, Veerashaiva College, Bellary - 583 104, Karnataka (India)] [Department of Physics, Veerashaiva College, Bellary - 583 104, Karnataka (India); Revanasiddappa, M. [Department of Chemistry, PES Institute of Technology, BSC, Bangalore - 560100 (India)] [Department of Chemistry, PES Institute of Technology, BSC, Bangalore - 560100 (India)

2013-11-15

379

Revisiting the low-temperature dielectric properties of ZnO  

NASA Astrophysics Data System (ADS)

Electric modulus spectroscopy and impedance analysis were used to investigate the low-temperature (˜100-333 K) dielectric properties of ZnO crystals. Two relaxations were observed. The low-temperature relaxation (R1) features a thermally activated behavior resulting from the bulk response. Our results convincingly demonstrate that this relaxation is a polaronic relaxation. The relaxing species for R1 are localized holes created by zinc vacancies instead of the commonly agreed oxygen vacancies. The high-temperature relaxation (R2) is a Maxwell-Wagner relaxation due to skin-layer effect as it can be eliminated by grinding off the sample surface. The inhomogeneous distribution of zinc interstitials leads to the formation of the skin layer. Interestingly, an abnormal dielectric behavior contrary to the thermally activated behavior was found for the R2 relaxation. This abnormal behavior was confirmed to be related to the positive temperature coefficient of resistance due to the metal-insulator transition occurring within the skin layer.

Wang, Chunchang; Liu, Lina; Li, Qiuju; Huang, Shouguo; Zhang, Jian; Zheng, Jun; Cheng, Chao

2014-09-01

380

Transmission-Line Properties of Parallel Strips Separated by a Dielectric Sheet  

Microsoft Academic Search

A transmission line is made of a symmetrical pair of strip conductors, or a single strip and a ground plane, on opposite faces of a sheet of dielectric material. There is computed, to a close approximation, the relations among the dielectric constant of the sheet, the effective dielectric constant of the sheet and the empty space, the shape ratio, and

H. A. Wheeler

1965-01-01

381

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

382

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

383

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

384

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

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

385

Low temperature piezoelectric and dielectric properties of lead magnesium niobate titanate single crystals  

NASA Astrophysics Data System (ADS)

Lead magnesium niobate-lead titanate (PMN-xPT) single crystal plates were prepared close to the morphotropic phase boundary with PT compositions 27%-31%. The piezoelectric and dielectric properties of these plates at liquid-helium temperature (4.2 K) were obtained by fitting measured impedance curves. In particular, the piezoelectric strain constant e33 is found to be in the range of 5.1-5.7 C m-2 at 4.2 K, which indicates an extraordinarily large piezoelectric effect compared with other materials even at such a low temperature. This result shows that PMN-xPT single crystals are promising candidates for ultrasonic transducers at low temperatures.

Guo, Wei; Jin, Dafei; Wei, Wanchun; Maris, Humphrey J.; Tian, Jian; Huang, Xingling; Han, Pengdi

2007-10-01

386

Modeling of the dielectric properties of trabecular bone samples at microwave frequency.  

PubMed

In this paper, the dielectric properties of human trabecular bone are evaluated under physiological condition in the microwave range. Assuming a two components medium, simulation and experimental data are presented and discussed. A special experimental setup is developed in order to deal with inhomogeneous samples. Simulation data are obtained using finite difference time domain from a realistic sample. The bone mineral density of the samples are also measured. The simulation and experimental results of the present study suggest that there is a negative relation between bone volume fraction (BV/TV) and permittivity/conductivity: the higher the BV/TV, the lower the permittivity/conductivity. This is in agreement with the recently published in vivo data. PMID:24647649

Irastorza, Ramiro M; Blangino, Eugenia; Carlevaro, Carlos M; Vericat, Fernando

2014-05-01

387

Dielectric properties and electronic absorption: a comparison of novel azo- and oxo-bridged phthalocyanines.  

PubMed

The novel two homologous phthalocyanine (Pc) series (azo- and oxo-bridged) substituted with a 5-bromo-2-methoxyphenyl moiety were synthesized and characterized. The physical and chemical properties of the Pcs were compared with each other for the first time. The ac response of the Pcs was also studied by impedance measurements over a temperature range of 300-500 K. The real and imaginary parts of the impedance were found to be dependent on both frequency and temperature. The impedance spectra of the samples displayed semicircular arcs in the complex plane plot at all temperatures, with their centres lying below the real axis at a particular angle of depression indicating the distribution of relaxation times. Measurements showed that the dielectric permittivity of azo-bridged phthalocyanines is significantly higher than that of the oxo-bridged homologs. This result can be attributed to the limited electron delocalization ability of oxo-bridged homologs. PMID:25425444

Merve Yüzüak, M; Altun, Selçuk; Alt?ndal, Ahmet; Odaba?, Zafer

2015-01-21

388

Grain size effect on the nonlinear dielectric properties of barium titanate ceramics  

SciTech Connect

The nonlinear dielectric properties of dense BaTiO{sub 3} ceramics with grain size of 1 {mu}m-90 nm were investigated. In the finest ceramics, the permittivity reduces below 1000 and a remarkable nonhysteretic linear dc-tunability [{epsilon}(E)] is obtained at high field, above 40 kV/cm. The observed behavior was explained by considering the nanostructured ceramic as a composite formed by ferroelectric grains, whose nonlinearity is reducing, and by low-permittivity nonferroelectric grain boundaries, whose volume fraction increases when decreasing the grain size. Reducing the grain size in ferroelectric dense materials is an alternative route to accomplish the application requirements: nonhysteretic tunability and permittivity below 1000.

Curecheriu, Lavinia; Mitoseriu, Liliana [Department of Physics, Alexandru Ioan Cuza University, Bv. Carol I No. 11, Iasi 700506 (Romania); Buscaglia, Maria Teresa; Buscaglia, Vincenzo [Institute of Energetics and Interphases (IENI)-CNR, Via De Marini No. 6, I-16149 Genoa (Italy); Zhao, Zhe [Department of Materials and Environmental Chemistry, University of Stockholm, SE-10691 Stockholm (Sweden)

2010-12-13

389

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

390

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.

391

Comparison of dielectric properties between epoxy composites with nanosized clay fillers modified by primary amine and tertiary amine  

Microsoft Academic Search

Epoxy-based nanocomposites (NCs) were prepared using clay modified by either primary amine or tertiary amine, and the effect of the difference in modifier on the thermal and dielectric properties of the NCs were discussed. The NC with clay fillers modified by the primary amine, 1C, shows a glass transition end temperature (Teg) at a temperature 20°C lower than the neat

N. Tagami; M. Hyuga; Y. Ohki; T. Tanaka; T. Imai; M. Harada; M. Ochi

2010-01-01

392

Characterization and Properties of Electroless Nickel Plated Poly (ethylene terephthalate) Nonwoven Fabric Enhanced by Dielectric Barrier Discharge Plasma Pretreatment  

Microsoft Academic Search

In order to develop a more economical pretreatment method for electroless nickel plating, a dielectric barrier discharge (DBD) plasma at atmospheric pressure was used to improve the hydrophilicity and adhesion of poly (ethylene terephthalate) (PET) nonwoven fabric. The properties of the PET nonwoven fabric including its liquid absorptive capacity (WA), aging behavior, surface chemical composition, morphology of the surface, adhesion

Yamin Geng; Canhui Lu; Mei Liang; Wei Zhang

2010-01-01

393

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

394

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...

395

SiO2 stishovite under high pressure: Dielectric and dynamical properties and the ferroelastic phase transition  

E-print Network

SiO2 stishovite under high pressure: Dielectric and dynamical properties and the ferroelastic phase abundant elements, is about 50 GPa. Therefore, knowledge of the high-pressure behavior of SiO2, therefore- mentally. High-pressure x-ray diffraction data12 and the pres- sure dependence of infrared7 and Raman13

Oganov, Artem R.

396

Application of the discontinuous Galerkin time domain method in the simulation of the optical properties of dielectric particles  

E-print Network

A Discontinuous Galerkin Time Domain method (DGTD), using a fourth order Runge-Kutta time-stepping of Maxwell's equations, was applied to the simulation of the optical properties of dielectric particles in two-dimensional (2-D) geometry. As examples...

Tang, Guanglin

2012-07-16

397

Optical Properties of Ultrathin Films: Evidence for a Dielectric Anomaly at the Insulator-to-Metal Transition  

E-print Network

The insulator-to-metal (I=M) and insulator-to- superconductor (I=S) transitions are fundamental issues in modernOptical Properties of Ultrathin Films: Evidence for a Dielectric Anomaly at the Insulator-to-Metal Transition J. J. Tu,* C. C. Homes, and M. Strongin Department of Physics, Brookhaven National Laboratory

Lombardi, John R.

398

Formation and Dielectric Properties of Polyelectrolyte Multilayers Studied by a Silicon-on-Insulator Based Thin Film Resistor  

E-print Network

Formation and Dielectric Properties of Polyelectrolyte Multilayers Studied by a Silicon multilayers (PEMs) is investigated using a silicon-on-insulator based thin film resistor which is sensitive constants of the polyelectrolyte films and in the concentration of mobile ions within the films can

Bausch, Andreas

399

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

E-print Network

, dielectrical, optical and magnetic properties. Therefore, various structural PNCs with different that the morphology of the nanofiller has a significant effect on the crystallization behavior of the PANI during the nanofillers and polymer matrix. The mechanism of the SIP method is also elaborated in this work. 1

Guo, John Zhanhu

400

Role of fiber\\/matrix interphases on dielectric, friction, and mechanical properties of glass fiber-reinforced epoxy composites  

Microsoft Academic Search

This study compares the mechanical, tribological, and dielectric properties of glass fiber-reinforced epoxy (GFRE), presenting various fiber\\/matrix adhesions. Three GFRE composites were studied. The only difference between them is in the initial preparation of fibers which is intentionally simplified compared to the complex sizings used in industry. Thus, fibers treated with aminosilane or silicone coupling agents were compared with fibers

B. Kechaou; M. Salvia; K. Benzarti; C. Turki; Z. Fakhfakh; D. Tréheux

2012-01-01

401

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

402

Static properties of small Josephson tunnel junctions in an oblique magnetic field  

NASA Astrophysics Data System (ADS)

We have carried out a detailed experimental investigation of the static properties of planar Josephson tunnel junctions in presence of a uniform external magnetic field applied in an arbitrary orientation with respect to the barrier plane. We considered annular junctions, as well as rectangular junctions (having both overlap and cross-type geometries) with different barrier aspect ratios. It is shown how most of the experimental findings in an oblique field can be reproduced invoking the superposition principle to combine the classical behavior of electrically small junctions in an in-plane field together with the small junction behavior in a transverse field that we recently published [R. Monaco , J. Appl. Phys. 104, 023906 (2008)]. We show that the presence of a transverse field may have important consequences, which could be either voluntarily exploited in applications or present an unwanted perturbation.

Monaco, R.; Aaroe, M.; Mygind, J.; Koshelets, V. P.

2009-04-01

403

Non-linear optical properties of molecular systems under high static pressures  

NASA Astrophysics Data System (ADS)

Applied static pressure can largely modify the structure and dynamics of molecular systems, with consequences on their optical properties and chemical stability. When photochemical effects are exploited in conjunction with the structural and dynamical conditions attained at high density, chemical reactivity may become highly selective and efficient, yielding technologically attractive products. Non-linear optical spectroscopies are a powerful tool to investigate molecular energetics and dynamics, and thus unveil key aspects of the chemical reactivity at a molecular level. Their application to high-pressure samples is experimentally challenging, mainly because of the small sample dimensions and the non-linear effects generated in the anvil materials. In this paper we review the main results on the behavior of electronic states at high pressure, obtained by non-linear optical techniques, discussing the relationship between pressure-induced structural modifications and chemical reactivity, and the state of the art of ongoing research.

Citroni, M.; Fanetti, S.; Foggi, P.; Bini, R.

2014-05-01

404

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

PubMed Central

The measurement of viscoelasticity of cells in physiological environments with high spatio-temporal resolution is a key goal in cell mechanobiology. Traditionally only the elastic properties have been measured from quasi-static force-distance curves using the atomic force microscope (AFM). Recently, dynamic AFM-based methods have been proposed to map the local in vitro viscoelastic properties of living cells with nanoscale resolution. However, the differences in viscoelastic properties estimated from such dynamic and traditional quasi-static techniques are poorly understood. In this work we quantitatively reconstruct the local force and dissipation gradients (viscoelasticity) on live fibroblast cells in buffer solutions using Lorentz force excited cantilevers and present a careful comparison between mechanical properties (local stiffness and damping) extracted using dynamic and quasi-static force spectroscopy methods. The results highlight the dependence of measured viscoelastic properties on both the frequency at which the chosen technique operates as well as the interactions with subcellular components beyond certain indentation depth, both of which are responsible for differences between the viscoelasticity property maps acquired using the dynamic AFM method against the quasi-static measurements. PMID:24606928

Cartagena, Alexander; Raman, Arvind

2014-01-01

405

Laboratory measurements of dielectric properties of compact and granular materials, in relation with Rosetta mission.  

NASA Astrophysics Data System (ADS)

The European Rosetta spacecraft (s/c), launched in 2004, will be the first s/c to orbit a comet and place a lander module on its surface. In 2014, the s/c will rendezvous with the comet 67P/Churyumov-Gerasimenko and place the lander on its surface thereby allowing in situ and remote sensing of the comet nucleus. Two radio experiments, one passive (MIRO [1]) and one active (CONSERT [2]), are aboard the Rosetta s/c. MIRO, composed of two radiometers, with center band frequencies at 190 GHz and at 563 GHz to determine the brightness temperatures of the target surfaces and sub-surfaces, has already observed asteroids (2867) Steins [3] and (21) Lutetia [4]. CONSERT will investigate the deep interior of the nucleus using 90 MHz radio-waves transmitted from the orbiter through the nucleus and returned to the orbiter from the lander. To support interpretations of MIRO and CONSERT observations, a program of dielectric properties measurements is under development on a large range of frequencies encompassing those of the above-mentioned experiments. Several instruments for dielectric constant determination are available at IMS laboratory (Bordeaux, France): impedance analyzer, coaxial sensor, resonant cavities (measuring respectively at 100 MHz, 0.5-6 GHz, 1.2-13.4 GHz). Millimeter benches are available at both IMS and LERMA laboratories (measuring respectively at 30-110 GHz and 70-230 GHz). Taking into account the possible presence of regolith layers on the surface of asteroids or nuclei and the very low density of cometary nuclei [5], the dependence of the dielectric constant on the structure and porosity of given granular materials needs also to be investigated (while the thermal and hygrometric conditions are carefully monitored). We have already reported measurements obtained on various meteorites, possibly representative of some asteroid surfaces [6, 7]. We will also report systematic measurements obtained on a large sample of pyroclastic deposits from Etna, providing different sizes distributions (i.e. surface to volume ratios), and possibly porosities. Dielectric constant determination at 190 GHz typically suggests that the real part of dielectric constant slowly increases with grain size: 2.86 ± 0.06, 2.96 ± 0.02 and 3.13 ± 0.05 for sizes respectively lower than 50 µm, between 50 and 160 µm and between 160 and 355 µm. Additional series of measurements on compact and granular samples of meteoritic analogues, such as carbonaceous chondrites are also to take place. [1] Gulkis et al. , Space Sci. Rev., 128, 561-597, 2007. [2] Kofman et al. , Space Sci. Rev., 128, 413-432, 2007. [3] Gulkis et al. , Space. Sci. Rev., 58, 1077-1087, 2010. [4] Gulkis et al. , Space. Sci. Rev., doi: 10.1016/j.pss.2011.12.004, 2011. [5] Levasseur-Regourd et al. , Planet. Space Sci., 57, 221-228, 2009. [6] McFadden et al., 40th LPSC, 2887, 2009. [7] Brouet el al. , EPSC-DPS Joint Meeting, p. 1083, 2011.

Brouet, Y.; Levasseur-Regourd, A. C.; Encrenaz, P.; Gheudin, M.; Ciarletti, V.; Gulkis, S.; Jambon, A.; Ruffié, G.; Prigent, C.

2012-04-01

406

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

407

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

408

Average Dielectric Property Analysis of Complex Breast Tissue with Microwave Transmission Measurements  

PubMed Central

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

409

Application of a discontinuous Galerkin time domain method to simulation of optical properties of dielectric particles.  

PubMed

We applied a discontinuous Galerkin time domain (DGTD) method, using a fourth-order Runga-Kutta time stepping of the Maxwell equations, to the simulation of the optical properties of dielectric particles in two-dimensional (2D) geometry. As examples of the numerical implementation of this method, the single-scattering properties of 2D circular and hexagonal particles are presented. In the case of circular particles, the scattering phase matrix was computed using the DGTD method and compared with the exact solution. For hexagonal particles, the DGTD method was used to compute single-scattering properties of randomly oriented 2D hexagonal ice crystals, and results were compared with those calculated using a geometric optics method. We consider both shortwave (visible) and longwave (infrared) cases, with particle size parameters 50 and 100. In the hexagonal case, scattering results are also presented as a function of both incident and scattering angles, revealing a structure apparently not reported before. Using the geometric optics method, we are able to interpret this structure in terms of contributions from varying numbers of internal reflections within the crystal. PMID:20490244

Tang, Guanglin; Panetta, R Lee; Yang, Ping

2010-05-20

410

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

SciTech Connect

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

Echtermeyer, A.T.; McGeorge, D.; Buene, L. [Det Norske Veritas Research, Hoevik (Norway)

1993-12-31

411

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

412

Property and Lighting Manipulations for Static Volume Stylization Using a Painting Metaphor.  

PubMed

Although volumetric phenomena are important for realistic rendering and can even be a crucial component in the image, the artistic control of the volume's appearance is challenging. Appropriate tools to edit volume properties are missing, which can make it necessary to use simulation results directly. Alternatively, high-level modifications that are rarely intuitive, e.g., the tweaking of noise function parameters, can be utilized. Our work introduces a solution to stylize single-scattering volumetric effects in static volumes. Hereby, an artistic and intuitive control of emission, scattering and extinction becomes possible, while ensuring a smooth and coherent appearance when changing the viewpoint. Our method is based on tomographic reconstruction, which we link to the volumetric rendering equation. It analyzes a number of target views provided by the artist and adapts the volume properties to match the appearance for the given perspectives. Additionally, we describe how we can optimize for the environmental lighting to match a desired scene appearance, while keeping volume properties constant. Finally, both techniques can be combined. We demonstrate several use cases of our approach and illustrate its effectiveness. PMID:24636982

Klehm, Oliver; Ihrke, Ivo; Seidel, Hans-Peter; Eisemann, Elmar

2014-03-12

413

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

414

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

2015-04-01

415

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

416

Improving the dielectric and piezoelectric properties of screen-printed Low temperature PZT/polymer composite using cold isostatic pressing  

NASA Astrophysics Data System (ADS)

This paper reports an improvement in dielectric and piezoelectric properties of screen-printed PZT/polymer films for flexible electronics applications using Cold Isostatic Pressing (CIP). The investigation involved half and fully cured PZT/polymer composite pastes with weight ratio of 12:1 to investigate the effect of the CIP process on the piezoelectric and dielectric properties. It was observed that the highest dielectric and piezoelectric properties are achieved at pressures of 5 and 10 MPa for half and fully cured films respectively. The relative dielectric constants were 300 and 245 measured at 1 kHz for the half and fully cured samples. Using unoptimised poling conditions, the initial d33 values were 30 and 35 pC/N for the half and fully cured films, respectively. The fully cured sample was then poled using optimized conditions and demonstrated a d33 of approximately 44 pC/N which is an increase of 7% compared with non-CIP processed materials.

Almusallam, A.; Yang, K.; Cao, Z.; Zhu, D.; Tudor, J.; Beeby, S. P.

2014-11-01

417

Dielectric and Nonohmic Properties of CaCu3Ti4O12/SrTiO3 Ceramics  

NASA Astrophysics Data System (ADS)

In this work, (1 - x)CaCu3Ti4O12- xSrTiO3 [(1 - x)CCTO/ xST, x = 0% to 2%] ceramic samples were prepared by the solid-state reaction method. The dielectric and electrical properties of CaCu3Ti4O12 (CCTO) and CaCu3Ti4O12/SrTiO3 (CCTO/ST) ceramics were investigated. The results show that a small amount of Sr2+ can enter the lattice of CCTO. The mean grain size of the ceramic samples increased greatly for x = 0.5% and then decreased for x = 0.75% to 2%. ST addition and Sr2+ preferential occupancy in CCTO grains should be responsible for the change of the microstructure. Interestingly, the dielectric constant ( ?) of the 0.5% ST-added sample increased significantly while the dielectric loss (tan ?) remained low. With further increase of the ST content, the ? and tan ? values of the CCTO ceramics decreased monotonically while the nonlinear current-voltage properties were significantly enhanced. The change in the potential barrier height is thought to be the main cause for the opposite behaviors in the dielectric properties and nonohmic characteristics.

Xue, Renzhong; Liu, Dewei; Chen, Zhenping; Dai, Haiyang; Chen, Jing; Zhao, Gaoyang

2015-04-01

418

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

419

Enhanced dielectric properties of BaTiO3/poly(vinylidene fluoride) nanocomposites for energy storage applications  

NASA Astrophysics Data System (ADS)

In this work, homogeneous ceramics-polymer nanocomposites consisting of surface treated BaTiO3 (BT) particles as fillers and poly(vinylidene fluoride) polymer as matrix have been prepared using a solution casting process. The nanocomposites exhibit enhanced dielectric permittivity and reduced loss tangent. The frequency and temperature dependencies of the dielectric permittivity and loss tangent of the nanocomposites suggest that the introduced BT phase and interface areas contribute to the improvement of the dielectric responses. Meanwhile, the X-ray diffraction patterns and Differential Scanning Calorimetry (DSC) curves indicate that the incorporation of ceramic particles contributes to the decrease of the crystallite size, the increase of the crystallinity, and the shift of the crystallization temperature of the polymer matrix. Furthermore, the dielectric displacement and energy density of the nanocomposites are significantly enhanced and an energy density of 3.54 J/cm3 was obtained under an electric field of 200 MV/m with the BT concentration of 20 vol. %. The results indicate that the introduced ceramic fillers and interface areas have positive influences on the structure of the polymer matrix and contribute to the enhancement of the dielectric responses and energy storage properties of the nanocomposites.

Yu, Ke; Wang, Hong; Zhou, Yongcun; Bai, Yuanyuan; Niu, Yujuan

2013-01-01

420

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

421

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

422

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

423

Correlation between structural, magnetic, and dielectric properties of manganese substituted cobalt ferrite  

NASA Astrophysics Data System (ADS)

Manganese (Mn) substituted cobalt ferrites (CoFe2-xMnxO4, referred to CFMO) were synthesized and their structural, magnetic, and dielectric properties were evaluated. X-ray diffraction measurements coupled with Rietveld refinement indicate that the CFMO materials crystallize in the inverse cubic spinel phase. Temperature (T = 300 K and 10 K) dependent magnetization (M(H)) measurements indicate the long range ferromagnetic ordering in CoFe2-xMnxO4 (x = 0.00-0.15) ferrites. The cubic anisotropy constant (K1(T)) and saturation magnetization (Ms(T)) were derived by using the "law of approach" to saturation that describes the field dependence of M(H) for magnetic fields much higher than the coercive field (Hc). Saturation magnetization (Ms), obtained from the model, decreases with increasing temperature. For CoFe2O4, Ms decreases from 3.63 ?B per formula unit (f.u.) to 3.47 ?B/f.u. with increasing temperature from 10 to 300 K. CFMO (0.00-0.15) exhibit the similar trend while the magnitude of Ms is dependent on Mn-concentration. Ms-T functional relationship obeys the Bloch's law. The lattice parameter and magnetic moment calculated for CFMO reveals that Mn ions occupying the Fe and Co position at the octahedral site in the inverse cubic spinel phase. The structure and magnetism in CFMO are further corroborated by bond length and bond angle calculations. The dielectric constant dispersion of CFMO in the frequency range of 20 Hz-1 MHz fits to the modified Debye's function with more than one ion contributing to the relaxation. The relaxation time and spread factor derived from modeling the experimental data are ˜10-4 s and ˜0.35(±0.05), respectively.

Ramana, C. V.; Kolekar, Y. D.; Kamala Bharathi, K.; Sinha, B.; Ghosh, K.

2013-11-01

424

Mechanical property changes in porous low-k dielectric thin films during processing  

NASA Astrophysics Data System (ADS)

The design of future generations of Cu-low-k dielectric interconnects with reduced electronic crosstalk often requires engineering materials with an optimal trade off between their dielectric constant and elastic modulus. This is because the benefits associated with the reduction of the dielectric constant by increasing the porosity of materials, for example, can adversely affect their mechanical integrity during processing. By using load-dependent contact-resonance atomic force microscopy, the changes in the elastic modulus of low-k dielectric materials due to processing were accurately measured. These changes were linked to alterations sustained by the structure of low-k dielectric films during processing. A two-phase model was used for quantitative assessments of the elastic modulus changes undergone by the organosilicate skeleton of the structure of porous and pore-filled dielectrics.

Stan, G.; Gates, R. S.; Kavuri, P.; Torres, J.; Michalak, D.; Ege, C.; Bielefeld, J.; King, S. W.

2014-10-01

425

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

PubMed

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

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

2014-10-01

426

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.

427

Dielectric properties in heteroepitaxial Ba0.6Sr0.4TiO3 thin films: Effect of internal stresses and dislocation-type defects  

E-print Network

Dielectric properties in heteroepitaxial Ba0.6Sr0.4TiO3 thin films: Effect of internal stresses and dislocation-type defects C. L. Canedy, Hao Li,a) S. P. Alpay, L. Salamanca-Riba, A. L. Roytburd, and R. Ramesh out-of-plane lattice parameter. The low-frequency dielectric constant was measured to be significantly

Alpay, S. Pamir

428

Effect of splat morphology on the microstructure and dielectric properties of plasma sprayed barium titanate films  

NASA Astrophysics Data System (ADS)

In the thermal spray process, the film is built up by impingement of molten droplets onto substrate. Splats are created by flattening and spreading of the impacting droplets. Splat morphology can determine the microstructure, physical and mechanical properties of the coating. In this study, BaTiO3 films were deposited onto a mirror polished stainless steel substrates kept at three different temperatures (25, 300 and 600 °C). At the elevated temperatures, the substrate surface topography and the desorbtion of adsorbates and condensate at the substrate surface are two important factors which change the morphology of the individual splats, from splash morphology to disk-like shape. Splat morphology can determine deposit microstructure and improve the coating properties. The morphology of individual splats and the films were studied using scanning electron microscopy. Phase formation of the films was analyzed by X-ray diffraction. The surface topography of the substrates with different temperatures was analyzed using atomic force microscopy. Furthermore, X-ray photoelectron spectroscopy was performed to determine the chemical compositions of the surface substrate. Results indicated that the porosity in the film produced at room temperature was higher than that in the film deposited on the heated substrates. Also, the dielectric coefficient of the films was increased by decreasing the common defects from 120 to 505 for film deposited on as-received and heated substrates, respectively.

Pakseresht, A. H.; Rahimipour, M. R.; Vaezi, M. R.; Salehi, M.

2015-01-01

429

Room temperature magnetic and dielectric properties of cobalt doped CaCu3Ti4O12 ceramics  

NASA Astrophysics Data System (ADS)

CaCu3Ti4-xCoxO12 (x = 0, 0.2, 0.4) ceramics were prepared by a conventional solid state reaction, and the effects of cobalt doping on the room temperature magnetic and dielectric properties were investigated. Both X-ray diffraction and energy dispersive X-ray spectroscopy confirmed the presence of Cu and Co rich phase at grain boundaries of Co-doped ceramics. Scanning electron microscopy micrographs of Co-doped samples showed a striking change from regular polyhedral particle type in pure CaCu3Ti4O12 (CCTO) to sheet-like grains with certain growth orientation. Undoped CaCu3Ti4O12 is well known for its colossal dielectric constant in a broad temperature and frequency range. The dielectric constant value was slightly changed by 5 at. % and 10 at. % Co doping, whereas the second relaxation process was clearly separated in low frequency region at room temperature. A multirelaxation mechanism was proposed to be the origin of the colossal dielectric constant. In addition, the permeability spectra measurements indicated Co-doped CCTO with good magnetic properties, showing the initial permeability (?') as high as 5.5 and low magnetic loss (?? < 0.2) below 3 MHz. And the interesting ferromagnetic superexchange coupling in Co-doped CaCu3Ti4O12 was discussed.

Mu, Chunhong; Song, Yuanqiang; Wang, Haibin; Wang, Xiaoning

2015-05-01

430

Selective substitution and tetragonality by Co-doping of dysprosium and thulium on dielectric properties of barium titanate ceramics  

NASA Astrophysics Data System (ADS)

Barium titanate (BaTiO3) ceramics co-doped with rare-earth elements were investigated in terms of selective substitution and tetragonality. The dielectrics were designed by addition of various Dy2O3 and Tm2O3 contents, for a total of 1 mol. % concentration, and analyzed in a temperature range from -55°C to 150°C. The dielectric constant of the 0.7 mol. % Dy2O3 and the 0.3 mol. % Tm2O3 co-doped BaTiO3 was 2250, which was about 27% higher than those of specimens doped with 1 mol. % Tm2O3 and 1 mol. % Dy2O3 at room temperature. The tendency of dielectric properties was verified through the changes of lattice parameters and binding energy. The substitution of Dy3+ led to a decrease of tetragonality and grain growth; however, amphoteric substitution caused by the co-doping of Dy2O3 and Tm2O3 compensated for those adverse effects. It can be concluded that the improvement of dielectric properties originated from the increase of the site substitution rate of Dy3+ and Tm3+ ions according to the ionic size the in rare-earth doped BaTiO3 system.

Kim, Jungdae; Kim, Dowan; Kim, Jinseong; Kim, Yong-Nam; Hui, K. N.; Lee, Heesoo

2011-06-01

431

Multi-susceptibile Single-Phased Ceramics with Both Considerable Magnetic and Dielectric Properties by Selectively Doping  

PubMed Central

Multiferroic ceramics with extraordinary susceptibilities coexisting are vitally important for the multi-functionality and integration of electronic devices. However, multiferroic composites, as the most potential candidates, will introduce inevitable interface deficiencies and thus dielectric loss from dissimilar phases. In this study, single-phased ferrite ceramics with considerable magnetic and dielectric performances appearing simultaneously were fabricated by doping target ions in higher valence than that of Fe3+, such as Ti4+, Nb5+ and Zr4+, into BaFe12O19. In terms of charge balance, Fe3+/Fe2+ pair dipoles are produced through the substitution of Fe3+ by high-valenced ions. The electron hopping between Fe3+ and Fe2+ ions results in colossal permittivity. Whilst the single-phased ceramics doped by target ions exhibit low dielectric loss naturally due to the diminishment of interfacial polarization and still maintain typical magnetic properties. This study provides a convenient method to attain practicable materials with both outstanding magnetic and dielectric properties, which may be of interest to integration and multi-functionality of electronic devices. PMID:25835175

Liu, Chuyang; Zhang, Yujing; Jia, Jingguo; Sui, Qiang; Ma, Ning; Du, Piyi

2015-01-01

432

Multi-susceptibile Single-Phased Ceramics with Both Considerable Magnetic and Dielectric Properties by Selectively Doping.  

PubMed

Multiferroic ceramics with extraordinary susceptibilities coexisting are vitally important for the multi-functionality and integration of electronic devices. However, multiferroic composites, as the most potential candidates, will introduce inevitable interface deficiencies and thus dielectric loss from dissimilar phases. In this study, single-phased ferrite ceramics with considerable magnetic and dielectric performances appearing simultaneously were fabricated by doping target ions in higher valence than that of Fe(3+), such as Ti(4+), Nb(5+) and Zr(4+), into BaFe12O19. In terms of charge balance, Fe(3+)/Fe(2+) pair dipoles are produced through the substitution of Fe(3+) by high-valenced ions. The electron hopping between Fe(3+) and Fe(2+) ions results in colossal permittivity. Whilst the single-phased ceramics doped by target ions exhibit low dielectric loss naturally due to the diminishment of interfacial polarization and still maintain typical magnetic properties. This study provides a convenient method to attain practicable materials with both outstanding magnetic and dielectric properties, which may be of interest to integration and multi-functionality of electronic devices. PMID:25835175

Liu, Chuyang; Zhang, Yujing; Jia, Jingguo; Sui, Qiang; Ma, Ning; Du, Piyi

2015-01-01

433

Origins of enhanced dielectric properties in titania-modified tantalum pentoxide ceramics  

NASA Astrophysics Data System (ADS)

Tantalum oxide (Ta2O5)-based materials are of interest for various applications, including dynamic random access memories (DRAMS) and thermal and environmental barrier coatings (TBCs, EBCs). Widespread use, however, has been limited due to practical difficulties in densification of ceramic forms, and a lack of basic understanding of structure-processing-property relationships for Ta2O5-based ceramics. The current research was designed to investigate these relationships and to determine the origins of a previously reported dielectric enhancement for TiO2 -modified Ta2O5. Rapid and expansive grain growth associated with the L?H-Ta 2O5 phase transformation was found to trap residual porosity, so sintering at temperatures below the transformation was required for full densification. A simple and effective solution-coated powder processing route was developed to enable reduced-temperature densification of chemically-homogeneous TiO2-modified H-Ta2O5 ceramics for the first time. A new crystal structure of H-Ta2O5 based upon extensive polyhedral edge-sharing was verified using high-resolution X-ray diffraction at the Advanced Photon Source. Simulated diffraction patterns matched data collected at up to 1500°C out to 2theta values equivalent to 110° (CuKalpha). In-situ XRD and Raman studies both revealed two distinct phase transformations during cooling from the high-temperature prototypic phase for specimens containing ?5% TiO2, but only one transformation for specimens containing 8% TiO2, and revealed that the H-Ta2O5 form present at room temperature depended strongly upon TiO2 content. Dense and homogeneous specimens enabled the first detailed investigation into the electrical properties of TiO2-modified H-Ta2O 5 ceramics. Specimens containing 8% TiO2 exhibited dielectric constant (K) values of ˜280 at 20°C with tan delta values ˜0.01, but undoped specimens had tan delta values of ˜0.10 and DC resistivity values of <1011O·cm. Hyper-Raman spectroscopy revealed that the ionic polarizability (and thus the intrinsic K) of H-Ta 2O5 ceramics was independent of TiO2 content. Cryogenic electrical measurements suggested that the structural K ? 70-80, and showed that enhanced K values resulted from localized carriers related to compensation for deviations from the fully-edge-shared 89Ta2O 5-11TiO2 composition.

Brennecka, Geoffrey Lee

434

Dielectric Critical Slowing-Down in Hydrogen-Bonded Ferroelectrics: PbHPO4 and PbDPO4  

NASA Astrophysics Data System (ADS)

Complex dielectric constants of PbHPO4 and PbDPO4 have been studied at frequencies from 103 Hz to 109 Hz in the Curie temperature region. The Curie-Weiss behavior of the low-frequency dielectric constant is confirmed. The dielectric dispersion of the Debye type which shows a critical slowing-down has been observed in both materials. The phase transition is considered to be of an order-disorder type. The effects of deuteration in the static and dynamic dielectric properties are discussed.

Deguchi, Kiyoshi; Nakamura, Eiji

1988-02-01

435

The role of fabric in the quasi-static compressive mechanical properties of human trabecular bone from various anatomical locations  

Microsoft Academic Search

Osteoporosis leads to an increased risk of bone fracture. While bone density and architecture can be assessed in vivo with\\u000a increasing accuracy using CT and MRI, their relationship with the critical mechanical properties at various anatomical sites\\u000a remain unclear. The objective of this study was to quantify the quasi-static compressive mechanical properties of human trabecular\\u000a bone among different skeletal sites

Maiko Matsuura; Felix Eckstein; Eva-Maria Lochmüller; Philippe K. Zysset

2008-01-01

436

Microwave dielectric properties of ground and whole-muscle chicken meat and correlations with quality attributes  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dielectric spectra of whole-muscle and ground chicken meat samples were obtained with an open-ended coaxial-line probe between 0.5 GHz and 50 GHz at 23 oC. The spectra show a dielectric behavior consistent with that expected for materials with high water content with differences between the whole-mu...

437

Influence of dielectric core, embedding medium and size on the optical properties of gold nanoshells  

Microsoft Academic Search

The amplitudes of the dipole and quadrupole modes for gold nanoshells have been investigated with various dielectric constants for the core and the embedding medium and with various size of the nanoshells by means of Mie theory. With the increase in the dielectric constant of the core, it is found that the strengths of dipole and quadrupole modes become weak.

DaJian Wu; XiaoDong Xu; XiaoJun Liu

2008-01-01

438

Effects of bead-bead interactions on the static and dynamical properties of model polymer solutions  

NASA Astrophysics Data System (ADS)

The effects of segment-segment interactions on the static and dynamical properties of model polymer solutions are examined by Brownian dynamics simulations in the free-draining limit over a wide concentration range. A bead-and-spring model is used to describe the polymer chains at a coarse-grained level, in which segment-segment interactions are represented by a bead-bead pair potential with a Gaussian analytic form, ?uev(r)=A exp(-r2/2?2), where ?=1/kBT and A and ? are characteristic energy and distance scales, respectively. The chain dimensions, self-diffusion coefficient, and viscosity of the systems are studied as functions of number density of beads of the system, ?, at given excluded-volume potential parameters, A and ?. Our results show that in the limit of infinite dilution even for short chains (N~10) there is statistically significant scaling behavior in the static and dynamical properties. For a system with given values of A and ? the change in polymer coil size shows a realistic trend as the concentration of the system increases. In the dilute and concentrated regions the coil size decreases as a result of increasing interchain repulsions, while in the highly concentrated region the coil size increases again, showing a return to Rouse-like behavior because the intrapolymer and interpolymer segment-segment interactions become effectively indistinguishable for an arbitrary bead and to a large extent are ``balanced out.'' In the limit of infinite dilution, the self-diffusion coefficient of the center of mass, Dcm, depends on N only and not on the potential parameter A, while in contrast the specific viscosity ?sp depends on both N and A. As the concentration increases Dcm decreases and ?sp increases consistent with the behavior of real polymers. When the system becomes highly concentrated, however, both Dcm and ?sp unrealistically return to the Rouse limit. This suggests that from the concentrated region upward in concentration, the entanglement or the topological constraints caused by the physical connectivity of the chains significantly influence their dynamical behavior. The mean-field segment-segment interactions or excluded-volume effects incorporated in the current coarse-grained bead-spring approach cannot capture this entanglement effect, and therefore give rise to unrealistic dynamical behavior in the concentrated regime.

Xiao, C.; Heyes, D. M.

1999-11-01

439

Zirconia doped barium titanate induced electroactive ? polymorph in PVDF-HFP: high energy density and dielectric properties  

NASA Astrophysics Data System (ADS)

Zirconium-doped barium titanate (BZT-08, Ba(Ti0.92 Zr0.08)O3) particles were synthesized and PVDF-HFP-based composites were prepared by melt mixing to design materials with tunable dielectric and ferroelectric properties. Composites of PVDF-HFP and barium titanate (BT) particles were also prepared to realize the exceptional properties associated with the BZT-08-like stabilization of two ferroelectric phases, i.e. tetragonal and orthorhombic at room temperature. To facilitate the uniform dispersion and interfacial adhesion with the matrix, the particles were modified with (3-aminopropyl) triethoxysilane. The dependence of the dielectric and ferroelectric properties of the as-prepared composites were systematically investigated in this study with respect to a wide range of frequencies. The composites with BZT-08 exhibited the significantly high dielectric permittivity of ca. 26 (at 100 Hz) and a high energy density (2.7 J cm?3 measured on 100 ?m thick film) at room temperature with respect to the control PVDF-HFP and PVDF-HFP/BT composites. Interestingly, the BZT-08 particles facilitated the electroactive ? polymorph in the PVDF-HFP and enhanced polarization in the composites, leading to improved ferroelectric properties in the composites.

Sharma, Maya; Ranganatha, S.; Kalyani, Ajay Kumar; Ranjan, Rajeev; Madras, Giridhar; Bose, Suryasarathi

2014-12-01

440

Low-?' dielectric properties of UV-treated bi-axially oriented polypropylene films  

NASA Astrophysics Data System (ADS)

A 40 µm multilayer bi-axially oriented polypropylene (BOPP) film, was fabricated by the tenter process and its dielectric response was investigated after applying combined action of UV, humidity and heat. Dissipation factor (tan ?) and relative dielectric constant measurements were performed via the capacitance method for frequencies 20Hz-1 GHz. These results show that the relative dielectric constant (?') reduces towards ultra low values (1.8) with an increasing number of applied UV-condensation cycles without any subsequent increase in the dielectric loss. Having no added physical porosity and absence of fluorine atoms, the irradiated BOPP structures offer significant advantages over poly(tetrafluoroethylene) PTFE due to reduced polarization effects, lower dielectric constant values and chemical stability to the adjacent copper or aluminium conductors. Possible application fields are dry type high-voltage capacitors and insulation within electronic components.

Dervos, C. T.; Tarantili, P. A.; Athanassopoulou, M. D.

2009-07-01

441

Reflectivity (visible and near IR), Moessbauer, static magnetic, and X ray diffraction properties of aluminum-substituted hematites  

NASA Technical Reports Server (NTRS)

The effect of substituting iron by aluminum in polymorphs of Fe2O3 and FeOOH on their reflectivity characteristics was investigated by comparing data on visible and NIR reflectivities and on static magnetic, XRD, and Moessbauer properties for a family of aluminum-substituted hematites alpha-(Fe,Al)2O3, with compositions where the values of the Al/(Al+Fe) ratio were up to 0.61. Samples were prepared by oxidation of magnetite, dehydroxylation of goethite, and direct precipitation. The analytical methods used for obtaining diffuse reflectivity spectra (350-2200 nm), Moessbauer spectra, and static magnetic data are those described by Morris et al. (1989).

Morris, Richard V.; Schulze, Darrell G.; Lauer, Howard V., Jr.; Agresti, David G.; Shelfer, Tad D.

1992-01-01

442

Analysis of the static properties of cluster formations in symmetric linear multiblock This article has been downloaded from IOPscience. Please scroll down to see the full text article.  

E-print Network

Analysis of the static properties of cluster formations in symmetric linear multiblock copolymers. Phys.: Condens. Matter 23 (2011) 235106 (9pp) doi:10.1088/0953-8984/23/23/235106 Analysis of the static properties of cluster formations in symmetric linear multiblock copolymers N G Fytas1 and P E Theodorakis2

Theodorakis, Panagiotis E.

443

Improved dielectric properties of nanocomposites based on poly(vinylidene fluoride) and poly(vinyl alcohol)-functionalized graphene.  

PubMed

In this work, two series of nanocomposites of poly(vinylidene fluoride) (PVDF) incorporated with reduced graphene oxide (rGO) and poly(vinyl alcohol)-modified rGO (rGO-PVA) were fabricated using solution-cast method and their dielectric properties were carefully characterized. Infrared spectroscopy and atom force microscope analysis indicated that PVA chains were successfully grafted onto graphene through ester linkage. The PVA functionalization of graphene surface can not only prevent the agglomeration of original rGO but also enhance the interaction between PVDF and rGO-PVA. Strong hydrogen bonds and charge transfer effect between rGO-PVA and PVDF were determined by infrared and Raman spectroscopies. The dielectric properties of rGO-PVA/PVDF and rGO/PVDF nanocomposites were investigated in a frequency range from 10² Hz to 10? Hz. Both composite systems exhibited an insulator-to-conductor percolating transition as the increase of the filler content. The percolation thresholds were estimated to be 2.24 vol % for rGO-PVA/PVDF composites and 0.61 vol % for rGO/PVDF composites, respectively. Near the percolation threshold, the dielectric permittivity of the nanocomposites was significantly promoted, which can be well explained by interfacial polarization effect and microcapacitor model. Compared to rGO/PVDF composites, higher dielectric constant and lower loss factor were simultaneously achieved in rGO-PVA/PVDF nanocomposites at a frequency range lower than 1 × 10³ Hz. This work provides a potential design strategy based on graphene interface engineering, which would lead to higher-performance flexible dielectric materials. PMID:23110437

Wang, Dongrui; Bao, Yaru; Zha, Jun-Wei; Zhao, Jun; Dang, Zhi-Min; Hu, Guo-Hua

2012-11-01

444

Study on Ferroelectric and Dielectric Properties of La-Doped CaBi 4Ti 4O 15Based Ceramics  

Microsoft Academic Search

Lanthanum doped bismuth layer structured ferroelectrics (BLSFs) Ca1-xLaxBi4(Ti0.9W0.1)4O15(x = 0, 0.2. 0.3, 0.4, 0.6) ceramics were prepared by solid-state reaction method. X-ray diffraction (XRD) patterns showed that single phase was formed when x = 0 ? 0.6. The effects of La3+ doping on dielectric, piezoelectric and ferroelectric properties of Ca1-xLaxBi4(Ti0.9W0.1)4O15 ceramics were studied. Ca0.7La0.3Bi4(Ti0.9W0.1)4O15 ceramic had optimal properties, its dielectric

Xialian Zheng; Xinyou Huang; Chunhua Gao

2007-01-01

445

Temporal change in the electromechanical properties of dielectric elastomer minimum energy structures  

SciTech Connect

Dielectric elastomer minimum energy structures (DEMES) are soft electronic transducers and energy harvesters with potential for consumer goods. The temporal change in their electromechanical properties is of major importance for engineering tasks. Therefore, we study acrylic DEMES by impedance spectroscopy and by optical methods for a total time period of approx. 4.5 months. We apply either compliant electrodes from carbon black particles only or fluid electrodes from a mixture of carbon black particles and silicone oil. From the measurement data, the equivalent series capacitances and resistances as well as the bending angles of the transducers are obtained. We find that the equivalent series capacitances change in average between ?12?%/1000?h and ?4.0?%/1000?h, while the bending angles decrease linearly with slopes ranging from ?15?%/1000?h to ?7?%/1000?h. Transducers with high initial bending angles and electrodes from carbon black particles show the smallest changes of the electromechanical characteristics. The capacitances decrease faster for DEMES with fluid electrodes. Some DEMES of this type reveal huge and unpredictable fluctuations of the resistances over time due to the ageing of the contacts. Design guidelines for DEMES follow directly from the observed transient changes of their electromechanical performance.

Buchberger, G., E-mail: erda.buchberger@jku.at; Hauser, B.; Jakoby, B.; Hilber, W. [Institute for Microelectronics and Microsensors, Johannes Kepler University Linz, 4040 Linz (Austria); Schoeftner, J. [Institute of Technical Mechanics, Johannes Kepler University Linz, 4040 Linz (Austria); Bauer, S. [Department of Soft Matter Physics, Johannes Kepler University Linz, 4040 Linz (Austria)

2014-06-07

446

Assembling and compressing a semifluorinated alkane monolayer on a hydrophobic surface: Structural and dielectric properties  

SciTech Connect

We investigate the dynamic behavior upon lateral compression of a semifluorinated alkane F(CF{sub 2}){sub 8}(CH{sub 2}){sub 18}H (denoted F{sub 8}H{sub 18}), spread on the hydrophobic top of a suitable amphiphilic monolayer: namely, a natural {alpha}-helix alamethicin peptide (alam). We show, in particular, the formation of an asymmetric flat bilayer by compressing at the air-water interface a mixed Langmuir film made of F{sub 8}H{sub 18} and alam. The particular chemical structure of F{sub 8}H{sub 18}, the suitable structure of the underlying alam monolayer and its collapse properties, allow for a continuous compression of the upper F{sub 8}H{sub 18} monolayer while the density of the lower alam monolayer remains constant. Combining grazing incidence x-ray reflectivity, surface potential, and atomic force microscopy data allow for the determination of the orientation and dielectric constant of the upper F{sub 8}H{sub 18} monolayer.

El Abed, Abdel I.; Ionov, Radoslav; Daoud, Mohamed; Abillon, Olivier [Laboratoire de Neuro-Physique Cellulaire, Universite Rene Descartes, 45 rue des Saints-Peres, 75006 Paris (France); Laboratoire de Mecanique, Materiaux et Procedes, ESSTT, 5 Av. Taha Hussin, Tunis (Tunisia); Laboratoire de Physique Statistique, Ecole Normale Superieure, 24 rue Lhomond, 75005 Paris (France)

2004-11-01

447

Structural, magnetic, dielectric and optical properties of nickel ferrite nanoparticles synthesized by co-precipitation method  

NASA Astrophysics Data System (ADS)

Nickel ferrite nanoparticles were synthesized by wet chemical co-precipitation method and the corresponding temperature dependent structural, magnetic and optical properties of these nanoparticles have been investigated. X-ray diffraction patterns show the single phase cubic spinal crystal structure belonging to the space group Fd3m. The average crystallite size varies in the range 8-20 nm with varying sintering temperature. Raman spectroscopy exhibits a doublet-like peak behaviour which indicates the presence of mixed spinel structure. The saturation magnetization, coercivity and remanence increase with increasing sintering temperature from 250 to 550 °C. The non-saturation and low values of magnetization at high fields indicate the strong surface effects to magnetization in NiFe2O4 nanoparticles. The g-value calculated from electron spin resonance spectrum indicates the transfer of divalent metallic ion from octahedral to tetrahedral site (i.e. mixed spinel structure). The dielectric permittivity, loss tangent and ac conductivity measurements show strong temperature dependence at all frequencies. The observed ac conductivity response suggests that the conduction in ferrite nanoparticles is due to feeble polaron hopping between Fe3+/Fe2+ ions. Room temperature UV-vis diffuse spectra indicate that NiFe2O4 is an indirect band gap material with band gap ranges from 1.27 to 1.47 eV with varying sintering temperature. The photoluminescence study clearly indicates that the Ni2+ ions occupy both octahedral and tetrahedral sites confirming mixed spinel structure.

Joshi, Seema; Kumar, Manoj; Chhoker, Sandeep; Srivastava, Geetika; Jewariya, Mukesh; Singh, V. N.

2014-11-01

448

Optical properties and dielectric relaxation of polyvinylidene fluoride thin films doped with gadolinium chloride  

NASA Astrophysics Data System (ADS)

In this study, the properties of pure and GdCl3-doped polyvinylidene fluoride (PVDF) films were investigated. X-ray diffraction revealed that the PVDF was composed of mixed ? and ? phases. Adding GdCl3 to PVDF decreased the crystallinity of the polymer matrix. At room temperature, in the ultraviolet-visible range both the absorbance (a) and extinction coefficient (k) of PVDF decreased with GdCl3 content, demonstrating that the optical response of the doped films improved because of increasing optical energy gap (Eg). We also measured the dielectric loss (??), electric modulus (M?), and ac conductivity (?ac) at 300-450 K and 0.1-3000 kHz. The pure and doped PVDF exhibited different relaxation processes. The activation energy (Ea) of the ?c relaxation decreased with increasing GdCl3 content, following an Arrhenius relationship. The behavior of the ac conductivity revealed that the conduction mechanism for studied films followed correlated barrier hopping model. The hopping distance (R) was calculated at different temperatures for all investigated samples.