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1

Wave vector dependent static dielectric properties of associated liquids: Methanol  

Microsoft Academic Search

The static dielectric properties of liquid methanol and their wave vector dependence have been investigated using a molecular dynamics (MD) computer simulation and the reference hypernetted chain (RHNC) integral equation formalism. In the MD simulation we have used the site–site interaction model of methanol proposed by Haughney etal. [M. Haughney, M. Ferrario, and I.R. McDonald, J. Phys. Chem. 91, 4934

Teresa Fonseca; Branka M. Ladanyi

1990-01-01

2

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

3

Static polarizabilities of dielectric nanoclusters  

SciTech Connect

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

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

2005-11-15

4

Negative dielectric constant manifested by static electricity  

NASA Astrophysics Data System (ADS)

Negative dielectric constant has long been pursued for a possible revolution in electronics and photonics. It is usually found in systems containing free electrons under high frequency oscillating field, but not involving static charges or insulating materials. Here, we report the observation of the phenomenon in an insulating polymer containing static electricity, which lasts for several weeks, where negative capacitance persists from <1 Hz up to MHz frequency, also presenting an unusual spiral curve in impedance spectrum, producing inductors without bulky magnetic coils.

Yan, Han; Zhao, Cindy; Wang, Kevin; Deng, Lucy; Ma, Matthew; Xu, Gu

2013-02-01

5

Dielectric properties of epoxy nanocomposites  

Microsoft Academic Search

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

Santanu Singha; M. Joy Thomas

2008-01-01

6

DIELECTRIC PROPERTIES MEASUREMENT FOR AGRICULTURAL APPLICATIONS  

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...

7

Dielectric properties of glucose and maltose solutions  

NASA Astrophysics Data System (ADS)

We report molecular dynamics (MD) simulations of aqueous solutions of glucose and maltose. For each sugar, two concentrations were studied. The static and frequency-dependent dielectric properties of the solutions were calculated from MD trajectories of at least 5 ns length and compared to those of pure water. The contributions from the solute, the solvent, and the solute-solvent cross term were analyzed. In addition, for the more dilute glucose and maltose solutions a Voronoi analysis was carried out to distinguish between contributions from the first water shell and from unbound bulk water. The results of the glucose simulations were compared to available experimental data. While the static dielectric constant of the four solutions was found to be very similar to that of pure water, a number of differences could be discerned in the dielectric spectra. These findings for the overall frequency-dependent dielectric susceptibilities were rationalized by a dielectric component analysis. The importance of contributions from cross terms and from the solute depended on solute type (glucose or maltose) and concentration. In particular, we observed a linear correlation between the contribution of the solute-solvent cross term and the total number of hydroxyl groups of the solute (i.e., the number of solute molecules times the number of hydroxyl groups in a glucose or maltose molecule, respectively). The dielectric properties of water in the solutions could be rationalized as the superposition of two contributions, one originating from the bulklike free waters, the other from the waters in the first hydration shell of the saccharides.

Höchtl, P.; Boresch, S.; Steinhauser, O.

2000-06-01

8

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

9

Applications for Dielectric Properties of Agricultural Products  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

10

Dielectric properties of agricultural products and applications  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

11

Low Frequency Dielectric Properties of Polyether Electrolytes.  

National Technical Information Service (NTIS)

Beyond their interest as fundamental properties of a material, the dielectric constant and loss are of particular significance for ion conducting polymers. For example, the dielectric constant plays a fundamental role in the ability of a polymer to dissol...

J. J. Fontanella M. C. Wintersgill

1988-01-01

12

Dielectric properties of gel collected from shark electrosensors  

NASA Astrophysics Data System (ADS)

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

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

2003-03-01

13

Dielectric properties of flame resistant EPDM composites  

Microsoft Academic Search

Formulations of ethylene-propylene-diene rubber containing mixtures of aluminum hydroxide (ATH) and carbon black (HAF) as fillers were developed, aiming to achieve a synergism in properties, to fit national and international standards for application as insulation in electric wires and cables, yet keeping the fire resistance. After flammability determination, the developed compositions were analyzed for dielectric constant, dissipation factor, dielectric strength,

Cristine Canaud; Leila Léa Yuan Visconte; Márcio Antônio Sens; Regina Célia Reis Nunes

2000-01-01

14

Vibrational and dielectric properties of magnesium aluminate spinel: A first-principles study  

NASA Astrophysics Data System (ADS)

The vibrational and dielectric properties of MgAl 2 O 4 are investigated within the framework of density functional perturbation theory. Results of phonon frequencies at the Brillouin zone center, static dielectric constant, and electronic dielectric constant are reported. In comparison with experimental results, we find that the generalized gradient approximation potential results in more accurate phonon frequencies than local density approximation potential does. Dielectric, refractive index, extinction coefficient and infrared reflectance spectra of MgAl 2 O 4 are given, and the figures suggest that MgAl 2 O 4 presents good transmission properties in the spectrum range above 1000 cm - 1 and below 300 cm - 1 .

Zeng, Qingfeng; Zhang, Litong; Zhang, Xian; Chen, Qichao; Feng, Zhiqiang; Cai, Yongqing; Cheng, Laifei; Weng, Zuohai

2011-09-01

15

Workshop on Dielectric Properties and Electrical Breakdown of Biological Membranes.  

National Technical Information Service (NTIS)

The topic 'Dielectric Properties and Electrical Breakdown of Biological Membranes' was the topic of a workshop at the Conference on Electrical Insulation and Dielectric Phenomena on October 20, 2002, in Mexico. The workshop, supported by the IEEE Dielectr...

K. H. Schoenbach

2002-01-01

16

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

17

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

18

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

PubMed Central

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

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

2013-01-01

19

The dielectric properties of mica  

Microsoft Academic Search

Two methods used for determining the dielectric constant of thin sheets of mica are described and the errors discussed.The results of measurements on over 170 sheets of mica are given. The samples tested included best clear mica, ruby, green and brown in colour, stained and spotted samples, and also samples with gaseous inclusions. There were also samples of amber mica

D. W. Dye; L. Hartshorn

1924-01-01

20

Dielectric nanocomposites with insulating properties  

Microsoft Academic Search

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

Toshikatsu Tanaka

2005-01-01

21

Dielectric Properties of Polymers. A Bibliography.  

National Technical Information Service (NTIS)

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

D. W. Levi D. A. Teetsel

1966-01-01

22

Dielectrical Properties of Food Materials—2: Measurement Techniques  

Microsoft Academic Search

The knowledge of the electrical properties of the materials to be processed or measured is important in the design of the equipment. Dielectric properties determine the behavior of the materials, when subjected to high frequency or microwave fields in dielectric heating processes or cooking. This article is a review of the measurement techniques of the dielectrical properties of food materials.

FILIZ ?Ç?ER; TANER BAYSAL

2004-01-01

23

Modelling heterogeneous dielectric mixtures in the terahertz regime: a quasi-static effective medium theory  

NASA Astrophysics Data System (ADS)

We present a quasi-static effective medium theory for heterogeneous dielectric mixtures consisting of particles embedded in a host matrix. The model remains valid for all mixture concentrations and can also consider particle shape distributions, thus overcoming the restrictions of previous approaches. The theory is experimentally validated by highly accurate terahertz time domain spectroscopy measurements on three different polymeric compound systems. A comparison with commonly applied theories is given.

Scheller, Maik; Wietzke, Steffen; Jansen, Christian; Koch, Martin

2009-03-01

24

Local Dielectric Property of Cubic Hafnia  

NASA Astrophysics Data System (ADS)

The dielectric property of the cubic hafnia is investigated in terms of the polarizability density and the dielectric constant density defined by one of the authors. We study it by using the cluster model embedded in point charges which represent the surrounding atoms. It is shown that the cubic hafnia show complicated responses to external electric fields, in particular, rotational ones. We stress that the nanosize material should be studied in the local and tensor quantity analysis to describe rotational responses correctly. We also show that the choice of models, in particular, termination condition, is important for these analyses, by comparing the point charge model and the hydrogen termination model.

Fukushima, Akinori; Senami, Masato; Tsuchida, Yasushi; Tachibana, Akitomo

2010-11-01

25

Dielectric surface properties of Venus  

NASA Astrophysics Data System (ADS)

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.

1992-12-01

26

Anomalous Dielectric Properties of Carbon-Black Filled Elastomers.  

National Technical Information Service (NTIS)

Dielectric measurements covering nearly ten decades in frequency are given for a series of neoprene elastomers containing various amounts of conductive carbon black filler. The influence of the conductive filler upon the dielectric properties of the elast...

J. Burns

1993-01-01

27

Dielectric property and microstructure of a porous polymer material with ultralow dielectric constant  

NASA Astrophysics Data System (ADS)

This letter reports the synthesis and dielectric properties of a porous poly(arylethers) material with an ultralow dielectric constant for interlayer dielectric applications in microelectronics. The porous polymer films were fabricated by a method of organic phase separation and evaporation. A dielectric constant of 1.8 was achieved for a porous film with an estimated porosity of 40%. The characterization of microstucture for the porous film showed numerous nanopores with an average size of 3 nm distributed uniformly throughout the film.

Xu, Yuhuan; Tsai, Yi-Pin; Tu, K. N.; Zhao, Bin; Liu, Q.-Z.; Brongo, Maureen; Sheng, George T. T.; Tung, C. H.

1999-08-01

28

Dielectric properties of various nanocomposite materials  

SciTech Connect

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

Tuncer, Enis [ORNL; Polyzos, Georgios [ORNL; James, David Randy [ORNL; Sauers, Isidor [ORNL; Ellis, Alvin R [ORNL; More, Karren Leslie [ORNL

2010-01-01

29

Fundamentals of dielectric properties measurements and agricultural applications.  

PubMed

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

Nelson, Stuart O

2010-01-01

30

Ultra low-k dielectric mechanical property characterization  

Microsoft Academic Search

To meet electrical performance requirements, the industry is implementing ultra-low dielectric constant (ULK) materials in the back end of line interconnect structure. ULK dielectrics are inherently weak compared to traditional dielectrics and pose significant challenges to electronic packaging processes and reliability. Accurate mechanical properties are a prerequisite for upfront risk assessments associated with low-k integration using numerical simulations. In this

Vikas Gupta; Jie-Hua Zhao; Darvin Edwards; Clay Dustin Mortensen; Colby Heideman; David C. Johnson; K.-H. G. Lu; Paul S. Ho

2008-01-01

31

Studies of the structural, electronic and dielectric properties of Ca1-xSrxTiO3  

NASA Astrophysics Data System (ADS)

The lattice constants, band structure and dielectric properties of Ca1-xSrxTiO3 (0dielectric function and the static dielectric constant of the CSTO, optical permittivity and the static refractive index, are given to support the potential applications of the compounds in the future.

Chen, HaiChuan; Long, JianPing; Yang, Lijun; Wei, XueSong; Huang, KaMa

2012-09-01

32

Modification in dielectric properties: Effect of gamma radiation  

NASA Astrophysics Data System (ADS)

The present paper reports the influence in dielectric properties caused by gamma radiation. The dielectric parameters have been measured for both unirradiated and gamma irradiated 5CB nematic liquid crystal with temperature variation in the frequency range 100 Hz to 10 MHz. Dielectric permittivity with variation in temperature has also been observed. The dielectric permittivity is found to increase for gamma irradiated sample as compared to the unirradiated sample with variation in temperature and frequency and well explained in this paper.

Dixit, Sudhaker; Tripathi, Prachi; Manohar, Rajiv; Arora, A. K.

2013-06-01

33

Dielectric properties for monitoring the quality of heated oils  

Microsoft Academic Search

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

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

1992-01-01

34

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

35

Dielectric properties of supercooled cryoprotectant agents.  

PubMed

The dielectric properties of glycerol, propylene glycol, ethylene glycol and dimethyl sulphoxide have been measured in various aqueous concentrations generally sufficient to allow supercooling rather than freezing. The temperature range investigated is from -80 degrees C to +20 degrees C and the frequency range is 100 MHz to 2 GHz. The aim is to find the materials and conditions most favorable for very rapid re-warming of perfused biological tissue by electromagnetic fields, avoiding thermal runaway in the bulk and local non-uniformity of temperature. Frequencies below 500 MHz are generally indicated. PMID:8912380

Michelson, S C; Evans, S

1996-10-01

36

Dielectric and electrical properties of electrorheological carbon suspensions.  

PubMed

Measurements of electrorheological (ER) effects, dielectric properties, and electrical conductivity are made on an ER suspension composed of carbonaceous particles and silicone oil to understand the mechanism which governs the ER effect. In the frequency dependence of the dielectric permittivities, a dielectric dispersion is observed in the first-order dielectric permittivity, while in the third-order dielectric permittivity a resonance peak, which is due to shear-induced particle rotation, is recognized, showing that such dielectric properties are closely related to ER properties of the suspension. An electrical conduction mechanism, which is responsible for the ER effect, is also investigated from the dependence of dc electrical conductivity on electric-field strength and temperature. PMID:18342876

Negita, K; Misono, Y; Yamaguchi, T; Shinagawa, J

2008-03-14

37

Dielectric Properties of Solid-State Gelatin and Collagen  

Microsoft Academic Search

Dielectric properties of collagen and gelatin are studied in order to get detailed information concerning the properties of the incompletely crystallized part, and as a result to get more complete information about the structure of collagen. Two kinds of dielectric absorption, alpha- and beta- absorption, are observed in the temperature range between -70°C and 200°C and in the frequency range

Kuniomi Saiki; Yasushi Okamoto

1966-01-01

38

Dielectric properties of polyamide-imide  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

39

Investigation of microwave dielectric properties of biodiesel components.  

PubMed

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

Muley, Pranjali D; Boldor, Dorin

2012-10-17

40

Complex Dielectric Properties of Several Igneous and Metamorphic Rocks.  

National Technical Information Service (NTIS)

The complex dielectric properties of rocks are interesting scientifically and important practically. The scientific interest derives from a desire to understand the properties of materials, the electrical structure of the earth's crust, and the (electrica...

G. Simmons L. Caruso F. Miller

1980-01-01

41

Dielectric properties and long-wavelength optical modes of the high- kappa oxide LaAlO3  

Microsoft Academic Search

We present ab initio density-functional and self-interaction-corrected calculations on the structure, long-wavelength vibrational modes, and static dielectric properties of the crystalline high- kappa distorted-perovskite oxide LaAlO3 . The orientationally averaged dielectric constant kappa~=23.3 is in good agreement with experiment, and its value is dominated by the ionic response. We find it important to calculate the dynamical charges by a self-interaction-corrected

Pietro Delugas; Vincenzo Fiorentini; Alessio Filippetti

2005-01-01

42

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

Microsoft Academic Search

The dielectric properties (dielectric constant and loss) of a single crystal of yttrium iron garnet (Y3Fe5O12) were measured in the temperature range 77–725 K and in the frequency range 100 Hz-1 MHz. AC conductivity was derived from\\u000a dielectric constant and loss. DC conductivity was measured in the temperature range 30–725 K. Thermoelectric power (TEP) was\\u000a measured from 77–800 K. On

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

1998-01-01

43

Effect of Dielectric Property of Hydrous Dispersoid on Electrorheology  

NASA Astrophysics Data System (ADS)

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

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

44

Mechanical Properties of Polymer Dielectric Films at ElevatedTemperatures  

Microsoft Academic Search

The miniaturization of microelectronics has led to the use of polymer dielectric films with a thickness less than a micrometer. The use of polymer dielectric films has introduced new failure modes. To have a better understanding of these failures, knowledge of the mechanical properties is necessary. The through-plane elastic modulus and change in permittivity for a 1 mum thick Cyclotenetrade

M. van Soestbergen; L. J. Ernst; K. M. B. Jansen; W. D. van Driel

2006-01-01

45

The effect of colemanite on dielectric properties of polymers  

Microsoft Academic Search

The aim of this study is to investigate the effect of colemanite on dielectric properties of polymers. In this study polyester is used as the base polymer insulator. The electrical conductivity, relative permittivity and dissipation factor (tan¿) of polymers are measured as a function of colemanite concentration in polyester samples. After dielectric measurements are completed, breakdown strengths are evaluated for

Aysel ERSOY; Mukden UGUR; Ayten KUNTMAN; Ahmet MEREV; Berrak ÖZTÜRK

2009-01-01

46

Piezoelectric properties and dielectric losses in PVDF–PMMA blends  

Microsoft Academic Search

Piezoelectric properties and dielectric losses have been measured in polyvinylidene fluoride (PVDF)\\/polymethyl methacrylate (PMMA) blends to assess the value of this class of polymers as ultrasonic transducer materials. The electromechanical coupling factor kt has been found to become vanishingly small in blends having a PMMA content of about 20% by weight. For the same blend composition, the peak of dielectric

C. Domenici; D. De Rossi; A. Nannini; R. Verni

1984-01-01

47

Dielectric properties of electron beam irradiated polymer insulating material  

Microsoft Academic Search

This study examined the influence of electron beam irradiation on the electrical properties of polyetheretherketone (PEEK) in terms of its conduction current, relative dielectric constant (?r'), relative dielectric loss factor (?r''), and thermally stimulated current (TSC). The temperature at which conduction current steeply increases shifted to higher temperatures with increasing exposure dose. Ion hopping distance (a) shortened with increasing exposure

Katsuyoshi Shinyama; Makoto Baba; Shigetaka Fujita

1998-01-01

48

Dielectric properties of FeCl3 doped PVA films  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

49

Dielectric properties of human placenta, umbilical cord and amniotic fluid  

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

50

Dielectric properties of ferroelectric thin films with surface transition layers  

PubMed Central

By taking into account surface transition layers (STL), the dielectric properties of ferroelectric thin films described by the transverse Ising model are discussed in the framework of the mean field approximation. Functions of the intra-layer and inter-layer couplings are introduced to characterize STL, which makes the model more realistic compared to previous treatment of surface layers using uniform surface exchange interactions and a transverse field. The effects of physical parameters on the dielectric properties are quantified. The results obtained indicate that STL has very strong influence on the dielectric properties of ferroelectric thin films. Some of our theoretical results are in accord with the available experimental data.

Chen, Hui; Lu, Tianquan; Cui, Lian; Cao, Wenwu

2009-01-01

51

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

52

Interfacial Properties of Germanium Nitride Dielectric Layers on Germanium.  

National Technical Information Service (NTIS)

The enclosed report represents work performed at UCSD on Contract N00014-84-K-0459 entitled, 'Interfacial Properties of Germanium Nitride Dielectric Layers on Germanium', and provides a full account of the results obtained during the contract period: July...

L. G. Meiners

1986-01-01

53

Microwave Reflection Measurements of the Dielectric Properties of Concrete.  

National Technical Information Service (NTIS)

The use of microwave reflection measurements to continuously and nondestructively monitor the hydration of concrete is described. The method relies upon the influence of the free-water content on the dielectric properties of the concrete. Use of the metho...

G. G. Clemena

1983-01-01

54

Thermal and compositional properties of cocoa butter during static crystallization  

Microsoft Academic Search

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

Paul S. Dimick; Douglas M. Manning

1987-01-01

55

Optical Transmission Properties of Dielectric Aperture Arrays  

NASA Astrophysics Data System (ADS)

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

Yang, Tao

56

Millimeter wave analysis of the dielectric properties of oil shales  

NASA Astrophysics Data System (ADS)

Natural sedimentation processes give rise to fine layers in shales. If these layers alternate between organic-rich and organic-poor sediments, then the contrast in dielectric properties gives rise to an effective birefringence as the presence of hydrocarbons suppresses the dielectric constant of the host rock. We have measured these effects with a quasioptical millimeter wave setup that is rapid and noncontacting. We find that the strength of this birefringence and the overall dielectric permittivity provide two useful diagnostics of the organic content of oil shales.

Scales, John A.; Batzle, Michael

2006-07-01

57

The dielectric properties of the massive medium at finite density  

NASA Astrophysics Data System (ADS)

The action method, which is applied to discuss the dielectric properties of massless medium, the QCD or QED plasma, is extended to study the dielectric function (?) and the magnetic permeability (?-1) of the massive nuclear matter. Taking the ?NN interaction as an example, the essential features of the physical picture of the ? and the ?-1 are investigated at the finite nucleon density. The nontrivial structures of the dielectric function are found both in the space-like and the time-like regime. Through analyzing the physical mechanisms for two kinds of induced currents in the nuclear matter, we give the explanations for these two nontrivial structures.

Meng, Jin; Li, Jiarong

2004-01-01

58

Dielectric properties of certain biological materials at microwave frequencies.  

PubMed

In the medical field, microwaves play a larger role for treatment than diagnosis. For the detection of diseases by microwave methods, it is essential to know the dielectric properties of biological materials. For the present study, a cavity perturbation technique was employed to determine the dielectric properties of these materials. Rectangular cavity resonators were used to measure the complex permittivity of human bile, bile stones, gastric juice and saliva. The measurements were carried out in the S and J bands. It is observed that normal and infected bile have different dielectric constant and loss tangent. Dielectric constant of infected bile and gastric juice varies from patient to patient. Detection and extraction of bile stone with possible method of treatment is also discussed. PMID:15040525

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

2001-01-01

59

Dielectric properties of plasma polymerized furan thin film capacitors  

Microsoft Academic Search

The dielectric properties of radio frequency plasma polymerized Furan film capacitors were determined in the frequency range 1 kHz–1 MHz at various temperatures in the range 303–423 K. The dielectric constant was found to increase with the increase in the film thickness. The large increase in capacitance towards the low frequency region indicates the possibility of an interfacial polarization mechanism

D. Sakthi Kumar

1999-01-01

60

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

61

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

62

Investigation of Dielectric Properties of Liquid Crystals near Phase Transitions  

Microsoft Academic Search

Precise capacitance measurement has been performed near the phase transitions of scientifically important liquid crystals such as 8-CB. The details of the measurements to get high precision data on dielectric constant and its temperature dependence will be presented. The results show significant changes of the dielectric properties of the liquid crystal near the smectic-to-nematic and nematic-to-liquid phase transitions attributed to

Michael Kordell; Tracy Lawson; Chandra Prayaga; Laszlo Ujj

2010-01-01

63

Enhancement of dielectric and ferroelectric properties in ferroelectric superlattices  

Microsoft Academic Search

I studied theoretically the enhancement of remanent polarization and dielectric permittivity of interfacial-coupled ferroelectric superlattices based on the Landau–Ginzburg theory. Our model adopts the Landau–Khalatnikov equation to describe hysteresis behavior and takes the time-dependent space-charge-limited conductivity into account to investigate the ferroelectric and dielectric properties of ferroelectric superlattices. The results are in good agreement with recent experimental observations on the

Y. Zhou

2010-01-01

64

Dielectric properties of two polar nematic liquid crystals  

Microsoft Academic Search

The paper reports on the dielectric properties of two polar nematic liquid crystals, p-methoxybenzylidene-p'cyanoaniline (MBCA) and p-cyanobenzylidene-p'methoxyaniline (CBMA). The effect induced by dc and ac electric fields as well as magnetic field resulting in a deformation of the nematic director was studied at 10 kHz and 1 kHz. The dielectric anisotropies, splay elastic constants, and diamagnetic anisotropies as well as

Z. Belarbi-Massouras; G. Guillaud; F. Tournilhac; H. Acourag; B. Khelifa

1991-01-01

65

Interfacial effects on dielectric properties of polymer-particle nanocomposites  

NASA Astrophysics Data System (ADS)

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

Siddabattuni, Sasidhar Veeranjaneyulu

66

Rapid monitoring of selected food properties using microwave dielectric spectra  

Microsoft Academic Search

In this paper, a novel microwave measurement approach is presented, which is capable of determining selected food properties from the dielectric spectrum. Such properties could be the water content, a possible amount of additionally added water, the content of conducting ions or the percentage of other constituents, having a noticeable influence on the effective complex permittivity versus frequency. The approach

Frank Daschner; Reinhard Knoechel; Michael Kent

2000-01-01

67

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

PubMed

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

Ji, Zhen; Brace, Christopher L

2011-07-26

68

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.

Ji, Zhen; Brace, Christopher L

2011-01-01

69

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

PubMed

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

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

2013-03-18

70

Dielectric properties of carbon nanotubes/epoxy composites.  

PubMed

Material with high dielectric properties possesses the effect of energy storage and electric field homogenization, which plays an important role in the electrical and electronics domain, especially in the capacitor, electrical machinery and cable realm. In this paper, epoxy-based nanocomposites with high dielectric constant were fabricated by adding pristine and ozone functionalized multi-wall carbon nanotubes (MWCNTs). In the process-related aspect, the favorable technological parameter was obtained via reasonable arrangement and consideration of the dispersing methods including high-speed stirring and three-roller mill. As a result, a uniform dispersion status of MWCNTs in matrix has been guaranteed, which was observed by scanning and transmission electron microscopy. Meanwhile, the influence of different MWCNTs contents and diverse frequencies on the dielectric properties was compared. It was found that the dielectric constant of nano-composites decreased gradually with the increasing of frequency (10(3)-10(6) Hz). Moreover, as the content of MWCNTs increasing, the dielectric constant reached to a maximum of about 1,328 at 10(3) Hz when the pristine MWCNTs content was 0.5 wt.%. Accordingly, the DC conductivity results could interpret the peak value phenomenon by percolation threshold of MWCNTs. In addition, at the fixed content, the dielectric constant of epoxy-based nano-composites with ozone functionalized MWCNTs was lower than that of pristine ones. PMID:23646551

Peng, Jin-Ping; Zhang, Hui; Tang, Long-Cheng; Jia, Yu; Zhang, Zhong

2013-02-01

71

Static and dynamic properties of vortices in anisotropic magnetic disks  

Microsoft Academic Search

We investigate the effect of the magnetic anisotropy (Kz) on the static and dynamic properties of magnetic vortices in small disks. Our micromagnetic calculations reveal that for a range of Kz there is an enlargement of the vortex core. We analyze the influence of Kz on the dynamics of the vortex core magnetization reversal under the excitation of a pulsed

Tiago S. Machado; Tatiana G. Rappoport; Luiz C. Sampaio

2008-01-01

72

Microwave measurement and modeling of the dielectric properties of vegetation  

NASA Astrophysics Data System (ADS)

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

Shrestha, Bijay Lal

73

Dielectric properties of rubber ferrite composites containing mixed ferrites  

NASA Astrophysics Data System (ADS)

Rubber ferrite composites (RFC) are important since they have useful applications as microwave absorbers and flexible magnets. The mouldability of these composites into complex shapes is another advantage. The evaluation of their dielectric and magnetic properties is important in understanding the physical properties of these composites. Pre-characterized nickel zinc ferrites (Ni1-xZnxFe2O4 where 0icons/Journals/Common/leq" ALT="leq" ALIGN="TOP"/> xicons/Journals/Common/leq" ALT="leq" ALIGN="TOP"/>1 in steps of 0.2) prepared by ceramic techniques were incorporated in to a butyl rubber matrix according to a specific recipe to yield RFCs. The dielectric constant of ceramic Ni1-xZnxFe2O4 and the butyl rubber composites incorporated with Ni1-xZnxFe2O4 are studied as a function of frequency, composition, loading and temperature. The observed data indicates that the dependence of the dielectric constant on frequency follows Maxwell-Wagner interfacial polarization. The compositional (zinc content, i.e. x value) dependence shows that the dielectric constant increases initially and reaches a maximum value for the composition corresponding to x = 0.6 and thereafter it decreases. This can be explained on the basis of porosity and alternating current (AC) conductivity. It was also observed that the dielectric constant of the composite material increases with an increase of the volume fraction of the magnetic filler. These observations satisfy some mixture equations, which correlate the dielectric constant of the matrix, filler and the composites. The temperature dependence of the dielectric constant of the ceramic samples as well as the RFCs shows an increase with an increase of temperature at low frequencies. The dielectric constant of the blank butyl rubber was also determined. It was observed that for a blank sample (without filler) the dielectric constant decreases with an increase of temperature. This is due to the decrease in polymer density with increase in temperature. These results suggest that the magnetic and dielectric properties of RFCs can be manipulated by appropriate loading and a judicious choice of the magnetic filler. The modification of these properties will aid in the design of composite materials for microwave absorbers.

Anantharaman, M. R.; Sindhu, S.; Jagatheesan, S.; Malini, K. A.; Kurian, P.

1999-08-01

74

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

2012-06-15

75

General properties of dielectric optical antennas.  

PubMed

Using Mie theory we derive a number of general results concerning the resonances of spherical and cylindrical dielectric antennas. Specifically, we prove that the peak scattering cross-section of radiation-limited antennas depends only on the resonance frequency and thus is independent of refractive index and size, a result which is valid even when the resonator is atomic-scale. Furthermore, we derive scaling limits for the bandwidth of dielectric antennas and describe a cylindrical mode which is unique in its ability to support extremely large bandwidths even when the particle size is deeply subwavelength. Finally, we show that higher Q antennas may couple more efficiently to an external load, but the optimal absorption cross-section depends only on the resonance frequency. PMID:20052120

Schuller, Jon A; Brongersma, Mark L

2009-12-21

76

Low frequency electrical properties of selected dielectrics  

NASA Astrophysics Data System (ADS)

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

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

77

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

78

Low frequency electrical properties of selected dielectrics  

SciTech Connect

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

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

1984-01-01

79

Number of Dielectric Layers Dependence of Dielectric Properties and Residual Stress of Multilayer Ceramic Capacitors with Ni Electrodes  

NASA Astrophysics Data System (ADS)

The relationship between the residual stress and dielectric properties of multilayer ceramic capacitors with Ni electrodes (Ni-MLCCs) has been studied. Residual stress measurement by X-ray diffraction revealed that tensile stress inside MLCCs in the thickness direction increased with increasing number of dielectric layers. The increase in the ratio of the c-axis to the a-axis of BaTiO3 in the thickness direction of MLCCs was expected from the results of X-ray diffraction with increasing number of dielectric layers. The increase in dielectric constant and its temperature dependence with increasing number of dielectric layers were expectedly related to crystal structures.

Nakano, Yukie; Nomura, Takeshi; Takenaka, Tadashi

2004-08-01

80

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

Microsoft Academic Search

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

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

2003-01-01

81

Analyzing molecular static linear response properties with perturbed localized orbitals  

NASA Astrophysics Data System (ADS)

Perturbed localized molecular orbitals (LMOs), correct to first order in an applied static perturbation and consistent with a chosen localization functional, are calculated using analytic derivative techniques. The formalism is outlined for a general static perturbation and variational localization functionals. Iterative and (formally) single-step approaches are compared. The implementation employs an iterative sequence of 2×2 orbital rotations. The procedure is verified by calculations of molecular electric-field perturbations. Boys LMO contributions to the electronic static polarizability and the electric-field perturbation of the expectation value are calculated and analyzed for ethene, ethyne, and fluoroethene (H2C=CHF). For ethene, a comparison is made with results from a Pipek-Mezey localization. The calculations show that a chemically intuitive decomposition of the calculated properties is possible with the help of the LMO contributions and that the polarizability contributions in similar molecules are approximately transferable.

Autschbach, Jochen; King, Harry F.

2010-07-01

82

Analyzing molecular static linear response properties with perturbed localized orbitals.  

PubMed

Perturbed localized molecular orbitals (LMOs), correct to first order in an applied static perturbation and consistent with a chosen localization functional, are calculated using analytic derivative techniques. The formalism is outlined for a general static perturbation and variational localization functionals. Iterative and (formally) single-step approaches are compared. The implementation employs an iterative sequence of 2x2 orbital rotations. The procedure is verified by calculations of molecular electric-field perturbations. Boys LMO contributions to the electronic static polarizability and the electric-field perturbation of the r(2) expectation value are calculated and analyzed for ethene, ethyne, and fluoroethene (H(2)C=CHF). For ethene, a comparison is made with results from a Pipek-Mezey localization. The calculations show that a chemically intuitive decomposition of the calculated properties is possible with the help of the LMO contributions and that the polarizability contributions in similar molecules are approximately transferable. PMID:20687635

Autschbach, Jochen; King, Harry F

2010-07-28

83

Neoclassical dielectric property of a tokamak plasma  

SciTech Connect

The response of a tokamak plasma to a time-dependent axisymmetric radial electric field is considered. The bounce-averaged motion of magnetically trapped ions is shown to consist of a radial drift, in addition to the well-known toroidal precession. This is a neoclassical polarization drift, which is larger than the standard one by a factor B/sup 2//B/sup 2//sub theta/, the square of the ratio of total to poloidal magnetic fields. The resulting low-frequency dielectric constant is larger than the standard one by approximately the same factor, when the ions are in the banana regime of neoclassical theory.

Hinton, F.L.; Robertson, J.A.

1984-05-01

84

Kubo formula for frequency dispersion of dielectric permittivity and static conductivity of the Coulomb system  

NASA Astrophysics Data System (ADS)

It is proved that the Kubo formula for the conductivity ?(?) is valid at real frequencies ?. On this basis, an exact relation is derived for the static conductivity ? of the Coulomb system. It is shown that the static conductivity is determined by the time correlation function in the limit t??. It is proved that the permittivity ?(?) satisfies the Kramers-Kronig relations which take into account a singularity associated with static conductivity.

Bobrov, V. B.; Trigger, S. A.; Zagorodny, A. G.

2010-12-01

85

Dielectric properties of plasma polymerized pyrrole thin film capacitors  

Microsoft Academic Search

Plasma polymerized polymer film from pyrrole was produced by radio frequency plasma polymerization and their dielectric properties were studied in the frequency range from 1 kHz to 1 MHz at various temperatures from 303 to 423 K. The large increase in the capacitance towards the low frequency region indicates the possibility of an interfacial polarization mechanism prevailing in that region.

D. Sakthi Kumar; Yasuhiko Yoshida

2003-01-01

86

Dielectric Properties of Honeydew Melons and Correlation with Quality  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dielectric properties of three honeydew melon cultivars, grown and harvested to provide a range of maturities, were measured with an open-ended coaxial-line probe and impedance analyzer over the frequency range from 10 MHz to 1.8 GHz. Probe measurements were made on the external surface of the melo...

87

Dielectric properties and viscoelastic response in two-phase polymers  

Microsoft Academic Search

An electrorheological model is applied to results from dynamic mechanical analysis in order to relate low-frequency dielectric properties to viscoelastic response. The model describes polymers with two phases at the mesoscopic scale, with polar groups embedded in one of the phases. Calculations use an electrorheological representation, based on the Voigt model, to describe the two phases. Low-frequency electrical and mechanical

R. R. Mocellini; O. A. Lambri; C. L. Matteo; P. A. Sorichetti

2008-01-01

88

Measurement of Dielectric Properties of Minerals at Microwave Frequencies.  

National Technical Information Service (NTIS)

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

W. E. Webb R. H. Church

1986-01-01

89

Dielectric properties of biodegradable polylactic acid and starch ester  

Microsoft Academic Search

In order to examine the applicability of biodegradable polymers to the fields of electrical insulation, several dielectric properties of two typical biodegradable polymers, polylactic acid (PLA) and starch ester (SE), are examined. A fairly larger amount of space charge is accumulated in both polymers in comparison to low-density polyethylene (LDPE). This seems partly due to the presence of hydroxyl and

N. Hirail; Y. Maeno; H. Tamura; D. Kaneko; T. Tanaka; Y. Ohki; Y. Tajitsu; M. Kohtoh; S. Okabe

2004-01-01

90

MICROWAVE DIELECTRIC PROPERTIES OF SHELLED AND UNSHELLED PEANUTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dielectric properties of shelled and unshelled peanuts were measured with a free-space-transmission technique at room temperature (23 degrees C) between 2.0 and 18.0 GHz over wide ranges of bulk density and moisture content. For better accuracy a pair of horn/lens antennas providing a focused beam w...

91

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

Microsoft Academic Search

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

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

2010-01-01

92

Crystallization and dielectric properties of low temperature dielectrics containing Li 2O filler  

Microsoft Academic Search

Crystallization and dielectric properties of typical low temperature co-fired ceramics (LTCC) consisting of calcium zinc aluminoborosilicate glass and Al2O3 filler were investigated by substituting the Al2O3 filler partially with Li2O at the levels of 2–10wt%. Depending on the content of Li2O, densification was found significantly affected by early crystallization that resulted from the formation of unexpected crystalline phases including LiAlSiO4,

Won Bae Lim; Viswanathan S. Saji; Yong Soo Cho; Yong Gun Shul; Sangwoo Lim; Jae Hyuk Jang; Hong Ryul Lee

2008-01-01

93

Electrical conductivity and dielectric property of fly ash geopolymer pastes  

NASA Astrophysics Data System (ADS)

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

Hanjitsuwan, Sakonwan; Chindaprasirt, Prinya; Pimraksa, Kedsarin

2011-02-01

94

Dielectric properties of carbon fiber filled low-density polyethylene  

NASA Astrophysics Data System (ADS)

Carbon fiber (CF) filled low-density polyethylene (LDPE) matrix composites was prepared by means of the Hakke driver. The dielectric properties of the CF/LDPE composites as a function of the frequency and the volume fraction of CF were studied. The dielectric constants decrease slowly with increasing the frequency and rise gradually with increasing the CF contents in the composites. As the volume fraction of the CF is up to 0.20, an abrupt increase in the dielectric constant occurs, and accordingly electrical conductivity measured at low frequency increases rapidly at this volume fraction. The percolation theory and the simple concept of polarization in the capacitors are employed to explain these experimental results.

Dang, Zhimin; Shen, Yang; Fan, Lizhen; Cai, Ning; Nan, Cewen; Zhao, Shujin

2003-05-01

95

Dielectric properties of rubber ferrite composites containing mixed ferrites  

Microsoft Academic Search

Rubber ferrite composites (RFC) are important since they have useful applications as microwave absorbers and flexible magnets. The mouldability of these composites into complex shapes is another advantage. The evaluation of their dielectric and magnetic properties is important in understanding the physical properties of these composites. Pre-characterized nickel zinc ferrites (Ni1-xZnxFe2O4 where 0icons\\/Journals\\/Common\\/leq\\

M. R. Anantharaman; S. Sindhu; S. Jagatheesan; K. A. Malini; P. Kurian

1999-01-01

96

Electromagnetic properties of dielectric and magnetic composite material for antenna  

Microsoft Academic Search

Electromagnetic properties of dielectric and magnetic composite materials were studied with various weight fractions and particle\\u000a sizes of ferrite. The composite materials were prepared through Ni-Zn spinel ferrite and silicon elastomer, and were characterized\\u000a with regard to permittivity, permeability, loss tangente, and loss tangentu. Those properties of Ni-Zn spinel ferrite were approximately 7.0, 8.4, 0.01 and 0.1 MHz to 150

Sang-Hoon Park; Won-Ki Ahn; Jun-Sig Kum; Jeong-Keun Ji; Ki-Ho Kim; Won-Mo Seong

2009-01-01

97

MEASURING SOIL HYDROLOGIC PROPERTIES USING DIELECTRIC SENSORS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Knowledge of soil hydrologic properties is essential to many aspects of environmental research. Soil hydrologic properties determined from laboratory analyses often are non-representative of field conditions. In this work, we compare soil hydrologic properties determined in the field with values obt...

98

Evaluating the technological properties of powders from their dielectric permeability  

SciTech Connect

The assessment of the properties of powders used for making refractories is discussed. Because the existence of an integral influence of macro- and microparameters on the properties of the goods requires an extension of the range of defined parameters for the powders, the authors study the dielectric characteristics of powders and their influence and interaction with the properties of the resulting products. The objectives of the research consisted of two samples (D and V) of powdered fused periclase with mass proportions of magnesia of about 97%. The results of determining the grain-size composition of the two powders were obtained by the sedimentation method on the VSA-500 apparatus. The measured dielectric permeability of the mixture of powder and air was extrapolated for the compacted body from an equation. The technological properties of these powders were determined by preparing three groups (I, II, and III) of specimens. Results of the tests show that on the basis of the measurements of the dielectric permeability it is possible to assess operationally the technological properties of powders used for preparing bodies.

Sloushch, V.G.; Efremova, A.A.; Fridman, L.Y.; Gaenko, N.S.; Kortel', A.A.

1986-03-01

99

Rheological and dielectric properties of different gold nanoparticle sizes  

PubMed Central

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

2011-01-01

100

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

101

DIELECTRIC PROPERTIES OF IN-SHELL AND SHELLED PEANUTS AT MICROWAVE FREQUENCIES  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dielectric properties ( ', '') of ground samples of peanut (Arachis hypogaea L.) pods and kernels were measured for several densities, temperatures, and moisture contents, in the range of 300 to 3000 MHz. Dielectric mixture equations were used to correlate the dielectric properties with density. Th...

102

Correlation Between Dielectric Properties and Chemical Changes in Soybean Oil Derivatives  

Microsoft Academic Search

Dielectric properties of soybean oil derivatives were measured at frequency bands from 10 to 10 Hz at different temperatures. Relaxation times ?, activation enthalpies ?H, and entropy changes ?S for dielectric relaxation were calculated and related to the chemical changes of the samples. It was found that dielectric properties can be used in differentiating between epoxidized and nonepoxidized oils, and

I. Z. Selim

1997-01-01

103

Effects of silver incorporation on the dielectric and ferroelectric properties of PMN–PNN–PZT ceramics  

Microsoft Academic Search

The effects of silver addition on the sintering behavior, the dielectric, and ferroelectric properties of PMN–PNN–PZT piezoelectric ceramics for multilayer piezoelectric transformers were investigated. A small amount of silver promoted the sintering, but with more silver the density of the samples decreased. The silver incorporation affected the dielectric and ferroelectric properties of the samples. The dielectric constant presented an interesting

Ruzhong Zuo; Longtu Li; Xiaobing Hu; Zhilun Gui

2001-01-01

104

Soft Actuator for Robotic Applications Based on Dielectric Elastomer: Quasi-Static Analysis  

Microsoft Academic Search

In this paper a new soft actuator based on dielectric elastomer is proposed. The actuator, called an antagonistically-driven linear actuator (ANTLA), has the muscle-like characteristics capable of performing the motions such as forward\\/backward\\/controllable compliance. Due to its simplicity of configuration and ease of fabrication, it has the advantage to be scale-independently implemented in meso- or micro-scale robotic applications. Its basic

Hyoukryeol Choi; Sungmoo Ryew; K. M. Jung; H. M. Kim; Jae Wook Jeon; Jea-do Nam; Ryutaro Maeda; Kazuo Tanie

2002-01-01

105

Dielectric Properties of Phospholipids in Chloroform.  

National Technical Information Service (NTIS)

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

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

1971-01-01

106

Accurate identification of static nonlinear properties of wideband RF power amplifiers  

Microsoft Academic Search

In this paper, the dependence of the static nonlinear properties of the wideband RF power amplifiers on the applied signals has been discussed to illustrate the necessity to extract the static nonlinear properties in real time while applying the real modulated signal. A novel dynamic exponential weighted moving average method is proposed to extract the static nonlinear properties of the

Taijun Liu; Yan Ye; Slim Boumaiza; Mohamed Helaoui; Oualid Hammi; Fadhel M. Ghannouchi

2008-01-01

107

Design and properties of dielectric surface plasmon Bragg mirrors.  

PubMed

The ability of gratings made of dielectric ridges placed on top of flat metal layers to open gaps in the dispersion relation of surface plasmon polaritons (SPPs) is studied, both experimentally and theoretically. The gap position can be approximately predicted by the same relation as for standard optical Bragg stacks. The properties of the gap as a function of the grating parameters is numerically analyzed by using the Fourier modal method, and the presence of the gap is experimentally confirmed by leakage radiation microscopy. We also explore the performance of these dielectric gratings as SPP Bragg mirrors. The results show very good reflecting properties of these mirrors for a propagating SPP whose wavelength is inside the gap. PMID:20639935

Randhawa, Sukanya; González, María Ujué; Renger, Jan; Enoch, Stefan; Quidant, Romain

2010-07-01

108

Dielectric behaviour of some amides and formamides dissolved in nonpolar solvents under static electric field  

Microsoft Academic Search

Structural and associational aspects of polar amides (j) like formamide, acetamide, N-methyl acetamide (NMA), N,N-dimethyl formamide (DMF), N,N-dimethyl acetamide (DMA) and acetanilide\\u000a dissolved in the nonpolar solvent (i) benzene or 1,4-dioxan have been estimated from the measured static relative permittivity ?\\u000a 0ij\\u000a and high-frequency permittivity ?\\u000a ?ij\\u000a at different weight fractions w\\u000a j\\u000a s of polar solute at 35°C under static electric

S. Sahoo; S K SIT

2011-01-01

109

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

110

Dielectric Properties of Pumpable Food Materials at 915 MHz  

Microsoft Academic Search

Dielectric properties of pumpable food materials having a potential to be processed using a continuous flow microwave heating system were measured at 915 MHz and in the temperature range of 10–90°C. The products considered in this study were milk and dairy products (??: 70.0 to 50.8 and ??: 14.7 to 41.3), ready to eat puddings (??: 69.4 to 52.1 and

P. Coronel; J. Simunovic; K. P. Sandeep; P. Kumar

2008-01-01

111

Study of dielectrical properties of a new high permittivity material  

Microsoft Academic Search

High permittivity material is usually used to achieve larger stored energy in capacitors. In particular, many high permittivity materials has been used to achieve excellent stress control at cable terminations. In our paper we have investigated the dielectric properties of a new high permittivity BaTiO3\\/Al\\/LDPE composites with volume fraction of metal Al 0.20 and volume fraction of BaTiO3 from 0.10

Jiang Pingkai; Xu Chuanxiang; Liu Fuyi; Wang Shoutai

1995-01-01

112

Dielectric and structural properties of aqueous nonpolar solute mixtures.  

PubMed

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

Shvab, I; Sadus, Richard J

2012-09-28

113

Thermal and dielectric properties of sweetpotato puree  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

114

Dielectric properties of iron-bismuthate glass  

Microsoft Academic Search

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

Aswini Ghosh

1989-01-01

115

Dielectric and magnetic properties of low-temperature- fired ferrite-dielectric composites  

Microsoft Academic Search

The composition effects on the sintering behavior, microstructure evolution, dielectric and magnetic properties of BaO•(Nd0.8Bi0.2)2O3•4TiO2 (BNBT) + Bi2O3-B2O3 -SiO2-ZnO (BBSZ) glass-NiCuZn ferrite composites were investigated in developing low-temperature-fired composites for high frequency EMI devices. X-ray diffractometer (XRD), scanning electron microscopy (SEM), and a dilatometer were used to examine the BNBT + BBSZ glass powder to NiCuZn ferrite ratio effect on

Hsing-I Hsiang

2010-01-01

116

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

117

Molecular interactions in 1-pentanol +2-methyl-2-butanol mixtures: Static dielectric constant, viscosity and refractive index investigations at 5, 25 and 45°C  

Microsoft Academic Search

Static dielectric constants, refractive indices and viscosities of 1-pentanol +2-methyl-2-butanol mixtures were measured at 5, 25 and 45°C. The results show that the mixing of the two isomers modifies the polarizability and the resistence of viscous flow of the system depending on the composition and temperature. Short range intermolecular interactions producing hetero-alcohol open dimers are considered.

Alessandro D'Aprano; Ines Dorina Donato; Vincenzo Turco Liveri

1989-01-01

118

Dielectric, piezoelectric and strain properties of PMW-PNN-PZT  

Microsoft Academic Search

In this paper, the structural, dielectric, piezoelectric and strain properties of Pb[(Mg1\\/2W1\\/2)x-(Ni1\\/3Nb 2\\/3)0.15-x-(Zr0 .5Ti0.5 )0.85]O3 (X-0-0~0.10) ceramics were investigated with the substitution of Pb(Mg1\\/2W1\\/2)O3. According to the increase of the substitution amount of Pb(Mg1\\/2W1\\/2)O3, Curie temperatures and coercive fields were decreased by the decrease of the tetragonality. Up to the substitution amount of Pb(Mg1\\/2W1\\/2)O3 3 mol%, remnant polarization, dielectric constant

K.-H. Yoon; J.-H. Yoo; S.-K. Min; S.-H. Lee; J.-I. Hong; C.-Y. Park

2000-01-01

119

On the temperature dependent dielectric properties, conductivity and resistivity of MIS structures at 1 MHz  

Microsoft Academic Search

In this study, the temperature dependence of the dielectric properties, conductivity and resistivity of metal–insulator-semiconductor (MIS) structures have been investigated using capacitance (C) and conductance (G\\/?) measurements in wide temperature range of 120–400K at 1MHz. Calculation of the dielectric constant (??), dielectric loss (??), loss tangent (tan ?), ac conductivity (?ac), ac resistivity (?ac) and the real and imaginary parts

A. Ero?lu; A. Tataro?lu; ?. Alt?ndal

120

Microwave Dielectric Properties of XM46 and a Surrogate Liquid Propellant.  

National Technical Information Service (NTIS)

The microwave dielectric properties of liquid propellant (LP) XM46 were determined at room temperature from 2 to 20 GHz using a dielectric probe technique. The dielectric constant (permittivity) of LP was determined in support of possible studies of the f...

R. B. Bossoli

1998-01-01

121

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

122

Dielectric and structural properties of iron doped titanate nano-composites  

Microsoft Academic Search

TiO2 has been used for gas sensing devices (Mohammadi et al., 2007) photo catalytic devices (Litter and Navio, 1996) and photoelectric devices (Levy, 1997). Recently the dielectric properties of TiO2 have been of great interest for applications in the telecommunications industry due to its unusual high dielectric constant and low dielectric loss. The use of layers of high dielectric constant

Davinder Singh; Sunil Dutta Sharma; K. K. Saini; Chander Kant; Nafa Singh; S. C. Jain; C. P. Sharma

2007-01-01

123

Effect of Solvent on the Dielectric Properties of Nanocomposite Poly(methyl methacrylate)-Doped Titanium Dioxide Dielectric Films  

NASA Astrophysics Data System (ADS)

A poly(methyl methacrylate)-doped titanium dioxide (PMMA:TiO2) nanocomposite film was obtained by spin coating the nanocomposite solution onto a silicon substrate. The nanocomposite solutions were prepared by dissolving the PMMA and TiO2 nanopowder in three different types of organic solvent, namely, toluene, tetrahydrofuran (THF), and acetone. We found that the dielectric properties of the PMMA:TiO2 nanocomposite are dependent on the type of solvent used. The dielectric properties measured at a frequency of 1 kHz showed that acetone gives the highest dielectric constant and capacitance compared with toluene and THF. Toluene gives the lowest dielectric loss among the three. The topography and roughness of the PMMA:TiO2 nanocomposite indicate that a particular solvent results in a different kind of surface morphology.

Ismail, Lyly Nyl; Mohamad, Nik Noor Hafizah Nik; Shamsudin, Muhamad Salleh; Zulkefle, Habibah; Abdullah, Mohd Hanapiah; Herman, Sukreen Hana; Rusop, Mohamad

2012-06-01

124

Ferroelectric and dielectric properties of ferrite-ferroelectric ceramic composites  

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

125

Dielectric properties of stoichiometric and defect-induced hydroxyapatite  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

126

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

Microsoft Academic Search

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

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

1997-01-01

127

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

Microsoft Academic Search

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

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

1989-01-01

128

Number of Dielectric Layers Dependence of Dielectric Properties and Residual Stress of Multilayer Ceramic Capacitors with Ni Electrodes  

Microsoft Academic Search

The relationship between the residual stress and dielectric properties of multilayer ceramic capacitors with Ni electrodes (Ni-MLCCs) has been studied. Residual stress measurement by X-ray diffraction revealed that tensile stress inside MLCCs in the thickness direction increased with increasing number of dielectric layers. The increase in the ratio of the c-axis to the a-axis of BaTiO3 in the thickness direction

Yukie Nakano; Takeshi Nomura; Tadashi Takenaka

2004-01-01

129

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

2013-10-22

130

Atomistic determination of flexoelectric properties of crystalline dielectrics  

NASA Astrophysics Data System (ADS)

Upon application of a uniform strain, internal sublattice shifts within the unit cell of a noncentrosymmetric dielectric crystal result in the appearance of a net dipole moment: a phenomenon well known as piezoelectricity. A macroscopic strain gradient on the other hand can induce polarization in dielectrics of any crystal structure, even those which possess a centrosymmetric lattice. This phenomenon, called flexoelectricity, has both bulk and surface contributions: the strength of the bulk contribution can be characterized by means of a material property tensor called the bulk flexoelectric tensor. Several recent studies suggest that strain-gradient induced polarization may be responsible for a variety of interesting and anomalous electromechanical phenomena in materials including electromechanical coupling effects in nonuniformly strained nanostructures, “dead layer” effects in nanocapacitor systems, and “giant” piezoelectricity in perovskite nanostructures among others. In this work, adopting a lattice dynamics based microscopic approach we provide estimates of the flexoelectric tensor for certain cubic crystalline ionic salts, perovskite dielectrics, III-V and II-VI semiconductors. We compare our estimates with experimental/theoretical values wherever available and also revisit the validity of an existing empirical scaling relationship for the magnitude of flexoelectric coefficients in terms of material parameters. It is interesting to note that two independent groups report values of flexoelectric properties for perovskite dielectrics that are orders of magnitude apart: Cross and co-workers from Penn State have carried out experimental studies on a variety of materials including barium titanate while Catalan and co-workers from Cambridge used theoretical ab initio techniques as well as experimental techniques to study paraelectric strontium titanate as well as ferroelectric barium titanate and lead titanate. We find that, in the case of perovskite dielectrics, our estimates agree to an order of magnitude with the experimental and theoretical estimates for strontium titanate. For barium titanate however, while our estimates agree to an order of magnitude with existing ab initio calculations, there exists a large discrepancy with experimental estimates. The possible reasons for the observed deviations are discussed.

Maranganti, R.; Sharma, P.

2009-08-01

131

Synthesis and Dielectric Properties of Nanocrystalline BASRTIO3  

NASA Astrophysics Data System (ADS)

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

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

132

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

133

Measurement of dielectric and magnetic properties of soil  

SciTech Connect

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

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

1995-11-01

134

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.

2013-01-01

135

Microstructure and dielectric properties of biocarbon nanofiber composites.  

PubMed

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

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

2013-06-22

136

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

137

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

138

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...

139

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

Microsoft Academic Search

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

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

2008-01-01

140

Mechanical properties of dielectric elastomer actuators with smart metallic compliant electrodes  

Microsoft Academic Search

Dielectric elastomer actuator technology is based on electric field induced deformation. From the viewpoint of materials technology, many points must be addressed, among which are material dielectric properties, breakdown voltage, viscoelastic losses and elastomer spring mechanical properties. From the viewpoint of actuator manufacturing, we will mention elastomer thin film and fiber processing as well as compliant electrode design. However, among

Mohammed Benslimane; Peter Gravesen; Peter Sommer-Larsen

2002-01-01

141

TEMPERATURE-DEPENDENT DIELECTRIC PROPERTIES OF SELECTED SUBTROPICAL AND TROPICAL FRUITS AND ASSOCIATED INSECT PESTS  

Microsoft Academic Search

Knowledge of the dielectric properties of commodities and insect pests is important in developing thermal treatments for postharvest insect control based on radio frequency (RF) and microwave energy. The dielectric properties of six subtropical and tropical fruits along with four associated insect pests were measured between 1 and 1800 MHz using an open-ended coaxial-line probe technique and at temperatures between

S. Wang; M. Monzon; Y. Gazit; J. Tang; E. J. Mitcham; J. W. Armstrong

142

Free space measurement technique on dielectric properties of agricultural residues at microwave frequencies  

Microsoft Academic Search

Principles to determine dielectric properties measurement using microwave free-space transmission measurements technique is presented in this paper. The project's main objective was to measure the dielectric properties of different agricultural waste material at microwave frequencies, which in turn, can serve as a potential alternative, replacing conventional printed circuit board (PCB) using FR4 material. A system, which includes a PNA vector

F. H. Wee; P. J. Soh; A. H. M. Suhaizal; H. Nornikman; A. A. M. Ezanuddin

2009-01-01

143

Measuring the complex dielectric properties of forest fire ash at various temperatures  

Microsoft Academic Search

Little is currently known about the effects of microwave scattering on forest fires. A small number of published papers have illustrated significant return signals form large fires around the world. One of the possible sources is particulate scatter, however; little is known about their complex dielectric properties. The investigation of the complex dielectric properties from different Australian forest flora has

Thomas Baum; Lachlan Thomson; Kamran Ghorbani

2011-01-01

144

Effects of Acid, Salt and Soaking Time on the Dielectric Properties of Acidified Vegetables  

Microsoft Academic Search

In order to design a continuous microwave process for pasteurization of acidified vegetables, equilibration phenomena in acid and salt solutions must be examined with regards to changes in dielectric properties. The objective of this study was to examine the effects of acid and salt concentration on the dielectric properties of acidified vegetables. Broccoli florets and sweet potato cubes (1.2 cm)

Craig B. Koskiniemi; Van-Den Truong; Roger F. McFeeters; Josip Simunovic

2012-01-01

145

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

PubMed Central

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

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

2011-01-01

146

Sugar content in watermelon juice based on dielectric properties at 10.45GHz  

Microsoft Academic Search

Determination of sugar content in 10 matured red seedless watermelons by measuring the dielectric properties is described in this paper. The determination is made based on the comparison of watermelon juice and water with sugar mixture. The dielectric properties of both the extracted watermelon juice and water with sugar mixture are measured over the frequency range from 200 MHz to

M. M. Isa; N. Ibrahim; R. Shamsudin; M. H. Marhaban

2009-01-01

147

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

SciTech Connect

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

Zhu, X. H. [Department of Materials Science, Sichuan University, Chengdu 610064 (China); CEA, LETI, MINATEC, 17 Rue des Martyrs, F38054 Grenoble (France); Defaye, E.; Suhm, A.; Fribourg-Blanc, E.; Aied, M. [CEA, LETI, MINATEC, 17 Rue des Martyrs, F38054 Grenoble (France); Zhu, J. L.; Xiao, D. Q.; Zhu, J. G. [Department of Materials Science, Sichuan University, Chengdu 610064 (China)

2010-05-15

148

Structural and Dielectric Properties of Quartz-Water Interfaces  

SciTech Connect

The structure, orientation, and dielectric of water at the quartz|water interface has been examined under different hydration levels using classical molecular dynamics. The properties of 1H?O/10 Ų, 2H?O/10 Ų, 4H?O/10 Ų, and bulk water on quartz have been benchmarked against experimental data. Structurally, the simulations match existing sum-frequency spectroscopy data, which indicate the existence and orientation of both frozen and loosely bound water on the quartz surface. Good agreement has also been found with existing experimental dielectric data for the 1H?O/10 Ų level of hydration, and a clear difference has been found in the values of ?s = 48, ?| = 48, and ?? = 40 for the first slice of a bulk-water-solid interface and ?s= 30, ?| = 30, and ?? = 10 for that of 1H?O/10 Ų water coverage. Overall there is a fundamental difference in shielding between a single interface and the 1H?O/10 Å2 level of hydration.

Wander, Matthew C.; Clark, Aurora E.

2008-11-19

149

Sintering Behavior and Microwave Dielectric Properties of Tricalcium Phosphate Polymorphs  

NASA Astrophysics Data System (ADS)

The phase transformation and sintering behavior of tricalcium phosphate polymorphs [?- and ?-Ca3(PO4)2] are investigated using differential thermal analysis, X-ray powder diffraction, and dilatometry. The low-temperature phase, ?-Ca3(PO4)2, can be sintered at 1125 °C prior to phase transformation to ?-Ca3(PO4)2. However, it is difficult to obtain dense ?-Ca3(PO4)2 samples owing to volume expansion and subsequent microcrack formation during the transformation of ?-Ca3(PO4)2 to ?-Ca3(PO4)2. Herein, we develop ?-Ca3(PO4)2 with a density higher than 97% by microwave heating ?-Ca3(PO4)2 without any reversible phase transformation. Also, we initially explore the microwave dielectric properties of tricalcium phosphate. Both tricalcium phosphate polymorphs show dielectric constants lower than 10. Of importance is the fact that a dense ?-Ca3(PO4)2 sample has a high quality factor of 22,000 GHz.

Cho, In-Sun; Ryu, Hyun-Seung; Kim, Jeong-Ryeol; Kim, Dong-Wan; Hong, Kug Sun

2007-05-01

150

Magnetic properties and dielectric behavior in ferrite/ferroelectric particulate composites  

NASA Astrophysics Data System (ADS)

Particulate composites of ferrite and ferroelectric phases having the general formula (x)BaTiO3+(1 x)Ni0.92Co0.03Cu0.05Fe2O4 (where x is mole fraction of components that varies as 0.85, 0.70 and 0.55) were prepared by conventional double-sintering ceramic method. The presence of constituent phases was confirmed by X-ray diffraction (XRD) technique. The average grain size was determined by using scanning electron micrographs. The variation of dielectric constant and tan ? with frequency in the range 20 Hz 1 MHz was studied. The variation of loss tangent (tan ?) and dielectric constant with temperature at fixed frequencies of 1 kHz, 10 kHz, 100 kHz and 1 MHz was also studied. The saturation magnetization (Ms) and magnetic moment (?B in Bohr magnetons) are reported for all composites. The static magnetoelectric (ME) voltage coefficient was measured as a function of intensity of applied DC magnetic field. The changes were observed in dielectric properties as well as in ME output with variation in molar fraction of constituent phases. A maximum ME conversion factor of 538.59 ?V/cm G was observed for the composites with 70% BaTiO3+30% Ni0.92Co0.03Cu0.05Fe2O4. The present ME composites may be useful in preparing devices such as magnetic sensors and cables, etc.

Devan, R. S.; Chougule, B. K.

2007-04-01

151

Pyroelectric, dielectric and thermal properties of TGS, DTGS and TGFB  

Microsoft Academic Search

The pyroelectric coefficient, dielectric constant, specific heat and thermal diffusivity of TGS, DTGS and TGFB have been measured as a function of temperature. At a given Tc — T, the deuteration seems to increase the pyroelectric coefficient by a factor 1.35, with a smaller increase in the dielectric constant. For TGFB a good Curie law of the dielectric constant has

P. Felix; P. Gamot; P. Lacheau; Y. Raverdy

1977-01-01

152

Dispersion Studies of La Substitution on Dielectric Properties of Multiferroic BiFeO3 Ceramics  

NASA Astrophysics Data System (ADS)

Lanthanum (La)-substituted multiferroic Bi1-xLaxFeO3 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 Bi1-xLaxFeO3 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 (BiFeO3). 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.

2011-12-01

153

Study on microstructure and dielectric property of the BaTiO 3\\/epoxy resin composites  

Microsoft Academic Search

High dielectric permittivity barium titanate\\/epoxy resin (BaTiO3\\/EPR) composites with different size BaTiO3 particles were prepared and their dielectric properties were studied via a wide range of temperature and frequency. The results show that an appropriate silane coupling agent can be used in order to improve the interaction between BaTiO3 and EPR, and subsequently induces a high dielectric permittivity and a

Zhi-Min Dang; Yan-Fei Yu; Hai-Ping Xu; Jinbo Bai

2008-01-01

154

Dielectric properties of CaCu3Ti4O12 thin films  

Microsoft Academic Search

High dielectric CaCu3Ti4O12 (CCTO) thin films were successfully grown on LaAlO3(100) (LAO) crystalline substrates and on SrRuO3(SRO) conductive films on LAO substrates by the pulsed laser deposition (PLD) method. Microstructure and dielectric properties of (001) oriented (CCTO) epitaxial thin films were evaluated, and compared to those of CCTO polycrystalline bulk samples by x-ray diffraction, DC conductivity and dielectric measurements. The

Kyuho Cho; Naijuan Wu; A. Ignatiev; Jianren Li

2002-01-01

155

Comparison of dielectric properties and non-enzymatic browning kinetics around glass transition  

Microsoft Academic Search

Dielectric properties of maltodextrin- and poly(vinylpyrrolidone)-based food models designed for studying non-enzymatic browning rates in the vicinity of glass transition were determined at 9 frequencies from 0.1 to 1000 Hz at temperature range from ?100 to 150 °C. Dielectric spectra of both materials showed a ?-relaxation, an ?-relaxation and significant increase in dielectricity at temperatures above the ?-relaxation. The ?-

Satu M Lievonen; Yrjö H Roos

2003-01-01

156

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

157

Dielectric Properties of Lead Monoxide Filled Unsaturated Polyester Based Polymer Composites  

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

158

Dielectric Properties of BaTiO3Based Ceramics under High Electric Field  

Microsoft Academic Search

The dielectric properties under a high electric field (ac-field) of BaTiO3-based ceramics with core grains, shell grains and core-shell grains were compared with those of multilayer ceramic capacitors (MLCCs) with these three kinds of grains. The MLCCs with the X7R specification had a core-shell structure, and the relative dielectric permittivity (\\\\varepsilonr) of the dielectric layers in the MLCCs increased with

Takaaki Tsurumi; Hiroshige Adachi; Hirofumi Kakemoto; Satoshi Wada; Youichi Mizuno; Hirokazu Chazono; Hiroshi Kishi

2002-01-01

159

Electrical properties and distortion characteristics of MLCCs with composite dielectric material  

Microsoft Academic Search

The electrical properties and distortion characteristics of multilayer ceramic capacitors (MLCCs) with composite dielectric material, which consisted of ferroelectric and paraelectric phases were studied. In composite dielectrics, BaTiO3 (BTO) was used for the ferroelectric phase, while SrTiO3 (STO) and CaTiO3 CTO were used for the paraelectric phases. The dielectric ceramics with composite structure of MLCC were prepared with these perovskite

M. Miyauchi; K. Takano; A. Sato; Y. Nakano

2007-01-01

160

Dielectric properties of nanoscale multi-component systems: A first principles computational study  

Microsoft Academic Search

A new method has been developed within the framework of density functional theory to aid in the study of the dielectric properties\\u000a of multi-component systems, with explicit treatment of surface and interface effects. Specially, we have determined the position\\u000a dependent dielectric constant profiles for Si–SiO2 and SiO2-polymer systems. We find that at regions close to surfaces and interfaces, the dielectric

N. Shi; R. Ramprasad

2007-01-01

161

Effect of combined external uniaxial stress and dc bias on the dielectric property of BaTiO3-based dielectrics in multilayer ceramic capacitor: thermodynamics and experiments  

Microsoft Academic Search

The dielectric properties of (Nb, Y)-doped BaTiO3 in a multilayer ceramic capacitor (MLCC) under combined external uniaxial compressive stress and dc bias field were investigated at room temperature by using a modified Ginsburg-Landau-Devonshire thermodynamic theory and the dielectric measurement. It is found that although dc bias decreases the dielectric properties dominantly, the influence of the external uniaixial compressive stress should

Gang Yang; Zhenxing Yue; Tieyu Sun; Huanlin Gou; Longtu Li

2008-01-01

162

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

163

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

Microsoft Academic Search

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

E. R. Mognaschi; L. M. Laboranti

1994-01-01

164

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

165

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

166

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...

167

Dielectric properties of epoxy\\/alumina nanocomposite influenced by control of micrometric agglomerates  

Microsoft Academic Search

Introduction of metal oxide nanoparticles to polymer material is known to have unique dielectric behavior and significant advantages in electrical insulation performance in power apparatus. This paper presents an attempt to clarify the influence of dispersibility of nanoparticles, especially focusing on agglomerates, on dielectric properties of a nanocomposite system by changing particle dispersion processes. Experiments were carried out in epoxy\\/alumina

Muneaki Kurimoto; Hitoshi Okubo; Katsumi Kato; Masahiro Hanai; Yoshikazu Hoshina; Masafumi Takei; Naoki Hayakawa

2010-01-01

168

Effect of zinc oxide additives on the dielectric properties of steatite materials  

Microsoft Academic Search

The authors assess the effects of zinc oxides on the dielectric properties--specifically the permittivity, the tangent of the dielectric loss angle, and the bulk electrical resistivity--as well as on the sinterability and refractivity of a series of steatite ceramics composed of various ratios of the oxides of magnesium, silicon, aluminium, titanium, iron, barium, zirconium, potassium, and sodium.

A. V. Zonov; F. Ya. Kharitonov

1987-01-01

169

Measuring and modeling of radiofrequency dielectric properties of chicken breast meat  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

170

Temperature dependence of the dielectric properties of the insulation system of power transformers  

Microsoft Academic Search

Due to the age of power transformers in service, diagnostic methods to monitor the dielectric properties of the insulation have become a very important subject. One of the methods to do this is the Return Voltage Method that allows the calculation of the dielectric time constants of the two insulating materials cellulose and oil. These parameters are sensitive to the

Rainer Patsch; Johannes Menzel

2009-01-01

171

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

Microsoft Academic Search

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

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

2004-01-01

172

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

173

Crystallinity and dielectric properties of PEEK, poly(ether ether ketone)  

Microsoft Academic Search

The dependence of specific dielectric properties of polymers on their fundamental molecular parameters was investigated as part of a study involving HV insulation in spacecraft systems. As part of an effort to understand the causes of dielectric breakdown, this investigation focused on the effect of polymer morphology on the electrical characteristics of a poly (ether ether ketone) (PEEK), a high

T. W. Giants

1994-01-01

174

Correlation of optical and dielectric properties of water trees in polyethylene  

Microsoft Academic Search

Many experimental works report that the presence of water trees lowers the voltage needed for the initiation of dielectric breakdown in polyethylene. The influence of water trees on the dielectric breakdown is generally related to their length. Here, in addition to this spatial property, we consider the extinction of the light by the water trees due mainly to scattering of

1993-01-01

175

TEMPERATURE-DEPENDENT BEHAVIOR OF DIELECTRIC PROPERTIES OF BOUND WATAER IN GRAIN AT MICROWAVE FREQUENCIES.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Dielectric behavior of bound water in grain was investigated through measurement of the dielectric properties of hard red winter wheat at microwave frequencies over a wide temperature range between –80 degrees C and +10 degrees C. Measurements were performed in free space between 2 and 18 GHz on tw...

176

INVESTIGATING MEASUREMENTS OF THE DIELECTRIC PROPERTIES OF GRANULAR MATERIALS WITH MICROSTRIP ANTENNAS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Indirect dielectric-based methods for bulk density and moisture content determination in granular materials have the advantage of being nondestructive and instantaneous. Success of these methods relies in the first place on the accuracy with which the dielectric properties are measured and the relia...

177

Frequency and Temperature Dependent Dielectric Properties of Free-standing Strontium Titanate Thin Films  

Microsoft Academic Search

We will report on the frequency and temperature dependence of the complex dielectric function of free-standing strontium titanate (STO) films. STO is an incipient ferroelectric with electric-field tunable dielectric properties of utility in microwave electronics. The films are grown epitaxially via pulsed laser deposition on a variety of substrates, including lanthanum aluminate (LAO), neodymium gallate (NGO), and STO. An initial

Mark J. Dalberth; Renaud E. Stauber; Britt Anderson; John C. Price; Charles T. Rogers

1998-01-01

178

Effect of composition on coupled electric, magnetic, and dielectric properties of two phase particulate magnetoelectric composite  

NASA Astrophysics Data System (ADS)

The particulate composite materials of ferrite-ferroelectric ceramics viz. nickel-cobalt-copper ferrite (i.e., Ni0.94Co0.01Cu0.05Fe2O4) and barium titanate were synthesized by the double sintering ceramic technique. The presence of constituent phases in the composites was confirmed by x-ray diffraction studies. The average grain size was calculated by using a scanning electron micrograph. The electrical properties such as dc resistivity and thermo-emf were measured as a function of temperature and volume fraction of constituent phases. The ac conductivity was calculated from dielectric data in the frequency range from 100 Hz to 1 MHz. It is concluded that the conduction in the present composites is due to small polarons. The relative dielectric constant measured as a function of applied frequency varies with the variation in the dc resistivity and molar fraction of constituent phases. It shows dispersion in the lower frequency range. The hysteresis behavior was studied to understand the magnetic properties such as saturation magnetization (Ms) and magnetic moment (?B). The static magnetoelectric (ME) voltage coefficient was measured as a function of applied dc magnetic field. It increases first and then falls down with increasing magnetic field. The variation in ME response has been explained in terms of content of ferrite phase, resistivity of composites, and intensity of magnetic field. The maximum ME conversion factor of 637 ?V/cm Oe was observed for the composite with 30% Ni0.94Co0.01Cu0.05Fe2O4+70% BaTiO3. These composites may be useful as phase shifters, magnetic sensors, cables, etc.

Devan, R. S.; Chougule, B. K.

2007-01-01

179

Laboratory measurements of static and dynamic elastic properties in carbonate  

Microsoft Academic Search

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

Aiman M. Bakhorji

2010-01-01

180

Static and dynamic properties of multiple light scattering  

Microsoft Academic Search

We have examined the onset and evolution of multiple scattering of light on a series of latex dispersions as a function of increasing volume concentration ? of particles. We have shown that using vertically polarized incident light, the static scattered intensity becomes progressively depolarized, with increasing ?. The polarization of scattered light is completely random in the limit of strong

1993-01-01

181

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

PubMed

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

Samuel, D; Trabelsi, S

2012-08-01

182

Fire safety properties of some transformer dielectric liquids  

SciTech Connect

This paper reviews the fire hazard properties of some transformer fluids of reduced flammability. Fluids examined include a silicone (polydimethylsiloxane), a high molecular weight aliphatic hydrocarbon and a polyalphaolefin. Fire hazard properties determined include ease of ignition, flame spread, fire growth and rate of heat release (large scale pool burns), rate of smoke evolution, fire-gas and smoke toxicity, and extinguishment behaviour. Large, static pool burns performed to simulate a 'worst case' scenario for a catastrophic transformer failure. The effect of ignition method and pool diameter on fire hazard properties is presented. Results clearly show the beneficial effect of silica ash formation on the surface of a burning silicone transformer fluid. The white, reflective ash layer effectively shields the fluid beneath from energy feedback by the flame. This effect leads to a substantially lower fire hazard for the silicone than is found for the hydrocarbon fluids, which do not form protective ash or char layers. The silicones demonstrate a lower degree of hazard than the hydrocarbons in all of the fire properties examined.

Lipowitz, J.

1982-01-01

183

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

Microsoft Academic Search

Performance of materials and their compatibility determine the size of the electrical insulation in power equipment. For this reason dielectric properties of electrical insulation materials are needed for low temperature power applications. In this work we report the dielectric properties of four polymers: polyvinyl alcohol (PVA), poly(methyl methacrylate) (PMMA), polyvinyl butyral resin (PVB), and polyimide (PI-Kapton®). The dielectric measurements are

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

2008-01-01

184

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

Microsoft Academic Search

Performance of materials and their compatibility determine the size of the electrical insulation in power equipment. For this reason dielectric properties of electrical insulation materials are needed for low temperature power applications. In this work we report the dielectric properties of four polymers: polyvinyl alcohol (PVA), poly(methyl methacrylate) (PMMA), polyvinyl butyral resin (PVB), and polyimide (PI–Kapton®). The dielectric measurements are

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

2008-01-01

185

Dielectric properties of BaTiO3 polydomain crystals  

Microsoft Academic Search

The dielectric permittivity of BaTiO3 polydomain crystals with 90° domain walls is investigated over a wide frequency range. It is shown that reversible 90° reorientations of domains occuring in these crystals produce a great contribution to the dielectric permittivity, electromechanical coupling factors, piezoelectric constants and elastic compliance coefficients. Two regions of dispersion of permittivity which are related with piezoelectric oscillations

A. V. Turik; G. I. Khasabova

1978-01-01

186

Ag-Ba0.75Sr0.25TiO3 composites with excellent dielectric properties  

NASA Astrophysics Data System (ADS)

The percolative ceramic composites of Ba0.75Sr0.25TiO3/Ag (BST/Ag) with dense microstructure were sintered at a low temperature of 960 °C. Excellent dielectric properties, such as high dielectric constant (?r~24 000), low dielectric loss, and high dielectric tunability, were reported. The dielectric constant is found to be nearly temperature and frequency independent. It is essential to introduce the low-melting-point metal of silver into BST ceramics for significantly enhancing the dielectric properties of the composites. The superproperties make it potential to be used for electronic devices such as high charge-storage capacitors and tunable filters.

Huang, Jiquan; Cao, Yongge; Hong, Maochun; Du, Piyi

2008-01-01

187

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

NASA Astrophysics Data System (ADS)

Pure and magnesium sulfate-doped triglycine sulpho-phosphate (TGSP) single crystals were grown by solution method with the slow evaporation technique. Solubility of the samples in de-ionized water was found in various temperatures ranging from 30 to 60 °C. Single-crystal X-ray diffraction (XRD) studies on the grown crystals reveal the monoclinic crystal structure. Atomic absorption study (AAS) was carried out to confirm the presence of Mg2+ in the grown doped TGSP crystals. Dielectric constant and dielectric loss of undoped and magnesium sulfate-doped TGSP crystals were measured for various frequencies and temperatures. It is observed from the studies that solubility and dielectric properties like dielectric constant and dielectric loss increase when TGSP crystal is added with magnesium sulfate. Thermogravimetric and differential thermal analyses (TG/DTA) on the grown crystals have been carried out. The effect of impurity (magnesium sulfate) on structural, electrical and thermal properties of TGSP crystals has been investigated.

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

2008-12-01

188

Temperature dependence dielectric properties of modified barium titanate-PVB composites  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

189

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

190

Nausogenic properties of various dynamic and static force environments  

NASA Astrophysics Data System (ADS)

Motion sickness can occur when an accelerating force acting on the human body repeatedly changes amplitude and direction or both. It also can occur without any motion after transfer into a constant force field significantly different from Earth-gravity. Dynamic and static causes of motion sickness can be distinguished accordingly. Space sickness, too, has dynamic as well as static aspects. Dynamic space sickness might depend on increased bilateral differential sensitivity of the peripheral and central vestibular apparatus, whereas static space sickness may be caused by erroneous compensation of bilaterial asymmetries of the otolith-system in the microgravity environment. Experiments in airplanes, cars and on a vestibular sled have shown that the susceptibility to motion sickness is highest for changes of acceleration in the negative X-axis (as compared to the other axes) of the body. During reciprocating linear accelerations on the vestibular sled, standstill periods of movement and the direction of movement cannot correctly be indicated, because the peripheral vestibular apparatus lacks true motion detectors.

Von Baumgarten, R. J.; Vogel, H.; Kass, J. R.

191

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

NASA Astrophysics Data System (ADS)

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

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

2001-06-01

192

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

193

Dielectric properties of betaine phosphite and deuterated betaine phosphite films  

SciTech Connect

Polycrystalline films of betaine phosphite (BPI) and deuterated BPI have been grown by evaporation on LiNbO{sub 3}, {alpha}-SiO{sub 2}, {alpha}-Al{sub 2}O{sub 3}, and NdGaO{sub 3} substrates. These films consist of large single-crystal blocks in which the polar axis (b) lies in the substrate plane. The results of studying the dielectric properties of the films using interdigital electrodes, X-ray diffraction, and block images in a polarized-light microscope in reflection are reported. The film transition into the ferroelectric state at T = T{sub c} is accompanied by strong anomalies of the capacitance of the film/interdigital structure/substrate structure. The deuteration of BPI films leads to an increase in their temperature T{sub c}: from T{sub c} = 200 K for BPI-based structures to T{sub c} = 280 K for structures with a high degree of deuteration (d {approx} 90%).

Balashova, E. V., E-mail: balashova@mail.ioffe.ru; Krichevtsov, B. B.; Zaitseva, N. V. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Pankova, G. A. [Russian Academy of Sciences, Institute of Macromolecular Compounds (Russian Federation); Frederiks, I. D.; Lemanov, V. V. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

2011-01-15

194

Dielectric relaxation behaviour of Bi:SrTiO 3: II. Influence of heat treatment on dielectric properties  

Microsoft Academic Search

The study of the dielectric properties of (Sr1 ? 1.5x Bix) TiO3 ceramics in a range of temperatures and at several frequencies showed that a set of permittivity peaks situated around 200–300 K had frequency dispersion behaviour. These peaks were shifted to higher temperatures when the Bi content increased in the solid solution. The activation energy calculated for the relaxation

Yu Zhi; Ang Chen; P. M. Vilarinho; P. Q. Mantas; J. L. Baptista

1998-01-01

195

A dielectric property measurement system for thin samples based on a resonant cavity with three dielectric regions  

NASA Astrophysics Data System (ADS)

A new technique for measurement of the dielectric property of thin samples (some hundreds of micrometres) by means of a cylindrical resonant cavity is proposed. These measurements are usually subject to a number of problems mainly due to the presence of an air gap between the sample and the end plate against which it is placed. Maxwell equations have been solved for a cylindrical resonant cavity containing three dielectric regions. This configuration is well suited for the measurement of permittivity of thin samples for microwaves. Necessary software for analysis of the equations obtained has been developed and used to assess the systematic errors produced by the air gap, when the traditional TE01n cavity, with two dielectric regions, is used in the measurement of permittivity. The convenience of using three dielectric regions, instead of the traditional configuration with only two regions, is assessed in this paper. Theoretical results are compared with measurements performed at 15 GHz in Stycast, Macor and sapphire standard materials. It is shown that, with this new configuration, precise experimental data may be obtained for samples as thin as 0.3 mm.

Molla, J.

2002-01-01

196

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

NASA Astrophysics Data System (ADS)

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

Jean, Jau-Ho; Kuan, Tong-Hua

1995-04-01

197

Dielectric properties for the binary mixture of dimethylsuphoxide and dimethylacetamide with 2-nitrotoluene at microwave frequencies  

Microsoft Academic Search

The dielectric properties of various organic solvents and binary solvent mixtures at different temperatures over the frequency range of 10MHz–20GHz, are investigated using the time domain reflectometry technique, at various temperatures from 15 to 45°C. These solvent mixtures—dimethylacetamide–2-nitrotoluene and dimethylsulphoxide–2-nitrotoluene as well as pure solvents display a Debye type dispersion. Their frequency-dependent dielectric properties can be summarized by the three

Ajay Chaudhari; Harish Chaudhari; Suresh Mehrotra

2002-01-01

198

Dielectric and mechanical properties of porous Si 3N 4 ceramics prepared via low temperature sintering  

Microsoft Academic Search

Borophosphosilicate bonded porous silicon nitride (Si3N4) ceramics were fabricated in air using a conventional ceramic process. The porous Si3N4 ceramics sintered at 1000–1200°C shows a relatively high flexural strength and good dielectric properties. The influence of the sintering temperature and contents of additives on the flexural strength and dielectric properties of porous Si3N4 ceramics were investigated. Porous Si3N4 ceramics with

Yongfeng Xia; Yu-Ping Zeng; Dongliang Jiang

2009-01-01

199

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

Microsoft Academic Search

Compositional design and properties of a low-dielectric-constant silica composite containing borosilicate glass, high-silica glass and gallium oxide are described. A cristobalite-free silica dielectric with a high sintered density, >95%, is obtained at temperatures less than 1000° C. An analytical approach assuming the mixing rule is used to design compositions with desirable properties, and validated by experimental results. Compositions with a

Jau-Ho Jean; Tong-Hua Kuan

1995-01-01

200

Dielectric properties measurement of substrate and support materials  

NASA Astrophysics Data System (ADS)

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

Wu, Te-Kao

1990-08-01

201

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

202

Laboratory measurements of static and dynamic elastic properties in carbonate  

NASA Astrophysics Data System (ADS)

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

Bakhorji, Aiman M.

203

Static electrically charged fluids in terms of pressure: general property  

NASA Astrophysics Data System (ADS)

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

Bijalwan, Naveen

2011-07-01

204

Reflective Properties of Grid Structures with Dielectric Coating.  

National Technical Information Service (NTIS)

The based on the solution of an integral equation method for calculating electrodynamic characteristics of a half-wave dipole located above the grid screen with dielectric coating is considered in the article. The acquired analysis results allow to estima...

M. U. Sitsko V. I. Demidtchik

2002-01-01

205

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

PubMed

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

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

2013-06-01

206

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

PubMed

Electrorheological (ER) and dielectric properties under high electric fields were measured simultaneously on hydroxypropylcellulose suspension. When measuring these properties as a function of frequency of the electric field, we found a positive peak in each spectrum of the ER effect and the first-order dielectric permittivity while a negative one in the spectrum of the third-order dielectric permittivity with these peak frequencies nearly equal to (shear rate)/4pi . Referring to the well-known results for the particle rotation in the sheared suspension, it is suggested that the observed peaks are due to shear-induced particle rotation and the rotation occurs even under high electric field. On the basis of these results, effects of the particle rotation on the ER and the dielectric properties are discussed. PMID:15697367

Misono, Y; Negita, K

2004-12-28

207

Microstructure Study For Optimization Of Dielectric Property Of Electrical Porcelain  

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

208

Dielectric Properties of Soils at UHF and Microwave Frequencies  

Microsoft Academic Search

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

P. Hoekstra; A. Delaney

1974-01-01

209

Dielectric properties of zinc oxide\\/low density polyethylene nanocomposites  

Microsoft Academic Search

ZnO\\/low density polyethylene (LDPE) nanocomposites with either homogeneous or controlled inhomogeneous dispersions of ZnO nanoparticles were prepared. The dielectric constants of the composites with filler concentrations up to 40 vol.% were measured and compared with the dielectric constants of conventional submicron size ZnO filled LDPE composite. The filler particles were coated with silane coupling agents and mixed with LDPE to

J. I. Hong; P. Winberg; L. S. Schadler; R. W. Siegel

2005-01-01

210

Dielectric properties and crystalline characteristics of borosilicate glasses  

Microsoft Academic Search

Packaging substrates play a significant role in the development of large-scale integrated circuit. Low dielectric constant materials are expected in order to reduce the time delay of signal propaganda. On the other hand, sintering aid is required for low temperature co-firing process. Glass\\/ceramic composite system is considered one of the most promising candidates because of its both low dielectric constant

Zhongjian Wang; Yichen Hu; Hongkai Lu; Fang Yu

2008-01-01

211

Electrical conductivity and dielectric properties of sulfamic acid doped polyaniline  

Microsoft Academic Search

The temperature and frequency dependence of dielectric constant (??) and dielectric loss (??) is studied for different samples of polyaniline (PANI), doped with different concentration of sulfamic acid in the frequency range (10–100kHz) and temperature range (300–400K). The dc conductivity has also been measured to see the effect of sulfamic acid and the conduction mechanism has been explained by the

Sadia Ameen; Vazid Ali; M. Zulfequar; M. Mazharul Haq; M. Husain

2007-01-01

212

Microstructure Study For Optimization Of Dielectric Property Of Electrical Porcelain  

SciTech Connect

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

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

2010-06-29

213

Effect of DC bias on dielectric properties of nanocrystalline CuAlO2  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

214

Dielectric properties of the charge-ordered mixed oxide CaMn7O12  

NASA Astrophysics Data System (ADS)

We present in this paper a detailed investigation of the dielectric properties of the mixed oxide CaMn7O12 that shows a charge-ordering transition at TCO = 440 K. Surprisingly, this compound presents a high dielectric constant at room temperature. Data taken at several frequencies and temperatures point to relaxor dielectric behaviour, that can be attributed to the electronic inhomogeneities present in the material. Extrinsic Maxwell-Wagner effects make a significant contribution to this dielectric response, as revealed by the studies made on samples of different particle size and using different types of contact. The intrinsic dielectric constant of this material is ?r (intrinsic)'~30 at room temperature, a value that is relatively high for this type of compound and that we relate to the presence of the electronic process of charge ordering in this material.

Castro-Couceiro, A.; Yáñez-Vilar, S.; Rivas-Murias, B.; Fondado, A.; Mira, J.; Rivas, J.; Señarís-Rodríguez, M. A.

2006-04-01

215

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

SciTech Connect

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

Tuncer, Enis [ORNL

2006-01-01

216

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

SciTech Connect

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

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

2006-01-01

217

Correlations of the stability, static dipole polarizabilities, and electronic properties of yttrium clusters.  

PubMed

Static dipole polarizabilities for the ground-state geometries of yttrium clusters (Yn, n < or = 15) are investigated by using the numerically finite field method in the framework of density functional theory. The structural size dependence of electronic properties, such as the highest occupied molecular orbital-lowest occupied molecular orbital (HOMO-LUMO) gap, ionization energy, electron affinity, chemical hardness and softness, etc., has been determined for yttrium clusters. The energetic analysis, minimum polarizability principle, and principle of maximum hardness are used to characterize the stability of yttrium clusters. The correlations of stability, static dipole polarizabilities, and electronic properties are analyzed especially. The results show that static polarizability and electronic structure can reflect obviously the stability of yttrium clusters. The static polarizability per atom decreases slowly with an increase in the cluster size and exhibits a local minimum at the magic number cluster. The ratio of the mean static polarizability to the HOMO-LUMO gap has a much lower value for the most stable clusters. The static dipole polarizabilities of yttrium clusters are highly dependent on their electronic properties and are also partly related to their geometrical characteristics. A large HOMO-LUMO gap of an yttrium cluster usually corresponds to a large dipole moment. Strong correlative relationships of the ionization potential, softness, and static dipole polarizability are observed for yttrium clusters. PMID:19722531

Li, Xi-Bo; Wang, Hong-Yan; Lv, Ran; Wu, Wei-Dong; Luo, Jiang-Shan; Tang, Yong-Jian

2009-09-24

218

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

219

Effect of nanoparticles on the dielectric properties of polyimide  

NASA Astrophysics Data System (ADS)

As part of a search for a better dielectric for use in high energy density capacitors, polyimide (PI) films containing a layered material, zirconium orthophosphate, ZrO(H2PO4)2·xH2O (?-ZrP), were fabricated. PI has the advantage that it can be used to very high temperatures. To characterize the materials, x-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dielectric measurements (permittivity, loss and breakdown strength) were made. The permittivity and loss studies were also carried out on both neat PI films and ?-ZrP. The XRD, DSC and TGA results are consistent with amorphous composites. The effects of water or other impurities were observed in all three kinds of dielectric studies on all three types of material. For example, the relative permittivity of the composites decreased strongly when water was removed from the materials. Nonetheless, some increase in the relative permittivity of the dry nanocomposites was observed. Impurity or water-associated loss peaks were observed in all three types of material. The frequency and temperature dependences of the loss peaks made it possible to identify which were true relaxations. The effect of water is to decrease the dielectric strength of the composites. However, in both the wet and dry materials, the dielectric strength exhibits a maximum at a loading of about 5 wt% ?-ZrP.

Bestaoui-Spurr, Naima; Edmondson, C. A.; Wintersgill, M. C.; Fontanella, J. J.; Adams, Todd

2011-09-01

220

Microwave dielectric properties of glass-MCT low temperature co-firable ceramics  

Microsoft Academic Search

Interaction between the (Mg0.95Ca0.05)TiO3 (MCT) microwave dielectric materials and BaBSiO glass materials was examined. Rigorous interaction occurs when the MCT-glass composite materials were densified at 800–900 °C, which, fortunately, does not seriously degrade the microwave dielectric properties of the materials such that dielectric constant (K)=8–10 was achieved for MCT-glass composite materials, no matter whether they were in pellet or tape form.

Cheng-Sao Chen; Chen-Chia Chou; Chang-Shun Chen; I-Nan Lin

2004-01-01

221

Dielectric Properties and Phase Transition in CaCu3Ti4O12 at High Temperatures  

Microsoft Academic Search

The dielectric properties and structural behavior of perovskite-related CaCu3Ti4O12 were studied at high temperatures. The dielectric constant increases gradually with increasing temperature and shows a shoulder-like round anomaly at approximately 630 K at 10 kHz. At 732 K, a new dielectric anomaly was found, where the peak value of the dielectric constant, \\\\varepsilonpeak~= 2.8× 106 at a frequency of 10

Akira Onodera; Masaki Takesada; Keiichi Kawatani; Shogo Hiramatsu

2008-01-01

222

Temperature and frequency dependent electrical and dielectric properties of Al\\/SiO 2\\/pSi (MOS) structure  

Microsoft Academic Search

The electrical and dielectric properties of Al\\/SiO2\\/p-Si (MOS) structures were studied in the frequency range 10kHz–10MHz and in the temperature range 295–400K. The interfacial oxide layer thickness of 320Å between metal and semiconductor was calculated from the measurement of the oxide capacitance in the strong accumulation region. The frequency and temperature dependence of dielectric constant (??), dielectric loss (??), dielectric

?. Alt?ndal; M. M. Bülbül

2005-01-01

223

Enhanced dielectric and ferroelectric properties of Ca2+ substituted sodium bismuth titanate  

NASA Astrophysics Data System (ADS)

In order to find the environmental friendly materials for various possible applications in near future, We have synthesized a series of new complex perovskite oxides CaxNa1-x(Bi1/2Ti1/2)O3 (CNBT) (where x = 0.00, 0.25, 0.50 and 0.75) by solid state reaction technique and studied the effect of Ca substitution in Na(Bi1/2Ti1/2)O3 through the microstructure, dielectric and ferroelectric properties. The frequency dependence of the dielectric constant at room temperature shows that the value of dielectric constant increases with Ca2+ substitution at room temperature. The analysis of real part of the dielectric permittivity shows Debye like relaxation with frequency at room temperature. The polarization hysteresis loops plotted at room temperature reveal the ferroelectric property for all compositions of the CNBT samples.

Bharti, Chandrahas; Sen, A.; Sinha, T. P.

2013-02-01

224

Dielectric properties of egg whites and whole eggs as influenced by thermal treatments  

Microsoft Academic Search

Effects of cooking on dielectric properties of liquid whole eggs and liquid egg whites were studied in connection with radio frequency and microwave heating processes to preserve shelf-stable products. Dielectric measurements were made using an open-ended coaxial probe method over a temperature range of 20 and 120°C at radio frequencies 27 and 40MHz, and microwave frequencies 915 and 1800MHz. Thermal

Jian Wang; Juming Tang; Yifen Wang; Barry Swanson

2009-01-01

225

Dielectric properties and space charge behavior in SiC ceramic capacitor  

Microsoft Academic Search

Strong space charge response is observed in SiC ceramic capacitors at low frequencies up to 0.1 MHz. It leads to a dielectric constant of 2 910 000 at 100 Hz. The critical temperature is observed near 773 K. The losses decrease with increasing temperature. Strong frequency dependence of the dielectric properties is also detected. The SiC ceramic capacitor might be

Rui Zhang; Lian Gao; Hailong Wang; Jingkun Guo

2004-01-01

226

Study of the dielectric properties of barium titanate–polymer composites  

Microsoft Academic Search

A comparative study of complex dielectric properties has been carried out at the X-band of microwave frequencies of composites of barium titanate (BaTiO3) with two different polymer matrices: insulating polyaniline (PANI) powder (emeraldine base) and maleic resin. From these studies, it is observed that the composites of BaTiO3 with maleic resin show normal composite behavior and the dielectric constant follows

H. C. Pant; M. K. Patra; Aditya Verma; S. R. Vadera; N. Kumar

2006-01-01

227

Dielectric property of nickel\\/calcium copper titanate\\/Polyvinylidene Fluoride composite  

Microsoft Academic Search

This paper reports a nickel (100nm)\\/calcium copper titanate (1um)\\/ Polyvinylidene Fluoride three-phase composite prepared through a simple blending and hot-molding procedure. The microstructure and dielectric properties of the composites were analyzed using scanning electron microscope (SEM), and impedance analyzer. The results show that the dielectric constant ?r rises from 49 to 140 with the loss tangent increasing from 0.23 to

Wenhu Yang; Shuhui Yu; Rong Sun; Ruxu Du

2010-01-01

228

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

229

Microwave tunable dielectric properties of multilayer CNT membranes for smart applications  

NASA Astrophysics Data System (ADS)

Multilayer multiwall carbon nanotube (MWCNT) silicone composite membranes with thickness greater than 10 ?m were prepared with a spin-coating method. Dielectric permittivity and tunability of the circular membranes were measured from 0.1 to 7 GHz by using a single-port coaxial line method. The frequency and bias voltage dependent dielectric properties were interpreted based on percolation theory. The MWCNT membranes could be potentially used to develop smart components and structures working at radio wave or microwave frequencies.

Liu, L.; Yang, Z. H.; Kong, L. B.; Yin, W. Y.; Wang, S.

2012-09-01

230

Synthesis and dielectric properties of Fe doped SmCrO3 semiconductor ceramics  

NASA Astrophysics Data System (ADS)

Polycrystalline Fe doped SmCrO3 perovskite ceramics were characterized by X-ray diffraction (XRD). The dielectric properties of perovskite Fe doped SmCrO3 ceramics were investigated in the frequency range of 100Hz - 1MHz in the temperature range from 80 K to 300 K. These materials exhibited colossal dielectric constant value of ~ 104 at room temperature. The response is similar to that observed for relaxorferroelectrics. To get the detailed information IS data analysis was performed.

Prasad, Bandi Vittal; Rao, B. Venugopal; Narsaiah, K.; Rao, G. Narsinga; Chen, J. W.; Babu, D. Suresh

2013-06-01

231

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

Microsoft Academic Search

The associating behaviour of liquid caprylic acid has been studied by the determination of its dielectric properties. Experimental results of measurements of dielectric permittivity are reported. The molecular correlation factor was obtained with reference to the Kirkwood-Fröhlich theory and compared with the Abbott-Bolton model for non spherical molecules from above the MP to 392K. On going from low to high

E. R. Mognaschi; L. M. Laboranti; A. Chierico

1993-01-01

232

Terahertz dielectric properties of plasma-sprayed thermal-barrier coatings  

Microsoft Academic Search

We investigated the electromagnetic wave transmittance and dielectric properties of yttria partially stabilised zirconia thermal-barrier coatings by terahertz time-domain spectroscopy in which the samples were irradiated by a pulsed THz wave in the frequency range of 0.1–6.3THz. The coating microstructure was varied by changing the spray conditions and the THz transmittance and dielectric constants were examined as functions of frequency.

Makoto Watanabe; Seiji Kuroda; Hisashi Yamawaki; Mitsuharu Shiwa

2011-01-01

233

Dielectric, thermal, and mechanical properties of the semiorganic nonlinear optical crystal sodium p-nitrophenolate dihydrate  

Microsoft Academic Search

Physical properties such as dielectric, specific heat, thermal expansion, and mechanical hardness have been measured for sodium p-nitrophenolate dihydrate single crystals. The dielectric measurements were made both as a function of frequency (in the range 15 kHz-10 MHz) and temperature (in the range 30-80 °C). For the range of frequencies measured the values were found to vary between 4.03 and

S. Brahadeeswaran; H. L. Bhat; N. S. Kini; A. M. Umarji; P. Balaya; P. S. Goyal

2000-01-01

234

Dielectric, thermal, and mechanical properties of the semiorganic nonlinear optical crystal sodium p-nitrophenolate dihydrate  

Microsoft Academic Search

Physical properties such as dielectric, specific heat, thermal expansion, and mechanical hardness have been measured for sodium p-nitrophenolate dihydrate single crystals. The dielectric measurements were made both as a function of frequency (in the range 15 kHz–10 MHz) and temperature (in the range 30–80 °C). For the range of frequencies measured the values were found to vary between 4.03 and

S. Brahadeeswaran; H. L. Bhat; N. S. Kini; A. M. Umarji; P. Balaya; P. S. Goyal

2000-01-01

235

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

236

Dielectric and conductivity properties of composite polyaniline/polyurethane network  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

237

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

Microsoft Academic Search

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

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

2007-01-01

238

Static and dynamic properties of high-density metal honeycombs  

Microsoft Academic Search

Metal honeycombs are commonly used to absorb energy in applications involving impact because of their high-energy capacity to weight ratio. The energy capacity of a material will be affected by any strain-rate effect in the material; thus knowledge of this property is necessary for design purposes. The materials studied in this work were a thick-walled aluminum and stainless-steel honeycomb. A

W. E. Baker; T. C. Togami; J. C. Weydert

1998-01-01

239

Direct measurement of static yield properties of cohesive suspensions  

Microsoft Academic Search

A technique of yield stress investigation based upon the combined use of two devices (an applied stress rheometer and an instrument for measuring the propagation velocity of small amplitude, torsional shear waves) is described. Investigations into the low shear rate rheological properties of illitic suspensions are reported for shear rates, typically, in the range 10-4— 10-1 s-1 under applied stresses

A. E. James; D. J. A. Williams; P. R. Williams

1987-01-01

240

Dielectric properties of sodium nitrite particles embedded into porous alumina  

NASA Astrophysics Data System (ADS)

Porous anodic alumina templates were fabricated using a two-step anodization in oxalic and phosphoric acid solutions. Dielectric studies were carried out for ferroelectric sodium nitrite embedded into porous alumina. Phase transition temperature in sodium nitrite within porous alumina is shifted compared to the bulk ferroelectric Curie point. The sign of this shift depends on the experimental conditions of sample preparation.

Alexeeva, N. O.

2013-08-01

241

Dielectric properties of nickel-doped NaCl crystals  

Microsoft Academic Search

The influence of nickel impurities upon dielectric losses in natrium chloride crystals is studied. Experiments have shown that in non-heated samples, stored over prolonged periods of time, the majority of nickel is present in the form of aggregates and higher complexes. Their decomposition and the building up of dipoles depends in the first instance on sample heating and cooling methods.

M. Kaderka

1969-01-01

242

Measurement of dielectric properties in gigahertz to terahertz frequency range  

Microsoft Academic Search

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

Ming Li

2000-01-01

243

Influence of fibrous contaminants on dielectric property of XLPE insulation  

Microsoft Academic Search

The influence of fibrous contaminants on the electrical breakdown strength of crosslinked polyethylene (XLPE) insulated cables and the breakdown mechanism resulting from fibrous contaminants are discussed. It has been found that natural cotton fibers decrease the dielectric strength of the XLPE insulation much more than synthetic fibers, which means that cotton fabrics should not be allowed into the jointing room,

K. Kaminaga; S. Iida; S. Fukunaga; K. Yatsuka; Y. Inoue

1992-01-01

244

Structure and Properties of Epitaxial Dielectrics on gallium nitride  

Microsoft Academic Search

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 (epsilo) and high band gap energy (Eg), can

Virginia Danielle Wheeler

2009-01-01

245

The Dielectric Properties of Water and Heavy Water  

Microsoft Academic Search

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

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

1948-01-01

246

Properties of Transgenic Rapeseed Oil based Dielectric Liquid  

Microsoft Academic Search

Mineral oil is poorly biodegradable and has a low flash point. It does not satisfy the requirement of environmental sustainability and fireproofing. Whereas vegetable oil-based dielectric liquid is fully biodegradable and has a higher flash point and relative permittivity. This paper presents a type of insulating oil refined from a transgenic rapeseed oil. The oil-refining procedure is introduced. Chemical, physical

Xiaohu Li; Jian Li; Caixin Sun

2006-01-01

247

Effect of surface modification on dielectric and magnetic properties of metal powder\\/polymer nanocomposites  

Microsoft Academic Search

Metal nanopowder (Co and Fe)\\/polymer composites, both with and without surface modification by behenic acid, were fabricated and their dielectric and magnetic properties were measured at 1GHz to study the effect of surface modification on the electromagnetic properties. The relative permittivity and the real part of the permeability of the composites with surface modified powders were higher than those with

Kensaku Sonoda; Merja Teirikangas; Jari Juuti; Yasuo Moriya; Heli Jantunen

2011-01-01

248

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

Microsoft Academic Search

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

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

2009-01-01

249

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

PubMed

The dielectric properties of methylene blue (MB)-doped hydrogels were investigated by impedance spectroscopy. The real part (?') and the imaginary part (?") of the complex dielectric constant and the energy loss tangent/dissipation factor (tan ?) were measured in the frequency range of 10 Hz to 100 MHz at room temperature for pH 5.5 value. Frequency variations of the resistance, the reactance, and the impedance of the samples have also been investigated. The dielectric permittivity of the MB-doped hydrogels is sensitive to ionic conduction and electrode polarization in low frequency. Furthermore, the dielectric behavior in high-frequency parts was attributed to the Brownian motion of the hydrogen bonds. The ionic conduction for MB-doped samples was prevented for Cole-Cole plots, while the Cole-Cole plots for pure sample show equivalent electrical circuit. The alternative current (ac) conductivity increases with the increasing MB concentration and the frequency. PMID:23799863

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

2013-07-08

250

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

PubMed Central

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

2011-01-01

251

Static and dynamic magnetic properties of Co nanoparticles.  

PubMed

Co nanoparticles have been synthesized using wet-chemical methods. As-synthesized particles show a sharp low temperature peak in zero-field cooled (ZFC) magnetization well below the blocking transition temperature and this feature is associated with surface spin disorder. We have investigated the dynamic magnetic properties of Co using ac susceptibility and resonant RF transverse susceptibility (TS). We also studied the memory and relaxation effects in these nanoparticle systems. From these measurements we show a typical blocking behavior of an assembly of superparamagnetic nanoparticles with a wide distribution of blocking temperatures. The transverse susceptibility measurements on these particles show the presence of anisotropy even above the blocking temperature. The role of surface anisotropy and the size distribution of the particles on the observed memory and magnetic relaxation effects are discussed. PMID:19049180

Srinath, S; Poddar, P; Sidhaye, Deepti S; Prasad, B L V; Gass, J; Srikanth, H

2008-08-01

252

Effect of magnetic field on the dielectric properties of multiferroic composites  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

253

Local Dielectric Property of Hafnium and Lanthanum Atoms in HfLaOx  

NASA Astrophysics Data System (ADS)

In this work, we investigate the electronic contribution to local dielectric property of La2O3 and HfO2 using cluster models. The relation between the coordinate number of metal atoms and their bonding energy shows a hint that hafnia takes the cubic structure by the incorporation of La2O3 in HfO2. The local properties of polarizability and dielectric constant of La2O3 and HfO2 are closely similar to each other. It is considered to be one of the reasons why the incorporation of lanthanum atoms does not lower the permittivity of HfO2. We confirm this by the study of the local dielectric property of the HfLaOx cluster model. We compare the dielectric properties around an oxygen atom and that between the oxygen atom and a next metal atom. Our results show that the contribution to the dielectric response from the bond regions is not so large.

Fukushima, Akinori; Sugino, Shinya; Tsuchida, Yasushi; Senami, Masato; Tachibana, Akitomo

2010-12-01

254

Static and dynamic properties of thin-film ferromagnets  

NASA Astrophysics Data System (ADS)

We study the properties of thin ferromagnetic films with a uniaxial anisotropy perpendicular to the plane of the film. Describing the local magnetization as a vector of fixed length, we show that the energy in the thin film limit obeys a scaling relation, so that the system may be entirely described by rescaled anisotropy and applied field parameters. We develop a universal phase diagram for thin films in terms of these two variables. In particular, we study the behavior of films near the reorientation phase transition (RPT), the point at which the magnetostatic interaction overcomes the internal anisotropy to force the magnetization to lie in the plane. Previous studies have classified canted, polarized, and striped regions of the thermodynamic phase diagram, but have not found the boundaries of metastability necessary for an understanding of observed hysteresis curves. We determine these boundaries and the resulting hysteresis loops using analytic and numerical techniques. These loops match behavior observed in experiments. We proceed to investigate the dynamic properties of thin films, focusing in particular on the motion of domain walls down strips of thin ferromagnetic material. The rich internal structure of these walls greatly affects the motion when an external magnetic field is applied, leading to reduced mobility when the driving force is strong. In particular, in the wider strips used in many experimental studies, the wall is expected to contain a magnetic vortex at its heart. We develop a general collective coordinate method to describe the motion, valid for any number of coordinates used to model the wall. A two-coordinate model, using just the position of the vortex, leads to predictions for the average wall velocity that are in good agreement with numerical simulations of the full micromagnetic dynamics when the field is not too high. When the field is very high, additional coordinates are required. The formalism is sufficiently general as to allow the inclusion of spin current, and can be applied to films with in- or out-of-plane magnetic anisotropy.

Clarke, David J.

255

Influences of compressive stress and aging on dielectric properties of sodium bismuth titanate ceramics  

NASA Astrophysics Data System (ADS)

The influences of compressive stress and aging on dielectric properties of undoped and Fe-doped sodium bismuth titanate (NBT) ceramics were investigated. The dielectric properties were decreased significantly with the compressive stress applied parallel to the electric field direction, while the changes were reversed with the stress applied perpendicularly. In addition, lower changes of the dielectric properties with stress were observed in Fe-NBT ceramics, likely caused by an enhanced relaxor characteristic with the acceptor doping, which also reduced the aging rate in the ceramics. Finally, the aging behavior of the NBT and Fe-NBT ceramics followed the slightly stretched exponential law, and the aging rate in both ceramics was found to decrease with frequency, a result of the pinning of the polarization components. These observations clearly confirmed the role of the acceptor dopant in enhancing the relaxor ferroelectric characteristics in the NBT-based ceramics.

Sareein, T.; Unruan, M.; Ngamjarurojana, A.; Jiansirisomboon, S.; Watcharapasorn, A.; Yimnirun, R.

2009-04-01

256

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

NASA Astrophysics Data System (ADS)

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

Kagomiya, Isao; Suzuki, Itaru; Ohsato, Hitoshi

2009-09-01

257

Effect of Zr Substitution for Ti on the Dielectric and Ferroelectric Properties of Barium Titanate Thin Films  

Microsoft Academic Search

The paper reports the study of the effect of Zr contents on the dielectric, ferroelectric, leakage current and fatigue properties of Ba (ZrxTi1 ? x) O3 films. All these films exhibited high dielectric constant, which tends to be maximum for 5 at % (BZT5) Zr doped BaTiO3 film. The dielectric properties at the sub-switching ac oscillation field were analyzed following

R. S. Katiyar; A. Dixit; S. B. Majumder; A. S. Bhalla

2005-01-01

258

Electrical and dielectric properties of LiPON glasses  

Microsoft Academic Search

Analyzing the frequency dependences of real and imaginary part of the dielectric permittivities measured at various temperatures we can study the transport mechanisms connected with the ionic hopping motion of charge in ion conductive glasses. The experimental results getting from electric measurements on LiPON phosphate glasses are analyzed, discussed and compared. Arrhenius graphs constructed from d.c. and a.c. electrical measurements

Peter Hockicko; Peter Bury; Francisco Munoz

2012-01-01

259

Microwave dielectric properties of Li 2TiO 3 ceramics sintered at low temperatures  

Microsoft Academic Search

Li2TiO3 ceramics were prepared at the sintering temperatures from 1050 to 1250°C. The optimal microwave dielectric properties were ?r=23.29, Q×f=15,525GHz (5.9GHz), and ?f=35.05ppm\\/°C for the sample sintered at 1200°C. The microwave dielectric properties were improved obviously when the Li2TiO3 ceramics were sintered at low temperatures with small additions of H3BO3 (B2O3 in the form of H3BO3). Only monoclinic Li2TiO3 was

Jun Liang; Wen-Zhong Lu; Jia-Min Wu; Jian-Guo Guan

2011-01-01

260

High temperature millimeter wave characterization of the dielectric properties of advanced window materials  

NASA Astrophysics Data System (ADS)

Experimental methods have been developed to determine the dielectric properties of candidate radome materials at 35 and 94 GHz for temperatures up to 1700 C. Measurements have been carried out on fuzed silica, single crystal sapphire, hot-pressed silicon nitride, beryllium oxide and boron nitride as a function of temperature, composition and manufacturing procedures. Dielectric characterization data are presented in tabular and graphic forms to provide the necessary data base for evaluation of millimeter wave transmission properties of these materials in radome applications.

Ho, W. W.

1982-05-01

261

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

262

Dielectric electrorheological fluids: theory and experiment  

NASA Astrophysics Data System (ADS)

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

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

2003-06-01

263

Dielectric Properties of BaTiO3-Based Ceramics under High Electric Field  

NASA Astrophysics Data System (ADS)

The dielectric properties under a high electric field (ac-field) of BaTiO3-based ceramics with core grains, shell grains and core-shell grains were compared with those of multilayer ceramic capacitors (MLCCs) with these three kinds of grains. The MLCCs with the X7R specification had a core-shell structure, and the relative dielectric permittivity (\\varepsilonr) of the dielectric layers in the MLCCs increased with increasing ac-field. Similar behavior was observed in the MLCCs consisting of only cores, indicating that the core predominantly determined the dielectric properties of MLCCs under high ac-fields. The dielectric properties of MLCCs and ceramic plates consisting of only shell grains showed that the shell was the relaxor ferroelectrics. A slight change in the shell composition yielded a large shift of the peak temperature of \\varepsilonr. The shell improved the temperature stability of \\varepsilonr at low temperatures under low ac-fields. In a ceramic plate with relatively large BaTiO3 grains (approximately 3 ?m), the maximum \\varepsilonr was observed at a moderate ac-field, which was explained from the electric displacement vs electric field hysteresis curves of ferroelectric BaTiO3. The MLCCs and ceramics plates with fine BaTiO3 grains (0.4 to 0.5 ?m) showed similar dielectric behavior to the MLCC with the core-shell structure. The size effect of BaTiO3 played an important role in determining the temperature stability of \\varepsilonr. For future MLCCs with very thin dielectric layers, a microstructure with fine BaTiO3 grains and grain boundary layers of the shell was proposed.

Tsurumi, Takaaki; Adachi, Hiroshige; Kakemoto, Hirofumi; Wada, Satoshi; Mizuno, Youichi; Chazono, Hirokazu; Kishi, Hiroshi

2002-11-01

264

Predominant factors affecting the dielectric and piezoelectric properties of bismuth-containing complex perovskite solid solution  

NASA Astrophysics Data System (ADS)

To study the factors affecting the dielectric and piezoelectric properties of bismuth-containing complex perovskites, the solid solution (1-x)Pb(Mg1/3Nb2/3)O3 xBi(Mg2/3Nb1/3)O3 was prepared by the solid state reaction method and its dielectric and piezoelectric properties were investigated. It is found that (1) at room temperature, the nonlinearity of the DE-loop for Pb(Mg1/3Nb2/3)O3 is completely suppressed at a rather low x (<5%); (2) dielectric constant versus temperature curves deviate from the Curie Weiss law at a temperature Td much higher than the dielectric constant peak temperature Tm and Tm-Td decreases considerably with increasing x; and (3) frequency dispersion ?Tm=Tm (1 MHz)-Tm (10 kHz) increases with increasing x. Possible factors responsible for the variation of the dielectric and piezoelectric properties with x are discussed.

Wang, R.; Shimojo, Y.; Sekiya, T.; Itoh, M.

2005-06-01

265

Electronic Structure, Electrical and Dielectric Properties of BaSnO3 below 300 K  

NASA Astrophysics Data System (ADS)

The electronic structure, electrical and dielectric properties of barium stannate, a semiconducting perovskite oxide prepared by solid state ceramic route were studied by employing X-ray photoelectron spectroscopy (XPS), Mössbauer and impedance spectroscopic techniques in the temperature range 77-300 K. X-ray diffraction (XRD) pattern of BaSnO3 confirms the cubic structure. Scanning electron microscopy (SEM) images show high porosity in the sample and the average grain size was found to be about 1.85 ?m which corroborates with the particle size obtained through XRD line broadening analysis. Mössbauer spectra, at 298 and 78 K reveal that tin exists mainly in tetravalent, Sn4+ state. XPS study also shows the same results but it indicates the existence of a trace amount of Sn2+. Electrical conductivity and dielectric constant of this system have been measured in the temperature range 298 to 148 K and in the frequency range 10-2 to 106 Hz. Frequency and temperature dependent electrical conductivity/dielectric properties have been used to separate the contributions of grains and grain boundaries to the total observed conductivity and dielectric constant. Orientational polarisation and space charge polarisation contributes to the observed dielectric properties of the system.

Singh, Prabhakar; Brandenburg, Benjamin J.; Sebastian, C. Peter; Singh, Prakash; Singh, Sindhu; Kumar, Devendra; Parkash, Om

2008-05-01

266

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

267

Effect of iron oxide with Si on the dielectric properties in Mn-Zn ferrite  

NASA Astrophysics Data System (ADS)

In this paper, some of the results of dielectric study carried out using locally produced low cost Fe2O3 powder with 0.5 wt% of Si additive are being summarized. The dielectric properties were studied as a function of composition, frequency and temperature for a series of MnxZn1-xFe2O4 ferrite. The samples were prepared by the usual ceramic technique. It was observed that the values obtained for dielectric constant ?' and dielectric loss factor tan ? are much lower than those normally obtained for Mn-Zn ferrite prepared by pure Fe2O3 powder. The low values are attributed to the presence of Si, which suppress the ceramic grain growth. The low dielectric loss makes these samples attractive for use at high frequencies. Each of ?' and tan ? increases on increasing the temperature. Abnormal dielectric behavior observed for x = 0.99 due to forced migration of Fe ions from A sites to B sites at this composition.

Uzma, G.

2010-06-01

268

Design and FDTD analysis of open-ended coaxial probes for broadband high-temperature dielectric properties measurements  

Microsoft Academic Search

In conjunction with ongoing research in the area of microwave processing of materials and, in particular, in the microwave sintering of ceramics, the authors found it necessary to make dielectric properties measurements at temperatures as high as 1000°C. The authors have developed a new metallized ceramic coaxial probe for broadband, high-temperature dielectric properties measurements. Initial experience with the probe showed

S. Bringhurst; H. F. Iskander; P. Gartside

1994-01-01

269

Influence of frequency, grade, moisture and temperature on Green River oil shale dielectric properties and electromagnetic heating processes  

Microsoft Academic Search

Development of in situ electromagnetic (EM) retorting technologies and design of specific EM well logging tools requires an understanding of various process parameters (applied frequency, mineral phases present, water content, organic content and temperature) on oil shale dielectric properties. In this literature review on oil shale dielectric properties, we found that at low temperatures (<200°C) and constant oil shale grade,

J. Alexandra Hakala; William Stanchina; Yee Soong; Sheila Hedges

2011-01-01

270

The dielectric and optical properties of thin films at gigahertz and terahertz frequencies  

NASA Astrophysics Data System (ADS)

Thin films have attracted the attention of physicists because the dimensionally constraint system of the thin films can create an intermediate system between macroscopic systems and molecular systems. This system might show anomalies in the optical, electrical, mechanical, or magnetic properties, compared to the properties of bulk materials. The most conspicuous phenomena associated with the thin films are the anomalies of dielectric and optical properties. This thesis will investigate the anomalous phenomena of thin films by the study of the dielectric and optical properties of a variety of thin films at GHz and THz frequencies (in the millimeter and sub-millimeter wave regime). A coherent THz wave source and electro-optic detection method are used for the experiment. For a coherent THz frequency source, a THz emitter was used, which was driven by a 100 femto-second pulse from a Ti:sapphire laser to produce the coherent THz wave radiation while the electro-optic detector was gated by the laser pulse split from the laser for the coherent THz wave detection. The dielectric and optical properties of a variety of thin film materials are discussed and analyzed in detail. The microscopic structural contribution to the dielectric and optical properties of thin films are especially emphasized in this thesis. Because the currently available methods for the characterization of thin films at the THz frequency have difficulties when the films are in the range of nanometer to micron in thickness, a new method, THz differential time-domain spectroscopy, is developed. The theory of the THz differential time-domain spectroscopy is also developed to obtain information on the real and imaginary parts of dielectric properties and the optical properties. The dual phase lock-in detection was performed to measure the very small differential THz signal with a high dynamic range up to 105. This THz differential time-domain spectroscopy is able to characterize the properties of nanometer scaled thin films. A variety of materials have been experimentally investigated, including a 930 nm silicon dioxide film, a 1.8 mum parylene-n polymer free standing film, a 1.8 mum parylene-n polymer film on silicon substrate, a 300 nm parylene-n polymer film, a 100 nm tantalum oxide high dielectric film, protein monolayers, water molecule layer on the surface of ice crystal, and a carbon nanotube film. We found that there are anomalies in the dielectric and optical properties of several thin films. These anomalous behaviors are believed to be caused by fine grain formation, mechanical stresses, formation of interfacial layers, or rough interfaces during thin film deposition processes.

Lee, Kwang-Su

271

Effects of Constant Static Pressure on the Biological Properties of Porcine Aortic Valve Leaflets  

Microsoft Academic Search

An understanding of how mechanical forces impact cells within valve leaflets would greatly benefit the development of a tissue-engineered heart valve. In this study, the effect of constant ambient pressure on the biological properties of heart valve leaflets was evaluated using a custom-designed pressure system. Native porcine aortic valve leaflets were exposed to static pressures of 100, 140, or 170

Yun Xing; Zhaoming He; James N. Warnock; Stephen L. Hilbert; Ajit. P. Yoganathan

2004-01-01

272

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)], 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 V? 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 V? and propose refined values for the H-bond parameters.

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

2011-08-01

273

Dielectric and Pyroelectric Properties of HAp-BaTiO3 Composites  

Microsoft Academic Search

In order to mimic the electrical properties of natural bone, the present work investigated the dielectric, AC conductivity, pyroelectric and piezoelectric properties of HA-40 wt% BaTiO3 (HA-26 vol% BaTiO3) and HA-60 wt% BaTiO3 (HA-44 vol% BaTiO3) composites. Multistage spark plasma sintering was used to achieve the desired combination of properties. The electrical parameters were measured as a function of temperature

A. K. Dubey; B. Basu; K. Balani; R. Guo; A. S. Bhalla

2011-01-01

274

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

275

Effect of different low electric field conditions on the dielectric properties of Ehrlich tumor.  

PubMed

Studies of low electric fields (LEFs) effects on the permeability of the cell membrane are of great interest in molecular medicine. Electroendocytosis is a novel technique depends on using LEFs to incorporate macromolecules as anticancer drugs or genes into the cells. There are wide debates about the optimum electric conditions for electroendocytosis. In this article, Ehrlich tumor tissues were exposed to different LEFs voltages and frequencies in vitro. Dielectric properties before and after the exposure were determined. The results indicated that the exposed groups have significant high permittivity and conductivity compared to unexposed group, as well as having significant low impedance. The results indicated that dielectric measurements can be used to indicate the efficiency of electroendocytosis that as permittivity and conductivity of cell membranes increase, more molecules can passed into the cells. It was also indicated that, as the pulse amplitude increases, the LEFs influence increases, while changing pulse frequency has no obvious effect on dielectric properties of Ehrlich tumor. PMID:21554098

Shawki, Mamdouh M

2011-03-01

276

Size-dependent optical and dielectric properties of BiVO4 nanocrystals  

NASA Astrophysics Data System (ADS)

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

Sarkar, S.; Chattopadhyay, K. K.

2012-04-01

277

Temperature-dependent property measurements on multi-electroded thin-layer dielectrics  

SciTech Connect

A measurement system was designed and assembled for the automatic collection of electrical data for thin-layer dielectrics as a function of temperature. The dielectrics were deposited on platinized silicon by sol-gel processing, and the dielectric thickness was 0.2--0.4 [mu]m. Many ([gt]25) surface electrodes were formed by sputtering gold through a shadow mark, with a typical electrode size of 210[times]210 [mu]m[sup 2]. The measurement equipment was computer controlled, with three-axis digital stepping motors that could scan multi-electroded capacitors and collect statistically meaningful data. The temperature-dependent properties were measured between [minus]100 and 300 [degree]C as a function of frequency (100 Hz to 1 MHz) and applied field strength (0--50 MV/m). Data are reported for sol-gel-derived BaTiO[sub 3], PbZrO[sub 3], and (Pb,La)(Zr,Ti)O[sub 3] (i.e., PLZT) thin-layer capacitors. Capacitance values were typically 500--1000 pF, and the dielectric constant could be determined within a standard deviation of [plus minus]1.3%. Nanocrystalline BaTiO[sub 3] was found to have a dielectric constant of 210 at room temperature with no ferroelectric properties or dielectric anomalies between [minus]80 and 200 [degree]C. Antiferroelectric PbZrO[sub 3] had characteristic field-forced phase transformation behavior to the ferroelectric state with increasing bias. The field-induced polarization was approximately 300 mC/m[sup 2] and the coercive field was 22--28 MV/m. PLZT 8/65/35 had a dielectric constant of 556[plus minus]7 at 25 [degree]C, 100 KHz, and 50 mV.

Tani, T.; Xu, Z.; Moses, P.; Payne, D.A. (Department of Materials Science and Engineering, Materials Research Laboratory, and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States))

1994-06-01

278

Microstructure and dielectric properties of La 2O 3 doped amorphous SiO 2 films as gate dielectric material  

NASA Astrophysics Data System (ADS)

As a potential gate dielectric material, the La 2O 3 doped SiO 2 (LSO, the mole ratio is about 1:5) films were fabricated on n-Si (0 0 1) substrates by using pulsed laser deposition technique. By virtue of several measurements, the microstructure and electrical properties of the LSO films were characterized. The LSO films keep the amorphous state up to a high annealing temperature of 800 °C. From HRTEM and XPS results, these La atoms of the LSO films do not react with silicon substrate to form any La-compound at interfacial layer. However, these O atoms of the LSO films diffuse from the film toward the silicon substrate so as to form a SiO 2 interfacial layer. The thickness of SiO 2 layer is only about two atomic layers. A possible explanation for interfacial reaction has been proposed. The scanning electron microscope image shows the surface of the amorphous LSO film very flat. The LSO film shows a dielectric constant of 12.8 at 1 MHz. For the LSO film with thickness of 3 nm, a small equivalent oxide thickness of 1.2 nm is obtained. The leakage current density of the LSO film is 1.54 × 10 -4 A/cm 2 at a gate bias voltage of 1 V.

Shi, L.; Yuan, Y.; Liang, X. F.; Xia, Y. D.; Yin, J.; Liu, Z. G.

2007-01-01

279

Dielectric Properties and Coulomb Blockade Effect in Nano-Ag/Silicone Resin Modified Polyester Composite  

NASA Astrophysics Data System (ADS)

In order to modify material properties, nano Ag (diameter less than 20 nm) was successfully made from Ag colloidal sol and uniformly dispersed into silicone resin modified polyester (SP). The dielectric properties of the composite were studied. Resistivity- temperature characteristic of the composite is some different from that of pure SP. The maximal breakdown voltage of the composite is 112% of that of pure SP and dielectric loss can be 8 times of pure SP at power frequency. Dielectric constants of the composites all increased with various contents of nano Ag. Two types of shallow traps (0.52eV and 0.62eV) with trap densities (1.2 × 1010/cm3 and 2.0 × 1011/cm3) are found in the composite, which differs from those of pure SP (0.58eV, 3.1 × 1010/cm3) significantly. Resistivity of the composite is much greater than that of pure SP under cryogenic temperature (77K), which might be treated as the result of Coulomb Blockade effect. From the view of dielectric physics, the different characteristic between the composite and pure SP was discussed and a new concept of nano metal/dielectric materials composite used for device surface protection was introduced.

Dong, Xiaobing; Yin, Yi; Jiang, Xiuchen

280

Dielectric properties and surface hydrophobicity of silicone rubber under the influence of the artificial tropical climate  

Microsoft Academic Search

This paper reports the experimental results concerning the influence of the artificial tropical climate on dielectric properties (relative permittivity εr and dissipation factor tan ?) and surface hydrophobicity (contact angle) of silicone rubber. The samples being used are six different contents of new materials of high temperature vulcanized (HTV) and room temperature vulcanized (RTV) silicone rubbers with different filler levels.

S. Salama; K. T. Sirait; H. C. Kaerner

1998-01-01

281

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

Microsoft Academic Search

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

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

2008-01-01

282

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

Microsoft Academic Search

This dissertation is devoted to the development of new dielectric composite materials for potentially implementing the embedded capacitor technology. In this dissertation, you will be presented with the material development concepts, current status of research and heretofore the latest results that were obtained under the synthesis-structure-property research scheme. Embedded capacitor is an important emerging technology for meeting the performance and

Lai Qi

2004-01-01

283

Dielectric Properties and Crystalline Morphology of Low Density Polyethylene Blended with Metallocene Catalyzed Polyethylene  

Microsoft Academic Search

Dielectric properties of low-density polyethylene (LDPE) blended with metallocene catalyzed polyethylene (MPE) to 1, 3, 5 wt% of the latter are reported. It was found that the 1 wt% MPE blend had the lowest volume resistivity, the highest direct current (DC) breakdown strength and the least accumulated space charge. The crystalline morphology of the blends was studied through differential scanning

X. Wang; H. Q. He; D. M. Tu; C. Lei; Q. G. Du

2008-01-01

284

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

Microsoft Academic Search

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

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

1999-01-01

285

Dielectric properties of glucose in bulk aqueous solutions: Influence of electrode polarization and modeling  

Microsoft Academic Search

Impedance spectroscopy was applied to determine glucose concentration in the interstitial fluid for its potential use in diabetic monitoring. For this purpose, the changes in the measured dielectric properties due to the presence of glucose in water and saline solutions were examined between 40Hz and 110MHz. Electrode polarization (EP) was a dominant factor which shaped the spectrum at low frequencies.

Gilwon Yoon

2011-01-01

286

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

287

Physical and Chemical Analysis of Dielectric Properties and Differential Scanning Calorimetry Techniques on Buriti Oil  

Microsoft Academic Search

Dielectric constant (DC) analysis has been carried out on buriti oil (Mauritia flexuosa), in a scan temperature range of ?100–40°C. Fatty acid characterization was performed by gas crystallography and differential scanning calorimetry (DSC). Interesting physical characteristics were noted in a DC analysis on buriti oil. It revealed five different temperature anomalies, which were studied for the chemical properties of the

A. Garcia-Quiroz; S. G. C. Moreira; A. V. de Morais; A. S. Silva; G. N. da Rocha; P. Alcantara

2003-01-01

288

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

Microsoft Academic Search

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

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

289

Extraction of dielectric properties of multiple populations from dielectrophoretic collection spectrum data  

Microsoft Academic Search

In this paper we show how simplifying assumptions can be used to extract useful data from the dielectrophoretic collection spectrum, in particular for the cytoplasm, and hence determine the properties of multiple populations of cells within a sample. Specifically, the observation of the frequencies of onset of dielectric dispersion allows the identification and enumeration of populations of cells according to

Lionel M Broche; Fatima H Labeed; Michael P Hughes

2005-01-01

290

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...

291

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

292

A Novel Facility for High-temperature Containerless Processing and Property Characterization of Dielectrics  

Microsoft Academic Search

A novel facility for the containerless processing and study of oxide dielectric materials on the ground is described. The instrument uses an aerodynamic diffuser that permits contamination-free sample heating, allowing sufficient sample charging before electrostatic levitation can be effective. The physical concepts behind this new levitator, its hardware, and the associated thermophysical property measurement methods are successively reviewed. Containerless processing

Paul-Francois Paradis; Takehiko Ishikawa; Jianding Yu; Shinichi Yoda

2002-01-01

293

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

294

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

Microsoft Academic Search

The associating behaviour of heptadecanoic (margaric) and nonadecanoic acids has been studied by the determination of their dielectric properties. The correlation factor between molecular pairs was determined with reference to the Kirkwood-Fröhlich theory. An expression for the degree of association was obtained through simple statistical considerations based on the definition of the effective number of molecules carrying a dipole moment,

E. R. Mognaschi; A. Chierico

1989-01-01

295

Associating behaviour of pure polar liquids: Dielectric properties of undecylic acid  

Microsoft Academic Search

The associating behaviour of undecylic acid has been studied by the determination of its dielectric properties. The correlation factor between molecular pairs was obtained with reference to the Kirkwood-Fröhlich theory and compared with the Abbott-Bolton model for non spherical molecules. The results indicate a high degree of association with number of dimers decreasing with increasing temperature.

E. R. Mognaschi; A. Chierico

1987-01-01

296

Dielectric properties of pure polar liquids: associating behaviour of erucic acid  

Microsoft Academic Search

The results of a study of the associating behaviour of liquid erucic acid, made through the determination of its dielectric properties, are reported. The values obtained for the correlation factor between molecular pairs which exist due to hydrogen bonds, suggest the presence of dimerisation in the liquid phase, with the number of dimers decreasing with increasing temperature.

E. R. Mognaschi; A. Chierico; L. Zullino

1983-01-01

297

Associating behaviour of pure polar liquids: dielectric properties of n-valeric acid  

Microsoft Academic Search

The results are reported of a study of the associating behaviour of n-valeric acid, made through the determination of its dielectric properties. The values obtained for the correlation factor between molecular pairs, which exist due to hydrogen bonds, suggest the presence of a high degree of dimerisation in the liquid phase, with the number of dimers decreasing with increasing temperature.

E. R. Mognaschi; L. Zullino; A. Chierico

1984-01-01

298

Influence of temperature on dielectric properties of Fe-doped CaCu3Ti4O12 ceramics  

NASA Astrophysics Data System (ADS)

CaCu3Ti4-xFexO12 (0?x?0.2) ceramics were fabricated by a solid-state reaction method, and the dielectric properties were studied. Dielectric measurement performed at room temperature shows that with Fe content increasing from 0 to 0.2, the dielectric constant (??) decreases from about 5×104 to 50 in the frequency range from 1 kHz to 1 MHz, while ?? of all Fe-doped samples at high temperature re-increased to a high level of 105 below 10 kHz, characterized by dielectric temperature spectrum. Interestingly, two dielectric relaxations named as I and II are observed with the increasing of temperature. In order to catch the intrinsic relaxation mechanism, the IBLC model and modulus approach are adopted to clarify these fantastic dielectric properties.

Mu, Chunhong; Zhang, Huaiwu; He, Ying; Liu, Peng

2010-01-01

299

Annealing Effects on Properties of Ba(Zn1\\/3Ta2\\/3)O3 Dielectric Materials  

Microsoft Academic Search

Ba(Zn1\\/3Ta2\\/3)O3 dielectric materials were prepared by solid state reaction. The samples were sintered at temperatures in the range 1400-1600degC for 4 h. Morphostructural characterization was performed by using SEM and XRD. The dielectric properties were measured in the microwave range (6-7 GHz). An additional annealing at 1400 degC for 10 hours was performed in order to improve the dielectric parameters.

A. Ioachim; M. I. Toacsan; M. G. Banciu; L. Nedelcu; C. A. Dutu; E. Andronescu; S. Jinga

2006-01-01

300

Electrical properties of low-temperature-fired ferrite–dielectric composites  

Microsoft Academic Search

The effects of the BaO·(Nd0.8Bi0.2)2O3·4TiO2 (BNBT) to NiCuZn ferrite ratio and addition of Bi2O3–B2O3–SiO2–ZnO (BBSZ) glass on the sintering behavior, microstructure evolution, dielectric and magnetic properties of BNBT–NiCuZn ferrite composites were investigated in developing low-temperature-fired composites for high frequency electromagnetic interference (EMI) devices. The results indicate that these composites can be densified at 900°C and exhibit superior dielectric and magnetic

Hsing-I Hsiang; Tai-How Chen

2009-01-01

301

Effect of re-oxidation on dielectric properties in Ni-MLCC  

Microsoft Academic Search

The effect of re-oxidation treatment on the solubility of dopants and the dielectric properties of rare-earths (La, Ho) and\\u000a V-substituted BaTiO3 solid solutions, assuming the shell phase of X7R dielectrics, was investigated. Ho-V-substituted samples showed larger increase\\u000a of the lattice parameter and T\\u000a c by re-oxidation treatment compared with La-V-substituted samples. Electron spin resonance measurements revealed that the\\u000a oxidation of

Hiroshi Kishi; Youichi Mizuno; Tomoya Hagiwara; Hirokazu Orimo; Hitoshi Ohsato

2008-01-01

302

Materials science on the nano-scale for improvements in actuation properties of dielectric elastomer actuators  

NASA Astrophysics Data System (ADS)

We discuss various approaches to increasing the dielectric constant of elastomer materials, for use in dielectric elastomer actuators. High permittivity metal-oxide nano-particles can show elevated impact compared to larger size particles, but suffer from water uptake. Composites with conducting particles lead to extremely high permittivity caused by percolation, but they often suffer early breakdown. We present experiments on approaches combining metal-oxides and metal particles, which compensate for the drawbacks, and may lead to useful DEA materials in which all relevant properties are technologically useful. The key seems to be to avoid percolation and achieve a constant nearest-neighbor separation.

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

2010-03-01

303

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

SciTech Connect

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

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

2010-11-22

304

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

305

Charge-order driven multiferroic and magneto-dielectric properties of rare earth manganates  

Microsoft Academic Search

Charge-order driven magnetic ferroelectricity is shown to occur in several rare earth manganates of the general formula, Ln1?x\\u000a A\\u000a x\\u000a MnO3 (Ln = rare earth, A = alkaline earth). Charge-ordered manganates exhibit dielectric constant anomalies around the charge-ordering\\u000a or the antiferromagnetic transition temperature. Magnetic fields have a marked effect on the dielectric properties of these\\u000a compounds, indicating the presence of

Claudy Rayan Serrao; Jyoti Ranjan Sahu; Anirban Ghosh

2010-01-01

306

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

307

Static and dynamic mechanical properties and fracture morphology of EPDM composites containing silicate nanofibers and short PA66 microfibers  

Microsoft Academic Search

Ethylene propylene diene monomer rubber composites reinforced with micro- and nano-sized short fibers were made by mechanically blending of silanized fibrillar silicate (FS) nanofibers and polyamide 66 (PA-66) microfibers. A synergistic reinforcement on static and dynamic mechanical properties was revealed. When FS nanofibers and PA-66 microfibers were used together in an appropriate volume ratio, static and dynamic mechanical properties (such

Ming Tian; Shi Yin; Hua Zou; Lili Su; Liqun Zhang

2011-01-01

308

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

Microsoft Academic Search

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

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

1979-01-01

309

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

Microsoft Academic Search

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

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

1979-01-01

310

Microwave Absorber Properties of Magnetic and Dielectric Composite Materials  

NASA Astrophysics Data System (ADS)

In recent years, because of the rapid progress in wireless technology, microwave absorbers or noise suppressors have become necessary for a safe-electromagnetic-wave-level environment. To design microwave absorbers or noise suppressors, it is necessary to have knowledge of complex permittivity, ?r* and permeability, ?r*. In this report, we show the values of complex permeability, ?r* and permittivity, ?r* for a composite materials of magnetic (Iron, Fe, coated by Fe3O4) and dielectric (Titanium Oxide, TiO2), by changing Fe / TiO2 volume fraction ratio. As changing of these, we can change the values of complex permeability (?r* = ?r' - j?r") and complex permittivity (?r* = ?r' - j?r"). And the results are applied in the design of a microwave absorber which makes reflection losses and the central frequency to do a purpose, for example, necessary conditions of ETC (5.8GHz) use in Japan.

An, Young Joon; Nishida, Ken; Yamamoto, Takashi; Ueda, Shunkichi; Deguchi, Takeshi

311

Preparation and Dielectric Properties of Nanostructured ZnO Whiskers  

NASA Astrophysics Data System (ADS)

By a novel controlled combustion synthesis method, a large number of nanostructured ZnO whiskers with different morphologies, such as tetra-needles, long-leg tetra-needles and multi-needles, are prepared without any additive in open air at high temperature. The morphologies and crystalline structures of the as-prepared ZnO nanostructured whiskers are investigated by SEM and XRD. The possible growth mechanism on the nanostructured ZnO whiskers is proposed. The experimental results indicate that the dielectric constants and losses of the nanostructured ZnO whiskers are very low, demonstrating that the nanostructured ZnO whiskers are low-loss materials for microwave absorption in X-band. However, obvious microwave absorption in nanostructured ZnO whiskers is observed. The quasi-microantenna model may be attributed to the microwave absorption of the ZnO whiskers.

Shi, Xiao-Ling; Yuan, Jie; Zhou, Wei; Rong, Ji-Li; Cao, Mao-Sheng

2007-10-01

312

Correlation between growth dynamics and dielectric properties of epitaxial BaTiO3 films  

NASA Astrophysics Data System (ADS)

We report on the effect of the substrate temperature on the growth dynamics and dielectric properties of BaTiO3 epitaxial films on Nb:SrTiO3 (001) substrates. By real-time reflection high energy electron diffraction analysis, we quantitatively estimated the adatoms surface diffusivity as a function of temperature. The increase of the substrate temperature promotes surface diffusion, which reflects in the improvement of BaTiO3 ferroelectric properties up to 680 °C. Above this temperature, Ba re-evaporation occurs, leading to a rapid deterioration of the dielectric and ferroelectric properties. This work shed light on thermally activated physical mechanisms which determine the ferroelectric properties of BaTiO3 films.

Radaelli, G.; Brivio, S.; Fina, I.; Bertacco, R.

2012-03-01

313

Dielectric property of all-organic composite film composed of cobalt phthalocyanine and poly(vinylidene fluoride)  

NASA Astrophysics Data System (ADS)

Due to the mechanical flexibility, tunable properties and easy processing, polymer based composites, especially the electroactive polymer composites based on the poly(vinylidene fluoride), which can be applied in the sensors, transistors and the capacitors, have been widely investigated. In this paper, all-organic composite films composed of cobalt phthalocyanine and poly(vinylidene fluoride) with high dielectric permittivity are simply synthesized by solution casting on the glass. The dielectric property over the broad frequency from 1Hz to 107Hz is investigated. The high dielectric permittivity 86.4(102Hz), about 9 times of the pure poly(vinylidene fluoride), is achieved when the fraction of the cobalt phthalocyanine is 20wt% that is similar to other semiconductors reinforced polymer composites. The significant increase of the dielectric constant and the dielectric loss tangent can be explained by the threshold theory. The origin of dramatically enhancement of dielectric permittivity and dielectric loss tangent over the low frequency is the Maxwell-Wagner-Sillars polarization. The results show that the dielectric property is very sensitive to the fraction of cobalt phthalocyanine. Additionally, when the fraction of the cobalt phthalocyanine was 10wt%, the dielectric permittivity and the conductivity of composite films are 17.1 and 1.1×10-6s/cm respectively which indicated that it is potentially applied in the capacitors.

Yu, Li; Zhang, Yihe; Tong, Wangshu; Shang, Jiwu; Lv, Fengzhu; Ke, Shanming; Huang, Haitao

2011-11-01

314

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

315

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

316

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

NASA Astrophysics Data System (ADS)

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

Kobune, Masafumi; Takasaki, Keiko; Yazawa, Tetsuo

2006-09-01

317

Size and frequency dependent dielectric properties of tin (IV) oxide nanoparticles synthesized by gel combustion method  

NASA Astrophysics Data System (ADS)

Nanocrystalline Tin oxide (SnO2) material with different crystallite size was synthesized using gel combustion method by varying the fuel (C6H8O7) to oxidizer (HNO3) molar ratio as a process parameter. The effect of the molar ratio of fuel to oxidizer in the gel combustion method was investigated by inspecting the crystallite size of nano SnO2 powder. The prepared samples were characterized by using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Energy Dispersive Analysis X-ray Spectroscope (EDAX). The electrical properties of compressed nanocrystalline SnO2 were studied by using LCR meter. Frequency dependence dielectric properties of SnO2 nanoparticles were studied. Dielectric constant and loss tangent were found to be decrease with the increasing frequency. The Size dependent dielectric properties of SnO2 nano materials were studied for the samples with the crystallite size about 12nm, 18nm and 31nm. From the study it was observed that dielectric constant and loss tangent were highly influenced by the size of the nanoparticles.

Rajeeva, M. P.; Naveen, C. S.; Lamani, Ashok R.; Jayanna, H. S.

2013-06-01

318

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

PubMed

In this paper, a new dielectrophoresis (DEP) method based on capture voltage spectrum is proposed for measuring dielectric properties of biological cells. The capture voltage spectrum can be obtained from the balance of dielectrophoretic force and Stokes drag force acting on the cell in a microfluidic device with fluid flow and strip electrodes. The method was demonstrated with the measurement of dielectric properties of human colon cancer cells (HT-29 cells). From the capture voltage spectrum, the real part of Clausius-Mossotti factor of HT-29 cells for different frequencies of applied electric field was obtained. The dielectric properties of cell interior and plasma membrane were then estimated by using single-shell dielectric model. The cell interior permittivity and conductivity were found to be insensitive to changes in the conductivity of the medium in which the cells are suspended, but the measured permittivity and conductivity of cell membrane were found to increase with the increase of medium conductivity. In addition, the measurement of capture voltage spectrum was found to be useful in providing the optimum operating conditions for separating HT-29 cells from other cells (such as red blood cells) using dielectrophoresis. PMID:22662097

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

2012-03-01

319

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

320

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

PubMed Central

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

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

2012-01-01

321

Measuring In-Thickness Mechanical Properties of Sub Micron Polymer Dielectric Films  

Microsoft Academic Search

The ongoing miniaturization of microelectronics has led to low-K polymer dielectric films with a thickness of several tens of nanometers. These thin polymer films generally show time dependent material properties, that are different in lateral directions and in-thickness direction. Most techniques available for measuring the mechanical properties of thin films are only capable of obtaining the in-plane modulus. To have

M. van Soestbergen; L. J. Ernst; K. M. B. Jansen; W. D. van Driel; M. Bartek; A. Polyakov

2006-01-01

322

Dielectric properties and conductivity of carbon nanofiber\\/semi-crystalline polymer composites  

Microsoft Academic Search

The properties of semi-crystalline polymer nanocomposites are affected by the nanofillers directly and indirectly, as two phases, i.e., crystalline and amorphous, exist in the polymer. The effects of nanofillers on the two phases could be competitive. The dielectric properties and conductivity of carbon nanofibers (CNF)\\/semi-crystalline polymer nanocomposites are studied in this paper. CNF\\/polypropylene (PP) nanocomposites are prepared in experiment by

G. Sui; S. Jana; W. H. Zhong; M. A. Fuqua; C. A. Ulven

2008-01-01

323

Study on the dielectric property of diphasic polar glass-ceramics  

Microsoft Academic Search

A new kind of the oriented polar glass—ceramics i.e. the diphasic polar glass—ceramic (Sr2TiSi2O8 and SrTiO3) is first prepared. This unique material shows the piezoelectric property of Sr2TiSi2O8 crystal and the high dielectric property of SrTiO3 crystal.

Xie Weimin; Ding Zhenya; Zhang Peilin

1997-01-01

324

Investigation of the effects of nano-filler on dielectric properties of epoxy based composites  

Microsoft Academic Search

In this paper, epoxy resin based composites filled with nano-Al2O3 and nano-SiO2 individually were fabricated. The relationships between the dielectric properties and fillers properties (contents and particle size etc.) were investigated. The results showed that, for nano-SiO2 filled epoxy, relative permittivity (epsivr) and loss factor (tandelta) increased obviously when filler content was lower than about 0.1 wt.%, continue to increase

Huicheng Shi; Naikui Gao; Haiyun Jin; Gang Zhang; Zongren Peng

2009-01-01

325

Complex permittivity and microwave absorption properties of a composite dielectric absorber  

Microsoft Academic Search

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

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

2006-01-01

326

Measuring the dielectric properties of herpes simplex virus type 1 virions with dielectrophoresis  

Microsoft Academic Search

An investigation has been performed into the biophysical properties of the enveloped mammalian virus, herpes simplex virus type 1 (HSV-1). The dielectrophoretic behaviour of the virus particles was measured as a function of applied frequency (over the range 100 kHz–20 MHz) and conductivity of the suspending medium (over the range 1–100 mS m?1). The dielectric properties of the virus were

Michael P. Hughes; Hywel Morgan; Frazer J. Rixon

2002-01-01

327

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

328

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

329

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

330

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

331

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

NASA Astrophysics Data System (ADS)

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

Boresch, Stefan; Willensdorfer, Martin; Steinhauser, Othmar

2004-02-01

332

Thermodynamic properties and static structure factor for a Yukawa fluid in the mean spherical approximation.  

PubMed

This work presents the full analytic expressions for the thermodynamic properties and the static structure factor for a hard sphere plus 1-Yukawa fluid within the mean spherical approximation. To obtain these properties of the fluid type Yukawa analytically it was necessary to solve an equation of fourth order for the scaling parameter on a large scale. The physical root of this equation was determined by imposing physical conditions. The results of this work are obtained from seminal papers of Blum and Høye. We show that is not necessary the use the series expansion to solve the equation for the scaling parameter. We applied our theoretical result to find the thermodynamic and the static structure factor for krypton. Our results are in good agreement with those obtained in an experimental form or by simulation using the Monte Carlo method. PMID:22179758

Montes-Perez, J; Cruz-Vera, A; Herrera, J N

2011-12-18

333

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

334

Effects of Cr\\/Zn Substitutions on Dielectric Properties of CaCu3Ti4O12 (CCTO) Ceramics  

Microsoft Academic Search

Effects of Zn and Cr substitutions on dielectric properties of CaCu3-xZnxTi4-yCryO12 ceramics are reported. Dielectric measurements at room temperature for un-substituted CaCu3-xZnxTi4-yCryO12 (x = 0, y = 0) between 102-106 Hz showed dielectric constant of 2.7×104 at 102 Hz. Substitution of Zn for Cu in CaCu3-xZnxTi4-yCryO12 (y = 0, x = 0.10, 0.50)caused dielectric constant to drop with increasing x.

R. Rajmi; A. K. Yahya; M. S. M. Deni

2010-01-01

335

Analysis of the Dielectric Properties of Trunk Wood in Dominant Conifer Species from New England and Siberia  

Microsoft Academic Search

Data presented were collected for dominant conifer species from Durham, NH (white pine, Pinus strobus, Eastern hemlock, Tsuga canadensis); Howland, ME (red spruce, Picea rubens); and the Ermakovsky Permanent Study Area in south central Siberia, Russia (Siberian fir, Abies siberica and Siberian pine, Pinus siberica). Dielectric properties of trunk wood were measured using a C-band dielectric probe. For the Durham

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

1992-01-01

336

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.

2011-03-01

337

Effect of panel properties on the concentrated static load (CSL) performance of oriented strand board (OSB)  

Microsoft Academic Search

The relationship between concentrated static load (CSL) performance of oriented strand board (OSB)\\u000a and panel thickness, local density, and some mechanical properties (including modulus of elasticity (MOE),\\u000a modulus of rupture (MOR), and interlaminar shear strength in both major and minor directions) was investigated\\u000a using both a simple linear regression method and a stepwise multi-linear regression technique.\\u000a The sample boards were laboratory manufactured

Zheng Chen; Ning Yan; Paul Cooper

2008-01-01

338

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

339

Physical properties of Buchdahl's three-parameter static spherically symmetric perfect fluid metrics  

NASA Astrophysics Data System (ADS)

The physical properties of a static spherically symmetric perfect fluid metric proposed by Buchdahl are investigated. The general solution can be written in terms of associated Legendre functions. If the adiabatic sound speed is to be less than the velocity of light at the boundary of the sphere, its radius will be larger than 1.238 times the Schwarzschild radius. Two particular solutions are studied in detail.

Wils, Patrick

1990-05-01

340

Static and impact crack properties of a high-strength steel welded joint  

Microsoft Academic Search

In order to gain the benefits of weldable high-strength steels in pressurized equipment applications, satisfactory toughness and crack properties of the welded joint, both in the weld metal and the heat-affected –zone (HAZ), are required. Experimental investigations of toughness and crack resistance parameters through static and impact tests of a high-strength, low-alloy steel (HSLA) with a nominal yield strength of

M. Zrilic; V. Grabulov; Z. Burzic; M. Arsic; S. Sedmak

2007-01-01

341

Effect of Boron Addition on the Dielectric Properties of Giant Dielectric CaCu3Ti4O12  

Microsoft Academic Search

The recently discovered giant dielectric CaCu3Ti4O12 (CCTO) has been reported to show dielectric constant value as high as 80,000 for single crystals and around 10,000 for ceramics. However the dielectric constant is also associated with high dissipation factor. In the present study, it has been observed that the loss factor of CCTO can be reduced by B2O3 addition. The low

Ranabrata Mazumder; Anshuman Seal; Amarnath Sen; Himadri Sekhar Maiti

2005-01-01

342

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

343

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

344

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

NASA Astrophysics Data System (ADS)

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

Hasegawa, Keisuke

345

Effect of synthesis and acid purification methods on the microwave dielectric properties of single-walled carbon nanotube aqueous dispersions  

NASA Astrophysics Data System (ADS)

We characterized the microwave-frequency (0.5-6 GHz) dielectric properties of aqueous dispersions of pristine and purified single-walled carbon nanotubes (SWCNTs). SWCNTs were synthesized by two CVD-based methods and purified using two acid-based purification methods. We characterized the structural and chemical differences across SWCNT samples using Raman analysis, UV-Vis spectroscopy, atomic force microscopy, and thermogravimetric analysis. We found that the dielectric properties of the pristine SWCNT dispersions did not vary with synthesis method, but the dielectric properties of purified SWCNT dispersions were variably impacted by acid purification due to different degrees of morphological and chemical changes in the SWCNTs.

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

2013-09-01

346

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

347

A first-principles study of the dielectric properties of TiO2 polymorphs  

NASA Astrophysics Data System (ADS)

We present an analysis of the dielectric properties of the three polymorphs of TiO2 (rutile, anatase and brookite phases), using ab initio time-dependent density functional perturbation theory based on the Vignale-Kohn functional. We implement this functional, which incorporates many-body effects, using the periodic program BAND. The improved result for the density of states spectra for brookite is suggestive of increased titanium ion Jahn-Teller effects for this phase. The imaginary and real components of the frequency-dependent dielectric functions show notable dielectric anisotropies, with implications for excitonic interactions, for all three common phases of TiO2. Comparison of the electron energy-loss spectrum for undoped and doped rutile and anatase reveals the critical role of collective charge excitations in photocatalytic mechanisms. The correlation between plasmon peaks present at lower energies and decreased photocatalytic activity due to substitutional aluminum doping in combination with oxygen vacancies in rutile and anatase is highlighted. Moreover, there is clear correlation between dielectric properties and the microstructure of the TiO2 polymorphs as suggested via the framework of the Born effective charge and Hirshfeld charge distribution schemes.

Thilagam, A.; Simpson, D. J.; Gerson, A. R.

2011-01-01

348

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

PubMed

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

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

2011-10-17

349

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

350

Dielectric and Piezoelectric Properties of 10% KF-Doped BaTiO3 Ceramics  

NASA Astrophysics Data System (ADS)

10% KF-doped barium titanate powders, Ba0.9K0.1TiO2.9F0.1, were synthesized through a sol-gel process. The powders, calcined at 650 °C, consist of cubic crystalline particles of ˜70 nm in length; the particle size increases to ˜200 nm as the firing temperature increases to ca. 800 °C, above which F2 begins to evaporate. Dense ceramics were fabricated by the spark plasma sintering (SPS) method; the average grain size is ˜2 ?m in lengths. The ceramics, well annealed at 1,000 °C in an O2 gas flow, have good dielectric and piezoelectric properties; the piezoelectric d33 value is 230 pC/N at room temperature. At the ferroelectric Curie temperature TC = 47 °C, the dielectric constant and loss \\tan? are 10,000 and <5% at 10 kHz, respectively. The Curie-Weiss relation holds in the fully disordered cubic and ordered rhombohedral phases, showing the second order 1:2 relation. Below 10 kHz, large dielectric dispersion caused by a domain-wall motion appears at the temperature range of -50 to 107 °C. Some discussions are made for these dielectric properties of the ceramics.

Akishige, Yukikuni; Hiraki, Yuuta; Tsukada, Shinya; Xu, Jun; Morito, Shigekazu; Ohba, Takuya; Lee Walker, Ezekiel; Neogi, Arup

2010-08-01

351

Measurement of the Dielectric Properties Performed by HASI-PWA at the Huygens Landing Site: Implications for Titan Surface Characterization  

NASA Astrophysics Data System (ADS)

The safe landing of the Huygens Probe on Titan allowed the measurement of the dielectric properties of the surface. The Permittivity, Waves, and Altimetry (PWA) analyser, a subunit of the Huygens Atmospheric Structure Instrument (HASI), included a mutual impedance probe mounted on two booms that measured the dielectric properties of the surface during approximately 30 min. The array configuration on the booms, together with the coupling between the soil and the atmosphere, requires a careful evaluation of the attitude of the Huygens Probe on the surface for assessing the dielectric properties with good accuracy. In this paper we present the calibrated data set of PWA, including reference values to evaluate the permittivity and the conductivity of the surface. The dielectric properties contribute to the characterization of the medium and provide unique constraints of soil composition. Furthermore, surface measurements made with PWA at the landing site are useful for comparison with Cassini radar data, which evaluates surface properties at much larger scale.

Simoes, F.; Grard, R.; Hamelin, M.; Lopez-Moreno, J.; Schwingenschuh, K.; Beghin, C.; Berthelier, J.; Brown, V.; Chabassiere, M.; Falkner, P.; Ferri, F.; Fulchignoni, M.; Jernej, I.; Molina-Cuberos, G.; Trautner, R.; Tokano, T.

2007-05-01

352

An analysis of dielectric properties of synthetic ballast water at frequencies ranging from 300 to 3000 MHz.  

PubMed

Ballast water presents an important vector for introduction of aquatic invasive species in the coastal waters around the world. Currently there are no established technologies proven to completely eliminate this problem due to the particularities of the ballasting and de-ballasting operations (extremely large volumes of water, efficiency at destroying macro and micro organisms, environmental issues associated with chemical treatments). Continuous microwave heating presents a potential solution to this problem, but the design of suitable applicators depends on the dielectric properties of the ballast water to be processed. The study presented in this paper is focused on the dielectric properties (dielectric constant--epsilon'; dielectric loss--epsilon") of synthetic ballast water inoculated with four organisms at seven different temperatures in the frequency range of 300 to 3000 MHz. The dielectric properties of the mixtures were determined using a network analyzer and a dielectric probe kit using the open-ended coaxial probe method. Numerical analysis was performed on data collected across all frequencies involved with an emphasis placed on F.C.C. allotted frequencies of 433, 915 and 2450 MHz. The dielectric constant was relatively independent of frequency and the organism used, but it showed a remarkable decrease with temperature. The dielectric loss showed an extreme decrease with increasing frequency, marked differences between the different organisms and between different growth stages of the same organism, and a large relatively linear increase with increasing temperature. PMID:19227068

Boldor, Dorin; Ortego, Jeffrey; Rusch, Kelly A

2008-01-01

353

Temperature and Frequency Dependent Dielectric Properties of Cu0.5Tl0.5Ba2Ca3(Cu4- y Cd y )O12- ? Bulk Superconductor  

NASA Astrophysics Data System (ADS)

The temperature and frequency dependent dielectric properties of polycrystalline Cd-doped Cu0.5Tl0.5Ba2Ca3(Cu4- y Cd y )O12- ? ( y=0,0.25,0.5,0.75) bulk superconductor samples are investigated. The zero resistivity critical temperature { T c( R=0)} has decreased and normal state resistivity has increased with the increase of Cd-doping in Cu0.5Tl0.5Ba2Ca3(Cu4- y Cd y )O12- ? samples. The dielectric properties such as dielectric constants ( ?', ??), dielectric loss tangent (tan ?) and ac-conductivity ( ? ac ) are investigated by measuring the capacitance (C) and conductance (G) in the frequency range of 10 KHz to 10 MHz at different temperature from 80 K to 300 K. The negative capacitance (NC) is observed in all Cu0.5Tl0.5Ba2Ca3(Cu4- y Cd y )O12- ? samples. The large values of NC observed at lower frequencies and temperatures may be due to reduced thermal vibrations and enhanced polarizability of the material. The effect of Cd-doping on bulk properties, dc-resistivity ( ?) and ac-electrical conductivity ( ? ac ) of these superconductor samples are investigated. The polarization in Cu0.5Tl0.5Ba2Ca3(Cu4- y Cd y )O12- ? samples is most likely arising from the displacement of charges in CuO2/CdO2 planes relative to the static charges at Ba2+, Tl3+, and Cu2+ sites in Cu0.5Tl0.5Ba2O4- ? charge reservoir layers by external applied field.

Rahim, M.; Khan, Nawazish A.; Mumtaz, M.

2013-07-01

354

Exploring Soil Properties through Electromagnetic Sensor-based Complex Dielectric Permittivity  

NASA Astrophysics Data System (ADS)

Soil physical and chemical properties contain important information influencing soil quality as well as plant growth and yield, all of which ultimately impact hydrologic, ecologic and agricultural interests. Electromagnetic (EM) sensors are widely used for water content determination using a variety of measurement techniques, most of which are based on soil capacitance or travel-time analysis. Most measurements yield a single dielectric permittivity value (usually at an unknown frequency), which must be interpreted to derive the volumetric water content. Recent research associated with permittivity measurements in the frequency domain suggest that important soil features may be extracted there. The objectives of this work were to explore EM sensor-based frequency-domain measurements and their potential to reveal soil physical and chemical properties. Ten different EM sensors were evaluated using reference dielectric liquids and suspensions. Effective measurement frequencies for sensors outputing dielectric permittivity were estimated using spectra from network analyzer measurements. Eight different soils with varying texture were selected and permittivities were measured at different water contents to observe the potential for extracting soil properties from frequency-domain measurements. Measured permittivities using lower ‘fixed’ frequency sensors were larger in proportion to the fineness of the soil texture than higher frequency, time domain reflectometry (TDR) measurements. In spite of the challenges in separating relaxation and polarization processes, permittivities determined using multiple frequencies (e.g., 50 and 500 MHz) show potential for illuminating soil textural and other soil properties.

Jones, S. B.; Wang, C.; Robinson, D. A.; Tuller, M.

2009-12-01

355

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

356

Characterization of material properties of low temperature curing polymer dielectrics  

Microsoft Academic Search

Mechanical properties are typically used as a first-order comparison of different thin film microelectronic polymers. Tensile testing is commonly used to determine such mechanical properties (i.e. Young’s modulus, % elongation, tensile strength). Having accurate values generated under known, standardized test conditions is therefore an important consideration. We have found that the method of sample preparation and fixturing during test, gage

Alan Huffman; Marianne Butler; Jeffrey Piascik; Philip Garrou; Jay Im

2011-01-01

357

Hydrogen-Bonded Crystals of Exceptional Dielectric Properties  

Microsoft Academic Search

Hydrogen bonds are well known for governing the molecular association and crystal packing, as well as for their contribution\\u000a to the chemical and physical properties of substances. They affect the properties of materials as versatile as amphibole minerals,\\u000a KDP-type (—OH?O= bonded) ferroelectrics or biopolymers (e.g. cellulose). While the classical examples of such materials usually\\u000a concentrate on the —OH?O= bonds, recently

Andrzej Katrusiak

2008-01-01

358

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

SciTech Connect

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

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

2008-01-01

359

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

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

360

Material, Physical and Electronic Properties of Novel Medium-and High-K Gate Dielectrics  

NASA Astrophysics Data System (ADS)

Silicon dioxide has been used as a gate dielectric for CMOS technology since the 1960's. The aggressive shrinking of the CMOS device dimension to meet demanding speed and density drives the traditional SiO2 gate dielectric towards its thickness-scaling limit. Severe direct tunneling and reliability problems at extremely small thickness will soon set a barrier for this naturally given material. To replace SiO2, many alternative gate dielectrics have been studied. The search for new gate dielectrics has encompassed a wide range of materials from nitrided SiO2 to metal oxides with wide range of dielectric constant, k, such as Ta2O5, TiO2, Al2O3, HfSixOy , ZrSixOy, ZrO2 , HfO2, HfAlO3, ZrAlO3, LaAlO3 and SrTiO3. Alternative dielectric materials with a higher k-value provide a larger physical thickness than SiO2 to reduce the gate leakage. However barrier height and break down decreases with increasing dielectric constant, there is a tradeoff in selecting the high K materials. Morphology, phase stability and impurities incorporation of metal oxide films also play a critical role in controlling leakage, dopant diffusion and charge trapping. In addition, there are numerous challenges involved in the integration of these metal oxides. These integration challenges must be overcome to achieve the desired results of increased gate capacitance, reduced gate leakage and comparable performance and reliability to thermal SiO2 or oxynitride gate dielectrics. We will review the recent progress of the high K material developments including the impact of the deposition technique and chemical sources. The discussion includes formation of a low permittivity oxide at the metal oxide/silicon interface, chemical and thermal stability of various metal oxides in contact with the silicon and gate electrode, the impact of processing condition on material, physical and electrical properties of the metal oxide films.

Nguyen, Bich-Yen

2003-03-01

361

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. The volume of data that can potentially provide information on reservoir architecture and fluid distributions has increased enormously in the past decade. The techniques developed in this research will make it easier to use all the available data in an integrated fashion. While it is relatively easy to generate plausible reservoir models that honor static data such as core, log, and seismic data, it is far more difficult to generate plausible reservoir models that honor dynamic data such as transient pressures, saturations, and flow rates. As a result, the uncertainty in reservoir properties is higher than it could be and reservoir management can not be optimized. In this project, we have developed computationally efficient automatic history matching techniques for generating geologically plausible reservoir models which honor both static and dynamic data. Specifically, we have developed methods for adjusting porosity and permeability fields to match both production and time-lapse seismic data and have also developed a procedure to adjust the locations of boundaries between facies to match production data. In all cases, the history matched rock property fields are consistent with a prior model based on static data and geologic information. Our work also indicates that it is possible to adjust relative permeability curves when history matching production data.

Albert C. Reynolds; Dean S. Oliver; Yannong Dong; Ning Liu; Guohua Gao; Fengjun Zhang; Ruijian Li

2004-12-01

362

Investigation of novel optical scattering properties of micron-scale dielectric particles  

NASA Astrophysics Data System (ADS)

This dissertation presents an examination of novel optical scattering properties of micron-scale dielectric particles with applications to light scattering spectroscopy and ultrasensitive nanoparticle detection. Using the finite-difference time-domain (FDTD) method and Wentzel-Kramers-Brillouin (WKB) approximation, the spectral dependence of scattering cross sections of inhomogeneous and nonspherical dielectric particles is investigated. The equivalent volume-averaged scattering behavior is identified in light scattering by randomly inhomogeneous dielectric spheres, and the concept of the equiphase sphere is proposed to model light scattering by nonspherical dielectric particles. These approaches are useful for analyzing the spectral dependence of light scattering by inhomogeneous and nonspherical particles such as biological cells and nuclei. Applications of these studies include light scattering spectroscopy for probing cellular structures and morphology, and noninvasive detection of precancerous and early cancerous changes in the human epithelium. In addition, the near-field scattering properties of dielectric microcylinders and microspheres are investigated using the FDTD method and rigorous analytical theory. In particular, physical phenomena involving localized photonic "nanojets" are explored. First, it is shown that photonic nanojets have waists as narrow as about 100 nm (smaller than the diffraction limit), and propagate over several optical wavelengths without significant diffraction. Second and even more remarkably, it is shown that a photonic nanojet can increase the backscattering of visible light by a nanometer-scale particle located within the nanojet by several orders of magnitude. Both analytical and perturbation analyses are provided which show that the resulting backscattering by the nanoparticle is proportional to the third power of its size parameter. This is a significant dimensional increase relative to the classical Rayleigh backscattering intensity, which is proportional to the sixth power of the size parameter. Potential applications of this "super-enhanced" backscattering phenomenon include visible-light detection and characterization of nanoparticles as small as clusters of a few hundred atoms. Other potential applications include manipulation and modification of similarly sized nanoparticles.

Chen, Zhigang

363

Effect of surface modification on dielectric and magnetic properties of metal powder/polymer nanocomposites  

NASA Astrophysics Data System (ADS)

Metal nanopowder (Co and Fe)/polymer composites, both with and without surface modification by behenic acid, were fabricated and their dielectric and magnetic properties were measured at 1 GHz to study the effect of surface modification on the electromagnetic properties. The relative permittivity and the real part of the permeability of the composites with surface modified powders were higher than those with unmodified powders. Related dielectric losses remained at almost the same level, but magnetic losses were somewhat increased. The increase of relative permittivity could result from the increased volume fraction of interphase with a slightly higher relative permittivity at the particle/polymer interface than that of the bulk polymer. The increase in the real part of the permeability may be caused by suppression of the induced demagnetizing field due to suppression of eddy currents by a better particle distribution and a decrease in effective agglomerate size because of the surface modification.

Sonoda, Kensaku; Teirikangas, Merja; Juuti, Jari; Moriya, Yasuo; Jantunen, Heli

2011-09-01

364

Dielectric, ferroelectric and mechanical Properties of Microwave Sintered Bi based High temperature Piezoelectric Ceramics  

NASA Astrophysics Data System (ADS)

The sintering of advanced ceramics requires fast heating in order to avoid both grain growth and inter diffusion. In this context, the microwave sintering is a powerful method since it enables sintering in a short time. This paper reports the synthesis and characterization of Strontium Bismuth Titanate (SBTi) system. The material powder was prepared by solid state route and sintering was carried out by both conventional and microwave furnaces. Morphological, dielectric, ferroelectric and mechanical properties were studied for both samples. The dielectric constant and loss tangent of the conventional and microwave sintered samples have ranged between (185-195) & (0.005-0.007) and (195-220) & (0.004-0.006) respectively when measured at 1MHz frequency. The microwave sintering of the SBTi ceramics leads to higher densification (97% of the theoretical density), fine microstructure, and good mechanical and ferroelectric properties in much shorter duration of time compared to that of the conventional sintering process.

Angalakurthi, Rambabu; Raju, K. C. James

2011-10-01

365

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

366

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

367

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

2013-08-27

368

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...

369

Effects of SiC nanofibers addition on microstructure and dielectric properties of lead titanate ceramics  

Microsoft Academic Search

Dense perovskite ferroelectric PbTiO3 (or PT) ceramics reinforced with SiC nanofibers have been successfully fabricated by a simple solid-state mixed oxide and conventional sintering method. Phase formation, densification, microstructure and dielectric properties of the composites were investigated as a function of SiC content. Addition of SiC nanofibers to a PT matrix did not result in unexpected reaction phase. Microstructural observations

R. Wongmaneerung; P. Singjai; R. Yimnirun; S. Ananta

2009-01-01

370

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

371

Synthesis, transport and dielectric properties of polyaniline\\/Co 3 O 4 composites  

Microsoft Academic Search

Conducting polyaniline\\/cobaltous oxide composites have been synthesized using in situ deposition technique by placing fine graded\\/cobaltous oxide in polymerization mixture of aniline. The a.c. conductivity and\\u000a dielectric properties are studied by sandwiching the pellets of these composites between the silver electrodes. It is observed\\u000a that the values of conductivities increase up to 30 wt% of cobaltous oxide in polyaniline and

Shantala D. Patil; S. C. Raghavendra; M. Revansiddappa; P. Narsimha; M. V. N. Ambika Prasad

2007-01-01

372

Dielectric properties of rf sputtered Ta2O5 on rapid thermally nitrided Si  

Microsoft Academic Search

Dielectric properties, including leakage currents of stacked structures composed of rf sputtered Ta2O5 and ultrathin SiOxNy grown by rapid thermal nitridation (RTN) in N2O or NH3 ambient, have been investigated. It was previously established that the leakage current in the structures is controlled by both hopping conduction and tunnelling in the SiOxNy layer and Poole-Frenkel emission in Ta2O5. The analysis

N. Novkovski; A. Paskaleva; E. Atanassova

2005-01-01

373

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

374

Alternative dielectrics for advanced SOI MOSFETs: thermal properties and short channel effects  

Microsoft Academic Search

SOI devices exhibit excellent performance and scalability, but the presence of the buried oxide (BOX) induces self-heating. A possible solution is to replace the SiO2 BOX with other dielectrics that offer improved thermal conductance without degrading the electrical properties. The trade-off between short-channel and thermal effects in advanced SOI MOSFETs (10 nm thick, 20-50 nm long) is examined by comparing

N. Bresson; S. Cristoloveanu; K. Oshima; C. Mazure; F. Letertre; H. Iwai

2004-01-01

375

Mechanical and Dielectric Properties of NiZn Ferrite Powders-CTBN Modified Epoxy Resin Coatings  

Microsoft Academic Search

In this study, the effects of carboxyl terminated butadiene-acrylonitrile liquid rubber (CTBN) addition on the mechanical and dielectric properties of NiZn ferrite powders-CTBN modified epoxy resin coatings were investigated. It was observed that the occurrence of the small, dispersed spherical CTBN domains in the epoxy resin resulted from the phase separation between epoxy and CTBN could enhance the toughness and

Wei-Sheng Chen; Yu-Lun Chang; Hsing-I. Hsiang; Fu-Chi Hsu; Yun-Hwei Shen; Fu-Su Yen

2011-01-01

376

Filler-content Dependence of Dielectric Properties of Low-Density Polyethylene\\/MgO Nanocomposites  

Microsoft Academic Search

This paper reports measurement results of instrumental analyses, permittivity, conduction current, and space charge distribution profiles observed in low-density polyethylene\\/MgO nanocomposites with various filler contents, done with the intention to clarify the filler-content dependence of dielectric properties. The permittivity shows the lowest value in the sample with 1-phr fillers and then increases monotonically with an increase in filler content. The

Toshiaki Kikuma; Norikazu Fuse; Toshikatsu Tanaka; Yoshinao Murata; Yoshimichi Ohki

2006-01-01

377

Investigation on the dielectric properties of nano-titanium dioxide — low density polyethylene composites  

Microsoft Academic Search

Dielectric properties of nano-titanium dioxide (TiO2) with diameter about 25 nm - low density polyethylene (LDPE) composites were investigated at the temperature ranging from 293 K to 343 K with the frequency ranging from 0.1 Hz to 100 kHz in the present paper. Experimentally, we observed two peaks in the spectrums; one appears in both pure and incorporated LDPE (abbreviated

Li Shengtao; Yin Guilai; Ni Fengyan; Bai Suna; Li Jianying; Zhang Tuo

2010-01-01

378

Dielectric properties of the system AgI-CuI-CsI  

Microsoft Academic Search

The dielectric properties of the system AgI-CuI-CsI with four molar ratios namely 90-05-05, 70-15-15, 50-25-25 and 30-35-35 have been measured and the results discussed. The relaxational frequencies have been calculated and the activation energies obtained suggest the conduction to be mainly due to silver ions only. The conduction mechanism has been observed to be due to a hopping mechanism of

B. Nalini; S. Selvaskarapandian

1997-01-01

379

Phase analysis and microwave dielectric properties of LTCC TiO 2 with glass system  

Microsoft Academic Search

Glass–ceramic composites containing TiO2 (anatase, rutile) and modified borosilicate glasses were prepared and their sintering behaviour, phase evolution, interface reactions, and microwave dielectric properties were investigated as new candidates for low-temperature cofired ceramic (LTCC) materials. It was found that the addition of small amounts of borosilicate glasses lowered the sintering temperature of TiO2 from 1400 to 900 °C. X-ray diffraction results

Sung-Hun Yoon; Dong-Wan Kim; Seo-Yong Cho; Kug Sun Hong

2003-01-01

380

Electronic Structure, Electrical and Dielectric Properties of BaSnO3 below 300 K  

Microsoft Academic Search

The electronic structure, electrical and dielectric properties of barium stannate, a semiconducting perovskite oxide prepared by solid state ceramic route were studied by employing X-ray photoelectron spectroscopy (XPS), Mössbauer and impedance spectroscopic techniques in the temperature range 77-300 K. X-ray diffraction (XRD) pattern of BaSnO3 confirms the cubic structure. Scanning electron microscopy (SEM) images show high porosity in the sample

Prabhakar Singh; Benjamin J. Brandenburg; C. Peter Sebastian; Prakash Singh; Sindhu Singh; Devendra Kumar; Om Parkash

2008-01-01

381

Influence of silver migration on dielectric properties and reliability of relaxor based MLCCs  

Microsoft Academic Search

In order to study the micro-mechanism of silver migration which influences the reliability of relaxor based multilayer ceramic capacitors (MLCCs), micro-silver-doped PMN-PZN based relaxor ferroelectric ceramics were investigated for their microstructural and dielectric properties. SEM observations showed that the microstructure near the interface of MLCCs was greatly changed by the action of the inner silver\\/palladium electrode. The results indicate that

Ruzhong Zuo; Longtu Li; Zhilun Gui

2000-01-01

382

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

SciTech Connect

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

Takahara, H. (NTT Applied Electronics Labs., 3-9-11 Midoricho, Musashino-shi, Tokyo 180 (JP))

1989-08-01

383

Dielectric properties of gold-containing plasma-polymerized thin films  

Microsoft Academic Search

Electrical properties of gold-containing plasma-polymerized thin films have been studied in the dielectric regime (isolated conducting clusters dispersed in a polymeric matrix). dc measurements over a wide temperature range provide evidence for a transport process involving the matrix itself as opposed to tunneling directly across the insulating barrier between metallic clusters. The films display space-charge-limited conduction which is due to

P. Canet; C. Laurent; J. Akinnifesi; B. Despax

1992-01-01

384

Properties of the dielectric barrier discharge in mixtures of methane with helium  

Microsoft Academic Search

The influence of the chemical composition of the feeding gas mixtures CH4-He on the physical properties of dielectric barrier discharge was investigated experimentally as well as theoretically. Certain\\u000a changes in the shape of charge-voltage characteristics (Lissajous figures) were observed when the content of He was varied\\u000a within the range 0–90%. An increase of the He concentration was found to cause

K. V. Kozlov; P. Michel; H.-E. Wagner

1998-01-01

385

Effect of fluorine on moisture absorption and dielectric properties of SiOF films  

Microsoft Academic Search

The effect of fluorine on moisture absorption and dielectric properties of SiOF films as a function of SiF4\\/O2 gas flow ratio was investigated The films were deposited by using ECR plasma CVD with various gas flow ratios (SiF4\\/O2 = 0.2 ~ 1.6) diluted in Ar. Characterization of films was carried out accordingly in terms of the gas flow ratios. The

Seoghyeong Lee; Jong-Wan Park

1998-01-01

386

Dielectric properties and heating effect of multiferroic BiFeO 3 suspension  

Microsoft Academic Search

Bismuth ferrite (BiFeO3) ceramic particles of micro-meter size were prepared by a solid-state route. This study revealed an appropriate method to measure the dielectric properties of BiFeO3 particle suspension using a system designed by ourselves. The heating effect of the BiFeO3 suspension with applied AC voltage was confirmed. Application of this material in hyperthermia treatment of biological tissues with the

Zhonghua Dai; Yasuhisa Fujita; Yukikuni Akishige

2011-01-01

387

Dielectric and piezoelectric properties of hydroxyapatite-BaTiO3 composites  

Microsoft Academic Search

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 0.1 Hz to 1 MHz, 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.

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

2006-01-01

388

Dielectric and piezoelectric properties of hydroxyapatite-BaTiO3 composites  

Microsoft Academic Search

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 0.1 Hz to 1 MHz, 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.

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

389

Dielectric properties of butyl rubber-SrTiO3 flexible composite  

Microsoft Academic Search

Butyl rubber-SrTiO3 flexible composites were prepared through sigma mixing followed by hot pressing. The dielectric properties were studied at different frequencies. Theoretical models were used to predict the effective relative permittivity of the composites and the results were correlated with the experimental data. The relative permittivity of the composite was observed to increase with the volume fraction of the filler,

Dhanesh Thomas; J. Chameswary; M. T. Sebastian

2009-01-01

390

Investigating the Dielectric Property of Abnormal Grain Growth Hexagonal BaTiO3  

Microsoft Academic Search

In this work, the structural and dielectric properties of hexagonal BaTiO3 have been investigated. The samples are partially doped with Ga at Ti site to stabilize the hexagonal structure at room temperature. The abnormal grain growth (AGG) is observed on h-BaTi1 ? xGaxO3 samples at a higher sintering temperature. The Qxf values can be improved by Ga-doping in BaTiO3. By

Shu-Wei Lee; Chien-Ming Lei

2009-01-01

391

Modifications of the dielectric and thermal properties of vulcanized natural rubber due to iodine doping  

NASA Astrophysics Data System (ADS)

The marked changes in the dielectric and thermal properties of vulcanized cis-1,4-polyisoprene due to different iodine doping levels are investigated. The results show strong evidences of formation of conjugated sequences of unsaturated double bonds in the vulcanized polyisoprene backbone, through visible and infrared spectroscopic data. The dependence of the electrical conductivity, specific heat, and of the Young's modulus, upon doping, indicate the existence of a critical doping concentration for the onset of an order-disorder transition.

da Silva, M. D.; Miranda, L. C. M.

1994-05-01

392

Transmission and reflection properties of incident pulse in a dielectric slab doped with quantum dot  

NASA Astrophysics Data System (ADS)

In this paper, transmission and reflection properties of incident pulse in a dielectric slab which doped by quantum dot nanostructure via electron tunneling is studied. It is shown that by using the electron tunneling in a quantum dot, the transmission and reflection coefficients can be controlled at different wavelengths. Therefore, this model can be used as an all-optical filter which is suitable for next generation of all optical communication systems.

Asadpour, Seyyed Hossein; Soleimani, Hamid Rahimpour

2013-10-01

393

Maturity effects on dielectric properties of apples from 10 to 4500 MHz  

Microsoft Academic Search

Dielectric properties of external surface, internal tissue and juice of Fuji apples during the last two months of tree-ripening were measured with an open-ended coaxial-line probe and a network analyzer at 24 °C from 10 to 4500 MHz. The firmness, soluble solids content (SSC), pH, moisture content and electrical conductivity were also measured to determine whether permittivity is related to apple quality.

Wenchuan Guo; Xinhua Zhu; Stuart O. Nelson; Rong Yue; Hui Liu; Yi Liu

2011-01-01

394

Effect of Bi-substitution on the dielectric properties of polycrystalline yttrium iron garnet  

Microsoft Academic Search

The effect of Bi-substitution on the dielectric properties of yttrium iron garnet (YIG) was studied in this paper. The Bi-substituted YIG (YIG:Bi) polycrystalline samples, having composition of Y3?xBixFe5O12, were prepared by the solid-state reaction method. x varied from 0 to 1.2. The phase formation and microstructure were performed by X-ray diffraction and scanning electron microscopy, respectively. Ions valency was identified

Hongjie Zhao; Ji Zhou; Yang Bai; Zhilun Gui; Longtu Li

2004-01-01

395

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

396

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

NASA Astrophysics Data System (ADS)

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

Zhou, Xing

397

High Pressure effects on electrical resistivity and dielectric properties of nanocrystalline SnO2  

NASA Astrophysics Data System (ADS)

Nanocrystalline tin oxide (SnO2) was prepared by chemical precipitation method with different grain sizes. The X-ray diffraction studies showed the structural stability of nanocrystalline SnO2 under high-pressure. Electrical and dielectric properties were studied on these samples using complex impedance spectroscopy under different hydrostatic pressures. Electrical resistivity and dielectric studies showed a transition in nanocrystalline SnO2 when it was subjected to high-pressure. The transition pressures obtained from both the resistivity and dielectric measurements agree with each other. The transition pressures were found to increase considerably with the decrease in grain size. Dielectric constant was found to decrease with the reduction of grain size. In order to find whether the transition with pressure is structure- related or not, Raman spectroscopy was done at normal temperature and pressure (NTP) and as a function of pressure at room temperature. Raman modes at NTP showed lines which correspond to tetragonal rutile structure of SnO2. In situ high-pressure Raman measurements were carried out up to 3.38 GPa. No structural change was found with pressure.

Thangadurai, P.; Bose, A. Chandra; Ramasamy, S.; Kesavamoorthy, R.; Ravindran, T. R.

2005-10-01

398

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

399

Effect of sintering temperature on the structural, dielectric and ferroelectric properties of tungsten substituted SBT ceramics  

NASA Astrophysics Data System (ADS)

Structural, dielectric and ferroelectric properties of tungsten (W) substituted SrBi2(Ta1-xWx)2O9 (SBTW) [x=0.0, 0.025, 0.05, 0.075, 0.1 and 0.2] have been studied as a function of sintering temperature (1100-1250 °C). X-ray diffraction patterns confirm the single-phase layered perovskite structure formation up to x=0.05 at all sintering temperatures. The present study reveals an optimum sintering temperature of 1200 °C for the best properties of SBTW samples. Maximum Tc of ˜390 °C is observed for x=0.20 sample sintered at 1200 °C. Peak-dielectric constant (?r) increases from ˜270 to ˜700 on increasing x from 0.0 to 0.20 at 1200 °C sintering temperature. DC conductivity of the SBTW samples is nearly two to three orders lower than that of the pristine sample. Remnant polarization (Pr) increases with the W content up to x?0.075. A maximum 2Pr (˜25 ?C/cm2) is obtained with x=0.075 sample sintered at 1200 °C. The observed behavior is explained in terms of improved microstructural features, contribution from the oxygen and cationic vacancies in SBTW. Such tungsten substituted samples sintered at 1200 °C exhibiting enhanced dielectric and ferroelectric properties should be useful for memory applications.

Coondoo, Indrani; Panwar, Neeraj; Jha, A. K.

2011-02-01

400

Influence of Nd 2O 3 on the thermal and dielectric properties of Pb-based lead borosilicate glasses  

Microsoft Academic Search

Neodymium has been employed in various Pb-based glass compositions containing ZnO, MgO, CaO, and BaO, to obtain low melting glasses for use as dielectric materials. Thermal analysis (DTA, TMA) was applied for both qualitative and quantitative thermal properties (Tg, CTE) of the glasses, and impedance analysis of the dielectric properties (?r, tan?) was performed. It was found that with increasing

Byung-Hae Jung; Hyung-Sun Kim

2004-01-01

401

A Investigation of the Dielectric and Hysteresis Properties of Plzt Ferroelectric and Multilayer Composite Thin Films.  

NASA Astrophysics Data System (ADS)

The dielectric and hysteresis properties of ferroelectric and multilayer composite thin films were investigated. PLZT ferroelectrics were produced in bulk ceramic and thin film form from the same acetate precursor solutions in order to compare their electrical and physical properties. Bulk ceramics were hot pressed from chemically coprecipitated powders, and thin films were fabricated by spin and dip coating on Ag and Pt-coated Si substrates. Internal film stress from thermal expansion mismatch between films and substrates was found to contribute to differences in electrical properties and Curie temperatures between the thin film and bulk materials as were interface layer effects, grain size and mechanical clamping from the substrates. Rapid thermal processing (RTP) of PLZT thin films using an automated spin coat reactor was found to improve thin film dielectric and hysteresis properties as well as enhance perovskite phase formation, induce preferred (110) and (111) orientations, decrease grain size and increase microstructural uniformity. RTP films were compared with manually spin coated thin films with conventional furnace pyrolysis (CFP) in order to isolate the effects of heating rate from deposition technique. Heating rates of at least 70^circC per second were obtained by RTP versus 35^circC per second for CFP. The development of composite thin films further optimized PLZT thin film properties. Improved antiferroelectric -to-ferroelectric domain switching with decreased ferroelectric coercive field, increased induced polarization with decreased coercivity and polarization remanence for relaxor-type composites and increased hysteresis loop squareness for ferroelectric memory materials were among the advances compared with films of homogeneous PLZT composition. Experimental dielectric and hysteresis properties were described by a series capacitor model consisting of the linear and nonlinear properties of the individual composite components.

Dausch, David Edward

1995-01-01

402

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

NASA Astrophysics Data System (ADS)

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

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

2007-05-01

403

Effects of adding HfO2 on the microstructure and dielectric properties of giant dielectric constant ceramic CaCu3Ti4O12  

NASA Astrophysics Data System (ADS)

CaCu3Ti4O12 (CCTO), an unusual perovskite-like ceramic, is known for its extraordinarily high (˜10^4) and relatively frequency independent dielectric constant. It has drawn a lot of attention recently because of its potential applications in microelectronics and microwave devices. In this investigation, HfO2 powder was added to a pre-reacted CCTO powder, which was synthesized by a conventional solid-state reaction, at different concentrations from 1 to 70 wt% and the mixture was sintered into disc-shaped ceramic samples. The effects of adding HfO2 on the microstructure and dielectric properties of CCTO ceramics were investigated. In general, we found that the dielectric constant tends to increase with HfO2 addition up to 8 wt% and then decrease with further addition. Moreover, the dielectric loss was also influenced by the addition of HfO2, and a low loss tangent of ˜0.035 was obtained. The ac conductivity, impedance, complex dielectric permittivity and electric modulus graphs were used to analyze the data. These observations were explained on the basis of the internal-barrier-layer capacitor model with Maxwell-Wagner relaxations.

Yuan, W. X.; Hark, S. K.

2010-03-01

404

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

405

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

SciTech Connect

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

Li, X.T. [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Du, P.Y., E-mail: dupy@zju.edu.c [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Zhao, Y.L.; Tu, Y.; Dai, J.L.; Weng, W.J.; Han, G.R.; Song, C.L. [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

2010-11-15

406

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

407

Microstructures and dielectric properties of CaCu3Ti4O12 ceramics via combustion method  

NASA Astrophysics Data System (ADS)

CaCu3Ti4O12 (CCTO) powder was synthesized by the combustion method. The effect of sintering temperature was studied on dielectric properties of the prepared ceramic samples. They have the dielectric constant of ~31 000 and 80 000 for the grain size of 0.3 and 30-100 ?m. It is unusual for CCTO with a grain size of 0.3 ?m to have a dielectric constant of ~31 000. Their giant dielectric constant could be explained by a two-step internal-barrier-layer-capacitor model, associated with grain boundaries and domain boundaries. The existence of domain boundaries helped to explain the contradiction of the dielectric mechanisms between polycrystalline and single-crystal CCTO.

Yuan, W. X.; Li, Z. J.

2012-01-01

408

Dielectric Properties of BaTiO3Modified BiFeO3 Ceramics  

Microsoft Academic Search

Multiferroic BiFeO3 has attracted extensive interest due to its potential in several applications. However, pure-phase BiFeO3 is very difficult to obtain. Hence, mixing BiFeO3 with other ferroelectrics, such as BaTiO3, is another approach to obtain materials with possible multiferroic properties. In this study, the BiFeO3 was modified with addition of BaTiO3 via a simple solid state reaction method. Dielectric properties

Sujittra Chandarak; Athipong Ngamjarurojana; Suthum Srilomsak; Pitak Laoratanakul; Saroj Rujirawat; Rattikorn Yimnirun

2010-01-01

409

Millimeter-Wave Dielectric Properties of Cordierite/Indialite Glass Ceramics  

NASA Astrophysics Data System (ADS)

Millimeter-wave wireless communications with high data transfer and radar system for Pre-Crash Safety System have been developed recently. Cordierite (Mg2Al4Si5O18) is one of the silicates with good millimeter-wave dielectric properties. Cordierite has two polymorphs: cordierite and indialite. Cordierite is of low symmetry form with ordered structure, and indialite is of high symmetry form with disordered structure. In this study, indialite/cordierite glass ceramics are fabricated with good millimeter-wave properties. The \\mathit{Qf} values are dependent on the amount of indialite phase and crystallization conditions. Indialite with high symmetry showed higher \\mathit{Qf} values than cordierite with low symmetry. This result clearly shows that high symmetry results in high \\mathit{Qf} when the samples are prepared under the same crystallization conditions. However, these glass ceramics are very difficult to make under the same conditions because of non-uniform crystallization. These dielectric glass ceramics show high \\mathit{Qf} values of >200{,}000 GHz, low dielectric constant \\varepsilonr = 4.7, and \\mathit{TCf}= -27 ppm/°C.

Ohsato, Hitoshi; Kim, Jeong-Seog; Kim, A-Young; Cheon, Chae-Il; Chae, Ki-Woong

2011-09-01

410

Influence of titanium chloride addition on the optical and dielectric properties of PVA films  

NASA Astrophysics Data System (ADS)

Polymeric films based on polyvinyl alcohol (PVA) doped with titanium chloride (TiCl3) at different weight percent ratios were prepared using the solvent cast technique. The structural properties of these polymeric films are examined by XRD and FTIR studies. The complexation of the dopant with the polymer was confirmed by FTIR studies. The XRD pattern reveals that the amorphous domains of PVA polymer matrix increased with raising the TiCl3 content. The optical properties of these polymeric films were examined by optical absorption and emission spectroscopy. Electrical conductivity was measured at room temperature of pure PVA and PVA doped with different concentrations of TiCl3 from 20 Hz to 3 MHz. The conductivity was found to increase with the increase in dopant concentration. The dielectric constant (??) indicates a strong dielectric dispersion in the studied frequency range and increases as dopant content increases. This increase in both ? and ?? is attributed to the increase in the localized charges distribution. Moreover, a loss peak was identified in the dielectric loss spectra and it is attributed to the orientation of polar groups.

Abdelaziz, M.; Ghannam, Magdy M.

2010-02-01

411

The dielectric properties of charged nanoparticle colloids at radio and microwave frequencies  

NASA Astrophysics Data System (ADS)

Charged particle colloids typically consist of particles with negative surface charge suspended in an aqueous electrolyte solution. A layer of ions forms around each particle, and previous research has shown that the dynamics of this charge distribution, induced by an external field, lead to effective and potentially useful dielectric properties (Lyklema J and Van Leeuwen H P 1999 Adv. Colloid and Interface Sci. 83 33, O'Konski C T 1960 J. Phys. Chem. 64 605). Charged nanoparticle colloids are potentially of great benefit because they are extremely stable and their small dimensions make them highly versatile. Possible uses include electromagnetic shielding devices and medical applications. This research focuses on the dielectric properties of charged polystyrene nanoparticle colloids, which are investigated across a range of radio and microwave frequencies. The results show two distinct regions in the permittivity behaviour. The first is the dipolar relaxation of water at microwave frequencies. The second is a high amplitude, low frequency relaxation due to the diffusive motion of ions in the bulk electrolyte beyond the double layer. Effective control of the resulting dielectric response is demonstrated with particle size ranging from 20 to 220 nm. It is shown that the small nanoparticle sizes lead to faster relaxation times than those expected from conventional micron particle sizes, such that the loss extends to microwave frequencies. The results are fitted to a model where the zeta potential, xgr, and double layer thickness, kgr-1, are used as fitting parameters.

Hussain, Shahid; Youngs, Ian J.; Ford, Ian J.

2004-02-01

412

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

413

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

414

Dielectric properties of organic monolayers directly bonded on silicon probed by current sensing atomic force microscope  

NASA Astrophysics Data System (ADS)

The dielectric properties of alkyl monolayers with various chain lengths [CH3(CH2)n-1- (n=12, 14, 16, and 18)] covalently bonded to a hydrogen terminated n-type silicon (111) surface in a nanoscale region were evaluated using current sensing atomic force microscopy (AFM). A reliable electrical contact between the alkyl monolayers and the metal-coated AFM tip was achieved under slight stress. At a force less than 2 nN, current sharply increased as the bias was scanned over a critical value, showing that breakdown took place. The breakdown voltage linearly depended on the chain length of the alkyl monolayers and the dielectric strength of 2.0 GV/m was derived from the slope of this relation.

Zhao, Jianwei; Uosaki, Kohei

2003-09-01

415

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

NASA Astrophysics Data System (ADS)

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

Bar??, Behzad

2013-12-01

416

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

NASA Astrophysics Data System (ADS)

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

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

2009-07-01

417

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

NASA Astrophysics Data System (ADS)

Single-phase Bi0.80La0.20FeO3 (BLFO) and Bi0.80La0.20Fe1-xNbxO3 (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.

Singh, Hemant; Yadav, K. L.

2011-09-01

418

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

2011-09-13

419

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

NASA Astrophysics Data System (ADS)

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

Nefzi, H.; Sediri, F.

2013-05-01

420

Optical properties of metal-dielectric-metal microcavities in the THz frequency range.  

PubMed

We present an experimental and theoretical study of the optical properties of metal-dielectric-metal structures with patterned top metallic surfaces, in the THz frequency range. When the thickness of the dielectric slab is very small with respect to the wavelength, these structures are able to support strongly localized electromagnetic modes, concentrated in the subwavelength metal-metal regions. We provide a detailed analysis of the physical mechanisms which give rise to these photonic modes. Furthermore, our model quantitatively predicts the resonance positions and their coupling to free space photons. We demonstrate that these structures provide an efficient and controllable way to convert the energy of far field propagating waves into near field energy. PMID:20588522

Todorov, Y; Tosetto, L; Teissier, J; Andrews, A M; Klang, P; Colombelli, R; Sagnes, I; Strasser, G; Sirtori, C

2010-06-21

421

Properties and Microstructures of Low-Temperature-Processable Ultralow-Dielectric Porous Polyimide Films  

NASA Astrophysics Data System (ADS)

Coating of ultralow-dielectric (ultralow- k) polymers on high-speed and high-frequency circuitries can increase signal propagation speed and reduce crosstalk. High-temperature foamed films have ultralow- k properties, but are ineffective in noise reduction because of the presence of dense skins. Vapor-induced phase separation was used to fabricate porous polyimide films in this investigation. Scanning electron microscopy revealed that the films are homogeneous without skin layers. The pore size can be controlled from less than a micron to several microns. Electrical characterization revealed that the relative dielectric constant is reduced to as low as 1.7 and is stable between 8.2 GHz and 18 GHz. Usage of this new ultralow- k material as a substrate can help to improve circuit speed by more than 40% compared to the dense Kapton substrate, making this material well suited for use in wide-band and high-frequency applications.

Ren, Yuxing; Lam, David C. C.

2008-07-01

422

Dielectric properties of perovskite oxynitride epitaxial thin films  

NASA Astrophysics Data System (ADS)

Perovskite oxynitrides with the formula ABO2N are expected to show unique electric properties hardly accessible by conventional oxides. For example, N-2p orbitals tend to form a shallow band at the top of the oxygen-nature valence band. This enables us to develop narrow-bandgap ferroelectric materials with d^0 configuration, which is applicable to ferroelectrics-based photovoltaic cells. In this study, we fabricated (001)-oriented epitaxial thin films of SrTaO2N by nitrogen-plasma assisted pulsed laser deposition on (Nb-doped) SrTiO3 substrate. X-ray diffraction measurements revealed large lattice distortion (c/a of 1.015-1.03) due to compressive strain from substrate (mismatch of -3.2 %), though it is partially relaxed. The films had yellow color with a bandgap of about 600 nm. Ferroelectric behavior was observed at room temperature by piezoresponse force microscopy. As far as we know, this is the first experimental observation for ferroelectricity in perovskite oxynitrides. First principles calculations suggested that the ferroelectricity originates from trans-type nitrogen ordering, which can be driven by compressive strain.

Oka, Daichi; Hirose, Yasushi; Kamisaka, Hideyuki; Fukumura, Tomoteru; Hasegawa, Tetsuya; Ito, Seiji; Morita, Akira; Matsuzaki, Hiroyuki; Fukutani, Katsuyuki; Ishii, Satoshi; Sasa, Kimikazu; Sekiba, Daiichiro

2013-03-01

423

Improved Dielectric Properties of Low-Temperature-Sintered (Ba,Sr)TiO3-Based Ceramics by Ge Substitution  

NASA Astrophysics Data System (ADS)

Multilayer microwave dielectric materials with low sintering temperature are required for microwave phase shifters, filters, and true-time delay devices. We investigated the sintering and dielectric properties of (Ba0.6Sr0.4)(Ti1-xGex)O3 (BSTG; 0.05? x? 0.3) ceramics. As the Ge concentration was increased, the lattice constant of BSTG ceramics decreased, and Ba2Ge2TiO8, which is the liquid phase at low temperature, was formed. Ba2Ge2TiO8 liquid phase may increase the sintering density. The effect of Ge substitution is the decrease in the sintering temperature from over 1400 to 1150 °C in BST system ferroelectric ceramics. With increasing Ge concentration, the dielectric constant decreased from 2190 to 530, and the dielectric loss decreased up to 0.001 (at 1 MHz) with sintering at 1150 °C for 2 h. When Ge was substituted at 0.05 and 0.1 mol of Ti in the BST at 1150 °C, the dielectric constant, dielectric loss, tunability, Curie temperature, and figure of merit were 2184 and 1529, 0.002 and 0.001, 27 and 23%, -11 and -18 °C, and 135 and 230, respectively. These compositions show microwave dielectric properties comparable to those of (Ba0.5Sr0.5)TiO3 ferroelectrics, which are the important materials for tunable devices such as varactors, phase shifters, and frequency agile filters.

Jong-Yoon Ha,; Seok-Jin Yoon,; Dae-Yong Jeong,; Ji-Won Choi,

2010-07-01

424

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

SciTech Connect

Plutonium, because of its self-irradiation by alpha decay, ages by means of lattice damage and helium in-growth. These integrated aging effects result in microstructural and physical property changes. Because these effects would normally require decades to measure, studies are underway to assess the effects of extended aging on the physical properties of plutonium alloys by incorporating roughly 7.5 weight % of highly specific activity isotope {sup 238}Pu into the {sup 239}Pu metal to accelerate the aging process. This paper presents updated results of self-irradiation effects on {sup 238}Pu-enriched alloys measured by immersion density, dilatometry, and tensile tests. After nearly 90 equivalent years of aging, both the immersion density and dilatometry show that the enriched alloys continue to decreased in density by {approx}0.002% per year, without void swelling. Quasi-static tensile measurements show that the aging process increases the strength of plutonium alloys.

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

2008-07-31

425

Dielectric properties of (Ba 0.5Sr 0.5)TiO 3 thin films  

Microsoft Academic Search

The dielectric properties of (Ba0.5Sr0.5)TiO3 (BST) thin films with high electrical resistivity were investigated. BST films are deposited on Pt\\/TiO2\\/SiO2\\/Si substrates by a metal-organic deposition (MOD) method. The dielectric permittivity and ac conductivity of the films are measured in the frequency range 102–105 Hz. The dielectric permittivity ?r decreases slightly with frequency f, following the relationship ?r=a+bfn?1 (a, b and

Feng Yan; Peng Bao; Zhigang Zhang; Jinsong Zhu; Yening Wang; Helen L. W. Chan; Chung-Loong Choy

2000-01-01

426

Enhanced dielectric properties and sinterability of CaCu3Ti4O12 ceramics by Sr2+ doping  

NASA Astrophysics Data System (ADS)

CaCu3Ti4O12 ceramics substituted by Sr2+ for Ca2+ were prepared by the solid state reaction method. It was found that Sr2+ substitution increased the lattice constant of CaCu3Ti4O12 in a consistent manner. The dielectric properties, sinterability, and microstructures of the Ca1-xSrxCu3Ti4O12 ceramics were investigated. Large enhancement of dielectric properties (increase in dielectric constants and decrease in dielectric losses) was observed in the Ca1-xSrxCu3Ti4O12 ceramics at x=0.2 within the frequency range between 0.2 and 20 kHz. It was found that the doping of Sr2+ greatly improved the sinterability of Ca1-xSrxCu3Ti4O12 ceramics by largely reducing sintering temperature and promoting densification and grain growth during sintering.

Li, Wang; Qiu, Shen-Yu; Chen, Nan; Liu, Bing-Fa; Du, Guo-Ping

2010-02-01

427

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

428

Static and dynamic magnetic properties of densely packed magnetic nanowire arrays  

NASA Astrophysics Data System (ADS)

The static and dynamic magnetic properties of magnetic nanowire arrays with high packing density (>0.4) and wire diameter much greater than the exchange length have been studied by static and time-resolved magneto-optical Kerr effect measurements and micromagnetic simulations. The nanowires were formed by electrodeposition within a nanoporous template such that their symmetry axes lay normal to the plane of the substrate. A quantitative and systematic investigation has been made of the static and dynamic properties of the array, which lie between the limiting cases of a single wire and a continuous ferromagnetic thin film. In particular, the competition between anisotropies associated with the shape of the individual nanowires and that of the array as a whole has been studied. Measured and simulated hysteresis loops are largely anhysteretic with zero remanence, and the micromagnetic configuration is such that the net magnetization vanishes in directions orthogonal to the applied field. Simulations of the remanent state reveal antiferromagnetic alignment of the magnetization in adjacent nanowires and the formation of vortex flux closure structures at the ends of each nanowire. The excitation spectra obtained from experiment and micromagnetic simulations are in qualitative agreement for magnetic fields applied both parallel and perpendicular to the axes of the nanowires. For the field parallel to the nanowire axes, there is also good quantitative agreement between experiment and simulation. The resonant frequencies are initially found to decrease as the applied field is increased from remanence. This is the result of a change of mode profile within the plane of the array from nonuniform to uniform as the ground state evolves with increasing applied field. Quantitative differences between experimental and simulated spectra are observed when the field is applied perpendicular to the nanowire axes. The dependence of the magnetic excitation spectra upon the array packing density is explored, and dispersion curves for spin waves propagating within the array parallel to the nanowire axis are presented. Finally, a tunneling of end modes through the middle region of the nanowires was observed. The tunneling is more efficient for wires forming densely packed arrays, as a result of the extended penetration of the dynamic demagnetizing fields into the middle of the wires and due to the lowering of the tunneling barrier by the static demagnetizing field of the array.

Dmytriiev, O.; Al-Jarah, U. A. S.; Gangmei, P.; Kruglyak, V. V.; Hicken, R. J.; Mahato, B. K.; Rana, B.; Agrawal, M.; Barman, A.; Mátéfi-Tempfli, M.; Piraux, L.; Mátéfi-Tempfli, S.

2013-05-01

429

Electrical Properties of Low-Temperature-Compatible P-Channel Polycrystalline-Silicon TFTs Using High Gate Dielectrics  

Microsoft Academic Search

In this paper, we describe a systematic study of the electrical properties of low-temperature-compatible p-channel polycrystalline-silicon thin-film transistors (poly-Si TFTs) using HfO2 and HfSiOx, high-k gate dielectrics. Because of their larger gate capacitance density, the TFTs containing the high-k gate dielectrics exhibited superior device performance in terms of higher Ion\\/Ioff current ratios, lower subthreshold swings (SSs), and lower threshold voltages

Ming-Jui Yang; Chao-Hsin Chien; Yi-Hsien Lu; Chih-Yen Shen; Tiao-Yuan Huang

2008-01-01

430

Correlation between dielectric properties and sintering temperatures of polycrystalline CaCu3Ti4O12  

Microsoft Academic Search

Dielectric properties of polycrystalline CaCu3Ti4O12 (CCTO) pellets sintered in the temperature range 1000-1200°C were evaluated with impedance spectroscopy at frequency range of 102 to 107 Hz from 90 K to 294 K. A correlation has been established between the pair values of low frequency limit dielectric constant and the total resistivity and the sintering temperature. For example, the sample sintered

Jianren Li; Kyuho Cho; Naijuan Wu; Alex Ignatiev

2004-01-01

431

Grain boundary effect on the dielectric properties of CaCu3Ti4O12 ceramics  

Microsoft Academic Search

The electrical properties of CaCu3Ti4O12 ceramic materials, showing an enormously large dielectric constant, were investigated. It was found that the grain boundary plays an important role in the giant dielectric behaviour of these ceramics. Measurement of the electrical current density (J) versus the electrical field (E) was carried out. A good linear relationship between lnJ and E1\\/2 was found, which

Guozhong Zang; Jialiang Zhang; Peng Zheng; Jinfeng Wang; Chunlei Wang

2005-01-01

432

Effect of Sintering Temperature on the Dielectric Properties of CaCu3Ti4O12 Ceramics  

Microsoft Academic Search

The dielectric properties of CaCu3Ti4O12 ceramics sintered at various temperatures were investigated. Dielectric constants, ??, of CaCu3Ti4O12 ceramics were distributed between 2,000 and 100,000. The ?? of approximately 10, which had been reported by Subramanian et al., was obtained at a sintering temperature of 1080°C. Sintering at 1100 °C was necessary in order to obtain a dense ceramic sample, and

Rintaro Aoyagi; Makoto Iwata; Masaki Maeda

2007-01-01

433

Low-temperature sintering and microwave dielectric properties of CaWO 4 ceramics for LTCC applications  

Microsoft Academic Search

Microwave dielectric properties of CaWO4 ceramics were investigated as a function of H3BO3 and\\/or Bi2O3 content and sintering temperature. For a single addition of H3BO3 (1?x (wt.%)?5), the density of specimen increased up to 3wt.% H3BO3, and then decreased. The dielectric constant (K) and the quality factor (Q×f) of the specimens sintered at 850°C showed lower value than those of

Eung Soo Kim; Soon Ho Kim; Burtrand I. Lee

2006-01-01

434

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

435

Apparatus and method to measure dielectric properties (?' and V'') of ionic liquids  

NASA Astrophysics Data System (ADS)

Conventional techniques for measurement of dielectric properties of ionic liquids or electrolyte solutions fail because the samples are largely short circuited by the high electrical conductance. The object of the author's research activity was to elaborate an apparatus (microwave dielectrometer) and method suitable to measure the dielectric constant (V') and loss factor (V'') of well conducting ionic liquids and other solvents. This process is based on a revised waveguide method completed with an automatic calibration possibility. Contrary to conventional measuring methods this technique uses about 20 W/g power density. The measurements were carried out at 2.45 GHz frequency in the temperature range from 10 up to 100 °C. The obtained (V') and (V'') values of different solvents were compared with several published (calculated and measured) data. Statistical analysis was used to determine the error of measurements and distilled water was chosen as a standard for study of data dispersion. To accomplish statistical analysis, namely, the dielectric characteristics have to be determined at the same temperature. The values of variances were less or equal 1 in case of V' and decrease with increasing temperature. In case of V'' the variance data were much smaller.

Göllei, Attila; Vass, András; Pallai, Elisabeth; Gerzson, Miklós; Ludányi, Lajos; Mink, János

2009-04-01

436

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

437

Study of complex dielectric properties of lunar simulants and comparison with Apollo samples at microwave frequencies  

NASA Astrophysics Data System (ADS)

Laboratory characterization of dielectric properties of terrestrial analogues of lunar soil (JSC-1A) and comparison with lunar samples returned from various Apollo missions is made at different as well as normalized bulk density. Here measurements of dielectric constants and losses were made at four microwave frequencies such as 1.7 GHz, 2.5 GHz, 6.6 GHz and 31.6 GHz. Complex permittivity of lunar simulant was measured at temperature ranging from -190 °C to + 200 °C using Wave-Guide cell method. Comparison of permittivity of JSC-1A with Apollo sample also has been done at similar microwave frequencies. The investigations reveal that dielectric constant and loss factor of terrestrial analogues of lunar soil are temperature dependent. As temperature is gradually increased both these parameter (storage factor and loss factor) also gradually increases. These temperatures were chosen because the Moon undergoes at that extremes level of temperature. It is scorching heat at 110 °C during the day and freezing cold at -180 °C during night. The measured value of ? can be useful for designing passive as well as active sensors.

Calla, Om Prakash Narayan; Rathore, Inder Singh

2012-12-01

438

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

439

Thickness dependence of the dielectric properties of thermally evaporated Sb2Te3 thin films  

NASA Astrophysics Data System (ADS)

Sb2Te3 thin films of different thickness (23 - 350 nm) were prepared by thermal evaporation technique. The thickness dependence of the ac conductivity and dielectric properties of the Sb2Te3 films have been investigated in the frequency range 10 Hz- 100 kHz and within the temperature range 293-373K. Both the dielectric constant epsilon1 and dielectric loss factor epsilon2 were found to depend on frequency, temperature and film thickness. The frequency and temperature dependence of ac conductivity (?ac(?)) has also been determined. The ac conductivity of our samples satisfies the well known ac power law; i.e., ?ac(?) propto ?s where s<1 and independent of the film thickness. The temperature dependence of ac conductivity and parameter s is reasonably well interpreted by the correlated barrier hopping (CBH) model. The activation energies were evaluated for various thicknesses. The temperature coefficient of the capacitance (TCC) and permitivity (TCP) were determined as a function of the film thickness. The microstructure of the samples were analyzed using X-ray diffraction (XRD). This results are discussed on the base of the differences in their morphologies and thicknesses. The tendency for amorphization of the crystalline phases becomes evident as the film thickness increases.

Ulutas, K.; Deger, D.; Yakut, S.

2013-03-01

440

Dielectric, ferroelectric and magnetic properties of Mn-doped LuFeO3 ceramics  

NASA Astrophysics Data System (ADS)

LuFe1-xMnxO3 (x = 0, 0.05) ceramics with the orthorhombic distorted perovskite structure in space group Pbnm were synthesized using a solid-state reaction process. The dielectric, ferroelectric, and magnetic properties were investigated systematically. With Mn-substitution, the low temperature dielectric relaxation was suppressed and only one dielectric anomaly around 360-530 K was observed. Obvious ferroelectric hysteresis loops were detected at room temperature in LuFe0.95Mn0.05O3, the smaller polarization compared with LuFeO3 suggested the important role of the electron hopping between Fe2+ and Fe3+ ions in ferroelectricity. The results of thermal analysis indicated that the Néel temperature decreased with Mn-substitution, which could be ascribed to the weaker Fe3+-Mn3+ and Mn3+-Mn3+ exchange interactions compared with Fe3+-Fe3+ interaction. Due to the strong anisotropy of Mn3+ ions, a spin reorientation transition could be induced in LuFe0.95Mn0.05O3. Moreover, weak ferromagnetic characteristic was also detected at room temperature in LuFe0.95Mn0.05O3 ceramics.

Qin, Ying; Qiang Liu, Xiao; Ming Chen, Xiang

2013-01-01

441

Swift heavy ion irradiation induced modifications in magnetic and dielectric properties of Mn-Ca ferrite  

NASA Astrophysics Data System (ADS)

The effects of 200 MeV Ag15+ ion irradiation on structural, magnetic and dielectric properties of nanocrystalline Mn-Ca ferrite have been investigated. The specimens characterized using XRD confirmed the formation of cubic spinel structure. The TEM images revealed the spherical morphology consistent with the crystalline diameter. After irradiation by 200 MeV Ag ions, saturation magnetization, coercivity, and blocking temperature were enhanced appreciably which could be attributed to swift heavy ion (SHI) irradiation induced modifications in surface states of the nanoparticles, slight increase in crystallite size and cationic re-distribution. The dielectric measurements revealed that both dielectric constant (?r) and the loss tangent (tan ?) disperse normally as a function of frequency of the externally applied electric field. The increase in ?r and tan ? on irradiation could be attributed to the surface modifications through slight crystal growth and hence the availability of sufficient number of Fe2+/Mn3+ ions particularly at the octahedral site on grain boundaries showing a fair agreement with the magnetization results.

Dolia, S. N.; Sharma, P. K.; Dhawan, M. S.; Kumar, Sudhish; Prasad, Arun S.; Samariya, A.; Pareek, S. P.; Singhal, R. K.; Asokan, K.; Xing, Y. T.; Alzamora, M.; Saitovitach, E.

2012-02-01

442

Derivation of extracellular fluid volume fraction and equivalent dielectric constant of the cell membrane from dielectric properties of the human body. Part 2: A preliminary study for tracking the progression of surgical tissue injury  

Microsoft Academic Search

A study is conducted to determine whether the extracellular fluid (ECF) volume fraction and equivalent dielectric constant\\u000a of the cell membrane ?m, derived from the dielectric properties of the human body can track the progression of surgical tissue injury. Frequency-dependent\\u000a dielectric constants and electrical conductivities of body segments are obtained at surgical (trunk) and non-surgical sites\\u000a (arm and leg) from

T. Tatara; K. Tsuzaki

2000-01-01

443

Modeling and experimental study for the targeted design of dielectric properties of polymer composite materials  

NASA Astrophysics Data System (ADS)

Chemical bonding between the constituent phases of composite materials is necessary to ensure that the mechanical reinforcement of the dispersed phase is transferred to the bulk properties of the composite. At a chemical structural level, the interfacial region is comprised of molecules of the polymer matrix (as well as any interfacial chemical-coupling agents that may be present) bonded to the surface of the filler particle. This interfacial-bonding region is termed the "interphase" and results from the confining effect that the rigid filler particles have on the mobility of the polymer molecules in the matrix. In this text, the interphase power law model (IPL Model) is developed in order to determine the permittivity characteristics of this interphase region of complex composite systems. The IPL Model is based on a simple extension of the general power law model in which a composite system containing filler, interphase and matrix regions may be treated as a unique three-component composite system comprising two primary components (matrix and filler) and an interphase region that is inextricably dependent upon the characteristics of the filler and matrix components. The IPL Model provides a means to determine the interphase dielectric constant, dielectric loss and volume fraction of the overall composite system. The cause and effects of the interphase region on a variety of complex composite systems are investigated. Furthermore, an estimation of the effect of the change in the dielectric constant as a result of the chemical bonding of the polymer matrix at the filler surface of a composite system can be calculated using molecular polarizability equations. A molecular polarizability calculation is described and used to calculate the dielectric constant of the polymer phase and interphase of composite systems.

Todd, Michael George

444

Study of the material properties and suitability of plasma-deposited fluorine-doped silicon dioxides for low dielectric constant interlevel dielectrics  

Microsoft Academic Search

A major challenge for back-end interconnection technology as device geometries shrink is the development of low dielectric constant materials with good gap-filling properties that are suitable for microelectronics manufacturing. Recently, there has been much interest in fluorine-doped silicon dioxides (SiOF) as such a material. The advantages of a silicon dioxide based film from an integration standpoint make these films very

V. L. Shannon; M. Z. Karim

1995-01-01

445

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

NASA Astrophysics Data System (ADS)

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

Kolodiazhnyi, Taras

446

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

447

Electrical Properties of Metal-Insulator-Semiconductor Devices with High Permittivity Gate Dielectric Layers  

Microsoft Academic Search

\\u000a The electrical properties of metal-oxide-semiconductor capacitors with very thin high permittivity gate dielectric layers\\u000a like Si3N4, Ta2O5, and A12O3 are investigated. The field and temperature dependence of the gate current of these layers is analysed in order to determine\\u000a the electrical conduction mechanisms in these layers, as well as to extract important physical parameters like the tunneling\\u000a barrier height, electron

M. Houssa; P. W. Mertens; M. M. Heyns; A. Stesmans

448

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

449

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

Microsoft Academic Search

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 ?50nm 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

Amit Kumar; K. L. Yadav

2011-01-01

450

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

Microsoft Academic Search

Single-phase Bi0.80La0.20FeO3 (BLFO) and Bi0.80La0.20Fe1-xNbxO3 (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

Hemant Singh; K. L. Yadav

2011-01-01

451

Properties and Microstructures of Low-Temperature-Processable Ultralow-Dielectric Porous Polyimide Films  

Microsoft Academic Search

Coating of ultralow-dielectric (ultralow-k) polymers on high-speed and high-frequency circuitries can increase signal propagation speed and reduce crosstalk. High-temperature\\u000a foamed films have ultralow-k properties, but are ineffective in noise reduction because of the presence of dense skins. Vapor-induced phase separation\\u000a was used to fabricate porous polyimide films in this investigation. Scanning electron microscopy revealed that the films are\\u000a homogeneous without

Yuxing Ren; David C. C. Lam

2008-01-01

452

Dielectric Properties of Sol-Gel Derived Barium Strontium Titanate and Microwave Sintering of Ceramics  

Microsoft Academic Search

This thesis consists of two areas of research: (1) sol-gel processing of Ba_{rm 1-x}Sr_{rm x} TiO_3 ceramics and their dielectric properties measurement; and (2) microwave versus conventional sintering of ceramics such as Al_2 O_3, Ba_{ rm 1-x}Sr_{rm x}TiO_3, Sb-doped SnO _2 and YBa_2Cu _3O_7. Sol-gel powders of BaTiO_3, SrTiO_3, and their solid solutions were synthesized by the hydrolysis of titanium

Fathi A. Selmi

1991-01-01

453

Piezo-, pyro-, ferro-, and dielectric properties of ceramic/polymer composites obtained from two modifications of lead titanate  

NASA Astrophysics Data System (ADS)

Two modifications of lead titanate ceramic and the polyetherketoneketone polymer (PEKK) have been used to obtain two polymer/ceramic composites. The piezo-, pyro-, ferroelectric, and dielectric properties were studied. The calcium modified lead titanate/polyetherketoneketone (PTCa/PEKK) composite shows better piezo- and pyro-electric properties than that of the samarium and manganese modified lead titanate/polyetherketoneketone (PSTM/PEKK) composite. Also, a lower dielectric permittivity and remanent polarization values with a higher coercive field are obtained. The results are discussed considering the modifications made in the ceramic phases of each composite. The presented properties for both composites are still substantially lower than those in bulk ceramics.

Peláiz-Barranco, A.; Marin-Franch, P.

2005-02-01

454

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

PubMed

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 the same and other species. The differences between the properties of the same tissue for various animals are very small. The tissues properties at frequencies above 1 GHz correlate well with the water content. Practically all water in the skeletal muscle is in the free form, while in other tissues both free and bound water are present. PMID:7111397

Stuchly, M A; Kraszewski, A; Stuchly, S S; Smith, A M

1982-07-01

455

Optical and dielectric properties of neutron irradiated MgAl2O4 spinels  

NASA Astrophysics Data System (ADS)

The radiation effects on the optical and electrical properties of stoichiometric MgAl2O4 spinel specimens irradiated in FFTF—MOTA at temperatures between 385 and 750°C to fluence ranging from 5.3 to 24.9 × 1026 n m-2 (E ? 0.1 McV) are measured. In the optical properties a strong absorption in the ultraviolet range is observed together with a small band around 20 000 cm-1 (510 nm). Two strong luminescence emissions are also observed around 700 nm, with excitation spectra in the ultraviolet region. In the electrical properties a strong decrease of conductivity is observed in the temperature range from 0 to 500°C. Other techniques (like dielectric spectroscopy and EPR) have been used.

Ibarra, A.; Vila, R.; Garner, F. A.

1996-10-01

456

Important Changes in Microwave Scattering Properties of Young Snow-Covered Sea Ice as Indicated from Dielectric Modelling.  

National Technical Information Service (NTIS)

Winter measurements of the properties of young snow-covered fast ice are input into a mixture model to calculate the complex dielectric constant. Large changes in the electromagnetic properties of the medium occur over the 46 day period of measurements. T...

M. R. Drinkwater

1988-01-01

457

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

SciTech Connect

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

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

2011-08-15

458

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01