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Sample records for dielectric constant measurements

  1. Capacitive Cells for Dielectric Constant Measurement

    ERIC Educational Resources Information Center

    Aguilar, Horacio Munguía; Maldonado, Rigoberto Franco

    2015-01-01

    A simple capacitive cell for dielectric constant measurement in liquids is presented. As an illustrative application, the cell is used for measuring the degradation of overheated edible oil through the evaluation of their dielectric constant.

  2. BOREAS RSS-17 Dielectric Constant Profile Measurements

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Nickeson, Jaime (Editor); McDonald, Kyle C.; Zimmerman, Reiner; Way, JoBea

    2000-01-01

    The BOREAS RSS-17 team acquired and analyzed imaging radar data from the ESA's ERS-1 over a complete annual cycle at the BOREAS sites in Canada in 1994 to detect shifts in radar backscatter related to varying environmental conditions. This data set consists of dielectric constant profile measurements from selected trees at various BOREAS flux tower sites. The relative dielectric constant was measured at C-band (frequency = 5 GHz) as a function of depth into the trunk of three trees at each site, Measurements were made during April 1994 with an Applied Microwave Corporation field PDP fitted with a 0.358-cm (0.141-inch) diameter coaxial probe tip. The data are available in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  3. Dielectric Constant Measurements for Characterizing Lunar Soils

    NASA Technical Reports Server (NTRS)

    Anderson, Robert C.; Buehler, M.; Seshadri, S.; Kuhlman, G.; Schaap, M.

    2005-01-01

    The return to the Moon has ignited the need to characterize the lunar regolith using fast, reliable in-situ methods. Characterizing the physical properties of the rocks and soils can be very difficult because of the many complex parameters that influence the measurements. In particular, soil electrical property measurements are influenced by temperature, mineral type, grain size, porosity, and soil conductivity. Determining the dielectric constant of lunar materials may be very important in providing quick characterization of surface deposits, especially for the Moon. A close examination of the lunar regolith samples collected by the Apollo astronauts indicates that the rocks and soils on the Moon are dominated by silicates and oxides. In this presentation, we will show that determining the dielectric constant measurements can provide a simple, quick detection method for minerals that contain titanium, iron, and water. Their presence is manifest by an unusually large imaginary permittivity.

  4. Laboratory measurement of the complex dielectric constant of soils

    NASA Technical Reports Server (NTRS)

    Wiebe, M. L.

    1971-01-01

    The dielectric constant of a material is an extremely important parameter when considering passive radiometric remote sensing applications. This is because the emitted energy measured by a microwave radiometer is dependent on the dielectric constant of the surface being scanned. Two techniques of measuring dielectric constants are described. The first method involves a dielectric located in air. The second method uses basically the same theoretical approach, but the dielectric under consideration is located inside a section of waveguide.

  5. Let's Measure the Dielectric Constant of a Piece of Paper!

    ERIC Educational Resources Information Center

    Karlow, Edwin A.

    1991-01-01

    Described is a simple circuit with which students can observe the effect of common dielectric materials in a capacitor and measure the dielectric constant of a piece of paper. Discussed are the theory, apparatus construction, and experimental procedures for this activity. (CW)

  6. Measurements of the dielectric constants for planetary volatiles

    NASA Technical Reports Server (NTRS)

    Anicich, Vincent G.; Huntress, Wesley T., Jr.

    1987-01-01

    The model of Titan at present has the surface temperature, pressure, and composition such that there is a possibility of a binary ethane-methane ocean. Proposed experiments for future Titan flybys include microwave mappers. Very little has been measured of the dielectric properties of the small hydrocarbons at these radar frequencies. An experiment was conducted utilizing a slotted line to measure the dielectric properties of the hydrocarbons, methane to heptane, from room temperature to -180 C. Measurements of the real part of the dielectric constants are accurate to + or - 0.006 and the imaginary part (the loss tangent) of the liquids studied is less than or equal to 0.001. In order to verify this low loss tangent, the real part of the dielectric constant of hexane at 25 C was studied as a function of the frequency range of the slotted line system used. The dielectric constant of hexane at room temperature, between 500 MHz and 3 MHz, is constant within experimental error.

  7. Method of measuring dielectric constant using an oscilloscope

    NASA Astrophysics Data System (ADS)

    Nogi, Yasuyuki; Watanabe, Masayuki; Suzuki, Kiyomitsu; Ohkuma, Yasunori

    2015-09-01

    A simple relationship determining the dielectric constant of a material inserted in a parallel-plate capacitor is formulated from Gauss's law for a uniform electric field and the continuity condition of electric flux at the boundary of the material. The relationship suggests that the dielectric constant can be determined from the dependence of the charge stored on the capacitor on the thicknesses of the material and the air layer between the plates. A uniform field is created by applying an ac voltage to the plates, which includes a guard ring. The stored charge is estimated by using an oscilloscope to measure the voltage across a resistor inserted between the power supply and the capacitor. The results of the measurement are given for planar materials such as soda-lime glass, Bakelite, acrylic glass, and Teflon with a thickness of 0.5-1 cm.

  8. Measurement of the dielectric constant of lunar minerals and regolith

    NASA Astrophysics Data System (ADS)

    Trigwell, S.; Starnes, J.; Brown, C.; White, C.; White, T.; Su, M.; Mahdi, H. H.; Al-Shukri, H. J.; Biris, A.; Non Invasive ProspectingLunar Ores; Minerals

    2010-12-01

    For long-term lunar exploration, the priorities are excavation and beneficiation of lunar regolith for water, oxygen, energy production, and structural and shielding fabrication. This work is part of a project focusing on the utilization of Ground Penetrating Radar (GPR) to identify the presence of enriched areas of sub-surface minerals for excavation and ore processing. GPR detection of sub-surface minerals depends significantly on the differences in dielectric constant of the various minerals. One of the minerals in lunar regolith of interest is ilmenite for its use in oxygen production and a supply of titanium and iron. Several pure minerals (feldspar, spodumene, olivine, and ilmenite) and lunar simulant JSC-1A were sieved into several size fractions (<25, 25-50, 50-75, and 75-100 µm). A test cell with an attached shaker was constructed in a vacuum chamber and measurements of the dielectric constant of the minerals and simulant were taken as a function of particle size and packing density. The results showed that there was a direct correlation between the measured dielectric constant and packing density and that ilmenite had a much higher dielectric constant than the other minerals. Measurements were also taken on Apollo 14 lunar regolith as a comparison and compared to the literature to validate the results. Mixtures of pure silica powder and ilmenite in various concentrations (2, 5, 10, and 15%) were measured and it was determined that approximately 2-4% ilmenite in the mixtures could be distinguished. Core samples taken on the moon for all Apollo missions showed ilmenite concentrations ranging from 0.3-12%, depending upon whether it was in the mare or highlands regions, and so this data may significantly contribute to the use of GPR for mineral prospecting on the moon.

  9. Dielectric Constant Measurements on Lunar Soils and Terrestrial Minerals

    NASA Technical Reports Server (NTRS)

    Anderson, R. C.; Buehler, M. G.; Seshardri, S.; Schaap, M. G.

    2004-01-01

    The return to the Moon has ignited the need to characterize the lunar regolith using in situ methods. An examination of the lunar regolith samples collected by the Apollo astronauts indicates that only a few minerals (silicates and oxides) need be considered for in situ resource utilization (ISRU). This simplifies the measurement requirements and allows a detailed analysis using simple methods. Characterizing the physical properties of the rocks and soils is difficult because of many complex parameters such as soil temperature, mineral type, grain size, porosity, and soil conductivity. In this presentation, we will show that the dielectric constant measurement can provide simple detection for oxides such as TiO2, FeO, and water. Their presence is manifest by an unusually large imaginary permittivity.

  10. Measurement of the dielectric function spectra of low dielectric constant using the spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Horie, Masahiro; Postava, Kamil; Yamaguchi, Tomuo; Akashika, Kumiko; Hayashi, Hideki; Kitamura, Fujikazu

    2003-05-01

    The dielectric function spectra of low dielectric constants (low-k) materials have been determined using spectroscopic ellipsometry, normal incidence spectroscopic reflectometry, and Fourier transform infrared transmission spectrometry over a wide spectral range from 0.03 to 5.4 eV (230nm to 40.5um wavelength region). The electric and ionic contributions to the overall static dielectric constants 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 Electric 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 electric and ionic absorption.

  11. Dielectric Constant of Suspensions

    NASA Astrophysics Data System (ADS)

    Mendelson, Kenneth S.; Ackmann, James J.

    1997-03-01

    We have used a finite element method to calculate the dielectric constant of a cubic array of spheres. Extensive calculations support preliminary conclusions reported previously (K. Mendelson and J. Ackmann, Bull. Am. Phys. Soc. 41), 657 (1996).. At frequencies below 100 kHz the real part of the dielectric constant (ɛ') shows oscillations as a function of the volume fraction of suspension. These oscillations disappear at low conductivities of the suspending fluid. Measurements of the dielectric constant (J. Ackmann, et al., Ann. Biomed. Eng. 24), 58 (1996). (H. Fricke and H. Curtis, J. Phys. Chem. 41), 729 (1937). are not sufficiently sensitive to show oscillations but appear to be consistent with the theoretical results.

  12. On the Dielectric Constant for Acetanilide: Experimental Measurements and Effect on Energy Transport

    NASA Astrophysics Data System (ADS)

    Careri, G.; Compatangelo, E.; Christiansen, P. L.; Halding, J.; Skovgaard, O.

    1987-01-01

    Experimental measurements of the dielectric constant for crystalline acetanilide powder for temperatures ranging from - 140°C to 20°C and for different hydration levels are presented. A Davydov-soliton computer model predicts dramatic changes in the energy transport and storage for typically increased values of the dielectric constant.

  13. Measuring the spatial distribution of dielectric constants in polymers through quasi-single molecule microscopy.

    PubMed

    Hess, Chelsea M; Riley, Erin A; Palos-Chávez, Jorge; Reid, Philip J

    2013-06-13

    The variation in dielectric constant is measured for thin films of poly(methyl methacrylate) (PMMA) and poly(vinylidene fluoride) (PVDF) using confocal fluorescence microscopy. Spatial variation in the local dielectric constant of the polymer films on the ~250 nm length scale is measured using the solvochromatic emission from incorporated nile red (NR) at "quasi-single molecule" (10(-7) M) and true single molecule (SM) concentrations (10(-9) M). Correlation of the NR fluorescence wavelength maximum with dielectric constant is used to transform images of NR's emission maxima to spatial variation in local dielectric constant. We demonstrate that the distributions of dielectric environments measured in the quasi- and true SM approaches are equivalent; however, the enhanced signal rates present in the quasi-SM approach result in this technique being more efficient. In addition, the quasi-SM technique reports directly on the continuous spatial variation in dielectric constant, information that is difficult to obtain in true SM studies. With regards to the polymers of interest, the results presented here demonstrate that a limited distribution of dielectric environments is present in PMMA; however, a broad distribution of environments exists in PVDF consistent with this polymer existing as a distribution of structural phases. PMID:23735049

  14. In-line measurement of high temperature dielectric constant in the process of sintering

    SciTech Connect

    Zhou Jian; Cheng Jiping; Tang Yuling; Qiu Jinyu

    1996-12-31

    In this paper, a resonant cavity method is developed and some experimental results for measuring dielectric constants of ceramic samples (e.g., Al{sub 2}O{sub 3}) under different sintering temperatures are reported. The experiments show that this method has higher precision and good prospects of in-line monitoring the high temperature dielectric constant in the process of raising the temperature of the samples. These results provide some scientific experimental basis for physical research of ceramic materials.

  15. High temperature dielectric constant measurement - another analytical tool for ceramic studies?

    SciTech Connect

    Hutcheon, R.M.; Hayward, P.; Alexander, S.B.

    1995-12-31

    The automation of a high-temperature (1400{degrees}C), microwave-frequency, dielectric constant measurement system has dramatically increased the reproducibility and detail of data. One can now consider using the technique as a standard tool for analytical studies of low-conductivity ceramics and glasses. Simultaneous temperature and frequency scanning dielectric analyses (SDA) yield the temperature-dependent complex dielectric constant. The real part of the dielectric constant is especially sensitive to small changes in the distance and distribution of neighboring ions or atoms, while the absorptive part is strongly dependent on the position and population of electron/hole conduction bands, which are sensitive to impurity concentrations in the ceramic. SDA measurements on a few specific materials will be compared with standard differential thermal analysis (DTA) results and an attempt will be made to demonstrate the utility of both the common and complementary aspects of the techniques.

  16. L-band Dielectric Constant Measurements of Seawater (Oral presentation and SMOS Poster)

    NASA Technical Reports Server (NTRS)

    Lang, Roger H.; Utku, Cuneyt; LeVine, David M.

    2003-01-01

    This paper describes a resonant cavity technique for the measurement of the dielectric constant of seawater as a function of its salinity. Accurate relationships between salinity and dielectric constant (which determines emissivity) are needed for sensor systems such as SMOS and Aquarius that will monitor salinity from space in the near future. The purpose of the new measurements is to establish the dependence of the dielectric constant of seawater on salinity in contemporary units (e.g. psu) and to take advantage of modern instrumentation to increase the accuracy of these measurements. The measurement device is a brass cylindrical cavity 16cm in diameter and 7cm in height. The seawater is introduced into the cavity through a slender glass tube having an inner diameter of 0.1 mm. By assuming that this small amount of seawater slightly perturbs the internal fields in the cavity, perturbation theory can be employed. A simple formula results relating the real part of the dielectric constant to the change in resonant frequency of the cavity. In a similar manner, the imaginary part of the dielectric constant is related to the change in the cavity s Q. The expected accuracy of the cavity technique is better than 1% for the real part and 1 to 2% for the imaginary part. Presently, measurements of methanol have been made and agree with precision measurements in the literature to within 1% in both real and imaginary parts. Measurements have been made of the dielectric constant of seawater samples from Ocean Scientific in the United Kingdom with salinities of 10, 30, 35 and 38 psu. All measurements were made at room temperature. Plans to make measurements at a range of temperatures and salinities will be discussed.

  17. In-situ Microfluidic Measurement of the Dielectric Constant of Colloidal Particles

    NASA Astrophysics Data System (ADS)

    Manafirasi, Setareh; Leary, Thomas; Maldarelli, Charles

    2015-11-01

    The ability to manipulate micron-sized colloidal particles or biological cells in a liquid medium in microfluidic geometries is necessary in lab on a chip devices for micro scale biological analysis and diagnostics for sorting and directing the trafficking of the particles. In dielectrophoresis, a nonuniform electric (E) field is applied to move the particles along the gradient of the field energy, and the velocity is a function of the particle's dielectric constant. Measurement of the dielectric constant is necessary in order to scale field strengths for applications, and it is important to undertake this measurement in-situ as the particle's dielectric content can be modified by the suspending medium (e.g. adsorption onto the particle surface). In this talk we measure directly the dielectric constant of colloids in a microfluidic channel by applying an electric field with ``V''-shaped and planar electrodes on opposite sides of the channel. The cusp of the ``V'' shape concentrates the field to provide a sufficient field intensity gradient which is designed to be uniform across the height of the channel and to vary only with its width. Optical measurements of the diffusiophoretic velocity of polymer colloids are compared to simulations based on numerical solution of the E-field and particle hydrodynamics to obtain the particle dielectric constant and investigate the effect of biomolecule adsorption on the particle surface.

  18. A low dielectric constant customized phantom design to measure RF coil nonuniformity.

    PubMed

    Tofts, P S; Barker, G J; Dean, T L; Gallagher, H; Gregory, A P; Clarke, R N

    1997-01-01

    The selection of a suitable low dielectric constant liquid for radiofrequency coil nonuniformity measurements is described. Measurements of dielectric constant (relative permittivity) were made on a range of candidate liquids. After excluding liquids that were too inflammable or too viscous, Esso Bayol 82 oil (dielectric constant epsilon' = 2.37) was chosen. At 1.5 T, a 27 cm diameter cylindrical phantom (test object) filled with Bayol 82 has a maximum nonuniformity of 1.9% arising from radiofrequency standing waves. The maximum diameter cylinder that can be used without the nonuniformity exceeding 2% is given for a range of liquids and field strengths. The construction of customized containers that fit closely inside a radiofrequency head coil from glass fiber reinforced resin ("fiberglass") is described. Thermal expansion of the liquid takes place without a rise in the internal pressure in the container. PMID:9084027

  19. Measurement of x-ray dielectric constants with coherent transition radiation

    SciTech Connect

    Moran, M.J.; Dahling, B.A.; Piestrup, M.A.; Berman, B.L.; Kephart, J.O.

    1986-06-06

    A technique for measuring the energy-resolved angular distribution of longitudinally coherent transition radiation generated in multiple-foil targets has been developed. This paper will demonstrate how data generated by these measurements can be used to determine the dielectric constants of materials in the soft x-ray spectral region.

  20. Accurate measurements of the dielectric constant of seawater at L band

    NASA Astrophysics Data System (ADS)

    Lang, Roger; Zhou, Yiwen; Utku, Cuneyt; Le Vine, David

    2016-01-01

    This paper describes measurements of the dielectric constant of seawater at a frequency of 1.413 GHz, the center of the protected band (i.e., passive use only) used in the measurement of sea surface salinity from space. The objective of the measurements is to accurately determine the complex dielectric constant of seawater as a function of salinity and temperature. A resonant cylindrical microwave cavity in transmission mode has been employed to make the measurements. The measurements are made using standard seawater at salinities of 30, 33, 35, and 38 practical salinity units over a range of temperatures from 0°C to 35°C in 5°C intervals. Repeated measurements have been made at each temperature and salinity. Mean values and standard deviations are then computed. The total error budget indicates that the real and imaginary parts of the dielectric constant have a combined standard uncertainty of about 0.3 over the range of salinities and temperatures considered. The measurements are compared with the dielectric constants obtained from the model functions of Klein and Swift and those of Meissner and Wentz. The biggest differences occur at low and high temperatures.

  1. Accurate Measurements of the Dielectric Constant of Seawater at L Band

    NASA Technical Reports Server (NTRS)

    Lang, Roger; Zhou, Yiwen; Utku, Cuneyt; Le Vine, David

    2016-01-01

    This paper describes measurements of the dielectric constant of seawater at a frequency of 1.413 GHz, the center of the protected band (i.e., passive use only) used in the measurement of sea surface salinity from space. The objective of the measurements is to accurately determine the complex dielectric constant of seawater as a function of salinity and temperature. A resonant cylindrical microwave cavity in transmission mode has been employed to make the measurements. The measurements are made using standard seawater at salinities of 30, 33, 35, and 38 practical salinity units over a range of temperatures from 0 degree C to 35 degree C in 5 degree C intervals. Repeated measurements have been made at each temperature and salinity. Mean values and standard deviations are then computed. The total error budget indicates that the real and imaginary parts of the dielectric constant have a combined standard uncertainty of about 0.3 over the range of salinities and temperatures considered. The measurements are compared with the dielectric constants obtained from the model functions of Klein and Swift and those of Meissner and Wentz. The biggest differences occur at low and high temperatures.

  2. Accurate Measurements of the Dielectric Constant of Seawater at L Band

    NASA Technical Reports Server (NTRS)

    Lang, Roger H.; Utku, Cuneyt; Tarkocin, Yalcin; LeVine, David M.

    2010-01-01

    This report describes measurements of the dielectric constant of seawater at a frequency of 1.413 GHz that is at the center of the L-Sand radiometric protected frequency spectrum. Aquarius will be sensing the sea surface salinity from space in this band. The objective of the project is to refine the model function for the dielectric constant as a function of salinity and temperature so that remote sensing measurements can be made with the accuracy needed to meet the measurement goals (0.2 psu) of the Aquarius mission. The measurements were made, using a microwave cavity operated in the transmission configuration. The cavity's temperature was accurately regulated to 0.02 C by immersing it in a temperature controlled bath of distilled water and ethanol glycol. Seawater had been purchased from Ocean Scientific International Limited (OS1L) at salinities of 30, 35 and 38 psu. Measurements of these seawater samples were then made over a range of temperatures, from l0 C to 35 C in 5 C intervals. Repeated measurements were made at each temperature and salinity, Mean values and standard deviations were then computed. Total error budgets indicated that the real and imaginary parts of the dielectric constant had a relative accuracy of about l%.

  3. Measurements of the complex dielectric constant of sand and dust particles at 11 GHz

    NASA Astrophysics Data System (ADS)

    Al-Rizzo, Hussain M.; Al-Hafid, Hafid T.

    1988-03-01

    Measurements are reported of the refractive index (Delta-n) and loss tangent (tan delta) of dust particles in a laboratory-simulated model of dust storms, carried out at 11 GHz utilizing a confocal microwave open-cavity resonator. Four samples were used namely, sandy, silty, clayey silt, and clayey, for concentrations varying from 10-4 to 4 x 10-3 g/cu cm. The particle-size distribution (PSD) of each sample was measured by seiving along with the hydrometer technique. Dielectric-constant measurements were also conducted at bulk concentrations using the standing-wave technique for the dry samples and as a function of volumetric moisture content for up to 0.5 cu cm/cu cm. The complex dielectric constant of the dust particle material was evaluated by two approaches. In one the data for permittivities obtained over the whole range of measured concentrations were extrapolated to the particle densities of the samples. In the other a mixing formula was utilized for the determination of epsilon(s) from permittivities measured at bulk concentrations.

  4. Molecular properties of alternative refrigerants derived from dielectric-constant measurements

    SciTech Connect

    Barao, M.T.; Castro, C.A.N. de; Mardolcar, U.V.

    1997-03-01

    A review of the current work in Lisbon on the measurement of the dielectric constant of the liquid phase of some environmentally acceptable refrigerants proposed as alternative replacements of the chlorofluorocarbons (CFCs), responsible for the destruction of the ozone layer, is presented. Measurements on HCFC 141b, HCFC 142b, HCFC 123, HFC 134a, HFC 152a, and HFC 32 samples of stated purities of 99.8 mass % or better were performed as a function of pressure and temperature, in the temperature range from 200 to 300 K and at pressures up to 20 MPa. The ratio of the capacitances of a cell filled with the sample and under vacuum was measured with a direct capacitance method. The dielectric-constant measurements have a repeatability of 0.003% and an accuracy of 0.1%. The theory developed by Vedam et al. based on the Eulerian Strain and the Kirkwood equation for the variation of the modified molar polarization with temperature and density were applied to obtain the dipole moments of the refrigerants in the liquid state, to obtain a physical insight of the molecular behavior, and to understand the equilibrium configuration of these liquids.

  5. Quantum-dot size and thin-film dielectric constant: precision measurement and disparity with simple models.

    PubMed

    Grinolds, Darcy D W; Brown, Patrick R; Harris, Daniel K; Bulovic, Vladimir; Bawendi, Moungi G

    2015-01-14

    We study the dielectric constant of lead sulfide quantum dot (QD) films as a function of the volume fraction of QDs by varying the QD size and keeping the ligand constant. We create a reliable QD sizing curve using small-angle X-ray scattering (SAXS), thin-film SAXS to extract a pair-distribution function for QD spacing, and a stacked-capacitor geometry to measure the capacitance of the thin film. Our data support a reduced dielectric constant in nanoparticles. PMID:25531164

  6. The measurement of the dielectric constant of concrete pipes and clay pipes

    NASA Astrophysics Data System (ADS)

    McGraw, David

    To optimize the effectiveness of the rehabilitation of underground utilities, taking in consideration limitation of available resources, there is a need for a cost effective and efficient sensing systems capable of providing effective, in real time and in situ, measurement of infrastructural characteristics. To carry out accurate non-destructive condition assessment of buried and above ground infrastructure such as sewers, bridges, pavements and dams, an advanced ultra-wideband (UWB) based radar was developed at Trenchless Technology Centre (TTC) and Centre for Applied Physics Studies (CAPS) at Louisiana Tech University (LTU). One of the major issues in designing the FCC compliant UWB radar was the contribution of the pipe wall, presence of complex soil types and moderate-to-high moisture levels on penetration depth of the electromagnetic (EM) energy. The electrical properties of the materials involved in designing the UWB radar exhibit a significant variation as a result of the moisture content, mineral content, bulk density, temperature and frequency of the electromagnetic signal propagating through it. Since no measurements of frequency dependence of the dielectric permittivity and conductivities of the pipe wall material in the FCC approved frequency range exist, in this thesis, the dielectric constant of concrete and clay pipes are measured over a microwave frequency range from 1 Ghz to 10 Ghz including the effects of moisture and chloride content. A high performance software package called MU-EPSLN(TM) was used for the calculations. Data reduction routines to calculate the complex permeability and permittivity of materials as well as other parameters are also provided. The results obtained in this work will be used to improve the accuracy of the numerical simulations and the performances of the UWB radar system.

  7. Dielectric constants of soils at microwave frequencies

    NASA Technical Reports Server (NTRS)

    Geiger, F. E.; Williams, D.

    1972-01-01

    A knowledge of the complex dielectric constant of soils is essential in the interpretation of microwave airborne radiometer data of the earth's surface. Measurements were made at 37 GHz on various soils from the Phoenix, Ariz., area. Extensive data have been obtained for dry soil and soil with water content in the range from 0.6 to 35 percent by dry weight. Measurements were made in a two arm microwave bridge and results were corrected for reflections at the sample interfaces by solution of the parallel dielectric plate problem. The maximum dielectric constants are about a factor of 3 lower than those reported for similar soils at X-band frequencies.

  8. Method for rapidly determining the swelling-clay content in shales and shaly sandstone formations by high-frequency dielectric constant measurements

    SciTech Connect

    Kroeger, M.K.; Longo, J.M.; Steiger, R.P.; Leung, P.K.

    1989-10-24

    This patent describes a method for measuring the swelling-clay content of earth formations by dielectric measurements. It comprises: grinding a sample of the earth formation to a size suitable for testing; washing the sample with a fluid having a water activity substantially less than that of water; packing the washed sample into a sample cell suitable for dielectric measurement; measuring the dielectric constant of the washed sample at a preselected frequency; and comparing the measured dielectric constant of the rock sample to a calibration curve, to determine the swelling-clay content of the earth formation.

  9. Recent Results on the Accurate Measurements of the Dielectric Constant of Seawater at 1.413GHZ

    NASA Technical Reports Server (NTRS)

    Lang, R.H.; Tarkocin, Y.; Utku, C.; Le Vine, D.M.

    2008-01-01

    Measurements of the complex. dielectric constant of seawater at 30.00 psu, 35.00 psu and 38.27 psu over the temperature range from 5 C to 3 5 at 1.413 GHz are given and compared with the Klein-Swift results. A resonant cavity technique is used. The calibration constant used in the cavity perturbation formulas is determined experimentally using methanol and ethanediol (ethylene glycol) as reference liquids. Analysis of the data shows that the measurements are accurate to better than 1.0% in almost all cases studied.

  10. Lateral resolution improvement in scanning nonlinear dielectric microscopy by measuring super-higher-order nonlinear dielectric constants

    NASA Astrophysics Data System (ADS)

    Chinone, N.; Yamasue, K.; Hiranaga, Y.; Honda, K.; Cho, Y.

    2012-11-01

    Scanning nonlinear dielectric microscopy (SNDM) can be used to visualize polarization distributions in ferroelectric materials and dopant profiles in semiconductor devices. Without using a special sharp tip, we achieved an improved lateral resolution in SNDM through the measurement of super-higher-order nonlinearity up to the fourth order. We observed a multidomain single crystal congruent LiTaO3 (CLT) sample, and a cross section of a metal-oxide-semiconductor (MOS) field-effect-transistor (FET). The imaged domain boundaries of the CLT were narrower in the super-higher-order images than in the conventional image. Compared to the conventional method, the super-higher-order method resolved the more detailed structure of the MOSFET.

  11. Measurement of pressures up to 7 MPa applying pressure balances for dielectric-constant gas thermometry

    NASA Astrophysics Data System (ADS)

    Zandt, Thorsten; Sabuga, Wladimir; Gaiser, Christof; Fellmuth, Bernd

    2015-10-01

    For the determination of the Boltzmann constant by dielectric-constant gas thermometry, the uncertainty of pressure measurements in helium up to 7 MPa has been decreased compared with previous achievements (Sabuga 2011 PTB-Mitt. 121 247-55). This was possible by performing comprehensive cross-float experiments with a system of six special pressure balances and the synchronization of their effective areas. It is now possible to measure a helium pressure of 7 MPa with a relative standard uncertainty of 1.0 ppm applying a 2 cm2 piston-cylinder unit, the calibration of which is traceable to the SI base units.

  12. Dielectric constant microscopy for biological materials

    NASA Astrophysics Data System (ADS)

    Valavade, A. V.; Kothari, D. C.; Löbbe, C.

    2013-02-01

    This paper describes the work on the development of Dielectric Constant Microscopy for biological materials using double pass amplitude modulation method. The dielectric constant information can be obtained at nanometer scales using this technique. Electrostatic force microscopy images of biological materials are presented. The images obtained from the EFM technique mode clearly show inversion contrast and gives the spatial variation of tip-sample capacitance. The EFM images are further processed to obtain dielectric constant information at nanometer scales.

  13. Dielectric constant of water in the interface

    NASA Astrophysics Data System (ADS)

    Dinpajooh, Mohammadhasan; Matyushov, Dmitry V.

    2016-07-01

    We define the dielectric constant (susceptibility) that should enter the Maxwell boundary value problem when applied to microscopic dielectric interfaces polarized by external fields. The dielectric constant (susceptibility) of the interface is defined by exact linear-response equations involving correlations of statistically fluctuating interface polarization and the Coulomb interaction energy of external charges with the dielectric. The theory is applied to the interface between water and spherical solutes of altering size studied by molecular dynamics (MD) simulations. The effective dielectric constant of interfacial water is found to be significantly lower than its bulk value, and it also depends on the solute size. For TIP3P water used in MD simulations, the interface dielectric constant changes from 9 to 4 when the solute radius is increased from ˜5 to 18 Å.

  14. Dielectric constant of water in the interface.

    PubMed

    Dinpajooh, Mohammadhasan; Matyushov, Dmitry V

    2016-07-01

    We define the dielectric constant (susceptibility) that should enter the Maxwell boundary value problem when applied to microscopic dielectric interfaces polarized by external fields. The dielectric constant (susceptibility) of the interface is defined by exact linear-response equations involving correlations of statistically fluctuating interface polarization and the Coulomb interaction energy of external charges with the dielectric. The theory is applied to the interface between water and spherical solutes of altering size studied by molecular dynamics (MD) simulations. The effective dielectric constant of interfacial water is found to be significantly lower than its bulk value, and it also depends on the solute size. For TIP3P water used in MD simulations, the interface dielectric constant changes from 9 to 4 when the solute radius is increased from ∼5 to 18 Å. PMID:27394114

  15. Thermal conductivity and dielectric constant of silicate materials

    NASA Technical Reports Server (NTRS)

    Simon, I.; Wechsler, A. E.

    1968-01-01

    Report on the thermal conductivity and dielectric constant of nonmetallic materials evaluates the mechanisms of heat transfer in evacuated silicate powders and establishes the complex dielectric constant of these materials. Experimental measurements and results are related to postulated lunar surface materials.

  16. Dielectric constant of water at very high temperature and pressure

    PubMed Central

    Pitzer, Kenneth S.

    1983-01-01

    Pertinent statistical mechanical theory is combined with the available measurements of the dielectric constant of water at high temperature and pressure to predict that property at still higher temperature. The dielectric constant is needed in connection with studies of electrolytes such as NaCl/H2O at very high temperature. PMID:16593342

  17. Dielectric Constant of Suspensions of Blood Cells

    NASA Astrophysics Data System (ADS)

    Mendelson, Kenneth; Ackmann, James

    1996-03-01

    Measurements of the complex dielectric constant of suspensions of blood cells have recently been reported by Ackmann, et al.(J. J. Ackmann, et al., Ann. Biomed. Eng. 24), 58 (1996). At frequencies below 100 kHz, the real part of the dielectric constant (ɛ') goes through a maximum at a blood cell volume fraction of about 70%. Effective medium approximations do not agree well with this behavior. As a more realistic model, we are studying the grain consolidation model of Roberts and Schwartz(J. N. Roberts and L. M. Schwartz, Phys. Rev. B 31), 5990 (1985). We have used a finite element method to calculate the dielectric constant of this model for a cubic array of spheres. The simulations agree remarkably well with experiment. They suggest, however, that ɛ' may be showing oscillations rather than a simple maximum. Comparison of the simulated and experimental points suggests that this is not an artifact of the periodic array used in the model. Furthermore the simulations indicate that the maximum (or oscillations) disappears at low conductivities of the suspending fluid.

  18. New silicone dielectric elastomers with a high dielectric constant

    NASA Astrophysics Data System (ADS)

    Zhang, Zhen; Liu, Liwu; Fan, Jiumin; Yu, Kai; Liu, Yanju; Shi, Liang; Leng, Jinsong

    2008-03-01

    Dielectric elastomers (Des) are a type of EAPs with unique electrical properties and mechanical properties: high actuation strains and stresses, fast response times, high efficiency, stability, reliability and durability. The excellent figures of merit possessed by dielectric elastomers make them the most performing materials which can be applied in many domains: biomimetics, aerospace, mechanics, medicals, etc. In this paper, we present a kind of electroactive polymer composites based on silicone Dielectric elastomers with a high dielectric constant. Novel high DEs could be realized by means of a composite approach. By filling an ordinary elastomer (e.g. silicone) with a component of functional ceramic filler having a greater dielectric permittivity, it is possible to obtain a resulting composite showing the fruitful combination of the matrix's advantageous elasticity and the filler's high permittivity. Here we add the ferroelectric relaxor ceramics (mainly BaTiO3) which has high dielectric constant (>3000) to the conventional silicone Dielectric elastomers, to get the dielectric elastomer which can exhibit high elastic energy densities induced by an electric field of about 15 MV/m. Tests of the physical and chemical properties of the dielectric elastomers are conducted, which verify our supposes and offer the experimental data supporting further researches.

  19. Dielectric constant extraction of graphene nanostructured on SiC substrates from spectroscopy ellipsometry measurement using Gauss-Newton inversion method

    NASA Astrophysics Data System (ADS)

    Maulina, Hervin; Santoso, Iman; Subama, Emmistasega; Nurwantoro, Pekik; Abraha, Kamsul; Rusydi, Andrivo

    2016-04-01

    The extraction of the dielectric constant of nanostructured graphene on SiC substrates from spectroscopy ellipsometry measurement using the Gauss-Newton inversion (GNI) method has been done. This study aims to calculate the dielectric constant and refractive index of graphene by extracting the value of ψ and Δ from the spectroscopy ellipsometry measurement using GNI method and comparing them with previous result which was extracted using Drude-Lorentz (DL) model. The results show that GNI method can be used to calculate the dielectric constant and refractive index of nanostructured graphene on SiC substratesmore faster as compared to DL model. Moreover, the imaginary part of the dielectric constant values and coefficient of extinction drastically increases at 4.5 eV similar to that of extracted using known DL fitting. The increase is known due to the process of interband transition and the interaction between the electrons and electron-hole at M-points in the Brillouin zone of graphene.

  20. Dielectric constant of liquid alkanes and hydrocarbon mixtures

    NASA Technical Reports Server (NTRS)

    Sen, A. D.; Anicich, V. G.; Arakelian, T.

    1992-01-01

    The complex dielectric constants of n-alkanes with two to seven carbon atoms have been measured. The measurements were conducted using a slotted-line technique at 1.2 GHz and at atmospheric pressure. The temperature was varied from the melting point to the boiling point of the respective alkanes. The real part of the dielectric constant was found to decrease with increasing temperature and correlate with the change in the molar volume. An upper limit to all the loss tangents was established at 0.001. The complex dielectric constants of a few mixtures of liquid alkanes were also measured at room temperature. For a pentane-octane mixture the real part of the dielectric constant could be explained by the Clausius-Mosotti theory. For the mixtures of n-hexane-ethylacetate and n-hexane-acetone the real part of the dielectric constants could be explained by the Onsager theory extended to mixtures. The dielectric constant of the n-hexane-acetone mixture displayed deviations from the Onsager theory at the highest fractions of acetone. The dipole moments of ethylacetate and acetone were determined for dilute mixtures using the Onsager theory and were found to be in agreement with their accepted gas-phase values. The loss tangents of the mixtures exhibited a linear relationship with the volume fraction for low concentrations of the polar liquids.

  1. Investigation of Biodiesel Through Photopyroelectric and Dielectric-Constant Measurements as a Function of Temperature: Freezing/Melting Interval

    NASA Astrophysics Data System (ADS)

    Zanelato, E. B.; Machado, F. A. L.; Rangel, A. B.; Guimarães, A. O.; Vargas, H.; da Silva, E. C.; Mansanares, A. M.

    2015-06-01

    Biodiesel is a promising option for alternative fuels since it derives from natural and renewable materials; it is biodegradable and less polluting than fossil fuels. A gradual replacement of diesel by biodiesel has been adopted by many countries, making necessary the investigation of the physical properties of biodiesel and of its mixture in diesel. Photothermal techniques, specifically the photopyroelectric technique (PPE), have proved to be suitable in the characterization of biodiesel and of its precursor oils, as well as of the biodiesel/diesel mixtures. In this paper, we investigate thermal and electrical properties of animal fat-based biodiesel as a function of temperature, aiming to characterize the freezing/melting interval and the changes in the physical properties from the solid to the liquid phase. The samples were prepared using the transesterification method, by the ethylic route. Optical transmittance experiments were carried out in order to confirm the phase transition interval. Solid and liquid phases present distinct thermal diffusivities and conductivities, as well as dielectric constants. The PPE signal amplitude is governed by the changes in the thermal diffusivity/conductivity. As a consequence, the amplitude of the signal becomes like a step function, which is smoothed and sometimes delayed by the nucleation processes during cooling. A similar behavior is found in the dielectric constant data, which is higher in the liquid phase since the molecules have a higher degree of freedom. Both methods (PPE/dielectric constant) proved to be useful in the characterization of the freezing/melting interval, as well as to establish the distinction in the physical properties of solid and liquid phases. The methodology allowed a discussion of the cloud point and the pour point of the samples in the temperature variation interval.

  2. Dielectric constants of soils at microwave frequencies-2

    NASA Technical Reports Server (NTRS)

    Wang, J.; Schmugge, T.; Williams, D.

    1978-01-01

    The dielectric constants of several soil samples were measured at frequencies of 5 and 19 GHz using the infinite transmission line method. The results of these measurements are presented and discussed with respect to soil types and texture structures. A comparison is made with other measurements at 1.4 GHz. At all three frequencies, the dependence of dielectric constant on soil moisture can be approximated by two straight lines. At low moisture, the slope is less than at high moisture level. The intersection of the two lines is believed to be a function of soil texture.

  3. PECVD of low-dielectric constant films for ULSI

    NASA Astrophysics Data System (ADS)

    Shimogaki, Yukihiro

    1998-10-01

    We studied the reduction mechanism of the dielectric constant of F-doped silicon oxide films prepared by PECVD from SiH_4/N_2O/CF4 mixture. From the estimation of the dielectric constant at various frequencies, ranging from 1MHz to 100THz, using CV measurement, Kramers-Kronig relation and the square of the refractive index, we suggest that the dielectric constant due to ionic and electronic polarization is not the dominant factor in decreasing the dielectric constant. It is important to remove -OH in films to obtain very low dielectric constant F-doped silicon oxide films, because Si-OH is the main factor of the orientational polarization in silicon oxide films made by PECVD. To investigate the reaction mechanism which controls the film structure, we changed the residence time of gas in chamber by varying the flow rate. When the residence time in chamber decreases, the film deposition rate increases. We tried to explain flow rate dependency of the deposition rate using a simple CSTR (continuous stirred tank reactor) model. It can be concluded that there are two paths to deposit the films. One route is a deposition by the precursors with poor step coverage profile, and the other route is deposition through intermediates formed by gas phase reactions that contribute to have better step coverage. The overall gas phase reaction rate constant was estimated from these kinetic studies. Same approach was also carried out on the PECVD of C:F film deposition.

  4. Remote Sensing of Salinity: The Dielectric Constant of Sea Water

    NASA Technical Reports Server (NTRS)

    LeVine, David M.; Lang, R.; Utku, C.; Tarkocin, Y.

    2011-01-01

    Global monitoring of sea surface salinity from space requires an accurate model for the dielectric constant of sea water as a function of salinity and temperature to characterize the emissivity of the surface. Measurements are being made at 1.413 GHz, the center frequency of the Aquarius radiometers, using a resonant cavity and the perturbation method. The cavity is operated in a transmission mode and immersed in a liquid bath to control temperature. Multiple measurements are made at each temperature and salinity. Error budgets indicate a relative accuracy for both real and imaginary parts of the dielectric constant of about 1%.

  5. Temperature and moisture dependence of dielectric constant for silica aerogels

    SciTech Connect

    Hrubesh, L.H., LLNL

    1997-03-01

    The dielectric constants of silica aerogels are among the lowest measured for any solid material. The silica aerogels also exhibit low thermal expansion and are thermally stable to temperatures exceeding 500{degrees}C. However, due to the open porosity and large surface areas for aerogels, their dielectric constants are strongly affected by moisture and temperature. This paper presents data for the dielectric constants of silica aerogels as a function of moisture content at 25{degrees}C, and as a function of temperature, for temperatures in the range from 25{degrees}C to 450{degrees}C. Dielectric constant data are also given for silica aerogels that are heat treated in dry nitrogen at 500{degrees}C, then cooled to 25{degrees}C for measurements in dry air. All measurements are made on bulk aerogel spheres at 22GHz microwave frequency, using a cavity perturbation method. The results of the dependence found here for bulk materials can be inferred to apply also to thin films of silica aerogels having similar nano-structures and densities.

  6. Dielectric constant, dielectric virial coefficients, and dipole moments of 1,1,1,2-tetrafluoroethane

    SciTech Connect

    Barao, T.; Castro, C.A.N. de; Mardolcar, U.V.; Okambawa, R.; St-Arnaud, J.M.

    1995-11-01

    In this paper the authors report measurements of the dielectric constant of 1,1,1,2-tetrafluoroethane, HFC-134a, an environmentally acceptable refrigerant, under consideration as an alternative replacement of the chlorofluorocarbons, CFCs. The dipole moment in the gaseous phase was found to be (1.91 {+-} 0.19) D, and in the liquid phase (3.54 {+-} 0.01) D. The authors present values of the first three dielectric virial coefficients in the gaseous phase.

  7. Simple liquid models with corrected dielectric constants.

    PubMed

    Fennell, Christopher J; Li, Libo; Dill, Ken A

    2012-06-14

    Molecular simulations often use explicit-solvent models. Sometimes explicit-solvent models can give inaccurate values for basic liquid properties, such as the density, heat capacity, and permittivity, as well as inaccurate values for molecular transfer free energies. Such errors have motivated the development of more complex solvents, such as polarizable models. We describe an alternative here. We give new fixed-charge models of solvents for molecular simulations--water, carbon tetrachloride, chloroform, and dichloromethane. Normally, such solvent models are parametrized to agree with experimental values of the neat liquid density and enthalpy of vaporization. Here, in addition to those properties, our parameters are chosen to give the correct dielectric constant. We find that these new parametrizations also happen to give better values for other properties, such as the self-diffusion coefficient. We believe that parametrizing fixed-charge solvent models to fit experimental dielectric constants may provide better and more efficient ways to treat solvents in computer simulations. PMID:22397577

  8. Novel Materials with Effective Super Dielectric Constants for Energy Storage

    NASA Astrophysics Data System (ADS)

    Cortes, Francisco Javier Quintero; Phillips, Jonathan

    2015-05-01

    To test a theory of the recently discovered phenomenon of super dielectric behavior at very low frequency, the dielectric constants of several `pastes', composed of porous alumina powders filled to the point of incipient wetness with water containing dissolved sodium chloride, were measured. The effective dielectric low frequency constants of some of the pastes were greater than 1010, dramatically higher than that of any material ever reported. Moreover, the total energy density reported for one capacitor generated with NaCl-based super dielectric material is marginally higher than found in any prior report. These results are consistent with this recently postulated model of low frequency super dielectric behavior in porous, non-conductive materials saturated with ion-containing liquids: upon the application of an electric field, ions dissolved in the saturating liquid contained in the pores will travel to the ends of pore-filling liquid droplets creating giant dipoles. The fields of these giant dipoles oppose the applied field, reducing the net field created per unit of charge on the capacitor plates, effectively increasing charge/voltage ratio, hence capacitance. This is simply a version of the theory of `polarizable media' found in most classic texts on electromagnetism. Other observations reported here include (1) the impact of ion concentration on dielectric values, (2) a maximum voltage similar to that associated with the electrical breakdown of water, (3) the loss of capacitance upon drying, (4) the recovery of capacitance upon the addition of water to a dry super dielectric material, and (5) the linear relationship between capacitance and inverse thickness. All observations are consistent with the earlier proposed model of the super dielectric phenomenon. An extrapolation of results suggests this technology can lead to energy density greater than the best lithium-ion battery.

  9. Defect density and dielectric constant in perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Samiee, Mehran; Konduri, Siva; Ganapathy, Balaji; Kottokkaran, Ranjith; Abbas, Hisham A.; Kitahara, Andrew; Joshi, Pranav; Zhang, Liang; Noack, Max; Dalal, Vikram

    2014-10-01

    We report on measurement of dielectric constant, mid-gap defect density, Urbach energy of tail states in CH3NH3PbIxCl1-x perovskite solar cells. Midgap defect densities were estimated by measuring capacitance vs. frequency at different temperatures and show two peaks, one at 0.66 eV below the conduction band and one at 0.24 eV below the conduction band. The attempt to escape frequency is in the range of 2 × 1011/s. Quantum efficiency data indicate a bandgap of 1.58 eV. Urbach energies of valence and conduction band are estimated to be ˜16 and ˜18 meV. Measurement of saturation capacitance indicates that the relative dielectric constant is ˜18.

  10. Defect density and dielectric constant in perovskite solar cells

    SciTech Connect

    Samiee, Mehran; Konduri, Siva; Abbas, Hisham A.; Joshi, Pranav; Zhang, Liang; Dalal, Vikram; Ganapathy, Balaji; Kottokkaran, Ranjith; Noack, Max; Kitahara, Andrew

    2014-10-13

    We report on measurement of dielectric constant, mid-gap defect density, Urbach energy of tail states in CH{sub 3}NH{sub 3}PbI{sub x}Cl{sub 1−x} perovskite solar cells. Midgap defect densities were estimated by measuring capacitance vs. frequency at different temperatures and show two peaks, one at 0.66 eV below the conduction band and one at 0.24 eV below the conduction band. The attempt to escape frequency is in the range of 2 × 10{sup 11}/s. Quantum efficiency data indicate a bandgap of 1.58 eV. Urbach energies of valence and conduction band are estimated to be ∼16 and ∼18 meV. Measurement of saturation capacitance indicates that the relative dielectric constant is ∼18.

  11. Protein Dielectric Constants Determined from NMR Chemical Shift Perturbations

    PubMed Central

    Kukic, Predrag; Farrell, Damien; McIntosh, Lawrence P.; E., Bertrand García-Moreno; Jensen, Kristine Steen; Toleikis, Zigmantas; Teilum, Kaare; Nielsen, Jens Erik

    2015-01-01

    Understanding the connection between protein structure and function requires a quantitative understanding of electrostatic effects. Structure-based electrostatics calculations are essential for this purpose, but their use have been limited by a long-standing discussion on which value to use for the dielectric constants (εeff and εp) required in Coulombic models and Poisson-Boltzmann models. The currently used values for εeff and εp are essentially empirical parameters calibrated against thermodynamic properties that are indirect measurements of protein electric fields. We determine optimal values for εeff and εp by measuring protein electric fields in solution using direct detection of NMR chemical shift perturbations (CSPs). We measured CSPs in fourteen proteins to get a broad and general characterization of electric fields. Coulomb's law reproduces the measured CSPs optimally with a protein dielectric constant (εeff) from 3 to 13, with an optimal value across all proteins of 6.5. However, when the water-protein interface is treated with finite difference Poisson-Boltzmann calculations, the optimal protein dielectric constant (εp) rangedsfrom 2-5 with an optimum of 3. It is striking how similar this value is to the dielectric constant of 2-4 measured for protein powders, and how different it is from the εp of 6-20 used in models based on the Poisson-Boltzmann equation when calculating thermodynamic parameters. Because the value of εp = 3 is obtained by analysis of NMR chemical shift perturbations instead of thermodynamic parameters such as pKa values, it is likely to describe only the electric field and thus represent a more general, intrinsic, and transferable εp common to most folded proteins. PMID:24124752

  12. Negative Dielectric Constant Material Based on Ion Conducting Materials

    NASA Technical Reports Server (NTRS)

    Gordon, Keith L. (Inventor); Kang, Jin Ho (Inventor); Park, Cheol (Inventor); Lillehei, Peter T. (Inventor); Harrison, Joycelyn S. (Inventor)

    2014-01-01

    Metamaterials or artificial negative index materials (NIMs) have generated great attention due to their unique and exotic electromagnetic properties. One exemplary negative dielectric constant material, which is an essential key for creating the NIMs, was developed by doping ions into a polymer, a protonated poly(benzimidazole) (PBI). The doped PBI showed a negative dielectric constant at megahertz (MHz) frequencies due to its reduced plasma frequency and an induction effect. The magnitude of the negative dielectric constant and the resonance frequency were tunable by doping concentration. The highly doped PBI showed larger absolute magnitude of negative dielectric constant at just above its resonance frequency than the less doped PBI.

  13. Computing the dielectric constant of liquid water at constant dielectric displacement

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Sprik, Michiel

    2016-04-01

    The static dielectric constant of liquid water is computed using classical force field based molecular dynamics simulation at fixed electric displacement D . The method to constrain the electric displacement is the finite-temperature classical variant of the constant D method developed by Stengel, Spaldin, and Vanderbilt [Nat. Phys. 5, 304 (2009), 10.1038/nphys1185]. There is also a modification of this scheme imposing fixed values of the macroscopic field E . The method is applied to the popular SPC/E model of liquid water. We compare four different estimates of the dielectric constant, two obtained from fluctuations of the polarization at D =0 and E =0 and two from the variation of polarization with finite D and E . It is found that all four estimates agree when properly converged. The computational effort to achieve convergence varies, however, with constant D calculations being substantially more efficient. We attribute this difference to the much shorter relaxation time of longitudinal polarization compared to transverse polarization accelerating constant D calculations.

  14. Functionalised graphene sheets as effective high dielectric constant fillers

    PubMed Central

    2011-01-01

    A new functionalised graphene sheet (FGS) filled poly(dimethyl)siloxane insulator nanocomposite has been developed with high dielectric constant, making it well suited for applications in flexible electronics. The dielectric permittivity increased tenfold at 10 Hz and 2 wt.% FGS, while preserving low dielectric losses and good mechanical properties. The presence of functional groups on the graphene sheet surface improved the compatibility nanofiller/polymer at the interface, reducing the polarisation process. This study demonstrates that functionalised graphene sheets are ideal nanofillers for the development of new polymer composites with high dielectric constant values. PACS: 78.20.Ci, 72.80.Tm, 62.23.Kn PMID:21867505

  15. Role of dielectric constant in electrohydrodynamics of conducting fluids

    NASA Technical Reports Server (NTRS)

    Rhodes, Percy H.; Snyder, Robert S.; Roberts, Glyn O.

    1992-01-01

    Electrohydrodynamic (EHD) flows are driven by the interaction of an electric field with variations in electric conductivity or dielectric constant. In reported EHD experiments on the deformation of drops of immiscible dielectric fluids, the role of conductivity has tended to overshadow the role of dielectric constant. Often, large conductivity contrasts were convenient because the conductivities of the dielectric fluid were relatively uncertain. As a result, the observed effects were always qualitatively the same as if there had been no contrast in dielectric constant. Our early experiments studying the EHC deformations of cylindrical streams readily showed the conductivity effect but the dielectric constant effect was not discernible. We have modified our flow chamber and improved our method of observation and can now see an unequivocal dielectric constant effect which is in agreement with the prior theory. In this paper we first give a brief description of the physics of charge buildup at the interface of an immersed spherical drop or flowing cylindrical sample stream and then show how these charge distributions lead to interface distortions and accompanying viscous flows which constitute EHD. We next review theory and experiment describing the deformation of spherical drops. We show that in the reported drop deformation experiments, the contrast in dielectric constant was never sufficient to reverse the deformation due to the conductivity contrast. We review our work describing the deformation of a cylindrical stream of one fluid flowing in a parallel flow of another, and we compare the deformation equations with those for spherical drops. Finally, we show a definite experimental dielectric constant effect for cylindrical stream of aqueous polystyrene latex suspension. The dielectric constant varies with the frequency of the imposed electric field, and the associated EHD flow change is very apparent.

  16. Role of dielectric constant in electrohydrodynamics of conducting fluids

    NASA Astrophysics Data System (ADS)

    Rhodes, Percy H.; Snyder, Robert S.; Roberts, Glyn O.

    Electrohydrodynamic (EHD) flows are driven by the interaction of an electric field with variations in electric conductivity or dielectric constant. In reported EHD experiments on the deformation of drops of immiscible dielectric fluids, the role of conductivity has tended to overshadow the role of dielectric constant. Often, large conductivity contrasts were convenient because the conductivities of the dielectric fluid were relatively uncertain. As a result, the observed effects were always qualitatively the same as if there had been no contrast in dielectric constant. Our early experiments studying the EHC deformations of cylindrical streams readily showed the conductivity effect but the dielectric constant effect was not discernible. We have modified our flow chamber and improved our method of observation and can now see an unequivocal dielectric constant effect which is in agreement with the prior theory. In this paper we first give a brief description of the physics of charge buildup at the interface of an immersed spherical drop or flowing cylindrical sample stream and then show how these charge distributions lead to interface distortions and accompanying viscous flows which constitute EHD. We next review theory and experiment describing the deformation of spherical drops. We show that in the reported drop deformation experiments, the contrast in dielectric constant was never sufficient to reverse the deformation due to the conductivity contrast. We review our work describing the deformation of a cylindrical stream of one fluid flowing in a parallel flow of another, and we compare the deformation equations with those for spherical drops. Finally, we show a definite experimental dielectric constant effect for cylindrical stream of aqueous polystyrene latex suspension. The dielectric constant varies with the frequency of the imposed electric field, and the associated EHD flow change is very apparent.

  17. Aluminum nanoparticle/acrylate copolymer nanocomposites for dielectric elastomers with high dielectric constants

    NASA Astrophysics Data System (ADS)

    Hu, Wei; Zhang, Suki N.; Niu, Xiaofan; Liu, Chao; Pei, Qibing

    2014-03-01

    Dielectric elastomers are useful for large-strain actuation and energy harvesting. Their application has been limited by their low dielectric constants and consequently high driving voltage. Various fillers with high dielectric constants have been incorporated into different elastomer systems to improve the actuation strain, force output and energy density of the compliant actuators and generators. However, agglomeration may happen in these nanocomposites, resulting in a decrease of dielectric strength, an increase of leakage current, and in many instances the degree of enhancement of the dielectric constant. In this work, we investigated aluminum nanoparticles as nanofillers for acrylate copolymers. This metallic nanoparticle was chosen because the availability of free electrons could potentially provide an infinite value of dielectric constant as opposed to dielectric materials including ferroelectric nanocrystals. Moreover, aluminum nanoparticles have a self-passivated oxide shell effectively preventing the formation of conductive path. The surfaces of the aluminum nanoparticles were functionalized with methacrylate groups to assist the uniform dispersion in organic solutions and additionally enable copolymerization with acrylate copolymer matrix during bulk polymerization, and thus to suppress large range drifting of the nanoparticles. The resulting Al nanoparticle-acrylate copolymer nanocomposites were found to exhibit higher dielectric constant and increased stiffness. The leakage current under high electric fields were significantly lower than nanocomposites synthesized without proper nanoparticle surface modification. The dielectric strengths of the composites were comparable with the pristine polymers. In dielectric actuation evaluation, the actuation force output and energy specific work density were enhanced in the nanocomposites compared to the pristine copolymer.

  18. Dielectric constant well logging with current and voltage electrodes

    SciTech Connect

    Hoyer, W.A.; Kern, J.W.; Spann, M.M.

    1982-11-30

    This invention provides for methods and systems for measuring the dielectric constant of an earth formation. In a preferred embodiment, an alternating current is passed through a portion of the formation and a reference resistor in series with the portion. The capacitance and the dielectric constant of the portion may be determined from the phase difference between the voltage across the reference resistor and the voltage across the portion. This phase difference may be obtained by generating a voltage which is in phase with the voltage across the reference resistor, but which has the magnitude of the voltage across the portion. To obtain the phase difference by an alternate digital method, the voltage across the referenced resistor and the voltage across the portion are each transformed into a square wave signal. The two square wave signals are then compared to obtain the sign and the magnitude of the phase difference between the two square waves. In an alternate preferred embodiment, an alternating current is passed through the portion of the earth formation and through a capacitor and a resistor connected in series with the portion. The first dc signal is generated by filtering out the high frequency components from the product of the voltages across the capacitor and across the portion. A second dc signal is generated by filtering out the high frequency components from the product of the voltages across the referenced resistor and across the portion. The phase difference between the voltage across the portion and the current through the portion may be determined, from which the capacitance and the dielectric constant of the portion may then be calculated.

  19. An Improved Dielectric Constant Cell for Use in Student and Research Laboratories.

    ERIC Educational Resources Information Center

    Thompson, H. Bradford.; Walmsley, Judith A.

    1979-01-01

    Describes the latest stage in the design of an economical dielectric constant cell, tested in both instructional and research applications, that is suitable for student laboratories and for precision research measurements. (BT)

  20. Three dielectric constants and orientation order parameters in nematic mesophases

    NASA Astrophysics Data System (ADS)

    Yoon, Hyung Guen; Jeong, Seung Yeon; Kumar, Satyendra; Park, Min Sang; Park, Jung Ok; Srinivasarao, M.; Shin, Sung Tae

    2011-03-01

    Temperature dependence of the three components ɛ1 , ɛ2 , and ɛ3 of dielectric constant and orientation order parameters in the nematic phase of mesogens with rod, banana, and zero-order dendritic shape were measured using the in-plane and vertical switching geometries, and micro-Raman technique. Results on the well-known uniaxial (Nu) nematogens, E7 and 5CB, revealed two components ɛ1 = ~ɛ| | and ɛ2 = ~ɛ3 = ~ɛ⊥ , as expected. The three dielectric constants were different for two azo substituted (A131 and A103) and an oxadiazole based (ODBP-Ph-C12) bent core mesogens, and a Ge core tetrapode. In some cases, two of the components became the same indicating a loss of biaxiality at temperatures coinciding with the previously reported Nu to biaxial nematic transition. This interpretation is substantiated by micro-Raman measurements of the uniaxial and biaxial nematic order parameters. Supported by the US Department of Energy, Basic Energy Sciences grant ER46572 and by Samsung Electronics Corporation.

  1. Stability of aspartame in water: organic solvent mixtures with different dielectric constants.

    PubMed

    Sanyude, S; Locock, R A; Pagliaro, L A

    1991-07-01

    In order to examine the influence of solvent composition on the stability of aspartame (N-alpha-L-aspartyl-L-phenylalanine-1-methyl ester) in solution (5 mg/mL), the degradation of aspartame was carried out in water:methanol, water:ethanol, and water:glycerine mixtures with dielectric constant values of 45, 55, and 65, respectively. The rate of disappearance of aspartame was measured by a sensitive HPLC assay. The degradation rate of aspartame increased as the dielectric constant of the solvent mixture decreased in all three solvents systems. For example, at 60 degrees C, the degradation rate constants were 4.1, 5.9, and 8.4 x 10(-3) h-1 at dielectric constant of 65, 55, and 45, respectively. From these results, it can be concluded that the stability of aspartame in aqueous solutions cannot be enhanced by the replacement of water by solvents of lower dielectric constant. PMID:1941567

  2. Advanced concepts for transformers pressboard dielectric constant and mechanical strength

    SciTech Connect

    Not Available

    1982-03-01

    Of the numerous electrical considerations in a material, the value of the dielectric constant serves as an important criterion in designing proper insulation systems. The goal of this project was to find ways to reduce the dielectric constant of solid (fibrous) insulating materials. A literature search was made on cellulosic and synthetic fibers and also additives which offered the potential for dielectric constant reduction of the solid insulation. Sample board structures, were produced in the laboratory and tested for electrical, mechanical and chemical characteristics. Electrical tests determined the suitability of the material at transformer test and operating conditions. The mechanical tests established the physical characteristics of the modified board structures. Chemical tests checked the conductivity of the aqueous extract, acidity, and ash content. Further, compatibility with transformer oil and some aging tests were performed. An actual computer transformer design was made based on one of the modified board structures and the reduction in core steel and transformer losses were shown.

  3. Measuring sap flow, and other plant physiological conditions across a soil salinity gradient in the lower Colorado River at Cibola National Wildlife Refuge: Vegetation and soil physiology linkages with microwave dielectric constant

    NASA Astrophysics Data System (ADS)

    McDonald, K. C.; Lasne, Y.; Schroeder, R.; Morino, K.; Hultine, K. R.; Nagler, P. L.

    2009-12-01

    We used ground measurements to examine stand structure and evapotranspiration of Tamarix in the Cibola National Wildlife Refuge (CNWR) on the Lower Colorado River. Three Tamarix study sites were established at different distances from the Colorado River on a river terrace in the CNWR. The sites were chosen from aerial photographs to represent typical dense stands of Tamarix within the CNWR. The sites were representative of differing saline environments, with each having ground water with distinct salt concentration levels. Wells were established at the site to establish depth to water and the salinity concentration within the ground water. We monitored xylem sap flow within each of the three stands. In addition we measured leaf area index to characterize canopy structure. We compared ET, foliage density, depth to water, and salinity among the Tamarix sites to examine stand-level variability driven by the variations in salinity. We supplemented these collections with measurements to characterize soil and vegetation microwave dielectric properties and their relationship to physiologic parameters. The dielectric properties of a material describe the interaction of an electric field with the material. Previous field experiments have demonstrated that varying degrees of correlation exist between vegetation dielectric properties and tree canopy water status. Temporal variation of the dielectric constant of woody plant tissue may result from changes in water status (e.g., water content) and chemical composition, albeit to varying degrees of sensitivity. The varying amount of ground water salinity at CNWR offers a unique opportunity to examine the relationship between vegetation and soil dielectric constant as related to vegetation ecophysiology. A field portable vector network analyzer is used to measure the microwave dielectric spectrum of the soil and vegetation Combined with measurements of vegetation xylem sap flux and soil chemistry, these measurements allow

  4. Microwave dielectric constants of silicon, gallium arsenide, and quartz

    SciTech Connect

    Seeger, K.

    1988-06-01

    For a determination of the dielectric constants epsilon of semiconductors, a microwave transmission interference method has been applied. For the first time, a calculation is presented which yields the full interference spectrum, not only the position of the extremal points. A comparison of the theoretical and experimental spectra results in a higher precision than previously obtained. A metal evaporation of the sample faces which are in contact with the waveguide walls turns out to be very important. Relative dielectric constants of 11.6 for silicon, 12.8 for gallium arsenide, and 4.6 for crystalline quartz, all +- 0.05, have been obtained.

  5. Effect of vacuum-ultraviolet irradiation on the dielectric constant of low-k organosilicate dielectrics

    SciTech Connect

    Zheng, H.; Shohet, J. L.; Ryan, E. T.; Nishi, Y.

    2014-11-17

    Vacuum ultraviolet (VUV) irradiation is generated during plasma processing in semiconductor fabrications, while the effect of VUV irradiation on the dielectric constant (k value) of low-k materials is still an open question. To clarify this problem, VUV photons with a range of energies were exposed on low-k organosilicate dielectrics (SiCOH) samples at room temperature. Photon energies equal to or larger than 6.0 eV were found to decrease the k value of SiCOH films. VUV photons with lower energies do not have this effect. This shows the need for thermal heating in traditional ultraviolet (UV) curing since UV light sources do not have sufficient energy to change the dielectric constant of SiCOH and additional energy is required from thermal heating. In addition, 6.2 eV photon irradiation was found to be the most effective in decreasing the dielectric constant of low-k organosilicate films. Fourier Transform Infra-red Spectroscopy shows that these 6.2 eV VUV exposures removed organic porogens. This contributes to the decrease of the dielectric constant. This information provides the range of VUV photon energies that could decrease the dielectric constant of low-k materials most effectively.

  6. Graphene encapsulated rubber latex composites with high dielectric constant, low dielectric loss and low percolation threshold.

    PubMed

    Tian, Ming; Zhang, Jing; Zhang, Liqun; Liu, Suting; Zan, Xiaoqing; Nishi, Toshio; Ning, Nanying

    2014-09-15

    A dielectric composite with high dielectric constant, low dielectric loss and low percolation threshold was prepared by using the combined strategy of encapsulating of graphene oxide nanosheets (GONS) on carboxylated nitrile rubber (XNBR) latex particles and the in situ thermal reduction in GONS at a moderate temperature. The encapsulation of GONS on XNBR latex particles was mainly realized via the hydrogen bonding interactions between GONS and XNBR during latex mixing. A segregated graphene network was obtained at a low content of thermally reduced graphene (TRG), resulting in a low percolation threshold (0.25 vol.%). The dielectric constant at 100 Hz obviously increased from 23 for pure XNBR to 2211 and 5542 for the composite with 0.5 vol.% and 0.75 vol.% of TRG, respectively. The dielectric loss of the composites retained at a low value (less than 1.5). Meanwhile, the elastic modulus only slightly increased with the presence of 0.1-0.5 vol.% of TRG, keeping the good flexibility of the dielectric composites. This study provides a simple, low-cost and effective method to prepare high performance dielectric composites, facilitating the wide application of dielectric materials. PMID:24972295

  7. Dielectric constants of multiwall carbon nanotubes from direct current to microwave frequencies.

    PubMed

    Wang, Y C; Lue, J T; Pauw, K F

    2009-03-01

    A cylindrical rod constructed from a uniform mixture of multiwall carbon nanotubes and alumina powders dissolved in paraffin was inserted in the center of a radio frequency cavity. The real and imaginary dielectric constants of carbon tubes at various frequencies were measured, respectively, from the resonant frequencies and the quality factors, by a resistance-inductance-cacitance (RLC) meter and a microwave network analyzer. The dielectric rod benefits the protection of the sample from adsorbing moisture and preventing the rod from filling with air, thus making accurate measurments. A tunable probe specifically designed for the field pattern of a TM010 mode is delineated to improve the microwave coupling of the dielectric microwave resonator. This refined design is expected to facilitate the measurement yielding a significant manner. The real and imaginary parts of the dielectric constant of carbon nanotubes increase and decrease, respectively as frequencies increase satisfactorily in complying with the description from the free electron Drude model. PMID:19435033

  8. Thickness-dependent Dielectric Constant of Few-layer In2Se3 Nano-flakes

    NASA Astrophysics Data System (ADS)

    Wu, Di; Pak, Alexander; Liu, Yingnan; Wu, Xiaoyu; Ren, Yuan; Tsai, Yu-Hao; Lin, Min; Peng, Hailin; Hwang, Gyeong; Lai, Keji

    2015-03-01

    The dielectric constant or relative permittivity of active materials in electronic devices is a critical parameter for charging and screening effects. For layered two-dimensional (2D) materials, it is of great interest to understand how their dielectric constants depend on dimensionalities and the arrangement of crystal lattices. Here we present both experimental and theoretical investigations on the dielectric constant of few-layer In2Se3 nano-flakes grown on mica substrates by van der Waals epitaxy. A nondestructive microwave impedance microscope (MIM) is employed to simultaneously quantify the number of layers and local electrical and optical properties. The measured effective dielectric constant increases monotonically as a function of the thickness and saturates to the bulk value at around 6-8 quintuple layers. The same trend of layer-dependent dielectric constant is also revealed through a density functional theory approach. Our results of the dielectric response are expected to be significant for the applications of layered materials in nano-devices.

  9. Characterization of all the elastic, dielectric, and piezoelectric constants of uniaxially oriented poled PVDF films.

    PubMed

    Roh, Yongrae; Varadan, Vasundara V; Varadan, Vijay K

    2002-06-01

    Polyvinylidene fluoride (PVDF), a piezoelectric material, has many useful applications, for example, as sensors, transducers, and surface acoustic wave (SAW) devices. Models of performance of these devices would be useful engineering tools. However, the benefit of the model is only as accurate as the material properties used in the model. The purpose of this investigation is to measure the elastic, dielectric and piezoelectric properties over a frequency range, including the imaginary part (loss) of these properties. Measurements are difficult because poled material is available as thin films, and not all quantities can be measured in that form. All components of the elastic stiffness, dielectric tensor, and electromechanical coupling tensor are needed in the models. The material studied here is uniaxially oriented poled PVDF that has orthorhombic mm2 symmetry. Presented are the frequency dependence of all nine complex elastic constants, three complex dielectric constants, and five complex piezoelectric constants. The PVDF was produced at Raytheon Research Division, Lexington, MA. Measurements were made on thin films and on stacked, cubical samples. The elastic constants c44D and C55D, the dielectric constants epsilon11T and epsilon22T, as well as the piezoelectric constants g15 and g24 reported here have not been published before. The values were determined by ultrasonic measurements using an impedance analyzer and a least square data-fitting technique. PMID:12075977

  10. Novel Low Temperature Co-Fired Ceramic Material System Composed of Dielectrics with Different Dielectric Constants

    NASA Astrophysics Data System (ADS)

    Sakamoto, Sadaaki; Adachi, Hiroshige; Kaneko, Kazuhiro; Sugimoto, Yasutaka; Takada, Takahiro

    2013-09-01

    We found that the co-firing low temperature co-fired ceramic (LTCC) materials of different dielectric constants (ɛr) with Cu wiring is achievable using a novel, original design. It was confirmed that the dielectric characteristics of the dielectrics designed in this study are very suitable for the use of the dielectrics in electronic components such as filters mounted in high-speed radio communication equipment. The dielectric constants of the lower- and higher-dielectric-coefficient materials were 8.1 and 44.5, respectively, which are sufficiently effective for downsizing LTCC components. Observing the co-fired interface, it was confirmed that excellent co-firing conditions resulted in no mechanical defects such as delamination or cracks. On the basis of the results of wavelength dispersive X-ray spectrometry (WDX) and X-ray diffractometry (XRD), it was confirmed that co-firing with minimal interdiffusion was realized using the same glass for both dielectrics. It is concluded that the materials developed are good for co-firing in terms of the mechanical defects and interdiffusion that appear in them.

  11. Investigation of W-band dielectric constant of coals by free space method

    NASA Astrophysics Data System (ADS)

    Jia, Cheng-yan; Fan, Wei; Hu, Wei; Yang, Chuan-fa; Liu, Ling-yu; Chang, Tian-ying; Cui, Hong-liang

    2015-11-01

    The dielectric constant of Shandong anthracite coals of China was studied in the frequency range of 75~110 GHz (W-band), using the free space method for the first time. The measurement system is based on the Vector Network Analyzer of Agilent Technology and a VDI extension module with frequency range from 75 GHz to 110GHz. The dielectric constants of coals were calculated from the scattering parameters by implementing an algorithm. Correctness of the test results is verified by measuring the dielectric constant of air and timber. The dielectric constant of each selected coal with different moisture contents is investigated. It is found that both the real and imaginary parts of selected coals exhibit an apparent increasing trend with increasing water content of coals. The real part of coals with different water content varies from 2.61 to 4.97, and the imaginary part from 0.06 to 0.41 at the frequency of 110 GHz. We also obtained the diversification of the dielectric constant by increasing the frequency at the W-band. The real part of coals with different frequency varies from 3.85 to 3.91, and the imaginary part from 0.32 to 0.37 at W-band.

  12. Low Dielectric Constant Materials from Hollow Fibers and Plant Oil

    NASA Astrophysics Data System (ADS)

    Hong, Chang K.; Wool, Richard P.

    2003-03-01

    A new low dielectric constant (k) material suited to electronic materials applications was developed using hollow keratin fibers (HF) and chemically modified soyoil. High-speed microelectronics are facilitated by preventing the ``rubber necking", or slow-down of electrons on the printed wires through the use of low-k dielectrics. The unusual low k-value of the HF composite material derives both from the air (k = 1) in the hollow microcrystalline keratin fibers (k = 1.6), and the triglyceride molecules (k = 2.3), and is in the range of 1.7 to 2.7 at 100 MHz, depending on the HF fraction. These values are lower than that of the conventional silicon dioxide, (k = 3.8 to 4.2) or epoxy dielectric insulators. Also, the HF dielectric is lightweight (SG < 1) and rigid (Modulus > 2 GPa), with fracture toughness (1.0 MPa m^1/2) (and approximates the shape and feel of a silicon dioxide insulator. Multi-Chip-Module circuit printing results suggest that the low-cost composite made with HF (from avian sources) and plant oil (from soybean) has the potential to replace the dielectric in microchips and circuit boards in the ever-growing electronic materials field, in addition to many applications as a new lightweight composite material. Supported by EPA and DoE

  13. High strength, low dielectric constant fluorinated silica xerogel films

    NASA Astrophysics Data System (ADS)

    Gorman, B. P.; Orozco-Teran, Rosa A.; Roepsch, Jodi A.; Dong, Hanjiang; Reidy, Richard F.; Mueller, D. W.

    2001-12-01

    The mechanical, electrical, and microstructural properties of low-k fluorinated silica xerogels produced using a one step spin-on process are reported. Derived from a fluorinated silane monomer, these films are easily processed and exhibit very low dielectric constants (2.1 as processed and 2.3 after heat treating at 450 °C in air). Structural determination by Fourier transform infrared spectrophotometry indicates a fluorinated silica structure with shortened Si-O bonds; however, some of the fluorine is lost during annealing. Nanoindentation studies show high elastic moduli (12 GPa) and hardness (1 GPa). Microstructural analyses by transmission and scanning electron microscopy indicate an unusual morphology with highly linked features and pore sizes in the 20-30 nm range. We believe the low dielectric constants and robust mechanical properties are due to the unusual microstructure of these films.

  14. Electronic transport in two-dimensional high dielectric constant nanosystems.

    PubMed

    Ortuño, M; Somoza, A M; Vinokur, V M; Baturina, T I

    2015-01-01

    There has been remarkable recent progress in engineering high-dielectric constant two dimensional (2D) materials, which are being actively pursued for applications in nanoelectronics in capacitor and memory devices, energy storage, and high-frequency modulation in communication devices. Yet many of the unique properties of these systems are poorly understood and remain unexplored. Here we report a numerical study of hopping conductivity of the lateral network of capacitors, which models two-dimensional insulators, and demonstrate that 2D long-range Coulomb interactions lead to peculiar size effects. We find that the characteristic energy governing electronic transport scales logarithmically with either system size or electrostatic screening length depending on which one is shorter. Our results are relevant well beyond their immediate context, explaining, for example, recent experimental observations of logarithmic size dependence of electric conductivity of thin superconducting films in the critical vicinity of superconductor-insulator transition where a giant dielectric constant develops. Our findings mark a radical departure from the orthodox view of conductivity in 2D systems as a local characteristic of materials and establish its macroscopic global character as a generic property of high-dielectric constant 2D nanomaterials. PMID:25860804

  15. Electronic transport in two-dimensional high dielectric constant nanosystems

    DOE PAGESBeta

    Ortuño, M.; Somoza, A. M.; Vinokur, V. M.; Baturina, T. I.

    2015-04-10

    There has been remarkable recent progress in engineering high-dielectric constant two dimensional (2D) materials, which are being actively pursued for applications in nanoelectronics in capacitor and memory devices, energy storage, and high-frequency modulation in communication devices. Yet many of the unique properties of these systems are poorly understood and remain unexplored. Here we report a numerical study of hopping conductivity of the lateral network of capacitors, which models two-dimensional insulators, and demonstrate that 2D long-range Coulomb interactions lead to peculiar size effects. We find that the characteristic energy governing electronic transport scales logarithmically with either system size or electrostatic screeningmore » length depending on which one is shorter. Our results are relevant well beyond their immediate context, explaining, for example, recent experimental observations of logarithmic size dependence of electric conductivity of thin superconducting films in the critical vicinity of superconductor-insulator transition where a giant dielectric constant develops. Our findings mark a radical departure from the orthodox view of conductivity in 2D systems as a local characteristic of materials and establish its macroscopic global character as a generic property of high-dielectric constant 2D nanomaterials.« less

  16. Electronic transport in two-dimensional high dielectric constant nanosystems

    SciTech Connect

    Ortuño, M.; Somoza, A. M.; Vinokur, V. M.; Baturina, T. I.

    2015-04-10

    There has been remarkable recent progress in engineering high-dielectric constant two dimensional (2D) materials, which are being actively pursued for applications in nanoelectronics in capacitor and memory devices, energy storage, and high-frequency modulation in communication devices. Yet many of the unique properties of these systems are poorly understood and remain unexplored. Here we report a numerical study of hopping conductivity of the lateral network of capacitors, which models two-dimensional insulators, and demonstrate that 2D long-range Coulomb interactions lead to peculiar size effects. We find that the characteristic energy governing electronic transport scales logarithmically with either system size or electrostatic screening length depending on which one is shorter. Our results are relevant well beyond their immediate context, explaining, for example, recent experimental observations of logarithmic size dependence of electric conductivity of thin superconducting films in the critical vicinity of superconductor-insulator transition where a giant dielectric constant develops. Our findings mark a radical departure from the orthodox view of conductivity in 2D systems as a local characteristic of materials and establish its macroscopic global character as a generic property of high-dielectric constant 2D nanomaterials.

  17. Chemical and mineral composition of dust and its effect on the dielectric constant

    SciTech Connect

    Sharif, S.

    1995-03-01

    Chemical analysis is carried out for dust sample collected from central Sudan and the dust chemical constituents are obtained. The mineral composition of dust are identified by the X-ray diffraction techniques. The mineral quantities are obtained by a technique developed based on the chemical analytical methods. Analyses show that Quartz is the dominant mineral while the SiO{sub 2} is the dominant oxide. A simple model is derived for the dust chemical constituents. This model is used with models for predicting the mixture dielectric constant to estimate the dust dielectric constant; the results of which are seen to be in a good agreement with the measured values. The effects of the different constituents on the dust dielectric constant are studied and results are given.

  18. Preparation of dielectric coating of variable dielectric constant by plasma polymerization

    NASA Technical Reports Server (NTRS)

    Hudis, M.; Wydeven, T. (Inventor)

    1979-01-01

    A plasma polymerization process for the deposition of a dielectric polymer coating on a substrate comprising disposing of the substrate in a closed reactor between two temperature controlled electrodes connected to a power supply is presented. A vacuum is maintained within the closed reactor, causing a monomer gas or gas mixture of a monomer and diluent to flow into the reactor, generating a plasma between the electrodes. The vacuum varies and controls the dielectric constant of the polymer coating being deposited by regulating the gas total and partial pressure, the electric field strength and frequency, and the current density.

  19. Light induced dielectric constant of Alumina doped lead silicate glass based on silica sands

    NASA Astrophysics Data System (ADS)

    Diantoro, Markus; Natalia, Desi Ayu; Mufti, Nandang; Hidayat, Arif

    2016-04-01

    Numerous studies on glass ceramic compounds have been conducted intensively. Two major problems to be solved are to simplify the fabrication process by reducing melting temperature as well as improving various properties for various fields of technological application. To control the dielectric constant, the researchers generally use a specific dopant. So far there is no comprehensive study to control the dielectric constant driven by both of dopant and light intensity. In this study it is used Al2O3 dopant to increase the light induced dielectric constant of the glass. The source of silica was taken from local silica sands of Bancar Tuban. The sands were firstly leached using hydrochloric acid to improve the purity of silica which was investigated by means of XRF. Fabricating the glass samples were performed by using melting-glass method. Silica powder was mixed with various ratio of SiO2:Na2CO3:PbO:Al2O3. Subsequently, a mixture of various Al2O3 doped lead silicate glasses were melted at 970°C and directy continued by annealed at 300°C. The samples were investigated by XRD, FTIR, SEM-EDX and measuring dielectric constant was done using dc-capacitance meter with various light intensities. The investigation result of XRD patterns showed that the crystal structures of the samples are amorphous state. The introduction of Al2O3 does not alter the crystal structure, but significantly change the structure of the functional glass bonding PbO-SiO2 which was shown by the FTIR spectra. It was noted that some new peak peaks were exist in the doped samples. Measuring result of dielectricity shows that the dielectric constant of glass increases with the addition of Al2O3. Increasing the light intensity gives rise to increase their dielectric constant in general. A detail observation of the dielectric seen that there are discontinuous step-like of dielectric. Most likely a specific quantization mechanism occurs when glass exposed under light.

  20. ac conductivity and dielectric constant of conductor-insulator composites

    NASA Astrophysics Data System (ADS)

    Murtanto, Tan Benny; Natori, Satoshi; Nakamura, Jun; Natori, Akiko

    2006-09-01

    We study the complex admittance (ac conductivity and dielectric constant) of conductor-insulator composite material, based on a two-dimensional square network consisting of randomly placed conductors and capacitors. We derived some exact analytical relations between the complex admittances of high and low frequencies and of complementary conductor concentrations. We calculate the complex admittance by applying a transfer-matrix method to a square network and study the dependence on both the frequency and the conductor concentration. The numerical results are compared with an effective-medium theory, and the range of applicability and limitation of the effective-medium theory are clarified.

  1. Thickness-Dependent Dielectric Constant of Few-Layer In₂Se₃ Nanoflakes.

    PubMed

    Wu, Di; Pak, Alexander J; Liu, Yingnan; Zhou, Yu; Wu, Xiaoyu; Zhu, Yihan; Lin, Min; Han, Yu; Ren, Yuan; Peng, Hailin; Tsai, Yu-Hao; Hwang, Gyeong S; Lai, Keji

    2015-12-01

    The dielectric constant or relative permittivity (ε(r)) of a dielectric material, which describes how the net electric field in the medium is reduced with respect to the external field, is a parameter of critical importance for charging and screening in electronic devices. Such a fundamental material property is intimately related to not only the polarizability of individual atoms but also the specific atomic arrangement in the crystal lattice. In this Letter, we present both experimental and theoretical investigations on the dielectric constant of few-layer In2Se3 nanoflakes grown on mica substrates by van der Waals epitaxy. A nondestructive microwave impedance microscope is employed to simultaneously quantify the number of layers and local electrical properties. The measured ε(r) increases monotonically as a function of the thickness and saturates to the bulk value at around 6-8 quintuple layers. The same trend of layer-dependent dielectric constant is also revealed by first-principles calculations. Our results of the dielectric response, being ubiquitously applicable to layered 2D semiconductors, are expected to be significant for this vibrant research field. PMID:26575786

  2. Development of new polymers with ultra-low dielectric constant using gaseous CO2

    NASA Astrophysics Data System (ADS)

    Keshtov, Mukhamed; Said-Galiev, Ernest; Khokhlov, Alexei

    2012-07-01

    Fluorphenylsubstituted Polyphenylenes with low dielectric constant have been synthesized and following exposition of their films in gaseous CO2 and then fast heating at the temperature of 250-280°C give rise to high dielectric properties with dielectric constant of 1.58.

  3. Characterization of the Dielectric Constant in the Trichoderma reesei Cel7B Active Site.

    PubMed

    Song, Xiangfei; Wang, Yefei; Zhang, Shujun; Yan, Shihai; Li, Tong; Yao, Lishan

    2015-07-27

    An attempt is made to evaluate the dielectric constant of the Trichoderma reesei Cel7B active site. Through kinetic measurements, the pKa value of the catalytic acid E201 is determined. Mutations (away from E201) with net charge changes are introduced to perturb the E201 pKa. It is shown that the mutation with a +1 charge change (including G225R, G230R, and A335R) decreases the pKa of E201, whereas the mutation with a -1 charge change (including Q149E, A222D, G225D, and G230D) increases the pKa. This effect is consistent with the electrostatic interaction between the changed charge and the E201 side chain. The fitting of the experimental data yields an apparent dielectric constant of 25-80. Molecular dynamics simulations with explicit water molecules indicate that the high solvent accessibility of the active site contributes largely to the high dielectric constant. ONIOM calculations show that high dielectric constant benefits the catalysis through decreasing the energy of the transition state relative to that of the enzyme substrate complex. PMID:26114648

  4. An Explanation of the Photoinduced Giant Dielectric Constant of Lead Halide Perovskite Solar Cells.

    PubMed

    Almond, Darryl P; Bowen, Chris R

    2015-05-01

    A photoinduced giant dielectric constant of ~10(6) has been found in impedance spectroscopy measurements of lead halide perovskite solar cells. We report similar effects in measurements of a porous lead zirconate titanate (PZT) sample saturated with water. The principal effect of the illumination of the solar cell and of the introduction of water into the pore volume of the PZT sample is a significant increase in conductivity and dielectric loss. This is shown to exhibit low frequency power law dispersion. Application of the Kramers-Kronig relationships show the large measured values of permittivity to be related to the power law changes in conductivity and dielectric loss. The power law dispersions in the electrical responses are consistent with an electrical network model of microstructure. It is concluded that the high apparent values of permittivity are features of the microstructural networks and not fundamental effects in the two perovskite materials. PMID:26263342

  5. Nanocomposites of TiO2/cyanoethylated cellulose with ultra high dielectric constants

    NASA Astrophysics Data System (ADS)

    Madusanka, Nadeesh; Shivareddy, Sai G.; Hiralal, Pritesh; Eddleston, Mark D.; Choi, Youngjin; Oliver, Rachel A.; Amaratunga, Gehan A. J.

    2016-05-01

    A novel dielectric nanocomposite containing a high permittivity polymer, cyanoethylated cellulose (CRS) and TiO2 nanoparticles was successfully prepared with different weight percentages (10%, 20% and 30%) of TiO2. The intermolecular interactions and morphology within the polymer nanocomposites were analysed. TiO2/CRS nanofilms on SiO2/Si wafers were used to form metal–insulator–metal type capacitors. Capacitances and loss factors in the frequency range of 1 kHz–1 MHz were measured. At 1 kHz CRS-TiO2 nanocomposites exhibited ultra high dielectric constants of 118, 176 and 207 for nanocomposites with 10%, 20% and 30% weight of TiO2 respectively, significantly higher than reported values of pure CRS (21), TiO2 (41) and other dielectric polymer-TiO2 nanocomposite films. Furthermore, all three CRS-TiO2 nanocomposites show a loss factor <0.3 at 1 kHz and low leakage current densities (10‑6–10‑7 A cm‑2). Leakage was studied using conductive atomic force microscopy and it was observed that the leakage is associated with TiO2 nanoparticles embedded in the CRS polymer matrix. A new class of ultra high dielectric constant hybrids using nanoscale inorganic dielectrics dispersed in a high permittivity polymer suitable for energy management applications is reported.

  6. Nanocomposites of TiO₂/cyanoethylated cellulose with ultra high dielectric constants.

    PubMed

    Madusanka, Nadeesh; Shivareddy, Sai G; Hiralal, Pritesh; Eddleston, Mark D; Choi, Youngjin; Oliver, Rachel A; Amaratunga, Gehan A J

    2016-05-13

    A novel dielectric nanocomposite containing a high permittivity polymer, cyanoethylated cellulose (CRS) and TiO2 nanoparticles was successfully prepared with different weight percentages (10%, 20% and 30%) of TiO2. The intermolecular interactions and morphology within the polymer nanocomposites were analysed. TiO2/CRS nanofilms on SiO2/Si wafers were used to form metal-insulator-metal type capacitors. Capacitances and loss factors in the frequency range of 1 kHz-1 MHz were measured. At 1 kHz CRS-TiO2 nanocomposites exhibited ultra high dielectric constants of 118, 176 and 207 for nanocomposites with 10%, 20% and 30% weight of TiO2 respectively, significantly higher than reported values of pure CRS (21), TiO2 (41) and other dielectric polymer-TiO2 nanocomposite films. Furthermore, all three CRS-TiO2 nanocomposites show a loss factor <0.3 at 1 kHz and low leakage current densities (10(-6)-10(-7) A cm(-2)). Leakage was studied using conductive atomic force microscopy and it was observed that the leakage is associated with TiO2 nanoparticles embedded in the CRS polymer matrix. A new class of ultra high dielectric constant hybrids using nanoscale inorganic dielectrics dispersed in a high permittivity polymer suitable for energy management applications is reported. PMID:27040504

  7. How does static stretching decrease the dielectric constant of VHB 4910 elastomer?

    NASA Astrophysics Data System (ADS)

    Vu-Cong, T.; Nguyen-Thi, N.; Jean-Mistral, C.; Sylvestre, A.

    2014-03-01

    Subject to a voltage, dielectric elastomers deform by the effect of Maxwell stress which is depended directly on the dielectric constant of the material. The combination of large strain, soft elastic response and good dielectric properties has established VHB 4910 elastomer as the most used material for dielectric elastomer actuators. However, the effect of stretch on the dielectric constant for this elastomer is much debated topic while controversy results are demonstrated in the literature. The dielectric constant of this material is studied and demonstrated that it decreases slightly or hugely among the stretch but any pertinent response and any physic explications are validated by the scientific community. In this paper, we presented a detail study about dielectric behavior of VHB 4910 elastomer versus a broadband of stretch and temperature. We found that the dielectric constant of this material depends strongly on the stretch following a polynomial law. Among all the explanations of stretch dependence of the dielectric constant of VHB 4910 in the literature: the crystallization, the change of glass transition temperature, the decrease of dipole orientation, the electrostriction effect under stress; and based on our experimental result, we conclude that the decrease of dipole orientation seems the main reason to the drop of dielectric constant of VHB 4910 elastomer versus the stretch. We proposed also an accurate model describing the dielectric constant of this material for a large range of stretch and temperature.

  8. Complex dielectric constants for selected near-millimeter-wave materials at 245 GHz

    NASA Technical Reports Server (NTRS)

    Dutta, J. M.; Jones, C. R.; Dave, H.

    1986-01-01

    A double-beam instrument developed in this laboratory has been used to measure the complex dielectric constant of selected materials at 245 GHz. It is reported here the results for crystalline quartz, fused silica (Spectrosil WF and Dynasil 4000), beryllia (iso-pressed), boron nitride (hot-pressed), and a nickel ferrite (Trans-Tech 2-111). Results are compared with the data obtained by other researchers.

  9. Sub-THz complex dielectric constants of smectite clay thin samples with Na+/Ca++ ions

    NASA Astrophysics Data System (ADS)

    Rahman, Rezwanur; McCarty, Douglas K.; Prasad, Manika

    2015-09-01

    We implement a technique to characterize the electromagnetic properties at frequencies 100 to 165 GHz (3 cm-1 to 4.95 cm-1) of oriented smectite samples using an open cavity resonator connected to a submillimeter wave VNA (Vector Network Analyzer). We measured dielectric constants perpendicular to the bedding plane on oriented Na+ ion and Ca++ ion stabilized smectite samples deposited on a glass slide at ambient laboratory conditions (room temperature and room light). The clay layer is much thinner (˜30 μm) than the glass substrate (˜2.18 mm). The real part of dielectric constant, ɛre, is essentially constant over this frequency range but is larger in Na+ ion than in Ca++ ion infused clay. The total electrical conductivity (associated with the imaginary part of dielectric constant, ɛim) of both samples increases monotonically at lower frequencies (<110 GHz) but shows rapid increase for Na+ ions in the regime > 110 GHz. The dispersion of the samples display a dependence on the ionic strength in the clay interlayers, i.e., ζ potential in the Stern layers.

  10. Structure and performance of dielectric films based on self-assembled nanocrystals with a high dielectric constant

    SciTech Connect

    Huang, LM; Liu, SY; Van Tassell, BJ; Liu, XH; Byro, A; Zhang, HN; Leland, ES; Akins, DL; Steingart, DA; Li, J; O'Brien, S

    2013-09-24

    Self-assembled films built from nanoparticles with a high dielectric constant are attractive as a foundation for new dielectric media with increased efficiency and range of operation, due to the ability to exploit nanofabrication techniques and emergent electrical properties originating from the nanoscale. However, because the building block is a discrete one-dimensional unit, it becomes a challenge to capture potential enhancements in dielectric performance in two or three dimensions, frequently due to surface effects or the presence of discontinuities. This is a recurring theme in nanoparticle film technology when applied to the realm of thin film semiconductor and device electronics. We present the use of chemically synthesized. (Ba; Sr)TiO3 nanocrystals, and a novel deposition-polymerization technique, as a means to fabricate the dielectric layer. The effective dielectric constant of the film is tunable according to nanoparticle size, and effective film dielectric constants of up to 34 are enabled. Wide area and multilayer dielectrics of up to 8 cm(2) and 190 nF are reported, for which the building block is an 8 nm nanocrystal. We describe models for assessing dielectric performance, and distinct methods for improving the dielectric constant of a nanocrystal thin film. The approach relies on evaporatively driven assembly of perovskite nanocrystals with uniform size distributions in a tunable 7-30 nm size range, coupled with the use of low molecular weight monomer/polymer precursor chemistry that can infiltrate the porous nanocrystal thin film network post assembly. The intercrystal void space (low k dielectric volume fraction) is minimized, while simultaneously promoting intercrystal connectivity and maximizing volume fraction of the high k dielectric component. Furfuryl alcohol, which has good affinity to the surface of. (Ba; Sr ) TiO3 nanocrystals and miscibility with a range of solvents, is demonstrated

  11. Structure of low dielectric constant to extreme low dielectric constant SiCOH films: Fourier transform infrared spectroscopy characterization

    NASA Astrophysics Data System (ADS)

    Grill, Alfred; Neumayer, Deborah A.

    2003-11-01

    Carbon doped oxide dielectrics comprised of Si, C, O, and H (SiCOH) have been prepared by plasma enhanced chemical vapor deposition (PECVD) from mixtures of tetramethylcyclotetrasiloxane (TMCTS) and an organic precursor. The films have been analyzed by determining their elemental composition and by Fourier transform infrared spectroscopy with deconvolution of the absorption peaks. The analysis has shown that PECVD of TMCTS produces a highly crosslinked networked SiCOH film. Dissociation of TMCTS appears to dominate the deposition chemistry as evidenced by the multitude of bonding environments and formation of linear chains and branches. Extensive crosslinking of TMCTS rings occurs through Si-Si, Si-CH2-Si, Si-O-Si, and Si-CH2-O-Si moieties. The films deposited from mixtures of TMCTS and organic precursor incorporate hydrocarbon fragments into the films. This incorporation occurs most probably through the reaction of the organic precursor and the Si-H bonds of TMCTS. Annealing the SiCOH films deposited from TMCTS and organic precursor results in a large loss of carbon and hydrogen from the films resulting from the fragmentation and loss of the incorporated organic component. The deconvolution of the Si-O-Si asymmetric stretching band of the annealed films shows the existence of a larger fraction of a cage structure and a correspondingly smaller fraction of a networked (highly crosslinked) structure in the SiCOH films deposited from mixtures of TMCTS with organic precursor relative to the films deposited from TMCTS only. The evolution of the volatile hydrocarbon fragments during annealing results in the formation of nanopores and subsequent reduction of the dielectric constants of the films to extreme low-k values.

  12. Dielectric constant of fluids and fluid mixtures at criticality.

    PubMed

    Losada-Pérez, Patricia; Pérez-Sánchez, Germán; Cerdeiriña, Claudio A; Thoen, Jan

    2010-04-01

    The behavior of the dielectric constant epsilon of pure fluids and binary mixtures near liquid-gas and liquid-liquid critical points is studied within the concept of complete scaling of asymmetric fluid-fluid criticality. While mixing of the electric field into the scaling fields plays a role, pressure mixing is crucial as the asymptotic behavior of the coexistence-curve diameter in the epsilon-T plane is concerned. Specifically, it is found that the diameters, characterized by a |T-Tc|1-alpha singularity in the previous scaling formulation [J. V. Sengers, D. Bedeaux, P. Mazur, and S. C. Greer, Physica A 104, 573 (1980)], gain a more dominant |T-Tc|2beta term, whose existence is shown to be supported by literature experimental data. The widely known |T-Tc|1-alpha singularity of epsilon along the critical isopleth in the one-phase region is found to provide information on the effect of electric fields on the liquid-liquid critical temperature: from experimental data it is inferred that Tc usually decreases as the magnitude of the electric field is enhanced. Furthermore, the behavior of mixtures along an isothermal path of approach to criticality is also analyzed: theory explains why the observed anomalies are remarkably higher than those associated to the usual isobaric path. PMID:20481691

  13. High Apparent Dielectric Constant Inside a Protein Reflects Structural Reorganization Coupled to the Ionization of an Internal Asp

    PubMed Central

    Karp, Daniel A.; Gittis, Apostolos G.; Stahley, Mary R.; Fitch, Carolyn A.; Stites, Wesley E.; García-Moreno E., Bertrand

    2007-01-01

    The dielectric properties of proteins are poorly understood and difficult to describe quantitatively. This limits the accuracy of methods for structure-based calculation of electrostatic energies and pKa values. The pKa values of many internal groups report apparent protein dielectric constants of 10 or higher. These values are substantially higher than the dielectric constants of 2–4 measured experimentally with dry proteins. The structural origins of these high apparent dielectric constants are not well understood. Here we report on structural and equilibrium thermodynamic studies of the effects of pH on the V66D variant of staphylococcal nuclease. In a crystal structure of this protein the neutral side chain of Asp-66 is buried in the hydrophobic core of the protein and hydrated by internal water molecules. Asp-66 titrates with a pKa value near 9. A decrease in the far UV-CD signal was observed, concomitant with ionization of this aspartic acid, and consistent with the loss of 1.5 turns of α-helix. These data suggest that the protein dielectric constant needed to reproduce the pKa value of Asp-66 with continuum electrostatics calculations is high because the dielectric constant has to capture, implicitly, the energetic consequences of the structural reorganization that are not treated explicitly in continuum calculations with static structures. PMID:17172297

  14. The High Dielectric Constant of Staphylococcal Nuclease is Encoded in its Structural Architecture

    PubMed Central

    Goh, Garrett B.; Bertrand, García-Moreno E.; Brooks, Charles L.

    2011-01-01

    The pKa values of Lys-66, Glu-66 and Asp-66 buried in the interior of the staphylococcal nuclease Δ+PHS variant were reported to be shifted by as much as 5 pKa units from their normal values. Reproducing the pKa of these buried ionizable residues using continuum electrostatic calculations required the use of a high protein dielectric constant of 10 or higher. The apparent high dielectric constant has been rationalized as a consequence of a local structural reorganization or increased fluctuations in the microenvironment of the mutation site We have calculated the dielectric constant of Δ+PHS and the Lys-66, Asp-66 and Glu-66 mutants from first principles using the Kirkwood-Fröhlich equation, and discovered that staphylococcal nuclease has a naturally high dielectric constant ranging from 20 to 30. This high dielectric constant does not change significantly with the mutation of residue 66 or with the ionization of the mutated residues. Calculation of the spatial dependence of the dielectric constant for the microenvironment of residue-66 produces a value of about 10, which matches well with the apparent dielectric constant needed to reproduce pKa values from continuum electrostatic calculations. Our results suggest an alternative explanation that the high dielectric constant of staphylococcal nuclease is a property resulting from the intrinsic backbone fluctuations originating from its structural architecture. PMID:22085022

  15. Dielectric property measurement of zirconia fibers at high temperature

    SciTech Connect

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

    1995-12-31

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

  16. Use of the finite-element method for a dielectric-constant gas-thermometry experiment

    NASA Astrophysics Data System (ADS)

    Zandt, T.; Gaiser, C.; Fellmuth, B.; Haft, N.; Thiele-Krivoi, B.; Kuhn, A.

    2013-09-01

    The finite-element method is a well-established computational methodology for the numerical treatment of partial differential equations. It is primarily used for solving problems in applied engineering and science. In previous publications, we have shown that the method is suitable to solve problems in temperature metrology, for instance to predict temperature profiles and thermal equilibration processes in complex measurement setups. In this paper, the method is used for a primary thermometry experiment, namely dielectric-constant gas thermometry. Within the framework of an international project directed to the new definition of the base unit kelvin, measurements were performed at the triple point of water in order to determine the Boltzmann constant k. The finite-element method was used for the data evaluation in different ways: calculation of the effective compressibility of the measuring capacitor by describing the deformation of its electrodes under the influence of the pressure of the gas, the dielectric constant of which has to be determined; calculation of resonance frequencies for the determination of the elastic constants of the electrode material by resonant ultrasound spectroscopy; electrostatic simulations for calculating capacitance values; estimation of uncertainty components, which allowed to draw conclusions concerning the future reduction of uncertainty components.

  17. Large change in dielectric constant of CaCu3Ti4O12 under violet laser

    NASA Astrophysics Data System (ADS)

    Masingboon, C.; Thongbai, P.; King, P. D. C.; Maensiri, S.; Meevasana, W.

    2013-03-01

    This work reports the influence of light illumination on the dielectric constant of CaCu3Ti4O12 (CCTO) polycrystals which exhibit giant dielectric constant. When the CCTO samples were exposed to 405-nm laser light, the enhancement in capacitance as high as 22% was observed for the first time, suggesting application of light-sensitive capacitance devices. To understand this change better microscopically, we also performed electronic-structure measurements using photoemission spectroscopy, and measured the electrical conductivity of the CCTO samples under different conditions of light exposure and oxygen partial pressure. All these measurements suggest that this large change is driven by oxygen vacancy induced by the irradiation.

  18. Computing the Kirkwood g-Factor by Combining Constant Maxwell Electric Field and Electric Displacement Simulations: Application to the Dielectric Constant of Liquid Water.

    PubMed

    Zhang, Chao; Hutter, Jürg; Sprik, Michiel

    2016-07-21

    In his classic 1939 paper, Kirkwood linked the macroscopic dielectric constant of polar liquids to the local orientational order as measured by the g-factor (later named after him) and suggested that the corresponding dielectric constant at short-range is effectively equal to the macroscopic value just after "a distance of molecular magnitude" [ Kirkwood, J. Chem. Phys., 1939, 7, 911 ]. Here, we show a simple approach to extract the short-ranged Kirkwood g-factor from molecular dynamics (MD) simulation by superposing the outcomes of constant electric field E and constant electric displacement D simulations [ Zhang and Sprik, Phys. Rev. B: Condens. Matter Mater. Phys., 2016, 93, 144201 ]. Rather than from the notoriously slow fluctuations of the dipole moment of the full MD cell, the dielectric constant can now be estimated from dipole fluctuations at short-range, accelerating the convergence. Exploiting this feature, we computed the bulk dielectric constant of liquid water modeled in the generalized gradient approximation (PBE) to density functional theory and found it to be at least 40% larger than the experimental value. PMID:27352038

  19. High apparent dielectric constants in the interior of a protein reflect water penetration.

    PubMed Central

    Dwyer, J J; Gittis, A G; Karp, D A; Lattman, E E; Spencer, D S; Stites, W E; García-Moreno E, B

    2000-01-01

    A glutamic acid was buried in the hydrophobic core of staphylococcal nuclease by replacement of Val-66. Its pK(a) was measured with equilibrium thermodynamic methods. It was 4.3 units higher than the pK(a) of Glu in water. This increase was comparable to the DeltapK(a) of 4.9 units measured previously for a lysine buried at the same location. According to the Born formalism these DeltapK(a) are energetically equivalent to the transfer of a charged group from water to a medium of dielectric constant of 12. In contrast, the static dielectric constants of dry protein powders range from 2 to 4. In the crystallographic structure of the V66E mutant, a chain of water molecules was seen that hydrates the buried Glu-66 and links it with bulk solvent. The buried water molecules have never previously been detected in >20 structures of nuclease. The structure and the measured energetics constitute compelling and unprecedented experimental evidence that solvent penetration can contribute significantly to the high apparent polarizability inside proteins. To improve structure-based calculations of electrostatic effects with continuum methods, it will be necessary to learn to account quantitatively for the contributions by solvent penetration to dielectric effects in the protein interior. PMID:10969021

  20. Low-temperature 1 /f noise in microwave dielectric constant of amorphous dielectrics in Josephson qubits

    NASA Astrophysics Data System (ADS)

    Burin, Alexander L.; Matityahu, Shlomi; Schechter, Moshe

    2015-11-01

    The analytical solution for the low-temperature 1 /f noise in the microwave dielectric constant of amorphous films at frequency ν0˜5 GHz due to tunneling two-level systems (TLSs) is derived within the standard tunneling model including the weak dipolar or elastic TLS-TLS interactions. The 1 /f frequency dependence is caused by TLS spectral diffusion characterized by the width growing logarithmically with time. Temperature and field dependencies are predicted for the noise spectral density in typical glasses with universal TLSs. The satisfactory interpretation of the recent experiment by J. Burnett et al. [Nat. Commun. 5, 4119 (2014), 10.1038/ncomms5119] in Pt-capped Nb superconducting resonators is attained by assuming a smaller density of TLSs compared to ordinary glasses, which is consistent with the very high internal quality factor in those samples.

  1. Dielectric measurements of selected ceramics at microwave frequencies

    NASA Technical Reports Server (NTRS)

    Dahiya, J. N.; Templeton, C. K.

    1994-01-01

    Dielectric measurements of strontium titanate and lead titanate zirconate ceramics are conducted at microwave frequencies using a cylindrical resonant cavity in the TE(sub 011) mode. The perturbations of the electric field are recorded in terms of the frequency shift and Q-changes of the cavity signal. Slater's perturbation equations are used to calculate e' and e" of the dielectric constant as a function of temperature and frequency.

  2. A dielectric resonator method of measuring dielectric properties of low loss materials in the microwave region

    NASA Astrophysics Data System (ADS)

    Sheen, Jyh

    2008-05-01

    A technique for the measurement of dielectric properties of low loss and homogeneously isotropic media in the microwave region is studied. The measuring structure is a resonator made up of a cylindrical dielectric rod and conducting plates. The dielectric constants and loss tangents are computed from the resonant frequencies, structure dimensions and unloaded Qs of the TE01δ mode. A simple field model is introduced to analyze this resonator structure. Unlike other simple models, this model does not have the defect of low measurement accuracy of dielectric properties. Important factors affecting the dielectric properties measurements are introduced. Error sources for measurements are also discussed. The measurement accuracy is justified by comparing the results with those of other techniques. In addition, various methods for calculating the power factor and conducting loss and for measuring the conductivity of the conducting plates are discussed. The accuracies of certain of these methods have not previously been studied, but are given in this paper. The swept frequency capability was also studied. It was found that dielectric properties in microwave frequencies could be measured within a frequency range of 3 GHz.

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

    PubMed

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

    2016-02-24

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

  4. Dielectric constant enhancement of epoxy thermosets via formation of polyelectrolyte nanophases.

    PubMed

    Cong, Houluo; Li, Jingang; Li, Lei; Zheng, Sixun

    2014-12-18

    Poly(ethylene oxide)-block-poly(sodium p-styrenesulfonate) (PEO-b-PSSNa) diblock copolymer was synthesized and then incorporated into epoxy to obtain the nanostructured epoxy thermosets containing polyelectrolyte nanophases. This PEO-b-PSSNa diblock copolymer was synthesized via the radical polymerization of p-styrenesulfonate mediated with 4-cyano-4-(thiobenzoylthio)valeric ester-terminated poly(ethylene oxide). The formation of polyelectrolyte (i.e., PSSNa) nanophases in epoxy followed a self-assembly mechanism. The precursors of epoxy acted as the selective solvent of the diblock copolymer, and thus, the self-assembled nanostructures were formed. The self-organized nanophases were fixed through the subsequent curing reaction. By means of transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS), the morphologies of the nanostructured epoxy thermosets containing PSSNa nanophases were investigated. In the glassy state, the epoxy matrixes were significantly reinforced by the spherical PSSNa nanodomains, as evidenced by dynamic mechanical analysis. The measurement of dielectric properties showed that, with the incorporation of PSSNa nanophases, the dielectric constants of the epoxy thermoset were significantly increased. Compared to the control epoxy, the dielectric loss of the nanostructured thermosets still remained at quite a low level, although the values of dielectric loss were slightly increased with inclusion of PSSNa nanophases. PMID:25482332

  5. Critical behaviors of the conductivity and dielectric constant of Ti3SiC2/Al2O3 hybrids

    NASA Astrophysics Data System (ADS)

    Wu, Rui-Fen; Pan, Wei; Shi, Sui-Lin; Han, Ruo-Bing

    2007-09-01

    Ti3SiC2/Al2O3 hybrids were prepared by a spark plasma sintering process. The effective dc conductivity of the hybrids was measured at room temperature, which agrees with the percolation theory and follows the power law around the percolation threshold. The ac conductivity and dielectric constants of the hybrids were also characterized and follow the power law when the concentration of the conductive phase is close to the percolation threshold; meanwhile, the dielectric constant could increase over three orders of magnitude compared with Al2O3.

  6. Structure and performance of dielectric films based on self-assembled nanocrystals with a high dielectric constant

    NASA Astrophysics Data System (ADS)

    Huang, Limin; Liu, Shuangyi; Van Tassell, Barry J.; Liu, Xiaohua; Byro, Andrew; Zhang, Henan; Leland, Eli S.; Akins, Daniel L.; Steingart, Daniel A.; Li, Jackie; O'Brien, Stephen

    2013-10-01

    Self-assembled films built from nanoparticles with a high dielectric constant are attractive as a foundation for new dielectric media with increased efficiency and range of operation, due to the ability to exploit nanofabrication techniques and emergent electrical properties originating from the nanoscale. However, because the building block is a discrete one-dimensional unit, it becomes a challenge to capture potential enhancements in dielectric performance in two or three dimensions, frequently due to surface effects or the presence of discontinuities. This is a recurring theme in nanoparticle film technology when applied to the realm of thin film semiconductor and device electronics. We present the use of chemically synthesized (Ba,Sr)TiO3 nanocrystals, and a novel deposition-polymerization technique, as a means to fabricate the dielectric layer. The effective dielectric constant of the film is tunable according to nanoparticle size, and effective film dielectric constants of up to 34 are enabled. Wide area and multilayer dielectrics of up to 8 cm2 and 190 nF are reported, for which the building block is an 8 nm nanocrystal. We describe models for assessing dielectric performance, and distinct methods for improving the dielectric constant of a nanocrystal thin film. The approach relies on evaporatively driven assembly of perovskite nanocrystals with uniform size distributions in a tunable 7-30 nm size range, coupled with the use of low molecular weight monomer/polymer precursor chemistry that can infiltrate the porous nanocrystal thin film network post assembly. The intercrystal void space (low k dielectric volume fraction) is minimized, while simultaneously promoting intercrystal connectivity and maximizing volume fraction of the high k dielectric component. Furfuryl alcohol, which has good affinity to the surface of (Ba,Sr)TiO3 nanocrystals and miscibility with a range of solvents, is demonstrated to be ideal for the production of nanocomposites. The

  7. Thickness and electric-field-dependent polarizability and dielectric constant in phosphorene

    NASA Astrophysics Data System (ADS)

    Kumar, Piyush; Bhadoria, B. S.; Kumar, Sanjay; Bhowmick, Somnath; Chauhan, Yogesh Singh; Agarwal, Amit

    2016-05-01

    Based on extensive first-principles calculations, we explore the thickness-dependent effective dielectric constant and slab polarizability of few-layer black phosphorene. We find that the dielectric constant in ultrathin phosphorene is thickness-dependent and it can be further tuned by applying an out-of-plane electric field. The decreasing dielectric constant with reducing number of layers of phosphorene is a direct consequence of the lower permittivity of the outer layers and the increasing surface-to-volume ratio. We also show that the slab polarizability depends linearly on the number of layers, implying a nearly constant polarizability per phosphorus atom. Our calculation of the thickness- and electric-field-dependent dielectric properties will be useful for designing and interpreting transport experiments in gated phosphorene devices, wherever electrostatic effects such as capacitance and charge screening are important.

  8. The effect of diamic acid additives on the dielectric constant of polyimides

    NASA Technical Reports Server (NTRS)

    Stoakley, Diane M.; St. Clair, Anne K.

    1988-01-01

    The effect of six selected diamic acids additives (including 2,2-prime bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride-aniline (An); 4,4-prime-oxydiphthalic anhydride-An, 3,3-prime diaminodiphenyl sulfone-phthalic anhydride (PA); 4,4-prime-oxydianiline-PA; 2,2-bis 4(4-aminophenoxy)phenyl hexafluoropropane-PA; and 2,2-bis 4(3-aminophenoxy)phenyl hexafluoropropane-PA) on the dielectric constants of low-dielectric-constant polyimide resins was evaluated. It was found that the effect of the incorporation of the diamic acids on reducing the dielectric constant of polyimides may be limited as the dielectric constant of the base resin itself becomes very low. The additives were found to lower the resin's values of glass transition temperature, with no effect on thermooxidative stability.

  9. High dielectric constant nickel-doped titanium oxide films prepared by liquid-phase deposition

    NASA Astrophysics Data System (ADS)

    Lee, Ming-Kwei; Yen, Chih-Feng; Fan, Cho-Han

    2014-09-01

    The electrical characteristics of nickel-doped titanium oxide films prepared by liquid-phase deposition on p-type (100) silicon substrate were investigated. The aqueous solutions of ammonium hexafluorotitanate and boric acid were used as precursors for the growth of titanium oxide films and the dielectric constant is 29. The dielectric constant can be improved to 94 by nickel doping at the thermal annealing at 700 °C in nitrous oxide.

  10. Development of low dielectric constant alumina-based ceramics for microelectronic substrates

    SciTech Connect

    Wu, S. J.

    1993-05-01

    The performance of high speed computers depends not only on IC chips, but also on the signal propagation speed between these chips. The signal propagation delay in a computer is determined by the dielectric constant of the substrate material to which the IC chips are attached. In this study, a ceramic substrate with a low dielectric constant (k {approx} 5.0) has been developed. When compared with the traditional alumina substrate (k {approx} 10.0), the new material corresponds to a 37% decrease in the signal propagation delay. Glass hollow spheres are used to introduce porosity (k = 1.0) to the alumina matrix in a controlled manner. A surface coating technique via heterogeneous nucleation in aqueous solution has been used to improve the high temperature stability of these spheres. After sintering at 1,400 C, isolated spherical pores are uniformly distributed in the almost fully dense alumina matrix; negligible amounts of matrix defects can be seen. All pores are isolated from each other. Detailed analyses of the chemical composition find that the sintered sample consists of {alpha}-alumina, mullite and residual glass. Mullite is the chemical reaction product of alumina and the glass spheres. Residual glass exists because current firing conditions do not complete the mullitization reaction. The dielectric constant of the sintered sample is measured and then compared with the predicted value using Maxwell`s model. Mechanical strength is evaluated by a four-point bending test. Although the flexural strength decreases exponentially with porosity, samples with 34% porosity (k {approx} 5.0) still maintain adequate mechanical strength for the proper operation of a microelectronic substrate.

  11. Thermally driven sign switch of static dielectric constant of VO2 thin film

    NASA Astrophysics Data System (ADS)

    Kana Kana, J. B.; Vignaud, G.; Gibaud, A.; Maaza, M.

    2016-04-01

    Smart multifunctional materials exhibiting phase transition and tunable optical and/electrical properties provide a new direction towards engineering switchable devices. Specifically, the reversible, tunable and sign switch dielectric constants via external temperature stimuli observed in vanadium dioxide (VO2) make it a candidate of choice for tunable and switchable technologies devices. Here we report new aspect of the metal-insulator transition (MIT) through the sign switch of the static dielectric constant εS of pure VO2. As it is shown, the static dielectric constant showed an abrupt change from positive at T < 70 °C to negative at T > 70 °C. εS > 0 confirms the insulating phase where charges are localized while εS < 0 confirms the metallic phase of VO2 where charges are delocalized. We report for the first time the tunability of the dielectric constant from a negative sign for the static dielectric constant of VO2 thin film rarely found in real physical systems. We also demonstrate the tunability and switchability of the real and imaginary part of the dielectric constant (ε) via external temperature stimuli. More specifically, the real (ε) and Imaginary (ε) showed an abrupt thermal hysteresis which clearly confirms the phase transition.

  12. Low dielectric constant a-SiOC:H films as copper diffusion barrier

    NASA Astrophysics Data System (ADS)

    Koh, Yee Wee; Loh, Kian Ping; Rong, Liu; Wee, A. T. S.; Huang, Liu; Sudijono, J.

    2003-01-01

    A low-k dielectric barrier based on silicon oxycarbide for copper damascene processes has been developed in this work. The optimal process conditions that allow the deposition of silicon oxycarbide films with a dielectric constant of 3.74 and copper diffusion depth of 290 Å after thermal stress at 400 °C for 3 h has been identified. Copper diffusion depth is defined as the copper and dielectric interfacial region with three-order magnitude reduction in copper concentration. A multilayered structure consisting of black diamond/SiOC/Cu/TaN/Si is fabricated. 3-methyl silane and oxygen in varying concentration is used for the deposition of SiOC using plasma enhanced chemical vapor deposition. The composition of the films is studied by Fourier transform infrared spectroscopy. Dielectric constant and dielectric breakdown of the films are also evaluated. Secondary ion mass spectrometry is employed to investigate the copper diffusion property of the films. The electronic component of the dielectric constant has been found to be most significant in affecting the overall dielectric constant in SiOC films.

  13. An investigation of the relationship between tree water potential and dielectric constant

    NASA Technical Reports Server (NTRS)

    Mcdonald, Kyle C.; Zimmermann, Reiner; Way, Jobea; Oren, Ram

    1992-01-01

    An experiment that has been performed to verify the relationship between the dielectric constant of several tree species and their respective water potentials is described. The water potential, xylem flow and dielectric properties of five tree species were continuously monitored while simultaneously manipulating canopy transpiration and water status. An analysis of the data recorded during these manipulations is presented. Results of this analysis demonstrate a clear coincidence of change in dielectric constant and water status. The implication of this relationship for the utilization of remotely sensed data to study canopy water relations is explored. Preliminary backscatter modeling results demonstrate that the changes in dielectric constant that occur as a result of changes in water status are significant enough to be observable with microwave radar.

  14. Evaluation of the dielectric constant for RF shimming at high field MRI

    NASA Astrophysics Data System (ADS)

    Jayatilake, Mohan; Storrs, Judd; Chu, Wen-Jang; Lee, Jing-Huei

    2010-10-01

    Optimal image quality for Magnetic Resonance Imaging (MRI) at high fields requires a homogeneous RF (B1) field; however, the dielectric properties of the human brain result in B1 field inhomogeneities and signal loss at the periphery of the head. These result from constructive and destructive RF interactions of complex wave behaviour, which become worse with increasing magnetic field strength. Placement of a shim object with high-dielectric constant adjacent to the body has been proposed as a method for reducing B1 inhomogeneity by altering wave propagation within the volume of interest. Selecting the appropriate permittivity and quantity of material for the shim is essential. Whereas previous work has determined the dielectric properties of the shim empirically, this work introduces an improved theoretical framework for determining the requisite dielectric constant of the passive shim material directly by increasing the axial or minimizing the radial propagation constant.

  15. Image brightening in samples of high dielectric constant

    NASA Astrophysics Data System (ADS)

    Tropp, James

    2004-03-01

    An analytic solution is given for the electromagnetic problem of a lossy dielectric cylinder of infinite length, irradiated by a circularly polarized radiofrequency (RF) magnetic field; the NMR-active components of the field inside the cylinder are projected out by transforming the RF Hamiltonian to the rotating frame and retaining only those terms independent of time; it is noted that the resulting cartesian field components are required to be real. The squared magnitude of the NMR-active fields are then used to calculate the gradient-recalled images of the cylinder, for small tip angles of the magnetization; and the result is shown to predict almost quantitatively the intensity patterns of experimental proton images at 3.0 and 4.0 T, in a cylindrical phantom of radius 9.25 cm, filled with 0.05 M aqueous NaCl. In particular, the artifactual brightening at the center of the recorded image is convincingly reproduced in a simulation, whose underlying model excludes wave propagation along the direction of the cylinder axis. Formation of the artifact is explained in terms of the focussing of the RF magnetic field at the center of the cylinder, as illustrated by contour plots showing the time evolution of the rotating flux. An extended electromagnetic model—having the dielectric cylinder enclosed in a long, shielded volume resonator (e.g., of bird cage type)—is then sketched. The mathematical details appear in Appendix A; and the simulated images are shown to be virtually indistinguishable from those of the simpler original model. The theory of the Q, or quality factor, of the dielectric cylinder—considered itself as a resonant object—is developed for the enclosed cylinder model, where flux containment by the shield permits an unambiguous treatment of both the stored energy and the radiative losses. This is extended to treat the Q of a lossy dielectric sphere without shielding. Further plots of flux contours are given for the sphere, excited at 208 MHz with a

  16. Image brightening in samples of high dielectric constant.

    PubMed

    Tropp, James

    2004-03-01

    An analytic solution is given for the electromagnetic problem of a lossy dielectric cylinder of infinite length, irradiated by a circularly polarized radiofrequency (RF) magnetic field; the NMR-active components of the field inside the cylinder are projected out by transforming the RF Hamiltonian to the rotating frame and retaining only those terms independent of time; it is noted that the resulting cartesian field components are required to be real. The squared magnitude of the NMR-active fields are then used to calculate the gradient-recalled images of the cylinder, for small tip angles of the magnetization; and the result is shown to predict almost quantitatively the intensity patterns of experimental proton images at 3.0 and 4.0T, in a cylindrical phantom of radius 9.25cm, filled with 0.05M aqueous NaCl. In particular, the artifactual brightening at the center of the recorded image is convincingly reproduced in a simulation, whose underlying model excludes wave propagation along the direction of the cylinder axis. Formation of the artifact is explained in terms of the focussing of the RF magnetic field at the center of the cylinder, as illustrated by contour plots showing the time evolution of the rotating flux. An extended electromagnetic model--having the dielectric cylinder enclosed in a long, shielded volume resonator (e.g., of bird cage type)--is then sketched. The mathematical details appear in Appendix A; and the simulated images are shown to be virtually indistinguishable from those of the simpler original model. The theory of the Q, or quality factor, of the dielectric cylinder--considered itself as a resonant object--is developed for the enclosed cylinder model, where flux containment by the shield permits an unambiguous treatment of both the stored energy and the radiative losses. This is extended to treat the Q of a lossy dielectric sphere without shielding. Further plots of flux contours are given for the sphere, excited at 208 MHz with a uniform

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

    NASA Astrophysics Data System (ADS)

    Shrestha, Bijay Lal

    Some of the important applications of microwaves in the industrial, scientific and medical sectors include processing and treatment of various materials, and determining their physical properties. The dielectric properties of the materials of interest are paramount irrespective of the applications, hence, a wide range of materials covering food products, building materials, ores and fuels, and biological materials have been investigated for their dielectric properties. However, very few studies have been conducted towards the measurement of dielectric properties of green vegetations, including commercially important plant crops such as alfalfa. Because of its high nutritional value, there is a huge demand for this plant and its processed products in national and international markets, and an investigation into the possibility of applying microwaves to improve both the net yield and quality of the crop can be beneficial. Therefore, a dielectric measurement system based upon the probe reflection technique has been set up to measure dielectric properties of green plants over a frequency range from 300 MHz to 18 GHz, moisture contents from 12%, wet basis to 79%, wet basis, and temperatures from -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

  18. Solving constant-coefficient differential equations with dielectric metamaterials

    NASA Astrophysics Data System (ADS)

    Zhang, Weixuan; Qu, Che; Zhang, Xiangdong

    2016-07-01

    Recently, the concept of metamaterial analog computing has been proposed (Silva et al 2014 Science 343 160–3). Some mathematical operations such as spatial differentiation, integration, and convolution, have been performed by using designed metamaterial blocks. Motivated by this work, we propose a practical approach based on dielectric metamaterial to solve differential equations. The ordinary differential equation can be solved accurately by the correctly designed metamaterial system. The numerical simulations using well-established numerical routines have been performed to successfully verify all theoretical analyses.

  19. Microwave dielectric constant of liquid hydrocarbons: Application to the depth estimation of Titan's lakes

    NASA Astrophysics Data System (ADS)

    Paillou, Philippe; Mitchell, Karl; Wall, Stephen; Ruffié, Gilles; Wood, Charles; Lorenz, Ralph; Stofan, Ellen; Lunine, Jonathan; Lopes, Rosaly; Encrenaz, Pierre

    2008-03-01

    Cassini RADAR reveals the surface of Titan since flyby Ta acquired on October 2004. The RADAR instrument discovered volcanic structures, craters, dunes, channels, lakes and seas. In particular, flyby T16 realized in July 2006 imaged tens of radar-dark features close to Titan's north pole. They are interpreted as lakes filled with liquid hydrocarbons - mainly methane, a key material in the geologic and climatic history of Titan. In order to perform quantitative analysis and modeling of the radar response of Titan's lakes, the dielectric constant of liquid hydrocarbons is a crucial parameter, in particular to estimate the radar wave attenuation. We present here first measurements of the dielectric constant of LNG (Liquefied Natural Gas), mainly composed of methane, at Ku-band (10-13 GHz): we obtained a value $\\varepsilon$ = 1.75 - 0.002j. This value is used to model the radar backscattering of lakes observed during T16 flyby. Using a two-layer scattering model, we derive a relationship that is used to estimate a minimum depth for Titan's lakes. The proposed relationship is also coherent with the observation that the larger and then the deeper lakes are also the darker in radar images.

  20. Integration of high-dielectric constant Ta2O5 oxides on diamond for power devices

    NASA Astrophysics Data System (ADS)

    Cheng, Shaoheng; Sang, Liwen; Liao, Meiyong; Liu, Jiangwei; Imura, Masataka; Li, Hongdong; Koide, Yasuo

    2012-12-01

    The authors report on the direct integration of high-dielectric constant (high-k) Ta2O5 films on p-type single crystal diamond for high-power electronic devices. Crystallized hexagonal phase δ-Ta2O5 film is achieved on diamond by annealing the amorphous Ta2O5 film deposited by a sputter-deposition technique. The electrical properties of the Ta2O5 thin films are investigated by fabricating metal-insulator-semiconductor (MIS) diodes. The leakage current of the MIS diode is as low as 10-8 A/cm2 for the as-deposited amorphous Ta2O5 film and 10-2 A/cm2 for the crystallized film, which is 108 and 102 times lower than that of the Schottky diode at a forward bias of -3 V, respectively. The dielectric constant of the amorphous Ta2O5 films is measured to be 16 and increases to 29 after annealing at 800 °C. Different current leakage mechanisms and charge trapping behaviors are proposed for the amorphous and crystallized Ta2O5 thin films.

  1. Supercritical carbon dioxide extraction of porogens for the preparation of ultralow-dielectric-constant films

    SciTech Connect

    Toney, Michael F

    2003-06-20

    Supercritical carbon dioxide (SCCO2) extraction of a CO{sub 2}-soluble poly(propylene glycol) (PPG) porogen from poly(methylsilsesquioxane) (PMSSQ) cured to temperatures adequate to initiate matrix condensation, but still below the decomposition temperature of the porogen is demonstrated to produce nanoporous, ultralow dielectric constant thin films. Both closed and open cell porous structures were prepared simply by varying the porogen load in the organic/inorganic hybrid films. The porogen loads investigated in the present work ranged from 25-55 wt.%. Structural characterization of the samples conducted using transmission electron microscope (TEM), small angle X-ray scattering (SAXS) and Fourier transform infrared spectroscopy (FTIR) confirms the successful extraction of the porogen from the PMSSQ matrix at relatively low temperatures ({le} 200 C). The standard thermal decomposition process is performed at much higher temperatures (typically in the range of 400 C-450 C). The values of dielectric constants and refractive indices measured are in good agreement with the structural properties of these samples.

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

    PubMed

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

    2014-09-21

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

  3. A Conductivity and Dielectric Constant of Systems Near the Percolation Threshold.

    NASA Astrophysics Data System (ADS)

    Song, Yi.

    The ac conductivity and dielectric constant of macroscopically inhomogeneous systems near the percolation threshold vary as a power of the frequency, with (sigma) (PROPORTIONAL) (omega)('x), and (epsilon) (PROPORTIONAL) (omega)('-y). The two critical exponents x and y should satisfy a general scaling relation x + y = 1, if (sigma) and (epsilon) both obey scaling forms that have a single characteristic time scale. Two different percolation systems were studied experi- mentally in order to find the critical exponents x and y. The ac con- ductance and capacitance of these two systems were measured in the frequency range from 10 Hz to 13 MHz. The ac conductivity exponent x and ac dielectric constant exponent y from a three dimensional randomly mixed carbon-teflon system were found to be 0.86 (+OR-) 0.06 and 0.12 (+OR-) 0.04, respectively. The same critical exponents x and y were obtained on a planar chromium film system. Their values were x = 0.98 (+OR-) 0.09 and y = 0.08 (+OR-) 0.04. In order to complete the study, the dc conductivity exponent t and dc dielectric constant exponent s of these systems were also measured. They were in good agreement with well-established values. Two important mechanisms are responsible for the power law dependence of the ac conductivity and dielectric constant of systems near the percolation threshold. They are the interaction between percolation clusters and the fractal nature of these clus- ters. Two independent models based on these two mechanisms separately, namely the intercluster polarization (IP) model and the anomalous diffusion (AD) model, both predict power law behavior for (sigma) and (epsilon). The IP model predicts x (DBLTURN) 0.72 and y (DBLTURN) 0.28 for three dimensional (3D) systems and x = y = 0.5 for two dimensional (2D) systems; while the AD model predicts x (DBLTURN) 0.58 and y (DBLTURN) 0.42 for 3D systems and x (DBLTURN) 0.33 and y (DBLTURN) 0.67 for 2D systems. The experimental results of the ac conductivity

  4. Techniques for Measuring the Dielectric Properties of Agricultural Products

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  5. Increase of dielectric constant in PVDF by incorporating La1.8Sr0.2NiO4 into its matrix

    NASA Astrophysics Data System (ADS)

    Kumar, Rajnish; Goswami, Ashwin M.; Kar, Manoranjan

    2016-05-01

    To obtain the material with high dielectric constant and high dielectric strength for the technological applications, nanocomposite of Lanthanum Strontium Nickelete (La1.8Sr0.2NiO4) as nanofiller and polyvinylidene fluoride (PVDF) as polymer matrix has been prepared. The different nanofiler weight concentration varies from 2-8 weight percent. X-ray diffraction technique confirms the phase formation of nanocomposite. Differential scanning calorimeter (DSC) has been employed to study the percentage of crystallinity and Impedance measurement has been carried out to study the dielectric constant. DSC analysis shows decreasing trend of crystallinity whereas impedance analysis gives increasing dielectric constant with increasing La1.8Sr0.2NiO4 concentration in the nanocomposite. Also, these materials can be used as insulator in the transformer as the strength and dielectric behavior of present composite meets the technological requirements.

  6. Observation of giant dielectric constant in CdCu 3Ti 4O 12 ceramics

    NASA Astrophysics Data System (ADS)

    Zuo, Rongqing; Feng, Lixin; Yan, Yueyue; Chen, Bin; Cao, Guanghan

    2006-04-01

    Although CdCu 3Ti 4O 12 is isostructural to CaCu 3Ti 4O 12, the room temperature low-frequency dielectric constant of the former compound was reported to be ˜400, only 1/25 of that of the latter material [M.A. Subramanian, et al., J. Solid State Chem. 151 (2000) 323]. In this communication, we report that the dielectric constant of CdCu 3Ti 4O 12 can be remarkably increased by elevating the sintering temperature. The room temperature dielectric constant at 100 kHz achieves 9000, almost as much as that of CaCu 3Ti 4O 12, for the sample sintered at 1283 K. The appearance of giant dielectric constant in CdCu 3Ti 4O 12 is explained in terms of internal barrier layer capacitance (IBLC) effect with the subgrain boundary as the barrier. Our result supplies an approach in searching for new giant-dielectric-constant materials in the CaCu 3Ti 4O 12 family.

  7. Syndiotactic Polystyrene/Hybrid Silica Spheres of POSS Siloxane Composites Exhibiting Ultralow Dielectric Constant.

    PubMed

    Joseph, Angel Mary; Nagendra, Baku; Surendran, K P; Gowd, E Bhoje

    2015-09-01

    Homogeneously dispersed hybrid silica/syndiotactic polystyrene composites were investigated for low-κ dielectric applications. The composites were prepared by a solution blending method, and their microstructures were analyzed by SEM, TEM, and AFM. Crystallization and phase transformation behavior of sPS were investigated using differential scanning calorimetry and wide-angle X-ray diffraction. These composites exhibited improved thermal stability and reduced thermal expansion coefficients. Promising dielectric properties were observed for the composites in the microwave frequency region with a dielectric constant (κ = 1.95) and loss (tan δ = 10(-4)) at 5 GHz. PMID:26287385

  8. Introduction of effective dielectric constant to the Poisson-Nernst-Planck model

    NASA Astrophysics Data System (ADS)

    Sawada, Atsushi

    2016-05-01

    The Poisson-Nernst-Planck (PNP) model has been widely used for analyzing impedance or dielectric spectra observed for dilute electrolytic cells. In the analysis, the behavior of mobile ions in the cell under an external electric field has been explained by a conductive nature regardless of ionic concentrations. However, if the cell has parallel-plate blocking electrodes, the mobile ions may also play a role as a dielectric medium in the cell by the effect of space-charge polarization when the ionic concentration is sufficiently low. Thus the mobile ions confined between the blocking electrodes can have conductive and dielectric natures simultaneously, and their intensities are affected by the ionic concentration and the adsorption of solvent molecules on the electrodes. The balance of the conductive and dielectric natures is quantitatively determined by introducing an effective dielectric constant to the PNP model in the data analysis. The generalized PNP model with the effective dielectric constant successfully explains the anomalous frequency-dependent dielectric behaviors brought about by the mobile ions in dilute electrolytic cells, for which the conventional PNP model fails in interpretation.

  9. Elastomeric composites with high dielectric constant for use in Maxwell stress actuators

    NASA Astrophysics Data System (ADS)

    Szabo, Jeffrey P.; Hiltz, Johnathan A.; Cameron, Colin G.; Underhill, Royale S.; Massey, Jason; White, Brian; Leidner, Jacob

    2003-07-01

    Electroactive polymer actuators that utilize the Maxwell stress effect have generated considerable interest in recent years for use in applications such as artificial muscles, sensors, and parasitic energy capture. In order to maximize performance, the dielectric layer in Maxwell stress actuators should ideally have a high dielectric constant and high dielectric breakdown strength. In this study, the effect of high dielectric constant fillers on the electrical and mechanical properties of thin elastomeric films was examined. The fillers studied included the inorganic compounds titanium dioxide (TiO2), barium titanate (BaTiO3), and lead magnesium niobate-lead titanate (Pb(Mg1/3Nb2/3)O3-PbTiO). A high dielectric constant filler based on a polymeric conjugated ligand-metal complex, poly(copper phthalocyanine), was also synthesized and studied. Maxwell stress actuators fabricated with BaTiO3 dispersed in a silicone elastomer matrix were evaluated and compared with unfilled systems. A model was presented which relates filler volume fraction to actuation stress, strain, and elastic energy density at fields below dielectric breakdown. The model and experimental results suggest that for the case of strong filler particle-elastomer matrix interaction, actuation strain decreases with increasing filler content.

  10. Experimental study of the complex resistivity and dielectric constant of chrome-contaminated soil

    NASA Astrophysics Data System (ADS)

    Liu, Haorui; Yang, Heli; Yi, Fengyan

    2016-08-01

    Heavy metals such as arsenic and chromium often contaminate soils near industrialized areas. Soil samples, made with different water content and chromate pollutant concentrations, are often needed to test soil quality. Because complex resistivity and complex dielectric characteristics of these samples need to be measured, the relationship between these measurement results and chromium concentration as well as water content was studied. Based on soil sample observations, the amplitude of the sample complex resistivity decreased with an increase of contamination concentration and water content. The phase of complex resistivity takes on a tendency of initially decrease, and then increase with the increasing of contamination concentration and water content. For a soil sample with the same resistivity, the higher the amplitude of complex resistivity, the lower the water content and the higher the contamination concentration. The real and imaginary parts of the complex dielectric constant increase with an increase in contamination concentration and water content. Note that resistivity and complex resistivity methods are necessary to adequately evaluate pollution at various sites.

  11. Reduction of methylene green by EDTA: a relation between dielectric constant of medium and activated state.

    PubMed

    Qamar, Noshab; Azmat, Rafia; Naz, Raheela

    2013-01-01

    Kinetics of an alkaline reduction of the methylene green with ethylenediaminetetraaceticacid (EDTA) as a role of dielectric constant of the medium with anecdotal ionic strength in a diverse solvent system (aqueous mixtures of methanol) (10-30%) was studied by measuring the specific rate constant of the reaction spectrophotometrically at λ (max) = 660nm. An effort has been made to give an elucidation of vital role of dielectric constant of the medium captivating into reflection of single sphere and double sphere complex in reaction assortment. This investigation leads to disclose that single sphere complex of the dye and reductant was found to be the most suitable complex existed in a varied organic solvent. The deviation of the theoretical values from experimental results for single sphere and double sphere complex model in the presence of an alkali and nitrate ions were justified through HPLC analysis. HPLC analysis recommended that a considerable amount of the dye degrades in the existence of nitrate ion and alkali and additional peaks which may be of by-product were obtained. This leads to confirm the non identical values of single sphere and double sphere model in the occurrence of nitrate and an alkali. Rate of deletion of color showed a linear liaison with respect to water content below 30% and temperature between 20-40(o)C whereas an increase in the concentration of organic solvent showed the inhibition of dye decoloration at given optimum condition. Therefore study was restricted up to 30% of methanol binary mixtures. A mechanism of reduction of dye has been proposed based on verdict. PMID:23261728

  12. Dielectric Constant of Titan's South Polar Region from Cassini Radio Science Bistatic Scattering Observations

    NASA Astrophysics Data System (ADS)

    Marouf, E.; Rappaport, N.; French, R.; Simpson, R.; Kliore, A.; McGhee, C.; Schinder, P.; Anabtawi, A.

    2008-12-01

    Four out of six Radio Science bistatic scattering (bistatic-radar) observations of Titan's surface completed during the Cassini nominal mission yielded detectable quasi-specular 3.6 cm-λ (X-band) surface echoes, making Titan the most distant solar system object for which bistatic echoes have been successfully detected. Right circularly polarized sinusoidal signal was transmitted by Cassini and both the right and left circularly polarized (RCP and LCP) surface reflected components were observed at the 70-m stations of NASA Deep Space Network. Cassini was maneuvered continuously to track the region of Titan's surface where mirror-like (quasi-specular) reflected signals may be observed. The experiments were designed for incidence angles θ close to the Brewster, or polarization, angle of likely surface compositions. Careful measurement of the system noise temperature allowed determination of the absolute power in each polarized echo component and hence their ratio. The polarization ratio, the known observation geometry, and Fresnel reflection theory were then used to determine the dielectric constant ɛ. Three near-equatorial (~ 5 to 15° S) observations on flyby T14 inbound and outbound and on flyby T34 inbound yielded weak but clearly detectable echoes. The echoes were intermittent along the ground track, indicating mostly rough terrain occasionally interrupted by patches of relatively flat areas. For the two observations on T14, polarization ratio measurements for two localized but widely separated surface regions (~ 15° S, ~ 14 and 140° W) conducted at angles θ ~ 56° and 64°, close to the Brewster angle for ices, imply ɛ ~ 1.6 for both regions, suggesting liquid hydrocarbons although alternative interpretations are possible (Marouf et al., 2006 Fall AGU, P11A- 07). In sharp contrast, a single high latitude (~81-86° S, ~ 45-155° W) observation on T27 inbound yielded much stronger surface echoes that lasted for almost the full duration of the experiment

  13. Direct correlation between free volume and dielectric constant in a fluorine-containing polyimide blend

    NASA Astrophysics Data System (ADS)

    Ramani, R.; Ramachandran, R.; Amarendra, G.; Alam, S.

    2015-06-01

    The dielectric constant of fluorinated polyimides and their blends is known to decrease with increase in free volume due to decrease in the number of polarizable groups per unit volume. Interestingly, we report here a polyimide which when blended with a fluoro- polymer showed a positive deviation of dielectric constant with free volume. In our experiment, we have used a blend of poly(ether imide) and poly(vinylidene fluorine-co-hexafluoropropylene) and the interaction between them was studied using FTIR, XRD, TGA and SEM. The blend was investigated by PALS, DB and DEA. Surprisingly, with the increase in the free volume content in this blend, the dielectric constant also increases. This change is attributed to additional space available for the polarizable groups to orient themselves to the applied electric field.

  14. Boron Nitride Nanotube Mat as a Low- k Dielectric Material with Relative Dielectric Constant Ranging from 1.0 to 1.1

    NASA Astrophysics Data System (ADS)

    Hong, Xinghua; Wang, Daojun; Chung, D. D. L.

    2016-01-01

    This paper reports that a boron nitride nanotube (BNNT) mat containing air and 1.4 vol.% BNNTs is a low- k dielectric material for microelectronic packaging, exhibiting relative dielectric constant of 1.0 to 1.1 (50 Hz to 2 MHz) and elastic modulus of 10 MPa. The mat is prepared by compacting BNNTs at 5.8 kPa. This paper also presents measurements of the dielectric properties of BNNTs (mostly multiwalled). The relative dielectric constant of the BNNT solid in the mat decreases with increasing frequency, with attractively low values ranging from 3.0 to 6.2; the alternating-current (AC) electrical conductivity increases with increasing frequency, with attractively low values ranging from 10-10 S/m to 10-6 S/m and an approximately linear relationship between log conductivity and log frequency. The specific contact capacitance of the interface between BNNTs and the electrical contact decreases with increasing frequency, with attractively high values ranging from 1.6 μF/m2 to 2.3 μF/m2. The AC electrical resistivity of the BNNT-contact interface decreases with increasing frequency, with high values ranging from 0.14 MΩ cm2 to 440 MΩ cm2.

  15. Effects of porous carbon additives and induced fluorine on low dielectric constant polyimide synthesized with an e-beam

    SciTech Connect

    Im, Ji Sun; Bae, Tae-Sung; Lee, Sung Kyu; Lee, Sei-Hyun; Jeong, Euigyung; Kang, Phil Hyun; Lee, Young-Seak

    2010-11-15

    We report the synthesis of a polyimide matrix with a low dielectric constant for application as an intercalation material between metal interconnections in electronic devices. Porous activated carbon was embedded in the polyimide to reduce the dielectric constant, and a thin film of the complex was obtained using the spin-coating and e-beam irradiation methods. The surface of the thin film was modified with fluorine functional groups to impart water resistance and reduce the dielectric constant further. The water resistance was significantly improved by the modification with hydrophobic fluorine groups. The dielectric constant was effectively decreased by porous activated carbon. The fluorine modification also resulted in a low dielectric constant on the polyimide surface by reducing the polar surface free energy. The dielectric constant of polyimide film decreased from 2.98 to 1.9 by effects of porous activated carbon additive and fluorine surface modification.

  16. Microwave dielectric measurements of erythrocyte suspensions.

    PubMed

    Bao, J Z; Davis, C C; Swicord, M L

    1994-06-01

    Complex dielectric constants of human erythrocyte suspensions over a frequency range from 45 MHz to 26.5 GHz and a temperature range from 5 to 40 degrees C have been determined with the open-ended coaxial probe technique using an automated vector network analyzer (HP 8510). The spectra show two separate major dispersions (beta and gamma) and a much smaller dispersion between them. The two major dispersions are analyzed with a dispersion equation containing two Cole-Cole functions by means of a complex nonlinear least squares technique. The parameters of the equation at different temperatures have been determined. The low frequency behavior of the spectra suggests that the dielectric constant of the cell membrane increases when the temperature is above 35 degrees C. The real part of the dielectric constant at approximately 3.4 GHz remains almost constant when the temperature changes. The dispersion shifts with temperature in the manner of a thermally activated process, and the thermal activation enthalpies for the beta- and gamma-dispersions are 9.87 +/- 0.42 kcal/mol and 4.80 +/- 0.06 kcal/mol, respectively. PMID:8075351

  17. Dielectric constants of liquid formamide, N-methylformamide and dimethylformamide via molecular Ornstein-Zernike theory

    NASA Astrophysics Data System (ADS)

    Richardi, Johannes; Krienke, Hartmut; Fries, Pascal H.

    1997-07-01

    Kirkwood factors, yielding dielectric constants, are calculated from pair correlation functions, which are numerical solutions of the hypernetted-chain approximation of molecular Ornstein-Zernike (MOZ) theory. The combined influence of the molecular polarizability and the hydrogen bond strength is investigated. Using a reasonable diameter for the hydrogen size in the amide group, the MOZ Kirkwood factors and dielectric constants are in good agreement with the experimental values. This is explained by the statistical correlations between the orientations of two near molecules. This is consistent with hydrogen bonds, forming networks in formamide and chains in N-methylformamide.

  18. PREFACE: Dielectrics 2009: Measurement Analysis and Applications

    NASA Astrophysics Data System (ADS)

    Vaughan, Alun; Williams, Graham

    2009-07-01

    The conference Dielectrics 2009: Measurements, Analysis and Applications represents a significant milestone in the evolution of dielectrics research in the UK. It is reasonable to state that the academic study of dielectrics has led to many fundamental advances and that dielectric materials underpin the modern world in devices ranging from field effect transistors, which operate at extremely high fields, albeit low voltages, to the high voltage plants that provide the energy that powers our economy. The origins of the Dielectrics Group of the Institute of Physics (IOP), which organized this conference, can be traced directly back to the early 1960s, when Professor Mansel Davies was conducting research into the dielectric relaxation behaviour of polar liquids and solids at The Edward Davies Chemical Laboratories of the University College of Wales, Aberystwyth. He was already well-known internationally for his studies of molecular structure and bonding of small molecules, using infra-red-spectroscopy, and of the physical properties of hydrogen-bonded liquids and solids, using thermodynamic methods. Dielectric spectroscopy was a fairly new area for him and he realized that opportunities for scientists in the UK to gather together and discuss their research in this developing area of physical chemistry/chemical physics were very limited. He conceived the idea of forming a Dielectrics Discussion Group (DDG), which would act as a meeting point and provide a platform for dielectrics research in the UK and beyond and, as a result, a two-day Meeting was convened in the spring of 1968 at Gregynog Hall of the University of Wales, near Newtown, Montgomeryshire. It was organized by Mansel Davies, Alun Price and Graham Williams, all physical chemists from the UCW, Aberystwyth. Fifty scientists attended, being a mix of physical chemists, theoretical chemists, physicists, electrical engineers, polymer and materials scientists, all from the UK, except Dr Brendan Scaife of Trinity

  19. Dielectric Constant Modelling with Soil–Air Composition and Its Effect on Sar Radar Signal Backscattered over Soil Surface

    PubMed Central

    Zribi, Mehrez; Le Morvan, Aurélie; Baghdadi, Nicolas

    2008-01-01

    The objective of this paper is to present the contribution of a new dielectric constant characterisation for the modelling of radar backscattering behaviour. Our analysis is based on a large number of radar measurements acquired during different experimental campaigns (Orgeval'94, Pays de Caux'98, 99). We propose a dielectric constant model, based on the combination of contributions from both soil and air fractions. This modelling clearly reveals the joint influence of the air and soil phases, in backscattering measurements over rough surfaces with large clods. A relationship is established between the soil fraction and soil roughness, using the Integral Equation Model (IEM), fitted to real radar data. Finally, the influence of the air fraction on the linear relationship between moisture and the backscattered radar signal is discussed.

  20. Technique for Performing Dielectric Property Measurements at Microwave Frequencies

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B.; Jackson, Henry W.

    2010-01-01

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

  1. Application of the compensated Arrhenius formalism to explain the dielectric constant dependence of rates for Menschutkin reactions.

    PubMed

    Petrowsky, Matt; Glatzhofer, Daniel T; Frech, Roger

    2013-11-21

    The dependence of the reaction rate on solvent dielectric constant is examined for the reaction of trihexylamine with 1-bromohexane in a series of 2-ketones over the temperature range 25-80 °C. The rate constant data are analyzed using the compensated Arrhenius formalism (CAF), where the rate constant assumes an Arrhenius-like equation that also contains a dielectric constant dependence in the exponential prefactor. The CAF activation energies are substantially higher than those obtained using the simple Arrhenius equation. A master curve of the data is observed by plotting the prefactors against the solvent dielectric constant. The master curve shows that the reaction rate has a weak dependence on dielectric constant for values approximately less than 10 and increases more rapidly for dielectric constant values greater than 10. PMID:24156502

  2. Dependence of the dielectric constant of electrolyte solutions on ionic concentration: A microfield approach

    NASA Astrophysics Data System (ADS)

    Gavish, Nir; Promislow, Keith

    2016-07-01

    We present a microfield approach for studying the dependence of the orientational polarization of the water in aqueous electrolyte solutions upon the salt concentration and temperature. The model takes into account the orientation of the solvent dipoles due to the electric field created by ions, and the effect of thermal fluctuations. The model predicts a dielectric functional dependence of the form ɛ (c ) =ɛw-β L (3 α c /β ) ,β =ɛw-ɛms , where L is the Langevin function, c is the salt concentration, ɛw is the dielectric of pure water, ɛms is the dielectric of the electrolyte solution at the molten salt limit, and α is the total excess polarization of the ions. The functional form gives a remarkably accurate description of the dielectric constant for a variety of salts and a wide range of concentrations.

  3. Dependence of the dielectric constant of electrolyte solutions on ionic concentration: A microfield approach.

    PubMed

    Gavish, Nir; Promislow, Keith

    2016-07-01

    We present a microfield approach for studying the dependence of the orientational polarization of the water in aqueous electrolyte solutions upon the salt concentration and temperature. The model takes into account the orientation of the solvent dipoles due to the electric field created by ions, and the effect of thermal fluctuations. The model predicts a dielectric functional dependence of the form ɛ(c)=ɛ_{w}-βL(3αc/β),β=ɛ_{w}-ɛ_{ms}, where L is the Langevin function, c is the salt concentration, ɛ_{w} is the dielectric of pure water, ɛ_{ms} is the dielectric of the electrolyte solution at the molten salt limit, and α is the total excess polarization of the ions. The functional form gives a remarkably accurate description of the dielectric constant for a variety of salts and a wide range of concentrations. PMID:27575183

  4. Giant voltage-induced deformation of a dielectric elastomer under a constant pressure

    NASA Astrophysics Data System (ADS)

    Godaba, Hareesh; Foo, Choon Chiang; Zhang, Zhi Qian; Khoo, Boo Cheong; Zhu, Jian

    2014-09-01

    Dielectric elastomer actuators coupled with liquid have recently been developed as soft pumps, soft lenses, Braille displays, etc. In this paper, we investigate the performance of a dielectric elastomer actuator, which is coupled with water. The experiments demonstrate that the membrane of a dielectric elastomer can achieve a giant voltage-induced area strain of 1165%, when subject to a constant pressure. Both theory and experiment show that the pressure plays an important role in determining the electromechanical behaviour. The experiments also suggest that the dielectric elastomer actuators, when coupled with liquid, may suffer mechanical instability and collapse after a large amount of liquid is enclosed by the membrane. This failure mode needs to be taken into account in designing soft actuators.

  5. Correlation between the dielectric constant and porosity of nanoporous silica thin films deposited by the gas evaporation technique

    NASA Astrophysics Data System (ADS)

    Si, J. J.; Ono, H.; Uchida, K.; Nozaki, S.; Morisaki, H.; Itoh, N.

    2001-11-01

    Nanoporous silica thin films with low dielectric constants were deposited by gas evaporation of SiO2 nanoparticles in an argon atmosphere. With increasing gas pressure during the evaporation, the dielectric constant decreases, while the porosity increases. The correlation between the dielectric constant and porosity is well modeled by a serial connection of two capacitors, one with air and the other with SiO2 as the dielectric medium. This suggests that the dielectric constant of the nanoporous silica thin film using the gas evaporation technique is more effectively lowered by forming "uniformly" distributed voids of closed gaps than those of the nanoporous silica films with pores extending from the back to front surface. Therefore, the former nanoporous silica thin film requires less porosity to obtain a low dielectric constant and is regarded as an ideal low-k material.

  6. Process for lowering the dielectric constant of polyimides using diamic acid additives

    NASA Technical Reports Server (NTRS)

    Stoakley, Diane M. (Inventor); St.clair, Anne K. (Inventor)

    1990-01-01

    Linear aromatic polyimides with low dielectric constants are produced by adding a diamic acid additive to the polyamic acid resin formed by the condensation of an aromatic dianhydride with an aromatic diamine. The resulting modified polyimide is a better electrical insulator than state-of-the-art commercially available polyimides.

  7. THE ONSET OF ELECTRICAL BREAKDOWN IN DUST LAYERS: II. EFFECTIVE DIELECTRIC CONSTANT AND LOCAL FIELD ENHANCEMENT

    EPA Science Inventory

    Part 1 of the work has shown that electrical breakdown in dust layers obeys Paschen's Law, but occurs at applied field values which appear too small to initiate the breakdown. In this paper the authors show how an effective dielectric constant characterizing the dust layer can be...

  8. Estimation of dielectric constant of lunar material by HF sounder observation

    NASA Astrophysics Data System (ADS)

    Kobayashi, T.; Ono, T.

    Space borne radio sounding observation has been one of indispensable items in planetary missions An HF sounder Lunar Radar Sounder LRS will be onboard SELENE a lunar exploration program of Japan in 2007 Its primary objective is subsurface geologic structure of the Moon Especially mare regions are of strong interest of investigators because of its relatively smooth surface it is thought that smooth surface allows us to see subsurface feature with less difficulty However even if a clear subsurface image is obtained the data does not provide us with quantitative information unless the dielectric constant of the lunar subsurface material We propose a technique to estimate the dielectric constant of lunar material that utilizes HF sounder data of closely located multiple orbits The technique is applied to SAR images that are produced from HF sounder data and stands on the fact that the apparent position of subsurface object varies as a function of the dielectric constant of subsurface material Assuming a uniform subsurface material the displacement of images of a subsurface target should be consistent with that of observation orbits if the correct dielectric constant of the subsurface material is assumed A numerical model on geometrical optics estimates that the proposed technique requires a synthetic aperture larger than about 50km provided that the orbit altitude is 100km subsurface target depth is a few km and that the observation frequency is 5MHz with 2MHz bandwidth Some laboratory experiments were conducted to demonstrate validity of the

  9. A miniaturized flexible antenna printed on a high dielectric constant nanopaper composite.

    PubMed

    Inui, Tetsuji; Koga, Hirotaka; Nogi, Masaya; Komoda, Natsuki; Suganuma, Katsuaki

    2015-02-01

    A high-dielectric-constant and flexible cellulose nanopaper composite is prepared by mixing a small amount of silver nanowires with cellulose nanofibers. The nanopaper antenna is downsized by about a half when using the nanopaper substrate. The nanopaper antenna has potential in wearable wireless communication devices. PMID:25530578

  10. Dielectric Property Measurements to Support Interpretation of Cassini Radar Data

    NASA Astrophysics Data System (ADS)

    Jamieson, Corey; Barmatz, M.

    2012-10-01

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

  11. PREFACE: Dielectrics 2009: Measurement Analysis and Applications

    NASA Astrophysics Data System (ADS)

    Vaughan, Alun; Williams, Graham

    2009-07-01

    The conference Dielectrics 2009: Measurements, Analysis and Applications represents a significant milestone in the evolution of dielectrics research in the UK. It is reasonable to state that the academic study of dielectrics has led to many fundamental advances and that dielectric materials underpin the modern world in devices ranging from field effect transistors, which operate at extremely high fields, albeit low voltages, to the high voltage plants that provide the energy that powers our economy. The origins of the Dielectrics Group of the Institute of Physics (IOP), which organized this conference, can be traced directly back to the early 1960s, when Professor Mansel Davies was conducting research into the dielectric relaxation behaviour of polar liquids and solids at The Edward Davies Chemical Laboratories of the University College of Wales, Aberystwyth. He was already well-known internationally for his studies of molecular structure and bonding of small molecules, using infra-red-spectroscopy, and of the physical properties of hydrogen-bonded liquids and solids, using thermodynamic methods. Dielectric spectroscopy was a fairly new area for him and he realized that opportunities for scientists in the UK to gather together and discuss their research in this developing area of physical chemistry/chemical physics were very limited. He conceived the idea of forming a Dielectrics Discussion Group (DDG), which would act as a meeting point and provide a platform for dielectrics research in the UK and beyond and, as a result, a two-day Meeting was convened in the spring of 1968 at Gregynog Hall of the University of Wales, near Newtown, Montgomeryshire. It was organized by Mansel Davies, Alun Price and Graham Williams, all physical chemists from the UCW, Aberystwyth. Fifty scientists attended, being a mix of physical chemists, theoretical chemists, physicists, electrical engineers, polymer and materials scientists, all from the UK, except Dr Brendan Scaife of Trinity

  12. Using DelPhi capabilities to mimic protein’s conformational reorganization with amino acid specific dielectric constants

    PubMed Central

    Wang, Lin; Zhang, Zhe; Rocchia, Walter; Alexov, Emil

    2011-01-01

    Many molecular events are associated with small or large conformational changes occurring in the corresponding proteins. Modeling such changes is a challenge and requires significant amount of computing time. From point of view of electrostatics, these changes can be viewed as a reorganization of local charges and dipoles in response to the changes of the electrostatic field, if the cause is insertion or deletion of a charged amino acid. Here we report a large scale investigation of modeling the changes of the folding energy due to single mutations involving charged group. This allows the changes of the folding energy to be considered mostly electrostatics in origin and to be calculated with DelPhi assigning residue-specific value of the internal dielectric constant of protein. The predicted energy changes are benchmarked against experimentally measured changes of the folding energy on a set of 257 single mutations. The best fit between experimental values and predicted changes is used to find out the effective value of the internal dielectric constant for each type of amino acid. The predicted folding free energy changes with the optimal, amino acid specific, dielectric constants are within RMSD=0.86 kcal/mol from experimentally measured changes. PMID:24683422

  13. Low dielectric constant-based organic field-effect transistors and metal-insulator-semiconductor capacitors

    NASA Astrophysics Data System (ADS)

    Ukah, Ndubuisi Benjamin

    This thesis describes a study of PFB and pentacene-based organic field-effect transistors (OFET) and metal-insulator-semiconductor (MIS) capacitors with low dielectric constant (k) poly(methyl methacrylate) (PMMA), poly(4-vinyl phenol) (PVP) and cross-linked PVP (c-PVP) gate dielectrics. A physical method -- matrix assisted pulsed laser evaporation (MAPLE) -- of fabricating all-polymer field-effect transistors and MIS capacitors that circumvents inherent polymer dissolution and solvent-selectivity problems, is demonstrated. Pentacene-based OFETs incorporating PMMA and PVP gate dielectrics usually have high operating voltages related to the thickness of the dielectric layer. Reduced PMMA layer thickness (≤ 70 nm) was obtained by dissolving the PMMA in propylene carbonate (PC). The resulting pentacene-based transistors exhibited very low operating voltage (below -3 V), minimal hysteresis in their transfer characteristics, and decent electrical performance. Also low voltage (within -2 V) operation using thin (≤ 80 nm) low-k and hydrophilic PVP and c-PVP dielectric layers obtained via dissolution in high dipole moment and high-k solvents -- PC and dimethyl sulfoxide (DMSO), is demonstrated to be a robust means of achieving improved electrical characteristics and high operational stability in OFETs incorporating PVP and c-PVP dielectrics.

  14. Dielectric constant and loss tangent of Eccofoam PT, at 2.3 GHz, for various packing densities

    NASA Technical Reports Server (NTRS)

    Lane, F. L.

    1973-01-01

    The dielectric constant and loss tangent for Eccofoam PT, at various densities, are determined; the resulting density gradients are provided. The range of densites over which the dielectric constant and loss tangent are determined are from approximately 320 to 1280 kg/cu m (20 to 80 lb/cu ft).

  15. New high dielectric constant materials for tailoring the B1+ distribution at high magnetic fields

    NASA Astrophysics Data System (ADS)

    Haines, K.; Smith, N. B.; Webb, A. G.

    2010-04-01

    The spatial distribution of electromagnetic fields within the human body can be tailored using external dielectric materials. Here, we introduce a new material with high dielectric constant, and also low background MRI signal. The material is based upon metal titanates, which can be made into a geometrically-formable suspension in de-ionized water. The material properties of the suspension are characterized from 100 to 400 MHz. Results obtained at 7 T show a significant increase in image intensity in areas such as the temporal lobe and base of the brain with the new material placed around the head, and improved performance compared to purely water-based gels.

  16. Dielectric Maps of the Martian Polar Regions from MARSIS/Mex Surface Reflectivity Measurements

    NASA Astrophysics Data System (ADS)

    Beck, P.; Mouginot, J.; Pommerol, A.; Kofman, W. W.; Clifford, S. M.

    2011-12-01

    Most of classic remote-sensing methods probe the surface and very close subsurface of the Martian crust and are thus only sensitive to processes that occurred under the Amazonian climate. Sounding radar has the potential to probe deeper into the crust, revealing processes that occurred in a distant past.We report here on the completion and improvement of dielectric maps of the Martian polar regions assembled from MARSIS measurements, building upon the initial work of [1]. New data collected by MARSIS since 2008 have been incorporated to greatly increase the level of details in the northern hemisphere. In our presentation, we will briefly discuss the method used to extract values of dielectric con-stant from MARSIS measurements which was explained in details by [1]. As a reasonable ap-proximation, we show that these maps are representative of the average dielectric constant of the first 50 to 100 meters below the surface. We compare the dielectric maps of the northern and southern polar regions of Mars and note a stricking difference between both hemispheres. In the south, a strong decrease of the dielectric constant is consistent with the inferred limit for the presence of stable water ice in the ground. In the north, a similar decrease of dielectric constant is observed but it compasses a much broader area than the one where water ice is at equilibrium under the current climate. The dielectric constant pattern displays a much better correlation with the global topography and, to some extent, with the putative shorelines of the past ocean. Ancient water activity is likely responsible for the observed dielectric pattern. To test the link between the geologic nature of the terrains and the value of dielectric con-stant, we produced a composite geologic / dielectric map from the geologic map of [2] and our dielectric map. A detailed examination of this map confirms the strong link between the geologic nature of the formations and their dielectric constant. Hesperian

  17. Latest rocket measurements of the solar constant

    NASA Technical Reports Server (NTRS)

    Duncan, C. H.; Willson, R. C.; Kendall, J. M.; Harrison, R. G.; Hickey, J. R.

    1982-01-01

    Three rocket flights which carried a payload of absolute radiometers to measure the solar constant with an accuracy of plus or minus 0.5 per cent have been accomplished. Several of the rocket radiometers were duplicates of those aboard the Solar Maximum Mission and Nimbus spacecrafts. The values for the solar constant obtained by the rocket sensors for the three flight dates indicate an increase between the first and latter two flights approximately equivalent to the uncertainty of the measurements. The values for the solar constant for the three flights are 1367, 1372 and 1374 W/sq m.

  18. Chemical vapor deposition and characterization of zirconium tin titanate as a high dielectric constant material for potential electronic applications

    NASA Astrophysics Data System (ADS)

    Mays, Ebony Lynn

    Integrated circuit (IC) manufacturers increasingly need new high dielectric constant (epsilon) materials for gate stacks to maintain the pace of developing faster, higher capacity CMOS and DRAM devices. Identification of new high-epsilon materials that can be integrated into current manufacturing processes is critical to the continued development of IC devices. Using magnetron sputtering and a compositional spread approach, a key composition of amorphous zirconium tin titanate (a-ZTT) films was found to exhibit a dielectric constant from 50 to 70 and leakage currents from 10-9 to 10 -7 A/cm2 at 1 MV/cm. Chemical Vapor Deposition (CVD) is an attractive technique for deposition of ZTT films because it offers several advantages over sputter deposition. Many processing parameters can be controlled and varied in the optimization of the film microstructure and composition. In addition, high-epsilon phases of the compounds might be achieved at low temperatures by using plasma enhancement of the CVD process. Alternatively, use of ozone or other oxidants may allow complete oxidation of metal precursors at lower processing temperatures. The following discussion details the construction and modification of a CVD reactor for the deposition of ZTT thin films. In addition, characterization of a precursor "cocktail"---a solution containing all the metal components of the film---for the deposition of ZTT thin films is discussed. Discussion includes experiments characterizing the dielectric and device properties (dielectric constant, dielectric loss, capacitance, and leakage current) of CVD-grown, a-ZTT thin films using the precursor "cocktail". The importance of the relationship of the cation ratio in the precursor that is translated to the film and its relationship to the dielectric properties are shown. The device properties of ZTT films were measured using Capacitance-Voltage (CV) and Current-Voltage (IV) analysis, while dielectric properties were explored using Impedance

  19. RAPID COMMUNICATION: Control of grain size and size effect on the dielectric constant of diamond films

    NASA Astrophysics Data System (ADS)

    Ye, Haitao; Sun, Chang Q.; Hing, Peter

    2000-12-01

    This work reports that the optimum diamond grain size can be controlled by adjusting the flow rate of Ar/H2 in the reaction chamber through orthogonal optimization. The dielectric properties of the diamond films were investigated using an RCL (resistance-capacitance-inductance) meter. It was found that (i) the dominating factors in controlling the grain size are in the following order: Ar/H2 gas ratio, gas total pressure, plasma power and substrate temperature; (ii) increasing the Ar gas fraction reduces the grain size of synthetic diamond films; and (iii) reducing the grain size lowers the dielectric constant. The grain size effect on the dielectric behaviour can be explained by the change of the crystal field caused by surface bond contraction of the nanosized particles.

  20. Utilizing Calibrated GPS Reflected Signals to Estimate Soil Reflectivity and Dielectric Constant: Results from SMEX02

    NASA Technical Reports Server (NTRS)

    Katzberg, Stephen J.; Torres, Omar; Grant, Michael S.; Masters, Dallas

    2006-01-01

    Extensive reflected GPS data was collected using a GPS reflectometer installed on an HC130 aircraft during the Soil Moisture Experiment 2002 (SMEX02) near Ames, Iowa. At the same time, widespread surface truth data was acquired in the form of point soil moisture profiles, areal sampling of near-surface soil moisture, total green biomass and precipitation history, among others. Previously, there have been no reported efforts to calibrate reflected GPS data sets acquired over land. This paper reports the results of two approaches to calibration of the data that yield consistent results. It is shown that estimating the strength of the reflected signals by either (1) assuming an approximately specular surface reflection or (2) inferring the surface slope probability density and associated normalization constants give essentially the same results for the conditions encountered in SMEX02. The corrected data is converted to surface reflectivity and then to dielectric constant as a test of the calibration approaches. Utilizing the extensive in-situ soil moisture related data this paper also presents the results of comparing the GPS-inferred relative dielectric constant with the Wang-Schmugge model frequently used to relate volume moisture content to dielectric constant. It is shown that the calibrated GPS reflectivity estimates follow the expected dependence of permittivity with volume moisture, but with the following qualification: The soil moisture value governing the reflectivity appears to come from only the top 1-2 centimeters of soil, a result consistent with results found for other microwave techniques operating at L-band. Nevertheless, the experimentally derived dielectric constant is generally lower than predicted. Possible explanations are presented to explain this result.

  1. Quantum theory of the complex dielectric constant of free carriers in polar semiconductors

    SciTech Connect

    Jensen, B.

    1982-09-01

    The optical constants and reflectivity of a semiconductor are known as functions of the real and imaginary parts of the complex dielectric constant. The imaginary part of the complex dielectric constant e/sub 2/ is proportional to the optical conductivity, which has recently been calculated from the quantum density matrix equation of motion. The expression obtained for e/sub 2/ reduces to the Drude result, as obtained from the quasi-classical Boltzmann transport equation, in the limit of low frequencies and elastic scattering mechanisms, and to the quantum result found using time dependent perturbation theory in the limit of high frequencies. This paper derives the real part of the complex dielectric constant e/sub 1/ for a III-V or II-VI semiconductor with the band structure of the Kane theory, using the quantum density matrix method. The relation of e/sub 1/ to the second order perturbation energy of the system is shown, and the reflectivity is a minimum when the second order perturbation energy vanishes. The quantum calculation for e/sub 1/ gives approximately the same result as the Drude theory, except near the fundamental absorption edge, and reduces to the Drude result at low frequencies. Using the complex dielectric constant, the real and imaginary parts of the complex refractive index, the skin depth, and surface impedance, and the reflectivity are found. The plasma resonance is examined. The surface impedance and the skin depth are shown to reduce to the usual classical result in the limit that e/sub 1/ = 0 and w tau << 1, where w is the angular frequency of the applied field and tau is the electron scattering time.

  2. Hysteresis behaviour of low-voltage organic field-effect transistors employing high dielectric constant polymer gate dielectrics

    NASA Astrophysics Data System (ADS)

    Kim, Se Hyun; Yun, Won Min; Kwon, Oh-Kwan; Hong, Kipyo; Yang, Chanwoo; Choi, Woon-Seop; Eon Park, Chan

    2010-11-01

    Here, we report on the fabrication of low-voltage-operating pentacene-based organic field-effect transistors (OFETs) that utilize crosslinked cyanoethylated poly(vinyl alcohol) (CR-V) gate dielectrics. The crosslinked CR-V-based OFET could be operated successfully at low voltages (below 4 V), but abnormal behaviour during device operation, such as uncertainty in the field-effect mobility (μ) and hysteresis, was induced by the slow polarization of moieties embedded in the gate dielectric (e.g. polar functionalities, ionic impurities, water and solvent molecules). In an effort to improve the stability of OFET operation, we measured the dependence of μ and hysteresis on dielectric thickness, CR-V crosslinking conditions and sweep rate of the gate bias. The influence of the CR-V surface properties on μ, hysteresis, and the structural and morphological features of the pentacene layer grown on the gate dielectric was characterized and compared with the properties of pentacene grown on a polystyrene surface.

  3. Sol–gel composite material characteristics caused by different dielectric constant sol–gel phases

    NASA Astrophysics Data System (ADS)

    Kimoto, Keisuke; Matsumoto, Makoto; Kaneko, Tsukasa; Kobayashi, Makiko

    2016-07-01

    Ultrasonic transducers prepared by a sol–gel composite method have been investigated in the field of nondestructive testing (NDT). Sol–gel composite materials could be ideal piezoelectric materials for ultrasonic transducer applications in the NDT field, and a new sol–gel composite with desirable characteristics has been developed. Three kinds of sol–gel composite materials composed of different dielectric constant sol–gel phases, Pb(Zr,Ti)O3 (PZT), Bi4Ti3O12 (BiT), and BaTiO3 (BT), and the same piezoelectric powder phase, PbTiO3 (PT), were fabricated and their properties were compared quantitatively. As a result, the PT/BT, sol–gel composite with the highest dielectric constant sol–gel phase showed the highest d 33 and signal strength. In addition, only PT/BT was successfully poled by room-temperature corona poling with reasonable signal strength.

  4. Improved ground-state electronic structure and optical dielectric constants with a semilocal exchange functional

    NASA Astrophysics Data System (ADS)

    Vlček, Vojtěch; Steinle-Neumann, Gerd; Leppert, Linn; Armiento, Rickard; Kümmel, Stephan

    2015-01-01

    A recently published generalized gradient approximation functional within density functional theory (DFT) has shown, in a few paradigm tests, an improved KS orbital description over standard (semi)local approximations. The characteristic feature of this functional is an enhancement factor that diverges like s ln(s ) for large reduced density gradients s which leads to unusual properties. We explore the improved orbital description of this functional more thoroughly by computing the electronic band structure, band gaps, and the optical dielectric constants in semiconductors, Mott insulators, and ionic crystals. Compared to standard semilocal functionals, we observe improvement in both the band gaps and the optical dielectric constants. In particular, the results are similar to those obtained with orbital functionals or by perturbation theory methods in that it opens band gaps in systems described as metallic by standard (semi)local density functionals, e.g., Ge, α -Sn, and CdO.

  5. A molecular site-site integral equation that yields the dielectric constant

    NASA Astrophysics Data System (ADS)

    Dyer, Kippi M.; Perkyns, John S.; Stell, George; Pettitt, B. Montgomery

    2008-09-01

    Our recent derivation [K. M. Dyer et al., J. Chem. Phys. 127, 194506 (2007)] of a diagrammatically proper, site-site, integral equation theory using molecular angular expansions is extended to polar fluids. With the addition of atomic site charges we take advantage of the formal long-ranged potential field cancellations before renormalization to generate a set of numerically stable equations. Results for calculations in a minimal (spherical) angular basis set are presented for the radial distribution function, the first dipolar (110) projection, and the dielectric constant for two model diatomic systems. All results, when compared to experiment and simulation, are a significant quantitative and qualitative improvement over previous site-site theories. More importantly, the dielectric constant is not trivial and close to simulation and experiment.

  6. The super- and sub-critical effects for dielectric constant in diethyl ether.

    PubMed

    Drozd-Rzoska, Aleksandra; Rzoska, Sylwester J

    2016-06-14

    Results of dielectric constant (ε) studies in diethyl ether for the surrounding of the gas - liquid critical point, TC - 130 K < T < TC + 50 K, are presented. The analysis recalls the physics of critical phenomena for portraying ε (T) evolution along branches of the coexistence curve, along its diameter (d(T)) and in the supercritical domain for T > TC. For the ultrasound sonicated system, the split into coexisting phases disappeared and dielectric constant approximately followed the pattern of the diameter. This may indicate the possibility of the extension of the "supercritical technology" into the ultrasound "homogenized" subcritical domain: the "strength" and the range of the precritical effect of d(T) are ca. 10× larger than for ε (T > TC). PMID:27306017

  7. The super- and sub-critical effects for dielectric constant in diethyl ether

    NASA Astrophysics Data System (ADS)

    Drozd-Rzoska, Aleksandra; Rzoska, Sylwester J.

    2016-06-01

    Results of dielectric constant (ɛ) studies in diethyl ether for the surrounding of the gas - liquid critical point, TC - 130 K < T < TC + 50 K, are presented. The analysis recalls the physics of critical phenomena for portraying ɛ (T) evolution along branches of the coexistence curve, along its diameter (d(T)) and in the supercritical domain for T > TC. For the ultrasound sonicated system, the split into coexisting phases disappeared and dielectric constant approximately followed the pattern of the diameter. This may indicate the possibility of the extension of the "supercritical technology" into the ultrasound "homogenized" subcritical domain: the "strength" and the range of the precritical effect of d(T) are ca. 10× larger than for ɛ (T > TC).

  8. Anomalous change in dielectric constant of CaCu3Ti4O12 under violet-to-ultraviolet irradiation

    NASA Astrophysics Data System (ADS)

    Masingboon, C.; Eknapakul, T.; Suwanwong, S.; Buaphet, P.; Nakajima, H.; Mo, S.-K.; Thongbai, P.; King, P. D. C.; Maensiri, S.; Meevasana, W.

    2013-05-01

    The influence of light illumination on the dielectric constant of CaCu3Ti4O12 (CCTO) polycrystals is studied in this work. When exposed to 405-nm laser light, a reversible enhancement in the room temperature capacitance as high as 22% was observed, suggesting application of light-sensitive capacitance devices. To uncover the microscopic mechanisms mediating this change, we performed electronic structure measurements, using photoemission spectroscopy, and measured the electrical conductivity of the CCTO samples under different conditions of light exposure and oxygen partial pressure. Together, these results suggest that the large capacitance enhancement is driven by oxygen vacancies induced by the irradiation.

  9. Determination of plasma frequency, damping constant, and size distribution from the complex dielectric function of noble metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Mendoza Herrera, Luis J.; Arboleda, David Muñetón; Schinca, Daniel C.; Scaffardi, Lucía B.

    2014-12-01

    This paper develops a novel method for simultaneously determining the plasma frequency ωP and the damping constant γfr e e in the bulk damped oscillator Drude model, based on experimentally measured real and imaginary parts of the metal refractive index in the IR wavelength range, lifting the usual approximation that restricts frequency values to the UV-deep UV region. Our method was applied to gold, silver, and copper, improving the relative uncertainties in the final values for ωp (0.5%-1.6%) and for γfr e e (3%-8%), which are smaller than those reported in the literature. These small uncertainties in ωp and γfr e e determination yield a much better fit of the experimental complex dielectric function. For the case of nanoparticles (Nps), a series expansion of the Drude expression (which includes ωp and γfr e e determined using our method) enables size-dependent dielectric function to be written as the sum of three terms: the experimental bulk dielectric function plus two size corrective terms, one for free electron, and the other for bound-electron contributions. Finally, size distribution of nanometric and subnanometric gold Nps in colloidal suspension was determined through fitting its experimental optical extinction spectrum using Mie theory based on the previously determined dielectric function. Results are compared with size histogram obtained from Transmission Electron Microscopy (TEM).

  10. Determination of plasma frequency, damping constant, and size distribution from the complex dielectric function of noble metal nanoparticles

    SciTech Connect

    Mendoza Herrera, Luis J.; Arboleda, David Muñetón; Schinca, Daniel C.; Scaffardi, Lucía B.

    2014-12-21

    This paper develops a novel method for simultaneously determining the plasma frequency ω{sub P}   and the damping constant γ{sub free} in the bulk damped oscillator Drude model, based on experimentally measured real and imaginary parts of the metal refractive index in the IR wavelength range, lifting the usual approximation that restricts frequency values to the UV-deep UV region. Our method was applied to gold, silver, and copper, improving the relative uncertainties in the final values for ω{sub p} (0.5%–1.6%) and for γ{sub free} (3%–8%), which are smaller than those reported in the literature. These small uncertainties in ω{sub p} and γ{sub free} determination yield a much better fit of the experimental complex dielectric function. For the case of nanoparticles (Nps), a series expansion of the Drude expression (which includes ω{sub p} and γ{sub free} determined using our method) enables size-dependent dielectric function to be written as the sum of three terms: the experimental bulk dielectric function plus two size corrective terms, one for free electron, and the other for bound-electron contributions. Finally, size distribution of nanometric and subnanometric gold Nps in colloidal suspension was determined through fitting its experimental optical extinction spectrum using Mie theory based on the previously determined dielectric function. Results are compared with size histogram obtained from Transmission Electron Microscopy (TEM)

  11. Improved SPC force field of water based on the dielectric constant: SPC/ ε

    NASA Astrophysics Data System (ADS)

    Fuentes-Azcatl, Raúl; Mendoza, Noé; Alejandre, José

    2015-02-01

    In a recent work, Fuentes and Alejandre (2014) found that for TIP4P models there is a dipole moment of minimum density at 240 K and that the Lennard-Jones parameters can be adjusted to match the experimental dielectric constant at 300 K and the temperature of maximum density, respectively. The same procedure is used in this work to re-parameterize the simple point charge (SPC) model keeping the original geometry. The new model fails to reproduce the experimental self-diffusion coefficient and shear viscosity but improves the results at different temperatures and pressures of dielectric constant, isothermal compressibility, thermal expansion coefficient, surface tension, coexisting densities at the liquid-vapor interface, equation of state of ice Ih and equation of state of liquids at high pressures. A second model that reproduces the dielectric constant, self-diffusion coefficient and shear viscosity is proposed but the temperature of maximum density is 250 K, compared with the experimental value of 277 K. Both models improve the SPC/E results for almost all properties. The TIP3P model was also analyzed but the liquid density at 240 K always increases and a minimum in the dipole moment was not found. It is not possible to adjust for that model the charge distribution and short range interaction parameters to reproduce at the same time the target properties.

  12. Density fluctuations and dielectric constant of water in low and high density liquid states

    NASA Astrophysics Data System (ADS)

    Lascaris, Erik; Zhang, Cui; Galli, Giulia A.; Franzese, Giancarlo; Stanley, H. Eugene

    2012-02-01

    The hypothesis of a liquid-liquid critical point (LLCP) in the phase diagram of water, though first published many years ago, still remains the subject of a heated debate. According to this hypothesis there exists a critical point near T 244 K, and P 215 MPa, located at the end of a coexistence line between a high density liquid (HDL) and a low density liquid state (LDL). The LLCP lies below the homogenous nucleation temperature of water and it has so far remained inaccessible to experiments. We study a model of water exhibiting a liquid-liquid phase transition (that is a liquid interacting through the ST2 potential) and investigate the properties of dipolar fluctuations as a function of density, in the HDL and LDL. We find an interesting correlation between the macroscopic dielectric constants and the densities of the two liquids in the vicinity of the critical point, and we discuss possible implications for measurements close to the region where the LLCP may be located.

  13. Structure-property relationships of nano-foam polyimide films with low dielectric constant and high thermal stability

    SciTech Connect

    Cha, H.J.; Hedrick, J.; DiPietro, R.A.

    1996-10-01

    Thin polyimide films with dispersed nano-foam morphology have been prepared successfully for the purpose of obtaining low dielectric polymer insulators for microelectronic applications. They were obtained by utilizing triblock copolymers where the thermally stable polyimide component was derived from pyromellitic dianhydride (PMDA) with 1,1-bis(4-aminophenyl)-1-phenyl-2,2,2-trifluroroethane (3F) and thermally labile (polypropylene oxide) (PO) component comprised the outside block of the ABA triblock architecture. The domain shapes in thin films before foaming were irregular due to the non-equilibrium nature of preparation conditions. Final nano-foam shapes and sizes seem very similar to the initial morphology of PO domains. The measured dielectric constant was found to decrease to {approximately}2.3 for the foamed polyimide film with 18% porosity, as compared with ca. 2.9 for the homopolymer, and to remain stable at high temperatures.

  14. Microclimate, Water Potential, Transpiration, and Bole Dielectric Constant of Coniferous and Deciduous Tree Species in the Continental Boreal Ecotone of Central Alaska

    NASA Technical Reports Server (NTRS)

    Zimmermann, R.; McDonald, K.; Way, J.; Oren, R.

    1994-01-01

    Tree canopy microclimate, xylem water flux and xylem dielectric constant have been monitored in situ since June 1993 in two adjacent natural forest stands in central Alaska. The deciduous stand represents a mature balsam poplar site on the Tanana River floodplain, while the coniferous stand consists of mature white spruce with some black spruce mixed in. During solstice in June and later in summer, diurnal changes of xylem water potential were measured to investigate the occurrence and magnitude of tree transpiration and dielectric constant changes in stems.

  15. Low dielectric constant fibers from a fluorinated polymide for electronic packaging

    SciTech Connect

    Eashoo, M.; Buckley, L.J.; St. Clair, A.K.

    1996-10-01

    As the electronics industry moves toward higher frequencies, the need for laminate materials with enhanced dielectric properties is crucial. Since uniaxial composites are highly filled with reinforcing materials, fibers will play a significant role in lowering the overall dielectric constant of multi-layer printed wiring boards. Past fibers from a low dielectric constant ({epsilon}{prime} = 2.5) polyimide made from 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 2,2-bis [4-(4-aminophenoxy) phenyl] hexafluoropropane (4BDAF) were wet-spun into an ethyl alcohol/water bath using a dimethylacetamide (DMAc)/Polymer solution. Relatively weak filaments ({Epsilon}{prime} = 5.1 GPa) result from processing with DMAc, as the fiber core is very porous. A new spinning method, using controlled miscibility between the solvent and the coagulant, yielded solid core fibers using methylene chloride as the solvent. These 6FDA-4BDAF fibers have textile-like mechanical properties having; a modulus of 7-8 GPa, a tensile strength of 300-380 MPa, and a break strain of 4-7%.

  16. An all-organic composite actuator material with a high dielectric constant

    NASA Astrophysics Data System (ADS)

    Zhang, Q. M.; Li, Hengfeng; Poh, Martin; Xia, Feng; Cheng, Z.-Y.; Xu, Haisheng; Huang, Cheng

    2002-09-01

    Electroactive polymers (EAPs) can behave as actuators, changing their shape in response to electrical stimulation. EAPs that are controlled by external electric fields-referred to here as field-type EAPs-include ferroelectric polymers, electrostrictive polymers, dielectric elastomers and liquid crystal polymers. Field-type EAPs can exhibit fast response speeds, low hysteresis and strain levels far above those of traditional piezoelectric materials, with elastic energy densities even higher than those of piezoceramics. However, these polymers also require a high field (>70Vµm-1) to generate such high elastic energy densities (>0.1Jcm-3 refs 4, 5, 9, 10). Here we report a new class of all-organic field-type EAP composites, which can exhibit high elastic energy densities induced by an electric field of only 13Vµm-1. The composites are fabricated from an organic filler material possessing very high dielectric constant dispersed in an electrostrictive polymer matrix. The composites can exhibit high net dielectric constants while retaining the flexibility of the matrix. These all-organic actuators could find applications as artificial muscles, `smart skins' for drag reduction, and in microfluidic systems for drug delivery.

  17. Improved Approximation of Water Dielectric Permittivity for Calculation of Hamaker Constants.

    PubMed

    Nguyen

    2000-09-15

    Due to the highly polar nature with a multipeak absorption spectrum of water, the contribution of the relaxation in the microwave and infrared regions to the water dielectric spectrum is significant. The old data obtained by the Cauchy plot analysis of the parameters of the single-relaxation representation of water dielectric spectrum produce the discrepancy in the Hamaker constants computed by the complete continuum theory. New data are obtained by the direct fitting of the single-relaxation model to the complete water dielectric spectrum. The Hamaker constants computed using the improved approximate and the complete spectra for water permittivity are in good agreement. The Hamaker function of quartz-water-quartz and quartz-water-air systems computed using the improved approximation for water and the Cauchy plot approximation for quartz also agrees with that computed using the complete spectrum for both liquid water and crystalline quartz. The new data are to be used, instead of the old Cauchy plot analysis data, in the calculation of the van der Waals interaction across water films based on the available simplified expressions. Copyright 2000 Academic Press. PMID:10985848

  18. Sulfone-Containing Dipolar Glass Polymers with High Dielectric Constant and Low Loss Property

    NASA Astrophysics Data System (ADS)

    Zhu, Yufeng; Zhang, Zhongbo; Litt, Morton; Zhu, Lei

    Sulfone-containing polyoxetanes are designed and synthesized for high dielectric constant and low loss dipolar glasses. The precursor polymer, poly(3,3-bis(chloromethyl)oxetane) (PBCMO) is synthesized by bulk cationic polymerization with boron trifluoride diethyl etherate as initiator. The number-average molecular weight of PBCMO is 73 kDa, with a polydispersity of 1.53 as obtained from size-exclusion chromatography results. Post-modification of PBCMO yields the dipolar glass polymer, poly(3,3-bis(methylsulfonylmethyl)oxetane) (MST). Nuclear magnetic resonance result shows 100% conversion. Differential scanning calorimetry result indicates that MST has a glass transition temperature of ca. 120 °C. Due to the large dipole moment (4.25 D) and small size of the side-chain sulfone groups, MST exhibits a high dielectric constant of 8.7 and a low dissipation factor of 0.01 at 25 °C and 1 Hz. This study suggests that dipolar glass polymers with large dipole moments and small-sized dipoles in the side chains are promising candidates for high energy density and low loss dielectric applications. This work is supported by NSF Polymers Program (DMR-1402733).

  19. Dielectric Constants of Refrigerants R113, R114, R114B2, R115, R116, and R124

    NASA Astrophysics Data System (ADS)

    Kashiwagi, Hiroshi; Harada, Noboru; Tanaka, Yoshiyuki; Kubota, Hironobu; Makita, Tadashi

    The dielectric constants of six refrigerants have been measured in both gaseous and liquid phases. The fluids used and the experimental ranges of temperature and pressure are as follows : R113 (1, 2, 2- Trichlorotrifluoroethane CClF2CCl2F) : 298.15-423.15K, 0.1-17.3MPa, R1l4 (1, 2- Dichlorotetrafluoroethane CClF2CClF2) : 298.15-423.15K, 0.2-17.2MPa, R114B2 (1, 2- Dibromotetrafluoroethane CBrF2CBrF2) : 298.15-423.15K, 0.2-17.3MPa, R1l5 (Chloropentafluoroethane CClF2CF3) : 298.15 373.15K. O.1-17.1MPa, R1l6 (Hexafluoroethane CF3CF3) : 283.15-373.15 K, 0.2-16.9MPa, R124 (1-Chloro-2, 2, 2, -tetrafluoroethane CHClFCF3) : 273.15 373.15K, 0.1-10.5MPa The measurements were performed using a frequency-counting method on a relative basis with an uncertainty less than ±0.1%.The experimental results are given by polynomial equations. The smoothed value tables are also given for practical convenience. The pressure dependence of dielectric constants in liquid phase is represented by a similar expression to the Tait equation. The effects of pressure, temperature, and density on the dielectric constant and the molar polarization defined by the Clausius-Mossotti relation are discussed in term of polarity of molecules of each refrigerant.

  20. Enhancement of dielectric constant in transition metal doped ZnO nanocrystals

    NASA Astrophysics Data System (ADS)

    Singh, Swati; Dey, P.; Roy, J. N.; Mandal, S. K.

    2014-09-01

    We have presented dielectric studies on Zn1-xCoxO, Zn1-xFexO, and Zn1-xFex/2Cox/2O (x = doping level) semiconducting nanoparticles (˜2-40 nm). For all those samples, dielectric constant (є) is found to exhibit a maximum with x. Enhancement of є is found to be ˜250 times for Zn0.85Co0.15O and ˜400 times for Zn0.8Fe0.1Co0.1O from that of ZnO. Presence of effective higher oxidation state of transition metals ions in ZnO due to Fe/Co doping resulting in space charge polarization possibly yields this effect. The simultaneous existence of high є, semiconducting, and ferromagnetic like behaviour at 300 K seems to propose Zn0.8Fe0.1Co0.1O, promising for technological application.

  1. Spectral characterization of dielectric materials using terahertz measurement systems

    NASA Astrophysics Data System (ADS)

    Seligman, Jeffrey M.

    The performance of modern high frequency components and electronic systems are often limited by the properties of the materials from which they are made. Over the past decade, there has been an increased emphasis on the development of new, high performance dielectrics for use in high frequency systems. The development of these materials requires novel broadband characterization, instrumentation, and extraction techniques, from which models can be formulated. For this project several types of dielectric sheets were characterized at terahertz (THz) frequencies using quasi-optical (free-space) techniques. These measurement systems included a Fourier Transform Spectrometer (FTS, scalar), a Time Domain Spectrometer (TDS, vector), a Scalar Network Analyzer (SNA), and a THz Vector Network Analyzer (VNA). Using these instruments the THz spectral characteristics of dielectric samples were obtained. Polarization based anisotropy was observed in many of the materials measured using vector systems. The TDS was the most informative and flexible instrument for dielectric characterization at THz frequencies. To our knowledge, this is the first such comprehensive study to be performed. Anisotropy effects within materials that do not come into play at microwave frequencies (e.g. ~10 GHz) were found, in many cases, to increase measured losses at THz frequencies by up to an order of magnitude. The frequency dependent properties obtained during the course of this study included loss tangent, permittivity (index of refraction), and dielectric constant. The results were largely consistent between all the different systems and correlated closely to manufacturer specifications over a wide frequency range (325 GHz-1.5 THz). Anisotropic behavior was observed for some of the materials. Non-destructive evaluation and testing (NDE/NDT) techniques were used throughout. A precision test fixture was developed to accomplish these measurements. Time delay, insertion loss, and S-parameters were

  2. Quantum theory of the dielectric constant of a magnetized plasma and astrophysical applications. I.

    NASA Technical Reports Server (NTRS)

    Canuto, V.; Ventura, J.

    1972-01-01

    A quantum mechanical treatment of an electron plasma in a constant and homogeneous magnetic field is considered, with the aim of (1) defining the range of validity of the magnetoionic theory (2) studying the deviations from this theory, in applications involving high densities, and intense magnetic field. While treating the magnetic field exactly, a perturbation approach in the photon field is used to derive general expressions for the dielectric tensor. Numerical estimates on the range of applicability of the magnetoionic theory are given for the case of the 'one-dimensional' electron gas, where only the lowest Landau level is occupied.

  3. Effect of species structure and dielectric constant on C-band forest backscatter

    NASA Technical Reports Server (NTRS)

    Lang, R. H.; Landry, R.; Kilic, O.; Chauhan, N.; Khadr, N.; Leckie, D.

    1993-01-01

    A joint experiment between Canadian and USA research teams was conducted early in Oct. 1992 to determine the effect of species structure and dielectric variations on forest backscatter. Two stands, one red pine and one jack pine, in the Petawawa National Forestry Institute (PNFI) were utilized for the experiment. Extensive tree architecture measurements had been taken by the Canada Centre for Remote Sensing (CCRS) several months earlier by employing a Total Station surveying instrument which provides detailed information on branch structure. A second part of the experiment consisted of cutting down several trees and using dielectric probes to measure branch and needle permittivity values at both sites. The dielectric and the tree geometry data were used in the George Washington University (GWU) Vegetation Model to determine the C band backscattering coefficients of the individual stands for VV polarization. The model results show that backscatter at C band comes mainly from the needles and small branches and the upper portion of the trunks acts only as an attenuator. A discussion of variation of backscatter with specie structure and how dielectric variations in needles for both species may affect the total backscatter returns is provided.

  4. Dielectric constant estimation of the uppermost Basal Unit layer in the martian Boreales Scopuli region

    NASA Astrophysics Data System (ADS)

    Lauro, Sebastian E.; Mattei, Elisabetta; Soldovieri, Francesco; Pettinelli, Elena; Orosei, Roberto; Vannaroni, Giuliano

    2012-05-01

    An electromagnetic inversion model has been applied to echoes from the subsurface sounding Shallow Radar (SHARAD) to retrieve the dielectric properties of the uppermost Basal Unit (BU) beneath the North Polar Layered Deposits of Mars. SHARAD data have been carefully selected to satisfy the assumption of the inversion model which requires a stratigraphy consisting of mostly plane parallel layers. The resulting values of the dielectric constant have been interpreted in terms of a variable percentage of dust in an ice-dust mixture through the use of a mixing model for dielectric properties. The resulting dust content exceeds 65%, reaching perhaps 95%, depending on the permittivity values assumed for the dust. Such a concentration is higher than that obtained by Selvans et al. (Selvans, M.M., Plaut, J.J., Aharonson, O. [2010]. J. Geophys. Res, 115, E09003). This discrepancy could be justified considering that our observations refer to the uppermost BU layer, whereas Selvans et al. (Selvans, M.M., Plaut, J.J., Aharonson, O. [2010]. J. Geophys. Res, 115, E09003) probed the BU full thickness. Moreover, if the BU is considered spatially inhomogeneous, with very different dust content and thickness (Tanaka, K.L., Skinner, J.A., Fortezzo, C.M., Herkenhoff, K.E., Rodriguez, J.A.P., Bourke, M.C., Kolb, E.J., Okubo, C.H. [2008]. Icarus, 196, 318-358), the discrepancy could be furtherly reconciled.

  5. Strain-induced phase variation and dielectric constant enhancement of epitaxial Gd2O3

    NASA Astrophysics Data System (ADS)

    Shekhter, P.; Schwendt, D.; Amouyal, Y.; Wietler, T. F.; Osten, H. J.; Eizenberg, M.

    2016-07-01

    One of the approaches for realizing advanced high k insulators for metal oxide semiconductor field effect transistors based devices is the use of rare earth oxides. When these oxides are deposited as epitaxial thin films, they demonstrate dielectric properties that differ greatly from those that are known for bulk oxides. Using structural and spectroscopic techniques, as well as first-principles calculations, Gd2O3 films deposited on Si (111) and Ge (111) were characterized. It was seen that the same 4 nm thick film, grown simultaneously on Ge and Si, presents an unstrained lattice on Ge while showing a metastable phase on Si. This change from the cubic lattice to the distorted metastable phase is characterized by an increase in the dielectric constant of more than 30% and a change in band gap. The case in study shows that extreme structural changes can occur in ultra-thin epitaxial rare earth oxide films and modify their dielectric properties when the underlying substrate is altered.

  6. Measurement of dielectric and magnetic properties of soil

    SciTech Connect

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

    1995-11-01

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

  7. Modification of low dielectric constant materials for ULSI multilevel interconnection by ion implantation

    NASA Astrophysics Data System (ADS)

    Roy, Alok Nandini Usha

    As integrated circuit (IC) dimensions continue to decrease, RC delay, cross-talk noise, and power dissipation of the interconnect structure become limiting factors for ultra-large-scale integration of integrated circuits. Low dielectric constant materials are being introduced and developed to replace silicon dioxide as inter level dielectrics into current interconnect technologies to meet RC delay goals and minimize cross-talk. These low kappa films generally have dielectric constants less than 3 (vs. 4 for silicon dioxide) and very poor mechanical strength. The elastic modulus (E) of the low kappa film is typically less than 10Gpa, compared with 70Gpa for SiO2. The poor mechanical strength of the low kappa dielectric films increases the risk of thermo-mechanical failures within the Cu/low kappa interconnect structure; e.g. thin film delamination and cracking. Maintaining the mechanical integrity of the low kappa films with the stresses of fab processing, packaging and reliability testing has proven challenging. Therefore, surface hardening is necessary to withstand processing (e.g. CMP). This research work will address the methods to enhance the mechanical strength of low dielectric films. Results of two classes of material (i.e. Xerogel (porous) and methyl silsesquioxane (MSQ (organic)) are discussed. Thin films of Ultra-Low kappa materials such as Xerogel (kappa = 1.76) and porous MSQ (kappa = 2.2) were implanted with argon, neon, nitrogen, carbon and helium with 2 x 1015 cm-2 and 1 x 1016 cm-2 dose at energies varying from 20 to 150 keV at room temperature. In this work we showed that the surface hardness of the porous films can be improved five times as compared to the as-deposited porous films by implanting Ar with 1 x 10 16 cm-2 doses at 50 keV, sacrificing only a slight increase (˜15%) in dielectric constant (e.g., from 1.76 to 2.0). The hardness persists after 450°C annealing. The ion implantation process suppressed the moisture uptake in the porous low

  8. Dielectric function and magneto-optical Voigt constant of Cu2O: A combined spectroscopic ellipsometry and polar magneto-optical Kerr spectroscopy study

    NASA Astrophysics Data System (ADS)

    Haidu, Francisc; Fronk, Michael; Gordan, Ovidiu D.; Scarlat, Camelia; Salvan, Georgeta; Zahn, Dietrich R. T.

    2011-11-01

    Cuprous oxide is a highly interesting material for the emerging field of transparent oxide electronics. In this work the energy dispersion of the dielectric function of Cu2O bulk material is revised by spectroscopic ellipsometry measurements in an extended spectral range from 0.73 to 10 eV. For the first time, the magneto-optical Kerr effect was measured in the spectral range from 1.7 to 5.5 eV and the magneto-optical Voigt constant of Cu2O was obtained by numerical calculations from the magneto-optical Kerr effect spectra and the dielectric function.

  9. Theoretical Study of the Transverse Dielectric Constant of Superlattices and Their Alloys. Ph.D Thesis

    NASA Technical Reports Server (NTRS)

    Kahen, K. B.

    1986-01-01

    The optical properties of III to V binary and ternary compounds and GaAs-Al(x)Ga(1-x)As superlattices are determined by calculating the real and imaginary parts of the transverse dielectric constant. Emphasis is given to determining the influence of different material and superlattice parameters on the values of the index of refraction and absorption coefficient. In order to calculate the optical properties of a material, it is necessary to compute its electronic band structure. This was accomplished by introducing a partition band structure approach based on a combination of the vector k x vector p and nonlocal pseudopotential techniques. The advantages of this approach are that it is accurate, computationally fast, analytical, and flexible. These last two properties enable incorporation of additional effects into the model, such as disorder scattering, which occurs for alloy materials and excitons. Furthermore, the model is easily extended to more complex structures, for example multiple quantum wells and superlattices. The results for the transverse dielectric constant and absorption coefficient of bulk III to V compounds compare well with other one-electron band structure models and the calculations show that for small frequencies, the index of refraction is determined mainly by the contibution of the outer regions of the Brillouin zone.

  10. Porous AlN with a Low Dielectric Constant Synthesized Based on the Physical Vapor Transport Principle

    NASA Astrophysics Data System (ADS)

    Wang, Hua-Jie; Liu, Xue-Chao; Kong, Hai-Kuan; Xin, Jun; Gao, Pan; Shi, Er-Wei

    2016-07-01

    Porous AlN with low dielectric constant has been synthesized by the sacrificial template method based on the physical vapor transport principle. It is quite different from the traditional method that mixes the matrix with a pore-forming agent and utilizes liquid-phase sintering. The method consists of two parts. Firstly, AlN powder is placed in a graphite crucible. C/AlN composite can be formed by mixing decomposed AlN vapor and volatile carbon originated from a crucible at high temperature. Secondly, pores are formed after removing carbon from the C/AlN composite by an annealing process. The structure, morphology, porosity and properties of porous AlN are characterized. It is shown the obtained porous AlN has a thermal conductivity of 37.3 W/(m K) and a reduced dielectric constant of 5.5-6.1 (at 1 MHz). The porosity measured by a mercury porosimeter is 24.09%. It has been experimentally proved that porous AlN with a sufficiently porous structure and properties can be synthesized based on the vapor-phase principle.

  11. Study of Fluorine Addition Influence in the Dielectric Constant of Diamond-Like Carbon Thin Film Deposited by Reactive Sputtering

    NASA Astrophysics Data System (ADS)

    Trippe, S. C.; Mansano, R. D.

    The hydrogenated amorphous carbon films (a-C:H) or DLC (Diamond-Like Carbon) films are well known for exhibiting high electrical resistivity, low dielectric constant, high mechanical hardness, low friction coefficient, low superficial roughness and also for being inert. In this paper, we produced fluorinated DLC films (a-C:F), and studied the effect of adding CF4 on the above-mentioned properties of DLC films. These films were produced by a reactive RF magnetron sputtering system using a target of pure carbon in stable graphite allotrope. We performed measurements of electrical characteristic curves of capacitance as a function of applied tension (C-V) and current as a function of the applied tension (I-V). We showed the dielectric constant (k) and the resistivity (ρ) as functions of the CF4 concentration. On films with 65% CF4, we found that k = 2.7, and on films with 70% CF4, ρ = 12.3 × 1011 Ω cm. The value of the electrical breakdown field to films with 70% CF4 is 5.3 × 106 V/cm.

  12. Porous AlN with a Low Dielectric Constant Synthesized Based on the Physical Vapor Transport Principle

    NASA Astrophysics Data System (ADS)

    Wang, Hua-Jie; Liu, Xue-Chao; Kong, Hai-Kuan; Xin, Jun; Gao, Pan; Shi, Er-Wei

    2016-05-01

    Porous AlN with low dielectric constant has been synthesized by the sacrificial template method based on the physical vapor transport principle. It is quite different from the traditional method that mixes the matrix with a pore-forming agent and utilizes liquid-phase sintering. The method consists of two parts. Firstly, AlN powder is placed in a graphite crucible. C/AlN composite can be formed by mixing decomposed AlN vapor and volatile carbon originated from a crucible at high temperature. Secondly, pores are formed after removing carbon from the C/AlN composite by an annealing process. The structure, morphology, porosity and properties of porous AlN are characterized. It is shown the obtained porous AlN has a thermal conductivity of 37.3 W/(m K) and a reduced dielectric constant of 5.5-6.1 (at 1 MHz). The porosity measured by a mercury porosimeter is 24.09%. It has been experimentally proved that porous AlN with a sufficiently porous structure and properties can be synthesized based on the vapor-phase principle.

  13. Exploratory studies of new avenues to achieve high electromechanical response and high dielectric constant in polymeric materials

    NASA Astrophysics Data System (ADS)

    Huang, Cheng

    High performance soft electronic materials are key elements in advanced electronic devices for broad range applications including capacitors, actuators, artificial muscles and organs, smart materials and structures, microelectromechanical (MEMS) and microfluidic devices, acoustic devices and sensors. This thesis exploits new approaches to improve the electromechanical response and dielectric response of these materials. By making use of novel material phenomena such as large anisotropy in dipolar response in liquid crystals (LCs) and all-organic composites in which high dielectric constant organic solids and conductive polymers are either physically blended into or chemically grafted to a polymer matrix, we demonstrate that high dielectric constant and high electromechanical conversion efficiency comparable to that in ceramic materials can be achieved. Nano-composite approach can also be utilized to improve the performance of the electronic electroactive polymers (EAPs) and composites, for example, exchange coupling between the fillers and matrix with very large dielectric contrast can lead to significantly enhance the dielectric response as well as electromechanical response when the heterogeneity size of the composite is comparable to the exchange length. In addition to the dielectric composites, in which high dielectric constant fillers raise the dielectric constant of composites, conductive percolation can also lead to high dielectric constant in polymeric materials. An all-polymer percolative composite is introduced which exhibits very high dielectric constant (>7,000). The flexible all-polymer composites with a high dielectric constant make it possible to induce a high electromechanical response under a much reduced electric field in the field effect electroactive polymer (EAP) actuators (a strain of 2.65% with an elastic energy density of 0.18 J/cm3 can be achieved under a field of 16 V/mum). Agglomeration of the particles can also be effectively prevented

  14. Attenuation measurement of very low-loss dielectric waveguides by the cavity resonator method in the millimeter/submillimeter wavelength range

    NASA Astrophysics Data System (ADS)

    Shimabukuko, F. I.; Yeh, C.

    1989-03-01

    A dielectric waveguide shorted at both ends is constructed as a cavity resonator. By measuring the Q of this cavity, one can determine the attenuation constant of the guided mode on this dielectric structure. The complex permittivity of the dielectric waveguide material can also be derived from these measurements. Measurement were made at Ka-band for dielectric waveguides constructed of nonpolar, low-loss polymers such as Teflon, polypropylene, polyethylene, polyethylene, and Rexolite.

  15. Fundamentals of dielectric properties measurements and agricultural applications.

    PubMed

    Nelson, Stuart O

    2010-01-01

    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

  16. Stiff, strong, yet tough free-standing dielectric films of graphene nanosheets-polyurethane nanocomposites with very high dielectric constant and loss

    NASA Astrophysics Data System (ADS)

    Jan, Rahim; Habib, Amir; Gul, Iftikhar Hussain

    2016-01-01

    In this study, graphene nanosheets (GNS) prepared through a liquid exfoliation technique are dispersed in thermoplastic polyurethane (TPU) at a volume fraction (Vf) of up to 0.19. Then, the electrical and mechanical properties of the obtained composites are characterized. The dielectric spectroscopy shows an excessive variation in dielectric constant (1.1 to 3.53 × 107) and dielectric tangent loss (0.03 to 2515) with varying Vf over the frequency range of 25 kHz to 5 MHz. A considerable enhancement in electrical conductivity (DC) is found, from 3.87 × 10-10 S/m (base polymer) to 53.5 S/m for the 0.19 Vf GNS-TPU nanocomposite. The GNS-TPU composites are mechanically robust, with a considerable increase in stiffness (˜4-fold) and strength (almost twice), maintaining its ductility up to 0.09 Vf GNS. The high dielectric constant at lower frequencies is attributed to the well-established Maxwell-Wagner polarization effect, whereas the high dielectric tangent loss is due to leakage currents as a physical conducting network is formed at high filler loadings. The layered structure, high aspect ratio, and improved dispersion of GNS are the main reasons for the improvement in both the dielectric characteristics and the mechanical properties of the host polymer. [Figure not available: see fulltext.

  17. Spatially resolved dielectric constant of confined water and its connection to the non-local nature of bulk water.

    PubMed

    Schaaf, Christian; Gekle, Stephan

    2016-08-28

    We use molecular dynamics simulations to compute the spatially resolved static dielectric constant of water in cylindrical and spherical nanopores as occurring, e.g., in protein water pockets or carbon nanotubes. For this, we derive a linear-response formalism which correctly takes into account the dielectric boundary conditions in the considered geometries. We find that in cylindrical confinement, the axial component behaves similar as the local density akin to what is known near planar interfaces. The radial dielectric constant shows some oscillatory features when approaching the surface if their radius is larger than about 2 nm. Most importantly, however, the radial component exhibits pronounced oscillations at the center of the cavity. These surprising features are traced back quantitatively to the non-local dielectric nature of bulk water. PMID:27586940

  18. The change in dielectric constant, AC conductivity and optical band gaps of polymer electrolyte film: Gamma irradiation

    SciTech Connect

    Raghu, S. Subramanya, K. Sharanappa, C. Mini, V. Archana, K. Sanjeev, Ganesh Devendrappa, H.

    2014-04-24

    The effects of gamma (γ) irradiation on dielectric and optical properties of polymer electrolyte film were investigated. The dielectric constant and ac conductivity increases with γ dose. Also optical band gap decreased from 4.23 to 3.78ev after irradiation. A large dependence of the polymer properties on the irradiation dose was noticed. This suggests that there is a possibility of improving polymer electrolyte properties on gamma irradiation.

  19. Investigation on thermo-mechanical instability of porous low dielectric constant materials

    NASA Astrophysics Data System (ADS)

    Zin, Emil Hyunbae

    This study investigates the structural stability of porous low dielectric constant materials (PLK) under thermal and mechanical load and the influence of contributing factors including porosity as intrinsic factor and plasma damage and moisture absorption as extrinsic factors on thermo-mechanical instability of PLK in advanced Cu/PLK interconnects. For this purpose, a ball indentation creep test technique was developed to examine the thermal and mechanical instability of PLK at relevant load and temperature conditions in the interconnect structure. Our exploration with the ball indentation creep test found that PLK films plastically deforms with time, indicating that viscoplastic deformation does occur under relevant conditions of PLK processing. On the basis of the results that the increase of the indentation depth with time shows more noticeable difference in PLK films with higher porosity, plasma exposure, and moisture absorption, it is our belief that PLK stability is greatly affected by porosity, plasma damage and moisture. Viscous flow was found to be mechanism for the viscoplastic deformation at the temperature and load of real PLK integration processing. This finding was obtained from the facts that the kinetics of the indentation creep fit very well with the viscous flow model and the extracted stress exponent is close to unity. Based on the results of temperature dependence in all PLK films, the activation energy(~1.5eV) of the viscosity back calculated from the experimental value of the kinetics was found to be much small than that of a pure glass (> 4eV). This suggests that the viscous flow of PLK is controlled by chemical reaction happening in PLK matrix. The FT-IR measurement for the examination of chemical bond reconfiguration shows that the intensity of Si-OH bonds increases with the flow while that of Si-O-Si, -CHX and Si-CH 3 bonds decreases, indicating that chemical reactions are involved in the deformation process. From these findings, it is

  20. Electronic structure, optical dielectric constant and born effective charge of EuAlO3

    NASA Astrophysics Data System (ADS)

    Sakhya, Anup Pradhan; Dutta, Alo; Shannigrahi, Santiranjan; Sinha, TP

    2016-01-01

    EuAlO3 (EAO) is synthesized by the sol-gel process. The Rietveld refinement of the X-ray diffraction data shows that the material has orthorhombic structure with Pbnm space group. The density functional theory calculations are initiated with the experimental lattice parameters. The full potential linearized augmented plane wave method and projector augmented wave method are used to investigate the ground state properties of EAO. An indirect band gap of 1.8 eV is observed with the valence band maximum at the Γ point and the conduction band minimum at the R point. The X-ray photoemission spectroscopy (XPS) spectra of EAO are obtained in the energy window of 0-1000 eV. Using the electronic density of states, the valence band (VB) spectrum of EAO is generated and compared with the observed VB-XPS spectrum. The optical dielectric constant and the refractive index of the material are calculated for the photon energy radiation. The optical properties show a considerable anisotropy in the material. The Born effective charge of various elements and the dielectric tensor of EAO have been calculated.

  1. Segmental Dynamics and Dielectric Constant of Polysiloxane Polar Copolymers as Plasticizers for Polymer Electrolytes.

    PubMed

    Choi, U Hyeok; Liang, Siwei; Chen, Quan; Runt, James; Colby, Ralph H

    2016-02-10

    Dielectric relaxation spectroscopy was used to investigate the segmental dynamics of a series of siloxane-based polar copolymers combining pendant cyclic carbonates and short poly(ethylene oxide) (PEO) chains. The homopolymer with cyclic carbonate as the only side chain exhibits higher glass transition temperature Tg and dielectric constant εs than the one with only PEO side chains. For their copolymers the observed Tg (agreeing well with the predicted values from the Fox equation) and εs decrease with increasing PEO side chain content. These polar polymers exhibit a glassy β relaxation with Arrhenius character, attributed to local chain motions of side groups attached to the main chain, and a segmental α relaxation, associated with the glass transition with a Vogel temperature dependence. As PEO side chain content increases, narrowing of the local glassy β relaxation was observed in the copolymers. The segmental α dynamics were observed to be faster, with an increase in breadth and decrease in strength with increasing PEO side chain content. Owing to the trade-off between Tg and εs, copolymers of intermediate composition result in the highest ionic conductivity when these copolymers are used to plasticize Li single-ion conducting ionomers. PMID:26735584

  2. Skeletal silica characterization in porous-silica low-dielectric-constant films by infrared spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Takada, Syozo; Hata, Nobuhiro; Seino, Yutaka; Fujii, Nobutoshi; Kikkawa, Takamaro

    2005-06-01

    Porous-silica low-dielectric-constant (low-k) films were prepared using a sol-gel method based on the self-assembly of surfactant templates. No change in the refractive index at 633 nm nor in the infrared-absorption intensities of C-H and O-H stretching vibrations at around 2900 and 3400cm-1 of porous-silica low-k films were observed after annealing at each temperature from 523 to 723 K. On the other hand, the Young's elastic modulus and hardness increased with the increase of annealing temperature. The structure in the complex dielectric function of porous-silica low-k films observed in between 1000 and 1400cm-1 is assigned as the asymmetric stretching vibration mode of the Si-O-Si bond. By applying the effective-medium theory by Bruggeman to the experimental results from infrared spectroscopic ellipsometry, we analyzed the skeletal silica structures. The peak positions of transverse (ωTO) and longitudinal (ωLO) vibration modes for Si-O-Si network in the silica skeleton of porous-silica films changed from 1061 to 1068cm-1 and from 1219 to 1232cm-1, respectively, with the annealing temperature. It is shown that the ωLO2/ωTO2 of skeletal silica correlates with Young's elastic modulus of porous-silica low-k films.

  3. The effect of PECVD plasma decomposition on the wettability and dielectric constant changes in silicon modified DLC films for potential MEMS and low stiction applications

    SciTech Connect

    Ogwu, A. A.; Okpalugo, T. I. T.; McLaughlin, J. A. D.

    2012-09-15

    We have carried out investigations aimed at understanding the mechanism responsible for a water contact angle increase of up to ten degrees and a decrease in dielectric constant in silicon modified hydrogenated amorphous carbon films compared to unmodified hydrogenated amorphous carbon films. Our investigations based on surface chemical constituent analysis using Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), SIMS, FTIR, contact angle / surface energy measurements and spectroscopic ellipsometry suggests the presence of hydrophobic chemical entities on the surface of the films. This observation is consistent with earlier theoretical plasma chemistry predictions and observed Raman peak shifts in the films. These surface hydrophobic entities also have a lower polarizability than the bonds in the un-modified films thereby reducing the dielectric constant of the silicon modified films measured by spectroscopic ellipsometry. Ellipsometric dielectric constant measurement is directly related to the surface energy through Hamaker's constant. Our current finding is expected to be of benefit to understanding stiction, friction and lubrication in areas that range from nano-tribology to microfluidics.

  4. A Simple Method for Estimation of Dielectric Constants and Polarizabilities of Nonpolar and Slightly Polar Hydrocarbons

    NASA Astrophysics Data System (ADS)

    Panuganti, Sai R.; Wang, Fei; Chapman, Walter G.; Vargas, Francisco M.

    2016-07-01

    Many of the liquids that are used as electrical insulators are nonpolar or slightly polar petroleum-derived hydrocarbons, such as the ones used for cable and/or transformer oils. In this work, semi-empirical expressions with no adjustable parameters for the dielectric constant and the polarizability of nonpolar and slightly polar hydrocarbons and their mixtures are proposed and validated. The expressions that were derived using the Vargas-Chapman One-Third rule require the mass density and the molecular weight of the substance of interest. The equations were successfully tested for various hydrocarbons and polymers with dipole moments <0.23 and densities from 500 to 1200 kg\\cdot hbox {m}^{-3}. The predictions are in good agreement with the experimental data in a wide range of temperatures and pressures. The proposed expressions eliminate the need of extensive experimental data and require less input parameters compared to existing correlations.

  5. Dramatic increase in the oxygen reduction reaction for platinum cathodes from tuning the solvent dielectric constant.

    PubMed

    Fortunelli, Alessandro; Goddard, William A; Sha, Yao; Yu, Ted H; Sementa, Luca; Barcaro, Giovanni; Andreussi, Oliviero

    2014-06-23

    Hydrogen fuel cells (FC) are considered essential for a sustainable economy based on carbon-free energy sources, but a major impediment are the costs. First-principles quantum mechanics (density functional theory including solvation) is used to predict how the energies and barriers for the mechanistic steps of the oxygen reduction reaction (ORR) over the fcc(111) platinum surface depend on the dielectric constant of the solvent. The ORR kinetics can be strongly accelerated by decreasing the effective medium polarizability from the high value it has in water. Possible ways to realize this experimentally are suggested. The calculated volcano structure for the dependence of rate on solvent polarization is considered to be general, and should be observed in other electrochemical systems. PMID:24828005

  6. Determination of High-Frequency Dielectric Constant and Surface Potential of Graphene Oxide and Influence of Humidity by Kelvin Probe Force Microscopy.

    PubMed

    Salomão, Francisco C; Lanzoni, Evandro M; Costa, Carlos A; Deneke, Christoph; Barros, Eduardo B

    2015-10-20

    We use Kelvin probe force microscopy (KPFM) and capacitance coupling (dC/dz) to study the electrical properties of graphene oxide (GO). We propose using the dC/dz signal to probe the high frequency dielectric constant of mono- and few-layer GO. Our measurements suggest that the dynamic dielectric constant of GO is on the order of εGO ≅ 3.0 ε0, in the high frequency limit, and independent of the number of GO layers. The measurements are performed at a humidity controlled environment (5% of humidity). The effects of increasing humidity on both the dC/dz and KPFM measurements are analyzed. PMID:26393406

  7. Impact of electric-field dependent dielectric constants on two-dimensional electron gases in complex oxides

    SciTech Connect

    Peelaers, H.; Gordon, L.; Steiauf, D.; Janotti, A.; Van de Walle, C. G.; Krishnaswamy, K.; Sarwe, A.

    2015-11-02

    High-density two-dimensional electron gas (2DEG) can be formed at complex oxide interfaces such as SrTiO{sub 3}/GdTiO{sub 3} and SrTiO{sub 3}/LaAlO{sub 3}. The electric field in the vicinity of the interface depends on the dielectric properties of the material as well as on the electron distribution. However, it is known that electric fields can strongly modify the dielectric constant of SrTiO{sub 3} as well as other complex oxides. Solving the electrostatic problem thus requires a self-consistent approach in which the dielectric constant varies according to the local magnitude of the field. We have implemented the field dependence of the dielectric constant in a Schrödinger-Poisson solver in order to study its effect on the electron distribution in a 2DEG. Using the SrTiO{sub 3}/GdTiO{sub 3} interface as an example, we demonstrate that including the field dependence results in the 2DEG being confined closer to the interface compared to assuming a single field-independent value for the dielectric constant. Our conclusions also apply to SrTiO{sub 3}/LaAlO{sub 3} as well as other similar interfaces.

  8. FDR probe structure influence on the soil dielectric spectrum measurement

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The soil dielectric spectrum are related to the soil physical properties, and those are affected by the structure of the probe too. In order to determine how the probe structure influence the soil dielectric spectrum measurement, the two kinds of soils were measured at four water content level by 10...

  9. RF Field Enhancement with High Dielectric Constant (HDC) Pads in a Receive Array Coil at 3.0 T

    PubMed Central

    Yang, Qing X.; Luo, Wei; Rupprecht, Sebastian; Herse, Zachary; Sica, Christopher; Wang, Jianli; Cao, Zhipeng; Vesek, Jeffrey; Lanagan, Michael T.; Carluccio, Giuseppe; Ryu, Yeun-Chul; Collins, Christopher M.

    2012-01-01

    Purpose To investigate the use of a new high-dielectric constant (HDC) material for improving SNR and transmission efficiency for clinical MRI applications at 3T with cervical spine imaging. Materials and Methods Human subjects were imaged using a commercial cervical spine receive array coil on a clinical system with and without pads containing Barium Titanate beads in deuterium water placed around the neck. Numerical electromagnetic field simulations of the same configuration were also performed. Results Experimental and simulated maps of transmit and receive fields showed greater efficiency for imaging the cervical spine when the pads were present. Experimental measurements showed a significant improvement in SNR with the pads present and an average input power reduction of 46%. Conclusion Use of HDC material can enhance SNR and transmission efficiency for clinical imaging of the cervical spine at 3.0 T. PMID:23293090

  10. Enhanced Dielectric Constant for Efficient Electromagnetic Shielding Based on Carbon-Nanotube-Added Styrene Acrylic Emulsion Based Composite

    PubMed Central

    2010-01-01

    An efficient electromagnetic shielding composite based on multiwalled carbon nanotubes (MWCNTs)-filled styrene acrylic emulsion-based polymer has been prepared in a water-based system. The MWCNTs were demonstrated to have an effect on the dielectric constants, which effectively enhance electromagnetic shielding efficiency (SE) of the composites. A low conductivity threshold of 0.23 wt% can be obtained. An EMI SE of ~28 dB was achieved for 20 wt% MWCNTs. The AC conductivity (σac) of the composites, deduced from imaginary permittivity, was used to estimate the SE of the composites in X band (8.2–12.4 GHz), showing a good agreement with the measured results. PMID:20596498

  11. Enhanced dielectric constant for efficient electromagnetic shielding based on carbon-nanotube-added styrene acrylic emulsion based composite.

    PubMed

    Li, Yong; Chen, Changxin; Li, Jiang-Tao; Zhang, Song; Ni, Yuwei; Cai, Seng; Huang, Jie

    2010-01-01

    An efficient electromagnetic shielding composite based on multiwalled carbon nanotubes (MWCNTs)-filled styrene acrylic emulsion-based polymer has been prepared in a water-based system. The MWCNTs were demonstrated to have an effect on the dielectric constants, which effectively enhance electromagnetic shielding efficiency (SE) of the composites. A low conductivity threshold of 0.23 wt% can be obtained. An EMI SE of ~28 dB was achieved for 20 wt% MWCNTs. The AC conductivity (σac) of the composites, deduced from imaginary permittivity, was used to estimate the SE of the composites in X band (8.2-12.4 GHz), showing a good agreement with the measured results. PMID:20596498

  12. Mesostructured HfxAlyO2 Thin Films as Reliable and Robust Gate Dielectrics with Tunable Dielectric Constants for High-Performance Graphene-Based Transistors.

    PubMed

    Lee, Yunseong; Jeon, Woojin; Cho, Yeonchoo; Lee, Min-Hyun; Jeong, Seong-Jun; Park, Jongsun; Park, Seongjun

    2016-07-26

    We introduce a reliable and robust gate dielectric material with tunable dielectric constants based on a mesostructured HfxAlyO2 film. The ultrathin mesostructured HfxAlyO2 film is deposited on graphene via a physisorbed-precursor-assisted atomic layer deposition process and consists of an intermediate state with small crystallized parts in an amorphous matrix. Crystal phase engineering using Al dopant is employed to achieve HfO2 phase transitions, which produce the crystallized part of the mesostructured HfxAlyO2 film. The effects of various Al doping concentrations are examined, and an enhanced dielectric constant of ∼25 is obtained. Further, the leakage current is suppressed (∼10(-8) A/cm(2)) and the dielectric breakdown properties are enhanced (breakdown field: ∼7 MV/cm) by the partially remaining amorphous matrix. We believe that this contribution is theoretically and practically relevant because excellent gate dielectric performance is obtained. In addition, an array of top-gated metal-insulator-graphene field-effect transistors is fabricated on a 6 in. wafer, yielding a capacitance equivalent oxide thickness of less than 1 nm (0.78 nm). This low capacitance equivalent oxide thickness has important implications for the incorporation of graphene into high-performance silicon-based nanoelectronics. PMID:27355098

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

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

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

  14. Dielectric Loss Measurements on Raw Materials.

    ERIC Educational Resources Information Center

    Mwanje, J.

    1980-01-01

    Describes an experiment used to study dielectric properties of materials. Values of the dielectric loss tangent can be determined at low frequencies from Lissajous figures formed on an oscilloscope. Some mineral rock specimens show Debye-type relaxation peaks at frequencies in the region of 1 to 500 Hz. (Author/DS)

  15. Visualization of dielectric constant-electric field-temperature phase maps for imprinted relaxor ferroelectric thin films

    NASA Astrophysics Data System (ADS)

    Frederick, J. C.; Kim, T. H.; Maeng, W.; Brewer, A. A.; Podkaminer, J. P.; Saenrang, W.; Vaithyanathan, V.; Li, F.; Chen, L.-Q.; Schlom, D. G.; Trolier-McKinstry, S.; Rzchowski, M. S.; Eom, C. B.

    2016-03-01

    The dielectric phase transition behavior of imprinted lead magnesium niobate-lead titanate relaxor ferroelectric thin films was mapped as a function of temperature and dc bias. To compensate for the presence of internal fields, an external electric bias was applied while measuring dielectric responses. The constructed three-dimensional dielectric maps provide insight into the dielectric behaviors of relaxor ferroelectric films as well as the temperature stability of the imprint. The transition temperature and diffuseness of the dielectric response correlate with crystallographic disorder resulting from strain and defects in the films grown on strontium titanate and silicon substrates; the latter was shown to induce a greater degree of disorder in the film as well as a dielectric response lower in magnitude and more diffuse in nature over the same temperature region. Strong and stable imprint was exhibited in both films and can be utilized to enhance the operational stability of piezoelectric devices through domain self-poling.

  16. Stress measurements of planar dielectric elastomer actuators.

    PubMed

    Osmani, Bekim; Aeby, Elise A; Müller, Bert

    2016-05-01

    Dielectric elastomer actuator (DEA) micro- and nano-structures are referred to artificial muscles because of their specific continuous power and adequate time response. The bending measurement of an asymmetric, planar DEA is described. The asymmetric cantilevers consist of 1 or 5 μm-thin DEAs deposited on polyethylene naphthalate (PEN) substrates 16, 25, 38, or 50 μm thick. The application of a voltage to the DEA electrodes generates an electrostatic pressure in the sandwiched silicone elastomer layer, which causes the underlying PEN substrate to bend. Optical beam deflection enables the detection of the bending angle vs. applied voltage. Bending radii as large as 850 m were reproducibly detected. DEA tests with electric fields of up to 80 V/μm showed limitations in electrode's conductivity and structure failures. The actuation measurement is essential for the quantitative characterization of nanometer-thin, low-voltage, single- and multi-layer DEAs, as foreseen for artificial sphincters to efficiently treat severe urinary and fecal incontinence. PMID:27250436

  17. Measuring the cosmological constant with redshift surveys

    NASA Astrophysics Data System (ADS)

    Ballinger, W. E.; Peacock, J. A.; Heavens, A. F.

    1996-10-01

    It has been proposed that the cosmological constant {LAMBDA} might be measured from geometric effects on large-scale structure. A positive vacuum density leads to correlation function contours which are squashed in the radial direction when calculated assuming a matter-dominated model. We show that this effect will be somewhat harder to detect than previous calculations have suggested: the squashing factor is likely to be < 1.3, given realistic constraints on the matter contribution to {OMEGA}. Moreover, the geometrical distortion risks being confused with the redshift-space distortions caused by the peculiar velocities associated with the growth of galaxy clustering. These depend on the density and bias parameters via the combination β = {OMEGA}^0.6/b, and we show that the main practical effect of a geometrical flattening factor F is to simulate gravitational instability with B_eff_ ~ 0.5(F - 1). Nevertheless, with datasets of sufficient size it is possible to distinguish the two effects, We discuss in detail how this should be done, and give a maximum-likelihood method for extracting {LAMBDA} and βb from anisotropic power-spectrum data. New-generation redshift surveys of galaxies and quasars are potentially capable of detecting a non-zero vacuum density, if it exists at a cosmologically interesting level.

  18. Dielectric spectroscopy measurements for moisture prediction in vidalia onions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Microwave sensing offers an opportunity to determine nondestructively the amount of moisture in materials by sensing the dielectric properties of the material. Dielectric properties of Vidalia onions grown in southeastern Georgia were measured with an open-ended coaxial-line probe and network analyz...

  19. Effect of organic flux on the colossal dielectric constant of CaCu3Ti4O12 (CCTO)

    NASA Astrophysics Data System (ADS)

    Razdan, Vishnu; Singh, Abhishek; Arnold, Brad; Choa, Fow-Sen; Kelly, Lisa; Singh, N. B.

    2015-05-01

    We have used low temperature organics to achieve orientation of the grains of Ca2/3Cu3Ti4O12 (CCTO) compound to increase the resistivity. During the past fifteen years CCTO has been studied extensively for its performance as a dielectric capacitor. We have synthesized and grown large grains of pure Ca2/3Cu3Ti4O12 and doped compound, and studied the dielectric constant and resistivity. The grains were aligned by using a naphthalene-camphor eutectic. CCTO was mixed in the organic melt and oriented by the directional solidification method. This material has different characteristics than pure processed CCTO material. The effect of solidification conditions and its effect on the morphology and the dielectric constant, resistivity and loss tan delta of pure and doped CCTO are described in this article.

  20. Dynamics of a caged imidazolium cation-toward understanding the order-disorder phase transition and the switchable dielectric constant.

    PubMed

    Zhang, Xi; Shao, Xiu-Dan; Li, Si-Chao; Cai, Ying; Yao, Ye-Feng; Xiong, Ren-Gen; Zhang, Wen

    2015-03-18

    A molecular compass-like behaviour is found in a perovskite-type cage compound (HIm)2[KCo(CN)6] (HIm = imidazolium cation). The dynamic changes in the HIm cation from the static to rotating state along with the rearrangement of the host cage result in switchable and anisotropic dielectric constants. PMID:25579450

  1. Dipole correlation effects on the local field and the effective dielectric constant in composite dielectrics containing high-k inclusions.

    PubMed

    Allahyarov, Elshad; Löwen, Hartmut; Zhu, Lei

    2016-07-28

    Mixing dielectric polymers with high permittivity (high-k) inclusions can affect their electrical properties. In actuation applications of dielectric elastomers, the polarized inclusions generate additional volume polarization-related electrostriction. In energy storage applications, it is possible to store more energy in dielectric composites because of additional polarization of the inclusions and interfaces. However, mixing an electroactive polymer with high-k inclusions also brings several disadvantages. The expulsion of the field from the interior of high-k fillers and the presence of two poles on the filler surface along the applied field direction result in higher local fields EL near the inclusion poles. The resulting field enhancement lowers the breakdown field (Eb) threshold for the material and therefore compromises the actuation and energy storage capabilities of dielectric composites. To mitigate this issue, the dependence of EL on the morphology of inclusion distribution, the field localization effect in chained configurations, and the role of the dipole-dipole correlation effects in the enhancement of the dipolar field of inclusions are analyzed. We show that the dipolar correlation effects are strong in large inclusion composites and their contribution to the inclusion dipole moment μ and to the local fields EL can reach 30-50%. A new method for deriving the composite permittivity from the field EL distribution, based on a caged probe technique, is also presented. PMID:27357433

  2. Silicon Dioxide Film with Low Dielectric Constants using Liquid-Phase Deposition

    NASA Astrophysics Data System (ADS)

    Chanthamaly, Phonekeo; Arakawa, Taro; Haneji, Nobuo

    1999-10-01

    We propose a method which is advantageous for forming F bonds in the Si O network without any external energy assistance. This method can be used to grow SiO2 films in supersaturated fluorosilicic acid (H2SiF6) at room temperature. The dissociation reaction between H2SiF6 and H2O leads to the formation of silica and the deposition of SiO2 films on the surface of substrates. Because the reaction involves an aqueous acid which contains fluorine, F bonds are formed in the films naturally. The percentage of F atoms increased from 3.5 to 4.75% according to X-ray photoelectron sectroscopy (XPS) survey, and the F1S peak changed from 687.72 to 687.18 eV with an increase in concentration from 2.25 to 3.25 mol/l, respectively. In addition, due to the effect of F bonds inside the film, the dielectric constant also decreased from 3.7 to about 3. Atomic force microscopy (AFM) images showed that the surface roughness increased with increasing H2SiF6 concentration due to the attack of F; however, the maximum surface roghness was less than 0.5 nm.

  3. High-relative-dielectric-constant bismuth-niobium-oxide films prepared using Nb-rich precursor solution

    NASA Astrophysics Data System (ADS)

    Ariga, Tomoki; Inoue, Satoshi; Matsumoto, Shin; Onoue, Masatoshi; Miyasako, Takaaki; Tokumitsu, Eisuke; Shimoda, Tatsuya

    2015-09-01

    Various ceramic materials have been developed for electronic devices. Bismuth-niobium-oxide (BNO) films prepared by a chemical solution deposition (CSD) method have the cubic pyrochlore phase, high relative dielectric constant, and low tangent loss (tan δ). We found that a BNO cubic pyrochlore crystal was Nb-rich, even though its pyrochlore formula is A2B2O7. The crystallization temperature of BNO increased with increasing Nb ratio. The relative dielectric constants of BNO films were related to the Nb ratio in the precursor solution. The dielectric constant of the BNO films was 250 when the Bi and Nb ratios in BNO precursor solutions were 4 and 6, respectively, and the sintering temperature was 600 °C. In addition, the tan δ was less than 0.01 at 1 kHz, which is higher than the reported values of BNO systems despite using the CSD method. These results show that the properties of BNO films prepared by the CSD method were associated with the Nb ratio in the precursor solution. Furthermore, the dielectric characteristics indicated that the Nb-rich BNO films have potential applications in electronic devices.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  5. Optical constants, dispersion energy parameters and dielectric properties of ultra-smooth nanocrystalline BiVO4 thin films prepared by rf-magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Sarkar, S.; Das, N. S.; Chattopadhyay, K. K.

    2014-07-01

    BiVO4 thin films have been prepared through radio frequency (rf) magnetron sputtering of a pre-fabricated BiVO4 target on ITO coated glass (ITO-glass) substrate and bare glass substrates. BiVO4 target material was prepared through solid-state reaction method by heating Bi2O3 and V2O5 mixture at 800 °C for 8 h. The films were characterized by X-ray diffraction, UV-Vis spectroscopy, LCR meter, field emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy. BiVO4 thin films deposited on the ITO-glass substrate are much smoother compared to the thin films prepared on bare glass substrate. The rms surface roughness calculated from the AFM images comes out to be 0.74 nm and 4.2 nm for the films deposited on the ITO-glass substrate and bare glass substrate for the deposition time 150 min respectively. Optical constants and energy dispersion parameters of these extra-smooth BiVO4 thin films have been investigated in detail. Dielectric properties of the BiVO4 thin films on ITO-glass substrate were also investigated. The frequency dependence of dielectric constant of the BiVO4 thin films has been measured in the frequency range from 20 Hz to 2 MHz. It was found that the dielectric constant increased from 145 to 343 at 20 Hz as the film thickness increased from 90 nm to 145 nm (deposition time increased from 60 min to 150 min). It shows higher dielectric constant compared to the literature value of BiVO4.

  6. Analysis of the Dielectric constant of saline-alkali soils and the effect on radar backscattering coefficient: a case study of soda alkaline saline soils in Western Jilin Province using RADARSAT-2 data.

    PubMed

    Li, Yang-yang; Zhao, Kai; Ren, Jian-hua; Ding, Yan-ling; Wu, Li-li

    2014-01-01

    Soil salinity is a global problem, especially in developing countries, which affects the environment and productivity of agriculture areas. Salt has a significant effect on the complex dielectric constant of wet soil. However, there is no suitable model to describe the variation in the backscattering coefficient due to changes in soil salinity content. The purpose of this paper is to use backscattering models to understand behaviors of the backscattering coefficient in saline soils based on the analysis of its dielectric constant. The effects of moisture and salinity on the dielectric constant by combined Dobson mixing model and seawater dielectric constant model are analyzed, and the backscattering coefficient is then simulated using the AIEM. Simultaneously, laboratory measurements were performed on ground samples. The frequency effect of the laboratory results was not the same as the simulated results. The frequency dependence of the ionic conductivity of an electrolyte solution is influenced by the ion's components. Finally, the simulated backscattering coefficients measured from the dielectric constant with the AIEM were analyzed using the extracted backscattering coefficient from the RADARSAT-2 image. The results show that RADARSAT-2 is potentially able to measure soil salinity; however, the mixed pixel problem needs to be more thoroughly considered. PMID:25101317

  7. Analysis of the Dielectric Constant of Saline-Alkali Soils and the Effect on Radar Backscattering Coefficient: A Case Study of Soda Alkaline Saline Soils in Western Jilin Province Using RADARSAT-2 Data

    PubMed Central

    Li, Yang-yang; Zhao, Kai; Ren, Jian-hua; Ding, Yan-ling; Wu, Li-li

    2014-01-01

    Soil salinity is a global problem, especially in developing countries, which affects the environment and productivity of agriculture areas. Salt has a significant effect on the complex dielectric constant of wet soil. However, there is no suitable model to describe the variation in the backscattering coefficient due to changes in soil salinity content. The purpose of this paper is to use backscattering models to understand behaviors of the backscattering coefficient in saline soils based on the analysis of its dielectric constant. The effects of moisture and salinity on the dielectric constant by combined Dobson mixing model and seawater dielectric constant model are analyzed, and the backscattering coefficient is then simulated using the AIEM. Simultaneously, laboratory measurements were performed on ground samples. The frequency effect of the laboratory results was not the same as the simulated results. The frequency dependence of the ionic conductivity of an electrolyte solution is influenced by the ion's components. Finally, the simulated backscattering coefficients measured from the dielectric constant with the AIEM were analyzed using the extracted backscattering coefficient from the RADARSAT-2 image. The results show that RADARSAT-2 is potentially able to measure soil salinity; however, the mixed pixel problem needs to be more thoroughly considered. PMID:25101317

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

    NASA Astrophysics Data System (ADS)

    Francisca, Franco M.; Montoro, Marcos A.

    2012-05-01

    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%).

  9. Critical interparticle distance for the remarkably enhanced dielectric constant of BaTiO3-Ag hybrids filled polyvinylidene fluoride composites

    NASA Astrophysics Data System (ADS)

    Luo, Suibin; Yu, Shuhui; Fang, Fang; Lai, Maobai; Sun, Rong; Wong, Ching-Ping

    2014-06-01

    Discrete nano Ag-deposited BaTiO3 (BT-Ag) hybrids with varied Ag content were synthesized, and the hybrids filled polyvinylidene fluoride (PVDF) composites were prepared. The effect of Ag content on the dielectric properties of the composites were analyzed based on the diffused electrical double layer theory. Results showed that with a higher Ag content in BT-Ag hybrids, the dielectric constant of BT-Ag/PVDF composites increases fast with the filler loading, while the dielectric loss and conductivity showed a suppressed and moderate increase. The dielectric constant of BT-0.61Ag/PVDF (61 wt. % of Ag in BT-Ag hybrid) composites reached 613, with the dielectric loss of 0.29 at 1 kHz. It was deduced that remarkably enhanced dielectric constant appeared when the interparticle distance decreased to a critical value of about 20 nm.

  10. Technique for Performing Dielectric Property Measurements at Microwave Frequencies

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

  11. Corrosion in low dielectric constant Si-O based thin films: Buffer concentration effects

    SciTech Connect

    Zeng, F. W.; Lane, M. W.; Gates, S. M.

    2014-05-15

    Organosilicate glass (OSG) is often used as an interlayer dielectric (ILD) in high performance integrated circuits. OSG is a brittle material and prone to stress-corrosion cracking reminiscent of that observed in bulk glasses. Of particular concern are chemical-mechanical planarization techniques and wet cleans involving solvents commonly encountered in microelectronics fabrication where the organosilicate film is exposed to aqueous environments. Previous work has focused on the effect of pH, surfactant, and peroxide concentration on the subcritical crack growth of these films. However, little or no attention has focused on the effect of the conjugate acid/base concentration in a buffer. Accordingly, this work examines the “strength” of the buffer solution in both acidic and basic environments. The concentration of the buffer components is varied keeping the ratio of acid/base and therefore pH constant. In addition, the pH was varied by altering the acid/base ratio to ascertain any additional effect of pH. Corrosion tests were conducted with double-cantilever beam fracture mechanics specimens and fracture paths were verified with ATR-FTIR. Shifts in the threshold fracture energy, the lowest energy required for bond rupture in the given environment, G{sub TH}, were found to shift to lower values as the concentration of the base in the buffer increased. This effect was found to be much larger than the effect of the hydroxide ion concentration in unbuffered solutions. The results are rationalized in terms of the salient chemical bond breaking process occurring at the crack tip and modeled in terms of the chemical potential of the reactive species.

  12. Double-stacked dielectric resonator for sensitive EPR measurements.

    PubMed

    Jaworski, M; Sienkiewicz, A; Scholes, C P

    1997-01-01

    A new approximate method for predicting the resonant frequencies and for solving the field distribution problem of a cylindrical dielectric resonator (DR) is developed. The model proposed in this paper bridges the gap between rigorous and accurate finite-element or Green function-based numerical methods on the one hand and on the other hand, simple approximate solutions in which the field distribution can be described analytically, but the resulting frequency is accurate within a few percent only. In the method described here, the approximate solution for the microwave field distribution is modified by substituting different values of the radial separation constants inside and outside of the diskshaped DR. The model is generalized for the double-stacked DR structure and enables one to introduce corrections that take into account the presence of the shielding walls and of the cylindrical sample hole. Good agreement is found between experimental and calculated results for both the single and double-stacked structures that are designed around commercially available X-band DRs (9-10 GHz). For the resonant frequency of the lowest transverse-electric TEzero1 delta mode that is commonly used for EPR measurements, the accuracy of the method is better than 1%. Experimentally measured resonator filling factors are also in good agreement with those theoretically estimated. Both the theory and the experimental results suggest that the double-stacked DR structure with finite spacing between the ceramic cylinders is the most suitable for EPR measurements of long lossy samples. PMID:9169212

  13. New Dielectric Measurement Data to Determine the Permittivity of Seawater at 1.4313 Hz

    NASA Technical Reports Server (NTRS)

    Lang, R.; Zhou, Y.; Utku, C.; Levine, D.

    2012-01-01

    This paper describes the new measurements - made in 2010-2011 - of the dielectric constant of seawater at 1.413 GHz using a resonant cavity technique. The purpose of these measurements is to develop an accurate relationship concerning the dependence of the dielectric constant of seawater on temperature and salinity for use by the Aquarius inversion algorithm. Aquarius is a NASA/CONAE satellite mission launched in June of 2011 with the primary mission of measuring global sea surface salinity with a 1.413 GHz radiometer to an accuracy of 0.2 psu. A brass microwave cavity resonant at 1.413 GHz has been used to measure the dielectric constant of seawater. The seawater is introduced into the cavity through a capillary glass tube having an inner diameter of 0.1 mm. The change of resonant frequency and the cavity Q value are used to determine the real and imaginary parts of the dielectric constant of seawater. Measurements are automated with Visual Basic software developed at the George Washington University. In this paper, new results from measurements made since September 2010 will be presented for salinities of 30, 35 and 38 psu with a temperature range of 0 C to 35 C in intervals of 5 C. These measurements are more accurate than earlier measurements made in 2008. The new results will be compared to the Klein-Swift (KS) and Meissner-Wentz (MW) model functions. The importance of an accurate model function will be illustrated by using these model functions to invert the Aquarius brightness temperature to retrieve the salinity values. The salinity values will be compared to co-located in situ data collected by Argo buoys.

  14. Anomalous change in dielectric constant of CaCu{sub 3}Ti{sub 4}O{sub 12} under violet-to-ultraviolet irradiation

    SciTech Connect

    Masingboon, C.; Eknapakul, T.; Suwanwong, S.; Buaphet, P.; Nakajima, H.; Mo, S.-K.; Thongbai, P.; King, P. D. C.; Maensiri, S.; Meevasana, W.

    2013-05-20

    The influence of light illumination on the dielectric constant of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) polycrystals is studied in this work. When exposed to 405-nm laser light, a reversible enhancement in the room temperature capacitance as high as 22% was observed, suggesting application of light-sensitive capacitance devices. To uncover the microscopic mechanisms mediating this change, we performed electronic structure measurements, using photoemission spectroscopy, and measured the electrical conductivity of the CCTO samples under different conditions of light exposure and oxygen partial pressure. Together, these results suggest that the large capacitance enhancement is driven by oxygen vacancies induced by the irradiation.

  15. Molten salt synthesis of nanocrystalline phase of high dielectric constant material CaCu3Ti4O12.

    PubMed

    Prakash, B Shri; Varma, K B R

    2008-11-01

    Nanocrystalline powders of giant dielectric constant material, CaCu3Ti4O12 (CCTO), have been prepared successfully by the molten salt synthesis (MSS) using KCl at 750 degrees C/10 h, which is significantly lower than the calcination temperature (approximately 1000 degrees C) that is employed to obtain phase pure CCTO in the conventional solid-state reaction route. The water washed molten salt synthesized powder, characterized by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM) confirmed to be a phase pure CCTO associated with approximately 150 nm sized crystallites of nearly spherical shape. The decrease in the formation temperature/duration of CCTO in MSS method was attributed to an increase in the diffusion rate or a decrease in the diffusion length of reacting ions in the molten salt medium. As a consequence of liquid phase sintering, pellets of as-synthesized KCl containing CCTO powder exhibited higher sinterability and grain size than that of KCl free CCTO samples prepared by both MSS method and conventional solid-state reaction route. The grain size and the dielectric constant of KCl containing CCTO ceramics increased with increasing sintering temperature (900 degrees C-1050 degrees C). Indeed the dielectric constants of these ceramics were higher than that of KCl free CCTO samples prepared by both MSS method and those obtained via the solid-state reaction route and sintered at the same temperature. Internal barrier layer capacitance (IBLC) model was invoked to correlate the observed dielectric constant with the grain size in these samples. PMID:19198302

  16. Dielectric constant and low-frequency infrared spectra for liquid water and ice Ih within the E3B model

    SciTech Connect

    Shi, L.; Ni, Y.; Drews, S. E. P.; Skinner, J. L.

    2014-08-28

    Two intrinsic difficulties in modeling condensed-phase water with conventional rigid non-polarizable water models are: reproducing the static dielectric constants for liquid water and ice Ih, and generating the peak at about 200 cm{sup −1} in the low-frequency infrared spectrum for liquid water. The primary physical reason for these failures is believed to be the missing polarization effect in these models, and consequently various sophisticated polarizable water models have been developed. However, in this work we pursue a different strategy and propose a simple empirical scheme to include the polarization effect only on the dipole surface (without modifying a model's intermolecular interaction potential). We implement this strategy for our explicit three-body (E3B) model. Our calculated static dielectric constants and low-frequency infrared spectra are in good agreement with experiment for both liquid water and ice Ih over wide temperature ranges, albeit with one fitting parameter for each phase. The success of our modeling also suggests that thermal fluctuations about local minima and the energy differences between different proton-disordered configurations play minor roles in the static dielectric constant of ice Ih. Our analysis shows that the polarization effect is important in resolving the two difficulties mentioned above and sheds some light on the origin of several features in the low-frequency infrared spectra for liquid water and ice Ih.

  17. Low-dielectric-constant fluorinated diamond-like carbon thin films by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Yi, Jeong Woo

    Fluorinated amorphous carbon (a-C:F) thin films are developed for a low dielectric constant interlayer dielectric material from hexafluorobenze (C 6F6) or 1,1,1,2-tetrafluoroethane (FCH2CF 4) as the source gas and argon as the diluent gas in an asymmetric capacitively coupled rf (radio frequency) plasma reactor and an inductively coupled plasma reactor. Effects of input rf power, fluorination, applied bias voltage and post annealing on the properties of a-C:F films are investigated. For depositing a-C:F films from highly diluted C6F6 (3%) and argon (97%) in the capacitively rf plasma reactor at 150 mTorr, the dielectric constant of the film increases from 2.0 to 2.8 as the rf power is increased from 10 W to 70 W, while the optical energy gap decreases from 2.6 eV to 1.9 eV and the transparency in a ultra-violet range is degraded. At input power of 100 W, the deposited film exhibits high residual stress of 40 MPa and easily peeled off by a Scotch tape test. This is due to high self-bias voltage (-230 V) developed at the substrate holder during deposition. When depositing amorphous carbon films from tetrafluoroethane (TFE) and methane in the capacitively coupled plasma reactor, the incorporation of fluorine in the film is increased with increasing TFE fraction in the feed gas mixture. The dielectric constant of the a-C:F film deposited from pure TFE is as low as 2.3, but the film exhibits poor thermal stability while a-C:H (diamond-like carbon) film deposited from pure methane has a dielectric constant of 3.8 and shows good thermal stability up to 400°C. As the TFE content in the feed is increased, the dielectric constant and the refractive index decrease while the transparency of the film is enhanced significantly. When depositing a-C:F films from C6F6 (4 sccm) and Ar (5 sccm) in the inductively coupled rf plasma reactor, the bias voltage (from a separate 100 KHz source) applied to the substrate holder affects the film properties significantly. As the negative bias

  18. SILC decay in La 2O 3 gate dielectrics grown on Ge substrates subjected to constant voltage stress

    NASA Astrophysics Data System (ADS)

    Rahman, M. S.; Evangelou, E. K.; Androulidakis, I. I.; Dimoulas, A.; Mavrou, G.; Galata, S.

    2010-09-01

    The effect of constant voltage stress (CVS) on Pt/La 2O 3/ n-Ge MOS devices biased at accumulation is investigated and reported. It is found that the stress induced leakage current (SILC) initially increases due to electron charge trapping on pre-existing bulk oxide defects. After 10 s approximately, a clear decay of SILC commences which follows a t-n power law, with n lying between 0.56 and 0.75. This decay of SILC is not changed or reversed when the stressing voltage stops for short time intervals. The effect is attributed to the creation of new positively charged defects in the oxide because of the applied stressing voltage, while other mechanism such as dielectric relaxation proposed in the past is proved insufficient to explain the experimental data. Also high frequency capacitance vs. gate voltage ( C- V g) curves measured under different CVS conditions divulge the creation of defects and charge trapping characteristics of La 2O 3 preciously. At low CVS exemplify the generation positively charged defects, however at higher CVS charge trapping obeys a model that was previously proposed and is a continuous distribution of traps.

  19. Resonant ultrasound spectroscopy for elastic constant measurements

    SciTech Connect

    Dixon, R.D.; Migliori, A.; Roe, L.H.

    1993-12-31

    All objects exhibit vibrational resonances when mechanically excited. These resonant frequencies are determined by density, geometry, and elastic moduli. Resonant ultrasound spectroscopy (RUS) takes advantage of the known relationship between the parameters. In particular, for a freely suspended object, with three of the four parameters (vibrational spectra, density, geometry, or elastic moduli) known the remaining one can be calculated. From a materials characterization standpoint it is straight-forward to measure density and geometry but less so to measure all the elastic moduli. It has recently become possible to quickly and accurately measure vibrational spectra, and using code written at Los Alamos, calculate all the elastic moduli simultaneously. This is done to an accuracy of better than one percent for compression and 0.1 percent for shear. RUS provides rapid acquisition of materials information here-to-fore obtainable only with difficulty. It will greatly facilitate the use of real materials properties in models and thus make possible more realistic modeling results. The technique is sensitive to phase changes and microstructure. This offers a change to input real data into microstructure and phase change models. It will also enable measurement of moduli at locations in and about a weld thus providing information for a validating coupled thermomechanical calculations.

  20. Ellipsometric method for the measurement of temperature and optical constants of incandescent transition metals.

    PubMed

    Hansen, G P; Krishnan, S; Hauge, R H; Margrave, J L

    1989-05-15

    The development of a unique noncontact temperature measurement device utilizing rotating analyzer ellipsometry is described. The technique circumvents the necessity of spectral emissivity estimation by direct measurement concomitant with radiance brightness. Simultaneous determinations of dielectric constants and refractive indices allow changes in the physical and chemical state of a heated surface to be monitored. The results of optical property measurements at 633 nm as functions of temperature between 1000 and 2500 K for eight transition metals including Hf, Ir, Mo, Nb, Pd, Pt, Ta, and V are presented together with preliminary results of oxidation studies on iridium. PMID:20548762

  1. Ellipsometric method for the measurement of temperature and optical constants of incandescent transition metals

    NASA Technical Reports Server (NTRS)

    Hansen, George P.; Krishnan, Shankar; Hauge, Robert H.; Margrave, John L.

    1989-01-01

    The development of a unique noncontact temperature measurement device utilizing rotating analyzer ellipsometry is described. The technique circumvents the necessity of spectral emissivity estimation by direct measurement concomitant with radiance brightness. Simultaneous determinations of dielectric constants and refractive indices allow changes in the physical and chemical state of a heated surface to be monitored. The results of optical property measurements at 633 nm as functions of temperature between 1000 and 2500 K for eight transition metals including Hf, Ir, Mo, Nb, Pd, Pt, Ta, and V are presented together with preliminary results of oxidation studies on iridium.

  2. The electro-mechanical phase transition of Gent model dielectric elastomer tube with two material constants

    NASA Astrophysics Data System (ADS)

    Liu, Liwu; Luo, Xiaojian; Fei, Fan; Wang, Yixing; Leng, Jinsong; Liu, Yanju

    2013-04-01

    Applied to voltage, a dielectric elastomer membrane may deform into a mixture of two states under certain conditions. One of which is the flat state and the other is the wrinkled state. In the flat state, the membrane is relatively thick with a small area, while on the contrary, in the wrinkled state, the membrane is relatively thin with a large area. The coexistence of these two states may cause the electromechanical phase transition of dielectric elastomer. The phase diagram of idea dielectric elastomer membrane under unidirectional stress and voltage inspired us to think about the liquid-to-vapor phase transition of pure substance. The practical working cycle of a steam engine includes the thermodynamical process of liquid-to-vapor phase transition, the fact is that the steam engine will do the maximum work if undergoing the phase transition process. In this paper, in order to consider the influence of coexistent state of dielectric elastomer, we investigate the homogeneous deformation of the dielectric elastomer tube. The theoretical model is built and the relationship between external loads and stretch are got, we can see that the elastomer tube experiences the coexistent state before reaching the stretching limit from the diagram. We think these results can guide the design and manufacture of energy harvesting equipments.

  3. Planck’s constant as a natural unit of measurement

    NASA Astrophysics Data System (ADS)

    Quincey, Paul

    2013-09-01

    The proposed revision of SI units would embed Planck’s constant into the definition of the kilogram, as a fixed constant of nature. Traditionally, Planck’s constant is not readily interpreted as the size of something physical, and it is generally only encountered by students in the mathematics of quantum physics. Richard Feynman’s path integral formulation of quantum mechanics allows a neat visualization of the constant as the circumference of a surveyor’s wheel for measuring action along each path, making Planck’s constant a natural yardstick, almost literally. This approach is shown to have other benefits in the presentation of other basic quantum phenomena.

  4. Assembly of a high-dielectric constant thin TiOx layer directly on H-terminated semiconductor diamond

    NASA Astrophysics Data System (ADS)

    Zhao, Jing; Liu, Jiangwei; Sang, Liwen; Liao, Meiyong; Coathup, David; Imura, Masataka; Shi, Baogui; Gu, Changzhi; Koide, Yasuo; Ye, Haitao

    2016-01-01

    A high-dielectric constant (high-k) TiOx thin layer was fabricated on hydrogen-terminated diamond (H-diamond) surface by low temperature oxidation of a thin titanium layer in ambient air. The metallic titanium layer was deposited by sputter deposition. The dielectric constant of the resultant TiOx was calculated to be around 12. The capacitance density of the metal-oxide-semiconductor (MOS) based on the TiOx/H-diamond was as high as 0.75 μF/cm2 contributed from the high-k value and the very thin thickness of the TiOx layer. The leakage current was lower than 10-13 A at reverse biases and 10-7A at the forward bias of -2 V. The MOS field-effect transistor based on the high-k TiOx/H-diamond was demonstrated. The utilization of the high-k TiOx with a very thin thickness brought forward the features of an ideally low subthreshold swing slope of 65 mV per decade and improved drain current at low gate voltages. The advantages of the utilization high-k dielectric for diamond metal-oxide semiconductor field effect transistors are anticipated.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    SciTech Connect

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

    2012-06-01

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

  7. Four-probe methods for measurement of piezoresistance constants

    SciTech Connect

    Lyubimskii, V.M.; Semenov, A.I.

    1987-08-01

    Methods are described for simultaneous measurement of longitudinal and transverse piezoresistance constants, as well as measurement of the relative change in resistivity under deformation. The methods presented are simple and quicker than traditional four-probe methods.

  8. Cathode fall measurement in a dielectric barrier discharge in helium

    SciTech Connect

    Hao, Yanpeng; Zheng, Bin; Liu, Yaoge

    2013-11-15

    A method based on the “zero-length voltage” extrapolation is proposed to measure cathode fall in a dielectric barrier discharge. Starting, stable, and discharge-maintaining voltages were measured to obtain the extrapolation zero-length voltage. Under our experimental conditions, the “zero-length voltage” gave a cathode fall of about 185 V. Based on the known thickness of the cathode fall region, the spatial distribution of the electric field strength in dielectric barrier discharge in atmospheric helium is determined. The strong cathode fall with a maximum field value of approximately 9.25 kV/cm was typical for the glow mode of the discharge.

  9. Investigation of temperature dependent dielectric constant of a sputtered TiN thin film by spectroscopic ellipsometry

    SciTech Connect

    Tripura Sundari, S. Ramaseshan, R.; Jose, Feby; Dash, S.; Tyagi, A. K.

    2014-01-21

    The temperature dependence of optical constants of titanium nitride thin film is investigated using Spectroscopic Ellipsometry (SE) between 1.4 and 5 eV in the temperature range of 300 K to 650 K in steps of 50 K. The real and imaginary parts of the dielectric functions ε{sub 1}(E) and ε{sub 2}(E) marginally increase with increase in temperature. A Drude Lorentz dielectric analysis based on free electron and oscillator model are carried out to describe the temperature behavior. With increase in temperature, the unscreened plasma frequency and broadening marginally decreased and increased, respectively. The parameters of the Lorentz oscillator model also showed that the relaxation time decreased with temperature while the oscillator energies increased. This study shows that owing to the marginal change in the refractive index with temperature, titanium nitride can be employed for surface plasmon sensor applications even in environments where rise in temperature is imminent.

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

    SciTech Connect

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

    1996-12-31

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

  11. Dielectric measurement using an open ended coaxial line with an extended center conductor

    NASA Technical Reports Server (NTRS)

    Wegmueller, Urs; Guerra, Abel G.

    1992-01-01

    Permittivity may be determined by measuring the complex reflection coefficient of an open-ended coaxial line placed in contact with a test sample. This method works best for liquid samples. For the measurement of non-liquid materials problems can arise. A perfect preparation is needed to provide a good contact between the tip and the dielectric medium. At times, the dimension of the sensor cannot be freely chosen, as is the case for the measurement of the dielectric constant of the xylem layer of a living tree. The influence of the installation of the sensor on a tree's water status must be minimized by using a small sensor. In such cases the capacitance cannot be optimized. By extending the center conductor of the open-ended coaxial line, some of these problems can be avoided. This provides an additional tool to tune the capacitance of the sensor by adjusting the length of the extension. Therefore the measurement accuracy can be optimized. The sensor also becomes sensitive to a larger volume. A comparative study of a flush and extended tipped probes shows that the ability to measure the dielectric constant of trees has been notably increased due to the extension of the center conductor.

  12. Tuning of colossal dielectric constant in gold-polypyrrole composite nanotubes using in-situ x-ray diffraction techniques

    SciTech Connect

    Sarma, Abhisakh; Sanyal, Milan K.

    2014-09-15

    In-situ x-ray diffraction technique has been used to study the growth process of gold incorporated polypyrrole nanotubes that exhibit colossal dielectric constant due to existence of quasi-one-dimensional charge density wave state. These composite nanotubes were formed within nanopores of a polycarbonate membrane by flowing pyrrole monomer from one side and mixture of ferric chloride and chloroauric acid from other side in a sample cell that allows collection of x-ray data during the reaction. The size of the gold nanoparticle embedded in the walls of the nanotubes was found to be dependent on chloroauric acid concentration for nanowires having diameter more than 100 nm. For lower diameter nanotubes the nanoparticle size become independent of chloroauric acid concentration and depends on the diameter of nanotubes only. The result of this study also shows that for 50 nm gold-polypyrrole composite nanotubes obtained with 5.3 mM chloroauric acid gives colossal dielectric constant of about 10{sup 7}. This value remain almost constant over a frequency range from 1Hz to 10{sup 6} Hz even at 80 K temperature.

  13. Structural origins of high apparent dielectric constants experienced by ionizable groups in the hydrophobic core of a protein

    PubMed Central

    Chimenti, Michael S.; Castaneda, Carlos A.; Majumdar, Ananya; Bertrand Garcia-Moreno, E.

    2012-01-01

    The side chains of Lys-66, Asp-66, and Glu-66 in staphylococcal nuclease (SNase) are fully buried and surrounded mainly by hydrophobic matter, save for internal water molecules associated with carboxylic oxygen atoms. These ionizable side chains titrate with pKa values of 5.7, 8.8 and 8.9, respectively. To reproduce these pKa values with continuum electrostatics calculations the protein has to be treated with high dielectric constants. We have examined structural origins of these high apparent dielectric constants by using NMR spectroscopy to characterize the structural response to the ionization of these internal side chains. Substitution of Val-66 with Lys-66 and Asp-66 led to increased conformational fluctuations in the microenvironments surrounding these groups, even under conditions of pH where Lys-66 and Asp-66 are neutral. When Lys-66, Asp-66 and Glu-66 are charged the proteins remain almost fully folded but resonances for a few backbone amides adjacent to the internal ionizable residues are broadened. This suggests that the ionization of the internal groups promotes a local increase in dynamics on the intermediate timescale, consistent with either partial unfolding or increased backbone fluctuations in helix-1 near residue 66, or, less likely, with increased fluctuations of the charges side chains at position 66. These experiments confirm that the high apparent dielectric constants reported by the internal Lys-66, Asp-66 and Glu-66 reflect localized changes in conformational fluctuations without incurring detectable, global structural reorganization. To improve structure-based pKa calculations in proteins this coupling between ionization of internal groups and local changes in conformational fluctuations will have to be treated explicitly. PMID:21059359

  14. The effect of concentration- and temperature-dependent dielectric constant on the activity coefficient of NaCl electrolyte solutions

    SciTech Connect

    Valiskó, Mónika; Boda, Dezső

    2014-06-21

    Our implicit-solvent model for the estimation of the excess chemical potential (or, equivalently, the activity coefficient) of electrolytes is based on using a dielectric constant that depends on the thermodynamic state, namely, the temperature and concentration of the electrolyte, ε(c, T). As a consequence, the excess chemical potential is split into two terms corresponding to ion-ion (II) and ion-water (IW) interactions. The II term is obtained from computer simulation using the Primitive Model of electrolytes, while the IW term is estimated from the Born treatment. In our previous work [J. Vincze, M. Valiskó, and D. Boda, “The nonmonotonic concentration dependence of the mean activity coefficient of electrolytes is a result of a balance between solvation and ion-ion correlations,” J. Chem. Phys. 133, 154507 (2010)], we showed that the nonmonotonic concentration dependence of the activity coefficient can be reproduced qualitatively with this II+IW model without using any adjustable parameter. The Pauling radii were used in the calculation of the II term, while experimental solvation free energies were used in the calculation of the IW term. In this work, we analyze the effect of the parameters (dielectric constant, ionic radii, solvation free energy) on the concentration and temperature dependence of the mean activity coefficient of NaCl. We conclude that the II+IW model can explain the experimental behavior using a concentration-dependent dielectric constant and that we do not need the artificial concept of “solvated ionic radius” assumed by earlier studies.

  15. Measuring Boltzmann's Constant with Carbon Dioxide

    ERIC Educational Resources Information Center

    Ivanov, Dragia; Nikolov, Stefan

    2013-01-01

    In this paper we present two experiments to measure Boltzmann's constant--one of the fundamental constants of modern-day physics, which lies at the base of statistical mechanics and thermodynamics. The experiments use very basic theory, simple equipment and cheap and safe materials yet provide very precise results. They are very easy and…

  16. The Hubble constant and dark energy from cosmological distance measures

    SciTech Connect

    Ichikawa, Kazuhide; Takahashi, Tomo E-mail: tomot@cc.saga-u.ac.jp

    2008-04-15

    We study how the determination of the Hubble constant from cosmological distance measures is affected by models of dark energy and vice versa. For this purpose, constraints on the Hubble constant and dark energy are investigated using the cosmological observations of cosmic microwave background, baryon acoustic oscillations and type Ia supernovae. When one investigates dark energy, the Hubble constant is often a nuisance parameter; thus it is usually marginalized over. On the other hand, when one focuses on the Hubble constant, simple dark energy models such as a cosmological constant and a constant equation of state are usually assumed. Since we do not know the nature of dark energy yet, it is interesting to investigate the Hubble constant assuming some types of dark energy and see to what extent the constraint on the Hubble constant is affected by the assumption concerning dark energy. We show that the constraint on the Hubble constant is not affected much by the assumption for dark energy. We furthermore show that this holds true even if we remove the assumption that the universe is flat. We also discuss how the prior on the Hubble constant affects the constraints on dark energy and/or the curvature of the universe.

  17. Measuring liquid crystal elastic constants with free energy perturbations.

    PubMed

    Joshi, Abhijeet A; Whitmer, Jonathan K; Guzmán, Orlando; Abbott, Nicholas L; de Pablo, Juan J

    2014-02-14

    A first principles method is proposed to calculate the Frank elastic constants of nematic liquid crystals. These include the constants corresponding to standard splay, twist and bend deformations, and an often-ignored surface-like contribution known as saddle-splay. The proposed approach is implemented on the widely studied Gay-Berne (3, 5, 2, 1) model [J. G. Gay and B. J. Berne, J. Chem. Phys., 1981, 74, 3316], and the effects of temperature and system size on the elastic constants are examined in the nematic phase. The results of simulations for splay, twist, and bend elastic constants are consistent with those from previous literature reports. The method is subsequently applied to the saddle-splay elastic constant k24 which is found to exist at the limits of the Ericksen inequalities governing positive definite free energy. Finally, extensions of the method are discussed that present a new paradigm for in silico measurements of elastic constants. PMID:24837037

  18. Layered CU-based electrode for high-dielectric constant oxide thin film-based devices

    DOEpatents

    Auciello, Orlando

    2010-05-11

    A layered device including a substrate; an adhering layer thereon. An electrical conducting layer such as copper is deposited on the adhering layer and then a barrier layer of an amorphous oxide of TiAl followed by a high dielectric layer are deposited to form one or more of an electrical device such as a capacitor or a transistor or MEMS and/or a magnetic device.

  19. Effect of Solvent Dielectric Constant on the Formation of Large Flat Bilayer Stacks in a Lecithin/Hexadecanol Hydrogel.

    PubMed

    Nakagawa, Yasuharu; Nakazawa, Hiromitsu; Kato, Satoru

    2016-07-12

    We investigated the effect of dielectric properties of the aqueous medium on the novel type of hydrogel composed of a crude lecithin mixture (PC70) and hexadecanol (HD), in which charged sheet-like bilayers are kept far apart due to interbilayer repulsive interaction. We used dipropylene glycol (DPG) as a modifier of the dielectric properties and examined its effect on the hydrogel by synchrotron X-ray diffraction, differential scanning calorimetry (DSC), polarized optical microscopy, and freeze-fracture electron microscopy. We found that at a DPG weight fraction in the aqueous medium WDPG ≈ 0.4, the bilayer organization is transformed into unusually large flat bilayer stacks with a regular lamellar spacing of 6.25 nm and consequently disintegration of the hydrogel takes place. Semiquantitative calculation of the interbilayer interaction energy based on the Deyaguin-Landau-Verwey-Overbeek (DLVO) theory suggested that the reduction of the aqueous medium dielectric constant ε by DPG may lower the energy barrier preventing flat bilayers from coming closer together. We inferred that the size of the bilayer sheet increases because the reduction of ε promotes protonation of acidic lipids that work as edge-capping molecules. PMID:27322136

  20. Research & Developments for Millimeter-Wave Dielectric Forsterite with Low Dielectric Constant, High Q, and Zero Temperature Coefficient of Resonant Frequency

    NASA Astrophysics Data System (ADS)

    Tsunooka, Tsutomu; Ando, Minato; Suzuki, Sadahiko; Yasufuku, Yoshitoyo; Ohsato, Hitoshi

    2013-09-01

    Forsterite Mg2SiO4 is a candidate for millimeter-wave dielectrics because of its high Q and low dielectric constant ɛr. Commercial forsterite has been improved with a high Q of 240,000 GHz using high-purity and fine raw materials, and the temperature coefficient of resonant frequency (TCf) can also be adjusted to near-zero ppm/°C by adding 24 wt % rutile compared with that in a previous study. In this study, the TCf, TCɛ, and ɛr of forsterite ceramics with rutile added are studied for the tuning conditions. Zero ppm/°C TCf of the forsterite with 30 and 25 wt % rutile added was achieved at 1200 °C for 2.5 and 2.25 h, respectively. The ɛr values of the near-zero TCf forsterite with 30 and 25 wt % rutile added are 11.3 and 10.2, respectively.

  1. The local structure, infrared phonon modes and the origin of the dielectric constant in La2Hf2O7 thin film

    NASA Astrophysics Data System (ADS)

    Qi, Zeming; Cheng, Xuerui; Zhang, Guobin; Li, Tingting; Wang, Yuyin; Shao, Tao; Li, Chengxiang; He, Bo

    2012-03-01

    The local structure and dielectric properties of crystalline and amorphous La2Hf2O7 (LHO) thin film were studied by X-ray absorption spectroscopy and infrared spectroscopy. The basic infrared phonon modes with most contributions to the static dielectric constant of crystal LHO are preserved, which causes the considerable value of the static dielectric constant in the amorphous thin film. The preservation of the main infrared phonon modes in the amorphous thin film is because it has similar the nearest local structures around Hf and La atoms as the crystal LHO. This inheritance of the local structural and vibrational features of the crystal phase is the origin of the dielectric constant of the LHO thin film.

  2. Investigation of the feasibility of in-situ dielectric property measurements on neutron-irradiated ceramic insulators

    SciTech Connect

    Goulding, R.H.; Zinkle, S.J.

    1996-04-01

    Computer modeling and experimental benchtop tests have demonstrated that a capacitively loaded resonant coaxial cavity can produce accurate in-situ measurements of the loss tangent and dielectric constant of ceramic insulators at a frequency of {approx}80 MHZ during fission reactor irradiation. The start of the reactor irradiations has been postponed indefinitely due to budgetary constraints.

  3. Characterizing dielectric tensors of anisotropic materials from a single measurement

    NASA Astrophysics Data System (ADS)

    Smith, Paula Kay

    Ellipsometry techniques look at changes in polarization states to measure optical properties of thin film materials. A beam reflected from a substrate measures the real and imaginary parts of the index of the material represented as n and k, respectively. Measuring the substrate at several angles gives additional information that can be used to measure multilayer thin film stacks. However, the outstanding problem in standard ellipsometry is that it uses a limited number of incident polarization states (s and p). This limits the technique to isotropic materials. The technique discussed in this paper extends the standard process to measure anisotropic materials by using a larger set of incident polarization states. By using a polarimeter to generate several incident polarization states and measure the polarization properties of the sample, ellipsometry can be performed on biaxial materials. Use of an optimization algorithm in conjunction with biaxial ellipsometry can more accurately determine the dielectric tensor of individual layers in multilayer structures. Biaxial ellipsometry is a technique that measures the dielectric tensors of a biaxial substrate, single-layer thin film, or multi-layer structure. The dielectric tensor of a biaxial material consists of the real and imaginary parts of the three orthogonal principal indices (n x + ikx, ny +iky and nz + i kz) as well as three Euler angles (alpha, beta and gamma) to describe its orientation. The method utilized in this work measures an angle-of-incidence Mueller matrix from a Mueller matrix imaging polarimeter equipped with a pair of microscope objectives that have low polarization properties. To accurately determine the dielectric tensors for multilayer samples, the angle-of-incidence Mueller matrix images are collected for multiple wavelengths. This is done in either a transmission mode or a reflection mode, each incorporates an appropriate dispersion model. Given approximate a priori knowledge of the dielectric

  4. Dielectric loss measurements using an embedded transmission line resonator

    NASA Astrophysics Data System (ADS)

    Sarabi, Bahman; Stoutimore, M. J. A.; Khalil, Moe; Gladchenko, Sergiy; Kozen, Alexander; Rubloff, Gary; Wellstood, F. C.; Lobb, J. C.; Osborn, K. D.

    2011-03-01

    Lossy dielectrics are a major source of decoherence in superconducting qubits. Superconducting linear resonators have proven to be ideally suited for measuring loss in different dielectrics due to their versatility and relative simplicity in design, fabrication, and measurement. We will present data from samples where the low-loss coplanar resonators are fabricated on top of AlOx dielectric films grown using atomic layer deposition (ALD). Although the low-power loss can be extracted from this geometry, embedding the dielectric under study between metal films has advantages that we will discuss. In addition, ALD films can be grown conformally and without pinholes to small thicknesses in comparison to conventional PECVD films. This allows us to make lumped-element resonators with a relatively small footprint, which can easily be embedded within the transmission line. This research was supported by the Intelligence Advanced Research Projects Activity through the U.S. Army Research Office award No. W911NF-09-1-0351.

  5. Effects of Solvent Dielectric Constant and Viscosity on Two Rotational Relaxation Paths of Excited 9-(Dicyanovinyl) Julolidine.

    PubMed

    Yang, Songqiu; Han, Keli

    2016-07-14

    The understanding of the interplay between microenvironment and molecular rotors is helpful for designing and developing of molecular sensors of local physical properties. We present a study on the two rotational relaxation paths of excited 9-(dicyanovinyl) julolidine in several solvents. One rotational path (C-C single-bond rotation, τb) quickly leads to the formation of a twisted state. The other path (C═C double-bond rotation, τc) shows that the populations go back to the ground state directly via a conical intersection between the S1 and ground state. The increase in the solvent dielectric constant shows little effect on the τb lifetime for its small energy barrier (<0.01 eV), but τc lifetime is increased in larger dielectric constant solvents due to the larger energy gap at conical intersection. Both τb and τc are increased greatly with the increased solvent viscosity. τb is more sensitive to viscosity than τc may be due to its larger rotational moiety. PMID:26886050

  6. Inter-Comparison of SMOS and Aquarius Sea Surface Salinity: Effects of the Dielectric Constant and Vicarious Calibration

    NASA Technical Reports Server (NTRS)

    Dinnat, Emmanuel P.; Boutin, Jacqueline; Yin, Xiaobin; Le Vine, David M.

    2014-01-01

    Two spaceborne instruments share the scientific objective of mapping the global Sea Surface Salinity (SSS). ESA's Soil Moisture and Ocean Salinity (SMOS) and NASA's Aquarius use L-band (1.4 GHz) radiometry to retrieve SSS. We find that SSS retrieved by SMOS is generally lower than SSS retrieved by Aquarius, except for very cold waters where SMOS SSS is higher overall. The spatial distribution of the differences in SSS is similar to the distribution of sea surface temperature. There are several differences in the retrieval algorithm that could explain the observed SSS differences. We assess the impact of the dielectric constant model and the ancillary sea surface salinity used by both missions for calibrating the radiometers and retrieving SSS. The differences in dielectric constant model produce differences in SSS of the order of 0.3 psu and exhibit a dependence on latitude and temperature. We use comparisons with the Argo in situ data to assess the performances of the model in various regions of the globe. Finally, the differences in the ancillary sea surface salinity products used to perform the vicarious calibration of both instruments are relatively small (0.1 psu), but not negligible considering the requirements for spaceborne remote sensing of SSS.

  7. Impact of reductive N2/H2 plasma on porous low-dielectric constant SiCOH thin films

    NASA Astrophysics Data System (ADS)

    Cui, Hao; Carter, Richard J.; Moore, Darren L.; Peng, Hua-Gen; Gidley, David W.; Burke, Peter A.

    2005-06-01

    Porous low-dielectric constant (low-κ) SiCOH thin films deposited using a plasma-enhanced chemical-vapor deposition have been comprehensively characterized before and after exposure to a reactive-ion-etch-type plasma of N2 and H2 chemistry. The low-κ film studied in this work is a carbon-doped silicon oxide film with a dielectric constant (κ) of 2.5. Studies show that a top dense layer is formed as a result of significant surface film densification after exposure to N2/H2 plasma while the underlying bulk layer remains largely unchanged. The top dense layer is found to seal the porous bulk SiCOH film. SiCOH films experienced significant thickness reduction, κ increase, and leakage current degradation after plasma exposure, accompanied by density increase, pore collapse, carbon depletion, and moisture content increase in the top dense layer. Both film densification and removal processes during N2/H2 plasma treatment were found to play important roles in the thickness reduction and κ increase of this porous low-κ SiCOH film. A model based upon mutually limiting film densification and removal processes is proposed for the continuous thickness reduction during plasma exposure. A combination of surface film densification, thickness ratio increase of top dense layer to bulk layer, and moisture content increase results in the increase in κ value of this SiCOH film.

  8. Noncontact conductivity and dielectric measurement for high throughput roll-to-roll nanomanufacturing

    PubMed Central

    Orloff, Nathan D.; Long, Christian J.; Obrzut, Jan; Maillaud, Laurent; Mirri, Francesca; Kole, Thomas P.; McMichael, Robert D.; Pasquali, Matteo; Stranick, Stephan J.; Alexander Liddle, J.

    2015-01-01

    Advances in roll-to-roll processing of graphene and carbon nanotubes have at last led to the continuous production of high-quality coatings and filaments, ushering in a wave of applications for flexible and wearable electronics, woven fabrics, and wires. These applications often require specific electrical properties, and hence precise control over material micro- and nanostructure. While such control can be achieved, in principle, by closed-loop processing methods, there are relatively few noncontact and nondestructive options for quantifying the electrical properties of materials on a moving web at the speed required in modern nanomanufacturing. Here, we demonstrate a noncontact microwave method for measuring the dielectric constant and conductivity (or geometry for samples of known dielectric properties) of materials in a millisecond. Such measurement times are compatible with current and future industrial needs, enabling real-time materials characterization and in-line control of processing variables without disrupting production. PMID:26592441

  9. Noncontact conductivity and dielectric measurement for high throughput roll-to-roll nanomanufacturing.

    PubMed

    Orloff, Nathan D; Long, Christian J; Obrzut, Jan; Maillaud, Laurent; Mirri, Francesca; Kole, Thomas P; McMichael, Robert D; Pasquali, Matteo; Stranick, Stephan J; Liddle, J Alexander

    2015-01-01

    Advances in roll-to-roll processing of graphene and carbon nanotubes have at last led to the continuous production of high-quality coatings and filaments, ushering in a wave of applications for flexible and wearable electronics, woven fabrics, and wires. These applications often require specific electrical properties, and hence precise control over material micro- and nanostructure. While such control can be achieved, in principle, by closed-loop processing methods, there are relatively few noncontact and nondestructive options for quantifying the electrical properties of materials on a moving web at the speed required in modern nanomanufacturing. Here, we demonstrate a noncontact microwave method for measuring the dielectric constant and conductivity (or geometry for samples of known dielectric properties) of materials in a millisecond. Such measurement times are compatible with current and future industrial needs, enabling real-time materials characterization and in-line control of processing variables without disrupting production. PMID:26592441

  10. Noncontact conductivity and dielectric measurement for high throughput roll-to-roll nanomanufacturing

    NASA Astrophysics Data System (ADS)

    Orloff, Nathan D.; Long, Christian J.; Obrzut, Jan; Maillaud, Laurent; Mirri, Francesca; Kole, Thomas P.; McMichael, Robert D.; Pasquali, Matteo; Stranick, Stephan J.; Alexander Liddle, J.

    2015-11-01

    Advances in roll-to-roll processing of graphene and carbon nanotubes have at last led to the continuous production of high-quality coatings and filaments, ushering in a wave of applications for flexible and wearable electronics, woven fabrics, and wires. These applications often require specific electrical properties, and hence precise control over material micro- and nanostructure. While such control can be achieved, in principle, by closed-loop processing methods, there are relatively few noncontact and nondestructive options for quantifying the electrical properties of materials on a moving web at the speed required in modern nanomanufacturing. Here, we demonstrate a noncontact microwave method for measuring the dielectric constant and conductivity (or geometry for samples of known dielectric properties) of materials in a millisecond. Such measurement times are compatible with current and future industrial needs, enabling real-time materials characterization and in-line control of processing variables without disrupting production.

  11. Toward Automated Benchmarking of Atomistic Force Fields: Neat Liquid Densities and Static Dielectric Constants from the ThermoML Data Archive.

    PubMed

    Beauchamp, Kyle A; Behr, Julie M; Rustenburg, Ariën S; Bayly, Christopher I; Kroenlein, Kenneth; Chodera, John D

    2015-10-01

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

  12. Force Field Benchmark of Organic Liquids: Density, Enthalpy of Vaporization, Heat Capacities, Surface Tension, Isothermal Compressibility, Volumetric Expansion Coefficient, and Dielectric Constant

    PubMed Central

    2011-01-01

    The chemical composition of small organic molecules is often very similar to amino acid side chains or the bases in nucleic acids, and hence there is no a priori reason why a molecular mechanics force field could not describe both organic liquids and biomolecules with a single parameter set. Here, we devise a benchmark for force fields in order to test the ability of existing force fields to reproduce some key properties of organic liquids, namely, the density, enthalpy of vaporization, the surface tension, the heat capacity at constant volume and pressure, the isothermal compressibility, the volumetric expansion coefficient, and the static dielectric constant. Well over 1200 experimental measurements were used for comparison to the simulations of 146 organic liquids. Novel polynomial interpolations of the dielectric constant (32 molecules), heat capacity at constant pressure (three molecules), and the isothermal compressibility (53 molecules) as a function of the temperature have been made, based on experimental data, in order to be able to compare simulation results to them. To compute the heat capacities, we applied the two phase thermodynamics method (Lin et al. J. Chem. Phys.2003, 119, 11792), which allows one to compute thermodynamic properties on the basis of the density of states as derived from the velocity autocorrelation function. The method is implemented in a new utility within the GROMACS molecular simulation package, named g_dos, and a detailed exposé of the underlying equations is presented. The purpose of this work is to establish the state of the art of two popular force fields, OPLS/AA (all-atom optimized potential for liquid simulation) and GAFF (generalized Amber force field), to find common bottlenecks, i.e., particularly difficult molecules, and to serve as a reference point for future force field development. To make for a fair playing field, all molecules were evaluated with the same parameter settings, such as thermostats and barostats

  13. Noninvasive thickness measurements of metal films through microwave dielectric resonators

    NASA Astrophysics Data System (ADS)

    Jung, Ho Sang; Lee, Jae Hun; Han, Hyun Kyung; Lee, Sang Young

    2016-05-01

    Thicknesses of Pt films ranging from 60 to 950 nm are measured noninvasively using a TE 011-mode dielectric resonator with the resonant frequency of 8.5 - 9.8 GHz at temperatures of 77 K and 293 K. A cylindrical rutile rod is used as the dielectric, with a high- T C superconductive YBa2Cu3O7- δ film used as the bottom endplate of the resonator for measurements at 77 K. This method is based on two facts: i) Due to the electromagnetic interferences of incoming and reflected waves at the surface of the metal film surface, the effective surface resistance varies with the film thickness, and ii) the intrinsic surface resistance of normal metals is equal to the intrinsic surface reactance in the local limit. The measured thicknesses using the rutile resonator appear to be comparable with those obtained using a profilometer. [Figure not available: see fulltext.

  14. Direct measurement of the dielectric polarization properties of DNA.

    PubMed

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

    2014-09-01

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

  15. Direct measurement of the dielectric polarization properties of DNA

    PubMed Central

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

    2014-01-01

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

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

  18. Measurement of Local Peltier Constant at a Microcontact

    NASA Astrophysics Data System (ADS)

    Koyano, Mikio; Akashi, Naoya

    2009-07-01

    Our novel apparatus measures the local Peltier constant at a thermoelectric material microregion. A narrow metal needle probe contacts a sample mounted into a small adiabatic vacuum chamber with a pressure of about 10-4 Pa. A␣stepping-motor-type nano-actuator controls the probe’s contact pressure. We measured DC and AC I- V characteristics at the microcontact to determine thermoelectric properties. We measured I- V characteristics between the probe and a commercial (Bi,Sb)2Te3 surface. Measured values of local Peltier constants are of the same order as the bulk Peltier constant π: ca. 55 mV. They increase with increased contact resistance, suggesting that contact size affects thermoelectricity.

  19. Measurement of valence band structure in arbitrary dielectric films

    SciTech Connect

    Uhm, Han S.; Choi, Eun H.

    2012-10-15

    A new way of measuring the band structure of various dielectric materials using the secondary electron emission from Auger neutralization of ions is introduced. The first example of this measurement scheme is the magnesium oxide (MgO) films with respect to the application of the films in the display industries. The density of state in the valence bands of MgO film and MgO film with a functional layer (FL) deposited over a dielectric surface reveals that the density peak of film with a FL is considerably less than that of film, thereby indicating a better performance of MgO film with functional layer in display devices. The second example of the measurement is the boron-zinc oxide (BZO) films with respect to the application of the films to the development of solar cells. The measurement of density of state in BZO film suggests that a high concentration of boron impurity in BZO films may enhance the transition of electrons and holes through the band gap from the valence to the conduction band in zinc oxide crystals; thereby improving the conductivity of the film. Secondary electron emission by the Auger neutralization of ions is highly instrumental for the determination of the density of states in the valence band of dielectric materials.

  20. Effect of UV curing time on physical and electrical properties and reliability of low dielectric constant materials

    SciTech Connect

    Kao, Kai-Chieh; Cheng, Yi-Lung; Chang, Wei-Yuan; Chang, Yu-Min; Leu, Jihperng

    2014-11-01

    This study comprehensively investigates the effect of ultraviolet (UV) curing time on the physical, electrical, and reliability characteristics of porous low-k materials. Following UV irradiation for various periods, the depth profiles of the chemical composition in the low-k dielectrics were homogeneous. Initially, the UV curing process preferentially removed porogen-related CH{sub x} groups and then modified Si-CH{sub 3} and cage Si-O bonds to form network Si-O bonds. The lowest dielectric constant (k value) was thus obtained at a UV curing time of 300 s. Additionally, UV irradiation made porogen-based low-k materials hydrophobic and to an extent that increased with UV curing time. With a short curing time (<300 s), porogen was not completely removed and the residues degraded reliability performance. A long curing time (>300 s) was associated with improved mechanical strength, electrical performance, and reliability of the low-k materials, but none of these increased linearly with UV curing time. Therefore, UV curing is necessary, but the process time must be optimized for porous low-k materials on back-end of line integration in 45 nm or below technology nodes.

  1. Ultra-capacitor flexible films with tailored dielectric constants using electric field assisted assembly of nanoparticles

    NASA Astrophysics Data System (ADS)

    Batra, Saurabh; Cakmak, Miko

    2015-12-01

    In this study, the chaining and preferential alignment of barium titanate nanoparticles (100 nm) through the thickness direction of a polymer matrix in the presence of an electric field is shown. Application of an AC electric field in a well-dispersed solution leads to the formation of chains of nanoparticles in discrete rows oriented with their primary axis in the E-field direction due to dielectrophoresis. The change in the orientation of these chains was quantified through statistical analysis of SEM images and was found to be dependent on E-field, frequency and viscosity. When a DC field is applied a distinct layer consisting of dense particles was observed with micro-computed tomography. These studies show that the increase in DC voltage leads to increase in the thickness of the particle rich layer along with the packing density also increasing. Increasing the mutual interactions between particles due to the formation of particle chains in the ``Z''-direction decreases the critical percolation concentration above which substantial enhancement of properties occurs. This manufacturing method therefore shows promise to lower the cost of the products for a range of applications including capacitors by either enhancing the dielectric properties for a given concentration or reduces the concentration of nanoparticles needed for a given property.

  2. Ultra-capacitor flexible films with tailored dielectric constants using electric field assisted assembly of nanoparticles.

    PubMed

    Batra, Saurabh; Cakmak, Miko

    2015-12-28

    In this study, the chaining and preferential alignment of barium titanate nanoparticles (100 nm) through the thickness direction of a polymer matrix in the presence of an electric field is shown. Application of an AC electric field in a well-dispersed solution leads to the formation of chains of nanoparticles in discrete rows oriented with their primary axis in the E-field direction due to dielectrophoresis. The change in the orientation of these chains was quantified through statistical analysis of SEM images and was found to be dependent on E-field, frequency and viscosity. When a DC field is applied a distinct layer consisting of dense particles was observed with micro-computed tomography. These studies show that the increase in DC voltage leads to increase in the thickness of the particle rich layer along with the packing density also increasing. Increasing the mutual interactions between particles due to the formation of particle chains in the "Z"-direction decreases the critical percolation concentration above which substantial enhancement of properties occurs. This manufacturing method therefore shows promise to lower the cost of the products for a range of applications including capacitors by either enhancing the dielectric properties for a given concentration or reduces the concentration of nanoparticles needed for a given property. PMID:26593234

  3. Free-Space Time-Domain Method for Measuring Thin Film Dielectric Properties

    DOEpatents

    Li, Ming; Zhang, Xi-Cheng; Cho, Gyu Cheon

    2000-05-02

    A non-contact method for determining the index of refraction or dielectric constant of a thin film on a substrate at a desired frequency in the GHz to THz range having a corresponding wavelength larger than the thickness of the thin film (which may be only a few microns). The method comprises impinging the desired-frequency beam in free space upon the thin film on the substrate and measuring the measured phase change and the measured field reflectance from the reflected beam for a plurality of incident angles over a range of angles that includes the Brewster's angle for the thin film. The index of refraction for the thin film is determined by applying Fresnel equations to iteratively calculate a calculated phase change and a calculated field reflectance at each of the plurality of incident angles, and selecting the index of refraction that provides the best mathematical curve fit with both the dataset of measured phase changes and the dataset of measured field reflectances for each incident angle. The dielectric constant for the thin film can be calculated as the index of refraction squared.

  4. Measurements of the gravitational constant - why we need new ideas

    NASA Astrophysics Data System (ADS)

    Schlamminger, Stephan

    2016-03-01

    In this presentation, I will summarize measurements of the Newtonian constant of gravitation, big G, that have been carried out in the last 30 years. I will describe key techniques that were used by researchers around the world to determine G. Unfortunately, the data set is inconsistent with itself under the assumption that the gravitational constant does not vary in space or time, an assumption that has been tested by other experiments. Currently, several research groups have reported measurements with relative uncertainties below 2 ×10-5 , however, the relative difference between the smallest and largest reported number exceeds 5 ×10-4 . It is embarrassing that after over 200 years of measuring the gravitational constant, we do not have a better understanding of the numerical value of this constant. Clearly, we need new ideas to tackle this problem and now is the time to come forward with new ideas. The National Science Foundation is currently soliciting proposals for an Ideas Lab on measuring big G. In the second part of the presentation, I will introduce the Ideas Lab on big G and I am hoping to motivate the audience to think about new ideas to measure G and encourage them to apply to participate in the Ideas Lab.

  5. A Possible Geometric Measurement of the Cosmological Constant

    NASA Astrophysics Data System (ADS)

    Phillipps, S.

    1994-08-01

    A geometric means for the measurement of the cosmological constant {LAMBDA}, using the separations of quasar pairs, is suggested and a preliminary application is discussed. It is shown that significant constraints could be placed on {LAMBDA} with a sample of several hundred pairs of physically associated quasars at redshifts above 1.

  6. Measuring the Gas Constant "R": Propagation of Uncertainty and Statistics

    ERIC Educational Resources Information Center

    Olsen, Robert J.; Sattar, Simeen

    2013-01-01

    Determining the gas constant "R" by measuring the properties of hydrogen gas collected in a gas buret is well suited for comparing two approaches to uncertainty analysis using a single data set. The brevity of the experiment permits multiple determinations, allowing for statistical evaluation of the standard uncertainty u[subscript…

  7. Two-beam interferometer for optical constants measurements at near-millimeter wavelengths

    NASA Astrophysics Data System (ADS)

    Jones, C. R.; Dutta, J. M.; Davé, H.

    1984-03-01

    A simple and versatile instrument for the measurement of optical constants in the near millimeter spectral region is described. Studies of quasi-optical components used in this instrument for effective beam transmission and control are reported. These studies include transmission characteristics of dielectric waveguides and performance of a variable coupler based on frustrated total internal reflection. Operation of this instrument as a two-beam interferometer for determining the index of refraction or as a device to measure transmission for determining the absorption coefficient are described. Values measured with this instrument at 245 GHz, using an optically pumped molecular laser as the source, are reported for several low-loss materials. Appropriate corrections and error estimates are discussed. The potential for improvement and increased accuracies are discussed.

  8. Complex permittivity measurements of ferroelectrics employing composite dielectric resonator technique.

    PubMed

    Krupka, Jerzy; Zychowicz, Tomasz; Bovtun, Viktor; Veljko, Sergiy

    2006-10-01

    Composite cylindrical TE(0n1) mode dielectric resonator has been used for the complex permittivity measurements of ferroelectrics at frequency about 8.8 GHz. Rigorous equations have been derived that allowed us to find a relationship between measured resonance frequency and Q-factor and the complex permittivity. It has been shown that the choice of appropriate diameter of a sample together with rigorous complex angular frequency analysis allows precise measurements of various ferroelectric. Proposed technique can be used for materials having both real and imaginary part of permittivity as large as a few thousand. Variable temperature measurements were performed on a PbMg(1/3)Nb(2/3)O3 (PMN) ceramic sample, and the measured complex permittivity have shown good agreement with the results of measurements obtained on the same sample at lower frequencies (0.1-1.8 GHz). PMID:17036796

  9. History and progress on accurate measurements of the Planck constant

    NASA Astrophysics Data System (ADS)

    Steiner, Richard

    2013-01-01

    The measurement of the Planck constant, h, is entering a new phase. The CODATA 2010 recommended value is 6.626 069 57 × 10-34 J s, but it has been a long road, and the trip is not over yet. Since its discovery as a fundamental physical constant to explain various effects in quantum theory, h has become especially important in defining standards for electrical measurements and soon, for mass determination. Measuring h in the International System of Units (SI) started as experimental attempts merely to prove its existence. Many decades passed while newer experiments measured physical effects that were the influence of h combined with other physical constants: elementary charge, e, and the Avogadro constant, NA. As experimental techniques improved, the precision of the value of h expanded. When the Josephson and quantum Hall theories led to new electronic devices, and a hundred year old experiment, the absolute ampere, was altered into a watt balance, h not only became vital in definitions for the volt and ohm units, but suddenly it could be measured directly and even more accurately. Finally, as measurement uncertainties now approach a few parts in 108 from the watt balance experiments and Avogadro determinations, its importance has been linked to a proposed redefinition of a kilogram unit of mass. The path to higher accuracy in measuring the value of h was not always an example of continuous progress. Since new measurements periodically led to changes in its accepted value and the corresponding SI units, it is helpful to see why there were bumps in the road and where the different branch lines of research joined in the effort. Recalling the bumps along this road will hopefully avoid their repetition in the upcoming SI redefinition debates. This paper begins with a brief history of the methods to measure a combination of fundamental constants, thus indirectly obtaining the Planck constant. The historical path is followed in the section describing how the improved

  10. History and progress on accurate measurements of the Planck constant.

    PubMed

    Steiner, Richard

    2013-01-01

    The measurement of the Planck constant, h, is entering a new phase. The CODATA 2010 recommended value is 6.626 069 57 × 10(-34) J s, but it has been a long road, and the trip is not over yet. Since its discovery as a fundamental physical constant to explain various effects in quantum theory, h has become especially important in defining standards for electrical measurements and soon, for mass determination. Measuring h in the International System of Units (SI) started as experimental attempts merely to prove its existence. Many decades passed while newer experiments measured physical effects that were the influence of h combined with other physical constants: elementary charge, e, and the Avogadro constant, N(A). As experimental techniques improved, the precision of the value of h expanded. When the Josephson and quantum Hall theories led to new electronic devices, and a hundred year old experiment, the absolute ampere, was altered into a watt balance, h not only became vital in definitions for the volt and ohm units, but suddenly it could be measured directly and even more accurately. Finally, as measurement uncertainties now approach a few parts in 10(8) from the watt balance experiments and Avogadro determinations, its importance has been linked to a proposed redefinition of a kilogram unit of mass. The path to higher accuracy in measuring the value of h was not always an example of continuous progress. Since new measurements periodically led to changes in its accepted value and the corresponding SI units, it is helpful to see why there were bumps in the road and where the different branch lines of research joined in the effort. Recalling the bumps along this road will hopefully avoid their repetition in the upcoming SI redefinition debates. This paper begins with a brief history of the methods to measure a combination of fundamental constants, thus indirectly obtaining the Planck constant. The historical path is followed in the section describing how the

  11. Giant dielectric constant in TiO{sub 2}/Al{sub 2}O{sub 3} nanolaminates grown on doped silicon substrate by pulsed laser deposition

    SciTech Connect

    Walke, P.; Bouregba, R.; Mercey, B.; Lüders, U.; Lefevre, A.; Parat, G.; Lallemand, F.; Voiron, F.

    2014-03-07

    High quality amorphous nanolaminates by means of alternate Al{sub 2}O{sub 3} and TiO{sub 2} oxide sublayers were grown with atomic scale thickness control by pulsed laser deposition. A giant dielectric constant (>10 000), strongly enhanced compared to the value of either Al{sub 2}O{sub 3} or TiO{sub 2} or their solid solution, was observed. The dependence of the dielectric constant and the dielectric loss on the individual layer thickness of each of the constituting materials was investigated between 0.3 nm and 1 nm, in order to understand the prevailing mechanisms and allow for an optimization of the performances. An impedance study confirmed as the key source of the giant dielectric constant a Maxwell–Wagner type dielectric relaxation, caused by space charge polarization in the nanolaminate structure. The current work provides better insight of nanolaminates and their sublayer thickness engineering for potential applications.

  12. Dielectric abnormities in BaTi{sub 0.9}(Ni{sub 1/2}W{sub 1/2}){sub 0.1}O{sub 3} giant dielectric constant ceramics

    SciTech Connect

    Zhao Fei; Yue Zhenxing; Pei Jing; Yang Donghai; Gui Zhilun; Li Longtu

    2007-07-30

    BaTi{sub 0.9}(Ni{sub 1/2}W{sub 1/2}){sub 0.1}O{sub 3} ceramics were fabricated and their dielectric properties were investigated. With the sintering temperature increasing from 1250 to 1280 deg. C, the grain size abruptly increases from 1-2 to 20-40 {mu}m, accompanying significant changes in dielectric response. The samples with larger grains exhibit giant dielectric constant characteristics, which are considered to be mainly attributed to the domain boundary effect. The activation energies of the dielectric relaxation E{sub relax}=0.325 eV reveal the existence of microdomains in larger grains. The ac conductivity results also give the evidence of the domain boundary effect in the present ceramics.

  13. A nuclear data approach for the Hubble constant measurements

    SciTech Connect

    Pritychenko, B.

    2015-06-09

    An extraordinary number of Hubble constant measurements challenges physicists with selection of the best numerical value. The standard U.S. Nuclear Data Program (USNDP) codes and procedures have been applied to resolve this issue. The nuclear data approach has produced the most probable or recommended Hubble constant value of 67.00(770) (km/sec)/Mpc. This recommended value is based on the last 25 years of experimental research and includes contributions from different types of measurements. The present result implies (14.6±1.7) x 109 years as a rough estimate for the age of the Universe. The complete list of recommended results is given and possible implications are discussed.

  14. Dielectric Spectroscopy Measurements on Fruit, Meat, and Grain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dielectric spectroscopy is the study of dielectric properties (electrical characteristics) of materials and their variation with frequency or wavelength. Dielectric properties are electrical properties that determine how materials interact with electric fields such as those of high-frequency and m...

  15. Atom interferometer measurement of the newtonian constant of gravity.

    PubMed

    Fixler, J B; Foster, G T; McGuirk, J M; Kasevich, M A

    2007-01-01

    We measured the Newtonian constant of gravity, G, using a gravity gradiometer based on atom interferometry. The gradiometer measures the differential acceleration of two samples of laser-cooled Cs atoms. The change in gravitational field along one dimension is measured when a well-characterized Pb mass is displaced. Here, we report a value of G = 6.693 x 10(-11) cubic meters per kilogram second squared, with a standard error of the mean of +/-0.027 x 10(-11) and a systematic error of +/-0.021 x 10(-11) cubic meters per kilogram second squared. The possibility that unknown systematic errors still exist in traditional measurements makes it important to measure G with independent methods. PMID:17204644

  16. Grain size effect on the giant dielectric constant of CaCu{sub 3}Ti{sub 4}O{sub 12} nanoceramics prepared by mechanosynthesis and spark plasma sintering

    SciTech Connect

    Ahmad, Mohamad M.; Yamada, Koji

    2014-04-21

    In the present work, CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) nanoceramics with different grain sizes were prepared by spark plasma sintering (SPS) at different temperatures (SPS-800, SPS-900, SPS-975, and SPS-1050) of the mechanosynthesized nano-powder. Structural and microstructural properties were studied by XRD and field-emission scanning electron microscope measurements. The grain size of CCTO nanoceramics increases from 80 nm to ∼200 nm for the ceramics sintered at 800 °C and 975 °C, respectively. Further increase of SPS temperature to 1050 °C leads to micro-sized ceramics of 2–3 μm. The electrical and dielectric properties of the investigated ceramics were studied by impedance spectroscopy. Giant dielectric constant was observed in CCTO nanoceramics. The dielectric constant increases with increasing the grain size of the nanoceramics with values of 8.3 × 10{sup 3}, 2.4 × 10{sup 4}, and 3.2 × 10{sup 4} for SPS-800, SPS-900, and SPS-975, respectively. For the micro-sized SPS-1050 ceramics, the dielectric constant dropped to 2.14 × 10{sup 4}. The dielectric behavior is interpreted within the internal barrier layer capacitance picture due to the electrical inhomogeneity of the ceramics. Besides the resistive grain boundaries that are usually observed in CCTO ceramics, domain boundaries appear as a second source of internal layers in the current nanoceramics.

  17. Measurement of the strong coupling constant using τ decays

    NASA Astrophysics Data System (ADS)

    Buskulic, D.; Decamp, D.; Goy, C.; Lees, J.-P.; Minard, M.-N.; Mours, B.; Pietrzyk, B.; Alemany, R.; Ariztizabal, F.; Comas, P.; Crespo, J. M.; Delfino, M.; Fernandez, E.; Fernandez-Bosman, M.; Gaitan, V.; Garrido, Ll.; Mattison, T.; Pacheco, A.; Padilla, C.; Pascual, A.; Creanza, D.; de Palma, M.; Farilla, A.; Iaselli, G.; Maggi, G.; Maggi, M.; Natali, S.; Nuzzo, S.; Quattromini, M.; Ranieri, A.; Raso, G.; Romano, F.; Ruggieri, F.; Selvaggi, G.; Silvestris, L.; Tempesta, P.; Zito, G.; Chai, Y.; Hu, H.; Huang, D.; Huang, X.; Lin, J.; Wang, T.; Xie, Y.; Xu, D.; Xu, R.; Zhang, J.; Zhang, L.; Zhao, W.; Bauerdick, L. A. T.; Blucher, E.; Bonvicini, G.; Boudreau, J.; Casper, D.; Drevermann, H.; Forty, R. W.; Ganis, G.; Gay, C.; Hagelberg, R.; Harvey, J.; Haywood, S.; Hilgart, J.; Jacobsen, R.; Jost, B.; Knobloch, J.; Lehraus, I.; Lohse, T.; Lusiani, A.; Martinez, M.; Mato, P.; Meinhard, H.; Minten, A.; Miotto, A.; Miquel, R.; Moser, H.-G.; Palazzi, P.; Perlas, J. A.; Pusztaszeri, J.-F.; Ranjard, F.; Redlinger, G.; Rolandi, L.; Rothberg, J.; Ruan, T.; Saich, M.; Schlatter, D.; Schmelling, M.; Sefkow, F.; Tejessy, W.; Wachsmuth, H.; Wiedenmann, W.; Wildish, T.; Witzeling, W.; Wotschack, J.; Ajaltouni, Z.; Badaud, F.; Bardadin-Otwinowska, M.; El Fellous, R.; Falvard, A.; Gay, P.; Guicheney, C.; Henrard, P.; Jousset, J.; Michel, B.; Montret, J.-C.; Pallin, D.; Perret, P.; Podlyski, F.; Proriol, J.; Prulhière, F.; Saadi, F.; Fearnley, T.; Hansen, J. D.; Hansen, J. R.; Hansen, P. H.; Møllerud, R.; Nilsson, B. S.; Efthymiopoulos, I.; Kyriakis, A.; Simopoulou, E.; Vayaki, A.; Zachariadou, K.; Badier, J.; Blondel, A.; Bonneaud, G.; Brient, J. C.; Fouque, G.; Orteu, S.; Rougé, A.; Rumpf, M.; Tanaka, R.; Verderi, M.; Videau, H.; Candlin, D. J.; Parsons, M. I.; Veitch, E.; Moneta, L.; Parrini, G.; Corden, M.; Georgiopoulos, C.; Ikeda, M.; Lannutti, J.; Levinthal, D.; Mermikides, M.; Sawyer, L.; Wasserbaech, S.; Antonelli, A.; Baldini, R.; Bencivenni, G.; Bologna, G.; Bossi, F.; Campana, P.; Capon, G.; Cerutti, F.; Chiarella, V.; D'Ettorre-Piazzoli, B.; Felici, G.; Laurelli, P.; Mannocchi, G.; Murtas, F.; Murtas, G. P.; Passalacqua, L.; Pepe-Altarelli, M.; Picchi, P.; Colrain, P.; Ten Have, I.; Lynch, J. G.; Maitland, W.; Morton, W. T.; Raine, C.; Reeves, P.; Scarr, J. M.; Smith, K.; Smith, M. G.; Thompson, A. S.; Turnbull, R. M.; Brandl, B.; Braun, O.; Geweniger, C.; Hanke, P.; Hepp, V.; Kluge, E. E.; Maumary, Y.; Putzer, A.; Rensch, B.; Stahl, A.; Tittel, K.; Wunsch, M.; Belk, A. T.; Beuselinck, R.; Binnie, D. M.; Cameron, W.; Cattaneo, M.; Colling, D. J.; Dornan, P. J.; Dugeay, S.; Greene, A. M.; Hassard, J. F.; Lieske, N. M.; Nash, J.; Payne, D. G.; Phillips, M. J.; Sedgbeer, J. K.; Tomalin, I. R.; Wright, A. G.; Girtler, P.; Kneringer, E.; Kuhn, D.; Rudolph, G.; Bowdery, C. K.; Brodbeck, T. J.; Finch, A. J.; Foster, F.; Hughes, G.; Jackson, D.; Keemer, N. R.; Nuttall, M.; Patel, A.; Sloan, T.; Snow, S. W.; Whelan, E. P.; Kleinknecht, K.; Raab, J.; Renk, B.; Sander, H.-G.; Schmidt, H.; Steeg, F.; Walther, S. M.; Wanke, R.; Wolf, B.; Aubert, J.-J.; Bencheikh, A. M.; Benchouk, C.; Bonissent, A.; Carr, J.; Coyle, P.; Drinkard, J.; Etienne, F.; Nicod, D.; Papalexiou, S.; Payre, P.; Roos, L.; Rousseau, D.; Schwemling, P.; Talby, M.; Adlung, S.; Assmann, R.; Bauer, C.; Blum, W.; Brown, D.; Cattaneo, P.; Dehning, B.; Dietl, H.; Dydak, F.; Frank, M.; Halley, A. W.; Lauber, J.; Lütjens, G.; Lutz, G.; Männer, W.; Richter, R.; Rotscheidt, H.; Schröder, J.; Schwarz, A. S.; Settles, R.; Seywerd, H.; Stierlin, U.; Stiegler, U.; Denis, R. St.; Wolf, G.; Boucrot, J.; Callot, O.; Cordier, A.; Davier, M.; Duflot, L.; Grivaz, J.-F.; Heusse, Ph.; Jaffe, D. E.; Janot, P.; Kim, D. W.; Le Diberder, F.; Lefrançois, J.; Lutz, A.-M.; Schune, M.-H.; Veillet, J.-J.; Videau, I.; Zhang, Z.; Abbaneo, D.; Bagliesi, G.; Batignani, G.; Bosisio, L.; Bottigli, U.; Bozzi, C.; Calderini, G.; Carpinelli, M.; Ciocci, M. A.; Dell'Orso, R.; Ferrante, I.; Fidecaro, F.; Foà, L.; Focardi, E.; Forti, F.; Giassi, A.; Giorgi, M. A.; Gregorio, A.; Ligabue, F.; Mannelli, E. B.; Marrocchesi, P. S.; Messineo, A.; Palla, F.; Rizzo, G.; Sanguinetti, G.; Spagnolo, P.; Steinberger, J.; Tenchini, R.; Tonelli, G.; Triggiani, G.; Vannini, C.; Venturi, A.; Verdini, P. G.; Walsh, J.; Betteridge, A. P.; Carter, J. M.; Green, M. G.; March, P. V.; Mir, Ll. M.; Medcalf, T.; Quazi, I. S.; Strong, J. A.; West, L. R.; Botterill, D. R.; Clifft, R. W.; Edgecock, T. R.; Edwards, M.; Fisher, S. M.; Jones, T. J.; Norton, P. R.; Salmon, D. P.; Thompson, J. C.; Bloch-Devaux, B.; Colas, P.; Duarte, H.; Kozanecki, W.; Lançon, E.; Lemaire, M. C.; Locci, E.; Perez, P.; Perrier, F.; Rander, J.; Renardy, J.-F.; Rosowsky, A.; Roussarie, A.; Schuller, J.-P.; Schwindling, J.; Si Mohand, D.; Vallage, B.; Johnson, R. P.; Litke, A. M.; Taylor, G.; Wear, J.; Ashman, J. G.; Babbage, W.; Booth, C. N.; Buttar, C.; Carney, R. E.; Cartwright, S.; Combley, F.; Hatfield, F.; Thompson, L. F.; Barberio, E.; Böhrer, A.; Brandt, S.; Cowan, G.; Grupen, C.; Lutters, G.; Rivera, F.; Schäfer, U.; Smolik, L.; Della Marina, R.; Giannini, G.; Gobbo, B.; Ragusa, F.; Bellantoni, L.; Chen, W.; Cinabro, D.; Conway, J. S.; Cowen, D. F.; Feng, Z.; Ferguson, D. P. S.; Gao, Y. S.; Grahl, J.; Harton, J. L.; Jared, R. C.; Leclaire, B. W.; Lishka, C.; Pan, Y. B.; Pater, J. R.; Saadi, Y.; Sharma, V.; Schmitt, M.; Shi, Z. H.; Walsh, A. M.; Weber, F. V.; Lan Wu, Sau; Wu, X.; Zheng, M.; Zobernig, G.; Aleph Collaboration

    1993-06-01

    The strong coupling constant is determined from the leptonic branching ratios, the lifetime, and the invariant mass distribution of the hadronic final state of the τ lepton, using data accumulated at LEP with the ALEPH detector. The strong coupling constant measurement, αs( mτ2) = 0.330±0.046, evolved to the Z mass yields αs( MZ2) = 0.188±0.005. The error includes experimental and theoretical uncertainties, the latter evaluated in the framework of the Shifman, Vainshtein and Zakharov (SVZ) approach. The method allows the non-perturbative contribution to the hadronic decay rate to be determined to be 0.3±0.5%.

  18. Hybrid Cleaning Technology for Enhanced Post-Cu/Low-Dielectric Constant Chemical Mechanical Planarization Cleaning Performance

    NASA Astrophysics Data System (ADS)

    Ramachandran, Manivannan; Cho, Byoung-Jun; Kwon, Tae-Young; Park, Jin-Goo

    2013-05-01

    During chemical mechanical planarization (CMP), a copper/low-k surface is often contaminated by abrasive particles, organic materials and other additives. These contaminants need to be removed in the subsequent cleaning process with minimum material loss. In this study, a dilute amine-based alkaline cleaning solution is used along with physical force in the form of megasonic energy to remove particles and organic contaminants. Tetramethylammonium hydroxide (TMAH) and monoethanolamine (MEA) are used as an organic base and complexing agent, respectively, in the proposed solution. Ethanolamine acts as a corrosion inhibitor in the solution. Organic residue removal was confirmed through contact angle measurements and X-ray photoelectron spectroscopy analysis. Electrochemical studies showed that the proposed solution increases protection against corrosion, and that the hybrid cleaning technology resulted in higher particle removal efficiency from both the copper and low-k surfaces.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    The European Rosetta spacecraft (s/c), launched in 2004, will be the first s/c to orbit a comet and place a lander module on its surface. In 2014, the s/c will rendezvous with the comet 67P/Churyumov-Gerasimenko and place the lander on its surface thereby allowing in situ and remote sensing of the comet nucleus. Two radio experiments, one passive (MIRO [1]) and one active (CONSERT [2]), are aboard the Rosetta s/c. MIRO, composed of two radiometers, with center band frequencies at 190 GHz and at 563 GHz to determine the brightness temperatures of the target surfaces and sub-surfaces, has already observed asteroids (2867) Steins [3] and (21) Lutetia [4]. CONSERT will investigate the deep interior of the nucleus using 90 MHz radio-waves transmitted from the orbiter through the nucleus and returned to the orbiter from the lander. To support interpretations of MIRO and CONSERT observations, a program of dielectric properties measurements is under development on a large range of frequencies encompassing those of the above-mentioned experiments. Several instruments for dielectric constant determination are available at IMS laboratory (Bordeaux, France): impedance analyzer, coaxial sensor, resonant cavities (measuring respectively at 100 MHz, 0.5-6 GHz, 1.2-13.4 GHz). Millimeter benches are available at both IMS and LERMA laboratories (measuring respectively at 30-110 GHz and 70-230 GHz). Taking into account the possible presence of regolith layers on the surface of asteroids or nuclei and the very low density of cometary nuclei [5], the dependence of the dielectric constant on the structure and porosity of given granular materials needs also to be investigated (while the thermal and hygrometric conditions are carefully monitored). We have already reported measurements obtained on various meteorites, possibly representative of some asteroid surfaces [6, 7]. We will also report systematic measurements obtained on a large sample of pyroclastic deposits from Etna, providing

  20. High dielectric constant TiO2 thin films on a Ru electrode grown at 250 °C by atomic-layer deposition

    NASA Astrophysics Data System (ADS)

    Kim, Seong Keun; Kim, Wan-Don; Kim, Kyung-Min; Hwang, Cheol Seong; Jeong, Jaehack

    2004-11-01

    TiO2 thin films with high dielectric constants (83-100) were grown on a Ru electrode at a growth temperature of 250 °C using the atomic-layer deposition method. The as-deposited films were crystallized with rutile structure. Adoption of O3 with a very high concentration (400g/m3) was crucial for obtaining the rutile phase and the high dielectric constant. The leakage current density of a TiO2 film with an equivalent oxide thickness of 1.0-1.5 nm was 10-6-10-8A/cm2 at ±1V. All these electrical properties were obtained after limited postannealing where the annealing temperature was <500°C, which is crucial to the structural stability of the Ru electrode. Therefore, these TiO2 films are very promising as the capacitor dielectrics of dynamic random access memories. TiO2 films grown on a bare Si wafer or Pt electrode by the same process had anatase structure and a dielectric constant of ˜40.

  1. Millimeter wave complex dielectric permittivity and complex magnetic permeability measurements of absorbing materials

    NASA Astrophysics Data System (ADS)

    Tkachov, Igor Ivanovich

    2000-09-01

    This dissertation presents new methods for characterization of materials in the millimeter wave range. Historically, this has been the most difficult part of the electromagnetic spectrum for accurate measurements of material properties. New instrumentation has now been developed for operation in this frequency band. The new techniques developed in the course of this work allowed precise measurement of dielectric properties as well as the separation of magnetic properties from dielectric in the millimeter wave range. A new quasi-optical spectrometer with a waveguide reference channel has been designed and built for the precision measurement of the real part of dielectric permittivity of medium and highly absorbing materials over an extended W-band frequency range (70-118 GHz). A new method of phase measurement with this unique unbalanced quasi-optical waveguide bridge spectrometer has been developed. The phase of the electromagnetic wave transmitted through the specimen can be measured accurately, leading to the determination of the real part of the complex dielectric permittivity of moderate and highly absorbing dielectric materials with high precision. A simple quasi-optical transmission configuration of the spectrometer, a single free space channel provides the transmittance data with a high resolution from which the spectra of the imaginary part of dielectric permittivity of materials are evaluated accurately. A backward wave oscillator (BWO) is used as the source of tunable coherent radiation for the spectrometer. The high output power of the BWO and the high sensitivity of the receiver system, which employs a specially constructed liquid helium cooled InSb detector, enable adequate sensitivity in transmission for highly absorbing materials. Systematic study of dielectric and magnetic properties of various materials has been performed with the quasi-optical free space method in the millimeter wave range from 34GHz to 117GHz for the first time. Specific results

  2. Measuring elastic constants using non-contact ultrasonic techniques

    NASA Astrophysics Data System (ADS)

    Edwards, R. S.; Perry, R.; Cleanthous, D.; Backhouse, D. J.; Moore, I. J.; Clough, A. R.; Stone, D. I.

    2012-05-01

    The use of ultrasound for measuring elastic constants and phase transitions is well established. Standard measurements use piezoelectric transducers requiring couplant and contact with the sample. Recently, non-destructive testing (NDT) has seen an increase in the use of non-contact ultrasonic techniques, for example electromagnetic acoustic transducers (EMATs) and laser ultrasound, due to their many benefits. For measurements of single crystals over a range of temperatures non-contact techniques could also bring many benefits. These techniques do not require couplant, and hence do not suffer from breaking of the bond between transducer and sample during thermal cycling, and will potentially lead to a simpler and more adaptable measurement system with lower risk of sample damage. We present recent work adapting EMAT advances from NDT to measurements of single crystals at cryogenic temperatures and illustrate this with measurements of magnetic phase transitions in Gd64Sc36 using both contact and non-contact transducers. We discuss the measurement techniques implemented to overcome noise problems, and a digital pulse-echo-overlap technique, using data analysis in the frequency domain to measure the velocity.

  3. Rocket calibration of the Nimbus 6 solar constant measurements

    NASA Technical Reports Server (NTRS)

    Duncan, C. H.; Harrison, R. G.; Hickey, J. R.; Kendall, J. M., Jr.; Thekaekara, M. P.; Willson, R. C.

    1977-01-01

    Total solar irradiance was observed simultaneously outside the earth's atmosphere by three types of absolute cavity radiometers and duplicates of four of the Nimbus 6 Earth Radiation Budget (ERB) solar channels in a June 1976 sounding rocket experiment. The preliminary average solar constant result from the cavity radiometers is 1367 Wm (-2) with an uncertainty of less than + or - 0.5% in S.I. units. The duplicate ERB channel 3 on the rocket gave a value of 1389 Wm (-2) which agreed exactly with the Nimbus 6 ERB channel 3 measurement made simultaneously with the rocket flight.

  4. Measuring the Hubble Constant with the Hubble Space Telescope

    NASA Astrophysics Data System (ADS)

    Freedman, Wendy

    1996-05-01

    In a uniform and isotropic Universe, the relative expansion velocity v is proportional to the relative distance r such that v = H × r. Thus a determination of the present-day value of the Hubble constant H0 determines both the expansion timescale and the size scale of the Universe. The Hubble constant also provides constraints on the density of baryons produced in the Big Bang, the amount of dark matter, and how structure formed in the early Universe. The most accurate means of measuring the distances to nearby galaxies has proved to be the application of a relationship between the period and the luminosity for a class of supergiant variable stars known as classical Cepheids. Unfortunately the Cepheid variables are not intrinsically luminous enough to be measured out to distances where the velocities of recession of galaxies are a few thousand km/sec and thus dominate the peculiar velocities due to the gravitational interactions between galaxies (typically a few hundred km/sec). The Hubble Space Telescope Key Project on the Extragalactic Distance has been designed to measure a value of the Hubble constant accurate to ±10% [random + systematic]. The program has been designed to use Cepheid variables to determine the distances to a representative sample of about 20 galaxies both inside and out of small groups and in major clusters. These galaxies are being used to tie into methods with high internal precision ( ~ ±5%) that operate at greater distances, thereby allowing an accurate absolute calibration and an intercomparison of several independent techniques. Our preliminary result is that the value of the Hubble constant is 80 ± 17 km/sec/Mpc footnote Freedman, W. L. et al., Nature, 371, 757, (1994) New results will be presented based on observations of several new galaxies, including NGC 1365 in the nearby Fornax cluster. My collaborators on the HST Key Project team are R. Kennicutt, J. Mould, F. Bresolin, L. Ferrarese, H. Ford, J. Graham, M. Han, P. Harding, J

  5. Long range constant force profiling for measurement of engineering surfaces

    NASA Astrophysics Data System (ADS)

    Howard, L. P.; Smith, S. T.

    1992-10-01

    A new instrument bridging the gap between atomic force microscopes (AFMs) and stylus profiling instruments is described. The constant force profiler is capable of subnanometer resolution over a 15-μm vertical range with a horizontal traverse length of 50 mm. This long traverse length, coupled with the possibilities of utilizing standard radius, diamond measurement styli, make the force profiler more compatible with existing profiling instrument standards. The forces between the specimen and a diamond stylus tipped cantilever spring are sensed as displacements using a capacitance bridge. This displacement signal is then fed through a proportional plus integral controller to a high stability piezoelectric actuator to maintain a constant tip-to-sample force of approximately 100 nN. Much of the sensor head and traverse mechanism is made of Zerodur glass-ceramic to provide the thermal stability needed for long travel measurements. Profiles of a 30-nm silica step height standard and an 8.5-μm step etched on Zerodur are presented.

  6. Noncontact charge measurement of moving microparticles contacting dielectric surfaces

    NASA Astrophysics Data System (ADS)

    Nesterov, Alexander; Löffler, Felix; König, Kai; Trunk, Ulrich; Leibe, Klaus; Felgenhauer, Thomas; Stadler, Volker; Bischoff, Ralf; Breitling, Frank; Lindenstruth, Volker; Hausmann, Michael

    2007-07-01

    In this study examples for a noncontact procedure that allow the description of instant electric charging of moving microparticles that contact dielectric surfaces, for instance, of a flow hose are presented. The described principle is based on the measurement of induced currents in grounded metal wire probes, as moving particles pass close to the probe. The feasibility of the approach was tested with laser printer toner particles of a given size for different basic particle flow and charging conditions. An analytic description for the induced currents was developed and compared to observed effects in order to interpret the results qualitatively. The implementation of the presented procedure can be applied to transparent and nontransparent particle containers and flow lines of complex geometry which can be composed from the presented basic flow stream configurations.

  7. High Precision Measurement of the Avogadro Constant Based on Silicon

    NASA Astrophysics Data System (ADS)

    Becker, Peter

    2005-06-01

    This paper describes an attempt to replace the present definition of the kilogram with the mass of a certain number of carbon atoms. This requires determination of the Avogadro constant, NA, with a relative uncertainty of 1 × 10-8. Silicon crystals are used in this determination. At present, a limiting factor is the measurement of the average molar mass of natural Si. Consequently, a worldwide collaboration has been set up, to produce, approximately, 5 kg of 28Si single-crystal with an enrichment greater than 99.985% and of sufficient chemical purity to be used for the determination of NA with a target relative measurement uncertainty better than 2 × 10-8.

  8. Spectroscopic ellipsometry analysis of nanoporous low dielectric constant films processed via supercritical carbon dioxide for next-generation microelectronic devices

    NASA Astrophysics Data System (ADS)

    Othman, Maslina T.

    My research will address issues at the back-end-of-line in microelectronics fabrication, specifically the need for Low-k extendibility. The International Roadmap for Semiconductors (2005) suggested that interconnect insulation must be replaced with a material having an ultra-low dielectric constant (k) of < 2.0 and can withstand rigorous current process integration for the 65 nm technology. Creating porosity in the films produces k-values as low (1.0) air. In this research, supercritical CO2 (SCCO2) process is utilized to create pores, remove water, repair plasma-damaged sample and seal pores. These multi-step processing does not only produce low-k film but also create device reliability. Spectroscopy ellipsometric (SE) analysis is used to evaluate the performance of each process on porous film. In SE analysis, Cauchy, Bruggeman Effective Medium Approximation and graded models are used to model the processed samples. The depth profile SE analysis demonstrates the individual process performance based on its changes of refractive index (n) throughout the film thickness. SE also provide important film properties like thickness, porosity etc. In addition to SE, Fourier Transform Infra-red (FT-IR), Scanning Electron Microscopy (SEM) and electrical characterizations are used. Results show that SCCO2/co-solvents can extract porogens and remove water effectively at a significantly shorter time (≤1 hr) and at a low temperature (≤160°C) without thickness shrinkage in contrast with thermal annealing which uses 450°C and 5 hours without significantly shrinkage. SCCO2/TMCS removes water and terminates silanol group with methyl group, and hence preventing water re-adsorption which increases k. The dense layer on the sample surface that formed through the vapor treatment/HMDS helps to seal pores and prevent metal diffusion. This research also shows that patterning samples prior to porogen/water removal can minimize plasma damages on porous sample.

  9. The Newtonian gravitational constant: recent measurements and related studies

    NASA Astrophysics Data System (ADS)

    Gillies, George T.

    1997-02-01

    Improvements in our knowledge of the absolute value of the Newtonian gravitational constant, G, have come very slowly over the years. Most other constants of nature are known (and some even predictable) to parts per billion, or parts per million at worst. However, G stands mysteriously alone, its history being that of a quantity which is extremely difficult to measure and which remains virtually isolated from the theoretical structure of the rest of physics. Several attempts aimed at changing this situation are now underway, but the most recent experimental results have once again produced conflicting values of G and, in spite of some progress and much interest, there remains to date no universally accepted way of predicting its absolute value. The review will assess the role of G in physics, examine the status of attempts to derive its value and provide an overview of the experimental efforts that are directed at increasing the accuracy of its determination. Regarding the latter, emphasis will be placed on describing the instrumentational aspects of the experimental work. Related topics that are also discussed include the search for temporal variation of G and recent investigations of possible anomalous gravitational effects that lie outside of presently accepted theories.

  10. Coaxial probe and apparatus for measuring the dielectric spectra of high pressure liquids and supercritical fluid mixtures

    NASA Astrophysics Data System (ADS)

    Lee, Sung B.; Smith, Richard L.; Inomata, Hiroshi; Arai, Kunio

    2000-11-01

    A probe and apparatus were developed for measuring the dielectric spectra (complex permittivity) of high pressure liquids and supercritical fluid mixtures. The probe consisted a 2.2 mm semirigid coaxial cable that was cut off flat and mounted into a high pressure tube. The apparatus for measuring complex permittivity consisted of the dielectric probe, cell, densimeter, piston for varying the system density at constant composition, and magnetic pump for agitation and recirculation, all of which were housed in a constant temperature air bath. The probe is simple, robust, inexpensive, and further, its design allows for quick connection to high pressure systems. Probe accuracy is estimated to be ±0.5 in ɛ' and ±0.5 in ɛ″ from 200 MHz to 18 GHz based on replicate measurements of calibration and 2σ deviations over the interval. Dielectric spectra were measured over the 200 MHz-20 GHz range for methanol+carbon dioxide mixture at 323.2 K and a pressures up to 18 MPa.

  11. Langmuir probe measurements in a VHF dielectric plasma etcher

    NASA Astrophysics Data System (ADS)

    Dorf, Leonid; Ramaswamy, Kartik; Collins, Ken; Merry, Walter

    2008-10-01

    Langmuir probe (LP) measurements in a realistic VHF CCP discharge are complicated by a number of factors, such as absence of a well-defined DC ground reference and unpredictable behavior of standard electronic components at VHF. The VHF source can produce plasma very efficiently; therefore, to reach the same plasma density, VHF discharges require lower power than HF discharges. Nevertheless, even at low source power (˜100--200W with Ne<= 10^10 cm-3), RF potential in a VHF CCP discharge can be large, especially compared to that in an ICP discharge with similar parameters. Uncompensated RF potential distorts both electron and ion parts of the measured V-I characteristic, resulting in unrealistic plasma parameters. Here, we present preliminary results of our work to develop a LP system suitable for measurements in a 162 MHz dielectric plasma etcher. The probe design employs many previously developed RF compensation techniques. Furthermore, all electronic components of the probe and the measuring circuit were characterized using a network analyzer to select adequate values. The probe was used to study the effects of magnetic field, input power, pressure, and other operating conditions on electron and ion density profiles. Electron temperature was found to be in the range of 1.8 -- 3.5 eV, and the shape of ion saturation curve was found to be in agreement with OML theory.

  12. Damage by radicals and photons during plasma cleaning of porous low-k SiOCH. II. Water uptake and change in dielectric constant

    SciTech Connect

    Shoeb, Juline; Kushner, Mark J.

    2012-07-15

    Porous dielectric materials provide lower capacitances that reduce RC time delays in integrated circuits. Typical low-k materials include porous SiOCH-silicon dioxide with carbon groups, principally CH{sub 3}, lining the pores. With a high porosity, internally connected pores provide pathways for reactive species to enter into the material. Fluorocarbon plasmas are often used to etch SiOCH, a process that leaves a fluorocarbon polymer on the surface that must later be removed. During cleaning using Ar/O{sub 2} or He/H{sub 2} plasmas, reactions of radicals that diffuse into the SiOCH and photons that penetrate into the SiOCH can remove -CH{sub 3} groups. Due to its higher reactivity, cleaning with Ar/O{sub 2} plasmas removes more -CH{sub 3} groups than He/H{sub 2} plasmas, and so produce more free radical sites, such as -SiO{sub 2} Bullet (a -SiO{sub 2}-CH{sub 3} site with the -CH{sub 3} group removed).Upon exposure to humid air, these free radical sites can chemisorb H{sub 2}O to form hydrophilic Si-OH which can further physisorb H{sub 2}O through hydrogen bonding to form Si-OH(H{sub 2}O). With the high dielectric constant of water, even a small percentage of water uptake can significantly increase the effective dielectric constant of SiOCH. In this paper, we report on results from a computational investigation of the cleaning of SiOCH using Ar/O{sub 2} or He/H{sub 2} plasmas and subsequent exposure to humid air. The authors found that plasma cleaning with He/H{sub 2} mixtures produce less demethylation than cleaning with Ar/O{sub 2} plasmas, as so results in less water uptake, and a smaller increase in dielectric constant. The water that produces the increase in dielectric constant is roughly half chemisorbed and half physisorbed, the latter of which can be removed with mild heating. Sealing the pores with NH{sub 3} plasma treatment reduces water uptake and helps prevent the increase in dielectric constant.

  13. Dielectric constants of binary mixtures of propylene carbonate with dimethyl carbonate and ethylene carbonate from molecular dynamics simulation: comparison between non-polarizable and polarizable force fields

    NASA Astrophysics Data System (ADS)

    Lee, Sanghun; Park, Sung Soo

    2013-01-01

    Using non-polarizable and polarizable molecular dynamics simulations, binary mixtures of propylene carbonate + dimethyl carbonate and propylene carbonate + ethylene carbonate with various compositions were investigated. The polarizable model produces more reasonable estimation of dielectric constants than the non-polarizable model; however, combining the electronic continuum model with the non-polarizable MD improves the comparison between the two models. Fair agreement was found between the results from these simulations and available experimental data. In addition, for a better understanding of the mixing behaviour, the excess dielectric constants over the entire composition were calculated. By comparison of the two mixtures in various mole fractions, distinctive mixing behaviours of propylene carbonate + dimethyl carbonate (poorly symmetric mixture) and propylene carbonate + ethylene carbonate (highly symmetric mixture) were observed.

  14. Complex dielectric constant well logging means and method for determining the water saturation and the water resistivity of an earth formation

    SciTech Connect

    Sims, J.C.; Cox, P.T.; Simpson, R.S.

    1988-09-27

    This patent describes a well logging system for determining the water saturation of an earth formation and the resistivity of the water comprising: means for transmitting electromagnetic energy at a frequency lying within a range of frequencies from 10 MHz to 200 MHz into the earth formation from a borehole traversing the earth formation, means for receiving electromagnetic energies at two locations in the borehole from the earth formation, means for deriving a complex dielectric constant from the received electromagnetic energies, and means for deriving the water resistivity and the water saturation of the earth formation in accordance with a predetermined porosity of the earth formation and with the real and imaginary parts of the derived complex dielectric constant.

  15. Hydrogen bond network in the hydration layer of the water confined in nanotubes increasing the dielectric constant parallel along the nanotube axis.

    PubMed

    Qi, Wenpeng; Zhao, Hongwei

    2015-09-21

    The water confined in nanotubes has been extensively studied, because of the potential usages in drug delivery and desalination. The radial distribution of the dielectric constant parallel along the nanotube axis was obtained by molecular dynamics simulations in a carbon nanotube and a nanotube with a very small van der Waals potential. The confined water was divided into two parts, the middle part water and the hydration water. In both cases, the hydrogen bond orientation of the middle water is isotropic, while the hydrogen bonds in hydration layers are apt to parallel along the nanotube axis. Therefore, the hydration water has higher dipole correlations increasing the dielectric constant along the nanotube axis. PMID:26395729

  16. Measurements of Newton's gravitational constant and the length of day

    NASA Astrophysics Data System (ADS)

    Anderson, J. D.; Schubert, G.; Trimble, V.; Feldman, M. R.

    2015-04-01

    About a dozen measurements of Newton's gravitational constant, G, since 1962 have yielded values that differ by far more than their reported random plus systematic errors. We find that these values for G are oscillatory in nature, with a period of P = 5.899 +/- 0.062 \\text{yr} , an amplitude of (1.619 +/- 0.103) × 10-14 \\text{m}3 \\text{kg}-1 \\text{s}-2 , and mean-value crossings in 1994 and 1997. However, we do not suggest that G is actually varying by this much, this quickly, but instead that something in the measurement process varies. Of other recently reported results, to the best of our knowledge, the only measurement with the same period and phase is the Length of Day (LOD —defined as a frequency measurement such that a positive increase in LOD values means slower Earth rotation rates and therefore longer days). The aforementioned period is also about half of a solar activity cycle, but the correlation is far less convincing. The 5.9 year periodic signal in LOD has previously been interpreted as due to fluid core motions and inner-core coupling. We report the G/LOD correlation, whose statistical significance is 0.99764 assuming no difference in phase, without claiming to have any satisfactory explanation for it. Least unlikely, perhaps, are currents in the Earth's fluid core that change both its moment of inertia (affecting LOD) and the circumstances in which the Earth-based experiments measure G. In this case, there might be correlations with terrestrial-magnetic-field measurements.

  17. Time-dependent dielectric breakdown measurements of porous organosilicate glass using mercury and solid metal probes

    SciTech Connect

    Pei, Dongfei; Nichols, Michael T.; Shohet, J. Leon; King, Sean W.; Clarke, James S.; Nishi, Yoshio

    2014-09-01

    Time-dependent dielectric breakdown (TDDB) is one of the major concerns for low-k dielectric materials. During plasma processing, low-k dielectrics are subjected to vacuum ultraviolet photon radiation and charged-particle bombardment. To examine the change of TDDB properties, time-to-breakdown measurements are made to porous SiCOH before and after plasma exposure. Significant discrepancies between mercury and solid-metal probes are observed and have been shown to be attributed to mercury diffusion into the dielectric porosities.

  18. Preparation and Characterization of Ultralow-Dielectric-Constant Porous SiCOH Thin Films Using 1,2-Bis(triethoxysilyl)ethane, Triethoxymethylsilane, and a Copolymer Template

    NASA Astrophysics Data System (ADS)

    Fu, Shuang; Qian, Ke-Jia; Ding, Shi-Jin; Zhang, David Wei

    2011-10-01

    Ultralow-dielectric-constant ( k) porous SiCOH films have been prepared using 1,2-bis(triethoxysilyl)ethane, triethoxymethylsilane, and a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer template by means of spin-coating. The resulting films were characterized by cross-section scanning electron microscopy, small-angle x-ray diffraction, atomic force microscopy, Fourier-transform infrared spectroscopy, nanomechanical testing, and electrical measurements. Thermal treatment at 350°C for 2 h resulted in the formation of ultralow- k films with k of ˜2.0, leakage current density of 3 × 10-8 A/cm2 at 1 MV/cm, reduced modulus ( E r) of ˜4.05 GPa, and hardness ( H) of ˜0.32 GPa. After annealing between 400°C and 500°C for 30 min, the resulting films showed fluctuant k values of 1.85 to 2.22 and leakage current densities of 3.7 × 10-7 A/cm2 to 3 × 10-8 A/cm2 at 0.8 MV/cm, likely due to the change of the film microstructure. Compared with 350°C annealing, higher-temperature annealing can improve the mechanical strength of the ultralow- k film, i.e., E r ≈ 5 GPa and H ≈ 0.56 GPa after 500°C annealing.

  19. Precision measurement of the Newtonian gravitational constant using cold atoms.

    PubMed

    Rosi, G; Sorrentino, F; Cacciapuoti, L; Prevedelli, M; Tino, G M

    2014-06-26

    About 300 experiments have tried to determine the value of the Newtonian gravitational constant, G, so far, but large discrepancies in the results have made it impossible to know its value precisely. The weakness of the gravitational interaction and the impossibility of shielding the effects of gravity make it very difficult to measure G while keeping systematic effects under control. Most previous experiments performed were based on the torsion pendulum or torsion balance scheme as in the experiment by Cavendish in 1798, and in all cases macroscopic masses were used. Here we report the precise determination of G using laser-cooled atoms and quantum interferometry. We obtain the value G = 6.67191(99) × 10(-11) m(3) kg(-1) s(-2) with a relative uncertainty of 150 parts per million (the combined standard uncertainty is given in parentheses). Our value differs by 1.5 combined standard deviations from the current recommended value of the Committee on Data for Science and Technology. A conceptually different experiment such as ours helps to identify the systematic errors that have proved elusive in previous experiments, thus improving the confidence in the value of G. There is no definitive relationship between G and the other fundamental constants, and there is no theoretical prediction for its value, against which to test experimental results. Improving the precision with which we know G has not only a pure metrological interest, but is also important because of the key role that G has in theories of gravitation, cosmology, particle physics and astrophysics and in geophysical models. PMID:24965653

  20. Thrust Measurement of Dielectric Barrier Discharge (DBD) Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Ashpis, David E.; Laun, Matthew C.

    2013-11-01

    DBD plasma actuators generate a wall-jet that can be used for active flow control. We used an analytical balance to measure the thrust generated by the actuator, it is a common metric of its performance without external flow. We found that the measured force is afflicted by several problems; it drifts in time, not always repeatable, is unstable, and depends on the manner the voltage is applied. We report results of investigations of these issues. Tests were conducted on an actuator constructed of 1/4 inch thick high-density polyethylene (HDPE) dielectric with 100 mm long offset electrodes, with applied voltages up to 48 kV p-p and frequencies from 32 Hz to 2.5 kHz, and pure Sine and Trapezoidal waveforms. The relative humidity was in the range of 51-55%, corresponding to moisture range of 10,500 to13,000 ppm mass. Force readings were up to 500 mg, (approximately 50 mN/m). We found that the measured force is the net of the positive thrust generated by the wall-jet and an ``anti-thrust'' acting in the opposite direction. We propose a correction procedure that yields the plasma-generated thrust. The correction is based on voltage-dependent anti-thrust measured in the low frequency range of 20-40 Hz. We found that adjacent objects in a test setup affect the measured thrust, and verified it by comparing experiments with and without a metal enclosure, grounded and ungrounded. Uncorrected thrust varied by up to approximately +/-100%, and the corrected thrust variations were up to approximately 30%. Supported by NASA's FAP/Aerospace Sciences Project.

  1. Optical second-harmonic generation measurements of porous low-k dielectric materials

    NASA Astrophysics Data System (ADS)

    Atkin, Joanna; Shaw, Thomas; Laibowitz, Robert; Heinz, Tony

    2009-03-01

    Low-k dielectric materials based on porous carbon-doped oxides, with relative dielectric constants as low as 2.1, are widely used as thin insulating films in the microelectronics industry. Knowledge of these materials' basic electronic properties, such as energy gaps, barrier heights, and trap states, is essential for modeling their electrical leakage and stability characteristics. We use femtosecond laser pulses to probe the dynamics of charge-carrier transfer processes across Si/LKD interfacial barriers by optical second harmonic generation (SHG). Larger electric fields from multiphoton injection can be developed in Si/LKD systems compared to Si/SiO2, indicating a significantly higher density of traps in the LKD. This is consistent with previously reported measurements of trap density by photoinjection techniques^*. We will also discuss results on the dynamics of discharging and on the dependence of charging phenomena on layer thickness. ^*J. M. Atkin, D. Song, T. M. Shaw, E. Cartier, R. B. Laibowitz, and T. F. Heinz, J. Appl. Phys. 103, 094104 (2008).

  2. Machine learning aided diagnosis of hepatic malignancies through in vivo dielectric measurements with microwaves

    NASA Astrophysics Data System (ADS)

    Yilmaz, Tuba; Alp Kılıç, Mahmut; Erdoğan, Melike; Çayören, Mehmet; Tunaoğlu, Doruk; Kurtoğlu, İsmail; Yaslan, Yusuf; Çayören, Hüseyin; Enes Arıkan, Akif; Teksöz, Serkan; Cancan, Gülden; Kepil, Nuray; Erdamar, Sibel; Özcan, Murat; Akduman, İbrahim; Kalkan, Tunaya

    2016-07-01

    In the past decade, extensive research on dielectric properties of biological tissues led to characterization of dielectric property discrepancy between the malignant and healthy tissues. Such discrepancy enabled the development of microwave therapeutic and diagnostic technologies. Traditionally, dielectric property measurements of biological tissues is performed with the well-known contact probe (open-ended coaxial probe) technique. However, the technique suffers from limited accuracy and low loss resolution for permittivity and conductivity measurements, respectively. Therefore, despite the inherent dielectric property discrepancy, a rigorous measurement routine with open-ended coaxial probes is required for accurate differentiation of malignant and healthy tissues. In this paper, we propose to eliminate the need for multiple measurements with open-ended coaxial probe for malignant and healthy tissue differentiation by applying support vector machine (SVM) classification algorithm to the dielectric measurement data. To do so, first, in vivo malignant and healthy rat liver tissue dielectric property measurements are collected with open-ended coaxial probe technique between 500 MHz to 6 GHz. Cole–Cole functions are fitted to the measured dielectric properties and measurement data is verified with the literature. Malign tissue classification is realized by applying SVM to the open-ended coaxial probe measurements where as high as 99.2% accuracy (F1 Score) is obtained.

  3. Assessing Chicken Meat Freshness through Measurement of Radio-Frequency Dielectric Properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Change in freshness of chicken meat was assessed through measurement of the dielectric properties with a vector network analyzer and an open-ended coaxial-line probe between 200 MHz and 20 GHz at 23 oC. Chicken meat samples were stored in a refrigerator for 8 days at 4 oC. Changes in dielectric cons...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  6. Differential and double-differential dielectric spectroscopy to measure complex permittivity in transmission lines

    NASA Astrophysics Data System (ADS)

    Lanzi, Leandro; Carla, Marcello; M. C. Gambi, Cecilia; Lanzi, Leonardo

    2002-08-01

    This article presents and compares two differential methods for measuring the complex permittivity of dielectric materials: In the first method, two measuring cells built as coaxial transmission lines of identical cross section and terminations but different lengths are filled with a sample of the dielectric material. The complex dielectric permittivity is determined from the scattering parameter measurements and the length difference between the two cells, neglecting the resistive losses due to the cells. The second method is a double-differential one: Repeating measurements on the same cells empty, no other knowledge or limiting assumption is required.

  7. High-frequency dielectric behaviour of erbium substituted Ni-Zn ferrites

    NASA Astrophysics Data System (ADS)

    Kumar, K. Vijaya; Reddy, A. Chandra Shekhar; Ravinder, D.

    2003-07-01

    Dielectric properties such as dielectric constant ( ɛ') and dielectric loss tangent (tan δ) of mixed Ni-Zn-Er ferrites have been measured at room temperature in the frequency range 1-13 MHz using a HP 4192A impedance analyser. Plots of dielectric constant ( ɛ') versus frequency show a normal dielectric behaviour of spinel ferrites. The frequency dependence of dielectric loss tangent (tan δ) is found to be abnormal, giving a peak at certain frequency for all mixed Ni-Zn-Er ferrites. A qualitative explanation is given for the composition and frequency dependence of the dielectric constant and dielectric loss tangent. Plot of dielectric constant versus temperature has shown a transition near the Curie temperature for all the samples of Ni-Zn-Er ferrites. On the basis of these results an explanation for the dielectric mechanism in Ni-Zn-Er ferrites is suggested.

  8. Spectral Sensitivity Measured with Electroretinogram Using a Constant Response Method

    PubMed Central

    Rocha, Fernando Allan de Farias; Gomes, Bruno Duarte; Silveira, Luiz Carlos de Lima; Martins, Sonia Limara; Aguiar, Renata Genaro; de Souza, John Manuel; Ventura, Dora Fix

    2016-01-01

    A new method is presented to determine the retinal spectral sensitivity function S(λ) using the electroretinogram (ERG). S(λ)s were assessed in three different species of myomorph rodents, Gerbils (Meriones unguiculatus), Wistar rats (Ratus norvegicus), and mice (Mus musculus). The method, called AC Constant Method, is based on a computerized automatic feedback system that adjusts light intensity to maintain a constant-response amplitude to a flickering stimulus throughout the spectrum, as it is scanned from 300 to 700 nm, and back. The results are presented as the reciprocal of the intensity at each wavelength required to maintain a constant peak to peak response amplitude. The resulting S(λ) had two peaks in all three rodent species, corresponding to ultraviolet and M cones, respectively: 359 nm and 511 nm for mice, 362 nm and 493 nm for gerbils, and 362 nm and 502 nm for rats. Results for mouse and gerbil were similar to literature reports of S(λ) functions obtained with other methods, confirming that the ERG associated to the AC Constant-Response Method was effective to obtain reliable S(λ) functions. In addition, due to its fast data collection time, the AC Constant Response Method has the advantage of keeping the eye in a constant light adapted state. PMID:26800521

  9. Spectral Sensitivity Measured with Electroretinogram Using a Constant Response Method.

    PubMed

    Rocha, Fernando Allan de Farias; Gomes, Bruno Duarte; Silveira, Luiz Carlos de Lima; Martins, Sonia Limara; Aguiar, Renata Genaro; de Souza, John Manuel; Ventura, Dora Fix

    2016-01-01

    A new method is presented to determine the retinal spectral sensitivity function S(λ) using the electroretinogram (ERG). S(λ)s were assessed in three different species of myomorph rodents, Gerbils (Meriones unguiculatus), Wistar rats (Ratus norvegicus), and mice (Mus musculus). The method, called AC Constant Method, is based on a computerized automatic feedback system that adjusts light intensity to maintain a constant-response amplitude to a flickering stimulus throughout the spectrum, as it is scanned from 300 to 700 nm, and back. The results are presented as the reciprocal of the intensity at each wavelength required to maintain a constant peak to peak response amplitude. The resulting S(λ) had two peaks in all three rodent species, corresponding to ultraviolet and M cones, respectively: 359 nm and 511 nm for mice, 362 nm and 493 nm for gerbils, and 362 nm and 502 nm for rats. Results for mouse and gerbil were similar to literature reports of S(λ) functions obtained with other methods, confirming that the ERG associated to the AC Constant-Response Method was effective to obtain reliable S(λ) functions. In addition, due to its fast data collection time, the AC Constant Response Method has the advantage of keeping the eye in a constant light adapted state. PMID:26800521

  10. Benchmarking density functional perturbation theory to enable high-throughput screening of materials for dielectric constant and refractive index

    NASA Astrophysics Data System (ADS)

    Petousis, Ioannis; Chen, Wei; Hautier, Geoffroy; Graf, Tanja; Schladt, Thomas D.; Persson, Kristin A.; Prinz, Fritz B.

    2016-03-01

    We demonstrate a high-throughput density functional perturbation theory (DFPT) methodology capable of screening compounds for their dielectric properties. The electronic and ionic dielectric tensors are calculated for 88 compounds, where the eigenvalues of the total dielectric tensors are compared with single crystal and polycrystalline experimental values reported in the literature. We find that GGA/PBE has a smaller mean average deviation from experiments (MARD=16.2 %) when compared to LDA. The prediction accuracy of DFPT is lowest for compounds that exhibit complex structural relaxation effects (e.g., octahedra rotation in perovskites) and/or strong anharmonicity. Despite some discrepancies between DFPT results and reported experimental values, the high-throughput methodology is found to be useful in identifying interesting compounds by ranking. This is demonstrated by the high Spearman correlation factor (ρ =0.92 ). Finally, we demonstrate that DFPT provides a good estimate for the refractive index of a compound without calculating the frequency dependence of the dielectric matrix (MARD=5.7 %).

  11. Environmental effects on electron transfer from chlorophyll triplet to quinone: role of dielectric constant, viscosity and quinone structure in cellulose acetate films

    SciTech Connect

    Cheddar, G.; Tollin, G.

    1981-01-01

    The effects of environmental parameters on chlorophyll triplet quenching and electron transfer to quinones have been investigated in a system consisting of donor and acceptor incorporated into a cellulose acetate film which was subsequently exposed to solvent. Triplet quenching by a diffusional mechanism was found to occur in the dry film, with steric effects being a major determinant of quencher effectiveness. No formation of separated radicals was found under these conditions, probably because the high viscosity prevented separation of the initially formed radical-ion pair. When the film was subsequently exposed to water, triplet quenching became more effective and separated radical production occurred. This is attributed to effects of decreased microviscosity and increased dielectric constant. Both steric effects and quinone redox potential were found to influence radical yields. Rate constants for reverse electron transfer were independent of quinone redox potential. When solvents other than pure water were used, radical yields were observed to increase with the dielectric constant. This is ascribed to an increase in the ease of separation of the radical-ion pair.

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

    NASA Technical Reports Server (NTRS)

    Altshuller, Aubrey P

    1954-01-01

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

  13. Measurement of. cap alpha. /sub s/. [Strong fine structure constant

    SciTech Connect

    Clavelli, L.

    1983-01-01

    We point out that a number of QCD tests, relatively free of obvious nonperturbative corrections and other theoretical problems, are now available in e/sup +/e/sup -/ annihilation. By focusing on these tests, one can see the beginning of a confirmation of the running of the strong-coupling constant predicted by the renormalization group.

  14. A New Application for Radioimmunoassay: Measurement of Thermodynamic Constants.

    ERIC Educational Resources Information Center

    Angstadt, Carol N.; And Others

    1983-01-01

    Describes a laboratory experiment in which an equilibrium radioimmunoassay (RIA) is used to estimate thermodynamic parameters such as equilibrium constants. The experiment is simple and inexpensive, and it introduces a technique that is important in the clinical chemistry and research laboratory. Background information, procedures, and results are…

  15. A parallel measurement programme in high temperature dielectric property measurement: An update

    SciTech Connect

    Batt, J.; Sutton, W.H.; Binner, J.G.P.; Cross, T.E.

    1995-12-31

    Following the Materials Research Society Symposium on Microwave Processing of Materials held in San Francisco during April 1992 a Parallel Measurement Programme for high temperature dielectric properties was established. Initial results of this programme were presented at the ACerS symposium in Cincinnati in 1993 and preliminary results of the second stage at the MRS meeting in San Francisco in 1994. This paper will review the results obtained in the second stage of the programme since 1993 and give an inter-comparison of the applicability of the different measurement techniques.

  16. Microwave-Assisted Synthesis of High Dielectric Constant CaCu3Ti4O12 from Sol-Gel Precursor

    NASA Astrophysics Data System (ADS)

    Ouyang, Xin; Cao, Peng; Huang, Saifang; Zhang, Weijun; Huang, Zhaohui; Gao, Wei

    2015-07-01

    CaCu3Ti4O12 (CCTO) powders derived from sol-gel precursors were calcined and sintered via microwave radiation. The obtained CCTO powders were compared with that obtained via a conventional heating method. For microwave heating, 89.1 wt.% CCTO was achieved from the sol-gel precursor, after only 17 min at 950°C. In contrast, the conventional calcination method required 3 h to generate 87.6 wt.% CCTO content at 1100°C. In addition, the CCTO powders prepared through 17 min of microwave calcination exhibited a small particle size distribution of D50 = 3.826 μm. It was found that a lengthy hold time of 1 h by microwave sintering is required to obtain a high dielectric constant (3.14 × 103 at 102 Hz) and a reasonably low dielectric loss (0.161) in the sintered CCTO ceramic. Based upon the distinct microstructures, the dielectric responses of the CCTO samples sintered by different methods are attributed to space charge polarization and internal barrier layer capacitor mechanism.

  17. Correlation between band gap, dielectric constant, Young’s modulus and melting temperature of GaN nanocrystals and their size and shape dependences

    PubMed Central

    Lu, Haiming; Meng, Xiangkang

    2015-01-01

    With structural miniaturization down to the nanoscale, the detectable parameters of materials no longer remain constant but become tunable. For GaN nanocrystals example, the band gap increases while the dielectric constant, Young’s modulus and melting temperature decrease with decreasing the solid size. Herein, we developed the models to describe the size and shape dependences of these seemingly uncorrelated parameters for GaN nanocrystals, based on our established thermodynamic model for cohesive energy of metallic nanocrystals. Consistency between our theoretical predictions and the corresponding experimental or simulated results confirms the accuracy of the developed models and indicates the essentiality of cohesive energy in describing the effects of size and shape on the physicochemical properties of different low-dimensional systems. PMID:26582533

  18. High-index dielectric substrates with nearly constant reflectance for incident unpolarized or circularly polarized light over a wide range of incidence angles

    NASA Astrophysics Data System (ADS)

    Azzam, R. M. A.

    2015-06-01

    Dielectric substrates with refractive indices in the range n1 ≤ n ≤ n2, ? and ? exhibit nearly constant reflectance for incident unpolarized or circularly polarized light Ru(ϕ) over a wide range of incidence angle ϕ. For ?, Ru(ϕ) increases monotonically from ? at normal incidence by only 0.06% at ϕ = 45° and 1% at ϕ = 60°. For n2 = 4.6116, ? at the Brewster angle ϕB = 77.77° and the normalized reflectance shift |(Ru - R0)/R0| is constant reflectance for incident unpolarized light over a wide range of incidence angles at IR and visible wavelengths.

  19. Effect of dielectric constant, cavities in series, and cavities in parallel on the product distribution of the oligomerization of methane via microwave plasmas

    SciTech Connect

    Marun, C.; Suib, S.L.; Dery, M.; Harrison, J.B.; Kablaoui, M.

    1996-11-07

    The use of microwave-induced plasmas as a method to oligomerize methane to higher hydrocarbons has been studied. The pressure range used was 10-20 Torr and the applied power was 60 W. The microwave power is coupled to the plasma by means of either an Evenson or a Beenakker cavity, the Beenakker being the most effective. We explored the effect of the presence of a dielectric material on the product distribution for this reaction. The values of the dielectric constants for these materials varied from 2.6 for Pb(Ac){sub 2} to 10,000 for MnO{sub 2} relative to the vacuum. No direct correlation was found, but in some cases the selectivities toward C{sub 6s}to C{sub 8s} were enhanced. TiO{sub 2}and Li{sub 2}CO{sub 3} increased the selectivities toward C{sub 6s}. SnO{sub 2} was the best for selectivities to C{sub 7s}and C{sub 8s}. When a coating of Si/SiC on the reactor walls was present in the plasma zone, the selectivities toward C{sub 6s} and C{sub 7s} increased with respect to both materials (Si and SiC) by themselves. We also studied the effect of cavities in series and cavities in parallel on the oligomerization of methane with and without dielectric material in between the cavities. When methane and iodine are activated separately and then recombined, it seems that the oligomerization of methane is enhanced toward higher hydrocarbons. We found that when a dielectric material is placed in between and when the distance between the two cavities in series is the largest, the oligomerization of methane toward high molecular weight hydrocarbons is maximized. 45 refs., 9 figs., 1 tab.

  20. Measurement and analysis of cryogenic sapphire dielectric resonators and DROs

    NASA Technical Reports Server (NTRS)

    Dick, G. J.

    1987-01-01

    Presented are the experimental and computational results of a study on a new kind of dielectric resonator oscillator (DRO). It consists of a cooled, cylindrically symmetric sapphire resonator surrounded by a metallic shield and is capable of higher Q's than any other dielectric resonator. Isolation of fields to the sapphire by the special nature of the electromagnetic mode allows the very low loss of the sapphire itself to be expressed. Calculations show that the plethora of modes in such resonators can be effectively reduced through the use of a ring resonator with appropriate dimensions. Experimental results show Q's ranging from 3 x 10 to the 8th at 77 K to 10 to the 9th at 4.2 K. Performance is estimated for several types of DROs incorporating these resonators. Phase noise reductions in X-band sources are indicated at values substantially lower than those previously available.

  1. (abstract) Characterization of Tree Water Status and Dielectric Constant Changes of North American Boreal Forests in Combination with Synthetic Aperture Radar Remote Sensing

    NASA Technical Reports Server (NTRS)

    McDonald, K. C.; Zimmerman, R.; Way, J. B.

    1994-01-01

    The occurrence and magnitude of temporal and spatial tree water status changes in the boreal environment were studied in a floodplain forest in Alaska and in four forest types of Central Canada. Under limited water supply conditions from the rooted soil zone in early spring (freeze/thaw transition) and during summer, trees show declining water potentials. Coincidental change in tree water potential, tree transpiration and tree dielectric constant had been observed in previous studies performed in Mediterranean ecotones. If radar is sensitive to chances in tree water status as reflected through changes in dielectric constant, then radar remote sensing could be used to monitor the water status of forests. The SAR imagery is examined to determine the response of the radar backscatter to the ground based observations of the water status of forest canopies. Comparisons are made between stands and also along the large North-South gradient between sites. Data from SAR are used to examine the radar response to canopy physiological state as related to vegetation freeze/thaw and growing season length.

  2. Spin-coated and PECVD low dielectric constant porous organosilicate films studied by 1D and 2D solid-state NMR.

    PubMed

    Gerbaud, Guillaume; Hediger, Sabine; Bardet, Michel; Favennec, Laurent; Zenasni, Aziz; Beynet, Julien; Gourhant, Olivier; Jousseaume, Vincent

    2009-11-14

    In the research field of the sub-65 nm semiconductor industry, organosilicate SiOCH films with low dielectric constant (k < 2.4) need to be developed in order to improve the performance of integrated circuits [International Roadmap for Semiconductors (ITRS), San Jose, CA, 2004]. One way to produce SiOCH films of low dielectric constant is to introduce pores into the film. This is usually obtained in two steps. Firstly, co-deposition of a matrix precursor, with a sacrificial organic porogen, either by plasma enhanced chemical vapor deposition (PECVD) or spin-coating. Secondly, application of a specific thermal treatment to remove the porogen and create the porosity. This last step can be improved by adding to the thermal process a super-critical CO(2) treatment, an UV irradiation or an electronic bombardment (e-beam). In this study, the two deposition processes as well as the various treatments applied to eliminate the porogens were evaluated and compared using high-resolution solid-state NMR. For this purpose, hybrid (containing porogens) and porous films were extensively characterized on the basis of their (1)H, (13)C and (29)Si high-resolution NMR spectra. Information was obtained concerning the crosslinking of the Si skeleton. Spectral features could be correlated to the processes used. Isotropic chemical shift analyses and 2D correlation NMR experiments were used to show the existence and nature of the interactions between the matrix precursor and the organic porogen. PMID:19851550

  3. Dielectric constant tunability at microwave frequencies and pyroelectric behavior of lead-free submicrometer-structured (Bi0.5Na0.5)1-xBaxTiO3 ferroelectric ceramics.

    PubMed

    Martínez, Félix L; Hinojosa, Juan; Doménech, Ginés; Fernández-Luque, Francisco J; Zapata, Juan; Ruiz, Ramon; Pardo, Lorena

    2013-08-01

    In this article, we show that the dielectric constant of lead-free ferroelectric ceramics based on the solid solution (1-x)(Bi(0.5)Na(0.5))TiO(3)-xBaTiO(3), with compositions at or near the morphotropic phase boundary (MPB), can be tuned by a local applied electric field. Two compositions have been studied, one at the MPB, with x = 0.06 (BNBT6), and another one nearer the BNT side of the phase diagram, with x = 0.04 (BNBT4). The tunability of the dielectric constant is measured at microwave frequencies between 100 MHz and 3 GHz by a nonresonant method and simultaneously applying a dc electric field. As expected, the tunability is higher for the composition at the MPB (BNBT6), reaching a maximum value of 60% for an electric field of 900 V/cm, compared with the composition below this boundary (BNBT4), which saturates at 40% for an electric field of 640 V/cm. The high tunability in both cases is attributed to the fine grain and high density of the samples, which have a submicrometer homogeneous grain structure with grain size of the order of a few hundred nanometers. Such properties make these ceramics attractive for microwave tunable devices. Finally, we have tested these ceramics for their application as infrared pyroelectric detectors and we have found that the pyroelectric figure of merit is comparable to traditional lead-containing pyroelectrics. PMID:25004530

  4. Polycarbonate based three-phase nanocomposite dielectrics

    NASA Astrophysics Data System (ADS)

    Sain, P. K.; Goyal, R. K.; Prasad, Y. V. S. S.; Bhargava, A. K.

    2016-08-01

    Three-phase polycarbonate (PC) matrix nanocomposites are prepared using the solution method. One of the nanocomposite fillers is dielectric and the other is conducting. Lead zirconate titanate (PZT) is used as the dielectric filler. The conducting fillers, nano-Cu and multi-walled carbon nanotubes (MWCNTs), are used to make two different nanocomposites, MWCNT–PZT–PC and Cu–PZT–PC. The prepared nanocomposites are characterized using density measurement, x-ray diffractometry, scanning electron microscopy, energy dispersive x-ray spectroscopy, and differential scanning calorimetry. Percolation is absent in both three-phase nanocomposites within the study’s concentration window of conducting fillers. The dielectric properties of the nanocomposites are evaluated using a precision impedance analyser. The dielectric constant of the Cu–PZT–PC nanocomposite increases to 14 (a dissipation factor of 0.17), whereas in the case of the MWCNT–PZT–PC nanocomposite it increases to 8.5 (a dissipation factor of 0.002). The melting point of both nanocomposites decreases with respect to the control PC. The frequency (1 kHz to 1 MHz) and temperature (room temperature to 200 °C) dependence of the dielectric constant and dissipation factor are examined. For the Cu–PZT–PC nanocomposites, the dielectric constant decreases with increasing frequency, whereas in the case of the MWCNT–PZT–PC nanocomposites the dielectric constant is almost constant. The dielectric constant and dissipation factor exhibit a slight temperature dependence.

  5. Spatial concentration distribution analysis of cells in electrode-multilayered microchannel by dielectric property measurement.

    PubMed

    Yao, Jiafeng; Kodera, Tatsuya; Obara, Hiromichi; Sugawara, Michiko; Takei, Masahiro

    2015-07-01

    The spatial concentration distribution of cells in a microchannel is measured by combining the dielectric properties of cells with the specific structure of the electrode-multilayered microchannel. The dielectric properties of cells obtained with the impedance spectroscopy method includes the cell permittivity and dielectric relaxation, which corresponds to the cell concentration and structure. The electrode-multilayered microchannel is constructed by 5 cross-sections, and each cross-section contains 5 electrode-layers embedded with 16 micro electrodes. In the experiment, the dielectric properties of cell suspensions with different volume concentrations are measured with different electrode-combinations corresponding to different electric field distributions. The dielectric relaxations of different cell concentrations are compared and discussed with the Maxwell-Wagner dispersion theory, and the relaxation frequencies are analysed by a cell polarization model established based on the Hanai cell model. Moreover, a significant linear relationship with AC frequency dependency between relative permittivity and cell concentration was found, which provides a promising way to on-line estimate cell concentration in microchannel. Finally, cell distribution in 1 cross-section of the microchannel (X and Y directions) was measured with different electrode-combinations using the dielectric properties of cell suspensions, and cell concentration distribution along the microchannel (Z direction) was visualized at flowing state. The present cell spatial sensing study provides a new approach for 3 dimensional non-invasive online cell sensing for biological industry. PMID:26392831

  6. Spatial concentration distribution analysis of cells in electrode-multilayered microchannel by dielectric property measurement

    PubMed Central

    Yao, Jiafeng; Kodera, Tatsuya; Obara, Hiromichi; Sugawara, Michiko; Takei, Masahiro

    2015-01-01

    The spatial concentration distribution of cells in a microchannel is measured by combining the dielectric properties of cells with the specific structure of the electrode-multilayered microchannel. The dielectric properties of cells obtained with the impedance spectroscopy method includes the cell permittivity and dielectric relaxation, which corresponds to the cell concentration and structure. The electrode-multilayered microchannel is constructed by 5 cross-sections, and each cross-section contains 5 electrode-layers embedded with 16 micro electrodes. In the experiment, the dielectric properties of cell suspensions with different volume concentrations are measured with different electrode-combinations corresponding to different electric field distributions. The dielectric relaxations of different cell concentrations are compared and discussed with the Maxwell-Wagner dispersion theory, and the relaxation frequencies are analysed by a cell polarization model established based on the Hanai cell model. Moreover, a significant linear relationship with AC frequency dependency between relative permittivity and cell concentration was found, which provides a promising way to on-line estimate cell concentration in microchannel. Finally, cell distribution in 1 cross-section of the microchannel (X and Y directions) was measured with different electrode-combinations using the dielectric properties of cell suspensions, and cell concentration distribution along the microchannel (Z direction) was visualized at flowing state. The present cell spatial sensing study provides a new approach for 3 dimensional non-invasive online cell sensing for biological industry. PMID:26392831

  7. Dielectric constant and ordering effects of pure and doped KTaO3 quantum paraelectric; Cu-codoping enhancement effect

    NASA Astrophysics Data System (ADS)

    Trepakov, V. A.; Savinov, M. E.; Vikhnin, V. S.; Jastrabik, L.; Kapphan, S.; Syrnikov, P. P.

    ɛ'(T, f) and tan[δ(T, f)] spectra (10-300 K, 120 Hz-1 MHz) of pure KTaO3 (KTO), KTO: Li (0.1-3%), KTO: Fe 1%, KTO: Cu 0.83% below 70 K reveal a Debye-like universal Arrhenius relaxation with Δ ≈ 80-85 meV, τ0 ˜ 5 × 10-14s. In KTO: Li + Fe and KTO: Li + Cu this contribution increases, confirming dipole-pair ordering effects with the leading role of Li+ in pair relaxation (V. Trepakov et al., J. Phys.: Condens. Matter 7, 3785 (1995)). A dramatic Cu-codoping dielectric enhancement effect in KTO: Li + Cu was observed. In KTO: Li 3% + Cu 0.2% in region 50-60 K ɛ'(T) reveals a maximum of ˜ 105, accompanied by temperature hysteresis and dielectric loops. Ferroelectric-type phase transition with a critical dynamic central peak, induced by Cu2+(Ta)-VO centers as a slowest relaxator or oscillator in KTO: Li, is considered as an ɛ' enhancement cause. A possibility of incommensurate phase induced by Cu2+-VO centers and cluster-induced cooperative behavior is discussed too.

  8. Electric field modulation of the band gap, dielectric constant and polarizability in SnS atomically thin layers

    NASA Astrophysics Data System (ADS)

    Pan, Longfei; Zou, Bingsuo; Shi, Li-Jie

    2016-06-01

    The band structure and dielectric properties of multilayer SnS films have been investigated by density-functional theory total-energy calculations. It shows that electric field can tune the band gap of SnS multilayer and induce a phase transition from semiconductor to semi-metal. The critical electric field of phase transition for SnS bilayer is 0.09 V/Å, which is lower than MoS2(0.3 V/Å), MoSe2(0.25 V/Å), MoTe2(0.2 V/Å), WS2(0.27 V/Å) and WSe2(0.20 V/Å). Combining the electric structure with dielectric properties, we explain the reason why multilayer SnS films are more sensitive to the electric field. The sensitive response character to electric field makes SnS multilayer as a potential material for the nano-electronic and nano-optical devices.

  9. Constant frequency pulsed phase-locked loop measuring device

    NASA Technical Reports Server (NTRS)

    Yost, William T. (Inventor); Kushnick, Peter W. (Inventor); Cantrell, John H. (Inventor)

    1993-01-01

    A measuring apparatus is presented that uses a fixed frequency oscillator to measure small changes in the phase velocity ultrasonic sound when a sample is exposed to environmental changes such as changes in pressure, temperature, etc. The invention automatically balances electrical phase shifts against the acoustical phase shifts in order to obtain an accurate measurement of electrical phase shifts.

  10. Test results of a prototype dielectric microcalorimeter

    NASA Technical Reports Server (NTRS)

    Pfafman, T. E.; Silver, E.; Labov, S.; Beeman, J.; Goulding, F.; Hansen, W.; Landis, D.; Madden, N.

    1990-01-01

    The initial development work on a dielectric microcalorimeter is presented. It focuses on the dielectric properties of the ferroelectric material KTa(1-x)Nb(x)O3 (KTN). Measurements of the temperature dependent dielectric constant are given together with the first alpha particle detection results from a prototype composite microcalorimeter operating at 1.3 K. A nonthermal mechanism for detecting 6 MeV alpha particles in a monolithic KTN sample is also reported.

  11. Time and wavelength resolved measurements of the VUV excimer emission generated in a windowless dielectric barrier discharge (DBD) in argon

    NASA Astrophysics Data System (ADS)

    Ganesan, Rajesh; Kane, Deborah; Carman, Robert

    2011-10-01

    Temporal analysis of the VUV emission from a windowless dielectric barrier discharge in pure argon from 50-800 mbar were carried out to gain insight into the underlying kinetic processes relating to the first and second continuum emission bands of the Ar2* excimer. Pulsed excitation using bi-polar voltage pulses with 2% duty-cycle and 32kHz repetition frequency were employed to achieve a uniform discharge with well-controlled electrical breakdown characteristics. By comprehensively measuring the rising and decay time constants for ~50 individual wavelengths within the first and second continuum of argon covering the range λ = 107nm-140nm, the dominant collisional and radiative rates relating to Ar2* excimer production and loss have been obtained. The variation of time constants as a function of wavelength and gas pressure has been determined. The VUV emission curves at the transition phase between the first and second continuum have been analyzed in detail.

  12. Interconversion of mechanical and dielectrical relaxation measurements for dicyclohexylmethyl-2-methyl succinate.

    PubMed

    Díaz-Calleja, R; Garcia-Bernabé, A; Sanchis, M J; del Castillo, L F

    2005-11-01

    A comparison between results of dielectrical relaxation and dynamic mechanical spectroscopies is carried out for the alpha-relaxation of the ester dicyclohexyl methyl-2-methyl succinate (DCMMS). The results for the dielectric permittivity and the shear modulus measurements are presented according to the empirical Havriliak-Negami (HN) equation. By using the time-temperature principle a master curve in each case was obtained for several temperatures. The comparative analysis presented here is based on the assumption of a relationship between rotational and shear viscosities. The former one is associated to the dielectrical relaxation, whereas the latter is associated to mechanical relaxation. Both viscosities are not necessarily equal in general, and we assume that the difference between them is an important factor to appropriately compare the dielectrical and mechanical results. PMID:16383609

  13. Measured current drainage through holes in various dielectrics up to 2 kilovolts in a dilute plasma

    NASA Technical Reports Server (NTRS)

    Grier, N. T.; Mckinzie, D. J., Jr.

    1972-01-01

    The electron current drained from a plasma through approximately 0.05 cm diameter holes in eight possible space applicable dielectrics placed on a probe biased at voltages up to 2000 V dc have been determined both theoretically and experimentally. The dielectrics tested were Parylene C and N, Teflon FEP type C, Teflon TFE, Nomex, quartz 7940 Corning Glass, Mylar A, and Kapton H polymide film. A Laplace field was used to predict an upper limit for the drainage current. The measured current was less than the computed current for quartz, Teflon FEP, and the 0.0123 cm thick sample of Parylene N for all voltages tested. The drainage current through the other dielectrics became equal to or greater than the computed current at a voltage below 2000 V. The magnitudes of the currents were between 0.1 and 10 microamperes for most of the dielectrics.

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

    PubMed

    Zalai, Dénes; Tobak, Teodóra; Putics, Ákos

    2015-12-01

    Apoptosis is a common type of cell death in biopharmaceutical cell culture processes which causes decrease in viable cell density and product yield. The progression of apoptosis has been reported to influence the dielectric properties of mammalian cells; however, the on-line detection of these effects has been rarely described. This study provides a comprehensive analysis of the on-line detectability of dielectric changes upon apoptosis induction in an industrial fed-batch process of CHO cells expressing a recombinant monoclonal antibody. Using capacitance signals, measured at 25 frequencies, the impact of apoptosis on the dielectric spectra was investigated in eight bioreactor cultivations in which various process conditions were combined with two different apoptosis induction strategies (camptothecin treatment and glucose starvation). To differentiate the apoptosis-related information from the cell concentration-associated variance in the multivariate capacitance datasets, principal component analysis (PCA) was used. A second principal component, explaining an explicit proportion (>20%) of the variance, was identified to be related to dielectric changes induced by apoptosis. Furthermore, the analysis of caspase-3 and -7 activation and DNA fragmentation showed that the detected dielectric change occurred in the early phase of apoptosis. The presented results verify that apoptosis has a considerable impact on the dielectric features of CHO cells and it can be monitored on-line with the introduced tool-set combining capacitance measurement with multivariate data analysis. PMID:26440966

  15. Measuring Photoelastic Constants with Schaefer-Bergmann Diffraction

    NASA Astrophysics Data System (ADS)

    Pfeiffer, Jonathan B.; Wagner, Kelvin H.

    We present a new method for measuring the ratios of photoelastic coefficients using Schaefer-Bergmann diffraction. We demon- strate our technique for isotropic fused silica and the trigonal crystal α-BaB2O4. The measured results for fused silica agree with the known values to within 0.4%. For α-BaB2O4, we compare our Schaefer-Bergmann diffraction results by measuring the photoelastic coefficients with the established Dixon method.

  16. Dielectric Barrier Discharge (DBD) Plasma Actuators Thrust-Measurement Methodology Incorporating New Anti-Thrust Hypothesis

    NASA Technical Reports Server (NTRS)

    Ashpis, David E.; Laun, Matthew C.

    2014-01-01

    We discuss thrust measurements of Dielectric Barrier Discharge (DBD) plasma actuators devices used for aerodynamic active flow control. After a review of our experience with conventional thrust measurement and significant non-repeatability of the results, we devised a suspended actuator test setup, and now present a methodology of thrust measurements with decreased uncertainty. The methodology consists of frequency scans at constant voltages. The procedure consists of increasing the frequency in a step-wise fashion from several Hz to the maximum frequency of several kHz, followed by frequency decrease back down to the start frequency of several Hz. This sequence is performed first at the highest voltage of interest, then repeated at lower voltages. The data in the descending frequency direction is more consistent and selected for reporting. Sample results show strong dependence of thrust on humidity which also affects the consistency and fluctuations of the measurements. We also observed negative values of thrust or "anti-thrust", at low frequencies between 4 Hz and up to 64 Hz. The anti-thrust is proportional to the mean-squared voltage and is frequency independent. Departures from the parabolic anti-thrust curve are correlated with appearance of visible plasma discharges. We propose the anti-thrust hypothesis. It states that the measured thrust is a sum of plasma thrust and anti-thrust, and assumes that the anti-thrust exists at all frequencies and voltages. The anti-thrust depends on actuator geometry and materials and on the test installation. It enables the separation of the plasma thrust from the measured total thrust. This approach enables more meaningful comparisons between actuators at different installations and laboratories. The dependence on test installation was validated by surrounding the actuator with a large diameter, grounded, metal sleeve.

  17. Indirect measure of the dielectric permittivity via GPR measurements on a cooperative target with unknown location.

    NASA Astrophysics Data System (ADS)

    Soldovieri, F.; Pettinelli, E.; Persico, R.

    2009-04-01

    An accurate measure of the dielectric permittivity of the soil is of interest for several hydrological applications, as optimal irrigation and pollution monitoring, only to quote few examples [1, 2]. In addition, an accurate knowledge of the dielectric properties of the soil is of interest in the framework of inverse scattering approaches applied to GPR data in order to detect and image properly the buried targets of interest [3]. This work deals with an indirect measure of the dielectric permittivity of the soil starting from GPR surface data collected on a buried "cooperative" target, meant as an object buried on purpose whose extent is known a-priori and small in terms of the probing wavelength [4]. This target is exploited in order to achieve, from its image obtained from a suitable GPR data processing, an indirect measure of the dielectric permittivity of the embedding soil. GPR data processing is based on a linear microwave tomographic approach funded on the Born Approximation. Using this Born approach on two-dimensional inversion tests, we investigate the effect of the soil's electrical conductivity and permittivity on this indirect measure and demonstrate that the electrical field scattered by a spot-like buried object permits a good estimation of the soil permittivity even when no accurate information of the soil conductivity is available [5]. The feasibility of the approach will be tested by a deep numerical analysis that will point out also the effect of the extent and of the location of the cooperative target. Experimental results will be also presented in the case of data collected in controlled conditions [6]. [1] Lambot, S., Slob, E.C., van den Bosch, I., Stockbroeckx, B., Vanclooster,M., 2004b. Modeling of ground-penetrating radar for accurate characterization of subsurface electric properties. IEEE Transaction on Geoscience and Remote Sensing 42, 2555-2568. [2] Huisman, J., Hubbard, S., Redman, J., Annan, A., 2003. Measuring soil water content with

  18. The critical behavior of the dielectric constant in the polar + polar binary liquid mixture nitromethane + 3-pentanol: an unusual sign of its critical amplitude in the one-phase region.

    PubMed

    Leys, Jan; Losada-Pérez, Patricia; Troncoso, Jacobo; Glorieux, Christ; Thoen, Jan

    2011-07-14

    Dielectric constant measurements have been carried out in the one- and two-phase regions near the critical point of the polar + polar binary liquid mixture nitromethane + 3-pentanol. In the two-phase region, evidence for the |t|(2β) singularity in the coexistence-curve diameter has been detected, thus confirming the novel predictions of complete scaling theory for liquid-liquid criticality. In the one-phase region, an "unusual" negative sign for the amplitude of the |t|(1-α) singularity has been encountered for the first time in an upper critical solution temperature type of binary liquid mixture at atmospheric pressure. Mass density measurements have also been carried out to provide additional information related to such experimental finding, which entails an increase of the critical temperature T(c) under an electric field. PMID:21766958

  19. Preparation and microwave characterization of BaNd{sub 2-x}Sm{sub x}Ti{sub 4}O{sub 12} (0 {<=} x {<=} 2) ceramics and their effect on the temperature coefficient of dielectric constant in polytetrafluoroethylene composites

    SciTech Connect

    Stanly Jacob, K.; Satheesh, R.; Ratheesh, R.

    2009-10-15

    High dielectric and temperature-stable ceramic compositions have been prepared through solid-state ceramic route. The structure and microstructure of the ceramics have been studied using powder X-ray diffraction and scanning electron microscopic techniques. The dielectric properties of well-sintered ceramics are studied in the microwave frequency region using Hakki and Coleman post-resonator technique. The samples exhibited high dielectric constant (>77), relatively high quality factor (>1500) and near zero temperature coefficient of resonant frequency. Phase pure calcined ceramic materials are incorporated in the polytetrafluoroethylene matrix through a proprietary process comprising of sigma mixing, extrusion, calendering followed by hot pressing for the fabrication of planar circuit laminates. The effect of temperature coefficient of dielectric constant of the resultant polytetrafluoroethylene/ceramic composite materials is studied with respect to compositional variation of the filler materials.

  20. Science and technology of thin films and interfacial layers in ferroelectric and high-dielectric constant heterostructures and application to devices.

    SciTech Connect

    Auciello, O.; Materials Science Division

    2006-01-01

    The fabrication of the next generation of complex oxide thin film-based micro and nanoscale devices, such as, for example, low and high density nonvolatile ferroelectric random access memories (FeRAMS), high-dielectric constant (K) high-frequency devices, and the next generation of complimentary metal oxide semiconductor (CMOS) nanoscale devices based on high-K dielectrics, require understanding and control of film growth and interface processes as well as development of materials integration strategies with atomic scale control. In recent years, we developed and applied a unique combination of integrated film synthesis/in situ characterization and ex situ analytical techniques capable of providing information about thin film surface and interface processes at the atomic scale as required for the development of the devices mentioned above. These techniques are also useful for establishing composition-microstructure-property relationships critical for the integration of oxide thin films with semiconductor device platforms for the development of a whole new generation of micro and nanodevices based on film technologies beyond semiconductors and specifically silicon. Our recent work has been focused on developing diffusion barrier layers and heterostructured bottom electrodes that play a critical role in high-density FeRAM integration. We demonstrated that TiAl layers can be used as a material with a double diffusion barrier/bottom electrode functionality for integration of ferroelectric capacitors CMOS devices for fabrication of FeRAMs. We also demonstrated that control of interfaces is critical to the integration of high-K dielectric films with appropriate substrates for the fabrication of high-performance high-frequency devices, and here again a diffusion barrier such as the TiAl layer developed by our group is critical for such integration. These studies revealed that when properly oxidized, nanoscale thick amorphous Ti-Al-O layers exhibit properties that make

  1. High Dielectric Constants of Composites of Fiber-Like Copper Phthalocyanine-Coated Graphene Oxide Embedded in Poly(arylene Ether Nitriles)

    NASA Astrophysics Data System (ADS)

    Li, Jingwei; Pu, Zejun; Wang, Zicheng; Long, Ya; Jia, Kun; Liu, Xiaobo

    2015-07-01

    The surfaces of graphene oxide (GO) sheets were coated with fiber-like copper phthalocyanine (CuPc) by use of a solvothermal process. The product, GO@ CuPc, was used as a filler in high-performance poly(arylene ether nitrile) (PEN) composites. Films of the composites had high thermal stability, and glass-transition temperatures in the range 170-182°C. Thermogravimetric analysis revealed their initial decomposition temperatures were in the range 470-483°C. Scanning electron microscopy showed that dispersion of GO@ CuPc in PEN was much better than that of unmodified GO; this can be attributed to relatively strong interaction between GO@CuPc and the PEN matrix. All the composite films were highly flexible and had enhanced mechanical properties. Tensile strengths of the composites were as high as 89 MPa in the presence of 1 wt.% GO@CuPc, an increase of 20% compared with pure PEN film. Dielectric constants of the composite films were as high as 52 at 100 Hz when the GO@CuPc content was 5%. Because of these excellent mechanical and dielectric properties, PEN/GO@CuPc composites have much potential for use as film capacitors.

  2. Measured Capacitance Change Based on Dielectric Location Using Long Distance Measurement Electrodes with Additional Arc Electrodes

    NASA Astrophysics Data System (ADS)

    Ohchi, Masashi; Furukawa, Tatsuya

    The new measurement scheme for the permittivity distribution have been proposed and tested experimentally based on the measured capacitance using a pair of long distance electrodes with the cylindrical shield and the additional arc electrodes. We have proposed the method of the electric field visualization using the electric lines of force based on the scalar potential, moreover, we have presented the new strategy in the estimation of the capacitance based on the electrostatic energy. In the paper, we will describe the capacitance of experimental results using the experiment system, where acrylic rod are inserted, and numerical results using FEM. It is found out that the capacitance is greatly influenced by the electric field deviation due to the location of dielectrics.

  3. Magneto-optical measurement of anisotropy energy constant(s) for amorphous rare earth, transition metal alloys

    SciTech Connect

    Uber, R.E.; Mansuripur, M.

    1988-11-01

    Optical investigation of magneto-optical films is complementary to conventional torque and VSM magnetometry. In the authors' laboratory, they are now measuring anisotropy energy constants of RE-TM thin films at temperatures from ambient to 150/sup 0/C. An in-plane magnetic field (up to 16.5 KOe) is applied to a saturated sample with perpendicular magnetization. The movement away from the perpendicular direction is monitored using the polar Kerr effect. At the HeNe wavelength, the Kerr effect is principally due to the top 500 angstroms of the transition metal subnetwork in the films.

  4. Dielectric spectroscopy of watermelons for quality sensing

    NASA Astrophysics Data System (ADS)

    Nelson, Stuart O.; Guo, Wen-chuan; Trabelsi, Samir; Kays, Stanley J.

    2007-07-01

    Dielectric properties of four small-sized watermelon cultivars, grown and harvested to provide a range of maturities, were measured with an open-ended coaxial-line probe and an impedance analyser over the frequency range from 10 MHz to 1.8 GHz. Probe measurements were made on the external surface of the melons and also on tissue samples from the edible internal tissue. Moisture content and soluble solids content (SSC) were measured for internal tissue samples, and SSC (sweetness) was used as the quality factor for correlation with the dielectric properties. Individual dielectric constant and loss factor correlations with SSC were low, but a high correlation was obtained between the SSC and permittivity from a complex-plane plot of dielectric constant and loss factor, each divided by SSC. However, SSC prediction from the dielectric properties by this relationship was not as high as expected (coefficient of determination about 0.4). Permittivity data (dielectric constant and loss factor) for the melons are presented graphically to show their relationships with frequency for the four melon cultivars and for external surface and internal tissue measurements. A dielectric relaxation for the external surface measurements, which may be attributable to a combination of bound water, Maxwell-Wagner, molecular cluster or ion-related effects, is also illustrated. Coefficients of determination for complex-plane plots, moisture content and SSC relationship, and penetration depth are also shown graphically. Further studies are needed for determining the practicality of sensing melon quality from their dielectric properties.

  5. Coaxial-probe contact-force monitoring for dielectric properties measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  6. Impact of the spacer dielectric constant on parasitic RC and design guidelines to optimize DC/AC performance in 10-nm-node Si-nanowire FETs

    NASA Astrophysics Data System (ADS)

    Hong, Jae-Ho; Lee, Sang-Hyun; Kim, Ye-Ram; Jeong, Eui-Young; Yoon, Jun-Sik; Lee, Jeong-Soo; Baek, Rock-Hyun; Jeong, Yoon-Ha

    2015-04-01

    In this paper, we propose an optimized design for Si-nanowire FETs in terms of spacer dielectric constant (κsp), extension length (LEXT), nanowire diameter (Dnw), and operation voltage (VDD) for the sub-10 nm technology node. Using well-calibrated TCAD simulations and analytic RC models, we have quantitatively evaluated geometry-dependent parasitic series resistances (RSD) and capacitances (Cpara). Compared with low-κ spacers, high-κ spacers exhibit a higher on/off-current ratio with a lower RSD, but show severe degradation in their AC performance owing to a higher Cpara. Considering the trade-off between RSD and Cpara, optimal geometry-dependent κsp values at various supply voltages (VDD) are determined using gate delay (CV/I) and current-gain cutoff frequency (fT). We found that as LEXT and VDD decrease and Dnw increases, the optimal κsp value shifts from the high-κ to low-κ regime.

  7. Bulk-phase thermodynamic properties and dielectric constant of ethanol: an ab initio quantum mechanical approach combined with a statistical model

    NASA Astrophysics Data System (ADS)

    Pandey, Prasenjit; Chakraborty, Tanmoy; Mukherjee, Asok K.

    2013-10-01

    Ab initio theory at the HF/6-311G(d,p) level has been used to compute the hydrogen bonding thermodynamics in bulk liquid ethanol. Inter-cluster hydrogen bonding is assumed to mimic the H-bonding in bulk ethanol. Rotation of the clusters has been neglected, but translational and vibrational motions are taken into account for calculating bulk thermodynamic parameters. Results are well in agreement with an earlier report [J. Chem. Phys. 116, 4212 (2002)]. For a more accurate dipole moment of monomer, MP2/6-311++G(d,p) calculation was done. Use of the computed thermodynamic data in a statistical model yields the Kirkwood-Frohlich correlation factor and the dielectric constant of ethanol (21.0) close to the experimental value, 24.3 at 298 K.

  8. High dielectric constant observed in (1 − x)Ba(Zr{sub 0.07}Ti{sub 0.93})O{sub 3}–xBa(Fe{sub 0.5}Nb{sub 0.5})O{sub 3} binary solid-solution

    SciTech Connect

    Kruea-In, Chatchai; Eitssayeam, Sukum; Pengpat, Kamonpan; Rujijanagul, Gobwute

    2012-10-15

    Binary solid-solutions of the (1 − x)Ba(Zr{sub 0.07}Ti{sub 0.93})O{sub 3}–xBa(Fe{sub 0.5}Nb{sub 0.5}O{sub 3}) system, with 0.1 ≤ x ≤ 0.9,were fabricated via a solid-state processing technique. X-ray diffraction analysis revealed that all samples exhibited a single perovskite phase. The BaFe{sub 0.5}Nb{sub 0.5}O{sub 3} also promoted densification and grain growth of the system. Dielectric measurements showed that all samples displayed a relaxor like behavior. The x = 0.1 sample presented a dielectric-frequency and temperature with low loss tangent (<0.07 at 10 kHz). For x > 0.2 samples, the dielectric data showed a broad dielectric constant–temperature curve with a giant dielectric characteristic. In addition, a high dielectric constant > 50,000 (at 10 kHz and temperature > 150 °C) was observed for the x = 0.9 sample.

  9. Effects of He (90%)/H{sub 2} (10%) plasma treatment on electric properties of low dielectric constant SiCOH films

    SciTech Connect

    Kim, Hoonbae; Ha, Myung Hoon; Jung, Donggeun; Chae, Heeyeop; Kim, Hyoungsub

    2012-10-15

    In microelectronics industry, integration of the low dielectric constant (low-k) material films is a continuing issue due to the decreasing device feature size. To improve electric properties, various post-deposition treatments of the low-k material films can be used. In this work, we used room temperature treatment of He/H{sub 2} plasma and investigated the effects of plasma treatment on the electrical properties of low-k SiOCH films. Plasma treatment time changed from 300 to 1800 s. After treatment, the dielectric constant was decreased from 2.9 to 2.48, and the thickness of the low-k SiCOH films changed by only ∼5%. The leakage current densities of the low-k SiCOH films were decreased to ∼10{sup −11} A/cm{sup 2}, with treatment time ≥600 s. The breakdown occurred only around 2 V for films plasma-treated for 600 and 900 s. However, for 1800 s treatment time, the breakdown voltage was enhanced dramatically and breakdown occurred at applied voltage higher than 40 V. The surface composition change of the films after treatment was investigated by X-ray photoelectron spectroscopy (XPS). As the plasma treatment time was increased, the intensities of C-C/C-H and C-Si peaks were decreased while the intensities of Si-O and C-O peaks were increased. It is thought that increase of oxygen content of the SiCOH film, after plasma treatment, contributed to leakage current reduction and breakdown voltage increase.

  10. Measurement of dielectric loss tangent at cryogenic temperature using superconducting film resonator

    NASA Astrophysics Data System (ADS)

    Zhang, Yufang; Wang, Zhenqing

    2016-03-01

    We demonstrate that the superconducting film resonator can be used to accurately and quantitatively measure the microwave dielectric loss tangent of a variety of materials. Compared to traditional dielectric resonator loaded metal cavity method, it has advantage of small sample size (~2-3 orders of magnitude smaller than the old method), and much higher sensitivity to measure small loss tangent values as small as 10-5 at around 7 GHz band at cryogenic temperatures. This method can be utilized widely in study of mechanism of microwave loss at cryogenic temperature range, which is extremely important in superconducting microwave application areas, such as novel super quantum computers.

  11. Dynamic electrical response of thin dielectric films measured by Electrostatic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Williams, Clayton; Klein, Levente

    2002-03-01

    Electrostatic Force Microscopy measurements have been performed on thin dielectric films on conducting substrates. Cantilever oscillation amplitude versus distance curves are measured as a function of the frequency of the voltage applied between tip and sample. When a DC voltage is applied, the oscillation amplitude versus distance curve is significantly different from that when a low frequency (500 Hz) AC voltage is applied (cantilever resonance at 125 kHz). The frequency dependence of the AC force response for different dielectric films (SiO2 and Al_2O_3) are studied. The frequency dependence is accounted for by the movement of charge near the sample surface with a finite response time.

  12. Real-time dielectric-film thickness measurement system for plasma processing chamber wall monitoring

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Yong; Chung, Chin-Wook

    2015-12-01

    An in-situ real-time processing chamber wall monitoring system was developed. In order to measure the thickness of the dielectric film, two frequencies of small sinusoidal voltage (˜1 V) signals were applied to an electrically floated planar type probe, which is positioned at chamber wall surface, and the amplitudes of the currents and the phase differences between the voltage and current were measured. By using an equivalent sheath circuit model including a sheath capacitance, the dielectric thickness can be obtained. Experiments were performed in various plasma condition, and reliable dielectric film thickness was obtained regardless of the plasma properties. In addition, availability in commercial chamber for plasma enhanced chemical vapor deposition was verified. This study is expected to contribute to the control of etching and deposition processes and optimization of periodic maintenance in semiconductor manufacturing process.

  13. New dielectric sensors and sensing techniques for soil and snow moisture measurements.

    PubMed

    Stacheder, Markus; Koeniger, Franz; Schuhmann, Rainer

    2009-01-01

    Measurements of material moisture are essential in fields such as agriculture or civil engineering. Electromagnetic techniques, more precisely dielectric methods, have gained wide acceptance in the last decades. Frequency or Time Domain methods take advantage of the high dielectric permittivity of water compared to dry materials. This paper presents four new dielectric sensors for the determination of soil or snow water content. After a short introduction into the principles, both the hardware and operating mode of each sensor are described. Field test results show the advantages and potentials such as automatic measurement and profiling, state-of-ground detection or large-scale determination. From the results it follows that the presented sensors offer promising new tools for modern environmental research. PMID:22574056

  14. New Dielectric Sensors and Sensing Techniques for Soil and Snow Moisture Measurements

    PubMed Central

    Stacheder, Markus; Koeniger, Franz; Schuhmann, Rainer

    2009-01-01

    Measurements of material moisture are essential in fields such as agriculture or civil engineering. Electromagnetic techniques, more precisely dielectric methods, have gained wide acceptance in the last decades. Frequency or Time Domain methods take advantage of the high dielectric permittivity of water compared to dry materials. This paper presents four new dielectric sensors for the determination of soil or snow water content. After a short introduction into the principles, both the hardware and operating mode of each sensor are described. Field test results show the advantages and potentials such as automatic measurement and profiling, state-of-ground detection or large-scale determination. From the results it follows that the presented sensors offer promising new tools for modern environmental research. PMID:22574056

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  16. Inverse problem in anisotropic poroelasticity: drained constants from undrained ultrasound measurements.

    PubMed

    Berryman, James G; Nakagawa, Seiji

    2010-02-01

    Poroelastic analysis has traditionally focused on the relationship between dry and drained constants, which are assumed known, and the saturated or undrained constants, which are assumed unknown. However, there are many applications in this field of study for which the main measurements can only be made on the saturated/undrained system, and then it is uncertain what the effects of the fluids were on the system, since the drained constants remain a mystery. The work presented here shows how to deduce drained constants from undrained constants for anisotropic systems having symmetries ranging from isotropic to orthotropic. Laboratory ultrasound data are then inverted for the drained constants in three granular packings: one of glass beads, and two others for distinct types of more or less angular sand grain packings. Experiments were performed under uniaxial stress, which resulted in hexagonal (transversely isotropic) symmetry of the poroelastic response. One important conclusion from the general analysis is that the drained constants are uniquely related to the undrained constants, assuming that porosity, grain bulk modulus, and pore fluid bulk modulus are already known. Since the resulting system of equations for all the drained constants is linear, measurement error in undrained constants also propagates linearly into the computed drained constants. PMID:20136194

  17. Inverse problem in anisotropic poroelasticity: Drained constants from undrained ultrasound measurements

    SciTech Connect

    Berryman, J.G.; Nakagawa, S.

    2009-11-20

    Poroelastic analysis has traditionally focused on the relationship between dry or drained constants which are assumed known and the saturated or undrained constants which are assumed unknown. However, there are many applications in this field of study for which the main measurements can only be made on the saturated/undrained system, and then it is uncertain what the eects of the uids were on the system, since the drained constants remain a mystery. The work presented here shows how to deduce drained constants from undrained constants for anisotropic systems having symmetries ranging from isotropic to orthotropic. Laboratory ultrasound data are then inverted for the drained constants in three granular packings: one of glass beads, and two others for distinct types of more or less angular sand grain packings. Experiments were performed under uniaxial stress, which resulted in hexagonal (transversely isotropic) symmetry of the poroelastic response. One important conclusion from the general analysis is that the drained constants are uniquely related to the undrained constants, assuming that porosity, grain bulk modulus, and pore uid bulk modulus are already known. Since the resulting system of equations for all the drained constants is linear, measurement error in undrained constants also propagates linearly into the computed drained constants.

  18. Photothermal transfer function of dielectric mirrors for precision measurements

    NASA Astrophysics Data System (ADS)

    Ballmer, Stefan W.

    2015-01-01

    The photothermal transfer function from absorbed power incident on a dielectric mirror to the effective mirror position is calculated using the coating design as input. The effect is found to change in amplitude and sign for frequencies corresponding to diffusion length comparable to the coating thickness. Transfer functions are calculated for the T i -doped Ta2O5:SiO2 coating used in Advanced LIGO and for a crystalline AlxGa1 -xAs coating. The shape of the transfer function at high frequencies is shown to be a sensitive indicator of the effective absorption depth, providing a potentially powerful tool to distinguish coating-internal absorption from surface contamination related absorption. The sign change of the photothermal effect could also be useful to stabilize radiation pressure-based optomechanical systems. High frequency corrections to the previously published thermo-optic noise estimates are also provided. Finally, estimating the quality of the thermo-optic noise cancellation occurring in fine-tuned AlxGa1 -xAs coatings requires the detailed heat flow analysis done in this paper.

  19. Earth Radiation Budget Satellite extraterrestrial solar constant measurements - 1986-1987 increasing trend

    NASA Technical Reports Server (NTRS)

    Lee, Robert B., III; Barkstrom, Bruce R.; Harrison, Edwin F.; Gibson, Michael A.; Natarajan, Sudha M.; Edmonds, William L.; Mecherikunnel, Ann T.; Kyle, H. Lee

    1988-01-01

    From June 1986 through Nov 1987, the Earth Radiation Budget Satellite (ERBS) pyrheliometric measurements indicated that the solar constant was increasing approximately +0.02 percent per year. Earlier ERBS measurements indicated that the solar constant was declining approximately -0.03 percent per year during the 1984 through mid-1986 period. Since mid-1986 represents the beginning of solar cycle 22, it is believed that the reversal in the long-term solar constant trend may be linked to increased solar activity associated with the beginning of the 11-year sunspot cycle. The typical value of the solar constant was found to be 1365 Wm-2.

  20. Non-Contact Measurement of Density and Thickness Variation in Dielectric Materials

    NASA Technical Reports Server (NTRS)

    Roth, Ron

    2009-01-01

    This non-contact, single-sided terahertz electromagnetic measurement and imaging method characterizes micro structural (e.g., spatially-lateral density) and thickness variation in dielectric (insulating) materials. This method was demonstrated for space shuttle external tank sprayed-on foam insulation and has been designed for use as an inspection method for current and future NASA thermal protection systems and other dielectric material inspection applications where no contact can be made with the sample due to fragility and it is impractical to use ultrasonic methods

  1. Dielectric properties of emulsions and suspensions: mixture equations and measurement comparisons.

    PubMed

    Erle, U; Regier, M; Persch, C; Schubert, H

    2000-01-01

    Dielectric properties of water-in-oil emulsions, oil in water emulsions and limestone-in-water suspensions have been measured at 2.45 GHz by an open-ended coaxial-line probe. The results were compared to various equations for the dielectric properties of mixtures. The equation by Fricke and Mudgett describes best the behavior of oil-in-water emulsions and limestone in water suspensions. For water-in-oil emulsions the equation by Lichtenecker and Rother gives the best results. PMID:11098444

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  3. Non-contact C-V measurements of ultra thin dielectrics

    NASA Astrophysics Data System (ADS)

    Edelman, P.; Savtchouk, A.; Wilson, M.; D'Amico, J.; Kochey, J. N.; Marinskiy, D.; Lagowski, J.

    2004-07-01

    In this paper, we present a non-contact C-V technique for ultra-thin dielectrics on silicon. The technique uses incremental corona charging of dielectric and a measurement of the surface potential with a vibrating capacitive electrode. A differential quasistatic C-V curve is generated using time-resolved measurements. The technique incorporates transconductance corrections that enable corresponding ultra-low electrical oxide thickness (EOT) determination down to the sub-nanometer range. It also provides a means for monitoring the flat band voltage, V{FB}, the interface trap spectrum, D{IT}, and the total dielectric charge, Q{TOT}. This technique is seen as a replacement for not only MOS C-V measurements but also for mercury-probe C-V. In addition, EOT measurement by the corona C-V has a major advantage over optical thickness methods because it is not affected by water adsorption and molecular airborne contamination, MAC. These effects have been a problem for optical metrology of ultra-thin dielectrics.

  4. Single Nanoparticle-Based Heteronanojunction as a Plasmon Ruler for Measuring Dielectric Thin Films.

    PubMed

    Li, Li; Hutter, Tanya; Li, Wenwu; Mahajan, Sumeet

    2015-06-18

    Nondestructive, noninvasive and accurate measurement of thin film thicknesses on dielectric substrates is challenging. In this work a ruler for measuring thin film thicknesses utilizes the heteronanojunction construct formed between a plasmonic nanoparticle and a high refractive index nonplasmonic substrate. The high near-field sensitivity in the nanojunction renders it suitable for measuring the thickness of intervening dielectric thin films. We demonstrate this by controlling the thickness of dielectric spacer layers created by overgrowing SiO2 thin films on commercially available silicon substrates. While Rayleigh (using dark-field) scattering measurements show that the spectral response is well correlated to the thickness of SiO2 spacer layers the distance-dependence is much steeper with surface-enhanced Raman scattering (SERS). Good agreement between 3D simulations and experimental results confirm the plasmon ruler construct's sensitivity to the dielectric thin film spacing. Thus, we postulate that this single nanoparticle based heteronanojunction configuration can serve as a convenient and simple ruler in metrology of thin films as well as a platform for SERS-based detection even in cases where plasmonically active films are not a suitable substrate. PMID:26266605

  5. 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...

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

    PubMed

    Kumar, P; Coronel, P; Simunovic, J; Truong, V D; Sandeep, K P

    2007-05-01

    Continuous flow microwave sterilization is an emerging technology that 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 temperature range of 20 to 130 degrees C and compared with those measured by the conventional approach (under static conditions). The food products chosen for this study were skim milk, green pea puree, carrot puree, and salsa con queso. Second-order polynomial correlations for the dependence of dielectric properties at 915 MHz of the food products on temperature were developed. Dielectric properties measured under static and continuous flow conditions were similar for homogeneous food products such as skim milk and vegetable puree, but they were significantly different for salsa con queso, which is a multiphase food product. The results from this study suggest that, for a multiphase product, dielectric properties measured under continuous flow conditions should be used for designing a continuous flow microwave heating system. PMID:17995769

  7. Multisection transmission line scatter function theory for measurements of soil dielectric properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vector network analyzers measure both reflection (S11) and transmission (S21) functions, but S21 has not been used to estimate soil dielectric permittivity independently. The objectives of this study were to: (1) derive the mathematical model for S21 of a multisection transmission line, and (2) tes...

  8. An Undergraduate Experiment to Measure the Reflectances of a Dielectric Surface

    ERIC Educational Resources Information Center

    Driver, H. S. T.

    1978-01-01

    Describes an experiment for the measurement of the reflectances of dielectric surface. The experiment is analyzed in terms of the Stokes parameters and the Mueller calculus, and Malus law is derived. The experiment also provides an introduction to the properties of real linear polarizers. (Author/GA)

  9. Dielectric properties of marsh vegetation

    NASA Astrophysics Data System (ADS)

    Kochetkova, Tatiana D.; Suslyaev, Valentin I.; Shcheglova, Anna S.

    2015-10-01

    The present work is devoted to the measurement of the dielectric properties of mosses and lichens in the frequency range from 500 MHz to 18 GHz. Subjects of this research were three species of march vegetation - moss (Dicranum polysetum Michx), groundcedar (Diphasiastrum complanatum (L.) Holub) and lichen (Cladonia stellaris). Samples of vegetation were collected in Tomsk region, Western Siberia, Russia. Complex dielectric permittivity was measured in coaxial section by Agilent Technologies vector network analyzer E8363B. Green samples was measured for some moisture contents from 100% to 3-5 % during a natural drying. The measurements were performed at room temperature, which remained within 21 ÷ 23 ° C. The frequency dependence of the dielectric constant for the three species of marsh vegetation differ markedly. Different parts of the complex permittivity dependency on moisture were fitted by line for all frequency points. Two break point were observed corresponding to the transition of water in the vegetation in various phase states. The complex permittivity spectra of water in the vegetation allow determining the most likely corresponding dielectric model of water in the vegetation by the method of hypothesis testing. It is the Debye's model. Parameters of Debye's model were obtained by numerical methods for all of three states of water. This enables to calculate the dielectric constant of water at any frequency range from 500 MHz to 18 GHz and to find the parameters of the dielectric model of the vegetation.

  10. Modelling dielectric-constant values of concrete: an aid to shielding effectiveness prediction and ground-penetrating radar wave technique interpretation

    NASA Astrophysics Data System (ADS)

    Bourdi, Taoufik; Eddine Rhazi, Jamal; Boone, François; Ballivy, Gérard

    2012-10-01

    A number of efficient and diverse mathematical methods have been used to model electromagnetic wave propagation. Each of these methods possesses a set of key elements which eases its understanding. However, the modelling of the propagation in concrete becomes impossible without modelling its electrical properties. In addition to experimental measurements; material theoretical and empirical models can be useful to investigate the behaviour of concrete's electrical properties with respect to frequency, moisture content (MC) or other factors. These models can be used in different fields of civil engineering such as (1) electromagnetic compatibility which predicts the shielding effectiveness (SE) of a concrete structure against external electromagnetic waves and (2) in non-destructive testing to predict the radar wave reflected on a concrete slab. This paper presents a comparison between the Jonscher model and the Debye models which is suitable to represent the dielectric properties of concrete, although dielectric and conduction losses are taken into consideration in these models. The Jonscher model gives values of permittivity, SE and radar wave reflected in a very good agreement with those given by experimental measurements and this for different MCs. Compared with other models, the Jonscher model is very effective and is the most appropriate to represent the electric properties of concrete.

  11. Optical constants of CH3NH3PbBr3 perovskite thin films measured by spectroscopic ellipsometry.

    PubMed

    Alias, Mohd Sharizal; Dursun, Ibrahim; Saidaminov, Makhsud I; Diallo, Elhadj Marwane; Mishra, Pawan; Ng, Tien Khee; Bakr, Osman M; Ooi, Boon S

    2016-07-25

    The lack of optical constants information for hybrid perovskite of CH3NH3PbBr3 in thin films form can delay the progress of efficient LED or laser demonstration. Here, we report on the optical constants (complex refractive index and dielectric function) of CH3NH3PbBr3 perovskite thin films using spectroscopic ellipsometry. Due to the existence of voids, the refractive index of the thin films is around 8% less than the single crystals counterpart. The energy bandgap is around 2.309 eV as obtained from photoluminescence and spectrophotometry spectra, and calculated from the SE analysis. The precise measurement of optical constants will be useful in designing optical devices using CH3NH3PbBr3 thin films. PMID:27464113

  12. Effect of the addition of B{sub 2}O{sub 3} and BaO-B{sub 2}O{sub 3}-SiO{sub 2} glasses on the microstructure and dielectric properties of giant dielectric constant material CaCu{sub 3}Ti{sub 4}O{sub 12}

    SciTech Connect

    Shri Prakash, B.; Varma, K.B.R.

    2007-06-15

    The effect of the addition of glassy phases on the microstructure and dielectric properties of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) ceramics was investigated. Both single-component (B{sub 2}O{sub 3}) and multi-component (30 wt% BaO-60 wt% B{sub 2}O{sub 3}-10 wt% SiO{sub 2} (BBS)) glass systems were chosen to study their effect on the density, microstructure and dielectric properties of CCTO. Addition of an optimum amount of B{sub 2}O{sub 3} glass facilitated grain growth and an increase in dielectric constant. However, further increase in the B{sub 2}O{sub 3} content resulted in its segregation at the grain boundaries associated with a reduction in the grain size. In contrast, BBS glass addition resulted in well-faceted grains and increase in the dielectric constant and decrease in the dielectric loss. An internal barrier layer capacitance (IBLC) model was invoked to correlate the dielectric constant with the grain size in these samples. - Graphical abstract: Scanning electron micrograph of 30 wt% BaO-60 wt% B{sub 2}O{sub 3}-10 wt% SiO{sub 2} (BBS) glass-added CaCu{sub 3}Ti{sub 4}O{sub 12} ceramic on sintering.

  13. Effect of the addition of B 2O 3 and BaO-B 2O 3-SiO 2 glasses on the microstructure and dielectric properties of giant dielectric constant material CaCu 3Ti 4O 12

    NASA Astrophysics Data System (ADS)

    Shri Prakash, B.; Varma, K. B. R.

    2007-06-01

    The effect of the addition of glassy phases on the microstructure and dielectric properties of CaCu 3Ti 4O 12 (CCTO) ceramics was investigated. Both single-component (B 2O 3) and multi-component (30 wt% BaO-60 wt% B 2O 3-10 wt% SiO 2 (BBS)) glass systems were chosen to study their effect on the density, microstructure and dielectric properties of CCTO. Addition of an optimum amount of B 2O 3 glass facilitated grain growth and an increase in dielectric constant. However, further increase in the B 2O 3 content resulted in its segregation at the grain boundaries associated with a reduction in the grain size. In contrast, BBS glass addition resulted in well-faceted grains and increase in the dielectric constant and decrease in the dielectric loss. An internal barrier layer capacitance (IBLC) model was invoked to correlate the dielectric constant with the grain size in these samples.

  14. Measurements and Simulations of Surface Dielectric Barrier Discharges Used as Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Hoskinson, Alan R.

    2012-01-01

    This report is a Ph.D. dissertation performed under NRA cooperative agreement and submitted as part of the final report. Asymmetric surface dielectric barrier discharges (DBDs) have shown promise for use as aerodynamic actuators for active flow control. In this project we studied DBD actuators experimentally and numerically. Our DBDs used a symmetric triangular high voltage waveform to generate plasma in atmospheric pressure air. Time-averaged measurements indicated that the induced force of a single barrier actuator design (one electrode insulated from the plasma) can be increased exponentially above the results of previous studies by decreasing both the length and thickness of the electrode exposed to the plasma. This increased force may allow these devices to control flow separation in a wider range of flow environments. Experiments using an intensified digital camera to examine the plasma on time scales of a few nanoseconds showed that, in addition to the previously-observed filamentary and jet-like plasma structures, discharges with very thin exposed electrodes exhibited a weak but constant plasma immediately adjacent to those electrodes. In double-barrier actuators (both electrodes insulated), decreasing the diameter of the narrower electrode lead to increasing forces, and recorded images showed the simultaneous existence of both filamentary and jet-like plasma structures. The development and application of a time-dependent, two-dimensional computational fluid plasma model has aided in understanding the detailed physics of surface DBDs at all-time scales. For simulated single-barrier discharges, the model qualitatively reproduced the filamentary and jet-like micro-discharge structures. The model was somewhat successful in reproducing the observed characteristics of double-barrier actuators. For both actuator geometries, the model indicated that the majority of the forces induced on the neutral gas occur in between micro-discharges as the plasmas decay.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  16. Measurement of soil water content with dielectric dispersion frequency

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Frequency domain reflectometry (FDR) is an inexpensive and attractive methodology for repeated measurements of soil water content (SWC). Although there are some known measurement limitations for dry soil and sand, a fixed-frequency method is commonly employed using commercially available FDR probes....

  17. Effect of Annealing Temperature on Dielectric Constant and Bonding Structure of Low-k SiCOH Thin Films Deposited by Plasma Enhanced Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Lee, Sungwoo; Yang, Jaeyoung; Yeo, Sanghak; Lee, Jaewon; Jung, Donggeun; Boo, Jin-hyo; Kim, Hyoungsub; Chae, Heeyeop

    2007-02-01

    We investigated the effect of annealing temperature on the properties of SiCOH films deposited by plasma-enhanced chemical vapor deposition using or a mixture of Si-O containing and hydrocarbon precursors, decamethyl-cyclopentasiloxane (DMCPSO-C10H30O5Si5) and cyclohexane (CHex-C6H12). These SiCOH films were deposited at pressures of 0.6 and 1.5 Torr and the as-deposited SiCOH films were subjected to annealing temperatures from 25 to 500 °C in a furnace for 1 h in N2 ambient at a pressure of 1 atm. The relative dielectric constants, k, of the SiCOH films deposited at 0.6 and 1.5 Torr were 2.76 and 2.26, respectively, before the annealing process. The subsequent annealing of the SiCOH film at 500 °C further reduced the k values to as low as 2.31 and 1.85, respectively. Decreases in the refractive index, hardness, and modulus were observed as the annealing temperature increased to 450 °C. However, further increasing annealing temperature to 500 °C caused the refractive index, hardness, and modulus to increase again. Trends of decreases in both the hardness and modulus with increasing annealing temperature were found. The refractive index and the film thickness retention also decreased with increasing annealing temperature. The change in the k value as a function of the annealing temperature was correlated with the change in the Fourier transform infrared absorption peaks of C-Hx, Si-CH3, and Si-O related groups. As the annealing temperature increased, the intensity of both the CHx and Si-CH3 peaks decreased, respectively. In particular, the C-H2 (asymmetric and symmetric) peaks provide direct evidence of the presence of ethylene groups in the SiCOH films. Thus the decrease in intensity of the peaks corresponding to the CHx groups and Si-O cage structure in the SiCOH films was considered to be responsible for lowering they dielectric constant, refractive index, hardness and modulus of the films. The leakage current density of the SiCOH films at 1 MV/cm is obtained

  18. Electrode effects in dielectric spectroscopy measurements on (Nb +In) co-doped TiO2

    NASA Astrophysics Data System (ADS)

    Crandles, David; Yee, Susan; Savinov, Maxim; Nuzhnyy, Dimitri; Petzelt, Jan; Kamba, Stanislav; Prokes, Jan

    Recently, several papers reported the discovery of giant permittivity and low dielectric loss in (Nb+In) co-doped TiO2. A series of tests was performed which included the measurement of the frequency dependence of the dielectric permittivity and ac conductivity of co-doped (Nb+In)TiO2 as a function of electrode type, sample thickness and temperature. The data suggest that the measurements are strongly affected by the electrodes. The consistency between four contact van der Pauw dc conductivity measurements and bulk conductivity values extracted from two contact ac conductivity measurements suggest that the values of colossal permittivity are, at least in part, a result of Schottky barrier depletion widths that depend on electrode type and temperature. Nserc, Czech Science Foundation (Project 15-08389S).

  19. Elastic constants of α Ti-7Al measured using resonant ultrasound spectroscopy

    NASA Astrophysics Data System (ADS)

    Adebisi, R. A.; Sathish, S.; Pilchak, A. L.; Shade, P. A.

    2016-02-01

    The five independent elastic constants of a single-phase (α, HCP crystal structure) titanium alloy, Ti-7Al, have been measured for the first time using resonant ultrasound spectroscopy (RUS). RUS is a nondestructive evaluation method that mea-sures the mechanical resonance of solids and uses the resonance frequencies to extract a complete set of elastic constants of the solid material. The elastic constants of titanium alloys vary substantially depending on manufacturing history and composition. In addition, available data on the elastic constants of titanium alloys is limited. The elastic constants data for Ti-7Al are presented in this paper and the results are compared to the available data for other titanium alloys that are similar in composition.

  20. Fluid and microfluidic dielectric measurement using a cavity perturbation method at microwave C-band

    NASA Astrophysics Data System (ADS)

    Asghari, Aref

    The utilization of cavity perturbation technique in dielectric property measurement of fluid and micro-fluid is investigated in this thesis to better assist the ever-growing needs of science and technology for analysis and characterization of such materials in various applications from genetics, MEMS devices, to consumer product industry. Development of different techniques for measuring complex dielectric properties of fluid and micro-fluids at Giga (10 9)-Hz frequencies is of significant importance as their usage is increasingly coupled with infrared and microwave electromagnetic wavelengths. Conventional cavity perturbation method could provide a sensitive and convenient system for measuring fluids of low (e.g., epsilonr <10) permittivity that meets the assumptions of negligible perturbation to the electromagnetic field distribution in the cavity. Developing a methodology that uses conventional cavity perturbation method that is however suitable for a sensitive, accurate, and reliable measurement of high permittivity polar liquids at microwave C-band is the goal in the current work. Systematic studies are carried out, using de-ionic (DI) water as test specimens, to evaluate the influence of sample's container, volume, dimension, and temperature on the sensitivity and reliability of microwave dielectric measurement. The cavity perturbation measurement of DI water in a 1 mm diameter capillary tube showed well-defined temperature dependence of dielectric permittivity and loss coefficients of water. Observation of a permittivity peak in temperature range tested at 4GHz around -10 °C implies an important relaxation in low temperatures at microwave C-band, which corresponds to a critical slowing down of polarization reorientation in crystallized (icy) H2O. Numerical simulations using Finite Element Analysis (FEA) COMSOL suites were conducted to established the optimum amount of liquid water for cavity perturbation testing at microwave C-band (in perfectly conducting

  1. A METHOD FOR THE MEASUREMENT OF SITE-SPECIFIC TAUTOMERIC AND ZWITTERIONIC MICROSPECIES EQUILIBRIUM CONSTANTS

    EPA Science Inventory

    We describe a method for the individual measurement of simultaneously occurring, unimolecular, site-specific "microequilibrium" constants as in, for example, prototropic tautomerism and zwitterionic equilibria. Our method represents an elaboration of that of Nygren et al. (Anal. ...

  2. METHOD FOR THE MEASUREMENT OF SITE-SPECIFIC TAUTOMERIC AND ZWITTERIONIC MICROSPECIES EQUILIBRIUM CONSTANTS

    EPA Science Inventory

    We describe a method for the individual measurement of simultaneously occurring, unimolecular, site-specific “microequilibrium” constants as in, for example, prototropic tautomerism and zwitterionic equilibria. Our method represents an elaboration of that of Nygren et al. (Anal. ...

  3. Electrowetting on dielectric-based microfluidics for integrated lipid bilayer formation and measurement

    NASA Astrophysics Data System (ADS)

    Poulos, Jason L.; Nelson, Wyatt C.; Jeon, Tae-Joon; Kim, Chang-Jin ``Cj''; Schmidt, Jacob J.

    2009-07-01

    We present a microfluidic platform for the formation and electrical measurement of lipid bilayer membranes. Using electrowetting on dielectric (EWOD), two or more aqueous droplets surrounded by a lipid-containing organic phase were manipulated into contact to form a lipid bilayer at their interface. Thin-film Ag/AgCl electrodes integrated into the device enabled electrical measurement of membrane formation and the incorporation of gramicidin channels of two bilayers in parallel.

  4. Recent developments in RF and microwave dielectric measurements at the UK National Physical Laboratory

    SciTech Connect

    Clarke, R.N.

    1994-12-31

    Dielectric measurements have been performed at NPL over much of the twentieth century but work in the microwave region of the spectrum only commenced in earnest in the late 1960s. Instruments developed under that programme - TE{sub 01}-mode cavities and open resonators - remain in use today because they provide the most sensitive means of measuring very low dielectric losses in the frequency range 10 - 144 GHz. More recently, in the mid-1980s, a programme of very high loss materials measurements commenced which was originally concerned with biomedical applications but which has been extended to the characterization of foodstuffs, various polar dielectric liquids and Radio Absorbing Material (RAM). A major concern in all of this work has been the requirement to ensure that measurements are demonstrably traceable to national standards: usually impedance, attenuation or dimensional standards are the most relevant. Another important aspect of the work is the estimation and reduction of measurement uncertainties. In pursuit of these aims the laboratory has always sought to take part in measurement intercomparisons both at local and international levels. NPL is at present the pilot laboratory for a BIPM intercomparison of complex permittivities of polar reference liquids. A third aspect of the work is to extend existing techniques to enable them to perform measurements upon new types of sample, for example, or to cover different ranges of complex permittivity. This can be a very cost-effective way of extending measurement capability since it usually does not involve gross expenditure on new instrumentation. These aspects of the work will be illustrated in this review by reference to three recent dielectrics projects undertaken at NPL.

  5. Microwave dielectric behavior of vegetation material

    NASA Technical Reports Server (NTRS)

    Elrayes, Mohamed A.; Ulaby, Fawwaz T.

    1987-01-01

    The microwave dielectric behavior of vegetation was examined through the development of theoretical models involving dielectric dispersion by both bound and free water and supported by extensive dielectric measurements conducted over a wide range of conditions. The experimental data were acquired using an open-ended coaxial probe that was developed for sensing the dielectric constant of thin layers of materials, such as leaves, from measurements of the complex reflection coefficient using a network analyzer. The probe system was successfully used to record the spectral variation of the dielectric constant over a wide frequency range extending from 0.5 to 20.4 GHz at numerous temperatures between -40 to +40 C. The vegetation samples were measured over a wide range of moisture conditions. To model the dielectric spectrum of the bound water component of the water included in vegetation, dielectric measurements were made for several sucrose-water solutions as analogs for the situation in vegetation. The results were used in conjunction with the experimental data for leaves to determine some of the constant coefficients in the theoretical models. Two models, both of which provide good fit to the data, are proposed.

  6. Determination of the Hubble Space Telescope effective conic-constant error from direct image measurements.

    PubMed

    Meinel, A B; Meinel, M P; Schulte, D H

    1993-04-01

    Direct measurement of discernible features in the Hubble Space Telescope (HST) imagery has enabled a self-consistent determination to be made of the effective conic constant of HST images taken with planetary camera 6 (PC-6) of the wide field and planetary camera. Before being corrected for the contribution from PC-6, the conic constant is - 1.01429 +/- 0.0002. The correction for PC-6 is less accurately determined but probably lies between -0.0002 and 0.0004. As a result the HST optics are characterized best by a conic constant of - 1.0140 +/- 0.0003 as obtained from direct image measurements. PMID:20820304

  7. In situ method for real time measurement of dielectric film thickness in plasmas

    SciTech Connect

    Jang, Sung-Ho; Kim, Gun-Ho; Chung, Chin-Wook

    2010-01-15

    An in situ thickness measurement method of dielectric films (dual frequency method) was developed, and the thicknesses were measured in an inductively coupled plasma. This method uses a small ac bias voltage with two frequencies for thickness measurement. The dielectric thickness is obtained from measuring the amplitudes of the two frequency ac currents through a sensor, as well as using an equivalent circuit model describing impedance of the dielectric film and the plasma sheath. In the experiment, the thicknesses of Al{sub 2}O{sub 3} film could be accurately measured in real time. To check the measurement reliability, the dual frequency method was compared with reflection spectrophotometry as a technique for optical thickness diagnostics. It was found that the dual frequency method agrees closely with reflection spectrophotometry at various rf powers and pressures. In addition, this method is very simple and can be installed anywhere in plasma reactors, in contrast with optical methods; therefore, it is expected to be applied to in situ surface diagnostics for various processing plasmas.

  8. Dielectric measurement method for real-time monitoring of initial hardening of backfill materials used for underground construction

    NASA Astrophysics Data System (ADS)

    Karlovšek, Jurij; Schwing, Moritz; Chen, Zhen; Wagner, Norman; Williams, David J.; Scheuermann, Alexander

    2016-04-01

    The broadband dielectric measurement method based on the vector network analysis technique, in combination with an open-ended coaxial probe, was applied to the determination of the dielectric relaxation behaviour of one- and two-component backfilling grout materials in the frequency range from 40 MHz to 2 GHz. The cement hydration process and the gelling of commercial grouts was monitored in real-time to investigate the application of non-destructive testing methods in the tunnelling industry. It was found that the time-dependent dielectric relaxation behaviour can accurately reveal the different stages of the hydration process and delineate the start of gel hardening. These measurement results demonstrate the practicability of the real-time dielectric measurement method to determine the broadband dielectric parameters of conventional backfill materials used in underground construction to determine construction integrity using non-destructive testing methods.

  9. Calculation of Dielectric Response in Molecular Solids for High Capacitance Organic Dielectrics

    NASA Astrophysics Data System (ADS)

    Heitzer, Henry Matthew

    The dielectric response of a material is critically important in numerous scientific processes spanning the fields of biology, chemistry, materials science, and physics. While important across these fundamental disciplines, it remains difficult to determine theoretically the dielectric environment of a system. With recent advances in nanotechnology, biochemistry, and molecular electronics, it has become necessary to determine the dielectric response in molecular systems that are difficult to measure experimentally, such as nanoscale interfaces, highly disordered biological environments, or molecular materials that are difficult to synthesize. In these scenarios it is highly advantageous to determine the dielectric response through efficient and accurate calculations. A good example of where a theoretical prediction of dielectric response is critical is in the development of high capacitance molecular dielectrics. Molecular dielectrics offer the promise of cheap, flexible, and mass producible electronic devices when used in conjunction with organic semiconducting materials to form Organic Field Effect Transistors (OFETs). To date, molecular dielectrics suffer from poor dielectric properties resulting in low capacitances. A low capacitance dielectric material requires a much larger power source to operate the device in OFETs, leading to modest device performance. Development of better performing dielectric materials has been hindered due to the time it takes to synthesize and fabricate new molecular materials. An accurate and efficient theoretical technique could drastically decrease this time by screening potential dielectric materials and providing design rules for future molecular dielectrics. Here in, the methodology used to calculate dielectric properties of molecular materials is described. The validity of the technique is demonstrated on model systems, capturing the frequency dependence of the dielectric response and achieving quantitative accuracy compared

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

    NASA Astrophysics Data System (ADS)

    Nakano, Yukie; Nomura, Takeshi; Takenaka, Tadashi

    2004-08-01

    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.

  11. Measurement of the electron density in a subatmospheric dielectric barrier discharge by spectral line shape

    SciTech Connect

    Dong Lifang; Qi Yuyan; Liu Weiyuan; Fan Weili

    2009-07-01

    The electron density in a subatmospheric dielectric barrier discharge by using argon spectral line shape is measured for the first time. With the gas pressure increasing in the range of 1x10{sup 4} Pa-6x10{sup 4} Pa, the line profiles of argon 696.54 nm are measured. An asymmetrical deconvolution procedure is applied to separate the Gaussian and Lorentzian profile from the measured spectral line. The gas temperature is estimated by using rotational temperature of N{sub 2}{sup +}. By subtracting the van der Waals broadening and partial Lorentzian instrumental broadening from the Lorentzian broadening, the Stark broadening is obtained and used to estimate the electron density. It is found that the electron density in dielectric barrier discharge increases with the increase in gas pressure.

  12. Preparation and Dielectric Measurements of the Rare Earth Green Phases R2BaCuO(5-x) (R = Y, Sm, Gd, Dy, Ho, Er, Yb)

    NASA Technical Reports Server (NTRS)

    Gonzalez-Titman, Carlos

    1994-01-01

    It has been demonstrated that R2BaCuO(5-x) (R = Y, Sm, Gd, Dy, Ho, Er, Yb) does not undergo significant densification unless the sintering temperatures are near the incongruent melting point or the sintering times are long. Good quality powders of Y2BaCuO(5-x) have been synthesized by using oxide raw materials or precursors such as acetates and nitrates. The acetates- and the nitrates-derived yttrium green phase resulted in finer particle sizes, acceptable dielectric properties and lower melting temperatures than those processed via oxide raw materials. The hot pressing technique has been employed to produce a dense R2BaCuO(5-x) (R=Y,Gd) substrate with satisfactory dielectric properties. Reactivity to reducing conditions, i.e. graphite die, limited the optimization of the properties. A high sensitivity to the annealing atmosphere has been demonstrated in Y2BaCuO,.,,. Oxygen treatment at 950 OC has been shown to improve the dielectric properties while treatment in nitrogen, at the same temperature, degraded desirable properties. A high sensitivity to the annealing atmosphere has been demonstrated in Y2BaCuO(5-x). Oxygen treatment at 950 C has been shown to improve the dielectric properties while treatment in nitrogen, at the same temperature, degraded desirable properties. The dielectric constants of the rare earth green phases R2BaCuO(5-x) were found to be low. Relaxation peaks were detected at low temperatures (T less than 150 K) and at high temperatures (150 less than T greater than 420 K). The dielectric losses and conductivities at 77 K were measured to be in the range of 10(exp -4) and 10(exp -12) (Omega-cm)(exp -1), respectively. Many parameters were found to exhibit dependencies on the rare earth cation sizes.

  13. The Impact of Dielectric Constant Model and Surface Reference on Differences Between SMOS and Aquarius Sea Surface Salinity

    NASA Technical Reports Server (NTRS)

    Dinnat, E. P.; Boutin, J.; Yin, X.; LeVine, D. M.

    2014-01-01

    Two ongoing space missions share the scientific objective of mapping the global Sea Surface Salinity (SSS), yet their observations show significant discrepancies. ESA's Soil Moisture and Ocean Salinity (SMOS) and NASA's Aquarius use L-band (1.4 GHz) radiometers to measure emission from the sea surface and retrieve SSS. Significant differences in SSS retrieved by both sensors are observed, with SMOS SSS being generally lower than Aquarius SSS, except for very cold waters where SMOS SSS is the highest overall. Figure 1 is an example of the difference between the SSS retrieved by SMOS and Aquarius averaged over one month and 1 degree in longitude and latitude. Differences are mostly between -1 psu and +1 psu (psu, practical salinity unit), with a significant regional and latitudinal dependence. We investigate the impact of the vicarious calibration and retrieval algorithm used by both mission on these differences.

  14. Use of high and low frequency dielectric measurements in the NDE of adhesively bonded composite joints

    NASA Astrophysics Data System (ADS)

    Pethrick, R. A.; Hayward, D.; McConnell, B. K.; Crane, R. L.

    2005-05-01

    Dielectric spectroscopy has been developed as a non-destructive technique for assessment of moisture content and structural integrity of adhesively bonded joints. Knowledge of these parameters is particularly crucial for the aerospace industry, since environmental degradation of adhesive joints presents a major limit on their utilization. High and low frequency measurements have been carried out on joints assembled from CFRP adherend, and a commercially available adhesive (AF 163-2K). The samples have been aged in deionised water at 75oC to chart the effect water ingress has on bond durability. In addition, some joints have been exposed to cryogenic temperatures to mimic the conditions joints experience whilst an aircraft is in flight. In this way it has been possible to determine the extent of degradation caused by freezing of water within the joint structure. Dielectric behaviour of the joints was studied in both the frequency and in the time domain. Frequency domain analysis allows the amount and effects of moisture ingress in the bondline to be assessed, whereas the time domain highlights the onset of joint defects with increasing exposure time. Mechanical testing of the joints has been carried out to enable correlation between changes in strength and failure mechanism due to moisture ingress, with changes in the dielectric data. In addition, dielectric studies of the neat adhesive have been undertaken, as have gravimetric and dynamic mechanical thermal analysis. These have helped reveal the effects of ageing upon the adhesive layer itself.

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

    SciTech Connect

    Ferradini, C.; Jay-Gerin, J.

    1988-12-01

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

  16. In situ real-time monitoring of profile evolution during plasma etching of mesoporous low-dielectric-constant SiO{sub 2}

    SciTech Connect

    Gerung, Henry; Brinker, C. Jeffrey; Brueck, Steven R.J.; Han, Sang M.

    2005-03-01

    We have employed attenuated total reflection Fourier transforms infrared spectroscopy (ATR-FTIRS) to monitor the profile evolution of patterned mesoporous, low-dielectric-constant SiO{sub 2} films in situ and in real time during plasma etching. A stack of patterned photoresist, anti-reflective coating, and mesoporous SiO{sub 2} is etched in an inductively coupled plasma reactor, using CHF{sub 3} and Ar. During etching, the IR absorbance of Si-O-Si stretching modes near 1080 cm{sup -1} decreases, and the rate of decrease in Si-O-Si absorbance translates to the SiO{sub 2} removal rate. When corrected for the exponentially decaying evanescent electric field, the removal rate helps monitor the profile evolution and predict the final etch profile. The predicted profiles are in excellent agreement with the cross-sectional images taken by scanning electron microscopy. In a similar approach, we calculate the absolute total number of C-F bonds in the sidewall passivation and observe its formation rate as a function of time. Assuming that the thickness of the sidewall passivation tapers down towards the trench bottom, we deduce that C-F formation occurs mostly in the final stage of etching when the trench bottom meets the Ge ATR crystal and that a critical amount of C-F buildup is necessary to maintain the anisotropic etch profile.

  17. Helium Plasma Damage of Low-k Carbon Doped Silica Film: the Effect of Si Dangling Bonds on the Dielectric Constant

    NASA Astrophysics Data System (ADS)

    Li, Hailing; Wang, Qing; Ba, Dechun

    2014-11-01

    The low-k carbon doped silica film has been modified by radio frequency helium plasma at 5 Pa pressure and 80 W power with subsequent XPS, FTIR and optical emission spectroscopy analysis. XPS data indicate that helium ions have broken Si-C bonds, leading to Si-C scission with C(1s) lost seriously. The Si(2p), O(1s), peak obviously shifted to higher binding energies, indicating an increasingly oxidized Si(2p). FTIR data also show that the silanol formation increased with longer exposure time up to a week. Contrarily, the CH3 stretch, Si-C stretching bond and the ratio of the Si-O-Si cage and Si-O-Si network peak sharply decreased upon exposure to helium plasma. The OES result indicates that monovalent helium ions in plasma play a key role in damaging carbon doped silica film. So it can be concluded that the monovalent helium ions besides VUV photons can break the weak Si-C bonds to create Si dangling bonds and free methyl radicals, and the latter easily reacts with O2 from the atmosphere to generate CO2 and H2O. The bonds change is due to the Si dangling bonds combining with H2O, thereby, increasing the dielectric constant k value.

  18. Determination of magneto-optical constant of Fe films with weak measurements

    SciTech Connect

    Qiu, Xiaodong; Hu, Dejiao; Du, Jinglei; Gao, Fuhua; Zhang, Zhiyou; Zhou, Xinxing; Luo, Hailu

    2014-09-29

    In this letter, a detecting method for the magneto-optical constant is presented by using weak measurements. The photonic spin Hall effect (PSHE), which manifests itself as spin-dependent splitting, is introduced to characterize the magneto-optical constant, and a propagation model to describe the quantitative relation between the magneto-optical constant and the PSHE is established. According to the amplified shift of the PSHE detected by weak measurements, we determinate the magneto-optical constant of the Fe film sample. The Kerr rotation is measured via the standard polarimetry method to verify the rationality and feasibility of our method. These findings may provide possible applications in magnetic physics research.

  19. Optical measurement of Verdet constants of two electrooptic crystals and their applications to optical sensors

    NASA Astrophysics Data System (ADS)

    Li, Changsheng

    2013-12-01

    Verdet constants of beta-barium borate (BBO) and lead molybdate (PMO) crystals are measured experimentally by the method of comparison with a block of terbium-doped glass with a known Verdet constant. Experimental setups mainly include two prism polarizers, a solenoid and ac current supply, and signal processing circuits. The influences of light intensity fluctuation, applied magnetic field and signal processing circuits on measurement result of Verdet constant can be removed by using the method of comparison. For light wavelength of 635nm, the measured Verdet constants respectively are 5.80+/-0.06 rad/(T.m) for the BBO crystal and 54.6+/-1.1 rad/(T.m) for the PMO crystal. A novel optical current sensor based on electrooptic compensation is designed in principle using the BBO crystal.

  20. Metal Decorated Multi-Walled Carbon Nanotube/Polyimide Composites with High Dielectric Constants and Low Loss Factors

    NASA Technical Reports Server (NTRS)

    Ghose, Sayata; Watson, Kent A.; Dudley, Kenneth L.; Elliott, Holly A.; Smith, Joseph G.; Connell, John W.

    2009-01-01

    The measurement of observable electromagnetic phenomena in materials and their derived intrinsic electric material properties are of prime importance in the discovery and development of material systems for electronic and aerospace applications. Nanocomposite materials comprised of metal decorated multi-walled carbon nanotubes (MWCNTs) were prepared by a facile method and characterized. Metal particles such as silver, platinum and palladium with diameters ranging from less than 5 to over 50 nanometers were distributed randomly on the MWCNTs. The metal-containing MWCNTs were then melt mixed into a polymer matrix and the mixture extruded as ribbons. These extruded ribbons exhibited a moderate to high degree of MWCNT alignment as determined by HRSEM. These ribbons were then fabricated into test specimens while maintaining MWCNT alignment and subsequently characterized for electromagnetic properties at 8-12 GHz. The present study is focused on silver decorated MWCNTs dispersed in an Ultem polyimide matrix. The results of the electromagnetic characterization showed that certain sample configurations exhibited a decoupling of the permittivity and loss factor (?? and ??) indicating that these properties could be tailored within certain limits. The decoupling and independent control of these fundamental electrical material parameters offer a new class of materials with potential applications in electronics, microwave engineering and optics.

  1. Metal Decorated Multi-Walled Carbon Nanotube/Polyimide Composites with High Dielectric Constants and Low Loss Factors

    NASA Technical Reports Server (NTRS)

    Elliott, Holly A.; Dudley, Kenneth L.; Smith, Joseph G.; Connell, John W.; Ghose, Sayata; Watson, Kent A.; Sun, Keun J.

    2009-01-01

    The measurement of observable electromagnetic phenomena in materials and their derived intrinsic electrical material properties are of prime importance in the discovery and development of material systems for electronic and aerospace applications. Nanocomposite materials comprised of metal decorated multi-walled carbon nanotubes (MWCNTs) were prepared by a facile method and characterized. Metal particles such as silver(Ag), platinum(Pt) and palladium(Pd) with diameters ranging from less than 5 to over 50 nanometers were distributed randomly on the MWCNTs. The present study is focused on silver decorated MWCNTs dispersed in a polyimide matrix. The Ag-containing MWCNTs were melt mixed into Ultem(TradeMark) and the mixture extruded as ribbons. The extruded ribbons exhibited a moderate to high degree of MWCNT alignment as determined by HRSEM. These ribbons were then fabricated into test specimens while maintaining MWCNT alignment and subsequently characterized for electrical and electromagnetic properties at 8-12 GHz. The results of the electromagnetic characterization showed that certain sample configurations exhibited a decoupling of the permittivity (epsilon ) and loss factor (epsilon") indicating that these properties could be tailored within certain limits. The decoupling and independent control of these fundamental electrical material parameters offers a new class of materials with potential applications in electronics, microwave engineering and optics.

  2. Chemically prepared lead magnesium niobate dielectrics

    SciTech Connect

    Tuttle, B.A.; Voigt, J.A.; Sipola, D.L.; Olson, W.R.; Goy, D.M.

    1998-11-01

    A chemical solution powder synthesis technique has been developed that produces first, uniform powders of lead magnesium niobate (PMN) with 60 to 80 nm crystallite size. The synthesis technique was based on the dissolution of lead acetate and alkoxide precursors in acetic acid followed by precipitation with oxalic acid/propanol solutions. Lead magnesium niobate ceramics fabricated from these chemically derived powders had smaller, more uniform grain size and higher dielectric constants than ceramics fabricated from mixed oxide powders that were processed under similar thermal conditions. Chem-prep PMN dielectrics with peak dielectric constants greater than 22,000 and polarizations in excess of 29 {micro}C/cm{sup 2} were obtained for 1,100 C firing treatments. Substantial decreases in dielectric constant and polarization were measured for chemically prepared PMN ceramics fired at lower temperatures, consistent with previous work on mixed oxide materials.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    Measurement of the dielectric properties of ocular tissues up to 110 GHz was performed by the coaxial probe method. A coaxial sensor was fabricated to allow the measurement of small amounts of biological tissues. Four-standard calibration was applied in the dielectric property measurement to obtain more accurate data than that obtained with conventional three-standard calibration, especially at high frequencies. Novel data of the dielectric properties of several ocular tissues are presented and compared with data from the de facto database.

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

    PubMed

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

    2015-08-21

    Measurement of the dielectric properties of ocular tissues up to 110 GHz was performed by the coaxial probe method. A coaxial sensor was fabricated to allow the measurement of small amounts of biological tissues. Four-standard calibration was applied in the dielectric property measurement to obtain more accurate data than that obtained with conventional three-standard calibration, especially at high frequencies. Novel data of the dielectric properties of several ocular tissues are presented and compared with data from the de facto database. PMID:26237580

  5. Dielectric relaxation measurement and analysis of restricted water structure in rice kernels

    NASA Astrophysics Data System (ADS)

    Yagihara, Shin; Oyama, Mikio; Inoue, Akio; Asano, Megumi; Sudo, Seiichi; Shinyashiki, Naoki

    2007-04-01

    Dielectric relaxation measurements were performed for rice kernels by time domain reflectometry (TDR) with flat-end coaxial electrodes. Difficulties in good contact between the surfaces of the electrodes and the kernels are eliminated by a TDR set-up with a sample holder for a kernel, and the water content could be evaluated from relaxation curves. Dielectric measurements were performed for rice kernels, rice flour and boiled rice with various water contents, and the water amount and dynamic behaviour of water molecules were explained from restricted dynamics of water molecules and also from the τ-β (relaxation time versus the relaxation-time distribution parameter of the Cole-Cole equation) diagram. In comparison with other aqueous systems, the dynamic structure of water in moist rice is more similar to aqueous dispersion systems than to aqueous solutions.

  6. Composition-based prediction of dielectric properties of foods.

    PubMed

    Sun, E; Datta, A; Lobo, S

    1995-01-01

    Prediction of accurate dielectric property data from fundamental principles for systems as complex as foods has not been possible. Simple prediction models based on easily measurable composition data can serve many useful purposes. Literature dielectric data on foods and their composition were statistically correlated. Dielectric data on salt solutions were measured to explain some of the results. When composition data were not available, standard handbook compositions were used. Inclusion of all types of foods (meats, fruits, and vegetables) inhibited any useful correlation with composition. Based on a smaller data set of meats, both dielectric constant and loss increased with water and salt content. Dielectric constant generally decreased with temperature whereas dielectric loss decreased with temperature at lower salt concentrations and increased with temperature at higher salt concentrations. PMID:8600277

  7. Free energy perturbation method for measuring elastic constants of liquid crystals

    NASA Astrophysics Data System (ADS)

    Joshi, Abhijeet

    There is considerable interest in designing liquid crystals capable of yielding specific morphological responses in confined environments, including capillaries and droplets. The morphology of a liquid crystal is largely dictated by the elastic constants, which are difficult to measure and are only available for a handful of substances. In this work, a first-principles based method is proposed to calculate the Frank elastic constants of nematic liquid crystals directly from atomistic models. These include the standard splay, twist and bend deformations, and the often-ignored but important saddle-splay constant. The proposed method is validated using a well-studied Gay-Berne(3,5,2,1) model; we examine the effects of temperature and system size on the elastic constants in the nematic and smectic phases. We find that our measurements of splay, twist, and bend elastic constants are consistent with previous estimates for the nematic phase. We further outline the implementation of our approach for the saddle-splay elastic constant, and find it to have a value at the limits of the Ericksen inequalities. We then proceed to report results for the elastic constants commonly known liquid crystals namely 4-pentyl-4'-cynobiphenyl (5CB) using atomistic model, and show that the values predicted by our approach are consistent with a subset of the available but limited experimental literature.

  8. High Temperature Elastic Constants of Langatate from RUS Measurements up to 1100?C

    SciTech Connect

    Shyam, Amit; Lara-Curzio, Edgar

    2008-01-01

    This paper reports on the langatate (LGT) elastic constants and their temperature coefficients measured from room temperature (25degC) to 1100degC using resonant ultrasound spectroscopy (RUS). The constants were extracted by iteratively fitting the resonant peaks with those calculated by Lagrangian mechanics at each temperature where the RUS measurements were taken. In addition, the RUS technique was used to extract the elastic and piezoelectric constants in the 25degC to 120degC temperature range. The extraction of LGT elastic constants up to 1100degC presented in this paper represents a critical step towards the design and fabrication of LGT acoustic wave devices for high temperature and harsh environment applications.

  9. Henry's Law Constant of Organic Nitriles Measured with GC-FID

    NASA Astrophysics Data System (ADS)

    Brewer, B.; Gangoda, M.; Lee, S.

    2012-12-01

    Nitriles are important atmospheric VOCs that paly key roles in the atmospheric nitrogen cycle and secondary aerosol formation. Nitriles and their oxidation products also have serious health effects and thus are important air pollutants. Henry's law constant is an important physical and chemical parameter to determine how gas phase species participate into gas-to-particle conversion and cloud formation and affect human health. Yet, measurements of Henry's law constants of nitriles are entirely lacking. We have developed a simple measurement technique to detect Henry's law constants of organic compounds using gas chromatography flame ionization detector (GC-FID) coupled with a bubble column. In this presentation, we will show Henry's law constants of a number of atmospherically relevant organic nitrile compounds and their temperature dependence.

  10. How Measuring the Planck Constant gets to an Electronic Kilogram Standard

    SciTech Connect

    Steiner, Richard

    2007-08-01

    The best measurement of the Planck constant is now derived from the watt balance method. This method measures mechanical power, in reference units of the kilogram (artifact mass standard), second (atomic clocks), and meter (lasers), in ratio to electrical power, in reference units of the volt (Josephson effect) and ohm (quantum Hall effect). Of these reference standards, only the kilogram is still an artifact standard. Thus a high precision measurement of the Planck constant is equivalent to monitoring the SI kilogram artifact, and may be used to redefine the kilogram. This talk will summarize the complexity of making a Planck constant measurement, where there are interesting aspects of basic physics that appear when the ultimate precision of the standards laboratory is applied to obtain an uncertainty of 20 parts in a billion.

  11. Determination of Personalized IOL-Constants for the Haigis Formula under Consideration of Measurement Precision

    PubMed Central

    Leydolt, Christina; Menapace, Rupert; Eppig, Timo; Langenbucher, Achim

    2016-01-01

    The capabilities of a weighted least squares approach for the optimization of the intraocular lens (IOL) constants for the Haigis formula are studied in comparison to an ordinary least squares approach. The weights are set to the inverse variances of the effective optical anterior chamber depth. The effect of random measurement noise is simulated 100000 times using data from N = 69 cataract patients and the measurement uncertainty of two different biometers. A second, independent data set (N = 33) is used to show the differences that can be expected between both methods. The weighted least squares formalism reduces the effect of measurement error on the final constants. In more than 64% it will result in a better approximation, if the measurement errors are estimated correctly. The IOL constants can be calculated with higher precision using the weighted least squares method. PMID:27391100

  12. Non-contact ultrasonic spectroscopy measurement of elastic constants and ultrasonic attenuation

    SciTech Connect

    Schwarz, R.B.; Kuokkala, V.T.; Srinivasan, S.; Visscher, W.M.

    1991-01-01

    We have developed an ultrasonic spectroscopy method for measuring the elastic constants of solids in hostile environments and over a broad temperature regime. The sample is cut as a rectangular parallelepiped, approximately 1 mm{sup 3} in volume. One or two of the sample surfaces are coated with a thin film of a magnetostrictive material such as nickel. The sample is placed coaxially with two solenoids. One solenoid is used to generate an AC magnetic field of small amplitude which stretches the films. By sweeping the frequency of this field, the sample is excited successively into its various mechanical resonance modes. The second solenoid detects the mechanical resonances. The elastic constants are then deduced from the spectrum of mechanical resonances measured at constant temperature. The internal friction is deduced from the width of the resonance peaks. Because the technique is strictly non-contact (the sample may be encapsulated in a fused silica tube), it is deal for measuring elastic constants in hostile environments or under controlled atmospheres. In its present version the system allows us to measure the elastic constants and ultrasonic attenuation of a given sample between 80 and 100 K. The operation of the system is exemplified by measurements on amorphous Ni{sub 80}P{sub 20} and crystalline Ti{sub 60}Cr{sub 40}. 17 refs., 6 figs.

  13. Electrical Noise and the Measurement of Absolute Temperature, Boltzmann's Constant and Avogadro's Number.

    ERIC Educational Resources Information Center

    Ericson, T. J.

    1988-01-01

    Describes an apparatus capable of measuring absolute temperatures of a tungsten filament bulb up to normal running temperature and measuring Botzmann's constant to an accuracy of a few percent. Shows that electrical noise techniques are convenient to demonstrate how the concept of temperature is related to the micro- and macroscopic world. (CW)

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  15. Microwave Dielectric Properties Models for Grain and Seed

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  16. Mechanism of the typical relaxation process at low frequency based on dielectric measurements of water absorbed in porous titanium dioxide

    NASA Astrophysics Data System (ADS)

    Gao, Xin; Wang, Qiang; Sun, Gang; Li, Chenxi; Hu, Lin

    2016-02-01

    Dielectric spectroscopy is a valuable tool in physics, chemistry, biophysics, and materials science. However, there is still an argument about the typical relaxation process at low frequency, which is always masked by electrode polarization. Low-frequency dielectric measurements of water absorbed in porous titanium dioxide have been performed. The experimental results show that typical polarization at low frequency is caused by space-charge polarization. A model is proposed to explain the experimental results, which indicates that the electric field in the sample is close to 0. An effective circuit is given, and the calculation gives similar dielectric spectra to those measured in experiments, which confirms the physical model.

  17. Dielectric measurements at 30-40 GHz and 140 GHz performed on the specimen set of the NPL intercomparison exercise

    NASA Astrophysics Data System (ADS)

    Heidinger, R.; Koeniger, F.

    1991-10-01

    Ceramic samples (BeO, Macor and quartz) and polymeric samples (Rexolite, polyethylene) are measured for a near millimeter wavelength specimen intercomparison task. The data is used to relate the results of recently established dielectric measuring facilities to results from different techniques. The Ka band (30 to 40 GHz) and D band (140 GHz) are covered by two different Fabry-Perot resonator setups. Data evaluation is discussed in detail and various correction procedures to sample thickness are tested. The results of both frequency bands coincide for most specimens. The lowest dielectric loss is found in single crystal quartz. The dielectric loss increases strongly with frequency in Rexolite only and slightly in Macor.

  18. Influence of the dielectric surrounding of plasma on the electron density measurement by microwave interferometer

    NASA Astrophysics Data System (ADS)

    Andrasch, M.; Ehlbeck, J.; Weltmann, K.-D.

    2014-07-01

    Using a vector network analyzer a frequency resolved microwave interferometer is built up in the range of 42.5-50 GHz. Due to the frequency resolved measurement technique it is possible to investigate the influence of the surrounding dielectric material on the transmission. The experiments are performed on a fluorescent lamp, which is enclosed by a glass tube. Furthermore, a dielectric resonator is built up by two plane silica windows, placed perpendicular to the beam. It was found that the influence can be described by a one-dimensional model using equivalent circuits, which is in very good agreement with experimental results. In addition, the common technique of rotating the windows to reduce their influence is investigated.

  19. A novel microwave cancellation circuit for measuring nonlinear dielectric changes of polar solution under microwave fields

    NASA Astrophysics Data System (ADS)

    Sun, Hao-Ran; Huang, Ka-Ma

    2015-12-01

    In this paper, an experimental set-up based on a novel microstrip cancellation circuit is presented for investigating the effects of external microwave fields on the dielectric properties of polar solution. The circuit consists of a 3 dB Wilkinson power combiner, a conventional 20 dB backward coupler, and a specially designed 20 dB single-sectioned forward coupler. Besides, in order to realize a uniform electric field in the tested solution, a nicked microstrip ring is designed in the circuit. An improvement of measurement sensitivity in the proposed circuit was obtained when compared to the conventional transmission lines method. We exploit interference cancellation processes to suppress the probing signal at the output port under the principle that two identical amplitude signals with 180° phase difference will completely cancel each other. The measurements are carried out at the frequency of 2.45 GHz, and the temperature effects caused by microwave heating are excluded by the flowing fluid. Experimental results show that the dielectric properties of DMSO-methanol/ethanol mixtures change at the electric field intensity of 105 V m  -  1 and present a distinctly nonlinear dielectric change with the electric fields. The study of the microwave-material interaction has expanded our insights into the high-power microwave’s industry application.

  20. A Limited In-Flight Evaluation of the Constant Current Loop Strain Measurement Method

    NASA Technical Reports Server (NTRS)

    Olney, Candida D.; Collura, Joseph V.

    1997-01-01

    For many years, the Wheatstone bridge has been used successfully to measure electrical resistance and changes in that resistance. However, the inherent problem of varying lead wire resistance can cause errors when the Wheatstone bridge is used to measure strain in a flight environment. The constant current loop signal-conditioning card was developed to overcome that difficulty. This paper describes a limited evaluation of the constant current loop strain measurement method as used in the F-16XL ship 2 Supersonic Laminar Flow Control flight project. Several identical strain gages were installed in close proximity on a shock fence which was mounted under the left wing of the F- 1 6XL ship 2. Two strain gage bridges were configured using the constant current loop, and two were configured using the Wheatstone bridge circuitry. Flight data comparing the output from the constant current loop configured gages to that of the Wheatstone bridges with respect to signal output, error, and noise are given. Results indicate that the constant current loop strain measurement method enables an increased output, unaffected by lead wire resistance variations, to be obtained from strain gages.

  1. An AC constant-response method for electrophysiological measurements of spectral sensitivity functions.

    PubMed

    de Souza, J M; DeVoe, R D; Schoeps, C; Ventura, D F

    1996-10-01

    A number of methods have been used in the past to measure spectral sensitivity (S(lambda)) functions of electric responses in the visual system. We present here a microcomputer based, AC, constant-response method for automatic on-line measurement of S(lambda) in cells with or without a sustained tonic response. It is based on feedback adjustment of light intensity to obtain constant peak-to-peak amplitudes of response to a flickering stimulus as the spectrum is scanned between 300 and 700 nm in 4 nm steps. It combines the advantages of: (1) on-line presentation of S(lambda) curves; (2) constant light adaptation; (3) sampling of many points; and (4) fast data collection time. The system can be applied to sensitivity or threshold (e.g., S(lambda), dark adaptation, receptive field) measurements of any electrically recorded visual response. PMID:8912193

  2. Characterization of low dielectric constant plasma polymer films deposited by plasma-enhanced chemical vapor deposition using decamethyl-cyclopentasiloxane and cyclohexane as the precursors

    SciTech Connect

    Yang, Jaeyoung; Lee, Sungwoo; Park, Hyoungsun; Jung, Donggeun; Chae, Heeyeop

    2006-01-15

    We investigated the properties of plasma polymer films deposited by plasma-enhanced chemical vapor deposition using a mixture of decamethyl-cyclopentasiloxane (C{sub 10}H{sub 30}O{sub 5}Si{sub 5}) and cyclohexane (C{sub 6}H{sub 12}) as the precursors, which we refer to as plasma polymerized decamethyl-cyclopentasiloxane: cyclohexane (PPDMCPSO:CHex) films. The relative dielectric constants, k, of the plasma polymer films were correlated with the Fourier transform infrared absorption peaks of the C-Hx, Si-CH{sub 3}, and Si-O related groups. As the amount of the CHx species in the as-deposited plasma polymer films increased, the k value and the leakage current density of the thin films decreased. The subsequent annealing of the PPDMCPSO:CHex film at 400 deg. C for 1 h further reduced the k value to as low as k=2.05. This annealed PPDMCPSO:CHex thin film showed a leakage current density of the order of 4x10{sup -7} A/cm{sup 2} at 1 MV/cm and a breakdown field of 6.5 MV/cm. Through the bias-temperature stress test, it was estimated that the PPDMCPSO:CHex film with a k value of 2.05 would retain its insulating properties for ten years at 167 deg. C under an electrical field of 1 MV/cm, when it is presented as a layer adjacent to Cu/TaN(10 nm)

  3. Composite dielectric waveguides

    NASA Astrophysics Data System (ADS)

    Yamashita, E.; Atsuki, K.; Kuzuya, R.

    1980-09-01

    The modal analysis of a composite circular dielectric waveguide (CCDW) is presented. Computed values of the propagation constant of a CCDW are compared with those of the homogeneous circular dielectric waveguides (HCDW). Microwave experiments concerning the propagation constant of a CCDW of Teflon and Rexolite are described.

  4. Time constant measurement for control of induction heating processes for thixoforming

    NASA Astrophysics Data System (ADS)

    Gerlach, O.; Lechler, A.; Verl, A.

    2015-02-01

    In controlling induction heating systems, several measurement methods exist for controlled heating of metal billets into the semi-solid state for thixoforming. The most common approach is to measure the billet temperature, which suffers from various drawbacks leading to difficulties in process stability. The main disadvantages are the small temperature range of the process window and the alloy composition dependency of the correlation between temperature and liquid fraction. An alternative is to determine the liquid fraction of the billet by measuring the time constant of the load. Although time constant measurement is not affected by the mentioned problems, it is difficult to use it as a controlled variable. This paper shows that disturbances affecting time constant measurement are mainly caused by semiconductor losses inside the inverter. A method is introduced to compensate these losses. This method was implemented and tested in the embedded system of an induction heating unit, thereby showing that it is possible to use time constant measurement to determine the liquid fraction of a billet during induction heating.

  5. Estimation of Force Constants of Al from Diffuse Neutron Scattering Measurement

    NASA Astrophysics Data System (ADS)

    Makhsun; Hashimoto, Takuya; Sakuma, Takashi; Takahashi, Haruyuki; Kamishima, Osamu; Igawa, Naoki; Danilkin, Sergey A.

    2014-07-01

    Neutron diffraction measurement of an aluminum powder sample at 290 K was carried out at the high resolution powder diffractometer installed at JRR-3. Broad oscillations of the diffuse scattering intensity were observed and explained by the correlation effects among the thermal displacements of atoms. The interatomic force constants were determined from the correlation effects using a newly introduced equation. The derived force constants and the crystal structure of Al were used to estimate the phonon dispersion relations, phonon density of states, and specific heat by computer simulation. The calculated phonon dispersion relations and specific heat of Al are similar to those obtained from inelastic neutron scattering and specific heat measurements, respectively.

  6. Local measurements of the diffusion constant in multiple scattering media: Application to human trabecular bone imaging

    NASA Astrophysics Data System (ADS)

    Aubry, Alexandre; Derode, Arnaud; Padilla, Frédéric

    2008-03-01

    We present local measurements of the diffusion constant for ultrasonic waves undergoing multiple scattering. The experimental setup uses a coherent array of programmable transducers. By achieving Gaussian beamforming at emission and reception, an array of virtual sources and receivers located in the near field is constructed. A matrix treatment is proposed to separate the incoherent intensity from the coherent backscattering peak. Local measurements of the diffusion constant D are then achieved. This technique is applied to a real case: a sample of human trabecular bone for which the ultrasonic characterization of multiple scattering is an issue.

  7. First-principles calculation of dielectric response in molecule-based materials.

    PubMed

    Heitzer, Henry M; Marks, Tobin J; Ratner, Mark A

    2013-07-01

    The dielectric properties of materials are of fundamental significance to many chemical processes and the functioning of numerous solid-state device technologies. While experimental methods for measuring bulk dielectric constants are well-established, far less is known, either experimentally or theoretically, about the origin of dielectric response at the molecular/multimolecular scale. In this contribution we report the implementation of an accurate first-principles approach to calculating the dielectric response of molecular systems. We assess the accuracy of the method by reproducing the experimental dielectric constants of several bulk π-electron materials and demonstrating the ability of the method to capture dielectric properties as a function of frequency and molecular orientation in representative arrays of substituted aromatic derivatives. The role of molecular alignment and packing density on dielectric response is also examined, showing that the local dielectric behavior of molecular assemblies can diverge significantly from that of the bulk material. PMID:23734640

  8. AC conductivity and dielectric measurements of metal-free phthalocyanine thin films dispersed in polycarbonate

    NASA Astrophysics Data System (ADS)

    Riad, A. S.; Korayem, M. T.; Abdel-Malik, T. G.

    1999-10-01

    The dielectric constant and the dielectric loss of thin films of metal-free phthalocyanine dispersed in polycarbonate using ohmic gold electrodes are investigated in the frequency range 20-10 5 Hz and within the temperature range 300-388 K. The frequency dependence of the impedance spectra plotted in the complex plane shows semicircles. The Cole-Cole diagrams have been used to determine the molecular relaxation time, τ, The temperature dependence of τ is expressed by thermally activated process. The AC conductivity σ AC (ω) is found to vary as ωs with the index s⩽1, indicating a dominant hopping process at low temperatures. From the temperature dependence of AC conductivity, free carrier conduction with mean activation energy of 0.33 eV is observed at higher temperatures. Capacitance and loss tangent are found to decrease with increasing frequency and increase with increasing temperature. Such characteristics are found to be in good qualitative agreement with existing equivalent circuit model assuming ohmic contacts.

  9. Measurement of Hubble constant: non-Gaussian errors in HST Key Project data

    NASA Astrophysics Data System (ADS)

    Singh, Meghendra; Gupta, Shashikant; Pandey, Ashwini; Sharma, Satendra

    2016-08-01

    Assuming the Central Limit Theorem, experimental uncertainties in any data set are expected to follow the Gaussian distribution with zero mean. We propose an elegant method based on Kolmogorov-Smirnov statistic to test the above; and apply it on the measurement of Hubble constant which determines the expansion rate of the Universe. The measurements were made using Hubble Space Telescope. Our analysis shows that the uncertainties in the above measurement are non-Gaussian.

  10. Soil moisture, dielectric permittivity and emissivity of soil: effective depth of emission measured by the L-band radiometer ELBARA

    NASA Astrophysics Data System (ADS)

    Usowicz, Boguslaw; Lukowski, Mateusz; Marczewski, Wojciech; Usowicz, Jerzy; Lipiec, Jerzy; Rojek, Edyta; Slominska, Ewa; Slominski, Jan

    2014-05-01

    Due to the large variation of soil moisture in space and in time, obtaining soil water balance with an aid of data acquired from the surface is still a challenge. Microwave remote sensing is widely used to determine the water content in soil. It is based on the fact that the dielectric constant of the soil is strongly dependent on its water content. This method provides the data in both local and global scales. Very important issue that is still not solved, is the soil depth at which radiometer "sees" the incoming radiation and how this "depth of view" depends on water content and physical properties of soil. The microwave emission comes from its entire profile, but much of this energy is absorbed by the upper layers of soil. As a result, the contribution of each layer to radiation visible for radiometer decreases with depth. The thickness of the surface layer, which significantly contributes to the energy measured by the radiometer is defined as the "penetration depth". In order to improve the physical base of the methodology of soil moisture measurements using microwave remote sensing and to determine the effective emission depth seen by the radiometer, a new algorithm was developed. This algorithm determines the reflectance coefficient from Fresnel equations, and, what is new, the complex dielectric constant of the soil, calculated from the Usowicz's statistical-physical model (S-PM) of dielectric permittivity and conductivity of soil. The model is expressed in terms of electrical resistance and capacity. The unit volume of soil in the model consists of solid, water and air, and is treated as a system made up of spheres, filling volume by overlapping layers. It was assumed that connections between layers and spheres in the layer are represented by serial and parallel connections of "resistors" and "capacitors". The emissivity of the soil surface is calculated from the ratio between the brightness temperature measured by the ELBARA radiometer (GAMMA Remote

  11. Interfacial water dielectric-permittivity-profile measurements using atomic force microscopy.

    PubMed

    Teschke, O; Ceotto, G; de Souza, E F

    2001-07-01

    The arrangement of water molecules at charged aqueous interfaces is an important question in biology, electrochemistry, and geochemistry. Theoretical studies suggest that the molecules become arranged in several layers adjacent to a solid interface. Using atomic force microscopy we have measured the water dielectric-permittivity profile perpendicular to mica surfaces. The measured variable permittivity profile starting at epsilon approximately 4 at the interface and increasing to epsilon=80 about 10 nm from the surface suggests a reorientation of water molecule dipoles in the presence of the mica interfacial charge. PMID:11461268

  12. Dynamic measurement of bulk modulus of dielectric materials using a microwave phase shift technique

    NASA Technical Reports Server (NTRS)

    Barker, B. J.; Strand, L. D.

    1972-01-01

    A microwave Doppler shift technique was developed for measuring the dynamic bulk modulus of dielectric materials such as solid propellants. The system has a demonstrated time resolution on the order of milliseconds and a theoretical spatial resolution of a few microns. Accuracy of the technique is dependent on an accurate knowledge of the wavelength of the microwave in the sample being tested. Such measurement techniques are discussed. Preliminary tests with two solid propellants, one non-aluminized and one containing 16% aluminum, yielded reasonable, reproducible results. It was concluded that with refinements the technique holds promise as a practical means for obtaining accurate dynamic bulk modulus data over a variety of transient conditions.

  13. Measurements of the time constant for steady ionization in shaped-charge barium releases

    NASA Technical Reports Server (NTRS)

    Hoch, Edward L.; Hallinan, Thomas J.

    1993-01-01

    Quantitative measurements of three solar illuminated shaped-charge barium releases injected at small angles to the magnetic field were made using a calibrated color television camera. Two of the releases were from 1989. The third release, a reanalysis of an event included in Hallinan's 1988 study of three 1986 releases, was included to provide continuity between the two studies. Time constants for ionization, measured during the first 25 s of each release, were found to vary considerably. The two 1989 time constants differed substantially, and both were significantly less than any of the 1986 time constants. On the basis of this variability, we conclude that the two 1989 releases showed evidence of continuous nonsolar ionization. One release showed nonsolar ionization which could not he attributed to Alfven's critical ionization velocity process, which requires a component of velocity perpendicular to the magnetic field providing a perpendicular energy greater than the ionization potential.

  14. Hydrogen Balmer series measurements and determination of Rydberg's constant using two different spectrometers

    NASA Astrophysics Data System (ADS)

    Amrani, D.

    2014-07-01

    This paper investigates the use of two different methods, the optical and the computer-aided diffraction-grating spectrometer, to measure the wavelength of visible lines of Balmer series from the hydrogen atomic spectrum and estimate the value of Rydberg's constant. Analysis and interpretation of data showed that both methods, despite their difference in terms of the type of equipment used, displayed good performance in terms of precision of measurements of wavelengths of spectral lines. A comparison was carried out between the experimental value of Rydberg's constant obtained with both methods and the accepted value. The results of Rydberg's constant obtained with both the optical and computer-aided spectrometers were 1.099 28 × 10-7 m-1 and 1.095 13 × 10-7 m-1 with an error difference of 0.17% and 0.20% compared to the accepted value 1.097 373 × 10-7 m-1, respectively.

  15. The roles of the dielectric constant and the relative level of conduction band of high-k composite with Si in improving the memory performance of charge-trapping memory devices

    SciTech Connect

    Lu, Jianxin; Gong, Changjie; Ou, Xin; Lu, Wei; Yin, Jiang; Xu, Bo; Xia, Yidong; Liu, Zhiguo; Li, Aidong

    2014-11-15

    The memory structures Pt/Al{sub 2}O{sub 3}/(TiO{sub 2}){sub x}(Al{sub 2}O{sub 3}){sub 1−x}/Al{sub 2}O{sub 3}/p-Si(nominal composition x = 0.05, 0.50 and 0.70) were fabricated by using rf-magnetron sputtering and atomic layer deposition techniques, in which the dielectric constant and the bottom of the conduction band of the high-k composite (TiO{sub 2}){sub x}(Al{sub 2}O{sub 3}){sub 1−x} were adjusted by controlling the partial composition of Al{sub 2}O{sub 3}. With the largest dielectric constant and the lowest deviation from the bottom of the conduction band of Si, (TiO{sub 2}){sub 0.7}(Al{sub 2}O{sub 3}){sub 0.3} memory devices show the largest memory window of 7.54 V, the fast programming/erasing speed and excellent endurance and retention characteristics, which were ascribed to the special structural design, proper combination of dielectric constant and band alignment in the high-k composite (TiO{sub 2}){sub 0.7}(Al{sub 2}O{sub 3}){sub 0.3}.

  16. Preliminary Broadband Measurements of Dielectric Permittivity of Planetary Regolith Analog Materials Using a Coaxial Airline

    NASA Astrophysics Data System (ADS)

    Boivin, A.; Tsai, C. A.; Ghent, R. R.; Daly, M. G.

    2014-12-01

    When considering radar observations of airless bodies containing regolith, the radar backscatter coefficient is dependent upon the complex dielectric permittivity of the regolith materials. In many current applications of imaging radar data, uncertainty in the dielectric permittivity precludes quantitative estimates of such important parameters as regolith thickness and depth to buried features (e.g., lava flows on the Aristarchus Plateau on the Moon and the flows that surround the Quetzalpetlatl Corona on Venus). For asteroids, radar is an important tool for detecting and characterizing regoliths. Many previous measurements of the real and/or complex parts of the dielectric permittivity have been made, particularly for the Moon (on both Apollo samples and regolith analogues). However, no studies to date have systematically explored the relationship between permittivity and the various mineralogical components such as presence of FeO and TiO2. For lunar materials, the presence of the mineral ilmenite (FeTiO3), which contains equal portions FeO and TiO2, is thought to be the dominant factor controlling the loss tangent (tanδ, the ratio of the imaginary and real components of the dielectric permittivity). Ilmenite, however, is not the only mineral to contain iron in the lunar soil and our understanding of the effect of iron on the loss tangent is insufficient. Beyond the Moon, little is known about the effects on permittivity of carbonaceous materials. This is particularly relevant for missions to asteroids, such as the OSIRIS-REx mission to (101955) Bennu, a carbonaceous asteroid whose regolith composition is largely unknown. Here we present preliminary broadband (300 Mhz to 14 GHz) measurements on materials intended as planetary regolith analogs. Our ultimate goal is to establish a database of the effects of a wide range mineralogical components on dielectric permittivity, in support of the OSIRIS REx mission and ongoing Earth-based radar investigation of the Moon

  17. Determination of complex permittivity from propagation constant measurement with planar transmission lines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new two-standard calibration procedure is outlined for determining the complex permittivity of materials from the propagation constant measured with planar transmission lines. Once calibrated, a closed-form expression for the material permittivity is obtained. The effects of radiation and conducto...

  18. Dielectric relaxation study of mixtures of alkyl methacrylates and 1-alcohols using time-domain reflectometry

    NASA Astrophysics Data System (ADS)

    Sivagurunathan, P.; Dharmalingam, K.; Ramachandran, K.; Prabhakar Undre, B.; Khirade, P. W.; Mehrotra, S. C.

    2006-05-01

    Dielectric relaxation measurements on alkyl methacrylates (methyl methacrylate, ethyl methacrylate and butyl methacrylate) with 1-alcohols (1-propanol, 1-pentanol, 1-heptanol, 1-octanol and 1-decanol) have been carried out using time-domain reflectometry (TDR) over the frequency range 10 MHz to 20 GHz at 303 K for different concentrations of alcohols. The dielectric parameters, namely the static dielectric constant (ɛ0), the dielectric constant at microwave frequencies (ɛ∞) and the relaxation time (τ) were determined. The Kirkwood correlation factor, which contains information regarding solute-solvent interaction and corresponding structural information, the excess permittivity and the excess inverse relaxation time were also determined. The values of the static dielectric constant and the relaxation time increase with the percentage of alkyl methacrylates in the alcohol, whereas the static dielectric constant decreases and the relaxation time increases with an increase in the alkyl chain length of both the methacrylates and the alcohols.

  19. On the effective measurement frequency of time domain reflectometry in dispersive and nonconductive dielectric materials

    NASA Astrophysics Data System (ADS)

    Robinson, D. A.; Schaap, M. G.; Or, D.; Jones, S. B.

    2005-02-01

    Time domain reflectometry (TDR) is one of the most commonly used techniques for water content determination in the subsurface. The measurement results in a single bulk permittivity value that corresponds to a particular, but unknown, ``effective'' frequency (feff). Estimating feff using TDR is important, as it allows comparisons with other techniques, such as impedance or capacitance probes, or microwave remote sensing devices. Soils, especially those with high clay and organic matter content, show appreciable dielectric dispersion, i.e., the real permittivity changes as a function of frequency. Consequently, comparison of results obtained with different sensor types must account for measurement frequency in assessing sensor accuracy and performance. In this article we use a transmission line model to examine the impact of dielectric dispersion on the TDR signal, considering lossless materials (negligible electrical conductivity). Permittivity is inferred from the standard tangent line fitting procedure (KaTAN) and by a method of using the apex of the derivative of the TDR waveform (KaDER). The permittivity determined using the tangent line method is considered to correspond to a velocity associated with a maximum passable frequency; whereas we consider the permittivity determined from the derivative method to correspond with the frequency associated with the signal group velocity. The effective frequency was determined from the 10-90% risetime of the reflected signal. On the basis of this definition, feff was found to correspond with the permittivity determined from KaDER and not from KaTAN in dispersive dielectrics. The modeling is corroborated by measurements in bentonite, ethanol and 1-propanol/water mixtures, which demonstrate the same result. Interestingly, for most nonconductive TDR measurements, frequencies are expected to lie in a range from 0.7 to 1 GHz, while in dispersive media, feff is expected to fall below 0.6 GHz.

  20. On the effective measurement frequency of time domain reflectometry in dispersive and nonconductive dielectric materials

    NASA Astrophysics Data System (ADS)

    Robinson, D. A.; Schaap, M. G.; Or, D.; Jones, S. B.

    2005-02-01

    Time domain reflectometry (TDR) is one of the most commonly used techniques for water content determination in the subsurface. The measurement results in a single bulk permittivity value that corresponds to a particular, but unknown, "effective" frequency (feff). Estimating feff using TDR is important, as it allows comparisons with other techniques, such as impedance or capacitance probes, or microwave remote sensing devices. Soils, especially those with high clay and organic matter content, show appreciable dielectric dispersion, i.e., the real permittivity changes as a function of frequency. Consequently, comparison of results obtained with different sensor types must account for measurement frequency in assessing sensor accuracy and performance. In this article we use a transmission line model to examine the impact of dielectric dispersion on the TDR signal, considering lossless materials (negligible electrical conductivity). Permittivity is inferred from the standard tangent line fitting procedure (KaTAN) and by a method of using the apex of the derivative of the TDR waveform (KaDER). The permittivity determined using the tangent line method is considered to correspond to a velocity associated with a maximum passable frequency; whereas we consider the permittivity determined from the derivative method to correspond with the frequency associated with the signal group velocity. The effective frequency was determined from the 10-90% risetime of the reflected signal. On the basis of this definition, feff was found to correspond with the permittivity determined from KaDER and not from KaTAN in dispersive dielectrics. The modeling is corroborated by measurements in bentonite, ethanol and 1-propanol/water mixtures, which demonstrate the same result. Interestingly, for most nonconductive TDR measurements, frequencies are expected to lie in a range from 0.7 to 1 GHz, while in dispersive media, feff is expected to fall below 0.6 GHz.

  1. Constant current loop impedance measuring system that is immune to the effects of parasitic impedances

    NASA Technical Reports Server (NTRS)

    Anderson, Karl F. (Inventor)

    1994-01-01

    A constant current loop measuring system is provided for measuring a characteristic of an environment. The system comprises a first impedance positionable in the environment, a second impedance coupled in series with said first impedance and a parasitic impedance electrically coupled to the first and second impedances. A current generating device, electrically coupled in series with the first and second impedances, provides a constant current through the first and second impedances to produce first and second voltages across the first and second impedances, respectively, and a parasitic voltage across the parasitic impedance. A high impedance voltage measuring device measures a voltage difference between the first and second voltages independent of the parasitic voltage to produce a characteristic voltage representative of the characteristic of the environment.

  2. Measurement of the positron diffusion constants in polycrystalline molybdenum by the observation of positronium negative ions

    NASA Astrophysics Data System (ADS)

    Suzuki, Takuji; Iida, Simpei; Yamashita, Takashi; Nagashima, Yasuyuki

    2015-06-01

    We have measured the positron diffusion constants in polycrystalline molybdenum by the observation of positronium negative ions (Ps-). The Ps- ions emitted from the sample surface coated with Na were accelerated. The γ-rays from the accelerated Ps- ions were Doppler- shifted and thus the signals of self-annihilation of the Ps- ions were isolated from those of self-annihilation of para-positronium (p-Ps) or pair-annihilation of positrons in the bulk. Clear and reliable values of the diffusion constants have been obtained.

  3. Anharmonic properties of solids from measurements of the stress acoustic constant

    NASA Technical Reports Server (NTRS)

    Cantrell, J. H., Jr.

    1982-01-01

    The equations of elastic motion and their solutions are generalized in order to include nonzero homogeneous initial stresses and redefine the stress acoustic constants to include the effect of initial stress. In deriving the relationship between the stress acoustic constants and the strain-generalized Gruneisen parameters, implications in material anharmonicity and nonlinear thermoelasticity are discovered. It is found that the linear change in velocity obtained from these measurements is a nonlinear process resulting from anharmonicity in the interatomic potential. In addition, the thermal expansion coefficient can also be expressed in terms of linear combinations.

  4. Measurement of piezoelectric constants of lanthanum-gallium tantalate crystal by X-ray diffraction methods

    SciTech Connect

    Blagov, A. E.; Marchenkov, N. V. Pisarevsky, Yu. V.; Prosekov, P. A.; Kovalchuk, M. V.

    2013-01-15

    A method for measuring piezoelectric constants of crystals of intermediate systems by X-ray quasi-multiple-wave diffraction is proposed and implemented. This technique makes it possible to determine the piezoelectric coefficient by measuring variations in the lattice parameter under an external electric field. This method has been approved, its potential is evaluated, and a comparison with high-resolution X-ray diffraction data is performed.

  5. A search for varying fundamental constants using hertz-level frequency measurements of cold CH molecules

    PubMed Central

    Truppe, S.; Hendricks, R.J.; Tokunaga, S.K.; Lewandowski, H.J.; Kozlov, M.G.; Henkel, Christian; Hinds, E.A.; Tarbutt, M.R.

    2013-01-01

    Many modern theories predict that the fundamental constants depend on time, position or the local density of matter. Here we develop a spectroscopic method for pulsed beams of cold molecules, and use it to measure the frequencies of microwave transitions in CH with accuracy down to 3 Hz. By comparing these frequencies with those measured from sources of CH in the Milky Way, we test the hypothesis that fundamental constants may differ between the high- and low-density environments of the Earth and the interstellar medium. For the fine structure constant we find Δα/α=(0.3±1.1) × 10−7, the strongest limit to date on such a variation of α. For the electron-to-proton mass ratio we find Δμ/μ=(−0.7±2.2) × 10−7. We suggest how dedicated astrophysical measurements can improve these constraints further and can also constrain temporal variation of the constants. PMID:24129439

  6. A search for varying fundamental constants using hertz-level frequency measurements of cold CH molecules.

    PubMed

    Truppe, S; Hendricks, R J; Tokunaga, S K; Lewandowski, H J; Kozlov, M G; Henkel, Christian; Hinds, E A; Tarbutt, M R

    2013-01-01

    Many modern theories predict that the fundamental constants depend on time, position or the local density of matter. Here we develop a spectroscopic method for pulsed beams of cold molecules, and use it to measure the frequencies of microwave transitions in CH with accuracy down to 3 Hz. By comparing these frequencies with those measured from sources of CH in the Milky Way, we test the hypothesis that fundamental constants may differ between the high- and low-density environments of the Earth and the interstellar medium. For the fine structure constant we find Δα/α=(0.3 ± 1.1) × 10⁻⁷, the strongest limit to date on such a variation of α. For the electron-to-proton mass ratio we find Δμ/μ=(-0.7 ± 2.2) × 10⁻⁷. We suggest how dedicated astrophysical measurements can improve these constraints further and can also constrain temporal variation of the constants. PMID:24129439

  7. Test results of a prototype dielectric microcalorimeter

    SciTech Connect

    Pfafman, T.E.; Silver, E.; Labov, S. ); Beeman, J.; Goulding, F.; Hansen, W.; Landis, D.; Madden, N. )

    1990-08-13

    The initial development work on a dielectric microcalorimeter is presented. It focuses on the dielectric properties of the ferroelectric material KTa{sub 1-x}Nb{sub x}O{sub 3} (KTN). Measurements of the temperature dependent dielectric constant are given together with the first alpha particle detection results from a prototype composite microcalorimeter operating at 1.3 K. a non-thermal mechanism for detecting 6 MeV alpha particles in a monolithic KTN sample is also reported. 7 refs, 16 figs., 1 tab.

  8. Measurements of Nitric Oxide in a Plasma Generated by a Variable-Width, Constant Energy Discharge

    NASA Astrophysics Data System (ADS)

    Burnette, David; Adamovich, Igor; Lempert, Walter; Non-equilibrium Thermodynamics Laboratory Team

    2014-10-01

    A diffuse plasma filament within a low pressure sphere gap was generated using a high voltage, solid state switch. For a constant pressure and overvoltage, the peak current and voltage drop were altered by a change in the ballast resistor while a simultaneous adjustment to the variable pulse width was used to maintain a constant pulse energy. The discharge parameters were chosen to result in a quasi-steady state discharge with near constant current and very little change in size and uniformity for each condition studied. The absolute density and temporal evolution of nitric oxide (NO) was measured via laser-induced fluorescence for each condition. The effect of the pulse characteristics and estimated E/N on the formation of NO are discussed.

  9. Refractive index gradient measurement across the thickness of a dielectric film by the prism coupling method

    SciTech Connect

    Sokolov, Viktor I; Panchenko, Vladislav Ya; Seminogov, V N

    2012-08-31

    A method is proposed for measuring the refractive index gradient n(z) in nonuniformly thick dielectric films. The method is based on the excitation of waveguide modes in a film using the prism coupling technique and on the calculation of n(z) and film thickness H{sub f} with the help of the angular positions of the TE or TM modes. The method can be used for an arbitrary shape of the index modulation over the film thickness in the limit of a small gradient [{Delta} n(z)/n(z) || 1]. (laser applications and other topics in quantum electronics)

  10. Polar components of frying fats derived from data of dielectric measurements.

    PubMed

    Wegmüller, F

    1994-07-01

    The results of this work demonstrate that the quality of frying fats can be quantitatively tested with sufficient accuracy by dielectric measurements. Independently of the type of the frying fat and the fried food all converted food-oil-sensor data agreed within 2-sigma-error intervals with the polar amounts obtained by an improved version of the commonly used liquid chromatography. Furthermore, the easy handling of food-oil sensors allow thorough control of frying fats even by kitchen personnel. PMID:8067060

  11. Constraints on axion-nucleon coupling constants from measuring the Casimir force between corrugated surfaces

    NASA Astrophysics Data System (ADS)

    Bezerra, V. B.; Klimchitskaya, G. L.; Mostepanenko, V. M.; Romero, C.

    2014-09-01

    We obtain stronger laboratory constraints on the coupling constants of axion-like particles to nucleons from measurements of the normal and lateral Casimir forces between sinusoidally corrugated surfaces of a sphere and a plate. For this purpose, the normal and lateral additional forces arising in the experimental configurations due to the two-axion exchange between protons and neutrons are calculated. Our constraints following from measurements of the normal and lateral Casimir forces are stronger than the laboratory constraints reported so far for masses of axion-like particles larger than 11 and 8 eV, respectively. A comparison between various laboratory constraints on the coupling constants of axion-like particles to nucleons obtained from the magnetometer measurements, Eötvos- and Cavendish-type experiments, and from the Casimir effect is performed over the wide range of masses of axion-like particles from 10-10 to 20 eV.

  12. Constant frequency pulsed phase-locked-loop instrument for measurement of ultrasonic velocity

    SciTech Connect

    Yost, William T; Cantrell, John H; Kushnick, Peter W

    1991-10-01

    A new instrument based on a constant frequency pulsed phase-locked-loop (CFPPLL) concept has been developed to accurately measure the ultrasonicwavevelocity in liquids and changes in ultrasonicwavevelocity in solids and liquids. An analysis of the system shows that it is immune to many of the frequency-dependent effects that plague other techniques including the constant phase shifts of reflectors placed in the path of the ultrasonicwave.Measurements of the sound velocity in ultrapure water are used to confirm the analysis. The results are in excellent agreement with values from the literature, and establish that the CFPPLL provides a reliable, accurate way to measurevelocities, as well as for monitoring small changes in velocity without the sensitivity to frequency-dependent phase shifts common to other measurement systems. The estimated sensitivity to phase changes is better than a few parts in 10{sup 7}.

  13. Ultrasonic measurement of the elastic constants of potassium hydrogen phthalate single crystals

    NASA Astrophysics Data System (ADS)

    Alex, A. V.; Philip, J.

    2000-09-01

    Many organic crystals with orthorhombic symmetry exhibit electro-optic, ferroelectric, and triboluminescence properties. The potassium salt of phthalic acid (KAP), with the formula C8H5O4K, finds application in soft x-ray spectroscopy due to its large d spacing and has been reported to be piezoelectric as well. KAP crystallizes into orthorhombic structure with space group Pca21 All nine elastic constants of KAP have been determined by measuring the velocity of longitudinal and transverse ultrasonic waves propagating along different symmetry directions. Velocities have been measured by the ultrasonic pulse echo overlap technique by injecting waves generated by quartz transducers through a suitable bonding medium into the crystal. The McSkimin Δt correction has been applied to determine the velocities accurately. The temperature variation of selected elastic constants over the range 300-420 K has also been measured and reported.

  14. Cast dielectric composite linear accelerator

    DOEpatents

    Sanders, David M.; Sampayan, Stephen; Slenes, Kirk; Stoller, H. M.

    2009-11-10

    A linear accelerator having cast dielectric composite layers integrally formed with conductor electrodes in a solventless fabrication process, with the cast dielectric composite preferably having a nanoparticle filler in an organic polymer such as a thermosetting resin. By incorporating this cast dielectric composite the dielectric constant of critical insulating layers of the transmission lines of the accelerator are increased while simultaneously maintaining high dielectric strengths for the accelerator.

  15. Microwave dielectric measurements and tissue characteristics of the human brain: potential in localizing intracranial tissues

    NASA Astrophysics Data System (ADS)

    Axer, Hubertus; Gräßel, David; Steinhauer, Matthias; Stöhr, Peter; John, Andreas; Coenen, Volker A.; Jansen, Rolf H.; Keyserlingk, Diedrich Graf v.

    2002-05-01

    This study describes the measurements of dielectric properties in the microwave range to differentiate various human central nervous structures. Using a vector network analyser transmission and reflection coefficients were measured from 500 MHz to 18 GHz in four human formalin fixed human brains. The positions of the electrodes were marked, and the tissue was histologically stained to visualize the myelo- and the cytoarchitecture as well as the nerve fibre orientation at the electrodes. The profiles of the transmission coefficients showed a characteristic minimum peak. In order to describe this peak, a mathematical function was fitted. Parameters derived from digital image processing were used to characterize the myelo- and cytoarchitecure of the tissue at the electrodes. A multiple regression model, with the frequency at the transmission peak minimum as a dependent variable and two tissue characteristics at the two electrodes as independent variables, showed a multiple regression coefficient of 0.765. A neural network model was able to estimate the frequency at the transmission peak minimum from the tissue characteristics at the electrode. The measurements of dielectric properties are well suited to differentiate distinct intracerebral structures. The method could be used for online monitoring of the needle's position during a stereotactic intervention in neurosurgery.

  16. Low-temperature dielectric measurements of confined water in porous granites

    NASA Astrophysics Data System (ADS)

    Gonçalves da Silva, Hugo; Prezas, Pedro; Vinagre, Ana; Graça, Manuel F.; Monteiro, Jorge H.; Tlemçani, Mouhaydine; Moita, Patrícia; Pinho, António; Bezzeghoud, Mourad; Mendiratta, Sushil K.; Rosa, Rui N.

    2014-05-01

    Three different granitic rocks extracted from Évora (in the south of Portugal) where used to perform dielectric measurements in the frequency range from 100 Hz to 1 MHz and temperatures 100 - 350 K. Thin cylindrical samples were prepared and circular electrodes were established using silver conductive paint. A clear anomaly appears, for T ~ 200 - 220 K, in the dielectric measurements of the samples studied. This anomaly occurs in different materials and coincides with a phase transition of supercooled water. Tightly bounded water confined in the pores of the rock do not crystallize at 273 K, but form a metastable liquid down to 200 - 220 K increasing water polarization. Below this temperature water molecules solidify and polarizability decreases. The rock presenting the most sizeable anomaly has a very low specific surface area, ~ 0.09 m2g-1, and connected porosity, ~ 1.10 %. In addition, geochemical analyses reveal almost inexistence of water molecules in its structure confirming the role of confined water in the anomaly. Comparison between saturated, oven dried, and vacuum dried samples is done. Finally, a logarithmic dependency of the critical temperature for the supercooled water phase transition with the measuring frequency is found. The authors acknowledge the support of FCT (Portuguese Science and Technology Foundation) through the project PTDC/GEO-FIQ/4178/2012.

  17. Dielectric and electro-optic measurements of nematic liquid crystals doped with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Peterson, Matthew; Georgiev, Georgi; Atherton, Timothy; Cebe, Peggy

    We studied the effects of carbon nanotubes (CNTs) on the dielectric and electro-optic properties of nematic 5CB liquid crystals (LCs). Samples containing 0.01%, 0.10% and 1.00% CNTs by weight were prepared. Anti- parallel rubbed cells with a nominal thickness of 10 μm were prepared using indium tin oxide coated glass cells and a polyimide alignment layer. The capacitance and dissipation factor were measured using an Agilent 4284A precision LCR meter. From these measurements, the complex dielectric permittivity was determined as a function of frequency. Analysis of the low frequency regime (f <1000 Hz) indicates that 5CB samples containing CNTs have a higher conductance than neat samples. The Fréedericksz transition critical voltage was noted by a sharp increase in capacitance after an initial plateau. Numerical simulations of CNT-facilitated switching show that polarization induced on the nanotubes from capacitive effects can significantly reduce the critical voltage in DC electric fields, in agreement with experimental results. Measurements of the critical voltage over a range of frequencies will also be presented. Research was supported by the National Science Foundation, DMR1206010.

  18. The measurement system of birefringence and Verdet constant of optical fiber

    NASA Astrophysics Data System (ADS)

    Huang, Yi; Chen, Li; Guo, Qiang; Pang, Fufei; Wen, Jianxiang; Shang, Yana; Wang, Tingyun

    2013-12-01

    The Faraday magneto-optical effect of optical fiber has many applications in monitoring magnetic field and electric current. When a linearly polarized light propagates in the direction of a magnetic field, the plane of polarization will rotate linearly proportional to the strength of the applied magnetic field, which following the relationship of θF =VBl. θF is the Faraday rotation angle, which is proportional to the magnetic flux density B and the Verdet constant V . However, when the optical fiber contains the effect of linear birefringence, the detection of Faraday rotation angle will depend on the line birefringence. In order to determine the Verdet constant of an optical fiber under a linear birefringence, the fiber birefringence needs to be accurately measured. In this work, a model is applied to analyze the polarization properties of an optical fiber by using the Jones matrix method. A measurement system based on the lock-in amplifier technology is designed to test the Verdet constant and the birefringence of optical fiber. The magnetic field is produced by a solenoid with a DC current. A tunable laser is intensity modulated with a motorized rotating chopper. The actuator supplies a signal as the phase-locked synchronization reference to the signal of the lock-in amplifier. The measurement accuracy is analyzed and the sensitivity of the system is optimized. In this measurement system, the Verdet constant of the SMF-28 fiber was measured to be 0.56±0.02 rad/T·m at 1550nm. This setup is well suitable for measuring the high signal-to-noise ratio (SNR) sensitivity for lock-in amplifier at a low magnetic field strength.

  19. Reentrant radio-frequency resonator for automated phase-equilibria and dielectric measurements in fluids

    SciTech Connect

    Goodwin, A.R.; Mehl, J.B.; Moldover, M.R.

    1996-12-01

    A reentrant rf cavity resonator has been developed for automated detection of phase separation of fluid mixtures contained within the cavity. Successful operation was demonstrated by redetermining the phase boundaries of a CO{sub 2}+C{sub 2}H{sub 6} mixture in the vicinity of its critical point. We developed an accurate electrical model for the resonator and used helium to determine the deformation of the resonator under pressure. With the model and pressure compensation, the resonator was capable of very accurate dielectric measurements. We confirmed this by remeasuring the molar dielectric polarizability {ital A}{sub {epsilon}} of argon and obtained the result {ital A}{sub {epsilon}}=(4.140{plus_minus}0.006) cm{sup 3}/mol (standard uncertainty) in excellent agreement with published values. We exploited the capability for accurate dielectric measurements to determine the densities of the CO{sub 2}+C{sub 2}H{sub 6} mixture at the phase boundaries and to determine the dipole moment of 1,1,1,2,3,3-hexafluoropropane, a candidate replacement refrigerant. Near the operating frequency of 375 MHz the capacitor in the resonator has an impedance near 14 {Omega}. This low impedance is more tolerant of electrical conductivity within the test fluid and in parallel paths in the support structures than comparable capacitors operating at audio frequencies. This will be an advantage for operation at high temperatures where some conductivity must be expected in all fluids. Of further value for high-temperature applications, the present rf resonator has only two metal{endash}insulator joints. These joints seal coaxial cables; neither joint is subjected to large mechanical stresses and neither joint is required to maintain precise dimensional tolerances. The resonator is rugged and may be operated with inexpensive electronics.

  20. Pore type analysis using bore hole electrical images with new sonic and dielectric measurements

    SciTech Connect

    Watfa, M.; Nurmi, R.

    1987-05-01

    In carbonates and some complex sandstone reservoirs the determination of pore types is critical for an accurate reservoir analysis (saturation, permeability, effective porosity, producibility). Until recently, it has been necessary to retrieve rock samples of a reservoir formation to determine which types of pores are present. However, a well-log approach has been developed which permits both the recognition and quantitative interpretation of pore types. The approach is an integration of the newly developed electrical bore-hole imagery with dielectric and sonic measurements, geological sequence modeling, and a thorough formation evaluation analysis. This approach permits routine mapping of pore types and their respective volumes within reservoir zones. The reservoirs studied have included carbonates and sandstones with complex pore systems (mixtures of both primary and secondary pore types) in the San Andres and Smackover Formations in the USA and the Pre-Khuff, Khuff, Arab, Shuaiba, and Mishrif formations on the Arabian Peninsula. The analysis of electrical images and Archie equation exponent m variations in common carbonate depositional sequences generally permit the interpretation of both rock and pore types. The electrical images allow a direct analysis of rock fabric, porosity heterogeneity, and large individual pores such as vugs, channels, and fracture. Dielectric measurements, combined with more traditional analysis of porosity and fluid saturations, permit a level-by-level calculation of the exponent m, which is valuable in analyzing the smaller but more abundant pores, whereas the dielectric and sonic (shear, compressional, Stoneley) data provide additional quantification of pore types when related to total pore volume.

  1. Enhanced dielectric constant and relaxor behavior realized by dual stage sintering of Sr{sub 0.5}Ba{sub 0.5}Nb{sub 2}O{sub 6}

    SciTech Connect

    Rathore, Satyapal S. Vitta, Satish

    2014-04-24

    The relaxor ferroelectric compound, Sr{sub 0.5}Ba{sub 0.5}Nb{sub 2}O{sub 6} (SBN50) was synthesized by solid state reaction followed by sintering under two different conditions: single and dual stage sintering. The impact of sintering process on structural and dielectric properties has been studied in detail using X-ray diffraction, scanning electron microscopy and broadband dielectric spectroscopy. The crystal structure determined by performing Rietveld refinement of X-ray diffractogram was found to be identical in both cases. SBN50 crystallizes in the ferroelectric tetragonal tungsten bronze, P4bm structure. It was observed that uniform grain growth can be controlled by dual stage sintering and relatively narrow distribution of grains can be achieved with an average grain size of ∼15 μm. The dielectric studies show that SBN50 exhibits a relaxor ferroelectric behavior with the transformation taking place at ∼ 380 K due to formation of polar nano regions. Although both single and dual stage sintered SBN50 exhibits relaxor behaviour, the maximum dielectric constant of dual stage sintered SBN50 is found to be 1550 compare to 1440 for single stage sintering.

  2. Ultralow loss dielectric ribbon waveguide for millimeter/submillimeter waves

    NASA Astrophysics Data System (ADS)

    Yeh, C.; Shimabukuro, F. I.; Chu, J.

    1989-03-01

    By using high dielectric constant and low-loss dielectric material such as quartz, alumina, or sapphire and by specifically configuring the waveguide structure, a waveguide was designed for the millimeter/submillimeter wavelength range, which yields an attenuation constant for the dominant mode that is more than 100 times below that for an equivalent circular dielectric rod with identical cross-sectional area. This waveguide takes the form of a thin dielectric ribbon surrounded by lossless dry air and possess an attenuation constant as low as 20 dB/km. Analytical results on the attenuation constant and field extent of the dominant mode on this ribbon structure for several promising materials are given. Experiments have also been performed on ribbon guides made with rexolite. Excellent agreement was found between predicted and measured results.

  3. Time and Space Resolved Heat Transfer Measurements Under Nucleate Bubbles with Constant Heat Flux Boundary Conditions

    NASA Technical Reports Server (NTRS)

    Myers, Jerry G.; Hussey, Sam W.; Yee, Glenda F.; Kim, Jungho

    2003-01-01

    Investigations into single bubble pool boiling phenomena are often complicated by the difficulties in obtaining time and space resolved information in the bubble region. This usually occurs because the heaters and diagnostics used to measure heat transfer data are often on the order of, or larger than, the bubble characteristic length or region of influence. This has contributed to the development of many different and sometimes contradictory models of pool boiling phenomena and dominant heat transfer mechanisms. Recent investigations by Yaddanapyddi and Kim and Demiray and Kim have obtained time and space resolved heat transfer information at the bubble/heater interface under constant temperature conditions using a novel micro-heater array (10x10 array, each heater 100 microns on a side) that is semi-transparent and doubles as a measurement sensor. By using active feedback to maintain a state of constant temperature at the heater surface, they showed that the area of influence of bubbles generated in FC-72 was much smaller than predicted by standard models and that micro-conduction/micro-convection due to re-wetting dominated heat transfer effects. This study seeks to expand on the previous work by making time and space resolved measurements under bubbles nucleating on a micro-heater array operated under constant heat flux conditions. In the planned investigation, wall temperature measurements made under a single bubble nucleation site will be synchronized with high-speed video to allow analysis of the bubble energy removal from the wall.

  4. Measurement of the magnetic anisotropy energy constants for magneto-optical recording media

    NASA Technical Reports Server (NTRS)

    Hajjar, R. A.; Wu, T. H.; Mansuripur, M.

    1992-01-01

    Measurement of the magneto-optical polar Kerr effect is performed on rare earth-transition metal (RE-TM) amorphous films using in-plane fields. From this measurement and the measurement of the saturation magnetization using a vibrating sample magnetometer (VSM), the magnetic anisotropy constants are determined. The temperature dependence is presented of the magnetic anisotropy in the range of -175 to 175 C. The results show a dip in the anisotropy near magnetic compensation. This anomaly is explained based on the finite exchange coupling between the rare earth and transition metal subnetworks.

  5. Measurement of Oil-Film Pressures in Journal Bearings under Constant and Variable Loads

    NASA Technical Reports Server (NTRS)

    Buske, A.; Rolli, W.

    1949-01-01

    In a study of journal bearings, the measurement of the oil-film strength produces some significant information. A new instrument is described by means of which the pressure of the oil film in bearings (under constant or alternating load) can be measured and recorded. With this device, the pressure distribution in the lubricating film of a bearing bushing was measured (under different operating conditions on a journal bearing) in the pulsator-bearing-testing machine. These tests are described and discussed in the present report.

  6. Stabilization of the low temperature coefficient of dielectric constant of Ca{sub 5}Nb{sub 2}TiO{sub 12} by Zr doping

    SciTech Connect

    Cava, R.J.; Krajewski, J.J.

    1999-10-01

    Microwave communications devices involve the use of filters and resonators that have a ceramic dielectric as an essential component. To meet the requirements for use in such devices, dielectric materials must satisfy stringent property restriction. The effects of small amounts of Zr substitution for Ti in the low loss, low temperature coefficient dielectric material Ca{sub 5}Nb{sub 2}TiO{sub 12} are reported. Substitutions at the 1--5% level significantly increase the range of possible firing temperatures at which polycrystalline ceramics with low temperature coefficients can be obtained. This low temperature coefficient state is at the borderline between ordered and disordered states of the Ca, Nb, and Ti ions in the B sites of the perovskite lattice. The kinetics for ordering is apparently enhanced by the Zr substitutions.

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

    SciTech Connect

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

    2003-06-01

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

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

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin C.; Kaukler, William

    2009-01-01

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

  9. Dielectric Resonator for Ka-Band Pulsed EPR Measurements at Cryogenic Temperatures: Probehead Construction and Applications

    PubMed Central

    Astashkin, A.; Enemark, J. H.; Blank, A.; Twig, Y.; Song, Y.; Meade, T. J.

    2013-01-01

    The construction and performance of a Ka-band pulsed electron paramagnetic resonance (EPR) cryogenic probehead that incorporates dielectric resonator (DR) is presented. We demonstrate that the use of DR allows one to optimize pulsed double electron–electron resonance (DEER) measurements utilizing large resonator bandwidth and large amplitude of the microwave field B1. In DEER measurements of Gd-based spin labels, use of this probe finally allows one to implement the potentials of Gd-based labels in distance measurements. Evidently, this DR is well suited to any applications requiring large B1-fields and resonator bandwidths, such as electron spin echo envelope modulation spectroscopy of nuclei having low magnetic moments and strong hyperfine interactions and double quantum coherence dipolar spectroscopy as was recently demonstrated in the application of a similar probe based on an loop-gap resonator and reported by Forrer et al. (J Magn Reson 190:280, 2008). PMID:23626406

  10. Internal Friction and Dielectric Measurements in Lead Zirconate Titanate Ferroelectric Ceramics

    NASA Astrophysics Data System (ADS)

    Bourim, El Mostafa; Tanaka, Hidehiko; Gabbay, Maurice; Fantozzi, Gilbert

    2000-09-01

    Elastic modulus (Young’s modulus M and shear modulus G) and internal friction Q-1 are measured as a function of temperature from {-}180{\\degC} to 500°C in undoped lead zirconate titanate (PZT) ferroelectric ceramics in the range of kHz and low frequencies (0.1 to 1 Hz). New phase transition temperatures at the morphotropic zone at low temperatures are determined from the elastic modulus minimum. Permittivity \\varepsilon and dielectric loss \\tan(δ) are measured in the frequency range of 20 Hz to 10 kHz. Both mechanical and electrical measurements allow the observation of relaxation peaks in the ferroelectric phase. The Arrhenius plots of all these results show that it is possible to investigate these relaxation processes using both experimental techniques.

  11. Measurement of plasma parameter in Dielectric Barrier Discharge (DBD) by Moiré deflectometry technique

    NASA Astrophysics Data System (ADS)

    Salimi Meidanshahi, Fatemeh; Madanipour, Khosro; Shokri, Babak; Khani, Mohammad Reza; Borzoki, Hamid Razavi

    2015-05-01

    In this work it is shown that the refractive index and temperature distribution of atmospheric Dielectric Barrier Discharge (DBD) plasmas are measured by Moiré deflectometry. Fringe analysis is used to calculate Moiré deflection and to evaluate refractive index in different points of plasma. By Sa-Ha equation and considering the first ionization, the dependence of refractive index and temperature, electrons, ions and molecules number densities of DBD plasma is obtained. By knowing this relation between plasma parameters, the spatial distributions of the plasma refractive index and temperature are evaluated. The advantages of this method are: simplicity, non-contact, non-destructive measurement, low cost, high accuracy and direct measurement of refractive index gradient.

  12. All-optical measurement of elastic constants in nematic liquid crystals.

    PubMed

    Klus, Bartłomiej; Laudyn, Urszula A; Karpierz, Mirosław A; Sahraoui, Bouchta

    2014-12-01

    In this article we present a new all-optical method to measure elastic constants connected with twist and bend deformations. The method is based on the optical Freedericksz threshold effect induced by the linearly polarized electro-magnetic wave. In the experiment elastic constants are measured of commonly used liquid crystals 6CHBT and E7 and two new nematic mixtures with low birefringence. The proposed method is neither very sensitive on the variation of cell thickness, beam waist or the power of a light beam nor does it need any special design of a liquid crystal cell. The experimental results are in good agreement with the values obtain by other methods based on an electro-optical effect. PMID:25606956

  13. Measuring the fine structure constant with Bragg diffraction and Bloch oscillations

    NASA Astrophysics Data System (ADS)

    Yu, Chenghui; Estey, Brian; Parker, Richard; Dudley, Jordan; Müller, Holger

    2016-05-01

    We have demonstrated a new scheme for atom interferometry based on large-momentum-transfer Bragg beam splitters and Bloch oscillations. In this new scheme, we have achieved a resolution of δα / α =0.25ppb in the fine structure constant measurement, which gives up to 4.4 million radians of phase difference between freely evolving matter waves. We have suppressed many systematic effects known in most atom interferometers with Raman beam splitters such as light shift, Zeeman effect shift as well as vibration. We have also simulated multi-atom Bragg diffraction to understand sub-ppb systematic effects, and implemented spatial filtering to further suppress systematic effects. We present our recent progress toward a measurement of the fine structure constant, which will provide a stringent test of the standard model of particle physics.

  14. Measuring h /mCs and the Fine Structure Constant with Bragg Diffraction and Bloch Oscillations

    NASA Astrophysics Data System (ADS)

    Parker, Richard

    2016-05-01

    We have demonstrated a new scheme for atom interferometry based on large-momentum-transfer Bragg beam splitters and Bloch oscillations. In this new scheme, we have achieved a resolution of δα / α =0.25ppb in the fine structure constant measurement, which gives up to 4.4 million radians of phase difference between freely evolving matter waves. We suppress many systematic effects, e.g., Zeeman shifts and effects from Earth's gravity and vibrations, use Bloch oscillations to increase the signal and reduce the diffraction phase, simulate multi-atom Bragg diffraction to understand sub-ppb systematic effects, and implement spatial filtering to further suppress systematic effects. We present our recent progress toward a measurement of the fine structure constant, which will provide a stringent test of the standard model of particle physics.

  15. Improved measurement results for the Avogadro constant using a 28Si-enriched crystal

    NASA Astrophysics Data System (ADS)

    Azuma, Y.; Barat, P.; Bartl, G.; Bettin, H.; Borys, M.; Busch, I.; Cibik, L.; D'Agostino, G.; Fujii, K.; Fujimoto, H.; Hioki, A.; Krumrey, M.; Kuetgens, U.; Kuramoto, N.; Mana, G.; Massa, E.; Meeß, R.; Mizushima, S.; Narukawa, T.; Nicolaus, A.; Pramann, A.; Rabb, S. A.; Rienitz, O.; Sasso, C.; Stock, M.; Vocke, R. D., Jr.; Waseda, A.; Wundrack, S.; Zakel, S.

    2015-04-01

    New results are reported from an ongoing international research effort to accurately determine the Avogadro constant by counting the atoms in an isotopically enriched silicon crystal. The surfaces of two 28Si-enriched spheres were decontaminated and reworked in order to produce an outer surface without metal contamination and improved sphericity. New measurements were then made on these two reconditioned spheres using improved methods and apparatuses. When combined with other recently refined parameter measurements, the Avogadro constant derived from these new results has a value of NA = 6.022 140 76(12) × 1023 mol-1. The x-ray crystal density method has thus achieved the target relative standard uncertainty of 2.0  ×  10-8 necessary for the realization of the definition of the new kilogram.

  16. EXAFS measurements of bond-stretching force constants in arsenic and arsenic compounds

    NASA Astrophysics Data System (ADS)

    Tranquada, J. M.; Yang, C. Y.

    1987-07-01

    The Einstein frequency ν E obtained from temperature-dependent EXAFS measurements for the bond between an arsenic atom and a nearest neighbor in arsenic and certain arsenic halides and chalcogenides is considered. It is shown theoretically that in these materials ν E should be approximately equal to the "natural" frequency of the bond, and hence that ν E2 is proportional to the bond-stretching force constant ⨍ r. Experimental EXAFS measurements on crystalline ( c-) AsBr 3 and AsI 3, glassy ( g-) As 2S 3 and As 2Se 3, and amorphous ( a-) As yield force constants in reasonable agreement with those obtained from Raman and infrared studies.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

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

    PubMed

    Sasaki, K; Wake, K; Watanabe, S

    2014-08-21

    Numerous studies have reported the measurements of the dielectric properties of the skin. Clarifying the manner in which the human body interacts with electromagnetic waves is essential for medical research and development, as well as for the safety assessment of electromagnetic wave exposure. The skin comprises several layers: the epidermis, the dermis, and the subcutaneous fat. Each of these skin layers has a different constitution; however, the previous measurements of their dielectric properties were typically conducted on tissue which included all three layers of the skin. This study presents novel dielectric property data for the epidermis and dermis with in vitro measurement at frequencies ranging from 0.5 GHz to 110 GHz. Measured data was compared with literature values; in particular, the findings were compared with Gabriel's widely used data on skin dielectric properties. The experimental results agreed with the data reported by Gabriel for the dermis of up to 20 GHz, which is the upper limit of the range of frequencies at which Gabriel reported measurements. For frequencies of 20-100 GHz, the experimental results indicated larger values than those extrapolated from Gabriel's data using parametric expansion. For frequencies over 20 GHz, the dielectric properties provided by the parametric model tend toward the experimental results for the epidermis with increasing frequency. PMID:25082800

  19. The effect of interacting dark energy on local measurements of the Hubble constant

    NASA Astrophysics Data System (ADS)

    Odderskov, Io; Baldi, Marco; Amendola, Luca

    2016-05-01

    In the current state of cosmology, where cosmological parameters are being measured to percent accuracy, it is essential to understand all sources of error to high precision. In this paper we present the results of a study of the local variations in the Hubble constant measured at the distance scale of the Coma Cluster, and test the validity of correcting for the peculiar velocities predicted by gravitational instability theory. The study is based on N-body simulations, and includes models featuring a coupling between dark energy and dark matter, as well as two ΛCDM simulations with different values of σ8. It is found that the variance in the local flows is significantly larger in the coupled models, which increases the uncertainty in the local measurements of the Hubble constant in these scenarios. By comparing the results from the different simulations, it is found that most of the effect is caused by the higher value of σ8 in the coupled cosmologies, though this cannot account for all of the additional variance. Given the discrepancy between different estimates of the Hubble constant in the universe today, cosmological models causing a greater cosmic variance is something that we should be aware of.

  20. Shock tube measurements of high temperature rate constants for OH with cycloalkanes and methylcycloalkanes

    SciTech Connect

    Sivaramakrishnan, R.; Michael, J.V.

    2009-05-15

    High temperature experiments were performed with the reflected shock tube technique using multi-pass absorption spectrometric detection of OH radicals at 308 nm. The present experiments span a wide T-range, 801-1347 K, and represent the first direct measurements of the title rate constants at T>500 K for cyclopentane and cyclohexane and the only high temperature measurements for the corresponding methyl derivatives. The present work utilized 48 optical passes corresponding to a total path length {proportional_to}4.2 m. As a result of this increased path length, the high [OH] detection sensitivity permitted unambiguous analyses for measuring the title rate constants. The experimental rate constants in units, cm{sup 3} molecule{sup -1} s{sup -1}, can be expressed in Arrhenius form as k{sub OH+Cyclopentane}=(1.90{+-}0.30) x 10{sup -10}exp(-1705{+-}56 K/T) (813-1341 K), k{sub OH+Cyclohexane}=(1.86{+-}0.24) x 10{sup -10}exp(-1513{+-}123 K/T) (801-1347 K), k{sub OH+Methylcyclopentane}=(2.02{+-}0.19) x 10{sup -10}exp(-1799{+-}96 K/T) (859-1344 K), k{sub OH+Methylcyclohexane}=(2.55{+-}0.30) x 10{sup -10}exp(-1824{+-}114 K/T) (836-1273 K). These results and lower-T experimental data were used to obtain three parameter evaluations of the experimental rate constants for the title reactions over an even wider T-range. These experimental three parameter fits to the rate constants in units, cm{sup 3} molecule{sup -1} s{sup -1}, are k{sub OH+Cyclopentane}=1.390 x 10{sup -16}T{sup 1.779}exp(97 K/T)cm{sup 3} molecule{sup -1}s{sup -1} (209-1341 K), k{sub OH+Cyclohexane}=3.169 x 10{sup -16}T{sup 1.679}exp(119 K/T)cm{sup 3}molecule{sup -1}s{sup -1} (225-1347 K), k{sub OH+Methylcyclopentane}=6.903 x 10{sup -18}T{sup 2.148}exp(536 K/T)cm{sup 3}molecule{sup -1}s{sup -1} (296-1344 K), k{sub OH+Methylcyclohexane}=2.341 x 10{sup -18}T{sup 2.325}exp(602 K/T)cm{sup 3}molecule{sup -1}s{sup -1} (296-1273 K). High level electronic structure methods were used to characterize the first three