Sample records for apparent electrical conductivity

  1. Estimating Depth to Argillic Soil Horizons using Apparent Electrical Conductivity Response Functions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Maps of apparent electrical conductivity (ECa) of the soil profile are widely used in precision agriculture practice and research. A number of ECa sensors are commercially available, each with a unique response function (i.e., the relative contribution of soil at each depth to the integrated ECa rea...

  2. ESTIMATING PLANT-AVAILABLE WATER CAPACITY FOR CLAYPAN LANDSCAPES USING APPARENT ELECTRICAL CONDUCTIVITY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Within-field variability of plant available water (PAW) capacity is useful information for site-specific management, but is expensive to assess using traditional measurements. For Missouri claypan soils, relationships between soil apparent electrical conductivity (ECa) and topsoil thickness have bee...

  3. Apparent dependence of conductivity of a conducting polymer on an electric field in a field effect transistor configuration

    NASA Astrophysics Data System (ADS)

    Lu, Jin; Pinto, Nicholas J.; MacDiarmid, Alan G.

    2002-11-01

    A curious effect is reported whereby an electric field apparently greatly affects the conductivity of an organic polymer, poly-3,4-ethylenedioxythiophene (PEDOT), doped to the "metallic" conducting regime when it is used in an all-organic polymer field effect transistor configuration. The response time for change in current in the source/drain PEDOT polymer with a change of gate voltage is slow (?˜2 s), suggesting that ionic diffusion is involved in the phenomenon. It is suggested that the electric field changes only the conductivity of the lowly conducting polymer matrix, which contains highly conducting islands of PEDOT, thus changing the extent of percolation of electric charge between metallic islands, and thereby affecting the bulk conductivity of the PEDOT source/drain material.

  4. Reconstruction of apparent orthotropic conductivity tensor image using magnetic resonance electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Sajib, Saurav Z. K.; Kim, Ji Eun; Jeong, Woo Chul; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

    2015-03-01

    Magnetic resonance electrical impedance tomography visualizes current density and/or conductivity distributions inside an electrically conductive object. Injecting currents into the imaging object along at least two different directions, induced magnetic flux density data can be measured using a magnetic resonance imaging scanner. Without rotating the object inside the scanner, we can measure only one component of the magnetic flux density denoted as Bz. Since the biological tissues such as skeletal muscle and brain white matter show strong anisotropic properties, the reconstruction of anisotropic conductivity tensor is indispensable for the accurate observations in the biological systems. In this paper, we propose a direct method to reconstruct an axial apparent orthotropic conductivity tensor by using multiple Bz data subject to multiple injection currents. To investigate the anisotropic conductivity properties, we first recover the internal current density from the measured Bz data. From the recovered internal current density and the curl-free condition of the electric field, we derive an over-determined matrix system for determining the internal absolute orthotropic conductivity tensor. The over-determined matrix system is designed to use a combination of two loops around each pixel. Numerical simulations and phantom experimental results demonstrate that the proposed algorithm stably determines the orthotropic conductivity tensor.

  5. Calibration of EMI derived apparent electrical conductivity based on ERT measurements

    NASA Astrophysics Data System (ADS)

    Rudolph, S.; Mester, A.; van der Kruk, J.; Weihermüller, L.; Zimmermann, E.; Vereecken, H.

    2012-04-01

    Soil electrical conductivity (ECa) is an indirect measure for various soil physical and chemical parameters. Among non-invasive geophysical methods, electromagnetic induction (EMI) appears to be the most efficient one that is able to measure ECa over large areas in short time. However, this method currently does not provide quantitative values of ECa due to calibration problems. In the calibration approach of Lavoué et al. (2010) inverted electrical conductivity data from a 120 m long ERT (electrical resistivity tomography) calibration transect were used as input parameter for an electromagnetic forward model to predict ECa measured with EMI. To further improve this calibration method we conducted a field survey within an agricultural field for crop breeding studies. The entire field (60x100 m) was mapped with the EM38-MK2 (Geonics, Ontario, Canada), an EMI system with multiple coil spacing which measures the weighted average of ECa over four depth ranges, immediately after the harvest of sugar beet. On the basis of high-resolution ECa distribution maps, an area with high contrast in ECa was selected for calibrating the EMI sensor with ERT. Along a 30 m long transect EMI measurements with two different internal calibration settings were carried out. A Syscal Pro System (IRIS Instruments, Orleans France) and 120 electrodes with an electrode spacing of 0.25 m were used to measure the apparent resistivity of soil. Post processed ERT measurements were inverted using the robust inversion method of the RES2DINV software. Quantitative EM inductions measurements were derived by linear regression between measured and predicted ECa measurements. The observed offset between the repeated EMI measurements could be removed successfully. Furthermore, shortening and focusing the ERT measurements to a specific area of interest could reduce the measurement time for calibration significantly. Prospectively, the application of a quantitative multi-layer inversion of multi-configuration EMI data will enable the detection of quantitative horizontal and vertical conductivity changes over large areas.

  6. Spatial and Temporal Patterns of Apparent Electrical Conductivity: DUALEM vs. Veris Sensors for Monitoring Soil Properties

    PubMed Central

    Serrano, João; Shahidian, Shakib; da Silva, José Marques

    2014-01-01

    The main objective of this study was to compare two apparent soil electrical conductivity (ECa) sensors (Veris 2000 XA and DUALEM 1S) for mapping variability of soil properties in a Mediterranean shallow soil. This study also aims at studying the effect of soil cover vegetation on the ECa measurement by the two types of sensors. The study was based on two surveys carried out under two very different situations: in February of 2012, with low soil moisture content (SMC) and with high and differentiated vegetation development (non grazed pasture), and in February of 2013, with high SMC and with short and relatively homogeneous vegetation development (grazed pasture). The greater temporal stability of Veris sensor, despite the wide variation in the SMC and vegetation ground cover indicates the suitability of using this sensor for monitoring soil properties in permanent pastures. The survey carried out with the DUALEM sensor in 2012 might have been affected by the presence of a 0.20 m vegetation layer at the soil surface, masking the soil properties. These differences should be considered in the selection of ECa sensing systems for a particular application. PMID:24915182

  7. Investigating bioremediation of petroleum hydrocarbons through landfarming using apparent electrical conductivity measurements

    NASA Astrophysics Data System (ADS)

    Van De Vijver, Ellen; Van Meirvenne, Marc; Seuntjens, Piet

    2015-04-01

    Bioremediation of soil contaminated with petroleum hydrocarbons through landfarming has been widely applied commercially at large scale. Biodegradation is one of the dominant pollutant removal mechanisms involved in landfarming, but strongly depends on the environmental conditions (e.g. presence of oxygen, moisture content). Conventionally the biodegradation process is monitored by the installation of field monitoring equipment and repeated sample collection and analysis. Because the presence of petroleum hydrocarbons and their degradation products can affect the electrical properties of the soil, proximal soil sensors such as electromagnetic induction (EMI) sensors may provide an alternative to investigate the biodegradation process of these contaminants. We investigated the relation between the EMI-based apparent electrical conductivity (ECa) of a landfarm soil and the presence and degradation status of petroleum hydrocarbons. The 3 ha study area was located in an oil refinery complex contaminated with petroleum hydrocarbons, mainly composed of diesel. At the site, a landfarm was constructed in 1999. The most recent survey of the petroleum hydrocarbon concentrations was conducted between 2011 and 2013. The sampling locations were defined by a grid with a 10 m by 10 m cell size and on each location a sample was taken from four successive soil layers with a thickness of 0.5 m each. Because the survey was carried out in phases using different georeferencing methods, the final dataset suffered from uncertainty in the coordinates of the sampling locations. In September 2013 the landfarm was surveyed for ECa with a multi-receiver electromagnetic induction sensor (DUALEM-21S) using motorized conveyance. The horizontal measurement resolution was 1 m by 0.25 m. On each measurement location the sensor recorded four ECa values representative of measurement depths of 0.5 m, 1.0 m, 1.6 m and 3.2 m. After the basic processing, the ECa measurements were filtered to remove anomalies resulting from small metallic objects. Next, the ECa measurements were interpolated to average values for blocks of 2.5 m by 2.5 m using ordinary block kriging to meet the location uncertainty of the corresponding hydrocarbon concentration observations. Comparison of the block ECa values representative of different depths with the petroleum hydrocarbons concentrations observed in the different landfarm layers suggested a relationship between ECa and the level of biodegradation. Zones with a large ECa corresponded to zones where high microbial degradation activity was expected and vice versa. This indicates that EMI-based ECa surveying can support the monitoring of the bioremediation process in landfarms and subsequent decisions on operating parameters. Furthermore, studying the relationship between ECa and the petroleum hydrocarbon concentrations can improve the understanding of microbial degradation processes.

  8. Characterizing the spatial variability of soil infiltration using apparent electrical conductivity

    NASA Astrophysics Data System (ADS)

    Castro Franco, Mauricio; Domenech, Marisa; Aparicio, Virginia; Costa, José Luis

    2013-04-01

    Implementation of irrigation systems and models of water flow and solute transport, requires continuous and accurate hydrological information. Apparent electrical conductivity (ECa) has been used to characterize the spatial behavior of soil properties. The objective was to characterize the spatial variability of soil infiltration at farm scale using ECa measurements. ECa measurements of a 42 ha farm were collected for the top 0-30cm (ECa(s)) and 0-90cm (ECa(d)) soil using the Veris® 3100. ECa maps were generated for both depths, using geostatistical interpolation techniques. From these maps, three general areas were delineated, named High, Medium, and Low ECa zones. At each zone, three sub samples were collected. Infiltration, altimetry (Alt) and effective depth (ED) were measured. Soil samples were taken at two depths 0-30 (Sh) and 30-60 (Dp). Bulk density (?b), clay content and organic matter (OM) were analyzed. Infiltration rate (i) was estimated using a disc infiltrometer. Soil series were Petrocalcic Paleudoll and Typic Argiudoll. Spatial variability of soil properties were analyzed by descriptive statistics. High ECa zones showed greater Alt and lesser ED. Likewise, Sh and Dp soil samples had greater ?b and clay content, and lesser OM content. Medium and Low ECa zones were situated at similar areas of Alt and ED. Likewise, ?b and OM content showed similar values at the two studied depths. In the Medium ECa zone, clay content was higher in Sh sampler. In general, the lowest i was in the High ECa zone, while in Medium and Low ECa zones, i values were similar. ECa was associated with clay content and OM, therefore with ?b and i. It is concluded that spatial variability of soil infiltration could be characterized through ECa.

  9. SPATIAL VARIABILITY OF THE APPARENT ELECTRICAL CONDUCTIVITY AND CONE INDEX AS MEASURED WITH SENSING TECHNOLOGIES: ASSESSMENT AND COMPARISON

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Assessment and interpretation of the spatial variability of soil chemical and physical properties is very important for precision farming. The spatial variability of apparent electrical conductivity (ECa) and Cone Index (CI) for soil compaction was investigated with Veris 3100 and Profiler 3000 sens...

  10. APPARENT SOIL ELECTRICAL CONDUCTIVITY: PAST, PRESENT, AND FUTURE TRENDS IN APPLICATION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Adaptation of geophysical techniques from the measurement of geologic strata to the measurement of surface and near-surface soils for agricultural applications was the next logical step. No geophysical technique has had a greater impact on agriculture than the measurement of apparent soil electrica...

  11. Using Soil Apparent Electrical Conductivity to Optimize Sampling of Soil Penetration Resistance and to Improve the Estimations of Spatial Patterns of Soil Compaction

    PubMed Central

    Siqueira, Glécio Machado; Dafonte, Jorge Dafonte; Bueno Lema, Javier; Valcárcel Armesto, Montserrat; Silva, Ênio Farias França e

    2014-01-01

    This study presents a combined application of an EM38DD for assessing soil apparent electrical conductivity (ECa) and a dual-sensor vertical penetrometer Veris-3000 for measuring soil electrical conductivity (ECveris) and soil resistance to penetration (PR). The measurements were made at a 6?ha field cropped with forage maize under no-tillage after sowing and located in Northwestern Spain. The objective was to use data from ECa for improving the estimation of soil PR. First, data of ECa were used to determine the optimized sampling scheme of the soil PR in 40 points. Then, correlation analysis showed a significant negative relationship between soil PR and ECa, ranging from ?0.36 to ?0.70 for the studied soil layers. The spatial dependence of soil PR was best described by spherical models in most soil layers. However, below 0.50?m the spatial pattern of soil PR showed pure nugget effect, which could be due to the limited number of PR data used in these layers as the values of this parameter often were above the range measured by our equipment (5.5?MPa). The use of ECa as secondary variable slightly improved the estimation of PR by universal cokriging, when compared with kriging. PMID:25610899

  12. The Apparent Thermal Conductivity of Pozzolana Concrete

    NASA Astrophysics Data System (ADS)

    Bessenouci, M. Z.; Triki, N. E. Bibi; Khelladi, S.; Draoui, B.; Abene, A.

    The recent development of some lightweight construction materials, such as light concrete, can play an important role as an insulator, while maintaining sufficient levels of mechanical performance. The quality of insulation to provide depends on the climate, the exposure of the walls and also the materials used in the construction. The choice of a material to be used as an insulator, obviously, depends on its availability and its cost. This is a study of natural pozzolanas as basic components in building materials. It is intended to highlight their thermal advantage. It is economically advantageous to use pozzolana in substitution for a portion of the clinker as hydraulically active additions, as well as in compositions of lightweight concretes in the form of pozzolanic aggregate mixtures, which provide mechanical strengths that comply with current standards. A theoretical study is conducted on the apparent thermal conductivity of building materials, namely concrete containing pozzolana. Thermal modeling, apparent to that commonly used for porous materials, has been applied to pozzolana concrete. Experimental results on measurements of the apparent thermal conductivity of pozzolana concrete are reported in this study, using an approach that considers that concrete is composed of two solid ingredients, a binding matrix (hydrated cement paste) and all aggregates. A second comparative theoretical approach is used for the case where concrete consists of a solid phase and a fluid phase (air).

  13. Electrically conductive composite material

    DOEpatents

    Clough, Roger L. (Albuquerque, NM); Sylwester, Alan P. (Albuquerque, NM)

    1989-01-01

    An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistant pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like.

  14. Electrically conductive composite material

    DOEpatents

    Clough, R.L.; Sylwester, A.P.

    1989-05-23

    An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

  15. Electrically conductive composite material

    DOEpatents

    Clough, R.L.; Sylwester, A.P.

    1988-06-20

    An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

  16. Electrical Conduction Activity

    NSDL National Science Digital Library

    This resource provides an introductory activity on electrical conduction. As the module states, "electrical conduction, the movement of electrical charges, is a mechanism for passing energy and signals from one place to another." The activity covers concepts such as insulators, conductors, semiconductors, superconductors, and ballistic conduction at nanoscale. This module allows students to test their knowledge as they go. Although a preview of the activity is available, instructors and students are encouraged to sign up with the Electron Technologies site before starting to use these materials.

  17. Relationship between apparent soil electrical conductivity (ECa) and soil attributes at an experimental parcel under pasture in a region of Galicia, Spain

    NASA Astrophysics Data System (ADS)

    Marinho, M. D.; Paz-Gonzalez, A.; Dafonte, J. D.; Armesto, M. V.; Raposo, J. R.

    2012-12-01

    Spatial characterization of the variability of soil properties is a central point in site-specific agricultural management and precision agriculture. Geospatial measures of geophysical attributes are useful not only to rapidly characterize the spatial variability of soil properties but also for soil sampling optimization. This work reports partial results obtained at an experimental parcel under pasture located at Castro de Ribeira do Lea (Lugo/ Galicia/ Spain). An ECa automated survey was conducted in September 2011 employing an EM-38 DD (Geonics Ltd.) installed in a nonmetallic car, according to parallel lines spaced 10m one from each other and oriented at the east-west direction. The ECa values were recorded every second with a field computer and the locations were geo-referenced using a GPS. The entire survey was carried out in 1hour and 45 minutes and corrections due to differences in temperature were made. A total of 9.581 ECa registers were retained, configuring a sampling intensity of approximately 1 register per 1.5 m2. Employing the software ESAP 2.35 and the computational tool ESAP-RSSD, eighty positions were selected at the field to extract disturbed and undisturbed soil samples at two depths: 0.0-0.2m, 0.2-0.4m. Ten physical attributes (clay, silt, total sand, coarse sand and fine sand contents, soil bulk density, particle density, total porosity, soil water content, percentage of gravels) and 17 chemical attributes (soil organic matter-SOM, pH, P, K, Ca, Mg, Al, H+Al, Sum of bases-S, Cation exchange capacity-CEC, Base saturation-V%, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) were determined. The relationship between the geophysical variables and the soil attributes was performed using statistical and spatial analysis. There were significant correlations (p<0.01) between the geophysical variables and the textural attributes clay, silt, total sand and coarse sand contents. The biggest correlation (0.5623) was between ECa-V (vertical component) and clay content. Also, significant correlations (p<0.05) were found between the ECa-V and soil bulk density, total porosity, percentage of gravels and soil water content. Considering the chemical attributes, significant correlations (p< 0.01) were found between ECa-V and SOM and Cd, and between ECa-H (horizontal component) and SOM and Fe. Other significant correlations (p<0.05) were found between ECa-V and 6 soil chemical attributes: P, Ca, S, Fe, Ni and Pb. The biggest correlation was between ECa-V and SOM (-0.5942). In resume, clay content, SOM, Cd and Fe are the soil attributes better correlated with the observed variation of the ECa at the field. Additional analysis should be performed to compare the spatial patterns of these soil attributes and the ECa as a tool to proper define management zones in the area.

  18. Relationship between apparent soil electrical conductivity (ECa) and soil attributes at an experimental parcel under pasture in a region of Galicia, Spain.

    NASA Astrophysics Data System (ADS)

    Marinho, Mara de A.; Dafonte, Jorge D.; Armesto, Montserrat V.; Paz-González, Antonio; Raposo, Juan R.

    2013-04-01

    Spatial characterization of the variability of soil properties is a central point in site-specific agricultural management and precision agriculture. Geospatial measures of geophysical attributes are useful not only to rapidly characterize the spatial variability of soil properties but also for soil sampling optimization. This work reports partial results obtained at an experimental parcel under pasture located at Castro de Ribeira do Lea (Lugo/ Galicia/ Spain). An ECa automated survey was conducted in September 2011 employing an EM-38 DD (Geonics Ltd.) installed in a nonmetallic car, according to parallel lines spaced 10m one from each other and oriented at the east-west direction. The ECa values were recorded every second with a field computer and the locations were geo-referenced using a GPS. The entire survey was carried out in 1hour and 45 minutes and corrections due to differences in temperature were made. A total of 9.581 ECa registers were retained, configuring a sampling intensity of approximately 1 register per 1.5 m2. Employing the software ESAP 2.35 and the computational tool ESAP-RSSD, eighty positions were selected at the field to extract disturbed and undisturbed soil samples at two depths: 0.0-0.2m, 0.2-0.4m. Ten physical attributes (clay, silt, total sand, coarse sand and fine sand contents, soil bulk density, particle density, total porosity, soil water content, percentage of gravels) and 17 chemical attributes (soil organic matter-SOM, pH, P, K, Ca, Mg, Al, H+Al, Sum of bases-S, Cation exchange capacity-CEC, Base saturation-V%, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) were determined. The relationship between the geophysical variables and the soil attributes was performed using statistical and spatial analysis. There were significant correlations (p<0.01) between the geophysical variables and the textural attributes clay, silt, total sand and coarse sand contents. The biggest correlation (0.5623) was between ECa-V (vertical component) and clay content. Also, significant correlations (p<0.05) were found between the ECa-V and soil bulk density, total porosity, percentage of gravels and soil water content. Considering the chemical attributes, significant correlations (p< 0.01) were found between ECa-V and SOM and Cd, and between ECa-H (horizontal component) and SOM and Fe. Other significant correlations (p<0.05) were found between ECa-V and 6 soil chemical attributes: P, Ca, S, Fe, Ni and Pb. The biggest correlation was between ECa-V and SOM (-0.5942). In resume, clay content, SOM, Cd and Fe are the soil attributes better correlated with the observed variation of the ECa at the field. Additional analysis should be performed to compare the spatial patterns of these soil attributes and the ECa as a tool to proper define management zones in the area. Acknowledgements: This work was funded in part by Spanish Ministry of Science and Innovation (MICINN) in the frame of project CGL2009-13700-C02. Financial support from CAPES/GOV., Brazil, is also acknowledged by Prof. M. de A. Marinho.

  19. Electrical Conductivity in Insulator

    NASA Astrophysics Data System (ADS)

    Sinha, Anil Kumar

    2003-03-01

    ABSTRACT In insulating solid(Plastic Sheet)of 0.73mm thickness, the conduction process was ohmic at low D.C. electric feilds, but the feild strength increased the conductivity became feild dependent at high feilds and it exhibited some conductivity and the variation in conduction current was none-ohmic.The mechanism of electron transfer between two metallic electrodes separated by insulating material has received considerable attention. The electron transfer current was studied on 0.73mm plastic sheet and(I-V),(log I-log V),(log J-E^1/2)and (log o- 1/T) relations have been studied and the value of slope,electronic dielectric constant and activation energy for nature of conduction mechanism and process have been determined.The electrical conductivity measurements were carried out at room temperature (32.5 celcius)under high D.C. electric feilds of the order of 10^6 volt/meter.The sample of insulator(plastic sheet) was sandwiched between the aluminium electrodes of designed experimental cell,The effect of very high varying feilds at 32.5 celcius temperature,the electrical conduction has been proposed on the data obtained.The non-ohmic behavior in the sample seemed to start at an electric feild 3x10^6 volt/meter.In this case on data obtained it was concluded that "SCHOTTKY EMISSION MECHANISM" has been proposed. The activation energy was calculated by plotting(log o-1/T)characterstics at running temperature and it was found 0.325ev which is less than 1.0,It confirms predominance of Electronic Conduction. I=current in ampere V=volt T=temperature O=conductivity

  20. Electrical Conductivity in Textiles

    NASA Technical Reports Server (NTRS)

    2006-01-01

    Copper is the most widely used electrical conductor. Like most metals, though, it has several drawbacks: it is heavy, expensive, and can break. Fibers that conduct electricity could be the solutions to these problems, and they are of great interest to NASA. Conductive fibers provide lightweight alternatives to heavy copper wiring in a variety of settings, including aerospace, where weight is always a chief concern. This is an area where NASA is always seeking improved materials. The fibers are also more cost-effective than metals. Expenditure is another area where NASA is always looking to make improvements. In the case of electronics that are confined to small spaces and subject to severe stress, copper is prone to breaking and losing connection over time. Flexible conductive fibers eliminate that problem. They are more supple and stronger than brittle copper and, thus, find good use in these and similar situations. While clearly a much-needed material, electrically conductive fibers are not readily available. The cost of new technology development, with all the pitfalls of troubleshooting production and the years of testing, and without the guarantee of an immediate market, is often too much of a financial hazard for companies to risk. NASA, however, saw the need for electrical fibers in its many projects and sought out a high-tech textile company that was already experimenting in this field, Syscom Technology, Inc., of Columbus, Ohio. Syscom was founded in 1993 to provide computer software engineering services and basic materials research in the areas of high-performance polymer fibers and films. In 1999, Syscom decided to focus its business and technical efforts on development of high-strength, high-performance, and electrically conductive polymer fibers. The company developed AmberStrand, an electrically conductive, low-weight, strong-yet-flexible hybrid metal-polymer YARN.

  1. Electrical conduction in olivine

    SciTech Connect

    Schock, R. N.; Duba, A. G.; Shankland, T. J.

    1989-05-10

    This paper reports detailed measurements of electrical conductivitysigma and thermoelectric effect /ital S/ in the mineral olivine and in syntheticforsterite as functions of temperature in the range from 1000/degree/ to1500 /degree/C and oxygen partial pressure in the range from 10/sup /minus/10/ to10/sup 4/ Pa. The two most striking observations are strong conductivityanisotropy in forsterite and a sign change in /ital S/ in olivine at 1390 /degree/C.These results are interpreted to show that both materials have mixed ionic andextrinsic electronic conduction under these conditions. On the basis ofthese interpretations, we infer that forsterite conductivity is dominatedby electronic conduction in the /ital a/ and /ital b/ directions and probably bymovement involving magnesium vacancies in the /ital c/ direction, wherefar higher /ital P//sub O/sub 2//-independent conductivity is observed. Olivineappears to show mixed conduction under all the circumstances observed; at low temperature, electron holes dominate but are superseded bymagnesium vacancies at high temperatures./copyright/ American Geophysical Union 1989

  2. Electrically conductive alternating copolymers

    DOEpatents

    Aldissi, M.; Jorgensen, B.S.

    1987-08-31

    Polymers which are soluble in common organic solvents and are electrically conductive, but which also may be synthesized in such a manner that they become nonconductive. Negative ions from the electrolyte used in the electrochemical synthesis of a polymer are incorporated into the polymer during the synthesis and serve as a dopant. A further electrochemical step may be utilized to cause the polymer to be conductive. The monomer repeat unit is comprised of two rings, a pyrrole molecule joined to a thienyl group, or a furyl group, or a phenyl group. The individual groups of the polymers are arranged in an alternating manner. For example, the backbone arrangement of poly(furylpyrrole) is -furan-pyrrole-furan-pyrrole- furan-pyrrole. An alkyl group or phenyl group may be substituted for either or both of the hydrogen atoms of the pyrrole ring.

  3. Influence of surface conductivity on the apparent zeta potential of amorphous silica nanoparticles.

    PubMed

    Leroy, Philippe; Devau, Nicolas; Revil, André; Bizi, Mohamed

    2013-11-15

    Zeta potential is a physicochemical parameter of particular importance in describing ion adsorption and double layer interactions between charged particles. However, for metal-oxide nanoparticles, the conversion of electrophoretic mobility measurements into zeta potentials is difficult. This is due to their very high surface electrical conductivity, which is inversely proportional to the size of the particle. When surface conductivity is similar to or higher than the electrical conductivity of bulk water, it can significantly lower the electrophoretic mobility of the particles. It follows that the magnitude of the apparent zeta potential determined from the Smoluchowski equation (disregarding surface conductivity) can be grossly underestimated. We use a basic Stern model to describe the electrochemical properties and to calculate the true zeta potential of amorphous silica nanoparticles immersed in NaCl solution. The parameters of our surface complexation model are adjusted by potentiometric titration and electrophoretic mobility measurements at high salinity (10(-1)M NaCl). Electrophoretic mobilities are calculated using Henry's electrokinetic transport model with specific surface conductivities and zeta potentials estimated by our surface complexation model. The very good agreement of calculated and measured electrophoretic mobilities confirms that the true zeta potential corresponds to the electrical potential at the outer Helmholtz plane (OHP). Consequently, the shear plane might be located close to the OHP. The assumption of the presence of a stagnant diffuse layer at the amorphous silica/water interface is therefore not required. PMID:24011560

  4. Electrically Conductive Anodized Aluminum Surfaces

    NASA Technical Reports Server (NTRS)

    Nguyen, Trung Hung

    2006-01-01

    Anodized aluminum components can be treated to make them sufficiently electrically conductive to suppress discharges of static electricity. The treatment was conceived as a means of preventing static electric discharges on exterior satin-anodized aluminum (SAA) surfaces of spacecraft without adversely affecting the thermal-control/optical properties of the SAA and without need to apply electrically conductive paints, which eventually peel off in the harsh environment of outer space. The treatment can also be used to impart electrical conductivity to anodized housings of computers, medical electronic instruments, telephoneexchange equipment, and other terrestrial electronic equipment vulnerable to electrostatic discharge. The electrical resistivity of a typical anodized aluminum surface layer lies between 10(exp 11) and 10(exp 13) Omega-cm. To suppress electrostatic discharge, it is necessary to reduce the electrical resistivity significantly - preferably to < or = 10(exp 9) Omega-cm. The present treatment does this. The treatment is a direct electrodeposition process in which the outer anodized surface becomes covered and the pores in the surface filled with a transparent, electrically conductive metal oxide nanocomposite. Filling the pores with the nanocomposite reduces the transverse electrical resistivity and, in the original intended outer-space application, the exterior covering portion of the nanocomposite would afford the requisite electrical contact with the outer-space plasma. The electrical resistivity of the nanocomposite can be tailored to a value between 10(exp 7) and 10(exp 12) Omega-cm. Unlike electrically conductive paint, the nanocomposite becomes an integral part of the anodized aluminum substrate, without need for adhesive bonding material and without risk of subsequent peeling. The electrodeposition process is compatible with commercial anodizing production lines. At present, the electronics industry uses expensive, exotic, electrostaticdischarge- suppressing finishes: examples include silver impregnated anodized, black electroless nickel, black chrome, and black copper. In comparison with these competing finishes, the present nanocomposite finishes are expected to cost 50 to 20 percent less and to last longer.

  5. Electrically conductive polymer concrete coatings

    SciTech Connect

    Fontana, Jack J. (Shirley, NY); Elling, David (Centereach, NY); Reams, Walter (Shirley, NY)

    1990-01-01

    A sprayable electrically conductive polymer concrete coating for vertical d overhead applications is described. The coating is permeable yet has low electrical resistivity (<10 ohm-cm), good bond strength to concrete substrates, and good weatherability. A preferred formulation contains about 60 wt % calcined coke breeze, 40 wt % vinyl ester with 3.5 wt % modified bentonite clay. Such formulations apply evenly and provide enough rigidity for vertical or overhead structures so there is no drip or sag.

  6. Electrically conductive polymer concrete coatings

    DOEpatents

    Fontana, J.J.; Elling, D.; Reams, W.

    1988-05-26

    A sprayable electrically conductive polymer concrete coating for vertical and overhead applications is described. The coating is permeable yet has low electrical resistivity (<10 ohm-cm), good bond strength to concrete substrates, and good weatherability. A preferred formulation contains about 60 wt% calcined coke breeze, 40 wt% vinyl ester resin with 3.5 wt% modified bentonite clay. Such formulations apply evenly and provide enough rigidity for vertical or overhead structures so there is no drip or sag. 4 tabs.

  7. Electrical conductivity of heteroepitaxial diamond

    NASA Astrophysics Data System (ADS)

    Behravan, Mahdokht

    The purpose of this research is to understand the electrical conduction mechanisms of heteroepitaxial diamond by performing direct current (DC) electrical measurements. Of particular interest is the temperature dependence of the DC conductivity. The project takes advantage of recent advances at Michigan State University in the growth of diamond by chemical vapor deposition on lattice-matched substrates, i.e., by heteroepitaxy. This investigation represents the first detailed study of an electrical transport property of heteroepitaxial diamond. The characterization of the electrical properties of a wide bandgap, high resistivity material such as diamond requires low current, high temperature measurements. A number of new techniques were developed to perform reliable electronic measurements at elevated temperatures. The magnitude of the DC conductivity of heteroepitaxial diamond was found to be remarkably similar to that of high-purity, Type IIa natural diamond. Heteroepitaxial diamond exhibits thermally activated conductivity, with a single activation energy of 1.40+/-0.03 eV from 250 °C to 550 °C. This result is similar to previous measurements by other workers on Type Ila natural diamond, suggesting the presence of electronic states at comparable concentrations in materials of completely different origin.

  8. Electrically conductive rigid polyurethane foam

    DOEpatents

    Neet, T.E.; Spieker, D.A.

    1983-12-08

    A rigid, moldable polyurethane foam comprises about 2 to 10 weight percent, based on the total foam weight, of a carbon black which is CONDUCTEX CC-40-220 or CONDUCTEX SC, whereby the rigid polyurethane foam is electrically conductive and has essentially the same mechanical properties as the same foam without carbon black added.

  9. Electrical conductivity of ice VII

    PubMed Central

    Okada, Taku; Iitaka, Toshiaki; Yagi, Takehiko; Aoki, Katsutoshi

    2014-01-01

    It was discovered that a peak appears near a pressure of Pc = 10?GPa in the electrical conductivity of ice VII as measured through impedance spectroscopy in a diamond anvil cell (DAC) during the process of compression from 2?GPa to 40?GPa at room temperature. The activation energy for the conductivity measured in the cooling/heating process between 278?K and 303?K reached a minimum near Pc. Theoretical modelling and molecular dynamics simulations suggest that the origin of this unique peak is the transition of the major charge carriers from the rotational defects to the ionic defects. PMID:25047728

  10. Electrically conductive thermal control coatings

    NASA Technical Reports Server (NTRS)

    Shai, M. C. (inventor)

    1978-01-01

    A coating characterized by low thermal absorption, high thermal emittance and high electrical conductivity comprises: (1) a fired oxide pigment comprising a minor amount of aluminum oxide and a major amount of zinc oxide; (2) sufficient water to provide a mixture suitable for application to a substrate, is presented. The fired oxide pigment may further include a minor amount of cobalt oxide. The resulting coating is particularly useful for coating the surfaces of spacecraft and similar objects.

  11. Electrical conductivity in silicon nanomembranes

    NASA Astrophysics Data System (ADS)

    Zhang, Pengpeng; Nordberg, E. P.; Park, B.-N.; Celler, G. K.; Knezevic, I.; Evans, P. G.; Eriksson, M. A.; Lagally, M. G.

    2006-09-01

    Silicon nanomembranes (SiNMs) are very thin, large, free-standing or free-floating two-dimensional (2D) single crystals that can variously be flat, rolled into tubes, or made into any number of odd shapes, cut into millions of identical wires, used as conformal sheets, or chopped into tiny pieces. Because SiNMs are mostly surface or interface and little bulk, they have very interesting properties. We describe electrical conductivity in SiNMs. Because of trap states at the Si/SiO2 interface, bulk dopants become irrelevant to electronic transport when the membrane is thin enough. Replacing the oxide at one interface with the clean-Si surface reconstruction dramatically increases the nanomembrane conductivity. We provide a model for this behaviour. The dimer reconstruction surface states provide a means of 'surface doping'. Other materials with proper highest-occupied molecular orbital (HOMO) or lowest-unoccupied molecular orbital (LUMO) bands, when deposited on the Si surface, should produce the same conductivity effect, affording a broad opportunity for membrane-based sensors.

  12. SOIL ELECTRICAL CONDUCTIVITY AS A MANAGEMENT TOOL IN PRECISION FORESTRY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Apparent soil electrical conductivity (ECa) is a useful measurement and indicator of relative productivity of agronomic crops on some soil types. In non-saline soils, spatial variation in soil ECa is strongly related to texture, topsoil depth and profile variations; factors which spatially correlate...

  13. Lorentz and "apparent" transformations of the electric and magnetic fields

    E-print Network

    Tomislav Ivezic

    2006-07-21

    It is recently discovered that the usual transformations of the three-dimensional (3D) vectors of the electric and magnetic fields differ from the Lorentz transformations (LT) (boosts) of the corresponding 4D quantities that represent the electric and magnetic fields. In this paper, using geometric algebra formalism, this fundamental difference is examined representing the electric and magnetic fields by bivectors.

  14. Electric Conductivity of the QGP

    NASA Astrophysics Data System (ADS)

    Puglisi, Armando; Plumari, Salvatore; Greco, Vincenzo

    2015-05-01

    The transport coefficients of strongly interacting matter have attracted a great interest in the field of Quark-Gluon Plasma (QGP). In this work we compute electric conductivity ?el solving numerically the Relativistic Boltzmann Transport (RBT) equation in a uniform box with periodic boundary conditions considering 2—body scatterings. We compare numerical results obtained using two methods, Green-Kubo correlator and E-field method, with analytic formulas in Relaxation Time Approximation (RTA). We present results for the realistic case of the QGP system considering both a quasi-particle model tuned to lattice QCD thermodynamics as well as the case of a pQCD gas with a running coupling constant. Calculations based on RTA underestimate ?el of about 60%.

  15. Electrically-Conductive Polyaramid Cable And Fabric

    NASA Technical Reports Server (NTRS)

    Orban, Ralph F.

    1988-01-01

    Tows coated with metal provide strength and conductance. Cable suitable for use underwater made of electrically conductive tows of metal-coated polyaramid filaments surrounded by electrically insulating jacket. Conductive tows used to make conductive fabrics. Tension borne by metal-coated filaments, so upon release, entire cable springs back to nearly original length without damage.

  16. Gas Phase Pressure Effects on the Apparent Thermal Conductivity of JSC-1A Lunar Regolith Simulant

    NASA Technical Reports Server (NTRS)

    Yuan, Zeng-Guang; Kleinhenz, Julie E.

    2011-01-01

    Gas phase pressure effects on the apparent thermal conductivity of a JSC-1A/air mixture have been experimentally investigated under steady state thermal conditions from 10 kPa to 100 kPa. The result showed that apparent thermal conductivity of the JSC-1A/air mixture decreased when pressure was lowered to 80 kPa. At 10 kPa, the conductivity decreased to 0.145 W/m/degree C, which is significantly lower than 0.196 W/m/degree C at 100 kPa. This finding is consistent with the results of previous researchers. The reduction of the apparent thermal conductivity at low pressures is ascribed to the Knudsen effect. Since the characteristic length of the void space in bulk JSC-1A varies over a wide range, both the Knudsen regime and continuum regime can coexist in the pore space. The volume ratio of the two regimes varies with pressure. Thus, as gas pressure decreases, the gas volume controlled by Knudsen regime increases. Under Knudsen regime the resistance to the heat flow is higher than that in the continuum regime, resulting in the observed pressure dependency of the apparent thermal conductivity.

  17. Characterization of electrically conducting oxides

    SciTech Connect

    Anderson, H.U.; Sparlin, D.M.

    1989-01-01

    This report discusses some of the highlights and publications of this years work. Listed below are the areas of interest and progress within the program: The studies of the Ba{sub 2}YCu{sub 3}O{sub 7-x} system have shown that the conduction processes (metallic or small polaron) have little temperature dependence and are almost entirely a function of oxygen stoichiometry. The substitution of 10 to 20 m% Ca and Co into LaCrO{sub 3} has enabled the system to be sintered to >95% TD at 1400{degree}C without deterioration of either the electrical conductivity or high temperature stability of the resulting dense ceramics. An elucidation of the structure of the high temperature (1400{degree}C) phases of La substitute SrTiO{sub 3} has demonstrated our abilities to determine small changes in structure as well as to determine cation defect concentrations using x-ray powder diffraction methods. In this study we were able to show that the oxidized state of Sr{sub 1-x}La{sub x}TiO{sub 3} contained cation vacancies. The studies in the Y{sub 1-x}Ca{sub x}CrO{sub 3} system also are yielding some important results. They are showing that this oxide system is more stable toward reduction than LaCrO{sub 3}. The construction of dual high temperature controlled atmosphere dilatometer has been completed. An effective-medium theory of hopping transport in binary systems is explaining the conductivity changes that occur when Mn is substituted into LaCrO{sub 3}.

  18. Dependance of electric conduction on film thickness of conductive adhesives

    Microsoft Academic Search

    Yong Wei; Erol Sancaktar

    1995-01-01

    The effect of film thickness on the conduction behavior of electrically conductive adhesives is presented. For comparison purposes, an analytical relation is developed to predict three dimensional resistivity of particle filled conductive adhesives. This analysis reveals that the adhesive's resistivity depends on parameters, m, representing an average contact number and, Si, representing the average length of conductive paths between the

  19. Measurement of Apparent Thermal Conductivity of JSC-1A Under Ambient Pressure

    NASA Technical Reports Server (NTRS)

    Yuan, Zeng-Guang; Kleinhenz, Julie E.

    2011-01-01

    The apparent thermal conductivity of JSC-1A lunar regolith simulant was measured experimentally using a cylindrical apparatus. Eleven thermocouples were embedded in the simulant bed to obtain the steady state temperature distribution at various radial, axial, and azimuthal locations. The high aspect ratio of a cylindrical geometry was proven to provide a one-dimensional, axisymmetric temperature field. A test series was performed at atmospheric pressure with varying heat fluxes. The radial temperature distribution in each test fit a logarithmic function, indicating a constant thermal conductivity throughout the soil bed. However, thermal conductivity was not constant between tests at different heat fluxes. This variation is attributed to stresses created by thermal expansion of the simulant particles against the rigid chamber wall. Under stress-free conditions (20 deg C), the data suggest a temperature independent apparent conductivity of 0.1961 +/- 0.0070 W/m/ deg C

  20. Electrically conductive glass fibre reinforced epoxy resin

    Microsoft Academic Search

    M. Kupke; Hans-Peter Wentzel; Karl Schulte

    1998-01-01

    The research on an industrially manufactured, electrically conductive glass fibre reinforced epoxy prepreg for aviation applications\\u000a is reported. In a co-operative effort between Technical University Hamburg-Harburg (TUHH) and Daimler-Benz Aerospace Airbus\\u000a (DASA) a new glass-epoxy composite with both electrical and good mechanical properties was successfully developed. The electrical\\u000a conductivity was achieved adding carbon black as a conductive filler into the

  1. Influence of Humidity on the Apparent Thermal Conductivity of Concrete Pozzolan

    NASA Astrophysics Data System (ADS)

    Bessenouci, M. Z.; Bibi-Triki, N. E.; Bendimerad, S.; Nakoul, Z.; Khelladi, S.; Hakem, A.

    This work is a study of natural pozzolans as basic components in building materials. It is intended to highlight the thermal advantage of these materials. It is economically advantageous to the pozzolan used in lightweight concrete compositions as a mixture of aggregate pozzolan which provides mechanical strength that complies with current standards. The impact of humidity on the apparent thermal conductivity of concrete pozzolan considered as a porous material requires the best description of the phenomena which surrounds the heat transfer of different phases (liquid- solid-and air). The use of mixed model extended to three phases as a prediction of the thermal conductivity, highlights the importance of the liquid phase

  2. Combining Optical Transparency with Electrical Conductivity

    E-print Network

    Medvedeva, Julia E.

    1 Combining Optical Transparency with Electrical Conductivity: Challenges and Prospects Julia E in practice electrical conductivity [1­6]. This combination is achieved in several commonly used oxides ­ In2O properties. Exclusively oxides of the post-transition metals with Figure 1.1 (a) Schematic electronic band

  3. Electrical conduction models for isotropically conductive adhesive joints

    Microsoft Academic Search

    Li Li; James E. Morris

    1997-01-01

    An electrical conduction model for silver filled isotropically conductive adhesives (ICA) was developed. The model combines the microscopic resistance of the bulk silver particles and the contact between silver flakes with the macroscale resistor network calculation by percolation theory. The resistivities of the composites were calculated by resistor network simulations considering both contact effects and particle size effects. Three different

  4. Electrical conductivity of asphalt mortar containing conductive fibers and fillers

    Microsoft Academic Search

    Álvaro García; Erik Schlangen; Martin van de Ven; Quantao Liu

    2009-01-01

    The objective of this research is to examine the conductivity of asphalt mortar through the addition of electrically conductive fillers and fibers: graphite and steel wool, and prove that this material can be heated with induction energy. The effect of fibers content, sand–bitumen ratio and the combination of fillers and fibers on the resistivity of asphalt mortar was investigated. It

  5. Microwave heating of electrically conductive materials

    NASA Astrophysics Data System (ADS)

    Rybakov, K. I.; Semenov, V. E.

    2005-10-01

    In recent years, considerable interest has been drawn to microwave heating of powder metals and other electrically conductive materials. In this paper, we consider absorption of electromagnetic waves in materials with different effective conductivities for different microwave heating conditions. Specific features of microwave heating at the maxima of electric and magnetic fields in a standing-wave applicator are discussed. Absorption in materials containing conductive particles with dielectric shells are studied in detail using the effective-medium approximation.

  6. Electrically conductive polyimides containing silver trifluoroacetylacetonate

    NASA Technical Reports Server (NTRS)

    Rancourt, James D. (Inventor); Stoakley, Diane M. (Inventor); Caplan, Maggie L. (Inventor); St. Clair, Anne K. (Inventor); Taylor, Larry T. (Inventor)

    1996-01-01

    Polyimides with enhanced electrical conductivity are produced by adding a silver ion-containing additive to the polyamic acid resin formed by the condensation of an aromatic dianhydride with an aromatic diamine. After thermal treatment the resulting polyimides had surface conductivities in the range of 1.7.times.10.sup.-3 4.5 .OMEGA..sup.-1 making them useful in low the electronics industry as flexible, electrically conductive polymeric films and coatings.

  7. The Apparent Thermal Conductivity of Liquids Containing Solid Particles of Nanometer Dimensions: A Critique

    NASA Astrophysics Data System (ADS)

    Tertsinidou, Georgia; Assael, Marc J.; Wakeham, William A.

    2015-03-01

    There have been conflicting statements in the literature of the last twenty years about the behavior of the apparent thermal conductivity of two- or three-phase systems comprising solid particles with nanometer dimensions suspended in fluids. It has been a feature of much of the work that these multiphase systems have been treated as if a single-phase fluid and that the thermodynamic characteristics of the system have varied even though the systems have been given the same name. These so-called nanofluids have been the subject of a large number of investigations by a variety of different experimental techniques. In the current paper, we critically evaluate the studies of seven of the simplest particulate/fluid systems: Cu, CuO, {Al}2{O}3 , and {TiO}2 suspended in water and ethylene glycol. Our conclusion is that when results for exactly the same thermodynamic system are obtained with proven experimental techniques, the apparent thermal conductivity of the nanofluid exhibits no behavior that is unexpected and inconsistent with a simple model of conduction in stationary, multiphase systems. The wider variety of behavior that has been reported in the literature for these systems is therefore attributed to ill-characterization of the thermodynamic system and/or the application of experimental techniques of unproven validity.

  8. Electrical and thermal conductivities in dense plasmas

    SciTech Connect

    Faussurier, G., E-mail: gerald.faussurier@cea.fr; Blancard, C.; Combis, P.; Videau, L. [CEA, DAM, DIF, F-91297 Arpajon (France)

    2014-09-15

    Expressions for the electrical and thermal conductivities in dense plasmas are derived combining the Chester-Thellung-Kubo-Greenwood approach and the Kramers approximation. The infrared divergence is removed assuming a Drude-like behaviour. An analytical expression is obtained for the Lorenz number that interpolates between the cold solid-state and the hot plasma phases. An expression for the electrical resistivity is proposed using the Ziman-Evans formula, from which the thermal conductivity can be deduced using the analytical expression for the Lorenz number. The present method can be used to estimate electrical and thermal conductivities of mixtures. Comparisons with experiment and quantum molecular dynamics simulations are done.

  9. A simple numerical model of the apparent loss of eddy current conductivity due to surface roughness

    E-print Network

    Nagy, Peter B.

    of subsurface residual stresses in shot-peened specimens. This technique is based on the so- called electro change in electrical conductivity caused by shot peening is often distorted, or even completely experimental data from shot-peened copper specimens. q 2004 Elsevier Ltd. All rights reserved. Keywords: Eddy

  10. Laboratory Electrical Conductivity Measurement of Mantle Minerals

    Microsoft Academic Search

    Takashi Yoshino

    2010-01-01

    Electrical conductivity structures of the Earth’s mantle estimated from the magnetotelluric and geomagnetic deep sounding\\u000a methods generally show increase of conductivity from 10?4–10?2 to 100 S\\/m with increasing depth to the top of the lower mantle. Although conductivity does not vary significantly in the lower\\u000a mantle, the possible existence of a highly conductive layer has been proposed at the base of

  11. ELECTRICAL CONDUCTIVITY OF THE DEEP MANTLE

    E-print Network

    Cerveny, Vlastislav

    -3 ­105 s, based on observation of horizontal electric and magnetic fields, scales up to hundreds's magnetic field observed at permanent geomagnetic observatories, at temporary locations, measured from ships) Electrical conductivity of the deep mantle C2C Mari´ansk´e l´azne 2010 4 / 39 #12;Earth's magnetic field main

  12. Computer simulation of electrical conductivity of colloidal dispersions during aggregation

    NASA Astrophysics Data System (ADS)

    Lebovka, N. I.; Tarafdar, S.; Vygornitskii, N. V.

    2006-03-01

    The computation approach to the simulation of electrical conductivity of colloidal dispersions during aggregation is considered. We use the two-dimensional diffusion-limited aggregation model with multiple-seed growth. The particles execute a random walk, but lose their mobility after contact with the growing clusters or seeds. The two parameters that control the aggregation are the initial concentration of free particles in the system p and the concentration of seeds ? . The case of ?=1 , when all the particles are the immobile seeds, corresponds with the usual random percolation problem. The other limiting case of ?=0 , when all the particles walk randomly, corresponds to the dynamical percolation problem. The calculation of electrical conductivity and cluster analysis were done with the help of the algorithms of Frank-Lobb and Hoshen-Kopelman. It is shown that the percolation concentration ?c decreases from 0.5927 at ?=1 to 0 at ??0 . Scaling analysis was applied to study exponents of correlation length ? and of conductivity t . For all ?>0 this model shows universal behavior of classical 2d random percolation with ??t?4/3 . The electrical conductivity ? of the system increases during aggregation reaching up to a maximum at the final stage. The concentration dependence of conductivity ?(?) obeys the general effective medium equation with apparent exponent ta(?) that exceeds t . The kinetics of electrical conductivity changes during the aggregation is discussed. In the range of concentration pc(?)

  13. Electrical conductivity of the continental crust

    SciTech Connect

    Glover, P.W.J.; Vine, F.J. [Univ. College London, London (United Kingdom)] [Univ. College London, London (United Kingdom); [Univ. of East Anglia, Norwich (United Kingdom)

    1994-11-01

    Geophysical measurements indicate that the Earth`s continental lower crust has a high electrical conductivity for which no simple cause has been found. Explanation usually relies on either saline fluids saturating the pores, or interconnected highly conducting minerals such as graphite, Fe/Ti oxides and sulfides, providing conducting pathways. Attempts in the laboratory to clarify the problem have, hitherto, been unable to recreate conditions likely to be present at depth by controlling the confining pressure and pore fluid pressure applied to a rock saturated with saline fluids at temperatures between 270 C and 1000 C. Here we report conductivity data obtained using a cell designed to make such measurements on rocks saturated with saline fluids. Our results show that the conductivity of saturated samples of acidic rocks is explicable entirely in terms of conduction through the pore fluid whereas the conductivity of saturated basic rocks requires the presence of an additional conduction mechanism(s). We have used the experimental data to construct electrical conductivity/depth profiles for the continental crust, which, when compared with profiles obtained from magnetotelluric observations, demonstrate that a mid to lower crust composed of amphibolite saturated with 0.5 M NaCl shows electrical conductivities sufficient to explain conductivity/depth profiles for the continental crust inferred from geophysical measurements.

  14. The Theory of Electrical Conductivity Recent Developments

    Microsoft Academic Search

    William V. Houston

    1930-01-01

    This paper explains the electrical conductivity of metals in light of recent discoveries regarding the behavior of electrons. It is claimed that these discoveries have made possible a satisfactory theory of conduction. The more important discovery is that of the wave nature of the electrons. The other new discovery is known as Pauli's ``exclusion principle'' which states that no two

  15. Mechanisms of electrical conductivity in olivine

    SciTech Connect

    Schock, R.N.; Duba, A.G.; Shankland, T.J.

    1984-01-01

    Data on the electrical conductivity and the thermoelectric effect in single crystals indicate that the charge conduction mechanism in pure magnesium forsterite is electrons. The concentration of electrons can be varied by controlling the number of oxygen vacancies through manipulation of the oxygen pressure. For iron bearing olivine, the conduction mechanism is by electron holes localized on an iron ion. Since iron strongly affects the creep process as well, oxidation of iron is probably accompanied by the production of magnesium vacancies. 15 references.

  16. The electrical conductivity of zircaloy oxide films

    NASA Astrophysics Data System (ADS)

    Howlader, M. M. R.; Shiiyama, K.; Kinoshita, C.; Kutsuwada, M.; Inagaki, M.

    1998-03-01

    The electrical conductivity of Zircaloy-2, improved Zircaloy-2 and Zircaloy-4 oxide films has been measured using gold, copper and zirconium electrodes over the temperature range of 296-723 K. No notable discrepancies among the temperature dependence of electrical conductivity in the oxide films obtained from all electrodes were found. Depending on the activation behavior it is thought that the conductivity corresponds to the thermal excitation of electrons. The current-voltage characteristics of all oxide films show non-Ohmic behavior where the bulk current (electronic in nature) is associated with the Schottky and/or the Poole-Frenkel processes. On the basis of these results, it is concluded that the electron motion dominates the electrical conductivity of zircaloy oxide films. Therefore the slow-diffusing negative oxygen ions control the oxidation process of zircaloys.

  17. Ionic surface electrical conductivity in sandstone

    NASA Astrophysics Data System (ADS)

    Glover, Paul W. J.; Meredith, Philip G.; Sammonds, Peter R.; Murrell, Stanley A. F.

    1994-11-01

    Recent analyses of complex conductivity measurements have indicated that high-frequency dispersions encountered in rocks saturated with low-salinity fluids are due to ionic surface conduction and that the form of these dispersions may be dependent upon the nature of the pore and crack surfaces within the rock (Ruffet et al., 1991). Unfortunately, the mechanisms of surface conduction are not well understood, and no model based on rigorous physical principles exists. This paper is split into two parts: an experimental section followed by the development of a theoretical description of adsorption of ions onto mineral surfaces. We have made complex conductivity measurements upon samples of sandstone saturated with a range of different types and concentrations of aqueous solution with a frequency range of 20 Hz to 1 MHz. The frequency dependence of complex conductivity was analyzed using the empirical model of Cole and Cole (1941). The 'fractal' surface models of Le Mehaute and Crepy (1983), Po Zen Wong (1987), the Ruffet el at. (1991) were used to calculate apparent fractal pore surface dimensions for samples saturated with different solution types and concentrations. These showed a pronounced decrease of apparent fractal surface dimension with decreasing electrolyte concentration and a decrease of apparent fractal dimension with increasing relative ionic radius of the dominant cation in solution. A model for ionic surface concentration (ISCOM I) has been developed as the first step in producing a rigorous physicochemical model of surface conduction in quartz-dominated rocks. The results from ISCOM I show that quartz surfaces are overwhelmingly dominated by adsorbed Na(+) when saturated with NaCl solutions of salinities and pH found in actual geological situations. ISCOM I also shows that the concentration threshold for dominance of surface conduction over bulk conduction is aided by depletion of ions from the bulk fluid as a result of their adsorption onto the mineral surfaces as well as by changes in the ionic mobility in the surface conduction double-layer as the wetting solution becomes more dilute.

  18. Electrically conductive containment vessel for molten aluminum

    DOEpatents

    Holcombe, C.E.; Scott, D.G.

    1984-06-25

    The present invention is directed to a containment vessel which is particularly useful in melting aluminum. The vessel of the present invention is a multilayered vessel characterized by being electrically conductive, essentially nonwettable by and nonreactive with molten aluminum. The vessel is formed by coating a tantalum substrate of a suitable configuration with a mixture of yttria and particulate metal 10 borides. The yttria in the coating inhibits the wetting of the coating while the boride particulate material provides the electrical conductivity through the vessel. The vessel of the present invention is particularly suitable for use in melting aluminum by ion bombardment.

  19. Electrically conductive containment vessel for molten aluminum

    DOEpatents

    Holcombe, Cressie E. (Knoxville, TN); Scott, Donald G. (Oak Ridge, TN)

    1985-01-01

    The present invention is directed to a containment vessel which is particularly useful in melting aluminum. The vessel of the present invention is a multilayered vessel characterized by being electrically conductive, essentially nonwettable by and nonreactive with molten aluminum. The vessel is formed by coating a tantalum substrate of a suitable configuration with a mixture of yttria and particulate metal borides. The yttria in the coating inhibits the wetting of the coating while the boride particulate material provides the electrical conductivity through the vessel. The vessel of the present invention is particularly suitable for use in melting aluminum by ion bombardment.

  20. The electrical conductivity of the moon

    NASA Astrophysics Data System (ADS)

    Vanyan, L. L.

    1980-09-01

    Some new aspects of lunar electrical conductivity are examined with reference to available data for the earth. A mathematical analysis is employed to determine zones at the lunar surface where high-order harmonics of magnetic fields have the lowest contributing effect. Attention is given to results from magnetovariation lunar sounding and from Apollo 12 and Explorer 35 magnetometers. Implications discussed have bearing on knowledge of regional anomalies in lunar conductivity.

  1. Towards electrically conductive, self-healing materials

    Microsoft Academic Search

    Kyle A. Williams; Andrew J. Boydston; Christopher W. Bielawski

    2007-01-01

    A novel class of organometallic polymers comprising N-heterocyclic carbenes and transition metals was shown to have potential as an electrically conductive, self-healing material. These polymers were found to exhibit conductivities of the order of 10K3 Sc mK1 and showed structurally dynamic characteristics in the solid-state. Thin films of these materials were cast onto silicon wafers, then scored and imaged using

  2. Seismic-Velocity \\/ Electrical-Conductivity Relations

    Microsoft Academic Search

    B. Ursin

    2007-01-01

    Summary Cross-property relations are useful when some rock properties can be more easily measured than other properties. Relations between electrical conductivity and seismic velocity, stiffness moduli and density can be obtained by expressing the porosity in terms of those properties. There are many possibilities to combine the constitutive equations to obtain a relation, each one representing a given type of

  3. Recent advances on Electrically Conductive Adhesives

    Microsoft Academic Search

    Rongwei Zhang; Josh C. Agar; C. P. Wong

    2010-01-01

    As one of the promising lead-free interconnection materials, electrically conductive adhesive (ECA) has made considerable advances in recent years. Compared to metal solder, ECAs offer numerous advantages, such as environmental friendliness (elimination of lead usage and flux cleaning), mild processing conditions, fewer processing steps (reducing processing cost), low stress on the substrates and fine pitch capability. However, ECAs have some

  4. Global Electrical Conductivity Magnetic Satellite Induction Studies

    E-print Network

    Constable, Steve

    km. Skin depth can be a very useful indicator of energy penetration, but be careful! 2nd induction to measure Earth conductivity: · Magnetotelluric (MT) method Measure electric and magnetic fields · Geomagnetic depth sounding (GDS) method Measure horizontal and vertical magnetic fields 2nd

  5. The effect of conductive grain boundary impurities on electrical conductivity in polycrystalline olivine

    NASA Astrophysics Data System (ADS)

    Watson, H. C.; Roberts, J. J.; Tyburczy, J. A.

    2009-12-01

    Grain boundaries affect the rheological, mechanical, diffusive, and electrical properties of polycrystalline materials. In crustal and mantle rocks, they may provide a “fast conduction path” explaining areas of anomalously high electrical conductivity without necessitating intra-granular hydrogen or an interconnected melt or fluid phase. Conductive impurities on grain boundaries such as graphite or sulfide have been suggested to explain some field-based high-conductivity anomalies, but direct experimental studies have been few. Studies on grain boundary conductivity in polycrystalline monomineralic, dry olivine exist, but a systematic understanding of impure grain boundary conductivity remains unrealized. Bulk electrical conductivity and impedance spectroscopy of single crystal and polycrystalline San Carlos olivine and polycrystalline olivine with carbon or iron sulfide on grain boundaries were measured at 1GPa and 350o C-1200o C in a piston cylinder apparatus. Sometimes, impedance spectroscopy is the only tool that yields definitive evidence of a secondary (grain boundary) conduction mechanism. We demonstrate that grain boundary conductivity in series with grain interiors is more apparent in the presence of small amounts of carbon grain boundary impurities, whereas the presence of quenched iron sulfide melt on grain boundaries can enhance bulk conductivity even if full melt interconnectivity is not established. Specifically, the addition of 0.1 wt% (~0.16 vol%) C has no significant effect on bulk conductivity. In contrast, the addition of ~1.0 vol% Fe67S33 melt results in conductivity much higher than that of pure olivine, but lower than what is expected for a fully interconnected sulfide phase. We infer that the sulfide is partially connected on the grain boundaries and edges and has reached the electrical percolation threshold, but not the fluid percolation threshold. The effect of the addition of sulfide to the grain boundaries on electrical conductivity is similar to the effect of adding 0.01%-0.1% H to pure olivine. It may not always be necessary to have hydrogen or connected melt or fluid to account for anomalously high conductivity in some parts of the mantle or crust. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  6. Electrical conduction control of carbon nanowalls

    SciTech Connect

    Takeuchi, Wakana; Ura, Masato; Hori, Masaru [Department of Electrical Engineering and Computer Science, Nagoya University, Chikusa, Nagoya 468-8603 (Japan); Hiramatsu, Mineo [Department of Electrical and Electronic Engineering, Meijo University, Tempaku, Nagoya 468-8502 (Japan); Tokuda, Yutaka [Department of Electrical and Electronics Engineering, Aichi Institute of Technology, Yakusa, Toyota 470-0392 (Japan); Kano, Hiroyuki [NU Eco-Engineering Co., Ltd., Kurozasa, Miyoshi, Nishikamo 470-0201 (Japan)

    2008-05-26

    The electrical conduction behavior of carbon nanowalls (CNWs) has been evaluated by Hall measurement. CNWs, which comprise stacks of graphene sheets standing on the substrate, are fabricated by fluorocarbon/hydrogen plasma enhanced chemical vapor deposition. We have investigated the effect of N{sub 2} addition to C{sub 2}F{sub 6}/H{sub 2} system on the electrical properties of CNWs. The CNWs grown with the C{sub 2}F{sub 6}/H{sub 2} plasma exhibit p-type conduction. As a result of the nitrogen inclusion in the CNWs, the conduction type of the CNWs changes to n type. The carrier concentration is controllable by changing the flow rate of the additional N{sub 2} during the CNW growth process.

  7. Electrical conduction of a XLPE nanocomposite

    NASA Astrophysics Data System (ADS)

    Park, Yong-Jun; Sim, Jae-Yong; Lim, Kee-Joe; Nam, Jin-Ho; Park, Wan-Gi

    2014-07-01

    The resistivity, breakdown strength, and formation of space charges are very important factors for insulation design of HVDC cable. It is known that a nano-sized metal-oxide inorganic filler reduces the formation of space charges in the polymer nanocomposite. Electrical conduction of cross-linked polyethylene(XLPE) nanocomposite insulating material is investigated in this paper. The conduction currents of two kinds of XLPE nanocomposites and XLPE without nano-filler were measured at temperature of 303 ~ 363 K under the applied electric fields of 10 ~ 50 kV/mm. The current of the nanocomposite specimen is smaller than that of XLPE specimen without nano-filler. The conduction mechanism may be explained in terms of Schottky emission and multi-core model.

  8. Computer simulation of electrical conductivity of colloidal dispersions during aggregation.

    PubMed

    Lebovka, N I; Tarafdar, S; Vygornitskii, N V

    2006-03-01

    The computation approach to the simulation of electrical conductivity of colloidal dispersions during aggregation is considered. We use the two-dimensional diffusion-limited aggregation model with multiple-seed growth. The particles execute a random walk, but lose their mobility after contact with the growing clusters or seeds. The two parameters that control the aggregation are the initial concentration of free particles in the system p and the concentration of seeds psi. The case of psi=1, when all the particles are the immobile seeds, corresponds with the usual random percolation problem. The other limiting case of psi=0, when all the particles walk randomly, corresponds to the dynamical percolation problem. The calculation of electrical conductivity and cluster analysis were done with the help of the algorithms of Frank-Lobb and Hoshen-Kopelman. It is shown that the percolation concentration phi c decreases from 0.5927 at psi=1 to 0 at psi --> 0. Scaling analysis was applied to study exponents of correlation length v and of conductivity t. For all psi>0 this model shows universal behavior of classical 2d random percolation with v approximately t approximately 4/3. The electrical conductivity sigma of the system increases during aggregation reaching up to a maximum at the final stage. The concentration dependence of conductivity sigma(phi) obeys the general effective medium equation with apparent exponent ta(psi) that exceeds t. The kinetics of electrical conductivity changes during the aggregation is discussed. In the range of concentration Pc(phi)

  9. Electric conductance of highly selective nanochannels

    NASA Astrophysics Data System (ADS)

    Schnitzer, Ory; Yariv, Ehud

    2013-05-01

    We consider electric conductance through a narrow nanochannel in the thick-double-layer limit, where the space-charge Debye layers adjacent to the channel walls overlap. At moderate surface-charge densities the electrolyte solution filling the channel comprises mainly of counterions. This allows to derive an analytic closed-form approximation for the channel conductance, independent of the salt concentration in the channel reservoirs. The derived expression consists of two terms. The first, representing electromigratory transport, is independent of the channel depth. The second, representing convective transport, depends upon it weakly.

  10. Electrically conductive palladium containing polyimide films

    NASA Technical Reports Server (NTRS)

    Taylor, L. T.; St.clair, A. K.; Carver, V. C.; Furtsch, T. A. (inventors)

    1982-01-01

    Lightweight, high temperature resistant, electrically conductive, palladium containing polyimide films and methods for their preparation are described. A palladium (II) ion-containing polyamic acid solution is prepared by reacting an aromatic dianhydride with an equimolar quantity of a palladium II ion-containing salt or complex and the reactant product is cast as a thin film onto a surface and cured at approximately 300 C to produce a flexible electrically conductive cyclic palladium containing polyimide. The source of palladium ions is selected from the group of palladium II compounds consisting of LiPdCl4, PdS(CH3)2Cl2Na2PdCl4, and PdCl2. The films have application to aerodynamic and space structures and in particular to the relieving of space charging effects.

  11. Electrical conductivity of aqueous polymer solutions

    Microsoft Academic Search

    V. Raicu; A. BÎran; A. Iovescu; D. F. Anghel; S. Saito

    1997-01-01

    Theoretical equations were proposed to adequately simulate the electrical conductivity behavior of aqueous solutions of both\\u000a charged and uncharged polymers. The theory, based on the mixture equation of Boned and Peyrelasse, was experimentally verified\\u000a on poly(acrylic acid) (PAA) in water and poly(ethylene oxide) (PEO) in aqueous electrolyte solutions. The data analysis suggested\\u000a that both the polymer coils may be depicted

  12. A Homogeneous Electrically Conductive Silver Paste

    Microsoft Academic Search

    Jianguo Liu; Yu Cao; Xiaoye Wang; Jun Duan; Xiaoyan Zeng

    2010-01-01

    A homogeneous electrically conductive silver paste was developed using silver i-propylcarbamate ((CH3)2CHNHCOOAg) as the precursor of functional phase. The precursor had good solubility in water and methanol, high silver content (about 50 wt.%) and low decomposition temperature (below 200 °C). The paste was a non-Newtonian fluid with the viscosity depending significantly on the content of thickening agent (ethyl cellulose). When

  13. Electrically conducting polyimide film containing tin complexes

    NASA Technical Reports Server (NTRS)

    St. Clair, Anne K. (Inventor); Ezzell, Stephen A. (Inventor); Taylor, Larry T. (Inventor); Boston, Harold G. (Inventor)

    1996-01-01

    Disclosed is a thermally-stable SnO.sub.2 -surfaced polyimide film wherein the electrical conductivity of the SnO.sub.2 surface is within the range of about 3.0.times.10.sup.-3 to about 1.times.10.sup.-2 ohms.sup.-1,. Also disclosed is a method of preparing this film from a solution containing a polyamic acid and SnCl.sub.4 (DMSO).sub.2.

  14. Dissociation of fullerenol-70-d in aqueous solutions and their electric conductivity

    NASA Astrophysics Data System (ADS)

    Tyurin, D. P.; Semenov, K. N.; Charykov, N. A.; Cherepkova, I. A.; Keskinov, V. A.

    2015-05-01

    The concentration dependences of specific and molar electric conductivities and the hydrogen ion exponents of aqueous solutions of fullerenol-70-d obtained via the direct heterogenic catalytic oxidation of C70 with an alkali are studied. The concentration dependences of the apparent degree of dissociation and concentration dissociation constant of fullerenol-70-d in aqueous solutions are calculated using data on the electric conductivity and hydrogen ion exponent.

  15. Electrical Noise in Individual Conducting Polymer Nanowires

    NASA Astrophysics Data System (ADS)

    Kovalev, Alexey; Cao, Yanyan; Mayer, Theresa; Mallouk, Thomas

    2009-03-01

    Electrical property characterizations of conducting polymer nanostructures have been limited primarily to resistance measurements. Electrical noise is one aspect that is usually overlooked, yet critical to their device performance. Moreover, electrical noise is more sensitive to the polymer doping and microstructure than resistance, which makes it particularly interesting for sensor applications. In this talk, we will present the results on the electrical noise measurements of individual multisegmented electrodeposited nanowires based on Poly(3,4-ethylenedioxythiophene (PEDOT) [1]. The polymer was electrochemically doped with either poly(4-styrenesulfonic acid) (PSS) or perchlorate (ClO4). The nanowires had gold contacts on both ends and were measured in four-point and two-point configurations. We found that the electrical noise behavior is typical of 1/f noise, with a spectral density that depends on the polymer structure and is affected by the ambient conditions. Our data show that the contact noise represents a significant contribution to the total noise level. We will discuss the interpretation of these results assuming that the polymer is a disordered conductor. [1] Cao et al., Nano Letters Article ASAP

  16. Inductive Measurement of Plasma Jet Electrical Conductivity

    NASA Technical Reports Server (NTRS)

    Turner, Matthew W.; Hawk, Clark W.; Litchford, Ron J.

    2005-01-01

    An inductive probing scheme, originally developed for shock tube studies, has been adapted to measure explosive plasma jet conductivities. In this method, the perturbation of an applied magnetic field by a plasma jet induces a voltage in a search coil, which, in turn, can be used to infer electrical conductivity through the inversion of a Fredholm integral equation of the first kind. A 1-inch diameter probe was designed and constructed, and calibration was accomplished by firing an aluminum slug through the probe using a light-gas gun. Exploratory laboratory experiments were carried out using plasma jets expelled from 15-gram high explosive shaped charges. Measured conductivities were in the range of 3 kS/m for unseeded octol charges and 20 kS/m for seeded octol charges containing 2% potassium carbonate by mass.

  17. Electrically-conducting thermal-control coating

    NASA Technical Reports Server (NTRS)

    Shai, M. C.

    1978-01-01

    Coating comprised mainly of zinc and aluminum oxides is characterized by high thermal emittance, low thermal absorption, and high electrical conductivity. Originally developed to protect spacecraft, coating can be used to prevent charge buildup on components in other applications. Mixture is stable under ultraviolet and X-ray radiation and under bombardment by ionizing particles. It can be applied to aluminum, stainless steel, epoxy/fiberglass, and other substrates. When exposed to equivalent of 1,000 Sun-hours illumination, coating remained stable and retained its optical properties.

  18. Numerical method for calculating the apparent eddy current conductivity loss on randomly rough surfaces

    E-print Network

    Nagy, Peter B.

    characterize the subsurface residual stress and cold work distributions in shot-peened metal components. Unfortunately, the spurious surface roughness produced by the shot peening process causes an apparent loss shot-peened surfaces, which exhibit essentially exponential correlation function. It is also

  19. Tailoring the Thermoelectric Behavior of Electrically Conductive Polymer Composites

    E-print Network

    Moriarty, Gregory P.

    2013-05-21

    fabrication temperatures. These concerns have led research efforts into electrically conductive polymer composites prepared in ambient conditions from aqueous solutions. By combining polymer latex with carbon nanotubes (CNT), electrical conductivity can...

  20. Electrical Conductivity and Water in the Mantle Steven Constable

    E-print Network

    Constable, Steve

    Electrical Conductivity and Water in the Mantle Steven Constable Scripps Institution, Ashley Medin, Bob Parker, Jeff Roberts #12;Why mantle electrical conductivity? · Highly senstitive to phase transitions · Sensitive to mantle temperature · Influenced by volatiles and trace materials Water

  1. How Well Does Zone Sampling Based On Soil Electrical Conductivity Maps Represent Soil Variability

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Zone soil sampling is a method in which a field sampling is based on identifying homogenous areas using an easy to measure ancillary attribute such as apparent soil electrical conductivity (ECa). This study determined if ECa-directed zone sampling in two fields in northeastern Colorado could correc...

  2. CHARACTERIZING FIELD-SCALE SOIL VARIABILITY ACROSS THE MIDWEST WITH SOIL ELECTRICAL CONDUCTIVITY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Apparent profile soil electrical conductivity (ECa) can be an indirect indicator of a number of soil physical and chemical properties. Commercially available ECa sensors can be used to efficiently and inexpensively develop the spatially dense datasets desirable for describing within-field spatial so...

  3. PREDOMINANT PROPERTIES AFFECTING PROFILE SOIL ELECTRICAL CONDUCTIVITY IN THE US MIDWEST

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Commercially available sensors for measuring apparent profile soil electrical conductivity (ECa) can provide an indirect indication of a number of soil physical and chemical properties helpful in characterizing within-field variability for precision agriculture. The objective of this research was to...

  4. Estimating spatial variations in water content of clay soils from time-lapse electrical conductivity surveys

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water content (theta) is one of the most important drivers for many biogeochemical fluxes at different temporal and spatial scales. Hydrogeophysical non-invasive sensors that measure the soil apparent electrical conductivity (ECa) have been widely used to infer spatial and temporal patterns of...

  5. Investigation of Mechanical and Electrical Characteristics for Cracked Conductive Particle in Anisotropic Conductive Adhesive (ACA) Assembly

    Microsoft Academic Search

    Bin Xie; X. Q. Shi; Han Ding

    2008-01-01

    In an anisotropic conductive adhesive (ACA) assembly, the electrical conduction is usually achieved with the conductive particles between the bumps of integrated circuit (IC) and corresponding conductive tracks on the glass substrate. Fully understanding of the mechanical and electrical characteristics of ACA particles can help to optimize the assembly process and improve the reliability of ACA interconnection. Most conductive particles

  6. Electrical conductivity and thermopower of metallic helium

    NASA Astrophysics Data System (ADS)

    Shvets, V. T.; Kozitskii, S. V.

    2013-04-01

    The pair effective interionic interaction, electrical resistance, and thermopower of liquid metallic helium have been calculated over wide temperature and density ranges using the perturbation theory for the potential of electron-ion interaction. For conduction electrons, the random-phase approximation has been used taking into account the exchange interaction and correlations in the local-field approximation. The nuclear subsystem has been described by the hard-sphere model. The sphere diameter is the only parameter of the theory. The diameter and the system density at which helium is transformed from the singly ionized to doubly ionized state have been estimated based on an analysis of the pair effective interaction between helium nuclei. The case of doubly ionized helium atoms has been considered. The numerical calculations have been performed taking into account the perturbation theory in terms up to the third order. In all cases, the role of the third-order correction is significant. In the case of metallic helium, the values of the electrical resistance and its temperature dependence are characteristic of divalent simple liquid metals, as well as the dependences of the thermopower on the density and temperature.

  7. Electrical conductivity of thermally hydrogenated nanodiamond powders

    NASA Astrophysics Data System (ADS)

    Kondo, Takeshi; Neitzel, Ioannis; Mochalin, Vadym N.; Urai, Junichi; Yuasa, Makoto; Gogotsi, Yury

    2013-06-01

    Electrical properties of detonation diamond nanoparticles (NDs) with individual diameters of ˜5 nm are important for many applications. Although diamond is an insulator, it is known that hydrogen-terminated bulk diamond becomes conductive when exposed to water. We show that heating ND in hydrogen gas at 600-900 °C resulted in a remarkable decrease in resistivity from 107 to 105 ? cm, while the resistivity was essentially unchanged after treatment at 400 °C and lower temperatures. Fourier Transform Infrared Spectroscopy and X-ray photoelectron spectroscopy (XPS) studies revealed that hydrogenation of ND occurs at 600-900 °C, suggesting that the decrease in resistivity is based on transfer doping at the hydrogenated ND surface. Oxidation of the hydrogenated sample at 300 °C recovers resistivity to its original value. The resistivity of treated ND as a function of the O/C atomic ratio showed a transition from resistive (O/C ratio > 0.033) to conductive (O/C ratio < 0.033) state. This is consistent with the idea that the change in the resistivity is caused by the shift of the valence band maximum to above the Fermi level due to the dipole of the C-H bonds leading to transfer doping.

  8. Apparent negative activation energy in electrochemical insulating-to-conducting conversion at polymethylthiophene films

    Microsoft Academic Search

    Koichi Aoki; Jianquan Li

    1998-01-01

    An electrochemical conversion rate of poly(3-methylthiophene) films from the insulating state to the conducting state in dopant-rich solution decreased with an increase in temperature. The conversion rate defined here is the moving speed of the conducting front growing from the electrode toward the solution phase in response to the potential step. It was evaluated by time-variation of absorption at the

  9. Measurement of apparent thermal conductivity of multilayer insulations at low compressive loads.

    NASA Technical Reports Server (NTRS)

    Holmes, V. L.; Mccrary, L. E.; Krause, D. R.

    1972-01-01

    A description is presented of the test calorimeter, the experimental technique, and the results obtained in an evaluation of four multilayer insulations selected for application on future multilaunch space vehicles utilizing liquid hydrogen and oxygen for orbital operations. Particular attention is paid to techniques for minimizing error in obtaining thermal conductivity data. The effective conductivity for four high-performance insulations was determined at a minimum of four compressive loads in the range from 0.0001 to 0.1 psi. Results show that the thermal conductivity of multilayer insulations is insensitive to small changes in mechanical loading at 1 torr interstitial gas pressure, but becomes increasingly more sensitive to mechanical loading as the interstitial gas pressure is reduced.

  10. The influence of surface conductivity on the apparent zeta potential of TiO2 nanoparticles

    E-print Network

    Paris-Sud XI, Université de

    , the intrinsic zeta potential can have a larger amplitude, even in the case of simple 1:1 electrolytes like NaCl and KCl. Surface conductance of TiO2 nanoparticles immersed in a NaCl solution is estimated using a surface complexation model, and this parameter and particle size are incorporated into Henry's model

  11. Magnetic flowmeter for electrically conductive liquid

    DOEpatents

    Skladzien, Stanley B. (Elmhurst, IL); Raue, Donald J. (Naperville, IL)

    1982-01-01

    A magnetic flowmeter includes first and second tube sections each having ls of non-magnetic material. The first tube is suitably connected to a process for passing a flow of an electrically conductive fluid to be measured. The second tube is established as a reference containing a still medium and is maintained at the same temperature as the first tube. A rotatable magnet assembly is disposed between the two tubes with at least two magnets attached to radially extending arms from a central shaft. Each magnet includes an air gap suitably sized to pass astraddle the diameter along a portion of the length of each of the two tubes. The magnets are provided in matched pairs spaced 180.degree. apart such that signals will be simultaneously generated in signal leads attached to each of the two tubes. By comparing the signals from the two tubes and varying the rotating speed of the magnet assembly until the signals are equal, or attain a maximum, the flow velocity of the fluid within the first tube can be determined. Through temperature monitoring and appropriate heaters, the two tubes are maintained at the same temperature.

  12. Electrical Conduction Behavior of Cement-Matrix Composites

    E-print Network

    Chung, Deborah D.L.

    -matrix composites. 2. Resistive Behavior Cement paste is electrically conductive, with DC resistivity at 28 days the cement paste and the aggregate enhances the conductivity.[4] Whether aggregates (sand and stonesElectrical Conduction Behavior of Cement-Matrix Composites D.D.L. Chung (Submitted 26 March 2000

  13. Partial melting and electrical conductivity anomalies in the upper mantle

    Microsoft Academic Search

    T. J. Shankland; H. S. Waff

    1977-01-01

    For mantle regions of anomalously high electrical conductivity (greater than 0.1 S\\/m) the bulk conductivity is modeled by effective medium theory as a basalt melt fraction within a mainly olivine matrix. In order for the highly conducting melt to affect the bulk conductivity it must form interconnections, so that the very existence of mantle conductivity anomalies constitutes evidence for such

  14. Electrical conductivity of drying cement paste

    Microsoft Academic Search

    Farshad Rajabipour; Jason Weiss

    2007-01-01

    Previous research has shown that electrical measurements can be used to monitor moisture movement inside concrete. The interpretation\\u000a of these measurements is frequently based on empirical relationships between moisture changes and electrical properties of\\u000a concrete. As such, these empirical relationships can limit the application of the electrical measurements to a specific material\\u000a or exposure history. To facilitate the development of

  15. Dependence of electrical conduction on the film thickness of conductive adhesives: modeling, computer simulation, and experiment

    Microsoft Academic Search

    Yong Wei; Erol Sancaktar

    1996-01-01

    The effect of film thickness on the conduction behavior of electrically conductive adhesives is presented. For comparison purposes, an analytical relation is developed to predict the three-dimensional resistivity of particle-filled conductive adhesives. This analysis reveals that the adhesive's resistivity depends on parameters m, representing an average contact number, and Si, representing the average length of conductive paths between the conductive

  16. Electrical conductivity of thick film YSZ

    Microsoft Academic Search

    Oh Hyun Kwon; Gyeong Man Choi

    2006-01-01

    When yttria-stabilized zirconia (YSZ) electrolyte is coated and co-sintered on top of Ni–YSZ anode support, the measured conductivities of YSZ thick films (10–30 ?m thick) are often lower than that of bulk YSZ. In this study, we found the observation by fabricating free-standing YSZ thick films and measuring and comparing in-plain and across-plain conductivities. The in-plane conductivity of free-standing YSZ film

  17. Synthesis of novel electrically conducting polymers: Potential conducting Langmuir-Blodgett films and conducting polymers on defined surfaces

    NASA Technical Reports Server (NTRS)

    Zimmer, Hans

    1993-01-01

    Based on previous results involving thiophene derived electrically conducting polymers in which it was shown that thiophene, 3-substituted thiophenes, furans, and certain oligomers of these compounds showed electrical conductivity after polymerization. The conductivity was in the order of up to 500 S/cm. In addition, these polymers showed conductivity without being doped and most of all they were practically inert toward ambient conditions. They even could be used in aqueous media. With these findings as a guide, a number of 3-long-chain-substituted thiophenes and 1-substituted-3-long-chain substituted pyrrols were synthesized as monomers for potential polymeric electrically conducting Langmuir-Blodgett films.

  18. Electrically conducting ternary amorphous fully oxidized materials and their application

    NASA Technical Reports Server (NTRS)

    Giauque, Pierre (Inventor); Nicolet, Marc (Inventor); Gasser, Stefan M. (Inventor); Kolawa, Elzbieta A. (Inventor); Cherry, Hillary (Inventor)

    2004-01-01

    Electrically active devices are formed using a special conducting material of the form Tm--Ox mixed with SiO2 where the materials are immiscible. The immiscible materials are forced together by using high energy process to form an amorphous phase of the two materials. The amorphous combination of the two materials is electrically conducting but forms an effective barrier.

  19. Electrical conduction in HVDC mass-impregnated paper cable

    Microsoft Academic Search

    M. J. P. Jeroense; F. H. Kreuger

    2002-01-01

    HVDC cables play an important role in a growing number of HVDC links. For almost all of these cables, mass impregnated paper is used as electrical insulation. The electrical conductivity of this insulation is given by a commonly used empirical formula. This formula takes into account the temperature and stress dependency of the conductivity. This paper derives a physics-based equation

  20. Anisotropic electrical conductivity of MWCNT\\/PAN nanofiber paper

    Microsoft Academic Search

    Eun Ju Ra; Kay Hyeok An; Ki Kang Kim; Seung Yol Jeong; Young Hee Lee

    2005-01-01

    The electrospinning process has been used successfully to fabricate the multiwalled carbon nanotubes (MWCNTs)-embedded polyacrylonitrile (PAN) nanofiber paper. The diameters of nanofibers decreased with increasing CNT concentration. We found large anisotropic electrical conductivity, i.e., the electrical conductivity of the carbonized nanofiber paper along the spinning direction was about three times larger than that normal to the spinning direction, in good

  1. Electrical conductivity measurements of nanofluids and development of new correlations.

    PubMed

    Konakanchi, Hanumantharao; Vajjha, Ravikanth; Misra, Debasmita; Das, Debendra

    2011-08-01

    In this study the electrical conductivity of aluminum oxide (Al2O3), silicon dioxide (SiO2) and zinc oxide (ZnO) nanoparticles dispersed in propylene glycol and water mixture were measured in the temperature range of 0 degrees C to 90 degrees C. The volumetric concentration of nanoparticles in these fluids ranged from 0 to 10% for different nanofluids. The particle sizes considered were from 20 nm to 70 nm. The electrical conductivity measuring apparatus and the measurement procedure were validated by measuring the electrical conductivity of a calibration fluid, whose properties are known accurately. The measured electrical conductivity values agreed within +/- 1% with the published data reported by the manufacturer. Following the validation, the electrical conductivities of different nanofluids were measured. The measurements showed that electrical conductivity of nanofluids increased with an increase in temperature and also with an increase in particle volumetric concentration. For the same nanofluid at a fixed volumetric concentration, the electrical conductivity was found to be higher for smaller particle sizes. From the experimental data, empirical models were developed for three nanofluids to express the electrical conductivity as functions of temperature, volumetric concentration and the size of the nanoparticles. PMID:22103081

  2. Electrical Impedance Spectroscopy for Electro-Mechanical Characterization of Conductive Fabrics

    PubMed Central

    Bera, Tushar Kanti; Mohamadou, Youssoufa; Lee, Kyounghun; Wi, Hun; Oh, Tong In; Woo, Eung Je; Soleimani, Manuchehr; Seo, Jin Keun

    2014-01-01

    When we use a conductive fabric as a pressure sensor, it is necessary to quantitatively understand its electromechanical property related with the applied pressure. We investigated electromechanical properties of three different conductive fabrics using the electrical impedance spectroscopy (EIS). We found that their electrical impedance spectra depend not only on the electrical properties of the conductive yarns, but also on their weaving structures. When we apply a mechanical tension or compression, there occur structural deformations in the conductive fabrics altering their apparent electrical impedance spectra. For a stretchable conductive fabric, the impedance magnitude increased or decreased under tension or compression, respectively. For an almost non-stretchable conductive fabric, both tension and compression resulted in decreased impedance values since the applied tension failed to elongate the fabric. To measure both tension and compression separately, it is desirable to use a stretchable conductive fabric. For any conductive fabric chosen as a pressure-sensing material, its resistivity under no loading conditions must be carefully chosen since it determines a measurable range of the impedance values subject to different amounts of loadings. We suggest the EIS method to characterize the electromechanical property of a conductive fabric in designing a thin and flexible fabric pressure sensor. PMID:24892493

  3. Models proposed to explain the electrical conductivity of mixtures made of conductive and insulating materials

    Microsoft Academic Search

    F. Lux

    1993-01-01

    The electrical conductivity of mixtures of conductive and insulating materials is reviewed. In general, the conductivity of such mixtures increases drastically at a certain concentration of the conductive component, the so-called percolation concentration. Among the parameters influencing the percolation concentration, the filler distribution, filler shape, filler\\/matrix interactions and the processing technique are the most important ones. On the basis of

  4. Variable Anisotropic Brain Electrical Conductivities in Epileptogenic Foci

    PubMed Central

    Mandelkern, M.; Bui, D.; Salamon, N.; Vinters, H. V.; Mathern, G. W.

    2010-01-01

    Source localization models assume brain electrical conductivities are isotropic at about 0.33 S/m. These assumptions have not been confirmed ex vivo in humans. This study determined bidirectional electrical conductivities from pediatric epilepsy surgery patients. Electrical conductivities perpendicular and parallel to the pial surface of neocortex and subcortical white matter (n = 15) were measured using the 4-electrode technique and compared with clinical variables. Mean (±SD) electrical conductivities were 0.10 ± 0.01 S/m, and varied by 243% from patient to patient. Perpendicular and parallel conductivities differed by 45%, and the larger values were perpendicular to the pial surface in 47% and parallel in 40% of patients. A perpendicular principal axis was associated with normal, while isotropy and parallel principal axes were linked with epileptogenic lesions by MRI. Electrical conductivities were decreased in patients with cortical dysplasia compared with non-dysplasia etiologies. The electrical conductivity values of freshly excised human brain tissues were approximately 30% of assumed values, varied by over 200% from patient to patient, and had erratic anisotropic and isotropic shapes if the MRI showed a lesion. Understanding brain electrical conductivity and ways to non-invasively measure them are probably necessary to enhance the ability to localize EEG sources from epilepsy surgery patients. PMID:20440549

  5. Characteristics of thermoplastics containing electrically conducting asymmetric particles - anisotropic electrical conductivity of injection molded parts and extrusion behavior

    Microsoft Academic Search

    Jan Martinsson; James L. White

    1986-01-01

    The characteristics of compounds of acrylonitrile-butadiene-styrene and high impact polystyrene resins filled with carbon fibers, steel fibers, carbon black, and aluminum flakes have been investigated with special emphasis on electrical conductivity and flow behavior in a capillary rheometer. Compression- and injection-molded compounds were found to be highly electrically anisotropic. The components of the electrical conductivity tensor, were measured. Generally, kappa-11,

  6. High temperature electrically conducting ceramic heating element and control system

    Microsoft Academic Search

    C. R. Halbach; R. J. Page

    1975-01-01

    Improvements were made in both electrode technology and ceramic conductor quality to increase significantly the lifetime and thermal cycling capability of electrically conducting ceramic heater elements. These elements were operated in vacuum, inert and reducing environments as well as oxidizing atmospheres adding to the versatility of the conducting ceramic as an ohmic heater. Using stabilized zirconia conducting ceramic heater elements,

  7. EFFECTS OF TRITIUM GAS EXPOSURE ON ELECTRICALLY CONDUCTING POLYMERS

    Microsoft Academic Search

    M. Kane; E. Clark; R. Lascola

    2009-01-01

    Effects of beta (tritium) and gamma irradiation on the surface electrical conductivity of two types of conducting polymer films are documented to determine their potential use as a sensing and surveillance device for the tritium facility. It was shown that surface conductivity was significantly reduced by irradiation with both gamma and tritium gas. In order to compare the results from

  8. Structural and Electrical Study of Conducting Polymers

    NASA Astrophysics Data System (ADS)

    Shaktawat, Vinodini; Dixit, Manasvi; Saxena, N. S.; Sharma, Kananbala

    2010-06-01

    Pure and oxalic acid doped conducting polymers (polyaniline and polypyrrole) were chemically synthesized using ammonium persulfate (APS) as an oxidant. These samples were characterized through Scanning Electron Microscopy (SEM), which provides information about the surface topography of polymers. I-V characteristics have been recorded at room temperature as well as in the temperature range from 313 K to 463 K. So obtained characteristic curves were found to be linear. Temperature dependence of conductivity suggests a semiconducting nature in polyaniline samples with increase in temperature, whereas oxalic acid doped polypyrrole sample suggests a transition from semiconducting to metallic nature with the increase of temperature.

  9. Using electrical impedance tomography to map subsurface hydraulic conductivity

    DOEpatents

    Berryman, James G. (Danville, CA); Daily, William D. (Livermore, CA); Ramirez, Abelardo L. (Pleasanton, CA); Roberts, Jeffery J. (Livermore, CA)

    2000-01-01

    The use of Electrical Impedance Tomography (EIT) to map subsurface hydraulic conductivity. EIT can be used to map hydraulic conductivity in the subsurface where measurements of both amplitude and phase are made. Hydraulic conductivity depends on at least two parameters: porosity and a length scale parameter. Electrical Resistance Tomography (ERT) measures and maps electrical conductivity (which can be related to porosity) in three dimensions. By introducing phase measurements along with amplitude, the desired additional measurement of a pertinent length scale can be achieved. Hydraulic conductivity controls the ability to flush unwanted fluid contaminants from the surface. Thus inexpensive maps of hydraulic conductivity would improve planning strategies for subsequent remediation efforts. Fluid permeability is also of importance for oil field exploitation and thus detailed knowledge of fluid permeability distribution in three-dimension (3-D) would be a great boon to petroleum reservoir analysts.

  10. Electrical Switchability and Dry-Wash Durability of Conductive Textiles

    PubMed Central

    Wu, Bangting; Zhang, Bowu; Wu, Jingxia; Wang, Ziqiang; Ma, Hongjuan; Yu, Ming; Li, Linfan; Li, Jingye

    2015-01-01

    There is growing interest in the area of conductive textiles in the scientific and industrial community. Herein, we successfully prepared a conductive textile via covalently grafting polyaniline (PANI) onto cotton by a multi-step treatment process. The conductivity of the resultant fabric could be tuned by immersing in water having different pH values. The conductive and insulating properties of the textile could be conveniently switched by alternately immersing in acidic and alkaline bath solutions. Most importantly, the resultant conductive fabrics were able to withstand 40 simulated dry-wash cycles, with almost no decay in the electrical conductivity, indicating their excellent dry-wash durability. The present strategy for fabricating conductive fabrics with excellent switchability of electrical properties and dry-wash durability is expected to provide inspiration for the production of multifunctional conductive textiles for use in hash or sensitive conditions. PMID:26066704

  11. Electrical Switchability and Dry-Wash Durability of Conductive Textiles.

    PubMed

    Wu, Bangting; Zhang, Bowu; Wu, Jingxia; Wang, Ziqiang; Ma, Hongjuan; Yu, Ming; Li, Linfan; Li, Jingye

    2015-01-01

    There is growing interest in the area of conductive textiles in the scientific and industrial community. Herein, we successfully prepared a conductive textile via covalently grafting polyaniline (PANI) onto cotton by a multi-step treatment process. The conductivity of the resultant fabric could be tuned by immersing in water having different pH values. The conductive and insulating properties of the textile could be conveniently switched by alternately immersing in acidic and alkaline bath solutions. Most importantly, the resultant conductive fabrics were able to withstand 40 simulated dry-wash cycles, with almost no decay in the electrical conductivity, indicating their excellent dry-wash durability. The present strategy for fabricating conductive fabrics with excellent switchability of electrical properties and dry-wash durability is expected to provide inspiration for the production of multifunctional conductive textiles for use in hash or sensitive conditions. PMID:26066704

  12. The electrical conductivity of in vivo human uterine fibroids.

    PubMed

    DeLonzor, Russ; Spero, Richard K; Williams, Joseph J

    2011-01-01

    The purpose of this study was to determine the value of electrical conductivity that can be used for numerical modelling in vivo radiofrequency ablation (RFA) treatments of human uterine fibroids. No experimental electrical conductivity data have previously been reported for human uterine fibroids. In this study electrical data (voltage) from selected in vivo clinical procedures on human uterine fibroids were used to numerically model the treatments. Measured versus calculated power dissipation profiles were compared to determine uterine fibroid electrical conductivity. Numerical simulations were conducted utilising a wide range of values for tissue thermal conductivity, heat capacity and blood perfusion coefficient. The simulations demonstrated that power dissipation was insensitive to the exact values of these parameters for the simulated geometry, treatment duration, and power level. Consequently, it was possible to determine tissue electrical conductivity without precise knowledge of the values for these parameters. Results of this study showed that an electrical conductivity for uterine fibroids of 0.305?S/m at 37°C and a temperature coefficient of 0.2%/°C can be used for modelling Radio Frequency Ablation of human uterine fibroids at a frequency of 460?kHz for temperatures from 37°C to 100°C. PMID:21501027

  13. The effect of water on the electrical conductivity of olivine

    NASA Astrophysics Data System (ADS)

    Wang, Duojun; Mookherjee, Mainak; Xu, Yousheng; Karato, Shun-Ichiro

    2006-10-01

    It is well known that water (as a source of hydrogen) affects the physical and chemical properties of minerals-for example, plastic deformation and melting temperature-and accordingly plays an important role in the dynamics and geochemical evolution of the Earth. Estimating the water content of the Earth's mantle by direct sampling provides only a limited data set from shallow regions (<200km depth). Geophysical observations such as electrical conductivity are considered to be sensitive to water content, but there has been no experimental study to determine the effect of water on the electrical conductivity of olivine, the most abundant mineral in the Earth's mantle. Here we report a laboratory study of the dependence of the electrical conductivity of olivine aggregates on water content at high temperature and pressure. The electrical conductivity of synthetic polycrystalline olivine was determined from a.c. impedance measurements at a pressure of 4GPa for a temperature range of 873-1,273K for water contents of 0.01-0.08wt%. The results show that the electrical conductivity is strongly dependent on water content but depends only modestly on temperature. The water content dependence of conductivity is best explained by a model in which electrical conduction is due to the motion of free protons. A comparison of the laboratory data with geophysical observations suggests that the typical oceanic asthenosphere contains ~10-2wt% water, whereas the water content in the continental upper mantle is less than ~10-3wt%.

  14. Electrical conductivity studies of poly(ethyleneoxide)-poly(vinylalcohol) blends

    Microsoft Academic Search

    Rachna Mishra; K. J Rao

    1998-01-01

    The electrical conductivity studies have been conducted over the entire range of composition in poly(ethyleneoxide)-poly(vinylalcohol) blends over a wide frequency regime. The conductivity variation has been investigated using the modified Almond-West formulation of ?(w)=A1ws1+A2ws2 for different compositions and is found to fit the ac conductivity data better at all temperatures. The dielectric data were analysed using complex dielectric constant ?*,

  15. Microstructure, electrical conductivity, and piezoelectric properties of bismuth titanate

    Microsoft Academic Search

    Holly S. Shulman; Martin Testorf; Dragan Damjanovic; Nava Setter

    1996-01-01

    A study was conducted on the effects of microstructure, atmosphere, and several dopants on the electrical conductivity of bismuth titanate (BiâTiâOââ, BIT). Increased grain size increased the conductivity in undoped BIT as did acceptor dopants that substituted for either Bi (Ca and Sr) or Ti(Fe). A donor dopant (Nb) decreased the conductivity in BIT by as much as 3 orders

  16. Electrical conductivity of rocks at high pressures and temperatures

    NASA Technical Reports Server (NTRS)

    Parkhomenko, E. I.; Bondarenko, A. T.

    1986-01-01

    The results of studies of the electrical conductivity in the most widely distributed types of igneous rocks, at temperatures of up to 1200 C, at atmospheric pressure, and also at temperatures of up to 700 C and at pressures of up to 20,000 kg/sq cm are described. The figures of electrical conductivity, of activaation energy and of the preexponential coefficient are presented and the dependence of these parameters on the petrochemical parameters of the rocks are reviewed. The possible electrical conductivities for the depository, granite and basalt layers of the Earth's crust and of the upper mantle are presented, as well as the electrical conductivity distribution to the depth of 200 to 240 km for different geological structures.

  17. Tailoring the Thermoelectric Behavior of Electrically Conductive Polymer Composites 

    E-print Network

    Moriarty, Gregory P.

    2013-05-21

    containing an insulating stabilizer, sodium deoxycholate (DOC), the multi-walled carbon nanotube (MWNT)-filled composites showed a 5x increase in the Seebeck coefficient (S). TCPP did not have a distinct effect on the electrical conductivity (?...

  18. Measurement of Electrical Conductivity for a Biomass Fire

    PubMed Central

    Mphale, Kgakgamatso; Heron, Mal

    2008-01-01

    A controlled fire burner was constructed where various natural vegetation species could be used as fuel. The burner was equipped with thermocouples to measure fuel surface temperature and used as a cavity for microwaves with a laboratory quality 2-port vector network analyzer to determine electrical conductivity from S-parameters. Electrical conductivity for vegetation material flames is important for numerical prediction of flashover in high voltage power transmission faults research. Vegetation fires that burn under high voltage transmission lines reduce flashover voltage by increasing air electrical conductivity and temperature. Analyzer determined electrical conductivity ranged from 0.0058 - 0.0079 mho/m for a fire with a maximum temperature of 1240 K. PMID:19325812

  19. Correlation of electrical conductivity and thermal decomposition of phenolic materials

    SciTech Connect

    Johnson, R.T. Jr.; Biefeld, R.M.

    1983-01-01

    Changes in the temperature dependence of the electrical conductivity associated with thermal decomposition of several phenolic materials have been measured to 600/sup 0/C in nitrogen and air environments. The materials were phenolic resins reinforced with chopped glass fabric. Thermal decomposition product data and mass loss data were obtained from mass spectroscopy and thermal gravimetric analysis. Results showed that peaks in the conductivity temperature dependence were associated with material decomposition and/or outgassing, and that the presence of oxygen accelerates decomposition above approx. 450/sup 0/C. In the region of ohmic conduction (electric fields less than or equal to 4 x 10/sup 3/ V/cm), there was excellent correlation between thermal decomposition characteristics and the temperature dependent electrical properties. This correlation suggests that electrical conductivity can be used as a thermal analysis tool in characterizing phenolic materials.

  20. Electrical conductivity of rocks in the heating and cooling cycle

    Microsoft Academic Search

    Marcela Lastovicková; F. Janák

    1978-01-01

    Summary The values of the electrical conductivity, recorded during the heating and cooling cycle, of eclogites and basalts are compared. The observed difference in the values is explained by reversible and irreversible changes which take place in the samples.

  1. Electrical conductivity of nanocrystalline ceria and zirconia thin films

    Microsoft Academic Search

    Igor Kosacki; Toshio Suzuki; Vladimir Petrovsky; Harlan U Anderson

    2000-01-01

    The results of studies of the preparation, structure and electrical conductivity of ZrO2:16% Y and CeO2 thin films are presented. Dense films with grain size controlled in the region of 1–400 nm have been obtained on monocrystalline sapphire and polycrystalline Al2O3 substrates using a polymeric precursor spin coating method. The electrical conductivity of nanocrystalline thin films has been studied as

  2. Effects of Contact Resistance on Electrical Conductivity Measurements of SiC-Based Materials

    SciTech Connect

    Youngblood, Gerald E.; Thomsen, Edwin C.; Henager, Charles H.

    2012-04-17

    A combination 2/4-probe method was used to measure electrical resistances across a pure, monolithic CVD-SiC disc sample with contact resistance at the SiC/metallic electrode interfaces. By comparison of the almost simultaneous 2/4-probe measurements, the specific contact resistance and its temperature dependence were determined for two types (sputtered gold and porous nickel) electrodes from RT to ~700°C. The specific contact resistance values (Rc) behaved similarly for each type of metallic electrode: Rc >~1000 ?-cm2 at RT, decreasing continuously to ~1-10 ?-cm2 at 700°C. The temperature dependence of the inverse Rc indicated thermally activated electrical conduction across the SiC/metallic interface with an apparent activation energy of ~0.3 eV. For the flow channel insert application in a fusion reactor blanket, contact resistance potentially could reduce the transverse electrical conductivity by ~1/2.

  3. Effects of contact resistance on electrical conductivity measurements of SiC-based materials

    NASA Astrophysics Data System (ADS)

    Youngblood, G. E.; Thomsen, E. C.; Henager, C. H.

    2013-11-01

    A combination 2/4-probe method was used to measure electrical resistances across a pure, monolithic CVD-SiC disc sample with contact resistance at the SiC/metallic electrode interfaces. By comparison of the almost simultaneous 2/4-probe measurements, the specific contact resistance (Rc) and its temperature dependence were determined for two types (sputtered gold and porous nickel) electrodes from room temperature (RT) to ˜973 K. The Rc-values behaved similarly for each type of metallic electrode: Rc > ˜1000 ? cm2 at RT, decreasing continuously to ˜1-10 ? cm2 at 973 K. The temperature dependence of the inverse Rc indicated thermally activated electrical conduction across the SiC/metallic interface with an apparent activation energy of ˜0.3 eV. For the flow channel insert application in a fusion reactor blanket, contact resistance potentially could reduce the transverse electrical conductivity by about 50%.

  4. Transparent electrical conducting films by activated reactive evaporation

    Microsoft Academic Search

    R. Bunshah; P. Nath

    1982-01-01

    Process and apparatus for producing transparent electrical conducting thin films by activated reactive evaporation is disclosed. Thin films of low melting point metals and alloys, such as indium oxide and indium oxide doped with tin, are produced by physical vapor deposition. The metal or alloy is vaporized by electrical resistance heating in a vacuum chamber, oxygen and an inert gas

  5. Transparent electrical conducting films by activated reactive evaporation

    Microsoft Academic Search

    Rointan Bunshah; Prem Nath

    1982-01-01

    Process and apparatus for producing transparent electrical conducting thin films by activated reactive evaporation. Thin films of low melting point metals and alloys, such as indium oxide and indium oxide doped with tin, are produced by physical vapor deposition. The metal or alloy is vaporized by electrical resistance heating in a vacuum chamber, oxygen and an inert gas such as

  6. Electrical Conductivity of the Lower-Mantle Ferropericlase

    SciTech Connect

    Lin, J F; Weir, S T; Jackson, D D; Evans, W J; Vohra, Y K; Qiu, W; Yoo, C S

    2007-04-19

    Electrical conductivity of the lower-mantle ferropericlase-(Mg{sub 0.75},Fe{sub 0.25})O has been studied using designer diamond anvils to pressures over one megabar and temperatures up to 500 K. The electrical conductivity of (Mg{sub 0.75},Fe{sub 0.25})O gradually rises by an order of magnitude up to 50 GPa but decreases by a factor of approximately three between 50 to 70 GPa. This decrease in the electrical conductivity is attributed to the electronic high-spin to low-spin transition of iron in ferropericlase. That is, the electronic spin transition of iron results in a decrease in the mobility and/or density of the charge transfer carriers in the low-spin ferropericlase. The activation energy of the low-spin ferropericlase is 0.27 eV at 101 GPa, similar to that of the high-spin ferropericlase at relatively low temperatures. Our results indicate that low-spin ferropericlase exhibits lower electrical conductivity than high-spin ferropericlase, which needs to be considered in future geomagnetic models for the lower mantle. The extrapolated electrical conductivity of the low-spin ferropericlase, together with that of silicate perovskite, at the lower mantle pressure-temperature conditions is consistent with the model electrical conductivity profile of the lower mantle.

  7. Thermal and Electrical Conductivity Measurements of CDA 510 Phosphor Bronze

    NASA Technical Reports Server (NTRS)

    Tuttle, James E.; Canavan, Edgar; DiPirro, Michael

    2009-01-01

    Many cryogenic systems use electrical cables containing phosphor bronze wire. While phosphor bronze's electrical and thermal conductivity values have been published, there is significant variation among different phosphor bronze formulations. The James Webb Space Telescope (JWST) will use several phosphor bronze wire harnesses containing a specific formulation (CDA 510, annealed temper). The heat conducted into the JWST instrument stage is dominated by these harnesses, and approximately half of the harness conductance is due to the phosphor bronze wires. Since the JWST radiators are expected to just keep the instruments at their operating temperature with limited cooling margin, it is important to know the thermal conductivity of the actual alloy being used. We describe an experiment which measured the electrical and thermal conductivity of this material between 4 and 295 Kelvin.

  8. Electrically conductive nanocomposites made from cellulose nanofibrils and polyaniline.

    PubMed

    Mattoso, L H C; Medeiros, E S; Baker, D A; Avloni, J; Wood, D F; Orts, W J

    2009-05-01

    Electrically conductive nanocomposites from cellulose nanofibrils (CNF) were successfully produced by in situ polymerization of aniline onto CNF, and studied by open circuit potential (Voc), four probe direct current (dc) electrical conductivity, ultraviolet-visible (UV-Vis) spectroscopy and scanning electron microscopy (SEM). The oxidative polymerization of aniline using ammonium peroxydisulfate in hydrochloric acid aqueous solutions was realized by the addition of nanofibrils leading to an aqueous suspension of CNF coated with polyaniline (PANI). This procedure lead to stable, green suspensions of CNF coated with PANI in the emeraldine oxidation state as demonstrated by Voc and UV-Vis analyses. Electrically conductive films of this cellulose nanocomposite could be cast from aqueous solutions with conductivity close to the conducting polymer, yet with the potential for more useful flexible films. PMID:19452949

  9. Characteristics of thermoplastics containing electrically conducting asymmetric particles - anisotropic electrical conductivity of injection molded parts and extrusion behavior

    SciTech Connect

    Martinsson, J.; White, J.L.

    1986-10-01

    The characteristics of compounds of acrylonitrile-butadiene-styrene and high impact polystyrene resins filled with carbon fibers, steel fibers, carbon black, and aluminum flakes have been investigated with special emphasis on electrical conductivity and flow behavior in a capillary rheometer. Compression- and injection-molded compounds were found to be highly electrically anisotropic. The components of the electrical conductivity tensor, were measured. Generally, kappa-11, the flow direction conductivity, has the highest value and the thickness direction, and kappa-33 has the lowest. The injection-molded parts were usually electrically heterogeneous, with the conductivities highest at the greatest distances from the gate. The flow of these compounds through dies was investigated. Examination of material from the die entrance indicated streamline flow without entrance vortices. Extrudates were found to contain oriented particles. 25 references.

  10. CHARACTERIZATION OF SPATIAL VARIABILITY OF SOIL ELECTRICAL CONDUCTIVITY AND CONE INDEX USING COULTER AND PENETROMETER-TYPE SENSORS.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Assessment and management of spatial variability of soil chemical and physical properties are very important for precision farming. The spatial variability of apparent electrical conductivity (ECa) and penetration resistance expressed as cone index (CI) for soil compaction was investigated with Veri...

  11. Electrical conductivity measurement of iron at high static pressure

    NASA Astrophysics Data System (ADS)

    Gomi, H.; Ohta, K.; Hirose, K.

    2010-12-01

    The knowledge of the thermal conductivity of the core constrains the heat flow and the amount of radiogenic elements in the core [1]. The electrical conductivity of iron has been measured by shock compression experiments. The thermal conductivity can be then calculated using the Wiedemann-Franz law. Stacey and Loper [2] estimated the thermal conductivity of outer core liquid and suggested the absence of radiogenic heat source. However, no conductivity measurement has been carried out under core pressures by static experiments. In this study, we have conducted the electrical conductivity measurements of pure iron under high static pressure at room temperature in a diamond-anvil cell. The sample resistance was obtained by the four-terminal method. The results demonstrated that the conductivity increased with increasing pressure and dropped at ~15 GPa across phase transition from bcc to hcp structure. It then increased again with pressure up to 65 GPa. The electrical conductivity was determined to be about 1E7 S/m at 65 GPa. We estimated the electrical conductivity of iron under the CMB pressure and temperature condition to be ~ 1E6 S/m, which is comparable to the previous estimate by Stacey and Anderson [3]. The details of the experiments will be reported at the presentation. [1] Stevenson, D.J., 2003. Planetary magnetic fields. Earth Plan. Sci. Lett. 208, 1-11. [2] Stacey, F.D., Loper, D.E., 2007. Physics of the Earth Plan. Int. 161, 13-18. [3] Stacey, F.D., Anderson, O.L., 2001. Electrical and thermal conductivities of Fe-Ni-Si alloy under core conditions. Phys. Earth Planet. Inter. 124, 153-162.

  12. RIS-M-2478 ELECTRICAL CONDUCTIVITY, DEFECT STRUCTURE AND

    E-print Network

    RISØ-M-2478 ELECTRICAL CONDUCTIVITY, DEFECT STRUCTURE AND DENSITY IN THE CERIA - GADOLINIA SYSTEM X. Previous studies on the ceria-gadolinia system have mainly been done on oxides rich in ceria. The purpose-doped ceria i s one of the best oxygen-ion conductors known today. The ionic conductivities obtained

  13. Calculation of electrical conductivity from ion-aerosol balance equations

    Microsoft Academic Search

    Savita Dhanorkar; A. K. Kamra

    1997-01-01

    The ion-aerosol balance equations are solved to study the effect of aerosol concentration on electrical conductivity for different ionization rates taking bimodal lognormal size distribution for the grand average continental aerosol particles and using size dependent attachment and coagulation coefficients for the aerosol particles. The results show that the inverse relationship between the polar conductivity and aerosol concentration exists only

  14. Electrically conductive resinous bond and method of manufacture

    DOEpatents

    Snowden, T.M. Jr.; Wells, B.J.

    1985-01-01

    A method of bonding elements together with a bond of high strength and good electrical conductivity which comprises: applying an unfilled polyimide resin between surfaces of the elements to be bonded, heat treating said unfilled polyimide resin in stages between a temperature range of about 40 to 365/sup 0/C to form a strong adhesive bond between said elements, applying a metal-filled polyimide resin overcoat between said elements so as to provide electrical connection therebetween, and heat treating said metal-filled polyimide resin with substantially the same temperature profile as the unfilled polyimide resin. The present invention is also concerned with an adhesive, resilient, substantially void free bonding combination for providing a high strength, electrically conductive adhesive attachment between electrically conductive elements which comprises a major amount of an unfilled polyimide resin and a minor amount of a metal-filled polyimide resin.

  15. Electric field enhanced conductivity in strongly coupled dense metal plasma

    NASA Astrophysics Data System (ADS)

    Stephens, J.; Neuber, A.

    2012-06-01

    Experimentation with dense metal plasma has shown that non-negligible increases in plasma conductivity are induced when a relatively low electric field (˜6 kV/cm) is applied. Existing conductivity models assume that atoms, electrons, and ions all exist in thermal equilibrium. This assumption is invalidated by the application of an appreciable electric field, where electrons are accelerated to energies comparable to the ionization potential of the surrounding atoms. Experimental data obtained from electrically exploded silver wire is compared with a finite difference hydrodynamic model that makes use of the SESAME equation-of-state database. Free electron generation through both thermal and electric field excitations, and their effect on plasma conductivity are applied and discussed.

  16. Electrically conductive resinous bond and method of manufacture

    DOEpatents

    Snowden, Jr., Thomas M. (P.O. Box 4231, Clearwater, FL 33518); Wells, Barbara J. (865 N. Village Dr., Apt. 101B, St. Petersburg, FL 33702)

    1987-01-01

    A method of bonding elements together with a bond of high strength and good electrical conductivity which comprises: applying an unfilled polyimide resin between surfaces of the elements to be bonded, heat treating said unfilled polyimide resin in stages between a temperature range of about 40.degree. to 365.degree. C. to form a strong adhesive bond between said elements, applying a metal-filled polyimide resin overcoat between said elements so as to provide electrical connection therebetween, and heat treating said metal-filled polyimide resin with substantially the same temperature profile as the unfilled polyimide resin. The present invention is also concerned with an adhesive, resilient, substantially void free bonding combination for providing a high strength, electrically conductive adhesive attachment between electrically conductive elements which comprises a major amount of an unfilled polyimide resin and a minor amount of a metal-filled polyimide resin.

  17. Line tension and reduction of apparent contact angle associated with electric double layers

    E-print Network

    Dörr, Aaron

    2014-01-01

    The line tension of an electrolyte wetting a non-polar substrate is computed analytically and numerically. The results show that, depending on the value of the apparent contact angle, positive or negative line tension values may be obtained. Furthermore, a significant difference between Young's contact angle and the apparent contact angle measured several Debye lengths remote from the three-phase contact line occurs. When applying the results to water wetting highly charged surfaces, line tension values of the same order of magnitude as found in recent experiments can be achieved. Therefore, the theory presented may contribute to the understanding of line tension measurements and points to the importance of the electrostatic line tension. Being strongly dependent on the interfacial charge density, electrostatic line tension is found to be tunable via the pH value of the involved electrolyte. As a practical consequence, the stability of nanoparticles adsorbed at fluid-fluid interfaces is predicted to be depend...

  18. Electric and thermal conductivities of quenched neutron star crusts

    NASA Technical Reports Server (NTRS)

    Ogata, Shuji; Ichimaru, Setsuo

    1990-01-01

    The electric and thermal conductivities in the outer crustal matter of a neutron star quenched into a solid state by cooling are estimated using a Monte Carlo simulation of freezing transition for dense plasmas. The conductivities are calculated by the precise evaluation of the scattering integrals, using the procedure of Ichimaru et al. (1983) and Iyetomi and Ichimaru (1983). The results predict the conductivities lower, by a factor of about 3, than those with the single-phonon approximation.

  19. Detection of temperature distribution via recovering electrical conductivity in MREIT

    NASA Astrophysics Data System (ADS)

    In Oh, Tong; Kim, Hyung Joong; Jeong, Woo Chul; Chauhan, Munish; In Kwon, Oh; Woo, Eung Je

    2013-04-01

    In radiofrequency (RF) ablation or hyperthermia, internal temperature measurements and tissue property imaging are important to control their outputs and assess the treatment effect. Recently, magnetic resonance electrical impedance tomography (MREIT), as a non-invasive imaging method of internal conductivity distribution using an MR scanner, has been developed. Its reconstruction algorithm uses measured magnetic flux density induced by injected currents. The MREIT technique has the potential to visualize electrical conductivity of tissue with high spatial resolution and measure relative conductivity variation according to the internal temperature change based on the fact that the electrical conductivity of biological tissues is sensitive to the internal temperature distribution. In this paper, we propose a method to provide a non-invasive alternative to monitor the internal temperature distribution by recovering the electrical conductivity distribution using the MREIT technique. To validate the proposed method, we design a phantom with saline solution and a thin transparency film in a form of a hollow cylinder with holes to create anomalies with different electrical and thermal conductivities controlled by morphological structure. We first prove the temperature maps with respect to spatial and time resolution by solving the thermal conductivity partial differential equation with the real phantom experimental environment. The measured magnetic flux density and the reconstructed conductivity distributions using the phantom experiments were compared to the simulated temperature distribution. The relative temperature variation of two testing objects with respect to the background saline was determined by the relative conductivity contrast ratio (rCCR,%). The relation between the temperature and conductivity measurements using MREIT was approximately linear with better accuracy than 0.22 °C.

  20. GLOBE Videos: Hydrology Protocols - Electrical Conductivity (9:20 min)

    NSDL National Science Digital Library

    2012-08-03

    The video is a procedural guide to sampling electrical conductivity measurements in water bodies using standardized GLOBE protocols. It provides a step-by-step explanation of the field procedure and features students conducting the investigation and asking questions about measuring electrical conductivity and what these measurements mean with respect to water impurities and dissolved solids. The resource includes a video, transcript, and is supported by the Electrical Conductivity Protocol in the GLOBE Teacher's Guide. This is one of seven videos on hydrology in the 24-part instructional video series describing scientific protocols used by GLOBE (Global Learning and Observation to Benefit the Environment) a worldwide, hands-on, K-12 school-based science education program.

  1. Temperature distribution for electrically conductive and non-conductive materials during Field Assisted Sintering (FAST)

    Microsoft Academic Search

    Jan Räthel; Mathias Herrmann; Wieland Beckert

    2009-01-01

    During Field Assisted Sintering Technology (FAST) the temperature differences at two different positions were investigated using two pyrometers, an internal and an external one. Two substances, an electrically conductive (tungsten carbide) and a non-conductive material (96wt.% silicon nitride with 2wt.% alumina and yttria) were used to monitor the temperature differences between both pyrometers during heating, sintering shrinkage and dwell time

  2. Thermal conductivity and electrical resistivity of porous material

    NASA Technical Reports Server (NTRS)

    Koh, J. C. Y.; Fortini, A.

    1971-01-01

    Thermal conductivity and electrical resistivity of porous materials, including 304L stainless steel Rigimesh, 304L stainless steel sintered spherical powders, and OFHC sintered spherical powders at different porosities and temperatures are reported and correlated. It was found that the thermal conductivity and electrical resistivity can be related to the solid material properties and the porosity of the porous matrix regardless of the matrix structure. It was also found that the Wiedermann-Franz-Lorenz relationship is valid for the porous materials under consideration. For high conductivity materials, the Lorenz constant and the lattice component of conductivity depend on the material and are independent of the porosity. For low conductivity, the lattice component depends on the porosity as well.

  3. Peculiarities of coexistence of phases with different electric conductivities under the influence of an electric current

    E-print Network

    Elperin, Tov

    of an electric current Yu. Dolinsky* and T. Elperin The Pearlstone Center for Aeronautical Engineering Studies of coexistence of phases under the influence of the electric current, the phase equilibrium curve splits into two lines in a current-carrying system taking into account the difference of electric conductivities

  4. Line tension and reduction of apparent contact angle associated with electric double layers

    E-print Network

    Aaron Dörr; Steffen Hardt

    2014-11-05

    The line tension of an electrolyte wetting a non-polar substrate is computed analytically and numerically. The results show that, depending on the value of the apparent contact angle, positive or negative line tension values may be obtained. Furthermore, a significant difference between Young's contact angle and the apparent contact angle measured several Debye lengths remote from the three-phase contact line occurs. When applying the results to water wetting highly charged surfaces, line tension values of the same order of magnitude as found in recent experiments can be achieved. Therefore, the theory presented may contribute to the understanding of line tension measurements and points to the importance of the electrostatic line tension. Being strongly dependent on the interfacial charge density, electrostatic line tension is found to be tunable via the pH value of the involved electrolyte. As a practical consequence, the stability of nanoparticles adsorbed at fluid-fluid interfaces is predicted to be dependent on the pH value. The theory is suited for future incorporation of effects due to surfactants where even larger line tension values can be expected.

  5. Electric conductivity and oxygen permeability of modified cerium oxides

    Microsoft Academic Search

    Xiwang Qi; Y. S. Lin; C. T. Holt; S. L. Swartz

    2003-01-01

    Electrical conductivities of samarium (Sm), terbium (Tb), praseodymium (Pr) and zirconium (Zr) doped ceria membranes were measured in T = 600–900°C and pO2 = 10?22–0.21 atm. Doping Sm and Pr in CeO2 respectively enhances the ionic conductivity and electron-hole conductivity of ceria. Sm-Pr doped ceria exhibits both n-type (at lower pO2) and p-type (at high pO2) electronic and ionic conductivity

  6. Electrically Conductive Crust in Southern Tibet from INDEPTH Magnetotelluric Surveying

    PubMed

    Chen; Booker; Jones; Wu; Unsworth; Wei; Tan

    1996-12-01

    The crust north of the Himalaya is generally electrically conductive below depths of 10 to 20 km. This conductive zone approaches the surface beneath the Kangmar dome (dipping north) and extends beneath the Zangbo suture. A profile crossing the northern Yadong-Gulu rift shows that the high conductivity region extends outside the rift, and its top within the rift coincides with a bright spot horizon imaged on the INDEPTH CMP (common midpoint) profiles. The high conductivity of the middle crust is atypical of stable continental regions and suggests that there is a regionally interconnected fluid phase in the crust of the region. PMID:8939855

  7. Electrical conductivity of a bulk metallic glass composite

    NASA Astrophysics Data System (ADS)

    Wang, K.; Fujita, T.; Chen, M. W.; Nieh, T. G.; Okada, H.; Koyama, K.; Zhang, W.; Inoue, A.

    2007-10-01

    The authors report the electrical conductivity of a bulk metallic glass (BMG) based composite fabricated by warm extrusion of a mixture of gas-atomized glassy powders and ductile ?-brass powders. The conductivity of the BMG composite can be well modeled by the percolation theory and the critical percolation threshold volume of the high-conductive brass phase was estimated to be about 10%. It was found that the short irregular brass fibers can dramatically reduce the resistivity of the BMG, leading to an improved material with both high strength and good conductivity for functional applications.

  8. Electrical conduction properties of rare earth orthophosphates under reducing conditions

    Microsoft Academic Search

    Naoto Kitamura; Koji Amezawa; Yoshiharu Uchimoto; Yoichi Tomii; Teiichi Hanada; Naoichi Yamamoto

    2006-01-01

    Electrical conduction properties of Sr-doped PrPO4, NdPO4 and SmPO4 with the monazite structure were investigated at 500–925 °C under H2\\/H2O reducing conditions. From H\\/D isotope effects and p(H2)-dependencies of the conductivities, it was found that the materials dominantly conducted protons under the wet reducing conditions although the materials slightly showed n-type electronic conduction at higher temperatures. Based on p(H2O) and p(H2)-dependencies

  9. Electrical conductivity of polypropylene fibers with dispersed carbon fillers

    NASA Astrophysics Data System (ADS)

    Moskalyuk, O. A.; Aleshin, A. N.; Tsobkallo, E. S.; Krestinin, A. V.; Yudin, V. E.

    2012-10-01

    Polypropylene fibers with fillers in the form of carbon nanoparticles of four types (technical carbon, graphitized carbon nanofibers, multi-walled carbon nanotubes, and single-walled carbon nanotubes) have been synthesized. For all types of fillers, the electrical conductivity of the fibers has been measured as a function of the concentration of nanoparticles and the percolation thresholds have been determined. A correlation between the nanoparticle concentration and the electrical conductivity of the percolation cluster at the percolation threshold with the cross section, the axial ratio, and the shape of the nanoparticles dispersed in the polymer matrix has been discussed. The dependence of the electrical conductivity of the composite material with carbon nanofibers on the temperature has been measured.

  10. RELATIONSHIP OF SOIL PROFILE STRENGTH AND APPARENT SOIL ELECTRICAL CONDUCTIVITY TO CROP YIELD

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding characteristics of claypan soils has long been an issue for researchers and farmers because the high-clay subsoil has a pronounced effect on grain crop productivity. The claypan restricts water infiltration and storage within the crop root zone, but these effects are not uniform within...

  11. SOYBEAN ROOT DISTRIBUTION RELATED TO CLAYPAN SOIL PROPERTIES AND APPARENT SOIL ELECTRICAL CONDUCTIVITY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soybean [Glycine max (L.)] yield in claypan soils varies as a result of systematic relationships with soil properties and landscape position. This variability is likely caused by soil-landscape interactions with soybean roots. While much data exists on the landscape variability of yield, field obser...

  12. Thermal and Electrical Conductivities of Porous Si Membranes

    NASA Astrophysics Data System (ADS)

    Hagino, Harutoshi; Tanaka, Saburo; Tanimura, Naoki; Miyazaki, Koji

    2014-06-01

    The microstructure of materials affects thermal and electrical transport as well as the physical properties. The effects of the microstructure on both thermal and electrical transport in silicon membranes with periodic microporous structures produced from silicon-on-insulator wafers using microfabrication processes were studied. The in-plane thermal and electrical conductivities of the Si membranes were measured simultaneously by using a self-heating method. The measured thermal conductivity was compared with the result from the periodically laser-heating method. The thermal and electrical conductivities were much lower in the porous membranes than in the non-porous membrane. The measured thermal conductivity was much lower than expected based on values determined using classical models. A significant phonon size effect was observed even in microsized structures, and the mean free path for phonons was very long. It was concluded that phonon transport is quasi-ballistic and electron transport is diffuse in microporous Si structures. It was suggested that the microstructure had a different effect on thermal and electrical transport.

  13. Contamination from electrically conductive silicone tubing during aerosol chemical analysis

    SciTech Connect

    Yu, Yong; Alexander, M. L.; Perraud, Veronique; Bruns, Emily; Johnson, Stan; Ezell, Michael J.; Finlayson-Pitts, Barbara J.

    2009-06-01

    Electrically conductive silicone tubing is used to minimize losses in sampling lines during the analysis of airborne particle size distributions and number concentrations. We report contamination from this tubing using gas chromatography-mass spectrometry (GC-MS) of filter-collected samples as well as by particle mass spectrometry. Comparison of electrically conductive silicone and stainless steel tubing showed elevated siloxanes only for the silicone tubing. The extent of contamination increased with length of tubing to which the sample was exposed, and decreased with increasing relative humidity.

  14. Corrosion-protective coatings from electrically conducting polymers

    SciTech Connect

    Thompson, K.G.; Bryan, C.J. (National Aeronautics and Space Administration, Cocoa Beach, FL (United States). John F. Kennedy Space Center); Benicewicz, B.C.; Wrobleski, D.A. (Los Alamos National Lab., NM (United States))

    1991-01-01

    In a joint research effort involving the Kennedy Space Center and the Los Alamos National Laboratory, electrically conductive polymer coatings have been developed as corrosion-protective coatings for metal surfaces. At the Kennedy Space Center, the launch environment consists of marine, severe solar, and intermittent high acid/elevated temperature conditions. Electrically conductive polymer coatings have been developed which impart corrosion resistance to mild steel when exposed to saline and acidic environments. Such coatings also seem to promote corrosion resistance in areas of mild steel where scratches exist in the protective coating. Such coatings appear promising for many commercial applications.

  15. Corrosion-protective coatings from electrically conducting polymers

    SciTech Connect

    Thompson, K.G.; Bryan, C.J. [National Aeronautics and Space Administration, Cocoa Beach, FL (United States). John F. Kennedy Space Center; Benicewicz, B.C.; Wrobleski, D.A. [Los Alamos National Lab., NM (United States)

    1991-12-31

    In a joint research effort involving the Kennedy Space Center and the Los Alamos National Laboratory, electrically conductive polymer coatings have been developed as corrosion-protective coatings for metal surfaces. At the Kennedy Space Center, the launch environment consists of marine, severe solar, and intermittent high acid/elevated temperature conditions. Electrically conductive polymer coatings have been developed which impart corrosion resistance to mild steel when exposed to saline and acidic environments. Such coatings also seem to promote corrosion resistance in areas of mild steel where scratches exist in the protective coating. Such coatings appear promising for many commercial applications.

  16. Electrically conductive doped block copolymer of polyacetylene and polyisoprene

    DOEpatents

    Aldissi, Mahmoud (Los Alamos, NM)

    1985-01-01

    An electrically conductive block copolymer of polyisoprene and polyacetyl and a method of making the same are disclosed. The polymer is prepared by first polymerizing isoprene with n-butyllithium in a toluene solution to form an active isoprenyllithium polymer. The active polymer is reacted with an equimolar amount of titanium butoxide and subsequently exposed to gaseous acetylene. A block copolymer of polyisoprene and polyacetylene is formed. The copolymer is soluble in common solvents and may be doped with I.sub.2 to give it an electrical conductivity in the metallic regime.

  17. Corrosion-protective coatings from electrically conducting polymers

    NASA Technical Reports Server (NTRS)

    Thompson, Karen Gebert; Bryan, Coleman J.; Benicewicz, Brian C.; Wrobleski, Debra A.

    1991-01-01

    In a joint effort between NASA Kennedy and LANL, electrically conductive polymer coatings were developed as corrosion protective coatings for metal surfaces. At NASA Kennedy, the launch environment consist of marine, severe solar, and intermittent high acid and/or elevated temperature conditions. Electrically conductive polymer coatings were developed which impart corrosion resistance to mild steel when exposed to saline and acidic environments. Such coatings also seem to promote corrosion resistance in areas of mild steel where scratches exist in the protective coating. Such coatings appear promising for many commercial applications.

  18. Micromechanical approach for electrical resistivity and conductivity of sandstone

    NASA Astrophysics Data System (ADS)

    Nguyen, S. T.

    2014-12-01

    The objective of this work is to employ the micromechanical approach for the modeling of the electrical resistivity and of the conductivity of sandstone. This type of rock is considered as a mixture of solid mineral and porous space filled fully or partially by conductive water. The Eshelby's solution of a spheroidal inclusion in a homogeneous matrix is employed. The differential effective medium model (DEM) with different concepts of the microstructure is developed for the calculation of the resistivity. The parametric study clarifies the impact of the microscopic parameters on the macroscopic electrical properties. The simulations are compared with the classical empirical and theoretical approaches as well as with the laboratory measurements. The results show a strong impact of the microstructure (the shape of the pore, the presence of non-conductive fluids in the pore space, the connectivity of conductive fluid) on the macroscopic resistivity and conductivity of sandstone. This approach gives a link between the microscopic physical parameters of the rock and the macroscopic electrical parameters such as the cementation exponent and the electrical formation factor.

  19. Electrically Joining Mixed Conducting Oxides for High Temperature Applications

    SciTech Connect

    Weil, K. Scott; Hardy, John S.

    2003-01-06

    Mixed conducting oxides such as lanthanum strontium cobalt ferrite are currently being investigated for potential use as electrochemically active electrodes and catalytic membranes in a number of high temperature devices, including oxygen generators and solid oxide fuel cells (SOFC). However to take full advantage of the unique properties of these materials, reliable joining techniques need to be developed. What complicates joining in these applications is the requirement that the ceramic-to-metal junction be electrically conductive, so that current can either be drawn from the mixed conducting oxide, in the case of SOFC applications, or be carried to the oxide to initate ionic conduction, as required for oxygen separation and electrocatalysis. This paper outlines a new technique that is being developed to electrically join an oxide conductor to a metal current collector for high temperature electrochemical application.

  20. Diffusion and mobility of electrically conducting defects in olivine

    Microsoft Academic Search

    S. Constable; A. Duba

    2002-01-01

    Electrical conductivity of lherzolite (65% olivine), measured as a function of time after changes in the oxygen fugacity\\u000a (f\\u000a o2) of the surrounding CO2\\/CO atmosphere, is used to infer the diffusivity of the point defects responsible for conduction in olivine. A total of 63\\u000a equilibration runs at temperatures of 900, 1000, 1100, and 1200??C were fit using nonlinear parameter estimation

  1. Electrical conductivities of multi-wall carbon nano tubes

    Microsoft Academic Search

    K. Kaneto; M. Tsuruta; G. Sakai; W. Y. Cho; Y. Ando

    1999-01-01

    Electrical conductivities of individual multi-wall carbon nano tubes have been measured using a micro manipulator by two probe method. The nano tubes are 15~50 nm in diameter and longer than 20 ?m in length. The resistance of tubes is several k? per ?m, which gives the average conductivity as 1,000~2,000 S\\/cm. The current-voltage characteristics at high field are also studied

  2. Investigation of the electrical conductivity in perfused liver using micro electrical probe

    NASA Astrophysics Data System (ADS)

    Yi, Ming; Podhajsky, Ronald J.; Mahajan, Roop L.

    2011-03-01

    In this paper, we present the design, fabrication and calibration of new micro machined electrical probe and experimental studies on liver tissues using this probe. The probe was fabricated by photolithography and mounted in a catheter with 1.5mm in diameter, which can be used to measure local impedance of the biological tissues. After the calibration of the impedance at 500k Hz against different concentrations of saline water, the electrical conductivity can be obtained from the measured impedance value. The micro electrical probe was first used to investigate the effect of temperature elevation on the electrical conductivity liver tissues by different heating methods. Also, the electrical conductivity change caused by directional placement and perfusion rate was investigated on a perfused pig liver model. The experimental results show that the local electrical conductivity varies location to location and that the electrical conductivity has a strong directional dependence. Also by varying the perfusion rate, the probe shows that the local electrical conductivity varies linearly with the square root of perfusion rate. These results may be of great value to many biomedical applications.

  3. Electrical conductivity of dense hydrous magnesium silicates with implication for conductivity in the stagnant slab

    NASA Astrophysics Data System (ADS)

    Guo, Xinzhuan; Yoshino, Takashi

    2013-05-01

    Electrical conductivities of dense hydrous magnesium silicates (DHMS), phase A, super-hydrous phase B (SuB) and phase D, were measured by means of impedance spectroscopy in the frequency range of 10-1-106 Hz at temperatures up to 775, 700 and 700 K and pressures of 10, 18 and 22 GPa, respectively. For all phases, the increase in electrical conductivity (?) with temperature follows the Arrhenian formula: ?=?0exp(-(?H/kT)). The pre-exponential factors (?0) and activation enthalpies (?H) of phase A, SuB and phase D yield values of 7.28±0.82 S/m and 0.77±0.01 eV, 292±48 S/m and 0.83±0.01 eV and 1342±154 and 0.75±0.01 eV, respectively. Higher pressure DHMS phases show higher conductivity values. The electrical conductivities of phase D and super hydrous phase B are about two and one orders of magnitude higher than that of phase A in the same temperature range, respectively. Although the proton conduction is considered to be a dominant mechanism, there is no clear relationship between water content and conductivity. Rather the conductivity of DHMS phase is closely related to the O⋯O distance. The conductivity-depth profiles for a cold subduction zone were constructed based on the phase proportion predicted in the descending slab. The results show distinctly lower conductivity values than those geophysically observed beneath the northeastern China and the Philippine Sea, where the cold slab stagnates in the mantle transition zone. Consequently, the DHMS phases themselves cannot be a main contributor to enhance the conductivity in the stagnant slab. Dehydration of the stagnant slab would strongly enhance the conductivities in the transition zone beneath northeastern China and Philippine Sea.

  4. Seasonal changes in apparent hydraulic conductance and their implications for water use of European beech ( Fagus sylvatica L.) and sessile oak [ Quercus petraea (Matt.) Liebl] in South Europe

    Microsoft Academic Search

    I. Aranda; L. Gil; J. A. Pardos

    2005-01-01

    The water status of Fagus sylvatica L. and Quercus petraea (Matt) Liebl. was analysed during a cycle of progressive natural drought in southern Europe. Predawn (?pd) and midday water potential were measured in transpiring (?leaf) and non-transpiring leaves (?xyl). Furthermore, photosynthesis (A), stomatal conductance to water vapour (gs) and sap flow (Fd) were recorded on the same dates. Apparent leaf

  5. UNCERTAINTY EFFECTS ON ELECTRICAL CONDUCTIVITY AND PERMITTIVITY SPECTRA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil permittivity and electrical conductivity values are usually reported without error bars, which limits comparisons among different studies using different equipment. Uncertainty in measured permittivity spectra could be due to the measurement system (hardware) or sample-to-sample variation. Ther...

  6. Electrical Conduction and Dielectric Properties of Biodegradable Plastics

    Microsoft Academic Search

    Katsuyoshi Shinyama; Shigetaka Fujita

    2005-01-01

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

  7. Soil water sensor response to bulk electrical conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water monitoring using electromagnetic (EM) sensors can facilitate observations of water content at high temporal and spatial resolutions. These sensors measure soil dielectric permittivity (Ka) which is largely a function of volumetric water content. However, bulk electrical conductivity BEC c...

  8. Difiusion and Swelling Properties of Electrically Conductive Adhesives

    Microsoft Academic Search

    Richard Loewa; Juergen Wilde

    This work presents the behaviour of an Electrically Conductive Adhesive (ECA)in a humid environment. The adhesive consists of a highly silver fllled epoxy. Due to the organic structure of the polymer an ingression of water occurs. This leads to sev- eral changes in the constitutive behaviour. For example, a change in the visco-elastic constitutive behaviour occurs. Furthermore, a swelling of

  9. A Review of Conducting Polymers in Electrical Contact Applications

    Microsoft Academic Search

    J. W. McBride; L. Lam

    A review of recent developments in fretting studies in electrical contacts is presented, focusing on developments in conducting polymer surfaces. Fretting is known to be a major cause of contact deterioration and failure; commonly exhibited as the contact resistance increases from a few milliohms, in the case of a new metallic contacts, to in excess of several ohms for exposed

  10. TEMPORAL STABILITY OF SOIL ELECTRICAL CONDUCTIVITY IN IRRIGATED SANDY SOILS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The utility of bulk soil electrical conductivity (EC) remains elusive because of its complex interactions with soil properties. Nonetheless, a significant interest is emerging to utilize the spatial variability in EC to develop varying site-specific management. While the spatial variability of EC ...

  11. Electrical conductance of bolted copper joints for cryogenic applications

    E-print Network

    Paris-Sud XI, Université de

    Electrical conductance of bolted copper joints for cryogenic applications F. Blondelle · A. Sultan contact resistance measurements at low temperatures on copper-to-copper bolted joints. Our accurate resistances in sim- ple copper-to-copper bolted joints, used in our fast-cooling pulse-tube dilution

  12. Characterization of electrically conductive transition metal dichalcogenide lubricant films

    Microsoft Academic Search

    Harish C. Waghray

    1997-01-01

    Groups VB and VIB transition metal dichalcogenides with layered structures, are intrinsic solid lubricants, and constitute a class of materials with unique and unusual properties based on their extreme anisotropy. The primary objective of this investigation was to conduct a comprehensive study on the tribological and electrical properties of burnished and sputtered transition metal dichalcogenide films, and characterize the performance

  13. Oil well electrical cable with gas conducting channel and vent

    Microsoft Academic Search

    Neuroth

    1985-01-01

    An electrical cable especially useful in oil wells having a gas conducting channel beneath the outer sheath and a valved vent through the sheath to prevent explosive decompression. Gases entrained in the cable's insulation can exit from the insulation into the channel, move longitudinally of the cable along the channel and exit from the sheath via the vent. The cable

  14. Quantized Electrical Conductance of Carbon nanotubes(CNTs) Boxiao Chen

    E-print Network

    La Rosa, Andres H.

    ]. The circumference of the nano-tubes is represented by the magnitudes of the chiral vector, = n1 +m2Quantized Electrical Conductance of Carbon nanotubes(CNTs) By Boxiao Chen PH 464: Applied Optics is due to the scattering of electrons inside the cells. Carbon nanotubes (CNTs) have proposed to use

  15. Electrical conductivity enhancement in heterogeneously doped scandia-stabilized zirconia

    Microsoft Academic Search

    Chakrapani Varanasi; Chetan Juneja; Christina Chen; Binod Kumar

    2005-01-01

    Composites of 6mol% scandia-stabilized zirconia materials (6ScSZ) and nanosize Al2O3 powder (0–30wt.%) were prepared and characterized for electrical conductivity by the ac impedance method at various temperatures ranging from 300 to 950°C. All the composites characterized showed improved conductivity at higher temperatures compared to the undoped ScSZ. An average conductivity of 0.12Scm?1 was measured at 850°C for 6ScSZ+30wt.% Al2O3 composite

  16. Electrically conducting novel polymer films containing pi-stacks

    NASA Astrophysics Data System (ADS)

    Duan, Robert Gang

    1997-12-01

    The primary focus of this thesis is to expand our knowledge of ion radicals of ?-dimers and ?- stacks in solutions and apply these insights in the development and understanding of new electrically conducting polymers. Two types of the conducting polymers were investigated. The first is the conducting polymer composites embedded with ?-stacks of ion radicals. Flexible and air stable n-typed conducting thin films were prepared from imide/poly(vinyl alcohol) aqueous solutions. Conducting thin films of terthiophene/poly(methyl methacrylate) were cast from hexafluoro-2-propanol. Effects of casting conditions on the morphology and conductivity of the films were investigated. These films were fully characterized by UV- vis, NIR, IR, XRD, SEM and ESR. In the second type of conducting polymer system, PAMAM dendrimers generation 1 through 5 were peripherally modified with cationically substituted naphthalene diimide anion radicals. NMR, UV, IR, CV and Elemental Analysis were used to characterize modified dendrimers. Reduction with sodium dithionite in solution showed anion radicals were aggregated into ?-dimers and ?- stacks. Formamide was used to cast conducting dendrimer films. ESCA, SEM and optical microscope were used to study the composition and the morphology of the films. XRD showed complete amorphous nature of these films. NIR revealed that the ?-stack aggregation depend strongly on the casting temperature and the degree of reduction. Four- probe co-liner conductivity of the films is on the order of 10-2 to 10-1/ S/ cm-1. ESR and conductivity measurements also revealed the isotropic nature of the conductivity. Conductivity/humidity relationship was discovered by accidental breathing over the films. Using a home-made controlled humidity device and PACERTM hygrometer, the conductivity of the films can be varied quickly and reversibly within two orders of a magnitude. This phenomenon was probed with NIR, XRD and quartz crystal microbalance techniques. These studies suggest that the amorphous films absorb water from the air and at high humidity they are plasticized, allowing faster stack-to-stack electron hopping and increased conductivity. Films with conductivity as high as 18 S cm-1 can be achieved at 90% RH. These rare, n- type, air stable, free standing electric conducting films along with their fast and reversible nature of the conductivity/humidity response promises commercial applications.

  17. Electrical and thermal conductivity of low temperature CVD graphene: the effect of disorder

    SciTech Connect

    Lavrik, Nickolay V [ORNL; Datskos, Panos G [ORNL; Meyer III, Harry M [ORNL; Ivanov, Ilia N [ORNL; Fulvio, Pasquale F [ORNL; Dai, Sheng [ORNL; Chi, Miaofang [ORNL; Hensley, Dale K [ORNL; Vlassiouk, Ivan V [ORNL

    2011-01-01

    In this paper we present a study of graphene produced by chemical vapor deposition (CVD) under different conditions with the main emphasis on correlating the thermal and electrical properties with the degree of disorder. Graphene grown by CVD on Cu and Ni catalysts demonstrates the increasing extent of disorder at low deposition temperatures as revealed by the Raman peak ratio, I{sub G}/I{sub D}. We relate this ratio to the characteristic domain size, L{sub a}, and investigate the electrical and thermal conductivity of graphene as a function of L{sub a}. The electrical resistivity, {rho}, measured on graphene samples transferred onto SiO{sub 2}/Si substrates shows linear correlation with L{sub a}{sup -1}. The thermal conductivity, K, measured on the same graphene samples suspended on silicon pillars, on the other hand, appears to have a much weaker dependence on L{sub a}, close to K {approx} L{sub a}{sup 1/3}. It results in an apparent {rho} {approx} K{sup 3} correlation between them. Despite the progressively increasing structural disorder in graphene grown at lower temperatures, it shows remarkably high thermal conductivity (10{sup 2}-10{sup 3} W K{sup -1} m{sup -1}) and low electrical (10{sup 3}-3 x 10{sup 5} {Omega}) resistivities suitable for various applications.

  18. Toward a unified hydrous olivine electrical conductivity law

    NASA Astrophysics Data System (ADS)

    Gardés, Emmanuel; Gaillard, Fabrice; Tarits, Pascal

    2014-12-01

    has long been proposed that water incorporation in olivine has dramatic effects on the upper mantle properties, affecting large-scale geodynamics, and triggering high electrical conductivity. But the laboratory-based laws of olivine electrical conductivity predict contrasting effects of water, precluding the interpretation of geophysical data in term of mantle hydration. We review the experimental measurements of hydrous olivine conductivity and conclude that most of data are consistent when errors in samples water contents are considered. We report a new law calibrated on the largest database of measurements on hydrous olivine oriented single crystals and polycrystals. It fits most of measurements within uncertainties, and is compatible with most of geophysical data within petrological constraints on mantle olivine hydration. The conductivity anisotropy of hydrous olivine might be higher than dry olivine, but preferential orientation should produce moderate anisotropy (˜0-0.8 log unit). In the oceanic mantle, the enhancement of olivine conductivity is limited to ˜1 log unit in the maximum range of mantle olivine water concentrations (0-500 wt ppm). Strongest enhancements are expected in colder regions, like cratonic lithospheres and subduction settings. High conductivities in melt-free mantle require great depths and high water concentrations in olivine (>0.1 S/m at >250 km and >200 wt ppm). Thus, the hydration of olivine appears unlikely to produce the highest conductivities of the upper mantle.

  19. Proton conduction in water ices under an electric field.

    PubMed

    Cassone, Giuseppe; Giaquinta, Paolo V; Saija, Franz; Saitta, A Marco

    2014-04-24

    We report on a first-principles study of the effects produced by a static electric field on proton conduction in ordinary hexagonal ice (phase Ih) and in its proton-ordered counterpart (phase XI). We performed ab initio molecular dynamics simulations of both phases and investigated the effects produced by the field on the structure of the material, with particular attention paid to the phenomenon of proton transfer. We observed that in ice Ih molecules start to dissociate for field intensities around 0.25 V/Å, as in liquid water, whereas fields stronger than 0.36 V/Å are needed to induce a permanent proton flow. In contrast, in ice XI, electric fields as intense as 0.22 V/Å are already able to induce and sustain, through correlated proton jumps, an ionic current; this behavior suggests, somewhat counterintuitively, that the ordering of protons favors the autoprotolysis phenomenon. However, the same is not true for static conductivities. In fact, both crystalline phases show an ohmic behavior in the conduction regime, but the conductivity of ice Ih turns out to be larger than that of ice XI. We finally discuss the qualitative and quantitative importance of the conspicuous concentration of ionic defects generated by intense electric fields in determining the value of the conductivity, also through a comparison with the experimental data available for saline ices. PMID:24689531

  20. High Resolution Global Electrical Conductivity Variations in the Earth's Mantle

    NASA Astrophysics Data System (ADS)

    Kelbert, A.; Sun, J.; Egbert, G. D.

    2013-12-01

    Electrical conductivity of the Earth's mantle is a valuable constraint on the water content and melting processes. In Kelbert et al. (2009), we obtained the first global inverse model of electrical conductivity in the mantle capable of providing constraints on the lateral variations in mantle water content. However, in doing so we had to compromise on the problem complexity by using the historically very primitive ionospheric and magnetospheric source assumptions. In particular, possible model contamination by the auroral current systems had greatly restricted our use of available data. We have now addressed this problem by inverting for the external sources along with the electrical conductivity variations. In this study, we still focus primarily on long period data that are dominated by quasi-zonal source fields. The improved understanding of the ionospheric sources allows us to invert the magnetic fields directly, without a correction for the source and/or the use of transfer functions. It allows us to extend the period range of available data to 1.2 days - 102 days, achieving better sensitivity to the upper mantle and transition zone structures. Finally, once the source effects in the data are accounted for, a much larger subset of observatories may be used in the electrical conductivity inversion. Here, we use full magnetic fields at 207 geomagnetic observatories, which include mid-latitude, equatorial and high latitude data. Observatory hourly means from the years 1958-2010 are employed. The improved quality and spatial distribution of the data set, as well as the high resolution modeling and inversion using degree and order 40 spherical harmonics mapped to a 2x2 degree lateral grid, all contribute to the much improved resolution of our models, representing a conceptual step forward in global electromagnetic sounding. We present a fully three-dimensional, global electrical conductivity model of the Earth's mantle as inferred from ground geomagnetic observatory data, and use additional constraints to interpret these results in terms of mantle processes and compositional variations.

  1. Consequences of electrical conductivity in an orb spider's capture web.

    PubMed

    Vollrath, Fritz; Edmonds, Donald

    2013-12-01

    The glue-coated and wet capture spiral of the orb web of the garden cross spider Araneus diadematus is suspended between the dry silk radial and web frame threads. Here, we experimentally demonstrate that the capture spiral is electrically conductive because of necks of liquid connecting the droplets even if the thread is stretched. We examine how this conductivity of the capture spiral may lead to entrapment of charged airborne particles such as pollen, spray droplets and even insects. We further describe and model how the conducting spiral will also locally distort the Earth's ambient electric field. Finally, we examine the hypothesis that such distortion could be used by potential prey to detect the presence of a web but conclude that any effect would probably be too small to allow an insect to take evasive action. PMID:24323174

  2. Electrical conductivity and relaxation in mixed alkali tellurite glasses.

    PubMed

    Ghosh, S; Ghosh, A

    2007-05-14

    The authors have reported the electrical conductivity and the conductivity relaxation in mixed alkali tellurite glasses of compositions of 70TeO2-xNa2O-(30-x)Li2O in the frequency range from 10 Hz to 2 MHz and in the temperature range from room temperature to just below the glass transition temperature. They have analyzed the relaxation data in the framework of different models. They have observed the mixed alkali effect in the dc and ac conductivities, the crossover frequency, and the conductivity relaxation frequency as well as in their respective activation energies in these glasses. They have also observed the mixed alkali effect in the decoupling index. The scaling property of the modulus spectra of these mixed alkali glasses shows that the conductivity relaxation in the mixed alkali tellurite glasses is independent of temperature but depends on the glass compositions. PMID:17508813

  3. Electrical conductivity in two mixed-valence liquids.

    PubMed

    Yao, Wenzhi; Kelley, Steven P; Rogers, Robin D; Vaid, Thomas P

    2015-06-01

    Two different room-temperature liquid systems were investigated, both of which conduct a DC electrical current without decomposition or net chemical transformation. DC electrical conductivity is possible in both cases because of the presence of two different oxidation states of a redox-active species. One system is a 1?:?1 molar mixture of n-butylferrocene (BuFc) and its cation bis(trifluoromethane)sulfonimide salt, [BuFc(+)][NTf2(-)], while the other is a 1?:?1 molar mixture of TEMPO and its cation bis(trifluoromethane)sulfonimide salt, [TEMPO(+)][NTf2(-)]. The TEMPO-[TEMPO(+)][NTf2(-)] system is notable in that it is an electrically conducting liquid in which the conductivity originates from an organic molecule in two different oxidation states, with no metals present. Single-crystal X-ray diffraction of [TEMPO(+)][NTf2(-)] revealed a complex structure with structurally different cation-anion interactions for cis- and trans [NTf2(-)] conformers. The electron transfer self-exchange rate constant for BuFc/BuFc(+) in CD3CN was determined by (1)H NMR spectroscopy to be 5.4 × 10(6) M(-1) s(-1). The rate constant allowed calculation of an estimated electrical conductivity of 7.6 × 10(-5)?(-1) cm(-1) for BuFc-[BuFc(+)][NTf2(-)], twice the measured value of 3.8 × 10(-5)?(-1) cm(-1). Similarly, a previously reported self-exchange rate constant for TEMPO/TEMPO(+) in CH3CN led to an estimated conductivity of 1.3 × 10(-4)?(-1) cm(-1) for TEMPO-[TEMPO(+)][NTf2(-)], a factor of about 3 higher than the measured value of 4.3 × 10(-5)?(-1) cm(-1). PMID:25960288

  4. Rearrangement of 1D Conducting Nanomaterials towards Highly Electrically Conducting Nanocomposite Fibres for Electronic Textiles

    NASA Astrophysics Data System (ADS)

    Han, Joong Tark; Choi, Sua; Jang, Jeong In; Seol, Seung Kwon; Woo, Jong Seok; Jeong, Hee Jin; Jeong, Seung Yol; Baeg, Kang-Jun; Lee, Geon-Woong

    2015-03-01

    Nanocarbon-based conducting fibres have been produced using solution- or dry-spinning techniques. Highly conductive polymer-composite fibres containing large amounts of conducting nanomaterials have not been produced without dispersants, however, because of the severe aggregation of conducting materials in high-concentration colloidal solutions. Here we show that highly conductive (electrical conductivity ~1.5 × 105 S m-1) polymer-composite fibres containing carbon nanotubes and silver nanowires can be fabricated via a conventional solution-spinning process without any other treatment. Spinning dopes were fabricated by a simple mixing of a polyvinyl alcohol solution in dimethylsulfoxide with a paste of long multi-walled carbon nanotubes dispersed in organic solvents, assisted by quadruple hydrogen-bonding networks and an aqueous silver nanowire dispersion. The high electrical conductivity of the fibre was achieved by rearrangement of silver nanowires towards the fibre skin during coagulation because of the selective favourable interaction between the silver nanowires and coagulation solvents. The prepared conducting fibres provide applications in electronic textiles such as a textile interconnector of light emitting diodes, flexible textile heaters, and touch gloves for capacitive touch sensors.

  5. Synthesis of Conductive Nanofillers/Nanofibers and Electrical Properties of their Conductive Polymer Composites

    NASA Astrophysics Data System (ADS)

    Sarvi, Ali

    Thanks to their corrosion resistance, light weight, low cost, and ease of processing, electrically conducting polymer composites (CPCs) have received significant attention for the replacement of metals and inorganic materials for sensors, actuators, supercapacitors, and electromagnetic interference (EMI) shields. In this PhD thesis, high aspect ratio conductive nanofillers namely copper nanowires (CuNWs) and multiwall carbon nanotubes (MWCNTs) were coated with polyaniline (PANi) using solution mixing and in-situ polymerization method, respectively. Transmission electron microscopy (TEM) showed a smooth polyaniline nano-coating between 5--18 nm in thickness on the nanofillers' surface. The coating thickness and; consequently, electrical conductivity was controlled and tuned by polyaniline/aniline concentration in solution. Composites with tunable conductivity may be used as chemisensors, electronic pressure sensors and switches. Coated nanofillers demonstrated better dispersion in polystyrene (PS) and provided lower electrical percolation threshold. Dispersion of nanofillers in PS was investigated using rheological measurements and confirmed with electron micrographs and nano-scale images of CPCs. Polyaniline (PANi), when used as a coating layer, was able to attenuate electromagnetic (EM) waves via absorption and store electrical charges though pseudocapacitance mechanism. The dielectric measurements of MWCNT-PANi/PS composites showed one order of magnitude increase in real electrical permittivity compared to that of MWCNT/PS composites making them suitable for charge storage purposes. Incorporation of PANi also brought a new insight into conductive network formation mechanism in electrospun mats where the orientation of conductive high aspect ratio nanofillers is a major problem. Conductive nanofibers of poly(vinylidene fluoride) (PVDF) filled with coated multiwall carbon nanotubes (MWCNTs) were fabricated using electrospinning. These highly oriented PVDF nanofibers exhibited high beta (beta) crystal content and enhanced piezoelectricity. Moreover, multilayer electrospun nanofibers, in which MWCNTs were located at the shell layer, were fabricated for further decrease in electrical percolation threshold. In addition the PANi coated nanofillers, immiscible polymer blends (poly(methyl methacrylate) (PMMA) and styrene-acrylonitrile copolymer (SAN) blends) were employed to deliver lower percolation threshold via double percolation phenomenon. Conductivity measurements revealed a significant decrease in electrical percolation threshold (0.4 wt%) for PMMA70/SAN30 blends compared with MWCNT-filled SAN and PMMA (ca 0.8 wt%).

  6. Electrical stimulation to promote osteogenesis using conductive polypyrrole films.

    PubMed

    Hu, Wei-Wen; Hsu, Yi-Ting; Cheng, Yu-Che; Li, Chuan; Ruaan, Ruoh-Chyu; Chien, Chih-Cheng; Chung, Chih-Ang; Tsao, Chia-Wen

    2014-04-01

    In this study, we developed an electrical cell culture and monitoring device. Polypyrrole (PPy) films with different resistances were fabricated as conductive surfaces to investigate the effect of substrate-mediated electrical stimulation. The physical and chemical properties of the devices, as well as their biocompatibilities, were thoroughly evaluated. These PPy films had a dark but transparent appearance, on which the surface cells could be easily observed. After treating with the osteogenic medium, rat bone marrow stromal cells cultured on the PPy films differentiated into osteoblasts. The cells grown on the PPy films had up-regulated osteogenic markers, and an alkaline phosphatase activity assay showed that the PPy films accelerated cell differentiation. Alizarin red staining and calcium analysis suggested that the PPy films promoted osteogenesis. Finally, PPy films were subjected to a constant electric field to elucidate the effect of electrical stimulation on osteogenesis. Compared with the untreated group, electrical stimulation improved calcium deposition in the extracellular matrix. Furthermore, PPy films with lower resistances allowed larger currents to stimulate the surface cells, which resulted in higher levels of mineralization. Overall, these results indicated that this system exhibited superior electroactivity with controllable electrical resistance and that it can be coated directly to produce medical devices with a transparent appearance, which should be beneficial for research on electrical stimulation for tissue regeneration. PMID:24582219

  7. Electrical conductivity enhancement in heterogeneously doped scandia-stabilized zirconia

    NASA Astrophysics Data System (ADS)

    Varanasi, Chakrapani; Juneja, Chetan; Chen, Christina; Kumar, Binod

    Composites of 6 mol% scandia-stabilized zirconia materials (6ScSZ) and nanosize Al 2O 3 powder (0-30 wt.%) were prepared and characterized for electrical conductivity by the ac impedance method at various temperatures ranging from 300 to 950 °C. All the composites characterized showed improved conductivity at higher temperatures compared to the undoped ScSZ. An average conductivity of 0.12 S cm -1 was measured at 850 °C for 6ScSZ + 30 wt.% Al 2O 3 composite samples, an increase in conductivity up to 20% compared to the undoped 6ScSZ specimen at this temperature. Microstructural evaluation using scanning electron microscopy revealed that the ScSZ grain size was relatively unchanged up to 10 wt.% of Al 2O 3 additions. However, the grain size was reduced in samples with higher (20 and 30 wt.%) additions of Al 2O 3. Small grain size, reduced quantity of the 6ScSZ material (only 70%), and improved conductivity makes these ScSZ + 30 wt.% Al 2O 3 composites very attractive as electrolyte materials in view of their collective mechanical and electrical properties and cost requirements. The observed increase in conductivity values with the additions of an insulating Al 2O 3 phase is explained in light of the space charge regions at the 6ScSZ-Al 2O 3 grain boundaries.

  8. Spatial-decomposition analysis of electrical conductivity in ionic liquid.

    PubMed

    Tu, Kai-Min; Ishizuka, Ryosuke; Matubayasi, Nobuyuki

    2014-12-28

    The electrical conductivity of room temperature ionic liquid (IL) is investigated with molecular dynamics simulation. A trajectory of 1??s in total is analyzed for the ionic liquid [C4mim][NTf2] (1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and the anion is also called TFSI or TFSA), and the ion motions are examined in direct connection to the conductivity within the framework formulated previously [K.-M. Tu, R. Ishizuka, and N. Matubayasi, J. Chem. Phys. 141, 044126 (2014)]. As a transport coefficient, the computed electrical conductivity is in fair agreement with the experiment. The conductivity is then decomposed into the autocorrelation term of Nernst-Einstein form and the cross-correlation term describing the two-body motions of ions, and the cross-correlation term is further decomposed spatially to incorporate the structural insights on ion configurations into the dynamic picture. It is observed that the ion-pair contribution to the conductivity is not spatially localized and extends beyond the first coordination shell. The extent of localization of the cross-correlation effect in the conductivity is in correspondence to that of the spatial correlation represented by radial distribution function, which persists over nanometer scale. PMID:25554167

  9. Phase transformation, thermal expansion and electrical conductivity of lanthanum chromite

    SciTech Connect

    Gupta, Sapna; Mahapatra, Manoj K.; Singh, Prabhakar, E-mail: singh@engr.uconn.edu

    2013-09-01

    Graphical abstract: - Highlights: • Orthorhombic and rhombohedral phases co-exist at ?260 °C and cubic above 1000 °C. • Polymorphic changes with temperature in air and Ar–3%H{sub 2} are observed. • Lattice volume change in Ar–3%H{sub 2} atmosphere corresponds to Cr{sup 4+} ? Cr{sup 3+} transition. • Change in valence state of Cr{sup 4+} to Cr{sup 3+} results in lower electrical conductivity. • Experimental evidence is provided for poor densification of LaCrO{sub 3} in air. - Abstract: This paper addresses discrepancies pertaining to structural, thermal and electrical properties of lanthanum chromite. Experimental evidence is provided to support the hypothesis for poor densification in air as well as reduction in electrical conductivity in reducing atmosphere. Sintering condition for the synthesis of LaCrO{sub 3} was optimized to 1450 °C and 10 h. Thermo-analytical (differential scanning calorimetry – DSC) and high temperature X-ray diffraction (HT-XRD) studies show that orthorhombic lanthanum chromite transforms into rhombohedral structure at ?260 °C and cubic structure above 1000 °C. Co-existence of the structural phases and the variation in each polymorph with temperature in both air and 3%H{sub 2}–Ar atmosphere is reported. Presence and absence of Cr-rich phase at inter-particle neck are observed in oxidizing and reducing atmospheres respectively. The linear thermal expansion co-efficient was calculated to be 10.8 ± 0.2 × 10{sup ?6} °C{sup ?1} in the temperature range of RT–1400 °C. Electrical conductivity of lanthanum chromite was found to be 0.11 S/cm in air. A decrease in electrical conductivity (0.02 S/cm at 800 °C) of LaCrO{sub 3}, as observed in reducing atmosphere (3%H{sub 2}–Ar), corresponds to lattice volume change as indicated by peak shift in HT-XRD results.

  10. Investigation of Electrical Conduction in Vanadate Based Glasses

    NASA Astrophysics Data System (ADS)

    Barde, R. V.; Waghuley, S. A.

    The binary glassy systems 60V2O5-(40-x)P2O5 -xB2O3 were prepared by melt quenching technique. The mole of B2O3 was varies from 5 to 20 mol % with constant mol % of V2O5 during preparation of glass samples. The dc electrical conductivity of samples was measured in temperature range 303-473 K and found to be higher for sample 60 V2O5-20P2O5 -20B2O3. Using the Arrhenius equation of conductivity, the activation energy of conduction is estimated. The conduction in these glasses is takes place by phonon-assisted hopping between the localized states.

  11. Alterations of the apparent area expansivity modulus of red blood cell membrane by electric fields.

    PubMed Central

    Katnik, C; Waugh, R

    1990-01-01

    Red blood cell membrane exhibits a large resistance to changes in surface area. This resistance is characterized by the area expansivity modulus K, which relates the isotropic membrane force resultant, T, to the fractional change in membrane surface area delta A/Ao. The experimental technique commonly used to determine K is micropipette aspiration. Using this method, E. A. Evans and R. Waugh (1977, Biophys. J. 20:307-313) obtained a value of 450 dyn/cm for the modulus. In the present report, it is shown that the value of K, as determined using this method, is affected by electric potential differences applied across the tip of the pipette. Using Ag-AgCl electrodes and current clamping electronics, we obtained values for K ranging from 150 dyn/cm with -1.0 V applied, to 1,500 dyn/cm with 1.0 V applied. At 0.0 V the modulus obtained was approximately 500 dyn/cm. A reversible, voltage- and pressure-dependent change in the cell volume probably accounts for the effect of the voltage on the calculated value of the modulus. The use of lanthanum chloride or increasing the extra- and intracellular solute concentrations reduced the voltage dependence of the measurements. It was also found that when dissimilar metals were used to "ground" the pipette to the chamber to prevent lysis of cells by static charge, values for K ranged from 121 to 608 dyn/cm. Based on measurements made at zero applied volts, in the presence of 0.4 mM lanthanum and at high solute concentration, we conclude that the true value of the modulus is approximately 500 dyn/cm. PMID:2344470

  12. The Thermal Electrical Conductivity Probe (TECP) for Phoenix

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Hecht, Michael H.; Cobos, Doug R.; Campbell, Gaylon S.; Campbell, Colin S.; Cardell, Greg; Foote, Marc C.; Wood, Stephen E.; Mehta, Manish

    2009-01-01

    The Thermal and Electrical Conductivity Probe (TECP) is a component of the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) payload on the Phoenix Lander. TECP will measure the temperature, thermal conductivity and volumetric heat capacity of the regolith. It will also detect and quantify the population of mobile H2O molecules in the regolith, if any, throughout the polar summer, by measuring the electrical conductivity of the regolith, as well as the dielectric permittivity. In the vapor phase, TECP is capable of measuring the atmospheric H2O vapor abundance, as well as augment the wind velocity measurements from the meteorology instrumentation. TECP is mounted near the end of the 2.3 m Robotic Arm, and can be placed either in the regolith material or held aloft in the atmosphere. This paper describes the development and calibration of the TECP. In addition, substantial characterization of the instrument has been conducted to identify behavioral characteristics that might affect landed surface operations. The greatest potential issue identified in characterization tests is the extraordinary sensitivity of the TECP to placement. Small gaps alter the contact between the TECP and regolith, complicating data interpretation. Testing with the Phoenix Robotic Arm identified mitigation techniques that will be implemented during flight. A flight model of the instrument was also field tested in the Antarctic Dry Valleys during the 2007-2008 International Polar year. 2

  13. Single-photon heat conduction in electrical circuits

    E-print Network

    P. J. Jones; J. A. M. Huhtamäki; K. Y. Tan; M. Möttönen

    2011-07-14

    We study photonic heat conduction between two resistors coupled weakly to a single superconducting microwave cavity. At low enough temperature, the dominating part of the heat exchanged between the resistors is transmitted by single-photon excitations of the fundamental mode of the cavity. This manifestation of single-photon heat conduction should be experimentally observable with the current state of the art. Our scheme can possibly be utilized in remote interference-free temperature control of electric components and environment engineering for superconducting qubits coupled to cavities.

  14. Electrical conductivity of tissue at frequencies below 1 MHz

    NASA Astrophysics Data System (ADS)

    Gabriel, C.; Peyman, A.; Grant, E. H.

    2009-08-01

    A two-pronged approach, review and measurement, has been adopted to characterize the conductivity of tissues at frequencies below 1 MHz. The review covers data published in the last decade and earlier data not included in recent reviews. The measurements were carried out on pig tissue, in vivo, and pig body fluids in vitro. Conductivity data have been obtained for skeletal and myocardial muscle, liver, skull, fat, lung and body fluids (blood, bile, CSF and urine). A critical analysis of the data highlights their usefulness and limitations and enables suggestions to be made for measuring the electrical properties of tissues.

  15. Orbital dynamics of two electrically charged conducting spheres

    NASA Astrophysics Data System (ADS)

    Hoffmeister, Brent K.; Meyer, Deseree A.; Atkins, Brad M.; Franks, Gavin A.; Fuchs, Joshua T.; Li, Lulu; Sliger, Chase W.; Thompson, Jennifer E.

    2010-10-01

    The similar forms of Coulomb's law of electrostatics and Newton's law of gravitation suggest that two oppositely charged spheres can orbit each other by means of the electrostatic force. We demonstrate electrostatic binary orbits using two oppositely charged graphite coated Styrofoam® spheres. The experiment was conducted on the NASA aircraft Weightless Wonder which simulates weightless conditions. Videos of 23 orbital attempts were analyzed to investigate the dynamics and orbital stability of the two sphere system. The results support predictions of a recently developed theory that establishes criteria for stable orbits between two conducting, electrically charged spheres.

  16. Site-Dependent Evolution of Electrical Conductance from Tunneling to Atomic Point Contact

    NASA Astrophysics Data System (ADS)

    Kim, Howon; Hasegawa, Yukio

    2015-05-01

    Using scanning tunneling microscopy (STM), we investigated the evolution of electrical conductance between a Pb tip and Pb(111) surface from tunneling to atomic point contact at a site that was defined with atomic precision. We found that the conductance evolution depended on the contact site, for instance, on-top, bridge, or hollow (hcp and fcc) sites in the Pb lattice. In the transition from tunneling to contact regimes, the conductance measured at the on-top site was enhanced. In the point contact regime, the hollow sites had conductances larger than those of the other sites, and between the hollow sites, the hcp site had a conductance larger than that of the fcc site. We also observed the enhancement and reversal of the apparent height in atomically resolved high-current STM images, consistent with the results of the conductance traces. Our results indicate the importance of atomic configuration in the conductance of atomic junctions and suggest that attractive chemical interactions have a significant role in electron transport between contacting atoms.

  17. Site-Dependent Evolution of Electrical Conductance from Tunneling to Atomic Point Contact.

    PubMed

    Kim, Howon; Hasegawa, Yukio

    2015-05-22

    Using scanning tunneling microscopy (STM), we investigated the evolution of electrical conductance between a Pb tip and Pb(111) surface from tunneling to atomic point contact at a site that was defined with atomic precision. We found that the conductance evolution depended on the contact site, for instance, on-top, bridge, or hollow (hcp and fcc) sites in the Pb lattice. In the transition from tunneling to contact regimes, the conductance measured at the on-top site was enhanced. In the point contact regime, the hollow sites had conductances larger than those of the other sites, and between the hollow sites, the hcp site had a conductance larger than that of the fcc site. We also observed the enhancement and reversal of the apparent height in atomically resolved high-current STM images, consistent with the results of the conductance traces. Our results indicate the importance of atomic configuration in the conductance of atomic junctions and suggest that attractive chemical interactions have a significant role in electron transport between contacting atoms. PMID:26047248

  18. Nonideal ultrathin mantle cloak for electrically large conducting cylinders.

    PubMed

    Liu, Shuo; Zhang, Hao Chi; Xu, He-Xiu; Cui, Tie Jun

    2014-09-01

    Based on the concept of the scattering cancellation technique, we propose a nonideal ultrathin mantle cloak that can efficiently suppress the total scattering cross sections of an electrically large conducting cylinder (over one free-space wavelength). The cloaking mechanism is investigated in depth based on the Mie scattering theory and is simultaneously interpreted from the perspective of far-field bistatic scattering and near-field distributions. We remark that, unlike the perfect transformation-optics-based cloak, this nonideal cloaking technique is mainly designed to minimize simultaneously several scattering multipoles of a relatively large geometry around considerably broad bandwidth. Numerical simulations and experimental results show that the antiscattering ability of the metasurface gives rise to excellent total scattering reduction of the electrically large cylinder and remarkable electric-field restoration around the cloak. The outstanding cloaking performance together with the good features of and ultralow profile, flexibility, and easy fabrication predict promising applications in the microwave frequencies. PMID:25401449

  19. Grain size-dependent electrical conductivity of polycrystalline cerium oxide

    Microsoft Academic Search

    A. Tschöpe; E. Sommer; R. Birringer

    2001-01-01

    The electrical conductivity of polycrystalline cerium oxide was investigated in the nanometer and micrometer size range. Nanocrystalline samples of different grain size were prepared by uniaxial hot-pressing of nanocrystalline powder at various temperatures and pressures. Additional annealing at high temperatures was employed in order to obtain microcrystalline samples. An equivalent-circuit analysis of ac-impedance spectra based on the brick-layer model was

  20. Electrical conductivity for warm, dense aluminum plasmas and liquids.

    PubMed

    Desjarlais, M P; Kress, J D; Collins, L A

    2002-08-01

    The electrical conductivity of warm, dense aluminum plasmas and liquids is calculated using ab initio molecular dynamics and the Kubo-Greenwood formula. The density range extends from near solid to one-hundredth of solid density, and the temperature range extends from 6000 K to 30 000 K. This density and temperature range allows direct comparison with experimental results obtained with the tamped exploding wire technique. PMID:12241227

  1. Electrically Conductive Chitosan/Carbon Scaffolds for Cardiac Tissue Engineering

    PubMed Central

    2015-01-01

    In this work, carbon nanofibers were used as doping material to develop a highly conductive chitosan-based composite. Scaffolds based on chitosan only and chitosan/carbon composites were prepared by precipitation. Carbon nanofibers were homogeneously dispersed throughout the chitosan matrix, and the composite scaffold was highly porous with fully interconnected pores. Chitosan/carbon scaffolds had an elastic modulus of 28.1 ± 3.3 KPa, similar to that measured for rat myocardium, and excellent electrical properties, with a conductivity of 0.25 ± 0.09 S/m. The scaffolds were seeded with neonatal rat heart cells and cultured for up to 14 days, without electrical stimulation. After 14 days of culture, the scaffold pores throughout the construct volume were filled with cells. The metabolic activity of cells in chitosan/carbon constructs was significantly higher as compared to cells in chitosan scaffolds. The incorporation of carbon nanofibers also led to increased expression of cardiac-specific genes involved in muscle contraction and electrical coupling. This study demonstrates that the incorporation of carbon nanofibers into porous chitosan scaffolds improved the properties of cardiac tissue constructs, presumably through enhanced transmission of electrical signals between the cells. PMID:24417502

  2. Effect of water on the electrical conductivity of lower crustal clinopyroxene

    Microsoft Academic Search

    Xiaozhi Yang; Hans Keppler; Catherine McCammon; Huaiwei Ni; Qunke Xia; Qicheng Fan

    2011-01-01

    Electrical conductivity measurement of lower crustal clinopyroxeneH largely enhances the electrical conductivity of lower crustal clinopyroxeneLower crustal high conductivity may be caused by the main assemblages themselves

  3. Electrical conductivity of p-type BiOCl nanosheets.

    PubMed

    Myung, Yoon; Wu, Fei; Banerjee, Sriya; Park, Jeunghee; Banerjee, Parag

    2015-02-14

    High quality BiOCl nanosheets were fabricated using facile, room temperature hydrolysis of Bi(NO3)3 and HCl. The resulting nanosheets had dimensions of 500 nm with the exposed {001} facet. The band gap of the nanosheets was found to be 3.34 eV with conduction and valence band edges at -3.63 eV and -6.97 eV with respect to vacuum, respectively. The electrical conductivity of drop-cast BiOCl nanosheets was measured between aluminum patterned electrodes as a function of temperature and oxygen partial pressure (pO2). The activation energy for conduction in BiOCl was found to be 862 meV in the temperature range of 300-425 K and below 1000 mbar. The electrical conductivity varied with pO2, indicating ? ? pO2(1/4.05) and ? ? pO2(1/32) for low and sub atmospheric pressures, respectively. A prototypical device for low temperature (425 K) O2 sensing was demonstrated. PMID:25573144

  4. Electrical Conductivity Measurement and Anisotropy of Mylonite and Cataclasite

    NASA Astrophysics Data System (ADS)

    Omura, K.

    2001-12-01

    Resent studies of electromagnetic survey reveal the electrical conductivity structure at the deeper part of faults. There seems to be high conductivity region around the focal areas. The high conductivity may be related to the existence of water in rocks, which affect the strength and activity of faults, i.e., earthquake. Investigations on the electrical conductivity structure suggest important clues on the mechanism and conditions of earthquake occurrence. Rocks at the focal zone of a fault are expected to suffer from hard deformation and/or fracturing with alteration. Rocks have characteristic fabrics. They are called fault-related rocks, such as mylonite and cataclasite. We collected mylonite and cataclasite samples from the Hatagawa fracture zone in northeast Japan. The Hatagawa fracture zone is regarded as a major exhumed fault. We can observe the mylonite and cataclasite at a surface now that were produced from granitic rocks at the focal depth region in the past. We conducted measurements of electrical conductivities of the fault-related rocks at ambient condition, as a first step. We connected a frequency response analyzer and a potentiostat to measure AC impedance spectra. The combination of the two instruments performs sine wave correlation between signals passing trough a sample and a reference resistance. In addition, the potentiostat can measure a micro current. As a result, the measurement system is basically resistant to an electrical noise around the sample under severe condition and is able to measure up to 109 ? . We observed clearly foliations and lineations in mylonite samples. We cut each mylonite sample into three cylindrical chips parallel to three directions: parallel to both the foliation and the lineation (x-axis), parallel to the foliation and perpendicular to the lineation (y-axis), perpendicular to the foliation (z-axis). We did not observe any planar or linear fabric on the cataclasite samples. Porosities of the samples were less than 1 %. The conductivities at 1 Hz of samples under dry condition (samples are heated at 120 degree C for 6 hours) are about 10-8 1/? m and have little difference among samples. Under wet condition at the same frequency (samples were forcibly saturated by distilled water in a vacuum chamber), conductivities of all samples increased by more than one order of magnitude, but conductivities along three direction of mylonite are significantly different. The conductivity along x-axis and y -axis was higher by about one order and several times, respectively, than that along z-axis. This result suggests the distribution and connectivity of cracks in mylonite are anisotropic and more conductive water than rock matrix connected along x-axis. At focal deep region along a fault, cracks must be compacted, but, if thin sheets of water are distributed anisotropically in mylonite zone, some anisotropic conductivity structure may be detected.

  5. Flake Electrical Conductivity of Few-Layer Graphene

    PubMed Central

    2014-01-01

    The Kubo formula for the electrical conductivity of per stratum of few-layer graphene, up to five, is analytically calculated in both simple and Bernal structures within the tight-binding Hamiltonian model and Green's function technique, compared with the single-layer one. The results show that, by increasing the layers of the graphene as well as the interlayer hopping of the nonhybridized pz orbitals, this conductivity decreases. Although the change in its magnitude varies less as the layer number increases to beyond two,distinguishably, at low temperatures, it exhibits a small deviation from linear behavior. Moreover, the simple bilayer graphene represents more conductivity with respect to the Bernal case. PMID:24550711

  6. Flake electrical conductivity of few-layer graphene.

    PubMed

    Mousavi, Hamze; Khodadadi, Jabbar

    2014-01-01

    The Kubo formula for the electrical conductivity of per stratum of few-layer graphene, up to five, is analytically calculated in both simple and Bernal structures within the tight-binding Hamiltonian model and Green's function technique, compared with the single-layer one. The results show that, by increasing the layers of the graphene as well as the interlayer hopping of the nonhybridized p z orbitals, this conductivity decreases. Although the change in its magnitude varies less as the layer number increases to beyond two,distinguishably, at low temperatures, it exhibits a small deviation from linear behavior. Moreover, the simple bilayer graphene represents more conductivity with respect to the Bernal case. PMID:24550711

  7. Peroneal nerve conduction velocity after chronic electrical stimulation.

    PubMed

    Waters, R L; McNeal, D R; Tasto, J

    1975-06-01

    The effects of electric stimulation on nerve conduction velocity of the peroneal nerve via surgically implanted electrodes was evaluated in a group of nine hemiplegic patients. After a mean duration of 25 months nerve conduction velocity averaged 47.3 meters/sec in the uninvolved and 46.1 meters/sec in the stimulated (paretic) extremity. In a control group of ten hemiplegic subjects who did not receive stimulation, nerve conduction velocity averaged 43.1 meters/sec in the hemiplegic leg, and 41.3 meters/sec in the uninvolved leg. These differences were not statistically significant. Maximum dorsiflexion strength was increased in all patients following chronic stimulation. PMID:1079718

  8. Electrical probing of the spin conductance of mesoscopic cavities.

    PubMed

    Adagideli, I; Bardarson, J H; Jacquod, Ph

    2009-04-15

    We investigate spin-dependent transport in multiterminal mesoscopic cavities with spin-orbit coupling. Focusing on a three-terminal set-up we show how injecting a pure spin current or a polarized current from one terminal generates additional charge current and/or voltage across the two output terminals. When the injected current is a pure spin current, a single measurement allows us to extract the spin conductance of the cavity. The situation is more complicated for a polarized injected current, and we show in this case how two purely electrical measurements on the output currents give the amount of current that is solely due to spin-orbit interaction. This allows us to extract the spin conductance of the device in this case as well. We use random matrix theory to show that the spin conductance of chaotic ballistic cavities fluctuates universally about zero mesoscopic average and describe experimental implementations of mesoscopic spin to charge current converters. PMID:21825368

  9. Using High Resolution Complex Electrical Conductivity Measurements of Heterogeneous Rocks

    NASA Astrophysics Data System (ADS)

    Boitnott, G. N.; Bussod, G. Y.

    2009-12-01

    The complex electrical resistivity of a slab of Berea sandstone was measured using a four electrode probe in the frequency range of 1 Hz to 1 kHz. The measurements where made in the context of the development of a new high resolution methodology for the laboratory characterization of hydro-geophysical properties on core and field samples. Electrical conductivity maps with millimeter-scale resolution and measured at different pore fluid salinities are used to constrain dual conduction models (e.g. Waxman-Smits, 1968) that allow us to separate the contribution of electrical conduction through the pore fluid from surface conduction along mineral grain surfaces. Measured resistivity variations are observed to be structured in distinct layers at the scale of millimeters to centimeters and are well correlated with fine scale layering observed in thin section. The data is analyzed in conjunction with petrophysical maps of permeability and velocity variations. The maps of permeability, resistivity, and velocity all indicate that Berea sandstone contains measurable structural anisotropy at a variety of scales. The heterogeneities in petrophysical properties are in general rather weak, with permeability varying by a factor of 3 and velocity and resistivity varying by 7% and 19% respectively. Analyzed collectively, the data provides insights into the physical causes of the observed resistivity anomalies and allows us to interpret them as due to localized pore-scale variations in grain size, pore structure, and mineralogy. Correlations among these petrographic variables lead to the discovery that surface conductivity of the rock is negatively correlated with the conductivity due to the free electrolyte. Using this integrated petrophysical data-set, we build a predictive model of the meter-scale petrophysical properties that honors the intrinsic heterogeneity of the sample. The data and models are used as the foundation for a physically-based upscaling approach for understanding how petrophysical properties relate to flow and transport processes at scales difficult to measure in the laboratory. Through application of effective media and numerical models we show that the observed small-scale heterogeneity leads to anisotropy in electrical properties that correlates with anisotropy in relative permeability. The anisotropy is found to be a complex function of scale, salinity, and saturation.

  10. Assessment of cytoplasm conductivity by nanosecond pulsed electric fields.

    PubMed

    Denzi, Agnese; Merla, Caterina; Palego, Cristiano; Paffi, Alessandra; Ning, Yaqing; Multari, Caroline R; Cheng, Xuanhong; Apollonio, Francesca; Hwang, James C M; Liberti, Micaela

    2015-06-01

    The aim of this paper is to propose a new method for the better assessment of cytoplasm conductivity, which is critical to the development of electroporation protocols as well as insight into fundamental mechanisms underlying electroporation. For this goal, we propose to use nanosecond electrical pulses to bypass the complication of membrane polarization and a single cell to avoid the complication of the application of the "mixing formulas." Further, by suspending the cell in a low-conductivity medium, it is possible to force most of the sensing current through the cytoplasm for a more direct assessment of its conductivity. For proof of principle, the proposed technique was successfully demonstrated on a Jurkat cell by comparing the measured and modeled currents. The cytoplasm conductivity was best assessed at 0.32 S/m and it is in line with the literature. The cytoplasm conductivity plays a key role in the understanding of the basis mechanism of the electroporation phenomenon, and in particular, a large error in the cytoplasm conductivity determination could result in a correspondingly large error in predicting electroporation. Methods for a good estimation of such parameter become fundamental. PMID:25667343

  11. Dispersions of multiwalled carbon nanotubes in different nematic mesogens: The study of optical transmittance and electrical conductivity

    NASA Astrophysics Data System (ADS)

    Lisetski, L. N.; Minenko, S. S.; Fedoryako, A. P.; Lebovka, N. I.

    2009-01-01

    Optical transmittance and electric conductivity were studied for dispersions of multiwall carbon nanotubes (MWCNTs) in nematic liquid crystals of four different chemical classes (cyanobiphenyls, Schiff bases, azoxy compounds, and cyclohexanecarboxylic acids). The optical transmittance data showed deep integration of MWCNTs into the orientationally ordered nematic structure. The effect observed was apparently related to interactions between the MWCNTs and mesogen matrix, which appeared to be weaker when the nematic host was formed by non-aromatic molecules. Dependences of the electrical conductivity versus applied DC voltage were noticeably different for different nematic matrices. Voltage amplification of electrical conductivity was observed at relatively higher voltages (above 10 V). The increased threshold voltages for electrohydrodynamical instability in nematics were observed in MWCNT-doped dispersions.

  12. Miniatuization of the flowing fluid electric conductivity loggingtec hnique

    SciTech Connect

    Su, Grace W.; Quinn, Nigel W.T.; Cook, Paul J.; Shipp, William

    2005-10-19

    An understanding of both the hydraulic properties of the aquifer and the depth distribution of salts is critical for evaluating the potential of groundwater for conjunctive water use and for maintaining suitable groundwater quality in agricultural regions where groundwater is used extensively for irrigation and drinking water. The electrical conductivity profiles recorded in a well using the flowing fluid electric conductivity logging (FEC logging) method can be analyzed to estimate interval specific hydraulic conductivity and estimates of the salinity concentration with depth. However, irrigation wells that are common in agricultural regions have limited access into them because these wells are still in operation, and the traditional equipment used for FEC logging cannot fit through the small access pipe intersecting the well. A modified, miniaturized FEC logging technique was developed such that this logging method could be used in wells with limited access. In addition, a new method for injecting water over the entire screened interval of the well was developed to reduce the time required to perform FEC logging. Results of FEC logging using the new methodology and miniaturized system in two irrigation wells are also summarized.

  13. Improving the Electrical Conductivity of Polyaniline Through Molecular Control

    NASA Astrophysics Data System (ADS)

    Yoo, Joung Eun; Krekelberg, William; Bucholz, Tracy; Truskett, Thomas; Loo, Yueh-Lin

    2009-03-01

    We have investigated the electrical conductivity of polyaniline (PANI) that is template synthesized with a polymer acid of poly(2-acrylamido-2-methyl-1-propanesulfonic acid), PAAMPSA. The conductivity of PANI-PAAMPSA is determined by the particle density when PANI-PAAMPSA is cast as films. The PANI-PAAMPSA particle density can in turn be tuned by manipulating the molecular characteristics of PAAMPSA. Specifically, templating aniline polymerization with a higher molecular weight PAAMPSA results in bigger PANI-PAAMPSA particles; templating aniline polymerization with a broader molecular weight distribution PAAMPSA results in particles with a larger size distribution. The conductivity of drop-cast films of PANI-PAAMPSA therefore depends on how the particles pack in the solid state. In particular, we find the conductivity of PANI-PAAMPSA to increase with particle density. Additionally, PANI is preferentially segregated to the surface of these particles. The conductivity of PANI-PAAMPSA thus scales superlinearly with the surface area per unit volume of the cast film.

  14. Electrical Conductivity of Al3+-doped MgO

    NASA Astrophysics Data System (ADS)

    Watson, H. C.; van Orman, J. A.; Crispin, K. L.; Roberts, J. J.

    2010-12-01

    Periclase is thought to comprise about 15-20% of the lower mantle, making it the second most abundant phase present after magnesium silicate perovskite. Because cation diffusivity in periclase is relatively rapid compared to magnesium silicate perovskite, it may control bulk transport processes in the lower mantle. It is expected that trivalent cations such as Fe3+ and Al3+ are dissolved in lower mantle periclase at up to wt % levels. The addition of trivalent atoms such as Al3+ to pure MgO results in a charge imbalance that results in associated Mg-vacancies. It has recently been shown that these cation vacancies can form bound pairs with Al3+ in periclase, and these pairs strongly influence diffusive behavior of both Al and Mg in Al3+-doped periclase (Van Orman et al 2009). The concentration of trivalent atoms in periclase has been also shown to be strongly correlated with ionic conductivity in MgO (eg. Sempolinski and Kingery 1980). We have directly measured the electrical conductivity of pure MgO single crystals and single crystals of MgO doped with varying concentrations of Al3+ in air at atmospheric pressure. The temperatures of the experiments range from 850oC to 1400o C, and several heating and cooling cycles were performed on each sample. We find that the addition of ~0.5wt% - 1wt% Al3+ in MgO results in an a substantial increase in electrical conductivity of over an order of magnitude. We present these results in the context of model conductivities that have been calculated on the basis of our current understanding of Al3+ - vacancy bound pairs and ionic diffusion in trivalent-doped MgO. Finally, implications of these results to electrical conductivity and transport processes in the Earth’s lower mantle will be discussed. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 Van Orman, J.A., Li, C., Crispin, K.L., 2009. Aluminum diffusion and Al-vacancy association in periclase. Phys. Earth Planet. Int. 172, 34-42. Sempolinski, D.R., Kingery, W.D., 1980. Ionic conductivity and magnesium vacancy mobility in magnesium oxide. J. Am. Ceram. Soc. 63, 664-669.

  15. Transparent electrical conducting films by activated reactive evaporation

    DOEpatents

    Bunshah, R.; Nath, P.

    1982-06-22

    Process and apparatus for producing transparent electrical conducting thin films by activated reactive evaporation is disclosed. Thin films of low melting point metals and alloys, such as indium oxide and indium oxide doped with tin, are produced by physical vapor deposition. The metal or alloy is vaporized by electrical resistance heating in a vacuum chamber, oxygen and an inert gas such as argon are introduced into the chamber, and vapor and gas are ionized by a beam of low energy electrons in a reaction zone between the resistance heater and the substrate. There is a reaction between the ionized oxygen and the metal vapor resulting in the metal oxide which deposits on the substrate as a thin film which is ready for use without requiring post deposition heat treatment. 1 fig.

  16. Transparent electrical conducting films by activated reactive evaporation

    DOEpatents

    Bunshah, Rointan (Los Angeles, CA); Nath, Prem (Troy, MI)

    1982-01-01

    Process and apparatus for producing transparent electrical conducting thin films by activated reactive evaporation. Thin films of low melting point metals and alloys, such as indium oxide and indium oxide doped with tin, are produced by physical vapor deposition. The metal or alloy is vaporized by electrical resistance heating in a vacuum chamber, oxygen and an inert gas such as argon are introduced into the chamber, and vapor and gas are ionized by a beam of low energy electrons in a reaction zone between the resistance heater and the substrate. There is a reaction between the ionized oxygen and the metal vapor resulting in the metal oxide which deposits on the substrate as a thin film which is ready for use without requiring post deposition heat treatment.

  17. Preparation of Electrically Conductive Au Thin Films by Colloid Sedimentation.

    PubMed

    Petek, Urša; Bukovec, Peter; Kozjek Škofic, Irena

    2015-01-01

    A novel and facile wet-chemical method for the preparation of Au thin films is presented. These Au thin films were deposited on glass substrates by the gravitational sedimentation of Au colloids. The colloids were formed by chemical reduction in ethanol using HAuCl4 and NaBH4 with no added surfactants. Without stabilizing agents the colloids quickly aggregated, settled to the bottom and formed a thin film. The sedimentation of the colloids was monitored using UV-vis spectroscopy. Thin films with Au loads ranging between 0.25 and 4.0 g m-2 were prepared and characterized by means of UV-vis spectroscopy, electrical resistance measurements, optical microscopy, scanning electron microscopy, and cyclic voltammetry. The results showed that nanostructured Au films with a very high specific surface area were formed. The films were electrically conductive and partially transparent to visible light. PMID:26085408

  18. Electrical Conductivity Imaging Using Controlled Source Electromagnetics for Subsurface Characterization

    NASA Astrophysics Data System (ADS)

    Miller, C. R.; Routh, P. S.; Donaldson, P. R.

    2004-05-01

    Controlled Source Audio-Frequency Magnetotellurics (CSAMT) is a frequency domain electromagnetic (EM) sounding technique. CSAMT typically uses a grounded horizontal electric dipole approximately one to two kilometers in length as a source. Measurements of electric and magnetic field components are made at stations located ideally at least four skin depths away from the transmitter to approximate plane wave characteristics of the source. Data are acquired in a broad band frequency range that is sampled logarithmically from 0.1 Hz to 10 kHz. The usefulness of CSAMT soundings is to detect and map resistivity contrasts in the top two to three km of the Earth's surface. Some practical applications that CSAMT soundings have been used for include mapping ground water resources; mineral/precious metals exploration; geothermal reservoir mapping and monitoring; petroleum exploration; and geotechnical investigations. Higher frequency data can be used to image shallow features and lower frequency data are sensitive to deeper structures. We have a 3D CSAMT data set consisting of phase and amplitude measurements of the Ex and Hy components of the electric and magnetic fields respectively. The survey area is approximately 3 X 5 km. Receiver stations are situated 50 meters apart along a total of 13 lines with 8 lines bearing approximately N60E and the remainder of the lines oriented orthogonal to these 8 lines. We use an unconstrained Gauss-Newton method with positivity to invert the data. Inversion results will consist of conductivity versus depth profiles beneath each receiver station. These 1D profiles will be combined into a 3D subsurface conductivity image. We will include our interpretation of the subsurface conductivity structure and quantify the uncertainties associated with this interpretation.

  19. Electrical conductivity of dispersions: from dry foams to dilute suspensions

    E-print Network

    K. Feitosa; S. Marze; A. Saint-Jalmes; D. J. Durian

    2005-07-18

    We present new data for the electrical conductivity of foams in which the liquid fraction ranges from two to eighty percent. We compare with a comprehensive collection of prior data, and we model all results with simple empirical formul\\ae. We achieve a unified description that applies equally to dry foams and emulsions, where the droplets are highly compressed, as well as to dilute suspensions of spherical particles, where the particle separation is large. In the former limit, Lemlich's result is recovered; in the latter limit, Maxwell's result is recovered.

  20. Electrically Conductive Thick Film Made from Silver Alkylcarbamates

    Microsoft Academic Search

    Jianguo Liu; Xiangyou Li; Xiaoye Wang; Xiaoyan Zeng

    2010-01-01

    A homogeneous electrically conductive silver paste without solid or particle phase was developed using silver alkylcarbamates\\u000a [(C\\u000a n\\u000a H2n?1NHCOO)2Ag, n ? 4] as the precursor of the functional phase. The silver alkylcarbamates were light insensitive and had a low decomposition\\u000a temperature (below 200°C). The paste was a non-Newtonian fluid with viscosity significantly depending on the content of the\\u000a thickening agent ethyl cellulose.

  1. Estimation of electrical conductivity of a layered spherical head model using electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Fernández-Corazza, M.; von-Ellenrieder, N.; Muravchik, C. H.

    2011-12-01

    Electrical Impedance Tomography (EIT) is a non-invasive method that aims to create an electrical conductivity map of a volume. In particular, it can be applied to study the human head. The method consists on the injection of an unperceptive and known current through two electrodes attached to the scalp, and the measurement of the resulting electric potential distribution at an array of sensors also placed on the scalp. In this work, we propose a parametric estimation of the brain, scalp and skull conductivities using EIT over an spherical model of the head. The forward problem involves the computation of the electric potential on the surface, for given the conductivities and the injection electrode positions, while the inverse problem consists on estimating the conductivities given the sensor measurements. In this study, the analytical solution to the forward problem based on a three layer spherical model is first described. Then, some measurements are simulated adding white noise to the solutions and the inverse problem is solved in order to estimate the brain, skull and scalp conductivity relations. This is done with a least squares approach and the Nelder-Mead multidimensional unconstrained nonlinear minimization method.

  2. Electrical conductivity of noble gases at high pressures

    SciTech Connect

    Adams, J. R.; Reinholz, H.; Redmer, R.; Mintsev, V. B.; Shilkin, N. S.; Gryaznov, V. K. [Institut fuer Physik, Universitaet Rostock, D-18051 Rostock (Germany) and School of Physics, University of Western Australia, Crawley WA 6009 (Australia); Institut fuer Physik, Universitaet Rostock, D-18051 Rostock (Germany); Institute of Problems of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region (Russian Federation)

    2007-09-15

    Theoretical results for the electrical conductivity of noble gas plasmas are presented in comparison with experiment. The composition is determined within a partially ionized plasma model. The conductivity is then calculated using linear response theory, in which the relevant scattering mechanisms of electrons from ions, electrons, and neutral species are taken into account. In particular, the Ramsauer-Townsend effect in electron-neutral scattering is discussed and the importance of a correct description of the Coulomb logarithm in electron scattering by charged particles is shown. A detailed comparison with recent experiments on argon and xenon plasmas is given and results for helium and neon are also revisited. Excellent agreement between theory and experiment is observed, showing considerable improvement upon previous calculations.

  3. Electrically conductive PEDOT coating with self-healing superhydrophobicity.

    PubMed

    Zhu, Dandan; Lu, Xuemin; Lu, Qinghua

    2014-04-29

    A self-healing electrically conductive superhydrophobic poly(3,4-ethylenedioxythiophene) (PEDOT) coating has been prepared by chemical vapor deposition of a fluoroalkylsilane (POTS) onto a PEDOT film, which was obtained by electrochemical deposition. The coating not only maintained high conductivity with a low resistivity of 3.2 × 10(-4) ?·m, but also displayed a water contact angle larger than 156° and a sliding angle smaller than 10°. After being etched with O2 plasma, the coating showed an excellent self-healing ability, spontaneously regaining its superhydrophobicity when left under ambient conditions for 20 h. This superhydrophobicity recovery process was found to be humidity-dependent, and could be accelerated and completed within 2 h under a high humidity of 84%. The coating also exhibited good superhydrophobicity recovering ability after being corroded by strong acid solution at pH 1 or strong base solution at pH 14 for 3 h. PMID:24702588

  4. Electrical conductivity and dielectric behavior in sodium zinc divanadates

    NASA Astrophysics Data System (ADS)

    Sallemi, F.; Louati, B.; Guidara, K.

    2014-11-01

    The Na2ZnV2O7 compound was obtained by the conventional solid-state reaction. The sample was characterized by X-ray powder diffraction, Raman and impedance spectroscopy. The ac electrical conductivity and dielectric properties have been investigated in the frequency and temperature range of 200 Hz-1 MHz and 513 K-729 K, respectively. The direct current conductivity process is thermally activated. The frequency dependence of the conductivity is interpreted using the power law. The close values of activation energies obtained from the analysis of hopping frequency and dc conductivity implies that the transport is due to Na+ cation displacement parallel to (0 0 1) plane located between ZnO4 and VO4 tetrahedra. The evolution of the complex permittivity as a function of angular frequency was investigated. Several important parameters such as charge carrier concentration, ionic mobility and diffusion coefficient were determined. Thermodynamic parameters such as the free energy of activation ?F, the enthalpy ?H, and the change in entropy ?S have been calculated.

  5. Electric pulp tester conductance through various interface media.

    PubMed

    Mickel, André K; Lindquist, Kimberly A D; Chogle, Sami; Jones, Jefferson J; Curd, Francis

    2006-12-01

    A conducting media is necessary when using an electric pulp tester (EPT). The objective of this study was to observe differences in conductance through various media. We hypothesized that variations in current conductance through different media exist. The pulp chamber of a freshly extracted premolar was exposed, and the cathode of a voltmeter was inserted into the pulpal tissue. The anode was coupled to the EPT handpiece. The measurement taken during dry (no interface media) EPT tip-to-tooth contact was 0 V, which served as negative control. EPT tip directly touching the cathode measured 3.9V and served as positive control. A number of media readily available in the dental office were tested. Data was analyzed using single factor ANOVA. Listerine (3.3) conducted the most voltage (p<0.5). Of nonliquids, K-Y Brand UltraGel and Crest Baking Soda & Peroxide Whitening Tartar Control toothpaste recorded significantly (p<0.05) higher voltage readings (1.4 V). PMID:17174677

  6. Mantle electrical conductivity profile of Niger delta region

    NASA Astrophysics Data System (ADS)

    Obiora, Daniel N.; Okeke, Francisca N.; Yumoto, K.; Agha, Stan O.

    2014-06-01

    The mantle electrical conductivity-depth profile of the Niger delta region in Nigeria has been determined using solar quiet day ionospheric current (Sq). The magnetometer data obtained in 2010 from geomagnetic stations installed in Lagos by magnetic dataset (MAGDAS) in 2008 and data from magnetometers installed in some parts of Niger delta by Center for Basic Space Science, University of Nigeria, Nsukka, were employed in this study. Gauss spherical harmonic analysis (SHA) method was used to separate the internal and external field contributions to Sq current system. The result depicted that the conductivity profile rose steadily from about 0.032 S/m at a depth of 89 km to 0.041 S/m at 100 km and 0.09 S/m at 221 km. This high conductivity region agreed with the global seismic low velocity region, the asthenosphere. The conductivity profile continued increasing downward until it got to 0.157 S/m at a depth of about 373 km (close to the base of upper mantle), 0.201 S/m at 784 km and reached 0.243 S/m at a depth of 1179 km at the lower mantle.

  7. DNA-templated nanowires: morphology and electrical conductivity

    NASA Astrophysics Data System (ADS)

    Watson, Scott M. D.; Pike, Andrew R.; Pate, Jonathan; Houlton, Andrew; Horrocks, Benjamin R.

    2014-03-01

    DNA-templating has been used to create nanowires from metals, compound semiconductors and conductive polymers. The mechanism of growth involves nucleation at binding sites on the DNA followed by growth of spherical particles and then, under favourable conditions, a slow transformation to a smooth nanowire. The final transformation is favoured by restricting the amount of templated material per unit length of template and occurs most readily for materials of low surface tension. Electrical measurements on DNA-templated nanowires can be facilitated using three techniques: (i) standard current-voltage measurements with contact electrodes embedded in a dielectric so that there is a minimal step height at the dielectric/electrode boundary across which nanowires may be aligned by molecular combing, (ii) the use of a dried droplet technique and conductive AFM to determine contact resistance by moving the tip along the length of an individual nanowire and (iii) non-contact assessment of conductivity by scanned conductance microscopy on Si/SiO2 substrates.

  8. Spatial relationship between the productivity of cane sugar and soil electrical conductivity measured by electromagnetic induction

    NASA Astrophysics Data System (ADS)

    Siqueira, Glecio; Silva, Jucicléia; Bezerra, Joel; Silva, Enio; Montenegro, Abelardo

    2013-04-01

    The cultivation of sugar cane in Brazil occupies a prominent place in national production chain, because the country is the main world producer of sugar and ethanol. Accordingly, studies are needed that allow an integrated production and technified, and especially that estimates of crops are consistent with the actual production of each region. The objective of this study was to determine the spatial relationship between the productivity of cane sugar and soil electrical conductivity measured by electromagnetic induction. The field experiment was conducted at an agricultural research site located in Goiana municipality, Pernambuco State, north-east of Brazil (Latitude 07 ° 34 '25 "S, Longitude 34 ° 55' 39" W). The surface of the studied field is 6.5 ha, and its mean height 8.5 m a.s.l. This site has been under sugarcane (Saccharum officinarum sp.) monoculture during the last 24 years and it was managed burning the straw each year after harvesting, renewal of plantation was performed every 7 years. Studied the field is located 10 km east from Atlantic Ocean and it is representative of the regional landscape lowlands, whose soils are affected by salinity seawater, sugarcane plantations with the main economical activity. Soil was classified an orthic the Podsol. The productivity of cane sugar and electrical conductivity were measured in 90 sampling points. The productivity of cane sugar was determined in each of the sampling points in plots of 9 m2. The Apparent soil electrical conductivity (ECa, mS m-1) was measured with an electromagnetic induction device EM38-DD (Geonics Limited). The equipment consists of two units of measurement, one in a horizontal dipole (ECa-H) to provide effective measurement distance of 1.5 m approximately and other one in vertical dipole (ECa-V) with an effective measurement depth of approximately 0.75 m. Data were analyzed using descriptive statistics and geostatistical tools. The results showed that productivity in the study area reached values above 200 t ha-1, with higher values of productivity are concentrated in the region northern terrain. The maps of soil electrical conductivity (ECa-V and ECa-H) showed behavior similar to the productivity of cane sugar. The linear correlation showed values of 0.74 (yield x ECa-H) and 0.85 (yield x ECa-V). The adjusted semivariograms showed no similarity in the spatial pattern of pairs of semivariance. The electrical conductivity measured by electromagnetic induction has been shown as an important tool for predicting the productivity of sugar cane, however more studies are needed to determine the magnitude of the differences between such attributes.

  9. A transient hot-wire instrument for thermal conductivity measurements in electrically conducting liquids at elevated temperatures

    Microsoft Academic Search

    A. Alloush; W. B. Gosney; W. A. Wakeham

    1982-01-01

    This paper describes a novel type of transient hot-wire cell for thermal conductivity measurements on electrically conducting liquids. A tantalum wire of 25 ?m. diameter is used as the sensing element in the cell, and it is insulated from the conducting liquids by an anodic film of tantalum pentoxide, 70 nm thick. The cell is suitable for measurements on conducting

  10. Thermophysical Properties of Liquid Te: Density, Electrical Conductivity, and Viscosity

    NASA Technical Reports Server (NTRS)

    Li, C.; Su, C.; Lehoczky, S. L.; Scripa, R. N.; Ban, H.; Lin, B.

    2004-01-01

    The thermophysical properties of liquid Te, namely, density, electrical conductivity, and viscosity, were determined using the pycnometric and transient torque methods from the melting point of Te (723 K) to approximately 1150 K. A maximum was observed in the density of liquid Te as the temperature was increased. The electrical conductivity of liquid Te increased to a constant value of 2.89 x 10(exp 5 OMEGA-1m-1) as the temperature was raised above 1000 K. The viscosity decreased rapidly upon heating the liquid to elevated temperatures. The anomalous behaviors of the measured properties are explained as caused by the structural transitions in the liquid and discussed in terms of Eyring's and Bachiskii's predicted behaviors for homogeneous liquids. The Properties were also measured as a function of time after the liquid was coded from approximately 1173 or 1123 to 823 K. No relaxation phenomena were observed in the properties after the temperature of liquid Te was decreased to 823 K, in contrast to the relaxation behavior observed for some of the Te compounds.

  11. Recyclable and electrically conducting carbon nanotube composite films

    NASA Astrophysics Data System (ADS)

    Zou, Guifu; Jain, Menka; Yang, Hao; Zhang, Yingying; Williams, Darrick; Jia, Quanxi

    2010-03-01

    Carbon nanotube (CNT) composite films possess unique electrical, mechanical and thermal properties. In particular, some research has shown that CNT-polymer composite films greatly enhance the performance of organic light-emitting diodes. Therefore, CNT composite films have been intensively fabricated and applied. However, recent research has shown that CNTs carry carcinogenic risks in vivo. Therefore, how to collect and treat damaged or trashed CNT composite films are considerable tasks for scientists working in this area. From the viewpoint of environmental protection and saving resources, recycling the CNT composite films is the most efficient way to solve these problems. Here, we employ a benign water-soluble polymer, polyethyleneimine (PEI), to disperse CNTs and a general spin-coating process to prepare the homogeneous CNT composite films. The prepared CNT composite films exhibit good water-soluble properties and recyclability, i.e. they can be formed and dissolved in water. In addition, the long CNTs and high loading in the PEI matrix facilitates good electric conductivity in these CNT composite films. A significant improvement in the conductivity of the composite films is observed as the concentration of CNTs in the PEI increases, reaching as high as 43.73 S cm-1 when the CNT concentration is equal to 3%.

  12. Acidosis slows electrical conduction through the atrio-ventricular node

    PubMed Central

    Nisbet, Ashley M.; Burton, Francis L.; Walker, Nicola L.; Craig, Margaret A.; Cheng, Hongwei; Hancox, Jules C.; Orchard, Clive H.; Smith, Godfrey L.

    2014-01-01

    Acidosis affects the mechanical and electrical activity of mammalian hearts but comparatively little is known about its effects on the function of the atrio-ventricular node (AVN). In this study, the electrical activity of the epicardial surface of the left ventricle of isolated Langendorff-perfused rabbit hearts was examined using optical methods. Perfusion with hypercapnic Tyrode's solution (20% CO2, pH 6.7) increased the time of earliest activation (Tact) from 100.5 ± 7.9 to 166.1 ± 7.2 ms (n = 8) at a pacing cycle length (PCL) of 300 ms (37°C). Tact increased at shorter PCL, and the hypercapnic solution prolonged Tact further: at 150 ms PCL, Tact was prolonged from 131.0 ± 5.2 to 174.9 ± 16.3 ms. 2:1 AVN block was common at shorter cycle lengths. Atrial and ventricular conduction times were not significantly affected by the hypercapnic solution suggesting that the increased delay originated in the AVN. Isolated right atrial preparations were superfused with Tyrode's solutions at pH 7.4 (control), 6.8 and 6.3. Low pH prolonged the atrial-Hisian (AH) interval, the AVN effective and functional refractory periods and Wenckebach cycle length significantly. Complete AVN block occurred in 6 out of 9 preparations. Optical imaging of conduction at the AV junction revealed increased conduction delay in the region of the AVN, with less marked effects in atrial and ventricular tissue. Thus acidosis can dramatically prolong the AVN delay, and in combination with short cycle lengths, this can cause partial or complete AVN block and is therefore implicated in the development of brady-arrhythmias in conditions of local or systemic acidosis. PMID:25009505

  13. The relationship between electric elds, conductances and currents in the high-latitude ionosphere

    E-print Network

    Paris-Sud XI, Université de

    The relationship between electric ®elds, conductances and currents in the high-latitude ionosphere between electric ®elds, height-integrated conductivities and electric currents in the high allowing the determination of both ®eld-perpendicular electric current components. Over 1300 h of common

  14. Imaging in electrically conductive porous media without frequency encoding.

    PubMed

    Lehmann-Horn, J A; Walbrecker, J O

    2012-07-01

    Understanding multi-phase fluid flow and transport processes under various pressure, temperature, and salinity conditions is a key feature in many remote monitoring applications, such as long-term storage of carbon dioxide (CO(2)) or nuclear waste in geological formations. We propose a low-field NMR tomographic method to non-invasively image the water-content distribution in electrically conductive formations in relatively large-scale experiments (?1 m(3) sample volumes). Operating in the weak magnetic field of Earth entails low Larmor frequencies at which electromagnetic fields can penetrate electrically conductive material. The low signal strengths associated with NMR in Earth's field are enhanced by pre-polarization before signal recording. To localize the origin of the NMR signal in the sample region we do not employ magnetic field gradients, as is done in conventional NMR imaging, because they can be difficult to control in the large sample volumes that we are concerned with, and may be biased by magnetic materials in the sample. Instead, we utilize the spatially dependent inhomogeneity of fields generated by surface coils that are installed around the sample volume. This relatively simple setup makes the instrument inexpensive and mobile (it can be potentially installed in remote locations outside of a laboratory), while allowing spatial resolution of the order of 10 cm. We demonstrate the general feasibility of our approach in a simulated CO(2) injection experiment, where we locate and quantify the drop in water content following gas injection into a water-saturated cylindrical sample of 0.45 m radius and 0.9 m height. Our setup comprises four surface coils and an array consisting of three volume coils surrounding the sample. The proposed tomographic NMR methodology provides a more direct estimate of fluid content and properties than can be achieved with acoustic or electromagnetic methods alone. Therefore, we expect that our proposed method is relevant for geophysical applications, such as for monitoring CO(2) injections in saline aquifers or detecting water leakage into nuclear waste deposit sites installed in electrically conductive formations. PMID:22683582

  15. Electrical conductivity of wadsleyite at high temperatures and high pressures Lidong Dai a,b

    E-print Network

    Electrical conductivity of wadsleyite at high temperatures and high pressures Lidong Dai a,b , Shun 2009 Editor: L. Stixrude Keywords: electrical conductivity wadsleyite oxygen fugacity frequency water The electrical conductivity of wadsleyite aggregates has been determined under the broad range of thermodynamic

  16. Electrical Conductivity, Near-Infrared Absorption, and Thermal Lens Spectroscopic Studies of Percolation of Microemulsions

    E-print Network

    Reid, Scott A.

    Electrical Conductivity, Near-Infrared Absorption, and Thermal Lens Spectroscopic Studies studied below and above the percolation thresholds by electrical conductivity, near-infrared absorption quenching, neutron and light scattering, and electrical conductivity.1,2 However, in spite of these numerous

  17. Polymeric salt bridges for conducting electric current in microfluidic devices

    DOEpatents

    Shepodd, Timothy J. (Livermore, CA); Tichenor, Mark S. (San Diego, CA); Artau, Alexander (Humacao, PR)

    2009-11-17

    A "cast-in-place" monolithic microporous polymer salt bridge for conducting electrical current in microfluidic devices, and methods for manufacture thereof is disclosed. Polymeric salt bridges are formed in place in capillaries or microchannels. Formulations are prepared with monomer, suitable cross-linkers, solvent, and a thermal or radiation responsive initiator. The formulation is placed in a desired location and then suitable radiation such as UV light is used to polymerize the salt bridge within a desired structural location. Embodiments are provided wherein the polymeric salt bridges have sufficient porosity to allow ionic migration without bulk flow of solvents therethrough. The salt bridges form barriers that seal against fluid pressures in excess of 5000 pounds per square inch. The salt bridges can be formulated for carriage of suitable amperage at a desired voltage, and thus microfluidic devices using such salt bridges can be specifically constructed to meet selected analytical requirements.

  18. Electrical Conduction and Dielectric Properties of Biodegradable Plastics

    NASA Astrophysics Data System (ADS)

    Shinyama, Katsuyoshi; Fujita, Shigetaka

    We examined the electrical conduction and dielectric properties as well as thermal analysis of polylactic acid (PLA) that is biodegradable plastics. From the results of thermal analyses, it was found that the glass transition temperature (Tg) of PLA was about 60°C and the melting point (Tm) was about 166°C. For the temperature dependence of current density (J), J of PLA became smaller than LDPE, PP and Polyester in the temperature from room temperature to 90°C. However, when sample became 90°C or the higher, J of PLA became larger than other plastics. On the other hand, as a result of measuring J of the same sample again, it became small. For the relative permittivity (?r') indicated intermediate values between that of polyester and those of LDPE and PP.

  19. Electrically conductive, optically transparent polymer/carbon nanotube composites

    NASA Technical Reports Server (NTRS)

    Connell, John W. (Inventor); Smith, Jr., Joseph G. (Inventor); Harrison, Joycelyn S. (Inventor); Park, Cheol (Inventor); Watson, Kent A. (Inventor); Ounaies, Zoubeida (Inventor)

    2011-01-01

    The present invention is directed to the effective dispersion of carbon nanotubes (CNTs) into polymer matrices. The nanocomposites are prepared using polymer matrices and exhibit a unique combination of properties, most notably, high retention of optical transparency in the visible range (i.e., 400-800 nm), electrical conductivity, and high thermal stability. By appropriate selection of the matrix resin, additional properties such as vacuum ultraviolet radiation resistance, atomic oxygen resistance, high glass transition (T.sub.g) temperatures, and excellent toughness can be attained. The resulting nanocomposites can be used to fabricate or formulate a variety of articles such as coatings on a variety of substrates, films, foams, fibers, threads, adhesives and fiber coated prepreg. The properties of the nanocomposites can be adjusted by selection of the polymer matrix and CNT to fabricate articles that possess high optical transparency and antistatic behavior.

  20. Lunar magnetic permeability, magnetic fields, and electrical conductivity temperature

    NASA Technical Reports Server (NTRS)

    Parkin, C. W.

    1978-01-01

    In the time period 1969-1972 a total of five magnetometers were deployed on the lunar surface during four Apollo missions. Data from these instruments, along with simultaneous measurements from other experiments on the moon and in lunar orbit, were used to study properties of the lunar interior and the lunar environment. The principal scientific results from analyses of the magnetic field data are discussed. The results are presented in the following main categories: (1) lunar electrical conductivity, temperature, and structure; (2) lunar magnetic permeability, iron abundance, and core size limits; (3) the local remnant magnetic fields, their interaction with the solar wind, and a thermoelectric generator model for their origin. Relevant publications and presented papers are listed.

  1. Saline conducted electric coagulation (SCEC): original experience in experimental hepatectomy

    PubMed Central

    Ding, Guo-ping; Cao, Li-ping; Liu, Da-ren; Que, Ri-sheng

    2012-01-01

    Objective: To evaluate the feasibility and superiority of a new coagulating and hemostatic method named “saline conducted electric coagulation (SCEC)”. Methods: The Peng's multifunction operative dissector (PMOD) was modified to enable saline to effuse persistently out of its nib at a constant speed. In a group of six New Zealand rabbits, two hepatic lobes of each rabbits were resected respectively by SCEC and conventional electric coagulation (EC). The features of SCEC were recorded by photo and compared with conventional EC. After 7 d, the coagulating depth was measured in each residual hepatic lobe. Hepatic tissue was dyed by hematoxylin and eosin (HE) and studied under a microscope. Results: The coagulating depth increased with the continuation of SCEC time. Hepatectomies were performed successfully, no rabbit died in the perioperative period. The incisal surface of SCEC was gray-white with no red bleeding point. There was a thick solidified layer at the margin and a thin red-white intermittent layer between the solidified layer and normal hepatic tissue at the vertical section of SCEC. The mean coagulating depth of SCEC was 1.8 cm vs. 0.3 cm of conventional EC. Pathological examination showed a mild inflammatory reaction by SCEC. Conclusions: SCEC is a feasible and safe method for surgical hemostasis. As a new technique for liver resection, SCEC shows better coagulating effect and milder inflammatory reaction than conventional EC. Our study shows bloodless liver resection can also be performed by SCEC, especially for liver malignant tumor. PMID:22374610

  2. Electrical conductivity of intermediate magmas from Uturuncu Volcano (Bolivia)

    NASA Astrophysics Data System (ADS)

    Laumonier, Mickael; Gaillard, Fabrice; Sifre, David

    2015-04-01

    Magmas erupted at Uturuncu volcano (South Bolivia) comes from the Altiplano-Puna Magma Body (APMB, Chile-Bolivia), a crustal massive body of 80 km long by 10 km thick located at ~ 35 km depth named. Recent magneto telluric surveys reveal a resistivity lower than 1 ohm.m due to the presence of melt which could result in the reactivation of the volcano. In order to better constrain the resistivity profiles and thus the conditions of magma storage of the APMB, we have performed in situ electrical measurements on natural dacites and andesites from Uturuncu with a 4-wire set up in a piston cylinder and internally heated pressure vessel. The range of temperature (500 to 1300°C), pressure (0.3 to 2 Gpa), and the various water contents covers the respective ranges occurring at natural conditions. The results show that the conductivity increases with the temperature and the water content but slightly decreases with the pressure. Then a model was built from these results so as to help in (i) interpreting the electrical signature of natural magmas, (ii) constraining their conditions (chemical composition, temperature, pressure, water content, melt fraction) from the source to the storage location and (iii) providing information on the interior structure of a volcano and its reservoir.

  3. Electrical conductivity of carbonaceous chondrites and electric heating of meteorite parent bodies

    NASA Technical Reports Server (NTRS)

    Duba, AL

    1987-01-01

    Electromagnetic heating of rock-forming materials most probably was an important process in the early history of the solar system. Electrical conductivity experiments of representative materials such as carbonaceous chondrites are necessary to obtain data for use in electromagnetic heating models. With the assumption that carbon was present at grain boundaries in the material that comprised the meteorite parent bodies, the electrical heating of such bodies was calculated as a function of body size and solar distance using the T-Tauri model of Sonett and Herbert (1977). The results are discussed.

  4. The Deep Electrical Conductivity Structure of the Dead Sea Basin

    NASA Astrophysics Data System (ADS)

    Meqbel, N. M.; Ritter, O.; Weckmann, U.; Becken, M.; Munoz, G.

    2008-12-01

    The left-lateral Dead Sea transform (DST) is a major transform fault separating the Arabian plate in the east from the African and Sinai plates in the west. It extends from the Red Sea rift to the Taurus collision zone in eastern Turkey, with a total length of more than 1000 km. During its evolution, the DST formed several deep sedimentary (pull-apart) basins, such as the Gulf of Aqaba / Eilat, the Lake Tiberias and the Dead Sea basin (DSB). The DSB is the largest basin along the transform valley and probably the largest of these structures on earth. The basin is 135km long, 20km wide and according to an interpretation of gravity data the basin's sedimentary fill is assessed to 10km thickness. Within the framework of the multi-disciplinary DESIRE (Dead Sea Integrated Research) project, several geophysical methods were applied to investigate the southern part of the DSB, including magnetotellurics (MT), active reflection and refraction seismic, aero-gravity, and passive seismology. The MT data were acquired at 150 stations in 2006 along a 120 km long, approximately east-west oriented profile. Resistivity models obtained from two-dimensional inversion of the MT data reveal several robust features: Beneath the Dead Sea, extending to a depth of approximately 3 km, we observe extremely low electrical resistivity (0.1- 0.5 ? m). Embedded within this structure and located beneath the Al-Lisan Peninsula we observe a localized high resistivity body (> 100 ? m), which is interpreted as the Al Lisan salt diapir. The lateral boundaries of the DSB are clearly expressed in the resistivity model as abrupt changes from moderately low (~20 ? m) to high resistivity (> 1000 ? m) at depths of 3 and 4 km under the eastern and western segment of the profile, respectively. The locations of the boundaries coincide with the surface traces of the eastern and western border faults. Furthermore, the 2D model images two conductive layers beneath both, the eastern and western segments of the profile at varying depth ranges. Based on hydro-geological information the location and depth extent of these conductive layers appear to coincide with a shallow and a deeper aquifer. With our electrical conductivity model it is possible to delineate the saline/fresh water interface, particularly at the eastern shoreline of the Dead Sea. The border faults appear to prevent cross-fault fluid flow of the Dead Sea brines.

  5. Illuminating the electrical conductivity of the lowermost mantle from below

    NASA Astrophysics Data System (ADS)

    Jault, Dominique

    2015-07-01

    The magnetic field that originates in the earth's core is transformed across the electrically conducting mantle before being observed, at the earth's surface or above. Assuming that the conductivity depends only on radius, it has been customary to treat the mantle as a linear time-invariant filter for the core magnetic field, with properties (as a function of the frequency ?) specified by the transfer function ?(?). An high-frequency approximation to ?(?), which is derived from a three terms WKBJ expansion with ?-1/2 as small parameter, is found here to reproduce adequately, for low harmonic degrees and/or thin conducting layers, the exact solution, which is evaluated numerically. It is contrasted with the low-frequency estimation of ?, which consists in a perturbation procedure and in writing ?(?) as a series in powers of ? (? ? 0). The low-frequency theory is applied to the magnetic variations produced by the geostrophic core flows with about 6 yr period as the phase of these flows is independently determined from their effect on the length of the day. Apart from that, the low-frequency approximation overestimates the screening by the mantle of high-frequency signals, especially the low harmonic degree ones. In practice, the attenuating factor defined from the O(?2) term in the expansion of ? as ? ? 0 cannot be retrieved from analyses of geomagnetic time-series. Application of the mantle filter theory hinges on our knowledge about the time spectrum of the magnetic field at the core surface. The low-frequency theory had been previously applied to observatory series on the assumption that geomagnetic jerks occurring in the core are rare and isolated events. Rather than following up these earlier studies, I note that the spectral density function for the second time derivative of the main magnetic field coefficients is approximately independent of ? in a frequency range for which the mantle has undoubtedly negligible influence. In the absence of any other information, this scaling law is extrapolated to higher frequencies.

  6. Thermal and electrical conductivity of iron at Earth's core conditions.

    PubMed

    Pozzo, Monica; Davies, Chris; Gubbins, David; Alfè, Dario

    2012-05-17

    The Earth acts as a gigantic heat engine driven by the decay of radiogenic isotopes and slow cooling, which gives rise to plate tectonics, volcanoes and mountain building. Another key product is the geomagnetic field, generated in the liquid iron core by a dynamo running on heat released by cooling and freezing (as the solid inner core grows), and on chemical convection (due to light elements expelled from the liquid on freezing). The power supplied to the geodynamo, measured by the heat flux across the core-mantle boundary (CMB), places constraints on Earth's evolution. Estimates of CMB heat flux depend on properties of iron mixtures under the extreme pressure and temperature conditions in the core, most critically on the thermal and electrical conductivities. These quantities remain poorly known because of inherent experimental and theoretical difficulties. Here we use density functional theory to compute these conductivities in liquid iron mixtures at core conditions from first principles--unlike previous estimates, which relied on extrapolations. The mixtures of iron, oxygen, sulphur and silicon are taken from earlier work and fit the seismologically determined core density and inner-core boundary density jump. We find both conductivities to be two to three times higher than estimates in current use. The changes are so large that core thermal histories and power requirements need to be reassessed. New estimates indicate that the adiabatic heat flux is 15 to 16 terawatts at the CMB, higher than present estimates of CMB heat flux based on mantle convection; the top of the core must be thermally stratified and any convection in the upper core must be driven by chemical convection against the adverse thermal buoyancy or lateral variations in CMB heat flow. Power for the geodynamo is greatly restricted, and future models of mantle evolution will need to incorporate a high CMB heat flux and explain the recent formation of the inner core. PMID:22495307

  7. Investigation of thermal conductivity, viscosity, and electrical conductivity of graphene based nanofluids

    NASA Astrophysics Data System (ADS)

    Kole, Madhusree; Dey, T. K.

    2013-02-01

    Stable and well dispersed functionalized graphene-ethylene glycol (EG) + distilled water nanofluids having graphene nano-sheets (GnS) volume concentration between 0.041 and 0.395 vol. % are prepared without any surfactant. Graphene nano-sheets are prepared from high purity graphite powder by Hummers method followed by exfoliation and reduction by hydrogen gas. Thus, obtained hydrogen exfoliated graphene (HEG) is then functionalized using acid. The graphene nano-sheets are characterized using XRD, TEM, Raman spectroscopy, and FTIR spectroscopy. Thermal conductivity and viscosity measurements are performed both as a function of graphene loading and temperature between 10 and 70 °C. Thermal conductivity enhancement of ˜15% for a loading of 0.395 vol. % f-HEG is observed at room temperature. The measured nanofluid's thermal conductivity is explained well in terms of the expression derived by Nan et al. (J. Appl. Phys. 81, 6692 (1997)), which considers matrix-additive interface contact resistance of mis-oriented ellipsoidal particles. The viscosity of the prepared f-HEG nanofluids and the base fluid (EG + distilled water) displays non-Newtonian behaviour with the appearance of shear thinning and nearly 100% enhancement compared to the base fluid (EG + DI water) with f-HEG loading of 0.395 vol. %. Known theoretical models for nanofluid's viscosity fail to explain the observed f-HEG volume concentration dependence of the nanofluid's viscosity. Temperature dependence of the studied nanofluid between 10 and 70 °C is explained well by the correlations proposed earlier for nanofluids with spherical nanoparticles. Electrical conductivity of the f-HEG nanofluids shows significant enhancement of ˜8620% for 0.395 vol. % loading of f-HEG in a base fluid of 70:30 mixture of EG and distilled water.

  8. Tokamak electrical conductivity modified by electrostatic trapping in the applied electric field

    SciTech Connect

    Chang, C.S.

    1989-07-01

    Passing electrons traveling in the same direction as the applied Ohmic electric field, near the trapped-passing boundary, can get electrostatically trapped by the applied Ohmic potential, reverse their parallel flow direction, and become passing particles traveling in the opposite direction. The number of these electrons is proportional to the applied voltage and is small. But, the amount of change in their time-averaged parallel velocity by reversing their flow direction, is about twice the average parallel velocity of the barely passing electrons and is large. Hence, these electrostatically trapped particles can significantly contribute to the Ohmic electrical current. The new electrical conductivity is calculated in the banana regime using a pitch angle scattering operator, and the values are found to be significantly enhanced from previous neoclassical theories. 4 refs., 2 figs.

  9. Upper crustal fault zones: Constraining structure and dynamics using electrical conductivity

    NASA Astrophysics Data System (ADS)

    Hoffmann-Rothe, A.; Ritter, O.; Janssen, C.

    2003-04-01

    Upper crustal fault zones, either fossil or active, are often connected with electrical conductivity anomalies. These anomalies depend on properties such as the porosity/permeability of the fault zone material, the fluid content or the state of healing/cementation of the fault-fracture mesh; properties that moreover control the ability of a fault to accumulate strain. Structural heterogeneities caused by the faulting process are therefore believed to either increase or decrease the electrical conductivity in the fault's vicinity. We show results of two combined magnetotelluric and structural studies of large scale strike-slip dominated fault zones. The trench-linked West Fault (WF) in Northern Chile shows a pronounced anomaly of high conductivity confined to the central region of the fault. The zone of high conductivity is approximately 400 m wide and 1.5 km deep. Structural mapping reveals that this conductivity enhancement is closely related to a mesh of faults and fractures ('damage zone') that most likely provides a pathway for fluids. In contrast to this, the Dead Sea Transform Fault (DST) in Jordan shows no obvious evidence of such a fault zone conductor as the DST is expressed as the boundary between two different domains of conductivity on either side of the fault. Correspondingly, a marked macroscopic fault-fracture mesh in the fault core region is not developed. Comparison of the results from the WF with published data from the San Andreas Fault suggests generally a positive correlation of fault activity with geometric extent and conductivity of the fault zone conductor. However, the Dead Sea Transform Fault apparently does not comply with this scheme although it is active. It is possible that intense localisation of deformation caused the formation of a very narrow fault gouge, which cannot be resolved with the MT experiments. This result could suggest that the existence or non-existence of high conductivity in the central parts of large scale strike-slip fault zones is an indicator for the degree of strain localisation during faulting.

  10. Direct current conductivity of carbon nanofiber-based conductive polymer composites: effects of temperature and electric field.

    PubMed

    He, Lin Xiang; Tjong, Sie Chin

    2011-05-01

    Polymer composites based on high density polyethylene (HDPE) and carbon nanofiber (CNF) were fabricated by melt compounding. The dependences of electrical conductivity of HDPE-CNF composites on filler concentration, temperature, and applied electric field were investigated. The results showed that the conductivity of the HDPE-CNF composites follows the scaling law of percolation theory. Increasing temperature caused a sharp increase in the resistivity of HDPE-CNF composites near the melting temperature of HDPE, yielding a positive temperature coefficient (PTC) effect of resistance. The potential mechanisms involved in the PTC effect of such composites were analyzed. An investigation of the effect of electric field on the conductivity of HDPE-CNF composites revealed the presence of tunneling conduction. The tunneling conductivity increased with increasing filler content because of high tunneling frequency, and decreased with rising temperature as a result of gap widening between conducting CNF fillers. PMID:21780386

  11. Recent Developments in Mixed Ionic and Electronic Conducting Electrodes for the Alkali Metal Thermal Electric Converter (AMTEC)

    NASA Astrophysics Data System (ADS)

    Fletcher, Robert W.; Schwank, Johannes W.

    2003-01-01

    Mixed ionic and electronic conducting electrodes (MIECEs) have recently gained more attention in the development of the Alkali Metal Thermal Electric Converter (AMTEC). The advantage of MIECEs, as their name implies, is that they allow both electronic transport and ionic transport within the matrix of their materials. This lowers charge transport resistances, which lowers overall electrical resistances of the electrochemical system, and, thus, can improve reaction rates for a given apparent or superficial surface area of the electrode. The AMTEC system is a self-contained, self-regenerating compact technology that electrochemically converts heat directly to electricity. Our latest developments for AMTEC MIECEs are presented. These include electrodes formulated from various blends of titanium nitride or molybdenum with titanium dioxide. The general formulation, application, processing and testing methods for these electrodes are presented. Measured power densities of selected MIECEs are given. The physical morphology, and composition of our MIECEs are also described. Finally, a possible operational mechanism for these electrodes is proposed.

  12. Electric conductivity of the quark-gluon plasma investigated using a perturbative QCD based parton cascade

    NASA Astrophysics Data System (ADS)

    Greif, Moritz; Bouras, Ioannis; Greiner, Carsten; Xu, Zhe

    2014-11-01

    Electric conductivity is sensitive to effective cross sections among the particles of the partonic medium. We investigate the electric conductivity of a hot plasma of quarks and gluons, solving the relativistic Boltzmann equation. In order to extract this transport coefficient, we employ the Green-Kubo formalism and, independently, a method motivated by the classical definition of electric conductivity. To this end we evaluate the static electric diffusion current upon the influence of an electric field. Both methods give identical results. For the first time, we obtain numerically the Drude electric conductivity formula for an ultrarelativistic gas of quarks and gluons employing constant isotropic binary cross sections. Furthermore, we extract the electric conductivity for a system of massless quarks and gluons including screened binary and inelastic, radiative 2 ?3 perturbative QCD scattering. Comparing with recent lattice results, we find an agreement in the temperature dependence of the conductivity.

  13. Electrical conductivity of minerals and rocks Shun-ichiro Karato1

    E-print Network

    1 Electrical conductivity of minerals and rocks Shun-ichiro Karato1 and Duojun Wang1,2 1 : Yale-Blackwell #12;2 SUMMARY Electrical conductivity of most minerals is sensitive to hydrogen (water) content, temperature, major element chemistry and oxygen fugacity. The influence of these parameters on electrical

  14. ENS'05 Paris, France, 14-16 December 2005 LOW TEMPERATURE INVESTIGATION OF ELECTRICAL CONDUCTION IN

    E-print Network

    Paris-Sud XI, Université de

    : simulation and experiment Fig. 2: electrical equivalent schematic of a gated polySiNW considering a (3x9ENS'05 Paris, France, 14-16 December 2005 LOW TEMPERATURE INVESTIGATION OF ELECTRICAL CONDUCTION Investigation of electrical conduction in polysilicon nanowires (polySiNW) with nanograins (5 to 20nm), based

  15. The transient electromagnetic field of an electric line source above a plane conducting earth

    Microsoft Academic Search

    Bert Jan Kooij

    1991-01-01

    The pulsed electromagnetic radiation from an electric line source above a conducting earth is investigated theoretically. The modified Cagniard method is used to derive closed-form expressions for the electric and magnetic field anywhere above the conducting earth. Numerical results are presented for the electric field for different points of excitation and observation above the earth, as well as for different

  16. Measurement and Modeling the Atmospheric Electrical Conductivity for Monitoring the Air Pollution

    Microsoft Academic Search

    Nagaraja Kamsali; Jayati Datta; Bsn Prasad

    2008-01-01

    The electrical parameters such as ion mobility, small ion number density, and conductivity are important for understanding the electrical nature of the atmosphere. The small ions consisting of aggregates of a few molecules practically determine the electrical conductivity over the region. The number density of these ions is controlled by ionizing mechanisms for the production of ions and electrons, and

  17. Guar gum based biodegradable, antibacterial and electrically conductive hydrogels.

    PubMed

    Kaith, Balbir S; Sharma, Reena; Kalia, Susheel

    2015-04-01

    Guar gum-polyacrylic acid-polyaniline based biodegradable electrically conductive interpenetrating network (IPN) structures were prepared through a two-step aqueous polymerization. Hexamine and ammonium persulfate (APS) were used as a cross linker-initiator system to crosslink the poly(AA) chains on Guar gum (Ggum) backbone. Optimum reaction conditions for maximum percentage swelling (7470.23%) were time (min) = 60; vacuum (mmHg) = 450; pH = 7.0; solvent (mL) = 27.5; [APS] (mol L(-1)) = 0.306 × 10(-1); [AA] (mol L(-1)) = 0.291 × 10(-3) and [hexamine] (mol L(-1))=0.356 × 10(-1). The semi-interpenetrating networks (semi-IPNs) were converted into IPNs through impregnation of polyaniline chains under acidic and neutral conditions. Fourier transform infra-red spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) techniques were used to characterize the semi-IPNs and IPNs. Synthesized semi-IPNs and IPNs were further evaluated for moisture retention in different soils, antibacterial and biodegradation behavior. PMID:25660656

  18. Analytic electrical-conductivity tensor of a nondegenerate Lorentz plasma.

    PubMed

    Stygar, W A; Gerdin, G A; Fehl, D L

    2002-10-01

    We have developed explicit quantum-mechanical expressions for the conductivity and resistivity tensors of a Lorentz plasma in a magnetic field. The expressions are based on a solution to the Boltzmann equation that is exact when the electric field is weak, the electron-Fermi-degeneracy parameter Theta>1, and the electron-ion Coulomb-coupling parameter Gamma/Z<1. (Gamma is the ion-ion coupling parameter and Z is the ion charge state.) Assuming a screened 1/r electron-ion scattering potential, we calculate the Coulomb logarithm in the second Born approximation. The ratio of the term obtained in the second approximation to that obtained in the first is used to define the parameter regime over which the calculation is valid. We find that the accuracy of the approximation is determined by Gamma/Z and not simply the temperature, and that a quantum-mechanical description can be required at temperatures orders of magnitude less than assumed by Spitzer [Physics of Fully Ionized Gases (Wiley, New York, 1962)]. When the magnetic field B=0, the conductivity is identical to the Spitzer result except the Coulomb logarithm ln Lambda(1)=(ln chi(1)-1 / 2)+[(2Ze(2)/lambdam(e)v(2)(e1))(ln chi(1)-ln 2(4/3))], where chi(1) identical with 2m(e)v(e1)lambda/ variant Planck's over 2pi, m(e) is the electron mass, v(e1) identical with (7k(B)T/m(e))(1/2), k(B) is the Boltzmann constant, T is the temperature, lambda is the screening length, variant Planck's over 2pi is Planck's constant divided by 2pi, and e is the absolute value of the electron charge. When the plasma Debye length lambda(D) is greater than the ion-sphere radius a, we assume lambda=lambda(D); otherwise we set lambda=a. The B=0 conductivity is consistent with measurements when Z greater, similar 1, Theta greater, similar 2, and Gamma/Z less, similar 1, and in this parameter regime appears to be more accurate than previous analytic models. The minimum value of ln Lambda(1) when Z> or =1, Theta> or =2, and Gamma/Z< or =1 is 1.9. The expression obtained for the resistivity tensor (B not equal 0) predicts that eta( perpendicular )/eta( parallel ) (where eta( perpendicular ) and eta( parallel ) are the resistivities perpendicular and parallel to the magnetic field) can be as much as 40% less than previous analytic calculations. The results are applied to an idealized 17-MA z pinch at stagnation. PMID:12443340

  19. Laboratory measurements of electrical conductivities of hydrous and dry Mount Vesuvius melts under pressure

    Microsoft Academic Search

    A. Pommier; F. Gaillard; M. Pichavant; B. Scaillet

    2008-01-01

    Quantitative interpretation of MT anomalies in volcanic regions requires laboratory measurements of electrical conductivities of natural magma compositions. The electrical conductivities of three lava compositions from Mount Vesuvius (Italy) have been measured using an impedance spectrometer. Experiments were conducted on both glasses and melts between 400 and 1300°C, at both ambient pressure in air and high pressures (up to 400

  20. The role of acids in electrical conduction through ice David E. Stillman,1

    E-print Network

    Stillman, David E.

    The role of acids in electrical conduction through ice David E. Stillman,1 Joseph A. MacGregor,2] Electrical conduction through meteoric polar ice is controlled by soluble impurities that originate mostly from sea salt, biomass burning, and volcanic eruptions. The strongest conductivity response is to acids

  1. The Wilkes subglacial basin eastern margin electrical conductivity anomaly

    NASA Astrophysics Data System (ADS)

    Rizzello, Daniele; Armadillo, Egidio; Ferraccioli, Fausto; Caneva, Giorgio

    2014-05-01

    We have analyzed the deep conductivity structure at the transition between the Transantarctic Mountains (TAM) and the eastern margin of the WSB in NVL, by means of the GDS (Geomagnetic Deep Sounding) technique, in order to constrain the geodynamical interpretation of this antarctic sector. The TAM form the uplifted flank of the Mesozoic and Cenozoic West Antarctic Rift System. Structure of the TAM rift flank has been partially investigated with different geophysical approaches.The Wilkes Subglacial Basin is a broad depression over 400 km wide at the George V Coast and 1200 km long. Geology, lithospheric structure and tectonics of the Basin are only partially known because the Basin is buried beneath the East Antarctic Ice Sheet and is located in a remote region which makes geophysical exploration logistically challenging. Different authors have proposed contrasting hypothesis regarding the origin of the WSB: it could represent a region of rifted continental crust, or it may have a flexural origin or might represent an "extended terrane". Recently aerogeophysical investigations have demonstrated a strong structural control on the margin. Magnetovariational studies carried out at high geomagnetic latitudes are often hampered by source effects, mainly due to the closeness to the Polar Electrojet currents systems (PEJ). Its presence, in fact, makes the uniform magnetic field assumption, on which the magnetovariational methods are based on, often invalid, which outcome is a bias in the GDS transfer functions and to compromise the reliability of the inverted models. Data from the aforementioned campaigns have been then processed under the ISEE project (Ice Sheet Electromagnetic Experiment), aimed at evaluate and mitigate the bias effect of the PEJ on geomagnetic an magnetotelluric transfer functions at high geomagnetic latitudes, by means of suitable processing algorithms, developed upon a statistical analysis study on PEJ effects (Rizzello et al. 2013). Recent results allowed for a new processing of a wide dataset acquired during three different international Antarctic campaigns supported by the Italian Antarctic Project: the BACKTAM, WIBEM and WISE expeditions. The qualitative analysis of the induction arrows, in the period range 20-170 s, reveals an approximately 2D regional electrical conductivity pattern with a clear differentiation between the three Terrains crossed by the GDS transect we have re-analized: the Robertson Bay, the Bowers and the Wilson Terrain. Bi-dimensional conductivity models, jointly with magnetic and gravimetric profiles, suggest a differentiation of the investigated area in three crustal sectors separated by the Daniels Range and the Bowers Mts., in close relation with main known structural lineaments; to the West, a deep conductivity anomaly is associated with the transition to the Wilkes Subglagial Basin. We deem that such anomaly, together with the magnetic and gravimetric signatures, is compatible with an extensional regime in the eastern margin of the WSB. References Rizzello, D., Armadillo, E., Manzella, A."Statistical analysis of the polar electrojet influence on geomagnetic transfer functions estimates, over wide time and space scales". EGU 2013 General Assembly, Wien - poster presentation.

  2. Effective zero-thickness model for a conductive membrane driven by an electric field

    E-print Network

    Bazant, Martin Z.

    The behavior of a conductive membrane in a static (dc) electric field is investigated theoretically. An effective zero-thickness model is constructed based on a Robin-type boundary condition for the electric potential at ...

  3. Materials and methods for autonomous restoration of electrical conductivity

    DOEpatents

    Blaiszik, Benjamin J; Odom, Susan A; Caruso, Mary M; Jackson, Aaron C; Baginska, Marta B; Ritchey, Joshua A; Finke, Aaron D; White, Scott R; Moore, Jeffrey S; Sottos, Nancy R; Braun, Paul V; Amine, Khalil

    2014-03-25

    An autonomic conductivity restoration system includes a solid conductor and a plurality of particles. The particles include a conductive fluid, a plurality of conductive microparticles, and/or a conductive material forming agent. The solid conductor has a first end, a second end, and a first conductivity between the first and second ends. When a crack forms between the first and second ends of the conductor, the contents of at least a portion of the particles are released into the crack. The cracked conductor and the released contents of the particles form a restored conductor having a second conductivity, which may be at least 90% of the first conductivity.

  4. Excitation Transport and Electrical Conductivity in Disordered Media.

    NASA Astrophysics Data System (ADS)

    Franchi, Daniel S.

    The investigation of the incoherent/localization transition of excitations in classical and quantum systems has become a popular area of study. The location of the transition and the behavior around the transition, for example the critical exponents are candidates for universal properties when a percolation model is considered. Some of the existing methods to understand the transitions will be described and the quantities of interest will be defined. This includes the electrical conductivity which will be related by linear response theory to the diffusion for a percolation type model of excitons. I then examine two procedures developed by Loring, Mukamel and Franchi the self-consistent mode coupling (SCMC) and the effective dephasing approximation (EDA) which are based on the same general approach, but apply to different aspects of the disorder model. The SCMC applies only to models with spatial disorder where only a fraction of possible sites are active in transport. The EDA applies to quantum systems where there is site energy disorder. To find the qualitative behavior of each method, an appropriate lowest order approximation is made to each of these procedures. This is enough to take advantage of the fact that for the behavior around the transition (and in the localized regime) only the small cluster terms are dominate. Both methods predict the correct long time behavior of the transport quantities for diffusive behavior which is not found in any other dynamic theory of disordered systems. The features of the results, all of which are shown here as derivable from a single unified simplistic approach, are found to be in excellent agreement with those found from many different theories with disorder including fractal dynamics, long range interactions of excitons, the Anderson transition and the Haken-Strobl limit.

  5. Microstructural inhomogeneity of electrical conductivity in subcutaneous fat tissue.

    PubMed

    Kruglikov, Ilja L

    2015-01-01

    Microscopic peculiarities stemming from a temperature increase in subcutaneous adipose tissue (sWAT) after applying a radio-frequency (RF) current, must be strongly dependent on the type of sWAT. This effect is connected with different electrical conductivities of pathways inside (triglycerides in adipocytes) and outside (extra-cellular matrix) the cells and to the different weighting of these pathways in hypertrophic and hyperplastic types of sWAT. The application of the RF current to hypertrophic sWAT, which normally has a strongly developed extracellular matrix with high concentrations of hyaluronan and collagen in a peri-cellular space of adipocytes, can produce, micro-structurally, a highly inhomogeneous temperature distribution, characterized by strong temperature gradients between the peri-cellular sheath of the extra-cellular matrix around the hypertrophic adipocytes and their volumes. In addition to normal temperature effects, which are generally considered in body contouring, these temperature gradients can produce thermo-mechanical stresses on the cells' surfaces. Whereas these stresses are relatively small under normal conditions and cannot cause any direct fracturing or damage of the cell structure, these stresses can, under some supportive conditions, be theoretically increased by several orders of magnitude, causing the thermo-mechanical cell damage. This effect cannot be realized in sWAT of normal or hyperplastic types where the peri-cellular structures are under-developed. It is concluded that the results of RF application in body contouring procedures must be strongly dependent on the morphological structure of sWAT. PMID:25734656

  6. Depth of penetration of magnetic susceptibility and electric conductivity

    NASA Astrophysics Data System (ADS)

    Esparza, F.; Gomez-Trevino, E.; Medez-Delgado, S.

    2003-04-01

    We present a systematic, rigorous mathematical approach to establish the depth of penetration of magnetic susceptibility measurements. The problem is two fold. One needs to consider, on one side, the geometry of the source fields within the rock and, on the other, the fact that the effects of magnetization on the receiver are also geometry dependent. The combination of the two effects determines the depth of penetration of a magnetic susceptibility measurement. Our approach leads to compact integral formulas that relate the actual measurement to the depth profile of magnetic susceptibility within the rock. Any measurement can be represented as an average over depth of the susceptibility distribution within the rock. The degree of penetration is then readily quantified by a weighting function that depends on the types of source and receiver. Any given instrument is then characterized by its own weighting function. We present expressions of the weighting function for a variety of possible transmitter-receiver arrays. Our starting point is Maxwell's equation for the nonexistence of magnetic monopoles, which we apply to hypothetical magnetic monopoles later converted to dipoles and to other types of current sources commonly used in existing instruments. As a result, the instruments can be divided into two types: the ones that have the ability to focus at depth within the rock, and the ones that emphasize the outer portions of the samples. The appearance of negative measurements is explained by weighting functions with negative values operating on heterogeneous media. In general, we found that the depth of penetration of the coil arrays is smaller when operating for magnetic susceptibility as compared with the penetration when the same systems are used for sensing electrical conductivity.

  7. Electric conductivity of boron nitride thin films enhanced by in situ doping of zinc

    Microsoft Academic Search

    K. Nose; H. Oba; T. Yoshida

    2006-01-01

    The authors demonstrate that the electric conductivities of cubic and hexagonal boron nitride (c-BN and h-BN) thin films increased markedly by the in situ doping of zinc. The doped films were electrically semiconducting, and conductivities at room temperature increased from 10-8 to 10-2 Omega-1 cm-1 with increasing zinc concentration from 400 to 20 000 ppm. Activation energies for electric conduction

  8. Polypyrrole/Silicon Carbide Nanocomposites with Tunable Electrical Conductivity Pallavi Mavinakuli,

    E-print Network

    Guo, John Zhanhu

    Polypyrrole/Silicon Carbide Nanocomposites with Tunable Electrical Conductivity Pallavi Mavinakuli Conductive polypyrrole/SiC nanocomposites are fabricated via a facile oxidative polymerization approach using the material properties. Thermal gravimetric analysis demonstrates an improved thermal stability of polypyrrole

  9. Mapping of GeSbTe Thin Film Electrical Properties with Conductive AFM

    NASA Astrophysics Data System (ADS)

    Brocious, Jordan; Inglefield, Colin; Bobela, David; Herring, Thomas; Taylor, P. Craig

    2007-10-01

    The phase-change material system GeSbTe (GST) is currently used for optical data storage, however many details of the mechanism governing the phase change are not understood. GST's optical properties and electrical conductivities differ between the amorphous and crystalline phases. For instance, the electrical conductivity in the amorphous phase can be ˜10^3 times smaller than electrical conductivity in the crystalline phase. Thin films of Ge2Sb2Te5 and other alloys were created by a RF sputtering technique, which is known to produce amorphous samples. Crystalline regions were created after growth by localized laser heating. We characterized these films with Conductive Atomic Force Microscopy, which provides physical and electrical topography images. From this characterization we have identified sparse ˜100 nm highly conductive regions in the overall low-conductivity amorphous material. Although the laser treatment does not result in a uniformly conductive film, conductive regions in the treated material are significantly denser and larger.

  10. High thermal conductivity connector having high electrical isolation

    DOEpatents

    Nieman, Ralph C. (Downers Grove, IL); Gonczy, John D. (Oak Lawn, IL); Nicol, Thomas H. (St. Charles, IL)

    1995-01-01

    A method and article for providing a low-thermal-resistance, high-electrical-isolation heat intercept connection. The connection method involves clamping, by thermal interference fit, an electrically isolating cylinder between an outer metallic ring and an inner metallic disk. The connection provides durable coupling of a heat sink and a heat source.

  11. An improved model for predicting electrical conductance in nanochannels.

    PubMed

    Taghipoor, M; Bertsch, A; Renaud, Ph

    2015-02-14

    Nanochannel conductance measurements are commonly performed to characterize nanofluidic devices Theoretical analysis and experimental investigations imply that the nanochannel conductance does not follow the macro-scale models. It is generally accepted that the conductance of nanochannels deviates from the bulk and trend to a constant value at low concentrations. In this work, we present an improved model for the nanochannel conductance that takes into account the surface chemistry of the nanochannel wall. It figured out that the nanochannel conductance is no longer constant at low concentrations. The model predictions were compared with the experimental measurements and showed a very good agreement between the model and the experiments. PMID:25564382

  12. Evaluation of saline tracer performance during electrical conductivity groundwater monitoring.

    PubMed

    Mastrocicco, Micòl; Prommer, Henning; Pasti, Luisa; Palpacelli, Stefano; Colombani, Nicolò

    2011-04-25

    Saline solutions are the most commonly used hydrological tracers, because they can be easily and economically monitored by in situ instrumentation such as electrical conductivity (EC) loggers in wells or by geoelectrical measurements. Unfortunately, these low-cost techniques only provide information on the total concentration of ions in solution, i.e., they cannot resolve the ionic composition of the aqueous solution. This limitation can introduce a bias in the estimation of aquifer parameters where sorption phenomena between saline tracers and sediments become relevant. In general, only selected anions such as Cl(-) and Br(-) are recognised to be transported unretarded and they are referred to as conservative tracers or mobile anions. However, cations within the saline tracer may interact with the soil matrix through a range of processes such as ion exchange, surface complexation and via physical mass-transfer phenomena. Heterogeneous reactions with minerals or mineral surfaces may not be negligible where aquifers are composed of fine alluvial sediments. The focus of the present study was to examine and to quantify the bias between the aquifer parameters estimated during model-based interpretation of experimental data of EC measurements of saline tracer relative to the aquifer parameters found by specific measurements (i.e. via ionic chromatography, IC) of truly conservative species. To accomplish this, column displacement experiments with alluvial aquifer materials collected from the Po lowlands (Italy) were performed under water saturated conditions. The behaviour of six selected, commonly used saline tracers (i.e., LiCl, KCl, and NaCl; LiBr, KBr, and NaBr) was studied and the data analysed by inverse modelling. The results demonstrate that the use of EC as a tracer can lead to an erroneous parameterisation of the investigated porous media, if the reactions between solute and matrix are neglected. In general, errors were significant except for KCl and KBr, which is due to the weak interaction between dissolved K(+) and the sediment material. The study shows that laboratory scale pre-investigations can help with tracer selection and to optimise the concentration range targeted for in situ multilevel monitoring by unspecific geoelectrical instrumentation. PMID:21324545

  13. Intercomponent momentum transport and electrical conductivity of collisionless plasma

    NASA Technical Reports Server (NTRS)

    Wilhelm, H. E.

    1973-01-01

    Based on the Lenard-Balescu equation, the interaction integral for the intercomponent momentum transfer in a two-component, collisionless plasma is evaluated in closed form. The distribution functions of the electrons and ions are represented in the form of nonisothermal, displaced Maxwellians corresponding to the 5-moment approximation. As an application, the transport of electrical current in an electric field is discussed for infrasonic up to sonic electron-ion drift velocities.

  14. Electrical conductivity of polyvinyl alcohol-multiwall carbon nanotubes composites

    NASA Astrophysics Data System (ADS)

    Amrin, Sayed; Deshpande, V. D.

    2013-06-01

    The dc and ac conductivity of polyvinyl alcohol (PVA)-multiwalled carbon nanotube (MWNT) nanocomposites prepared by solution casting were investigated by employing dielectric relaxation spectroscopy in broad frequency range (0.1 Hz-10 MHz) at room temperature as a function of the conductive weight fraction (p) ranging from 0 to 2wt.%. The frequency dependence of the measured conductivity obeys the universal dynamic response (UDR); a dc plateau followed, by the power law above a critical frequency (fc).

  15. Phase Diagrams of Electric-Fduced Aggregation in Conducting Colloids

    NASA Technical Reports Server (NTRS)

    Khusid, B.; Acrivos, A.

    1999-01-01

    Under the application of a sufficiently strong electric field, a suspension may undergo reversible phase transitions from a homogeneous random arrangement of particles into a variety of ordered aggregation patterns. The surprising fact about electric-field driven phase transitions is that the aggregation patterns, that are observed in very diverse systems of colloids, display a number of common structural features and modes of evolution thereby implying that a universal mechanism may exist to account for these phenomena. It is now generally believed that this mechanism emanates from the presence of the long-range anisotropic interactions between colloidal particles due to their polarization in an applied field. But, in spite of numerous applications of the electric-field-driven phenomena in biotechnology, separation, materials engineering, chemical analysis, etc. our understanding of these phenomena is far from complete. Thus, it is the purpose of the proposed research to develop a theory and then test experimentally, under normal- and low-gravity conditions, the accuracy of the theoretical predictions regarding the effect of the synergism of the interparticle electric and hydrodynamic interactions on the phase diagram of a suspension. The main results from our theoretical studies performed to-date enable one to trace how the variations of the electrical properties of the constituent materials influence the topology of the suspension phase diagram and then, by using an appropriate phase diagram, to evaluate how the electric-field-induced transformations will depend on the frequency and the strength of the applied field.

  16. Improved Electrical Conductivity of Graphene Films Integrated with Metal Nanowires

    E-print Network

    tin oxide films in electrochromic (EC) devices. The successful integration of such graphene/NW films. KEYWORDS: Graphene, nanowires, transparent conductive films, electrochromic devices Due to low electron

  17. Space Charge and Electrical Conduction Properties of Polypropylene Copolymer Films

    NASA Astrophysics Data System (ADS)

    Nakane, Emi; Kaneko, Kazue; Mori, Tatsuo; Mizutani, Teruyoshi; Takino, Hiroshi; Ishioka, Mitsugu

    We investigated the space charge and charging current characteristics in polypropylene copolymer films polymerized with metallocene and Ziegler-Natta catalysts, respectively. Positive and negative homo space charges were observed and their amounts showed maxima at 40 °C. Charge carriers injected from the semiconducting (SC) electrode were dominant at 60 °C. The copolymerization of ethylene enhanced the apparent carrier mobility and the charging current. Evaporated Al electrode showed much less carrier injection than Al plate or SC electrode (mechanically-contacted electrode). Carrier injection from SC electrode was dominant than that from Al plate. These suggest that the space charge formation depends on not only electrode materials but also contact conditions.

  18. Measurement of Electrical Conductivity of Weakly Nonideal Multicomponent Plasma Mixtures Generated From Dielectric Materials

    Microsoft Academic Search

    Mofreh R. Zaghloul; Miyara S. Al Na'imi; Mohamed A. Bourham

    2009-01-01

    Nonideal complex multicomponent plasmas generated from dielectric compound materials are of crucial importance to many critical technologies, and the need to measure and determine the electrical conductivity of these plasmas is imperative. In this paper, we present preliminary successful measurements of the electrical conductivity of weakly nonideal partially ionized complex plasma mixtures generated from dielectric materials. The complex multicomponent partially

  19. Electrical conductivity of thermoresponsive shape-memory polymer with embedded micron sized Ni powder chains

    Microsoft Academic Search

    J. S. Leng; X. Lan; Y. J. Liu; S. Y. Du; W. M. Huang; N. Liu; S. J. Phee; Q. Yuan

    2008-01-01

    The electrical resistivity of a thermoresponsive polyurethane shape-memory polymer (SMP) filled with micron sized Ni powders is investigated in this letter. We show that, by forming conductive Ni chains under a weak static magnetic field (0.03 T), the electrical conductivity of the SMP composite in the chain direction can be improved significantly, which makes it more suitable for Joule heat

  20. Thermally conductive electrically insulating aromatic silicone film adhesive for the New Horizons mission

    Microsoft Academic Search

    Keith S. Caruso; Patrick Hogue; Kareem M. Monib

    2004-01-01

    This paper describes the characterization of a thermally conductive, electrically insulating aromatic silicone film adhesive used in a flexible heat sink assembly that is part of an optical telescope aboard the planned New Horizons mission to Pluto and the Kuiper Belt. This application requires high thermal conductivity, high electrical resistance, low-temperature flexibility, resistance to creep, and very low outgassing. Post-cure

  1. Evaluation and identification of electrical and thermal conduction mechanisms in carbon nanotube\\/epoxy composites

    Microsoft Academic Search

    Florian H. Gojny; Malte H. G. Wichmann; Bodo Fiedler; Ian A. Kinloch; Wolfgang Bauhofer; Alan H. Windle; Karl Schulte

    2006-01-01

    Nanostructured modification of polymers has opened up new perspectives for multi-functional materials. In particular, carbon nanotubes (CNTs) have the potential to realise electrically conductive polymers with improved or retaining mechanical performance. This study focuses on the evaluation of both, the electrical and thermal conductivity of nanoparticulate filled epoxy resins. We discuss the results with regard to the influence of the

  2. Sensing the water content of honey from temperature-dependent electrical conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In order to predict water content in honey, electrical conductivity was measured on blossom honey types of milk-vetch, jujube and yellow-locust with water content of 18%-37% between 5-40ºC. Regression models of electrical conductivity were developed as functions of water content and temperature. The...

  3. Electrical conductivity of diopside: evidence for oxygen vacancies

    USGS Publications Warehouse

    Huebner, J.S.; Voigt, D.E.

    1988-01-01

    Impedance spectra for two natural single crystals of diopside were obtained at 800 to 1300??C and 1-bar pressure over the frequency range 0.001 Hz to 100 kHz in a system closed to all components but oxygen. At both higher and lower fO2 values, no fO2 dependence of conductivity was observed, indicating the presence of different conduction mechanisms. At temperatures less than 1000??C, the activation energy is 1.3 eV, also suggesting a different conduction mechanism. Thus, at least four regimes are necessary to describe the conductivity of this diopside in T-fO2 space. The approximately -1/(7 ?? 1) value of d(log ??)/d(log fO2) in a high-temperature geologic region suggests a reaction by which oxygen vacancies control the conductivity. This relatively pure diopside is much less conducting than olivine or orthopyroxene. A second diopside with greater Fe content but otherwise similar in composition to the near-end-member diopside, is more conducting, has a smaller activation energy (1.0 eV) over the range 1050 to 1225??C, and shows only a weak negative fO2 dependence; suggesting that oxygen vacancies are present but are not the dominant defect in controlling the conductivity. -from Authors

  4. Electrical conduction in metal-glass composite materials

    Microsoft Academic Search

    V. K. Nagesh

    1976-01-01

    The importance of the surface characteristics of the glass phase used in the development of conducting thick film systems was investigated. The system studied was the lead borosilicate glass-silver system. By surface activation of the glass particles, a conducting thick film microstructure was developed using a reduced amount of silver compared to commerical compositions. Thick films with resistivities of the

  5. The improved electrical conductivity of carbon nanofibers by fluorinated MWCNTs

    Microsoft Academic Search

    Ji Sun Im; Sang Jin Kim; Phil Hyun Kang; Young-Seak Lee

    2009-01-01

    In order to increase the conductivity of carbon nanofiber sheet, conductive multi wall carbon nanotubes (MWCNTs) was added into the carbon fibers. The dispersion of MWCNTs into the fibers and adhesion between carbon fibers and MWCNTs were improved through fluorine modification on surface of MWCNTs. By fluorination treatment, hydrophobic functional group was introduced on the surface of MWCNTs improving the

  6. The role of electric charge in microdroplets impacting on conducting surfaces

    E-print Network

    Gomez, Alessandro

    of electric charge on the droplets affects the impact process is yet to be addressed. On dielectric surfacesThe role of electric charge in microdroplets impacting on conducting surfaces Weiwei Deng phenomenology is revealed by temporally resolved image sequences of electrically charged ethanol microdroplets

  7. Investigations of plasma cleaning on the reliability of electrically conductive adhesives

    Microsoft Academic Search

    J. E. Morris; S. Probsthain

    2000-01-01

    For the replacement of solder as the usual connection between electrical components by Isotropic Electrically Conductive Adhesives (ICAs), it is important to maintain mechanical and electrical properties comparable to the solder's characteristics. One performance area capable of improvement is the mechanical adhesion between the ICA and the contact surface. Plasma cleaning of surfaces should provide better mechanical strength and contact

  8. Reversible temperature regulation of electrical and thermal conductivity using liquid-solid phase transitions.

    PubMed

    Zheng, Ruiting; Gao, Jinwei; Wang, Jianjian; Chen, Gang

    2011-01-01

    Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions. PMID:21505445

  9. Reversible temperature regulation of electrical and thermal conductivity using liquid–solid phase transitions

    PubMed Central

    Zheng, Ruiting; Gao, Jinwei; Wang, Jianjian; Chen, Gang

    2011-01-01

    Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions. PMID:21505445

  10. Evaluation of electrical conductivity and equations of state of non-ideal plasma through microsecond timescale underwater electrical wire explosion

    SciTech Connect

    Sheftman, D.; Krasik, Ya. E. [Physics Department, Technion, Haifa 32000 (Israel)

    2011-09-15

    Experimental and simulation results of underwater electrical Cu, Al, and W wire explosions in the microsecond timescale are presented. It was shown that the electrical conductivity results for Cu and Al agree well with modified Lee-More and quantum molecular dynamic models for temperatures above 10 kK. The equation of state (EOS) values based on SESAME tables for Cu and Al were slightly modified for intermediate temperatures in order to obtain fitting between experimental and simulated exploding wire radial expansion. Also, it was shown that the electrical conductivity results and the EOS evaluation differ significantly from the results obtained in nanosecond timescale experiments. Finally, it was found that underwater electrical W wire explosion is characterized by the appearance of non-uniformities along the z-axis of the wire. This phenomena adds uncertainty to the possibility of applying this type of experiments for evaluation of the electrical conductivity and EOS of W.

  11. Evaluation of electrical conductivity and equations of state of non-ideal plasma through microsecond timescale underwater electrical wire explosion

    NASA Astrophysics Data System (ADS)

    Sheftman, D.; Krasik, Ya. E.

    2011-09-01

    Experimental and simulation results of underwater electrical Cu, Al, and W wire explosions in the microsecond timescale are presented. It was shown that the electrical conductivity results for Cu and Al agree well with modified Lee-More and quantum molecular dynamic models for temperatures above 10 kK. The equation of state (EOS) values based on SESAME tables for Cu and Al were slightly modified for intermediate temperatures in order to obtain fitting between experimental and simulated exploding wire radial expansion. Also, it was shown that the electrical conductivity results and the EOS evaluation differ significantly from the results obtained in nanosecond timescale experiments. Finally, it was found that underwater electrical W wire explosion is characterized by the appearance of non-uniformities along the z-axis of the wire. This phenomena adds uncertainty to the possibility of applying this type of experiments for evaluation of the electrical conductivity and EOS of W.

  12. Temperature Dependence of AC Electrical Conductivity of PVA-PPy-FeCl3 Composite Polymer Films

    Microsoft Academic Search

    Mohd Hamzah Harun; Elias Saion; Anuar Kassim; Muhd Yousuf Hussain; Iskandar Shahrim Mustafa; Muhd Ahmad Ali Omer

    2008-01-01

    The alternate current (ac) electrical conductivity of poly(vinyl alcohol)- polypyrrole-ferric chloride (PVA-PPy-FeCl3) composite films has been investigated at different temperatures at a frequency ranging from 20 Hz to 1 MHz. The electrical conductivity of the composite increased with increasing temperature and it obeys power law A?s in which s in the range 0.3electrical

  13. Highly Electrically Conductive Nanocomposites Based on PolymerInfused Graphene Sponges

    PubMed Central

    Li, Yuanqing; Samad, Yarjan Abdul; Polychronopoulou, Kyriaki; Alhassan, Saeed M.; Liao, Kin

    2014-01-01

    Conductive polymer composites require a threedimensional 3D network to impart electrical conductivity. A general method that is applicable to most polymers for achieving a desirable graphene 3D network is still a challenge. We have developed a facile technique to fabricate highly electrical conductive composite using vacuumassisted infusion of epoxy into graphene sponge GS scaffold. Macroscopic GSs were synthesized from graphene oxide solution by a hydrothermal method combined with freeze drying. The GSepoxy composites prepared display consistent isotropic electrical conductivity around 1Sm, and it is found to be close to that of the pristine GS. Compared with neat epoxy, GSepoxy has a 12ordersofmagnitude increase in electrical conductivity, attributed to the compactly interconnected graphene network constructed in the polymer matrix. This method can be extended to other materials to fabricate highly conductive composites for practical applications such as electronic devices, sensors, actuators, and electromagnetic shielding. PMID:24722145

  14. Investigation of the electrical conductivity of propylene glycol-based ZnO nanofluids

    NASA Astrophysics Data System (ADS)

    White, Steven Bryan; Shih, Albert Jau-Min; Pipe, Kevin Patrick

    2011-04-01

    Electrical conductivity is an important property for technological applications of nanofluids that has not been widely studied. Conventional descriptions such as the Maxwell model do not account for surface charge effects that play an important role in electrical conductivity, particularly at higher nanoparticle volume fractions. Here, we perform electrical characterizations of propylene glycol-based ZnO nanofluids with volume fractions as high as 7%, measuring up to a 100-fold increase in electrical conductivity over the base fluid. We observe a large increase in electrical conductivity with increasing volume fraction and decreasing particle size as well as a leveling off of the increase at high volume fractions. These experimental trends are shown to be consistent with an electrical conductivity model previously developed for colloidal suspensions in salt-free media. In particular, the leveling off of electrical conductivity at high volume fractions, which we attribute to counter-ion condensation, represents a significant departure from the "linear fit" models previously used to describe the electrical conductivity of nanofluids.

  15. Investigation of the electrical conductivity of propylene glycol-based ZnO nanofluids

    PubMed Central

    2011-01-01

    Electrical conductivity is an important property for technological applications of nanofluids that has not been widely studied. Conventional descriptions such as the Maxwell model do not account for surface charge effects that play an important role in electrical conductivity, particularly at higher nanoparticle volume fractions. Here, we perform electrical characterizations of propylene glycol-based ZnO nanofluids with volume fractions as high as 7%, measuring up to a 100-fold increase in electrical conductivity over the base fluid. We observe a large increase in electrical conductivity with increasing volume fraction and decreasing particle size as well as a leveling off of the increase at high volume fractions. These experimental trends are shown to be consistent with an electrical conductivity model previously developed for colloidal suspensions in salt-free media. In particular, the leveling off of electrical conductivity at high volume fractions, which we attribute to counter-ion condensation, represents a significant departure from the "linear fit" models previously used to describe the electrical conductivity of nanofluids. PMID:21711869

  16. Transient ULF Electric and magnetic fields of an electrical current source in a medium with continuously varying conductivity

    Microsoft Academic Search

    Shogo Kozaki

    1977-01-01

    Recent analytical studies of ULF electromagnetic fields in the atmosphere are reviewed. These fields have their origin in the discharge of thunderclouds. The problem for a vertical electrical dipole source played in an atmosphere where the conductivity increases exponentially with altitude is described. The analytical expressions for the electric and magnetic field, which vary in time and space, are approximately

  17. Evaluation of electrical conductivity and equations of state of non-ideal plasma through microsecond timescale underwater electrical wire explosion

    Microsoft Academic Search

    D. Sheftman; Ya. E. Krasik

    2011-01-01

    Experimental and simulation results of underwater electrical Cu, Al, and W wire explosions in the microsecond timescale are presented. It was shown that the electrical conductivity results for Cu and Al agree well with modified Lee-More and quantum molecular dynamic models for temperatures above 10 kK. The equation of state (EOS) values based on SESAME tables for Cu and Al

  18. Evaluation of DC electric field distribution of PPLP specimen based on the measurement of electrical conductivity in LN2

    NASA Astrophysics Data System (ADS)

    Hwang, Jae-Sang; Seong, Jae-Kyu; Shin, Woo-Ju; Lee, Jong-Geon; Cho, Jeon-Wook; Ryoo, Hee-Suk; Lee, Bang-Wook

    2013-11-01

    High temperature superconducting (HTS) cable has been paid much attention due to its high efficiency and high current transportation capability, and it is also regarded as eco-friendly power cable for the next generation. Especially for DC HTS cable, it has more sustainable and stable properties compared to AC HTS cable due to the absence of AC loss in DC HTS cable. Recently, DC HTS cable has been investigated competitively all over the world, and one of the key components of DC HTS cable to be developed is a cable joint box considering HVDC environment. In order to achieve the optimum insulation design of the joint box, analysis of DC electric field distribution of the joint box is a fundamental process to develop DC HTS cable. Generally, AC electric field distribution depends on relative permittivity of dielectric materials but in case of DC, electrical conductivity of dielectric material is a dominant factor which determines electric field distribution. In this study, in order to evaluate DC electric field characteristics of the joint box for DC HTS cable, polypropylene laminated paper (PPLP) specimen has been prepared and its DC electric field distribution was analyzed based on the measurement of electrical conductivity of PPLP in liquid nitrogen (LN2). Electrical conductivity of PPLP in LN2 has not been reported yet but it should be measured for DC electric field analysis. The experimental works for measuring electrical conductivity of PPLP in LN2 were presented in this paper. Based on the experimental works, DC electric field distribution of PPLP specimen was fully analyzed considering the steady state and the transient state of DC. Consequently, it was possible to determine the electric field distribution characteristics considering different DC applying stages including DC switching on, DC switching off and polarity reversal conditions.

  19. Imparting Electrical Conductivity into Asphalt Composites Using Graphite

    E-print Network

    Baranikumar, Aishwarya

    2013-07-09

    strength results for (b) Indirect tensile resilient modulus regular and conductive asphalt results at different temperatures (c) Indirect tensile fatigue life graph for regular and conductive asphalt composites... the temperature of asphalt concrete because the healing can be accelerated with increase of temperature (Bonnaure et al. 1982; Daniel and Kim 2001). Liu et al. (2010a; 21 2010b; 2010c) and Garcia showed the possibility of promoting self-healing by induction...

  20. Probing electrical conduction behavior of BaSnO3

    Microsoft Academic Search

    Shail Upadhyay; Ashok Kumar Sahu; Devendra Kumar; Om Parkash

    1998-01-01

    The ac conductivity, sigmaac of BaSnO3 has been measured in the temperature range 310-520 K and frequency range 100 Hz-1 MHz. Below 420 K the conductivity is almost independent of temperature while between 420 and 520 K it is temperature dependent. At 100 kHz the activation energy of these two regions is 0.08 and 0.35 eV, respectively. It has been

  1. Survey of conducted transients in the electrical system of a passenger automobile

    Microsoft Academic Search

    J. Alkalay; R. Ebrahimian; H. Kendall; M. Laskowski; A. Lee; D. Noderer

    1989-01-01

    As part of an effort to develop automotive electromagnetic compatibility (EMC) test procedures for evaluating conducted emissions and conducted susceptibility at the component level, an extensive survey of the electrical transients was conducted at various locations within the electrical\\/electronic system of a late-model automobile. Simultaneous measurements were made at selected potential sources of transients and at power-line inputs of potentially

  2. Pricing and Firm Conduct in California's Deregulated Electricity Market

    E-print Network

    California at Berkeley. University of

    generating firms bid into a daily auction for the right to supply power to the electrical grid. Policymakers of the Program on Workable Energy Regulation (POWER). POWER is a program of the University of California Energy-utility generators raised prices slightly above unilateral market power levels in 2000, but fell far short

  3. Studies on the electrical conduction in silver telluride thin films

    Microsoft Academic Search

    P. Gnanadurai; N. Soundararajan; C. E. Sooriamoorthi

    2003-01-01

    The temperature dependence of the electrical resistance of unannealed and annealed silver telluride thin films of different thickness between 30 and 110 nm, prepared by thermal evaporation at a pressure of 2 × 10-5 mbar, has been studied. The films are polycrystalline. It is found that metastable defects influence the phase transition in unannealed films. The annealed films undergo a

  4. Different Clinical Electrodes Achieve Similar Electrical Nerve Conduction Block

    PubMed Central

    Boger, Adam; Bhadra, Narendra; Gustafson, Kenneth J.

    2015-01-01

    Objective Evaluate the suitability of four electrodes previously used in clinical experiments for peripheral nerve electrical block applications. Approach We evaluated peripheral nerve electrical block using three such clinical nerve cuff electrodes (the Huntington helix, the Case self-sizing spiral and the Flat Interface Nerve Electrode) and one clinical intramuscular electrode (the Memberg electrode) in five cats. Amplitude thresholds for block using 12 or 25 kHz voltage-controlled stimulation, onset response, and stimulation thresholds before and after block testing were determined. Main results Complete nerve block was achieved reliably and the onset response to blocking stimulation was similar for all electrodes. Amplitude thresholds for block were lowest for the Case Spiral electrode (4 ± 1 Vpp) and lower for the nerve cuff electrodes (7 ± 3 Vpp) than for the intramuscular electrode (26 ± 10 Vpp). A minor elevation in stimulation threshold and reduction in stimulus-evoked urethral pressure was observed during testing, but the effect was temporary and did not vary between electrodes. Significance Multiple clinical electrodes appear suitable for neuroprostheses using peripheral nerve electrical block. The freedom to choose electrodes based on secondary criteria such as ease of implantation or cost should ease translation of electrical nerve block to clinical practice. PMID:23986089

  5. Machining of electrically conductive CVD diamond tool blanks using EDM

    Microsoft Academic Search

    R. H. Olsen; R. C. Dewes; D. K. Aspinwall

    2004-01-01

    The paper reviews the manufacture, microstructure and physical\\/mechanical properties of thick film chemical vapour deposited (CVD) diamond in relation to its use for cutting tools. In contrast to polycrystalline diamond (PCD), CVD diamond contains no metallic second phase, its microstructure comprising solely of columnar diamond grains. Experimental research involving an L27 Taguchi orthogonal array is presented relating to the electrical

  6. Steady-state electrical conduction in the periodic Lorentz gas

    Microsoft Academic Search

    N. I. Chernov; G. L. Eyink; J. L. Lebowitz; Ya. G. Sinai

    1993-01-01

    We study nonequilibrium steady states in the Lorentz gas of periodic scatterers when an electric external field is applied and the particle kinetic energy is held fixed by a “thermostat” constructed according to Gauss’ principle of least constraint (a model problem previously studied numerically by Moran and Hoover). The resulting dynamics is reversible and deterministic, but does not preserve Liouville

  7. Damage detection and conductivity evolution in carbon nanofiber epoxy via electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Tallman, T. N.; Gungor, S.; Wang, K. W.; Bakis, C. E.

    2014-04-01

    Utilizing electrically conductive nanocomposites for integrated self-sensing and health monitoring is a promising area of structural health monitoring (SHM) research wherein local changes in conductivity coincide with damage. In this research we conduct proof of concept investigations using electrical impedance tomography (EIT) for damage detection by identifying conductivity changes and by imaging conductivity evolution in a carbon nanofiber (CNF) filled epoxy composite. CNF/epoxy is examined because fibrous composites can be manufactured with a CNF/epoxy matrix thereby enabling the entire matrix to become self-sensing. We also study the mechanisms of conductivity evolution in CNF/epoxy through electrical impedance spectroscopy (EIS) testing. The results of these tests indicate that thermal expansion is responsible for conductivity evolution in a CNF/epoxy composite.

  8. Simultaneous measurement of electrical conductance and thermopower of single benzenedithiol molecular junctions

    NASA Astrophysics Data System (ADS)

    Kaneko, Satoshi; Nakamura, Yuuga; Matsushita, Ryuuji; Marqués-González, Santiago; Kiguchi, Manabu

    2015-06-01

    We have developed a system for the simultaneous measurement of electrical conductance and thermopower of the single benzenedithiol (BDT) molecular junction, which was characterized by inelastic electron tunneling spectroscopy, at low temperature. The simultaneous measurements revealed a negative correlation between the electrical conductance and the thermopower. Strong metal–molecule coupling at the single BDT molecular junction leads to high conductance and low thermopower because of the broadening of the conduction orbital, which explains the negative correlation. The observed fluctuation in conductance and thermopower reflects the change in the metal–molecule contact configuration and molecular orientation.

  9. Effect of elastic recovery on the electrical contact resistance in anisotropic conductive adhesive assemblies

    Microsoft Academic Search

    Melida Chin; James R. Barber; S. Jack Hu

    2006-01-01

    The successful design of anisotropic conductive adhesive (ACA) assemblies depends mainly on the accurate prediction of their electrical contact resistance. Among the parameters that influence this resistance, the bonding force used to compress the conductive particles against the conductive tracks during the assembly process is very important. This paper investigates how the contact resistance changes as the bonding force is

  10. The impulse photopyroelectric method for thermal characterization of electrically conducting polymers

    Microsoft Academic Search

    A. Frandas; H. Jalink; R. Turcu; M. Brie

    1995-01-01

    For electrically conducting polypyrole films, the thermal diffusivity and thermal conductivity were obtained by modeling the signals from the photopyroelectric flash technique with a one-dimensional four-layer system. This method has a number of advantages over the sinusoidal excitation: wide thickness range, fast acquisition, simple and cheap setup. This first thermal characterization of polypyrole films shows an increasing thermal conductivity with

  11. Electrical and Thermal Conductivity of Liquid Iron at Core Pressures and Temperatures: First-Principles Calculations

    Microsoft Academic Search

    N. de Koker; G. Steinle-Neumann; V. Vlcek

    2010-01-01

    The ability of liquid iron to transport heat and electric charge by conduction at extreme pressure and temperature is of paramount importance to the thermal history of the core. Thermal conductivity determines the amount of heat conducted along the core adiabat, i.e. heat not available for generation of the magnetic field, and also strongly controls the time required for the

  12. A Note on the Paper ``Electrical Conduction Between Metallic Microparticles''

    Microsoft Academic Search

    R. M. Hill

    1966-01-01

    The photoresponse of Nb.O. diodes with oxide films less than 400 A thick shows no interference effects. A metal-insulator-metal diode is a resonant cavity for optical radiation.7 ,8 Interference of electromagnetic radiation in the cavity is equivalent to the establishment of standing waves within the oxide. The maximum photoresponse of Nb-Nb.O.-metal diodes occurs when the electric vector of the standing

  13. Electrical Conduction in Glass Ceramics Containing Metal Nanodispersoids

    Microsoft Academic Search

    Tapas Kumar Kundu; Sourish Banerjee; Dipankar Chakravorty

    2003-01-01

    Silver particles of diameters ranging from 3.4 to 25.8 nm have been grown within a glass ceramic by controlling the morphology of the crystalline phase. The fractal dimension of the crystal phase has a marked effect on the particle diameter. The DC electrical resistivity of the glass-ceramic metal nanocomposites has been measured over the temperature range from 100 to 300

  14. Microstructure–electrical conductivity relationships in nanocrystalline ceria thin films

    Microsoft Academic Search

    Toshio Suzuki; Igor Kosacki; Harlan U Anderson

    2002-01-01

    A study of nanocrystalline oxide thin film processing and influence of microstructure on the electrical properties of nanocrystalline Gd3+-doped CeO2 thin films was reported. Nanocrystalline films on sapphire substrate were prepared using a polymeric precursor spin coating technique. The grain size of these films depends upon the annealing temperatures and the dopant content, where higher content of dopant realized smaller

  15. Electrical conductivity of lunar surface rocks - Laboratory measurements and implications for lunar interior temperatures

    NASA Technical Reports Server (NTRS)

    Schwerer, F. C.; Huffman, G. P.; Fisher, R. M.; Nagata, T.

    1974-01-01

    Results are reported for laboratory measurements of the dc and low-frequency ac electrical conductivity of three lunar rocks with ferrous iron contents of 5 to 26 wt %. The measurements were made at temperatures ranging from 20 to 1000 C, and Mossbauer spectroscopy was used to determine the dependence of electrical conductivity on furnace atmosphere. It is found that the magnitude of electrical conductivity generally increases with increasing iron content. A comparison of the data on these samples with data on terrestrial olivines and pyroxenes shows that the electrical conductivity of anhydrous silicate minerals is influenced primarily by the concentration, oxidation state, and distribution of iron, while the silicate crystal structure is only of secondary importance. Lunar interior temperatures are deduced from experimental lunar conductivity profiles, and the resulting temperature-depth profiles are found to be consistent with those calculated for two different lunar evolutionary models as well as with various experimental constraints.

  16. Electrical conductivity of electrolytes applicable to natural waters from 0 to 100 degrees C

    USGS Publications Warehouse

    McCleskey, R. Blaine

    2011-01-01

    The electrical conductivities of 34 electrolyte solutions found in natural waters ranging from (10-4 to 1) mol?kg-1 in concentration and from (5 to 90) °C have been determined. High-quality electrical conductivity data for numerous electrolytes exist in the scientific literature, but the data do not span the concentration or temperature ranges of many electrolytes in natural waters. Methods for calculating the electrical conductivities of natural waters have incorporated these data from the literature, and as a result these methods cannot be used to reliably calculate the electrical conductivity over a large enough range of temperature and concentration. For the single-electrolyte solutions, empirical equations were developed that relate electrical conductivity to temperature and molality. For the 942 molar conductivity determinations for single electrolytes from this study, the mean relative difference between the calculated and measured values was 0.1 %. The calculated molar conductivity was compared to literature data, and the mean relative difference for 1978 measurements was 0.2 %. These data provide an improved basis for calculating electrical conductivity for most natural waters.

  17. Comparative study of electrically conductive thick films with and without glass

    Microsoft Academic Search

    Zongrong Liu; D. D. L. Chung

    2004-01-01

    An air-fireable, glass-free, electrically conductive thick-film material (96.6% Ag, 1.38% Cu, 0.28% Al, 0.35% Ti, and 1.39%\\u000a Sn by weight) and a conventional glass-containing, electrically conductive thick-film materials (96.6% Ag and 3.4% glass frit\\u000a by weight), both on alumina substrates, were studied by electrical, mechanical, thermal, and microscopic methods. The volume\\u000a electrical resistivity of the glass-free thick film (2.510?6 ?cm,

  18. Nanostructured Cu-Cr alloy with high strength and electrical conductivity

    SciTech Connect

    Islamgaliev, R. K., E-mail: saturn@mail.rb.ru; Nesterov, K. M. [Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, Ufa 450000 (Russian Federation); Bourgon, J.; Champion, Y. [ICMPE-CNRS, Université Paris 12, 6-8 rue Henri Dunant, 94320 Thiais, cedex (France); Valiev, R. Z. [Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, Ufa 450000 (Russian Federation); Laboratory for Mechanics of Bulk Nanostructured Materials, Saint Petersburg State University, 198504 Peterhof, Saint Petersburg (Russian Federation)

    2014-05-21

    The influence of nanostructuring by high pressure torsion (HPT) on strength and electrical conductivity in the Cu-Cr alloy has been investigated. Microstructure of HPT samples was studied by transmission electron microscopy with special attention on precipitation of small chromium particles after various treatments. Effect of dynamic precipitation leading to enhancement of strength and electrical conductivity was observed. It is shown that nanostructuring leads to combination of high ultimate tensile strength of 790–840?MPa, enhanced electrical conductivity of 81%–85% IACS and thermal stability up to 500?°C. The contributions of grain refinement and precipitation to enhanced properties of nanostructured alloy are discussed.

  19. Electrical conduction mechanism in bulk ceramic insulators at high voltages until dielectric breakdown

    NASA Astrophysics Data System (ADS)

    Neusel, C.; Jelitto, H.; Schneider, G. A.

    2015-04-01

    In order to develop and verify a dielectric breakdown model for bulk insulators thicker than 100 ?m, the knowledge of the dominating conduction mechanism at high electric fields, or respectively voltages, is necessary. The dielectric breakdown is the electrical failure of an insulator. In some existing breakdown models, ohmic conduction is assumed as dominating conduction mechanism. For verification, the dominating dc conduction mechanism of bulk insulators at room temperature was investigated by applying high voltages up to 70 kV to the insulator until dielectric breakdown occurs. Four conduction models, namely, ohmic, space charge limited, Schottky, and Poole-Frenkel conduction, were employed to identify the dominating conduction mechanism. Comparing the calculated permittivities from the Schottky and Poole-Frenkel coefficients with experimentally measured permittivity, Schottky and Poole-Frenkel conduction can be excluded as dominating conduction mechanism. Based on the current density voltage characteristics (J-V-curve) and the thickness-dependence of the current density, space charge limited conduction (SCLC) was identified to be the dominating conduction mechanism at high voltages leading to dielectric breakdown. As a consequence, breakdown models based on ohmic conduction are not appropriate to explain the breakdown of the investigated bulk insulators. Furthermore, the electrical failure of the examined bulk insulators can only be described correctly by a breakdown model which includes SCLC as conduction mechanism.

  20. Electrical conductivity of cationized ferritin decorated gold nanoshells

    NASA Astrophysics Data System (ADS)

    Cortez, Rebecca; Slocik, Joseph M.; Van Nostrand, Joseph E.; Halas, Naomi J.; Naik, Rajesh R.

    2012-06-01

    We report on a novel method of controlling the resistance of nanodimensional, gold-coated SiO2 nanoparticles by utilizing biomolecules chemisorbed to the nanoshell surface. Local electronic transport properties of gold-coated nanoshells were measured using scanning conductance microscopy. These results were compared to transport properties of identical gold nanoshells biofunctionalized with cationized ferritin protein both with and without an iron oxide core (apoferritin). Measured resistances were on the order of mega-ohms. White light irradiation effects on transport properties were also explored. The results suggest that the light energy influences the nanoshells' conductivity. A mechanism for assembly of gold nanoshells with cationized ferritin or cationized apoferritin is proposed to explain the resistivity dependence on irradiation.

  1. Electrical conductivity of single organic molecules in ultra high vacuum

    NASA Astrophysics Data System (ADS)

    Pires, Ellis John

    Measurement of the I(V ) characteristics of single molecules is the first step towards the realisation of molecular electronic devices. In this thesis, the electronic transport properties of alkanedithiol (ADT) and alkylthiol-terminated oligothiophene molecules are investigated under ultrahigh vacuum (UHV) using a scanning tunnelling microscope (STM). Two techniques are employed that rely upon stochastic molecular bridge formation between gold STM tip and substrate; a novel I(V; s) method is proven to be a powerful alternative to the well-known I(s) method. For ADTs, three temperature-independent (180 - 390 K) conduction groups are identified, which arise from different contact-substrate coordination geometries. The anomalous reduction of conductance at small chain lengths reported by other groups for non-UHV conditions is far less pronounced here; all groups closely follow the anticipated exponential decay.

  2. Iodine doped carbon nanotube cables exceeding specific electrical conductivity of metals

    PubMed Central

    Zhao, Yao; Wei, Jinquan; Vajtai, Robert; Ajayan, Pulickel M.; Barrera, Enrique V.

    2011-01-01

    Creating highly electrically conducting cables from macroscopic aggregates of carbon nanotubes, to replace metallic wires, is still a dream. Here we report the fabrication of iodine-doped, double-walled nanotube cables having electrical resistivity reaching ?10?7??.m. Due to the low density, their specific conductivity (conductivity/weight) is higher than copper and aluminum and is only just below that of the highest specific conductivity metal, sodium. The cables exhibit high current-carrying capacity of 104?105?A/cm2 and can be joined together into arbitrary length and diameter, without degradation of their electrical properties. The application of such nanotube cables is demonstrated by partly replacing metal wires in a household light bulb circuit. The conductivity variation as a function of temperature for the cables is five times smaller than that for copper. The high conductivity nanotube cables could find a range of applications, from low dimensional interconnects to transmission lines. PMID:22355602

  3. Development of eddy current microscopy for high resolution electrical conductivity imaging using atomic force microscopy.

    PubMed

    Nalladega, V; Sathish, S; Jata, K V; Blodgett, M P

    2008-07-01

    We present a high resolution electrical conductivity imaging technique based on the principles of eddy current and atomic force microscopy (AFM). An electromagnetic coil is used to generate eddy currents in an electrically conducting material. The eddy currents generated in the conducting sample are detected and measured with a magnetic tip attached to a flexible cantilever of an AFM. The eddy current generation and its interaction with the magnetic tip cantilever are theoretically modeled using monopole approximation. The model is used to estimate the eddy current force between the magnetic tip and the electrically conducting sample. The theoretical model is also used to choose a magnetic tip-cantilever system with appropriate magnetic field and spring constant to facilitate the design of a high resolution electrical conductivity imaging system. The force between the tip and the sample due to eddy currents is measured as a function of the separation distance and compared to the model in a single crystal copper. Images of electrical conductivity variations in a polycrystalline dual phase titanium alloy (Ti-6Al-4V) sample are obtained by scanning the magnetic tip-cantilever held at a standoff distance from the sample surface. The contrast in the image is explained based on the electrical conductivity and eddy current force between the magnetic tip and the sample. The spatial resolution of the eddy current imaging system is determined by imaging carbon nanofibers in a polymer matrix. The advantages, limitations, and applications of the technique are discussed. PMID:18681706

  4. (Revised May 25, 2012) (1) To understand Ohm's law, used to describe the behavior of electrical conduction in many

    E-print Network

    Collins, Gary S.

    of electrical conduction in many materials and circuits. (2) To calculated the electrical power dissipated resistor, in an electrical circuit. (4) To learn how to connect electrical circuits to allow the electrical tungsten-filament light bulb. INTRODUCTION One of the most basic electrical circuits is a resistor

  5. Tunable single-photon heat conduction in electrical circuits

    E-print Network

    P. J. Jones; J. A. M. Huhtamäki; M. Partanen; K. Y. Tan; M. Möttönen

    2012-05-21

    We build on the study of single-photon heat conduction in electronic circuits taking into account the back-action of the superconductor--insulator--normal-metal thermometers. In addition, we show that placing capacitors, resistors, and superconducting quantum interference devices (SQUIDs) into a microwave cavity can severely distort the spatial current profile which, in general, should be accounted for in circuit design. The introduction of SQUIDs also allows for in situ tuning of the photonic power transfer which could be utilized in experiments on superconducting quantum bits.

  6. An evaluation of total body electrical conductivity to estimate body composition of largemouth bass 

    E-print Network

    Barziza, Daniel Eugene

    1998-01-01

    Information about body composition of fish is important for the assessment and management of fish stocks. Measurement of total body electrical conductivity (TOBEC) recently has been used to estimate the body composition of several fish species in a...

  7. Electromagnetic sounding and crustal electrical conductivity in the region of the Wopmay Orogen, Northwest Territories, Canada!

    E-print Network

    Jones, Alan G.

    Electromagnetic sounding and crustal electrical conductivity in the region of the Wopmay Orogen of a very resistive layered Earth model derived from inversion of magnetotelluric sounding data at a central

  8. Electrical conductivity of SbF5 doped polyacetylene M. Rolland, P. Bernier

    E-print Network

    Boyer, Edmond

    the temperature dependence of the thermoelectric power of doped (CH)x and explained their experi- mental results electrical anisotropy with a longi- tudinal to transverse conductivity ratio roughly equal to ten [7

  9. Mixed ionic and electronic conducting electrode studies for an alkali metal thermal to electric converter

    Microsoft Academic Search

    Yuyan Guo

    2006-01-01

    This research focuses on preparation, kinetics, and performance studies of mixed ionic and electronic conducting electrodes (MIEE) applied in an alkali metal thermal to electric converter (AMTEC). Two types of MIEE, metal\\/sodium titanate and metal\\/beta\\

  10. EVIDENCE FOR MICROBIAL ENHANCED ELECTRICAL CONDUCTIVITY IN HYDROCARBON-CONTAMINATED SEDIMENTS

    EPA Science Inventory

    Electrical conductivity of sediments during microbial mineralization of diesel was investigated in a mesoscale column experiment consisting of biotic contaminated and uncontaminated columns. Microbial population numbers increased with a clear pattern of depth zonation within the ...

  11. An emulsion polymerization process for soluble and electrically conductive polyaniline

    SciTech Connect

    Kinlen, P.J.; Ding, Y.; Graham, C.R.; Liu, J.; Remsen, E.E.

    1998-07-01

    A new emulsion process has been developed for the direct synthesis of the emeraldine salt of polyaniline (PANI) that is soluble in organic solvents. The process entails forming an emulsion composed of water, a water soluble organic solvent (e.g., 2-butoxyethanol), a water insoluble organic acid (e.g., dinonylnaphthalene sulfonic acid) and aniline. Aniline is protonated by the organic acid to form a salt which partitions into the organic phase. As oxidant (ammonium peroxydisulfate) is added, PANI salt forms in the organic phase and remains soluble. As the reaction proceeds, the reaction mixture changes from an emulsion to a two phase system, the soluble PANI remaining in the organic phase. With dinonylnaphthalene sulfonic acid (DNNSA) as the organic acid, the resulting product is truly soluble in organic solvents such as xylene and toluene (not a dispersion), of high molecular weight (M{sub w} > 22,000), film forming and miscible with many polymers such as polyurethanes, epoxies and phenoxy resins. As cast, the polyaniline film is only moderately conductive, (10{sup {minus}5} S/cm), however treatment of the film with surfactants such as benzyltriethylammonium chloride (BTEAC) or low molecular weight alcohols and ketones such as methanol and acetone increases the conductivity 2--3 orders of magnitude.

  12. An evaluation of total body electrical conductivity to estimate body composition of largemouth bass

    E-print Network

    Barziza, Daniel Eugene

    1998-01-01

    AN EVALUATION OF TOTAL BODY ELECTRICAL CONDUCTIVITY TO ESTIMATE BODY COMPOSITION OF LARGEMOUTH BASS A Thesis by DANIEL EUGENE BARZIZA Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE August 1998 Major Subject: Nutrition AN EVALUATION OF TOTAL BODY ELECTRICAL CONDUCTIVITY TO ESTIMATE BODY COMPOSITION OF LARGEMOUTH BASS A Thesis by DANIEL EUGENE BARZIZA Submitted to Texas Ak...

  13. Effect of CNT decoration with silver nanoparticles on electrical conductivity of CNT-polymer composites

    Microsoft Academic Search

    Peng Cheng Ma; Ben Zhong Tang; Jang-Kyo Kim

    2008-01-01

    A simple approach to decorate carbon nanotube (CNT) with silver nanoparticles (Ag-NPs) was developed to enhance the electrical conductivity of CNT. CNTs were functionalized using ball milling in the presence of ammonium bicarbonate, followed by reduction of silver ions in N, N-dimethylformamide, producing silver decorated CNTs (Ag@CNTs). The Ag@CNTs were employed as conducting filler in epoxy resin to fabricate electrically

  14. Somatic Cell Count, Electrical Conductivity, and Serum Albumin Concentration for Detecting Bovine Mastitis

    Microsoft Academic Search

    R. F. Sheldrake; G. D. McGregor; R. J. T. Hoare

    1983-01-01

    Cell concentration, electrical conduc- tivity, and serum albumin concentration of milk were evaluated for predicting infection status of quarters in three herds. Probability of misclassifying quarters was lowest for cell concentration. For discriminating quarters infected with Staphylococcus aureus from quarters free from infection, probability of misclassifi- cation for cell concentration ranged from 8 to 20% among herds. For electrical conductivity

  15. Cardiovascular and Physiologic Effects of Conducted Electrical Weapon Discharge in Resting Adults

    Microsoft Academic Search

    Jeffrey D. Ho; James R. Miner; Dhanunjaya R. Lakireddy; Laura L. Bultman; William G. Heegaard

    2006-01-01

    Objectives: The TASER is a conducted electrical weapon (CEW) that has been used on people in custody. Individuals occasionally die unexpectedly while in custody, proximal to the application of a CEW. In this study, the authors sought to examine the effects of CEW application in resting adult volunteers to deter- mine if there was evidence of induced electrical dysrhythmia or

  16. Effects of surface-active demulsifiers on electrical conductivity of emulsions of water in crude oil

    Microsoft Academic Search

    A. A. Yunusov; G. M. Akhmadiev; G. A. Babalyan

    1984-01-01

    This article examines the effects of various emulsifiers on the electrical conductivity (EC) of emulsions of water in crude oil under conditions approaching the conditions prevailing in crude oil demulsification in electrocoalescing vessels. It is assumed that the EC of inverse hydrocarbon emulsions depends on the strength of the electric field. Beginning at a field strength of some hundreds of

  17. Analysis of electrically conductive silver ink on stretchable substrates under tensile load

    Microsoft Academic Search

    Sari Merilampi; Toni Björninen; Veikko Haukka; Pekka Ruuskanen; Leena Ukkonen; Lauri Sydänheimo

    2010-01-01

    Electrical conductors were printed by the screen printing method on stretchable PVC substrates and on fabrics. Polymer thick film silver ink was used as the conductive medium. The electrical performance and the structure of the ink film were investigated in unloaded conditions and under strain. In addition, the ink film morphology was examined. The goal of this study was to

  18. Predictions of the electrical conductivity and charging of the cloud particles in Jupiter's atmosphere

    Microsoft Academic Search

    R. C. Whitten; W. J. Borucki; K. O'Brien; S. N. Tripathi

    2008-01-01

    The electrical conductivity and electrical charge on cloud particles (composed of ammonia, ammonium hydrosulfide, and water) in the atmosphere of Jupiter are computed for pressures between 5.5 and 0.1 bars. The source of ionization is galactic cosmic rays (GCR). The distribution of charge among the various reservoirs is a function of altitude and the total area of the aerosol particles.

  19. Predictions of the Electrical Conductivity and Charging of the Aerosols in Titan's Atmosphere

    Microsoft Academic Search

    R. C. Whitten; W. J. Borucki; E. L. Bakes; E. Barth; S. Tripathi

    2004-01-01

    The electrical conductivity and electrical charge on the aerosols in the atmosphere of Titan will be presented for altitudes between 0 and 400 km as well as for both daytime and nighttime conditions. Ionization due to both galactic cosmic rays and electron precipitation from Saturn's magnetosphere is included. This ionization results in the production of free electrons and the primary

  20. Base metal alloys with self-healing native conductive oxides for electrical contact materials

    E-print Network

    Alpay, S. Pamir

    Base metal alloys with self-healing native conductive oxides for electrical contact materials M surfaces are used ubiquitously in electrical and electronic contacts for the interconnection of compo. Aindow,1,a S. P. Alpay,1 Y. Liu,1 J. V. Mantese,2 and B. S. Senturk1 1 Institute of Materials Science

  1. Estimating topsoil water content of clay soils with data from time-lapse electrical conductivity surveys

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Spatial estimation of soil water content (') at the field, hillslope, or catchment scale is required in numerous applications. Time-lapse electrical resistivity and electrical conductivity surveys were recognized as the useful source of information about both spatial variations in soil water conten...

  2. Near Surface Electrical Characterization of Hydraulic Conductivity: From Petrophysical Properties to Aquifer Geometries—A Review

    Microsoft Academic Search

    Lee Slater

    2007-01-01

    This paper reviews the recent geophysical literature addressing the estimation of saturated hydraulic conductivity (K) from static low frequency electrical measurements (electrical resistivity, induced polarization (IP) and spectral induced\\u000a polarization (SIP)). In the first part of this paper, research describing how petrophysical relations between electrical properties\\u000a and effective (i.e. controlling fluid transport) properties of (a) the interconnected pore volumes and

  3. Influence of FeO and H on the electrical conductivity of olivine

    NASA Astrophysics Data System (ADS)

    Dai, Lidong; Karato, Shun-ichiro

    2014-12-01

    The influence of Fe (iron) and H (hydrogen) on the electrical conductivity of olivine was investigated. Synthetic olivine aggregates with the XFe = Fe/(Fe + Mg) (molar ratio) = 21-64% with the water content of 84-620 ppm wt (Paterson calibration) were prepared and their electrical conductivity was measured at P = 4 GPa and T = 873-1473 K. The impedance spectroscopy was used to calculate the DC electrical conductivity. We found that electrical conductivity of samples increases with increasing FeO content in both anhydrous and hydrous olivine. However, the way in which FeO enhances electrical conductivity is different between anhydrous and hydrous olivine. In anhydrous sample, the activation energy is reduced with FeO content and hence the effect of FeO content is large at low temperatures, but its effect is small at mantle temperatures. In contrast, FeO content does not affect the activation energy in hydrous olivine, and consequently, the magnitude of FeO effect is nearly independent of temperature. For both anhydrous and hydrous olivine, the influence of FeO is only modest at high temperatures (increase in conductivity by a factor of ?2 for the increase in FeO by 20% (e.g., from 10 to 30%)). In contrast, the FeO content has relatively large effects at low temperatures for anhydrous olivine. However, the role of hydrogen is large at low temperatures and hydrogen mechanism dominates under most cases. Therefore the influence of FeO on electrical conductivity is small at all temperatures for a plausible range of water content. We conclude that the water (hydrogen) content in a terrestrial planet can be inferred from observed conductivity without substantial influence of FeO if the temperature is constrained. The present results provide a basis for the interpretation of electrical conductivity model of other planets with different FeO contents.

  4. Effect of Lubricants and Annealing Treatment on the Electrical Conductivity and Microstructure of Rolled Copper Foil

    NASA Astrophysics Data System (ADS)

    Xiong, Sang; Sun, Jianlin; Xu, Yang; Yan, Xundong

    2015-07-01

    X-ray diffraction and transmission electron microscopy have been used to study the microstructure of copper foil during rolling. Annealing was used to release work hardening of rolled copper foil (RCF), and electrical conductivity was determined by use of a PPMS-9 comprehensive physical property-measurement system. The microstructure and electrical conductivity of RCF are discussed. Our results showed that the relative intensity of the (220) diffraction peak increased continuously with decreasing sample thickness and that rolling induced preferred orientation. Many obvious crystallographic defects were present; these seriously affected electrical conductivity. The electrical conductivity of RCF decreases with increasing lattice distortion and micro defects which occur during deformation, especially when the surface adsorbs lubricant. However, annealing reduced lattice distortion and the scattering of conducting electrons at these defects, thus improving the electrical properties. For foil thickness in the range 25-180 ?m, annealing temperatures in the range 150-300°C, and annealing times in the range 2.5-3.0 h, the electrical conductivity of RCF increased with increasing thickness and annealing temperature, and decreased with increasing annealing time.

  5. Resolving Lithological Units in the Vadose Zone from Temporal Changes in Electrical Conductivity

    NASA Astrophysics Data System (ADS)

    Chang, J. P.; Knight, R. J.

    2014-12-01

    Obtaining estimates of hydraulic properties in the vadose zone is a challenge. Laboratory experiments using core samples from the field are not typically representative of true field conditions, and direct hydrologic field measurements are typically limited in spatial extent. Here, we propose to resolve lithologic variation in the vadose zone though geophysical methods, and specifically by examining temporal changes in electrical conductivity. Because different lithologies have different hydraulic properties, they will exhibit different temporal changes in water content during infiltration and drainage. Simulations of infiltration through various vadose zone models shows, as expected, that water content in clays and silts generally show very little variation over time, whereas water content in sands shows rapid and significant changes over time. Although water content cannot be directly measured in the field, it is highly correlated with electrical conductivity. Therefore, we examine the time derivatives of electrical conductivity data to monitor the rates of change in water content over time. Because geophysical measurements are often noisy, we estimate derivatives using the continuous wavelet transform rather than standard numerical differentiation. By implementing this method on synthetic noisy data, we find that rates of change in water content, and hence electrical conductivity, are consistently close to zero in clays, slightly variable in silts, and highly variable in sands. Application of this method to electrical conductivity probe data from a region of known lithology supports these observations and suggests that examining temporal changes in electrical conductivity can be used to resolve different lithologies in the vadose zone.

  6. Single flexible nanofiber to achieve simultaneous photoluminescence-electrical conductivity bifunctionality.

    PubMed

    Sheng, Shujuan; Ma, Qianli; Dong, Xiangting; Lv, Nan; Wang, Jinxian; Yu, Wensheng; Liu, Guixia

    2015-02-01

    In order to develop new-type multifunctional composite nanofibers, Eu(BA)3 phen/PANI/PVP bifunctional composite nanofibers with simultaneous photoluminescence and electrical conductivity have been successfully fabricated via electrospinning technology. Polyvinyl pyrrolidone (PVP) is used as a matrix to construct composite nanofibers containing different amounts of Eu(BA)3 phen and polyaniline (PANI). X-Ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), fluorescence spectroscopy and a Hall effect measurement system are used to characterize the morphology and properties of the composite nanofibers. The results indicate that the bifunctional composite nanofibers simultaneously possess excellent photoluminescence and electrical conductivity. Fluorescence emission peaks of Eu(3+) ions are observed in the Eu(BA)3 phen/PANI/PVP photoluminescence-electrical conductivity bifunctional composite nanofibers. The electrical conductivity reaches up to the order of 10(-3) ?S/cm. The luminescent intensity and electrical conductivity of the composite nanofibers can be tuned by adjusting the amounts of Eu(BA)3 phen and PANI. The obtained photoluminescence-electrical conductivity bifunctional composite nanofibers are expected to possess many potential applications in areas such as microwave absorption, molecular electronics, biomedicine and future nanomechanics. More importantly, the design concept and construction technique are of universal significance to fabricate other bifunctional one-dimensional naonomaterials. PMID:24817327

  7. High frequency electrical conduction block of the pudendal nerve

    NASA Astrophysics Data System (ADS)

    Bhadra, Narendra; Bhadra, Niloy; Kilgore, Kevin; Gustafson, Kenneth J.

    2006-06-01

    A reversible electrical block of the pudendal nerves may provide a valuable method for restoration of urinary voiding in individuals with bladder-sphincter dyssynergia. This study quantified the stimulus parameters and effectiveness of high frequency (HFAC) sinusoidal waveforms on the pudendal nerves to produce block of the external urethral sphincter (EUS). A proximal electrode on the pudendal nerve after its exit from the sciatic notch was used to apply low frequency stimuli to evoke EUS contractions. HFAC at frequencies from 1 to 30 kHz with amplitudes from 1 to 10 V were applied through a conforming tripolar nerve cuff electrode implanted distally. Sphincter responses were recorded with a catheter mounted micro-transducer. A fast onset and reversible motor block was obtained over this range of frequencies. The HFAC block showed three phases: a high onset response, often a period of repetitive firing and usually a steady state of complete or partial block. A complete EUS block was obtained in all animals. The block thresholds showed a linear relationship with frequency. HFAC pudendal nerve stimulation effectively produced a quickly reversible block of evoked urethral sphincter contractions. The HFAC pudendal block could be a valuable tool in the rehabilitation of bladder-sphincter dyssynergia.

  8. Electrical conductivity response of poly(phenylene-vinylene)/zeolite composites exposed to ammonium nitrate.

    PubMed

    Kamonsawas, Jirarat; Sirivat, Anuvat; Niamlang, Sumonman; Hormnirun, Pimpa; Prissanaroon-Ouajai, Walaiporn

    2010-01-01

    Poly(p-phenylenevinylene) (PPV) was chemically synthesized via the polymerization of p-xylene-bis(tetrahydrothiophenium chloride) monomer and doped with H(2)SO(4). To improve the electrical conductivity sensitivity of the conductive polymer, Zeolites Y (Si/Al = 5.1, 30, 60, 80) were added into the conductive polymer matrix. All composite samples show definite positive responses towards NH(4)NO(3). The electrical conductivity sensitivities of the composite sensors increase linearly with increasing Si/Al ratio: with values of 0.201, 1.37, 2.80 and 3.18, respectively. The interactions between NH(4)NO(3) molecules and the PPV/zeolite composites with respect to the electrical conductivity sensitivity were investigated through the infrared spectroscopy. PMID:22219677

  9. Measurements of Electrical and Thermal Conductivity of Iron Under Earth's Core Conditions

    NASA Astrophysics Data System (ADS)

    Ohta, K.; Kuwayama, Y.; Shimizu, K.; Yagi, T.; Hirose, K.; Ohishi, Y.

    2014-12-01

    Secular cooling of the Earth's core induces the convection of the conductive liquid outer core, which generates the geomagnetic field, and the growth of the solid inner core. Since iron is the primary component of the Earth's core, the electrical and thermal conductivity of iron in both solid and liquid states are key pieces of information for estimating the transport properties of the core. We performed electrical and thermal conductivity measurements on iron under core conditions in a laser-heated diamond anvil cell. Our electrical conductivity measurements on iron clearly show resistivity saturation phenomena in iron under high pressure and high temperature conditions as predicted in a recent laboratory-based model for the core conductivity (Gomi et al., 2013). Direct measurements of thermal diffusivity of iron have been also preformed at high pressures by using the pulsed light heating thermoreflectance technique, which enable us to confirm the validity of the Wiedemann-Franz law toward transition metal under high pressure.

  10. Continuous monitoring of sweating by electrical conductivity measurement.

    PubMed

    Shamsuddin, A K; Togawa, T

    1998-08-01

    A method of continuous monitoring of sweating was developed in which sweat was detected by changes in the conductivity of perfusing water. An ion-free solution was perfused at a constant flow rate through a chamber attached to the skin surface. The chamber was designed so that the electrodes were installed inside at the inlet and outlet, and a 14 mm3 channel was constructed at the bottom to wash out sweat. The 90% response time was 0.12 s. Attaching the chamber to the palm allowed measurements to be made with the subject seated in a comfortable environment. The sweat rate and heart rate were measured simultaneously with an air-ventilation chamber and a heart rate counter, respectively, with the subjects at rest, and under stresses such as grasping hands and doing mental arithmetic. This method yields sweat responses similar to those obtained with an air-ventilation chamber and simultaneous heart rate measurements. The main advantages of this method are faster response time and smaller observation area. PMID:9735888

  11. The effect of dissimilatory Iron reduction, Nitrate reduction and microbial growth electrical conductivity

    NASA Astrophysics Data System (ADS)

    Regberg, Aaron B.

    In this dissertation changes in measured electrical conductivity are related to measured changes in aqueous concentrations of ions. In previous work anomalous increases in electrical conductivity measured in and around contaminated aquifers have been associated with biogeochemical activity. The respiration and growth of micro-organisms has been suggested as a possible cause of these conductivity signals. However, a quantitative link between the activity of micro-organisms and electrical conductivity has not been established. Normally, the bulk electrical conductivity (?b) of a water-saturated sediment responds to changes in concentrations of ions in solution. If micro-organisms in the subsurface are catalyzing mineral dissolution or precipitation, ? b may be affected by changing concentration of ions in the pore fluids. In this dissertation changes in the fluid electrical conductivity (? f) and ob are related to changes in chemical concentrations at multiple scales. Changes in of can be interpreted as reaction rates if the stoichiometry of the reaction is understood. Results from batch experiments demonstrate that measured changes in ?f over time document rates of abiotic and biotic reduction of goethite. Rates of change in conductivity are related quantitatively to rates of reduction. In two column reactors packed with sediments from Oyster Virginia and fed with a flowing input containing dissolved acetate, measured changes in ? b initially document biogeochemical reaction rates of iron reduction or nitrate reduction in the sediment. Eventually, ?b becomes decoupled from changes in chemical concentrations and increases significantly. Fe(II) adsorption does not cause ?b to become decoupled from aqueous chemistry. Instead, this decoupling is attributed to the growth and presence of an electrically conductive biofilm. Reactive transport modeling is used to constrain the amount of biomass produced in each reactor. A value for electrical conductivity is estimated that depends on the calculated growth in biomass and the assumed density of that biomass. For iron-reducing conditions biofilms, the model is consistent with values of biofilm conductivity > 2.2 S/m, and for nitrate reducing conditions, with conductivity > 300 S/m. The value for biofilm conductivity for iron-reducing conditions seems reasonable, but the value for nitrate-reducing conditions, ~ 60 times more conductive than sea water, may be unreasonably large. Nonetheless, these values are the first estimates for biofilm electrical conductivity based on column reactor experiments. The results of a field-scale tracer test involving nitrate reduction are also presented. The results suggest that electrical conductivity may be able to track biogeochemical activity if the tracers are large enough and conductive enough to be detectable. Finally, results of preliminary electrochemical experiments designed to directly measure the conductivity of biofilms are presented. Methods for improving the accuracy of these experiments are proposed. The research presented in this dissertation provides examples for when quantitative relationships between measured changes in of and ob and measured changes in aqueous chemistry can be defined. In situations where ob increases at rates faster than observed changes in fluid chemistry, conductive biofilms are suggested as a theoretical explanation for this phenomenon. This research lays the groundwork for further investigations into the existence of electrically conductive biofilms. Additionally, methods for constructing field-scale experiments are suggested. A framework for interpreting electrical conductivity data with respect to biogeochemical reactions is also described.

  12. Electrically conductive, black thermal control coatings for space craft application. II - Silicone matrix formulation

    NASA Technical Reports Server (NTRS)

    Hribar, V. F.; Bauer, J. L.; O'Donnell, T. P.

    1986-01-01

    Five black electrically conductive thermal-control coatings have been formulated and tested for application on the Galileo spacecraft. The coatings consisted of organic and inorganic systems applied on titanium and aluminum surfaces. The coatings were tested under simulated space environment conditions. Coated specimens were subjected to thermal radiation and convective and conductive heating from -196 to 538 C. Mechanical, physical, thermal, electrical, and optical characteristics, formulation, mixing, application, surface preparation of substrates, and a method of determining electrical resistance are presented for the silicone matrix formulation designated as GF-580.

  13. Solid State Physics View of Liquid State Chemistry III. Electrical Conductance of Pure and Impure Water

    NASA Astrophysics Data System (ADS)

    Binbin, Jie; Chihtang, Sah

    2014-04-01

    The ‘abnormally’ high electrical conductivity of pure water was recently studied by us using our protonic bond, trap and energy band model, with five host particles: the positive and negative protons, and the amphoteric protonic trap in three charge states, positive, neutral and negative. Our second report described the electrical charge storage capacitance of pure and impure water. This third report presents the theory of particle density and electrical conductance of pure and impure water, including the impuritons, which consist of an impurity ion bonded to a proton, proton-hole or proton trap and which significantly affect impure waters' properties.

  14. Electrical conductivity and thermal decomposition of high temperature phenolic- and silicone-based materials

    SciTech Connect

    Johnson, R.T. Jr.; Biefeld, R.M.

    1981-01-01

    The temperature dependence of the electrical conductivity and thermal decomposition characterisitcs of several phenolic and silicone resins reinforced with glass chopped fabric or cloth have been measured to 600 to 700/sup 0/C in a nitrogen atmosphere. The electrical results are correlated with mass loss and thermal decomposition product data obtained using mass spectroscopy and thermal gravimetric analysis. Peaks in the conductivity temperature dependence and deviations from ohmic behavior are found to be associated with material decomposition and/or outgassing. Results show a direct correlation between thermal stability and temperature dependent electrical characteristics.

  15. Change in the electrical conductivity of SnO2 crystal from n-type to p-type conductivity

    NASA Astrophysics Data System (ADS)

    Villamagua, Luis; Stashans, Arvids; Lee, Po-Ming; Liu, Yen-Shuo; Liu, Cheng-Yi; Carini, Manuela

    2015-05-01

    The long-sought fully transparent technology will not come true if the n region of the p-n junction does not get as well developed as its p counterpart. Both experimental and theoretical efforts have to be used to study and discover phenomena occurring at the microscopic level in SnO2 systems. In the present paper, using the DFT + U approach as a main tool and the Vienna ab initio Simulation Package (VASP) we reproduce both intrinsic n-type as well as p-type conductivity in concordance to results observed in real samples of SnO2 material. Initially, an oxygen vacancy (1.56 mol% concentration) combined with a tin-interstitial (1.56 mol% concentration) scheme was used to achieve the n-type electrical conductivity. Later, to attain the p-type conductivity, crystal already possessing n-type conductivity, was codoped with nitrogen (1.56 mol% concentration) and aluminium (12.48 mol% concentration) impurities. Detailed explanation of structural changes endured by the geometry of the crystal as well as the changes in its electrical properties has been obtained. Our experimental data to a very good extent matches with the results found in the DFT + U modelling.

  16. Carbon-enhanced electrical conductivity during fracture of rocks

    NASA Astrophysics Data System (ADS)

    Roberts, J. J.; Duba, A. G.; Mathez, E. A.; Shankland, T. J.; Kinzler, R.

    1999-01-01

    Changes in electrical resistance during rock fracture in the presence of a carbonaceous atmosphere have been investigated using Nugget sandstone and Westerly granite. The experiments were performed in an internally heated, gas-pressure vessel with a load train that produced strain rates between 10-6 and 10-5 s-1. Samples were deformed at temperatures of 354° to 502°C and pressures of 100 to 170 MPa in atmospheres of Ar or mixtures of 95% CO2 with 5% CO or 5% CH4, compositions that are well within the field of graphite stability at the run conditions. In experiments using Nugget sandstone, resistance reached a minimum value when the maximum temperature was achieved and good electrode contact was made. The resistance then increased as the experiment continued, probably due to dry out of the sample, a change in the oxidation state of the Fe-oxide associated with the cement, or destruction of current-bearing pathways. At approximately 200-MPa end load, the rock sample failed. Plots of load and resistance versus time show several interesting features. In one experiment, for example, as the end load reached about 175 MPa, resistance stopped increasing and remained fairly constant for a period of approximately 0.5 hour. During loading, the end load displayed small decreases that were simultaneous with small decreases in resistance; when the end load (and the displacement) indicated rock failure, resistance decreased dramatically, from ˜150 M? to 100 M?. In a single experiment, the Westerly granite also showed a decrease in resistance during dilatancy. The nature and distribution of carbon in the run products were studied by electron microprobe and time-of-flight secondary-ion mass spectroscopy (TOP-SIMS). Carbon observed by mapping with the former is clearly observed on micro-cracks that, based on the microtexture, are interpreted to have formed during the deformation. The TOF-SIMS data confirm the electron-probe observations that carbon is present on fracture surfaces. These observations and experimental results lead to the hypothesis that as microfractures open in the time leading up to failure along a fracture, carbon is deposited as a continuous film on the new, reactive mineral surfaces, and this produces a decrease in resistance. Subsequent changes in resistance occur as connectivity of the initial fracture network is altered by continued deformation. Such a process may explain some electromagnetic effects associated with earthquakes.

  17. PHYSICAL REVIEW B 85, 184201 (2012) Electrical and thermal conductivity of Al liquid at high pressures and temperatures

    E-print Network

    Steinle-Neumann, Gerd

    2012-01-01

    PHYSICAL REVIEW B 85, 184201 (2012) Electrical and thermal conductivity of Al liquid at high to obtain values of electrical () and thermal conductivity () for compressed aluminum liquid at temperatures data and studies of solid metals.6­9 No experimental data of electrical () and thermal conductivity

  18. Temperature dependence of the electrical conductivity of selenous acid and its transition metal selenites

    Microsoft Academic Search

    B. A. El-Sayed; A. A. A. Emara; F. S. M. Abd El-Hameed; S. M. Shaaban

    1996-01-01

    The electric conductivity has been measured over a wide range of temperatures including phase transition temperatures of selenous acid and its transition metal selenites. The effect of hydrogen bonding formation of the crystal structure, as well as, the ion pair formation on the conduction mechanism in the low and high temperature regions was visualized using infrared spectra. The values of

  19. Column displacement experiments to evaluate electrical conductivity effects on electromagnetic soil water sensing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bulk electrical conductivity (EC) in superactive soils has been shown to strongly influence electromagnetic sensing of permittivity. However, these effects are dependent on soil water content and temperature as well as the pore water conductivity. We carried out isothermal column displacement experi...

  20. Effects of molecular structure on electrical conduction in low-density polyethylene above its melting point

    Microsoft Academic Search

    K. Iida; J. S. Kim; S. Nakamura; G. Sawa

    1992-01-01

    The electrical conduction of various kinds of low-density polyethylene (LDPE) has been studied above the melting point. LDPEs are characterized by the amount and types of branches, double bonds, and oxygen-containing groups. Two components of conduction currents were found: one obeyed Ohm's law in the low field range and the other was proportional to the square of the field at

  1. Dust charging and electrical conductivity in the day and nighttime atmosphere of Mars

    Microsoft Academic Search

    M. Michael; S. N. Tripathi; S. K. Mishra

    2008-01-01

    Understanding aerosol charging and atmospheric conductivity are necessary in describing the global electric circuit, the aerosol coagulation rate, aerosol-cloud interaction and their subsequent affect on the climate. The importance of aerosol charging for the conductivity variations of the lower Martian atmosphere during both day and night is calculated. Galactic cosmic rays are the dominant ionizing agent in the lower atmosphere,

  2. Electrical resistivity and thermal conductivity of liquid Fe alloys at high P and T, and

    E-print Network

    Steinle-Neumann, Gerd

    Electrical resistivity and thermal conductivity of liquid Fe alloys at high P and T, and heat flux is sustained by magnetohydrodynamic convection within the metallic liquid core. In a thermally advecting core, which depends sensitively on the thermal conductivity of liquid iron and its alloys with candidate light

  3. MAGNETIC RESONANCE - ELECTRICAL IMPEDANCE TOMOGRAPHY (MR-EIT): A new technique for high resolution conductivity imaging

    Microsoft Academic Search

    B. Murat EYUBOGLU; Ozlem Birgul; Y. Ziya Ider

    In this study, a new imaging modality for high resolution conductivity imaging is proposed. Both, the surface potentials and the magnetic fields produced by the probing current are measured. Surface potentials are measured by using conventional electrical impedance tomography techniques and high resolution magnetic field measurements are performed by using magnetic resonance imaging techniques. The conductivity distribution is reconstructed iteratively,

  4. Electrical Conductivity and Sodium Adsorption Ratio Changes Following Annual Applications of Animal Manure Amendments

    Microsoft Academic Search

    J. Clemn Turner; Jeffory A. Hattey; Jason G. Warren; Chad J. Penn

    2010-01-01

    Field experiments were conducted to evaluate the effects of repeated annual manure applications on sodium adsorption ratios and electrical conductivity in semi-arid environments. Swine effluent, beef manure, and anhydrous ammonia were annually applied at loading rates of 0, 56, 168, and 504 kg nitrogen (N) ha to an irrigated, conventionally tilled, continuous corn (Zea mays L.) cropping study in the

  5. Electrical Conductivity Measurement through the Loaded Q Factor of a Resonant Cavity

    E-print Network

    Research, P.O. Box 515, S. J. Campos, 12201-970 SP, Brazil Abstract=We present a method for measuring. INTRODUCTION In the method presented here, the electrical conductivity measurement of metallic materials. of the conductor penetrated by the fields due to skin effect. Now if we replace the upper disk (with conductivity R

  6. Effective electrical conductivity of carbon nanotube-polymer composites: a simplified model and its validation

    NASA Astrophysics Data System (ADS)

    Jang, Sung-Hwan; Yin, Huiming

    2015-04-01

    A simplified model is presented to predict the effective electrical conductivity of carbon nanotube(CNT)-polymer composite with different material proportions, which is validated by the experiments of multi-walled CNT/polydimethylsiloxane (PDMS) composites. CNTs are well dispersed in a PDMS matrix, and the mixture is then cured and cast into thin films for electrical characterization. The CNTs are assumed to be statistically uniformly distributed in the PDMS matrix with the three-dimensional (3D) waviness. As the proportion of CNTs increases to a certain level, namely the percolation threshold, the discrete CNTs start to connect with each other, forming a 3D network which exhibits a significant increase of effective electrical conductivity. The eight-chain model has been used to predict the effective electrical conductivity of the composite, in which the contact resistance between CNTs has been considered through the Simmons’ equation. The eight-chain network features can be significantly changed with the modification to mixing process, CNT length and diameter, and CNT clustering and curling. A Gaussian statistics-based formulation is used to calculate the effective length of a single CNT well dispersed in the matrix. The modeling results of effective electrical conductivity agree with the experiments very well, which are highly dependent on a contact resistance between CNTs and the waviness of the CNTs. The effect of inner-nanotube distance and diameter of CNTs on the effective electrical conductivity of the CNT/PDMS composite is also discussed.

  7. Synthesis, electrical and thermal conductivities, and potential applications of graphite fluoride fibers

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh; Long, Martin; Stahl, Mark

    1988-01-01

    Graphite fluoride fibers can be produced by fluorinating pristine or intercalated graphite fibers. The higher the degree of graphitization of the fibers, the higher the temperature needed to reach the same degree of fluorination. Structural damage during high temperature fluorination can be reduced or eliminated by pretreating the fibers with bromine and/or fluorine. The electrical resistivity of the fibers was in the 0.01 to 10 to the 11th ohm-cm range. The thermal conductivity of these fibers ranged from 5 to 75 W/m-K, which is much larger than the thermal conductivity of glass (1.1 W/m-K), the commonly used fiber in epoxy composites. A composite made from graphite fluoride fibers and epoxy or PTFE may be highly thermally conducting and electrically insulating or semiconducting. The electrically insulating product may be used as heat sinks for electrical or electronic instruments.

  8. Electrical conductivity of high-pressure liquid hydrogen by quantum Monte Carlo methods.

    PubMed

    Lin, Fei; Morales, Miguel A; Delaney, Kris T; Pierleoni, Carlo; Martin, Richard M; Ceperley, D M

    2009-12-18

    We compute the electrical conductivity for liquid hydrogen at high pressure using Monte Carlo techniques. The method uses coupled electron-ion Monte Carlo simulations to generate configurations of liquid hydrogen. For each configuration, correlated sampling of electrons is performed in order to calculate a set of lowest many-body eigenstates and current-current correlation functions of the system, which are summed over in the many-body Kubo formula to give ac electrical conductivity. The extrapolated dc conductivity at 3000 K for several densities shows a liquid semiconductor to liquid-metal transition at high pressure. Our results are in good agreement with shock-wave data. PMID:20366267

  9. Field and temperature dependence of the small polaron hopping electrical conductivity in 1D disordered systems.

    PubMed

    Triberis, G P; Dimakogianni, M

    2009-09-23

    We investigate the effect of the electric field and the temperature on the electrical conductivity of one-dimensional disordered systems due to phonon assisted hopping of small polarons. The microscopic transport mechanism is treated within the framework of the generalized molecular crystal model and the Kubo formula, while percolation theoretical arguments lead to analytical expressions for the macroscopic behavior of the electrical conductivity at high (multi-phonon assisted hopping) and low (few-phonon assisted hopping) temperatures under the influence of moderate electric fields. The theoretical results are successfully applied to recent experimental findings for a wide temperature range and from low up to moderate electric fields. Comparison is made with other theories. PMID:21832371

  10. Electrically Conductive Space-Durable Polymeric Films for Spacecraft Thermal and Charge Control

    Microsoft Academic Search

    John Lennhoff; George Harris; Jason Vaughn; David Edwards; James Zwiener

    1999-01-01

    There is a significant requirement for an electrically conductive thermal control film for the dissipation of spacecraft charging. The present state-of-the-art technology for charge control is based upon thin vapour-deposited indium tin oxide (ITO) conductive coatings on Teflon or Kapton films. These ITO coated films suffer from a range of problems, including no bulk conductivity, poor space durability and a

  11. Limits on irradiation-induced thermal conductivity and electrical resistivity in silicon carbide materials

    Microsoft Academic Search

    L. L. Snead

    2004-01-01

    Thermal conductivity and electrical resistivity of SiC materials is given for fast neutron fluences up to 7.7×1025 n\\/cm2 at irradiation temperatures of 300, 500 and 800 °C. In situ radiation-induced conductivity is also measured for ionizing dose rates up to ?5 Gy\\/s (X-ray). Thermal conductivity degradation for CVD SiC is presented in detail exhibiting a substantial reduction from the non-irradiated

  12. Electrical conductivities of aluminum, copper, and tungsten observed by an underwater explosion

    SciTech Connect

    Sasaki, Toru [Department of Electrical Engineering, Nagaoka University of Technology, Kamitomioka 1603-1, Nagaoka, Niigata 940-2188 (Japan); Nakajima, Mitsuo; Kawamura, Tohru; Horioka, Kazuhiko [Department of Energy Sciences, Tokyo Institute of Technology, Nagatsuta 4259, Midori-ku, Yokohama 226-8502 (Japan)

    2010-08-15

    Conductivities of dense aluminum, copper, and tungsten are evaluated using exploding wire discharges in water. Evolutions of the radius and the electrical resistance of exploding wire are measured together with direct pyrometric estimation of the temperature. The conductivities are evaluated based on the measurements and their density dependence is compared with theoretical predictions at a fixed temperature. The results indicate that regardless of materials, the conductivity has a minimum around 3% of solid density at temperature of 5000 K.

  13. The impulse photopyroelectric method for thermal characterization of electrically conducting polymers

    NASA Astrophysics Data System (ADS)

    Frandas, A.; Jalink, H.; Turcu, R.; Brie, M.

    1995-05-01

    For electrically conducting polypyrole films, the thermal diffusivity and thermal conductivity were obtained by modeling the signals from the photopyroelectric flash technique with a one-dimensional four-layer system. This method has a number of advantages over the sinusoidal excitation: wide thickness range, fast acquisition, simple and cheap setup. This first thermal characterization of polypyrole films shows an increasing thermal conductivity with dopant ion concentration.

  14. Dielectrophoresis of nanoscale dsDNA and humidity effects on its electrical conductivity

    E-print Network

    S. Tuukkanen; A. Kuzyk; J. J. Toppari; V. P. Hytonen; T. Ihalainen; P. Torma

    2005-10-31

    The dielectrophoresis method for trapping and attaching nanoscale double-stranded DNA between nanoelectrodes was developed. The method gives a high yield of trapping single or a few molecules only which enables transport measurements at the single molecule level. Electrical conductivity of individual 140-nm-long DNA molecules was measured, showing insulating behavior in dry conditions. In contrast, clear enhancement of conductivity was observed in moist conditions, relating to the interplay between the conformation of DNA molecules and their conductivity.

  15. (Revised May 25, 2012) (1) To understand Ohm's law, used to describe the behavior of electrical conduction in many

    E-print Network

    Collins, Gary S.

    of electrical conduction in many materials and circuits. (2) To calculate the electrical power dissipated resistor, in an electrical circuit. (4) To learn how to connect electrical components so that the current) and a standard tungsten-filament light bulb. INTRODUCTION One of the most basic electrical circuits is a resistor

  16. RF tumour ablation: computer simulation and mathematical modelling of the effects of electrical and thermal conductivity.

    PubMed

    Lobo, S M; Liu, Z-J; Yu, N C; Humphries, S; Ahmed, M; Cosman, E R; Lenkinski, R E; Goldberg, W; Goldberg, S N

    2005-05-01

    This study determined the effects of thermal conductivity on RF ablation tissue heating using mathematical modelling and computer simulations of RF heating coupled to thermal transport. Computer simulation of the Bio-Heat equation coupled with temperature-dependent solutions for RF electric fields (ETherm) was used to generate temperature profiles 2 cm away from a 3 cm internally-cooled electrode. Multiple conditions of clinically relevant electrical conductivities (0.07-12 S m-1) and 'tumour' radius (5-30 mm) at a given background electrical conductivity (0.12 S m-1) were studied. Temperature response surfaces were plotted for six thermal conductivities, ranging from 0.3-2 W m-1 degrees C (the range of anticipated clinical and experimental systems). A temperature response surface was obtained for each thermal conductivity at 25 electrical conductivities and 17 radii (n=425 temperature data points). The simulated temperature response was fit to a mathematical model derived from prior phantom data. This mathematical model is of the form (T=a+bRc exp(dR) s(f) exp(g)(s)) for RF generator-energy dependent situations and (T=h+k exp(mR)+n?exp(p)(s)) for RF generator-current limited situations, where T is the temperature (degrees C) 2 cm from the electrode and a, b, c, d, f, g, h, k, m, n and p are fitting parameters. For each of the thermal conductivity temperature profiles generated, the mathematical model fit the response surface to an r2 of 0.97-0.99. Parameters a, b, c, d, f, k and m were highly correlated to thermal conductivity (r2=0.96-0.99). The monotonic progression of fitting parameters permitted their mathematical expression using simple functions. Additionally, the effect of thermal conductivity simplified the above equation to the extent that g, h, n and p were found to be invariant. Thus, representation of the temperature response surface could be accurately expressed as a function of electrical conductivity, radius and thermal conductivity. As a result, the non-linear temperature response of RF induced heating can be adequately expressed mathematically as a function of electrical conductivity, radius and thermal conductivity. Hence, thermal conductivity accounts for some of the previously unexplained variance. Furthermore, the addition of this variable into the mathematical model substantially simplifies the equations and, as such, it is expected that this will permit improved prediction of RF ablation induced temperatures in clinical practice. PMID:16019848

  17. Towards Practical Application of Paper based Printed Circuits: Capillarity Effectively Enhances Conductivity of the Thermoplastic Electrically Conductive Adhesives

    NASA Astrophysics Data System (ADS)

    Wu, Haoyi; Chiang, Sum Wai; Lin, Wei; Yang, Cheng; Li, Zhuo; Liu, Jingping; Cui, Xiaoya; Kang, Feiyu; Wong, Ching Ping

    2014-09-01

    Direct printing nanoparticle-based conductive inks onto paper substrates has encountered difficulties e.g. the nanoparticles are prone to penetrate into the pores of the paper and become partially segmented, and the necessary low-temperature-sintering process is harmful to the dimension-stability of paper. Here we prototyped the paper-based circuit substrate in combination with printed thermoplastic electrically conductive adhesives (ECA), which takes the advantage of the capillarity of paper and thus both the conductivity and mechanical robustness of the printed circuitsweredrastically improved without sintering process. For instance, the electrical resistivity of the ECA specimen on a pulp paper (6 × 10-5?.cm, with 50 wt% loading of Ag) was only 14% of that on PET film than that on PET film. This improvement has been found directly related to the sizing degree of paper, in agreement with the effective medium approximation simulation results in this work. The thermoplastic nature also enables excellent mechanical strength of the printed ECA to resist repeated folding. Considering the generality of the process and the wide acceptance of ECA technique in the modern electronic packages, this method may find vast applications in e.g. circuit boards, capacitive touch pads, and radio frequency identification antennas, which have been prototyped in the manuscript.

  18. Investigating Electricity: Testing for Electrical Conductivity (Conductors and Insulators) Using a Variety of Materials

    NSDL National Science Digital Library

    In this lab, the students will test a variety of materials to discover which items are conductors and which items are insulators. They will discuss, classify, record data, and develop new questions relating to electricity.

  19. Enhanced Electrical Conductivity due to Morphological Changes in Polyanaline-Titania Core-Shell Nanocomposites

    NASA Astrophysics Data System (ADS)

    Coates, Nelson; Liu, Jianfeng; Segalman, Rachel; Urban, Jeffrey

    2015-03-01

    Conducting polymer-inorganic nanoparticle composites are a valuable class of advanced materials with a wide range of applications due their extensive physical and chemical tunability. Although effective medium theories are often used to predict the behavior of these materials, the actual physical properties can be distinctly different from their constituents due to a variety of structural or electrical interfacial interactions that may manifest. Here, we present electrical conductivity data for TiO2 nanoparticles coated with polyanaline, along with structural characterization of the conducting polymer as a function of component volume fraction. For these composites, we find that the electrical conductivity cannot be explained by a 2-component effective medium theory, but rather is correlated to a structural change in the polymer. We hypothesize that the organic-inorganic interface induces a structural change in a region of polymer surrounding the nanoparticle which improves the electrical conductivity of the composite. These results emphasize the importance of controlling interfacial interactions in organic-inorganic composites, and demonstrate the potential for using such interactions as a way to tune electrical transport.

  20. Electrical conductivity and phase transition studies of TiO2-BaO system

    NASA Astrophysics Data System (ADS)

    Beg, Saba; Haneef, Sadaf

    2015-01-01

    The solid solution of BaTiO3 was prepared by conventional solid state reaction. The electrical conductivity of TiO2-BaO system has been studied at different temperatures for various molar ratios. The isothermal conductivity increases with BaO concentration due to the vacancy migration phenomenon. It has been found that the electrical conductivity after attaining a maximum value at 240°C decreases with increase in temperature due to the collapse of the fluorite framework. A second rise in conductivity in the temperature range 470-540°C indicates the phase transition of TiO2 from anatase to rutile. AC Impedance measurements proved that the oxide ion conductivity predominantly arises from the grain contribution. The sample characterization and the study of phase transition changes were done by using XRD, FT-IR and DSC measurements. On increasing the concentration of BaO the transition temperature shifts towards higher side.

  1. Electrical and thermal conductivity of discontinuously reinforced aluminum composites at sub-ambient temperatures

    SciTech Connect

    Geiger, A.L. [Advanced Composite Materials Corp., Greer, SC (United States)] [Advanced Composite Materials Corp., Greer, SC (United States); Hasselman, D.P.H. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering] [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering; Welch, P. [Gencorp Aerojet, Azusa, CA (United States). Electronic Systems Div.] [Gencorp Aerojet, Azusa, CA (United States). Electronic Systems Div.

    1997-09-01

    The electrical and thermal conductivities of two SiC particle-reinforced aluminum-matrix composites were measured over the temperature range of 80--300 K. Because of the relatively low value of electrical conductivity of the SiC, the composite conductivity data agreed closely with those of the matrix with spherical pores, as predicted by the theory of Maxwell. The experimental data for the thermal conductivity of the composite exceeded the values predicted for the matrix phase with spherical holes, indicative of a contribution by the silicon carbide reinforcement. This contribution was significant at the higher temperatures but approached zero at the lowest temperature levels. Data analysis suggested that this effect could be attributed to a decrease in the thermal conductance at the Al-SiC interface with decreasing temperature, due to a corresponding increase in phonon scattering or other mechanisms.

  2. Electrical conductivity measurement of excised human metastatic liver tumours before and after thermal ablation

    PubMed Central

    Haemmerich, Dieter; Schutt, David J; Wright, Andrew W; Webster, John G; Mahvi, David M

    2009-01-01

    We measured the ex vivo electrical conductivity of eight human metastatic liver tumours and six normal liver tissue samples from six patients using the four electrode method over the frequency range 10 Hz to 1 MHz. In addition, in a single patient we measured the electrical conductivity before and after the thermal ablation of normal and tumour tissue. The average conductivity of tumour tissue was significantly higher than normal tissue over the entire frequency range (from 4.11 versus 0.75 mS cm?1 at 10 Hz, to 5.33 versus 2.88 mS cm?1 at 1 MHz). We found no significant correlation between tumour size and measured electrical conductivity. While before ablation tumour tissue had considerably higher conductivity than normal tissue, the two had similar conductivity throughout the frequency range after ablation. Tumour tissue conductivity changed by +25% and ?7% at 10 Hz and 1 MHz after ablation (0.23?0.29 at 10 Hz, and 0.43?0.40 at 1 MHz), while normal tissue conductivity increased by +270% and +10% at 10 Hz and 1 MHz (0.09?0.32 at 10 Hz and 0.37?0.41 at 1 MHz). These data can potentially be used to differentiate tumour from normal tissue diagnostically. PMID:19349647

  3. High and highly anisotropic electrical conductivity of the asthenosphere due to hydrogen diffusion in olivine

    NASA Astrophysics Data System (ADS)

    Dai, Lidong; Karato, Shun-ichiro

    2014-12-01

    Experimental studies on electrical conductivity in hydrated olivine had been made only at relatively low temperatures. The extrapolation of these data to asthenosphere temperatures shows that explaining high and highly anisotropic conductivity by hydrogen is difficult. We present new experimental results on the electrical conductivity in hydrated olivine single crystals measured under a broader temperature range than before (T (temperature) = 573-1373 K at P (pressure) = 4 GPa). The new results agree well with the previous results at low temperatures (T < 900 K), whereas at higher temperatures (T > 1000 K) substantial deviations from the previous results are observed: (i) anisotropy in conductivity increases with temperature, and (ii) activation energies at high temperature regime are substantially higher than those at lower T. The high temperature behavior is consistent with a model invoking diffusion of two-protons at M-site vacancy, whereas the low temperature behavior suggests conduction by more mobile species such as free proton. The present results (i) explain the discrepancy between different previous studies conducted under different temperature regimes, and (ii) show that most of geophysical observations on the electrical conductivity in the asthenosphere including the high and highly anisotropic conductivity can be explained by high water content in the asthenosphere that is consistent with the geochemical model. Combining with a previous model of low seismic wave velocity of the asthenosphere, a subsolidus model invoking the role of hydrogen provides a unified explanation for the geophysical anomalies of the asthenosphere.

  4. A numerical study of the influence of interconnected conductive paths in electrically resistive rocks

    NASA Astrophysics Data System (ADS)

    Mandolesi, E.; Moorkamp, M.; Jones, A. G.

    2013-12-01

    Several electromagnetic (EM) geophysical methods focus on the EM properties of rocks and sediments to determine a reliable image of the subsurface, while the same electromagnetic properties are measured in the laboratory with a wide range of instruments and techniques. None of these measurements return an unequivocal result. The hypothesis related to the presence of interconnected pathways of electrically conductive materials in resistive hosts has been studied with increasing interest in recent years, and the comprehension of phenomena that scale from the microstructures of the rocks up to field electrical conductivity measurements represents the boundary that prevents the direct comparison between laboratory data and field data. In recent years some numerical approaches have been investigated to understand the effects of interconnected pathways of conductors on field measurements, usually restricting the studies to direct current (DC) sources. Bearing in mind the time-variating nature of natural electromagnetic sources that take a role in field measurements, we numerically simulated the effects of such EM sources on the conductivity measured on the surface of a three-dimensional realistic body embedded in an uniform host by using electromagnetic induction equations. Since most real rocks are poor conductors, we modeled a two-phase mixture of rock and interconnected conductive elements (representing melts, saline fluids, sulphidic, carbonitic, or metallic sediments, etc.), randomly generated within the background host. We compared the electrical conductivity measured from a sample of randomly generated models with the electrical conductivity limits predicted by Hashin-Shtrikman bounds.

  5. Laboratory studies of the electrical conductivity of silicate perovskites at high pressures and temperatures

    NASA Technical Reports Server (NTRS)

    Li, Xiaoyuan; Jeanloz, Raymond

    1990-01-01

    The electrical conductivities of two silicate perovskites and a perovskite-magnesiowuestite assemblage, all having an atomic ratio of Mg to Fe equal to 0.88/0.12, have been measured with alternating current and direct current (dc) techniques at simultaneously high pressures and temperatures. Measurements up to pressures of 80 GPa and temperatures of 3500 K, using a laser-heated diamond anvil cell, demonstrate that the electrical conductivity of these materials remains below 10-3 S/m at lower mantle conditions. The activation energies for electrical conduction are between 0.1 and 0.4 eV from the data, and the conduction in these perovskites is ascribed to an extrinsic electronic process. The new measurements are in agreement with a bound that was previously obtained from dc measurements for the high-PT conductivity of perovskite-dominated assemblages. The results show that the electrical conductivity of (Mg/0.88/Fe/0.12)SiO3 perovskite differs significantly from that of the earth's deep mantle, as inferred from geophysical observations.

  6. Electrical conductivity improvement of strontium titanate doped lead vanadate glasses by nanocrystallization

    NASA Astrophysics Data System (ADS)

    El-Desoky, M. M.; Zayed, H. S. S.; Ibrahim, F. A.; Ragab, H. S.

    2009-11-01

    The structural and electrical conductivity ( ?) of annealed SrTiO 3-PbO 2-V 2O 5 glasses were studied. The annealing of initially glass samples leads to formation of nanocrystalline grains embedded in the glassy matrix. XRD patterns of the glass-ceramic samples show that nanocrystals were embedded in the glassy matrix with an average grain size of 32 nm. The glass-ceramic nanocrystals obtained by annealing at temperatures close to the crystallization temperature Tc exhibit enhancement of electrical conductivity up to four orders of magnitude than initially glasses. The enhancement of the electrical conductivity due to annealing was attributed to two interdependent factors: (i) an increase of concentration of V 4+-V 5+ pairs; and (ii) formation of defective, well-conducting regions along the glass-crystallites interfaces. From the conductivity temperature relation, it was found that small polaron hopping model was applicable at temperature above ?D/2 ( ?D, the Debye temperature). The electrical conduction at T > ?D/2 was due to non-adiabatic small polaron hopping (SPH) of electrons between vanadium ions. The parameters obtained from the fits of the experimental data to this model appear reasonable and are consistent with glass composition.

  7. Enhanced thermoelectric efficiency via orthogonal electrical and thermal conductances in phosphorene.

    PubMed

    Fei, Ruixiang; Faghaninia, Alireza; Soklaski, Ryan; Yan, Jia-An; Lo, Cynthia; Yang, Li

    2014-11-12

    Thermoelectric devices that utilize the Seebeck effect convert heat flow into electrical energy and are highly desirable for the development of portable, solid state, passively powered electronic systems. The conversion efficiencies of such devices are quantified by the dimensionless thermoelectric figure of merit (ZT), which is proportional to the ratio of a device's electrical conductance to its thermal conductance. In this paper, a recently fabricated two-dimensional (2D) semiconductor called phosphorene (monolayer black phosphorus) is assessed for its thermoelectric capabilities. First-principles and model calculations reveal not only that phosphorene possesses a spatially anisotropic electrical conductance, but that its lattice thermal conductance exhibits a pronounced spatial-anisotropy as well. The prominent electrical and thermal conducting directions are orthogonal to one another, enhancing the ratio of these conductances. As a result, ZT may reach the criterion for commercial deployment along the armchair direction of phosphorene at T = 500 K and is close to 1 even at room temperature given moderate doping (?2 × 10(16) m(-2) or 2 × 10(12) cm(-2)). Ultimately, phosphorene hopefully stands out as an environmentally sound thermoelectric material with unprecedented qualities. Intrinsically, it is a mechanically flexible material that converts heat energy with high efficiency at low temperatures (?300 K), one whose performance does not require any sophisticated engineering techniques. PMID:25254626

  8. Reinforced carbon nanotubes as electrically conducting and flexible films for space applications.

    PubMed

    Atar, Nurit; Grossman, Eitan; Gouzman, Irina; Bolker, Asaf; Hanein, Yael

    2014-11-26

    Chemical vapor deposition (CVD)-grown entangled carbon nanotube (CNT) sheets are characterized by high electrical conductivity and durability to bending and folding. However, since freestanding CNT sheets are mechanically weak, they cannot be used as stand-alone flexible films. In this work, polyimide (PI) infiltration into entangled cup-stacked CNT (CSCNT) sheets was studied to form electrically conducting, robust, and flexible films for space applications. The infiltration process preserved CNTs' advantageous properties (i.e., conductivity and flexibility), prevented CNT agglomeration, and enabled CNT patterning. In particular, the CNT-PI films exhibited ohmic electrical conductance in both the lateral and vertical directions, with a sheet resistivity as low as 122 ?/?, similar to that of as-grown CNT sheets, with minimal effect of the insulating matrix. Moreover, this high conductivity was preserved under mechanical and thermal manipulations. These properties make the reported CNT-PI films excellent candidates for applications where flexibility, thermal stability, and electrical conductivity are required. Particularly, the developed CNT-PI films were found to be durable in space environment hazards such as high vacuum, thermal cycling, and ionizing radiation, and hence they are suggested as an alternative for the electrostatic discharge (ESD) protection layer in spacecraft thermal blankets. PMID:25366559

  9. Base metal alloys with self-healing native conductive oxides for electrical contact materials

    NASA Astrophysics Data System (ADS)

    Aindow, M.; Alpay, S. P.; Liu, Y.; Mantese, J. V.; Senturk, B. S.

    2010-10-01

    Base metals for electrical contacts exhibit high bulk conductivities but form low-conductivity native oxide scales in air, leading to unacceptably high contact resistances. Here we show that alloying base metals can lead to higher conductivity native scales by: doping to enhance carrier concentration; inducing mixed oxidation states to give electron/polaron hopping; and/or phase separation for conducting pathways. Data from Cu-La, Fe-V, and Ni-Ru alloys demonstrate the viability of these approaches, yielding contact resistances up to 106 times lower than that for oxidized Cu.

  10. Electrical conductivity modeling and research of polypropylene composites filled with carbon black

    NASA Astrophysics Data System (ADS)

    Stepashkina, A. S.; Tsobkallo, E. S.; Alyoshin, A. N.

    2014-12-01

    Composites of polypropylene filled with carbon black (PP/CB composite) at different concentrations were prepared by melt mixing followed by compression molding. The dependence of electrical resistance on the filler mass fraction was experimentally received. It was shown that the received dependence had the threshold character. The composite kept dielectric properties at the filler concentration below the threshold and at the concentration above the threshold the electrical resistance decreased more than on 8-10 orders. The theoretical description of electrical conductivity of the composite was offered. Experimental data of the dependence between electrical resistance and the filler mass fraction agreed with the theoretical. The process of conductivity in the PP/CB composite was simulated by means of the Monte-Carlo method for threshold mass fraction estimation.

  11. Spatial conductivity mapping of carbon nanotube composite thin films by electrical impedance tomography for sensing applications

    NASA Astrophysics Data System (ADS)

    Hou, Tsung-Chin; Loh, Kenneth J.; Lynch, Jerome P.

    2007-08-01

    This paper describes the application of electrical impedance tomography (EIT) to demonstrate the multifunctionality of carbon nanocomposite thin films under various types of environmental stimuli. Carbon nanotube (CNT) thin films are fabricated by a layer-by-layer (LbL) technique and mounted with electrodes along their boundaries. The response of the thin films to various stimuli is investigated by relying on electric current excitation and corresponding boundary potential measurements. The spatial conductivity variations are reconstructed based on a mathematical model for the EIT technique. Here, the ability of the EIT method to provide two-dimensional mapping of the conductivity of CNT thin films is validated by (1) electrically imaging intentional structural defects in the thin films and (2) mapping the film's response to various pH environments. The ability to spatially image the conductivity of CNT thin films holds many promises for developing multifunctional CNT-based sensing skins.

  12. Electrical Conductivity in Magnesium-Doped Al_2 O_3 Crystal at Moderate Temperatures

    E-print Network

    M. Tardío; R. Ramírez; R. González; Y. Chen; M. R. Kokta

    2000-04-08

    AC and DC electrical measurements between 273 and 800 K were used to characterize the electrical conductivity of Al_2 O_3:Mg single crystals containing [Mg]^{0} center. At low fields contacts are blocking. At high fields, electrical current flows steadily through the sample and the I-V characteristic corresponds to a directly biased barrier whit a series resistance (bulk resistance). AC measurements yield values for the junction capacitance as well as for the sample resistance, and provide perfectly reproducible conductivity values. The conductivity varies linearly whit the [Mg]^{0} concentration and a thermal activation energy of 0.68 eV was obtained, which agrees very well with the activation energy previously reported for motion of free holes.

  13. Study of insulating electrical conductivity in hydrogenated amorphous silicon–nickel alloys at very low temperature

    Microsoft Academic Search

    A. Narjis; A. El kaaouachi; L. Limouny; S. Dlimi; A. Sybous; J. Hemine; R. Abdia; G. Biskupski

    2011-01-01

    On the insulating side of the metal–insulator transition (MIT), the study of the effect of low temperatures T on the electrical transport in amorphous silicon–nickel alloys a-Si1?yNiy:H exhibits that the electrical conductivity follows, at the beginning, the Efros–Shklovskii Variable Range Hopping regime (ES VRH) with T?1\\/2. This behaviour showed that long range electron–electron interaction reduces the Density Of State of

  14. Numerical Investigation of Entropy Generation in Unsteady MHD Generalized Couette Flow with Variable Electrical Conductivity

    PubMed Central

    Chinyoka, T.; Makinde, O. D.

    2013-01-01

    The thermodynamic second law analysis is utilized to investigate the inherent irreversibility in an unsteady hydromagnetic generalized Couette flow with variable electrical conductivity in the presence of induced electric field. Based on some simplified assumption, the model nonlinear governing equations are obtained and solved numerically using semidiscretization finite difference techniques. Effects of various thermophysical parameters on the fluid velocity, temperature, current density, skin friction, the Nusselt number, entropy generation number, and the Bejan number are presented graphically and discussed quantitatively. PMID:23956691

  15. Numerical investigation of entropy generation in unsteady MHD generalized Couette flow with variable electrical conductivity.

    PubMed

    Chinyoka, T; Makinde, O D

    2013-01-01

    The thermodynamic second law analysis is utilized to investigate the inherent irreversibility in an unsteady hydromagnetic generalized Couette flow with variable electrical conductivity in the presence of induced electric field. Based on some simplified assumption, the model nonlinear governing equations are obtained and solved numerically using semidiscretization finite difference techniques. Effects of various thermophysical parameters on the fluid velocity, temperature, current density, skin friction, the Nusselt number, entropy generation number, and the Bejan number are presented graphically and discussed quantitatively. PMID:23956691

  16. Predictions of the electrical conductivity and charging of the aerosols in Titan's atmosphere

    Microsoft Academic Search

    W. J. Borucki; R. C. Whitten; E. L. O. Bakes; E. Barth; S. Tripathi

    2006-01-01

    The electrical conductivity and electrical charge on the aerosols in atmosphere of Titan are computed for altitudes between 0 and 400 km. Ionization of methane and nitrogen due to galactic cosmic rays (GCR) is important at night where these ions are converted to ion clusters such as CH+5CH4, C7H+7, C4H+7, and H4C7N+. The ubiquitous aerosols observed also play an important

  17. Simple model of skeletal matter composed of magnetized electrically conducting thin rods

    Microsoft Academic Search

    A. B. Kukushkin; K. V. Cherepanov

    2005-01-01

    A simple electrodynamic model for describing the behavior of a skeletal matter composed of magnetized, electrically conducting thin rods (1D magnetic dipoles) is proposed. It is aimed at modeling the self-assembling of a skeletal matter from carbon nanotubes (or similar nanodust), as suggested for interpreting the experimental data on the long-lived filamentary structures in the high-current electric discharges. Here the

  18. Diagnostic issues with measuring electrical conductivity and equation of state data from Ohmically exploded planar foils

    Microsoft Academic Search

    E. L. Ruden; P. Poulsen; J. F. Camacho; S. K. Coffey; J. E. Beach; D. J. Brown; T. C. Grabowski; C. W. Gregg; M. R. Kostora; B. M. Martinez; J. V. Parker

    2008-01-01

    Diagnostic development is underway for the simultaneous dynamic measurement of local electrical conductivity, pressure, density, specific energy, and temperature of an LiF tamped planar metal foil exploded by a 36 muF, 50 kV capacitor bank discharge. Voltage differentials measure the foil's electric field, a B-dot probe measures surface current density, a laser velocity interferometer (VISAR) measures foil thickness, and a

  19. Effect of firing atmosphere on air-fireable glass-free electrically conductive thick film

    Microsoft Academic Search

    Zongrong Liu; D. D. L. Chung

    2005-01-01

    The firing atmosphere (air, oxygen, and argon) was found to affect the electrical and mechanical properties of an air-fireable\\u000a electrically conductive glass-free silver-based thick film. For the optimum firing temperature of 930C, air results in the\\u000a lowest resistivity, but a minor amount of pinholes; oxygen results in the largest thickness, the smoothest surface, and no\\u000a pinhole; and argon results in

  20. Electrically conductive zinc oxide (ZnO) nanostructures prepared by solgel spin-coating

    Microsoft Academic Search

    M. H. Mamata; M. Rusop; Z. Zulkifli

    2010-01-01

    The electrically conductive zinc oxide (ZnO) nanostructures prepared by sol-gel spin coating are presented. This project has been focused on electrical, optical and structural properties of Al doped ZnO thin film. The effects of Al doping concentration at 0~5 at.% on the Al doped ZnO thin film properties have been investigated. This project involves 3 processes which are thin film

  1. Electrically Conductive Zinc Oxide (ZnO) Nanostructures Prepared by Sol-gel Spin-coating

    Microsoft Academic Search

    M. H. Mamat; A. S. Rodzi; M. Rusop

    2011-01-01

    The electrically conductive zinc oxide (ZnO) nanostructures prepared by sol-gel spin coating are presented. This project has been focused on electrical, optical and surface morphology properties of Al (aluminium) doped ZnO thin film. The effect of Al doping concentration at 0~5 at.% on the Al doped ZnO Thin film properties have been investigated. This project involves 3 processes which are

  2. Electrically Conductive Zinc Oxide (ZnO) Nanostructures Prepared by Sol-gel Spin-coating

    Microsoft Academic Search

    M. H. Mamat; A. S. Rodzi; M. Rusop

    2011-01-01

    The electrically conductive zinc oxide (ZnO) nanostructures prepared by sol-gel spin coating are presented. This project has been focused on electrical, optical and surface morphology properties of Al (aluminium) doped ZnO thin film. The effect of Al doping concentration at 0?5 at.% on the Al doped ZnO Thin film properties have been investigated. This project involves 3 processes which are

  3. Theoretical calculations of the temperature dependence of the electrical and thermal conductivities of liquid gallium

    Microsoft Academic Search

    M. Sayem El-Daher; Richard D. Murphy

    2005-01-01

    The electrical and thermal resistivities of liquid gallium are calculated over a range of temperatures above the melting point\\u000a using the solutions of the Boltzmann equation. The experimental x-ray structure factor of Waseda and the form factor derived\\u000a using the Heine-Abarenkov model potential are used in these calculations. The ratio of the electrical and thermal conductivities\\u000a is calculated and compared

  4. Electrical conductivity during incipient melting in the oceanic low-velocity zone.

    PubMed

    Sifré, David; Gardés, Emmanuel; Massuyeau, Malcolm; Hashim, Leila; Hier-Majumder, Saswata; Gaillard, Fabrice

    2014-05-01

    The low-viscosity layer in the upper mantle, the asthenosphere, is a requirement for plate tectonics. The seismic low velocities and the high electrical conductivities of the asthenosphere are attributed either to subsolidus, water-related defects in olivine minerals or to a few volume per cent of partial melt, but these two interpretations have two shortcomings. First, the amount of water stored in olivine is not expected to be higher than 50 parts per million owing to partitioning with other mantle phases (including pargasite amphibole at moderate temperatures) and partial melting at high temperatures. Second, elevated melt volume fractions are impeded by the temperatures prevailing in the asthenosphere, which are too low, and by the melt mobility, which is high and can lead to gravitational segregation. Here we determine the electrical conductivity of carbon-dioxide-rich and water-rich melts, typically produced at the onset of mantle melting. Electrical conductivity increases modestly with moderate amounts of water and carbon dioxide, but it increases drastically once the carbon dioxide content exceeds six weight per cent in the melt. Incipient melts, long-expected to prevail in the asthenosphere, can therefore produce high electrical conductivities there. Taking into account variable degrees of depletion of the mantle in water and carbon dioxide, and their effect on the petrology of incipient melting, we calculated conductivity profiles across the asthenosphere for various tectonic plate ages. Several electrical discontinuities are predicted and match geophysical observations in a consistent petrological and geochemical framework. In moderately aged plates (more than five million years old), incipient melts probably trigger both the seismic low velocities and the high electrical conductivities in the upper part of the asthenosphere, whereas in young plates, where seamount volcanism occurs, a higher degree of melting is expected. PMID:24784219

  5. Effects of Extremity Elevation and Health Factors On Soft Tissue Electrical Conductivity

    NASA Astrophysics Data System (ADS)

    Feldkamp, J. R.; Heller, J.

    2009-01-01

    Two clinical studies were completed using an auto-tuned induction coil conductivity sensor (ICCS) to determine the effects of a variety of factors on the electrical conductivity of soft tissue. In addition to fifteen "subject variables" such as blood pressure and others, we have specifically focused on considering the role of such factors as gender, age, BMI, smoking and elevation of extremities. Measurements were made at seven sites on either side of the body for a total of fourteen. Higher conductivities were obtained for women than men at all sites. At five sites, where age was a significant factor, conductivity was found to decline with increased age. Interestingly, smokers as a group tended to have reduced conductivity, suggesting that aging and smoking have similar effects on the microvasculature of soft tissue. Generally speaking, electrical conductivity is observed to increase in response to increased elevation at sites located on extremities. Considering just healthy adults, a definite pattern of elevation-induced electrical conductivity displacement emerges when subjects are flagged according to high, low or moderate blood pressure. We suggest that violations of this pattern may provide a method for identifying those individuals in an early stage of peripheral vascular disease.

  6. Ab initio study of high pressure liquid silica: electrical conductivity and structure.

    NASA Astrophysics Data System (ADS)

    Stixrude, L. P.; Scipioni, R.

    2014-12-01

    The transport properties of silicate liquids are important for understanding the thermal evolution of giant impact targets, magma oceans, and the possibility of silicate dynamos in the early Earth and in other rocky planets. However, little is known about the electrical conductivity of silicate liquids over the relevant pressure-temperature regime. Here, we focus on silica as one of the most abundant components and a model system for understanding transport properties in silicates. We perform first principles molecular dynamics simulations over the pressure-temperature encompassing that of the early Earth, and compute the electrical conductivity via the Green-Kubo formula. The electrical conductivity of the liquid substantially exceeds that of crystalline phases at all conditions. We find that along isotherms the conductivity of silica liquid reaches a maximum near 40 percent compression, remarkably similar to the compression at which 5-fold Si-O coordination is most abundant. The conductivity decreases upon further compression. The conductivity increases rapidly with increasing temperature at all pressures. We explore the underlying physical mechanisms of the computed variations of conductivity with pressure and temperature and discuss the implications of our results for magnetic field generation in basal magma oceans.

  7. Nerve growth factor-immobilized polypyrrole: bioactive electrically conducting polymer for enhanced neurite extension.

    PubMed

    Gomez, Natalia; Schmidt, Christine E

    2007-04-01

    Biomaterials that present multiple stimuli are attractive for a number of biomedical applications. In particular, electrical and biological cues are important factors to include in interfaces with neurons for applications such as nerve conduits and neural probes. Here, we report the combination of these two stimuli, by immobilizing nerve growth factor (NGF) on the surface of the electrically conducting polymer polypyrrole (PPy). NGF was immobilized using an intermediate linker provided by a layer of polyallylamine conjugated to an arylazido functional group. Upon exposure to UV light and activation of the azido groups, NGF was fixed to the substrate. Three different surface concentrations were obtained (0.21-0.98 ng/mm(2)) and similar levels of neurite extension were observed on immobilized NGF as with soluble NGF. Additionally, electrical stimulation experiments were conducted with the modified polymer and revealed a 50% increase in neurite outgrowth in PC12 cells compared to experiments without electrical stimulation. This novel modification of PPy provides both electrical and biological stimulation, by presenting tethered growth factors and only producing a small decrease in the material's properties (conductivity approximately 10 S cm(-1)) when compared to other modification techniques (conductivity approximately 10(-3)-10(-6) S cm(-1)). PMID:17111407

  8. Electrical conductive nanopolymers based on bisphenol F epoxy resin reinforced with nano polypyrrole

    NASA Astrophysics Data System (ADS)

    Bitarafhaghighi, Vahidreza

    In this study, spherical polypyrrole (PPy) nanostructure has successfully served as nanofiller for obtaining epoxy resin polymer nanocomposites (PNCs). The effects of nanofiller loading level on mechanical properties, thermal stability, electrical conductivity, and dielectric properties were systematically studied. The dynamic storage and loss modulii were studied, together with the glass-transition temperature (Tg) being obtained from the peak of tan delta. The PPy nanofillers could increase the electrical conductivity. Finally, the real permittivity was observed to increase with increasing the PPy loading, and the enhanced permittivity was analyzed by the interfacial polarization.

  9. Statistical properties of Joule heating rate, electric field and conductances at high latitudes

    NASA Astrophysics Data System (ADS)

    Aikio, A. T.; Selkälä, A.

    2009-07-01

    Statistical properties of Joule heating rate, electric field and conductances in the high latitude ionosphere are studied by a unique one-month measurement made by the EISCAT incoherent scatter radar in Tromsø (66.6 cgmlat) from 6 March to 6 April 2006. The data are from the same season (close to vernal equinox) and from similar sunspot conditions (about 1.5 years before the sunspot minimum) providing an excellent set of data to study the MLT and Kp dependence of parameters with high temporal and spatial resolution. All the parameters show a clear MLT variation, which is different for low and high Kp conditions. Our results indicate that the response of morning sector conductances and conductance ratios to increased magnetic activity is stronger than that of the evening sector. The co-location of Pedersen conductance maximum and electric field maximum in the morning sector produces the largest Joule heating rates 03-05 MLT for Kp?3. In the evening sector, a smaller maximum occurs at 18 MLT. Minimum Joule heating rates in the nightside are statistically observed at 23 MLT, which is the location of the electric Harang discontinuity. An important outcome of the paper are the fitted functions for the Joule heating rate as a function of electric field magnitude, separately for four MLT sectors and two activity levels (Kp<3 and Kp?3). In addition to the squared electric field, the fit includes a linear term to study the possible anticorrelation or correlation between electric field and conductance. In the midday sector, positive correlation is found as well as in the morning sector for the high activity case. In the midnight and evening sectors, anticorrelation between electric field and conductance is obtained, i.e. high electric fields are associated with low conductances. This is expected to occur in the return current regions adjacent to auroral arcs as a result of ionosphere-magnetosphere coupling, as discussed by Aikio et al. (2004) In addition, a part of the anticorrelation may come from polarization effects inside high-conductance regions, e.g. auroral arcs. These observations confirm the speculated effect of small scale electrodynamics, which is not included in most of the global modeling efforts of Joule heating rate.

  10. Electrically conductive doped block copolymer of polyacetylene and polyisoprene. [Soluble in organic solvents

    DOEpatents

    Aldissi, M.

    1984-06-27

    An electrically conductive block copolymer of polyisoprene and polyacetylene and a method of making the same are disclosed. The polymer is prepared by first polymerizing isoprene with n-butyllithium in a toluene solution to form an active isoprenyllithium polymer. The active polymer is reacted with an equimolar amount of titanium butoxide and subsequently exposed to gaseous acetylene. A block copolymer of polyisoprene and polyacetylene is formed. The copolymer is soluble in common solvents and may be doped with I/sub 2/ to give it an electrical conductivity in the metallic regime.

  11. Thermal conductivity, electrical resistivity, and thermopower of aerospace alloys from 4 to 300 K.

    NASA Technical Reports Server (NTRS)

    Hust, J. G.; Weitzel, D. H.; Powell, R. L.

    1971-01-01

    Measurement of thermal conductivity, electrical resistivity, and thermopower for several aerospace alloys: titanium alloy A110-AT, aluminum alloy 7039, Inconel 718, and Hastelloy X. Tables and graphs of the measured properties and Lorenz ratio are presented over the range from 4 to 300 K. Comparisons to other measurements and theoretical analysis of the data are included. The uncertainties of the property data are estimated as 0.7 to 2.5% for thermal conductivity, 0.25% in electrical resistivity, and about 0.1 microvolt/K in thermopower.

  12. Heat capacities and electrical conductivities of 1-ethyl-3-methylimidazolium-based ionic liquids

    Microsoft Academic Search

    Ya-Hung Yu; Allan N. Soriano; Meng-Hui Li

    2009-01-01

    We present the heat capacities and electrical conductivities of five [Emim] 1-ethyl-3-methylimidazolium-based ionic liquids: [Emim][BF4] (tetrafluoroborate), [Emim][CF3SO3] (trifluoromethanesulfonate), [Emim][C2N3] (dicyanamide), [Emim][C2H5SO4] (ethylsulfate), and [Emim][MDEGSO4] (2-(2-methoxyethoxy) ethylsulfate). The heat capacities were measured using a differential scanning calorimeter (DSC) over the temperature ranging from (303.2 to 358.2)K. The electrical conductivities were measured over the temperature ranging from (293.2 to 353.2)K using a

  13. Breakdown characteristics of an isolated conducting object in a uniform electric field

    NASA Technical Reports Server (NTRS)

    Grothaus, M. G.; Trost, T. F.

    1986-01-01

    A laboratory experiment was conducted to determine the physical processes involved in the electrical breakdown of a particular spark gap arrangement. The gap consists of an isolated conducting ellipsoid located midway between two large flat electrodes. Gradual increase of the applied electric field, E, in the gap produces corona on the ellipsoid tips followed by flashover in a leader-arc sequence. The leader phase consists of the abrupt formation of ionized channels which partially bridge the gap and then decay prior to the arc. Measurements of dE/dt and of current were made, and photographs were taken with an image converter. Experimental parameters are listed.

  14. Inductive Measurement of Plasma Jet Electrical Conductivity (MSFC Center Director's discretionary Fund). Part 2

    NASA Technical Reports Server (NTRS)

    Turner, M. W.; Hawk, C. W.; Litchford, R. J.

    2001-01-01

    Measurement of plasma jet electrical conductivity has utility in the development of explosively driven magnetohydrodynamic (MHD) energy converters as well as magnetic flux compression reaction chambers for nuclear/chemical pulse propulsion and power. Within these types of reactors, the physical parameter of critical importance to underlying MHD processes is the magnetic Reynolds number, the value of which depends upon the product of plasma electrical conductivity and velocity. Therefore, a thorough understanding of MHD phenomena at high magnetic Reynolds number is essential, and methods are needed for the accurate and reliable measurement of electrical conductivity in high-speed plasma jets. It is well known that direct measurements using electrodes suffer from large surface resistance, and an electrodeless technique is desired. To address this need, an inductive probing scheme, originally developed for shock tube studies, has been adapted. In this method, the perturbation of an applied magnetic field by a plasma jet induces a voltage in a search coil, which, in turn, can be used to infer electrical conductivity through the inversion of a Fredholm integral equation of the first kind. A 1-in.-diameter probe using a light-gas gun. Exploratory laboratory experiments were carried out using plasma jets expelled from 15-g shaped charges. Measured conductivities were in the range of 4 kS/m for unseeded octol charges and 26 kS/m for seeded octol charges containing 2-percent potassium carbonate by mass.

  15. Electrical conductivity of orthopyroxene: Implications for the water content of the asthenosphere

    PubMed Central

    Dai, Lidong; Karato, Shun-ichiro

    2009-01-01

    Electrical conductivity of minerals is sensitive to water content and hence can be used to infer the water content in the mantle. However, previous studies to infer the water content in the upper mantle were based on pure olivine model of the upper mantle. Influence of other minerals particularly that of orthopyroxene needs to be included to obtain a better estimate of water content in view of the high water solubility in this mineral. Here we report new results of electrical conductivity measurements on orthopyroxene, and apply these results to estimate the water content of the upper mantle of Earth. We found that the electrical conductivity of orthopyroxene is enhanced by the addition of water in a similar way as other minerals such as olivine and pyrope garnet. Using these new results, we calculate the electrical conductivity of pyrolite mantle as a function of water content and temperature incorporating the temperature and water fugacity-dependent hydrogen partitioning. Reported values of asthenosphere conductivity of 4 × 10?2?10?1 S/m corresponds to the water content of 0.01–0.04 wt%, a result in good agreement with the petrological model of the upper mantle. PMID:20009379

  16. Dynamics of Space Charge Polarization and Electrical Conduction in Low Alkali Boroaluminosilicate Glasses

    NASA Astrophysics Data System (ADS)

    Dash, Priyanka

    Low alkali boroaluminosilicate glasses are of tremendous interest for high temperature electronics primarily due to their superior high temperature dielectric properties and extraordinary energy densities. Therefore, evaluating factors causing electrical conduction in these materials is of great importance since it has direct correlation with the device reliability and performance. This research focuses on understanding dynamics of space charge polarization and mechanisms controlling electrical conduction in these glasses. Both DC and AC characterization techniques were developed to elucidate electronic and ionic conduction mechanisms under a variety of temperatures, electric field and frequency conditions. Ionic conduction and space charge polarization have been studied in low alkali glasses as a function of electric field and temperature by thermally stimulated depolarization and low frequency impedance spectroscopy. Moreover, due to the low alkali content in these glasses, it was possible to study the transport properties of alkaline earth ions in multicomponent silicate glasses. It was observed that the potential energy barrier height for ionic hopping was reduced at high electric field. Impedance spectroscopy and second harmonic generation microscopy techniques were applied to determine the thickness and electric field distribution across the cation depleted layer that was generated during the thermoelectric poling. Both of these measurements show that the depletion layer thickness depends on the poling conditions and the intrinsic breakdown strength of the material. In addition, a relationship between the charge and electric field distribution in the depletion layer was determined for a number of glasses with different alkali content. The high breakdown strength of these glasses facilitated the study of electronic conduction under fields greater than 108 V/m. Conduction under these high fields was investigated using high field thermally stimulated depolarization current measurements. The electrons participating in the high field conduction were generated in the depletion layer through Poole-Frenkel emission. This involves field-enhanced excitation of electrons from the trapped states to the conduction band of the glass. It is suggested that high field intrinsic breakdown in thin alkali free boroaluminosilicate glasses may occur when the conduction band gets populated by electrons emitted through Poole-Frenkel emission. Consequently breakdown can occur through an avalanche effect.

  17. Serotonin Regulates Electrical Coupling via Modulation of Extrajunctional Conductance: H-current

    PubMed Central

    Szabo, Theresa M.; Caplan, Jonathan S.; Zoran, Mark J.

    2010-01-01

    Synaptic strength can be highly variable from animal to animal within a species or over time within an individual. The process of synaptic plasticity induced by neuromodulatory agents might be unpredictable when the underlying circuits subject to modulation are themselves inherently variable. Serotonin (5-hydroxytryptomine; 5HT) and serotonergic signaling pathways are important regulators of animal behavior and are pharmacological targets in a wide range of neurological disorders. We have examined the effect of 5HT on electrical synapses possessing variable coupling strengths. While 5HT decreased electrical coupling at synapses with weak electrical connectivity, synapses with strong electrical coupling were less affected by 5HT treatment, as follows from the equations used for calculating coupling coefficients. The fact that the modulatory effect of 5HT on electrical connections was negatively correlated with the strength of electrical coupling suggests that the degree of electrical coupling within a neural network impacts subsequent neuromodulation of those synapses. Biophysical studies indicated that these effects were primarily due to 5HT-induced modulation of membrane currents that indirectly affect junctional coupling at synaptic contacts. In support of these experimental analyses, we created a simple model of coupled neurons to demonstrate that modulation of electrical coupling could be due solely to 5HT effects on H-channel conductance. Therefore, variability in the strength of electrical coupling in neural circuits can determine the pharmacological effect of this neuromodulatory agent. PMID:20599836

  18. Electric conductivity and aggregation of anthracite and graphite particles in concretes

    SciTech Connect

    E.A. Fanina; A.N. Lopanov [Belgorod State Technological University, Belgorod (Russian Federation)

    2009-02-15

    A statistical model of the electric conductivity of a heterogeneous system based on coal and a binding agent is presented. In this system, a conductive phase appears because of particle aggregation. The model was tested in the systems of anthracite and graphite in cement stone. The consistency between the experimental and calculated electric conductivities with a correlation coefficient higher than 0.9 was found on a linear interpolation of model parameters. It was found that the presence of a surfactant (cetylpyridinium chloride) and a high-molecular-weight compound (polyvinyl acetate) changed the number of particles in anthracite and graphite aggregates to affect the specific conductivity of the heterogeneous system. 9 refs., 5 figs., 1 tab.

  19. Role of semiconductivity and ion transport in the electrical conduction of melanin

    PubMed Central

    Mostert, Albertus B.; Powell, Benjamin J.; Pratt, Francis L.; Hanson, Graeme R.; Sarna, Tadeusz; Gentle, Ian R.; Meredith, Paul

    2012-01-01

    Melanins are pigmentary macromolecules found throughout the biosphere that, in the 1970s, were discovered to conduct electricity and display bistable switching. Since then, it has been widely believed that melanins are naturally occurring amorphous organic semiconductors. Here, we report electrical conductivity, muon spin relaxation, and electron paramagnetic resonance measurements of melanin as the environmental humidity is varied. We show that hydration of melanin shifts the comproportionation equilibrium so as to dope electrons and protons into the system. This equilibrium defines the relative proportions of hydroxyquinone, semiquinone, and quinone species in the macromolecule. As such, the mechanism explains why melanin at neutral pH only conducts when “wet” and suggests that both carriers play a role in the conductivity. Understanding that melanin is an electronic-ionic hybrid conductor rather than an amorphous organic semiconductor opens exciting possibilities for bioelectronic applications such as ion-to-electron transduction given its biocompatibility. PMID:22615355

  20. A novel approach to model hydraulic and electrical conductivity in fractal porous media

    NASA Astrophysics Data System (ADS)

    Ghanbarian, B.; Daigle, H.; Sahimi, M.

    2014-12-01

    Accurate prediction of conductivity in partially-saturated porous media has broad applications in various phenomena in porous media, and has been studied intensively since the 1940s by petroleum, chemical and civil engineers, and hydrologists. Many of the models developed in the past are based on the bundle of capillary tubes. In addition, pore network models have also been developed for simulating multiphase fluid flow in porous media and computing the conductivity in unsaturated porous media. In this study, we propose a novel approach using concepts from the effective-medium approximation (EMA) and percolation theory to model hydraulic and electrical conductivity in fractal porous media whose pore-size distributions exhibit power-law scaling. In our approach, the EMA, originally developed for predicting electrical conductivity of composite materials, is used to predict the effective conductivity, from complete saturation to some intermediate water content that represents a crossover point. Below the crossover water content, but still above a critical saturation (percolation threshold), a universal scaling predicted by percolation theory, a power law that expresses the dependence of the conductivity on the water content (less a critical water saturation) with an exponent of 2, is invoked to describe the effective conductivity. In order to evaluate the accuracy of the approach, experimental data were used from the literature. The predicted hydraulic conductivities for most cases are in excellent agreement with the data. In a few cases the theory underestimates the hydraulic conductivities, which correspond to porous media with very broad pore-size distribution in which the largest pore radius is more than 7 orders of magnitude greater than the smallest one. The approach is also used to predict the saturation dependence of the electrical conductivity for experiments in which capillary pressure data are available. The results indicate that the universal scaling of the electrical conductivity is valid from the percolation threshold all the way up to the complete saturation point. Our results confirm those reported previously by Ewing and Hunt (2006) who argued that the electrical conductivity should follow universal scaling over the entire range of saturation.

  1. Electrical conductivity as a measure of the continuity of titanium and vanadium thin films

    Microsoft Academic Search

    F. A. Burgmann; S. H. N. Lim; D. G. McCulloch; B. K. Gan; K. E. Davies; D. R. McKenzie; M. M. M. Bilek

    2005-01-01

    We investigate titanium (Ti) and vanadium (V) film growth on amorphous carbon (a-C) and silicon oxide (SiO2) substrates using in situ electrical conductivity measurements and electron microscopy. The aim is to determine the minimum thickness of a continuous layer so that multilayer coatings of fine period can be constructed. We applied a model for thin film metallic conduction to develop

  2. Lithosphere Heterogeneity beneath Tien Shan from Petrology and Electrical Conductivity of Xenoliths

    Microsoft Academic Search

    N. S. Bagdassarov; V. Batalev; V. Egorova

    2009-01-01

    The shortening of Tien Shan and the evolution of its crust thickness have been evaluated from the P-T geothermobarometry of xenoliths and the comparison of their electrical conductivity with the conductivities obtained from the inversion of magneto-telluric data. P-T equilibration conditions of mafic granulites and spinel lherzolites found in basaltic outcrop Orthosuu in the Southern Tien Shan, indicated a paleogeotherm

  3. Microstructures and electrical conductance of silver nanocrystalline thin films on flexible polymer substrates

    Microsoft Academic Search

    R. X. Wang; X. M. Tao; Y. Wang; G. F. Wang; S. M. Shang

    2010-01-01

    Using sputtering technique, silver nanocrystalline thin films were deposited on two different polymer substrates, namely pretreated nylon and polyester fabrics, under identical conditions. It is found that the difference of the electrical conductance between the two samples is quite large. The highest conductivity obtained from the coated nylon fabric is 2.4×107Sm?1, indicating the feasibility to fabricate wearable electrodes using silver

  4. Kinetics of electrical conductivity of TATB detonation products as an indicator of growth of carbon nanoparticles

    Microsoft Academic Search

    M. M. Gorshkov; K. F. Grebenkin; A. L. Zherebtsov; V. T. Zaikin; V. M. Slobodenyukov; O. V. Tkachev

    2007-01-01

    Two stages of growth of electrical conductivity of detonation products of plastic-bonded TATB are registered: a fast stage\\u000a with a characteristic time of 0.1 sec, which is commensurable with the time of chemical reactions, and a subsequent slow stage, which lasts for 0.5–1.0 sec until specimen unloading begins. Under the assumption of the thermal mechanism of conductivity emergence, the second

  5. Electrical Conduction Mechanism in Bi4Ti3O12 Single Crystal

    Microsoft Academic Search

    Masatake Takahashi; Yuji Noguchi; Masaru Miyayama

    2002-01-01

    To reveal the influence of lattice defects on electrical conduction of bismuth titanate (Bi4Ti3O12: BIT), one of the bismuth layer structured ferroelectrics, changes in lattice parameters and weight by high-temperature annealing and the dependence of conductivity on oxygen partial pressure (Po2) were examined for BIT powders and single crystals, respectively. Decrease in lattice parameters and weight loss by annealing suggested

  6. Generation of Electrical Conductivity Data of Al using Ab-initio Molecular Dynamics simulations

    NASA Astrophysics Data System (ADS)

    Mishra, Vinayak; Chaturvedi, S.

    2011-07-01

    Electrical conductivity data of Al for the densities from normal to a fraction of normal density and temperatures up to a few thousand Kelvin are important inputs for the hydrodynamic simulations of exploding aluminium foils. We have generated conductivity data of aluminium, by using ab-initio molecular dynamics simulations and the Kubo Greenwood formula. ABINIT code has been used for performing AIMD simulations. Our results are in good agreement with published results.

  7. The interaction of ozone with bio-fuel, revealed by electrical conduction and infrared spectroscopy

    Microsoft Academic Search

    H. N. Cunha; F. L. A. J. Silva; J. Melo; E. H. S. Cavalcanti; T. M. Fonseca; E. U. K. Melcher; A. M. N. Lima; H. M. Laborde; H. Neff

    2011-01-01

    The interaction of ozone with bio-fuel has been investigated. The highly reactive gas promotes accelerated oxidation, along with changes of the electrical conductivity. The materials specific parameter is monitored by a specially designed thin-film resistor sensor, integrated within a micro-fluidic flow cell. Recordings of the ozone induced conductivity (OiC) are presented for bio-diesel samples, processed from cotton seed oil, blended

  8. Electronic energy gap of molecular hydrogen from electrical conductivity measurements at high shock pressures

    NASA Technical Reports Server (NTRS)

    Nellis, W. J.; Mitchell, A. C.; Mccandless, P. C.; Erskine, D. J.; Weir, S. T.

    1992-01-01

    Electrical conductivities were measured for liquid D2 and H2 shock compressed to pressures of 10-20 GPa (100-200 kbar), molar volumes near 8 cu cm/mol, and calculated temperatures of 2900-4600 K. The semiconducting energy gap derived from the conductivities is 12 eV, in good agreement with recent quasi-particle calculations and with oscillator frequencies measured in diamond-anvil cells.

  9. Electrical conductivity of the ZrO 2–Ln 2O 3 (Ln=lanthanides) system

    Microsoft Academic Search

    Y. Arachi; H. Sakai; O. Yamamoto; Y. Takeda; N. Imanishai

    1999-01-01

    The electrical conductivity of the system ZrO2–Ln2O3 (Ln=lanthanides) has been measured as a function of dopant concentration in a temperature range 350–1000°C. The Arrhenius plots of the conductivity showed a distinct curvature near 600–700°C. The migration enthalpy of oxide ions and the association enthalpy of oxide ion vacancies with the dopant lanthanide ions were estimated from the difference of the

  10. Ab initio determination of electrical and thermal conductivity of liquid aluminum

    Microsoft Academic Search

    Vanina Recoules; Jean-Paul Crocombette

    2005-01-01

    We present here a technique to compute electronic thermal conductivity of fluids using quantum-molecular dynamics and the formulation of Chester-Tellung for the Kubo-Greenwood formula. In order to validate our implementation, the electrical and thermal conductivities of liquid aluminum were determined from 70K above the melting point up to 10000K . Results agree well with experimental data for Al at 1000K

  11. In situ measurement of electrical conductivity of Zircaloy oxides and their formation mechanism under electron irradiation

    NASA Astrophysics Data System (ADS)

    Howlader, M. M. R.; Kinoshita, C.; Shiiyama, K.; Kutsuwada, M.; Inagaki, M.

    1999-02-01

    Insitu electrical conductivity of Zircaloy-2, improved Zircaloy-2 and Zircaloy-4 oxide films has been measured with 1 MeV electron irradiation using gold, copper and zirconium electrodes during beam-on and -off in the temperature range of 296-680 K in order to find the rate controlling factor of oxidation of the alloy. Current-voltage characteristics of all oxides during irradiation show almost ohmic behavior for Zircaloy-2 and Zircaloy-4 oxides, and non-ohmic for improved Zircaloy-2 oxide where the current is electronic in nature and may be associated with ohmic and Schottky and/or Poole-Frenkel processes, respectively. The electrical conductivity of such films under irradiation, called radiation induced conductivity (RIC), is proportional to the irradiation flux and it is predominantly due to electronic excitation. Subsequent subjection of the specimens under irradiation with beam-on and -off shows RIC by electron excitation from the valence to conduction band and annealing of the conductivity at temperature, respectively. It is concluded that the electron motion dominates the electrical conductivity of Zircaloy oxides. Therefore, the slow-diffusing negative oxygen ions control the oxidation process of Zircaloys.

  12. Electrical and electrothermal conductivities of the ionospheres of Planets. II. Earth, Mars, and Venus

    SciTech Connect

    Pavlov, A.V.

    1986-07-01

    The coefficients of the electrical and electrothermal conductivity were calculated for the dayside ionospheres of Earth, Mars, and Venus in the first, second, and third approximations of the decomposition by the Sonin polynomials method of Chapman-Enskog. The influence of the magnitude of the magnetic field H on the size of these coefficients and on the speed of convergence of the decomposition by Sonin polynomials is examined for the ionospheres of Mars and Venus. In the same context the influence of H on the contribution of the coefficients of ionic conductivity to the coefficients of the total conductivity is examined. It is shown that in practical calculations in the Earth's ionosphere the generally accepted first approximation of Hall, Pederson, and Cowling to the coefficients of electrical conductivity should be used. In calculations of these coefficients in the ionospheres of Mars and Venus one should use the first approximation near H greater than or equal to 100 ..gamma.. and the second approximation near H less than or equal to 10 ..gamma... In the ionospheres of Earth, Mars, and Venus one should take the second approximation for the coefficients of electrical conductivity along the magnetic field and the third approximation for the coefficients of electrothermal conductivity. In the ionosphere of Earth, one may neglect thermal currents in the Hall and Pederson directions.

  13. Electrical conductivity and permeability of partially molten mantle rocks: results from digital rock physics experiments

    NASA Astrophysics Data System (ADS)

    Miller, K.; Montesi, L.; Zhu, W.

    2014-12-01

    Estimates of overall melt content beneath mid-ocean ridges inferred from magnetotelluric tomography (MT) studies vary widely between 1 and 10 vol. %. Much of this variation may arise from a lack of understanding about how melt geometry influences the bulk electrical conductivity of partially molten mantle rock, especially at low melt fraction. We present results from experiments in which we numerically calculate the electrical conductivity and permeability using high-resolution, three-dimensional melt geometries of olivine-basalt systems obtained via synchrotron X-ray microtomography (SX?T). Starting materials consist of San Carlos olivine and Fo90 basalt mixed in various proportions to achieve nominal melt fraction of 0.02 to 0.20 when melted. Samples were prepared by isostatically pressing samples at 1.5GPa and 1350°C for a minimum of 1 week (Zhu et al., 2011; Science) and then quenched, turning the melt to basaltic glass. Samples were imaged using SX?T at the Advanced Photon Source at Argonne National Labs to obtain three-dimensional, 700 nm-per-pixel digital reconstructions. Grayscale data was segmented using Avizo® software (Miller et al., 2014; EPSL), and binary images were used as computational domains in numerical experiments to determine bulk electrical conductivity and permeability. Numerical experiments were carried out on several statistically representative subvolumes per sample using finite difference techniques. Olivine and melt are treated as conductive and insulative phases, respectively. To calculate conductivity, Laplace's equation is solved for the electric potential, assuming zero electric flux across phase boundaries. Ohm's Law yields the bulk conductivity of the sample. To calculate permeability, Stokes' equations are solved using the artificial compressibility method on a staggered grid. Darcy's law then gives the permeability of the subvolume. We fit permeability and electrical conductivity values to power laws in order to establish empirical relationships with melt fraction. We compare with experimental studies. By linking permeability and electrical conductivity to melt content, we are able to better guide interpretations of geophysical data and constrain melt connectivity and transport at mid-ocean ridges.

  14. Breakup of a supported drop of a viscous conducting liquid in a uniform electric field.

    PubMed

    Higuera, F J

    2008-07-01

    Numerical computations and order-of-magnitude estimates are used to describe the time evolution of a drop of a very viscous liquid of finite electrical conductivity attached to a metallic plate which is suddenly subject to a uniform electric field. Under the action of the electric stresses induced at its surface, the drop elongates in the direction of the field, and charged droplets are emitted when the strength of the field is higher than a certain critical value. A stationary emission mode exists in which the attached drop develops a conical tip and a thin jet, with small droplets emitted from the end of the jet in a process that involves the formation of a long ligament. The flow rate and the electric current carried by the stream of droplets emitted in this mode are determined by the flow and the transfer of charge in the attached drop, in particular in a small region around its tip and in a leading stretch of the jet, where the solution is nearly stationary despite the transient character of the jet further downstream. A simplified analysis of the stationary regions is carried out to elucidate the effects of the physical properties of the liquid (electrical conductivity, permittivity, viscosity, and surface tension), the volume of the drop, and the strength of the applied field. For high electrical conductivities and applied fields well above its critical value, the electrical and viscous stresses are large compared to surface tension stresses, and their balance gives a flow rate proportional to the square of the applied field. The electric current is then that of a stationary electrified jet fed with this flow rate. PMID:18764057

  15. Energy-Saving Sintering of Electrically Conductive Powders by Modified Pulsed Electric Current Heating Using an Electrically Nonconductive Die

    NASA Astrophysics Data System (ADS)

    Ito, Mikio; Kawahara, Kenta; Araki, Keita

    2014-04-01

    Sintering of Cu and thermoelectric Ca3Co4O9 was tried using a modified pulsed electric current sintering (PECS) process, where an electrically nonconductive die was used instead of a conventional graphite die. The pulsed electric current flowed through graphite punches and sample powder, which caused the Joule heating of the powder compact itself, resulting in sintering under smaller power consumption. Especially for the Ca3Co4O9 powder, densification during sintering was also accelerated by this modified PECS process.

  16. Frequency-and electric-field-dependent conductivity of single-walled carbon nanotube networks of varying density

    E-print Network

    Gruner, George

    Frequency- and electric-field-dependent conductivity of single-walled carbon nanotube networks October 2007; published 20 February 2008 We present measurements of the frequency- and electric-field-dependent conductivity of single-walled car- bon nanotube SWCNT networks of various densities. The ac conductivity

  17. Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer

    DOEpatents

    Spahn, O.B.; Lear, K.L.

    1998-03-10

    The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g., Al{sub 2}O{sub 3}), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3--1.6 {mu}m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation. 10 figs.

  18. Electrical properties of polypropylene-based composites controlled by multilayered distribution of conductive particles.

    PubMed

    Gao, Wanli; Zheng, Yu; Shen, Jiabin; Guo, Shaoyun

    2015-01-28

    Materials consisting of alternating layers of pure polypropylene (PP) and carbon black filled polypropylene (PPCB) were fabricated in this work. The electrical behaviors of the multilayered composites were investigated from two directions: (1) Parallel to interfaces. The confined layer space allowed for a more compact connection between CB particles, while the conductive pathways tended to be broken up with increasing number of layers leading to a distinct enhancement of the electrical resistivity due to the separation of insulated PP layers. (2) Vertical to interfaces. The alternating assemblies of insulated and conductive layers like a parallel-plate capacitor made the electrical conductivity become frequency dependent. Following the layer multiplication process, the dielectric permittivity was significantly enhanced due to the accumulation of electrical charges at interfaces. Thus, as a microwave was incident on the dielectric medium, the interfacial polarization made the main contribution to inherent dissipation of microwave energy, so that the absorbing peak became strengthened when the material had more layers. Furthermore, the layer interfaces in the multilayered system were also effective to inhibit the propagation of cracks in the stretching process, leading to a larger elongation at the break than that of the PP/CB conventional system, which provided a potential route to fabricate electrical materials with optimal mechanical properties. PMID:25549245

  19. Steplike electric conduction in a classical two-dimensional electron system through a narrow

    E-print Network

    Steplike electric conduction in a classical two-dimensional electron system through Non-centrosymmetric superconductivity in d-electron compounds Visualization of the Spatial ferromagnetic quantum criticality in the heavy-fermion iron oxypnictide Ce(Ru1-xFex)PO Vacancy trapping

  20. A Full-Body Tactile Sensor Suit Using Electrically Conductive Fabric and Strings

    Microsoft Academic Search

    Masayuki Inaba; Yukiko Hoshino; Ken'ichiro Nagasaka; Tatsuo Ninomiya; Satoshi Kagami; Hirochika Inoue

    1996-01-01

    We present design and implementation of a tactile sensor system, sensor suit, that covers the entire body of a robot. The sensor suit is designed to be soft and flexible and to have a large number of sensing regions. We have built the sensor suit using electrically conductive fabric and string. The current version of the sensor suit has 192

  1. Temperature-Electrical Conductivity Relation of Water for Environmental Monitoring and Geophysical Data Inversion

    Microsoft Academic Search

    Masaki Hayashi

    2004-01-01

    Electrical conductivity (EC) is widely used for monitoring the mixing of fresh water and saline water, separating stream hydrographs, and geophysical mapping of contaminated groundwater. The measured EC values at various temperatures need to be reported as corresponding to a standard temperature because EC is dependent on temperature. An arbitrary constant is commonly used for temperature compensation assuming that EC-temperature

  2. Evidence for microbial enhanced electrical conductivity in hydrocarbon-contaminated sediments

    Microsoft Academic Search

    Estella A. Atekwana; Eliot A. Atekwana; D. Dale Werkema; Jonathan P. Allen; Laura A. Smart; Joseph W. Duris; Daniel P. Cassidy; William A. Sauck; Silvia Rossbach

    2004-01-01

    Bulk electrical conductivity of sediments during microbial mineralization of diesel was investigated in a mesoscale laboratory experiment consisting of biotic contaminated and uncontaminated columns. Population numbers of oil degrading microorganisms increased with a clear pattern of depth zonation within the contaminated column not observed in the uncontaminated column. Microbial community structure determined from ribosomal DNA intergenic spacer analysis showed a

  3. The hydromagnetic stability of the hardcore pinch with small electrical conductivity

    Microsoft Academic Search

    R. J. Bickerton; I. J. Spalding

    1962-01-01

    The hydromagnetic stability of a simplified hardcore system is examined in the limit of very small electrical conductivity. It is shown that instabilities develop due to the rapid penetration of magnetic field into the plasma and the growth rates are calculated. A model experiment using liquid mercury has been carried out and the results are compared with the theory. Good

  4. Conducted and radiated emissions in distributed automotive dual voltage vehicle electrical systems

    Microsoft Academic Search

    M. C. Di Piazza; A. Ragusa; G. Tine; G. Vitale

    2003-01-01

    In this paper a study on conducted and radiated emissions in new dual voltage (14 V\\/42 V) automotive electrical systems is presented. The experimental investigations reported in this paper have the objective of finding out the main characteristics of the involved electromagnetic phenomena taking into account the final application of the drive in the automotive environment. The investigation is particularly

  5. Effects of nano-sized particles on electrical and thermal conductivities of polymer composites

    Microsoft Academic Search

    Lianhua Fan; Bin Su; Jianmin Qu; C. P. Wong

    2004-01-01

    Polymer composite materials, for their cost-effectiveness and design flexibility, have been widely employed in electronic packaging industry. They possess unique characteristics combining the low-temperature processability of organic polymer matrix and the various functionalities endowed by the other components in the composites. Electrically conductive adhesives (ECAs) have been explored as an environment friendly interconnection technique. While they have many potential advantages

  6. Grain size-dependent electrical conductivity of polycrystalline cerium oxide II: Space charge model

    Microsoft Academic Search

    A. Tschöpe

    2001-01-01

    The effect of space charges along grain boundaries on the electrical conductivity of polycrystalline mixed ionic\\/electronic conductors (MIECs) was investigated. The bulk concentrations of point defects were calculated using the defect chemistry of corresponding single crystalline materials, taking into account the charge neutrality condition. The accumulation or depletion of charged point defects in space charge layers along grain boundaries was

  7. Role of specimen thickness on the electrical conductivity of single crystalline alumina under electron irradiation

    E-print Network

    Howlader, Matiar R

    be considered carefully before designing the coating and window materials of fusion reactors. © 2001 American in fusion reactors. Hodgson3 first reported a phenomenon, called radiation induced electrical degradation and no surface degradation in the specimen, rather than only a sort of decrease of the conductivity with total

  8. Conductive shape memory nanocomposites for high speed electrical Xiaofan Luo and Patrick T. Mather*

    E-print Network

    Mather, Patrick T.

    thermal conductivities, and (3) inertness to electromagnetic stimuli (in contrast with SMAs), due to the electrical insulation of most polymeric materials. Research efforts have begun to address these challenges. For example, with regard to challenge (3) listed above, electro-active materials systems have been developed7

  9. Electrical Conductivity Study of Carbon Nanotube Yarns, 3-D Hybrid Braids and their Composites

    Microsoft Academic Search

    Philip D. Bradford; Alexander E. Bogdanovich

    2008-01-01

    Long continuous yarns consisting solely of carbon nanotubes may be the future of specialty composites requiring unique multi-functional properties. Many of such yarns were incorporated in a hybrid composite here, to demonstrate for the first time, their effect on increasing the electrical conductivity of an otherwise insulating composite. Six-ply nanotube yarns produced by University of Texas at Dallas were used

  10. Electrical Conductivity of Molten ZnCl2 at Temperature as High as 1421 K

    NASA Astrophysics Data System (ADS)

    Salyulev, Alexander B.; Potapov, Alexei M.

    2015-02-01

    The electrical conductivity of molten ZnCl2 was measured in a wide temperature range (?T=863 K) to a temperature as high as 1421 K that is 417 degrees above the boiling point of the salt. At the temperature maximum of the own vapor pressure of the salt reached several megapascals.

  11. Fuel cell components and systems having carbon-containing electrically-conductive hollow fibers

    DOEpatents

    Langry, Kevin C.; Farmer, Joseph C.

    2014-07-08

    According to one embodiment, a system includes a structure having an ionically-conductive, electrically-resistive electrolyte/separator layer covering an inner or outer surface of a carbon-containing electrically-conductive hollow fiber and a catalyst coupled to the hollow fiber, an anode extending along at least part of a length of the structure, and a cathode extending along at least part of the length of the structure, the cathode being on an opposite side of the hollow fiber as the anode. In another embodiment, a method includes acquiring a structure having an ionically-conductive, electrically-resistive electrolyte/separator layer covering an inner or outer surface of a carbon-containing electrically-conductive hollow fiber and a catalyst along one side thereof, adding an anode that extends along at least part of a length of the structure, and adding a cathode that extends along at least part of the length of the structure on an opposite side as the anode.

  12. Density, Electrical Conductivity and Viscosity of Hg(0.8)Cd(0.2)Te Melt

    NASA Technical Reports Server (NTRS)

    Li, C.; Scripa, R. N.; Ban, H.; Su, C.-H.; Lehoczky, S. L.

    2004-01-01

    The density, viscosity, and electrical conductivity of Hg(0.8)Cd(0.2)Te melt were measured as a function of temperature. A pycnometric method was used to measure the melt density in the temperature range of 1072 to 1122 K. The viscosity and electrical conductivity were determined using a transient torque method from 1068 to 1132 K. The density result from this study is within 0.3% of the published data. However, the current viscosity result is approximately 30% lower than the existing data. The electrical conductivity of Hg(0.8)Cd(0.2)Te melt as a function of temperature, which is not available in the literature, is also determined. The analysis of the temperature dependent electrical conductivity and the relationship between the kinematic viscosity and density indicated that the structure of the melt appeared to be homogeneous when the temperature was above 1090 K. A structural transition occurred in the Hg(0.8)Cd(0.2)Te melt as the temperature was decreased to below 1090 K

  13. Seismic reflections and electrical conductivity: A case of Holmes's curious dog?

    E-print Network

    Jones, Alan G.

    Seismic reflections and electrical conductivity: A case of Holmes's curious dog? Frederick A. Cook point to which you wish to draw my attention?'' ``To the curious incident of the dog in the night time.'' ``The dog did nothing in the night time.'' ``That was the curious incident,'' remarked Sherlock Holmes

  14. The Lorentz forces on an electrically conducting sphere in an alternating magnetic field

    Microsoft Academic Search

    Udaya B. Sathuvalli; Yildiz Bayazitoglu

    1996-01-01

    A method to calculate the Lorentz force on an electrically conducting sphere placed in an arbitrary sinusoidally varying magnetic field is developed. The crux of this method lies in expressing the external magnetic held and the eddy current density in the sphere in terms of a “source function” of the current sources and a “skin depth dependent function”. The general

  15. The preparation of transparent electrically conducting indium oxide films by reactive vacuum evaporation

    Microsoft Academic Search

    K. G. Gopchandran; B Joseph; J. T. Abraham; P Koshy; V. K. Vaidyan

    1997-01-01

    Indium oxide thin films deposited by reactive thermal evaporation of indium in an oxygen atmosphere at different substrate temperatures and oxygen partial pressures are characterized by X-ray diffraction, scanning electron microscopy, optical transmission and electrical resistivity. Preparation conditions are optimized to obtain highly transparent and conducting ln2O3 films.

  16. Analytic formulation for the ac electrical conductivity in two- temperature, strongly coupled, overdense plasma: FORTRAN subroutine

    SciTech Connect

    Cauble, R. [Lawrence Livermore National Lab., CA (United States); Rozmus, W. [Alberta Univ., Edmonton, AB (Canada)

    1993-10-21

    A FORTRAN subroutine for the calculation of the ac electrical conductivity in two-temperature, strongly coupled, overdense plasma is presented. The routine is the result of a model calculation based on classical transport theory with application to plasmas created by the interaction of short pulse lasers and solids. The formulation is analytic and the routine is self-contained.

  17. Electrically Conductive Polymeric Nanocomposites Prepared in Alcohol Dispersion of Multiwalled Carbon Nanotubes

    Microsoft Academic Search

    Don-Young Kim; Rira Jung; Hun-Sik Kim; Hyoung-Joon Jin

    2008-01-01

    In this study, electrically conductive microspheres were prepared by the adsorption of multiwalled carbon nanotubes (MWCNTs) on the surfaces of polymeric microspheres (polystyrene and poly(methylmethacrylate)) in MWCNT-dispersed alcohols (methanol, ethanol, and isopropanol) without surfactants. The stability of the MWCNT dispersions was measured using a recently developed multiple light scattering measurement instrument (Turbiscan). The individual MWCNTs on the surfaces of the

  18. J. Geomag. Geoelectr., 45, 707728, 1993 Constraints on Mantle Electrical Conductivity

    E-print Network

    Constable, Steve

    J. Geomag. Geoelectr., 45, 707­728, 1993 Constraints on Mantle Electrical Conductivity from Field's mantle to depths of at least 1800 km, is obtained by averaging published, single-site response functions with recent diamond anvil measurements of lower mantle materials. Extension of the global response to higher

  19. Electrical Conductivity of Dense Quark Matter with Fluctuations and Magnetic Field Included

    E-print Network

    B. O. Kerbikov; M. A. Andreichikov

    2015-03-02

    We investigate the electrical conductivity(EC) of dense quark matter in the vicinity of the phase transition line. We show that: (i) At high density the Drude EC does not depend on the magnetic field up to $eB \\sim 10^{19} \\ G$. (ii) In the precritical region the fluctuation EC (paraconductivity) dominates over the Drude one.

  20. Fertilizer-induced changes in rhizosphere electrical conductivity: relation to forest tree seedling root

    E-print Network

    -1 Fertilizer-induced changes in rhizosphere electrical conductivity: relation to forest tree-765-494-3608/9461) Received 1 July 2004; accepted in revised form 19 April 2005 Key words: Controlled-release fertilizer, Ion toxicity, Mineral nutrition, Reforestation, Salinity, Soil osmotic potential Abstract. Fertilization

  1. The Relative Contributions of Electric Field Ionospheric Conductance to the Auroral Electrojets

    NASA Astrophysics Data System (ADS)

    Cho, Eun-Ah; Ahn, Byung-Ho; Moon, Yong-Jae

    2000-06-01

    We examine the relative contributions of the electric field and ionospheric conductance to the auroral electrojets. For this purpose we used magnetometer data obtained from the International Magnetospheric Study (IMS) meridian chains of observatories for March 17, 18, and 19, 1978. Based on the study by Allen & Kroehl (1975), we redefine the AU and AL indices by utilizing the magnetic disturbance data obtained from the AE stations located within limited magnetic local time (MLT) sectors; i.e., 1500 MLT 1800 and 0000 MLT 0300, respectively. The current densities of the eastward and westward electrojets are calculated based on the AU and AL indices thus defined. Under the assumption that the Hall conductance at the dusk sector is mainly caused by the solar EUV radiation, we estimate the electric field contribution to the AU index. Assuming further that electric field distributions at dawn and dusk sectors are comparable, it is also possible to estimate the contribution of the Hall conductance associated with auroral particle precipitation to the AL index. From this study it is noted that the electric fields and Hall conductances thus estimated show significant correlations with the AU and AL indices, respectively, suggesting that the AU and AL indices are closely associated with the directly driven and loading-unloading processes of substorms.

  2. Density Functional Theory in High Energy Density Physics: phase-diagram and electrical conductivity of water

    Microsoft Academic Search

    Thomas R. Mattsson

    2007-01-01

    Atomistic simulations employing Density Functional Theory (DFT) have recently emerged as a powerful way of increasing our understanding of materials and processes in high energy density physics. Knowledge of the properties of water (equation of state, electrical conductivity, diffusion, low-energy opacity) is essential for correctly describing the physics of giant planets as well as shock waves in water. Although a

  3. Electrical conductivity of a femtosecond laser generated plasma channel in air

    NASA Astrophysics Data System (ADS)

    Ladouceur, H. D.; Baronavski, A. P.; Lohrmann, D.; Grounds, P. W.; Girardi, P. G.

    2001-03-01

    We have measured the time-dependent electrical resistance of a plasma channel created in air by a self-guiding TW femtosecond laser pulse. The plasma conductivity over a 200 ns time interval has been determined from a nonlinear low-inductance circuit model of the experiment. The circuit model incorporates the decay kinetics of the plasma channel and the initial electron density.

  4. Electrical Conductivity in Polymer Composites Containing Metal Nanowires: Simulation and Experiment

    Microsoft Academic Search

    Sadie White; Tarun Vemulkar; John Fischer; Karen Winey

    2009-01-01

    The study of rod percolation behavior has resurfaced in recent years, because it explains electrical conductivity in polymer nanocomposites containing carbon nanotubes and metal nanowires. Common processing techniques result in fillers with L\\/D < 50, so traditional models, which are only strictly correct in the limit of L\\/D ˜?, are ineffective at predicting percolation in these systems. We present a

  5. A Review on Current Research Trends in Die Sinking Electrical Discharge Machining of Conductive Ceramics

    Microsoft Academic Search

    Shruti Mehta

    In recent years, incessant research in material science has encouraged the engineering and development of advanced ceramic materials. Such materials satisfy the needs of high end applications in the areas of aerospace, automotive, defense, biological and nuclear fields. Whereas, due to inherent capability of machining of any conductive material irrespective of its hardness and strength, Electrical Discharge machining process has

  6. Determination of water saturation using gas phase partitioning tracers and time-lapse electrical conductivity measurements

    SciTech Connect

    Johnson, Timothy C.; Oostrom, Martinus; Truex, Michael J.; Thomle, Jonathan N.; Wietsma, Thomas W.

    2013-05-01

    Water saturation is an important indicator of contaminant distribution and plays a governing role in contaminant transport within the vadose zone. Understanding the water saturation distribution is critical for both remediation and contaminant flux monitoring in unsaturated environments. In this work we propose and demonstrate a method of remotely determining water saturation levels using gas phase partitioning tracers and time-lapse bulk electrical conductivity measurements. The theoretical development includes the partitioning chemistry for the tracers we demonstrate (ammonia and carbon dioxide), as well as a review of the petrophysical relationship governing how these tracers influence bulk conductivity. We also investigate methods of utilizing secondary information provided by electrical conductivity breakthrough magnitudes induced by the tracers. We test the method on clean, well characterized, intermediate-scale sand columns under controlled conditions. Results demonstrate the capability to predict partitioning coefficients and accurately monitor gas breakthrough curves along the length of the column according to the corresponding electrical conductivity response, leading to accurate water saturation estimates. This work is motivated by the need to develop effective characterization and monitoring techniques for contaminated deep vadose zone environments, and provides a proof-of-concept toward uniquely characterizing and monitoring water saturation levels at the field scale and in three-dimensions using electrical resistivity tomography.

  7. Electrical conductivity of low-temperature NaCl-KCl-ZrCl4 melts

    NASA Astrophysics Data System (ADS)

    Salyulev, A. B.; Khokhlov, V. A.; Red'kin, A. A.

    2014-08-01

    The dependences of the electrical conductivity of NaCl-KCl-ZrCl4 molten mixtures with a molar ratio NaCl : KCl = 8 : 29 on the temperature (temperature range of 300-540°C) and the ZrCl4 concentration (54.3-75.2 mol %) have been measured for the first time using unique cells.

  8. Compartment D115, typical officer's stateroom, starboard side, note electrical conduct ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Compartment D-115, typical officer's stateroom, starboard side, note electrical conduct on ceiling, corrugated dividing wall, wood furnishings and cabinetry. Ceiling hook may have been used for hanging wet clothing or oilskins. (089) - USS Olympia, Penn's Landing, 211 South Columbus Boulevard, Philadelphia, Philadelphia County, PA

  9. First-principles calculations of the equation of state and electrical conductivity of steel

    Microsoft Academic Search

    Thomas R. Mattsson; Michael P. Desjarlais

    2003-01-01

    Quantum molecular dynamics based on density functional theory offers a new paradigm for determination of dense-plasma properties. The variation of pressure and electrical conductivity with density and temperature can be calculated without empirical input. For aluminum, our calculations [1] are in very good agreement with exploding wire data. Here we study stainless steel between 4000 and 30000 K using the

  10. Electric Conduction in Semiconductors: A Pedagogical Model Based on the Monte Carlo Method

    ERIC Educational Resources Information Center

    Capizzo, M. C.; Sperandeo-Mineo, R. M.; Zarcone, M.

    2008-01-01

    We present a pedagogic approach aimed at modelling electric conduction in semiconductors in order to describe and explain some macroscopic properties, such as the characteristic behaviour of resistance as a function of temperature. A simple model of the band structure is adopted for the generation of electron-hole pairs as well as for the carrier…

  11. Thermal and electrical conductivity of poly( l-lactide)\\/multiwalled carbon nanotube nanocomposites

    Microsoft Academic Search

    Hun-Sik Kim; Yun Seok Chae; Byung Hyun Park; Jin-San Yoon; Minsung Kang; Hyoung-Joon Jin

    2008-01-01

    Multiwalled carbon nanotubes (MWCNTs) are considered to be the ideal reinforcing agent for high-strength polymer composites, because of their fantastic mechanical strength, high electrical and thermal conductivity and high aspect ratio. Polymer\\/MWCNTs composites are easily molded, and the resulting shaped plastic articles have a perfect surface appearance compared with polymer composites made using usual carbon or glass fibers. Good interfacial

  12. Symmetry of Two-Terminal Nonlinear Electric Conduction A. Lofgren,1

    E-print Network

    Taylor, Richard

    Symmetry of Two-Terminal Nonlinear Electric Conduction A. Lo¨fgren,1 C. A. Marlow,2 I. Shorubalko,1 January 2004) The well-established symmetry relations for linear transport phenomena cannot, in general, be applied in the nonlinear regime. Here we propose a set of symmetry relations with respect to bias voltage

  13. The electrical and thermal conductivity of woven pristine and intercalated graphite fiber–polymer composites

    Microsoft Academic Search

    James R Gaier; Yvonne YoderVandenberg; Steven Berkebile; Heather Stueben; Frederick Balagadde

    2003-01-01

    A series of woven fabric laminar composite plates and narrow strips were fabricated from a variety of pitch-based pristine and bromine intercalated graphite fibers in an attempt to determine the influence of the weave on the electrical and thermal conduction. It was found generally that these materials can be treated as if they are homogeneous plates. The rule of mixtures

  14. Effect of Electrical Conductivity of the Soil Solution on Stem Elongation in Fertigated

    E-print Network

    Lieth, J. Heinrich

    Effect of Electrical Conductivity of the Soil Solution on Stem Elongation in Fertigated Roses · Results of effect of salinity on stem length · Summary/Conclusions #12;Background · Previous research-based irrigation techniques ­ Left us with the question: why? ­ Evidence suggested salinity might be an issue

  15. Calculation of conductance for triangular multi-barrier structure in a constant electric field

    NASA Astrophysics Data System (ADS)

    Luo, Min; Yu, Guanxia; Xia, Lijuan

    2015-07-01

    The current density expression and the unit area conductance for one-dimensional triangular multi-barrier structure in the presence of a constant electric field have been derived. For a selected range of parameters of semiconductor materials, the characteristics of unit area conductance versus the applied voltage have been investigated by the numerical calculations, and then the influence on the curve of the unit area conductance-voltage changing with the temperature, the width of the barrier and the height of the barrier have been analyzed.

  16. Holographic electrical and thermal conductivity in strongly coupled gauge theory with multiple chemical potentials

    E-print Network

    Sachin Jain

    2010-04-05

    We study transport coefficients of strongly coupled gauge theory in the presence of multiple chemical potential which are dual to rotating D3, M2 and M5 brane. Using the general form of the perturbation equations, we compute DC-electrical conductivity at finite temperature as well as at zero temperature. We also study thermal conductivity for the same class of black holes and show that thermal conductivity and viscosity obeys Wiedemann-Franz like law even in the presence of multiple chemical potential.

  17. The electrical conductivity of Norway spruce needle diffusate as affected by certain air pollutants.

    PubMed

    Keller, T

    1986-06-01

    Four-year-old potted Norway spruce (Picea abies (L.) Karst.) grafts established with scion material from three mature trees, were exposed to either long-term fumigation with SO(2), with and without water stress, or long-term ozone fumigation. The electrical conductivity of the needle diffusate was measured after the needles had been washed with chloroform and then leached in distilled water. Although none of the treatments caused visible symptoms of injury, SO(2) fumigation and water stress both caused an increase in diffusate conductivity, but the effects were not synergistic. Ozone fumigation lowered both conductivity and nutrient ion concentration in the leachate. PMID:14975911

  18. Electrical conductivity of Pd47Ni47Si6 amorphous membrane while hydrogen permeation

    NASA Astrophysics Data System (ADS)

    Prochwicz, Wojciech P.; St?pie?, Zdzis?aw M.

    2013-10-01

    Hydrogen diffusion through an amorphous membrane causes local disorders in the structure which can be detected through the measurement of changes of the electrical conductivity. Detecting these changes and comparing them directly with the amount of the permeated hydrogen provides information on the efficiency of separation, which can be used in hydrogen sensor and analyzer technology. This paper presents the results of electrical resistivity measurement of Pd47Ni47Si6 alloy amorphous membrane while hydrogen permeation flux was being changed along with the temperature. It was found that hydrogen changes the nature of the resistivity and the temperature coefficient of resistivity is negative, however, starting from the temperature of 365 K, its value becomes smaller. In order to explain this phenomenon thorough and detailed measurements of phase transitions were made with the use of differential scanning calorimetry and X-ray diffractometry. On the basis of the research an attempt was made to explain the recorded changes of electrical conductivity.

  19. Electric conductivity of the quark-gluon plasma investigated using Boltzmann transport theory

    NASA Astrophysics Data System (ADS)

    Greif, Moritz; Bouras, Ioannis; Xu, Zhe; Greiner, Carsten

    2015-05-01

    The electric conductivity of a hot quark-gluon plasma is obtained numerically by solving the relativistic Boltzmann equation. We use a relativistic, semi-classical partonic cascade including screened binary and inelastic, radiative 2 ? 3 perturbative QCD scattering. We employ the Green-Kubo formula and, independently, evaluate the static electric current established by the influence of an external electric field, in order to extract the conductivity. Both numerical methods give the same result. By using only constant, isotropic cross sections, we are able to compare the numerical results and analytic formulas with excellent agreement. Using pQCD scattering with running coupling in the transport code allows us to contrast our results with recent lattice QCD data.

  20. Electric conductive pattern element fabricated using commercial inkjet printer for paper-based analytical devices.

    PubMed

    Matsuda, Yu; Shibayama, Shobu; Uete, Keigo; Yamaguchi, Hiroki; Niimi, Tomohide

    2015-06-01

    Herein, we proposed the addition of an inkjet-printed conductive pattern to paper-based analytical devices (PADs) in order to expand their applications. An electric conductive pattern was easily, quickly, and inexpensively fabricated using a commercial inkjet printer. The addition of a printed electric element will enhance the applications of PADs without the loss of properties such as cost efficiency, disposability, and portability. In this study, we applied an inkjet-printed heater to a piece of paper and investigated its characteristics. The use of the heater as a valve, concentrator, and heat source for chemical reactions on PADs was investigated. Previously, these functions were difficult to realize with PADs. The inkjet-printed heater was used as a valve and concentrator through evaporation of the working fluid and solvent, and was also found to be useful for providing heat for chemical reactions. Thus, the combination of printed electric circuits and PADs has many potential applications. PMID:25952643

  1. Improving the electrical conductivity of carbon nanotube networks: a first-principles study.

    PubMed

    Li, Elise Y; Marzari, Nicola

    2011-12-27

    We address the issue of the low electrical conductivity observed in carbon nanotube networks using first-principles calculations of the structure, stability, and ballistic transport of different nanotube junctions. We first study covalent linkers, using the nitrene-pyrazine case as a model for conductance-preserving [2 + 1] cycloadditions, and discuss the reasons for their poor performance. We then characterize the role of transition-metal adsorbates in improving mechanical coupling and electrical tunneling between the tubes. We show that the strong hybridization between the transition-metal d orbitals with the ? orbitals of the nanotube can provide an excellent electrical bridge for nanotube-nanotube junctions. This effect is maximized in the case of nitrogen-doped nanotubes, thanks to the strong mechanical coupling between the tubes mediated by a single transition metal adatom. Our results suggest effective strategies to optimize the performance of carbon nanotube networks. PMID:22059779

  2. Carbon nanotubes increase the electrical conductivity of fibroblast-seeded collagen hydrogels.

    PubMed

    MacDonald, Rebecca A; Voge, Christopher M; Kariolis, Mihalis; Stegemann, Jan P

    2008-11-01

    Carbon nanotubes are attractive as additives in fiber-reinforced composites due to their high aspect ratio, strength and electrical conductivity. In the present study, solubilized collagen Type I was polymerized in the presence of dispersed single-walled carbon nanotubes (SWNT) and human dermal fibroblast cells (HDF) to produce collagen-SWNT composite biomaterials with HDF embedded directly in the matrix. The resulting constructs, with SWNT loadings of 0 (control), 0.8, 2.0 and 4.0 wt.% SWNT, were cultured and electrical properties were evaluated in the frequency range 5-500 kHz at days 3 and 7. All collagen-SWNT hydrogel matrices underwent HDF-mediated gel compaction over time in culture, but the presence of SWNT significantly decreased the rate and extent of gel compaction. Viability of HDF in all constructs was consistently high and cell morphology was not affected by the presence of SWNT. However, cell number at day 7 in culture decreased with increasing SWNT loading. Electrical conductivity of the constructs varied from 3 to 7 mS cm(-1), depending on SWNT loading level. Conductivity increased uniformly with increasing wt.% of SWNT (R=0.78) and showed a modest frequency dependence, suggesting that the electrical percolation threshold had not been reached in these materials. These data demonstrate that the electrical conductivity of cell-seeded collagen gels can be increased through the incorporation of carbon nanotubes. Protein-SWNT composite materials may have application as scaffolds for tissue engineering, as substrates to study electrical stimulation of cells, and as transducers or leads for biosensors. PMID:18706876

  3. Method for electrically producing dispersions of a nonconductive fluid in a conductive medium

    DOEpatents

    DePaoli, D.W.; Tsouris, C.; Feng, J.Q.

    1998-06-09

    A method is described for use in electrically forming dispersions of a nonconducting fluid in a conductive medium that minimizes power consumption, gas generation, and sparking between the electrode of the nozzle and the conductive medium. The method utilizes a nozzle having a passageway, the wall of which serves as the nozzle electrode, for the transport of the nonconducting fluid into the conductive medium. A second passageway provides for the transport of a flowing low conductivity buffer fluid which results in a region of the low conductivity buffer fluid immediately adjacent the outlet from the first passageway to create the necessary protection from high current drain and sparking. An electrical potential difference applied between the nozzle electrode and an electrode in contact with the conductive medium causes formation of small droplets or bubbles of the nonconducting fluid within the conductive medium. A preferred embodiment has the first and second passageways arranged in a concentric configuration, with the outlet tip of the first passageway withdrawn into the second passageway. 4 figs.

  4. Electrical Conductivity of H2O-CO2 rich-Melt at mantle conditions: interpretation of the LAB using petrology-based 1D conductivity profiles.

    NASA Astrophysics Data System (ADS)

    Sifre, D.; Gaillard, F.; Hashim, L.; Massuyeau, M.; Gardés, E.; Hier-Majumder, S.

    2014-12-01

    Electromagnetic data images mantle regions more conductive than that of dry olivine. There is no doubt that melt is thermodynamically stable and present in the LAB, but how they can impact on mantle electrical conductivity remains debated. In addition, gravitational segregation and fast melt upwelling, being expected if melt fraction exceeds 2 vol. %, is thought to seriously restrict the role of partial melting at the level of the LAB. Petrological studies realized some 30 years ago have shown that peridotites exposed at the P-T-fO2 conditions of the LAB produced H2O and CO2 rich-melts. The segregation of such melts is not expected since they constitute only about 0.5 vol. % of the peridotite, but electrical conductivities of these melts are poorly known. Therefore, electrical conductivity experiments have been performed in piston cylinder on H2O-CO2 rich melts. Different melt compositions have been explored, from carbonated melts to basalts. The effects of chemical compositions and volatiles on these melts have been determined. The electrical conductivity measurements have shown that hydrous carbonated melts are very conductive, and the incorporation of basalt decreases the conductivity. With these new data, a semi-empirical law predicting the conductivity as a function of H2O and CO2 contents has been produced. Based on this law and the electrical conductivity of olivine, 1D conductivity profiles were constructed. With these profiles, the effect of volatiles content (partitioned between the melt and in the solids), melt fractions (mixing law and interconnection of the melt) and different temperature regimes on conductivity are discussed. These calculations are conducted on oceanic and continental settings with different ages. The electrical conductivities of the mantle is thus a powerful tool to track the fundamental process of mantle incipient melting, which is in turn narrowly associated to the cycling of H2O and CO2 in the upper mantle.

  5. Electrically conductive polyaniline-coated electrospun poly(vinylidene fluoride) mats

    NASA Astrophysics Data System (ADS)

    Merlini, Claudia; Barra, Guilherme; Ramoa, Sílvia; Contri, Giseli; Almeida, Rosemeire; D´Ávila, Marcos; Soares, Bluma

    2015-02-01

    Electrically conductive polyaniline (PANI)-coated electrospun poly(vinylidene fluoride) (PVDF) mats were fabricated through aniline (ANI) oxidative polymerization on electrospun PVDF mats. The effect of polymerization condition on structure and property of PVDF/PANI mats was investigated. The electrical conductivity and PANI content enhanced significantly with increasing ANI concentration due to the formation of a conducting polymer layer that completely coated the PVDF fibers surface. The PANI deposition on the PVDF fibers surface increased the Young Modulus and the elongation at break reduced significantly. Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) revealed that the electrospun PVDF and PVDF/PANI mats display a polymorph crystalline structure, with absorption bands associated to the ?, ? and ? phases.

  6. Exploiting redox chemistries to manipulate structure and electrical conductivity in polymer acid-doped polyaniline

    NASA Astrophysics Data System (ADS)

    Tarver, Jacob; Fan, Joline; Loo, Yueh-Lin

    2011-03-01

    Template synthesis of polyaniline on poly(2-acrylamido-2-methyl-1-propanesulfonic acid) yields electrostatically stabilized particles that can be aqueously dispersed and cast into thin films; electrical conductivity in these films scales with inter-particle connectivity. Previous research has shown that solvent annealing with dichloroacetic acid (DCA) induces structural rearrangement of polymer chains and consequently enhances the electrical conductivity by up to two orders of magnitude (from 0.4 to 40 S/cm). Alternatively, the electrostatic interactions between polyaniline and its template can be neutralized through chemical reduction with hydrazine monohydrate, after which the polymer undergoes extensive structural rearrangement; subsequent exposure to nitric oxide leads to reassociation of polyaniline and its polymer acid dopant. Enhanced conductivity is observed following this chemical redox process, and is attributed to extensive polymer chain relaxation and concurrent elimination of the particulate nature of template-synthesized polyaniline.

  7. Releasing dye encapsulated in proteinaceous microspheres on conductive fabrics by electric current.

    PubMed

    Shimanovich, Ulyana; Perelshtein, Ilana; Cavaco-Paulo, Artur; Gedanken, Aharon

    2012-06-27

    The current paper reports on the relase properties of conductive fabrics coated with proteinaceous microspheres containing a dye. The release of the dye was achieved by passing an electric current through the fabric. The conductivity of the polyester fibers resulted from nanosilver (Ag NPs) coated on the surface of these fibers. Both types of coatings (nanosilver coating and the coating of the proteinaceous microspheres) were performed using high-intensity ultrasonic waves. Two different types of dyes, hydrophilic RBBR (Remazol Brilliant Blue R) and hydrophobic ORO (Oil Red O), were encapsulated inside the microspheres (attached to the surface of polyester) and then released by applying an electric current. The Proteinaceous Microsphere (PM)-coated conductive fabrics could be used in medicine for drug release. The encapsulated dye can be replaced with a drug that could be released from the surface of fabrics by applying a low voltage. PMID:22551441

  8. Electrical conductivity measurements of aqueous fluids under pressure with a hydrothermal diamond anvil cell.

    PubMed

    Ni, Huaiwei; Chen, Qi; Keppler, Hans

    2014-11-01

    Electrical conductivity data of aqueous fluids under pressure can be used to derive the dissociation constants of electrolytes, to assess the effect of ionic dissociation on mineral solubility, and to interpret magnetotelluric data of earth's interior where a free fluid phase is present. Due to limitation on the tensile strength of the alloy material of hydrothermal autoclaves, previous measurements of fluid conductivity were mostly restricted to less than 0.4 GPa and 800?°C. By adapting a Bassett-type hydrothermal diamond anvil cell, we have developed a new method for acquiring electrical conductivity of aqueous fluids under pressure. Our preliminary results for KCl solutions using the new method are consistent with literature data acquired with the conventional method, but the new method has great potential for working in a much broader pressure range. PMID:25430149

  9. Electrical conductivity of hot expanded aluminum: experimental measurements and ab initio calculations.

    PubMed

    Recoules, Vanina; Renaudin, Patrick; Clérouin, Jean; Noiret, Pierre; Zérah, Gilles

    2002-11-01

    Experimental measurements and theoretical calculations of the electrical conductivity of aluminum are presented in the strongly coupled partially degenerate regime (rho=0.3 g/cm(3), 5000electrical plasma discharges up to 1.5 GPa. Aluminum properties were determined theoretically by ab initio molecular dynamics simulations in the local density approximation, from which the conductivity was computed using the Kubo-Greenwood formula. The theoretical results were validated in the dense coupled regime against previously published experimental results and then applied to our experimental low density regime, showing that the theoretical results overestimate the experimental conductivities. PMID:12513612

  10. Effect of static magnetic fields on the base conductance and electric breakdown of bilayer lipid membranes

    SciTech Connect

    Simonov, A.N.; Kuznetsov, A.N.; Livshits, V.A.

    1986-07-01

    Static magnetic fields (MF) having inductions of 0.85 to 1.1 T were found to have an effect on the base conductance and electric breakdown of bilayer lipid membranes (BLM) formed from egg lecithin in decane. In membranes with a low specific resistance (R /SUB SP/ < 10/sup 7/ ..cap omega.. X cm/sup 2/ and membranes in a state of ''stress,'' MF parallel to the BLM plane will increase the conductance, current fluctuations, and probability of rupture. Magnetic fields perpendicular to the membranes have no effect on their conductance. In electric breakdown, MF parallel to the membranes prolong the stage of steady-state currents and shorten that of the prebreakdown fluctuations, while MF perpendicular to the membranes shorten the stage of steady-state currents and have no effect on that of the prebreakdown fluctuations. These effects appear to be due to the influence of MF on the formation probability and diameter of ''hydrophilic'' pores.

  11. Phase diagram and electrical conductivity of high energy-density water from density functional theory.

    PubMed

    Mattsson, Thomas R; Desjarlais, Michael P

    2006-07-01

    The electrical conductivity and structure of water between 2000-70,000 K and 0.1-3.7 g/cm3 is studied by finite temperature density functional theory (DFT). Proton conduction is investigated quantitatively by analyzing diffusion, the pair-correlation function, and Wannier center locations, while the electronic conduction is calculated in the Kubo-Greenwood formalism. The conductivity formulation is valid across three phase transitions (molecular liquid, ionic liquid, superionic, electronic liquid). Above 100 GPa the superionic phase directly borders an electronically conducting fluid, not an insulating ionic fluid, as previously concluded. For simulations of high energy-density systems to be quantitative, we conclude that finite temperature DFT should be employed. PMID:16907407

  12. Electrospun conducting polymer nanofibers and electrical stimulation of nerve stem cells.

    PubMed

    Prabhakaran, Molamma P; Ghasemi-Mobarakeh, Laleh; Jin, Guorui; Ramakrishna, Seeram

    2011-11-01

    Tissue engineering of nerve grafts requires synergistic combination of scaffolds and techniques to promote and direct neurite outgrowth across the lesion for effective nerve regeneration. In this study, we fabricated a composite polymeric scaffold which is conductive in nature by electrospinning and further performed electrical stimulation of nerve stem cells seeded on the electrospun nanofibers. Poly-L-lactide (PLLA) was blended with polyaniline (PANi) at a ratio of 85:15 and electrospun to obtain PLLA/PANi nanofibers with fiber diameters of 195 ± 30 nm. The morphology, chemical and mechanical properties of the electrospun PLLA and PLLA/PANi scaffolds were carried out by scanning electron microscopy (SEM), X-ray photo electron spectroscopy (XPS) and tensile instrument. The electrospun PLLA/PANi fibers showed a conductance of 3 × 10?? S by two-point probe measurement. In vitro electrical stimulation of the nerve stem cells cultured on PLLA/PANi scaffolds applied with an electric field of 100 mV/mm for a period of 60 min resulted in extended neurite outgrowth compared to the cells grown on non-stimulated scaffolds. Our studies further strengthen the implication of electrical stimulation of nerve stem cells on conducting polymeric scaffolds towards neurite elongation that could be effective for nerve tissue regeneration. PMID:21813321

  13. Differential fiber-specific block of nerve conduction in mammalian peripheral nerves using kilohertz electrical stimulation.

    PubMed

    Patel, Yogi A; Butera, Robert J

    2015-06-01

    Kilohertz electrical stimulation (KES) has been shown to induce repeatable and reversible nerve conduction block in animal models. In this study, we characterized the ability of KES stimuli to selectively block specific components of stimulated nerve activity using in vivo preparations of the rat sciatic and vagus nerves. KES stimuli in the frequency range of 5-70 kHz and amplitudes of 0.1-3.0 mA were applied. Compound action potentials were evoked using either electrical or sensory stimulation, and block of components was assessed through direct nerve recordings and muscle force measurements. Distinct observable components of the compound action potential had unique conduction block thresholds as a function of frequency of KES. The fast component, which includes motor activity, had a monotonically increasing block threshold as a function of the KES frequency. The slow component, which includes sensory activity, showed a nonmonotonic block threshold relationship with increasing KES frequency. The distinct trends with frequency of the two components enabled selective block of one component with an appropriate choice of frequency and amplitude. These trends in threshold of the two components were similar when studying electrical stimulation and responses of the sciatic nerve, electrical stimulation and responses of the vagus nerve, and sensorimotor stimulation and responses of the sciatic nerve. This differential blocking effect of KES on specific fibers can extend the applications of KES conduction block to selective block and stimulation of neural signals for neuromodulation as well as selective control of neural circuits underlying sensorimotor function. PMID:25878155

  14. Spectroscopic determination of electrical conductivity in an MHD duct from absolute intensity measurements

    NASA Technical Reports Server (NTRS)

    Wang, S. Y.; Smith, M.

    1977-01-01

    Measurements of the electrical conductivity in the NASA Lewis cesium seeded, H2-O2 MHD duct have been previously reported. In order to corroborate the above measurements and to analyze the possibility of nonuniform seed injection as a cause of the deviations, a spectroscopic investigation of the plasma conductivity has been undertaken. Transverse profiles of the absolute integrated intensity were measured from the optically thin lines of CSI-.5664 microns and .5636 microns. Radial profiles of emission coefficient were obtained from the measured transverse profiles of intensity by Abel inversion. Radial profiles of electrical conductivity were then obtained under two different assumptions. In the first, the Cs seed fraction is assumed uniform and equal to the measured flow rate at the time when the temperature and conductivity were obtained. In the second method, the local temperature and pressure are taken to be those given by a one-dimensional channel calculation including heat transfer and friction. In this case profiles of conductivity and seed fractions are obtained. The results of the two methods are compared to the previously measured conductivity.

  15. Electrical and Thermal Conductivity of Iron and Iron-Silicon Alloy at High Pressures

    NASA Astrophysics Data System (ADS)

    Seagle, C. T.; Cottrell, E.; Fei, Y.; Hummer, D. R.; Prakapenka, V.

    2011-12-01

    The efficiency of heat transfer in Earth's core controls the dynamics of convection and limits the power available for the geodynamo, the process which generates Earth's magnetic field. For this reason, energetic understanding of Earth's interior requires knowledge of the thermal conductivity of the core. We have measured the electrical resistivity of iron and iron-silicon alloy at high pressures in the diamond anvil cell using a four probe method (van der Pauw); thermal conductivity is proportional to the electrical resistivity via the Wiedemann-Franz law. We present a new model which describes the pressure and temperature dependence of the thermal conductivity of iron and iron-silicon alloys. The data and model predict that the thermal conductivity of Earth's core is significantly higher than previously suggested; implying enhanced conductive heat transport in the core. When the conducted heat flux within the core is compared to reasonable assumptions of the core mantle boundary heat flux-the total heat escaping the core, one concludes that a thermally stratified layer is likely to develop at the top of the outer core. If this thermally stratified layer is stable over geologic time, chemical gradients may develop at the boundary of the stratification due to changes in the bulk composition of the fluid outer core associated with chemical fractionation during inner core growth. This thermo-chemical stratification provides a possible explanation for recent seismic observations of slow wave speeds in the top ~300 km of the outer core.

  16. Preparation of Nanostructured Materials and Electrical Conductance in Complex Physical Systems

    NASA Astrophysics Data System (ADS)

    Cai, Weilong

    Production of materials with controlled physical characteristics presents a fundamentally new method for materials science. A new facility has been designed and built using evaporation onto a moving liquid surface. Using this technique metallic particles with diameters less than 200 A with well-characterized surfaces can be prepared. The applications of these nanostructured particles to fundamental investigations is discussed. Particular attention has been given to the investigations of electrical transport in three complex physical systems. Aqueous colloidal dispersions of alpha - Fe_2O_3 particles (average diameter 65 nm) have been prepared at different volume concentrations. The electrical conduction of these composites has been investigated as a function of particle concentration, temperature (from 77 K to 300 K), frequency (including the d.c. case) of the applied electric field, and the strength (up to 7 kOe) of the applied magnetic field. The conductivity increases with particle concentration and with temperature. The frequency dependence of conductivity obeys a power law with an index slightly less than unity and decreasing somewhat with increasing temperature. These observations are interpreted with a model of conduction by electron hopping between localized states. The composites also show an increase in conductivity with the application of a magnetic field. This conductivity enhancement is believed to result from field -induced agglomeration and particle chaining. The ferromagnetic Curie temperature (T _{c}) has been determined for Fe -Ge alloys as a function of Ge concentration (up to ~10 at.%) using electrical resistivity studies. The investigation shows that addition of Ge to Fe causes a small, gradual increase in T_{c} , reaching the maximum value of ~ 1050 K at ~1.5 at.%Ge, followed by a gradual decrease with higher Ge concentrations. This behavior is in sharp contrast with the usual theories which predict decrease of T_{c} with increasing the concentration of non-magnetic particles. At present time, there are no theories capable of explaining this phenomenon. The electrical conductivity of polypyrrole as a function of temperature has been investigated. The observed temperature dependence can be described by lnsigma ~ T^{-{1over 4} }. The experimental results are quantitatively analyzed in the framework of Mott's variable range hopping model. Although this model gives a reasonable description of the conductivity, it does not afford a complete description of the transport properties of polypyrrole.

  17. Electrical conduction mechanisms and dielectric constants of nanostructured methyl violet 2B thin films

    NASA Astrophysics Data System (ADS)

    Zeyada, H. M.; Makhlouf, M. M.

    2015-06-01

    The uniform thin films of methyl violet 2B, MV2B, with thicknesses ranged from 96 to 300 nm, have been successfully prepared by spin coating technique. X-ray diffraction showed that the powder and pristine thin film of MV2B have amorphous structure. The amorphous pristine films become polymorphous nanocrystallites after annealing at 433 K. The electrical properties of MV2B thin films have been studied. There are a number of operational environments where the performance of MV2B thin films is likely to be affected significantly on their electrical properties and dielectric constants such as the differences of film thicknesses, temperatures and frequencies. It was found that the DC conductivity of MV2B films increases with increasing temperature. The extrinsic conduction mechanism is operating in temperature range of 288-360 K with activation energy of 0.16 eV, and the conduction in extrinsic region is explained via applying Mott model for variable range hopping. The intrinsic conduction mechanism is operating in temperatures >360 K with activation energy of 0.91 eV. The conduction in intrinsic region is explained by applying band to band transitions theory. The AC electrical conductivity and dielectric relaxation of MV2B thin films in the temperature range 365-473 K and in frequency range 0.1-100 kHz has been also studied. It has been shown that theoretical curves generated from correlated barrier hopping, CBH, model gives the best fitting with experimental results. Analysis of these results proved that conduction occurs by phonon-assisted hopping between localized states and it is performed by bipolaron hopping mechanism. The temperature and frequency dependence of both the real and imaginary parts of dielectric constant have been investigated.

  18. Looking for Correlations Between Electrical Conductivity and Viscosity in Magmatic Liquids

    NASA Astrophysics Data System (ADS)

    Poe, B.; Di Genova, D.

    2011-12-01

    Both the viscosity and electrical conductivity (EC) of a magma can vary by several orders of magnitude over either small changes in temperature or chemical composition. The electrical properties of a silicate liquid are mostly dependent on the concentrations and mobilities of low valence, weakly bonded cations, such as sodium and potassium. In contrast, its viscosity depends highly on silica content, as well as total alkali to aluminum ratio. Both viscosity and EC are strongly sensitive to the presence of even small concentrations of dissolved H2O. Above the glass transtion temperature (Tg), a number of parallels suggest that given its electrical conductivity, the viscosity of a silicate melt can be estimated to a satisfactory degree. As the liquid approaches Tg, however, the transition from ductile to brittle behaviour does not appear to be easily recognizable through any of its electrical properties. We examine several recent experimental results that may reveal some of the more important parameters linking electrical properties and rheological properties in this critical temperature regime for both simple and more complex natural silicate liquids.

  19. Interior-architectured ZnO nanostructure for enhanced electrical conductivity via stepwise fabrication process

    PubMed Central

    2014-01-01

    Fabrication of ZnO nanostructure via direct patterning based on sol-gel process has advantages of low-cost, vacuum-free, and rapid process and producibility on flexible or non-uniform substrates. Recently, it has been applied in light-emitting devices and advanced nanopatterning. However, application as an electrically conducting layer processed at low temperature has been limited by its high resistivity due to interior structure. In this paper, we report interior-architecturing of sol-gel-based ZnO nanostructure for the enhanced electrical conductivity. Stepwise fabrication process combining the nanoimprint lithography (NIL) process with an additional growth process was newly applied. Changes in morphology, interior structure, and electrical characteristics of the fabricated ZnO nanolines were analyzed. It was shown that filling structural voids in ZnO nanolines with nanocrystalline ZnO contributed to reducing electrical resistivity. Both rigid and flexible substrates were adopted for the device implementation, and the robustness of ZnO nanostructure on flexible substrate was verified. Interior-architecturing of ZnO nanostructure lends itself well to the tunability of morphological, electrical, and optical characteristics of nanopatterned inorganic materials with the large-area, low-cost, and low-temperature producibility. PMID:25258595

  20. A new method of calculating electrical conductivity with applications to natural waters

    NASA Astrophysics Data System (ADS)

    McCleskey, R. Blaine; Nordstrom, D. Kirk; Ryan, Joseph N.; Ball, James W.

    2012-01-01

    A new method is presented for calculating the electrical conductivity of natural waters that is accurate over a large range of effective ionic strength (0.0004-0.7 mol kg-1), temperature (0-95 °C), pH (1-10), and conductivity (30-70,000 ?S cm-1). The method incorporates a reliable set of equations to calculate the ionic molal conductivities of cations and anions (H+, Li+, Na+, K+, Cs+, NH4+, Mg2+, Ca2+, Sr2+, Ba2+, F-, Cl-, Br-, SO42-, HCO3-, CO32-, NO3-, and OH-), environmentally important trace metals (Al3+, Cu2+, Fe2+, Fe3+, Mn2+, and Zn2+), and ion pairs (HSO4-, NaSO4-, NaCO3-, and KSO4-). These equations are based on new electrical conductivity measurements for electrolytes found in a wide range of natural waters. In addition, the method is coupled to a geochemical speciation model that is used to calculate the speciated concentrations required for accurate conductivity calculations. The method was thoroughly tested by calculating the conductivities of 1593 natural water samples and the mean difference between the calculated and measured conductivities was -0.7 ± 5%. Many of the samples tested were selected to determine the limits of the method and include acid mine waters, geothermal waters, seawater, dilute mountain waters, and river water impacted by municipal waste water. Transport numbers were calculated and H+, Na+, Ca2+, Mg2+, NH4+, K+, Cl-, SO42-, HCO3-, CO32-, F-, Al3+, Fe2+, NO3-, and HSO4-substantially contributed (>10%) to the conductivity of at least one of the samples. Conductivity imbalance in conjunction with charge imbalance can be used to identify whether a cation or an anion measurement is likely in error, thereby providing an additional quality assurance/quality control constraint on water analyses.