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1

Assessing the temporal stability of spatial patterns of soil apparent electrical conductivity using geophysical methods  

NASA Astrophysics Data System (ADS)

Cocoa remains in the same field for decades, resulting in plantations dominated with aging trees growing on variable and depleted soils. We determined the spatio-temporal variability of key soil properties in a (5.81 ha) field from the International Cocoa Genebank, Trinidad using geophysical methods. Multi-year (2008-2009) measurements of apparent electrical conductivity at 0-0.75 m (shallow) and 0.75-1.5 m (deep) were conducted. Apparent electrical conductivity at deep and shallow gave the strongest linear correlation with clay-silt content (R = 0.67 and R = 0.78, respectively) and soil solution electrical conductivity (R = 0.76 and R = 0.60, respectively). Spearman rank correlation coefficients ranged between 0.89-0.97 and 0.81- 0.95 for apparent electrical conductivity at deep and shallow, respectively, signifying a strong linear dependence between measurement days. Thus, in the humid tropics, cocoa fields with thick organic litter layer and relatively dense understory cover, experience minimal fluctuations in transient properties of soil water and temperature at the topsoil resulting in similarly stable apparent electrical conductivity at shallow and deep. Therefore, apparent electrical conductivity at shallow, which covers the depth where cocoa feeder roots concentrate, can be used as a fertility indicator and to develop soil zones for efficient application of inputs and management of cocoa fields.

De Caires, Sunshine A.; Wuddivira, Mark N.; Bekele, Isaac

2014-10-01

2

Effect of Soil Water on Apparent Soil Electrical Conductivity and Texture Relationships in a Dryland Field.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Precision farming (PF) research has shown that when high salinity levels are not present, apparent soil electrical conductivity (ECa) is usually strongly correlated with soil texture. Mapping ECa has been promoted as a means for identifying management zones that are needed for variable application ...

3

Calibration of EMI derived apparent electrical conductivity based on ERT measurements  

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

4

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

PubMed Central

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

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

2014-01-01

5

Using Multivariate Geostatistics to Assess Patterns of Spatial Dependence of Apparent Soil Electrical Conductivity and Selected Soil Properties  

PubMed Central

The apparent soil electrical conductivity (ECa) was continuously recorded in three successive dates using electromagnetic induction in horizontal (ECa-H) and vertical (ECa-V) dipole modes at a 6 ha plot located in Northwestern Spain. One of the ECa data sets was used to devise an optimized sampling scheme consisting of 40 points. Soil was sampled at the 0.0–0.3?m depth, in these 40 points, and analyzed for sand, silt, and clay content; gravimetric water content; and electrical conductivity of saturated soil paste. Coefficients of correlation between ECa and gravimetric soil water content (0.685 for ECa-V and 0.649 for ECa-H) were higher than those between ECa and clay content (ranging from 0.197 to 0.495, when different ECa recording dates were taken into account). Ordinary and universal kriging have been used to assess the patterns of spatial variability of the ECa data sets recorded at successive dates and the analyzed soil properties. Ordinary and universal cokriging methods have improved the estimation of gravimetric soil water content using the data of ECa as secondary variable with respect to the use of ordinary kriging. PMID:25614893

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

2014-01-01

6

Apparent Thermal Conductivity Of Multilayer Insulation  

NASA Technical Reports Server (NTRS)

Mathematical model of apparent or effective thermal conductivity between two successive layers of multilayer thermal insulation (MLI) offers potential for optimizing performance of insulation. One gains understanding of how each physical mechanism contributes to overall flow of heat through MLI blanket. Model helps analyze engineering tradeoffs among such parameters as number of layers, thicknesses of gaps between layers, types of spacers placed in gaps, weight, overall thickness, and effects of foregoing on apparent thermal conductivity through blanket.

Mcintosh, Glen E.

1995-01-01

7

Spatial variability of soil apparent electrical conductivity(ECa) and the water table depth in an alluvial valley under different uses.  

NASA Astrophysics Data System (ADS)

The apparent soil electrical conductivity (ECa), measured by contact or by electromagnetic induction (EMI), has been widely used as a variable that is correlated with physical and chemical soil properties. Therefore this property is used as a parameter in precision agriculture, to enable assessment of soil spatial variability and defining management units, allowing obtaining information about other soil properties like texture, salinity, water content, among others. These conditions are adequate to study spatial variability of data with the help of geostatistics, which models the spatial variability of soil properties, allowing the construction of spatial variability maps unbiased and with minimum variance. Thus, the goal this work was assess the variability special of electrical conductivity apparent soil (ECa) and the water table level in an alluvial valley in the brazilian semi-arid adopting different uses. The studied alluvial valley is located in Pesqueira (Pernambuco State, Brazil) and has 421.0 hectares. The main soil types occurring in the valley are: Fluvic Neosols , litholic Neossols and regolithic Neosols . Climate according to Koppen's classification is BSsh type, with total annual rainfall average of 730mm. The attributes evaluated in this study were sampled at 88 piezometric wells. The apparent soil electrical conductivity (ECa) was measured by electromagnetic induction with the EM38 device (Geonics Ltd) in vertical dipole (effective depth 1.5m). The ground water table was determined in piezometric wells with the aid of a measuring tape. Data were analyzed by using descriptive statistics and geostatistical tools. The land use map was constructed using field verification and spatialized by means of GIS. The attributes analyzed showed Normal frequency distribution. ECa readings ranged between 8 and 79 mS m-1. The major differences between the ECa values are due to the variation of water content in soil and distance from the water table at the soil surface. The water table in the study area ranged from 0.8 to 3.8 m deep. The Pearson linear correlation found for the data in the study was zero (r = -0.0185). The Gaussian model was the best fit to the data, and the water table had the highest range value (a = 500.00 m). The maps of spatial variability of water table and ECa have similar spatial behavior, indicating that where the water table is deeper at places with the lowest ECa.

Siqueira, G. M.; Fontes Júnior, R. V. P.; Montenegro, A. A. A.; Barros, Y. L.; Silva, E. F. F.

2012-04-01

8

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

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

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

2014-01-01

9

The Apparent Thermal Conductivity of Pozzolana Concrete  

NASA Astrophysics Data System (ADS)

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).

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

10

Polymers that Conduct Electricity.  

ERIC Educational Resources Information Center

Although polymers are regarded as electrical insulators, it was discovered that they can be made to conduct electricity. This discovery has opened vast new practical and theoretical areas for exploration by physicists and chemists. Research studies with these conducting polymers and charge-transfer salts as well as possible applications are…

Edelson, Edward

1983-01-01

11

Electrically conductive composite material  

DOEpatents

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.

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

1989-05-23

12

Electrically conductive composite material  

DOEpatents

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.

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

1988-06-20

13

Electrically conductive material  

DOEpatents

An electrically conductive material for use in solid oxide fuel cells, electrochemical sensors for combustion exhaust, and various other applications possesses increased fracture toughness over available materials, while affording the same electrical conductivity. One embodiment of the sintered electrically conductive material consists essentially of cubic ZrO.sub.2 as a matrix and 6-19 wt. % monoclinic ZrO.sub.2 formed from particles having an average size equal to or greater than about 0.23 microns. Another embodiment of the electrically conductive material consists essentially at cubic ZrO.sub.2 as a matrix and 10-30 wt. % partially stabilized zirconia (PSZ) formed from particles having an average size of approximately 3 microns.

Singh, Jitendra P. (Bollingbrook, IL); Bosak, Andrea L. (Burnam, IL); McPheeters, Charles C. (Woodridge, IL); Dees, Dennis W. (Woodridge, IL)

1993-01-01

14

Electrically conductive material  

DOEpatents

An electrically conductive material is described for use in solid oxide fuel cells, electrochemical sensors for combustion exhaust, and various other applications possesses increased fracture toughness over available materials, while affording the same electrical conductivity. One embodiment of the sintered electrically conductive material consists essentially of cubic ZrO[sub 2] as a matrix and 6-19 wt. % monoclinic ZrO[sub 2] formed from particles having an average size equal to or greater than about 0.23 microns. Another embodiment of the electrically conductive material consists essentially at cubic ZrO[sub 2] as a matrix and 10-30 wt. % partially stabilized zirconia (PSZ) formed from particles having an average size of approximately 3 microns. 8 figures.

Singh, J.P.; Bosak, A.L.; McPheeters, C.C.; Dees, D.W.

1993-09-07

15

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)

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.

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

2013-04-01

16

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)

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.

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

2012-12-01

17

Electrical Conductivity in Textiles  

NASA Technical Reports Server (NTRS)

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.

2006-01-01

18

Electrically conductive alternating copolymers  

DOEpatents

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.

Aldissi, M.; Jorgensen, B.S.

1987-08-31

19

ESTABLISHEMENT OF CRACK INDEXES BY ELECTRICAL APPARENT RESISTIVITY DATA  

E-print Network

ESTABLISHEMENT OF CRACK INDEXES BY ELECTRICAL APPARENT RESISTIVITY DATA A. Samouelian (1,2), I 6759, 45067 Orleans Cedex 2 France. Soil cracks, whose formation are associated to natural climate phenomena, play an im- portant role in water and gas transfer. Detecting cracks by non

Boyer, Edmond

20

Electrically Conductive Anodized Aluminum Surfaces  

NASA Technical Reports Server (NTRS)

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.

Nguyen, Trung Hung

2006-01-01

21

Electrical Conductivity of Cryolite Melts  

NASA Astrophysics Data System (ADS)

This paper proposes an equation for the electrical conductivity of multicomponent cryolite-based mixtures. The equation is based on a physical model which assumes that the conductivity is proportional to the number density of the effective electric charges in the melt. The various authors in the available literature show a great discrepancy in conductivity data of cryolite-based melts. The equation based on the physical model enables determination of which set of data is preferable. Special consideration in this respect is given to the influence of magnesium flouride and lithium flouride additions to the melt.

Fellner, P.; Grjotheim, K.; Kvande, H.

1985-11-01

22

Electric conductivity of plasma in solar wind  

NASA Astrophysics Data System (ADS)

One of the most important parameters in MHD description of the solar wind is the electric conductivity of plasma. There exist now two quite different approaches to the evaluation of this parameter. In the first one a value of conductivity taken from the most elaborated current theory of plasma should be used in calculations. The second one deals with the empirical, phenomenological value of conductivity. E.g.: configuration of interplanetary magnetic field, stretched by the expanding corona, depends on the magnitude of electrical conductivity of plasma in the solar wind. Knowing the main empirical features of the field configuration, one may estimate the apparent phenomenological value of resistance. The estimations show that the electrical conductivity should be approximately 1013 times smaller than that calculated by Spitzer. It must be noted that the empirical value should be treated with caution. Due to the method of its obtaining it may be used only for 'large-scale' description of slow processes like coronal expansion. It cannot be valid for 'quick' processes, changing the state of plasma, like collisions with obstacles, e.g., planets and vehicles. The second approach is well known in large-scale planetary hydrodynamics, stemming from the ideas of phenomenological thermodynamics. It could formulate real problems which should be solved by modern plasma physics, oriented to be adequate for complicated processes in space.

Chertkov, A. D.

1995-06-01

23

Electrically conductive rigid polyurethane foam  

DOEpatents

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.

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

1983-12-08

24

Electrically conductive rigid polyurethane foam  

DOEpatents

A rigid, polyurethane foam comprises about 2-10 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.

Neet, Thomas E. (Grandview, MO); Spieker, David A. (Olathe, KS)

1985-03-19

25

Electrical Conductivity in Transition Metals  

ERIC Educational Resources Information Center

The aim of this "Science Note" is to describe how to test the electron-sea model to determine whether it accurately predicts relative electrical conductivity for first-row transition metals. In the electron-sea model, a metal crystal is viewed as a three-dimensional array of metal cations immersed in a sea of delocalised valence…

Talbot, Christopher; Vickneson, Kishanda

2013-01-01

26

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

E-print Network

A simple numerical model of the apparent loss of eddy current conductivity due to surface roughness of eddy current conductivity has been suggested as a possible means to allow the nondestructive evaluation, the path of the eddy current must follow a more tortuous route in the material, which produces a reduction

Nagy, Peter B.

27

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

E-print Network

Numerical method for calculating the apparent eddy current conductivity loss on randomly rough Because of their frequency-dependent penetration depth, eddy current measurements are capable of mapping of eddy current conductivity, thereby decreasing the accuracy of the measurements, especially in thermally

Nagy, Peter B.

28

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...

29

Electrical Conductivity of Ferritin Proteins by Conductive AFM  

NASA Technical Reports Server (NTRS)

Electrical conductivity measurements were performed on single apoferritin and holoferritin molecules by conductive atomic force microscopy. Conductivity of self-assembled monolayer films of ferritin molecules on gold surfaces was also measured. Holoferritin was 5-25 times more conductive than apoferritin, indicating that for holoferritin most electron-transfer goes through the ferrihydrite core. With 1 V applied, the average electrical currents through single holoferritin and apoferritin molecules were 2.6 PA and 0.19 PA, respectively.

Xu, Degao; Watt, Gerald D.; Harb, John N.; Davis, Robert C.

2005-01-01

30

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

NASA Technical Reports Server (NTRS)

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

Yuan, Zeng-Guang; Kleinhenz, Julie E.

2011-01-01

31

Effects of pressure, temperature and volume on the electrical conductivity of polymer electrolytes  

Microsoft Academic Search

Three features of the electrical conductivity of ion conducting polymers are described. First, it is shown how the ratio of the apparent isochoric activation energy to the isobaric activation enthalpy, EV*\\/H*, can be used to separate the contributions of volume and temperature to the electrical conductivity. Next, the effect of pressure on the conductivity is considered. Finally, the concept of

J. T. Bendler; J. J. Fontanella; M. F. Shlesinger; M. C. Wintersgill

32

Nanopatterned Electrically Conductive Films of Semiconductor Nanocrystals  

E-print Network

We present the first semiconductor nanocrystal films of nanoscale dimensions that are electrically conductive and crack-free. These films make it possible to study the electrical properties intrinsic to the nanocrystals ...

Mentzel, Tamar

33

IN SITU APPARENT CONDUCTIVITY MEASUREMENTS AND MICROBIAL POPULATION DISTRIBUTION AT A HYDROCARBON CONTAMINATED SITE  

EPA Science Inventory

We investigated the bulk electrical conductivity and microbial population distribution in sediments at a site contaminated with light non-aqueous phase liquid (LNAPL). The bulk conductivity was measured using in situ vertical resistivity probes, while the most probable number met...

34

Influence of Humidity on the Apparent Thermal Conductivity of Concrete Pozzolan  

NASA Astrophysics Data System (ADS)

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

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

35

Electrically conductive connection for an electrode  

DOEpatents

An electrically conductive connection for an electrode assembly of an electrolyte cell in which aluminum is produced by electrolysis in a molten salt is described. The electrode assembly comprises an electrode flask and a conductor rod. The flask has a collar above an area of minimum flask diameter. The electrically conductive connection comprises the electrode flask, the conductor rod and a structure bearing against the collar and the conductor rod for pulling the conductor rod into compressive and electrical contact with the flask.

Hornack, Thomas R. (Lower Burrell, PA); Chilko, Robert J. (Lower Burrell, PA)

1986-01-01

36

Electrically conductive polyimides containing silver trifluoroacetylacetonate  

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

37

Calibration-free electrical conductivity measurements for highly conductive slags  

SciTech Connect

This research involves the measurement of the electrical conductivity (K) for the ESR (electroslag remelting) slag (60 wt.% CaF{sub 2} - 20 wt.% CaO - 20 wt.% Al{sub 2}O{sub 3}) used in the decontamination of radioactive stainless steel. The electrical conductivity is measured with an improved high-accuracy-height-differential technique that requires no calibration. This method consists of making continuous AC impedance measurements over several successive depth increments of the coaxial cylindrical electrodes in the ESR slag. The electrical conductivity is then calculated from the slope of the plot of inverse impedance versus the depth of the electrodes in the slag. The improvements on the existing technique include an increased electrochemical cell geometry and the capability of measuring high precision depth increments and the associated impedances. These improvements allow this technique to be used for measuring the electrical conductivity of highly conductive slags such as the ESR slag. The volatilization rate and the volatile species of the ESR slag measured through thermogravimetric (TG) and mass spectroscopy analysis, respectively, reveal that the ESR slag composition essentially remains the same throughout the electrical conductivity experiments.

MACDONALD,CHRISTOPHER J.; GAO,HUANG; PAL,UDAY B.; VAN DEN AVYLE,JAMES A.; MELGAARD,DAVID K.

2000-05-01

38

Electrical and thermal conductivities in dense plasmas  

SciTech Connect

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.

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

2014-09-15

39

Electrical and thermal conductivities in dense plasmas  

NASA Astrophysics Data System (ADS)

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.

Faussurier, G.; Blancard, C.; Combis, P.; Videau, L.

2014-09-01

40

Electrically Conductive Polyimide Films Containing Gold Surface  

NASA Technical Reports Server (NTRS)

Polyimide films exhibiting high thermo-oxidative stability and including electrically conductive surface layers containing gold made by casting process. Many variations of basic process conditions, ingredients, and sequence of operations possible, and not all resulting versions of process yield electrically conductive films. Gold-containing layer formed on film surface during cure. These metallic gold-containing polyimides used in film and coating applications requiring electrical conductivity, high reflectivity, exceptional thermal stability, and/or mechanical integrity. They also find commercial potential in areas ranging from thin films for satellite antennas to decorative coatings and packaging.

Caplan, Maggie L.; Stoakley, Diane M.; St. Clair, Anne K.

1994-01-01

41

Electrical conductivity effects in polyethylene terephthalate films  

NASA Astrophysics Data System (ADS)

Electrical conductivity effects in biaxially stretched polyethylene terephthalate (PET) films of 6 ?m thickness and 68% degree of crystallinity were investigated by means of dielectric relaxation spectroscopy in the frequency range 10-2-106 Hz and at temperatures higher than the glass transition temperature (˜85 °C) up to 190 °C. The formalisms of complex permittivity, electric modulus, and impedance were employed to analyze the experimental data. The results are discussed in terms of dc conductivity, conductivity current relaxation, interfacial Maxwell-Wagner-Sillars polarization, ? peak, space-charge polarization, and electrode polarization. They are compared with the predictions of models for the electrical and dielectric properties of ion-conducting polymers. The dc conductivity values determined from dc measurement, from ac conductivity plots and from complex impedance plots agree well with each other. Their temperature dependence is described by the Vogel-Tammann-Fulcher equation and classifies PET as a fragile system.

Neagu, E.; Pissis, P.; Apekis, L.

2000-03-01

42

Electrical conductivity effects in polyethylene terephthalate films  

Microsoft Academic Search

Electrical conductivity effects in biaxially stretched polyethylene terephthalate (PET) films of 6 mum thickness and 68% degree of crystallinity were investigated by means of dielectric relaxation spectroscopy in the frequency range 10-2-106 Hz and at temperatures higher than the glass transition temperature (~85 °C) up to 190 °C. The formalisms of complex permittivity, electric modulus, and impedance were employed to

E. Neagu; P. Pissis; L. Apekis

2000-01-01

43

Comparison of Electromagnetic Induction and Direct Sensing of Soil Electrical Conductivity  

Microsoft Academic Search

et al. (1989) modeled ECa as a function of soil water content (both the mobile and immobile fractions), the Apparent profile soil electrical conductivity (ECa) can be an indi- electrical conductivity (EC) of the soil water, soil bulk rect indicator of a number of soil physical and chemical properties. Commercially available ECa sensors can be used to efficiently and density,

K. A. Sudduth; N. R. Kitchen; G. A. Bollero; D. G. Bullock; W. J. Wiebold

2003-01-01

44

Computer simulation of electrical conductivity of colloidal dispersions during aggregation  

NASA Astrophysics Data System (ADS)

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(?)

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

2006-03-01

45

Electrically conductive connection for an electrode  

DOEpatents

An electrically conductive connection for an electrode assembly of an electrolyte cell in which aluminum is produced by electrolysis in a molten salt is described. The electrode assembly comprises an electrode flask and a conductor rod. The flask has a collar above an area of minimum flask diameter. The electrically conductive connection comprises the electrode flask, the conductor rod and a structure bearing against the collar and the conductor rod for pulling the conductor rod into compressive and electrical contact with the flask. 2 figs.

Hornack, T.R.; Chilko, R.J.

1986-09-02

46

Electrically conductive and thermally conductive materials for electronic packaging  

NASA Astrophysics Data System (ADS)

The aim of this dissertation is to develop electrically or thermally conductive materials that are needed for electronic packaging and microelectronic cooling. These materials are in the form of coatings and are made from pastes. The research work encompasses paste formulation, studying the process of converting a paste to a conductive material, relating the processing conditions to the structure and performance, and evaluating performance attributes that are relevant to the application of these conductive materials. The research has resulted in new information that is valuable to the microelectronic industry. Work on electrically conductive materials emphasizes the development of electrical interconnection materials in the form of air-firable glass-free silver-based electrically conductive thick films, which use the Ti-Al alloy as the binder and are in contrast to conventional films that use glass as the binder. The air-firability, as enabled by minor additions of tin and zinc to the paste, is in contrast to previous glass-free films that are not firable. The recommended firing condition is 930°C in air. The organic vehicle in the paste comprises ethyl cellulose, which undergoes thermal decomposition during burnout of the paste. The ethyl cellulose is dissolved in ether, which facilitates the burnout. Excessive ethyl cellulose hinders the burnout. A higher heating rate results in more residue after burnout. The presence of silver particles facilitates drying and burnout. Firing in air gives lower resistivity than firing in oxygen. Firing in argon gives poor films. Compared to conventional films that use glass as the binder, these films, when appropriately fired, exhibit lower electrical resistivity (2.5 x 10-6 O.cm) and higher scratch resistance. Work on thermally conductive materials addresses thermal interface materials, which are materials placed at the interface between a heat sink and a heat source for the purpose of improving the thermal contact. Heat dissipation is the most critical problem in the microelectronic industry. This work emphasizes the development of thermal interface materials in the form of phase change materials, namely paraffin wax, which melts at 48°C. The addition of boron nitride particles to the wax improves the performance, as indicated by the thermal contact conductance between copper surfaces. The melting of the wax improves the conformability of the thermal interface material, thereby enhancing the conductance. Pressure applied in the direction perpendicular to the plane of the interface also enhances the conductance. With 15 wt. % BN and a pressure of 0.3 MPa, a thermal contact conductance comparable to that attained by using solder (applied in the molten state) as the thermal interface material has been attained.

Liu, Zongrong

47

Optically Transparent, Electrically Conductive Composite Medium  

NASA Astrophysics Data System (ADS)

The development of an optically transparent yet electrically conductive material made with a composite structure having preferentially arranged conductive paths is described. The medium contains many vertically aligned but laterally isolated chains of ferromagnetic spheres dispersed in a sheet of transparent polymer. The sheet material transmits more than 90 percent of the incident light and is highly conductive only in the thickness direction. When suitably modified, the material exhibits on-off electrical switchability at a certain threshold pressure. These characteristics confer potential usefulness for visual communication devices such as write pads or touch-sensitive screens.

Jin, S.; Tiefel, T. H.; Wolfe, R.; Sherwood, R. C.; Mottine, J. J., Jr.

1992-01-01

48

Making Complex Electrically Conductive Patterns on Cloth  

NASA Technical Reports Server (NTRS)

A method for automated fabrication of flexible, electrically conductive patterns on cloth substrates has been demonstrated. Products developed using this method, or related prior methods, are instances of a technology known as 'e-textiles,' in which electrically conductive patterns ar formed in, and on, textiles. For many applications, including high-speed digital circuits, antennas, and radio frequency (RF) circuits, an e-textile method should be capable of providing high surface conductivity, tight tolerances for control of characteristic impedances, and geometrically complex conductive patterns. Unlike prior methods, the present method satisfies all three of these criteria. Typical patterns can include such circuit structures as RF transmission lines, antennas, filters, and other conductive patterns equivalent to those of conventional printed circuits. The present method overcomes the limitations of the prior methods for forming the equivalent of printed circuits on cloth. A typical fabrication process according to the present method involves selecting the appropriate conductive and non-conductive fabric layers to build the e-textile circuit. The present method uses commercially available woven conductive cloth with established surface conductivity specifications. Dielectric constant, loss tangent, and thickness are some of the parameters to be considered for the non-conductive fabric layers. The circuit design of the conductive woven fabric is secured onto a non-conductive fabric layer using sewing, embroidery, and/or adhesive means. The portion of the conductive fabric that is not part of the circuit is next cut from the desired circuit using an automated machine such as a printed-circuit-board milling machine or a laser cutting machine. Fiducials can be used to align the circuit and the cutting machine. Multilayer circuits can be built starting with the inner layer and using conductive thread to make electrical connections between layers.

Chu, Andrew; Fink, Patrick W.; Dobbins, Justin A.; Lin, Greg Y.; Scully, Robert C.; Trevino, Robert

2008-01-01

49

Partial-melt electrical conductivity: Influence of melt composition  

SciTech Connect

The electrical conductivity of a partial melt is influenced by many factors, including melt conductivity, crystalline conductivity, and melt fraction, each of which is influenced by temperature. We have performed measurements of bulk conductivity as a function of temperature of an Fo{sub 80}-basalt partial melt between 684{degree} and 1244{degree}C at controlled oxygen fugacity. Melt fraction and composition variations with temperature calculated using MELTS [Ghiorso and Sack, 1995] indicate that the effect on melt conductivity of changing melt composition is balanced by changes in temperature (T). Thus bulk conductivity as a function of T or melt fraction in this system can be calculated assuming a constant melt conductivity. The bulk conductivity is well modeled by simple parallel calculations, by the Hashin-Shtrikman upper bound, or by Archie{close_quote}s law ({sigma}{sub partial melt}/{sigma}{sub melt}=C{sub 1}X{sub m}{sup n}). We estimate apparent values of the Archie{close_quote}s law parameters between 1150{degree} and 1244 {degree}C as C{sub 1}=0.73{plus_minus}0.02 and n=0.98{plus_minus}0.01. Estimates of the permeability of the system are obtained by using an electrical conductivity-critical scale length relationship and range from {approximately}10{sup {minus}14} to 10{sup {minus}18} m{sup 2}, comparing favorably with previously published values. {copyright} 1999 American Geophysical Union

Roberts, J.J. [Lawrence Livermore National Laboratory, Livermore, California (United States)] [Lawrence Livermore National Laboratory, Livermore, California (United States); Tyburczy, J.A. [Department of Geology, Arizona State University, Tempe (United States)] [Department of Geology, Arizona State University, Tempe (United States)

1999-04-01

50

Electrically conductive containment vessel for molten aluminum  

DOEpatents

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.

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

1984-06-25

51

Electrically conductive containment vessel for molten aluminum  

DOEpatents

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.

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

1985-01-01

52

Electrical conductivity and impedance behaviour of hydrogels  

NASA Astrophysics Data System (ADS)

The impedance and electrical conductivity behavior of gellan gum hydrogels containing the conducting fillers poly(3,4- ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) and vapour grown carbon nanofibers (VGCNF) is presented. Impedance analysis showed that an equivalent circuit consisting of a Warburg element in series with a resistor could be used to model the gels' behavior. It is demonstrated that the addition of the conducting fillers PEDOT:PSS and VGCNFs can result in a measurable improvement in the conductivity of hydrogels with high water content and swelling ratios. Incorporation of combinations of these conducting fillers resulted in an improvement of the conductivity of gellan gum-containing hydrogels with water content (swelling ratio) of at least 97.5% (40) from 1.2 +/- 0.1 mS/cm to 4 +/- 0.6 mS/cm.

Warren, Holly; in het Panhuis, Marc

2014-08-01

53

Observations and parameterization of the stratospheric electrical conductivity  

NASA Astrophysics Data System (ADS)

Simultaneous in situ measurements of the stratospheric electrical conductivity, made from multiple balloon platforms during the 1992-1993 Extended Life Balloon-Borne Observatories (ELBBO) experiment, have yielded the most comprehensive data set on the stratospheric electrical conductivity. The ELBBO project involved launches of five superpressure balloons into the stratosphere from Dunedin, New Zealand, beginning November 10, 1992, and lasting through March 18, 1993. Most of the balloons floated at a constant altitude of 26 km for over 3 months, covered a wide range of latitudes from the South Pole to 28°S, and circled around the southern hemisphere several times. On average, the positive polar conductivity (conductivity of positive ions alone) was about 15% higher than that of the negative conductivity, suggesting that differences may exist between the mobilities of positive and negative ions. Data from each polarity of polar conductivity also indicate persistent, apparently organized, short-term and localized variations, with amplitude within 30% of the mean value. In corrected geomagnetic (CGM) coordinates the conductivity variations were found to be a function of latitude but not of longitude. The total conductivity can increase 150% from low latitude to high latitude, and does remain nearly constant at latitudes above 55° (namely, the cosmic ray knee latitude). Calculations based on ionization theory demonstrate that the latitudinal variations in the conductivity measurements were mainly due to the latitudinal variations in incident galactic cosmic ray intensity, with only little effect from the air temperature variations. The calculations shown here also suggest that small ions (as opposed to large ions) provide the main contribution to the stratospheric conductivity. The comparisons between conductivity measurements and models show that commonly used models can underestimate the latitudinal variation by a factor of 2. In this paper the stratospheric conductivity is parameterized based on the measurements, and a simple empirical model is presented in geographic coordinates.

Hu, Hua; Holzworth, Robert H.

1996-12-01

54

Calculation of electric fields in conductive media  

SciTech Connect

A method is presented, based upon finite-difference forms of Laplace's equation, for the iterative calculation of three-dimensional electric field distributions in electrically conductive media. The method, while generally applicable to any conductive media, will be presented with emphasis on its use for the prediction of power density in tissue when radio-frequency hyperthermia is utilized in the treatment of cancer. A computer code which performs these calculations has been written in BASIC so that it may be adapted to relatively inexpensive desktop computers for use in treatment planning. Example calculations of the distribution of electric potential, gradient, and power density with specific electrode configurations are presented. Applications and limitations of the technique are discussed.

Doss, J.D.

1982-07-01

55

Electrical properties of ion conducting molybdate glasses  

NASA Astrophysics Data System (ADS)

The electrical conductivity and conductivity relaxation of xAg2O-(1-x )MoO3 glasses have been reported in the frequency range of 10Hz-2MHz and temperature range of 183-413K. The dc conductivity and activation energy for the binary silver molybdate glasses have been compared with those of Ag+ ion conducting binary phosphate, borate, and tellurite glasses. The silver molybdate glasses exhibit the highest conductivity and the lowest activation energy of the glasses formed with other glass formers such as phosphate, borate, and tellurite containing the same modifier Ag+ ions. We have analyzed the ac conductivity using the power law and the electric modulus formalisms. We have observed that the concentration of mobile Ag+ ions is not thermally activated and only 10%-25% of the total Ag+ ions contribute to the dynamic processes and are independent of the Ag2O content. We have observed that the conductivity relaxation is highly nonexponential. The motion of Ag+ ions is decoupled more and more from the viscous motion of the glassy matrix with the increase of Ag2O content in the investigated glass composition.

Bhattacharya, S.; Ghosh, A.

2006-12-01

56

Electrical conduction of a XLPE nanocomposite  

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

57

Electrical conduction control of carbon nanowalls  

SciTech Connect

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.

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

58

Dislocation electrical conductivity of synthetic diamond films  

SciTech Connect

A relationship between the electric resistance of single-crystal homoepitaxial and polycrystalline diamond films and their internal structure has been investigated. It is established that the electrical conductivity of undoped homoepitaxial and polycrystalline diamond films is directly related to the dislocation density in them. A relation linking the resistivity {rho} ({approx}10{sup 13}-10{sup 15} {omega} cm) with the dislocation density {gamma} ({approx}10{sup 14}-4 x 10{sup 16} m{sup -2}) is obtained. The character of this correlation is similar for both groups of homoepitaxial and polycrystalline diamond films. Thin ({approx}1-8 {mu}m) homoepitaxial and polycrystalline diamond films with small-angle dislocation boundaries between mosaic blocks exhibit dislocation conductivity. The activation energy of dislocation acceptor centers was calculated from the temperature dependence of the conductivity and was found to be {approx}0.3 eV. The conduction of thick diamond films (h > 10 {mu}m) with the resistivity {rho} {approx} 10{sup 8} {omega} cm is determined by the conduction of intercrystallite boundaries, which have a nondiamond hydrogenated structure. The electronic properties of the diamond films are compared with those of natural semiconductor diamonds of types IIb and Ic, in which dislocation acceptor centers have activation energies in the range 0.2-0.35 eV and are responsible for hole conduction.

Samsonenko, S. N., E-mail: snsamsonenko@mail.ru; Samsonenko, N. D. [Donbass National Academy of Civil Engineering and Architecture (Ukraine)

2009-05-15

59

Computer simulation of electrical conductivity of colloidal dispersions during aggregation.  

PubMed

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)

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

2006-03-01

60

Electrically conducting superhydrophobic microtextured carbon nanotube nanocomposite  

NASA Astrophysics Data System (ADS)

We report a simple and inexpensive method of producing an electrically conductive superhydrophobic polymer surface by adding multiwall carbon nanotubes directly into the polymer poly(dimethylsiloxane) (PDMS) matrix and replicating micro/nanotexture using a replication master prepared by ultrafast-laser microtexturing process. No additional coatings on conducting PDMS are required to achieve water contact angles greater than 161°. The conductivity can be controlled by changing the percent MWCNT added to PDMS and at a bulk loading of 4.4 wt% we report a conductivity improvement over pure PDMS by a factor of more than 1011 with electrical resistivity ? = 761 ? cm. This combined behavior of a conductive, superhydrophobic nanocomposite has exciting applications for allowing a new class of enclosures providing EMI shielding, water repellency and sensing to provide built-in temperature feedback. The effect of temperature on the nanocomposite was investigated and a negative temperature coefficient of resistance (-0.037 ?/K) similar to that of a thermistor was observed.

Caffrey, Paul O.; Gupta, Mool C.

2014-09-01

61

Electrically conductive palladium containing polyimide films  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

62

Electrical Conduction in the Early Universe  

E-print Network

The electrical conductivity has been calculated in the early universe at temperatures below as well as above the electroweak vacuum scale, $T_c\\simeq 100$GeV. Debye and dynamical screening of electric and magnetic interactions leads to a finite conductivity, $\\sigma_{el}\\sim T/\\alpha\\ln(1/\\alpha)$, at temperatures well below $T_c$. At temperatures above, $W^\\pm$ charge-exchange processes -- analogous to color exchange through gluons in QCD -- effectively stop left-handed charged leptons. However, right-handed leptons can carry current, resulting in $\\sigma_{el}/T$ being only a factor $\\sim \\cos^4\\theta_W$ smaller than at temperatures below $T_c$.

H. Heiselberg

1999-02-19

63

Electrically conducting polyimide film containing tin complexes  

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

64

The electrical conductivity of sodium polysulfide melts  

SciTech Connect

The sodium polysulfide melt has been described by a macroscopic model. This model considers the melt to be composed of sodium cations, monosulfide anions, and neutral sulfur solvent. The transport equations of concentrated-solution theory are used to derived the governing equations for this binaryelectrolyte melt model. These equations relate measurable transport properties to fundamental transport parameters. The focus of this research is to measure the electrical conductivity of sodium polysulfide melts and calculate one of fundamental transport parameters from the experimental data. The conductance cells used in the conductivity measurements are axisymmetric cylindrical cells with a microelectrode. The electrode effects, including double-layer capacity, charge transfer resistance, and concentration overpotential, were minimized by the use of the alternating current at an adequately high frequency. The high cell constants of the conductance cells not only enhanced the experimental accuracy but also made the electrode effects negligible. The electrical conductivities of sodium polysulfide Na{sub 2}S{sub 4} and Na{sub 2}S{sub 5} were measured as a function of temperature (range: 300 to 360{degree}C). Variations between experiments were only up to 2%. The values of the Arrhenius activation energy derived from the experimental data are about 33 kJ/mol. The fundamental transport parameter which quantifies the interaction within sodium cations and monosulfide anions are of interest and expected to be positive. Values of it were calculated from the experimental conductivity data and most of them are positive. Some negative values were obtained probably due to the experimental errors of transference number, diffusion coefficient, density or conductivity data.

Meihui Wang

1992-06-01

65

[The electrical conductivity of triggered lightning channel].  

PubMed

Spectra of return strokes for artificial triggered lightning were obtained by optical multi-channel analyzer (OMA) in Shandong region. Compared with previous spectra of natural lightning, additional lines of ArI 602.5 nm and ArII 666.5 nm were observed. Under the model of local thermodynamic equilibrium, electronic temperatures of the lightning channel plasma were obtained according to the relative line intensities. Meanwhile, with semi-empirical method the electron density was obtained by Halpha line Stark broadening. In combination with plasma theory, electrical conductivity of the lightning channel has been calculated for the first time, and the characteristic of conductivity for lightning channel was also discussed. The relation between the electrical conductivity of channel and the return stroke current was analyzed, providing reference data for further work on computing return stroke current. Results show that the lightning channel is a good conductor, and electrons are the main carrier of channel current. The brightness of artificial triggered lightning channel is usually higher than that of natural lightning, and its current is smaller than that of the natural lightning. PMID:18306764

Zhang, Hua-ming; Yuan, Ping; Su, Mao-gen; Lü, Shi-hua

2007-10-01

66

A transport coefficient: the electrical conductivity  

E-print Network

I describe the lattice determination of the electrical conductivity of the quark gluon plasma. Since this is the first extraction of a transport coefficient with a degree of control over errors, I next use this to make estimates of other transport related quantities using simple kinetic theory formulae. The resulting estimates are applied to fluctuations, ultra-soft photon spectra and the viscosity. Dimming of ultra-soft photons is exponential in the mean free path, and hence is a very sensitive probe of transport.

Sourendu Gupta

2005-04-30

67

Tailoring the Thermoelectric Behavior of Electrically Conductive Polymer Composites  

E-print Network

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...

Moriarty, Gregory P.

2013-05-21

68

Photovoltaic device having light transmitting electrically conductive stacked films  

DOEpatents

A light transmitting electrically conductive stacked film, useful as a light transmitting electrode, including a first light transmitting electrically conductive layer, having a first optical thickness, a second light transmitting layer, having a second optical thickness different from the optical thickness of the first layer, and an electrically conductive metallic layer interposed between and in initimate contact with the first and second layers.

Weber, Michael F. (St. Paul, MN); Tran, Nang T. (St. Paul, MN); Jeffrey, Frank R. (St. Paul, MN); Gilbert, James R. (St. Paul, MN); Aspen, Frank E. (St. Paul, MN)

1990-07-10

69

Nonequilibrium Molecular Dynamics Simulation of Electric Conduction Tatsuro YUGE  

E-print Network

Nonequilibrium Molecular Dynamics Simulation of Electric Conduction Tatsuro YUGE Ã? , Nobuyasu ITO1y for electric conduction, and study transport phenomena by molecular dynamics simulation. We observe. The electrical conductivity is almost independent of the impurity distribution and the system size

Shimizu, Akira

70

Chapter A6. Section 6.3. Specific Electrical Conductance  

USGS Publications Warehouse

Electrical conductance is a measure of the capacity of a substance to conduct an electrical current. The specific electrical conductance (conductivity) of water is a function of the types and quantities of dissolved substances it contains, normalized to a unit length and unit cross section at a specified temperature. This section of the National Field Manual (NFM) describes U.S. Geological Survey (USGS) guidance and protocols for measurement of conductivity in ground and surface waters.

Radtke, Dean B.; Davis, Jerri V.; Wilde, Franceska D.

2005-01-01

71

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...

72

Relationship between cotton yield and soil electrical conductivity, topography, and landsat imagery  

Technology Transfer Automated Retrieval System (TEKTRAN)

Understanding spatial and temporal variability in crop yield is a prerequisite to implementing site-specific management of crop inputs. Apparent soil electrical conductivity (ECa), soil brightness, and topography are easily obtained data that can explain yield variability. The objectives of this stu...

73

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...

74

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...

75

Accuracy issues in electromagnetic induction sensing of soil electrical conductivity for precision agriculture  

Microsoft Academic Search

Soil apparent electrical conductivity (ECa) has been used as a surrogate measure for such soil properties as salinity, moisture content, topsoil depth (TD), and clay content. Measurements of ECa can be accomplished with commercially available sensors and can be used to efficiently and inexpensively develop the dense datasets desirable for describing within-field spatial variability in precision agriculture. The objective of

K. A. Sudduth; S. T. Drummond; N. R. Kitchen

2001-01-01

76

Autumnal leaf conductance and apparent photosynthesis by saplings and sprouts in a recently disturbed northern hardwood forest  

Microsoft Academic Search

Summary  Leaf surface conductance and apparent photosynthesis were measured during late summer and autumn on saplings and sprouts of\\u000a pin cherry (Prunus pensylvanica), yellow birch (Betula alleghaniensis), American beech (Fagus grandifolia), and sugar maple (Acer saccharum) naturally revegetating a site in the northern hardwood forest 5 years following a commercial whole-tree harvest. Prior to\\u000a the disturbance (i.e., the harvest) the site

Jeffrey S. Amthor; David S. Gill; F. Herbert Bormann

1990-01-01

77

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

NASA Technical Reports Server (NTRS)

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.

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

1972-01-01

78

Ouabain decreases apparent potassium-conductance in proximal tubules of the amphibian kidney  

Microsoft Academic Search

According to a previous study from this laboratory, the electrochemical gradient for potassium across the peritubular cell membrane of proximal tubules in the isolated perfused frog kidney increases following the application of ouabain. In order to test, if this phenomenon were due to a decrease of potassium conductance, the effects of ouabain on cell membrane resistances and the sensitivity of

G. Messner; W. Wang; M. Paulmichl; H. Oberleithner; F. Lang

1985-01-01

79

Development of electrically\\/thermally conducting polymer-matrix composites  

Microsoft Academic Search

Polymer-matrix composites that are (i) electrically conducting or (ii) thermally conducting but electrically insulating were developed. A goal was to enhance the conductivity, while maintaining good mechanical properties. An in-situ technology for forming an electrically conducting network in a polymer-matrix composite during composite fabrication was developed. One variation of this technology involved the use of a particulate filler that melted

Lin

1993-01-01

80

Magnetic flowmeter for electrically conductive liquid  

DOEpatents

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.

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

1982-01-01

81

Thermal Conductivity and Elastic Constants of PEDOT:PSS with High Electrical Conductivity  

E-print Network

1 Thermal Conductivity and Elastic Constants of PEDOT:PSS with High Electrical Conductivity Jun Liu of the thermal conductivity of these highly conducting polymers is of interest for evaluating their potential conductivity along multiple directions of thick (>20 µm) drop-cast PEDOT films, that the thermal conductivity

Cahill, David G.

82

Role of Dislocation Movement in the Electrical Conductance of Nanocontacts  

PubMed Central

Dislocation is a lattice imperfection of crystalline materials. Dislocation movement is induced during plastic deformation and influences the mechanical properties. Although the role of dislocation in mechanical properties has been well understood, the role of dislocation in electrical properties is completely lacking. Only Matthiessen's rule addresses the electrical influence of dislocations at the macroscale. Here, we show that the electrical conductance change due to dislocations and show their movements through in situ observation of a gold nanocontact. The density of the dislocations in the gold nanocontact did not affect the electrical conductance. The repeated and discrete dislocation movements resulted in an electrical conductance oscillation. Our results demonstrate how dislocations and their movements affect electric conductance at the nanoscale. This instability issue will cause a big problem for future electric devices such as ultra low power electric devices and nanowire photovoltaic devices. PMID:22953044

Ishida, Tadashi; Kakushima, Kuniyuki; Mizoguchi, Teruyasu; Fujita, Hiroyuki

2012-01-01

83

Electric conductivity of doped triglycine sulphate crystals  

NASA Astrophysics Data System (ADS)

Attention is given to the conductivity values of both pure and doped triglycine sulfate (TGS) crystals at room and transition temperatures. TGS doped with such organic and inorganic dopants as nitroanilines, serine, and leucine, exhibit an increase in DC conductivity, while those doped with L-alanine show a decrease in conductivity by comparison with a pure TGS crystal.

Batra, A. K.; Mathur, S. C.

1985-06-01

84

Electrical Conduction through Nerve and DNA  

Microsoft Academic Search

The aim of the present study was to analyse electric resistivity at different ambient temperatures between 300 to 20K in the frog sciatic nerve and salmon sperm DNA. When the electrical contacts were leaned just into the sciatic nerve, an increase of the sciatic nerve resistivity was observed for 240 K < T < 300 K and a rise of

H. Abdelmelek; A. El-May; Ben Hamouda; M. Ben Salem; J. M. Pequignot; M. Sakly

2003-01-01

85

Method of forming an electrically conductive cellulose composite  

DOEpatents

An electrically conductive cellulose composite includes a cellulose matrix and an electrically conductive carbonaceous material incorporated into the cellulose matrix. The electrical conductivity of the cellulose composite is at least 10 .mu.S/cm at 25.degree. C. The composite can be made by incorporating the electrically conductive carbonaceous material into a culture medium with a cellulose-producing organism, such as Gluconoacetobacter hansenii. The composites can be used to form electrodes, such as for use in membrane electrode assemblies for fuel cells.

Evans, Barbara R. (Oak Ridge, TN); O'Neill, Hugh M. (Knoxville, TN); Woodward, Jonathan (Ashtead, GB)

2011-11-22

86

Synthesis and electrical conductivity of multilayer silicene  

NASA Astrophysics Data System (ADS)

The epitaxial growth and the electrical resistance of multilayer silicene on the Ag(111) surface has been investigated. We show that the atomic structure of the first silicene layer differs from the next layers and that the adsorption of Si induces the formation of extended silicene terraces surrounded by step bunching. Thanks to the controlled contact formation between the tips of a multiple probe scanning tunneling microscope and these extended terraces, a low sheet resistance, albeit much higher than the electrical resistance of the underlying silver substrate, has been measured, advocating for the electrical viability of multilayer silicene.

Vogt, P.; Capiod, P.; Berthe, M.; Resta, A.; De Padova, P.; Bruhn, T.; Le Lay, G.; Grandidier, B.

2014-01-01

87

Proton-irradiation-induced anomaly in the electrical conductivity of a hydrogen-bonded ferroelastic system  

SciTech Connect

An anomalous abrupt drop in the electrical conductivity has been observed at the ferroelastic phase transition of a proton-irradiated system of hydrogen-bonded TlH{sub 2}PO{sub 4}. As a result of the high-resolution {sup 31}P NMR chemical-shift measurements, distinct changes in the atomic displacements due to the irradiation were identified in the ferroelastic and paraelastic phases. Besides, {sup 1}H NMR spin-spin relaxation measurements revealed a change due to the irradiation in the proton dynamics at the ferroelastic phase transition, apparently accounting for the much-reduced electrical conductivity in the paraelastic phase of the irradiated system.

Kim, Se-Hun [Department of Physics and Institute for Nano Science, Korea University, Seoul 136-713 (Korea, Republic of); Faculty of Science Education, Jeju National University, Jeju 690-756 (Korea, Republic of); Lee, Kyu Won; Lee, Cheol Eui [Department of Physics and Institute for Nano Science, Korea University, Seoul 136-713 (Korea, Republic of); Lee, Kwang-Sei [Department of Nano Systems Engineering, Center for Nano Manufacturing, Inje University, Gimhae 621-749, Gyeongnam (Korea, Republic of)

2009-11-01

88

Electrical conductivity and partial melting of mafic rocks under pressure  

Microsoft Academic Search

We demonstrate the importance of electric conductivity measurements of partially molten mafic rocks by examining of Oman gabbro, Karelia olivinite, Ronda and Spitzbergen peridotites. The electrical conductivities of these rocks were estimated using the impedance spectroscopy at temperatures between 800°C and 1450°C and at pressures between 0.3 and 2 GPa in experiments performed in a piston cylinder apparatus. At temperatures

J. Maumus; N. Bagdassarov; H. Schmeling

2005-01-01

89

Electrical Conductivity Behaviour of Chemical Functionalized MWCNTs Epoxy Nanocomposites  

Microsoft Academic Search

Few attempt to study the effects of chemical functionalized carbon nanotubes (CNTs) on the electrical conductivity of nanocomposites, instead to increase dispersion and interfacial bonding strength between CNTs and polymer matrix for improvement of mechanical properties. Therefore, in this study the electrical conductivity of two types' chemical functionalized (Carboxylated and Octadecylated) multi-walled carbon nanotubes (MWCNTs), non ionic surfactant additive MWCNTs

Abu Bakar Sulong; Nurhamidi Muhamad; Jaafar Sahari

2009-01-01

90

Observations and parameterization of the stratospheric electrical conductivity  

Microsoft Academic Search

Simultaneous in situ measurements of the stratospheric electrical conductivity, made from multiple balloon platforms during the 1992-1993 Extended Life Balloon-Borne Observatories (ELBBO) experiment, have yielded the most comprehensive data set on the stratospheric electrical conductivity. The ELBBO project involved launches of five superpressure balloons into the stratosphere from Dunedin, New Zealand, beginning November 10, 1992, and lasting through March 18,

Hua Huand; Robert H. Holzworth

1996-01-01

91

Master Thesis Proposal Eddy Current Imaging of Electrically Conducting Media  

E-print Network

Master Thesis Proposal Eddy Current Imaging of Electrically Conducting Media Domenico Lahaye and optimization techniques en- abling the eddy current imaging of electrically conducting media. Examples: · perform a literature study into topics such as eddy current imaging, inverse problems including

Vuik, Kees

92

Electrically conducting ternary amorphous fully oxidized materials and their application  

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

93

Clinorotation effects on virus infected wheat leaf tissue electric conductivity  

NASA Astrophysics Data System (ADS)

We present our results on the electric conductivity of Apogee wheat leaf tissue infected with wheat streak mosaic virus and grown under simulated microgravity conditions. It is shown that the electric conductivity measurements may be effective in the detection of physiologic changes in plants caused by the impact of abiotic and biotic agents.

Mishchenko, L. T.; Torop, V. V.; Mishchenko, I. A.

94

Delineating Hydraulic Conductivity with Direct Push Electrical Conductivity and High-Resolution Slug Testing  

NASA Astrophysics Data System (ADS)

Direct push technology continues to make advances in efficiently measuring water related parameters in unconsolidated sediments. A direct push subsurface profiling technique used during field investigations measures the electrical conductivity (EC) of sediments and fluid surrounding the EC probe. The EC geophysical method is typically used for gross lithologic definition. When numerous direct push EC profiles are completed, a general impression of vertical and lateral variation of subsurface lithology can be inferred. Unfortunately, these EC profiles do not directly measure the hydraulic conductivity, even though the profiles may indicate the presence of fine-grained material such as silt and clay, which are known to affect the hydraulic conductivity. The direct push EC vertical profiles can be obtained quickly and efficiently over an extended area. These EC profiles can be examined for regions that display a subsurface EC response with a potentially interesting behavior of the hydraulic conductivity. At selected locations, 5cm (2 inch) PVC monitoring wells with appropriate screen lengths can be installed by direct push techniques. We have developed equipment and techniques for performing high-resolution slug tests efficiently in 5cm (2 inch) wells. Correlation of the EC response and the high-resolution slug test results can aid in developing a 3-D picture of the hydraulic conductivity distribution at a given site. In this paper, we present the results of such a correlation for a well located near the Geohydrologic Experiment and Monitoring Site (GEMS) at the University of Kansas in the Kansas River valley. During the installation of this well with direct push equipment, it was discovered that the EC log indicated a prominent but relatively thin silt-clay layer at depth, which is somewhat unusual for this area. We routinely perform high-resolution slug testing efficiently over intervals as small as 7.5cm (3 inches) to 15cm (6 inches); therefore, we decided to see if high-resolution slug testing could accurately delineate this layer of apparent reduced hydraulic conductivity. Results show good correlation between the EC profile and the high-resolution slug test profile. Coupling direct push EC profiling with high-resolution slug testing may provide an efficient way to establish a detailed representation of the hydraulic conductivity distribution in a given area.

Healey, J. M.; McElwee, C. D.; Engard, B.

2004-12-01

95

Electrical Impedance Spectroscopy for Electro-Mechanical Characterization of Conductive Fabrics  

PubMed Central

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

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

2014-01-01

96

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

Microsoft Academic Search

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

F. Lux

1993-01-01

97

Structural and Electrical Study of Conducting Polymers  

NASA Astrophysics Data System (ADS)

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.

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

2010-06-01

98

Surface electrical conductivity of single crystal spinel in cesium vapor. Final report  

SciTech Connect

The operation of a thermionic fuel element (TFE) requires the maintenance of good electrical resistance between the anode and cathode, and between the electrodes and the TFE body. A program of research was established as part of the TOPAZ International Program (TIP) with the purpose of investigating the degradation of TFE electrical insulators. The major emphasis of this research has been on the interactions of oxide ceramics with cesium (Cs) vapor, and the resurfacing decrease of surface resistivity. Previous work has studied the surface electrical conductivity of sapphire exposed to Cs. In this report the authors describe the results of an experimental investigation of the surface electrical conductivity of single crystal magnesium aluminate spinel at temperatures ranging from 573K to 923K, in the presence of cesium vapor at pressures up to 1 Torr. The interest in spinel has arisen in view of its apparent resistance to radiation damage.

Agnew, P.; Ing, J.L.

1995-04-02

99

Electrically conducting novel polymer films containing pi-stacks  

Microsoft Academic Search

The primary focus of this thesis is to expand our knowledge of ion radicals of pi-dimers and pi- 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 pi-stacks of ion radicals. Flexible and air stable

Robert Gang Duan

1997-01-01

100

Electrically conductive adhesives for surface mount solder replacement  

Microsoft Academic Search

Electrically conductive adhesives offer a lead free, relatively low temperature process for attachment of surface mount components to printed circuit boards (PCB's). The National Center for Manufacturing Sciences (NCMS) Conductive Adhesives project has defined a requirement for an isotropically conductive adhesive (ICA). In this study, 25 commercially available silver-filled epoxies were evaluated for joint resistance stability on copper and tin\\/lead

Michael Zwolinski; Julie Hickman; Holly Rubin; Yulia Zaks; Shaun McCarthy; Thomas Hanlon; Peter Arrowsmith; Arun Chaudhuri; Ralph Hermansen; S. Lan; Duane Napp

1996-01-01

101

Electrical Conductivity in a Mixed-Species Biofilm  

PubMed Central

Geobacter sulfurreducens can form electrically conductive biofilms, but the potential for conductivity through mixed-species biofilms has not been examined. A current-producing biofilm grown from a wastewater sludge inoculum was highly conductive with low charge transfer resistance even though microorganisms other than Geobacteraceae accounted for nearly half the microbial community. PMID:22706052

Lau, Joanne; Nevin, Kelly P.; Franks, Ashley E.; Tuominen, Mark T.; Lovley, Derek R.

2012-01-01

102

Electrically conductive lines on cellulose nanopaper for flexible electrical devices.  

PubMed

Highly conductive circuits are fabricated on nanopapers composed of densely packed 15-60 nm wide cellulose nanofibers. Conductive materials are deposited on the nanopaper and mechanically sieved through the densely packed nanofiber networks. As a result, their conductivity is enhanced to the level of bulk silver and LED lights are successfully illuminated via these metallic conductive lines on the nanopaper. Under the same deposition conditions, traditional papers consisting of micro-sized pulp fibers produced very low conductivity lines with non-uniform boundaries because of their larger pore structures. These results indicate that advanced, lightweight and highly flexible devices can be realized on cellulose nanopaper using continuous deposition processes. Continuous deposition on nanopaper is a promising approach for a simple roll-to-roll manufacturing process. PMID:23793980

Hsieh, Ming-Chun; Kim, Changjae; Nogi, Masaya; Suganuma, Katsuaki

2013-10-01

103

Electrically conductive lines on cellulose nanopaper for flexible electrical devices  

NASA Astrophysics Data System (ADS)

Highly conductive circuits are fabricated on nanopapers composed of densely packed 15-60 nm wide cellulose nanofibers. Conductive materials are deposited on the nanopaper and mechanically sieved through the densely packed nanofiber networks. As a result, their conductivity is enhanced to the level of bulk silver and LED lights are successfully illuminated via these metallic conductive lines on the nanopaper. Under the same deposition conditions, traditional papers consisting of micro-sized pulp fibers produced very low conductivity lines with non-uniform boundaries because of their larger pore structures. These results indicate that advanced, lightweight and highly flexible devices can be realized on cellulose nanopaper using continuous deposition processes. Continuous deposition on nanopaper is a promising approach for a simple roll-to-roll manufacturing process.

Hsieh, Ming-Chun; Kim, Changjae; Nogi, Masaya; Suganuma, Katsuaki

2013-09-01

104

Assembly for electrical conductivity measurements in the piston cylinder device  

DOEpatents

An assembly apparatus for measurement of electrical conductivity or other properties of a sample in a piston cylinder device wherein pressure and heat are applied to the sample by the piston cylinder device. The assembly apparatus includes a body, a first electrode in the body, the first electrode operatively connected to the sample, a first electrical conductor connected to the first electrode, a washer constructed of a hard conducting material, the washer surrounding the first electrical conductor in the body, a second electrode in the body, the second electrode operatively connected to the sample, and a second electrical conductor connected to the second electrode.

Watson, Heather Christine (Dublin, CA); Roberts, Jeffrey James (Livermore, CA)

2012-06-05

105

Electrical Conductivity of the Neutron Star Crust at Low Temperatures  

E-print Network

Abstract—The electrical conductivity of the neutron star crust at low temperatures is calculated by taking into account the mixing of the electron wave functions due to the interaction with the crystal lattice of atomic nuclei. We show that the previously existed model of exponential reduction of the electron–ion scattering rate can lead to an overestimation of the electrical conductivity by several orders of magnitude. We propose a simple interpolation formula for use in applications that joins the previously known results of calculating the electrical conductivity at high temperatures with the low-temperature asymptotics found here. DOI: 10.1134/S1063773712010021

A. I. Chugunov

2011-01-01

106

Using electrical impedance tomography to map subsurface hydraulic conductivity  

DOEpatents

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.

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

2000-01-01

107

Electrical conductivity and partial melting of mafic rocks under pressure  

NASA Astrophysics Data System (ADS)

We demonstrate the importance of electric conductivity measurements of partially molten mafic rocks by examining of Oman gabbro, Karelia olivinite, Ronda and Spitzbergen peridotites. The electrical conductivities of these rocks were estimated using the impedance spectroscopy at temperatures between 800°C and 1450°C and at pressures between 0.3 and 2 GPa in experiments performed in a piston cylinder apparatus. At temperatures below and above melting, samples were equilibrated during durations on the order of 200 h. Our results show that a jump in electrical conductivity can be correlated with the temperature range slightly above the solidus, due to the delayed formation of an interconnected melt phase. Thin sections of quenched samples were used to estimate volume fractions and chemical compositions of the partial melts. The increase of the electrical conductivity compares well with the connectivity of melt in partially molten samples. Above the solidus, the electrical conductivity increases by ˜1 to 2 orders of magnitude in comparison with the conductivity of non-melted rock below solidus. When a complete melt connectivity is established, the charge transport follows the network of the formed melt films at grain boundaries. Durations of up to ?200 h are required in order to reach a steady state electrical resistance in a partially molten rock sample. The experimental results were compared with the conductivity data obtained from magnetotelluric (MT) and electromagnetic (EM) measurements in the Northern part of the mid-Atlantic ridge where a series of axial magma chambers (AMC) are presumably located. There is good agreement between the measured electric conductivity of gabbroic samples with a melt fraction of 10 to 13 vol.% and the conductivity estimated at AMC, beneath the central part of Reykjanes ridge, as well as between the conductivity of partially molten peridotites and the source zone beneath the mid-Atlantic ridge at ?60 km.

Maumus, J.; Bagdassarov, N.; Schmeling, H.

2005-10-01

108

Software optimization for electrical conductivity imaging in polycrystalline diamond cutters  

NASA Astrophysics Data System (ADS)

We previously reported on an electrical conductivity imaging instrument developed for measurements on polycrystalline diamond cutters. These cylindrical cutters for oil and gas drilling feature a thick polycrystalline diamond layer on a tungsten carbide substrate. The instrument uses electrical impedance tomography to profile the conductivity in the diamond table. Conductivity images must be acquired quickly, on the order of 5 sec per cutter, to be useful in the manufacturing process. This paper reports on successful efforts to optimize the conductivity reconstruction routine, porting major portions of it to NVIDIA GPUs, including a custom CUDA kernel for Jacobian computation.

Bogdanov, G.; Wiggins, J.; Bertagnolli, K.; Ludwig, R.

2014-02-01

109

Software optimization for electrical conductivity imaging in polycrystalline diamond cutters  

SciTech Connect

We previously reported on an electrical conductivity imaging instrument developed for measurements on polycrystalline diamond cutters. These cylindrical cutters for oil and gas drilling feature a thick polycrystalline diamond layer on a tungsten carbide substrate. The instrument uses electrical impedance tomography to profile the conductivity in the diamond table. Conductivity images must be acquired quickly, on the order of 5 sec per cutter, to be useful in the manufacturing process. This paper reports on successful efforts to optimize the conductivity reconstruction routine, porting major portions of it to NVIDIA GPUs, including a custom CUDA kernel for Jacobian computation.

Bogdanov, G.; Ludwig, R. [Department of Electrical and Computer Engineering, Worcester Polytechnic Institute, 100 Institute Rd, Worcester, MA 01609 (United States); Wiggins, J.; Bertagnolli, K. [US Synthetic, 1260 South 1600 West, Orem, UT 84058 (United States)

2014-02-18

110

Electrical conductivity of rocks in the heating and cooling cycle  

Microsoft Academic Search

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.

Marcela Lastovicková; F. Janák

1978-01-01

111

Electrical Circuit Analogues of Thermal Conduction and Diffusion  

ERIC Educational Resources Information Center

After briefly reviewing equations of conduction and diffusion, and voltage and charge in electrical circuits, a simple experiment is given that allows students practical experience in a theoretical realm of physics. (MDR)

Tomlin, D. H.; Fullarton, G. K.

1978-01-01

112

Measurement of Electrical Conductivity for a Biomass Fire  

PubMed Central

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

Mphale, Kgakgamatso; Heron, Mal

2008-01-01

113

Effect of volatile components on electrical conductivity of mantle materials  

NASA Astrophysics Data System (ADS)

Recent laboratory electrical conductivity measurements of the main mantle constituent minerals have refined our understanding of the effect of water, carbon and iron contents on electrical conductivity. Especially effect of water on electrical conductivity of nominally anhydrous minerals has been substantially investigated. These studies suggested that proton conduction in nominally anhydrous minerals can elevate the electrical conductivity compared to the dry condition. However, if the water exists along grain boundaries, the proton conduction is completely masked by contribution of grain boundary water to the bulk conductivity. This phenomena was confirmed by the conductivity measurement at high temperatures (> 1000 K), leading to higher conductivity due to the grain boundary water generated by dehydration of sample. For nominally anhydrous minerals containing water in its crystal structure, water must partition between crystal and fluid. Thus when certain amount of grain boundary water exists, we cannot directly estimate water content in minerals based on a comparison between laboratory and geophysical data. Volatile components such as water and carbon dioxide in mantle materials can largely reduce the melting temperature. For example, solidus temperature of carbonate-bearing peridotite is below the normal mantle geotherm up to the 330 km depth. Solidus of water-saturated peridotite is low enough to generate partial melting through the upper mantle and the transition zone. Electrical conductivity of partial molten carbonate peridotite showed that the conductivity of the carbonate melt is nearly one order of magnitude higher than those of silicate melt in peridotite. In addition, electrical conductivity of hydrous basalt also show enhancement of the conductivity. Considering the effect of water and carbon on the bulk conductivity, the conductivity of volatile-bearing peridotites could be significantly higher than that of the volatile-free peridotites. Because melts contaning volatile components have smaller temperature dependence (low activation energy), the high conductivity can be accomplished even if temperature is largely lower than the normal mantle geotherm. Therefore, the electrical conductivity of the Earth's mantle would be controlled by the trace amount of volatile components.

Yoshino, T.; Katsura, T.; Shimojuku, A.

2011-12-01

114

Soft electrical contacts for conductivity measurements of molecularly modified surfaces  

Microsoft Academic Search

A portable conductivity setup, using soft electrical contacts, is proposed to measure the charge transport properties of molecularly modified solid surfaces. The present technique facilitates the conductivity measurements of both single and back-to-back metal–semiconductor junctions formed on soft matter using liquid mercury columns as electrical contacts. The utility of the above setup is demonstrated for back-to-back junctions using bare and

R K Hiremath; M K Rabinal; B G Mulimani

2009-01-01

115

Soft electrical contacts for conductivity measurements of molecularly modified surfaces  

Microsoft Academic Search

A portable conductivity setup, using soft electrical contacts, is proposed to measure the charge transport properties of molecularly modified solid surfaces. The present technique facilitates the conductivity measurements of both single and back-to-back metal-semiconductor junctions formed on soft matter using liquid mercury columns as electrical contacts. The utility of the above setup is demonstrated for back-to-back junctions using bare and

R. K. Hiremath; M. K. Rabinal; B. G. Mulimani

2009-01-01

116

Variation of middle atmospheric electrical conductivity with solar activity  

Microsoft Academic Search

The electrical conductivity is an important parameter of stratosphere and mesosphere. It plays a vital role in global electric circuit. The stratospheric conductivity is mainly due to cosmic rays produced ionisation while in mesosphere the solar U.V. radiation, 1216Å produces ionisation. It is well known that both cosmic rays and solar U.V. radiation intensity show solar cycle effect. In order

S. P. Gupta

2004-01-01

117

Electrical conductivity of tungsten near its critical point  

NASA Astrophysics Data System (ADS)

Electrical conductivity of fluid tungsten under subcritical and supercritical conditions has been measured. Fast wire explosions are used to create the corresponding states. The heavy-particle density varies from 4×1021 to 6×1022 cm-3, the temperature from 3700 up to 13 000 K. The measured electrical conductivity mainly depends on the averaged density and seems to be independent of the temperature within the experimental errors. The measurements are compared with theoretical models.

Kloss, A.; Motzke, T.; Grossjohann, R.; Hess, H.

1996-11-01

118

Modeling of the conductive ring electrical impedance tomography sensor  

Microsoft Academic Search

Conductive ring electrical impedance tomography sensor presents a new way to take non-invasive measurements of resistance for electrical tomography. This paper introduces its advantageous features and develops a model for the sensor. Verified by experiment, this model enables the raw measurement data to be converted to material impedance data, providing accurate input data for reconstruction algorithms.

Gu Jun; Yin Wuliang; Wang Chao; Wang Huaxiang

2009-01-01

119

Thermal and Electrical Conductivity Measurements of CDA 510 Phosphor Bronze  

NASA Technical Reports Server (NTRS)

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.

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

2009-01-01

120

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

E-print Network

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...

Dörr, Aaron

2014-01-01

121

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

NASA Astrophysics Data System (ADS)

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%.

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

2013-11-01

122

Electrostatic Discharge Sensitivity and Electrical Conductivity of Composite Energetic Materials  

SciTech Connect

Composite energetic material response to electrical stimuli was investigated and a correlation between electrical conductivity and ignition sensitivity was examined. The composites consisted of micrometer particle aluminum combined with another metal, metal oxide, or fluoropolymer. Of the nine tested mixtures, aluminum with copper oxide was the only mixture to ignite by electrostatic discharge with minimum ignition energy (MIE) of 25 mJ and an electrical conductivity of 1246.25 nS; two orders of magnitude higher than the next composite. This study showed a similar trend in MIE for ignition triggered by a discharged spark compared with a thermal hot wire source.

Michael A. Daniels; Daniel J. Prentice; Chelsea Weir; Michelle L. Pantoya; Gautham Ramachandran; Tim Dallas

2013-02-01

123

Scaling of the electrical conductivity of granular media  

NASA Astrophysics Data System (ADS)

We derive the scaling properties of the dependence of the macroscopic electrical conductivity of granular media (e.g., sands) with a surface mechanism of electrical conduction on the grain size, when the medium is subjected to a given mechanical stress. In order to eliminate the influence of the inter-grain junction capacity, the direct electrical current is considered. We determine the applicability restrictions on the theory which disregards the ultimate crushing compression strength, adhesion, and the effect of charge carrier tunneling at grain junctions beyond the contact surface area. Solutions for several regular packings of grains are obtained as well.

Goldobin, D. S.; Krauzin, P. V.

2014-05-01

124

A conducting ball in an axial electric field  

E-print Network

We describe the distribution of a charge, the electric moments of arbitrary order and the force acting on a conducting ball on the axis of the axial electric field. We determine the full charge and the dipole moments of the first order for a conducting ball in an arbitrary inhomogeneous harmonic electric field. All statements are formulated in the form of theorems with proofs basing on properties of the matrix of moments of the Legendre polynomials. The analysis and proof of these properties are presented in Appendix.

Alexander Savchenko

2012-12-26

125

The behaviour of low conducting liquid in modulated electric field  

Microsoft Academic Search

The electrothermoconvective instability of a low conducting liquid in modulated electric field of a plane horizontal capacitor is investigated in the electrohydrodynamic (EHD) approximation for arbitrary field modulation frequencies and various shapes (harmonic and triangular). The charge formation is produced either due to dielectrophoresis or due to the nonhomogeneous conductivity. The Floquet theory is used to find the convection thresholds.

B. L. Smorodin

2002-01-01

126

Electrically conductive adhesives: a prospective alternative for SMD soldering?  

Microsoft Academic Search

Conductive adhesives offer a new prospective way for electrical connection of SMD components to printed circuit boards, because of their lower possible curing temperature, fine pitch capability, higher flexibility than solder, and process simplicity. However, the long-term behavior of conductive adhesive joints under various climatic conditions shows large variations with the type of adhesive and metallization used and needs further

J. C. Jagt; P. J. M. Beris; G. F. C. M. Lijten

1995-01-01

127

ION AND TEMPERATURE DEPENDENCE OF ELECTRICAL CONDUCTANCE FOR NATURAL WATERS  

EPA Science Inventory

Four empirical equations describing the temperature dependence of electrical conductance of aqueous solutions are compared for the case of single electrolytes. The best method uses a modified Walden product where the log of the ratio between the conductances at two temperatures i...

128

Distinguishability of Conductivities by Electric Current Computed Tomography  

Microsoft Academic Search

We give criteria for the distinguishability of two different conductivity distributions inside a body by electric current computed tomography (ECCT) systems with a specified precision. It is shown in a special case how these criteria can be used to determine the measurement precision needed to distinguish between two different conductivity distributions. It is also shown how to select the patterns

David Isaacson

1986-01-01

129

Investigation on the shielding effectiveness properties of electrically conductive textiles  

Microsoft Academic Search

This paper is devoted to investigate which basic mechanisms are responsible for the major part of the shielding of conductive textiles by means of measurement of the shielding effectiveness (SE). Both woven and nonwoven textiles with different thickness, nickel amount and fabric geometry are examined. Results show that the electrically conductive textiles tested present different SE and surface resistivity values

Leonardo Sandrolini; Ugo Reggiani

2008-01-01

130

Electrically conductive resinous bond and method of manufacture  

DOEpatents

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.

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

131

Electrically conductive resinous bond and method of manufacture  

DOEpatents

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.

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

1985-01-01

132

Soft electrical contacts for conductivity measurements of molecularly modified surfaces  

NASA Astrophysics Data System (ADS)

A portable conductivity setup, using soft electrical contacts, is proposed to measure the charge transport properties of molecularly modified solid surfaces. The present technique facilitates the conductivity measurements of both single and back-to-back metal-semiconductor junctions formed on soft matter using liquid mercury columns as electrical contacts. The utility of the above setup is demonstrated for back-to-back junctions using bare and chemically modified silicon surfaces with organic molecules belonging to ethynylbenzene (EBZ) series. The measured conductivity is found to be very sensitive to the dipole moment of bonded organic molecules.

Hiremath, R. K.; Rabinal, M. K.; Mulimani, B. G.

2009-01-01

133

Detection of temperature distribution via recovering electrical conductivity in MREIT.  

PubMed

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. PMID:23552880

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

2013-04-21

134

Effect of orientation on electrically conducting thermoplastic composite properties  

SciTech Connect

Properties of electrically conducting composites made from low density polyethylene (LDPE), high density polyethylene (HDPE), and polypropylene (PP) filled with nickel flake are being studied as a function of nickel concentration and draw ratio. The effect on electrical conduction, crystallinity, melt temperature, tensile modulus, and elongation at break are being tested. The melt temperature increases with increasing nickel concentration. The electrical conduction increases slowly with increased nickel concentration to the percolation volume fraction, then increases sharply. Orientation by uniaxial stretching of the films should allow conductive pathways to form throughout the polymer more easily by forcing particles closer together, thus reducing the percolation volume fraction. This process could be caused by both alignment of the polymer chains and by stress induced crystallization that forces the particles into smaller amorphous regions.

Genetti, W.B.; Grady, B.P. [Univ. of Oklahoma, Norman, OK (United States)

1996-10-01

135

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

NASA Astrophysics Data System (ADS)

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.

Dörr, Aaron; Hardt, Steffen

2014-08-01

136

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

Microsoft Academic Search

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

Jan Räthel; Mathias Herrmann; Wieland Beckert

2009-01-01

137

Electrical conductivity of stishovite as a function of water content  

NASA Astrophysics Data System (ADS)

The electrical conductivity of stishovite with various Al2O3 and H2O contents was measured at 12 GPa of pressure (P) and temperatures (T) up to 1900 K in a Kawai-type multi-anvil apparatus. Starting materials were pre-synthesized at 12 GPa and 1673 K from various mixtures of SiO2, Al2O3 and Al(OH)3. The synthesized stishovite aggregates contained various H2O concentrations up to 0.25 wt.%. The conductivity of relatively dry stishovite was almost constant independently of Al content, whereas the conductivity significantly increased with increasing H2O content in stishovite. All electrical conductivity data fit the formula for electrical conductivity ?=?0Cexp{-[?H0-?CW1/3]/kT}, where ?0 is the pre-exponential term, CW is the H2O concentration, ?H0 is the activation enthalpy at very low H2O concentration, and k is the Boltzmann constant. The activation enthalpy decreased from 1.22 to 0.90 eV with increasing H2O content from 0.01 to 0.22 wt.%. A nearly linear correlation of the conductivity values on the H2O content suggests that the dominant mechanism of charge transport in stishovite is proton conduction. Although electrical conductivity of hydrous stishovite is higher than that of garnet in the subducted oceanic crust, small amount of hydrous stishovite is insufficient to raise conductivity. On the other hand, hydrous stishovite can contribute to the high conductivity occasionally observed at the mantle transition zone, if the subducted Archean continental crusts with tonalite-trondhjemite-granodiorite (TTG) composition were accumulated above the 660 km seismic discontinuity.

Yoshino, Takashi; Shimojuku, Akira; Li, Danyang

2014-02-01

138

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

E-print Network

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

Elperin, Tov

139

Electrically conducting shape memory polymer composites for electroactive actuator  

NASA Astrophysics Data System (ADS)

We have tried to apply electroactive shape memory polymer to smart actuator. Electroactive shape memory can be achieved by applying an electric field to shape memory polymer without any thermal heating as conventional shape memory polymers. For it, electrically conducting shape memory composites were prepared by incorporating carbon nanotube into polymer matrix. A segmented polyurethane block copolymer composed of 4,4'-methylene bis (phenylisocyanate), polycaprolactone, and 1,4-butanediol was synthesized to be used as shape memory polymer, and carbon nanotube was used after surface-modification by an acid. It was found that nanotube-reinforced composites could show high electrical conductivity with increased modulus at only several weight percentages of nanotube, and electroactive shape recovery effect more than 80% could be obtained. Consequently, electric field-stimulated shape memory could be demonstrated through combined composites of polyurethane and nanotube.

Jung, Yong Chae; Goo, Nam Seo; Cho, Jae Whan

2004-07-01

140

Multi-rate flowing Wellbore electric conductivity logging method  

SciTech Connect

The flowing wellbore electric conductivity logging method involves the replacement of wellbore water by de-ionized or constant-salinity water, followed by constant pumping with rate Q, during which a series of fluid electric conductivity logs are taken. The logs can be analyzed to identify depth locations of inflow, and evaluate the transmissivity and electric conductivity (salinity) of the fluid at each inflow point. The present paper proposes the use of the method with two or more pumping rates. In particular it is recommended that the method be applied three times with pumping rates Q, Q /2, and 2Q. Then a combined analysis of the multi-rate data allows an efficient means of determining transmissivity and salinity values of all inflow points along a well with a confidence measure, as well as their inherent or far-field pressure heads. The method is illustrated by a practical example.

Tsang, Chin-Fu; Doughty, Christine

2003-04-22

141

Shear induced electrical behaviour of conductive polymer composites  

NASA Astrophysics Data System (ADS)

The time-dependent electrical resistance of polymethylmethacrylate containing carbon black was measured under oscillatory shear in the molten state. The electrical signal was oscillating exactly at the doubled frequency of the oscillatory shear deformation. Moreover, the experimental results gave a hint to the development of conductive structures in polymer melts under shear deformation. It was shown that the flow induced destruction of conductive paths dominates over the flow induced build-up in the beginning of the shear deformations. However, for longer times both competitive effects reach a dynamic equilibrium and only the thermally induced build-up of pathways influences the changes in the composite resistance during the shear. Furthermore, the oscillating electrical response depends clearly on the deformation amplitude applied. A simple physical model describing the behaviour of conductive pathways under shear deformation was derived and utilized for the description of the experimental data.

Starý, Zden?k; Krückel, Johannes; Schubert, Dirk W.

2013-04-01

142

Effect of humidity on electrical conductivity of zinc stearate nanofilms  

Microsoft Academic Search

In this work, stearic acid (StAc) and zinc stearate (ZnSt2) nanofilms were deposited on glass and silver substrates using Langmuir–Blodgett (LB) film technique and their structural and electrical properties were investigated. X-ray diffraction and IR techniques revealed that more crystalline and better films were obtained from ZnSt2 compare to StAc. Electrical conductivity of ZnSt2 LB films with 13 layers having

Serdar Ozturk; Devrim Balkose; Salih Okur; Junzo Umemura

2007-01-01

143

Electrical and thermal conductivity of hybrid nanocomposites with giant strain  

NASA Astrophysics Data System (ADS)

The prospect of electronic circuits that are stretchable and bendable promises tantalizing applications such as skin-like electronics, conformable sensors, and lightweight solar cells. The optimization of electronic, thermal, and mechanical properties of conductive and extensible materials is necessary for the application of energy device. Here we demonstrate the theoretical prediction for the electrical conductivity of the nanocomposites compared with experimental results. Also, we present the giant dependence of electrical conductivity on strain and the large positive thermal expansion that can be expected for the elastomer matrix. The percolation threshold (26 vol% of Ag, average interparticle distance model) and Poisson's ratio (Vt=0.33, Vw=0.2) of nanocomposites are significant factors that can determine the electrical and thermal conductivity with giant strain. The thermal conductivity for the electronically conducting elastomeric film is relatively high at the zero-strain state, and shows a non-metallic temperature dependence consistent with phonon transport. The observed combinational property of a very small dependence of conductivity on temperature with an exponential dependence can be suitable for for the mechanical strain sensing.

Chun, Kyoung-Yong; Kim, Shi Hyeong; Shin, Min Kyoon; Spinks, Geoffrey M.; Aliev, Ali E.; Baughman, Ray H.; Kim, Seon Jeong

2013-04-01

144

Contamination from electrically conductive silicone tubing during aerosol chemical analysis  

SciTech Connect

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.

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

2009-06-01

145

Contamination from electrically conductive silicone tubing during aerosol chemical analysis  

NASA Astrophysics Data System (ADS)

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.

Yu, Yong; Liz Alexander, M.; Perraud, Veronique; Bruns, Emily A.; Johnson, Stanley N.; Ezell, Michael J.; Finlayson-Pitts, Barbara J.

146

Electrically conducting porphyrin and porphyrin-fullerene electropolymers  

DOEpatents

Compounds with aryl ring(s) at porphyrin meso position(s) bearing an amino group in position 4 relative to the porphyrin macrocycle, and at least one unsubstituted 5 (hydrogen-bearing) meso position with the 10-, 15-, and/or 20-relationship to the aryl ring bearing the amino group, and metal complexes thereof, feature broad spectral absorption throughout the visible region. These compounds are electropolymerized to form electrically conducting porphyrin and porphyrin-fullerene polymers that are useful in photovoltaic applications. The structure of one such electrically conducting porphyrin polymer is shown below. ##STR00001##

Gust, Jr., John Devens; Liddell, Paul Anthony; Gervaldo, Miguel Andres; Bridgewater, James Ward; Brennan, Bradley James; Moore, Thomas Andrew; Moore, Ana Lorenzelli

2014-03-11

147

Corrosion-protective coatings from electrically conducting polymers  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

148

Micromechanical approach for electrical resistivity and conductivity of sandstone  

NASA Astrophysics Data System (ADS)

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.

Nguyen, S. T.

2014-12-01

149

Rubber-like electrically conductive polymeric materials with shape memory  

NASA Astrophysics Data System (ADS)

This paper presents a heating-responsive shape memory polymeric material, which is not only rubber-like at room temperature and above its shape recovery temperature, but also electrically conductive. This polymeric material is made of silicone, melting glue (MG), and carbon black (CB). The influence of volume fractions of MG and CB on the elasticity, electrical resistivity, and shape memory effect of the polymeric material is systematically investigated. The feasibility of Joule heating for shape recovery is experimentally demonstrated with an electric power of 31 V.

Cui, H. P.; Song, C. L.; Huang, W. M.; Wang, C. C.; Zhao, Y.

2013-05-01

150

Electrically Joining Mixed Conducting Oxides for High Temperature Applications  

SciTech Connect

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.

Weil, K. Scott; Hardy, John S.

2003-01-06

151

Electrical conduction in impregnants for all-film power capacitors  

Microsoft Academic Search

The conduction properties of some impregnants (monodibenzyltoluene and phenylxylylethane) used in the all-film capacitors technology are investigated. The intent of this research contribution is to perform detailed investigations of these properties in a substantial range of electric fields (from 10?2 to 102 V ?m?1). Measurements of the macroscopic charge transport properties (conductivity, mobility, and viscosity) at low field are reported

Christian Brosseau

1991-01-01

152

Electrical resistivity imaging of conductive plume dilution in fractured rock  

Microsoft Academic Search

Electrical resistance tomography (ERT) was used to monitor a conductive plume dilution experiment that was conducted in fractured\\u000a basalt in order to assess its applications in this type of fractured-rock environment. Tap water was injected into an injection\\u000a well for 34 days to dilute a pre-existing potassium chloride (KCl) plume at a site in Idaho, USA. No further fluids were introduced

Robin E. Nimmer; James L. Osiensky; Andrew M. Binley; Kenneth F. Sprenke; Barbara C. Williams

2007-01-01

153

Revisited modeling of Titan’s middle atmosphere electrical conductivity  

NASA Astrophysics Data System (ADS)

The atmospheric electrical conductivity measured by the Permittivity, Wave and Altimetry (PWA) subsystem on board the Huygens probe, during the landing mission on Titan, has been modeled in the present work. Previous modeling studies showed a Galactic Cosmic Ray (GCR) peak of conductivity at a higher altitude and a quantitative overestimation in the altitude range 0-100 km compared to that observed by the PWA instrument. Recently the PWA data was revisited and provided new constraints on the conductivity at altitudes 100-180 km. Because the aerosols in the atmosphere are known to alter the electron concentration, using a detailed distribution of the aerosols at all altitudes, the electron conductivity has been calculated in the altitude range 0-180 km. By using a variable range of photoemission threshold for the aerosols, the present model is able to reasonably predict the altitude at which the GCR peak of conductivity occurs and to meet the new constraints for the conductivity profile.

Mishra, Alabhya; Michael, Marykutty; Tripathi, Sachchida Nand; Béghin, Christian

2014-08-01

154

A model of electrical conduction in cardiac tissue including fibroblasts.  

PubMed

Fibroblasts are abundant in cardiac tissue. Experimental studies suggested that fibroblasts are electrically coupled to myocytes and this coupling can impact cardiac electrophysiology. In this work, we present a novel approach for mathematical modeling of electrical conduction in cardiac tissue composed of myocytes, fibroblasts, and the extracellular space. The model is an extension of established cardiac bidomain models, which include a description of intra-myocyte and extracellular conductivities, currents and potentials in addition to transmembrane voltages of myocytes. Our extension added a description of fibroblasts, which are electrically coupled with each other and with myocytes. We applied the extended model in exemplary computational simulations of plane waves and conduction in a thin tissue slice assuming an isotropic conductivity of the intra-fibroblast domain. In simulations of plane waves, increased myocyte-fibroblast coupling and fibroblast-myocyte ratio reduced peak voltage and maximal upstroke velocity of myocytes as well as amplitudes and maximal downstroke velocity of extracellular potentials. Simulations with the thin tissue slice showed that inter-fibroblast coupling affected rather transversal than longitudinal conduction velocity. Our results suggest that fibroblast coupling becomes relevant for small intra-myocyte and/or large intra-fibroblast conductivity. In summary, the study demonstrated the feasibility of the extended bidomain model and supports the hypothesis that fibroblasts contribute to cardiac electrophysiology in various manners. PMID:19283480

Sachse, Frank B; Moreno, A P; Seemann, G; Abildskov, J A

2009-05-01

155

Effect of iron content on the electrical conductivity of perovskite and magnesiowuestite assemblages at lower mantle conditions  

NASA Technical Reports Server (NTRS)

The electrical conductivity of (Mg/0.76/Fe/0.24/)SiO3 perovskite and of an assemblage of (Mg/0.89/Fe/0.11/)SiO3 perovskite + (Mg/0.70/Fe/0.30/)O magnesiowiestite was measured at pressures of 45-80 GPa and temperatures from 295 to 3600 K. The apparent activation energy for electrical conduction is 0.24 (+ or - 0.10) eV for the perovskite and 0.20 (+ or - 0.08) eV for the perovskite + magnesiowuestite assemblage. Comparing present results with those derived previously for Fe-poor samples, it is found that the electrical conductivities of both the silicate perovskite and the perovskite + magnesiowuestite assemblage depend strongly on iron content. Thus, the electrical conductivity distribution inside the earth could provide an important constraint in modeling the composition of the lower mantle.

Li, Xiaoyuan; Jeanloz, Raymond

1991-01-01

156

Electrical conducting properties of proton-conducting terbium-doped strontium cerate membrane  

Microsoft Academic Search

The electrical conduction behavior of SrCe0.95Tb0.05O3?? (SCTb) was investigated in different gases at high temperatures. In air, oxygen or nitrogen SCTb shows small electronic-hole conduction below 800°C and oxygen ionic conduction over 800°C with activation energy about 30 kJ\\/mol and 164–181 kJ\\/mol respectively. SCTb becomes a protonic conductor in hydrogen or methane in 500–900°C, with the proton conductivity in the

Xiwang Qi; Y. S. Lin

1999-01-01

157

Characterization of electrically conductive transition metal dichalcogenide lubricant films  

Microsoft Academic Search

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

Harish C. Waghray

1997-01-01

158

Tunable Electrical Conductivity of Individual Graphene Oxide Sheets  

E-print Network

Tunable Electrical Conductivity of Individual Graphene Oxide Sheets Reduced at "Low" Temperatures 30, 2008 ABSTRACT Step-by-step controllable thermal reduction of individual graphene oxide sheets graphene-based material, such as graphene oxide, has only recently attracted atten- tion.16-25 The main

159

FIELD manual: Calculation of electric fields in conducting media  

NASA Astrophysics Data System (ADS)

A computer program (FIELD) written in BASIC that may be used to calculate electric potential, gradient, and power density distribution in conducting media is discussed. Either cylindrical or rectangular coordinate systems may be used. Information is supplied to assist users in providing necessary data for the program and in interpreting output. A program listing is appended.

Doss, J. D.

1981-10-01

160

Electrical Conductivity of milk: ability to predict mastitis status  

Microsoft Academic Search

Electrical conductivity (EC) of milk has been intro- duced as an indicator trait for mastitis over the last decade, and it may be considered as a potential trait in a breeding program where selection for improved udder health is included. In this study, various EC traitswereinvestigatedfortheirassociationwithudder health. In total, 322 cows with 549 lactations were in- cluded in the study.

E. Norberg; H. Hogeveen; I. R. Korsgaard; N. C. Friggens; K. H. M. N. Sloth; P. Lovendahl

2004-01-01

161

Electrical conductivity of hydrogen shocked to megabar pressures  

SciTech Connect

The properties of ultra-high pressure hydrogen have been the subject of much experimental and theoretical study. Of particular interest is the pressure-induced insulator-to-metal transition of hydrogen which, according to recent theoretical calculations, is predicted to occur by band-overlap in the pressure range of 1.5-3.0 Mbars on the zero temperature isotherm. Extremely high pressures are required for metallization since the low-pressure band gap is about 15 eV. Recent static-pressure diamond anvil cell experiments have searched for evidence of an insulator-to-metal transition, but no conclusive evidence for such a transition has yet been supplied. Providing conclusive evidence for hydrogen metallization is difficult because no technique has yet been developed for performing static high-pressure electrical conductivity experiments at megabar pressures. The authors report here on electrical conductivity experiments performed on H{sub 2} and D{sub 2} multi-shocked to megabar pressures. Electrical conductivities of dense fluid hydrogen at these pressures and temperatures reached are needed for calculations of the magnetic fields of Jupiter and Saturn, the magnetic fields being generated by convective dynamos of hot, dense, semiconducting fluid hydrogen. Also, since electrical conduction at the pressure-temperature conditions being studied is due to the thermal excitation of charge carriers across the electronic band gap, these experiments yield valuable information on the width of the band gap at high densities.

Weir, S.T.; Nellis, W.J.; Mitchell, A.C.

1993-08-01

162

www.VadoseZoneJournal.org Electrical Conductivity Imaging  

E-print Network

in an Arctic Ecosystem, through Advanced Inversion of Electromagnetic Induction Data Characterizing the spatial electromagnetic induction (EMI) data with portable tools (e.g., EM38, GEM2, or DUALEM) over large regions, EMI conductivity; EMI, electromagnetic induction; ERT, electrical resistance tomography; MCMC, Markov chain Monte

Hubbard, Susan

163

Toward a unified hydrous olivine electrical conductivity law  

NASA Astrophysics Data System (ADS)

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.

Gardés, Emmanuel; Gaillard, Fabrice; Tarits, Pascal

2014-12-01

164

Composite yarns of multiwalled carbon nanotubes with metallic electrical conductivity.  

PubMed

Unique macrostructures known as spun carbon-nanotube fibers (CNT yarns) can be manufactured from vertically aligned forests of multiwalled carbon nanotubes (MWCNTs). These yarns behave as semiconductors with room-temperature conductivities of about 5 x 10(2) S cm(-1). Their potential use as, for example, microelectrodes in medical implants, wires in microelectronics, or lightweight conductors in the aviation industry has hitherto been hampered by their insufficient electrical conductivity. In this Full Paper, the synthesis of metal-CNT composite yarns, which combine the unique properties of CNT yarns and nanocrystalline metals to obtain a new class of materials with enhanced electrical conductivity, is presented. The synthesis is achieved using a new technique, self-fuelled electrodeposition (SFED), which combines a metal reducing agent and an external circuit for transfer of electrons to the CNT surface, where the deposition of metal nanoparticles takes place. In particular, the Cu-CNT and Au-CNT composite yarns prepared by this method have metal-like electrical conductivities (2-3 x 10(5) S cm(-1)) and are mechanically robust against stringent tape tests. However, the tensile strengths of the composite yarns are 30-50% smaller than that of the unmodified CNT yarn. The SFED technique described here can also be used as a convenient means for the deposition of metal nanoparticles on solid electrode supports, such as conducting glass or carbon black, for catalytic applications. PMID:20665629

Randeniya, Lakshman K; Bendavid, Avi; Martin, Philip J; Tran, Canh-Dung

2010-08-16

165

Microbial interspecies electron transfer via electric currents through conductive minerals  

PubMed Central

In anaerobic biota, reducing equivalents (electrons) are transferred between different species of microbes [interspecies electron transfer (IET)], establishing the basis of cooperative behaviors and community functions. IET mechanisms described so far are based on diffusion of redox chemical species and/or direct contact in cell aggregates. Here, we show another possibility that IET also occurs via electric currents through natural conductive minerals. Our investigation revealed that electrically conductive magnetite nanoparticles facilitated IET from Geobacter sulfurreducens to Thiobacillus denitrificans, accomplishing acetate oxidation coupled to nitrate reduction. This two-species cooperative catabolism also occurred, albeit one order of magnitude slower, in the presence of Fe ions that worked as diffusive redox species. Semiconductive and insulating iron-oxide nanoparticles did not accelerate the cooperative catabolism. Our results suggest that microbes use conductive mineral particles as conduits of electrons, resulting in efficient IET and cooperative catabolism. Furthermore, such natural mineral conduits are considered to provide ecological advantages for users, because their investments in IET can be reduced. Given that conductive minerals are ubiquitously and abundantly present in nature, electric interactions between microbes and conductive minerals may contribute greatly to the coupling of biogeochemical reactions. PMID:22665802

Kato, Souichiro; Hashimoto, Kazuhito; Watanabe, Kazuya

2012-01-01

166

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

167

Electrical conductivity and dielectric property of fly ash geopolymer pastes  

NASA Astrophysics Data System (ADS)

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

Hanjitsuwan, Sakonwan; Chindaprasirt, Prinya; Pimraksa, Kedsarin

2011-02-01

168

Unconventional approaches to combine optical transparency with electrical conductivity  

NASA Astrophysics Data System (ADS)

The combination of electrical conductivity and optical transparency in the same material known to be a prerogative of only a few oxides of post-transition metals, such as In, Sn, Zn and Cd manifests itself in a distinctive band structure of the transparent conductor host. While the oxides of other elements with s2 electronic configuration, for example, Mg, Ca, Sc and Al, also exhibit the desired optical and electronic features, they have not been considered as candidates for achieving good electrical conductivity because of the challenges of efficient carrier generation in these wide-bandgap materials. Here we demonstrate that alternative approaches to the problem not only allow for attaining the transport and optical properties which compete with those in currently utilized transparent conducting oxides (TCO), but also significantly broaden the range of materials with a potential of being developed into novel functional transparent conductors.

Dross, F.; Robbelein, J.; Vandevelde, B.; van Kerschaver, E.; Gordon, I.; Beaucarne, G.; Poortmans, J.

2007-10-01

169

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

PubMed

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

Vollrath, Fritz; Edmonds, Donald

2013-12-01

170

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

NASA Astrophysics Data System (ADS)

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.

Vollrath, Fritz; Edmonds, Donald

2013-12-01

171

Copper-Filled Electrically Conductive Adhesives with Enhanced Shear Strength  

NASA Astrophysics Data System (ADS)

In this study, the effects of diethyl carbitol (diluent) and tertiary amines on the electrical, mechanical, and rheological properties of the Cu-filled polyurethane-based electrically conductive adhesives (ECAs) were investigated. Significant difference could be observed in the electrical resistivity and shear strength of ECA prepared with different amount of diethyl carbitol. Reduced electrical resistivity was found in ECAs prepared with addition of tertiary amines, but no obvious change was observed in the shear strength of the ECA joint. Rheological property of the ECA paste was investigated in order to understand the correlation of the viscosity of ECA paste and electrical resistivity and shear strength of ECA joint. Results revealed that decrease in viscosity of the ECA paste reduced electrical resistivity and enhanced shear strength of ECA joint. A Cu-filled polyurethane-based ECA with considerably low electrical resistivity at the magnitude order range of 10-3 ? cm, and significantly high shear strength (above 17 MPa) could be achieved.

Ho, Li-Ngee; Nishikawa, Hiroshi

2014-09-01

172

Spatial-decomposition analysis of electrical conductivity in ionic liquid.  

PubMed

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

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

2014-12-28

173

Spatial-decomposition analysis of electrical conductivity in ionic liquid  

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

174

Optimization and Testing of Electrically Conductive Spacecraft Coatings  

NASA Technical Reports Server (NTRS)

This is the final report discussing work done for the Space Environmental Effects (SEE) program in the Materials and Processes Laboratory, on electrically conductive thermal control coatings. These thermal control coatings are being developed to have several orders of magnitude lower electrical resistivity than most available thermal control coatings. Extensive research has taken place over the last few years to develop a variety of spacecraft coatings with the unique property of being able to conduct surface charge to a substrate or grounding system. The ability to conduct surface charge to a safe point, while maintaining optical properties and performance, is highly advantageous in maintaining operational space based systems. Without this mechanism the surface of a spacecraft can accumulate charge to the point that a catastrophic electrical breakdown can occur, resulting in damage to or failure of the spacecraft. Ultimately, use of this type of coating will help mitigate many of the concerns that NASA and the space industry still have for their space based systems. The unique coatings studied here fall into two specific categories: 1) broadband absorber and 2) selective absorber. These coatings have controllable solar absorptance and electrical surface resistivity values over the designated ranges. These coatings were developed under an SBIR program which focused on the development of such constituents and coatings. This project focused on simulated space environmental effects testing with the intent of using this data to help optimize the stability and initial properties of these coatings.

Mell, Richard J.

2001-01-01

175

Effect of electrically conducting walls on rotating magnetoconvection  

NASA Astrophysics Data System (ADS)

In an experiment carried out by Aurnou and Olson [J. Fluid Mech. 430, 283 (2001)] thermal convection in a liquid gallium layer in the presence of a uniform vertical magnetic field was investigated. The critical Rayleigh number at the onset of magnetoconvection was determined as a function of the Chandrasekhar number Q (the ratio of the Lorentz force to the viscous force) and the Taylor number Ta (the squared ratio of the Coriolis force to the viscous force). In the experimental apparatus, the upper and lower boundaries of the liquid gallium layer were electrically conducting copper plate walls. This paper presents a study of the effect of electrically conducting walls on rotating magnetoconvection. It is shown that the electrical properties of the walls have significant effects on the characteristics of rotating magnetoconvection when both the Chandrasekhar number Q and the Taylor number Ta are sufficiently large. It is demonstrated that, as a consequence of the electrically conducting walls, oscillatory magnetoconvection can become steady and the critical Rayleigh number can change by as much as 60%. The problem of convectively driven Alfvén waves in a rotating fluid layer in the presence of a uniform vertical magnetic field is discussed in an appendix.

Zhang, Keke; Weeks, Mark; Roberts, Paul

2004-06-01

176

Evaluation of electrical conductivity of Cu and Al through sub microsecond underwater electrical wire explosion  

NASA Astrophysics Data System (ADS)

Sub-microsecond timescale underwater electrical wire explosions using Cu and Al materials have been conducted. Current and voltage waveforms and time-resolved streak images of the discharge channel, coupled to 1D magneto-hydrodynamic simulations, have been used to determine the electrical conductivity of the metals for the range of conditions between hot liquid metal and strongly coupled non-ideal plasma, in the temperature range of 10-60 KK. The results of these studies showed that the conductivity values obtained are typically lower than those corresponding to modern theoretical electrical conductivity models and provide a transition between the conductivity values obtained in microsecond time scale explosions and those obtained in nanosecond time scale wire explosions. In addition, the measured wire expansion shows good agreement with equation of state tables.

Sheftman, D.; Shafer, D.; Efimov, S.; Krasik, Ya. E.

2012-03-01

177

Effect of orientation anisotropy on calculating effective electrical conductivities  

NASA Astrophysics Data System (ADS)

This paper develops an analytical effective medium theory (EMT) equation for calculating the effective conductivity of a mixture based on Maxwell's and Maxwell-Garnett's theories, extended to higher volume fractions using Bruggeman's unsymmetrical treatment (BUT), with a long term goal of extending the treatment to mixtures more representative of real materials in order to calculate their effective electrical conductivity. The development accounts for spheroid shaped inclusions of varying degrees of anisotropic orientation. The orientation is described by the introduction of a distribution function. Two methodologies valid for the inclusion dilute limit were used to evaluate the effective conductivity: one based on Maxwell's far field approach, and the other based on the Maxwell-Garnett in the matrix approach. It was found that while the dilute limit equations for the effective conductivity were different, the final EMT equations derived by applying BUT collapsed to the same formula which was generalized for anisotropic orientation based on the distribution function presented.

Myles, Timothy D.; Peracchio, Aldo A.; Chiu, Wilson K. S.

2014-05-01

178

Fluctuation conductivity in superconductors in strong electric fields  

NASA Astrophysics Data System (ADS)

We study the effect of a strong electric field on the fluctuation conductivity within the time-dependent Ginzburg-Landau theory for the case of arbitrary dimension. Our results are based on the analytical derivation of the velocity distribution law for the fluctuation Cooper pairs, from the Boltzmann equation. Special attention is drawn to the case of small nonlinearity of conductivity, which can be investigated experimentally. We obtain a general relation between the nonlinear conductivity and the temperature derivative of the linear Aslamazov-Larkin conductivity, applicable to any superconductor. For the important case of layered superconductors, we derive an analogous relation between the small nonlinear correction for the conductivity and the fluctuational magnetoconductivity. On the basis of these relations, we provide experimental methods for determining both the lifetime constant of metastable Cooper pairs above Tc and the coherence length. A systematic investigation of the third harmonic of the electric field generated by a harmonic current can serve as an alternative method for the examination of the metastable Cooper-pair relaxation time.

Mishonov, Todor; Posazhennikova, Anna; Indekeu, Joseph

2002-02-01

179

The Thermal Electrical Conductivity Probe (TECP) for Phoenix  

NASA Technical Reports Server (NTRS)

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

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

180

Single-photon heat conduction in electrical circuits  

E-print Network

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.

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

2011-07-14

181

Compensation Effect in Electrical Conduction Process: Effect of Substituent Group  

NASA Astrophysics Data System (ADS)

The semiconductive properties of Vitamin A acid (Retinoic Acid), a long chain conjugated polyene, were studied as a function of the adsorption of different vapours. A compensation effect was observed in the electrical conduction process; unlike that in Vitamin A alcohol and Vitamin A acetate the compensation temperature was observed on the lower side of the experimental temperature (T0?285 K). It is concluded that the terminal \\diagdown\\diagupC=0 group conjugated to the polyene chain plays an important role in the manifestation of the compensation effect. Various conduction parameters have been evaluated.

Mitra, Bani; Misra, T. N.

1987-05-01

182

Orbital dynamics of two electrically charged conducting spheres  

NASA Astrophysics Data System (ADS)

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.

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

183

Equation of state and electrical conductivity of expanded Al  

NASA Astrophysics Data System (ADS)

Ab-initio molecular dynamics (AIMD) simulations have been performed for generating equation of state (EOS) data as well as atomic configurations of expanded states of Al. The generated atomic configurations have been used for the calculation of electrical conductivity. AIMD simulations have been performed using the ABINIT code and electrical conductivity has been calculated using the Kubo-Greenwood formula as implemented in ABINIT. The generated equation of state data have been fitted to a three-term EOS model using adjustable parameters of ionic and electronic Gruneisen parameters. This three-term EOS model has been used to estimate critical density, temperature and pressure in the liquid-vapour region. The calculated values of critical density, temperature and pressure show good agreement with results available in the literature.

Mishra, V.; Mehra, V.; Chaturvedi, S.

2012-07-01

184

Electrical Conduction and Breakdown Properties of Several Biodegradable Polymers  

Microsoft Academic Search

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

Y. Ohki; N. Hirai

2007-01-01

185

Electrical conductivity and dielectric property of fly ash geopolymer pastes  

Microsoft Academic Search

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

Sakonwan Hanjitsuwan; Prinya Chindaprasirt; Kedsarin Pimraksa

2011-01-01

186

Electrical conductivity for warm, dense aluminum plasmas and liquids.  

PubMed

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

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

2002-08-01

187

Electrical studies on silver based fast ion conducting glassy materials  

SciTech Connect

Among all the available fast ion conductors, silver based glasses exhibit high conductivity. Further, glasses containing silver iodide enhances fast ion conducting behavior at room temperature. Glasses of various compositions of silver based fast ion conductors in the AgI?Ag{sub 2}O?[(1?x)B{sub 2}O{sub 3}?xTeO{sub 2}] (x=0 to1 mol% in steps of 0.2) glassy system have been prepared by melt quenching method. The glassy nature of the compounds has been confirmed by X-ray diffraction. The electrical conductivity (AC) measurements have been carried out in the frequency range of 1 KHz–3MHz by Impedance Analyzer in the temperature range 303–423K. The DC conductivity measurements were also carried out in the temperature range 300–523K. From both AC and DC conductivity studies, it is found that the conductivity increases and activation energy decreases with increasing the concentration of TeO{sub 2} as well as with temperature. The conductivity of the present glass system is found to be of the order of 10{sup ?2} S/cm at room temperature. The ionic transport number of these glasses is found to be 0.999 indicating that these glasses can be used as electrolyte in batteries.

Rao, B. Appa, E-mail: apparao.bojja@gmail.com; Kumar, E. Ramesh, E-mail: apparao.bojja@gmail.com; Kumari, K. Rajani, E-mail: apparao.bojja@gmail.com; Bhikshamaiah, G., E-mail: apparao.bojja@gmail.com [Department of Physics, Osmania University, Hyderabad-500007 (India)

2014-04-24

188

Electrically Conductive Chitosan/Carbon Scaffolds for Cardiac Tissue Engineering  

PubMed Central

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

2015-01-01

189

MOCVD of coated conductors with electrically conductive buffer layers and their electrical field  

NASA Astrophysics Data System (ADS)

A new MOCVD technique was developed for the deposition of oxides at a controlled low oxygen partial pressure, which enable to coat textured metal tapes with electrical conductive perovskites. In a RTR MOCVD-system metal tapes were coated with electrical conductive (La, Ba)MnO3, (La, Sr)MnO3, (La, Sr, Pb)MnO3 and (La, Ba)2CuO4 buffer layers and YBCO. In the same RTR-system YBCO was deposited on different buffered metal tapes. Computer calculations were used to characterise the behaviour for a weak superconducting part of a CC-tape with a conductive buffer layer system.

Stadel, O.; Samoilenkov, S. V.; Muydinov, R.; Schmidt, J.; Keune, H.; Wahl, G.; Henning, A.; Kurrat, M.; Gorbenko, O. Yu; Korsakov, I. E.; Melnikov, O. V.; Kaul, A. R.

2006-06-01

190

Electric-hydraulic conductivity correlation in fractured crystalline bedrock: Central Landfill, Rhode Island, USA  

NASA Astrophysics Data System (ADS)

Remote sensing and geoelectrical methods were used to find water-bearing fractures in the Scituate granite under the Central Landfill of Rhode Island. These studies were necessary to evaluate the integrity of the sanitary landfill and for planning safe landfill extensions. The most useful results were obtained with fracture trace analysis using Landsat and SLAR imagery in combination with ground-based resistivity measurements using Schlumberger vertical electrical soundings based on the assumption of horizontally layered strata. Test borings and packer tests confirmed, in the presence of a lineament and low bedrock resistivity, the probable existence of high bedrock fracture density and high average hydraulic conductivity. However, not every lineament was found to be associated with high fracture density and high hydraulic conductivity. Lineaments alone are not a reliable basis for characterising a landfill site as being affected by fractured bedrock. Horizontal fractures were found in borings located away from lineaments. High values of hydraulic conductivity were correlated with low bedrock resistivities. Bedrock resistivities between 60 and 700 ? m were associated with average hydraulic conductivities between 4 and 60 cm/day. In some cases very low resistivities were confined to the upper part of the bedrock where the hydraulic conductivity was very large. These types of fractures apparently become narrower in aperture with depth. Bedrock zones having resistivities greater than 1000 ? m showed, without exception, no flow to the test wells. Plots of bedrock resistivity versus the average hydraulic conductivity indicate that the resistivity decreases with increasing hydraulic conductivity. This relationship is inverse to that found in most unconsolidated sediments and is useful for estimating the hydraulic conductivity in groundwater surveys in fractured bedrock. In appropriate settings such as the Central Landfill site in New England, this electric-hydraulic correlation relationship, supplemented by lineament trace analysis, can be used effectively to estimate the hydraulic conductivity in bedrock from only a limited number of resistivity depth soundings and test wells.

Frohlich, Reinhard K.; Fisher, John J.; Summerly, E.

1996-10-01

191

Method for electrically isolating an electrically conductive member from another such member  

DOEpatents

The invention relates to methods for electrically isolating a first electrically conductive member from another such member by means of an electrically insulating medium. In accordance with the invention, the insulating medium is provided in the form of MgO which contains a dopant selected from lithium, copper, cobalt, sodium, silver, gold and hydrogen. The dopant is present in the MgO in an amount effective to suppress dielectric breakdown of the MgO, even at elevated temperatures and in the presence of electrical fields.

Tsang, K.L.; Chen, Y.

1984-02-09

192

Nature of surface electrical conductivity in natural sands, sandstones, and clays  

Microsoft Academic Search

The electrical conductivity of rocks results from conduction through the bulk solution occupying the pores and from surface conduction occurring at the fluid\\/grain interface. The nature of the surface electrical conductivity of shaly and clean sands and sandstones is examined. Surface conduction is characterized by the specific surface conductance which is the sum of three contributions: (i) Conduction within the

A. Revil; P. W. J. Glover

1998-01-01

193

Electrical conductivity of p-type BiOCl nanosheets.  

PubMed

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

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

2015-01-29

194

High temperature electrically conducting ceramic heating element and control system  

NASA Technical Reports Server (NTRS)

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, a furnace was fabricated and demonstrated to have excellent thermal response and cycling capability. The furnace was used to melt platinum-20% rhodium alloy (melting point 1904 C) with an isothermal ceramic heating element having a nominal working cavity size of 2.5 cm diameter by 10.0 cm long. The furnace was operated to 1940 C with the isothermal ceramic heating element. The same furnace structure was fitted with a pair of main heater elements to provide axial gradient temperature control over a working cavity length of 17.8 cm.

Halbach, C. R.; Page, R. J.

1975-01-01

195

Flake Electrical Conductivity of Few-Layer Graphene  

PubMed Central

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

2014-01-01

196

Flake electrical conductivity of few-layer graphene.  

PubMed

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

Mousavi, Hamze; Khodadadi, Jabbar

2014-01-01

197

Effect of water on the electrical conductivity of lower crustal clinopyroxene  

Microsoft Academic Search

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

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

2011-01-01

198

Electrical conduction in impregnants for all-film power capacitors  

NASA Astrophysics Data System (ADS)

The conduction properties of some impregnants (monodibenzyltoluene and phenylxylylethane) used in the all-film capacitors technology are investigated. The intent of this research contribution is to perform detailed investigations of these properties in a substantial range of electric fields (from 10-2 to 102 V ?m-1). Measurements of the macroscopic charge transport properties (conductivity, mobility, and viscosity) at low field are reported for the temperature range 293-373 K. Evidence of ionic conduction is found from these results. It is possible to evaluate the ionic dissociation parameter of ionic species [e.g., TBAP (tetrabutylammonium picrate)] by studying solutions of known electrolytes in well-purified solvents. Combining this information with the corresponding investigation in well-purified liquids, it is found that the residual ionic conductivity of these fluids corresponds to 10-10-10-11 mol/l equivalent TBAP. In the high-field region, particular emphasis is given to the quantitative interpretation of the current (electrical losses) versus applied field characteristics. Bulk effects associated with the field-enhanced ionic dissociation (Onsager theory) are observed when the impregnant contains an ionic surfactant such as sodium di-(2-ethylhexyl) sulphosuccinate, while unipolar injection in the neighborhood of the metallic electrodes is evidenced in solutions containing small amounts of ammonium picrate electrolytes (TBAP, triisoamylammonium picrate). It is found here that the high-field conduction mechanisms in purified liquids can be attributed to a charge injection phenomena. A physical analysis that satisfactorily predicts the high-field conduction behavior of these fluids is further proposed and discussed in connection with recent numerical simulations.

Brosseau, Christian

1991-11-01

199

The bedrock electrical conductivity structure of Northern Ireland  

NASA Astrophysics Data System (ADS)

An airborne geophysical survey of the whole of Northern Ireland has provided over 4.8 M estimates of the bedrock conductivity over the wide range of geological formations present. This study investigates how such data can be used to provide additional knowledge in relation to existing digital geological map information. A by-product of the analysis is a simplification of the spatially aggregated information obtained in such surveys. The methodology used is a GIS-based attribution of the conductivity estimates using a lithological classification of the bedrock formations. A 1:250k geological classification of the data is performed leading to a 56 unit lithological and geostatistical analysis of the conductivity information. The central moments (medians) of the classified data are used to provide a new digital bedrock conductivity map of Northern Ireland with values ranging from 0.32 to 41.36 mS m-1. This baseline map of conductivities displays a strong correspondence with an existing 4 quadrant, chrono-geological description of Northern Ireland. Once defined, the baseline conductivity map allows departures from the norm to be assessed across each specific lithological unit. Bulk electrical conductivity is controlled by a number of petrophysical parameters and it is their variation that is assessed by the procedures employed. The igneous rocks are found to display the largest variability in conductivity values and many of the statistical distributions are multi-modal. A sequence of low-value modes in these data are associated with intrusives within volcanic complexes. These and much older Neoproterzoic rocks appear to represent very low porosity formations that may be the product of rapid cooling during emplacement. By way of contrast, extensive flood basalts (the Antrim lavas) record a well-defined and much higher median value (12.24 mS m-1) although they display complex spatial behaviour in detail. Sedimentary rocks appear to follow the broad behaviours anticipated by standard theoretical descriptions of rock electrical properties that allow for a term due to grain surface conduction (e.g. the presence of clay). Single lithology sedimentary rocks are represented by an increasing set of conductivities through the sequence sandstone (4.91 mS m-1), limestone (8.41 mS m-1) and mudstone (17.85 mS m-1) with argillaceous rocks providing a conductivity of 41.1 mS m-1. In the case of both sandstone and limestone, the single lithology conductivities are significantly less than their mixed lithology counterparts. Mudrocks display a bimodal statistical distribution and an extended analysis of these rocks is carried out across a Carboniferous basin. The results clearly indicate that non-shale mudstones are distinctly less conductive than their shale counterparts. Shale formations display rapid and large movements in conductivity and it is suggested that the observed sensitivity may be due to competing surface conduction effects due to clay and organic material. A study of the variation of conductivity with geological period is also performed. Both a decreasing trend with age and a modulation that peaks in the Triassic period are observed.

Beamish, David

2013-08-01

200

Electric conductivity from the solution of the relativistic Boltzmann equation  

NASA Astrophysics Data System (ADS)

We present numerical results of electric conductivity ?el of a fluid obtained solving the relativistic transport Boltzmann equation in a box with periodic boundary conditions. We compute ?el using two methods: the definition itself, i.e., applying an external electric field, and the evaluation of the Green-Kubo relation based on the time evolution of the current-current correlator. We find a very good agreement between the two methods. We also compare numerical results with analytic formulas in relaxation time approximation (RTA) where the relaxation time for ?el is determined by the transport cross section ?tr , i.e., the differential cross section weighted with the collisional momentum transfer. We investigate the electric conductivity dependence on the microscopic details of the two-body scatterings: isotropic and anisotropic cross section as well as massless and massive particles. We find that the RTA underestimates considerably ?el ; for example, at screening masses mD˜T , such underestimation can be as large as a factor of 2. Furthermore, we study a more realistic case for a quark-gluon system (QGP) considering both a quasiparticle model tuned to lattice QCD (lQCD) thermodynamics, as well as the case of a perturbative QCD (pQCD) gas with running coupling. Also, for these cases more directly related to the description of the QGP system, we find that the RTA significantly underestimates the ?el by about 60%-80%.

Puglisi, A.; Plumari, S.; Greco, V.

2014-12-01

201

Testing and Optimization of Electrically Conductive Spacecraft Coatings  

NASA Astrophysics Data System (ADS)

This is the final report discussing the work done for the Space Environments and Effects (SEE) Program. It discusses test chamber design, coating research, and test results on electrically thermal control coatings. These thermal control coatings are being developed to have several orders of magnitude higher electrical conductivity than most available thermal control coatings. Most current coatings tend to have a range in surface resistivity from 1,011 to 1,013 ohms/sq. Historically, spacecraft have had thermal control surfaces composed of dielectric materials of either polymers (paints and metalized films) or glasses (ceramic paints and optical solar reflectors). Very seldom has the thermal control surface of a spacecraft been a metal where the surface would be intrinsically electrically conductive. The poor thermal optical properties of most metals have, in most cases, stopped them from being used as a thermal control surface. Metals low infrared emittance (generally considered poor for thermal control surfaces) and/or solar absorptance, have resulted in the use of various dielectric coatings or films being applied over the substrate materials in order to obtain the required optical properties.

Mell, R. J.; Wertz, G. E.

2001-12-01

202

Electrically conductive gold- and copper-metallized DNA origami nanostructures.  

PubMed

This work demonstrates the use of a circuit-like DNA origami structure as a template to fabricate conductive gold and copper nanostructures on Si surfaces. We improved over previous results by using multiple Pd seeding steps to increase seed uniformity and density. Our process has also been characterized through atomic force microscopy, particle size distribution analysis, and scanning electron microscopy. We found that four successive Pd seeding steps yielded the best results for electroless metal plating on DNA origami. Electrical resistance measurements were done on both Au- and Cu-metallized nanostructures, with each showing ohmic behavior. Gold-plated DNA origami structures made under optimal conditions had an average resistivity of 7.0 × 10(-5) ?·m, whereas copper-metallized structures had a resistivity as low as 3.6 × 10(-4) ?·m. Importantly, this is the first demonstration of electrically conductive Cu nanostructures fabricated on either DNA or DNA origami templates. Although resistivities for both gold and copper samples were larger than those of the bulk metal, these metal nanostructures have the potential for use in electrically connecting small structures. In addition, these metallized objects might find use in surface-enhanced Raman scattering experiments. PMID:23419143

Geng, Yanli; Pearson, Anthony C; Gates, Elisabeth P; Uprety, Bibek; Davis, Robert C; Harb, John N; Woolley, Adam T

2013-03-12

203

Electrical conductivity of the ceramic AIN under irradiation  

NASA Astrophysics Data System (ADS)

Aluminum nitride has been proposed as electrically insulating coating in connection with blankets made of vanadium alloys. Irradiations were performed with an applied DC electric field of 100 kV/m, using a 104 MeV ?-particle beam. The dose achieved were 0.1 dpa at 300°C, 0.05 dpa at 400°C, and 0.06 dpa at 500°C. The out-of-beam conductivity ? 0 decreased at all temperatures employed during early stage of irradiation. Before 0.02 dpa had been reached, ? 0 dropped to low values of typically (2-4) × 10 -11 (? m) -1. Although a moderate increase can be observed during further irradiation, ? 0 remained below the initial value of the unirradiated specimen for all temperatures. That is, there is no significant evidence for radiation induced electrical degradation. The in-beam conductivity ?, measured continuously during irradiation, also decreased by at least one order of magnitude. Relevant damage dose and ionization rate dependencies of ? and ? 0 will be discussed.

Lindau, R.; Möslang, A.

1996-10-01

204

Miniatuization of the flowing fluid electric conductivity loggingtec hnique  

SciTech Connect

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.

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

2005-10-19

205

Measurements of middle-atmosphere electric fields and associated electrical conductivities  

NASA Technical Reports Server (NTRS)

A simple antenna for measuring the vertical electric field in the 'middle atmosphere' has been flown on a number of rocket-launched parachute-borne payloads. The data from the first nine such flights, launched under a variety of geophysical conditions, are presented, along with electrical conductivities measured simultaneously. The data include indications of layered peaks of several volts per meter in the mesospheric field at high and low latitudes in situations of relatively low conductivity. During an auroral 'REP' event the electric field reversed direction in the lower stratosphere, accompanied by a substantial enhancement in conductivity. The data generally do not confirm speculations based only on the extension of the thunderstorm circuit from below or the mapping of ionospheric and magnetospheric fields from above, but seem to require, in addition, internal generation processes in the middle atmosphere.

Hale, L. C.; Croskey, C. L.; Mitchell, J. D.

1981-01-01

206

Electrical Conductivity of Al3+-doped MgO  

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

207

Transparent electrical conducting films by activated reactive evaporation  

DOEpatents

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.

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

1982-01-01

208

Development of Tailorable Electrically Conductive Thermal Control Material Systems  

NASA Technical Reports Server (NTRS)

The optical characteristics of surfaces on spacecraft are fundamental parameters in controlling its temperature. Passive thermal control coatings with designed solar absorptance and infrared emittance properties have been developed and been in use for some time. In this total space environment, the coating must be stable and maintain its desired optical properties for the course of the mission lifetime. The mission lifetimes are increasing and in our quest to save weight, newer substrates are being integrated which limit electrical grounding schemes. All of this has already added to the existing concerns about spacecraft charging and related spacecraft failures or operational failures. The concern is even greater for thermal control surfaces that are very large. One way of alleviating such concerns is to design new thermal control material systems (TCMS) that can help to mitigate charging via providing charge leakage paths. The object of this program was to develop two types of passive electrically conductive TCMS.

Deshpande, M. S.; Harada, Y.

1998-01-01

209

Electrical Conductivity in Polymer Blends/ Multiwall Carbon Nanotubes  

SciTech Connect

Carbon nanotubes (CNT) based polymer composites have emerged as the future multifunctional materials in view of its exceptional mechanical, thermal and electrical properties. One of the major interests is to develop conductive polymer composites preferably at low concentration of CNT utilizing their high aspect ratio (L/D) for numerous applications, which include antistatic devices, capacitors and materials for EMI shielding. In this context, polymer blends have emerged as a potential candidate in lowering the percolation thresholds further by the utilization of 'double-percolation' which arises from the synergistic improvements in blend properties associated with the co-continuous morphology. Due to strong inter-tube van der Waals' forces, they often tend to aggregate and uniform dispersion remains a challenge. To overcome this challenge, we exploited sodium salt of 6-aminohexanoic acid (Na-AHA) which was able to assist in debundlling the multiwall carbon nanotubes (MWNT) through 'cation-{pi}' interactions during melt-mixing leading to percolative 'network-like' structure of MWNT within polyamide6 (PA6) phase in co-continuous PA6/acrylonitrile butadiene styrene (ABS) blends. The composite exhibited low electrical percolation thresholds of 0.25 wt% of MWNT, the lowest reported value in this system so far. Retention of 'network-like structure' in the solid state with significant refinement was observed even at lower MWNT concentration in presence Na-AHA, which was assessed through AC electrical conductivity measurements. Reactive coupling was found to be a dominant factor besides 'cation-{pi}' interactions in achieving low electrical percolation in PA6/ABS+MWNT composites.

Kulkarni, Ajit R.; Bose, Suryasarathi; Bhattacharyya, Arup R. [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai-400076 (India)

2008-10-23

210

Electrical Conductivity in Polymer Blends/ Multiwall Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

Carbon nanotubes (CNT) based polymer composites have emerged as the future multifunctional materials in view of its exceptional mechanical, thermal and electrical properties. One of the major interests is to develop conductive polymer composites preferably at low concentration of CNT utilizing their high aspect ratio (L/D) for numerous applications, which include antistatic devices, capacitors and materials for EMI shielding. In this context, polymer blends have emerged as a potential candidate in lowering the percolation thresholds further by the utilization of `double-percolation' which arises from the synergistic improvements in blend properties associated with the co-continuous morphology. Due to strong inter-tube van der Waals' forces, they often tend to aggregate and uniform dispersion remains a challenge. To overcome this challenge, we exploited sodium salt of 6-aminohexanoic acid (Na-AHA) which was able to assist in debundlling the multiwall carbon nanotubes (MWNT) through `cation-?' interactions during melt-mixing leading to percolative `network-like' structure of MWNT within polyamide6 (PA6) phase in co-continuous PA6/acrylonitrile butadiene styrene (ABS) blends. The composite exhibited low electrical percolation thresholds of 0.25 wt% of MWNT, the lowest reported value in this system so far. Retention of `network-like structure' in the solid state with significant refinement was observed even at lower MWNT concentration in presence Na-AHA, which was assessed through AC electrical conductivity measurements. Reactive coupling was found to be a dominant factor besides `cation-?' interactions in achieving low electrical percolation in PA6/ABS+MWNT composites.

Kulkarni, Ajit R.; Bose, Suryasarathi; Bhattacharyya, Arup R.

2008-10-01

211

Characterization of electrically conductive transition metal dichalcogenide lubricant films  

NASA Astrophysics Data System (ADS)

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 under sliding electrical contact conditions. Evaluation was done using a pin-on-disc tribometer, modified to allow simultaneous monitoring of friction and contact resistance. Resistivities were measured using a static four point probe. The optimal conditions for sputter depositing transition metal dichalcogenides using the DV-602 sputtering system were determined as 10 microns of argon pressure and a rf power of 200 W. Some of the dichalcogenides did not form adherent films on stainless steel substrates under the experimental conditions. A dual source cosputtering (Cu/NbTesb2) technique is discussed, which improved the film-substrate adherence significantly, and provides a new way for the development of other thin film materials. The cosputtered Cu appears to alter the lattice parameters in the dichalcogenide crystal structure and consequently leads to improved adhesion and electrical properties. The sliding contact electrical behavior of the films was found to be related to the electronic configuration, crystal packing and structure. The group VB (Nb, Ta) metal dichalcogenides exhibited better electrical properties than the group VIB (Mo, W) metal dichalcogenide films, because of the presence of delocalized nonbonding electrons in the group VB compounds. Sputtered films with better adherence to the substrate illustrated improved friction and wear life in comparison to the burnished films. The sputtered films with greater amount of metallic character, purity, crystallinity and better adhesion reduced the contributions to the overall contact resistance. The increased metallic character of the sputtered films implies that the free electrons in the valency band are closer to the fermi level of the metal, and hence illustrate lower sliding contact resistance as compared to the burnished films. A conduction-lubrication-wear mechanism is presented, which was derived from the asperity flash temperature rise. The ohmic heating affects on the conduction-lubrication-wear mechanism of films are also discussed. The coefficient of friction, sliding contact resistance, wear rates, static four point resistivities and the asperity flash temperature estimates are presented.

Waghray, Harish C.

212

Application of electrical and electromagnetic depth sounding in highly conductive sediments: The concept of vertical electrical anisotropy  

NASA Astrophysics Data System (ADS)

“Nördlinger Ries” is a meteorite crater in the Bavarian ‘Alb’ of Germany that was formed 15 million years ago, and subsequently filled with salty water. Evaporation resulted in an approximately 300 meter thick layer of young, highly conductive sediments. Audio-frequency Magnetotelluric (AMT) and geoelectric depth sounding (VES) techniques were used to analyze the electrical properties of these sediments. The apparent resistivities measured by the two methods are different, which can be explained by vertical electrical anisotropy (horizontal layering). Applying a joint forward modelling technique with resistivity variations found by a Monte Carlo method results in a best fit model containing a large number of layers, while separate inversions of the two data sets yield 3-layer models. Comparisons of the coefficient of anisotropy with drilling core samples demonstrate the reliability of the results. One difficulty of the AMT method is the low signal-to-noise ratio, because of the source’s deadband. Some suggestions for an “intelligent” processing are presented. Kerch (this session) is employing the result of the integrated conductivity as an input for 3D modelling of collected MT data.

Köhler, A.; Bahr, K.

2010-12-01

213

Sinterability and electrical conductivity of calcium-doped lanthanum chromites  

Microsoft Academic Search

Calcium-doped lanthanum chromites, (La1-xCax) (Cr1-y Cay O3, have been synthesized to investigate effects of calcium doping on sinterability and electrical conductivity. X-ray diffractometric results have revealed that in addition to normal perovskites (La1-xCaxCrO3), chromium-deficient perovskites can exist as a single phase in the composition region 0.1 x < 0.3, although the deficit of chromium is small. These chromium-deficient perovskites show

N. Sakai; T. Kawada; H. Yokokawa; M. Dokiya; T. Iwata

1990-01-01

214

Electrical conductivity of orthopyroxene and plagioclase in the lower crust  

Microsoft Academic Search

The electrical conductivities of lower crustal orthopyroxene and plagioclase, as well as their dependence on water content,\\u000a were measured at 6–12 kbar and 300–1,000°C on both natural and pre-annealed samples prepared from fresh mafic xenolith granulites.\\u000a The complex impedance was determined in an end-loaded piston cylinder apparatus by a Solarton-1260 Impedance\\/Gain Phase analyzer\\u000a in the frequency range of 0.1–106 Hz.

Xiaozhi Yang; Hans Keppler; Catherine McCammon; Huaiwei Ni

2011-01-01

215

Control of electrical conduction in DNA using hole doping  

Microsoft Academic Search

Control of electrical conduction in DNA using hole doping H.Y.Lee1, M.Taniguchi1, K.H.Yoo2, Y.Otsuka1 H.Tanaka1 and T.Kawai1 1The Institute of Scientific and Industrial Research(ISIR), Osaka University, Osaka, Japan. 2Department of Physics, Younsei University, Seoul, Korea Possible applications of DNA molecules in electronic devices and biosensors were suggested almost ten years ago A DNA structure containing a single type of base pair

Hea-Yeon Lee; Masateru Taniguchi; K. H. Yoo; Youichi Otsuka; Hidekazu Tanaka; Tomoji Kawai

2002-01-01

216

Electrical conductivity anisotropy of partially molten peridotite under shear deformation  

NASA Astrophysics Data System (ADS)

Recent ocean bottom magnetotelluric investigations have revealed a high-conductivity layer (HCL) with high anisotropy characterized by higher conductivity values in the direction parallel to the plate motion beneath the southern East Pacific Rise (Evans et al., 2005) and beneath the edge of the Cocos plate at the Middle America trench offshore of Nicaragua (Naif et al., 2013). These geophysical observations have been attributed to either hydration (water) of mantle minerals or the presence of partial melt. Currently, aligned partial melt has been regarded as the most preferable candidate for explaining the conductivity anisotropy because of the implausibility of proton conduction (Yoshino et al., 2006). In this study, we report development of the conductivity anisotropy between parallel and normal to shear direction on the shear plane in partial molten peridotite as a function of time and shear strain. Starting samples were pre-synthesized partial molten peridotite, showing homogeneous melt distribution. The partially molten peridotite samples were deformed in simple shear geometry at 1 GPa and 1723 K in a DIA-type apparatus with uniaxial deformation facility. Conductivity difference between parallel and normal to shear direction reached one order, which is equivalent to that observed beneath asthenosphere. In contrast, such anisotropic behavior was not found in the melt-free samples, suggesting that development of the conductivity anisotropy was generated under shear stress. Microstructure of the deformed partial molten peridotite shows partial melt tends to preferentially locate grain boundaries parallel to shear direction, and forms continuously thin melt layer sub-parallel to the shear direction, whereas apparently isolated distribution was observed on the section perpendicular to the shear direction. The resultant melt morphology can be approximated by tube like geometry parallel to the shear direction. This observation suggests that the development of conductivity anisotropy is caused by the realignment of partial melt (forming tube-like melt) parallel to shear direction in the silicate matrix. Finally, the high anisotropy of conductivity in the direction of plate motion can be well explained by anisotropic interconnection of melt in partially molten rocks at the top of asthenosphere, but not hydration of nominally anhydrous minerals. Therefore, our results provide the direct experimental evidence for supporting these geophysically observed high-conductivity anisotropy at the LAB and verify the validity of partial melting hypothesis (Yoshino et al., 2006; Naif et al., 2013). References Evans, R. L. et al. Geophysical evidence from the MELT area for compositional controls on oceanic plates. Nature 437, 249-252 (2005). Naif, S., Key, K., Constable, S. & Evans, R. L. Melt-rich channel observed at the lithosphere-asthenosphere boundary. Nature 495, 356-359 (2013). Yoshino, T., Matsuzaki, T., Yamashita, S. & Katsura, T. Hydrous olivine unable to account for conductivity anomaly at the top of the asthenosphere. Nature 443, 973-976 (2006).

Zhang, B.; Yoshino, T.; Yamazaki, D.; Manthilake, G. M.; Katsura, T.

2013-12-01

217

Electrical Modulation of the Local Conduction at Oxide Tubular Interfaces  

SciTech Connect

Hetero-interfaces between complex oxides have sparked considerable interest due to their fascinating physical properties and offer new possibilities for next-generation electronic devices. The key to realize practical applications is the control through external stimulus. In this study, we take the self-assembled BiFeO3-CoFe2O4 hetero-interface as a model system to demonstrate the non-volatile electric control of the local conduction at the complex oxide tubular interface. The fundamental mechanism behind this modulation was explored based on static and dynamic conducting atomic force microscopy. We found the movement of oxygen vacancies in the BiFeO3-CoFe2O4 heterostructure is the key to drive this intriguing behavior. This study delivers a possibility of designing new device for next-generation electronic devices.

Hsieh, Ying-Hui [National Chiao Tung University, Hsinchu, Taiwan] [National Chiao Tung University, Hsinchu, Taiwan; Strelcov, Evgheni [ORNL] [ORNL; Jia-Ming, Liou [National Cheng Kung University, Tainan, Taiwan] [National Cheng Kung University, Tainan, Taiwan; Chia-Ying, Shen [National Chiao Tung University, Hsinchu, Taiwan] [National Chiao Tung University, Hsinchu, Taiwan; Yi-Chun, Chen [National Cheng Kung University, Tainan, Taiwan] [National Cheng Kung University, Tainan, Taiwan; Kalinin, Sergei V [ORNL] [ORNL; Ying-Hao, Chu [National Chiao Tung University, Hsinchu, Taiwan] [National Chiao Tung University, Hsinchu, Taiwan

2013-01-01

218

Electrical modulation of the local conduction at oxide tubular interfaces.  

PubMed

Heterointerfaces between complex oxides have sparked considerable interest due to their fascinating physical properties and their offering of new possibilities for next-generation electronic devices. The key to realize practical applications is the control through external stimuli. In this study, we take the self-assembled BiFeO3-CoFe2O4 tubular interface as a model system to demonstrate the nonvolatile electric control of the local conduction at the complex oxide tubular interface. The fundamental mechanism behind this modulation was explored based on static and dynamic conductive atomic force microscopies. We found the movement of oxygen vacancies in the BiFeO3-CoFe2O4 heterostructure is the key to drive this intriguing behavior. This study delivers a possibility in developing next-generation electronic devices. PMID:24016142

Hsieh, Ying-Hui; Strelcov, Evgheni; Liou, Jia-Ming; Shen, Chia-Ying; Chen, Yi-Chun; Kalinin, Sergei V; Chu, Ying-Hao

2013-10-22

219

Electrical conductivity measurements on disk-shaped samples.  

PubMed

We have developed a sample holder design that allows for electrical conductivity measurements on a disk-shaped sample. The sample holder design is based on and compatible with popular measurement systems that are currently restricted to bar-shaped samples. The geometrical correction factors which account for the adjusted measurement configuration were calculated using finite element modeling for a broad range of sample and measurement geometries. We also show that the modeling results can be approximated by a simple analytical fit function with excellent accuracy. The proposed sample holder design is compatible with a concurrent measurement of the Seebeck coefficient. The chosen sample geometry is furthermore compatible with a thermal conductivity measurement using a laser flash apparatus. A complete thermoelectric characterization without cutting the sample is thus possible. PMID:25085170

de Boor, J; Zabrocki, K; Frohring, J; Müller, E

2014-07-01

220

Electrical conduction in nanodomains in congruent lithium tantalate single crystal  

SciTech Connect

The electrical current flow behavior was investigated for nanodomains formed in a thin congruent lithium tantalate (LiTaO{sub 3}) single-crystal plate. When the nanodomains were relatively large, with diameters of about 100?nm, current flow was detected along the domain wall. However, when they were about 40?nm or smaller, the current flowed through the entire nanodomain. Schottky-like rectifying behavior was observed. Unlike the case of LiNbO{sub 3}, optical illumination was not required for current conduction in LiTaO{sub 3}. A clear temperature dependence of the current was found indicating that the conduction mechanism for nanodomains in LiTaO{sub 3} may involve thermally activated carrier hopping.

Cho, Yasuo [Research Institute of Electrical Communication, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577 (Japan)

2014-01-27

221

Stimulation of neurite outgrowth using an electrically conducting?polymer  

PubMed Central

Damage to peripheral nerves often cannot be repaired by the juxtaposition of the severed nerve ends. Surgeons have typically used autologous nerve grafts, which have several drawbacks including the need for multiple surgical procedures and loss of function at the donor site. As an alternative, the use of nerve guidance channels to bridge the gap between severed nerve ends is being explored. In this paper, the electrically conductive polymer—oxidized polypyrrole (PP)—has been evaluated for use as a substrate to enhance nerve cell interactions in culture as a first step toward potentially using such polymers to stimulate in vivo nerve regeneration. Image analysis demonstrates that PC-12 cells and primary chicken sciatic nerve explants attached and extended neurites equally well on both PP films and tissue culture polystyrene in the absence of electrical stimulation. In contrast, PC-12 cells interacted poorly with indium tin oxide (ITO), poly(l-lactic acid) (PLA), and poly(lactic acid-co-glycolic acid) surfaces. However, PC-12 cells cultured on PP films and subjected to an electrical stimulus through the film showed a significant increase in neurite lengths compared with ones that were not subjected to electrical stimulation through the film and tissue culture polystyrene controls. The median neurite length for PC-12 cells grown on PP and subjected to an electrical stimulus was 18.14 ?m (n = 5643) compared with 9.5 ?m (n = 4440) for controls. Furthermore, animal implantation studies reveal that PP invokes little adverse tissue response compared with poly(lactic acid-co-glycolic acid). PMID:9256415

Schmidt, Christine E.; Shastri, Venkatram R.; Vacanti, Joseph P.; Langer, Robert

1997-01-01

222

Electric pulp tester conductance through various interface media.  

PubMed

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

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

2006-12-01

223

Measurements of the apparent thermal conductivity of multi-layer insulation between 20 K and 90 K  

SciTech Connect

NASA has the need to efficiently store cryogenic propellants in space for long periods of time. One method to improve storage efficiency is to use multi-layer insulation (MLI), a technique that minimizes the boiling rate due to radiation heat transfer. Typically, the thermal performance of MLI is determined by measuring the rate of evaporation of liquid nitrogen from a calibrated cryostat. The main limitation with this method is that testing conditions are restricted by the boiling temperature of the LN{sub 2}, which may not match the requirements of the application. The Multi-Layer Insulation Thermal Conductivity Experiment (MIKE) at the National High Magnetic Field Laboratory is capable of measuring the effective thermal conductivity of MLI at variable boundary temperatures. MIKE uses cryo-refrigerators to control boundary temperatures in the calorimeter and a calibrated thermal link to measure the heat load. To make the measurements requested by NASA, MIKE needed to be recalibrated for the 20 K to 90 K range. Also, due to the expectation of a lower heat transfer rate, the heat load support rod material was changed to one with a lower thermal conductivity to ensure the temperature difference seen on the cold rod could be measurable at the estimated heat load. Presented are the alterations to MIKE including calibration data and heat load measurements on new load-bearing MLI supplied by NASA.

Hurd, Joseph A.; Van Sciver, Steven W. [National High Magnetic Field Laboratory Tallahassee, FL 32310 USA and FAMU-FSU College of Engineering, Department of M.E., Tallahassee, FL 32310 (United States)

2014-01-29

224

Printability and Electrical Conductivity of UV Curable MWCNT Ink  

NASA Astrophysics Data System (ADS)

Composites reinforced with multiwalled carbon nanotubes (MWCNT) in a photosensitive acrylic matrix were successfully synthesized and their printing, rheological, and electrical behavior was characterized. The shape of the reinforcement MWCNT particles was analyzed by transmission electron microscopy. The MWCNT were mixed in the acrylic polymer at increasing concentrations until the percolation threshold was determined at 2 wt.% with a conductivity of 4.26 × 10-4 S/cm. The large increase in viscosity with addition of MWCNT showed the need for a printing system capable of dispensing solutions of up to 613 × 103 cp. Lines were printed with a precision dispensing system mounted in computer controlled x-y-z stages, while an integrated ultraviolet light emission diode dot with a single wavelength of 385 nm cured seconds after the ink was dispensed. The wetting properties of the composite with respect to polyester, polyethylene terephthalate, polyimide, and paper films were analyzed with a goniometer. The relationship between the contact angle, pattern accuracy, and electrical conductivity was determined for each substrate.

Ortega, Ada; Park, Byungwoo; Kim, Nam Soo

2014-12-01

225

Density, viscosity and electrical conductivity of protic alkanolammonium ionic liquids.  

PubMed

Ionic liquids are molten salts with melting temperatures below the boiling point of water, and their qualification for applications in potential industrial processes does depend on their fundamental physical properties such as density, viscosity and electrical conductivity. This study aims to investigate the structure-property relationship of 15 ILs that are primarily composed of alkanolammonium cations and organic acid anions. The influence of both the nature and number of alkanol substituents on the cation and the nature of the anion on the densities, viscosities and electrical conductivities at ambient and elevated temperatures are discussed. Walden rule plots are used to estimate the ionic nature of these ionic liquids, and comparison with other studies reveals that most of the investigated ionic liquids show Walden rule values similar to many non-protic ionic liquids containing imidazolium, pyrrolidinium, tetraalkylammonium, or tetraalkylphosphonium cations. Comparison of literature data reveals major disagreements in the reported properties for the investigated ionic liquids. A detailed analysis of the reported experimental procedures suggests that inappropriate drying methods can account for some of the discrepancies. Furthermore, an example for the improved presentation of experimental data in scientific literature is presented. PMID:21298175

Pinkert, André; Ang, Keng L; Marsh, Kenneth N; Pang, Shusheng

2011-03-21

226

Magnetoresistance, electrical conductivity, and Hall effect of glassy carbon  

SciTech Connect

These properties of glassy carbon heat treated for three hours between 1200 and 2700/sup 0/C were measured from 3 to 300/sup 0/K in magnetic fields up to 5 tesla. The magnetoresistance was generally negative and saturated with reciprocal temperature, but still increased as a function of magnetic field. The maximum negative magnetoresistance measured was 2.2% for 2700/sup 0/C material. Several models based on the negative magnetoresistance being proportional to the square of the magnetic moment were attempted; the best fit was obtained for the simplest model combining Curie and Pauli paramagnetism for heat treatments above 1600/sup 0/C. Positive magnetoresistance was found only in less than 1600/sup 0/C treated glassy carbon. The electrical conductivity, of the order of 200 (ohm-cm)/sup -1/ at room temperature, can be empirically written as sigma = A + Bexp(-CT/sup -1/4) - DT/sup -1/2. The Hall coefficient was independent of magnetic field, insensitive to temperature, but was a strong function of heat treatment temperature, crossing over from negative to positive at about 1700/sup 0/C and ranging from -0.048 to 0.126 cm/sup 3//coul. The idea of one-dimensional filaments in glassy carbon suggested by the electrical conductivity is compatible with the present consensus view of the microstructure.

Baker, D.F.

1983-02-01

227

Electrical resistivity imaging of conductive plume dilution in fractured rock  

NASA Astrophysics Data System (ADS)

Electrical resistance tomography (ERT) was used to monitor a conductive plume dilution experiment that was conducted in fractured basalt in order to assess its applications in this type of fractured-rock environment. Tap water was injected into an injection well for 34 days to dilute a pre-existing potassium chloride (KCl) plume at a site in Idaho, USA. No further fluids were introduced artificially during a 62-day monitoring period. Both surface ERT and cross-borehole ERT were used to monitor dilution and displacement of the plume. A square grid of land-surface electrodes was used with the surface ERT. Three-dimensional images of surface ERT delineated areas of increased and decreased resistivities. Increasing resistivities are attributed to dilution/displacement of the KCl solution by tap-water invasion or the influx of seasonal recharge. Decreasing resistivities resulted from redistribution of residual KCl solution. Cross-borehole ERT was conducted between the injection well and each of seven surrounding monitoring wells. Polar plots of the injection-well resistivity data in the direction of each monitoring well delineate specific locations where tap water seeped from the injection well via preferential flow paths determined by time-dependent resistivity increases. Monitoring-well data indicate locations of clustered and isolated regions of resistivity changes.

Nimmer, Robin E.; Osiensky, James L.; Binley, Andrew M.; Sprenke, Kenneth F.; Williams, Barbara C.

2007-08-01

228

Electrically Conductive Multiphase Polymer Blend Carbon-Based Composites  

NASA Astrophysics Data System (ADS)

The use of multiphase polymer blends provides unique morphologies and properties to reduce the percolation concentration and increase conductivity of carbon-based polymer composites. These systems offer improved conductivity, temperature stability and selective distribution of the conductive filler through unique morphologies at significantly lower conductive filler concentration. In this work, the kinetic and thermodynamic effects on a series of multiphase conductive polymer composites were investigated. The polymer blend phase morphology, filler distribution, electrical conductivity, and rheological properties of CB-filled PP/PMMA/EAA conductive polymer composites were determined. Thermodynamic and kinetic parameters were found to influence the morphology development and final composite properties. The morphology and CB distribution were found to be kinetically driven when annealed for a short period of time following the shear-intensive mixing process, whereas the three-phase polymer blend morphology is driven by thermodynamics when given sufficient time under high temperature annealing conditions in the melt state. At short annealing times, the CB distribution was influenced by the compounding sequence where the CB was added after being premixed with one of the polymer phases or directly added to the three phase polymer melt, but again was thermodynamically driven at longer annealing times with the CB migrating to the EAA phase. The resistivity was found to decrease by a statistically significant amount to similar levels for all of the composite systems with increasing annealing time, providing evidence of gradual phase coalescence to a tri-continuous morphology and CB migration. The addition of CB via the PP and EAA masterbatch results in significantly faster percolation and lower resistivity compared to when added direct to the system during compounding after 30 minutes annealing by a statistically significant amount. Dynamic oscillatory shear rheology using small-amplitude oscillations was used to probe for differences in the tri-continuous morphology and attempt to characterize the CB distribution with annealing time. Minor differences were observed in the PP/PMMA/(EAA-CB) as a function of annealing time, while the rheological behavior was not observed to be significantly different for the other multiphase composites as a function of annealing, nor for the compounding sequence after the same annealing time.

Brigandi, Paul James

229

DC-electrical conductivity as a method for monitoring radiation curing of unsaturated polyester resins III. Evaluation of results  

NASA Astrophysics Data System (ADS)

The results of DC-electrical conductivity monitoring of radiation and thermally initiated crosslinking of unsaturated polyester resins are interpreted using conductivity data itself instead of commonly used logarithmic data form. The main setbacks of logarithmic conductivity data were the shift toward longer reaction time compared to non-logarithmic conductivity data and extraction analysis results and pronounced scattering at the end of the reaction so it was impossible to detect vitrification point. By revision of approach to analysis of results, full sensitivity of the electrical conductivity method to structural changes in the reacting system was shown. The apparent rate constants calculated from conductivity itself showed the influence of upper liquid-liquid transition on the rate of radiation induced reaction that could not be seen if the logarithm of conductivity was used. Influence of dose rate effects and electrical field effects on reaction rate were detected too and confirmed by DSC measurements. All details of reaction can be detected using first derivative of conductivity and in the case of thermally initiated reaction two maxims of reaction rate were found that are probably caused by local increase of temperature due to highly exothermic reaction.

Puci?, Irina; Ranogajec, Franjo

1999-01-01

230

Imaging in electrically conductive porous media without frequency encoding  

NASA Astrophysics Data System (ADS)

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 (CO2) 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 m3 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 CO2 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 CO2 injections in saline aquifers or detecting water leakage into nuclear waste deposit sites installed in electrically conductive formations.

Lehmann-Horn, J. A.; Walbrecker, J. O.

2012-07-01

231

Effect of Plasma-Nitric Acid Treatment on the Electrical Conductivity of Flexible Transparent Conductive Films  

NASA Astrophysics Data System (ADS)

A flexible transparent electrically conductive film (FTCF) was formed on a poly(ethylene terephthalate) film by spraying single-walled carbon nanotubes dispersed with sodium dodecyl benzene sulfonate in water and, to improve the electrical conductivity of FTCF, the effect on plasma treatment followed by nitric acid treatment was investigated. The Ar plasma treatment was effective in dissociating the surfactant and removing impurities attached to the surface of the carbon nanotubes (CNTs). Therefore, through a cyclic treatment composed of an Ar plasma treatment and nitric acid treatment, more effective removal of surfactant and impurities attached to the spray-coated CNTs could be obtained than a cyclic treatment without the plasma treatment. With the optimized cyclic treatment, the sheet resistance (?s) of the spray-coated CNTs could be decreased up to 45% by removing most of the surfactant and impurities. Using the repeated cyclic treatment, the FTCF having the ?s of 160 ?/square at 81.5% optical transmittance at the wavelength of 550 nm could be obtained.

Phuong Pham, Viet; Jo, Young Woo; Oh, Jong Sik; Kim, Soo Min; Park, Jin Woo; Kim, Sung Hee; Jhon, Myung S.; Yeom, Geun Young

2013-07-01

232

Electric field-induced chemical locomotion of conducting objects  

NASA Astrophysics Data System (ADS)

Externally triggered motion of small objects has potential in applications ranging from micromachines, to drug delivery, and self-assembly of superstructures. Here we present a new concept for the controlled propulsion of conducting objects with sizes ranging from centimetres to hundreds of micrometres. It is based on their polarization, induced by an electric field, which triggers spatially separated oxidation and reduction reactions involving asymmetric gas bubble formation. This in turn leads to a directional motion of the objects. Depending on the implied redox chemistry and the device design, the speed can be controlled and the motion can be switched from linear to rotational. This type of chemical locomotion is an alternative to existing approaches based on other principles.

Loget, Gabriel; Kuhn, Alexander

2011-11-01

233

Polymeric salt bridges for conducting electric current in microfluidic devices  

DOEpatents

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.

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

2009-11-17

234

Microwave synthesis of electrically conductive gold nanowires on DNA scaffolds.  

PubMed

Biological molecules, in particular DNA, have shown great potential to be used as interconnects of nanodevices and computational elements. In this research, we synthesized electrically conductive gold nanowires for the first time exploiting an electroless and microwave heating method for 120-180 s. Our results indicate that DNA serves as a reducing and nonspecific capping agent for the growth of nanowires. The current voltage ( I- V) characteristics of the Au nanowires are continuous, exhibiting Ohmic behavior having low contact resistance with the gold electrodes. The nanowires have a diameter of 10-15 nm in solution and of 20-30 nm in immobilized DNA with resistivity comparable to pure metals. The method is highly selective with deposition confined to the DNA itself. The nanowires we fabricated can be used as building blocks for functional nanodevices, sensors, and optoelectronics. PMID:18671418

Kundu, Subrata; Liang, Hong

2008-09-01

235

Vortex Lines and Monopoles in Electrically Conducting Plasmas  

NASA Astrophysics Data System (ADS)

Based on the phi-mapping topological current theory and the decomposition of gauge potential theory, the vortex lines and the monopoles in electrically conducting plasmas are studied. It is pointed out that these two topological structures respectively inhere in two-dimensional and three-dimensional topological currents, which can be derived from the same topological term vec n . (?ivec n × ?jvec n), and both these topological structures are characterized by the phi-mapping topological numbers-Hopf indices and Brouwer degrees. Furthermore, the spatial bifurcation of vortex lines and the generation and annihilation of monopoles are also discussed. At last, we point out that the Hopf invariant is a proper topological invariant to describe the knotted solitons.

Wang, Ji-Biao; Ren, Ji-Rong; Li, Ran

2009-02-01

236

Lunar magnetic permeability, magnetic fields, and electrical conductivity temperature  

NASA Technical Reports Server (NTRS)

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.

Parkin, C. W.

1978-01-01

237

Formulation of electrically conductive thermal-control coatings  

NASA Technical Reports Server (NTRS)

The development and formulation of electrically conductive thermal control coating was undertaken for use on the International Sun Earth Explorer spacecraft. The primary effort was to develop a coating with a bulk resistivity of less than 100,000 ohm/sqm, an optical absorptance of approximately 0.55, and a normal emittance of 0.90. The required stability in space called for a bulk resistivity of less than 100,000 ohm/sq m, an absorptance of less than 0.67, and a normal emittance of 0.90 after exposure to approximately 4 x 10 to the 16th proton/sq cm of solar-wind particles and 5300 equivalent sun-hours. These exposures represent 2 years of ISEE flight conditions. Both the unsuccessful formulation efforts and the successful use of oxide pigments fired at 1448 K are described. Problems relative to the reactivity of specific coating vehicles exposed to high humidity are discussed.

Shai, M. C.

1978-01-01

238

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

E-print Network

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

Paris-Sud XI, Université de

239

Electrical conductivity measurements of polymer thin films on metal substrates  

SciTech Connect

Topographical measurements by AFM and other manometer scanning probes often do not adequately distinguish between phases along composite surfaces. In the case of insulator structures (e.g., thin films; particles) on metal substrates, manometer scans of electrical conductivity offer a convenient tool for interpreting topography. Electrical contact is made with commercial Si{sub 3}N{sub 4} AFM tips coated with Au, Ag, W, or Au-Pd. Voltages ranging from 100 mV to 10 volts are applied to the tip and the metal substrate is grounded through an electrometer to measure the resulting current. The tips are mounted in a commercial AFM (Digital Instruments Nanoscope III); topographical and current scans are acquired simultaneously in the contact mode. Freshly grown, 300-nm thick, polytetrafluoroethylene (PTFE) films on stainless steel substrates yield no measurable current. Thinner films or those exposed to mechanical abrasion exhibit numerous patches with two current levels-sub {mu}A and > {mu}A signals - which often correlate with topography. We interpret these signals and discuss possible applications to thin film characterization and tribology.

Hipps, K.; Dickinson, J.T.; Jensen, L.C. [Washington State Univ., Pullman, WA (United States)

1995-12-01

240

Laboratory derived constraints on electrical conductivity beneath Slave craton  

NASA Astrophysics Data System (ADS)

The depth profile of the electrical conductivity, ?(d), beneath the Central Slave craton (Canada) has been reconstructed with the help of laboratory measurements carried out on peridotite xenoliths. ?(T) of xenoliths was determined in the piston-cylinder apparatus at 1 and 2 GPa and from 600 to 1150 °C. ?(T) of xenoliths follows the Arrhenius dependence with the activation energy, E, varying from 2.10 to 1.44 eV depending on temperature range and the Mg-number. The calculated xenolith geotherm and the suggested lithology beneath the Central Slave have been used to constrain ?(d) as follows: ?(d) in the crust varies between 0.5×10-5 and 10-3 S/m; the lithospheric ?(d) sharply decreases below the Moho at 39.4 km to 0.5×10-8 S/m, which corresponds to 460 °C, and then gradually increases with the depth d to 0.5×10-2 S/m. The modeled MT-response of the constrained ?(d) profile has been compared with MT-observations [Jones, A.G., Lezaeta, P., Ferguson, I.J., Chave, A.D., Evans, R.L., Garcia, X., Spratt J., 2003. The electrical structure of the Slave craton. Lithos, 71, 505-527]. The general trend of the calculated MT-response based on the ?(d) model mimics the MT-inversion of the field data from the Central Slave.

Bagdassarov, Nikolai S.; Kopylova, Maya G.; Eichert, Sandrine

2007-04-01

241

Electrical conduction and dielectric studies of ZnO pellets  

NASA Astrophysics Data System (ADS)

A series of Zinc Oxide pellets sintered at different temperatures was studied by means of dielectric spectroscopy in the wide frequency range of 1-106 Hz and temperature interval from -100 °C to 30 °C. Electrical conductivity was analysed using Jonsher's universal power law, and the values of s were found to decrease with the increase in temperature, which agrees well with the correlation barrier hopping (CBH) model. As the temperature increased, energy activation Edc became less than 0.39 eV and dc conductivity (?dc) values in the range of 1.9×10-14-9.7×10-10 ? m-1 were observed. The dielectric modulus showed ionic polarisation at the intermediate and high frequencies related to oxygen interstitial Oi, oxygen vacancy VO and Zinc interstitial Zni. At low frequency, it revealed a Maxwell-Wagner-Sillars relaxation with barrier heights of grain boundaries between 0.74 and 0.88 eV for all the studied pellets.

Chaari, Mariem; Matoussi, Adel

2012-09-01

242

The Deep Electrical Conductivity Structure of the Dead Sea Basin  

NASA Astrophysics Data System (ADS)

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.

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

2008-12-01

243

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

PubMed

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

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

2012-05-17

244

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

NASA Astrophysics Data System (ADS)

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.

Kole, Madhusree; Dey, T. K.

2013-02-01

245

High-pressure and high-temperature measurements of electrical conductivity in basaltic rocks from Mount Etna, Sicily, Italy  

NASA Astrophysics Data System (ADS)

We have investigated the electrical properties of Etnean rocks by in situ complex impedance spectroscopy using a multianvil apparatus. From these measurements we determined the electrical conductivity of a lava flow sample, whose basaltic composition can be considered close to that of the parent magma and also that of a mafic nodule representative of the high-density cumulates interpreted as responsible for the main high-velocity anomaly observed beneath the volcano. The electrical conductivities of the two samples were measured at pressures of 0.9 and 1.5 GPa and temperatures from 400 to 1100°C at frequencies from 0.1 to 105 Hz. To investigate the electrical properties of the Etnean products as a function of partial melting, a few experiments were performed in a piston-cylinder apparatus prior to the electrical measurements. The obtained data were approximated using an equivalent circuit fitting technique. For the lava flow sample, electrical conductivity displays Arrhenian behavior over the entire investigated temperature range, with an activation energy of ˜0.8 eV. Within the uncertainties of our measurements, we do not observe any effect of pressure on conductivity between 0.9 and 1.5 GPa. On the contrary, experiments performed on the series of partially molten samples indicate that conductivity increases with increasing quantity of glass. While conductivities of samples with minor amounts of glass are comparable to that of the lava flow starting material, with increased melting, conductivity can increase by as much as a factor of 3. The mafic nodule was observed to have a conductivity higher than the lava flow sample (e.g., at 800°C and 0.9 GPa, a factor of 4 higher). However, scatter in the data is somewhat higher in comparison to the lava flow sample, most likely because of the coarse texture of the samples and a consequence to their chemical and structural heterogeneity. Using our results, we illustrate the effects that a layer of hot magma surrounded by a cooler wall rock has on apparent resistivities determined by one-dimensional forward calculations. Our modeling demonstrates that both size and depth of magmatic intrusions strongly influence apparent resistivity and that these parameters can be extracted from field data if the electrical properties of the rocks below the surface are well understood.

Scarlato, Piergiorgio; Poe, Brent T.; Freda, Carmela; Gaeta, Mario

2004-02-01

246

The role of electronic and ionic conduction in the electrical conductivity of carbon fiber reinforced cement  

E-print Network

, the electrical con- ductivity allows applications such as electrical grounding, lightning protection, deicing, electromagnetic interference shielding and electrostatic discharge protection. Because of the attractive

Chung, Deborah D.L.

247

Capillary electrohydrostatics of conducting drops hanging from a nozzle in an electric field  

SciTech Connect

A hybrid boundary element/finite element method is used to determine the axisymmetric equilibrium shapes and stability of a conducting drop hanging from a nozzle of length H[sub 2] that is attached to the top plate of a parallel-plate capacitor. The finite element method is used to solve the Young-Laplace equation for drop shape and the boundary element method is used to solve an integral equation for the electric field distribution on the drop and solid surfaces. The new results suggest that immediately upon loss of equilibrium sonic pendant drops jet from their tips whereas others go unstable by ejecting annular jets from their periphery. The temporal evolution of the instability or jetting phenomena cannot of course be determined by the present static analysis. By repeatedly increasing the number of elements on drop surfaces, which would be prohibitively costly if the electric field were calculated by finite element or difference methods, the apparent cone angle at the tip of drops tending toward conical is determined. Although the apparent cone angle is a function of D, this angle is shown to lie between 40[degree] and 50[degree] when D = 0: it increases monotonically with nozzle length and is bound above by the Taylor limit of 49.3[degree]. Moreover, the variation of the critical field strength for instability [var epsilon], with plate spacing H and nozzle length H[sub 2] and the asymptotic values approached by [epsilon][sub c] as H and H[sub 2] grow without bound are also evaluated. These results are of primary importance in capillary electrohydrostatics and in the development and design of electrodispersion apparatus finding use in the production of ceramic precursor Powders and in chemical separations.

Harris, M.T.; Basaran, O.A. (Oak Ridge National Lab., TN (United States))

1993-12-01

248

Optically transparent and electrically conducting epitaxial Ta2O films  

NASA Astrophysics Data System (ADS)

An optically transparent and electrically conducting oxide Ta2O epitaxial thin film has been fabricated and characterized. In our experiments, we grew epitaxial Ta films on r-cut sapphire crystal substrates, which were subsequently oxidized into Ta2O films. The x-ray ?-2? scan peaks match the American Society for Testing and Materials x-ray powder data card for Ta2O (18-1302) with a cubic structure. The x-ray photoelectron spectroscopic measurements indicated Ta 4f peak energy values between those for Ta and TaO whereas the O /Ta atomic ratio is between 0.5 and 1. Resistivity-temperature measurements showed a metallic behavior with resistivity values in the range of (1.5-3.3)×10-4?cm at 293K. Optical measurements on 25-100nm thick films indicated that they are transparent in the range of 400-2000nm and have an energy band gap between 2.04 and 2.17eV. The Hall mobility and carrier density of the films were in the range of 62-110cm2V-1s-1 and (1.9-3.0)×1020cm-3, respectively.

Gnanarajan, S.; Lam, S. K. H.; Foley, C. P.

2007-03-01

249

Electrical conductivity measurements of strongly coupled W plasmas  

NASA Astrophysics Data System (ADS)

Nonideal plasmas of tungsten were produced by vaporizing thin wires of 0.1 mm and 0.3 mm in diameter in small glass capillaries (in air) by means of a short-pulse current from an electrical discharge. For a short period of time, the inner wall of the rigid glass capillary confines the plasma until the induced pressure shock wave disintegrates the capillary. Spectroscopic measurements were carried out on the ejected plasma close to the end of the capillary. The plasma temperature was obtained by fitting a Planck function to the measured continuum spectrum. The resistance was derived from the voltage across the plasma and the current through the plasma. The plasma radius was determined with an intensified charge-coupled device camera and a streak camera and allowed the derivation of the conductivity. Particle densities were of the order of 1022 particle/cm3 and electron temperatures were in the range from 10 kK to 22 kK. These measurements are compared with theoretical models and previous work.

Saleem, S.; Haun, J.; Kunze, H.-J.

2001-11-01

250

Electrical Conductivity Measurements in Strongly Coupled Metal Plasmas  

NASA Astrophysics Data System (ADS)

The coupling parameter ?=e^2/akT, where a is the mean ion-ion separation, expresses the ratio of the mean potential energy of ions in a plasma to their mean kinetic energy. Plasma is said to be strongly coupled when ? is greater than unity. Transport properties of strongly coupled plasmas are of interest in the study of the structure of dense astrophysical objects and gaseous planetary interiors, as well as in arcs and laser-produced plasmas. We are attempting to measure the electrical conductivity of strongly coupled metal plasmas (copper, tungsten and aluminum) in the temperature range 8-30 kK, in a density range from about 1/2 solid density down to about 10-3 times solid density. They may have coupling parameters ? ranging from as high as 100 down to unity Plasmas are created by rapid vaporization of metal wire in a glass capillary or in a water bath which act as a tamper, slowing the expansion rate. The effect of the tamper is to force the interior pressure of the plasma to be fairly uniform. Streak photography serves to determine the growth of the plasma radius in time, allowing determination of mean density. Temperature is deduced from the measured energy input in conjunction with an equation of state from the LANL sesame database(SESAME: The Los Alamos National Laboratory Equation of State Database, Report No. LA-UR-92-3407, Ed. S. P. Lyon and J. D. Johnson, Group T-1 (unpublished)), and a brightness temperature may be obtained from radiation measurements. The column resistance is simply determined from time-resolved voltage and current measurements. For temperatures less than about 14,000K, as density decreases from the highest values measured, the conductivity falls roughly as the cube of density, reaches a minimum, and subsequently rises to approach the Spitzer prediction at low density. The rate of change of conductivity with density becomes less rapid as temperature increases, and the minimum becomes less pronounced, disappearing altogether above about 20,000K. These results are compared with several theoretical predictions.

Desilva, Alan

1998-11-01

251

Analytic electrical-conductivity tensor of a nondegenerate Lorentz plasma.  

PubMed

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

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

2002-10-01

252

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

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

253

IMAGING OF ELECTRODE MOVEMENT AND CONDUCTIVITY CHANGE IN ELECTRICAL IMPEDANCE TOMOGRAPHY  

E-print Network

IMAGING OF ELECTRODE MOVEMENT AND CONDUCTIVITY CHANGE IN ELECTRICAL IMPEDANCE TOMOGRAPHY Camille G-mail: adler@site.uottawa.ca Abstract Electrical Impedance Tomography (EIT) applies and measures elec- trical in conductivity image re- constructions. Keywords-- Electrical impedance tomography; inverse problems

Adler, Andy

254

Finite-element analysis of the electric field distribution in conductance cell  

Microsoft Academic Search

The finite-element method (FEM) for the modeling of the electric field distribution in impedance cells designed according to the assumptions of the van der Pauw method of electrical conductivity (specific conductance) measurement has been used. Particularly, the effect of electrode-electrolyte solution interface (EESI) on the electric field distribution has been studied. It has been found that the EESI of current

Zdzislaw Szczepanik; Zbigniew Rucki; Zbigniew Moron

2003-01-01

255

Hygrothermal Stability of Electrical Contacts Made from Silver and Graphite Electrically Conductive Pastes  

NASA Astrophysics Data System (ADS)

The hygrothermal stability of electrical contacts made from silver and graphite electrically conductive pastes is comparatively evaluated by measurement of the increase in contact electrical resistance during immersion in water at 15°C and 40°C. The pastes are silver paint, silver paint with a nonconductive epoxy overcoat, silver epoxy, and graphite colloid. Each electrical contact is made between a seven-strand tin-coated copper wire and the surface of a carbon fiber epoxy-matrix composite. Silver paint and graphite colloid penetrate the spaces among the 130-?m-diameter strands, but silver epoxy does not. Partly due to its low penetrability and the silver flake (15 ?m) preferred orientation, silver epoxy gives contacts of significantly higher resistance than silver paint. Graphite colloid is comparable to silver epoxy in the resistance. Among the four pastes, silver paint with an epoxy overcoat is most durable, though it gives slightly higher resistance than silver paint without epoxy. Silver epoxy is less durable than silver paint without an epoxy overcoat, particularly at 40°C, due to the low hygrothermal stability of epoxy. Graphite colloid is even less durable than silver epoxy, due to its being water based.

Wang, Shoukai; Pang, Dick S.; Chung, D. D. L.

2007-01-01

256

Materials and methods for autonomous restoration of electrical conductivity  

DOEpatents

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.

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

257

LETTER doi:10.1038/nature11031 Thermal and electrical conductivity of iron at Earth's  

E-print Network

LETTER doi:10.1038/nature11031 Thermal and electrical conductivity of iron at Earth's core and theoretical difficulties. Here we use density functional theory to compute these conductivities in liquid iron of the electrical and thermal conductivity (k) of iron at Earth

Alfè, Dario

258

Magnetic resonance electrical impedance tomography (MREIT) for high-resolution conductivity imaging  

Microsoft Academic Search

Cross-sectional imaging of an electrical conductivity distribution inside the human body has been an active research goal in impedance imaging. By injecting current into an electrically conducting object through surface electrodes, we induce current density and voltage distributions. Based on the fact that these are determined by the conductivity distribution as well as the geometry of the object and the

Eung Je Woo; Jin Keun Seo

2008-01-01

259

EOSC 252 Assignment 2 Effective Electrical Conductivity of Rocks  

E-print Network

data are important for the interpretation of natural electromagnetic induction in the seafloor from as artificial sources of electromagnetic induction. Electrical resistivity studies are used widely to prospect

Jellinek, Mark

260

High thermal conductivity connector having high electrical isolation  

DOEpatents

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.

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

1995-01-01

261

Electrical conductivity and density of state of boron nitride nanotubes due to electronic correlation  

NASA Astrophysics Data System (ADS)

The temperature behavior of electrical conductivity of boron nitride nanotubes (6, 0) in the context of Hubbard model at the paramagnetic sector. The effect of electronic correlation on the energy gap of boron nitride nanotube (BNNT) is investigated. Interacting electronic Green's function matrix has been found within GW approximation. Using Kubo formula, electrical conductivity of the system has been calculated. The results show that the band gap in the density of state decreases with Coulomb repulsion strength. Moreover, the increase of electronic correlation leads to decrease electrical conductivity of BNNT. Also the electrical conductivity shows an exponential behavior in terms of temperature at all the values of electron-electron interaction parameter.

Rezania, H.

2014-07-01

262

Evaluation of saline tracer performance during electrical conductivity groundwater monitoring  

NASA Astrophysics Data System (ADS)

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.

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

2011-04-01

263

Study of electrical conductivity response upon formation of ice and gas hydrates from salt solutions by a second generation high pressure electrical conductivity probe  

NASA Astrophysics Data System (ADS)

We recently reported the development of a high pressure electrical conductivity probe (HP-ECP) for experimental studies of formation of gas hydrates from electrolytes. The onset of the formation of methane-propane mixed gas hydrate from salt solutions was marked by a temporary upward spike in the electrical conductivity. To further understand hydrate formation a second generation of window-less HP-ECP (MkII), which has a much smaller heat capacity than the earlier version and allows access to faster cooling rates, has been constructed. Using the HP-ECP (MkII) the electrical conductivity signal responses of NaCl solutions upon the formation of ice, tetrahydrofuran hydrates, and methane-propane mixed gas hydrate has been measured. The concentration range of the NaCl solutions was from 1 mM to 3M and the driving AC frequency range was from 25 Hz to 5 kHz. This data has been used to construct an "electrical conductivity response phase diagrams" that summarize the electrical conductivity response signal upon solid formation in these systems. The general trend is that gas hydrate formation is marked by an upward spike in the conductivity at high concentrations and by a drop at low concentrations. This work shows that HP-ECP can be applied in automated measurements of hydrate formation probability distributions of optically opaque samples using the conductivity response signals as a trigger.

Sowa, Barbara; Zhang, Xue Hua; Kozielski, Karen A.; Dunstan, Dave E.; Hartley, Patrick G.; Maeda, Nobuo

2014-11-01

264

Study of electrical conductivity response upon formation of ice and gas hydrates from salt solutions by a second generation high pressure electrical conductivity probe.  

PubMed

We recently reported the development of a high pressure electrical conductivity probe (HP-ECP) for experimental studies of formation of gas hydrates from electrolytes. The onset of the formation of methane-propane mixed gas hydrate from salt solutions was marked by a temporary upward spike in the electrical conductivity. To further understand hydrate formation a second generation of window-less HP-ECP (MkII), which has a much smaller heat capacity than the earlier version and allows access to faster cooling rates, has been constructed. Using the HP-ECP (MkII) the electrical conductivity signal responses of NaCl solutions upon the formation of ice, tetrahydrofuran hydrates, and methane-propane mixed gas hydrate has been measured. The concentration range of the NaCl solutions was from 1 mM to 3M and the driving AC frequency range was from 25 Hz to 5 kHz. This data has been used to construct an "electrical conductivity response phase diagrams" that summarize the electrical conductivity response signal upon solid formation in these systems. The general trend is that gas hydrate formation is marked by an upward spike in the conductivity at high concentrations and by a drop at low concentrations. This work shows that HP-ECP can be applied in automated measurements of hydrate formation probability distributions of optically opaque samples using the conductivity response signals as a trigger. PMID:25430143

Sowa, Barbara; Zhang, Xue Hua; Kozielski, Karen A; Dunstan, Dave E; Hartley, Patrick G; Maeda, Nobuo

2014-11-01

265

Electric field studies: TLE-induced waveforms and ground conductivity impact on electric field propagation  

NASA Astrophysics Data System (ADS)

We review in this paper main results obtained from electric field (from VLF to HF) measurement campaigns realized by CEA in the framework of the Eurosprite program [Neubert et al., 2005, 2008] from 2003 to 2009 in France in different configurations. Two main topics have been studied: sprite or elve induced phenomena (radiation or perturbation) and wave propagation. Using a network of 4 stations, VLF radiations from sprite have been successfully located at 10 km from the sprite parent lightning, in agreement with possible sprite location, generally displaced from the parent lightning. The MF (300 kHz - 3 MHz) source bursts were identified simultaneously with the occurrence of sprites observed with cameras [Farges et al., 2004; Neubert et al., 2008]. These observations are compared to recent broadband measurements, assumed to be due to relativistic electron beam radiation related to sprites [Fullekrug et al., 2009]. Recently, in 2009, with a new instrumentation, an ELF tail has been clearly measured after the lightning waveform, while sprites were observed at about 500 km from our station. This ELF tail is usually observed at distances higher than thousand km and is associated to sprite generation. This opens the capacity to measure the charge moment of the parent-lightning, using such measurement close to the source. Farges et al. [2007] showed that just after a lightning return stroke, a strong transient attenuation is very frequently observed in the MF waves of radio transmissions. They showed that this perturbation is due to heating of the lower ionosphere by the lightning-induced EMP during few milliseconds. These perturbations are then the MF radio signature of the lightning EMP effects on the lower ionosphere, in the same way as elves correspond to their optical signature. The experiment also provided the electric field waveforms directly associated to elves, while lightning were not detected by Météorage. Many of them present a double peak feature. The propagation of the electromagnetic waves generated by lightning has also been studied in the frequency range 1 kHz-1MHz at distances lower than 1000 km from the lightning source. A propagation model has been developed to determine the ground waves which propagate in a homogenous medium using the analytical expression given by Maclean and Wu [1993]. This approach takes into account the electric finite conductivity and the fact that the Earth is spherical, which allow us to deal with over-the-horizon propagation. We installed in 2008 four stations which were more or less aligned - the maximum distance between two stations was about 870 km. Two stations were located close to the Mediterranean Sea and the two others inside the continent, at the centre of France. This station distribution and the observation period (from August to December) allowed statistical and physical studies, such as the influence of the electric conductivity on wave propagation. Comparison of electric field spectra, measured after propagation only over sea and only over ground, showed clearly the effects of ground conductivity on propagation. Comparison between observations and modelling has been used to evaluate the ground conductivity. In the future we will implement the sky-wave inside our model and validate it with the database.

Farges, Thomas; Garcia, Geraldine; Blanc, Elisabeth

2010-05-01

266

Thermal transporting properties of electrically conductive polyaniline films as organic thermoelectric materials  

Microsoft Academic Search

Thermal transporting properties of electrically conductive polyaniline films were first investigated in wide range of temperatures\\u000a above room temperature as organic thermoelectric materials. Thermal conductivities of various protonic acid-doped polyaniline\\u000a films were measured by combination of a laser flash method and a differential scanning calorimeter in relation with electrical\\u000a conductivity and a kind of dopant. The thermal conductivities thus measured

Hu Yan; Norina Sada; Naoki Toshima

2002-01-01

267

Physical modeling of electrical conduction in printed circuit board insulation  

E-print Network

This thesis is concerned with understanding the degradation of electrical and electronic components in automobiles due to environmental effects. A special emphasis is placed on understanding the physical processes underlying ...

Sarathy, Vasanth

2005-01-01

268

Control of electrical conduction in DNA using oxygen hole doping  

Microsoft Academic Search

Using oxygen adsorption experiments on poly (dG)-poly (dC) DNA molecules, we found that their conductance can be easily controlled by several orders of magnitudes using oxygen hole doping, which is a characteristic behavior of a p-type semiconductor. It also suggests that the conductance of the DNA under doping results from charge carrier transport, not from an ionic conduction. On the

Hea-Yeon Lee; Hidekazu Tanaka; Yoichi Otsuka; Kyung-Hwa Yoo; Jeong-O. Lee; Tomoji Kawai

2002-01-01

269

Role of black carbon electrical conductivity in mediating hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) transformation on carbon surfaces by sulfides.  

PubMed

Recent research has demonstrated that black carbons catalyze the transformation of a range of nitrated explosives sorbed to the carbon surfaces in the presence of sulfides. Although surface oxygenated functional groups, particularly quinones, and electrical conductivity have both been hypothesized to promote these reactions, the importance of these properties has not been tested. In this work, the importance of electrical conductivity was addressed by producing chars of increasing electrical conductivity via pyrolysis of wood shavings at increasing temperature. The reactivity of chars with respect to transformation of the explosive RDX in the presence of sulfides correlated with electrical conductivity. Oxygenated functional groups were apparently not involved, as demonstrated by the elimination of reactivity of an activated carbon after ozone treatment or sorption of model quinones to the activated carbon surface. Although RDX transformation correlated with char electrical conductivity, no RDX transformation was observed when RDX was physically separated from sulfides but electrically connected through an electrochemical cell. RDX transformation occurred in the presence of a surface-associated sulfur species. The correlation with char electrical conductivity suggests that sulfides are oxidized on carbon surfaces to products that serve as potent nucleophiles promoting RDX transformation. PMID:23725551

Xu, Wenqing; Pignatello, Joseph J; Mitch, William A

2013-07-01

270

Phase Diagrams of Electric-Fduced Aggregation in Conducting Colloids  

NASA Technical Reports Server (NTRS)

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.

Khusid, B.; Acrivos, A.

1999-01-01

271

Combining Proximal and Penetrating Soil Electrical Conductivity Sensors for High Resolution Digital Soil Mapping  

Technology Transfer Automated Retrieval System (TEKTRAN)

Proximal ground conductivity sensors produce high spatial resolution maps that integrate the bulk electrical conductivity (ECa) of the soil profile. Variability in conductivity maps must either be inverted to profile conductivity, or be directly calibrated to profile properties for meaningful interp...

272

The Electrical Conductivity Of Partly Ionized Helium Plasma  

SciTech Connect

In this paper we analyzed atoms influence on electro conductivity, partially ionized helium plasma, in temperature region 5 000 K - 40 000 K and pressure 0.1 - 10 atm. Electro conductivity was calculated using 'Frost like' formula and Random Phase Approximation method and Semi-Classical (SC) approximation.

Sreckovic, Vladimir A.; Ignjatovic, Ljubinko; Mihajlov, A. A. [Institute of Physics, PO Box 57, 11001 Belgrade (Serbia and Montenegro)

2007-04-23

273

Preparation of Electrically Conductive Polystyrene/Carbon Nanofiber Nanocomposite Films  

ERIC Educational Resources Information Center

A simple and effective approach to prepare conductive polystyrene/carbon nanofiber (PS/CNF) nanocomposite films via a solution dispersion method is presented. Inexpensive CNF, which has a structure similar to multi-walled carbon nanotubes, is chosen as a nanofiller in this experiment to achieve conductivity in PS films. A good dispersion is…

Sun, Luyi; O'Reilly, Jonathan Y.; Tien, Chi-Wei; Sue, Hung-Jue

2008-01-01

274

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

Microsoft Academic Search

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

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

2008-01-01

275

Thermal and electrical conduction in the compaction direction of exfoliated graphite  

E-print Network

Thermal and electrical conduction in the compaction direction of exfoliated graphite of the compaction and graphite layer preferred orientation on the thermal and electrical conductions in the compaction direction of graphite-flake-based exfoliated graphite have been decoupled. The compact

Chung, Deborah D.L.

276

Electrical conductivity and dielectric properties of PMMA\\/expanded graphite composites  

Microsoft Academic Search

PMMA\\/expanded graphite (EG) composites were prepared by direct solution blending of PMMA with the expanded graphite filler. Electrical conductivity and dielectric properties of the composites were measured by a four-point probe resistivity determiner and a dielectric analyzer (DEA). Interestingly, only 1 wt.% filler content was required to reach the percolation threshold (?) of transition in electrical conductivity from an insulator

Wenge Zheng; Shing-Chung Wong

2003-01-01

277

Humic substances mineralization: the variation of pH, electrical conductivity and optical density  

Microsoft Academic Search

Humic substances mineralization: the variation of pH, electrical conductivity and optical density. The variation of pH, electrical conductivity and optical density was described during the mineralization of humic substances (humic acid: HA and fulvic acid: FA) extracted from different sources: sediment, dissolved organic matter from 120 days of decomposition of aquatic macrophytes (Scirpus cubensis and Cabomba piauhyensis) and from water

Rodovia Washington Luis

278

Imparting Electrical Conductivity into Asphalt Composites Using Graphite  

E-print Network

different types of graphite having different particle shapes and sizes are selected to investigate their effect on conductivity control. The volume resistivity of the asphalt mastic specimens containing various concentrations of graphite is evaluated...

Baranikumar, Aishwarya

2013-07-09

279

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

PubMed Central

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

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

2011-01-01

280

Different Clinical Electrodes Achieve Similar Electrical Nerve Conduction Block  

PubMed Central

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

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

2015-01-01

281

Electrical conductivity of cobalt-titanium substituted SrCaM hexaferrites  

NASA Astrophysics Data System (ADS)

A series of polycrystalline M-type hexagonal ferrites with the composition Sr0.5Ca0.5CoxTixFe12-2xO19 (where x=0.0-0.8) were prepared by the conventional ceramic technique. The electrical conductivity has been measured from 300 to 590 K. The dc conductivity, ?dc, exhibited a semiconductor behavior. The negative sign of thermoelectric power coefficient S reveals that all samples are n-type semiconductors. Both ?dc and mobility, ?d, increases with the substitution of Co2+ and Ti4+ ions, reach maximum at x=0.4 and start decreasing at x>0.4. Many conduction mechanisms were discussed to explain the electric conduction in the system. It was found that the hopping conduction is the predominant conduction mechanism. For samples with compositional parameter x=0.0 and 0.8, the band conduction mechanism shares in electric conduction beside the hopping process.

Eraky, M. R.

2012-03-01

282

A variety of finite difference methods to the thermistor with a new modified electrical conductivity  

Microsoft Academic Search

We consider the numerical solution of a one-dimensional thermistor (thermo-electric) problem with a new modified step function electrical conductivity which is an inherently non-linear function of the temperature. A variety of finite difference methods are applied to solve the problem using a new modification of the step function electrical conductivity to be satisfied the physical phenomena of the problem.

S. Kutluay; A. R. Bahadir; A. Özdes

1999-01-01

283

Highly Electrically Conductive Nanocomposites Based on PolymerInfused Graphene Sponges  

PubMed Central

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

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

2014-01-01

284

Highly Electrically Conductive Nanocomposites Based on PolymerInfused Graphene Sponges  

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

285

Highly electrically conductive nanocomposites based on polymer-infused graphene sponges.  

PubMed

Conductive polymer composites require a three-dimensional 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 vacuum-assisted 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 GS/epoxy composites prepared display consistent isotropic electrical conductivity around 1 S/m, and it is found to be close to that of the pristine GS. Compared with neat epoxy, GS/epoxy has a 12-orders-of-magnitude 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

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

2014-01-01

286

Doping dependence of electrical and thermal conductivity of nanoscale polyaniline thin films  

NASA Astrophysics Data System (ADS)

We performed simultaneous characterization of electrical and thermal conductivity of 55 nm thick polyaniline (PANI) thin films doped with different levels of camphor sulfonic acids (CSAs). The effect of the doping level is more pronounced on electrical conductivity than on thermal conductivity of PANIs, thereby greatly affecting their ratio that determines the thermoelectric efficiency. At the 60% (the molar ratio of CSA to phenyl-N repeat unit of PANI) doping level, PANI exhibited the maximum electrical and thermal conductivity due to the formation of mostly delocalized structures. Whereas polarons are the charge carriers responsible for the electrical conduction, phonons are believed to play a dominant role in the heat conduction in nanoscale doped PANI thin films.

Jin, Jiezhu; Wang, Qing; Haque, M. A.

2010-05-01

287

Electrical conductivity imaging using gradient B\\/sub z\\/ decomposition algorithm in magnetic resonance electrical impedance tomography (MREIT)  

Microsoft Academic Search

In magnetic resonance electrical impedance tomography (MREIT), we try to visualize cross-sectional conductivity (or resistivity) images of a subject. We inject electrical currents into the subject through surface electrodes and measure the z component Bz of the induced internal magnetic flux density using an MRI scanner. Here, z is the direction of the main magnetic field of the MRI scanner.

Ohin Kwon; Eung Je Woo; Jin Keun Seo

2004-01-01

288

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

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

289

Electrical Characterization and Morphological Studies of Conducting Polymer Nanofibers  

NASA Technical Reports Server (NTRS)

Doped polyaniline blended with poly(ethylene oxide) has been electrospun in air to give fibers with diameters in the range 3 nm 200 nm. These fibers were captured on wafers of degenerately doped Si/SiO2 by placing the wafer in the path of the fiber jet formed during the electrospinning process. Individual fibers were contacted using shadow mask evaporation and were also captured on prepatterned wafers. Fibers having diameters greater than 100 nm show a slight increase in the conductivity as compared to the bulk film, while fibers with diameters less than 30 nm had lower conductivity than the bulk. Data on Scanning Conductance Microscopy along the length of individual fibers will be presented. For fibers where the diameter was not uniform, we found that below a certain diameter ( approx.15 nm) the fiber was less conducting as compared to thicker diameter fibers. Dependence of the fiber conductivity on a gate bias is underway and these results will also be presented.

Pinto, N. J.; Zhou, Y. X.; Freitag, M.; Johnson, A. T.; MacDiarmid, A. G.; Mueller, C. H.; Theofylaktos, N.; Robinson, D. C.; Miranda, F. A.

2003-01-01

290

Electrical conductivity of rubidium and cesium salts of heteropoly acids  

SciTech Connect

The conductivity of solid heteropoly compounds with the formulas A/sub 3/PM/sub 12/O/sub 40/ .nH/sub 2/O and A/sub 2/HPM/sub 12/O/sub 40/ .nH/sub 2/O, where A=Rb, Cs, and M=Mo, W, is determined by measuring the electrochemical impedance at frequencies ranging from 0.1 to 100 KHz. The salts of heteropoly acids, and in particular the salts of Cs and Rb, are of interest because of their proton conductivity. The amount of Cs and Rb was determined gravimetrically in the form of the tetraphenylborates, following the preliminary dissolution of a weighed sample with gentle heating in a dilute NaOH solution. The authors conclude from this work that the conductivities of the di- and trisubstituted salts of the heteropoly acids are of the same order of magnitude.

Leonova, L.S.; Korosteleva, A.I.; Kovalenko, V.I.; Ukshe, E.A.

1985-06-01

291

Electrical conductivity and Seebeck coefficient of (La, Ca) (Cr, Co)O 3  

Microsoft Academic Search

Electrical conductivity and Seebeck coefficients of (La, Ca) (Cr, Co)O3 were measured as a function of temperature. The electrical conductivity as measured in air from 100 to 1100 °C increased with increasing Co and Ca content. The Seebeck coefficients were positive, indicating p-type conductivity. The substitution of Co for Cr significantly decreased the Seebeck coefficients, indicating that the substitution resulted

R. Koc; H. U. Anderson

1992-01-01

292

Demonstration of the Electrical Conductivity Jump Produced by the Olivine-Spinel Transition  

Microsoft Academic Search

The electrical conductivity of both the olivine and spinel polymorphs of Fe2SiO, has been determined at 300 to 1200øK and at 31 to 62 kb by means of a tetrahedral anvil-type high-pressure apparatus. It is established that the olivine-spinel transition is responsible for the discontinuous change in the electrical conductivity of Fe2SiO, the conductivity jump at the time of the

Syun-Iti Akimoto; Hideyuki Fujisawa

1965-01-01

293

Influence of Humidity on the Electrical Conductivity of Synthesized DNA Film on Nanogap Electrode  

Microsoft Academic Search

We have studied the electrical conductivity of DNA film using nanogap electrodes. Current-voltage measurements and alternating current measurements were performed for analysis of conductivity. The electrical conductivity of the DNA films of poly(dG)\\\\cdotpoly(dC) are found to depend strongly on the humidity. The resistance of poly(dG)\\\\cdotpoly(dC) decreases dramatically with increasing relative humidity. The contact resistance between DNA film and Au electrodes

Yoichi Otsuka; Hea-yeon Lee; Jian-hua Gu; Jeong-O Lee; Kyung-Hwa Yoo; Hidekazu Tanaka; Hitoshi Tabata; Tomoji Kawai

2002-01-01

294

Electrically Conductive Bulk Composites through a Contact-Connected Aggregate  

PubMed Central

This paper introduces a concept that allows the creation of low-resistance composites using a network of compliant conductive aggregate units, connected through contact, embedded within the composite. Due to the straight-forward fabrication method of the aggregate, conductive composites can be created in nearly arbitrary shapes and sizes, with a lower bound near the length scale of the conductive cell used in the aggregate. The described instantiation involves aggregate cells that are approximately spherical copper coils-of-coils within a polymeric matrix, but the concept can be implemented with a wide range of conductor elements, cell geometries, and matrix materials due to its lack of reliance on specific material chemistries. The aggregate cell network provides a conductive pathway that can have orders of magnitude lower resistance than that of the matrix material - from 1012 ohm-cm (approx.) for pure silicone rubber to as low as 1 ohm-cm for the silicone/copper composite at room temperature for the presented example. After describing the basic concept and key factors involved in its success, three methods of implementing the aggregate into a matrix are then addressed – unjammed packing, jammed packing, and pre-stressed jammed packing – with an analysis of the tradeoffs between increased stiffness and improved resistivity. PMID:24349239

Nawroj, Ahsan I.; Swensen, John P.; Dollar, Aaron M.

2013-01-01

295

Electrically-conductive Low-Permeability Pressure Seal  

NASA Technical Reports Server (NTRS)

Metal-plated butyl rubber seal has been devised for enclosures of electronic equipment that must be maintained under dry, inert atmosphere. Seal prevents gas leakage over prolonged periods, while conductivity suppresses electromagnetic emissions from sealed equipment. Seal is formed by depositing aluminum or gold onto molded-in-place butyl rubber gasket and surrounding areas of flange.

Krieg, H. C.

1982-01-01

296

Detecting Water Stress in Trees Using Stem Electrical Conductivity Measurements  

Microsoft Academic Search

Using time domain refl ectometry (TDR), we studied stem water content (?stem), stem elec- trical conductivity (?stem), and their ratio for 220 d in stressed, installation-cured, living trees of four species. Lysimeter-grown mango (Mangifera indica L.), banana (Musa acuminata Colla), date (Phoenix dactylifera L.), and olive (Olea europaea L.) were subjected to several types of mild (intensity and duration) water

Arie Nadler; Eran Raveh; Uri Yermiyahu; Marcos Lado; Ahmed Nasser; Mordechai Barak; Steve Green

2008-01-01

297

Electrical Conductivity Images of South African Continental Collision Zones  

NASA Astrophysics Data System (ADS)

Within the framework of the German-South African geo-scientific research initiative Inkaba yeAfrica several magnetotelluric (MT) field experiments were conducted along the Agulhas-Karoo transect in South Africa. This 600km long transect is designed to cross the Cape Fold Belt, the Namaqua-Natal Mobile Belt (NNMB), the Karoo Basin and the transition into the Kaapvaal Craton. At the same time, the transect crosses the Beattie Magnetic Anomaly and the Southern Cape Conductive Belt, two of Earth's largest continental geophysical anomalies. In this presentation we will focus on the ~ 1.2-1.0 Ga old convergent margin represented by the Kaapvaal craton-bounding Proterozoic Namaqua-Natal orogenic belt. Along the northernmost segment of the transect, we deployed over 120 MT sites along the 250km profile with a site spacing of 2-4km. With our experiment we focussed on a high-resolution image of the Mobile Belt-Craton transition on lithospheric scale. The MT data show a predominantly 2D behaviour; however, some sites show strong 3D effects, which are consistently observed over a 15km long segment. Anisotropic and 3D modelling studies show that these effects are caused by the unique setting of the extremely resistive rocks of the Kaapvaal Craton in combination with very conductive shallow structures. 2D- and 3D inversion results exhibit a shallow conductivity anomaly: a sub-horizontal, high conductivity band in the upper 5km of the NNMB. In view of other MT data collected in the area, we can map this anomaly over an area of 400km2. Based on deep borehole information, we are able to correlate the conductive band with the black shale and pyrite rich Whitehill formation within the Karoo basin, which seems to wedge out in vicinity of the Craton transition. In mid to lower crustal levels, the MT models show the transition from the untypically conductive rocks of the Proterozoic mobile belt and the extremely resistive rocks of the Kaapvaal Craton.

Weckmann, U.; Ritter, O.; Becken, M.; Pek, J.; de Wit, M.

2008-12-01

298

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

299

In situ network structure, electrical and thermal properties of conductive epoxy resin–carbon black composites for electrical heater applications  

Microsoft Academic Search

Epoxy composites at high carbon black (CB) concentration exhibited good electrical and thermal stability, which can make them attractive for consideration in heating devices and conducting composite applications. The effect of CB on the network structure of epoxy composites, like volume fraction of epoxy network (Vr), the extent of CB reinforcing (?), interparticle distance between conductive particles (IPD), epoxy–solvent interaction

F El-Tantawy; K Kamada; H Ohnabe

2002-01-01

300

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

Microsoft Academic Search

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

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

2010-01-01

301

Transparent electrically conducting thin films for spacecraft temperature control applications  

NASA Technical Reports Server (NTRS)

Thin transparent films of In2O3 or In2O3 + SnO2 prepared by evaporation or sputtering have been tested for use as surface layers for spacecraft temperature control coatings. The films are intended to prevent nonuniform electric charge buildup on the spacecraft exterior. Film thicknesses of 300 to 500 A were found to be optimal in terms of durability and minimum impact on the solar absorptance and the thermal emissivity of the underlayers. As a verification of their suitability for long-duration space missions, the films were subjected to simulated solar UV plus proton irradiation in a vacuum.

Hass, G.; Heaney, J. B.; Toft, A. R.

1979-01-01

302

Electrical conductivity of single organic molecules in ultra high vacuum  

NASA Astrophysics Data System (ADS)

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.

Pires, Ellis John

303

Poole-Frenkel conduction in high alternating electric fields  

Microsoft Academic Search

Measurements are reported for the first time of electronic conduction in silicon monoxide films under alternating fields of high amplitude-sufficiently high to cause a significant lowering of the coulombic barriers at donor-like sites in the material. This ac Poole-Frenkel effect has an entirely different dependence on temperature and frequency from the familiar dc effect and offers insight into the dynamics

A. K. Jonscher; C. K. Loh

1971-01-01

304

Magnetic pesonance imaging of electrical conductivity in the human brain  

Microsoft Academic Search

In this study, conductivity distribution of the human brain were obtained using 1.5 magnetic resonance (MR) imaging system. MR images were obtained with motion-probing gradients (MPGs) applied in three orthogonal directions at 25 equally spaced b factors from 200 to 5000 s\\/mm2. The b factor was defined as b = gamma2G 2delta2(Delta - delta\\/3), where gamma is the gyromagnetic ratio

M. Sekino; Y. Inoue; S. Ueno

2005-01-01

305

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

USGS Publications Warehouse

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.

McCleskey, R. Blaine

2011-01-01

306

Electrical conductivity anisotropy of natural deformed talc rocks and serpentinite at 3 GPa  

NASA Astrophysics Data System (ADS)

The electrical conductivity anisotropy of deformed natural talc rocks and serpentinite was investigated using an impedance analyzer in the frequency range 10-3-106 Hz along three directions: the direction parallel to lineation of oriented minerals (X direction), the direction perpendicular to lineation on the foliation plane (Y direction), and the direction perpendicular to the foliation (Z direction) at 3 GPa. The temperature ranges for the conductivity measurements were 500-1000 K for talc rock, and 500- 900K for serpentinite. The talc rock is composed of talc and the serpentinite is mainly composed of antigorite and a small amount of tremolite and ilmenite opaque mineral. For both rocks, the electrical conductivities parallel to the X direction and the Z direction are the highest and the lowest, respectively. The electrical conductivity anisotropy for the talc rocks is stronger than that for the serpentinite. Electrical conductivities of the serpentinite are higher than the talc rock. The electrical conductivities of talc and serpentinite sample with higher water content (>7 wt.%) are similar with hydrous olivine single crystal (water content about 177 ppm). The electrical conductivity increases in orders of talc, serpentine and brucite, indicating the dependence of the electrical conductivity on water content. The activation enthalpy of talc rock is the lowest (0.59 eV) in the X direction and the highest (0.68 eV) in the Z direction. The activation enthalpies of the serpentinite in different directions show the consistent value, 0.74 eV, for the experiments using Mo electrodes. In the case of using Ni electrodes, the activation enthalpies are 0.70 eV, 0.66 eV and 0.68 eV for the measurements in X, Y and Z direction respectively. The higher electrical conductivity and the lower activation enthalpy of the serpentine using Ni-NiO buffer are attributed to the higher fO2 of Ni-NiO buffer. The electrical conductivity anisotropy strongly depends on the crystal structure and orientation of minerals during deformation. Furthermore, grain interior conductivity, grain boundary conductivity (?gb) and electrode reaction can be recognized from the impedance arcs. Relationship between log?gb and reciprocal temperature shows the linear relationship as well as the grain interior conductivity. The total electrical conductivities are reduced by the grain boundary conductivities.

Guo, X.; Yoshino, T.; Yamazaki, D.; Katayama, I.

2010-12-01

307

Nanostructured Cu-Cr alloy with high strength and electrical conductivity  

SciTech Connect

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.

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

308

Tunable single-photon heat conduction in electrical circuits  

E-print Network

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.

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

2012-05-21

309

Electric conductivity of nanocluster polyoxomolybdates in the solid state and solutions  

NASA Astrophysics Data System (ADS)

The electric conductivity of nanocluster polyoxomolybdates (POMs) Mo132 and Mo72Fe30 with a keplerate structure in aqueous solutions, of these POMs in the solid state, and of Mo138 with a toroidal structure was studied. Data on the concentration dependence of the equivalent electric conductivity in solutions and on the specific conductivity of the solid samples were obtained. Solid Mo132 showed predominantly electron type of conductivity at nearly room temperatures due to the presence of molybdenum at different oxidation levels; Mo72Fe30, which has metal components at the highest oxidation levels, was found to be poor electric conductor; Mo138, which has a lower content of low-valence molybdenum than Mo132, showed intermediate conductivity and a reversible transition between the proton and electron types of conductivity.

Ostroushko, A. A.; Grzhegorzhevskii, K. V.

2014-06-01

310

Electrical and thermal conductivities of reduced graphene oxide/polystyrene composites  

NASA Astrophysics Data System (ADS)

The author reports an experimental study of electrical and thermal transport in reduced graphene oxide (RGO)/polystyrene (PS) composites. The electrical conductivity (?) of RGO/PS composites with different RGO concentrations at room temperature shows a percolation behavior with the percolation threshold of ˜0.25 vol. %. Their temperature-dependent electrical conductivity follows Efros-Shklovskii variable range hopping conduction in the temperature range of 30-300 K. The thermal conductivity (?) of composites is enhanced by ˜90% as the concentration is increased from 0 to 10 vol. %. The thermal conductivity of composites approximately linearly increases with increasing temperature from 150 to 300 K. Composites with a higher concentration show a stronger temperature dependence in the thermal conductivity.

Park, Wonjun; Hu, Jiuning; Jauregui, Luis A.; Ruan, Xiulin; Chen, Yong P.

2014-03-01

311

Iodine doped carbon nanotube cables exceeding specific electrical conductivity of metals  

PubMed Central

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

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

2011-01-01

312

An emulsion polymerization process for soluble and electrically conductive polyaniline  

SciTech Connect

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.

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

1998-07-01

313

Substituent effects on the electrical conductivities of the phenazine derivatives  

NASA Technical Reports Server (NTRS)

The and/or photoconductivities of 16 substituted phenazines having methoxy, hydroxy, chloro, nitro, amino or t-butyl group at 1-, 2-, 1, 6- or 2,7- positions of the phenazine ring measured by using the surface type cells. The energy gaps of the dark conductivities in the range 2.0 to 2.3 were independent of the kinds and the positions of the substituent groups, although the photo-absorption wavelength of the evaporated films changed with them. No correlation between photoconductivity and fluorescence was observed. The photocurrent was affected by the position of the substituents; namely, the photocurrents of the 1,6-di-substituted phenazines. When the substituent at 1,6-positions was hydroxy or amino group, however, the photocurrents decreased. The photocurrents decreased drastically in the presence of oxygen.

Sugimoto, A.; Furuyama, S.; Inoue, H.; Imoto, E.

1984-01-01

314

Improvement of Electrical Contact Reliability by Conductive Polymer Coated Elastomer Structure in Woven Electronic Textiles  

NASA Astrophysics Data System (ADS)

This article presents an improvement in the stability and durability of the electrical contacts employed in flexible devices. A coating of poly(3,4-ethylenedioxythiophene): poly(4-styrenesulfonate) in form of a solid conductive layer on a silicone elastomer structure is employed in creating an electrical circuit embedded into the fabric of a woven electronic textile, where the coating serves as an electrical contact between weft and warp ribbons. When the contact load increases to 1 mN, then, due to the flexibility of the structure, an electric current begins to flow through the circuit. The structure can sextuplicate the life of the electrical contact.

Yamashita, Takahiro; Takamatsu, Seiichi; Miyake, Koji; Itoh, Toshihiro

2012-12-01

315

Ab initio determination of electrical and thermal conductivity of liquid aluminum  

NASA Astrophysics Data System (ADS)

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 . The Lorentz number, defined as K/?T , where K is the thermal conductivity, ? is the electrical conductivity, and T is the temperature, is close to the ideal value of 2.44×10-8 for metals, and the Wiedemann-Franz law is verified.

Recoules, Vanina; Crocombette, Jean-Paul

2005-09-01

316

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

E-print Network

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...

Barziza, Daniel Eugene

1998-01-01

317

Exact Scaling Laws for Electrical Conductivity Properties of Nematic Polymer Nanocomposite Monodomains**  

E-print Network

Exact Scaling Laws for Electrical Conductivity Properties of Nematic Polymer Nanocomposite transition. Only as h2 ® 1 is perfect alignment achieved: a limit that is never approached in nanocomposites

Zhou, Ruhai

318

Enhanced Thermoelectric Efficiency via Orthogonal Electrical and Thermal Conductances in Phosphorene  

E-print Network

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. High ZT (>2) has been achieved in materials via all-scale hierarchical architecturing. This efficiency holds at high temperatures (700K~900K) but quickly diminishes at lower temperatures. 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 that phosphorene possesses spatially-anisotropic electrical and thermal conductances. The prominent electrical and thermal conducting directions are orthogonal to one another, enhancing the ratio of...

Fei, Ruixiang; Soklaski, Ryan; Yan, Jia-An; Lo, Cynthia; Yang, Li

2014-01-01

319

Measurement of the thermal properties of electrically conducting fluids using coated transient hot wires  

SciTech Connect

Measurements of fluid thermal properties using the transient hot-wire technique are described. When bare hot wires are used in electrically conducting fluids there are additional measurement uncertainties due to the formation of electric double layers on the surfaces of the wires and the cell wall. If the electrical conductivity of the fluid is large enough there is also significant power generation in the fluid. These measurement uncertainties can be eliminated by electrically insulating the hot wires with a thin film. The use of tantalum hot wires with an anodized layer of tantalum pentoxide is demonstrated with measurements on nonpolar argon and polar 1,1,1,2 tetrafluoroethane (R134a). Although coated tantalum hot wires have been used previously in a transient mode to measure the thermal conductivity of liquids, this work is the first demonstration of the use of coated wires to measure thermal conductivity in the liquid, vapor, and supercritical gas phases.

Perkins, R.A. [National Institute of Standards and Technology, Boulder, CO (United States)

1994-12-31

320

Measurement of the thermal properties of electrically conducting fluids using coated transient hot wires  

SciTech Connect

Measurements of fluid thermal properties using the transient hot-wire technique are described. When bare hot wires are used in electrically conducting fluids there are additional measurement uncertainties due to the formation of electric double layers on the surfaces of the wires and the cell wall. If the electrical conductivity of the fluid is large enough there is also significant power generation in the fluid. These measurement uncertainties can be eliminated by electrically insulating the hot wires with a thin film. The use of tantalum hot wires with an anodized layer of tantalum pentoxide is demonstrated with measurements on nonpolar argon and polar 1,1,1,2 tetrafluorethane (R134a). Although coated tantalum hot wires have been used previously in a transient mode to measure the thermal conductivity of liquids, this work is the first demonstration of the use of coated wires to measure thermal conductivity in the liquid, vapor, and supercritical gas phases.

Perkins, R.A. [National Inst. of Standards and Technology, Boulder, CO (United States). Thermophysics Div.

1994-09-01

321

Lunar temperature and global heat flux from laboratory electrical conductivity and lunar magnetometer data  

Microsoft Academic Search

Three-layer monotonic electrical conductivity models for the lunar interior to a depth of 600 km are used in conjunction with laboratory measurements of the electrical conductivity of olivine and pyroxene to estimate a temperature-depth profile. The temperatures calculated for depths of 400-600 km are consistent with attenuation of the seismic shear wave. The temperature calculated at a depth of 100-250

C. P. Sonett; A. Duba

1975-01-01

322

Temperature Dependence of Electrical Conduction in Pb(Zr,Ti)O3 Thin Films  

Microsoft Academic Search

The temperature dependence of electrical conduction in lead-zirconate-titanate (PZT) thin film about 470 nm thickness has been investigated. The conduction mechanism below 150 kV\\/cm is ohmic. For larger electric fields (> 150 kV\\/cm), it is found that the extracted dynamic dielectric constant is larger than the reported value if Poole-Frenkel emission method is assumed. While the extracted dynamic dielectric constant

T. K. Kundu; Joseph Ya-Min Lee

2005-01-01

323

Light transmissive electrically conductive oxide electrode formed in the presence of a stabilizing gas  

DOEpatents

A light transmissive, electrically conductive oxide is doped with a stabilizing gas such as H.sub.2 and H.sub.2 O. The oxide is formed by sputtering a light transmissive, electrically conductive oxide precursor onto a substrate at a temperature from 20.degree. C. to 300.degree. C. Sputtering occurs in a gaseous mixture including a sputtering gas and the stabilizing gas.

Tran, Nang T. (Cottage Grove, MN); Gilbert, James R. (Maplewood, MN)

1992-08-04

324

Electrical conductivity and equation of state measurements on planetary fluids at high pressures and temperatures  

SciTech Connect

Hugoniot equation-of-state, shock temperature, and electrical conductivity measurements are reported for fluids believed to be the primary constituents of the planets Uranus and Neptune. The equation-of-state results are compared with calculations performed using a statistical mechanical, chemical equilibrium computer code and electrical conductivities are discussed in terms of the recently measured magnetic field of Uranus. 4 refs., 2 figs., 1 tab.

Hamilton, D.C.; Nellis, W.J.; Holmes, N.C.; Radousky, H.B.; Ree, F.H.; Nicol, M.

1987-07-01

325

Electrical conductivity and Young's modulus of flexible nanocomposites made by metal-ion implantation  

E-print Network

Electrical conductivity and Young's modulus of flexible nanocomposites made by metal Abstract The mechanical and electrical properties of nanocomposites created by gold and titanium homogeneous amor- phous composite with the PDMS up to 18 nm thick. Using TEM micrographs, the metal volume

Lausanne, Ecole Polytechnique Fédérale de

326

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

E-print Network

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

Alpay, S. Pamir

327

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

Microsoft Academic Search

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

C. K. Wong; F. G. Shin

2005-01-01

328

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...

329

Electric Conduction in Solids: a Pedagogical Approach Supported by Laboratory Measurements and Computer Modelling Environments  

NASA Astrophysics Data System (ADS)

In this paper we present a pedagogic approach aimed at modeling electric conduction in semiconductors, built by using NetLogo, a programmable modeling environment for building and exploring multi-agent systems. `Virtual experiments' are implemented to confront predictions of different microscopic models with real measurements of electric properties of matter, such as resistivity. The relations between these electric properties and other physical variables, like temperature, are, then, analyzed.

Bonura, A.; Capizzo, M. C.; Fazio, C.; Guastella, I.

2008-05-01

330

Electrical Conductivity Response toward Ketone Vapors of Poly(Para-Phenylene Vinylene)/Zeolite Y Composites  

NASA Astrophysics Data System (ADS)

Investigation of the effect of 3 different types of cation types in Zeolite Y; Zeolite Y(Si/Al=5.1, Na+), Zeolite Y(Si/Al=5.1, NH3+), Zeolite Y(Si/Al=5.1, H+) on the electrical conductivity sensitivity when exposed to the 3 different types of ketone vapors (Acetone, Methyl Ethyl Ketone(MEK) and Methyl Iso Buthyl Ketone(MIBK)), which are flammable and toxic components in order to improve the selectivity and sensitivity of dPPV/Zeolite Y and the interactions between the ketone molecules and the composites with respect to the electrical conductivity sensitivity are investigated though the infrared spectroscopy(FTTIR). All composites show definite positive responses towards the ketone vapors (Acetone, Methyl Ethyl Ketone (MEK), Methyl Iso-Buthyl Ketone (MIBK)). The electrical conductivity sensitivities of the composites increase linearly with increasing surface area of the Zeolite Y. The highest electrical conductivity sensitivity is obtained with the dPPV_/Zeolite Y (Si/Al = 5.1, NH4+), higher than those of dPPV_/Zeolite Y (Si/Al = 5.1, Na+) and dPPV_/Zeolite Y (Si/Al = 5.1, H+) when exposed to acetone. Amongst the Ketone vapors, acetone induces the highest electrical conductivity sensitivity, whereas MIBK induces the lowest electrical conductivity sensitivity.

Kamonsawas, Jirarat; Sirivat, Anuvat

2012-02-01

331

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

PubMed

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. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24817327

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

2015-02-01

332

Electrical stimulation of nerve cells using conductive nanofibrous scaffolds for nerve tissue engineering.  

PubMed

Fabrication of scaffolds with suitable chemical, mechanical, and electrical properties is critical for the success of nerve tissue engineering. Electrical stimulation was directly applied to electrospun conductive nanofibrous scaffolds to enhance the nerve regeneration process. In the present study, electrospun conductive nanofibers were prepared by mixing 10 and 15 wt% doped polyaniline (PANI) with poly (epsilon-caprolactone)/gelatin (PG) (70:30) solution (PANI/PG) by electrospinning. The fiber diameter, pore size, hydrophilicity, tensile properties, conductivity, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy spectra of nanofibers were determined, and the in vitro biodegradability of the different nanofibrous scaffolds was also evaluated. Nanofibrous scaffolds containing 15% PANI was found to exhibit the most balanced properties to meet all the required specifications for electrical stimulation for its enhanced conductivity and is used for in vitro culture and electrical stimulation of nerve stem cells. 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay and scanning electron microscopy results showed that conductive nanofibrous scaffolds are suitable substrates for the attachment and proliferation of nerve stem cells. Electrical stimulation through conductive nanofibrous PANI/PG scaffolds showed enhanced cell proliferation and neurite outgrowth compared to the PANI/PG scaffolds that were not subjected to electrical stimulation. PMID:19496678

Ghasemi-Mobarakeh, Laleh; Prabhakaran, Molamma P; Morshed, Mohammad; Nasr-Esfahani, Mohammad Hossein; Ramakrishna, Seeram

2009-11-01

333

Carbon-enhanced electrical conductivity during fracture of rocks  

NASA Astrophysics Data System (ADS)

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.

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

1999-01-01

334

High-performance electrically conductive silver paste prepared by silver-containing precursor  

NASA Astrophysics Data System (ADS)

A high-performance electrically conductive silver paste with no solid particles before drying and/or sintering is developed, in which silver-containing precursor is employed as conductive functional phase. Thermogravimetry analysis, volume electrical resistivity tests and sintering experiments show that the paste with about 14 wt.% silver pristine content is able to achieve the volume electrical resistivity of (2-3) ×10-5 ? cm after it is sintered at 220°C. A micro-pen direct-writing process indicates that it is very suitable for the fabrication of high-resolution (25 ?m) and high-integration devices and apparatus.

Liu, Jianguo; Cao, Yu; Li, Xiangyou; Wang, Xiaoye; Zeng, Xiaoyan

2010-09-01

335

Aspect Ratio and Loading Effects of Multiwall Carbon Nanotubes in Epoxy for Electrically Conductive Adhesives  

Microsoft Academic Search

Isotropic conductive adhesives (ICAs) filled with metal particles are commercially available as alternatives to solder joining in electronic packaging. Replacing metal fillers with multiwall carbon nanotubes (MWCNTs) offers the potential benefits of being corrosion resistant, high strength and lightweight. Traditional metal filled ICAs require high metal loading to ensure electrical conductivity, which may cause problems with respect to reliability and

Jing Li; Janet K. Lumpp; Rodney Andrews; David Jacques

2008-01-01

336

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

Microsoft Academic Search

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

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

1992-01-01

337

Estimating the electrical conductivity of cement paste pore solutions from OH ?, K + and Na + concentrations  

Microsoft Academic Search

A proposed method for estimating the electrical conductivity of cement paste pore solution at 25 °C is based on the concentrations of OH?, K+ and Na+. The approach uses an equation that is a function of the solution ionic strength, and requires a single coefficient for each ionic species. To test the method, the conductivity of solutions containing mixtures of

K. A. Snyder; X. Feng; B. D. Keen; T. O. Mason

2003-01-01

338

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

Technology Transfer Automated Retrieval System (TEKTRAN)

How Well Does Zone Sampling Based On Soil Electrical Conductivity Maps Represent Soil Variability. Dale L. Shaner A study was conducted determined if ECa-directed zone sampling could predict soil texture and soil organic matter (SOM) patterns of samples taken by a more intensive grid sample method...

339

ThermoelectricPower Factor for Electrically ConductivePolymers Ali Shakouri and Suquan Li  

E-print Network

of pristine (undoped) conducting polymers is the n-conjugated system which is formed by the overlap of carbon pz orbitals and alternating carbon-carbon bond lengths [2,3,24]. Approximately twenty prototypes with the increase in electrical conductivity for the highest values achieved to date. Theoreticaldescription

340

An analysis of transverse electric scattering from a rectangular channel in a conducting plane  

Microsoft Academic Search

The problem of transverse electric plane wave scattering from a rectangular channel which is engraved in a perfect conducting plane is investigated. A Fourier transform technique is employed to express the scattered field in the spectral domain in terms of parallel-plate waveguide modes. The boundary conditions are enforced on the conducting surface and the channel aperture to obtain simultaneous equations

Tah J. Park; Hyo J. Eom; Kuniaki Yoshitomi

1993-01-01

341

Electrical conductivity of magma in the course of crystallization controlled by their residual liquid composition  

NASA Astrophysics Data System (ADS)

The electrical conductivity of a magma in the course of crystallization was experimentally investigated in the temperature range of 1350-1018°C. Large samples of basaltic composition with a homogeneous crystal content were synthesized in a gas mixing furnace at 1 atm pressure. The samples were analyzed by electron microprobe. The relative proportions of the phases as a function of temperature were determined. Depending on temperature, the phase assemblies included quenched silicate liquid, ±plagioclase, ±pyroxene, ±Fe-Ti oxides. The crystal content varied from 0 to 80 wt %. In response to partial crystallization, the residual liquid changed composition from basalt, to andesite, to dacite liquid. The electrical conductivity of the partially crystallized basaltic samples was measured. In addition, above liquidus conductivity measurements were conducted on compositions matching the residual liquid at different temperature. These supplemental electrical measurements allowed us to discriminate the effect of crystal content from the effect of changing liquid composition associated with partial crystallization. Combining with the modified Archie's law a set of constraints describing the conductivity of the residual liquid versus chemical composition and temperature, we propose an equation to calculate changes in conductivity associated with partial magma crystallization. We showed how the composition of the residual liquid is critical on the electrical behavior of crystal-liquid system. The model overcomes the previous difficulties in finding a robust model for describing the electrical behavior of crystal-liquid systems. The effect of liquid composition on the electrical conductivity is related to diffusion mechanisms and transport properties in molten silicate. Combining known constraints on Na tracer diffusion and our conductivity results confirms the statements that sodium is the dominant charge carrier silicate liquids from basalt to rhyolite. These findings revealed that we need a comprehensive model that can predict the conductivity of molten silicate as a function of chemical composition.

Gaillard, F.; Marziano, G. Iacono

2005-06-01

342

3? method to measure thermal properties of electrically conducting small-volume liquid  

NASA Astrophysics Data System (ADS)

This work presents a method to measure the thermal conductivity and heat capacity of electrically conducting small-volume liquid samples using the 3? technique. A mathematical model of heat transfer is derived to determine the thermal properties from the 3? signal considering the device geometry. In order to validate the model, an experimental apparatus has been designed and set up to measure the thermal properties (thermal conductivity and heat capacity) of seven different liquid samples. The results show good agreement with other literature values, demonstrating that the suggested method is effective for measuring the thermal properties of electrically conducting liquids. More importantly, the result with a sample volume of 1?l demonstrates the resolution of the thermal conductivity as precise as 0.01% which corresponds to a thermal-conductivity change of 10-4W/mK in the case of water-based solutions.

Choi, Sun Rock; Kim, Joonwon; Kim, Dongsik

2007-08-01

343

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

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

344

Vapor sensing mechanism of acid on copper phthalocyanine thin films studied by electrical conductivity  

NASA Astrophysics Data System (ADS)

The electrical conductivity of thin films of iron phthalocyanine on glass substrates by thermal evaporation technique have been investigated. The electrical conductivity of thin films of these complexes changes when exposed to oxidizing and reducing gases such as halogens, ammonia, water and NOX. Thermal activation energy in the intrinsic region and impurity scattering region can be calculated by using Arrhenius plot. The dark conductivity and photoconductivity have been taken at different temperatures in the range 312-389 K. These films have been studied as chemical sensors for dilute sulphuric acid.

Singh, Sukhwinder; Saini, G. S. S.; Tripathi, S. K.

2013-06-01

345

Electrical conductivity of high-pressure liquid hydrogen by quantum Monte Carlo methods.  

PubMed

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

Lin, Fei; Morales, Miguel A; Delaney, Kris T; Pierleoni, Carlo; Martin, Richard M; Ceperley, D M

2009-12-18

346

The effect of pressure on the electrical conductivity of olivine under the hydrogen-rich conditions  

NASA Astrophysics Data System (ADS)

The influence of pressure on the hydrogen-assisted electrical conductivity in olivine has been studied under conditions of 4-10 GPa and 873-1273 K. Synthetic polycrystalline olivine samples with the water content of 160 ppm wt (Paterson calibration) were used and the electrical conductivity was determined from the results of the impedance spectroscopy. We found that the pressure reduces the hydrogen-assisted electrical conductivity, but its magnitude is small: between 4 and 10 GPa, the difference is a factor of ?2.5 for the same water content and temperature. The pressure dependence is characterized by a negative activation volume and the negative dependence of the pre-exponential factor on pressure. Such anomalous behavior is explained by a model where hydrogen-related defect is considered as a weak inclusion in a strong matrix. We use these new data to calculate the electrical conductivity contrast at the 410-km discontinuity. We found that if the water content of the mantle does not change with depth, there should be a large (a factor of ?10) drop in conductivity from above to below the 410-km discontinuity. In contrast, geophysically inferred electrical conductivity increases at 410-km suggesting the increase in water content from above to below the 410-km discontinuity. The present results are used to compare several previous results obtained at different pressures. It was shown that our results agree well with most of previous studies but not with (Yoshino et al., 2009). Possible causes for this discrepancy are discussed.

Dai, Lidong; Karato, Shun-ichiro

2014-07-01

347

Effect of water on the electrical conductivity of lower crustal clinopyroxene  

NASA Astrophysics Data System (ADS)

The electrical conductivity of lower crustal clinopyroxene was measured at 6-12 kbar, 250-1000°C, and Ni-NiO buffer conditions. The dependence of electrical conductivity on water content was studied using both natural and preannealed samples separated from a fresh xenolith granulite, with water contents from 0 to 375 ppm. An end-loaded piston cylinder apparatus and a Solarton-1260 Impedance/Gain Phase Analyzer were used in the study over a frequency range of 0.01-106 Hz to obtain the complex impedance spectra. The results show that the influence of pressure is very weak relative to temperature and water content and that two distinct mechanisms with different activation enthalpies dominate electrical conduction under dry and wet conditions. For the dry sample, the activation enthalpy is ˜102 kJ/mol and the main charge carriers are small polarons, i.e., hopping of electron holes between ferrous and ferric irons. For wet samples, the electrical conductivity is significantly enhanced with an activation enthalpy of ˜70 kJ/mol and the charge carriers are likely to be protons. Under hydrous conditions, the activation enthalpies are nearly independent of water content and the conductivity is a function of water content with an exponent of ˜1. As a major constituent of granulites with >60% modal volume in some regions, clinopyroxene containing minor amounts of water may contribute significantly to the high electrical conductivity in the lower crust, especially under stable continental regions.

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

2011-04-01

348

Effect of strain on the electrical conductivity of a styrene-butadiene rubber  

NASA Astrophysics Data System (ADS)

When the carbon black-filled rubbers are stretched, the electrical resistivity increases at lower extension ranges, and then it decreases with further extension. This complex behavior is attributed to the morphology changes of carbon black particles during extension, i.e., breaking and forming conducting paths. In this study, highly conductive carbon blacks were compounded with high styrene content SBR matrix with contents varying from 5phr, 10phr, 15phr and 20phr. All the compounds measured the electrical resistance at room temp., 40°C, 80°C, respectively. The electrical resistances are decreased as the conductive carbon blacks are higher and temperature is increased. The electrical resistivity and tensile behaviors were investigated as a function of stretching at 80°C. The conductive carbon black-filled a styrene-butadiene rubber vulcanizate showed much higher conductivity and the electrical resistivity is more stable by increase of contents. In tensile behaviors, as the contents of conductive carbon blacks increase, it shows the increase of strength.

Kim, Young Hee; Lim, Jee Young; Jose, Jobin; Kim, Jae Young; Lee, Gi-Bbeum; Gent, Alan N.; Nah, Changwoon

2010-04-01

349

Field and temperature dependence of the small polaron hopping electrical conductivity in 1D disordered systems.  

PubMed

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

Triberis, G P; Dimakogianni, M

2009-09-23

350

Hydrogen Effects on the Electrical Conductivity of Pulsed Laser Deposited ZnO Thin Films  

Microsoft Academic Search

Well c-axis oriented 320 nm and 160 nm thick ZnO thin films were deposited with pulsed laser deposition on Pt\\/Ti\\/SiO2\\/Si(100) substrates. Diode characteristics of Au\\/ZnO\\/Pt in electrical conductivity were observed. The conductivity in forward bias was sensitive to the hydrogen annealing but almost insensitive in reverse bias. The conductivity of 320 nm thick film in forward bias increased from 6.1

Tae Kwon Song; M. H. Kim; S. S. Kim; W. J. Kim; R. K. Ko; K. J. Song

2005-01-01

351

Enhancement of energy density in organic redox capacitor by improvement of electric conduction network  

NASA Astrophysics Data System (ADS)

Organic compounds have attracted attention as inexpensive and environmentally friendly active materials for energy storage devices. Among them, quinonic compounds can achieve high power capabilities because of their fast redox reactions. To utilize the organic compounds, which have a poor electrical conductivity and which are soluble in the electrolyte, the construction of electric conductive network to hold the organic compounds is necessary. In this study, we enhanced the capacity in aqueous redox-capacitors with quinonic and hydroquinonic organic compounds supported in nanoporous carbon by adding a small amount of another highly conductive carbon. The improvement of the electric conduction path enabled a high loading ratio of organic active material to nanoporous carbon (>70 wt%) in the electrode with a high utilization rate. It also achieved the high energy density of 30 Wh kg-1 in the organic redox capacitor.

Komatsu, Daiki; Tomai, Takaaki; Honma, Itaru

2015-01-01

352

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.

353

Nanoscale electrical and mechanical characteristics of conductive polyaniline network in polymer composite films.  

PubMed

The presence and characteristics of a connected network of polyaniline (PANI) within a composite coating based on polyester acrylate (PEA) has been investigated. The bulk electrical conductivity of the composite was measured by impedance spectroscopy. It was found that the composite films containing PANI have an electrical conductivity level in the range of semiconductors (order of 10(-3) S cm(-1)), which suggests the presence of a connected network of the conductive phase. The nanoscopic distribution of such a network within the cured film was characterized by PeakForce tunneling atomic force microscopy (AFM). This method simultaneously provides local information about surface topography and nanomechanical properties, together with electrical conductivity arising from conductive paths connecting the metallic substrate to the surface of the coating. The data demonstrates that a PEA-rich layer exists at the composite-air interface, which hinders the conductive phase to be fully detected at the surface layer. However, by exposing the internal structure of the composites using a microtome, a much higher population of a conductive network of PANI, with higher elastic modulus than the PEA matrix, was observed and characterized. Local current-voltage (I-V) spectroscopy was utilized to investigate the conduction mechanism within the nanocomposite films, and revealed non-Ohmic characteristics of the conductive network. PMID:25295701

Jafarzadeh, Shadi; Claesson, Per M; Sundell, Per-Erik; Pan, Jinshan; Thormann, Esben

2014-11-12

354

Towards practical application of paper based printed circuits: capillarity effectively enhances conductivity of the thermoplastic electrically conductive adhesives.  

PubMed

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 circuits were drastically 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. PMID:25182052

Wu, Haoyi; Chiang, Sum Wai; Lin, Wei; Yang, Cheng; Li, Zhuo; Liu, Jingping; Cui, Xiaoya; Kang, Feiyu; Wong, Ching Ping

2014-01-01

355

Towards Practical Application of Paper based Printed Circuits: Capillarity Effectively Enhances Conductivity of the Thermoplastic Electrically Conductive Adhesives  

NASA Astrophysics Data System (ADS)

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.

Wu, Haoyi; Chiang, Sum Wai; Lin, Wei; Yang, Cheng; Li, Zhuo; Liu, Jingping; Cui, Xiaoya; Kang, Feiyu; Wong, Ching Ping

2014-09-01

356

Electrical and thermal conductivity of discontinuously reinforced aluminum composites at sub-ambient temperatures  

SciTech Connect

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.

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

357

Electrical conductivity and phase transition studies of TiO2-BaO system  

NASA Astrophysics Data System (ADS)

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.

Beg, Saba; Haneef, Sadaf

2015-01-01

358

The electrical conductivities of candidate beam-waveguide antenna shroud materials  

NASA Astrophysics Data System (ADS)

The shroud on the beam-waveguide (BWG) antenna at DSS 13 is made from highly magnetic American Society for Testing and Materials (ASTM) A36 steel. Measurements at 8.42 GHz showed that this material (with paint) has a very poor electrical conductivity that is 600 times worse than aluminum. In cases where the BWG mirrors might be slightly misaligned, unintentional illumination and poor electrical conductivity of the shroud walls can cause system noise temperature to be increased significantly. This potential increase of noise temperature contribution can be reduced through the use of better conductivity materials for the shroud walls. An alternative is to attempt to improve the conductivity of the currently used ASTM A36 steel by means of some type of plating, surface treatment, or high-conductivity paints. This article presents the results of a study made to find improved materials for future shrouds and mirror supports.

Otoshi, T. Y.; Franco, M. M.

1994-05-01

359

The Electrical Conductivities of Candidate Beam-Waveguide Antenna Shroud Materials  

NASA Astrophysics Data System (ADS)

The shroud on the beam-waveguide (BWG) antenna at DSS 13 is made from highly magnetic American Society for Testing and Materials (ASTM) A36 steel. Measurements at 8.42 GHz showed that this material (with paint) has a very poor electrical conductivity that is 600 times worse than aluminum. In cases where the BWG mirrors might be slightly misaligned, unintentional illumination and poor electrical conductivity of the shroud walls can cause system noise temperature to be increased significantly. This potential increase of noise temperature contribution can be reduced through the use of better conductivity materials for the shroud walls. An alternative is to attempt to improve the conductivity of the currently used ASTM A36 steel by means of some type of plating, surface treatment, or high-conductivity paints. This article presents the results of a study made to find improved materials for future shrouds and mirror supports.

Otoshi, T. Y.; Franco, M. M.

1994-01-01

360

Magnetic field configuration and electrical conductivity of plasma in the solar wind  

NASA Astrophysics Data System (ADS)

A solution is obtained for the magnetic and electric fields generated by a magnetized and electrified rotating sphere in a strictly radial flow of finite-conductivity plasma in the case of an arbitrary dependence of conductivity on radius and a constant flow velocity. The solution is applied to the solar wind, and the main features of the magnetic field configuration are used to determine the phenomenological conductivity of the plasma, which turns out to be 13 orders of magnitude smaller than the Spitzer conductivity. It is shown that the high electrical resistance of the solar wind can be explained by assuming that all the electrons are practically 'trapped' by the field of very intense Langmuir oscillations, whose energy density is equal to the thermal pressure of the plasma. The conductivity of the solar wind near the earth's magnetosphere should increase owing to the fact that the degree of trapping decreases as the plasma interacts with the geomagnetic field.

Chertkov, A. D.

361

Enhanced Thermoelectric Efficiency via Orthogonal Electrical and Thermal Conductances in Phosphorene.  

PubMed

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

Fei, Ruixiang; Faghaninia, Alireza; Soklaski, Ryan; Yan, Jia-An; Lo, Cynthia; Yang, Li

2014-11-12

362

Laboratory studies of the electrical conductivity of silicate perovskites at high pressures and temperatures  

NASA Technical Reports Server (NTRS)

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.

Li, Xiaoyuan; Jeanloz, Raymond

1990-01-01

363

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

NASA Astrophysics Data System (ADS)

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.

Aindow, M.; Alpay, S. P.; Liu, Y.; Mantese, J. V.; Senturk, B. S.

2010-10-01

364

Electrical conductivity modeling and research of polypropylene composites filled with carbon black  

NASA Astrophysics Data System (ADS)

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.

Stepashkina, A. S.; Tsobkallo, E. S.; Alyoshin, A. N.

2014-12-01

365

Electric field studies: TLE-induced waveforms and ground conductivity impact on electric field propagation  

Microsoft Academic Search

We review in this paper main results obtained from electric field (from VLF to HF) measurement campaigns realized by CEA in the framework of the Eurosprite program [Neubert et al., 2005, 2008] from 2003 to 2009 in France in different configurations. Two main topics have been studied: sprite or elve induced phenomena (radiation or perturbation) and wave propagation. Using a

Thomas Farges; Geraldine Garcia; Elisabeth Blanc

2010-01-01

366

Hygrothermal Stability of Electrical Contacts Made from Silver and Graphite Electrically Conductive Pastes  

E-print Network

, University at Buffalo, State University of New York, Buffalo, NY14260-4400, USA. 2.--E-mail: ddlchung@buffalo in water at 15°C and 40°C. The pastes are silver paint, silver paint with a nonconductive epoxy overcoat is even less durable than silver epoxy, due to its being water based. Key words: Electrical contact

Chung, Deborah D.L.

367

Mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogels  

DOEpatents

A method of making a mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel, including the steps of dispersing nanotubes in an aqueous media or other media to form a suspension, adding reactants and catalyst to the suspension to create a reaction mixture, curing the reaction mixture to form a wet gel, drying the wet gel to produce a dry gel, and pyrolyzing the dry gel to produce the mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel. The aerogel is mechanically robust, electrically conductive, and ultralow-density, and is made of a porous carbon material having 5 to 95% by weight carbon nanotubes and 5 to 95% carbon binder.

Worsley, Marcus A; Baumann, Theodore F; Satcher, Jr., Joe H

2014-04-01

368

Absence of an ideal single-walled carbon nanotube forest structure for thermal and electrical conductivities.  

PubMed

We report the fundamental dependence of thermal diffusivity and electrical conductance on the diameter and defect level for vertically aligned single-walled carbon nanotube (SWCNT) forests. By synthesizing a series of SWCNT forests with continuous control of the diameter and defect level over a wide range while holding all other structures fixed, we found an inverse and mutually exclusive relationship between the thermal diffusivity and the electrical conductance. This relationship was explained by the differences in the fundamental mechanisms governing each property and the optimum required structures. We concluded that high thermal diffusivity and electrical conductance would be extremely difficult to simultaneously achieve by a single SWCNT forest structure within current chemical vapor deposition synthetic technology, and the "ideal" SWCNT forest structure would differ depending on application. PMID:24090543

Chen, Guohai; Futaba, Don N; Kimura, Hiroe; Sakurai, Shunsuke; Yumura, Motoo; Hata, Kenji

2013-11-26

369

Quantum transport in strongly disordered crystals: Electrical conductivity with large negative vertex corrections  

NASA Astrophysics Data System (ADS)

We propose a renormalization scheme of the Kubo formula for the electrical conductivity with multiple backscatterings contributing to the electron-hole irreducible vertex derived from the asymptotic limit to high spatial dimensions. We use this vertex to represent the two-particle Green function via a symmetrized Bethe-Salpeter equation in momentum space. We further utilize the dominance of a pole in the irreducible vertex to an approximate diagonalization of the Bethe-Salpeter equation and a non-perturbative representation of the electron-hole correlation function. The latter function is then used to derive a compact representation for the electrical conductivity at zero temperature without the necessity to evaluate separately the Drude term and vertex corrections. The electrical conductivity calculated in this way remains nonnegative also in the strongly disordered regime where the localization effects become significant and the negative vertex corrections in the standard Kubo formula overweight the Drude term.

Janiš, Václav; Pokorný, Vladislav

2012-12-01

370

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

NASA Astrophysics Data System (ADS)

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

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

2005-03-01

371

Electrical Conductivity of an Anisotropic Quark Gluon Plasma : A Quasiparticle Approach  

E-print Network

The study of transport coefficients of strongly interacting matter got impetus after the discovery of perfect fluid ever created at ultrarelativistic heavy ion collision experiments. In this article, we have calculated one such coefficient viz. electrical conductivity of the quark gluon plasma (QGP) phase which exhibits a momentum anisotropy. Relativistic Boltzmann's kinetic equation has been solved in the relaxation-time approximation to obtain the electrical conductivity. We have used the quasiparticle description to define the basic properties of QGP. We have compared our model results with the corresponding results obtained in different lattice as well as other model calculations. Furthermore, we extend our model to calculate the electrical conductivity at finite chemical potential.

P. K. Srivastava; Lata Thakur; Binoy Krishna Patra

2015-01-15

372

Electrical Conductivity of an Anisotropic Quark Gluon Plasma : A Quasiparticle Approach  

E-print Network

The study of transport coefficients of strongly interacting matter got impetus after the discovery of perfect fluid ever created at ultrarelativistic heavy ion collision experiments. In this article, we have calculated one such coefficient viz. electrical conductivity of the quark gluon plasma (QGP) phase which exhibits a momentum anisotropy. Relativistic Boltzmann's kinetic equation has been solved in the relaxation-time approximation to obtain the electrical conductivity. We have used the quasiparticle description to define the basic properties of QGP. We have compared our model results with the corresponding results obtained in different lattice as well as other model calculations. Furthermore, we extend our model to calculate the electrical conductivity at finite chemical potential.

Srivastava, P K; Patra, Binoy Krishna

2015-01-01

373

Relationships between fluid-rock interactions and the electrical conductivity of sandstones  

NASA Astrophysics Data System (ADS)

Batch and flow-through experiments were performed on quartz-feldspar granular aggregates and sandstone samples to investigate time-dependent effects of fluid-rock interactions on fluid and rock conductivity, respectively. The experiments were conducted at temperatures up to 164 °C, at confining and pore pressures up to 10 and 5 MPa, respectively, and for up to 136 days. It showed that changes in rock conductivity were unequivocally related to changes in pore fluid conductivity. It is inferred that these changes were dependent on kinetically controlled dissolution reactions between the mineral grains and the fluid. The time-dependent signature of rock conductivity implied a detectable transition from initial dissolution toward some state of equilibrium. The response of rock conductivity to temperature changes followed an Arrhenius-type behavior. An exploratory kinetic evaluation of the conductivity data for sandstone samples yielded an apparent activation energy Ea? of approximately 32 kJ/mol. A concurrent chemical fluid analysis showed that this is an integrated value over all reactions occurring in parallel within a sample. These reactions namely concern silica and silicate dissolution but also the dissolution of accessory salt minerals. It is concluded that measuring the evolution of rock conductivity in combination with chemical pore fluid analysis constitutes a powerful and quantitative tool for monitoring time-dependent changes in pore fluid chemistry and thus fluid-rock interactions in real time.

Schepers, A.; Milsch, H.

2013-07-01

374

Wireless Sensing System Using Open-circuit, Electrically-conductive Spiral-trace Sensor  

NASA Technical Reports Server (NTRS)

A wireless sensing system includes a sensor made from an electrical conductor shaped to form an open-circuit, electrically-conductive spiral trace having inductance and capacitance. In the presence of a time-varying magnetic field, the sensor resonates to generate a harmonic response having a frequency, amplitude and bandwidth. A magnetic field response recorder wirelessly transmits the time-varying magnetic field to the sensor and wirelessly detects the sensor's response frequency, amplitude and bandwidth.

Woodard, Stanley E. (Inventor); Taylor, Bryant D. (Inventor)

2013-01-01

375

Numerical investigation of entropy generation in unsteady MHD generalized Couette flow with variable electrical conductivity.  

PubMed

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

Chinyoka, T; Makinde, O D

2013-01-01

376

Numerical Investigation of Entropy Generation in Unsteady MHD Generalized Couette Flow with Variable Electrical Conductivity  

PubMed Central

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

Chinyoka, T.; Makinde, O. D.

2013-01-01

377

Electrical conductivity evolution of non-saturated carbonate rocks during deformation up to failure  

NASA Astrophysics Data System (ADS)

We present electrical conductivity measurements (at a fixed frequency of 1 kHz) performed on three directions on limestone samples from the quarry of Meriel, during uniaxial tests of deformation up to failure. Samples were saturated from 100 to 80 per cent by drainage. The samples showed brittle fracture with Young's modulus in the range 10-13 MPa. Formation factor (sample resistivity divided by water resistivity) values range between 2 and 4. In saturated conditions the electrical measurements reflect the initial rock compaction, followed by dilatancy due to new axial cracks formation and finally crack coalescence, fracture localization and failure. The conductivity increase is related to the crack porosity ?c, which starts to increase at relatively low stress (31 per cent of strength). The magnitude of the electrical conductivity variation is 1-4 per cent of the initial value. We show that when saturation is decreased the conductivity increase occurs earlier during the deformation process, from 68 to 17 per cent of strength for 100 to 80 per cent of water saturation, respectively, so that the decrease in conductivity at low stress is less and less present. The induced relative rock conductivity variation in non-saturated and undrained conditions is the result of two competing effects: the relative porosity variation and the relative saturation variation during the deformation process. During compaction the electrical conductivity can show either a small decrease or a small increase; since the size of the partially saturated pores and cracks is reduced, the water occupies a larger percentage of the pore space, and then conductivity can be increased at this stage. We show a continuous increase of the conductivity both during the compaction and the dilatancy phases when the initial saturation is about 80-85 per cent. Finally a power law is shown between conductivity and stress, so that the relative electrical conductivity increase is larger as one goes along the compression process. Just before failure, at 90-95 per cent of strength, the rate increase in horizontal conductivity drops, so that the anisotropy between axial and radial conductivity is about 0.5-2 per cent. At failure a drastic increase of this anisotropy can be seen, up to 5-6 per cent (CME21, CME24 and CME13 samples).

Jouniaux, Laurence; Zamora, Maria; Reuschlé, Thierry

2006-11-01

378

Application of conductive polymers, scaffolds and electrical stimulation for nerve tissue engineering.  

PubMed

Among the numerous attempts to integrate tissue engineering concepts into strategies to repair nearly all parts of the body, neuronal repair stands out. This is partially due to the complexity of the nervous anatomical system, its functioning and the inefficiency of conventional repair approaches, which are based on single components of either biomaterials or cells alone. Electrical stimulation has been shown to enhance the nerve regeneration process and this consequently makes the use of electrically conductive polymers very attractive for the construction of scaffolds for nerve tissue engineering. In this review, by taking into consideration the electrical properties of nerve cells and the effect of electrical stimulation on nerve cells, we discuss the most commonly utilized conductive polymers, polypyrrole (PPy) and polyaniline (PANI), along with their design and modifications, thus making them suitable scaffolds for nerve tissue engineering. Other electrospun, composite, conductive scaffolds, such as PANI/gelatin and PPy/poly(?-caprolactone), with or without electrical stimulation, are also discussed. Different procedures of electrical stimulation which have been used in tissue engineering, with examples on their specific applications in tissue engineering, are also discussed. PMID:21413155

Ghasemi-Mobarakeh, Laleh; Prabhakaran, Molamma P; Morshed, Mohammad; Nasr-Esfahani, Mohammad Hossein; Baharvand, Hossein; Kiani, Sahar; Al-Deyab, Salem S; Ramakrishna, Seeram

2011-04-01

379

Increase of electrical conductivity with pressure as an indicator of conduction through a solid phase in midcrustal rocks  

NASA Astrophysics Data System (ADS)

Rocks freshly cored from depth at the German continental scientific drilling site (KTB) offer an opportunity to study transport properties in relatively unaltered samples resembling material in situ. Electrical conductivity ? was measured to 250 MPa pressure, and room temperature on 1 M NaCl-saturated amphibolites from 4 to 5 km depth. An unexpected feature was an increase of ? with pressure P that appeared (anisotropically) in most samples. To characterize this behavior, we fitted the linear portion of log ? versus P to obtain two parameters: the slope dlog?/dP (of order 10-3 MPa-1) and the zero-pressure intercept ?0. Samples of positive and negative slopes behave differently. Those having negative slopes show strong correlation of ?0 with a fluid property (permeability). This behavior indicates that fluids exert the dominant control on ?0 at low pressure when ?0 is greatest, which is typical behavior observed in previous studies. In contrast, samples with positive slopes lack a correlation of ?0 with permeability, indicating that fluids are less important to positive pressure behavior. Another result is that samples of negative dlog?/dP have uncorrelated slopes and initial conductivities. In significant contrast, samples of positive slopes have the greatest P dependence for lowest initial conductivity ?0, that is, the less fluid, the more positive dlog?/dP. Hence positive dlog?/dP is consistent with reconnection of solid phases into a conductive texture better resembling that of rock at depth. Detailed examination of one sample by electron probe and scanning electron microscope reveals the presence of carbon on internal cleavage surfaces in amphibole, the most abundant mineral present. Thus carbon probably dominates the reconnection, but total ? still involves fluids as well as Fe-Ti oxides. For the KTB location it is inferred that the reason mid to deep crustal electrical conductivities modeled from geophysical measurements are so much higher than conductivities of silicates is the presence of interconnected good conductors involving films of carbon on surfaces and other solid phases.

Shankland, T. J.; Duba, A. G.; Mathez, E. A.; Peach, C. L.

1997-07-01

380

Lunar temperature and global heat flux from laboratory electrical conductivity and lunar magnetometer data  

NASA Technical Reports Server (NTRS)

Three-layer monotonic electrical conductivity models for the lunar interior to a depth of 600 km are used in conjunction with laboratory measurements of the electrical conductivity of olivine and pyroxene to estimate a temperature-depth profile. The temperatures calculated for depths of 400-600 km are consistent with attenuation of the seismic shear wave. The temperature calculated at a depth of 100-250 km yields a heat flow that is in good agreement with the directly measured lunar heat flow. The temperature, however, is sufficiently close to melting that mascon anisostasy would not be maintained. Thus a better conductor is required at this depth.

Sonett, C. P.; Duba, A.

1975-01-01

381

Breakdown characteristics of an isolated conducting object in a uniform electric field  

NASA Technical Reports Server (NTRS)

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.

Grothaus, M. G.; Trost, T. F.

1986-01-01

382

Thermal conductivity, electrical resistivity, and thermopower of aerospace alloys from 4 to 300 K.  

NASA Technical Reports Server (NTRS)

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.

Hust, J. G.; Weitzel, D. H.; Powell, R. L.

1971-01-01

383

Electrically conductive doped block copolymer of polyacetylene and polyisoprene. [Soluble in organic solvents  

DOEpatents

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.

Aldissi, M.

1984-06-27

384

Magnetic field of the solar wind - A stationary kinematic solution with a finite electric conductivity  

NASA Astrophysics Data System (ADS)

The stationary models by Parker (1963) for the magnetic field in the solar wind and by Schatten (1969) for the 'source surface' in the solar corona are generalized. The configuration of the interplanetary magnetic field, stretched by the expanding corona, depends on the magnitude of the electrical conductivity, sigma, of the solar wind plasma. Knowing the main empirical features of the field configuration, one may estimate the phenomenological value of sigma. The estimates show that the electrical conductivity should be approximately 10 exp 13 times smaller than that calculated by Spitzer (1956).

Chertkov, A. D.

385

Enhanced Thermoelectric Efficiency via Orthogonal Electrical and Thermal Conductances in Phosphorene  

NASA Astrophysics Data System (ADS)

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. High ZT (>2) has been achieved in materials via all-scale hierarchical architecturing. This efficiency holds at high temperatures (700K~900K) but quickly diminishes at lower temperatures. 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 that phosphorene possesses spatially-anisotropic electrical and thermal conductances. The prominent electrical and thermal conducting directions are orthogonal to one another, enhancing the ratio of these conductances. As a result, ZT can reach 2.5 (the criterion for commercial deployment) along the armchair direction of phosphorene at T=500K and is greater than 1 even at room temperature given moderate doping (~2 x 10^16 m-2). Ultimately, phosphorene 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 (~ 300K) - one whose performance does not require any sophisticated engineering techniques.

Fei, Ruixiang; Faghaninia, Alireza; Soklaski, Ryan; Yan, Jia-An; Lo, Cynthia; Yang, Li

2014-11-01

386

Inductive Measurement of Plasma Jet Electrical Conductivity (MSFC Center Director's discretionary Fund). Part 2  

NASA Technical Reports Server (NTRS)

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.

Turner, M. W.; Hawk, C. W.; Litchford, R. J.

2001-01-01

387

Dynamics of Space Charge Polarization and Electrical Conduction in Low Alkali Boroaluminosilicate Glasses  

NASA Astrophysics Data System (ADS)

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.

Dash, Priyanka

388

Electrical conductivity of alkali feldspar solid solutions at high temperatures and high pressures  

NASA Astrophysics Data System (ADS)

The electrical conductivities of alkali feldspar solid solutions ranging in chemical composition from albite (NaAlSi3O8) to K-feldspar (KAlSi3O8) were measured at 1.0 GPa and temperatures of 873-1,173 K in a multi-anvil apparatus. The complex impedance was determined by the AC impedance spectroscopy technique in the frequency range of 0.1-106 Hz. Our experimental results revealed that the electrical conductivities of alkali feldspar solid solutions increase with increasing temperature, and the linear relationship between electrical conductivity and temperature fits the Arrhenius formula. The electrical conductivities of solid solutions increase with the increasing Na content at constant temperature. At 1.0 GPa, the activation enthalpy of solid solution series shows strong dependency on the composition, and there is an abrupt increase from the composition of Or40Ab60 to Or60Ab40, where it reaches a value of 0.96 eV. According to these results in this study, it is proposed that the dominant conduction mechanism in alkali feldspar solid solutions under high temperature and high pressure is ionic conduction. Furthermore, since the activation enthalpy is less than 1.0 eV for the alkali feldspar solid solutions, it is suggested to be a model where Na+ and K+ transport involves an interstitial mechanism for electrical conduction. The change of main charge carriers can be responsible for the abrupt increase in the activation energy for Or60Ab40. All electrical conductivity data were fitted by a general formula in order to show the dependence of activation enthalpy and pre-exponential factor on chemical composition. Combining our experimental results with the effective medium theory, we theoretically calculated the electrical conductivity of alkali feldspar granite, alkali feldspar quartz syenite, and alkali feldspar syenite with different mineral content and variable chemical composition of alkali feldspar at high temperatures at 1.0 GPa, and the calculated results are almost in agreement with previous experimental studies on silicate rocks.

Hu, Haiying; Li, Heping; Dai, Lidong; Shan, Shuangming; Zhu, Chengming

2013-01-01

389

Serotonin Regulates Electrical Coupling via Modulation of Extrajunctional Conductance: H-current  

PubMed Central

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

Szabo, Theresa M.; Caplan, Jonathan S.; Zoran, Mark J.

2010-01-01

390

Ab initio determination of electrical and thermal conductivity of liquid aluminum  

Microsoft Academic Search

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

Vanina Recoules; Jean-Paul Crocombette

2005-01-01

391

Electrical conductivity and space charge in LDPE containing TiO2 nanoparticles  

Microsoft Academic Search

Electrical conductivity (DC) and space charge accumulation were studied in samples of low density polyethylene to which nano-sized and micro-sized TiO2 (anatase) particles and a dispersant had been added. Sample thicknesses were in the range 150-200 ?m. At applied field strengths of 10 and 20 kV\\/mm, the conductivity at 30 °C, measured in vacuum in samples containing 10 % w\\/w

R. J. Fleming; T. Pawlowski; A. Ammala; P. S. Casey; K. A. Lawrence

2005-01-01

392

Preparation and characterization of optically transparent and electrically conductive polyethylene-supported graphene films  

NASA Astrophysics Data System (ADS)

A simple mechanical technique for polyethylene (LDPE) film coating by a thin graphene layer is here described. This technique is based on the exfoliation of nanocrystalline graphite (few-layer graphene, FLG) by application of shear-stress, and it leads to a thin graphene layer on the plastic substrate with characteristics of good electrical conductivity and perfect transparency in the visible spectral region. These transparent-conductive films are suitable for ITO replacement in optoelectronics and photovoltaics.

Carotenuto, G.; Romeo, V.; Schiavo, L.; Ausanio, G.; Nicolais, L.

2014-05-01

393

Novel zirconia-based superionic conductors: The electrical conductivity of Y-Zr-O-N materials  

SciTech Connect

The effect of nitrogen incorporation into yttria-stabilized zirconia on the electrical conductivity is investigated by impedance spectroscopy. Under isothermal conditions, the conductivity depends on the total concentration of anion vacancies, independent of doping with aliovalent cations (Y{sup 3+}) or anions (N{sup 3{minus}}). The analysis of the Arrhenius plots results in higher activation energies for the oxynitrides than for nitrogen-free Y-Zr-O samples.

Wendel, J.; Laqua, W. [Justus-Liebig-Univ. Giessen (Germany). Inst. fur Anorganische und Analytische Chemie I] [Justus-Liebig-Univ. Giessen (Germany). Inst. fur Anorganische und Analytische Chemie I; Lerch, M. [Julius-Maximilians-Univ. Wuerzburg (Germany). Lehrstuhl fuer Silicatchemie] [Julius-Maximilians-Univ. Wuerzburg (Germany). Lehrstuhl fuer Silicatchemie

1999-01-01

394

Sensitivity to molecular order of the electrical conductivity in oligothiophene monolayer films.  

PubMed

Using conducting probe atomic force microscopy (CAFM), we show that electrical conductivity in oligothiophene molecular films deposited on SiO(2)/Si wafers is extremely sensitive to degree of crystalline order in the film. By locally distorting the molecular order in the films through the controlled application of pressure with the AFM tip, the lateral charge transport was reduced by factors varying from 2 to 10, even when no changes in the height of the film could be observed. PMID:23244532

Martin, Florent; Hendriksen, Bas L M; Katan, Allard J; Qi, Yabing; Mauldin, Clayton; Fréchet, Jean M J; Salmeron, Miquel

2013-01-29

395

The interaction of ozone with bio-fuel, revealed by electrical conduction and infrared spectroscopy  

Microsoft Academic Search

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

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

396

Water chemistry and electrical conductivity database for rivers in Yellowstone National Park, Wyoming  

USGS Publications Warehouse

This study aims to quantify relations between solute concentrations (especially chloride) and electrical conductivity for several rivers in Yellowstone National Park (YNP), by using automated samplers and conductivity meters. Norton and Friedman (1985) found that chloride concentrations and electrical conductivity have a good correlation in the Falls, Snake, Madison, and Yellowstone Rivers. However, their results are based on limited sampling and hydrologic conditions and their relation with other solutes was not determined. Once the correlations are established, conductivity measurements can then be used as a proxy for chloride concentrations, thereby enabling continuous heat-flow estimation on a much finer timescale and at lower cost than is currently possible with direct sampling. This publication serves as a repository for all data collected during the course of the study from May 2010 through July 2011, but it does not include correlations between solutes and conductivity or recommendations for quantification of chloride through continuous electrical conductivity measurements. This will be the object of a future document.

Clor, Laura E.; McCleskey, R. Blaine; Huebner, Mark A.; Lowenstern, Jacob B.; Heasler, Henry P.; Mahony, Dan L.; Maloney, Tim; Evans, William C.

2012-01-01

397

Flexible electrically conductive nanocomposite membrane based on bacterial cellulose and polyaniline.  

PubMed

The novel conductive polyaniline/bacterial cellulose (PANI/BC) nanocomposite membranes have been synthesized in situ by oxidative polymerization of aniline with ammonium persulfate as an oxidant and BC as a template. The resulting PANI-coated BC nanofibrils formed a uniform and flexible membrane. It was found that the PANI nanoparticles deposited on the surface of BC connected to form a continuous nanosheath by taking along the BC template, which greatly increases the thermal stability of BC. The content of PANI and the electrical conductivity of composites increased with increasing reaction time from 30 to 90 min, while the conductivity decreased because of the aggregation of PANI particles by further prolonging the reaction time. In addition, the acids remarkably improve the accessibility and reactivity of the hydroxyl groups of BC. The results indicate that the composites exhibit excellent electrical conductivity (the highest value was 5.0 × 10(-2) S/cm) and good mechanical properties (Young's modulus was 5.6 GPa and tensile strength was 95.7 MPa). Moreover, the electrical conductivity of the membrane is sensitive to the strain. This work provides a straightforward method to prepare flexible films with high conductivity and good mechanical properties, which could be applied in sensors, flexible electrodes, and flexible displays. It also opens a new field of potential applications of BC materials. PMID:21671578

Hu, Weili; Chen, Shiyan; Yang, Zhenhua; Liu, Luting; Wang, Huaping

2011-07-01

398

Electrical properties of polypropylene-based composites controlled by multilayered distribution of conductive particles.  

PubMed

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

Gao, Wanli; Zheng, Yu; Shen, Jiabin; Guo, Shaoyun

2015-01-28

399

Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer  

DOEpatents

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.

Spahn, O.B.; Lear, K.L.

1998-03-10

400

Automated management of nutrient solutions based on target electrical conductivity, ph, and nutrient concentration ratios  

Microsoft Academic Search

An algorithm to automatically formulate the composition and prepare nutrient solutions for soilless cultures based on desired characteristics given as target values is proposed. To formulate the complete ionic composition of a nutrient solution, standard recommendations referring to the following solution characteristics should be available: (i) electrical conductivity (EC), (ii) pH, (iii) concentration ratios of macronutrients (meq basis), and (iv)

Dimitrios Savvas; Konstantinos Adamidis

1999-01-01

401

Electric Conduction in Semiconductors: A Pedagogical Model Based on the Monte Carlo Method  

ERIC Educational Resources Information Center

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…

Capizzo, M. C.; Sperandeo-Mineo, R. M.; Zarcone, M.

2008-01-01

402

The electrical conductivity of water at dynamic pressures from 5 to 40 GPa  

Microsoft Academic Search

The electrical conductivity of water was measured under shock loading by explosives. The experiments in the pressure range from 5 to 15 GPa were made with shock waves produced by cylindrical charges made of RDX\\/TNT 60\\/40. The higher pressures up to 40 GPa were reached by Mach reflection in a cylindrical tube of explosive filled with water. The results can

K. Hollenberg

1983-01-01

403

Laminarization of a submerged jet of electrically conducting fluid by means of a longitudinal magnetic field  

Microsoft Academic Search

A method of laminarizing electrically conducting jet flows by means of the combined use of a longitudinal magnetic field and inlet devices which form an initial velocity profile with smooth variation at the edge of the jet and a low perturbation level is proposed. An experimental investigation of delayed transition in a circular submerged jet, which demonstrates the high efficiency

V. M. Ievlev; V. B. Levin

1989-01-01

404

Electrical conductivity of copper and aluminum at high temperatures and pressures  

SciTech Connect

Accurate values of material properties are needed for predicting the performance of magnetocumulative generators, rail guns, and other pulsed power systems. Previous electrical conductivity measurements are extended to pressures above 1 Mbar and utilized in a simple model for flux diffusion in aluminum and copper at high field conditions.

Mitchell, A.C.; Keeler, R.N.

1986-01-01

405

Mechanically robust, electrically conductive and stimuli-responsive binary network hydrogels enabled by superelastic graphene aerogels.  

PubMed

The architecture of the nanofiller phase in polymer nanocomposites matters! Polymer hydrogels that can combine stimuli-responsiveness with excellent electrically conductivity and mechanical strength can be fabricated by incorporation of the polymer into an ultralight and superelastic graphene aerogel to form a binary network. PMID:24634392

Qiu, Ling; Liu, Diyan; Wang, Yufei; Cheng, Chi; Zhou, Kun; Ding, Jie; Truong, Van-Tan; Li, Dan

2014-05-28

406

Electrical and optical properties of Zn–In–Sn–O transparent conducting thin films  

Microsoft Academic Search

Indium tin oxide (ITO) is one of the widely used transparent conductive oxides (TCO) for application as transparent electrode in thin film silicon solar cells or thin film transistors owing to its low resistivity and high transparency. Nevertheless, indium is a scarce and expensive element and ITO films require high deposition temperature to achieve good electrical and optical properties. On

Paz Carreras; Aldrin Antony; Fredy Rojas; Joan Bertomeu

407

Fuel cell components and systems having carbon-containing electrically-conductive hollow fibers  

DOEpatents

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.

Langry, Kevin C.; Farmer, Joseph C.

2014-07-08

408

Density, Electrical Conductivity and Viscosity of Hg(0.8)Cd(0.2)Te Melt  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

409

Electrical conductivity and current-voltage characteristics of alumina with or without neutron and electron irradiation  

E-print Network

-ku, Fukuoka 812-8581, Japan b Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak, Ibarakiken 311-1313, Japan Abstract The in situ measurement of electrical conductivity and of current) of alumina under irradiation are two of the critical issues for its application to fusion reactors. Many

Howlader, Matiar R

410

Anomalous diffusivity and electric conductivity for low concentration electrolytes in nanopores S. K. Lai1,  

E-print Network

Anomalous diffusivity and electric conductivity for low concentration electrolytes in nanopores S properties of electrolytes in nanopores. The realistic primitive model and the restrictive primitive model widely used in the statistical mechanics of liquid-state theory are applied to model the electrolytes

411

Seismic reflections and electrical conductivity: A case of Holmes's curious dog?  

E-print Network

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

Jones, Alan G.

412

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

413

Conductivity and current density image reconstruction using harmonic Bz algorithm in magnetic resonance electrical impedance tomography  

Microsoft Academic Search

Magnetic resonance electrical impedance tomography (MREIT) is to provide cross-sectional images of the conductivity distribution ? of a subject. While injecting current into the subject, we measure one component Bz of the induced magnetic flux density B = (Bx, By, Bz) using an MRI scanner. Based on the relation between ?2Bz and ??, the harmonic Bz algorithm reconstructs an image

Suk Hoon Oh; Byung Il Lee; Eung Je Woo; Soo Yeol Lee; Min Hyoung Cho; Ohin Kwon; Jin Keun Seo

2003-01-01

414

A Simple Demonstration of the High-Temperature Electrical Conductivity of Glass  

ERIC Educational Resources Information Center

We usually think of glass as a good electrical insulator; this, however, is not always the case. There are several ways to show that glass becomes conducting at high temperatures, but the following approach, devised by Brown University demonstration manager Gerald Zani, may be one of the simplest to perform.

Chiaverina, Chris

2014-01-01

415

Effect of repetitive laser pulses on the electrical conductivity of intervertebral disc tissue  

SciTech Connect

The thermomechanical effect of 1.56-{mu}m fibre laser pulses on intervertebral disc cartilage has been studied using ac conductivity measurements with coaxial electrodes integrated with an optical fibre for laser radiation delivery to the tissue. The observed time dependences of tissue conductivity can be interpreted in terms of hydraulic effects and thermomechanical changes in tissue structure. The laserinduced changes in the electrical parameters of the tissue are shown to correlate with the structural changes, which were visualised using shadowgraph imaging. Local ac conductivity measurements in the bulk of tissue can be used to develop a diagnostic/monitoring system for laser regeneration of intervertebral discs. (laser biology and medicine)

Omel'chenko, A I; Sobol', E N [Institute of Laser and Information Technologies, Russian Academy of Sciences, Troitsk, Moscow Region (Russian Federation)

2009-03-31

416

Nanoscale electrical property studies of individual GeSi quantum rings by conductive scanning probe microscopy  

PubMed Central

The nanoscale electrical properties of individual self-assembled GeSi quantum rings (QRs) were studied by scanning probe microscopy-based techniques. The surface potential distributions of individual GeSi QRs are obtained by scanning Kelvin microscopy (SKM). Ring-shaped work function distributions are observed, presenting that the QRs' rim has a larger work function than the QRs' central hole. By combining the SKM results with those obtained by conductive atomic force microscopy and scanning capacitance microscopy, the correlations between the surface potential, conductance, and carrier density distributions are revealed, and a possible interpretation for the QRs' conductance distributions is suggested. PMID:23194252

2012-01-01

417

Electrically conducting poly(para-phenylene sulfide) prepared by doping with nitrosyl salts from solution  

NASA Astrophysics Data System (ADS)

Para(polyphenylene sulfide) may be doped spontaneously and rapidly with nitrosyl salts (NOPF6, NOSbF6) from solution to yield an electrically conducting material (10-1ohm-1cm-1). The level of conductivity is primarily dependent on the extent of dopant incorporation, which in turn is determined by the polymer’s crystallinity; the more amorphous the polymer, the more dopant it takes up and the more conductive it becomes. The incorporation of dopants produces irreversible chemical changes in the polymer resulting in the deterioration of its mechanical properties.

Rubner, Michael; Cukor, Peter; Jopson, Harriet; Deits, Walter

1982-03-01

418

Monte Carlo Simulation of the Electrical Conductivity of Rubber Compounds During Silanization  

NASA Astrophysics Data System (ADS)

Monte Carlo simulation of temperature dependence of electric conductivity of a model mixture system, which involves reaction with first order kinetics, was carried out on the basis of chemical kinetics laws. The temperature dependence of the conductivity of rubber compounds during the process of silane treatment was studied experimentally. Simulated temperature dependence of conductivity was compared with measured experimental results. The obtained experimental results and the data derived from numerical simulation are in satisfactory agreement. Effective method for monitoring and control of silane treatment of rubber compounds directly during the material preparation process can be proposed on the basis of the abovementioned finding.

Hronkovi?, Ján; Kubliha, Marian; Minárik, Stanislav; Bošák, Ondrej; Tóth, Martin; Kalužný, Ján

2010-01-01

419

Method for electrically producing dispersions of a nonconductive fluid in a conductive medium  

DOEpatents

A method 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.

DePaoli, David W. (Knoxville, TN); Tsouris, Constantinos (Oak Ridge, TN); Feng, James Q. (Fairport, NY)

1998-01-01

420

SIGMELTS: A Web-portal for Electrical Conductivity Calculations in Geosciences  

NASA Astrophysics Data System (ADS)

We present a freely available and easy-to-use web application called SIGMELTS allowing the calculation of the electrical conductivity of geomaterials at relevant conditions for the Earth’s crust and mantle. By compiling previous results of electrical measurements in laboratory, this software enables to discriminate between the effect of different parameters on the bulk conductivity of silicate melts, carbonatites, fluids, minerals and mantle materials, such as the temperature (T), the pressure (P), the composition, the water content, the oxygen fugacity (fO2) and the crystal content. Different existing geometrical models are proposed to calculate the bulk conductivity of a two-phase mixture. Based on the electrical conductivity value of a mantle anomaly, an application has also been developed to determine the corresponding melt fraction at defined conditions (T, P, composition). This web application aims at improving the accessibility to laboratory data in order to precise the interpretation of MT profiles. Although there are examples of where the laboratory data have been used to interpret field data, there are also many instances where there are disconnects between those interpreting field MT data and the laboratory results. SIGMELTS also underlines that new electrical measurements in laboratory are needed to enlarge the present electrical database, particularly at high pressure conditions. An illustration of the use of SIGMELTS will be presented, in which calculations are applied to subduction zone related volcanic zone in the Central Andes. Along with petrological considerations, field and laboratory electrical data allow discrimination between the different hypotheses regarding the formation and rise from depth of melts and fluids and to quantify their storage conditions.

Le Trong, E.; Pommier, A.

2010-12-01

421

Electrical conductivity of pyrope-rich garnet at high temperature and high pressure  

NASA Astrophysics Data System (ADS)

Garnet is one of the important constituent minerals in the upper mantle and the transition zone of the Earth's mantle. However, there were very few previous works on its electrical conductivity. We have measured the electrical conductivity of single crystal of pyrope-rich garnet (˜Py 73-Alm 14-Grs 13) under the conditions of 4-16 GPa, 873-1473 K and frequency range from 10 -2 to 10 6 Hz, with a range of water content (from less than 10 to 7000 H/10 6 Si). A KAWAI-type multi-anvil apparatus and a Solarton-1260 Impedance/Gain Phase analyzer were used in this study. The impedance spectra showed two circles correspondent to the intrinsic resistivity of the crystal and to the effects of charge accumulation at the electrodes. The DC electrical conductivity was determined by the impedance spectroscopy. Molybdenum and molybdenum oxide solid buffer was used to control the oxygen fugacity. Results on hydrous and anhydrous samples were compared to determine the influence of water content on the electrical conductivity of single crystal garnet. Under anhydrous conditions, the electrical conductivity of garnet increases with temperature and decreases with pressure. When we used a thermal activation parameterization, we obtain the following relationship: ? = A exp(-( E* + PV*)/ RT), A = 1036(±236) (1 - 0.044(±0.007) P(GPa)) S/m or A = exp[7.16(±0.37) (1 - 0.012(±0.009) P(GPa))] S/m, E* = 128 ± 6 kJ/mol and V* = 2.50 ± 0.48 cm 3/mol. Hydrous garnet crystals have significantly higher electrical conductivity with different temperature and pressure sensitivity, and the conductivity in these samples increases with the water content. The results can be summarized as ?=A?Cwr exp[-(E+PV)/RT] with A = 1950 (+870, -600) S/m, r = 0.63 ± 0.19, E* = 70 ± 5 kJ/mol and V* = -0.57 ± 0.05 cm 3/mol. These results are similar to those obtained by Wang et al. [Wang, D.J., Mookherjee, M., Xu, Y.S., Karato. S., 2006. The effect of water on the electrical conductivity of olivine. Nature 443, 977-980] for olivine, Huang et al. [Huang, X.G., Xu, Y.S., Karato, S., 2005. Water content in the transition zone from electrical conductivity of wadsleyite and ringwoodite. Nature 434, 746-749] for wadsleyite and ringwoodite and we suggest that the mechanism of hydrogen conduction is likely common to these minerals. We conclude that hydrogen enhances the electrical conductivity of pyrope-rich garnet and its effect increases with pressure but decreases with temperature. At a typical pressure and temperature in the upper mantle, the influence of water is substantial.

Dai, Lidong; Karato, Shun-ichiro

2009-09-01

422

Electrical conductivity of hot expanded aluminum: experimental measurements and ab initio calculations.  

PubMed

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

Recoules, Vanina; Renaudin, Patrick; Clérouin, Jean; Noiret, Pierre; Zérah, Gilles

2002-11-01

423

Polyimide nanocomposites based on functionalized graphene sheets: Morphologies, thermal properties, and electrical and thermal conductivities  

NASA Astrophysics Data System (ADS)

Polyimide (PI) films were prepared by reacting 4,4'-(4,4'-isopropylidene-diphenoxy)-bis(phthalic anhydride) and 1,3-bis(4-aminophenoxy)benzene. The 4-phenylbutylamine-functionalized graphene sheets (PBA-GSs) used for the preparation of the PI nanocomposite films were prepared by mixing a dispersion of graphite oxide with a solution of the ammonium salt of 4-phenylbutylamine (PBA). PI nanocomposite films containing different amounts of PBA-GS (0-10 wt%) were compared in terms of their morphologies, thermal properties, and electrical and thermal conductivities. Only a small amount of PBA-GS was required to improve the thermal properties and thermal conductivities of the PI; the maximum enhancements in these parameters were observed at 1 and 3 wt% PBA-GS, respectively. In contrast, the electrical conductivity of the PI hybrid films continued to increase with increasing PBA-GS content from 1 to 10 wt%.

Heo, Cheol; Chang, Jin-Hae

2013-10-01

424

Terahertz electrical conductivity and optical characterization of composite nonaligned single- and multiwalled carbon nanotubes  

NASA Astrophysics Data System (ADS)

We employed noncontact terahertz time-domain spectroscopy to investigate and compare the electrical/optical properties of nonaligned single-walled carbon nanotube and nonaligned multiwalled carbon nanotube thin films. Using Drude-Lorentz model together with the Maxwell Garnett effective medium theory, we determined the electrical conductivities from the extracted data of differential complex terahertz analysis in the frequency range of 0.1 to 2 THz. The results demonstrate that the conductivity of isotropic single-walled carbon nanotube thin film is almost two times larger compared to isotropic multiwalled carbon nanotube thin film due to the increased number of surface defects and the availability of mobile carriers. By using Drude-Lorentz model, the broadening optical density and conductivity can be studied at higher frequencies.

Dadrasnia, Ehsan; Puthukodan, Sujitha; Lamela, Horacio

2014-01-01

425

Comparison of electrical conductivities of various brain phantom gels: Developing a ‘Brain Gel Model’  

PubMed Central

The use of conducting gels to mimic brain and other tissues is of increasing interest in the development of new medical devices. Currently, there are few such models that can be utilized at physiologic temperatures. In this work, the conductivities of agar, agarose and gelatin gels were manipulated by varying NaCl concentration from 0–1 mg/ml. The AC conductivity was measured at room and physiological temperatures (37°C) in the 100–500 Hz frequency range. Conductivity (?) was nearly independent of frequency but increased linearly with NaCl concentration and was higher at physiological temperatures in these gels. A formula for predicting conductivity as a function of NaCl concentration was derived for each gel type. The overall goal is to develop a ‘brain gel model’, for studying low frequency electrical properties of the brain and other tissues at physiological temperatures. PMID:23139442

Kandadai, Madhuvanthi A.; Raymond, Jason L.; Shaw, George J.

2012-01-01

426

Electrical conductivity studies on CuBr containing Al2O3 particles  

NASA Technical Reports Server (NTRS)

The conductivity of CuBr was studied and the role of a second phase, Al2O3, dispersed in CuBr was tested. CuBr melts at 493 C and exhibits three phases in the solid state. CuBr is a good ionic conductor with a transport number for copper ions of virtually unity with weighed proportions of the appropriate chemicals used. The CuBr materials were heated above melting point of CuBr, and the samples were sandwiched between copper electrodes. The ac conductivity, was determined at 1 kHz between 25 and 440 C depending on the sample. It was shown that at low temperatures, the conductivity for CuBr (Al2O3) increased by as much as 100, whereas in the beta phase the conductivity of CuBr containing Al2O3 decreased. The electrical conductivity studies are in agreement with earlier data.

Dubec, P. M.; Wagner, J. B., Jr.

1984-01-01

427

Model of sand formations for joint simulation of elastic moduli and electrical conductivity  

NASA Astrophysics Data System (ADS)

This paper presents an approach for the joint simulation of elastic-wave velocities (compressional and shear waves) and electrical conductivity for clastic rocks using a unified microstructural model. We treat clastic formations as porous composite materials containing two components: solid grains and pores completely saturated with fluids (gas-water-oil mixture). The effective shapes of both components correspond to triaxial ellipsoids. For calculating the effective properties of such a composite, we apply the self-consistent effective media approximation (EMA) method. This method treats all components equally without introducing any host and requires having knowledge of their shapes. To determine the pore and grain effective aspect ratios, we have used a set of experimental data that included the empirical regression equations published for the elastic-wave velocities in clean sandstone formations and Archie's law for the electrical conductivity. By applying the inversion procedure that consists of minimizing the difference between the experimental and EMA-predicted data, the aspect ratios of grains and pores as a porosity function have been obtained. Based on this relation and knowing individual property components (elastic and electrical conductivity) for grains and conductivity for pore saturating fluids, we can calculate effective properties of the clean sandstone formations. We demonstrate that to simplify the simulation of effective properties, grains and pores can be approximated by spheroids. However, in this case, the relative errors that the inversion process yields are higher in comparison with those of the three-axis ellipsoids. Additionally, we have determined the aspect ratios of components for several velocity equations (including different confinement pressures) and various cementation factors 'm' in Archie's law. We have modelled electrical conductivity for clastic formations with different water mineralization and oil saturation. The effective conductivity obtained by using our approach reflects a good fit with the published experimental data.

Aquino-López, A.; Mousatov, A.; Markov, M.

2011-12-01

428

Temperature Behavior of Electric Relaxational Effects due to Ionic Conductivity in Liquid Lactones  

NASA Astrophysics Data System (ADS)

This paper concerns the studies of temperature and frequency behavior of the complex impedance, electric modulus, and electric conductivity due to an ionic current in liquid ?-butyrolactone (GBL) and ?-valerolactone (GVL). The frequency of the applied electric stimulus (500 Hz to 5 MHz) corresponds to the static dielectric regime of the lactones. The studies were performed in the temperature range of 263 K to 313 K. It was shown that in the static dielectric case, the dc ionic conductivity ( ? DC) and the static dielectric permittivity {(\\varepsilon_s)} determine the relaxational behavior of the impedance ( Z*) and the electric modulus ( M*) of the molecular liquids and both spectra are of the Debye-type characterized by the same conductivity relaxation time ( ? ? ). Both ? DC and ? ? of GBL and GVL fairly well fulfill an Arrhenius temperature dependence with very similar values of the thermal activation energy {E_{?_DC} ? E_{tau_?} ? 25 kJ . mol^{-1}} . The temperature dependence of the static dielectric permittivity and its temperature derivative is analyzed and interpreted in terms of the dipolar aggregation in the studied lactones.

?wiergiel, J.; Jad?yn, J.

2012-05-01

429

New method for solving inductive electric fields in the non-uniformly conducting ionosphere  

NASA Astrophysics Data System (ADS)

We present a new calculation method for solving inductive electric fields in the ionosphere. The time series of the potential part of the ionospheric electric field, together with the Hall and Pedersen conductances serves as the input to this method. The output is the time series of the induced rotational part of the ionospheric electric field. The calculation method works in the time-domain and can be used with non-uniform, time-dependent conductances. In addition, no particular symmetry requirements are imposed on the input potential electric field. The presented method makes use of special non-local vector basis functions called the Cartesian Elementary Current Systems (CECS). This vector basis offers a convenient way of representing curl-free and divergence-free parts of 2-dimensional vector fields and makes it possible to solve the induction problem using simple linear algebra. The new calculation method is validated by comparing it with previously published results for Alfvén wave reflection from a uniformly conducting ionosphere.

Vanhamäki, H.; Amm, O.; Viljanen, A.

2006-10-01

430

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

NASA Astrophysics Data System (ADS)

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 inner core to reach its current size. Electrical conductivity sets the rate of magnetic field dissipation, and consequently the amount of energy required to sustain the geodynamo. Also, because these properties tightly control the heat budget within the core, they dictate the extent to which radiogenic heat need to be invoked to obtain thermal history models that are in agreement with geophysical and paleomagnetic observations. Current estimates for electrical conductivity of iron at conditions characteristic of Earth's core are rather uncertain, constraining the value only to within a factor of three. Thermal conductivity values are subsequently obtained by applying the Wiedemann-Franz relation, the validity of which has not been rigorously shown at extreme pressures. In addition, electronic transport properties are expected to depend strongly on pressure (P) and temperature (T), as well as on the concentration (X) of light elements in the liquid metal. However, with no data available on these variations, geophysical studies in which these values are applied invariably assume them to be constant. In an effort to improve our understanding of the P-T-X behavior of electronic transport properties in the core, and also to test the various assumptions made in their determination, we have performed first-principles calculations of the electrical and thermal conductivity of liquid iron over a large range of pressure and temperature conditions, including those characteristic of Earth's core. Compositions respectively doped with silicon, oxygen and sulphur are also considered. These calculations involve using first-principles molecular dynamics to generate a series of uncorrelated liquid structures at constant temperature and density, for which the electronic transport properties are then computed using the Kubo-Greenwood equation. Our aim is to construct a parameterized model for the thermal and electrical conductivity of liquid iron as a function of pressure, temperature and light element composition, which can be applied in geodynamo simulations and thermal history models for planetary cores. Preliminary results indicate a strong pressure and temperature dependence, with the Wiedemann-Franz relation only approximately satisfied. Implications of these results for models of the thermal history of the core will be considered and discussed.

de Koker, N.; Steinle-Neumann, G.; Vl?ek, V.

2010-12-01

431

Nonlinear optical and electrical conductivity properties of Carbon Nanotubes (CNT) doped in Sol-Gel matrices  

NASA Astrophysics Data System (ADS)

Carbon-nanotubes (CNT) are fascinating compounds, exhibiting exceptional electrical, thermal conductivity, mechanical strength, and nonlinear optical (NLO) properties. Their unique structures involve large ?-?* electronic clouds. The energy level schemes thus created allow many electronic transitions between the ground and the excited states. The present work involves CNT-doped hybrid organic-inorganic glass composites prepared by a Fast-sol-gel method. Such composite glasses solidify without shrinkage or crack formation, and exhibit promising properties as optical devices. In this work we have studied nonlinear optical and electrical conductivity properties. The CNT composite glasses exhibited enhanced absorption at 532 nm, and saturable absorption at 1064 nm. The enhanced absorption at 532 was attributed to 2-photon absorption; saturable absorption was attributed to depletion of the absorbing ground-state, and was analyzed using the modified Frantz-Nodvik equation. Absorption cross-sections were extracted for the saturable absorption phenomenon. Such CNT composites glasses may be used as "optical limiting" filters in lasers near 532 nm, or as saturable absorbing filters for passive laser Q-switching near 1064 nm. The CNT composites electrical conductivity was studied as a function of the CNT concentration and modeled by a percolation theory. The maximal measured conductivity was ? ?10-3 (?cm)-1 for the CNT composites, representing a conductivity increase of at least 12 orders of magnitude compared to that of pure silica. A quite low percolation threshold was obtained, ?c = 0.22 wt.% CNT. Electrostatic Force Microscopy (EFM) and Conductive mode Atomic Force Microscopy (C-AFM) studies revealed that the conductivity occurs at the micro-level among the CNTs dispersed in the matrix.

Pokrass, Mariana; Burshtein, Zeev; Bar, Galit; Gvishi, Raz

2014-09-01

432

Electrical Conductivity of H2O-CO2 rich-Melt in the Mantle and the construction of petrology-based conductivity profiles  

NASA Astrophysics Data System (ADS)

Electromagnetic data images mantle regions more conductive than that of dry olivine. There is no doubt that melt are thermodynamically stable and present in the LAB, but how they can impact on mantle electrical conductivity remains debated. In particular, 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. But electrical conductivities of these melts are poorly known. So we have been performed electrical conductivity experimentation in piston cylinder on H2O-CO2 rich melts. We have explored different melt compositions, from carbonated melts to basalts. We have determined the effect of chemical compositions and volatiles on these melts. 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, we have produced a semi-empirical law predicting the conductivity as a function of H2O and CO2 contents. Based on this law and the electrical conductivity of olivine, we have constructed 1D conductivity profiles. With these profiles, we discuss the effect of volatiles content (in the melt and in the mantle), melt fractions (mixing law and interconnection of the melt) and T-P on conductivity. And finally, we conclude that the electrical conductivities of the mantle is a powerful 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.

Sifre, David; Hashim, Leïla; Gaillard, Fabrice

2014-05-01

433

Interior-architectured ZnO nanostructure for enhanced electrical conductivity via stepwise fabrication process.  

PubMed

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

Chong, Eugene; Kim, Sarah; Choi, Jun-Hyuk; Choi, Dae-Geun; Jung, Joo-Yun; Jeong, Jun-Ho; Lee, Eung-Sug; Lee, Jaewhan; Park, Inkyu; Lee, Jihye

2014-01-01

434

Interior-architectured ZnO nanostructure for enhanced electrical conductivity via stepwise fabrication process  

NASA Astrophysics Data System (ADS)

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.

Chong, Eugene; Kim, Sarah; Choi, Jun-Hyuk; Choi, Dae-Geun; Jung, Joo-Yun; Jeong, Jun-Ho; Lee, Eung-sug; Lee, Jaewhan; Park, Inkyu; Lee, Jihye

2014-08-01

435

A new method of calculating electrical conductivity with applications to natural waters  

NASA Astrophysics Data System (ADS)

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.

McCleskey, R. Blaine; Nordstrom, D. Kirk; Ryan, Joseph N.; Ball, James W.

2012-01-01

436

A new method of calculating electrical conductivity with applications to natural waters  

USGS Publications Warehouse

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.

McCleskey, R. Blaine; Nordstrom, D. Kirk; Ryan, Joseph N.; Ball, James W.

2012-01-01

437

Electrically conducting polymers as templating interfaces for fabrication of copper nanotubes.  

PubMed

Submicrometer tubes have been fabricated by a polymer-based template approach using electroless deposition. The copper was deposited on polystyrene fibers functionalized with an interfacial electrically conducting polyaniline thin film layer. Thermal degradation of the functionalized fiber templates resulted in copper tubes of diameter 1600 ± 50 nm with wall thicknesses ranging between 100 and 200 nm. The morphology and elemental analysis of copper coaxial fibers was analyzed using SEM and EDS. Electrical properties were analyzed using FTIR and PXRD was used to study crystal structure of copper nanotubes. PMID:22455497

Mushibe, Eliud K; Andala, Dickson; Murphy, Steven C; Raiti-Palazzolo, Kate; Duffy-Matzner, Jetty L; Jones, Wayne E

2012-04-24

438