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1

Apparent soil electrical conductivity measurements in agriculture  

Microsoft Academic Search

The field-scale application of apparent soil electrical conductivity (ECa) to agriculture has its origin in the measurement of soil salinity, which is an arid-zone problem associated with irrigated agricultural land and with areas having shallow water tables. Apparent soil electrical conductivity is influenced by a combination of physico-chemical properties including soluble salts, clay content and mineralogy, soil water content, bulk

D. L. Corwin; S. M. Lesch

2005-01-01

2

Characterizing soil spatial variability with apparent soil electrical conductivity  

Microsoft Academic Search

Spatial characterization of the variability of soil physico-chemical properties is a fundamental element of (i) soil quality assessment, (ii) modeling non-point source pollutants in soil, and (iii) site-specific crop management. Apparent soil electrical conductivity (ECa) is a quick, reliable measurement that is frequently used for the spatio-temporal characterization of edaphic (e.g., salinity, water content, texture, and bulk density) and anthropogenic

D. L. Corwin; S. M. Lesch

2005-01-01

3

Exploring the spatial relations between soil physical properties and apparent electrical conductivity  

Microsoft Academic Search

Relations between the apparent electrical conductivity of the soil (ECa) and top- and sub-soil physical properties were examined for two arable fields in southern England (Crowmarsh Battle Farms and the Yattendon Estate). The spatial variation of ECa and the soil properties was explored geostatistically. The variogram ranges showed that ECa varied on a similar spatial scale to many of the

Z. L. Carroll; M. A. Oliver

2005-01-01

4

World's Oldest Cotton Experiment: Relationships between Soil Chemical and Physical Properties and Apparent Electrical Conductivity  

Microsoft Academic Search

Measuring and mapping apparent soil electrical conductivity (ECa) is a potentially useful tool for delineating soil variability. The “Old Rotation,” the world's oldest continuous cotton (Gossypium hirsutum L.) experiment (ca. 1896), provides a valuable resource for evaluating soil spatial variability. The objectives of this study were to determine the relationship between soil chemical and physical properties and ECa in the

D. W. Reeves; J. N. Shaw; C. C. Mitchell

2006-01-01

5

Using apparent soil electrical conductivity (EC a ) to characterize vineyard soils of high clay content  

Microsoft Academic Search

The adoption of precision viticulture requires a detailed knowledge of variation in soil chemical, physical and profile properties.\\u000a This study evaluates the usefulness of apparent electrical conductivity (ECa) data within a GIS framework to identify variations in soil chemical and physical properties and moisture content. The work\\u000a was conducted in a vineyard located in the Carneros Region (Napa Valley, California).

José Ramon Rodríguez-Pérez; Richard E. Plant; Jean-Jacques Lambert; David R. Smart

6

Investigation and modelling of the influence of soil moisture content and soil temperature on apparent electrical conductivity  

NASA Astrophysics Data System (ADS)

Time-lapse shallow ground-based electromagnetic induction (EMI) measurements are often applied to monitor the dynamics of vadose zone soil water content. However, the relationship between the measured apparent electrical conductivity (ECa) and soil water content is not straightforward. First, apparent ECa reflects a depth-weighted value of the ground's electrical conductivity distribution. Linking it directly to a water content value down to a specific depth is therefore not possible. Secondly, the electrical conductivity of the bulk soil depends on the influence of several factors. The major contribution to a change in electrical conductivity is known to be caused by the amount of dissolved ions in the pore fluid, variations in soil water content and soil temperature. In addition, electrical conductivity depends on clay content. There exists no universal petrophysical relationship that relates the sum of all these parameters to electrical conductivity. The separation of the different influences remains challenging since EMI devices are applied in a non-destructive manner and profile information about soil textural properties, soil water content, soil temperature and the soil electrical conductivity is usually not accessible. We use a time series of TDR-measured soil water contents and soil electrical conductivities together with soil temperature data measured at various depths of a soil profile at the Grenzhof test site to investigate the influence of soil water content and temperature on the soil's electrical conductivity. Subsequently, we apply forward modelling of electrical conductivity to estimate the response of the EMI device on temperature-corrected and uncorrected electrical conductivity profiles. Preliminary results show, that the influence of a change in soil water content on apparent electrical conductivity conducts only few mS/m and is often influenced by simultaneous occurring changes in soil temperature.

Denk, Astrid; Dietrich, Peter; van der Kruk, Jan; Roth, Kurt; Wollschläger, Ute

2014-05-01

7

Characterizing the spatial variability of soil infiltration using apparent electrical conductivity  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

8

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

9

Apparent Thermal Conductivities of Fiberglass Insulation  

Microsoft Academic Search

This paper deals with the thermal characterization of fiberglass insu lation used in baking oven applications. The apparent thermal conductivities of fiber glass bats were measured with a commercially available guarded hot plate k-tester as a function of density, thickness, hot and cold surface emissivities and mean tempera ture levels applicable to range operation and self cleaning conditions. An axisym

N. Abuaf; H. Jaster

1990-01-01

10

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

11

Effectiveness of apparent electrical conductivity surveys at varying soil water contents for assessing soil and water dynamics across a rainfed mountain olive orchard in SW Spain.  

NASA Astrophysics Data System (ADS)

Knowledge and understanding of the spatio-temporal variability of soil physical and chemical properties at the field or micro-catchment scale are of prime importance for many agricultural and environmental applications that aim at soil, water and carbon conservation. Geophysical methods, such as electromagnetic induction (EMI), are nowadays a key tool to monitor these properties across relevant scales, as a result of their non-destructive nature and their capability to survey repeatedly large areas within a small time window. Geophysical instrument response depends on the electromagnetic properties of the subsoil and for EMI in particular moist soil conditions are generally considered as most suitable for data acquisition. In water-limited environments, such as those under Mediterranean climate, these conditions are not met during large periods of the year, apparently hampering the usefulness of the method in these regions. The aim of this study is to obtain a better understanding of the sensor response and the contribution of soil properties to the geophysical signals under varying water contents. An experimental micro-catchment in SW Spain under rainfed olive cultivation was surveyed for apparent electrical conductivity (ECa) on 11 moments in time using a Dualem-21S. In addition, ECa and soil water content (SWC) was measured at 48 locations throughout the catchment on each survey date. At each of these locations, soil profile samples were analyzed for texture, soil organic matter content (SOM), soil depth, gravel content, and bulk density. Overall, correlations between the different soil properties and ECa improved with increasing SWC, although the ECa patterns remained constant in time. Time-lapse imaging offers the most promising results under the conditions of this study, but still requires at least one survey under wet soil conditions. Despite the smaller correlations between ECa and soil properties under dry conditions, ECa patterns are still relevant for assessing soil and water dynamics at the field or micro-catchment scale.

Aura, Pedrera,; De Vijver, Ellen, Van; Karl, Vanderlinden,; Sergio, Martos-Rosillo; Meirvenne, Marc, Van; Espejo-Pérez, Antonio, J.; Encarnación V., Taguas,; Giráldez, Juan, V.

2013-04-01

12

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

13

Apparent thermal conductivity measurements by an unguarded technique  

NASA Astrophysics Data System (ADS)

An unguarded longitudinal heat flow apparatus for measuring the apparent thermal conductivity (lambda/sub a) of insulations was tested. Heat flow is provided by a horizontal electrically heated Nichrome screen sandwiched between test samples that are bounded by temperature controlled copper plates and 9 cm of mineral fiber insulation. A determinate error analysis shows lambda/sub a/ measurement uncertainty to be less than + or - 1.7% for insulating materials as thin as 3 cm. Three-dimensional thermal modeling indicates negligible error in lambda/sub a/ due to edge loss for insulations up to 7.62 cm thick when the temperature difference across the sample is measured at the screen center. System repeatability and reproducibility were determined to be + or - 0.2%. Differences of lambda/sub a/ results from the screen tester and results from the National Bureau of Standards were 0.1% for a 10-kg/m(3) Calibration Transfer Standard and 0.9% for 127-kg/m(3) fibrous glass board (SRM 1450b). Measurements on fiberglass and rock wool batt insulations showed the dependence of lambda/sub a/ on density, temperature, temperature difference, plate emittance, and heat flow direction. Results obtained for lambda/sub a/ as a function of density at 240C differed by less than 2% from values obtained with a guarded hot plate. It is demonstrated that this simple technique has the accuracy and sensitivity needed for useful lambda/sub a/ measurements on thermal insulating materials.

Graves, R. S.; Yarbrough, D. W.; McElroy, D. L.

14

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

15

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 consistant pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like.

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

1989-01-01

16

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

17

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

18

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

19

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

20

Electrical Conductivity of Olivine  

Microsoft Academic Search

The electrical conductivity a of single crystals of olivine of 0, 7.7, 8.2, 9.4, and 26.4 mole % fayalite has been measured up to 1200øC and 7.5 kb. Samples from different localities with approximately the same fayalite content and impurity levels have electrical conductivities that differ by 2-3 orders of magnitude. It is proposed that the oxidation state of the

Al Duba

1972-01-01

21

Electrical conductivity and  

Microsoft Academic Search

Nevertheless, it should be noted in Figures 1 and 7 and Tables I and II that the changes in the electrical conductivity values are not of orders of magnitude, indicating conduction in the metallic regime of a percolation curve. Furthermore, due to the determined chemical composition of second-phase particles, it is believed that the aluminum silicon eutectic phase acts as

A. Manzano-Ramirez; E. Nava-Vazquez; J. Gonzalez-Hernandez

1993-01-01

22

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

23

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

24

Anomalous electrical conductivity of nanoscale colloidal suspensions.  

PubMed

The electrical conductivity of colloidal suspensions containing nanoscale conducting particles is nontrivially related to the particle volume fraction and the electrical double layer thickness. Classical electrochemical models, however, tend to grossly overpredict the pertinent effective electrical conductivity values, as compared to those obtained under experimental conditions. We attempt to address this discrepancy by appealing to the complex interconnection between the aggregation kinetics of the nanoscale particles and the electrodynamics within the double layer. In particular, we model the consequent alterations in the effective electrophoretic mobility values of the suspension by addressing the fundamentals of agglomeration-deagglomeration mechanisms through the pertinent variations in the effective particulate dimensions, solid fractions, as well as the equivalent suspension viscosity. The consequent alterations in the electrical conductivity values provide a substantially improved prediction of the corresponding experimental findings and explain the apparent anomalous behavior predicted by the classical theoretical postulates. PMID:19206448

Chakraborty, Suman; Padhy, Sourav

2008-10-28

25

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

NASA Astrophysics Data System (ADS)

Because of their frequency-dependent penetration depth, eddy current measurements are capable of mapping the near-surface depth profile of the electrical conductivity. This technique is used to nondestructively characterize the subsurface residual stress and cold work distributions in shot-peened metal components. Unfortunately, the spurious surface roughness produced by the shot peening process causes an apparent loss of eddy current conductivity, thereby decreasing the accuracy of the measurements, especially in thermally relaxed specimens where the primary material effects are significantly reduced. In this paper, a numerical method is introduced based on the Rayleigh approximation for calculating the apparent eddy current conductivity loss exhibited by 1D randomly rough surfaces. The relevant boundary conditions are satisfied using the so-called point-by-point technique, and the results are first compared to the previously developed Rayleigh-Fourier technique for a 1D sinusoidal corrugation. Pseudorandom surface profiles of different autocorrelation functions are considered. It is found that the Gaussian model lends itself the best to numerical simulations, but it significantly underestimates the apparent eddy current conductivity loss expected on real shot-peened surfaces, which exhibit essentially exponential correlation function. It is also demonstrated that the Lorentzian model is numerically less stable, but physically closer to the exponential one. The latter could not be simulated reliably by the present numerical technique because of its slowly decaying high-frequency spectral components.

Yu, Feng; Nagy, Peter B.

2004-06-01

26

Electrical conduction in olivine  

Microsoft Academic Search

This paper reports detailed measurements of electrical conductivitysigma and thermoelectric effect \\/ital S\\/ in the mineral olivine and in syntheticforsterite as functions of temperature in the range from 1000\\/degree\\/ to1500 \\/degree\\/C and oxygen partial pressure in the range from 10\\/sup \\/minus\\/10\\/ to10⁴ Pa. The two most striking observations are strong conductivityanisotropy in forsterite and a sign change in \\/ital S\\/

Robert N. Schock; Alfred G. Duba; Thomas J. Shankland

1989-01-01

27

Electrically conductive anodized aluminum coatings  

NASA Technical Reports Server (NTRS)

A process for producing anodized aluminum with enhanced electrical conductivity, comprising anodic oxidation of aluminum alloy substrate, electrolytic deposition of a small amount of metal into the pores of the anodized aluminum, and electrolytic anodic deposition of an electrically conductive oxide, including manganese dioxide, into the pores containing the metal deposit; and the product produced by the process.

Alwitt, Robert S. (Inventor); Liu, Yanming (Inventor)

2001-01-01

28

Electrical conductivity of mantle minerals  

NASA Astrophysics Data System (ADS)

Electrical conductivity of mantle minerals Deep electrical conductivity profiles can provide constraints on the thermal and chemical state of the mantle. Especially, electrical conductivity is very sensitive to small amount of hydrogen and iron contents in minerals. Accurate knowledge of electrical conductivity of mantle minerals is needed to constrain water and/or iron contents in the mantle as a function of depth. We have investigated the electrical properties of olivine, wadsleyite, ringwoodite and majorite, which are main constituent minerals of the upper mantle by in situ electrical conductivity measurement using multianvil apparatus. The starting materials were olivine (Fo91) for olivine, wadsleyite and ringwoodite, and glass powder with composition of pyrolite minus olivine for majorite, respectively. In most cases, molybdenum disk electrode connecting to the sample was used as an oxygen buffer media, whose oxygen fugacity is close to Fe-FeO buffer. The electrical conductivities of the samples were measured at various pressures from 3 and 20 GPa and temperatures up to 2000K at low frequencies ranging from 0.01 to 0.1 Hz. For all the dry samples, electrical conductivity displays Arrhenian behavior over the entire investigated temperature range. In the high temperature range above 1700K, activation energies (more than 1.5 eV) tend to be higher than those in the lower temperature range (less than 1.5 eV). The absolute values of electrical conductivity (S/m) for each mineral are very similar to each other. From these measurements we noted that the electrical conductivities of dry olivine, wadsleyite and ringwoodite (less than 100 wt. ppm of water) are much lower than those previously reported (e.g., Xu et al., 1998). While conductivities of samples with certain amounts of hydrogen are comparable to that of the dry one, conductivity increases with increasing hydrogen concentrations. Activation energies of hydrogen-bearing nominally anhydrous minerals we measured decreases with increasing hydrogen concentration from nearly 1 to 0.5 eV. Using our results, we can estimate the electrical conductivity profile of the upper mantle. Comparing the reference model of Utada et al. (2003), our modeling demonstrates that the electrical conductivity of the upper mantle up to 410km discontinuity (i.e. olivine stability field) is close to that of dry olivine, whereas the electrical conductivities of dry wadsleyite, ringwoodite and majorite are much lower than the reference model. Therefore, a presence of hydrogen in their minerals or the other conductors is required to explain the high conductivity in the transition zone. References Xu, Y., Poe, B. T., Shankland, T. J. & Rubie, D. C., Electrical conductivity of olivine, wadsleyite and ringwoodite under upper-mantle conditions. Science 280, 1415-1418 (1998). Utada, H., Koyama, T., Shimizu, H. & Chave, A. D., A semi-global reference model for electrical conductivity in the mid-mantle beneath the north Pacific region. Geophys. Res. Lett. 30, 1194, doi:10.1029/2002GL016902 (2003).

Yoshino, T.; Manthilake, G.; Nishi, M.; Katsura, T.

2006-12-01

29

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

30

The instantaneous apparent resistivity tensor: a visualization scheme for LOTEM electric field measurements  

NASA Astrophysics Data System (ADS)

Long-offset transient electromagnetic (LOTEM) data have traditionally been represented as early- and late-time apparent resistivities. Time-varying electric field data recorded in a LOTEM survey made with multiple sources can be represented by an `instantaneous apparent resistivity tensor'. Three independent, coordinate-invariant, time-varying apparent resistivities can be derived from this tensor. For dipolar sources, the invariants are also independent of source orientation. In a uniform-resistivity half-space, the invariant given by the square root of the tensor determinant remains almost constant with time, deviating from the half-space resistivity by a maximum of 6 per cent. For a layered half-space, a distance-time pseudo-section of the determinant apparent resistivity produces an image of the layering beneath the measurement profile. As time increases, the instantaneous apparent resistivity tensor approaches the direct current apparent resistivity tensor. An approximate time-to-depth conversion can be achieved by integrating the diffusion depth formula with time, using the determinant apparent resistivity at each instant to represent the resistivity of the conductive medium. Localized near-surface inhomogeneities produce shifts in the time-domain apparent resistivity sounding curves that preserve the gradient, analogous to static shifts seen in magnetotelluric soundings. Instantaneous apparent resistivity tensors calculated for 3-D resistivity models suggest that profiles of LOTEM measurements across a simple 3-D structure can be used to create an image that reproduces the main features of the subsurface resistivity. Where measurements are distributed over an area, maps of the tensor invariants can be made into a sequence of images, which provides a way of `time slicing' down through the target structure.

Caldwell, T. Grant; Bibby, Hugh M.

1998-12-01

31

Dynamics of electrically conducting fluids  

NASA Astrophysics Data System (ADS)

Electrically conducting fluids are described by the magneto-hydrodynamic (MHD) formalism that combines the classical laws of fluid mechanics and electromagnetism. After a brief review of this formalism, several examples of electrically conducting fluids will be discussed. For instance, liquid metal flows are important in several industrial applications including the steel industry as well as in the description of geophysical flows and laboratory experiments on the dynamo effect. Also, plasmas represent an important class of electrically conductive fluids when they are treated in the limit of continuous media. Plasma physics is relevant in the study of various astrophysical systems as well as in laboratory experiments on magnetic confinement fusion. The importance of MHD effects for the ITER (International Thermonuclear Experimental Reactor) experiment will also be briefly discussed. Numerical simulations of the MHD equations play an increasingly important role in the description of electrically conducting fluids. Recent numerical results will be presented and MHD turbulence will be analyzed in terms of energy transfers, locality functions as well as sub-grid scale modeling in large eddy simulations.

Carati, Daniele

2010-11-01

32

Electric conductivity of plasma in solar wind  

NASA Technical Reports Server (NTRS)

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 10(exp 13) 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.

1995-01-01

33

Electrical conductivity of ice VII.  

PubMed

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

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

2014-01-01

34

Electrically conductive thermal control coatings  

NASA Technical Reports Server (NTRS)

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

Shai, M. C. (inventor)

1978-01-01

35

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

NASA Technical Reports Server (NTRS)

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

Yuan, Zeng-Guang; Kleinhenz, Julie E.

2011-01-01

36

Electrical Conductivity Measurements via a Low-Voltage Conductivity Channel  

Microsoft Academic Search

The electrical conductivity in combustion gases with four different compositions (2% potassium with 0%, 10%, 15%, and 20% aluminum by mass added to a hydrocarbon fuel burned in gaseous oxygen) was determined experimentally using conductivity channels with two geometrical configurations, one with a constant bore and one with a tapered bore. Electrical conductivity for these conditions was calculated using the

Robert Rhodes; Trevor Moeller; Dennis Keefer

2012-01-01

37

Electrical Conductivity of Serpentinized Rocks to 6 Kilobars  

Microsoft Academic Search

Electrical conductivity of serpentinized rocks from the Indian Ocean ridge is 3-4 orders of magnitude higher than that of serpentine-free peridotitc, hornblende gabbro, and basalt from the same area and from the Tonga trench. The enhanced conduction is apparently characteristic of many but not all serpentine-rich rocks and may be due in part to high porosity and in part to

R. M. Stesky; W. F. Brace

1973-01-01

38

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

39

Flexible silicone adhesive with high electrical conductivity  

Microsoft Academic Search

Technology that couples high electrical conductivity with silicone performance characteristics suitable for electrical interconnection of substrates having a mismatch of thermal coefficients of expansion (TCE) is discussed. The silver filled silicone compositions are processed and cured in a similar manner to conventional heat-cured silicone adhesives. The resulting products are both highly flexible and highly conductive, exhibiting volume resistivities down to

Michael A. Lutz; Richard L. Cole

1989-01-01

40

Review article Influence of electric conductivity management  

E-print Network

Review article Influence of electric conductivity management on greenhouse tomato yield and fruit quality Martine DORAISa,b*, Athanasios P. PAPADOPOULOSa, André GOSSELINb a Greenhouse and Processing Crops / tomato / electrical conductivity / salinity / fruit quality / greenhouse Résumé ­ Influence de la régie

Boyer, Edmond

41

Electrical conductivity of the Earth's lower mantle  

Microsoft Academic Search

THE electrical conductivity of the Earth's lower mantle constrains both the propagation to the surface of geomagnetic disturbances in the core and the nature of core-mantle coupling. Extrapolations of laboratory measurements on materials representative of the lower mantle agree weakly1,2 or not at all3,4 with recent geophysical models5-8 of lower-mantle electrical conductivity based on variations of magnetic and electrical fields

T. J. Shankland; J. Peyronneau; J.-P. Poirier

1993-01-01

42

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

43

Electrical, structural and processing properties of electrically conductive adhesives  

Microsoft Academic Search

There is growing interest in the potential of electrically conductive metal-loaded polymer adhesives. Eight commercial electrically conductive adhesive pastes for solder replacement in surface mount technology (SMT) and other microelectronic applications were selected for study, including both thermosetting and thermoplastic examples. All were silver based, except for one nickel-polymer composite. The properties on which this work was focused were the

Li Li; Christine Lizzul; Hansoo Kim; Isaac Sacolick; James E. Morris

1993-01-01

44

Laboratory Electrical Conductivity Measurement of Mantle Minerals  

Microsoft Academic Search

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

Takashi Yoshino

2010-01-01

45

Electrical conductivity of concrete containing silica fume  

Microsoft Academic Search

The influence of silica fume on concrete properties represents an important technical research. In general, silica fume tends to improve both mechanical characteristics and durability of concrete. Thus the electrical properties of concrete containing silica fume can be studied to clarify its physical performance during hydration. The electrical conductivity of neat cement, mortar and concrete pastes was measured during setting

S. A. Abo El-Enein; M. F. Kotkata; G. B. Hanna; M. Saad; M. M. Abd El Razek

1995-01-01

46

Global Electrical Conductivity Magnetic Satellite Induction Studies  

E-print Network

induction to measure Earth conductivity: · Magnetotelluric (MT) method Measure electric and magnetic fields-varying magnetic field induces electric currents in conductors. � E = - B t Secondary magnetic fields created by these currents appose the primary magnetic field. So, conductors attenuate magnetic fields. 2nd

Constable, Steve

47

CHARACTERISATION OF AN ELECTRICALLY CONDUCTIVE POLYMER COMPLEX  

Microsoft Academic Search

Polyaniline (PANI) is at present one of the most promising conductive polymers due to a number of important reasons including its chemical stability combined with high levels of electrical conductivity. Additionally, we have found that, following an in-situ deformation process, this polymer is suitable for the production of composites exhibiting a phase separated morphology with continuous fibrils of PANI in

Ricardo H. Cruz-Estrada; Michael J. Folkes

48

Electrical conductivity of concrete containing silica fume  

SciTech Connect

The influence of silica fume on concrete properties represents an important technical research. In general, silica fume tends to improve both mechanical characteristics and durability of concrete. Thus the electrical properties of concrete containing silica fume can be studied to clarify its physical performance during hydration. The electrical conductivity of neat cement, mortar and concrete pastes was measured during setting and hardening. The ordinary Portland cement was partially replaced by different amounts of silica fume by weight. The changes in the electrical conductivity were reported during setting and hardening after gauging with water. The results of this study showed that the electrical conductivity can be used as an indication for the setting characteristics as well as the structural changes of the hardened pastes made with and without silica fume.

Abo El-Enein, S.A.; Kotkata, M.F. [Ain Shams Univ., Cairo (Egypt)] [Ain Shams Univ., Cairo (Egypt); Hanna, G.B.; Saad, M.; Abd El Razek, M.M. [Building Research Center, Cairo (Egypt)] [Building Research Center, Cairo (Egypt)

1995-12-01

49

Mechanisms of electrical conductivity in olivine  

SciTech Connect

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

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

1984-01-01

50

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

51

Soliton electric generators based on conducting polymers  

NASA Astrophysics Data System (ADS)

Iodide doping produces charge carriers in ?-conjugated polymers. Motivated by the SSH theoretical model of solitons in one-dimensional conjugated polymers, chemical doping of polyacetylene film is experimentally carried out to generate solitons. An Arago-type wheel electric generator is assembled based on the doped polyacetylene in place of a copper or aluminium plate. This is the first report of electric generation in conducting polymers based on solitons.

Goto, Hiromasa

2014-03-01

52

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

53

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

54

Electrical Conductivity of Hydrogen-Bonded Polymers  

Microsoft Academic Search

The d.c. electrical conductivity of poly-gamma-benzyl-L-glutamate (PBLG), nylon 66 and calf thymus DNA has been investigated experimentally as the examples of hydrogen-bonded polymers. Energy gaps which are assumed to be the twice of the activation energy are determined by the temperature variation of conductance in the solid dry state; 2.07± 0.05 eV for PBLG in alpha-helix, 2.00± 0.05 eV for

Yasuhiro Miyoshi; Nobuhiko Saitô

1968-01-01

55

Electrical conductivity of warm expanded aluminum  

Microsoft Academic Search

The electronic and ionic structures of warm expanded aluminum are determined self-consistently using an average-atom formalism based on density-functional theory and Gibbs–Bogolyubov inequality. Ion configurations are generated using a least-square fit of the pair distribution function deduced from the average-atom model calculations. The electrical conductivity of the system is computed from the Kubo–Greenwood formula for the optical conductivity implemented in

Gerald Faussurier; Christophe Blancard; Patrick Renaudin; Pier-Luigi Silvestrelli

2006-01-01

56

Fundamental study of electrically conductive adhesives (ECAs)  

Microsoft Academic Search

Variations of volume resistivity of three electrically conductive adhesives (Ag-filled epoxy, Ag-filled cyanate ester, and Ni-filled epoxy) during 85°C\\/85%RH aging were studied. Volume resistivity of the two Ag-filled ECAs decreased slightly at the beginning of aging and then remained stable. However, the volume resistivity of the Ni-filled epoxy increased substantially. Joint resistance variations of these conductive adhesives with different metals

C. P. Wong; D. Lu; L. Meyers; Q. K. Tong

1997-01-01

57

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

58

Electrical conductivity of dense metal plasmas  

Microsoft Academic Search

The composition of dense metal plasmas is calculated considering higher ionization stages of the atoms. A system of coupled mass action laws is solved self-consistently taking into account medium corrections which lead to pressure ionization at high densities. The electrical conductivity is calculated within linear response theory. The interactions between the various species are treated on T matrix level. The

Ronald Redmer

1999-01-01

59

Electrically conductive containment vessel for molten aluminum  

Microsoft Academic Search

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

C. E. Holcombe; D. G. Scott

1985-01-01

60

Electrically conductive containment vessel for molten aluminum  

Microsoft Academic Search

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

C. E. Holcombe; D. G. Scott

1984-01-01

61

Thermal and electrical contact conductance studies  

NASA Technical Reports Server (NTRS)

Prediction of electrical and thermal contact resistance for pressed, nominally flat contacts is complicated by the large number of variables which influence contact formation. This is reflected in experimental results as a wide variation in contact resistances, spanning up to six orders of magnitude. A series of experiments were performed to observe the effects of oxidation and surface roughness on contact resistance. Electrical contact resistance and thermal contact conductance from 4 to 290 K on OFHC Cu contacts are reported. Electrical contact resistance was measured with a 4-wire DC technique. Thermal contact conductance was determined by steady-state longitudinal heat flow. Corrections for the bulk contribution ot the overall measured resistance were made, with the remaining resistance due solely to the presence of the contact.

Vansciver, S. W.; Nilles, M.

1985-01-01

62

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

63

Magnetotelluric apparent conductivity and seismic p-wave tomography comparison, Rio Grande Rift, Southwestern USA  

NASA Astrophysics Data System (ADS)

During the summers of 2012 and 2013, magnetotelluric (MT) data was collected in three transects across the Rio Grande Rift in Colorado and New Mexico. Previous seismological studies, including both regional deployments and EarthScope USArray Transportable Array (TA), have shown that a wide area of upper mantle below the Rio Grande Rift is seismically slow, but the cause of this is unclear. MT has the potential to help reduce the ambiguity in determining the cause of the seismically slow anomaly. Electrical conductivity determined from MT and elastic parameters determined from seismic experiments have different sensitivities to temperature, partial melt, hydration and composition; together these methods can be used to constrain the physical, chemical, and thermal state of the lithosphere, and to investigate changes in it throughout the rift. These constraints can help distinguish between different rift opening models such as the rift unzipping south to north or being rotated open. We have used a cross correlation algorithm to pick teleseismic P-wave arrival times from twenty-two events recorded by TA stations in Colorado and New Mexico from 2008 - 2010. Our teleseismic picks were used to create maps and profiles of travel time residuals that can be compared with existing tomographic images and with our new MT data. We have forward modeled select MT data to produce 1-D models of conductivity versus depth, which can then be compared to the average travel time residuals at TA stations in proximity to the MT profile. The travel time residuals across the three MT lines are also qualitatively compared to cross-sections of the Schmandt & Humphreys (2010) P-wave tomography model.

Harding, J.; Sheehan, A. F.; Feucht, D. W.; Bedrosian, P.; O'Rourke, C. T.

2013-12-01

64

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

65

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

66

The electrical conductivity of levitated liquids  

SciTech Connect

The electrical conductivities of aerodynamically levitated liquid spheres have been determined by an electrodeless method. It is shown that this technique is reliable over a wide range of temperatures; results are presented for a variety of systems including metals, semiconductors at room temperature and at their melting points, and solid and liquid Al{sub 2}O{sub 3}. {copyright} {ital 1997 American Institute of Physics.}

Enderby, J.E.; Ansell, S. [Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Argonne National Laboratory, Argonne, Illinois 60439 (United States); Krishnan, S. [Containerless Research, Inc., 910 University Place, Evanston, Illinois (United States)] [Containerless Research, Inc., 910 University Place, Evanston, Illinois (United States); Price, D.L.; Saboungi, M. [Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Argonne National Laboratory, Argonne, Illinois 60439 (United States)

1997-07-01

67

Transverse electric conductivity of quantum collisional plasmas  

E-print Network

Formulas for calculation of transverse dielectric function and transverse electric conductivity in quantum collisional plasmas under arbitrary degree of degeneracy of the electron gas are received. The Wigner - Vlasov - Boltzmann kinetic equation with collision integral in BGK (Bhatnagar, Gross and Krook) form in coordinate space is used. Various special cases are investigated. The case of fully degenerate quantum plasma was considered separately. Comparison with Lindhard's formula has been realized.

A. V. Latyshev; A. A. Yushkanov

2010-02-04

68

Electrical conductivity of warm expanded Al  

SciTech Connect

The electronic and ionic structures of warm expanded aluminum are determined self-consistently using an average-atom formalism based on density-functional theory and Gibbs-Bogolyubov inequality. Ion configurations are generated using a least-squares fit of the pair distribution function deduced from the average-atom model calculations. The electrical conductivity is computed from the Kubo-Greenwood formula for the optical conductivity implemented in a molecular dynamics scheme based on density-functional theory. This method allows us to go beyond the Ziman approach used in the average-atom formalism. Moreover, it is faster than performing quantum molecular dynamics simulations to obtain ion configurations for the conductivity calculation. Numerical results and comparisons with experiments are presented and discussed.

Faussurier, G.; Blancard, C.; Renaudin, P. [Departement de Physique Theorique et Appliquee, CEA/DAM Ile-de-France, Boite Postale 12-F-91680 Bruyeres-le-Chatel (France); Silvestrelli, P. L. [Dipartimento di Fisica 'G. Galilei', Universita di Padova, via Marzolo 8, I-35131 Padova (Italy) and DEMOCRITOS National Simulation Center, Trieste (Italy)

2006-02-15

69

Inductive Measurement of Plasma Jet Electrical Conductivity  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

70

Electrical conductivity of water-bearing magmas  

NASA Astrophysics Data System (ADS)

Phase diagrams and chemical analyzes of crystals and glass inclusions of erupted lavas tell us that most explosive volcanic eruptions were caused by extremely water-rich pre-eruptive conditions. Volcanologists estimate volcanic hazards by the pre-eruptive water content of lavas erupted in the past and they hypothesize that future eruptions should show similar features. Alternatively, the development of methods allowing direct estimation of water content of magmas stored in the Earth’s interior would have the advantage of providing direct constraints about upcoming rather than past eruptions. Geoelectrical sounding, being the most sensitive probe to the chemical state of the Earth’s interior, seems a promising tool providing that its interpretation is based on relevant laboratory constraints. However, the current database of electrical conductivity of silicate melt merely constrains anhydrous composition. We have therefore undertaken an experimental program aiming at elucidating the effect of water on the electrical conductivity of natural magmas. Measurements (impedance spectroscopy) are performed using a two electrodes set-up in an internally heated pressure vessel. The explored temperature and pressure range is 25-1350°C and 0.1-400MPa. The material used is a natural rhyolitic obsidian. Hydration of this rhyolite is first performed in Pt capsules with 0.5, 1, 2 and 6wt% of water. In a second step, the conductivity measurements are performed at pressure and temperature in a modified Pt capsule. One end of the capsule is arc-welded whereas the other end is closed with the help of a BN cone and cement through which an inner electrode is introduced in the form a Pt wire. The capsule is used as outer electrode. The electrical cell has therefore a radial geometry. The rhyolite is introduced in the cell in the form of a cylinder drilled in the previously hydrated glass. At dwell condition, the melt is sandwiched between two slices of quartz avoiding any deformation of the electrode-melt system. Primary results reveal a slightly negative effect of pressure of the conductivity of the nominally anhydrous rhyolite. The conductivity of water-bearing rhyolites is 0.5-2 orders of magnitude higher than dry basalt under otherwise the same conditions. Electrical conductivity is therefore a good probe of the chemical state of natural magmas.

Gaillard, F.

2003-04-01

71

Electrical Conductivity in Sunspots and Evershed Flow  

NASA Astrophysics Data System (ADS)

The Return Flux Sunspot model (Osherovich, 1982) suggests that a magnetic separatrix on the boundary between the umbra and penumbra separates magnetic lines that go up to the corona from magnetic lines that return to the photosphere. Using the Kawakami (1983) observations of the magnetic field and outflow in unipolar round sunspots, we calculate the electrical conductivity across the sunspot within the framework of the RF model and compare it with values previously suggested. References: Kawakami, H., 1983. Publ. Astron. Soc. Japan 35, 459. Osherovich, V.A., 1982, Solar Phys. 88, 119. Osherovich, V.A. and H.A. Garcia, 1990, GRL, 17, 2273.

Garcia, H. A.; Osherovich, V. A.

2003-05-01

72

Building Maps of Local Apparent Conductivity of the Epicardium with a 2-D  

E-print Network

the parameters of an electrophysiological model of the heart from a set of electrical recordings. The chosen. First, we perform an initial adjustment including the choice of initial conditions and of a setVeigh are with the Laboratory of Cardiac Energetics, National Heart Lung and Blood Institute, National Institute of Health

Paris-Sud XI, Université de

73

Apparent Molar Volume, Heat Capacity, and Conductance of Lithium Bis (trifluoromethylsulfone)imide in Glymes and Other Aprotic Solvents  

Microsoft Academic Search

Lithium bis(trifluoromethylsulfone)imide (LiTFSI) is a promising electrolyte for high-energy lithium batteries due to its high solubility in most solvents and electrochemical stability. To characterize this electrolyte in solution, its conductance and apparent molar volume and heat capacity were measured over a wide range of concentration in glymes, tetraethylsulfamide (TESA), acetonitrile, ?-butyrolactone, and propylene carbonate at 25°C and were compared with

Dany Brouillette; Gérald Perron; Jacques E. Desnoyers

1998-01-01

74

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

75

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

76

Theoretical Prediction of Electrical Conductivity in Saturated and Unsaturated Soil  

Microsoft Academic Search

A conceptual model is proposed for the prediction of the electrical conductivity of bulk soil in saturated and in unsaturated states. The model is based on the hypothesis that the tortuosity factor affecting the bulk soil electrical conductivity is identical to that defined for prediction of the soil hydraulic conductivity. Simple mathematical functions are derived to forecast the soil electrical

Y. Mualem; S. P. Friedman

1991-01-01

77

Electrical conductivity, temperatures, and fluids in the lower crust  

Microsoft Academic Search

We have compiled both laboratory and worldwide field data on electrical conductivity to help understand the physical implications of deep crustal electrical profiles. Regional heat flow was used to assign temperatures to each layer in regional electrical conductivity models: we avoided those data where purely conductive heat flow suggested temperatures more than about 1000°C, substantially higher than solidus temperatures and

Thomas J. Shankland; Mark E. Ander

1983-01-01

78

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

79

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

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

Electrically conductive, immobilized bioanodes for microbial fuel cells  

NASA Astrophysics Data System (ADS)

The power densities of microbial fuel cells with yeast cells as the anode catalyst were significantly increased by immobilizing the yeast in electrically conductive alginate electrodes. The peak power densities measured as a function of the electrical conductivity of the immobilized electrodes show that although power increases with rising electrical conductivity, it tends to saturate beyond a certain point. Changing the pH of the anode compartment at that point seems to further increase the power density, suggesting that proton transport limitations and not electrical conductivity will limit the power density from electrically conductive immobilized anodes.

Ganguli, R.; Dunn, B.

2012-07-01

82

The thermal and electrical conductivities of metals at high temperatures  

Microsoft Academic Search

A method of investigating the electrical and thermal conductivities of metals at high temperatures is described. The theory of the method depends upon the application of ideas which are fundamental in the study of electrical contact phenomena. The ratio of the thermal to the electrical conductivity of platinum has been determined from 1200° C to the melting point (1773° C)

M. R. Hopkins

1957-01-01

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

Ultrahigh Strength and High Electrical Conductivity in Copper  

Microsoft Academic Search

Methods used to strengthen metals generally also cause a pronounced decrease in electrical conductivity, so that a tradeoff must be made between conductivity and mechanical strength. We synthesized pure copper samples with a high density of nanoscale growth twins. They showed a tensile strength about 10 times higher than that of conventional coarse-grained copper, while retaining an electrical conductivity comparable

Lei Lu; Yongfeng Shen; Xianhua Chen; Lihua Qian; K. Lu

2004-01-01

85

Radiation Fluence dependent variation in Electrical conductivity of Cu nanowires  

SciTech Connect

Electrical conductivity of Cu nanowires varies with diameter of nanowires. However, keeping the diameter of nanowires constant, a variation in their electrical conductivity is observed after they irradiated with gamma rays and neutrons. On the basis of I-V characteristics drawn at room temperature, decrease in the conductivity of Cu nanowires is observed, as compared to that of pristine nanowires.

Gehlawat, Devender; Chauhan, R. P.; Sonkawade, R. G. [Department of physics, National institute of Technology, Kurukshetra-136119 (India); IUAC, New Delhi (India)

2011-07-15

86

Electrically conductive articles and processes for their fabrication  

Microsoft Academic Search

This patent describes a electrically conductive articles and processes for their fabrication. They comprise a refractory substrate, a flexible electrically conductive crystalline cuprate layer, a release layer interposed between the flexible conductive cuprate layer and the substrate, the release layer being comprised of at least on of the metals of groups 8 to 11 and periods 5 and 6 of

J. M. Mir; L. S. Hung

1991-01-01

87

Partial melting and electrical conductivity anomalies in the upper mantle  

Microsoft Academic Search

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

T. J. Shankland; H. S. Waff

1977-01-01

88

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

89

Electrical conductivity measurement on DKDP Crystals with different deuterated degrees  

NASA Astrophysics Data System (ADS)

Ten DKDP single crystals with deuterated degrees ranging from 0 to 90 % were grown by a rapid growth method. The electrical conductivities of these crystals were measured along a and c directions at room temperature. The electrical conductivity increases with the increase for deuterium content. Also, the electrical conductivities of certain crystals were measured at various temperatures ranging from 20 to 130 °C. The values of activation energy decrease as the increase of deuterium content. The present study indicates that the deuterium tunneling frequency is smaller than that of hydrogen, which may be the reason why the variation of electrical conductivity happens after the substitution of hydrogen for deuterium in KDP crystal.

Liu, Baoan; Yin, Xin; Zhao, Minglei; Zhang, Qinghua; Xu, Mingxia; Ji, Shaohua; Zhu, Lili; Zhang, Lisong; Sun, Xun; Xu, Xinguang

2012-10-01

90

Non-Contact Electrical Conductivity Measurement Technique for Molten Metals  

NASA Technical Reports Server (NTRS)

A non-contact technique of measuring the electrical conductivity (or resistivity) of conducting liquids while they are levitated by the high temperature electrostatic levitator in a high vacuum is reported.

Rhim, W. K.; Ishikawa, T.

1998-01-01

91

Electrical conductivity of olivine single crystals at high temperature  

Microsoft Academic Search

The electrical conductivity in three single crystal specimens of olivine (fayalite mole %; 7.4, 8.4 and 12.6) is measured along the three crystallographic orientations in the temperature range of 600° to 1200°K. There are two different mechanisms with different activation energy for electrical conduction; presumably the impurity (Fe) conduction is predominant above 800°K and extrinsic conduction is predominant below 800°K.

Yoji Kobayashi; Hiroshi Maruyama

1971-01-01

92

Electrical Conductivity of Metal Powders under Shock Compression  

Microsoft Academic Search

The electrical conductivity of a series of metal powders under shock compression is measured by an electrocontact technique. Initially, the metal particles are covered by an oxide film, and the powder is non-conducting. Under shock compression, the powder acquires macroscopic conductivity. The electrical conductivity of the shock-compressed powder depends substantially on the metal, porosity, particle size, and shock-wave pressure. The

S. D. Gilev

2005-01-01

93

Electrical Conductivity Measurement of Oxides Melts  

Microsoft Academic Search

Notwithstanding on variety of existing processes of induction skull melting of oxides, electrical and thermal properties of oxides melts are practically unknown. From the other hand, liquid-phase synthesis of Hi-Tech oxides materials such as new ceramics, monocrystals and glasses, requires knowledge of melts properties up to 3700 K. Inasmuch as the main physical property, which influence to the melt power

I. Pozniak; A. Pechenkov; A. Shatunov

94

Electrical conduction of thin bismuth films  

Microsoft Academic Search

The electrical resistivity of thin bismuth films, thermally evaporated onto freshly cleaved mica and glass substrates has\\u000a been studied. Measurements were carried out in a wide range of temperatures and thicknesses. The data measured for thicker\\u000a films were fitted to aFuchs-Sondheimer model withp=0, while the abrupt rise of resistivity for very thin films is described assuming a tunnelling mechanism for

A. H. Abou El Ela; S. Mahmoud; M. A. Mahmoud

1982-01-01

95

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

96

Electrical Conductivities of Nonideal Iron and Nickel Plasmas  

Microsoft Academic Search

Summary form only given. Electrical conductivities of iron and nickel plasmas are calculated using a nonideal plasma ionization balance model that takes into account the excess free energy due to strong Coulomb coupling between charged particles in the pressure- ionization regime. A linear mixture rule is utilized that takes account of both the electron-ion and electron-neutral collisions. The electrical conductivities

Inho Kim; Sung-Hyun Baek; Deok-Kyu Kim

2007-01-01

97

Electrical conductivity measurements of nanofluids and development of new correlations.  

PubMed

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

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

2011-08-01

98

Electrical conductivity anisotropy in alkali feldspar at high pressure  

NASA Astrophysics Data System (ADS)

Magnetotelluric studies have shown that electrical conductivity in the crust is highly anisotropic. Knowledge of the anisotropy of crustal minerals, such as feldspar and quartz, is essential to interpreting this phenomenon. Feldspars are the most abundant minerals in the earth's crust, and thus, the electrical conductivity of feldspars may help in understanding of the bulk conductivity of the crust. The electrical conductivities of single-crystal and polycrystalline feldspars have been previously studied, but few studies have considered the electrical conductivity of single alkali feldspars. In this study, we investigated the electrical conductivity of alkali feldspars at different orientations under high temperatures and pressures through several heating and cooling cycles. The starting materials were natural alkali feldspar minerals collected from Beijing, China. The samples contain 65 % potassium-rich host (microcline) and 30 % sodium-rich exsolution lamellae (albite), as well as ~5% minor phases. The impedance spectrum measurements were carried out in a high-pressure cubic-anvil apparatus.All complex impedance measurements were performed at 1 GPa using a Solartron 1260 impedance phase analyzer. Impedance arcs representing crystal conductivity occur in the frequency range of ~10^3-10^6 Hz. The electrical conductivity of alkali feldspars increased with increasing temperature. The highest electrical conductivities in alkali feldspars were measured along the a-axis, with somewhat lower conductivities along the b-axis and the lowest conductivities along the c-axis, suggesting minor anisotropy. The activation enthalpies ranged from 100 to 110 kJ/mol. The electrical conductivity of alkali feldspar is mildly anisotropic, with an anisotropy factor of approximately 2. The minor anisotropy in conductivity for alkali feldspar may not account for the anisotropy of the crust. This work is supported by the Important Field Knowledge Innovation Program (KZCX2-YW-QN608), National Natural Science Foundation of China (No. 40774036)

Wang, D.; Yu, Y.

2013-12-01

99

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

100

Strain sensing behavior of electrically conductive fibers under large deformation  

Microsoft Academic Search

Electrically conductive fiber\\/yarn\\/fabric is one of the promising materials as flexible conductive sensors because of their sensitivity to strain, temperature and humidity. Aiming at developing of effective flexible sensors, this study investigates experimentally the strain sensing behavior of PPy (polypyrrole)-coated Lycra fibers, showing that the electrically resistance of the conductive fibers changes with the deformation of fibers. The variation in

J. P. Wang; P. Xue; X. M. Tao

2011-01-01

101

Electrically Conductive Flame Sprayed Aluminum Coatings on Textile Substrates  

Microsoft Academic Search

In this study, electrically conductive and flexible aluminum coatings using powder and wire flame spraying were successfully\\u000a deposited onto diverse textiles. The influences of various process parameters and fabric materials on the electrical conductivity\\u000a and microstructure of the metal-fabric composites were investigated. Preliminary results show that to obtain excellent coating\\u000a surface conductivity values a specific coating quantity of higher than

Joël Voyer; Peter Schulz; Martha Schreiber

2008-01-01

102

Temperature dependence of electrical conductivity and lunar temperatures  

NASA Technical Reports Server (NTRS)

Metallic conduction mechanicsms are probably not important in lunar materials because of the small amounts of free metal and metallic oxides present. This is confirmed by the extremely low conductivities measured to date and the fact that the conductivity increases with temperature. The major conduction mechanicsm appears to be ionic. This conduction mechanism is very strongly controlled by temperature, by deviations from stoichiometry, by electric field strengths, and by oxygen fugacity.

Olhoeft, G. R.; Strangway, D. W.; Sharpe, H.; Frisillo, A. L.

1974-01-01

103

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

104

Band Structure and Electrical Conductivity in Semiconductors  

NSDL National Science Digital Library

In this experiment, we will, 1. understand how conductivity in semiconductors depends on carrier concentration and mobility, and how these depend on temperature, 2. distinguish between intrinsic and extrinsic temperature regimes and identify the applicable temperature range from an examination of measured data, 3. appreciate and utilize the advantages of the four-probe resistance measurement technique, 4. calculate the energy band gap for doped Si and pure Ge, 5. calculate the temperature dependent coefficient of the majority carriers, 6. through experimental realizations, appreciate a physical understanding of the band gap structure of semiconductors.

Khalid, Asma; Anwar, Muhammad S.; Zia, Wasif

2012-07-08

105

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

Microsoft Academic Search

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

Jan Martinsson; James L. White

1986-01-01

106

Grain size effect on the electrical conductivity of clinopyroxene  

NASA Astrophysics Data System (ADS)

Complex impedance spectra of polycrystalline samples (with grain size fractions ~5-63, 63-160 and 160-250 ?m) and a single crystal sample (with orientation parallel to b), prepared from a natural megacryst augite, were measured in a piston cylinder apparatus at 10 kbar and 500-1,000°C and with a Solartron 1260 Impedance/Gain Phase analyzer over a frequency range of 0.1-106 Hz. The main charge carriers are attributed to small polarons, and the activation enthalpy is 83 ± 3 to 90 ± 3 kJ/mol. The measured electrical conductivity shows no difference between the polycrystalline and single crystal samples, suggesting independence of electrical conductivity on grain size given a change above ~5 ?m. The electrical conductivity of augite is much higher than that of olivine, indicating that, if regionally enriched, augites may lead to zones of high electrical conductivity and electrical anisotropy in the deep lithosphere.

Yang, Xiaozhi; Heidelbach, Florian

2012-06-01

107

Anisotropy of the electrical conductivity of lithium heptagermanate crystals  

NASA Astrophysics Data System (ADS)

The electrical conductivity ? of single crystals of lithium heptagermanate Li2Ge7O15 is studied in an electric field in the frequency range 0.5-100 kHz at temperatures ranging from 300 to 700 K. Heating the crystal above 500 K gives rise to a pronounced anisotropy in the electrical conductivity, which differs in magnitude by one to two orders of magnitude for different directions of the measurement field along the crystallographic axes. It is shown that an increase in the electrical conductivity ? with increasing temperature originates from charge transfer with an activation energy U = 1.04 eV. It is assumed that the thermally activated contribution to the electrical conductivity is governed by transport of lithium interstitial ions along channels in the structure of the Li2Ge7O15 compound.

Volnyanski?, M. D.; Trubitsyn, M. P.; Obaidat, Yahia A. H.

2008-03-01

108

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

109

Electrically Conductive Crust in Southern Tibet from INDEPTH Magnetotelluric Surveying  

Microsoft Academic Search

The crust north of the Himalaya is generally electrically conductive below depths of 10 to 20 km. This conductive zone approaches the surface beneath the Kangmar dome (dipping north) and extends beneath the Zangbo suture. A profile crossing the northern Yadong-Gulu rift shows that the high conductivity region extends outside the rift, and its top within the rift coincides with

Leshou Chen; John R. Booker; Alan G. Jones; Nong Wu; Martyn J. Unsworth; Wenbo Wei; Handong Tan

1996-01-01

110

EFFECTS OF TRITIUM GAS EXPOSURE ON ELECTRICALLY CONDUCTING POLYMERS  

Microsoft Academic Search

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

M. Kane; E. Clark; R. Lascola

2009-01-01

111

High performance electrically conductive adhesives (ECAs) modified with novel aldehydes  

Microsoft Academic Search

Electrically conductive adhesives (ECAs) have been proposed as one of the major alternatives for tin\\/lead solders in electronic packaging. However, the conductivity of ECA is inferior to that of solders due to the physical contact between conductive fillers and insulative organic lubricants on Ag flakes. In this study, novel aldehydes were introduced into a typical ECA formulation. During the curing

Yi Li; Andrew Whitman; Kyoung-sik Moon; C. P. Wong

2005-01-01

112

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

113

The Electrical Conductance of Semipermeable Membranes  

PubMed Central

The first paper of this series presented a general formulation of the problem of stationary ion flow through membranes. The second treated in detail the special case of unipolar flow across membranes separating symmetric electrolytes. In this, the third paper of the series, we deal with another special case, that of bipolar flow between symmetric electrolytes. Here it is assumed that the total current is carried by both positive and negative permeant ions. The restriction to symmetric electrolytes implies that all ions present in the membrane and surrounding solutions have valences of identical absolute magnitude. After extracting from the general development a set of equations appropriate to the special case being considered, we outline a procedure for the numerical solution of the conductance problem for this case. Numerical results, presented as part of a discussion of approximate analytic methods of solution, establish the utility of these methods. A discussion of the significance of this work for membrane studies is presented in conclusion. PMID:19211007

Bruner, L. J.

1967-01-01

114

Conductivity and electric field variations with altitude in the stratosphere  

NASA Technical Reports Server (NTRS)

Data regarding electric field, derived current density, and conductivity are presented for two balloons from the Electrodynamics of the Middle Atmosphere experiment which underwent the longest period of daily altitude variation. The magnetic L values range from 4.3 to 9.5 for the 18 days of Southern Hemisphere statistics, and the average conductivity and vertical electric fields are given. Simultaneous measurements of the average conductivity scale height and the vertical electric-field scale height indicate that vertical current density does not vary with altitude in the 10-28-km range. The measured conductivity varies significantly at a given altitude on a particular day, and some conductivity data sets are similar to other measurements between 10 and 30 km. Comparisons of the measured data to predictions from models of stratospheric conductivity demonstrate significant discrepancies.

Holzworth, Robert H.

1991-01-01

115

Electrically Conductive Flame Sprayed Aluminum Coatings on Textile Substrates  

NASA Astrophysics Data System (ADS)

In this study, electrically conductive and flexible aluminum coatings using powder and wire flame spraying were successfully deposited onto diverse textiles. The influences of various process parameters and fabric materials on the electrical conductivity and microstructure of the metal-fabric composites were investigated. Preliminary results show that to obtain excellent coating surface conductivity values a specific coating quantity of higher than 20 mg/cm2 is required. After further optimization of the spraying parameters, very good specific surface conductivities (˜500 SA) could be obtained even with reduced coating quantities. Through an adequate parameter optimization a reduction in the specific coating quantity was also achieved while high conductivity values were retained. In addition, when the coating quantity was reduced, the flexibility of the fabric substrates was better conserved. This investigation illustrates that optimized electrically conductive composites with flexible fabric substrates can be produced without any preliminary thermal or chemical fabric specifications.

Voyer, Joël; Schulz, Peter; Schreiber, Martha

2008-12-01

116

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

117

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 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.

Aaron Dörr; Steffen Hardt

2014-11-05

118

Microstructure, electrical conductivity, and piezoelectric properties of bismuth titanate  

Microsoft Academic Search

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

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

1996-01-01

119

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

120

Shock-induced electrical conductivity in some ferroelectrics  

Microsoft Academic Search

This paper gives the results of measurement of shock-induced electrical conductivity in ferroelectrics: PKR-1 lead zirconate-titanate\\u000a piezoceramic, deuterated triglycerine sulphate single crystal, and polymer polyvinylidene fluoride.

V. A. Bragunets; V. G. Simakov; V. A. Borisenok; S. V. Borisenok; V. A. Kruchinin

2010-01-01

121

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

122

Measurement of electrical conductivity for a biomass fire.  

PubMed

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

2008-08-01

123

Imparting Electrical Conductivity into Asphalt Composites Using Graphite  

E-print Network

publications showed the potential of graphite in mitigating the sudden transition. The study presented herein investigates possibility of precisely controlling the electrical conductivity of asphalt concrete only by adding filler size graphite powder. Nine...

Baranikumar, Aishwarya

2013-07-09

124

Temperature-dependent electrical conductivity of soda-lime glass  

NASA Technical Reports Server (NTRS)

The objective of this educational exercise was to demonstrate the difference between the electrical conductivity of metals and ceramics. A list of the equipment and supplies and the procedure for the experiment are presented.

Bunnell, L. Roy; Vertrees, T. H.

1993-01-01

125

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

126

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

127

Electrical conductivity in shaly sands with geophysical applications  

Microsoft Academic Search

We develop a new electrical conductivity equation based on Bussian's model and accounting for the different behavior of ions in the pore space. The tortuosity of the transport of anions is independent of the salinity and corresponds to the bulk tortuosity of the pore space which is given by the product of the electrical formation factor F and the porosityp.

A. Revil; L. M. Cathles; S. Losh; J. A. Nunn

1998-01-01

128

Metal-Filled Polymer Combining Electric Conductivity and Gas Blasting  

Microsoft Academic Search

Metal-filled polymer (MFP) electrodes are presented producing extensive interactions with the switching arc. These electrode materials have an electric conductivity of a few percent of a good electric conductor like copper. Under the thermal stress of an arc spot they evaporate hydrogen and other gases yielding a strong axial gas blast effect on the arc column. Thus arc voltage and

B. Gengenbach; URSULA MAYER; ROLAND MICHAL; JENS RADBRUCH

1985-01-01

129

Electrical Conductivity of Hydrous Single Crystal San Carlos Olivine  

NASA Astrophysics Data System (ADS)

The electrical conductivity of anhydrous San Carlos olivine is too low to explain the observed electrical conductivity of Earth's upper mantle. Although the solubility of hydrogen in olivine is relatively low at mantle P and T conditions, it has been estimated that even at concentrations of less than 1000 ppm, electrical conductivity is enhanced by as much as a factor of one hundred, based on a conduction mechanism involving hydrogen diffusion (Karato, Nature 347, 272-273, 1990). In this study we have measured the electrical conductivity of hydrated San Carlos olivine single crystals, oriented along (100), (010) and (001). SCO single crystals were first oriented, machined into 2 mm diameter cylinders, and then sandwiched between layers of a talc+brucite mix in sealed Pt capsules for hydration runs at pressures up to 8 GPa and 1200°C in a multianvil apparatus. Recovered samples were then cut into wafers ranging from 0.2 to 0.6 mm in thickness for subsequent complex impedance measurements to determine electrical conductivity, also carried out at high pressure. For the electrical measurements, temperatures were limited to about 700°C in order to minimize loss of water from the sample. FTIR spectroscopy was used to determine water content of samples both before and after the electrical measurements. Preliminary results indicate that at concentrations of a few hundred ppm water, conductivities are several orders of magnitude higher than for dry olivine. Activation energies decrease with increasing water content, indicating that extrapolation of conductivities to higher temperatures leads to a smaller overall effect. However, based on these results, at upper mantle conditions, the presence of minor amounts of hydrogen in olivine is sufficient to bridge the gap between the conductivity of dry olivine and that of the mantle.

Poe, B.; Romano, C.; Nestola, F.; Rubie, D.

2005-12-01

130

Electrical conductivity of silver bismuth borate tellurite glasses  

NASA Astrophysics Data System (ADS)

The AC electrical conductivity of (Ag 2O) x (Bi 2O 3) 30 (B 2O 3) 60-x (TeO 2) 10 glass ( x=0, 2, 4, 5, 10, 15 and 20) were measured at different temperatures and frequencies. The results obtained indicated that glasses containing silver<5 mol% have values nearly approximately equal to AC electrical conductivity. A slight decrease was observed with increasing Ag 2O concentration up to 4 mol%. However, the AC electrical conductivity values increase with increasing silver content, i.e. ?5 mol%. The AC electrical conductivity values, increased with increasing frequency and follow the power law, ?AC= A?s. The frequency exponent s was found to be dependent on frequency and temperature. The s values tended to increase to unity as the temperature decreased. Such results suggest that the correlated barrier-hopping (CBH) model is appropriate for explaining the AC electrical conductivity in these glasses. A pronounced increase in the dielectric loss values was observed with increasing silver content. These reflect the effect of Ag + ions charge carriers on the electrical conductivity of such glasses.

Ali, A. A.; Shaaban, M. H.

2008-07-01

131

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

132

Electrical conductivity anisotropy in partially molten peridotite under shear deformation  

NASA Astrophysics Data System (ADS)

The electrical conductivity of partially molten peridotite was measured during deformation in simple shear at 1 GPa in a DIA type apparatus with a uniaxial deformation facility. To detect development of electrical anisotropy during deformation of partially molten system, the electrical conductivity was measured simultaneously in two directions of three principal axes: parallel and normal to the shear direction on the shear plane, and perpendicular to the shear plane. Impedance spectroscopy measurement was performed at temperatures of 1523 K for Fe-bearing and 1723 K for Fe-free samples, respectively, in a frequency range from 0.1 Hz to 1 MHz. The electrical conductivity of partially molten peridotite parallel to shear direction increased to more than one order of magnitude higher than those normal to shear direction on the shear plane. This conductivity difference is consistent with the magnitude of the conductivity anisotropy observed in the oceanic asthenosphere near the Eastern Pacific Rise. On the other hand, conductivity perpendicular to the shear plane decreased gradually after the initiation of shear and finally achieved a value close to that of olivine. The magnitude and development style of conductivity anisotropy was almost the same for both Fe-bearing and Fe-free melt-bearing systems, and also independent of shear strain. However, such conductivity anisotropy was not developed in melt-free samples during shear deformation, suggesting that the conductivity anisotropy requires a presence of partial melting under shear stress. Microstructural observations of deformed partially molten peridotite samples demonstrated that conductivity anisotropy was attributed to the elongation of melt pockets parallel to the shear direction. Horizontal electrical conductivity anisotropy revealed by magnetotelluric surveys in the oceanic asthenosphere can be well explained by the realignment of partial melt induced by shear stress.

Zhang, Baohua; Yoshino, Takashi; Yamazaki, Daisuke; Manthilake, Geeth; Katsura, Tomoo

2014-11-01

133

Thermal conductivity, electrical conductivity and specific heat of copper-carbon fiber composite  

NASA Technical Reports Server (NTRS)

A new material of copper/carbon fiber composite is developed which retains the properties of copper, i.e., its excellent electrical and thermal conductivity, and the property of carbon, i.e., a small thermal expansion coefficient. These properties of the composite are adjustable within a certain range by changing the volume and/or the orientation of the carbon fibers. The effects of carbon fiber volume and arrangement changes on the thermal and electrical conductivity, and specific heat of the composite are studied. Results obtained are as follows: the thermal and electrical conductivity of the composite decrease as the volume of the carbon fiber increases, and were influenced by the fiber orientation. The results are predictable from a careful application of the rule of mixtures for composites. The specific heat of the composite was dependent, not on fiber orientation, but on fiber volume. In the thermal fatigue tests, no degradation in the electrical conductivity of this composite was observed.

Kuniya, Keiichi; Arakawa, Hideo; Kanai, Tsuneyuki; Chiba, Akio

1988-01-01

134

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

135

The electrical conductivity of an isotropic olivine mantle  

Microsoft Academic Search

In order to extend the useful temperature range of interpretation of olivine electrical conductivity sigma, the nonlinear iterative Marquardt technique is used to fit experimental data over the range 720-1500 C to a parametric form. The model describes conduction by migration of two different thermally activated defect populations with activation energies A1 and A2, and preexponential terms sigma (1) and

Steven Constable; Thomas J. Shankland; Al Duba

1992-01-01

136

Effect of Pressure on the Electrical Conductivity of Alkali Metals  

Microsoft Academic Search

A calculation of the electrical conductivity of alkali metals is carried out within the limit of the one-electron approximation. The band structure obtained by Ham and the phonon spectrum determined by experiments are taken into account in the calculation. The absolute values of the conductivity of Li, Na and K at room temperature are evaluated and compared with experiments. The

Akira Hasegawa

1964-01-01

137

Dendritic Ca2 -Activated K Conductances Regulate Electrical  

E-print Network

Dendritic Ca2 -Activated K Conductances Regulate Electrical Signal Propagation in an Invertebrate the intracellular concentration of free Ca2 was reduced by a high-affinity Ca2 buffer. Ca2 released in the neurite signal propagation. Key words: calcium; dendrite; calcium-activated potassium conductance

Wessel, Ralf

138

Calculation of Electrical and Thermal Conductivities of Metallurgical Plasmas  

E-print Network

) ) Calculation of Electrical and Thermal Conductivities of Metallurgical Plasmas by G. J. Dunn Abstract A simplified road map ofthe plasma physics literature for calculation ofelectrical and thermal of the extensive literature on calculation of plasma elec- trical and thermal conductivities. An attempt is made

Eagar, Thomas W.

139

Electrical conductivity of materials from mixed aluminum and silicon nitrides  

Microsoft Academic Search

To determine the raechanism responsible for conduction in aluminum nitride, a study was made of the electrical conductivity of A1N with and without silicon nitride at various temperatures and partial nitrogen pressures in the gaseous phase. Measurements were made also of the thermo-emf of these materials. Tests were carried out on polycrystalline cylindrical specimens of 18 mm diameter prepared from

A. G. Gorbatov; V. M. Kamyshov

1970-01-01

140

Enhanced electrical conduction in aluminum wires coated with carbon nanotubes  

Microsoft Academic Search

Electrophoretic deposition was used to create SWCNT nanosized coatings on commercial aluminum wires. Electrical measurements showed an increase in the conductivity of about 160%. Due to the semiconductor nature of a fraction of the deposited SWCNTs, the high conductivity of the coated wires did not substantially decrease with increasing temperature (up to 600K). Instead, increasing temperature and current were observed

Ricardo H. R. Castro; Pilar Hidalgo; Eric C. Diniz

2011-01-01

141

Excimer Laser Induced Electrical Conductivity and Nanostructures in Polymers.  

NASA Astrophysics Data System (ADS)

The generation of substantial electrical conductivity in high temperature polymers and thin film C_ {60} by means of KrF (248 nm) excimer laser irradiation has been investigated. Formation of both laser ablated surface structures and laser induced electrically conducting wires in polymers with nanometer dimensions is also demonstrated. The electrical conductivity of polymers has been changed by up to 18 orders of magnitude by laser irradiation, obtaining values exceeding 10 Omega^ {-1} cm^{-1} . The conducting material consists of graphitized carbon clusters whose size varies from 2-50 nm. The conduction mechanism is phonon assisted variable range hopping. The large change in the electrical conductivity is an example of a three dimensional percolative metal-insulator phase transition. The critical volume fraction is determined to be Phi_{rm c} = 0.30 +/- 0.05 and the critical exponent is t = 2.2 +/- 0.4. The electrical conductivity of thin film C _{60} has been altered by more than seven orders of magnitude with laser irradiation, obtaining values of 1 Omega^{ -1} cm^{-1}. The threshold for KrF laser ablation of C_{60 } is determined to be 20 +/- 2 mJ/cm^2.. Modification of the surface morphology and the electrical conductivity of polymers with high spatial resolution using excimer lasers has also been achieved. Using holographic techniques with a KrF excimer laser, periodic lines structures with periods ranging from 166 nm to 950 nm were ablated into polyimide (Kapton^{rm TM }) and polybenzimidazole (PBI). The nonlinear nature of laser ablation permits linewidths as small as 30 nm to be obtained, exceeding the resolution expected from linear optics. These experiments establish a new spatial resolution limit for laser ablation and illustrate the dependence of resolution on material properties. This technique was combined with the ability to modify the electrical conductivity of polymers to produce an array of permanently electrically conducting wires in polyimide with a 0.5 ?m width and a 0.9 mu m period. The electrical conductivity of these submicron wires exceeded 1 Omega^ {-1} cm^{-1}. .

Phillips, Harvey Monroe

142

Electric field enhanced conductivity in strongly coupled dense metal plasma  

SciTech Connect

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

Stephens, J.; Neuber, A. [Center for Pulsed Power and Power Electronics, Texas Tech University, Lubbock, Texas 79409 (United States)

2012-06-15

143

Functional microscopy tip fabrication by an electric conductive nanowire.  

PubMed

The functional microscopy tip was fabricated by an electric conductive nanowire (NW). Single crystalline nickel silicide (NiSi) NW grown by plasma-enhanced chemical vapor deposition has an excellent electrical conductivity. On behalf of the advantages in tiny size and conductivity of NiSi NW, it was utilized as a nanoscale probe. Dielectrophoretic method was applied to position the NW. The NiSi NW containing solution was dropped in an ac electric field applying system to align the NiSi NW on a Si cantilever. The fabricated NiSi NW-sitting functional microscopy tip obtained the information of topography and electrical signals from a nanoscale structure. It shows the high potential of nanoscale microscopy tip fabrication at reduced processing steps. PMID:20358923

Kim, Joondong; Yun, Ju-Hyung; Hyun, Moon Seop; Shin, Young-Hyun; Park, Yun Chang; Lee, JiHye; Jeong, Sohee; Han, Chang-Soo

2010-05-01

144

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

145

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

146

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

147

Electric and thermal conductivities of quenched neutron star crusts  

NASA Technical Reports Server (NTRS)

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

Ogata, Shuji; Ichimaru, Setsuo

1990-01-01

148

The role of acids in electrical conduction through ice  

NASA Astrophysics Data System (ADS)

Electrical conduction through meteoric polar ice is controlled by soluble impurities that originate mostly from sea salt, biomass burning, and volcanic eruptions. The strongest conductivity response is to acids, yet the mechanism causing this response has been unclear. Here we elucidate conduction mechanisms in ice using broadband dielectric spectroscopy of meteoric polar ice cores. We find that conduction through polycrystalline polar ice is consistent with Jaccard theory for migration of charged protonic point defects through single ice crystals, except that bulk DC conduction is impeded by grain boundaries. Neither our observations nor modeling using Archie's Law support the hypothesis that grain-boundary networks of unfrozen acids cause significant electrolytic conduction. Common electrical logs of ice cores (by electrical conductivity measurement [ECM] or dielectric profiling [DEP]) and the attenuation of radio waves in ice sheets thus respond to protonic point defects only. This response implies that joint interpretation of electrical and chemical logs can determine impurity partitioning between the lattice and grain boundaries or inclusions. For example, in the Greenland Ice Core Project (GRIP) ice core from central Greenland, on average more than half of the available lattice-soluble impurities (H+, Cl-, NH4+) create defects. Understanding this partitioning could help further resolve the nature of past changes in atmospheric chemistry.

Stillman, David E.; MacGregor, Joseph A.; Grimm, Robert E.

2013-03-01

149

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

Microsoft Academic Search

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

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

2005-01-01

150

Electrically Conductive Crust in Southern Tibet from INDEPTH Magnetotelluric Surveying  

PubMed

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

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

1996-12-01

151

Electrical conductivity of aqueous solutions of aluminum salts  

Microsoft Academic Search

We present experimental measurements of the specific electrical conductivity (sigma) in aqueous solutions of aluminum salts at different temperatures, covering all salt concentrations from saturation to infinite dilution. The salts employed were AlCl3 , AlBr3 , AlI3 , and Al(NO3)3 , which present a 1:3 relationship between the electrical charges of anion and cation. In addition, we have measured the

J. Vila; E. Rilo; L. Segade; O. Cabeza; L. M. Varela

2005-01-01

152

Electrical conduction behavior of cement-matrix composites  

Microsoft Academic Search

In this work, the electrical conduction behavior of cement-matrix composites is reviewed, with a focus on the resistive, thermoelectric\\u000a and electromagnetic behavior, in addition to the effect of strain and of damage on the resistive behavior. Admixtures such\\u000a as short fibers are effective for enhancing the electrical behavior and for providing p-type and n-type cement matrix composites.

D. D. L. Chung

2002-01-01

153

Electrical Conductivity of Carbonated Melts at Mantle Conditions  

NASA Astrophysics Data System (ADS)

Many regions in the Earth's mantle show elevated electrical conductivity (0.02 S.m-1 at 1 S.m-1). A correct interpretation of the petrological nature of the conductive mantle is critical for our understanding of mantle geodynamics. For decades, such anomalously high mantle conductivities have been attributed as mineralogical defects associated to few tens of ppm water incorporated in olivine. Most recent experimental surveys, however, refute this hydrous olivine model. Conductive mantle regions could then reflect partial melting. Melting in the Earth's mantle has long been proved by geochemical observations and experimental petrology on peridotite rocks as being triggered by volatile species (water, carbon dioxide, halogens). Volatiles-assisted melting generally produces small melt fraction. Hydrated and carbonated melts are potential candidates, but their electrical conductivity at HP and HT remains poorly constrained. This study reports electrical conductivity measurements on volatile-rich melts at P and T mantle conditions. We investigated on chemical compositions produced by melting of peridotite that would interact with CO2-H2O and Cl. Such liquid compositions are carbonate melts, hydrous carbonate melts and carbonated basalt melts, depending on P and T. A new system allowing in situ electrical conductivity measurements in piston cylinder has been deployed. This design has been specifically adapted to perfom measurements on liquid samples with elevated electrical conductivities. The chemical compositions investigated are pure liquid CaCO3 and CaMg(CO3)2, to which, cloride (as salts), silicate (as basalt) and water (as brucite) have been added. Experiments have been realized at 3 GPa pressure and at temperatures of 1000-1700°C. Impedance spectrometry measurements are realized using a Solartron gainphase analyser. In the liquid state, which was identified at T varying from 1000-1700°C depending on chemical compositions, all investigated samples are extremely conductive, i.e. >100 S.m-1. It is 5 orders of magnitude more conductive than mantle olivine and 2 orders of magnitude more conductive than basalt at similar P and T. The conductivities of samples, depending on chemical compositions, increase with temperature and Arrhenius relationships can be adjusted. Activation energies of different chemical compositions vary from 40 to 126 kJ.mol-1. Measurements performed on carbonated basalts (with 5-15 wt% SiO2) indicate that they are almost as conductive as pure molten carbonate. Carbonated melts are expected to be produced in different tectonic regimes of mantle. Based on these new data and electrical conductivity of olivine, we propose a re-interpretation of electrical conductivity in the mantle involving small quantities of volatile-rich melts. Less than 0.5% of melt could explain electrical conductivity values of 0.1 S.m-1. This is equivalent to 400 ppm of CO2 and 150 ppm of H2O in the conductive mantle.

Sifre, D.; Gaillard, F.

2012-12-01

154

Corrosion-protective coatings from electrically conducting polymers  

SciTech Connect

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

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

1991-12-31

155

Corrosion-protective coatings from electrically conducting polymers  

SciTech Connect

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

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

1991-01-01

156

Instrumentation development for electrical conductivity imaging in polycrystalline diamond cutters  

NASA Astrophysics Data System (ADS)

We previously reported on an electrical conductivity non-destructive inspection methodology for polycrystalline diamond cutters. These cylindrical cutters for oil and gas drilling feature a thick polycrystalline diamond layer on a tungsten carbide substrate. We use electrical impedance tomography to image the conductivity in the diamond table. In this paper we report on progress in preparing this instrument for factory deployment. Instrument enhancements include an adjustable part holder, a field-swappable sensor and GPU-enabled software capable of rapidly acquiring images.

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

2013-01-01

157

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.

158

Self-healable electrically conducting wires for wearable microelectronics.  

PubMed

Electrically conducting wires play a critical role in the advancement of modern electronics and in particular are an important key to the development of next-generation wearable microelectronics. However, the thin conducting wires can easily break during use, and the whole device fails to function as a result. Herein, a new family of high-performance conducting wires that can self-heal after breaking has been developed by wrapping sheets of aligned carbon nanotubes around polymer fibers. The aligned carbon nanotubes offer an effective strategy for the self-healing of the electric conductivity, whereas the polymer fiber recovers its mechanical strength. A self-healable wire-shaped supercapacitor fabricated from a wire electrode of this type maintained a high capacitance after breaking and self-healing. PMID:25044134

Sun, Hao; You, Xiao; Jiang, Yishu; Guan, Guozhen; Fang, Xin; Deng, Jue; Chen, Peining; Luo, Yongfeng; Peng, Huisheng

2014-09-01

159

Carbonatite melts and electrical conductivity in the asthenosphere.  

PubMed

Electrically conductive regions in Earth's mantle have been interpreted to reflect the presence of either silicate melt or water dissolved in olivine. On the basis of laboratory measurements, we show that molten carbonates have electrical conductivities that are three orders of magnitude higher than those of molten silicate and five orders of magnitude higher than those of hydrated olivine. High conductivities in the asthenosphere probably indicate the presence of small amounts of carbonate melt in peridotite and can therefore be interpreted in terms of carbon concentration in the upper mantle. We show that the conductivity of the oceanic asthenosphere can be explained by 0.1 volume percent of carbonatite melts on average, which agrees with the carbon dioxide content of mid-ocean ridge basalts. PMID:19039132

Gaillard, Fabrice; Malki, Mohammed; Iacono-Marziano, Giada; Pichavant, Michel; Scaillet, Bruno

2008-11-28

160

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

161

Electrical conductivities of multi-wall carbon nano tubes  

Microsoft Academic Search

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

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

1999-01-01

162

Electrical Conduction and Dielectric Properties of Biodegradable Plastics  

Microsoft Academic Search

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

Katsuyoshi Shinyama; Shigetaka Fujita

2005-01-01

163

Modeling the passive cardiac electrical conductivity during ischemia  

E-print Network

to the collapse of capillaries after cardiac arrest. However measurements by Fleishhauer et al. [6] suggest1 Modeling the passive cardiac electrical conductivity during ischemia Jeroen G. Stinstra, Shibaji Shome, Bruce Hopenfeld and Rob S. Macleod Abstract-- A geometrical model of cardiac tissue was used

MacLeod, Rob S.

164

Radiation Effect on Thermal and Electric Conductivity of Reactor Graphite.  

National Technical Information Service (NTIS)

Results are presented on the measurement of the heat and electric conduction properties of the standard reactor graphite in the initial and irradiated states in the temperature interval from 20 to 600 exp 0 C, pointing to a significant reduction of the he...

P. A. Platonov, E. I. Trofimchuk, V. I. Karpukhin

1976-01-01

165

Electrical conductivity for warm, dense aluminum plasmas and liquids  

Microsoft Academic Search

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

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

2002-01-01

166

Human cardiovascular effects of a new generation conducted electrical weapon  

Microsoft Academic Search

ObjectivesThe conducted electrical weapon (CEW) is used by law enforcement to control potentially violent people. Much of the research in CEW safety has focused on the TASER X26, which uses a single deployment cartridge. New Generation CEW (NGCEW) technology has been developed that uses a different circuit and multiple cartridges that can be simultaneously deployed. The objective of this study

Jeffrey D. Ho; Donald M. Dawes; Robert F. Reardon; Seth R. Strote; Sebastian N. Kunz; Rebecca S. Nelson; Erik J. Lundin; Benjamin S. Orozco; James R. Miner

2011-01-01

167

Physiological Effects of a Conducted Electrical Weapon on Human Subjects  

Microsoft Academic Search

Study objective: Sudden death after a conducted electrical weapon exposure has not been well studied. We examine the effects of a single Taser exposure on markers of physiologic stress in healthy humans. Methods: This is a prospective trial investigating the effects of a single Taser exposure. As part of their police training, 32 healthy law enforcement officers received a 5-second

Gary M. Vilke; Christian M. Sloane; Katie D. Bouton; Fred W. Kolkhorst; Saul D. Levine; Tom S. Neuman; Edward M. Castillo; Theodore C. Chan

2007-01-01

168

Bifurcation phenomena and dynamo e ect in electrically conducting uids  

E-print Network

. Electrically conducting uids in motion can act as self-excited dynamos. The magnetic #12;elds of celestial bodies like the Earth and the Sun are generated by such dynamos. Their theory aims at modeling, in which for a prescribed ow the linear induction equation is solved and growth rates of the magnetic #12

Seehafer, Norbert

169

Electric Conductivity from the solution of the Relativistic Boltzmann Equation  

E-print Network

We present numerical results of electric conductivity $\\sigma_{el}$ of a fluid obtained solving the Relativistic Transport Boltzmann equation in a box with periodic boundary conditions. We compute $\\sigma_{el}$ 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 $\\sigma_{el}$ is determined by the transport cross section $\\sigma_{tr}$, i.e. the differential cross section weighted with the collisional momentum transfer. We investigate the electric conductivity dependence on the microscopic details of the 2-body scatterings: isotropic and anisotropic cross-section, and massless and massive particles. We find that the RTA underestimates considerably $\\sigma_{el}$; for example at screening masses $...

Puglisi, A; Greco, V

2014-01-01

170

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

171

Predicting permeability and electrical conductivity of sedimentary rocks from microgeometry  

SciTech Connect

The determination of hydrologic parameters that characterize fluid flow through rock masses on a large scale (e.g., hydraulic conductivity, capillary pressure, and relative permeability) is crucial to activities such as the planning and control of enhanced oil recovery operations, and the design of nuclear waste repositories. Hydraulic permeability and electrical conductivity of sedimentary rocks are predicted from the microscopic geometry of the pore space. The cross-sectional areas and perimeters of the individual pores are estimated from two-dimensional scanning electron micrographs of rock sections. The hydraulic and electrical conductivities of the individual pores are determined from these geometrical parameters, using Darcy's law and Ohm's law. Account is taken of the fact that the cross-sections are randomly oriented with respect to the channel axes, and for possible variation of cross-sectional area along the length of the pores. The effective medium theory from solid-state physics is then used to determine an effective average conductance of each pore. Finally, the pores are assumed to be arranged on a cubic lattice, which allows the calculation of overall macroscopic values for the permeability and the electrical conductivity. Preliminary results using Berea, Boise, Massilon and Saint-Gilles sandstones show reasonably close agreement between the predicted and measured transport properties. 12 refs., 5 figs., 1 tab.

Schlueter, E.M.; Cook, N.G.W. (Lawrence Berkeley Lab., CA (USA) California Univ., Berkeley, CA (USA). Dept. of Materials Science and Mineral Engineering); Zimmerman, R.W.; Witherspoon, P.A. (Lawrence Berkeley Lab., CA (USA))

1991-02-01

172

On the flow dependency of the electrical conductivity of blood.  

PubMed

Experiments presented in the literature show that the electrical conductivity of flowing blood depends on flow velocity. The aim of this study is to extend the Maxwell-Fricke theory, developed for a dilute suspension of ellipsoidal particles in an electrolyte, to explain this flow dependency of the conductivity of blood for stationary laminar flow in a rigid cylindrical tube. Furthermore, these theoretical results are compared to earlier published measurement results. To develop the theory, we assumed that blood is a Newtonian fluid and that red blood cells can be represented by oblate ellipsoids. If blood flows through a cylindrical tube, shear stresses will deform and align the red blood cells with one of their long axes aligned parallel to the stream lines. The pathway of a low-frequency (< 1 MHz) alternating electrical current will be altered by this orientation and deformation of the red blood cells. Consequently, the electrical conductivity in the flow direction of blood increases. The theoretically predicted flow dependency of the conductivity of blood corresponds well with experimental results. This theoretical study shows that red blood cell orientation and deformation can explain quantitatively the flow dependency of blood conductivity. PMID:15248541

Hoetink, A E; Faes, Th J C; Visser, K R; Heethaar, R M

2004-07-01

173

Microbial interspecies electron transfer via electric currents through conductive minerals.  

PubMed

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

2012-06-19

174

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

175

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

176

Public exhibit for demonstrating the quantum of electrical conductance  

E-print Network

We present a new robust setup that explains and demonstrates the quantum of electrical conductance for a general audience and which is continuously available in a public space. The setup allows users to manually thin a gold wire of several atoms in diameter while monitoring its conductance in real time. During the experiment, a characteristic step-like conductance decrease due to rearrangements of atoms in the cross-section of the wire is observed. Just before the wire breaks, a contact consisting of a single atom with a characteristic conductance close to the quantum of conductance can be maintained up to several seconds. The setup is operated full-time, needs practically no maintenance and is used on different educational levels.

Huisman, E H; van der Pal, J P; de Jonge, R M; van der Wal, C H

2011-01-01

177

Electrical conductivity and relaxation in mixed alkali tellurite glasses  

NASA Astrophysics Data System (ADS)

The authors have reported the electrical conductivity and the conductivity relaxation in mixed alkali tellurite glasses of compositions of 70TeO2-xNa2O-(30-x)Li2O in the frequency range from 10Hzto2MHz and in the temperature range from room temperature to just below the glass transition temperature. They have analyzed the relaxation data in the framework of different models. They have observed the mixed alkali effect in the dc and ac conductivities, the crossover frequency, and the conductivity relaxation frequency as well as in their respective activation energies in these glasses. They have also observed the mixed alkali effect in the decoupling index. The scaling property of the modulus spectra of these mixed alkali glasses shows that the conductivity relaxation in the mixed alkali tellurite glasses is independent of temperature but depends on the glass compositions.

Ghosh, S.; Ghosh, A.

2007-05-01

178

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

179

Electrical conductivity of orthopyroxene and plagioclase in the lower crust  

NASA Astrophysics Data System (ADS)

The electrical conductivities of lower crustal orthopyroxene and plagioclase, as well as their dependence on water content, were measured at 6-12 kbar and 300-1,000°C on both natural and pre-annealed samples prepared from fresh mafic xenolith granulites. The complex impedance was determined in an end-loaded piston cylinder apparatus by a Solarton-1260 Impedance/Gain Phase analyzer in the frequency range of 0.1-106 Hz. The spectra usually show an arc over the whole frequency range at low temperature and an arc plus a tail in the high and low frequency range, respectively, at high temperature. The arc is due to conduction in the sample interior, while the tails are probably due to electrode effects. Different conduction mechanisms have been identified under dry and hydrous conditions. For the dry orthopyroxene, the activation enthalpy is ~105 kJ/mol, and the conduction is likely due to small polarons, e.g., electrons hopping between Fe2+ and Fe3+. For the dry plagioclase, the activation enthalpy is ~161 kJ/mol, and the conduction may be related to the mobility of Na+. For the hydrous samples, the activation enthalpy is ~81 kJ/mol for orthopyroxene and ~77 kJ/mol for plagioclase, and the electrical conductivity is markedly enhanced, probably due to proton conduction. For each mineral, the conductivity increases with increasing water content, with an exponent of ~1, and the activation enthalpies are nearly independent of water content. Combining these data with our previous work on the conductivity of lower crustal clinopyroxene, the bulk conductivity of lower crustal granulites is modeled, which is usually >~10-4 S/m in the range of 600-1,000°C. We suggest that the high electrical conductivity in most regions of the lower crust, especially where it consists mostly of granulites, can be explained by the main constitutive minerals, particularly if they contain some water. Contributions from other highly conducting materials such as hydrous fluids, melts, or graphite films are not strictly necessary to explain the observed conductivities.

Yang, Xiaozhi; Keppler, Hans; McCammon, Catherine; Ni, Huaiwei

2012-01-01

180

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

181

Concentration and Mobility of Electrically-Conducting Defects in Olivine  

NASA Astrophysics Data System (ADS)

We have collected measurements of electrical conductivity and thermopower as a function of temperature and oxygen fugacity (f O2) on a sample of San Quintin dunite (95% olivine), and measurements of electrical conductivity equilibration after changes in f O2 on Mt.Porndon lherzolite (65% olivine). Both data sets have been analysed using nonlinear parameter inversion of mathematical models relating conductivity, thermopower, and diffusion kinetics to temperature, f O2, time, and defect concentration and mobility. From the dunite thermopower/conductivity data we are able to estimate the concentration and mobilities of electrically conducting defects. Our model allows electrons, small polarons (Fe+++ on Fe++ sites), and magnesium vacancies (V'' Mg) to contribute to conduction, but only polarons and V'' Mg are required by our data. Polarons dominate conduction below 1300°~C; at this temperature conduction, is equal for the two defects at all f O2 tested. Thermopower measurements allow us to estimate defect concentration independently from mobility, and so we can back out polaron mobility as 12.2x 10-6 exp(-1.05~eV/kT) m2V-1s-1 and magnesium vacancy mobility as 2.72x 10-6 exp(-1.09~eV/kT) m2V-1s-1. Electrical conductivity of the lherzolite, measured as a function of time after changes in the oxygen fugacity of the surrounding CO2/CO atmosphere, is used to infer the diffusivity of the point defects associated with the oxidation reactions. An observed f O2 dependence in the time constants associated with equilibration implies two species of fixed diffusivity, each with f O2-dependent concentrations. Although the rate-limiting step may not necessarily be associated with conducting defects, when time constants are converted to mobilities, the magnitudes and activation energies agree extremely well with the model presented above for the dunite, after one free parameter (effective grain size) is fit at a plausible 1.6~mm diameter. Not only does this study represent one of the few direct measurements of polaron mobility, but the very good agreement between two independent measurement techniques (thermopower versus equilibration kinetics) and two independent samples (dunite versus lherzolite) provides some level of confidence in the results. We are currently extending these modeling techniques to study olivine defect mobility anisotropy.

Constable, S.; Roberts, J.; Duba, A.

2002-12-01

182

Inflow and outflow signatures in flowing wellbore electrical conductivity logs  

SciTech Connect

Flowing wellbore electrical-conductivity logging provides a means to determine hydrologic properties of fractures, fracture zones, or other permeable layers intersecting a borehole in saturated rock. The method involves analyzing the time-evolution of fluid electrical-conductivity logs obtained while the well is being pumped and yields information on the location, hydraulic transmissivity, and salinity of permeable layers, as well as their initial (or ambient) pressure head. Earlier analysis methods were restricted to the case in which flows from the permeable layers or fractures were directed into the borehole. More recently, a numerical model for simulating flowing-conductivity logging was adapted to permit treatment of both inflow and outflow, including analysis of natural regional flow in the permeable layer. However, determining the fracture properties with the numerical model by optimizing the match to the conductivity logs is a laborious trial-and-error procedure. In this paper, we identify the signatures of various inflow and outflow features in the conductivity logs to expedite this procedure and to provide physical insight for the analysis of these logs. Generally, inflow points are found to produce a distinctive signature on the conductivity logs themselves, enabling the determination of location, inflow rate, and ion concentration in a straightforward manner. Identifying outflow locations and flow rates, on the other hand, can be done with a more complicated integral method. Running a set of several conductivity logs with different pumping rates (e.g., half and double the original pumping rate) provides further information on the nature of the feed points. In addition to enabling the estimation of flow parameters from conductivity logs, an understanding of the conductivity log signatures can aid in the design of follow-up logging activities.

Doughty, Christine; Tsang, Chin-Fu

2002-08-28

183

Electrical conductivity of aqueous solutions of aluminum salts  

NASA Astrophysics Data System (ADS)

We present experimental measurements of the specific electrical conductivity (?) in aqueous solutions of aluminum salts at different temperatures, covering all salt concentrations from saturation to infinite dilution. The salts employed were AlCl3 , AlBr3 , AlI3 , and Al(NO3)3 , which present a 1:3 relationship between the electrical charges of anion and cation. In addition, we have measured the density in all ranges of concentrations of the four aqueous electrolyte solutions at 298.15K . The measured densities show an almost linear behavior with concentration, and we have fitted it to a second order polynomial with very high degree of approximation. The measurement of the specific conductivity at constant temperature reveals the existence of maxima in the conductivity vs concentration curves at molar concentrations around 1.5M for the three halide solutions studied, and at approximately 2M for the nitrate. We present a theoretical foundation for the existence of these maxima, based on the classical Debye-Hückel-Onsager hydrodynamic mean-field framework for electrical transport and its high concentration extensions, and also a brief consideration of ionic frictional coefficients using mode-coupling theory. We also found that the calculated values of the equivalent conductance vary in an approximately linear way with the square root of the concentration at concentrations as high as those where the maximum of ? appears. Finally, and for completeness, we have measured the temperature dependence of the electrical conductivity at selected concentrations from 283to353K , and performed a fit to an exponential equation of the Vogel-Fulcher-Tamman type. The values of the calculated temperatures of null mobility of the four salts are reported.

Vila, J.; Rilo, E.; Segade, L.; Cabeza, O.; Varela, L. M.

2005-03-01

184

Electrical conductivity of olivine: New experimental results and a unified model for hydrogen-assisted conduction  

NASA Astrophysics Data System (ADS)

Although extensive experimental studies have been carried out on the hydrogen-assisted electrical conductivity in olivine, a few important issues remain unclear. We have conducted new experiments (i) on the pressure effects, (ii) on the influence of Fe content, and (iii) on the influence of oxygen fugacity on hydrogen-assisted conductivity to clarify these issues. The pressure effect is important in resolving the difference between Wang et al. (2006) and Yoshino et al. (2009) and also in evaluating the conductivity jump at the 410-km discontinuity. Our new results show only a small effect of pressure indicating that (i) the difference between Wang et al. (2006) and Yoshino et al. (2009) is not due to the pressure effect, and that (ii) there must be a large drop in conductivity at 410-km boundary if the water content in the upper mantle is the same as that of the transition zone. We also conducted a series of experiments to determine the influence of Fe on hydrogen-assisted conductivity. Both Fe and hydrogen enhance conductivity, but their combined effect was not characterized. We found that Fe effect and hydrogen effect are connected: for given hydrogen content, conductivity is higher for a sample with higher Fe content. This implies that the hydrogen mobility is enhanced by Fe. The results have potential applications for Fe-rich planets such as Mars. We are also conducting a series of experiments to see the influence of oxygen fugacity on hydrogen-assisted conductivity. A similar study was made for wadsleyite showing the negative dependence of conductivity on oxygen fugacity showing a simple model of hydrogen-assisted conductivity (i.e., all hydrogen atoms contribute equally to conductivity) does not work. Our new results will provide strong constraints on the mechanism of hydrogen-assisted conduction in olivine. A hybrid model explains a broad range of observations including the discrepancies between diffusion data and electrical conductivity, and predicts that hydrogen-assisted conductivity will be highly anisotropic at high temperatures.

Karato, S.; Dai, L.

2013-12-01

185

The bedrock electrical conductivity map of the UK  

NASA Astrophysics Data System (ADS)

Airborne electromagnetic (AEM) surveys, when regionally extensive, may sample a wide-range of geological formations. The majority of AEM surveys can provide estimates of apparent (half-space) conductivity and such derived data provide a mapping capability. Depth discrimination of the geophysical mapping information is controlled by the bandwidth of each particular system. The objective of this study is to assess the geological information contained in accumulated frequency-domain AEM survey data from the UK where existing geological mapping can be considered well-established. The methodology adopted involves a simple GIS-based, spatial join of AEM and geological databases. A lithology-based classification of bedrock is used to provide an inherent association with the petrophysical rock parameters controlling bulk conductivity. At a scale of 1:625k, the UK digital bedrock geological lexicon comprises just 86 lithological classifications compared with 244 standard lithostratigraphic assignments. The lowest common AEM survey frequency of 3 kHz is found to provide an 87% coverage (by area) of the UK formations. The conductivities of the unsampled classes have been assigned on the basis of inherent lithological associations between formations. The statistical analysis conducted uses over 8 M conductivity estimates and provides a new UK national scale digital map of near-surface bedrock conductivity. The new baseline map, formed from central moments of the statistical distributions, allows assessments/interpretations of data exhibiting departures from the norm. The digital conductivity map developed here is believed to be the first such UK geophysical map compilation for over 75 years. The methodology described can also be applied to many existing AEM data sets.

Beamish, David

2013-09-01

186

Electrical Conductivity Measurements on Hydrous Carbonate Melts at Mantle Pressure  

NASA Astrophysics Data System (ADS)

Electromagnetic methods image mantle regions in the asthenosphere with elevated conductivity (0.1 to 1 S.m-1), which constrasts with the conductivity of dry olivine (10-2 to 10-3 S.m-1). A correct interpretation of the petrological nature of the conductive mantle is critical for our understanding of mantle geodynamics because such conductive regions indicate mantle rocks with physical and chemical properties that importantly deviates from the canonical peridotites. For decades, such anomalously high mantle conductivities have been attributed to mineralogical defects associated to few tens of ppm water incorporated in olivine. Most recent experimental surveys, however, refute this hydrous olivine model. Conductive mantle regions could then reflect partial melting. The presence of melts in the Earth's mantle has long been proved by geochemical observations and experimental petrology on peridotite rocks. The requirement for melting in the asthenospheric mantle is the presence of volatile species (water, carbon dioxide, halogens). Small melt fractions are then produced by small volatile contents and they are the first liquids produced by melting magma. This study reports electrical conductivity measurements on such melts at mantle pressure and temperature. We investigated on melt chemical compositions produced by melting of peridotite that would interact with CO2-H2O and Cl. Such melts are carbonatite melts, carbonated silicate melts, hydrous carbonate melts, hydrous basalts. A new system allowing in situ electrical conductivity measurements in piston cylinder has been deployed. This design has been specifically adapted to perfom measurements on liquid samples with elevated electrical conductivities. The chemical compositions investigated are pure liquid CaCO3 and CaMg(CO3)2, to which, cloride (as salts), silicate (as basalts) and water (as brucite) have been added. Experiments have been realized at 1.5 and 2.7 GPa pressure and temperature of 1000-1700° C. Impedance spectrometry measurements are realized using a Solartron gainphase analyser. In the liquid state, which was identified at T varying from 1000-1700° C depending on chemical compositions, all investigated samples are extremely conductive, i.e. >100 S.m-1. It is 10,000 times more conductive than mantle olivine at similar P and T. The conductivities of samples increase with temperature and Arrhenius relationships can be adjusted. Activation energies depend on chemical compositions and vary from 40 to 80 kJ.mol-1. Conductivity of melts increases in the following sequence: CaCO3 < MgCa(CO3)2 < (MgCa(CO3)2)0.9 (NaCl)0.1 < (CaCO3)0.45 (NaCl)0.1 (MgH2O2)0.45. The latter melt composition is a simplified synthetic analogue of fluid inclusions entrapped in diamonds. Its electrical conductivity increases to >200 S.m-1 at 1410° C and 2.7 GPa. An electromagnetic survey (Tarits et al, this session) identifies a conductive mantle underneath mid-ocean ridge from 100 to nearly 500 km of depth. The determined conductivity, 0.1 S.m-1, is obtained considering 0.07 volume % of hydrous carbonated melts in peridotite rocks. This is equivalent to a peridotite with 175 ppm CO2 and 67 ppm water stored as small melt fraction wetting grain boundaries. Geochemical and geodynamic implications are discussed by Gaillard (this session).

Sifre, D.; Gaillard, F.

2012-04-01

187

Optimum depth of investigation and conductivity response rejection of the different electromagnetic devices measuring apparent magnetic susceptibility  

Microsoft Academic Search

Electromagnetic susceptibility surveys are valuable for archaeological prospection owing to their ability to cover large areas of land. Their use, however, is often compromised by the conductivity in fluence of the soil and the limited investigation depth of the susceptibility response. To examine these constraints further, we compared the characteristics of two types of apparatus: coincident loop (e.g. Bartington MS2

Christophe Benech; Eric Marmet

1999-01-01

188

Effect of Cerium on Mechanical Performance and Electrical Conductivity of Aluminum Rod for Electrical Purpose  

Microsoft Academic Search

The effect of rare earth element Ce on mechanical performance and electrical conductivity of aluminum rod for electrical purpose were studied under industrial production condition. Using optical microscope, SEM, TEM, EDS and X-ray diffractometer, the microstructure and phase composition of aluminum rod were measured and analyzed. The results indicate that the content of rare earth element Ce is between 0.05%

Li Pengfei; Wu Zhigang; Wang Yunli; Gao Xizhu; Wang Zaiyun; Li Zhiqiang

2006-01-01

189

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

190

Electrical conductivity of a seeded H2/O2 system  

NASA Astrophysics Data System (ADS)

The feasibility of using a H2/O2 system as a working fluid in an open-cycle MHD generator is considered. The variation of the electrical conductivity of the seeded combustion products of a H2/O2 system with temperature has been determined and the results have been compared with the available data for acetylene-oxygen and water-gas-oxygen systems. Although the conductivity of a H2/O2 system is smaller than that of hydrocarbon fuels, it is sufficient at higher temperatures for MHD application.

Sawhney, B. K.; Hussain, S. Q.; Swithenbank, J.

1980-03-01

191

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

192

Nanotube Networks in Polymer Nanocomposites: Rheology and Electrical Conductivity  

Microsoft Academic Search

Single-walled carbon nanotube (SWNT)\\/poly(methyl methacrylate) (PMMA) nanocomposites were prepared via our coagulation method providing uniform dispersion of the nanotubes in the polymer matrix. Optical microscopy, Raman imaging, and SEM were employed to determine the dispersion of nanotube at different length scales. The linear viscoelastic behavior and electrical conductivity of these nanocomposites were investigated. At low frequencies, Gbecomes almost independent of

Fangming Du; Robert C. Scogna; Wei Zhou; Stijn Brand; John E. Fischer; Karen I. Winey

2004-01-01

193

Grain size-dependent electrical conductivity of polycrystalline cerium oxide  

Microsoft Academic Search

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

A. Tschöpe; E. Sommer; R. Birringer

2001-01-01

194

Electric conductivity of neutron-irradiated aluminum alloys  

Microsoft Academic Search

The effect of ionizing radiation, temperature, and products of the radiolysis of water on the materials of fuel elements used\\u000a in nuclear reactors during operation is examined. The effect of irradiation in a reactor on the electric conductivity and\\u000a the change of the linear dimensions of the alloys SAV-1 and AMG-2 are investigated. It can be concluded on the basis

S. A. Baitelesov; V. N. Sandalov; F. R. Kungurov; U. A. Khalikov

2011-01-01

195

Electrical conductivity of dense copper and aluminum plasmas  

Microsoft Academic Search

Measurements are reported of the electrical conductivity of dense copper and aluminum plasmas in the temperature range 10-30 kK, in a density range from about one-fifth solid density down to 0.02 g\\/cm3. Plasmas were created by rapid vaporization of metal wires in a water bath. At temperatures below about 15 kK, as density decreases from the highest values measured, the

A. W. Desilva; J. D. Katsouros

1998-01-01

196

ELECTRICAL CONDUCTION IN SINGLE-CRYSTAL ALUMINUM THIN FILMS  

Microsoft Academic Search

Electrical conduction in thin (400?1500 Å) single-crystal aluminum films vacuum evaporated on NaCl substrates is explained by a simple model and verified by experimental results. The resistivity of the inter-island boundaries is accounted for by considering the film structure as a metal—insulator matrix and calculating its equivalent resistivity. An unambiguous comparison can then be made with the Fuchs—Sondheimer theory of

T. S. Jayadevaiah; Robert E. Kirby

1969-01-01

197

Conducted Electrical Weapons: A User’s Perspective  

Microsoft Academic Search

\\u000a Since the mid-1970s, law enforcement officials have used conducted electrical weapons (CEWs) with varying degrees of success\\u000a to control violent individuals who resist arrest or help. The TASER® devices have been the most widely used CEWs, ranging\\u000a from the original 7-watt models (minimally effective as pain-compliance tools) to the 26-watt M-26 model (very effective as\\u000a neuromuscular incapacitation tools) and now

Greg Meyer

198

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

199

Joining Mixed Conducting Oxides Using an Air-Fired Electrically Conductive Braze  

SciTech Connect

Due to their mixed oxygen ion and electron conducting properties, ceramics such as lanthanum strontium cobalt ferrites (LSCF) are attractive materials for use in active electrochemical devices such as solid oxide fuel cells (SOFC) and oxygen separation membranes. However, to take full advantage of the unique properties of these materials, reliable joining techniques need to be developed. If such a joining technique yields a ceramic-to-metal junction that is also electrically conductive, the hermetic seals in the device could provide the added function of either drawing current from the mixed conducting oxide, in the case of SOFC applications, or carrying it to the oxide to initate ionic conduction, in the case of oxygen separation and electrocatalysis applications. This would greatly reduce the need for complex interconnect design, thereby simplifying one of the major challenges faced in SOFC development. A process referred to as reactive air brazing (RAB) has been developed in which firing a Ag-CuO filler material in air creates a functional ceramic-to-metal junction, in which the silver-based matrix of the braze affords both metallic ductility and conductivity in the joint. Investigating a range of Ag-CuO alloy combinations determined that compositions containing between 1.4 and 16 mol% CuO appear to offer the best combination of wettability, joint strength, and electrical conductivity.

Hardy, John S.; Kim, Jin Yong Y.; Weil, K. Scott

2004-10-01

200

Experimental investigation of the electrical conductivity of aluminum foil electric explosion processes  

Microsoft Academic Search

The behavior of the electrical conductivity of aluminum foil during rapid energy inputs is studied experimentally. The relative resistance of exploding aluminum foil is plotted versus time. It is shown that the rapid increase in resistance observed in the experiment cannot be attributed to evaporation surface waves. Mechanisms which do not associate the loss in conductivity during explosion with complete

A. P. Baikov; L. S. Gerasimov; A. M. Iskoldskii

1975-01-01

201

Simultaneously improving electrical properties and stabilizing contact resistance of electrically conductive adhesives by using aminoaldehydes  

Microsoft Academic Search

In order to simultaneously improve the conductivity and stabilize the contact resistance of electrically conductive adhesives (ECAs) containing silver flakes, different types of aminoaldehydes as multifunctional additives, N, N-dimethyl-4-aminobenzaldehyde (DABA), benzaldehyde (BA) as a comparison and formamide (FA), were introduced into ECAs formulations. The results showed that when the optimal levels of FA, BA and DABA were individually added into

HONG GAO; LAN LIU; YUAN-FANG LUO; DE-MIN JIA; JIA-SHENG LU

2011-01-01

202

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

203

Electrical Conductivity Measurement and Anisotropy of Mylonite and Cataclasite  

NASA Astrophysics Data System (ADS)

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

Omura, K.

2001-12-01

204

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

205

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

206

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

207

Interwall interactions and electrical conductance in telescoping carbon nanotubes  

NASA Astrophysics Data System (ADS)

Telescopically aligned carbon nanotubes, where the inner core shells are pulled out from the house shells with larger diameters in multi-walled nanotubes, are good systems to interwall interactions and their effect on electron conduction. In several tight-binding calculations, there exists some controversy in the quantum conductance of telescoping nanotubes. In this work, using the non-equilibrium matrix Green function approach within the first principles local-density-functional approximation, we study the quantum transport behavior of the (5,5)/(10,10) telescoping nanotube. Varying the hybridized double wall region, we investigate the effect of interwall interactions on the electron transport and compare the results with those obtained from tight-binding calculations. Although individual tubes have two conducting channels at the Fermi level, only one channel gives rise to electrical conduction with antiresonance dips in transmission, while the other channel is suppressed. Thus, the maximum conductance is close to G0, in contrast to single ?-orbital tight-binding calculations, which showed the maximum conductance close to 2 G0. Our first-principles calculations indicate that the tight-binding model significantly overestimates the interwall coupling between the inner and outer shells.

Kang, Yong-Ju; Kim, Yong-Hoon; Chang, Kee Joo

2007-03-01

208

Electrical conductivity of gold-implanted alumina nanocomposite  

NASA Astrophysics Data System (ADS)

We have carried out ion implantation of gold into alumina ceramic substrates and measured the surface resistivity as a function of implantation dose. The Au ion energy was 40 keV and the dose spanned the range 2.7-8.9 × 1016 cm-2. Imaging of the implanted material by transmission electron microscopy revealed that the implanted gold self-assembles into nanoparticles, thus forming a gold-alumina nano-composite. The surface resistivity measurements were compared with the predictions of a model based on percolation theory, in which electron transport through the composite is explained by conduction through a random resistor network formed by the Au nanoparticles. The electrical conductivity of a composite, near the critical conductor-insulator transition, is given by ? ? ?0(x-xc)t, where ?0 is the saturation conductivity for which the material still remains a composite, x is the normalized metal atom concentration of the conducting phase, xc is the critical concentration, or percolation threshold and t is the critical exponent. Excellent agreement was found between the experimental results and the predictions of the theory, and the results are consistent with prior related (but more limited) work. The percolation dose was 4.4 × 1016 cm-2, and the critical exponent obtained was t = 1.4 ± 0.1. We conclude that the conductivity process is due to percolation and that the contribution from tunneling conduction is negligible.

Salvadori, M. C.; Teixeira, F. S.; Sgubin, L. G.; Cattani, M.; Brown, I. G.

2013-09-01

209

Electrical actuation of electrically conducting and insulating droplets using ac and dc voltages  

NASA Astrophysics Data System (ADS)

Electrical actuation of liquid droplets at the microscale offers promising applications in the fields of microfluidics and lab-on-chip devices. Much prior research has targeted the electrical actuation of electrically conducting liquid droplets using dc voltages (classical electrowetting). Electrical actuation of conducting droplets using ac voltages and the actuation of insulating droplets (using dc or ac voltages) has remained relatively unexplored. This paper utilizes an energy-minimization-based analytical framework to study the electrical actuation of a liquid droplet (electrically conducting or insulating) under ac actuation. It is shown that the electromechanical regimes of classical electrowetting, electrowetting under ac actuation and insulating droplet actuation can be extracted from the generic electromechanical actuation framework, depending on the electrical properties of the droplet, the underlying dielectric layer and the frequency of the actuation voltage. This paper also presents experiments which quantify the influence of the ac frequency and the electrical properties of the droplet on its velocity under electrical actuation. The velocities of droplets moving between two parallel plates under ac actuation are experimentally measured; these velocities are then related to the actuation force on the droplet which is predicted by the electromechanical model developed in this work. It is seen that the droplet velocities are strongly dependent on the frequency of the ac actuation voltage; the cut-off ac frequency, above which the droplet fails to actuate, is experimentally determined and related to the electrical conductivity of the liquid. This paper then analyzes and directly compares the various electromechanical regimes for the actuation of droplets in microfluidic applications.

Kumari, N.; Bahadur, V.; Garimella, S. V.

2008-10-01

210

Electric Conductivity from the solution of the Relativistic Boltzmann Equation  

E-print Network

We present numerical results of electric conductivity $\\sigma_{el}$ of a fluid obtained solving the Relativistic Transport Boltzmann equation in a box with periodic boundary conditions. We compute $\\sigma_{el}$ 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 $\\sigma_{el}$ is determined by the transport cross section $\\sigma_{tr}$, i.e. the differential cross section weighted with the collisional momentum transfer. We investigate the electric conductivity dependence on the microscopic details of the 2-body scatterings: isotropic and anisotropic cross-section, and massless and massive particles. We find that the RTA underestimates considerably $\\sigma_{el}$; for example at screening masses $m_D \\sim \\,T$ 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 quasi-particle model, tuned to lQCD thermodynamics, as well as the case of a pQCD gas with running coupling. Also for these cases more directly related to the description of the QGP system, we find that RTA significantly underestimate the $\\sigma_{el}$ by about a $60-80\\%$.

A. Puglisi; S. Plumari; V. Greco

2014-08-29

211

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

212

Electrical conductivity of insulating polymer nanoscale layers: environmental effects.  

PubMed

As electronic devices are scaled down to submicron sizes, it has become critical to obtain uniform and robust insulating nanoscale polymer films. For that reason, we address the electrical properties of grafted polymer layers made of poly(glycidyl methacrylate), polyacrylic acid, poly(2-vinylpyridine), and polystyrene with thicknesses of 10-20 nm. It was found that layers insulating under normal ambient conditions can display a significant increase in conductivity as the environment changes. Namely, we demonstrated that the in-plane electrical conductivity of the polymer grafted layers can be changed by at least two orders of magnitude upon exposure to water or organic solvent vapors. Conductive properties of all polymer grafted films under study could also be significantly enhanced with an increase in temperature. The observed phenomenon makes possible the chemical design of polymer nanoscale layers with reduced or enhanced sensitivity to the anticipated change in environmental conditions. Finally, we demonstrated that the observed effects could be used in a micron-sized conductometric transducing scheme for the detection of volatile organic solvents. PMID:24336834

Bliznyuk, Valery; Galabura, Yuriy; Burtovyy, Ruslan; Karagani, Pranay; Lavrik, Nickolay; Luzinov, Igor

2014-02-01

213

DNA sequencing using electrical conductance measurements of a DNA polymerase  

NASA Astrophysics Data System (ADS)

The development of personalized medicine--in which medical treatment is customized to an individual on the basis of genetic information--requires techniques that can sequence DNA quickly and cheaply. Single-molecule sequencing technologies, such as nanopores, can potentially be used to sequence long strands of DNA without labels or amplification, but a viable technique has yet to be established. Here, we show that single DNA molecules can be sequenced by monitoring the electrical conductance of a phi29 DNA polymerase as it incorporates unlabelled nucleotides into a template strand of DNA. The conductance of the polymerase is measured by attaching it to a protein transistor that consists of an antibody molecule (immunoglobulin G) bound to two gold nanoparticles, which are in turn connected to source and drain electrodes. The electrical conductance of the DNA polymerase exhibits well-separated plateaux that are ~3 pA in height. Each plateau corresponds to an individual base and is formed at a rate of ~22 nucleotides per second. Additional spikes appear on top of the plateaux and can be used to discriminate between the four different nucleotides. We also show that the sequencing platform works with a variety of DNA polymerases and can sequence difficult templates such as homopolymers.

Chen, Yu-Shiun; Lee, Chia-Hui; Hung, Meng-Yen; Pan, Hsu-An; Chiou, Jin-Chern; Huang, G. Steven

2013-06-01

214

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

215

Transparent electrical conducting films by activated reactive evaporation  

DOEpatents

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

Bunshah, R.; Nath, P.

1982-06-22

216

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

217

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

218

Electrical conductivity of samarium–ytterbium zirconate ceramics  

Microsoft Academic Search

(Sm1?xYbx)2Zr2O7 (0?x?1.0) ceramic powders were prepared by chemical-coprecipitation and calcination method, and were pressureless-sintered at 1973K for 10h to fabricate dense bulk materials. (Sm1?xYbx)2Zr2O7 has a single phase with a pyrochlore or defect fluorite structure, depending mainly upon the Yb content. They are found to be pyrochlores for 0?x?0.1, and defect fluorites for 0.3?x?1.0. The electrical conductivity of (Sm1?xYbx)2Zr2O7 was

Zhan-Guo Liu; Jia-Hu Ouyang; Yu Zhou; Xiao-Liang Xia

2009-01-01

219

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

220

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

221

Electrical conductivity measurements on disk-shaped samples  

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

222

Electrical conduction in nanodomains in congruent lithium tantalate single crystal  

NASA Astrophysics Data System (ADS)

The electrical current flow behavior was investigated for nanodomains formed in a thin congruent lithium tantalate (LiTaO3) 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 LiNbO3, optical illumination was not required for current conduction in LiTaO3. A clear temperature dependence of the current was found indicating that the conduction mechanism for nanodomains in LiTaO3 may involve thermally activated carrier hopping.

Cho, Yasuo

2014-01-01

223

Electrically conductive PEDOT coating with self-healing superhydrophobicity.  

PubMed

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

Zhu, Dandan; Lu, Xuemin; Lu, Qinghua

2014-04-29

224

Electrical-Impedance Tomography for Opaque Multiphase Flows in Metallic (Electrically-Conducting) Vessels  

Microsoft Academic Search

A novel electrical-impedance tomography (EIT) diagnostic system, including hardware and software, has been developed and used to quantitatively measure material distributions in multiphase flows within electrically-conducting (i.e., industrially relevant or metal) vessels. The EIT system consists of energizing and measuring electronics and seven ring electrodes, which are equally spaced on a thin nonconducting rod that is inserted into the vessel.

SCOTT G. LITER; JOHN R. TORCZYNSKI; KIM A. SHOLLENBERGER; STEVEN L. CECCIO

2002-01-01

225

Electrical conductivity and dielectric behavior in sodium zinc divanadates  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

226

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

227

Mantle electrical conductivity profile of Niger delta region  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

228

Electrical conductivity of shocked water from density functional theory.  

SciTech Connect

We present Density Functional Theory (DFT) calculations of water in a region of phase space of interest in shock experiments. The onset of electrical conductivity in shocked water is determined by ionic conductivity, with the electron contribution dominating at higher pressures. The ionic contribution to the conduction is calculated from proton diffusion (Green-Kubo formula) and the electronic contribution is calculated using the Kubo-Greenwood formula [1]. The calculations are performed with VASP, a plane-wave pseudopotential code. At 2000K and a density of 2.3 g/cc, we find a significant dissociation of water into H, OH, and H3O, not only intermittent formation of OH - H3O pairs as suggested earlier for 2000 K and 1.95 g/cc [2]. The calculated conductivity is compared to experimental data [3]. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Safety Administration under contract DE-AC04-94AL85000. This project was supported by the Sandia LDRD office. [1] M. P. Desjarlais, J. D. Kress, and L. A. Collins; Phys. Rev. B 66, 025401 (2002). [2] E. Schwegler, et al. Phys. Rev. Lett. 87, 265501 (2001). [3] P.M. Celliers, et. al. Physics of Plasmas 11, L41 (2004).

Desjarlais, Michael Paul; Mattsson, Thomas Kjell Rene

2005-07-01

229

EFFECTS OF TRITIUM GAS EXPOSURE ON ELECTRICALLY CONDUCTING POLYMERS  

SciTech Connect

Effects of beta (tritium) and gamma irradiation on the surface electrical conductivity of two types of conducting polymer films are documented to determine their potential use as a sensing and surveillance device for the tritium facility. It was shown that surface conductivity was significantly reduced by irradiation with both gamma and tritium gas. In order to compare the results from the two radiation sources, an approximate dose equivalence was calculated. The materials were also sensitive to small radiation doses (<10{sup 5} rad), showing that there is a measurable response to relatively small total doses of tritium gas. Spectroscopy was also used to confirm the mechanism by which this sensing device would operate in order to calibrate this sensor for potential use. It was determined that one material (polyaniline) was very sensitive to oxidation while the other material (PEDOT-PSS) was not. However, polyaniline provided the best response as a sensing material, and it is suggested that an oxygen-impermeable, radiation-transparent coating be applied to this material for future device prototype fabrication. A great deal of interest has developed in recent years in the area of conducting polymers due to the high levels of conductivity that can be achieved, some comparable to that of metals [Gerard 2002]. Additionally, the desirable physical and chemical properties of a polymer are retained and can be exploited for various applications, including light emitting diodes (LED), anti-static packaging, electronic coatings, and sensors. The electron transfer mechanism is generally accepted as one of electron 'hopping' through delocalized electrons in the conjugated backbone, although other mechanisms have been proposed based on the type of polymer and dopant [Inzelt 2000, Gerard 2002]. The conducting polymer polyaniline (PANi) is of particular interest because there are extensive studies on the modulation of the conductivity by changing either the oxidation state of the main backbone chain, or by protonation of the imine groups [de Acevedo, 1999]. There are several types of radiation sensors commercially available, including ionization chambers, geiger counters, proportional counters, scintillators and solid state detectors. Each type has advantages, although many of these sensors require expensive electronics for signal amplification, are large and bulky, have limited battery life or require expensive materials for fabrication. A radiation sensor constructed of a polymeric material could be flexible, light, and the geometry designed to suit the application. Very simple and inexpensive electronics would be necessary to measure the change in conductivity with exposure to radiation and provide an alarm system when a set change of conductivity occurs in the sensor that corresponds to a predetermined radiation dose having been absorbed by the polymer. The advantages of using a polymeric sensor of this type rather than those currently in use are the flexibility of sensor geometry and relatively low cost. It is anticipated that these sensors can be made small enough for glovebox applications or have the ability to monitor the air tritium levels in places where a traditional monitor cannot be placed. There have been a few studies on the changes in conductivity of polyaniline specifically for radiation detection [de Acevedo, 1999; Lima Pacheco, 2003], but there have been no reports on the effects of tritium (beta radiation) on conducting polymers, such as polyaniline or polythiophene. The direct implementation of conducting polymers as radiation sensor materials has not yet been commercialized due to differing responses with total dose, dose rate, etc. Some have reported a large increase in the surface conductivity with radiation dose while others report a marked decrease in conductive properties; these differing observations may reflect the competing mechanisms of chain scission and cross-linking. However, it is clear that the radiation dose effects on conducting polymers must be fully understood before these materials can be used

Kane, M.; Clark, E.; Lascola, R.

2009-12-16

230

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

231

Stationary cylindrical vortex in a viscous electrically conducting fluid  

NASA Astrophysics Data System (ADS)

An exact solution of the magnetohydrodynamic equations is constructed which describes steady vortex flow in a stationary cylinder on the axis of which a conductor carrying a known current is located. The solution is obtained under the assumption that the fluid is viscous and has finite electrical conductivity and that the magnetic field has only the axial and azimuthal components in a cylindrical coordinate system. It is found that the action of the Lorentz force is compensated by changing the pressure. Fluid flow occurs from the periphery to the axis of the cylinder under a pressure gradient, with flow rotation and swirling. The fluid flow causes a concentration of the magnetic lines near the axis of the cylinder, providing an exponential decrease in the magnetic field strength with distance from the axis. This flow can be considered as a model of a local increase in the magnetic field strength due to the transfer of its force lines by the flow of the electrically conducting fluid.

Baikin, A. N.; Golovin, S. V.

2013-07-01

232

Effect of Scattering by Fluidization of Electrically Conductive Beads on Electrical Field Intensity Profile in Microwave Dryers  

Microsoft Academic Search

A technology to apply a fluidized bed of electrically conductive beads is proposed to improve uniformity of the electric field intensity in microwave dryers, which are required for uniform heating of wet media. The principle of this effectiveness lies in a dynamic random scattering of microwave due to motion of the conductive beads in the bed. The electrically conductive beads

Yoshinori Itaya; Shigeru Uchiyama; Shigenobu Hatano; Shigekatsu Mori

2005-01-01

233

On the stability of the electrical resistivity and the contact resistance of electrically conductive modified silicone elastomers  

Microsoft Academic Search

Cable accessories for medium- and high voltage applications contain field grading and field zoning parts or layers. These parts often consist of electrically conductive modified silicone elastomers. The electrical conductivity is achieved by using selected and long-term tested carbon blacks. Conductive layers and parts are used to provide safety against exposure, inner shielding and an electrical contact to metallic parts

Jens Lambrecht; Martin Grunwald; Roland Bärsch

2010-01-01

234

Acidosis slows electrical conduction through the atrio-ventricular node.  

PubMed

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

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

2014-01-01

235

On the electrical conductivity of metal matrix composites containing high volume fractions of non-conducting inclusions  

Microsoft Academic Search

Different predictive models—the Maxwell mean field approach, the differential effective medium scheme, the 2- and 3-phase self-consistent, and 3-point model—for the electrical conductivity of two-phase materials are assessed based on electrical conductivity measurements of metal matrix composites with non-conducting inclusions produced by gas pressure infiltration. The volume fraction of non-conducting phase, namely equiaxed or angular alumina particles of various sizes

L. Weber; J. Dorn; A. Mortensen

2003-01-01

236

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

237

Optical and Electrical Diagnostics of the Effects of Conductivity on Liquid Phase Electrical Discharge  

Microsoft Academic Search

The influence of solution conductivity on liquid phase pulsed electrical discharge was investigated by optical emission spectroscopy in a reactor with point-to-plane electrode geometry. The emission intensities of hydroxyl (OH) radical, hydrogen (H) radical, and oxygen (O) radical were measured using an emission intensity calibration method which used argon gas as a chemical actinometer. Control experiments showed that the addition

Kai-Yuan Shih; Bruce R. Locke

2011-01-01

238

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

239

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

240

Chemical Events in Conducting and Synaptic Membrances during Electrical Activity  

PubMed Central

Evidence has accumulated in recent years for the central role of proteins and enzymes in the function of cell membranes. In the chemical theory proposed for the generation of bioelectricity, i.e., for the control of the ion permeability changes of excitable membranes, the protein assembly associated with the action of acetylcholine plays an essential role. Support of the theory by recent protein studies in which the excitable membranes of the highly specialized electric tissue were used will be discussed. A scheme is presented indicating the possible sequence of chemical reactions that change ion permeability after excitation. A sequence of chemical events within the excitable membranes of the synaptic junctions, i.e., within the pre- and postsynaptic membranes, similar to that proposed for the conducting membranes, is presented in a second scheme as an alternative to the hypothesis of the role of acetylcholine as a transmitter between two cells. Images PMID:4332011

Nachmansohn, David

1971-01-01

241

Electrically conductive, optically transparent polymer/carbon nanotube composites  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

242

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

243

Electrically Conductive Metal Polymer Nanocomposites for Electronics Applications  

NASA Astrophysics Data System (ADS)

An electrically conductive nanocomposite composed of thermoplastic elastomer and nanosized silver particles was developed. Nanosized silver particles were produced by the liquid flame spraying method. Nanocomposites were produced employing a batch mixing process in the melt state. The percolation curve and the minimum resistivity as a function of silver content were defined. A plasticized styrene block-copolymer was used as the matrix polymer. The results showed that the agglomeration of the silver particles has a major influence on the percolation threshold and the resistivity of the compound. With slightly agglomerated silver particles a percolation threshold with a silver content of 13 16 vol.% was achieved. The corresponding resistivity was 2.0 × 10-1 ? cm. With heavily agglomerated particles the resistivity is high (2.9 × 103 ? cm), even with a silver content of 20 vol.%. With a low primary silver particle size (under 100 nm), the resistivity of the compound was high (5.6 × 105 ? cm).

Karttunen, Mikko; Ruuskanen, Pekka; Pitkänen, Ville; Albers, Willem M.

2008-07-01

244

System and method for determining velocity of electrically conductive fluid  

NASA Technical Reports Server (NTRS)

A flowing electrically-conductive fluid is controlled between an upstream and downstream location thereof to insure that a convection timescale of the flowing fluid is less than a thermal diffusion timescale of the flowing fluid. First and second nodes of a current-carrying circuit are coupled to the fluid at the upstream location. A current pulse is applied to the current-carrying circuit so that the current pulse travels through the flowing fluid to thereby generate a thermal feature therein at the upstream location. The thermal feature is convected to the downstream location where it is monitored to detect a peak associated with the thermal feature so-convected. The velocity of the fluid flow is determined using a time-of-flight analysis.

Polzin, Kurt A. (Inventor); Korman, Valentin (Inventor); Markusic, Thomas E. (Inventor); Stanojev, Boris Johann (Inventor)

2008-01-01

245

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 have been in use for some time. In this total space environment, the coating must be stable and maintain its desired optical properties as well as mechanical 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 added to already 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 objective of this program was to develop two types of passive electrically conductive TCMS. The first was a highly absorbing/emitting black surface and the second was a low (alpha(sub s)/epsilon(sub N)) type white surface. The surface resistance goals for the black absorber was 10(exp 4) to 10(exp 9) Omega/square, and for the white surfaces it was 10(exp 6) to 10(exp 10) Omega/square. Several material system concepts were suggested and evaluated for space environment stability and electrical performance characterization. Our efforts in designing and evaluating these material systems have resulted in several developments. New concepts, pigments and binders have been developed to provide new engineering quality TCMS. Some of these have already found application on space hardware, some are waiting to be recognized by thermal designers, and some require further detailed studies to become state-of-the-art for future space hardware and space structures. Our studies on baseline state-of-the-art materials and conductive concepts have resulted in several important findings that are of interest to all thermal designers and systems integrators.

Deshpande, M. S.; Harada, Y.

1997-01-01

246

Electrical Conduction and Dielectric Relaxation in Polyethylene Terephthalate Succinate  

NASA Astrophysics Data System (ADS)

Electrical conduction and complex permittivity are examined in polyethylene terephthalate succinate, focusing on their relations to dielectric relaxation processes. Both the real and imaginary parts of complex permittivity, namely dielectric constant ?r' and dielectric loss factor ?r'', increase with a decrease in frequency, especially at high temperatures. They are both ascribed to the transport of ionic mobile carriers. Namely, the carrier transport forms conduction current that should contribute to ?r''. On this occasion, if charge exchange does not occur at the two electrodes, heterocharge layers should be formed before the electrodes. This should increase the charge density on the electrodes, thus contributing to ?r'. In addition to the increase in ?r' and ?r'' due to mobile ions, two relaxation processes, one due to micro-Brownian motion of dipoles and the other due to orientation and magnitude change of the dipole moment induced by two end groups in the polymer main chain, are observed. Corresponding to these two relaxation processes, two thermally stimulated discharge current (TSDC) peaks appear. The two TSDC peaks as well as the increment in ?r' and ?r'' become larger when the crystallinity of the sample decreases.

Kato, Fukutaro; Ohki, Yoshimichi

247

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

248

Anisotropy of the electrical conductivity and mechanical properties of extruded aluminum alloys  

Microsoft Academic Search

1.Recrystallized extruded rods and strips of aluminum alloys with a fibrous structure and texture show anisotropy of the electrical conductivity.2.A correlation was found between the anisotropy of the electrical conductivity and the anisotropy of the ultimate strength.

N. M. Naumov; P. G. Miklyaev; I. I. Novikov

1972-01-01

249

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

NASA Technical Reports Server (NTRS)

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

Duba, AL

1987-01-01

250

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

251

Nonstoichiometric Zinc Oxide and Indium-Doped Zinc Oxide: Electrical Conductivity and 111In-TDPAC Studies  

Microsoft Academic Search

Indium-doped zinc oxide powders have been prepared which show room-temperature electrical conductivities as high as 30 ??1cm?1. The indium doping apparently occurs as Zn1?xInxO, Zn1?yInyO1+y\\/2, or a combination of these. Optimum conductivity occurs for Zn1?xInxO where the maximum value ofxobtained was about 0.5 at%. This substitution results in a lattice volume expansion of 0.4%. The degrees of sample reduction were

Ruiping Wang; Arthur W. Sleight; Roland Platzer; John A. Gardner

1996-01-01

252

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

253

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

254

D-H Interdiffusion Coefficients in Olivine: Implications for Electrical Conductivity in the Upper Mantle  

NASA Astrophysics Data System (ADS)

Knowledge about hydrogen diffusivity in mantle minerals is critical for understanding point defects and defect dominated processes such as creep and electrical conductivity. Hydrogen chemical diffusion coefficients have been used to constrain diffusivities of small polarons and Mg vacancies (Kohlstedt and Mackwell, 1998). Furthermore chemical diffusion coefficients have been used to calculate hydrogen contribution to electrical conductivity in olivine (Karato, 1990), however hydrogen self diffusion coefficients are more appropriate. In this study we use +{2}H as a traceable species of hydrogen to simulate the process of hydrogen self diffusion. Deuterium (+{2}H, sometimes referred to as D) was interdiffused into hydrogen (+{1}H) saturated, oriented, single crystal San Carlos olivine. We measured +{2}H and +{1}H profiles across samples from each of these experiments and fit interdiffusion coefficients (D_{D-H}). For olivine between 750-900 °C at 2 GPa we measured D_{D-H, [100]} = 10+{(-5.0 +/- 1.4)}*e+{(-135 +/- 30 kJ/mol)/(RT)} m+{2}/s. This value is 1 order of magnitude lower than D_{Exch, [100]}, the chemical diffusion coefficient for +{1}H based redox exchange in San Carlos olivine (Kohlstedt and Mackwell, 1998). Activation energies for D_{Exch, [100]} and D_{D-H, [100]} are very similar. We measured D_{D-H, [001]} = 10+{-12.0 +/- 0.2} m+{2}/s at 900 °C and 2 GPa; however only upper bound estimates for D_{D-H, [010]} and for D_{D-H, [001]} at lower temperatures could be determined with D_{D-H, [010]} D_{D-H, [001]} < 10+{-13} m+{2}/s. From comparison of D_{D-H} and D_{Exch} we calculate small polaron diffusion coefficients associated with redox exchange reactions (D_{h, [100]} = 10+{(-4.9 +/- 1.4)}*e+{(-135 +/- 30 kJ/mol)/(RT)} m+{2}/s) and confirm previous estimates of metal vacancy diffusion coefficients (D_{V(Me)} = D_{Incorp}/3). These +{2}H-+{1}H interdiffusion coefficients are used with the Nernst-Einstein relation to calculate electrical conductivity in hydrous olivine for comparison to experimental values. These calculations incorporate polaron and metal vacancy mobility estimates from anhydrous conductivity experiments. For 100 ppmw H_{2}O, 2 GPa and 900 °C, the calculated electrical conductivity by hydrogen is 0.7-2.4 log units lower and activation energy is 60% higher than reported electrical conductivity measurements (Wang et al., 2006; Yoshino et al., 2006; Yoshino et al., 2009, Poe et al., 2010). Thus current estimates of defect concentrations and mobilities from diffusion experiments and measured dry and wet electrical conductivities are not mutually consistent. The calculation presented here would require unrealistically high amounts of H_{2}O to account for high electrical conductivity anomalies measured at asthenosphere depths. However, the apparent differences in activation energy suggest that multiple types of hydrogen defects/species may occur and would need to be considered in the relationship between hydrogen diffusion and conduction in olivine.

Du Frane, W. L.; Tyburczy, J. A.; Sharp, T. G.

2010-12-01

255

Physicochemical properties of the soil-saturation extracts: estimation from electrical conductivity  

Microsoft Academic Search

With the aim of estimating certain physico-chemical properties of soil-saturation extracts from electrical conductivity, we prepared saturation extracts from 67 soil samples having different quantitative and qualitative salt contents. The solution of each saturation extract was vacuum pumped, and used to determine the electrical conductivity (EC), electrical conductivity calculated (ECc), ionic composition and total soluble salts. The analyses for kinds

M. Simón; I. Garc??a

1999-01-01

256

Experimental investigation of the effective electrical conductivity of aluminum oxide nanofluids  

Microsoft Academic Search

This paper reports an experimental work on the measurement of effective electrical conductivity of aqueous suspensions of aluminum oxide nanoparticles (nanofluids). Experiments were performed both as a function of volume fraction and temperature to examine the effects of their variations on the electrical conductivity of alumina nanofluids. The results indicate considerable enhancement of electrical conductivity with both increase in volume

Suvankar Ganguly; Sudipta Sikdar; Somnath Basu

2009-01-01

257

Electrically Conductive And Infrared Transparent Thin Metal Film Coatings  

NASA Astrophysics Data System (ADS)

Electrically conductive (EC) and Infrared (IR) transparent thin metal film coatings for the 3 - 5 um and 8 - 12 um wavebands have been developed. Surface resistivity from 5 to 200 ohms/square have been studied. A transmittance value as high as 90% at 10.6 um has been achieved. The performance of these developed coatings are compared with the characteristics of the few IR transparent EC coatings reported in the literature. The fundamental difficulties in producing a highly transparent, wide optical bandwidth coating with low resistivity are discussed. The choice of a semiconductor or metal type EC coating are compared. The optical performance of these two types of IR EC coatings are calculated for equal electrical properties (surface resistivities). Induced transmission optical designs for both EC coating types are presented and the peak transmittance, and bandwidth achieved are compared. Measured results are compared with the calculated values. To date, the developed IR EC coatings have been vacuum deposited on ZnS, ZnSe, Ge, MgF2, Al203 and IR transmitting glass substrates materials. These coatings have also been deposited on a variety of flat optics and on a near hemispherical dome (9" diameter). Some present appli-cations and potential applications of these IR EC coatings are discussed. For example, a 3 - 5 um/millimeter wave aspheric beamsplitter has been produced. Electromagnetic Inter-ference (EMI) shielding of a MgF2 dome with a 3 - 5 um IR EC coating has been accomplished and verified by measurements.

Bright, Clark I.

1986-12-01

258

Electrical conduction and glass relaxation in alkali- silicate glasses  

NASA Astrophysics Data System (ADS)

Electrical response measurements from 1 Hz to 1 MHz between 50o and 540oC were made on potassium, sodium and lithium-silicate glasses with low alkali oxide contents. Conductivity and electrical relaxation responses for both annealed and air quenched glasses of the same composition were compared. Quenching was found to lower the dc conductivity, ?dc, and activation energy as well as increase the pre-exponential term when compared to the corresponding annealed glass of the same composition. All of the glasses exhibited Arrhenius behavior in the log ?dc against 1/T plots. A sharp decrease in ?dc was observed for glasses containing alkali concentrations of 7 mol% or less. The ?dc activation energy exhibited similar behavior when plotted as a function of alkali composition and was explained in terms of a mixture of the weak and strong electrolyte models. The depression angle for fits to the complex impedance data were also measured as a function of thermal history, alkali concentration and alkali species. These results were interpreted in terms of changes in the distribution of relaxation times. Annealed samples from a single melt of a 10 mol% K2O-90SiO2 glass were reheated to temperatures ranging from 450o to 800oC, held isothermally for 20 min, and then quenched in either air or silicon oil. The complex impedance of both an annealed and the quenched samples were then measured as a function of temperature from 120o to 250oC. The ?dc was found to be remain unaffected by heat treatments below 450oC, to increase rapidly over an approximate 200oC range of temperatures that was dependent on cooling rate and to be constant for heat treatments above this range. This behavior is interpreted in terms of the mean structural relaxation time as a function of temperature and cooling rate near the glass transition temperature and glass transformation ranges. A more detailed definition for the transition and transformation temperatures and ranges was also provided.

Angel, Paul William

259

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.

260

Electrical equivalence of electrospray ionization with conducting and nonconducting needles.  

PubMed

An electrical equivalent circuit is derived for the electrospray process. It is a series circuit which consists of the power supply, the electrochemical contact to the solution, the solution resistance (R(s)), a constant-current regulator which represents the processes of charge separation and charge transport in the gap between the spray needle aperture and the counter electrode, and charge neutralization at the counter electrode. A current i, established by the constant-current regulator flows throughout the entire circuit. Current-voltage curves are developed for each element in the circuit. From these it is shown that in the case where R(s) is negligible (the power supply is connected directly to a conducting needle) the shape of the current-voltage curve is dictated by the constant-current regulator established by the charge separation process, the gap, and the counter electrode. The solution resistance may be significant if a nonconducting needle is used so that the electrochemical contact to the solution is remote from the tip. Experiments with a nonconducting spray needle quantify the effect of the solution resistance on the current-voltage curve. Subtracting the iRs voltage from Vapp (power supply voltage) yields the current-voltage curve for the constant-current regulator. When iRs drop is a significant fraction of Vapp, the current-voltage curve of the constant-current regulator is changed substantially from the case when the solution resistance is negligible. PMID:10489527

Jackson, G S; Enke, C G

1999-09-01

261

Effects of gold nanoparticles and lithium hexafluorophosphate on the electrical conductivity of PMMA  

Microsoft Academic Search

An increase in electrical conductivity of a polymeric system can be realized by adding conductive fillers and\\/or dissolving a salt in a suitable solvent or polymer through formation of ionic conduction. An appropriate solvent that can form complexes with alkali metal cations is critical to providing electrical conductivity enhancements to a wide variety of polymers. In this study, we investigated

Soumen Jana; Amin Salehi-Khojin; Wei-Hong Zhong; Hui Chen; Xiong Liu; Qun Huo

2007-01-01

262

The Wilkes subglacial basin eastern margin electrical conductivity anomaly  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

263

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

264

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

E-print Network

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 $2\\leftrightarrow 3$ perturbative QCD scattering. Comparing with recent lattice results, we find an agreement in the temperature dependence of the conductivity.

Moritz Greif; Ioannis Bouras; Zhe Xu; Carsten Greiner

2014-08-29

265

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

E-print Network

] Electrical conduction through meteoric polar ice is controlled by soluble impurities that originate mostly (by electrical conductivity measurement [ECM] or dielectric profiling [DEP]) and the attenuation interpretation of electrical and chemical logs can determine impurity partitioning between the lattice and grain

Stillman, David E.

266

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

E-print Network

Electrical Conductivity Measurement through the Loaded Q Factor of a Resonant Cavity J. J. Barroso the electrical conductivity of metallic materials that relies on the ratio of two loaded Q factors, QR replacing the aluminum plate with the one fabricated from the material to be examined. Electrical

267

Electrical conductivity of lyotropic and thermotropic ionic liquid crystals consisting of metal alkanoates  

Microsoft Academic Search

The electrical properties of ionic smectic liquid crystal (ISLCs), specifically, (i) oriented and non?oriented samples of lyotropic ISLC potassium caproate and (ii) oriented samples of thermotropic ISLC cobalt decanoate, are investigated in detail. The electrical conductivity of lyotropic smectic potassium caproate is higher than that of isotropic electrolytes. A giant anisotropy in the electrical conductivity of oriented samples of thermotropic

Yuriy Garbovskiy; Alexander Kovalchuk; Alexandra Grydyakina; Svitlana Bugaychuk; Tatyana Mirnaya; Gertruda Klimusheva

2007-01-01

268

Journal of Crystal Growth 280 (2005) 490494 Electrical conductivity and photoreflectance of nanocrystalline  

E-print Network

containing more than 79% Cu are metallic conductors with excellent electrical conductivity via a percolation. Copper nitride; B2. Electrical properties 1. Introduction In recent years, copper nitride, the mostJournal of Crystal Growth 280 (2005) 490­494 Electrical conductivity and photoreflectance

Zexian, Cao

269

Studies of electrical conduction in pyroelectric DTGS: PVDF composites  

NASA Astrophysics Data System (ADS)

The AC and DC conductivities of pyroelectric composite, deuterated triglycine sulfate (DTGS): polyvinylidene fluoride (PVDF) having 15%, 20%, and 40% DTGS content (by weight) have been measured at temperature ranging from room temperature to 55 °C. The ac conductivity of composites at 1 MHz shows very weak temperature dependence. The dc conductivity for 20% and 40% DTGS content (by weight) composites shows activated behavior.

Batra, Ashok K.; Simmons, M.; Guggilla, Padmaja; Aggarwal, M. D.; Lal, R. B.

2004-06-01

270

ELECTRICAL CONDUCTIVITY AND SCATTERING MATRIX FOR DIRAC OPERATORS ON MANIFOLDS WITH CYLINDRICAL CONTACTS  

Microsoft Academic Search

In the static limit of linear response theory, the electrical con- ductivity is a linear operator taking closed electric flelds into closed electric current densities. The induced mapping in cohomology is called the electrical conductance. Using the notion of relative de Rham cohomology of a mani- fold M with boundary, we give a thorough discussion of what is meant by

MATTHIAS LESCH; FLORIAN MERZ; MARTIN R. ZIRNBAUER

271

Electrical conductivity as an indicator of iron reduction rates in abiotic and biotic systems  

Microsoft Academic Search

Although changes in bulk electrical conductivity (?b) in aquifers have been attributed to microbial activity, ?b has never been used to infer biogeochemical reaction rates quantitatively. To explore the use of electrical conductivity to measure reaction rates, we conducted iron oxide reduction experiments of increasing biological complexity. To quantify reaction rates, we propose composite reactions that incorporate the stoichiometry of

Aaron Regberg; Kamini Singha; Ming Tien; Flynn Picardal; Quanxing Zheng; Jurgen Schieber; Eric Roden; Susan L. Brantley

2011-01-01

272

Evaluation of saline tracer performance during electrical conductivity groundwater monitoring.  

PubMed

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

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

2011-04-25

273

76 FR 75875 - Plan for Conduct of 2012 Electric Transmission Congestion Study  

Federal Register 2010, 2011, 2012, 2013

...DEPARTMENT OF ENERGY Plan for Conduct of 2012 Electric Transmission Congestion Study AGENCY: Office of...in connection with the preparation of a study of electric transmission congestion pursuant to section...

2011-12-05

274

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

E-print Network

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

Bazant, Martin Z.

275

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

276

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

277

Anisotropy of synthetic quartz electrical conductivity at high pressure and temperature  

Microsoft Academic Search

AC measurements of the electrical conductivity of synthetic quartz along various orientations were made between 0.1 and 1 MHz, at ?855?1601 K and at 1.0 GPa. In addition, the electrical conductivity of quartz along the c axis has been studied at 1.0–3.0 GPa. The impedance arcs representing bulk conductivity occur in the frequency range of 103–106 Hz, and the electrical

Duojun Wang; Heping Li; Li Yi; Takuya Matsuzaki; Takashi Yoshino

2010-01-01

278

The microstructure and electrical conductivity of WO 3-doped SrTiO 3 ceramics  

Microsoft Academic Search

The effects of WO3 addition and sintering condition on the microstructure and electrical conductivity of SrTiO3 ceramics have been investigated. When Po2 ? 10?10 atm, the room temperature electrical conductivity was proportional logarithmically to WO3 content. Whereas when Po2 > 10?10 atm, the electrical conductivity increased with WO3 content up to 1.2 mol%. When the WO3 content is higher than

In-Kyu You; Jae-Dong Byun; Yoon-Ho Kim

1996-01-01

279

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

280

Effects of nitrogen plasma post-treatment on electrical conduction of carbon nanowalls  

NASA Astrophysics Data System (ADS)

For utilization in future electronic application of graphene materials, nitrogen (N) atom doping into graphene sheets is an important technology. We investigated the electrical conduction of carbon nanowalls (CNWs), consisting of stacks of graphene sheets standing vertically on substrates. By post-treatment for 30 s, the electrical conductivity of CNWs increased. On the other hand, as the post-treatment time increased, the electrical conductivity decreased. According to Hall measurement, the carrier density decreased with increasing post-treatment time, while the carrier mobility increased. Consequently, the electrical conduction of the CNWs was successfully controlled by N2 plasma treatment.

Cho, Hyung Jun; Kondo, Hiroki; Ishikawa, Kenji; Sekine, Makoto; Hiramatsu, Mineo; Hori, Masaru

2014-04-01

281

Electrical conduction in metal-glass composite materials  

Microsoft Academic Search

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

V. K. Nagesh

1976-01-01

282

Size Effect Variation of the Electrical Conductivity of Metals  

Microsoft Academic Search

This paper records experiments and theoretical work concerned with the variation of conductivity with size in metals. Experimental results for the conductivity in thin wires of pure sodium of varying diameter in the absence of a magnetic field and also in the presence of longitudinal and transverse magnetic fields are given. Using the general statistical theory of metals the variation

D. K. C. MacDonald; K. Sarginson

1950-01-01

283

Pricing and Firm Conduct in California's Deregulated Electricity Market  

E-print Network

. University of California Energy Institute 2539 Channing Way Berkeley, California 94720-5180 www generating firms bid into a daily auction for the right to supply power to the electrical grid. Policymakers and fall 2000. The incumbent utilities were required to purchase power at high wholesale prices and to sell

California at Berkeley. University of

284

Different clinical electrodes achieve similar electrical nerve conduction block  

NASA Astrophysics Data System (ADS)

Objective. We aim to 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 the 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 the 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.

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

2013-10-01

285

Influence of surface conductivity on the apparent zeta potential of TiO2 nanoparticles: application to the modeling of their aggregation kinetics.  

PubMed

Titanium dioxide nanoparticles (TiO2 NPs) are extensively used in consumer products. The release of these NPs into aquatic environments raises the question of their possible risks to the environment and human health. The magnitude of the threat may depend on whether TiO2 NPs are aggregated or dispersed. Currently, limited information is available on this subject. A new approach based on DLVO theory is proposed to describe aggregation kinetics of TiO2 NPs in aqueous dispersions. It has the advantage of using zeta potentials directly calculated by an electrostatic surface complexation model whose parameters are calibrated by ab initio calculations, crystallographic studies, potentiometric titration and electrophoretic mobility experiments. Indeed, the conversion of electrophoretic mobility measurements into zeta potentials is very complex for metal oxide nanoparticles. This is due to their very high surface electrical conductivity associated with the electromigration of counter and co-ions in their electrical double layer. Our model has only three adjustable parameters (the minimum separation distance between NPs, the Hamaker constant, and the effective interaction radius of the particle), and predicts very well the stability ratios of TiO2 NPs measured at different pH values and over a broad range of ionic strengths (KCl aqueous solution). We found an effective interaction radius that is significantly smaller than the radius of the aggregate and corresponds to the radius of surface crystallites or small clusters of surface crystallites formed during synthesis of primary particles. Our results confirm that DLVO theory is relevant to predict aggregation kinetics of TiO2 NPs if the double layer interaction energy is estimated accurately. PMID:23806415

Bouhaik, Izzeddine Sameut; Leroy, Philippe; Ollivier, Patrick; Azaroual, Mohamed; Mercury, Lionel

2013-09-15

286

Electrical conductivity and dielectric properties of sulfamic acid doped polyaniline  

Microsoft Academic Search

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

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

2007-01-01

287

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

288

Electrical conductivity of transition metal containing crystalline zirconium phosphate materials  

Microsoft Academic Search

?-Zirconium phosphate (?-ZrP) has been prepared in various transition metal containing forms, and their structure (identified by XRD), thermal behaviour and specific surface area were determined and their electrical resistivity was measured. On the basis of experimental data, the monoclinic cell parameters for Co(II), Ni(II), Cu(II), and Zn(II) containing crystalline zirconium phosphates were calculated. They showed characteristic thermal decomposition and

L Szirtes; J Megyeri; E Kuzmann; Z Klencsár

2001-01-01

289

Anisotropy of electrical conductivity in aluminum trichloride-intercalated graphite  

Microsoft Academic Search

We have examined the basal-plane and c-axis electrical resistivity (rhoa and rhoc) of first-, second-, and fourth-stage (s) graphite intercalation compounds containing aluminum trichloride from 4.2<=T<=295 K. The basal-plane results are similar for all stages: rhoa is a nonlinear function of T, and all rho(295 K)\\/rho(4.2 K) values are less than 10. The rhoc(T) behavior is stage dependent: for s=1,

E. McRae; J. F. Marché; P. Pernot; R. Vangelisti

1989-01-01

290

Electrical conductivity of aluminum and titanium base reinforced composites  

Microsoft Academic Search

1.For aluminum reinforced with steel fibers, increasing the fiber concentration to 50–60 vol. % produces only a small increase in the electrical resistivity of the composite. At higher fiber concentrations the rate of ascent of the? vs Vf curve sharply increases.2.For titanium base composites reinforced with molybdenum fibers, at low reinforcing phase contents (of the order of 10–20 vol.%) the

D. M. Karpinos; V. Kh. Kadyrov; V. S. Klimenko; T. K. Miroshnikova; V. Ya. Fefer

1974-01-01

291

Electrical properties of ?-crosslinked hydrogels incorporating organic conducting polymers  

NASA Astrophysics Data System (ADS)

Hydrogel composites containing nanoparticles of the protonated emeraldine form of polyaniline (PANI-PE) have been synthesised by ?-irradiation, using either polyvinyl pyrrolidone (PVP) or polyvinyl alcohol (PVA) as steric stabilisers. Swelling behaviour of both hydrogels is reported, together with an electrical characterisation of composites, before and after gel network formation, performed by cyclic voltammetry and impedance spectroscopy. Similarities and differences between the two composite systems are discussed.

Dispenza, C.; Fiandaca, G.; Lo Presti, C.; Piazza, S.; Spadaro, G.

2007-08-01

292

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

293

Measurement of soil water content and electrical conductivity by time domain reflectometry: a review  

Microsoft Academic Search

Non-destructive measurement of soil water content and electrical conductivity has been desired for many years. Recent development of time domain reflectometry (TDR) enables us to simultaneously obtain soil water content and electrical conductivity using a single probe with a minimal disturbance of soil. Research on water and solute transport in porous media using TDR has flourished in the last few

K. Noborio

2001-01-01

294

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

Microsoft Academic Search

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

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

2006-01-01

295

Advantages of Fused Deposition Modeling for Making Electrically Conductive Plastic Patterns  

Microsoft Academic Search

There are many applications where electrically conductive plastic patterns are needed. The most usual way to make electrically conductive patterns is coating a plastic part by a thin layer of metal. It's well known the different procedures for metalizing plastic parts but most of them aim to obtain either aesthetic or functional metallic coating with high level of adherence, finishing

M. D. Monzon; N. Diaz; A. N. Benitez; M. D. Marrero; P. M. Hernandez

2010-01-01

296

The influence of particle shape and size on electric conductivity of metal–polymer composites  

Microsoft Academic Search

The effective electric conductivity of metal–polymer composite is investigated theoretically as a function of the electric conductivities of the constituents, of the particle shape and size and of the volume of loading. And, in order to consider the interaction between the metal particles, a self-consistent way is used to improve this function. Firstly, the percolation threshold decreases rapidly with increasing

Qingzhong Xue

2004-01-01

297

Electrical conductivity field analysis for evaluation of FSW joints in AA6013 and AA7075 alloys  

Microsoft Academic Search

To fully characterize Friction Stir Welding several techniques are required, mainly destructive, as hardness or metallographic testing. However, there is still a need for developing dedicated methods, preferably non-destructive. Electrical conductivity, based on a different physical principle, may constitute an alternative. The present study aims to characterize the electrical conductivity in friction stir welds and to investigate the correlation between

T. G. Santos; P. Vilaça; R. M. Miranda

2011-01-01

298

Refractory, electrically conductive, mixed materials containing boron nitride and process for their manufacture  

Microsoft Academic Search

The invention is refractory, electrically conductive, mixed materials based on hexagonal boron nitride and at least one electrically conductive component such as titanium boride and zirconium boride, and having a density of at leadt about 95% of the theoretical density and nondirection-dependent properties, which have been manufactured from powder mixtures that are practically free of oxygen and metal and comprise

K. Hunold; A. Lip; K. Reinmuth

1985-01-01

299

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

NASA Astrophysics Data System (ADS)

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

Sheftman, D.; Krasik, Ya. E.

2011-09-01

300

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

301

Electrically conductive bulk composites through a contact-connected aggregate.  

PubMed

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 10(12) 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

302

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

303

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

304

An electrical conductivity inspection methodology of polycrystalline diamond cutters  

NASA Astrophysics Data System (ADS)

The polycrystalline diamond cutter (PDC) is widely used in oil and gas drilling operations. It is manufactured by sintering diamond powder onto a tungsten carbide substrate at 6 GPa and 1500 C. During sintering, molten cobalt from the substrate infiltrates the diamond table. The residual metal content correlates with cutter performance. We present an instrument that employs electrical impedance tomography capable of imaging the 3D metal content distribution in the diamond table. These images can be used to predict cutter performance as well as detect flaws.

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

2012-05-01

305

Electrical-Impedance Tomography for Opaque Multiphase Flows in Metallic (Electrically-Conducting) Vessels  

SciTech Connect

A novel electrical-impedance tomography (EIT) diagnostic system, including hardware and software, has been developed and used to quantitatively measure material distributions in multiphase flows within electrically-conducting (i.e., industrially relevant or metal) vessels. The EIT system consists of energizing and measuring electronics and seven ring electrodes, which are equally spaced on a thin nonconducting rod that is inserted into the vessel. The vessel wall is grounded and serves as the ground electrode. Voltage-distribution measurements are used to numerically reconstruct the time-averaged impedance distribution within the vessel, from which the material distributions are inferred. Initial proof-of-concept and calibration was completed using a stationary solid-liquid mixture in a steel bench-top standpipe. The EIT system was then deployed in Sandia's pilot-scale slurry bubble-column reactor (SBCR) to measure material distributions of gas-liquid two-phase flows over a range of column pressures and superficial gas flow rates. These two-phase quantitative measurements were validated against an established gamma-densitometry tomography (GDT) diagnostic system, demonstrating agreement to within 0.05 volume fraction for most cases, with a maximum difference of 0.15 volume fraction. Next, the EIT system was combined with the GDT system to measure material distributions of gas-liquid-solid three-phase flows in Sandia's SBCR for two different solids loadings. Accuracy for the three-phase flow measurements is estimated to be within 0.15 volume fraction. The stability of the energizing electronics, the effect of the rod on the surrounding flow field, and the unsteadiness of the liquid temperature all degrade measurement accuracy and need to be explored further. This work demonstrates that EIT may be used to perform quantitative measurements of material distributions in multiphase flows in metal vessels.

LITER, SCOTT G.; TORCZYNSKI, JOHN R.; SHOLLENBERGER, KIM A.; CECCIO, STEVEN L.

2002-10-01

306

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

Microsoft Academic Search

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

D. Sheftman; Ya. E. Krasik

2011-01-01

307

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

308

Improving the electrical conductivity of CuCrO 2 thin film by N doping  

Microsoft Academic Search

N-doped CuCrO2 thin films were prepared by using radio frequency magnetron sputtering technique. The XRD and XPS measurements were used to confirm the existence of the N acceptors in CuCrO2 thin films. Hall measurements show the p-type conduction for all films. The electrical conductivity increases rapidly with the increase in N doping concentration, and the maximum of the electrical conductivity

Guobo Dong; Ming Zhang; Xueping Zhao; Hui Yan; Chunyu Tian; Yonggang Ren

2010-01-01

309

Measurements of Terahertz Electrical Conductivity of Intense Laser-Heated Dense Aluminum Plasmas  

Microsoft Academic Search

We report the electrical conductivity of laser-produced warm dense aluminum plasmas measured using single-shot ultrafast terahertz (THz) frequency spectroscopy. In contrast with experiments performed at optical frequencies, measurements based upon THz probe reflectivity directly determine a quasi-dc electrical conductivity, and therefore the analysis does not require a free-electron Drude model based extrapolation to recover the near zero frequency conductivity. In

K. Y. Kim; B. Yellampalle; J. H. Glownia; A. J. Taylor; G. Rodriguez

2008-01-01

310

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

Microsoft Academic Search

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

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

1989-01-01

311

Electrically conductive and mechanically elastic titanium nitride ceramic microsprings.  

PubMed

The structural and functional characterizations of titanium nitride (TiN) advanced ceramic microsprings (CMSs), with a coil diameter of several micrometers and synthesized by chemical vapor deposition (CVD) were investigated by microscopy techniques. The CMSs were sufficiently mechanically elastic for extension to more than 1.3 times their original size, and they spontaneously contracted to their original state on releasing the tension. To explore their application to a microdevice, a method of manufacturing TiN-CMS microcircuit elements was developed. The I-V plots of the elements indicated that the CMSs were as conductive as metals. PMID:24738385

Yang, Shaoming; Chen, Xiuqin; Yamamoto, Kazuo; Iitake, Masanori; Nishio-Hamane, D; Sakai, Hideki; Abe, Masahiko

2014-06-01

312

The role of hydrogen in the electrical conductivity of the upper mantle  

Microsoft Academic Search

Experimental data on the solubility and diffusivity of hydrogen in olivine are used to estimate its effect on the electrical conductivity. It is concluded that the observed high conductivity in the asthenosphere can be attributed to solid-state conductivity in olivine if a small amount of hydrogen is present. Partial melting of the asthenosphere on a global scale is therefore not

S. Karato

1990-01-01

313

High temperature performance of low stress electrically conductive adhesives in electronic applications  

Microsoft Academic Search

The electronics industry has shown an increased interest in low stress, flexible, electrically conductive adhesives for harsh environment applications. These include the assembly of materials with large CTE mismatches or high peel strength requirements for 3D-MID and flexible substrate technologies. Depending on the application requirements different flexible conductive adhesives can be considered. Recent product development has focused on highly conductive,

G. Dreezen; L. Theunissen; G. Luyckx; P. Dooling; A. Borak

2008-01-01

314

High frequency electrical conduction block of the pudendal nerve  

NASA Astrophysics Data System (ADS)

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

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

2006-06-01

315

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

316

Latent synthesis of electrically conductive surface-silvered polyimide films.  

PubMed

A facile ambient temperature route to the fabrication of surface silver-metallized polyimide films is described. Silver(I) trifluoromethanesulfonate or silver(I) nitrate and a polyimide, derived from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride and an equimolar amount of 4,4'-oxydianiline and 3,5-diaminobenzoic acid, were dissolved together in dimethylacetamide. Silver(I)-doped films were prepared at thicknesses of 25-40 microm and depleted of solvent by evaporation at ambient temperature and low humidity. The silver(I)-ion-containing films were then treated with aqueous solutions of the reducing agents hydrazine hydrate and hydroxylamine, which brought forth surface-silvered films exhibiting conductivity on the order of bulk polycrystalline silver accompanied by modest-to-high specular reflectivity. PMID:20355773

Davis, Luke M; Abelt, Christopher J; Scott, Joseph L; Orlova, Evguenia; Thompson, David W

2009-01-01

317

Electrical conductivity of copper/SbF 5-intercalated graphite composite wires  

NASA Astrophysics Data System (ADS)

Recently, unusually high room temperature electrical conductivities rivalling those of pure copper and silver have been reported in graphite intercalated with strong acid fluorides such as antimony pentafluoride and arsenic pentafluoride. With a view to technologically take advantage of such high conductivities in electrical equipment, composite wires consisting of an outer copper sheath and an inner core of graphite intercalated with antimony pentafluoride were fabricated in the present study. The intercalated graphite core was characterized for its density, crystal structure and crystallographic orientation; and the electrical conductivity of the composite wires was measured using the four-paint probe method. The electrical conductivities of the composite wires were found to be substantially lower than that of pure copper and essentially equal to the conductivity contribution of the outer copper sheath alone.

Singhal, S. C.

1980-01-01

318

DC Electrical Conductivity of Silicon Carbide Ceramics and Composites for Flow Channel Insert Applications  

SciTech Connect

High purity chemically vapor-deposited silicon carbide (SiC) and 2D continuous SiC fiber, chemically vapor-infiltrated SiC matrix composites with pyrocarbon interphases were examined for temperature dependent (RT to 800 C) electrical conductivity and the influence of neutron irradiation on it. In the 2D composites, trans-thickness electrical conductivity was dominated by bypass conduction via interphase network at relatively low temperatures, whereas conduction through SiC constituents dominated at higher temperatures. The Influence of neutron irradiation on electrical properties appeared very strong for SiC, resulting typically in by orders lower ambient conductivity and steeper temperature dependency. Through-thickness electrical conductivity of neutron-irradiated 2D SiC composites with thin PyC interphase will likely in the order of 10 S/m in the typical operating temperature range for flow channel inserts. Mechanisms of electrical conduction in the composites and irradiation-induced modification of electrical conductivity of the composites and their constituents are discussed.

Katoh, Yutai [ORNL; Kondo, Sosuke [ORNL; Snead, Lance Lewis [ORNL

2009-01-01

319

Comparative study of electrically conductive thick films with and without glass  

Microsoft Academic Search

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

Zongrong Liu; D. D. L. Chung

2004-01-01

320

Electrical Conductivity Measurements of Nanofibers Electrospun from Polyaniline/Polyethylene Oxide Blends  

NASA Astrophysics Data System (ADS)

Electrically conducting fibers of polyaniline doped with Camphorsulfonic acid PAn.HCSA in the Polyethylene Oxide (PEO) matrix were prepared using the non-mechanical electrospinning technique. The morphology of the fibers was studied using the scanning electron microscope (SEM) and Transmission electron microscope (TEM), showing a uniform thickness along the fiber length. The fibers had a diameter ranging from 800nm to 2?m. The electrical conductivity of the non-woven fibrous mat and the cast film was measured using the four-point probe method, for different concentrations of Pan.HCSA in the blend. Some possible factors affecting the electrical conductivity of the fibers/films were discussed.

Khan, Saima; Khan, Aurangzeb; Kordesch, Martin

2007-03-01

321

Electrical conductivity of open-cell metal foams K.P. Dharmasena and H.N.G. Wadley  

E-print Network

Electrical conductivity of open-cell metal foams K.P. Dharmasena and H.N.G. Wadley Department to represent an open-cell aluminum foam and a simplified electrical resistor network derived to model low in electrical conductivity at a fixed relative density. Low frequency electrical conductivity measurements

Wadley, Haydn

322

Conducting polymers. VI. Effect of doping with iodine on the dielectrical and electrical conduction properties of polyacrylonitrile  

NASA Astrophysics Data System (ADS)

The effect of doping of polyacrylonitrile (PAN) with iodine on the dielectical properties and ac conductivity as a function of temperature and frequency is investigated. Thermogravimetric analysis, TGA, and FTIR measurements show that PAN undergoes degradation starting at 523 K. Doping PAN with I2 enhances the ac electrical conductivity ?ac in the temperature range under investigation due to oligomerization of the nitrile groups giving a conjugated polyimine. The thermal activation energy, ?E, is calculated for PAN and PAN/I2 and found to be in the range 0.16-1.16 eV at 0.1 kHz. The correlated barrier hopping (CBH) conduction mechanism is found to be the dominant conduction mechanism for PAN and PAN/I2 samples.

El-Ghamaz, N. A.; Diab, M. A.; Zoromba, M. Sh.; El-Sonbati, A. Z.; El-Shahat, O.

2013-10-01

323

Synthesis and characterization of electrical conducting porous carbon structures based on resorcinol-formaldehyde  

NASA Astrophysics Data System (ADS)

Electrical conducting carbon (ECC) porous structures were explored by changing the pyrolysis temperature of organic xerogel compounds prepared by sol-gel method from resorcinol-formaldehyde (RF) mixtures in acetone using picric acid as catalyst. The effect of this preparation parameter on the structural and electrical properties of the obtained ECCs was studied. The analysis of the obtained results revealed that the polymeric insulating xerogel phase was transformed progressively with pyrolysis temperature into carbon conducting phase; this means the formation of long continuous conducting path for charge carriers to move inside the structure with thermal treatment and the samples exhibited tangible percolation behaviour where the percolation threshold can be determined by pyrolysis temperature. The temperature-dependent conductivity of the obtained ECC structures shows a semi-conducting behaviour and the I( V) characteristics present a negative differential resistance. The results obtained from STM micrographs revealed that the obtained ECC structures consist of porous electrical conducting carbon materials.

Najeh, I.; Ben Mansour, N.; Mbarki, M.; Houas, A.; Nogier, J. Ph.; El Mir, L.

2009-10-01

324

Phase Diagram and Electrical Conductivity of High Energy-Density Water from Density Functional Theory  

Microsoft Academic Search

The electrical conductivity and structure of water between 2000 70000K and 0.1 3.7g\\/cm3 is studied by finite temperature density functional theory (DFT). Proton conduction is investigated quantitatively by analyzing diffusion, the pair-correlation function, and Wannier center locations, while the electronic conduction is calculated in the Kubo-Greenwood formalism. The conductivity formulation is valid across three phase transitions (molecular liquid, ionic liquid,

Thomas R. Mattsson; Michael P. Desjarlais

2006-01-01

325

Review of Recent Advances in Electrically Conductive Adhesive Materials and Technologies in Electronic Packaging  

Microsoft Academic Search

Electrically Conductive Adhesives (ICAs: Isotropic Conductive Adhesives; ACAs: An-isotropic Conductive Adhesives; and NCAs: Non-conductive Adhesives) offer promising material solutions for fine pitch interconnects, low cost, low-temperature process and environmentally clean approaches in the electronic packaging technology. ICAs have been developed and used widely for traditional solder replacement, especially in surface mount devices and flip chip application. These also need to

Myung Jin Yim; Yi Li; Kyoung-sik Moon; Kyung Wook Paik; C. P. Wong

2008-01-01

326

Nonstoichiometric zinc oxide and indium-doped zinc oxide: Electrical conductivity and {sup 111}In-TDPAC studies  

SciTech Connect

Indium-doped zinc oxide powders have been prepared which show room-temperature electrical conductivities as high as 30 {Omega}{sup {minus}1} cm{sup {minus}1}. The indium doping apparently occurs as Zn{sub 1-x}In{sub x}O,Zn{sub 1-y}In{sub y}O{sub 1+y/2}, or a combination of these. Optimum conductivity occurs for Zn{sub 1-x}In{sub x}O where the maximum value of x obtained was about 0.5 at%. The degrees of sample reduction were determined by iodimetric titration. Time differential perturbed angular correlation (TDPAC) spectroscopy on indium doped zinc oxide is consistent with indium substituting at normal zinc sites in the ZnO lattice. TDPAC studies on zinc oxide annealed under zinc vapors show a second environment for the {sup 111}In probe. In this case, there is an unusually high temperature dependence of the electric field gradient which may be caused by a nearby zinc interstitial. An important conclusion of this work is that zinc interstitials are not ionized and do not therefore contribute significantly to the increased conductivity of reduced zinc oxide.

Wang, R.; Sleight, A.W.; Platzer, R.; Gardner, J.A. [Oregon State Univ., Corvallis, OR (United States)] [Oregon State Univ., Corvallis, OR (United States)

1996-02-15

327

Nonstoichiometric Zinc Oxide and Indium-Doped Zinc Oxide: Electrical Conductivity and 111In-TDPAC Studies  

NASA Astrophysics Data System (ADS)

Indium-doped zinc oxide powders have been prepared which show room-temperature electrical conductivities as high as 30 ? -1cm -1. The indium doping apparently occurs as Zn 1- xIn xO, Zn 1- yIn yO 1+ y/2 , or a combination of these. Optimum conductivity occurs for Zn 1- xIn xO where the maximum value of xobtained was about 0.5 at%. This substitution results in a lattice volume expansion of 0.4%. The degrees of sample reduction were determined by iodimetric titration. Time differential perturbed angular correlation (TDPAC) spectroscopy on indium doped zinc oxide is consistent with indium substituting at normal zinc sites in the ZnO lattice. TDPAC studies on zinc oxide annealed under zinc vapors show a second environment for the 111In probe. In this case, there is an unusually high temperature dependence of the electric field gradient which may be caused by a nearby zinc interstitial. An important conclusion of this work is that zinc interstitials are not ionized and do not therefore contribute significantly to the increased conductivity of reduced zinc oxide.

Wang, Ruiping; Sleight, Arthur W.; Platzer, Roland; Gardner, John A.

1996-02-01

328

Simultaneous Modeling of Thermopower and Electrical Conduction in Olivine Steven Constable1  

E-print Network

. Introduction An understanding of defect chemistry is important in the study of the electrical conductiv- ity of the dominant charge carrier, resulting from the migration of the conducting species from the hotter electrode

Constable, Steve

329

EVIDENCE FOR MICROBIAL ENHANCED ELECTRICAL CONDUCTIVITY IN HYDROCARBON-CONTAMINATED SEDIMENTS  

EPA Science Inventory

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

330

Electrical Resistivity and Thermal Conductivity of Nine Selected AISI Stainless Steels.  

National Technical Information Service (NTIS)

This technical report reviews the available experimental data and information on the electrical resistivity and thermal conductivity of nine selected AISI stainless steels and presents the recommended values from near absolute zero (1 K) to above the melt...

C. Y. Ho T. K. Chu

1977-01-01

331

The electrical conductivity of CuCrZr alloy after SPD processing  

NASA Astrophysics Data System (ADS)

CuCrZr alloys exhibit very good relation between mechanical properties and electrical conductivity. However, for its use in some advanced applications improvement of mechanical strength while preserving high electrical conducting is required. Therefore, in this work a CuCrZr alloy was subjected to a series of thermo-mechanical treatments, including solution annealing and water quenching, SPD processing (using hydrostatic extrusion and ECAP) as well as aging in order to improve mechanical strength. The influence of these processing procedures on microstructure features and mechanical properties was determined by TEM observation and microhardness measurements, respectively. Electrical conductivity of the samples was measured by four-points method. The results have shown that it is possible to improve mechanical strength while preserving good electrical conductivity by a proper combination of SPD processing and heat treatment.

Lipi?ska, M.; Bazarnik, P.; Lewandowska, M.

2014-08-01

332

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

333

Effects of Water Adsorption and Surface Oxidation on the Electrical Conductivity of Silicon Nanocrystal Films  

NASA Astrophysics Data System (ADS)

Electrical conductivities of thin films of silicon nanocrystals (4-6 nm) exhibit high sensitivity to water vapor. Specifically, water adsorption on the surface of silicon nanocrystal (NC) films increases their electrical conductivity by a factor of four at room temperature and an order of magnitude at 175 K. The increase in conductivity is reversible and can manifest as peaks or hysteresis loops in temperature-dependent conductivity measurements even when the measurements are conducted under vacuum at 10-5 Torr and in the presence of only residual amounts of water vapor. Hydrogen-terminated silicon nanocrystals are easily oxidized to form submonolayer to monolayer of chemically bound oxygen on their surfaces when annealed at 300°C in a glovebox with 0.1 ppm of water vapor. Annealing under vacuum at 300°C retains H-passivation without oxidation. The electrical conductivity of films made from hydrogen-terminated silicon nanocrystals is 200 times higher than the electrical conductivity of films made from silicon nanocrystals with a monolayer of chemically bound oxygen. However, the conductivities of both types of films increase upon adsorption of water on the nanocrystal surfaces. These findings underscore the importance of controlling silicon nanocrystal surfaces in determining the electrical properties of their thin films.

Rastgar, Neema

334

A four-layer model for interpreting electrical conductivity measurements of clay soils near agricultural lagoons  

E-print Network

interpretation model 9 Figure 2. Soil profile used as the basis for the model developed by Brune and Zheng 11 Figure 3. Relative response functions for the EM-34 meter 13 Figure 4. Topographic map of dairy 1 (elevations in meters) 28 Figure 5. Topographic... bulk electrical conductivity must be interpreted to give information on pore water quality. Brune and Zheng (1993) have developed a model for interpreting E M meter readings which produces estimates of pore water electrical conductivity and anion...

Jones, John Richard

2012-06-07

335

The effects of aluminum content, temperature and impurities on the electrical conductivity of synthetic bayer liquors  

Microsoft Academic Search

The electrical conductivity of pure sodium aluminate solutions with compositions in the range 93 to 128 gl?1 free soda and O to 125 gl?1’ alumina was investigated over the temperature range 40 to 70 °C. Under these conditions, the solution electrical conductivity\\u000a was found to vary as a linear function of temperature. For a given free soda content, the temperature

G. R. Browne; C. W. P. Finn

1981-01-01

336

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

337

Massive electrical conductivity enhancement of multilayer graphene/polystyrene composites using a nonconductive filler.  

PubMed

We report a massive increase in the electrical conductivity of a multilayer graphene (MLG)/polystyrene composite following the addition of nonconducting silica nanoparticles. The nonconducting filler acts as a highly effective dispersion aid, preventing the sheetlike MLG from restacking or agglomerating during the solvent casting process used to fabricate the composite. The enhanced dispersion of the MLG leads to orders of magnitude enhancement in electrical conductivity compared to samples without this filler. PMID:25226457

Chakraborty, Indrani; Bodurtha, Kevin J; Heeder, Nicholas J; Godfrin, Michael P; Tripathi, Anubhav; Hurt, Robert H; Shukla, Arun; Bose, Arijit

2014-10-01

338

Thermally conductive and electrically insulating epoxy nanocomposites with thermally reduced graphene oxide-silica hybrid nanosheets  

NASA Astrophysics Data System (ADS)

We herein report on the preparation of epoxy nanocomposites, which had enhanced thermal conductivities but were still electrical insulators, incorporating hybrid nanosheets (NSs) with sandwich structures composed of thermally reduced graphene oxide (TRGO) and silica. The silica layer covered the surface of the TRGO, hindering electrical conduction and effectively forming a 3D phonon transport channel that had a unique effect on the electrical and thermal properties of the epoxy matrix. A 1 wt% TRGO-silica NS epoxy nanocomposite maintained an electrical resistivity of 2.96 × 1011 ? cm, and its thermal conductivity was 0.322 W m-1 K-1, which is 61% higher than the conductivity of an epoxy nanocomposite without TRGO-silica NSs (0.2 W m-1 K-1).We herein report on the preparation of epoxy nanocomposites, which had enhanced thermal conductivities but were still electrical insulators, incorporating hybrid nanosheets (NSs) with sandwich structures composed of thermally reduced graphene oxide (TRGO) and silica. The silica layer covered the surface of the TRGO, hindering electrical conduction and effectively forming a 3D phonon transport channel that had a unique effect on the electrical and thermal properties of the epoxy matrix. A 1 wt% TRGO-silica NS epoxy nanocomposite maintained an electrical resistivity of 2.96 × 1011 ? cm, and its thermal conductivity was 0.322 W m-1 K-1, which is 61% higher than the conductivity of an epoxy nanocomposite without TRGO-silica NSs (0.2 W m-1 K-1). Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr01471a

Hsiao, Min-Chien; Ma, Chen-Chi M.; Chiang, Jen-Chi; Ho, Kuan-Ku; Chou, Tsung-Yu; Xie, Xiaofeng; Tsai, Cheng-Hsun; Chang, Li-Hsueh; Hsieh, Chien-Kuo

2013-06-01

339

Influence of mixing conditions on rheological behavior and electrical conductivity of polyamides filled with carbon black  

Microsoft Academic Search

The introduction of carbon black in a polyamide matrix allows one to obtain conductive materials because of the formation\\u000a of a filler network. Resulting electrical properties depend, among others, on the processing conditions. In a first part,\\u000a we investigate the influence of mixing conditions (rotor speed, temperature, mixing time) on electrical conductivity. Then,\\u000a in a second part, we try to

Mathilde Leboeuf; Nessim Ghamri; Benoît Brulé; Thierry Coupez; Bruno Vergnes

2008-01-01

340

Theory of electric field measurements conducted in the magnetosphere with electric probes  

Microsoft Academic Search

From the preceding discussion of possible errors and from the probe dimensions given in Tables IV and V the conclusion can be drawn that there should be no great difficulties in making rough (10–20%) measurements of electric fields in the ionosphere. With moderate efforts (using metallized balloons) it should also be possible to obtain order of magnitude estimates of electric

U. Fahleson

1967-01-01

341

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

342

Quasi-DC Terahertz Electrical Conductivity Measurements of Dense Aluminum Plasma  

Microsoft Academic Search

We report on our investigation of electrical transport in ultrashort laser-heated aluminum. By measuring the complex electrical conductivity at terahertz (THz = 10^12 Hz) frequencies, we explore the dependence of electrical transport across the material phase transition from the cold solid to the dense plasma state. Using optical-pump, terahertz-probe spectroscopy, we measure the phase shifts and absorption of terahertz probe

George Rodriguez; Balakishore Yellampalle; James Glownia; Antoinette Taylor; Ki-Yong Kim

2007-01-01

343

Electrical measurements in the atmosphere and the Ionosphere over an active thunderstorm. II - Direct current electric fields and conductivity  

NASA Technical Reports Server (NTRS)

On August 9, 1981, a series of three rockets was launched over an air mass thunderstorm off the eastern seaboard of Virginia while simultaneous stratospheric and ground-based electric field measurements were made. The conductivity was substantially lower at most altitudes than the conductivity profiles used by theoretical models. Direct current electric fields over 80 mV/m were measured as far away as 96 km from the storm in the stratosphere at 23 km altitude. No dc electric fields above 75 km altitude could be identified with the thunderstorm, in agreement with theory. However, vertical current densities over 120 pA/sq m were seen well above the classical 'electrosphere' (at 50 or 60 km). Frequent dc shifts in the electric field following lightning transients were seen by both balloon and rocket payloads. These dc shifts are clearly identifiable with either cloud-to-ground (increases) or intercloud (decreases) lightning flashes.

Holzworth, R. H.; Kelley, M. C.; Siefring, C. L.; Hale, L. C.; Mitchell, J. D.

1985-01-01

344

Development of novel, flexible, electrically conductive adhesives for next-generation microelectronics interconnect applications  

Microsoft Academic Search

In this paper, a novel flexible electrically conductive adhesive (FECA) has been designed for electronic interconnect applications that require high flexibility at the interconnects, such as assembly and repair of flexible circuits on flexible substrates and connectors. The physical properties of the resulting FECAs such as the elastic moduli, glass transition temperatures, adhesion strength and electrical properties were characterized by

Yi Li; M. J. Yim; K. Moon; R. W. Zhang; C. P. Wong

2008-01-01

345

Development of transparent and flexible electrically conductive adhesives for microelectronics applications  

Microsoft Academic Search

A novel flexible electrically conductive adhesive (FECA) has been designed for electronic interconnect applications that require high flexibility on the flexible substrates and connectors. The physical properties of the resulting ECAs such as the elastic modulus, glass transition temperatures, adhesion strength and electrical properties were characterized by differential scanning calorimetry (DSC), dynamic mechanical analyzer (DMA), die shear tester and RCL

Rongwei Zhang; Wei Wang; Kyoung-sik Moon; Hongjing Jiang; Wei Lin; C. P. Wong

2008-01-01

346

Influence of temperature on the electrical conductivity of leachate from municipal solid waste.  

PubMed

A bioreactor landfill is designed to manage municipal solid waste, through accelerated waste biodegradation, and stabilisation of the process by means of the controlled addition of liquid, i.e. leachate recirculation. The measurement of electrical resistivity by Electrical Resistivity Tomography (ERT) allows to monitor water content present in the bioreactors. Variations in electrical resistivity are linked to variations in moisture content and temperature. In order to overcome this ambiguity, two laboratory experiments were carried out to establish a relationship between temperature and electrical conductivity: the first set of measurements was made for leachate alone, whereas the second set was made with two different granular media saturated with leachate. Both experiments confirm a well known increase in conductivity of about 2% degrees C(-1). However, higher suspended matter concentrations lead to a lower dependence of electrical conductivity on temperature. Furthermore, for various porous media saturated with an identical leachate, the higher the specific surface of the granular matrix, the lower the effective bulk electrical conductivity. These observations show that a correct understanding of the electrical properties of liquids requires the nature and (in particular) the size of the electrical charge carriers to be taken into account. PMID:16600494

Grellier, Solenne; Robain, Henri; Bellier, Gérard; Skhiri, Nathalie

2006-09-01

347

Homogenization limit and asymptotic decay for electrical conduction in biological tissues in the high radiofrequency range  

Microsoft Academic Search

We derive a macroscopic model of electrical conduction in biological tissues in the high radio-frequency range, which is relevant in applications like electric impedance tomogra- phy. This model is derived via a homogenization limit by a microscopic formulation, based on Maxwell's equations, taking into account the periodic geometry of the microstructure. We also study the asymptotic behavior of the solution

Roberto Gianni; Paolo Bisegna; Daniele Andreucci; Micol Amar

2010-01-01

348

Electrical conductivity in granular media and Branly's coherer: A simple experiment  

E-print Network

- mogeneous media such as granular media, as well as the influence of electromagnetic wavesElectrical conductivity in granular media and Branly's coherer: A simple experiment Eric Falcona experiment can illustrate certain electrical transport properties of metallic granular media. At a low

Falcon, Eric

349

Influence of FeO and H on the electrical conductivity of olivine  

NASA Astrophysics Data System (ADS)

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

Dai, Lidong; Karato, Shun-ichiro

2014-12-01

350

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

351

Electrically conductive polymeric materials with high stretchability and excellent elasticity by a surface coating method.  

PubMed

Electrically conductive polymer films with high stretchability and excellent elasticity were simply fabricated by coating a conductive layer on the surface of an elastomer film. The material used for the conductive layer was a high-shear processed poly[styrene-b-(ethylene-co-butylene)-b-styrene] triblock copolymer (SEBS)/multiwalled carbon nanotubes (MWCNTs) nanocomposite with 20 wt.-% MWCNTs loading. The nanocomposites were first dissolved in toluene to form a stable solution and then were coated onto the SEBS film by spin coating. The alignment of MWCNTs in the coated layer and the interface between the base film and the coated layer were investigated. It was found that almost all the MWCNTs are aligned parallel to the base film and that there is good adhesion between the two layers. The fabricated films show high electrical conductivity and almost same stretchability and elasticity as the base film. Moreover, the films exhibit extremely high electrical conductive retention after applying high strain. PMID:21433173

Li, Yongjin; Zhao, Liping; Shimizu, Hiroshi

2011-02-01

352

Noninvasive Imaging of Head-Brain Conductivity Profiles Using Magnetic Resonance Electrical Impedance Imaging  

PubMed Central

Magnetic resonance electrical impedance tomography (MREIT) is a recently introduced non-invasive conductivity imaging modality, which combines the magnetic resonance current density imaging (CDI) and the traditional electrical impedance tomography (EIT) techniques. MREIT is aimed at providing high spatial resolution images of electrical conductivity, by avoiding solving the well-known ill-posed problem in the traditional EIT. In this paper, we review our research activities in MREIT imaging of head-brain tissue conductivity profiles. We have developed several imaging algorithms and conducted a series of computer simulations for MREIT imaging of the head and brain tissues. Our work suggests MREIT brain imaging may become a useful tool in imaging conductivity distributions of the brain and head. PMID:18799394

Zhang, Xiaotong; Yan, Dandan; Zhu, Shanan; He, Bin

2008-01-01

353

Electrical Conductivity Response of Poly(Phenylene-vinylene)/Zeolite Composites Exposed to Ammonium Nitrate  

PubMed Central

Poly(p-phenylenevinylene) (PPV) was chemically synthesized via the polymerization of p-xylene-bis(tetrahydrothiophenium chloride) monomer and doped with H2SO4. To improve the electrical conductivity sensitivity of the conductive polymer, Zeolites Y (Si/Al = 5.1, 30, 60, 80) were added into the conductive polymer matrix. All composite samples show definite positive responses towards NH4NO3. The electrical conductivity sensitivities of the composite sensors increase linearly with increasing Si/Al ratio: with values of 0.201, 1.37, 2.80 and 3.18, respectively. The interactions between NH4NO3 molecules and the PPV/zeolite composites with respect to the electrical conductivity sensitivity were investigated through the infrared spectroscopy. PMID:22219677

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

2010-01-01

354

Experimental characterization and numerical modeling of tissue electrical conductivity during pulsed electric fields for irreversible electroporation treatment planning.  

PubMed

Irreversible electroporation is a new technique to kill cells in targeted tissue, such as tumors, through a nonthermal mechanism using electric pulses to irrecoverably disrupt the cell membrane. Treatment effects relate to the tissue electric field distribution, which can be predicted with numerical modeling for therapy planning. Pulse effects will change the cell and tissue properties through thermal and electroporation (EP)-based processes. This investigation characterizes these changes by measuring the electrical conductivity and temperature of ex vivo renal porcine tissue within a single pulse and for a 200 pulse protocol. These changes are incorporated into an equivalent circuit model for cells and tissue with a variable EP-based resistance, providing a potential method to estimate conductivity as a function of electric field and pulse length for other tissues. Finally, a numerical model using a human kidney volumetric mesh evaluated how treatment predictions vary when EP- and temperature-based electrical conductivity changes are incorporated. We conclude that significant changes in predicted outcomes will occur when the experimental results are applied to the numerical model, where the direction and degree of change varies with the electric field considered. PMID:22231669

Neal, Robert E; Garcia, Paulo A; Robertson, John L; Davalos, Rafael V

2012-04-01

355

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

NASA Astrophysics Data System (ADS)

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

Binbin, Jie; Chihtang, Sah

2014-04-01

356

Morphology and electrical properties of SrTiO 3-films on conductive oxide films  

Microsoft Academic Search

The effect of various electrically conductive oxides on the morphology and the electrical properties of SrTiO3 films (STO) was investigated by means of scanning electron microscopy, impedance analysis and leakage current measurement (DC). LaNiO3 (LNO), La0.5Sr0.5CoO3 (LSCO) and La0.7Sr0.3MnO3 (LSMO) as electrically conductive oxides were deposited on platinized silicon wafers by chemical solution deposition (CSD) via the propionate route. Subsequently

K Reichmann; T Schneller; S Hoffmann-Eifert; U Hasenkox; R Waser

2001-01-01

357

The use of silane coupling agents in the design of electrically stable interfaces of 6061 T6 aluminum alloy surfaces and epoxy-based electrically conductive adhesives  

Microsoft Academic Search

Electrically conductive interfaces between metal surfaces, including aluminum, are commonly formed by means of bonding with an electrically conductive adhesive. Humid environments induce an increase in electrical resistance between aluminum objects bonded in this manner. However, joints that are electrically stable through stress testing in environments of elevated temperature and humidity (85°C and 80% RH for up to 137.5 h)

L. J. Matienzo; F. D. Egitto; P. E. Logan

2003-01-01

358

Use of fathometers and electrical-conductivity probes to monitor riverbed scour at bridge piers  

USGS Publications Warehouse

Two methods, a fathometer system and an electrical- conductivity probe system, were developed to monitor scour at bridge piers. The scour-monitoring systems consisted of a sensor (fathometer or electrical- conductivity probe), power supply, data logger, relay, and system program. The fathometer system was installed and tested at a bridge over the Leipsic River at Leipsic, Delaware, and at a bridge over Sinepuxent Bay near Ocean City. Maryland. Field data collected indicate that fathometers can be used to identify and monitor the riverbed elevation if post processing of the data and trends in the data are used to determine the riverbed location in relation to the transducer. The accuracy of the system is approximately the same as the resolution of the fathometer. Signal scatter can be a major source of error in the data. The electrical- conductivity probe system was installed and tested at a bridge over the Pamunkey River near Hanover, Virginia. The approximate elevation of the riverbed is determined by comparing conductivities of the surface-water flow with conductivities of submerged bed material from sensors located in each. Field data collected indicate that an electrical- conductivity probe, as tested, has limited usefulness in identifying and monitoring the riverbed elevation during high flows. As the discharge increases, the concentration of sediment in the surface-water flow increases, especially near the riverbed. Conductivities, measured at the sensors in the surface-water flow could not be distinguished from conductivities measured at the shallowest sensor in the submerged bed material.

Hayes, D. C.; Drummond, F. E.

1995-01-01

359

Controlled Electromagnetic Sources for Measuring Electrical Conductivity Beneath the Oceans 1. Forward Problem and Model Study  

Microsoft Academic Search

Exact closed-form expressions for the electromagnetic induction fields produced by vertical and horizontal current sources in the conducting ocean overlying a one-dimensional earth are derived from the Maxwell equations. Numerical methods for the evaluation of the solutions are given, including correction for the finite size of real sources. Simple models of the electrical conductivity structure of the ocean crust and

Alan D. Chave; Charles S. Cox

1982-01-01

360

Universal properties of thermal and electrical conductivity of gauge theory plasmas from holography  

E-print Network

We propose that for conformal field theories admitting gravity duals, the thermal conductivity is fixed by the central charges in a universal manner. Though we do not have a proof as yet, we have checked our proposal against several examples. This proposal, if correct, allows us to express electrical conductivity in terms of thermodynamical quantities even in the presence of chemical potential.

Sachin Jain

2009-12-14

361

Upper Mantle Composition Beneath the Petit-Spot Area in Northwestern Pacific: Insights From Electrical Conductivity  

Microsoft Academic Search

The mantle composition beneath the petit-spot area, where is about 500 km offshore from Japan Trench in northwestern Pacific, is discussed through electrical conductivity obtained by seafloor magnetotelluric (MT) survey. The seafloor MT data were collected using ocean bottom electromagnetometers (OBEMs) at four sites with the spacing of 100-150 km, between May and August, 2005. The survey was conducted as

K. Baba; M. Ichiki; N. Abe; N. Hirano

2007-01-01

362

Reflective Probing of the Electrical Conductivity of Hot Aluminum in the Solid, Liquid, and Plasma Phases  

Microsoft Academic Search

The physics of dense aluminum in transition between metallic and insulating states of the solid, liquid, and plasma phases is probed in thermally equilibrated, inertially confined, laser heated targets. Time resolved laser probes measure the reflectivity of thin aluminum layers embedded inside the target. The electrical conductivity is inferred from the reflectivity with a free-electron Drude conduction model. It is

Andrew N. Mostovych; Yung Chan

1997-01-01

363

State of lithosphere beneath Tien Shan from petrology and electrical conductivity of xenoliths  

Microsoft Academic Search

The shortening of Tien Shan and the evolution of its lithosphere have been evaluated from P-T geothermobarometry of xenoliths and from comparison of their electrical conductivity with conductivities obtained from the inversion of magnetotelluric (MT) data. Spinel lherzolite and granulite xenoliths found in basaltic outcrop Ortosuu represent upper mantle and crust beneath southern Tien Shan. The spinel lherzolite xenoliths correspond

N. Bagdassarov; V. Batalev; V. Egorova

2011-01-01

364

Electrical conductivities of aluminum, copper, and tungsten observed by an underwater explosion  

Microsoft Academic Search

Conductivities of dense aluminum, copper, and tungsten are evaluated using exploding wire discharges in water. Evolutions of the radius and the electrical resistance of exploding wire are measured together with direct pyrometric estimation of the temperature. The conductivities are evaluated based on the measurements and their density dependence is compared with theoretical predictions at a fixed temperature. The results indicate

Toru Sasaki; Mitsuo Nakajima; Tohru Kawamura; Kazuhiko Horioka

2010-01-01

365

Electrical Conductivity of Solutions of Aluminium (III), Gallium (III) and Indium (III) Iodides in Alkyl Iodides  

Microsoft Academic Search

SEVERAL investigations have been devoted to the electrical conductivity of aluminium halides in alkyl halide solutions1-5. The conductance of these solutions has been attributed to the formation of some complexes or addition compounds composed of both interacting molecules. No investigations on analogous systems with gallium and indium halides have hitherto been performed. In order to gain more information of the

A. Halpern; A. POLACZEK

1963-01-01

366

In-situ production of electrically conductive fibres in polyaniline-SBS blends  

Microsoft Academic Search

Blending of electro-conductive monofilaments with more traditional insulating materials is a promising approach for the production of composites for applications in static dissipative packaging and in industrial textiles. Accordingly, we report on a favourable method for manufacturing these kinds of material which involves generating the fibres in-situ, that is, during the actual forming process. Electrically conductive polyaniline (PANI) was thermally

R. H. Cruz-Estrada; M. J. Folkes

2000-01-01

367

Electrically conductive tungsten silicide coatings for EMI\\/RFI shielding of optically transparent windows  

Microsoft Academic Search

Conductive metal mesh coatings on external surfaces of infrared (IR) windows reduce the electromagnetic and radio frequency interference (EMI\\/RFI) but are mechanically soft and easily damaged. Surface-doped semiconductors, such as gallium arsenide, have optical absorption and emission problems, while semiconducting carbide coatings, such as germanium carbide, suffer performance loss at the low end of the required temperature range. Electrically conductive

E. Savrun; H. Del Aguila

1998-01-01

368

Electrically conductive adhesive with ?-conjugated self-assembled molecular wire junctions for enhanced electrical and thermal properties  

Microsoft Academic Search

Anisotropic conductive adhesives\\/films (ACAs\\/ACFs) have been developed as a promising lead-free interconnect material in the electronic industry. However, due to the restricted contact area and poor interfacial bonding between ACAs and metal bond pads, the ACA joints have lower electrical conductivity and poorer current carrying capability than that of solders. In this study, we investigated the current carrying capability of

Rongwei Zhang; Yi Li; Myung Jin Yim; Kyoung Sik Moon; Daoqiang Daniel Lu; C. P. Wong

2008-01-01

369

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

370

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

371

Electrical conductivity of ferroelectric sodium vanadate, rubidium vanadate, cesium vanadate and their solid solutions  

Microsoft Academic Search

The d.c. electrical conductivity of sodium vanadate, rubidium vanadate, cesium vanadate and their solid solutions sodium-rubidium\\u000a vanadate and sodium-cesium vanadate were studied by a two-probe method in the temperature range covering their transition\\u000a points. The electrical conductivity shows sharp change at the phase transition temperature of these materials. In NaVO3, RbVO3 and CsVO3, increase in d.c. conductivity is observed in

V V Patil; A P Kashid; SH Chavan

1989-01-01

372

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

373

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

374

Development of a high pressure electrical conductivity probe for experimental studies of gas hydrates in electrolytes  

NASA Astrophysics Data System (ADS)

We previously reported the development of a high pressure automated lag time apparatus and a high pressure video cell for experimental study of nucleation and growth of gas hydrates. Here we report the development of a high pressure electrical conductivity probe that monitors the electrical conductivity of an electrolyte that is subjected to a linear cooling ramp at elevated hydrate-forming-gas pressures. The electrical conductivity steadily decreases as the linear cooling progresses because of the increasing viscosity of the electrolyte and the consequently decreasing mobility of the ions. The onset of the formation of methane-propane mixed gas hydrate films at the gas-electrolyte interface is marked by an upward spike in the electrical conductivity. The physical mechanisms behind this phenomenon remain to be elucidated. Continued cooling of the electrolyte to, and subsequent holding of, the temperature at 273 K eventually results in decreased electrical conductivity. This conductivity signal can be used for the detection of the onset of the formation of gas hydrates in optically opaque samples that contain electrolytes.

Maeda, Nobuo

2013-01-01

375

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

376

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

PubMed Central

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. 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

377

Electronmagnetic induction probe calibration for electrical conductivity measurements and moisture content determination of Hanford high level waste  

SciTech Connect

Logic of converting EMI measured electrical conductivity to moisture with expected uncertainty. Estimates from present knowledge, assumptions, and measured data. Archie`s Law has been used since the 1940`s to relate electrical conductivity in porous media to liquid volume fraction. Measured electrical conductivity to moisture content uses: Porosity, Interstitial liquid electrical conductivity, Solid particle density,Interstitial liquid density, and interstitial liquid water content. The uncertainty of assumed values is calculated to determine the final moisture wt.% result uncertainty.

Wittekind, W.D., Westinghouse Hanford

1996-05-23

378

Electrical conduction along endothelial cell tubes from mouse feed arteries: confounding actions of glycyrrhetinic acid derivatives  

PubMed Central

BACKGROUND AND PURPOSE Electrical conduction along endothelium of resistance vessels has not been determined independently of the influence of smooth muscle, surrounding tissue or blood. Two interrelated hypotheses were tested: (i) Intercellular conduction of electrical signals is manifest in endothelial cell (EC) tubes; and (ii) Inhibitors of gap junction channels (GJCs) have confounding actions on EC electrical and Ca2+ signalling. EXPERIMENTAL APPROACH Intact EC tubes were isolated from abdominal muscle feed (superior epigastric) arteries of C57BL/6 mice. Hyperpolarization was initiated with indirect (ACh) and direct (NS309) stimulation of intermediate- and small-conductance Ca2+-activated K+ channels (IKCa/SKCa). Remote membrane potential (Vm) responses to intracellular current injection defined the length constant (?) for electrical conduction. Dye coupling was evaluated following intracellular microinjection of propidium iodide. Intracellular Ca2+ dynamics were determined using Fura-2 photometry. Carbenoxolone (CBX) or ?-glycyrrhetinic acid (?GA) was used to investigate the role of GJCs. KEY RESULTS Steady-state Vm of ECs was ?25 mV. ACh and NS309 hyperpolarized ECs by ?40 and ?60 mV respectively. Electrical conduction decayed monoexponentially with distance (??1.4 mm). Propidium iodide injected into one EC spread into surrounding ECs. CBX or ?GA inhibited dye transfer, electrical conduction and EC hyperpolarization reversibly. Both agents elevated resting Ca2+ while ?GA inhibited responses to ACh. CONCLUSIONS AND IMPLICATIONS Individual cells were effectively coupled to each other within EC tubes. Inhibiting GJCs with glycyrrhetinic acid derivatives blocked hyperpolarization mediated by IKCa/SKCa channels, regardless of Ca2+ signalling, obviating use of these agents in distinguishing key determinants of electrical conduction along the endothelium. PMID:22168386

Behringer, Erik J; Socha, Matthew J; Polo-Parada, Luis; Segal, Steven S

2012-01-01

379

Computation of Electrical Conductivity of Multicomponent Aqueous Systems in Wide Concentration and Temperature Ranges  

Microsoft Academic Search

A comprehensive model for calculating the electrical conductivity of multicomponent aqueous systems has been developed. In the infinite-dilution limit, the temperature dependence of ionic conductivities is calculated on the basis of the concept of structure-breaking and structure- making ions. At finite concentrations, the concentration dependence of conductivity is calculated from the dielectric continuum-based mean-spherical-approximation (MSA) theory for the unrestricted primitive

Andrzej Anderko; Malgorzata M. Lencka

1997-01-01

380

Influence of pressure on the electrical conductivity of metal powders used as fillers in polymer composites  

Microsoft Academic Search

In this work, the influence of pressure on the electrical conductivity of metal powders (copper, nickel, and iron), used as fillers in conductive polymer composites, was investigated. It was found that the conductivity of the powders as a function of the applied pressure, P, is described by the equation: ?=k(P-P0)n. In this equation, P0 is the minimal pressure necessary for

Ye. P. Mamunya; H. Zois; L. Apekis; E. V. Lebedev

2004-01-01

381

High-temperature electrical conductivity and point defects in lead zirconate-titanate  

Microsoft Academic Search

The electrical conductivity and thermoelectric power of lead zitconate-titanate Pb(Ti0.47Zr0.53)O3 (PZT) have been studied at temperatures up to 1000°C in gaseous ambients with controlled partial pressures of both volatile components: lead oxide and oxygen. The experimental results show the small polaron conduction mechanism in PZT. The predominant point defects, as obtained from the oxygen pressure dependences of the conductivity and

V. V. Prisedsky; V. I. Shishkovsky; V. V. Klimov

1977-01-01

382

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

383

Relationship between the hydraulic conductivity and electric properties for investigating the alluvium aquifer  

NASA Astrophysics Data System (ADS)

In this study, to understand relationship between hydraulic conductivity and electrical properties in alluvial aquifer, some indoor experiments and field electrical surveys were conducted. Soil sampled from alluvial aquifer and various size of quartz sand particles were saturated in NaCl solution which had 100 ohm-m. Then their porosity, hydraulic conductivity, time domain induced polarization and spectral induced polarization were measured. As a result, hydraulic conductivity and resistivity of quartz sand had proportional relation but, chargeability and phase difference of it showed small value also, hydraulic conductivity did not show clear tendency. Through this experiment, it was possible to identify which quartz sand had almost no response from induced polarization survey. Moreover, for silty sand, hydraulic conductivity and resistivity had proportional relation, hydraulic conductivity and chargeability had inverse proportional relation and hydraulic conductivity and phase difference had proportional relation. Through this experiment, silty sand showed correlation between hydraulic conductivity and electrical property. When field resistivity survey was conducted at alluvial aquifer, it showed wider range of values than the values from indoor experiment. Therefore, it is difficult to estimate accurate hydraulic conductivity of alluvial aquifer by applying hydraulic conductivity-resistivity interaction formula from indoor experiment to field resistivity survey. However, through comparison between resistivity survey result and borehole data, it was acknowledged that parts with low resistivity were clayey stratum and parts with high resistivity were gravel stratum. Consequently, estimating relative hydraulic conductivity distribution was able to be determined. However, followed by result of time domain induced polarization survey, clayey sand stratum did not have high chargeability. Through this field induced polarization survey experiment, it looks difficult to estimate hydraulic conductivity distribution.

Park, Samgyu; Kim, Soodong; Hamm, Se-Yeong

2014-05-01

384

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

E-print Network

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

Steinle-Neumann, Gerd

385

Preparation and properties of electrically conducting ceramics based on indium oxide-rare earth oxides-hafnium oxides  

SciTech Connect

Electrically conducting refractory oxides based on adding indium oxide to rare earth-stabilized hafnium oxide are being studied for use in magnetohydrodynamic (MHD) generators, fuel cells, and thermoelectric generators. The use of indium oxide generally increases the electrical conductivity. The results of measurements of the electrical conductivity and data on corrosion resistance in molten salts are presented.

Marchant, D.D.; Bates, J.L.

1983-09-01

386

Investigation of electrical conductivity and equations of state of non-ideal plasma through underwater electrical wire explosion  

NASA Astrophysics Data System (ADS)

The results of experiments and magnetohydrodynamic simulations of nanosecond time scale underwater electrical explosions of Al, Cu, and W wires are presented. Experiments were performed using a nanosecond pulsed generator with a ˜30 kA amplitude and ˜60 ns rise time current pulse. The electrical conductivity of the tested materials in the density and temperature ranges of 0.1-20 g/cm3 and 0.03-8 eV, respectively, is presented. It is shown that for the physical conditions obtained in these experiments, the equation of state data used in the SESAME tables must be modified in order to reproduce the experimental results. Also, it was shown that the electrical conductivity of the metals does not consistently fit over the entire range of experimental conditions with either of the transport models presented.

Sheftman, D.; Krasik, Ya. E.

2010-11-01

387

Upper mantle electrical conductivity for seven subcontinental regions of the Earth  

USGS Publications Warehouse

Spherical harmonic analysis coefficients of the external and internal parts of the quiet-day geomagnetic field variations (Sq) separated for the 7 continental regions of the observatories have been used to determine conductivity profiles to depths of about 600 km by the Schmucker equivalent substitute conductor method. The profiles give evidence of increases in conductivity between about 150 and 350 km depth, then a general increase in conductivity thereafter. For South America we found a high conductivity at shallow depths. The European profile showed a highly conducting layer near 125 km. At the greater depths, Europe, Australia and South America had the lowest values of conductivity. North America and east Asia had intermediate values whereas the African and central Asian profiles both showed the conductivities rising rapidly beyond 450 km depth. The regional differences indicate that there may be considerable lateral heterogeneity of electrical conductivity in the Earth's upper mantle. -Authors

Campbell, W. H.; Schiffmacher, E. R.

1988-01-01

388

A Chemically Polymerized Electrically Conducting Composite of Polypyrrole Nanoparticles and Polyurethane for Tissue Engineering  

PubMed Central

A variety of cell types respond to electrical stimuli, accordingly many conducting polymers (CPs) have been used as tissue engineering (TE) scaffolds, one such CP is polypyrrole (PPy). PPy is a well studied biomaterial with potential TE applications due to its electrical conductivity and many other beneficial properties. Combining its characteristics with an elastomeric material, such as polyurethane (PU), may yield a hybrid scaffold with electrical activity and significant mechanical resilience. Pyrrole was in situ polymerized within a PU emulsion mixture in weight ratios of 1:100, 1:20, 1:10 and 1:5, respectively. Morphology, electrical conductivity, mechanical properties and cytocompatibility with C2C12 myoblast cells were characterized. The polymerization resulted in a composite with a principle base of PU interspersed with an electrically percolating network of PPy nanoparticles. As the mass ratio of PPy to PU increased so did electrical conductivity of the composites. In addition, as the mass ratio of PPy to PU increased, stiffness of the composite increased while maximum elongation length decreased. Ultimate tensile strength was reduced by approximately 47% across all samples with the addition of PPy to the PU base. Cytocompatibility assay data indicated no significant cytotoxic effect from the composites. Static cellular seeding of C2C12 cells and subsequent differentiation showed myotube formation on the composite materials. PMID:21681943

Broda, Christopher R.; Lee, Jae Y.; Sirivisoot, Sirinrath; Schmidt, Christine E.; Harrison, Benjamin S.

2011-01-01

389

Electrical conductivity of cobalt-titanium substituted SrCaM hexaferrites  

NASA Astrophysics Data System (ADS)

A series of polycrystalline M-type hexagonal ferrites with the composition Sr 0.5Ca 0.5Co xTi xFe 12-2 xO 19 (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 Co 2+ and Ti 4+ 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

390

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

391

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

392

Electrical conductivity and dielectric relaxation behavior of fluorescein sodium salt (FSS)  

NASA Astrophysics Data System (ADS)

The ac and dc electrical conductivities and dielectric properties of the fluorescein sodium salt (FSS) have been investigated. The direct current (dc) conductivity shows that the compound is a typical organic semiconductor, as its electrical conductivity increases with increasing temperature. The dc electrical activation energy ?E? and the room temperature electrical conductivity equal 0.35 eV and 1.26×10-9 (, respectively. The alternating current (ac) conductivity of the investigated compound obeys the power law : ?(?)=A(T).?, where s<1. The obtained results have been discussed in terms of the correlated barrier hopping (CBH) model. The density of localized states NF(E) at the Fermi level and the binding energy Wm were calculated. The dielectric constant ?1(?) and dielectric loss ?2(?) have been found to decrease with increasing frequency and to increase with increasing temperature over the studied ranges. The value of the maximum barrier height WM obtained from Austin and Guintini equations agree with each other. The correlation between the ac conduction and the dielectric properties in organic FSS were verified.

Mansour, Sh. A.; Yahia, I. S.; Sakr, G. B.

2010-08-01

393

Reinforced carbon nanotubes as electrically conducting and flexible films for space applications.  

PubMed

Chemical vapor deposition (CVD)-grown entangled carbon nanotube (CNT) sheets are characterized by high electrical conductivity and durability to bending and folding. However, since freestanding CNT sheets are mechanically weak, they cannot be used as stand-alone flexible films. In this work, polyimide (PI) infiltration into entangled cup-stacked CNT (CSCNT) sheets was studied to form electrically conducting, robust, and flexible films for space applications. The infiltration process preserved CNTs' advantageous properties (i.e., conductivity and flexibility), prevented CNT agglomeration, and enabled CNT patterning. In particular, the CNT-PI films exhibited ohmic electrical conductance in both the lateral and vertical directions, with a sheet resistivity as low as 122 ?/?, similar to that of as-grown CNT sheets, with minimal effect of the insulating matrix. Moreover, this high conductivity was preserved under mechanical and thermal manipulations. These properties make the reported CNT-PI films excellent candidates for applications where flexibility, thermal stability, and electrical conductivity are required. Particularly, the developed CNT-PI films were found to be durable in space environment hazards such as high vacuum, thermal cycling, and ionizing radiation, and hence they are suggested as an alternative for the electrostatic discharge (ESD) protection layer in spacecraft thermal blankets. PMID:25366559

Atar, Nurit; Grossman, Eitan; Gouzman, Irina; Bolker, Asaf; Hanein, Yael

2014-11-26

394

D.C. electrical conductivity and conduction mechanism of some azo sulfonyl quinoline ligands and uranyl complexes.  

PubMed

Supramolecular coordination of dioxouranium(VI) heterochelates 5-sulphono-7-(4'-X phenylazo)-8-hydroxyquinoline HL(n) (n=1, X=CH(3); n=2, X=H; n=3, X=Cl; n=4, X=NO(2)) have been prepared and characterized with various physico-chemical techniques. The infrared spectral studies showed a monobasic bidentate behavior with the oxygen and azonitrogen donor system. The temperature dependence of the D.C. electrical conductivity of HL(n) ligands and their uranyl complexes has been studied in the temperature range 305-415 K. The thermal activation energies E(a) for HL(n) compounds were found to be in the range 0.44-0.9 eV depending on the nature of the substituent X. The complexation process decreased E(a) values to the range 0.043-045 eV. The electrical conduction mechanism has been investigated for all samples under investigation. It was found to obey the variable range hopping mechanism (VRH). PMID:21906992

El-Ghamaz, N A; Diab, M A; El-Sonbati, A Z; Salem, O L

2011-12-01

395

Drag Forces, Neutral Wind and Electric Conductivity Changes in the Ionospheric E Region  

E-print Network

The neutrals in the Earth environment are in fact free and subjected to drag forces (by ions). In this study we show that drag or friction forces in the ionosphere-thermosphere system initiate changes in the plasma flow, neutral wind, and the conductivity, as well. Ions and electrons embedded in neutral wind field of velocity u acquire drifts perpendicular both to the initial neutral wind velocity and to the ambient magnetic field producing a perpendicular electric current. This perpendicular electric current is defined by a conductivity derived previously and the polarization electric field u x B. Self-consistently, the free neutrals acquires an additional neutral velocity component perpendicular to the initial neutral wind velocity u. The Pedersen and Hall currents wane within a specific time inversely proportional to neutral-ion collision frequency. These findings are relevant to a better understanding of electric current generation, distribution and closure in weakly ionized plasmas where charged particle...

Nenovski, Petko

2014-01-01

396

Viscous and Joulean power losses in liquid-metal sliding electrical contacts with finite electrically conducting electrodes  

SciTech Connect

Designing high performance liquid-metal sliding electrical contacts for homopolar machinery requires a precise knowledge of the magnitudes of the viscous and Joulean losses under various operating conditions. The liquid metal, which is confined to a channel between a rotor and stator, is subjected to a large external magnetic induction while transporting current. Significant power losses can occur in these devices. The geometry and electrical conductivity of the channel walls have a significant effect on these losses. In past theoretical work, copper electrodes were generally treated as perfect electrical conductors as compared to the liquid metals. Calculations based on this perfectly conducting electrode approximation predicted unrealistically high power losses. In the present study, the effects of electrodes with finite conductivity on both the viscous dissipation and Joulean heating will be explored. Numerical results are presented for both radial and axial magnetic inductions. It is found that the magnetic induction orientation has a significant impact on the losses. The results of this type of analysis can be used to minimize the power losses in the design of liquid-metal sliding electrical contacts.

Talmage, G.; Mazumder, S. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Mechanical Engineering] [Pennsylvania State Univ., University Park, PA (United States). Dept. of Mechanical Engineering; Brown, S.H.; Sondergaard, N.A. [Naval Warfare Center, Annapolis, MD (United States). Carderock Div.] [Naval Warfare Center, Annapolis, MD (United States). Carderock Div.

1995-12-01

397

Percolation transition in water-in-oil microemulsions. Electrical conductivity measurements  

SciTech Connect

The low-frequency (600 Hz) electric conductivity of water-in-oil microemulsions composed of water, cyclohexane, SDS, and 1-pentanol was measured. The structure of these microemulsions previously was described in the low water concentration range (water concentration approx. 10/sup -2/) as a suspension of minute droplets (diameter approx. 100 angstroms) with weak mutual interaction. Neutron scattering measurements show that the structure of droplets remains unchanged up to a water concentration of 0.30. At low water concentration, the electric conductivity is due to the mean charge of the droplets. The electric conductivity increases steeply over 5 orders of magnitude when the concentration of droplets increases. A second transition is observed at high water concentration: the microemulsion is inverted from water-in-oil to oil-in-water. The effect of both additional alcohol and ionic strength of water are discussed. 17 references.

Lagues, M.; Sauterey, C.

1980-12-25

398

Equation of state and electrical conductivity of a strongly correlated aluminum plasma  

NASA Astrophysics Data System (ADS)

We present experimental measurements and theoretical estimations of the equation of state and of the electrical conductivity of a hot expanded aluminum plasma (T=1-3 eV, ?=0.1-0.3 g/cc, P=15 kbar, ?=Z^2e^2/akT ~=1). The plasma was obtained with a new experimental facility : Enceinte à Plasma Isochore (EPI) designed to confine electrical plasma discharges up to 25kbar. Theoretically, the properties were determined by ab initio molecular dynamics simulations in the DFT/LDA-GGA approximation, from which the conductivity was computed using Kubo-Greenwood formula. Equation of state and electrical conductivity are compared with Sesame tables and with a Lee and More approach using a self consistent estimation of the ionization. As suggested by ab initio simulations, Al2 molecules and Aln clusters seem to play an important role in this regime, explaining discrepancies between models.

Clerouin, Jean

2001-10-01

399

Oxygen potential, electrical conductivity and defect structure of titanium-doped uranium dioxide  

NASA Astrophysics Data System (ADS)

The oxygen potential of (U 0.993Ti 0.007)O 2 + x was measured by means of thermogravimetry in the range of 1173 ? T/ K. ? 1373 and 10 -16 ? PO2/ Pa ? 10 -4, and the electrical conductivity by the four inserted wires method in the range from 10 -15 to 10 -16Pa at 1173 K. Both the oxygen potential and the electrical conductivity of UO2+ x were decreased by doping with titanium ions, which can not be interpreted by the substitutional model, but may be explained by assuming the Ti 4+ interstitials as the predominant defect. From the oxygen partial pressure dependence of the compositional deviation from stoichiometry and that of the electrical conductivity for (U 0.993Ti 0.007)O 2 + x, the defect structure was discussed with the complex defect model consisting of interstitial titanium ions, oxygen vacancies and two kinds of interstitial oxygens.

Tsuji, Toshihide; Matsui, Tsuneo; Abe, Masahiro; Naito, Keiji

1989-11-01

400

D.C. electrical conductivity and magnetic susceptibility of polythiophene doped with iodine  

NASA Astrophysics Data System (ADS)

Polythiophene was chemically synthesized, undoped and then re-doped with iodine. FTIR spectra confirm iodine doping. XRD analysis is used to calculate crystallinity of the samples. Electrical conductivity measurements were carried out using two probe technique in the temperature range from 300 K to 373 K. Undoped and doped samples show semi conducting nature. After doping the conductivity increases by eight orders of magnitude at 318 K. Magnetic susceptibility measurements were carried out using Guoy's method, both samples show diamagnetic nature. Conductivity and magnetic susceptibility measurements indicate that predominant charge carriers, in the iodine doped polythiophene, are bipolarons.

Chourasia, Ashish B.; Kelkar, Deepali S.

2013-06-01

401

Electrically Conductive Zinc Oxide (ZnO) Nanostructures Prepared by Sol-gel Spin-coating  

Microsoft Academic Search

The electrically conductive zinc oxide (ZnO) nanostructures prepared by sol-gel spin coating are presented. This project has been focused on electrical, optical and surface morphology properties of Al (aluminium) doped ZnO thin film. The effect of Al doping concentration at 0~5 at.% on the Al doped ZnO Thin film properties have been investigated. This project involves 3 processes which are

M. H. Mamat; A. S. Rodzi; M. Rusop

2011-01-01

402

Electrically Conductive Zinc Oxide (ZnO) Nanostructures Prepared by Sol-gel Spin-coating  

Microsoft Academic Search

The electrically conductive zinc oxide (ZnO) nanostructures prepared by sol-gel spin coating are presented. This project has been focused on electrical, optical and surface morphology properties of Al (aluminium) doped ZnO thin film. The effect of Al doping concentration at 0?5 at.% on the Al doped ZnO Thin film properties have been investigated. This project involves 3 processes which are

M. H. Mamat; A. S. Rodzi; M. Rusop

2011-01-01

403

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

404

Equation of state and electrical conductivity of a strongly correlated aluminum plasma  

Microsoft Academic Search

We present experimental measurements and theoretical estimations of the equation of state and of the electrical conductivity of a hot expanded aluminum plasma (T=1-3 eV, rho=0.1-0.3 g\\/cc, P=15 kbar, Gamma=Z^2e^2\\/akT ~=1). The plasma was obtained with a new experimental facility : Enceinte à Plasma Isochore (EPI) designed to confine electrical plasma discharges up to 25kbar. Theoretically, the properties were determined

Jean Clerouin

2001-01-01

405

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

Microsoft Academic Search

Experimental measurements and theoretical calculations of the electrical conductivity of aluminum are presented in the strongly coupled partially degenerate regime (rho=0.3 g\\/cm3, 5000electrical plasma discharges up to 1.5 GPa. Aluminum properties were determined theoretically by ab initio molecular dynamics simulations in the local density

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

2002-01-01

406

Electrically conducting nanopatterns formed by chemical e-beam lithography via gold nanoparticle seeds.  

PubMed

We report the formation of thiol nanopatterns on SAM covered silicon wafers by converting sulfonic acid head groups via e-beam lithography. These thiol groups act as binding sites for gold nanoparticles, which can be enhanced to form electrically conducting nanostructures. This approach serves as a proof-of-concept for the combination of top-down and bottom-up processes for the generation of electrical devices on silicon. PMID:22201225

Schaal, Patrick A; Besmehn, Astrid; Maynicke, Eva; Noyong, Michael; Beschoten, Bernd; Simon, Ulrich

2012-02-01

407

Evolution of the health of concrete structures by electrically conductive GFRP (glass fiber reinforced plastic) composites  

Microsoft Academic Search

The function and performance of self-diagnostic composites embedded in concrete blocks and piles were investigated by bending\\u000a tests and electrical resistance measurement. Carbon powder (CP) and carbon fiber (CF) were introduced into glass fiber reinforced\\u000a plastic (GFRP) composites to provide electrical conductivity. The CPGFRP composite displays generally good performance in\\u000a various bending tests of concrete block and piles compared to

Soon-Gi Shin

2002-01-01

408

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

409

Electrical conductivity during incipient melting in the oceanic low-velocity zone.  

PubMed

The low-viscosity layer in the upper mantle, the asthenosphere, is a requirement for plate tectonics. The seismic low velocities and the high electrical conductivities of the asthenosphere are attributed either to subsolidus, water-related defects in olivine minerals or to a few volume per cent of partial melt, but these two interpretations have two shortcomings. First, the amount of water stored in olivine is not expected to be higher than 50 parts per million owing to partitioning with other mantle phases (including pargasite amphibole at moderate temperatures) and partial melting at high temperatures. Second, elevated melt volume fractions are impeded by the temperatures prevailing in the asthenosphere, which are too low, and by the melt mobility, which is high and can lead to gravitational segregation. Here we determine the electrical conductivity of carbon-dioxide-rich and water-rich melts, typically produced at the onset of mantle melting. Electrical conductivity increases modestly with moderate amounts of water and carbon dioxide, but it increases drastically once the carbon dioxide content exceeds six weight per cent in the melt. Incipient melts, long-expected to prevail in the asthenosphere, can therefore produce high electrical conductivities there. Taking into account variable degrees of depletion of the mantle in water and carbon dioxide, and their effect on the petrology of incipient melting, we calculated conductivity profiles across the asthenosphere for various tectonic plate ages. Several electrical discontinuities are predicted and match geophysical observations in a consistent petrological and geochemical framework. In moderately aged plates (more than five million years old), incipient melts probably trigger both the seismic low velocities and the high electrical conductivities in the upper part of the asthenosphere, whereas in young plates, where seamount volcanism occurs, a higher degree of melting is expected. PMID:24784219

Sifré, David; Gardés, Emmanuel; Massuyeau, Malcolm; Hashim, Leila; Hier-Majumder, Saswata; Gaillard, Fabrice

2014-05-01

410

The electrical conductivity during incipient melting in the oceanic low velocity zone  

PubMed Central

A low viscosity layer in the upper mantle, the Asthenosphere, is a requirement for plate tectonics1. The seismic low velocities and the high electrical conductivities of the Asthenosphere are attributed either to sub-solidus water-related defects in olivine minerals2-4 or to a few volume percents of partial melt5-8 but these two interpretations have shortcomings: (1) The amount of H2O stored in olivine is not expected to be higher than 50 ppm due to partitioning with other mantle phases9, including pargasite amphibole at moderate temperatures10, and partial melting at high temperatures9; (2) elevated melt volume fractions are impeded by the too cold temperatures prevailing in the Asthenosphere and by the high melt mobility that can lead to gravitational segregation11,12. Here we determined the electrical conductivity of CO2-H2O-rich melts, typically produced at the onset of mantle melting. Electrical conductivity modestly increases with moderate amounts of H2O and CO2 but it dramatically increases as CO2 content exceeds 6 wt% in the melt. Incipient melts, long-expected to prevail in the asthenosphere10,13-15, can therefore trigger its high electrical conductivities. Considering depleted and enriched mantle abundances in H2O and CO2 and their effect on the petrology of incipient melting, we calculated conductivity profiles across the Asthenosphere for various plate ages. Several electrical discontinuities are predicted and match geophysical observations in a consistent petrological and geochemical framework. In moderately aged plates (>5Ma), incipient melts most likely trigger both the seismic low velocities and the high electrical conductivities in the upper part of the asthenosphere, whereas for young plates4, where seamount volcanism occurs6, higher degree of melting is expected. PMID:24784219

Sifre, David; Gardes, Emmanuel; Massuyeau, Malcolm; Hashim, Leila; Hier-Majumder, Saswata; Gaillard, Fabrice

2014-01-01

411

Investigating the electrical conductivity of volcanic ash and its effect on HV power systems  

NASA Astrophysics Data System (ADS)

Volcanic ash contamination of high voltage (HV) power networks compromises the reliability of society’s electricity supply. Ash-induced insulator flashover is a common problem on transmission networks during explosive eruptions, which is attributed to the high conductivity (?), low resistivity (?) of volcanic ash. However, there have been few studies which have investigated the electrical conductivity of volcanic ash and how it may be influenced by different volcanological and environmental factors. In this study we have used a simple and rapid testing method to measure the influence of ash composition, grain size, soluble salt content, compaction and moisture (water) content on ash conductivity. We also developed physically, chemically and electrically equivalent ash proxies to be used for current and future laboratory experimentation. Results indicate that dry volcanic ash is non-conducting (? > 1.56 × 107 ?m), however, the conductivity of volcanic ash increases abruptly with the adsorption of water. Further increase in conductivity has been observed with increasing soluble salt content and compaction. All grain sizes (<32 ?m to 1.4 mm) can exhibit high conductivity values (? < 100 ?m) and therefore have similar potential to cause flashover on HV insulation. The methodology development and results herein represent a benchmark for in-field testing during volcanic crises and for future studies.

Wardman, J. B.; Wilson, T. M.; Bodger, P. S.; Cole, J. W.; Johnston, D. M.

2012-01-01

412

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

413

Electrical Conductivity Response of Poly (phenylene vinylene) / Zeolite Composites Exposed to Ethanol vapour  

NASA Astrophysics Data System (ADS)

Conducting polymers such as poly (p-phenylene vinylene) (PPV) can serve as the active material in organic vapor sensor because PPV possesses good optical and electrical properties. PPV can be synthesized by a relative simple technique and doped with sulfuric acid to improve its electrical properties. The composites of 10% (v/v) doped PPV and ZSM-5 zeolites (Si/Al = 23, 50, 80, 280) were prepared by dry mixing to be used as an ethanol vapor sensor. The four-point probe technique was used to evaluate the effects of doping molar ratio and Si/Al ratio when the sensing materials were exposed to ethanol vapor. When exposed to ethanol vapor, the electrical conductivity response of the doped PPV and ZSM-5 zeolites increased with increasing mole of sulfuric acid but decreased as the ratio Si/Al increased. Although the doped PPV showed positive response when exposed to ethanol vapor but the composites of 10% (v/v) PPV/ ZSM-5 zeolites showed negative electrical conductivity responses, similar to those of the undoped PPV and ZSM-5 zeolites. The difference in the interaction between ethanol molecules and the sensing materials on the electrical conductivity responses were investigated by the FT-IR measurements.

Yimlamai, Intira; Sirivat, Anuvat

2010-03-01

414

Nerve growth factor-immobilized polypyrrole: Bioactive electrically conducting polymer for enhanced neurite extension  

PubMed Central

Biomaterials that present multiple stimuli are attractive for a number of biomedical applications. In particular, electrical and biological cues are important factors to include in interfaces with neurons for applications such as nerve conduits and neural probes. Here, we report the combination of these two stimuli, by immobilizing nerve growth factor (NGF) on the surface of the electrically conducting polymer polypyrrole (PPy). NGF was immobilized using an intermediate linker provided by a layer of polyallylamine conjugated to an arylazido functional group. Upon exposure to UV light and activation of the azido groups, NGF was fixed to the substrate. Three different surface concentrations were obtained (0.21–0.98 ng/mm2) and similar levels of neurite extension were observed on immobilized NGF as with soluble NGF. Additionally, electrical stimulation experiments were conducted with the modified polymer and revealed a 50% increase in neurite outgrowth in PC12 cells compared to experiments without electrical stimulation. This novel modification of PPy provides both electrical and biological stimulation, by presenting tethered growth factors and only producing a small decrease in the material's properties (conductivity ~10 S cm?1) when compared to other modification techniques (conductivity ~10?3–10?6 S cm?1. PMID:17111407

Gomez, Natalia; Schmidt, Christine E.

2010-01-01

415

Effect of twist and porosity on the electrical conductivity of carbon nanofiber yarns  

NASA Astrophysics Data System (ADS)

This study focuses on the effect of twist and porosity on the electrical conductivity of carbon nanofiber (CNF) yarns. The process of fabrication of CNF yarns included the synthesis of aligned ribbons of polyacrylonitrile (PAN) nanofibers via electrospinning. The PAN ribbons were twisted into yarns with twist levels ranging from zero twist to high twists of 1300 turn per meter (tpm). The twist imposed on the ribbons substantially improved the interactions between nanofibers and reduced the porosity. The PAN yarns were subsequently stabilized in air, and then carbonized in nitrogen at 1100?° C for 1 h. Compressive stresses developed between the PAN nanofibers as a result of twist promoted interfusion between neighboring nanofibers, which was accelerated by heating the yarns during stabilization to temperatures above the glass transition of PAN. The electrical conductivity of the yarns was measured with a four point probe measurement technique. Although increasing the twist promotes electrical conductivity between nanofibers by forming junctions between them, our results indicate that the electrical conductivity does not continuously increase with increasing twist, but reaches a threshold value after which it starts to decrease. The causes for this behavior were studied through experimental techniques and further explored using a yarn-equivalent electrical circuit model.

Chawla, S.; Naraghi, M.; Davoudi, A.

2013-06-01

416

Effect of twist and porosity on the electrical conductivity of carbon nanofiber yarns.  

PubMed

This study focuses on the effect of twist and porosity on the electrical conductivity of carbon nanofiber (CNF) yarns. The process of fabrication of CNF yarns included the synthesis of aligned ribbons of polyacrylonitrile (PAN) nanofibers via electrospinning. The PAN ribbons were twisted into yarns with twist levels ranging from zero twist to high twists of 1300 turn per meter (tpm). The twist imposed on the ribbons substantially improved the interactions between nanofibers and reduced the porosity. The PAN yarns were subsequently stabilized in air, and then carbonized in nitrogen at 1100 °C for 1 h. Compressive stresses developed between the PAN nanofibers as a result of twist promoted interfusion between neighboring nanofibers, which was accelerated by heating the yarns during stabilization to temperatures above the glass transition of PAN. The electrical conductivity of the yarns was measured with a four point probe measurement technique. Although increasing the twist promotes electrical conductivity between nanofibers by forming junctions between them, our results indicate that the electrical conductivity does not continuously increase with increasing twist, but reaches a threshold value after which it starts to decrease. The causes for this behavior were studied through experimental techniques and further explored using a yarn-equivalent electrical circuit model. PMID:23727878

Chawla, S; Naraghi, M; Davoudi, A

2013-06-28

417

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

418

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

419

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

420

Electrical conductivity and thermal stability measurements of a mixed perovskite oxide system  

SciTech Connect

For the mixed perovskite oxide system (Sr/sub 0.8125/La/sub 0.1875/ ) (Zr/sub 0.75/Fe/sub x/Ru/sub 0.25-x/)O/sub 3-delta/ , electrical conductivities were measured in air as a function of temperature and Ru/Fe ratio. Liquidus and solidus temperatures were determined in air by the laser melting point measurement technique. The substitution of Ru for Fe was found to increase the electrical conductivity by over an order of magnitude while decreasing the solidus temperature of the Fe-rich solid solution by less than 10%.

Sukkar, M.H.; Sadoway, D.R.

1982-05-01

421

Electrical conductivity of activated carbon-metal oxide nanocomposites under compression: a comparison study.  

PubMed

From a granular commercial activated carbon (AC) and six metal oxide (Al2O3, Fe2O3, SnO2, TiO2, WO3 and ZnO) precursors, two series of AC-metal oxide nanocomposites were prepared by wet impregnation, oven-drying at 120 °C, and subsequent heat treatment at 200 or 850 °C in an inert atmosphere. Here, the electrical conductivity of the resulting products was studied under moderate compression. The influence of the applied pressure, sample volume, mechanical work, and density of the hybrid materials was thoroughly investigated. The DC electrical conductivity of the compressed samples was measured at room temperature by the four-probe method. Compaction assays suggest that the mechanical properties of the nanocomposites are largely determined by the carbon matrix. Both the decrease in volume and the increase in density were relatively small and only significant at pressures lower than 100 kPa for AC and most nanocomposites. In contrast, the bulk electrical conductivity of the hybrid materials was strongly influenced by the intrinsic conductivity, mean crystallite size, content and chemical nature of the supported phases, which ultimately depend on the metal oxide precursor and heat treatment temperature. The supported nanoparticles may be considered to act as electrical switches either hindering or favouring the effective electron transport between the AC cores of neighbouring composite particles in contact under compression. Conductivity values as a rule were lower for the nanocomposites than for the raw AC, all of them falling in the range of semiconductor materials. With the increase in heat treatment temperature, the trend is toward the improvement of conductivity due to the increase in the crystallite size and, in some cases, to the formation of metals in the elemental state and even metal carbides. The patterns of variation of the electrical conductivity with pressure and mechanical work were slightly similar, thus suggesting the predominance of the pressure effects rather than the volume ones. PMID:25331935

Barroso-Bogeat, A; Alexandre-Franco, M; Fernández-González, C; Macías-García, A; Gómez-Serrano, V

2014-10-22

422

Electrical conductivity as a test for the integrity of latex gloves  

SciTech Connect

Surgical latex gloves have been used to protect patients against bacterial infections introduced by health-care workers. As a result of the Acquired Immune Deficiency Syndrome (AIDS) epidemic, the concern has shifted, with more emphasis on the protection of the health-care worker from the patient. These gloves often have defects, holes, which allow bacteria to penetrate. There are a number of methods to test the integrity of these gloves before they are donned. The present standard test is to fill the glove with 1000 ml of water and visually inspect the exterior for water leaks. Another method allows the gloves to be tested while being worn. This is done by measuring the electrical conductivity through the latex, from the hand to an external conductive solution. We have investigated the use of electrical conductivity to test sterile latex gloves, both with and without holes. We have studied various phenomena associated with this testing and conducted simultaneous electrical and viral penetration tests. Our conclusions are as follows. (1) Electrical conductivity test method for gloves while they are being worn is very dependent on the specific glove being tested, primarily on the conductivity of the intact glove. (2) In the best of cases, reliable results could be expected for only about one hour of wear and for holes larger than 10s of [mu]ms. (3) There are practical problems that may disqualify the electrical conductivity test for routine use. (4) The test may prove to be valuable as a QA test procedure for nonconductive materials and garments made from these materials because it has greater sensitivity than presently used methods. (5) The effective sizes of holes in latex increase much faster when the latex is stretched than would be predicted from the elongation of the latex.

Stampfer, J.F.; Kissane, R.J.; Schauer, S.M.

1993-02-01

423

Electrical conductivity as a test for the integrity of latex gloves  

SciTech Connect

Surgical latex gloves have been used to protect patients against bacterial infections introduced by health-care workers. As a result of the Acquired Immune Deficiency Syndrome (AIDS) epidemic, the concern has shifted, with more emphasis on the protection of the health-care worker from the patient. These gloves often have defects, holes, which allow bacteria to penetrate. There are a number of methods to test the integrity of these gloves before they are donned. The present standard test is to fill the glove with 1000 ml of water and visually inspect the exterior for water leaks. Another method allows the gloves to be tested while being worn. This is done by measuring the electrical conductivity through the latex, from the hand to an external conductive solution. We have investigated the use of electrical conductivity to test sterile latex gloves, both with and without holes. We have studied various phenomena associated with this testing and conducted simultaneous electrical and viral penetration tests. Our conclusions are as follows. (1) Electrical conductivity test method for gloves while they are being worn is very dependent on the specific glove being tested, primarily on the conductivity of the intact glove. (2) In the best of cases, reliable results could be expected for only about one hour of wear and for holes larger than 10s of {mu}ms. (3) There are practical problems that may disqualify the electrical conductivity test for routine use. (4) The test may prove to be valuable as a QA test procedure for nonconductive materials and garments made from these materials because it has greater sensitivity than presently used methods. (5) The effective sizes of holes in latex increase much faster when the latex is stretched than would be predicted from the elongation of the latex.

Stampfer, J.F.; Kissane, R.J.; Schauer, S.M.

1993-02-01

424

Model simulations of strong atmospheric conductivity disturbances and induced responses of the Global Electric Circuit  

NASA Astrophysics Data System (ADS)

Electrical conductivity in the troposphere and stratosphere is an important quantity that determines the distribution of currents in the GEC (Global Electric Circuit), as well as the potential difference between the Earth and the ionosphere. Recently, progress in modeling atmospheric conductivity has been achieved by integrating the conductivity calculation into an AC-GCM (atmospheric chemistry general circulation model), which provides all relevant data. In this study, WACCM (Whole Atmosphere Community Climate Model) is used for conductivity calculations and an analysis of the effects of strong disturbances on the GEC. This includes volcanic eruptions of Pinatubo in 1991 and the super volcano Toba, polar stratospheric clouds, radioactive releases, and the recent strong galactic cosmic ray maximum. In general, there is a decrease in conductivity from enhanced aerosol number densities, resulting from volcanic eruptions or polar stratospheric clouds. Conductivity is increased by additional ionization sources such as radioactive releases, or galactic cosmic ray increases such as during the last solar minimum. The effects of such events on conductivity, column and total resistance, and estimate effects on current distribution and the earth-ionosphere potential difference will be quantified. Percentage change in conductivity at 20 km altitude two months after the Toba volcanic eruption (WACCM model simulation). The enhanced aerosol concentrations lead to a "conductivity hole" between 30°S and 45° N.

Baumgaertner, A. J.; Lehto, E.; Neely, R. R.; English, J. M.; Zhu, Y.; Lucas, G.; Thayer, J. P.

2013-12-01

425

Electrical and thermal conduction in atomic layer deposition nanobridges down to 7 nm thickness.  

PubMed

While the literature is rich with data for the electrical behavior of nanotransistors based on semiconductor nanowires and carbon nanotubes, few data are available for ultrascaled metal interconnects that will be demanded by these devices. Atomic layer deposition (ALD), which uses a sequence of self-limiting surface reactions to achieve high-quality nanolayers, provides an unique opportunity to study the limits of electrical and thermal conduction in metal interconnects. This work measures and interprets the electrical and thermal conductivities of free-standing platinum films of thickness 7.3, 9.8, and 12.1 nm in the temperature range from 50 to 320 K. Conductivity data for the 7.3 nm bridge are reduced by 77.8% (electrical) and 66.3% (thermal) compared to bulk values due to electron scattering at material and grain boundaries. The measurement results indicate that the contribution of phonon conduction is significant in the total thermal conductivity of the ALD films. PMID:22224582

Yoneoka, Shingo; Lee, Jaeho; Liger, Matthieu; Yama, Gary; Kodama, Takashi; Gunji, Marika; Provine, J; Howe, Roger T; Goodson, Kenneth E; Kenny, Thomas W

2012-02-01

426

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

427

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

428

Experimental study of electrical conduction in RuO 2 -based thick resistive films  

Microsoft Academic Search

Electrical conduction and noise of thick resistive films prepared from RuO2 and lead borosilicate glass were studied. Two series of pastes were prepared differing by the specific surface area of RuO2 powder (77 m2\\/g and 24 m2\\/g). It was concluded that two regions on resistanceR versus volume fractionv of conducting component characteristics may be specified. For small values ofv resistance

K. Bobran

1989-01-01

429

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

430

The effect of water and iron content on electrical conductivity of upper mantle rocks.  

NASA Astrophysics Data System (ADS)

Geophysical observations (MT and GDS) show the conductivity anomaly which may be related to the presence of water and melting. Recently, several researchers have estimated the water content in the transition zone (Huang et al. 2005; Yoshino et al. 2008) and the upper mantle (Wang et al.2006; Yoshino et al. 2006) by electrical conductivity methods. They may underestimate the water content, especially, Yoshino et al did too much underestimate. However, other coexisting phases such as pyroxene and its high-pressure polymorphs may also contribute to the bulk conductivity of the mantle. To test this hypothesis, we measured the electrical conductivity of upper mantle rocks- dunite, pyroxenite and lherzolite at ~ 2-3 GPa and ~1273-1573 K using impedance spectra within a frequency range of 0.1~1000000 Hz. The oxygen fugacity was controlled by a Mo-MoO2 solid buffer. The results show that the electrical conductivity of lherzolite and pyroxenite are ~ half and one order of magnitude higher than that of dunite. These differences were interpreted through a preliminary model involving water and iron content effects on the electrical conductivity. We extrapolated our results and compared the results with some of geophysical observations of the upper mantle. Our results indicate the maximum water content in oceanic upper mantle is as high as ~ 0.09wt % and suggest that pyroxenes dominate the bulk conductivity of upper mantle in hydrous conditions. These results indicated that our model with various water contents could explain the conductivity anomaly in the oceanic upper mantle without involving the presence of partial melt at these depths. This work was supported by national natural science foundation of china (40774036); the special grant from the president of Chinese Academy of Sciences and Graduate University of Chinese Academy Sciences.

Wang, D.; Yi, L.

2008-12-01

431