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1

Electrical Conductivity.  

ERIC Educational Resources Information Center

Examines Drude's classical (1900) theory of electrical conduction, details the objections to and successes of the 1900 theory, and investigates the Quantum (1928) theory of conduction, reviewing its successes and limitations. (BT)

Allen, Philip B.

1979-01-01

2

Electrical Conductivity.  

ERIC Educational Resources Information Center

Explains how electrical conductivity (EC) can be used to measure ion concentration in solutions. Describes instrumentation for the measurement, temperature dependence and EC, and the EC of common substances. (PR)

Hershey, David R.; Sand, Susan

1993-01-01

3

Electrical Conductivity Protocol  

NSDL National Science Digital Library

The purpose of this resource is to measure the conductivity of water at a freshwater hydrology site. Students calibrate and take electrical conductivity measurements using an electrical conductivity meter. Students estimate the total dissolved solids from the electrical conductivity measurements.

The GLOBE Program, UCAR (University Corporation for Atmospheric Research)

2003-08-01

4

Electrically conductive diamond electrodes  

DOEpatents

An electrically conductive diamond electrode and process for preparation thereof is described. The electrode comprises diamond particles coated with electrically conductive doped diamond preferably by chemical vapor deposition which are held together with a binder. The electrodes are useful for oxidation reduction in gas, such as hydrogen generation by electrolysis.

Swain, Greg (East Lansing, MI) [East Lansing, MI; Fischer, Anne (Arlington, VA), [Arlington, VA; Bennett, Jason (Lansing, MI) [Lansing, MI; Lowe, Michael (Holt, MI) [Holt, MI

2009-05-19

5

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

6

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

7

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

8

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

9

Electrical Conduction Activity  

NSDL National Science Digital Library

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

2012-10-02

10

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

11

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

12

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

13

Electrical Conductivity in Textiles.  

National Technical Information Service (NTIS)

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 NAS...

2006-01-01

14

Electrical Conduction in Ice.  

National Technical Information Service (NTIS)

In an attempt to resolve the conflict existing in the literature as to dc electrical conductivity of ice, an extensive series of measurements has been made. Since surface conduction is a possible cause of some of the confusion, both bulk and surface condu...

P. R. Camp W. Kiszenick D. A. Arnold

1967-01-01

15

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

16

Electric field variations measured continuously in free air over a conductive thin zone in the tilted Lias-epsilon black shales near Osnabrück, Northwest Germany  

NASA Astrophysics Data System (ADS)

Common studies on the static electric field distribution over a conductivity anomaly use the self-potential method. However, this method is time consuming and requires nonpolarizable electrodes to be placed in the ground. Moreover, the information gained by this method is restricted to the horizontal variations of the electric field. To overcome the limitation in the self-potential technique, we conducted a field experiment using a non conventional technique to assess the static electric field over a conductivity anomaly. We use two metallic potential probes arranged on an insulated boom with a separation of 126 cm. When placed into the electric field of the free air, a surface charge will be induced on each probe trying to equalize with the potential of the surrounding atmosphere. The use of a plasma source at both probes facilitated continuous and quicker measurement of the electric field in the air. The present study shows first experimental measurements with a modified potential probe technique (MPP) along a 600-meter-long transect to demonstrate the general feasibility of this method for studying the static electric field distribution over shallow conductivity anomalies. Field measurements were carried out on a test site on top of the Bramsche Massif near Osnabrück (Northwest Germany) to benefit from a variety of available near surface data over an almost vertical conductivity anomaly. High resolution self-potential data served in a numerical analysis to estimate the expected individual components of the electric field vector. During the experiment we found more anomalies in the vertical and horizontal components of the electric field than self-potential anomalies. These contrasting findings are successfully cross-validated with conventional near surface geophysical methods. Among these methods, we used self-potential, radiomagnetotelluric, electric resistivity tomography and induced polarization data to derive 2D conductivity models of the subsurface in order to infer the geometrical properties and the origin of the conductivity anomaly in the survey area. The presented study demonstrates the feasibility of electric field measurements in free air to detect and study near surface conductivity anomalies. Variations in Ez correlate well with the conductivity distribution obtained from resistivity methods. Compared to the self-potential technique, continuously free air measurements of the electric field are more rapid and of better lateral resolution combined with the unique ability to analyze vertical components of the electric field which are of particular importance to detect lateral conductivity contrasts. Mapping Ez in free air is a good tool to precisely map lateral changes of the electric field distribution in areas where SP generation fails. MPP offers interesting application in other geophysical techniques e.g. in time domain electromagnetics, DC and IP. With this method we were able to reveal a ca. 150 m broad zone of enhanced electric field strength.

Gurk, M.; Bosch, F. P.; Tougiannidis, N.

2013-04-01

17

Electrical Conduction Assessment  

NSDL National Science Digital Library

This brief assessment on Electrical Conduction is intended to be used after students have completed the introductory activity on the topic, which may be located here. The assessment consists of 8 multiple choice and short answer questions. The other educational modules in this series can be found here. Instructors and students are encouraged to sign up with the Electron Technologies site here before starting to use these materials.

2012-10-02

18

Electrical conductivity of mantle minerals  

Microsoft Academic Search

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

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

2006-01-01

19

Electrical conduction in olivine  

SciTech Connect

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

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

1989-05-10

20

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

21

Moldable Electrically Conductive Polymer Compositions.  

National Technical Information Service (NTIS)

Accordingly, it is an object of this invention to obtain high electrical conductivity in a polymeric composition. Another object is to provide a bulky, moldable polymeric composition that conducts electricity. Another object is to provide a polymeric comp...

O. K. Kim

1985-01-01

22

Electrically Conductive Polymer Concrete Overlays.  

National Technical Information Service (NTIS)

The development of a built-up, electrically conductive polymer concrete overlay and a premixed, electrically conductive polymer concrete mortar for use on bridge decks and other concrete members, in conjunction with cathodic protection systems, is reporte...

R. P. Webster J. J. Fontana W. Reams

1985-01-01

23

Time and spatial resolved optical and electrical characteristics of continuous and time modulated RF plasmas in contact with conductive and dielectric substrates  

NASA Astrophysics Data System (ADS)

Cold atmospheric pressure plasma jets are often used as a remote plasma source for substrate treatments. However, this substrate acts as an electrode and this additional electrode can induce effects on plasma parameters such as the dissipated power, gas temperature, etc. In this work the influence of substrates of different conductivity and permittivity in direct contact with three different operational modes of atmospheric pressure RF plasma jets is investigated. Two different electrode configurations (creating either a linear or a cross electric field) and, for the linear field configuration, two voltage modulations (continuous RF and kHz pulsed RF) have been studied. Electrical and optical diagnostic methods have been performed in order to get quantitative data of the change in plasma dissipated power and gas temperature, when the plasma is in direct contact with the substrate. In all three investigated cases the power dissipation and gas temperature, significantly increase when the plasma is in direct contact with a conductive substrate. The increase of power is attributed to a change of the equivalent electrical circuit, leading to a more favourable matching between the power input and the plasma source.

Hofmann, Sven; van Gils, Koen; van der Linden, Steven; Iseni, Sylvain; Bruggeman, Peter

2014-03-01

24

Electrically Conductive Polymer Concrete Coatings.  

National Technical Information Service (NTIS)

A sprayable electrically conductive polymer concrete coating for vertical and overhead applications is described. The coating is permeable yet has low electrical resistivity (<10 ohm-cm), good bond strength to concrete substrates, and good weatherability....

J. J. Fontana D. Elling W. Reams

1988-01-01

25

Electrically Conductive Polymer Compositions.  

National Technical Information Service (NTIS)

A conductive polymer composite system is made by dissolving an electron donating polymer and a simple or complex N-methylphenazinium TCNQ salt in a mutual solvent and casting a film of the resulting solution on a suitable substrate.

O. K. Kim

1983-01-01

26

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

27

Electrically Conductive Anodized Aluminum Surfaces  

NASA Technical Reports Server (NTRS)

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

Nguyen, Trung Hung

2006-01-01

28

Electrically Conductive Polymer Concrete Overlays.  

National Technical Information Service (NTIS)

The use of cathodic protection to prevent the corrosion of reinforcing steel in concrete structures has been well established. Application of a durable, skid-resistant electrically conductive polymer concrete overlay would advance the use of cathodic prot...

J. J. Fontana R. P. Webster

1984-01-01

29

Electrically Conductive Polymer Concrete Coatings.  

National Technical Information Service (NTIS)

The corrosion of reinforcing steel embedded in concrete causes cracks and delamination in the concrete. The application of impressed current cathodic protection utilizing electrically conductive polymer concrete to distribute the current across concrete b...

J. J. Fontana

1985-01-01

30

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

31

Electrical conduction in polymer dielectrics  

NASA Technical Reports Server (NTRS)

The use of polymer dielectrics with moderate resistivities could reduce or eliminate problems associated with spacecraft charging. The processes responsible for conduction and the properties of electroactive polymers are reviewed, and correlations drawn between molecular structure and electrical conductivity. These structure-property relationships led to the development of several new electroactive polymer compositions and the identification of several systems that have the requisite thermal, mechanical, environmental and electrical properties for use in spacecraft.

Cotts, D. B.

1985-01-01

32

Electrical conductivity of carbonaceous powders  

Microsoft Academic Search

The present paper deals with the electrical conductivity of a number of carbonaceous powders undergoing a low compaction. It is shown that the contributions to the conductivity of such samples are too numerous and too complex to be solved exactly. Hence, several criteria are proposed in order to quantify the behaviour of moderately compressed powders, and thus derive several useful

A. Celzard; J. F. Marêché; F. Payot; G. Furdin

2002-01-01

33

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

34

Electrical conductivity of chondritic meteorites  

NASA Technical Reports Server (NTRS)

The electrical conductivity of samples of the Murchison and Allende carbonaceous chondrites is 4 to 6 orders of magnitude greater than rock forming minerals such as olivine for temperatures up to 700 C. The remarkably high electrical conductivity of these meteorites is attributed to carbon at the grain boundaries. Much of this carbon is produced by pyrolyzation of hydrocarbons at temperatures in excess of 150 C. As the temperature increases, light hydrocarbons are driven off and a carbon-rich residue or char migrates to the grain boundaries enhancing electrical conductivity. Assuming that carbon was present at the grain boundaries in the material which comprised the meteorite parent bodies, the electrical heating of such bodies was calculated as a function of body size and solar distance during a hypothetical T-Tauri phase of the sun. Input conductivity data for the meteorite parent body were the present carbonaceous chondrite values for temperatures up to 840 C and the electrical conductivity values for olivine above 840 C.

Duba, AL; Didwall, E. M.; Burke, G. J.; Sonett, C. P.

1987-01-01

35

Electrically conductive polymer concrete coatings  

DOEpatents

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

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

1988-05-26

36

Electrically conductive polymer concrete coatings  

DOEpatents

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

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

1990-03-13

37

Electrically conductive polymer concrete coatings  

DOEpatents

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

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

1990-01-01

38

Electrically conductive polymer concrete overlays  

NASA Astrophysics Data System (ADS)

The use of cathodic protection to prevent the corrosion of reinforcing steel in concrete structures has been well established. Application of a durable, skid-resistant electrically conductive polymer concrete overlay would advance the use of cathodic protection for the highway industry. Laboratory studies indicate that electrically conductive polymer concrete overlays using conductive fillers, such as calcined coke breeze, in conjunction with polyester or vinyl ester resins have resistivities of 1 to 10 ohm-cm. Both multiple-layer and premixed mortar-type overlays were made. Shear bond strengths of the conductive overlays to concrete substrates vary from 600 to 1300 psi, with the premixed overlays having bond strengths 50 to 100% higher than the multiple-layer overlays.

Fontana, J. J.; Webster, R. P.

1984-08-01

39

The electrical conductivity of lherzolite  

SciTech Connect

Electrical conductivity as a function of oxygen fugacity (f{sub O2}) between 10{sup {minus}5} Pa and 1 Pa, temperature between 700{degrees}C and 1200{degrees}C, and time over a period of 1700 hours are reported for a lherzolite nodule from Mount Porndon, Australia. Analysis of complex impedance collected at 100 Hz, 1 kHz, and 10 kHz indicates that there is significant frequency dispersion in this rock at temperatures below 900{degrees}C-1000{degrees}C. By choosing the resistance of an equivalent parallel RC network at the frequency having minimum phase, the effect of dispersion is largely avoided. Conductivity as a function of time, collected following changes in f{sub O2} at 1010 and 1200{degrees}C, has been analyzed to determine the diffusivity of defects relating f{sub O2} to the electrical conduction mechanism in olivine. The diffusivities so obtained are in remarkably good agreement with those determined from strain measurements during creep tests, which implies that magnetism vacancies are the rate-limiting step for conductivity reequilibration after f{sub O2} changes. A longer-term process is observed in this rock in which the conductivity drifts upward or downward with a time constant of hundreds of hours after initial reequilibration to gas mix (f{sub O2}) changes. The authors speculate that this long-term drift could be related to equilibration of the iron distribution between coexisting olivine and pyroxene as a function of f{sub O2}. The lherzolite conductivity data are not significantly different from measurements made on olivine single crystals and polycrystals, even though the rock contains about 34 model % pyroxene. This consistency of laboratory measurements of electrical conductivity of olivines from many localities and geological settings supports the use of recent models relating mantle temperature with electrical conductivity in the interpretation of mantle geo/electromagnetic soundings. 33 refs., 11 figs., 3 tabs.

Duba, A. [Lawrence Livermore National Lab., CA (United States); Constable, S. [Scripps Institution of Oceanography, La Jolla, CA (United States)

1993-07-10

40

Electrical Conductivity in Transition Metals  

ERIC Educational Resources Information Center

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

Talbot, Christopher; Vickneson, Kishanda

2013-01-01

41

Electrically conductive rigid polyurethane foam  

DOEpatents

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

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

1983-12-08

42

Electrically conductive rigid polyurethane foam  

Microsoft Academic Search

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

Th. E. Neet; D. A. Spieker

1985-01-01

43

Electrically conductive rigid polyurethane foam  

Microsoft Academic Search

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

T. E. Neet; D. A. Spieker

1983-01-01

44

Electrically conductive black optical paint  

NASA Technical Reports Server (NTRS)

An electrically conductive flat black paint has been developed for use on the Galileo spacecraft which will orbit Jupiter in the late 1980s. The paint, designed for equipment operating in high-energy radiation fields, has multipurpose functions. Its electrical conductivity keeps differential charging of the spacecraft external surfaces and equipment to a minimum, preventing the buildup of electrostatic fields and arcing. Its flat black aspect minimizes the effects of stray light and unwanted reflectances, when used in optical instruments and on sunshades. Its blackness is suitable, also, for thermal control, when the paint is put on spacecraft surfaces. The paint has good adherence properties, as measured by tape tests, when applied properly to a surface. The electrically conductive paint which was developed has the following characteristics: an electrical resistivity of 5 x 10 to the 7th ohms per square; a visual light total reflectance of approximately 5 percent; an infrared reflectance of 0.13 measured over a spectrum from 10 to the (-5.5) power to 0.001 meter; a solar absorptivity, alpha-s, of 0.93, and a thermal emissivity, epsilon, of 0.87, resulting in an alpha-s/epsilon of 1.07. The formula for making the paint and the process for applying it are described.

Birnbaum, M. M.; Metzler, E. C.; Cleland, E. L.

1983-01-01

45

Electrical conductivity of ice VII  

PubMed Central

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.

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

2014-01-01

46

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

47

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

48

Continuous Status Indicator for Electrical Protection Device.  

National Technical Information Service (NTIS)

This invention is a continuous visual indicator circuit to monitor the status of an electrical protection device that has been located within an electrical circuit, between a power source and an electrical load, to avoid current overload. My indicator cir...

K. K. Chopra

2003-01-01

49

Electrical conductivity and corrosion protection properties of conductive paint coatings  

Microsoft Academic Search

Purpose – The purpose of this paper is to investigate the electrical conductivity and corrosion protection properties of a conductive coating composed of epoxy resin and carbon black in a sodium chloride (NaCl) solution. Design\\/methodology\\/approach – The conductive coating was prepared by combining epoxy resin, hardener, and carbon black. The electrical conductivity of the paint was studied with a DC

M. N. Masri; Z. M. Yunus; A. R. M. Warikh; A. A. Mohamad

2010-01-01

50

Study on Electrical Conductivity of Coal.  

National Technical Information Service (NTIS)

One of the engineering techniques in underground coal gasification is the electrical linking of holes drilled into the coal seam. The magnitude of electrical conductivity is one of the factors that will determine whether electrical linking is appropriate....

H. Ohuchi J. Soma T. Isobe

1968-01-01

51

Characterization of electrically conducting oxides  

SciTech Connect

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

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

1989-01-01

52

Electrical Conductivity of Ferritin Proteins by Conductive AFM  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

53

Effective electrical conductivity of a nonuniform plasma  

NASA Technical Reports Server (NTRS)

A simple nonuniformity model for calculating effective electrical conductivity and Hall parameter is proposed. The model shows that the effective conductivity can be significantly reduced by nonuniformities in the Hall parameter, even if the local conductivity is uniform.

Nichols, L. D.

1975-01-01

54

Electrically conductive fibers thermally isolate temperature sensor  

NASA Technical Reports Server (NTRS)

Mounting assembly provides thermal isolation and an electrical path for an unbacked thermal sensor. The sensor is suspended in the center of a plastic mounting ring from four plastic fibers, two of which are coated with an electrically conductive material and connected to electrically conductive coatings on the ring.

De Waard, R.; Norton, B.

1966-01-01

55

The electrical conduction in polyimide nanocomposites  

Microsoft Academic Search

The electrical properties of polyimide based nanocomposites were fully investigated by isothermal steady-state current, dielectric spectroscopy, and thermally stimulated current measurements. The effect of nano fillers on the dielectric properties was evaluated via the interfacial polarization as well as the electrical conduction mechanism study. The electrical conduction of polyimide nanocomposites is found to be thermally assisted ionic in nature. The

Yang Cao; Patricia C Irwin

2003-01-01

56

Electrical conductivity imaging by magnetic resonance electrical impedance tomography (MREIT).  

PubMed

Magnetic resonance electrical impedance tomography (MREIT) is a recently developed imaging technique that combines MRI and electrical impedance tomography (EIT). In MREIT, cross-sectional electrical conductivity images are reconstructed from the internal magnetic field density data produced inside an electrically conducting subject when an electrical current is injected into the subject. In this work the results of an electrical conductivity imaging experiment are presented, along with some practical considerations regarding MREIT. The MREIT experiment was performed with a 0.3 Tesla MRI system on a phantom made of two compartments with different electrical conductivities. The current density inside the phantom was measured by the MR current density imaging (MRCDI) technique. The measured current density was then used for conductivity image reconstruction by the J-substitution algorithm. The conductivity phantom images obtained with an injection current of 28mA showed conductivity errors of about 25.5%. PMID:14523975

Oh, Suk H; Han, Jae Y; Lee, Soo Y; Cho, Min H; Lee, Byung I; Woo, Eung J

2003-10-01

57

Electrically conductive glass fibre reinforced epoxy resin  

Microsoft Academic Search

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

M. Kupke; Hans-Peter Wentzel; Karl Schulte

1998-01-01

58

Electrical conduction in fluoropolymer films  

Microsoft Academic Search

Isothermal charging, discharging and transport currents in fluoropolymer films are measured in the temperature range of 50 to 200°C at electric fields to 40 MV\\/m. The currents are measured as a function of time elapsed after the application of steady state voltages in the range of 1 to 104 s. Charging currents increase with time to 103 s, depending upon

Z. Leo Wu; G. R. Govinda Raju

1995-01-01

59

High Temperature Electrical Conductivity of Aluminum Nitride.  

National Technical Information Service (NTIS)

The electrical conductivity of high purity (99.8 pct) AlN has been determined using both a-c and d-c techniques. Measurements were made at temperatures between 700 and 1000 C and in a nitrogen pressure range of 1 to .001 atm. The electrical conductivity i...

R. W. Francis W. L. Worrell

1975-01-01

60

Qualification of black electrically conductive paint  

NASA Technical Reports Server (NTRS)

A paint having low electrical resistance has been developed. Using a low outgassing polyurethane resin, specific amounts of conductive carbon particles were added to produce paint compositions having a range of electrical resistance. Methods of testing for electrical resistance are discussed. The adhesion of these paints has been tested successfully over the temperature range from liquid nitrogen temperature up to 80 C (176 F).

Park, J. J.; Clatterbuck, C. H.

1979-01-01

61

Electrical conduction models for isotropically conductive adhesive joints  

Microsoft Academic Search

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

Li Li; James E. Morris

1997-01-01

62

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

63

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

64

Sprayable Electrically Conductive Polymer Concrete Coatings.  

National Technical Information Service (NTIS)

A sprayable electrically conductive polymer concrete coating for vertical and overhead applications has been developed. The technology, in conjunction with impressed current cathodic protection, can be used to prevent corrosion of the embedded reinforcing...

J. J. Fontana W. Reams D. Elling

1985-01-01

65

Electrically Conductive Containment Vessel for Molten Aluminum.  

National Technical Information Service (NTIS)

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 nonreac...

C. E. Holcombe D. G. Scott

1984-01-01

66

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

67

Electrically Conductive White Thermal-Control Paint  

NASA Technical Reports Server (NTRS)

Report describes development of white thermal-control paint intended for use on spacecraft. Paint required to exhibit combination of high emittance (equal to or greater than 0.90), low absorptance (equal to or less than 0.20), and electrical conductivity sufficient to prevent charging with static electricity to potentials beyond range of plus or minus 10 V.

Hsieh, Cheng-Hsien; Forsberg, Gustaf A.; O'Donnell, Timothy P.

1995-01-01

68

Electrical conductivity of nickel nanostrand polymer composites  

NASA Astrophysics Data System (ADS)

The electrical conductivity properties of nickel nanostrands in polymer composite systems are investigated and characterized. Recently developed nickel nanostrands feature a three-dimensionally interconnecting and branching nanostructure that is shown to be highly effective at imparting electrical conductivity in polymer composites. A systematic investigation of material behaviors is undertaken, with results that have been or will be published in a series of journal articles. The content of the studies that form these articles is given herein as the core content of this work. The first study investigates the basic electrical and mechanical properties of nanostrands in a single polymer system. Key results indicate a strong dependence of conductivity properties on processing conditions, volume fraction of conductor, and sample geometry. Mechanical properties are not significantly altered by the presence of nanostrands. The dispersed nanostrand structure is next investigated through the development of statistical topology tools that can quantify nanostrand dispersions and correlate them to the electrical resistivity of composite films. Quantification of the dispersed nanostructure is a significant improvement over common literature approaches. The next step tests full percolation characterization across multiple polymer systems, and indicates a strong dependence on electrical resistivity between polymer types. Polymer constituent properties are found to be poor predictors of nanostrand composites conductivities, though further testing of addition metrics is expected to bring improved correlation. The concluding investigation seeks electrical conductivity percolation models for nanostrand composites. Existing models show only moderate accuracy, and a newly developed combined percolation tunneling approached is suggested for improved fit to measured conductivity.

Hansen, Nathan D.

69

Electrical conductivities of deep mantle materials  

NASA Astrophysics Data System (ADS)

The electrical conductivity is one of key physical properties of the Earth’s mantle. Joint analyses with the geomagnetic observations and laboratory-based electrical conductivity models provide us more constraints on the propagation of the geomagnetic signals to the Earth’s surface, the nature of the core-mantle coupling, the subtle chemistry and temperature of the deep Earth. In spite of its importance, the measurements on electrical conductivities of lower mantle materials have been mainly performed at relatively lower pressures below 40 GPa (e.g., Shankland et al., 1993). Although recently discovered iron spin transition and post-perovskite phase transition may have significant effect on the electrical conductivity of lower mantle, it has not been investigated. Relation between electrical property and crystal structure in FeO at high pressure and temperature conditions is also still unknown (e.g., Knittle and Jeanloz, 1986). We performed the electrical conductivity measurements on the deep mantle materials at in-situ high pressures and temperatures in a laser-heated diamond anvil cell. We examined the effect of iron spin transition both in perovskite and ferropericlase and post-perovskite phase transition on the electrical conductivity. High-pressure metallization in FeO was also investigated. In addition, electrical conductivities of natural pyrolitic mantle and MORB materials were measured at high pressure and temperature covering the entire lower mantle conditions. It was found in this study that iron spin transition in both ferropericlase and perovskite significantly diminished its electrical conductivity (Ohta et al., 2007, 2008, 2010a), while post-perovskite phase transition increased the electrical conductivity by several orders of magnitude (Ohta et al., 2008). Measured conductivity of normal NiAs-type FeO showed metallic behavior, which was contradictory to those of B1 and rB1 phases. In contrast to the previous laboratory-based models, our data demonstrate that the conductivity of pyrolite does not increase monotonically but varies dramatically with depth in the lower mantle (Ohta et al., 2010b). These new findings surely have important implications for the chemistry and dynamics of deep mantle and core.

Ohta, K.; Hirose, K.; Shimizu, K.; Ohishi, Y.

2010-12-01

70

Continuously variable transmission: Assessment of applicability to advance electric vehicles  

NASA Technical Reports Server (NTRS)

A brief historical account of the evolution of continuously variable transmissions (CVT) for automotive use is given. The CVT concepts which are potentially suitable for application with electric and hybrid vehicles are discussed. The arrangement and function of several CVT concepts are cited along with their current developmental status. The results of preliminary design studies conducted on four CVT concepts for use in advanced electric vehicles are discussed.

Loewenthal, S. H.; Parker, R. J.

1981-01-01

71

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

72

Balloon observations of stratospheric electricity above the South Pole - Vertical electric field, conductivity, and conduction current  

Microsoft Academic Search

Results are summarized of measurements of the electrical conductivity and vertical component of the vector electric field acquired from eight stratospheric balloon flights launched from the South Pole in the austral summer of 1985-1986. The data are a contribution to the set of global atmospheric electricity measurements and extend the work of Cobb (1977) to determine the electrical environment of

G. J. Byrne; J. R. Benbrook; E. A. Bering

1991-01-01

73

Electrical conductivity of hot QCD matter.  

PubMed

We study the electric conductivity of hot QCD matter at various temperatures T within the off-shell parton-hadron-string dynamics transport approach for interacting partonic, hadronic or mixed systems in a finite box with periodic boundary conditions. The response of the strongly interacting system in equilibrium to an external electric field defines the electric conductivity ?(0). We find a sizable temperature dependence of the ratio ?(0)/T well in line with calculations in a relaxation time approach for T(c)electric conductor than Cu or Ag (at room temperature). PMID:23683192

Cassing, W; Linnyk, O; Steinert, T; Ozvenchuk, V

2013-05-01

74

Advanced continuously variable transmissions for electric and hybrid vehicles  

NASA Technical Reports Server (NTRS)

A brief survey of past and present continuously variable transmissions (CVT) which are potentially suitable for application with electric and hybrid vehicles is presented. Discussion of general transmission requirements and benefits attainable with a CVT for electric vehicle use is given. The arrangement and function of several specific CVT concepts are cited along with their current development status. Lastly, the results of preliminary design studies conducted under a NASA contract for DOE on four CVT concepts for use in advanced electric vehicles are reviewed.

Loewenthal, S. H.

1980-01-01

75

Airborne measurements of atmospheric electrical conductivities  

NASA Astrophysics Data System (ADS)

Atmospheric electrical polar conductivities were measured using a Gerdien condenser mounted on an aircraft. These surveys, conducted over the western coast of South India, have detected enhanced conductivities associated with the placer deposits of the radioactive mineral monazite found in this region. The data reflect the variation in the level of surface radioactivity along the flight routes. In one flight that rose over the sea up to 1 km, the effect of radioactivity was seen to extend up to this point. Over land the influence of the surface radioactivity on electrical conductivity is mostly confined to the region of occurrence of the deposits. These studies also suggest the possibility of employing the Gerdien condenser in preliminary surveys to detect the presence of radioactivity.

Sampath, S.; Sasi Kumar, V.; Murali Das, S.

1994-12-01

76

The electrical conductivity of the moon  

NASA Astrophysics Data System (ADS)

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

Vanyan, L. L.

1980-09-01

77

Electric conductivity and bootstrap current in tokamak.  

National Technical Information Service (NTIS)

A modified Ohm's law for the electric conductivity calculation is presented, where the modified ohmic current can be compensated by the bootstrap current. A comparison of TEXT tokamak experiment with the theories shows that the modified Ohm's law is a mor...

Mao Jianshan Wang Maoquan

1996-01-01

78

Calculation of electric fields in conductive media  

SciTech Connect

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

Doss, J.D.

1982-07-01

79

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

80

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

81

Ionization and electrical conductivity of dense carbon  

NASA Astrophysics Data System (ADS)

The electrical conductivity of a dense carbon plasma has been calculated by using a linear mixture rule considering various interactions among electrons, atoms, and ions in the density and temperature ranges of 10-5 - 10 g cm-3 and 104 - 105 K, respectively. The non-ideal Saha equation is used to obtain the plasma composition and the degree of ionization successfully. The present calculation spans from the weakly coupled, nondegenerate region to the strong coupled, degenerate domain. The calculated conductivity is in reasonable agreement with the explosive wire measurement and the quantum kinetic calculation. A nonmetal-metal transition is predicted to occur at 0.56 g cm-3 at temperatures lower than 3 × 104 K based on the calculation of the electrical conductivity.

Fu, Zhijian; Sun, Xiaowei; Quan, Weilong

2013-02-01

82

DC electrical conductivity study of cerium doped conducting glass systems  

NASA Astrophysics Data System (ADS)

The glass samples of composition 60V2O5-5P2O5-(35-x)B2O3-xCeO2, (1 <= x <= 5) were prepared by the conventional melt quench method. The samples were characterized by X-ray diffraction and thermo gravimetric-differential thermal analysis. The glass transition temperature and crystallization temperature determined from TG-DTA analysis. The DC electrical conductivity has been carried out in the temperature range 303-473 K. The maximum conductivity and minimum activation energy were found to be 0.039 Scm-1 and 0.15 eV at 473 K for x=1, respectively.

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

2013-06-01

83

Electrical Conductance and Reversible Conductance Switching in Molecular Junctions  

NASA Astrophysics Data System (ADS)

A technology is demonstrated to fabricate reliable molecular metal-molecule-metal junctions with unprecedented device diameters up to 100 ?m. The yield of these molecular junctions is close to unity. Stability investigations have shown a shelf life of years and no deterioration upon cycling. Key ingredients are the use of a conducting polymer layer (PEDOT:PSS) sandwiched between the self-assembled monolayer (SAM) and the top electrode to prevent electrical shorts, and processing in lithographically defined vertical interconnects (vias) to prevent both parasitic currents and interaction between the environment and the SAM [1--3]. Furthermore, a fully functional solid-state molecular electronic switch is manufactured by conventional processing techniques. The molecular switch is based on a monolayer of photochromic diarylethene molecules sandwiched between two electrodes. The monolayer reversibly switches the conductance by more than one order of magnitude between the two conductance states via optical addressing. This bidirectional conductance switch operates as an electronic ON/OFF switch and as a reprogrammable data storage unit that can be optically written and electronically read [4]. [4pt] [1] Nature, 441, 69--72 (2006). [0pt] [2] Proc. Natl Acad. Sci USA, 104, 11161-11167 (2007). [0pt] [3] Nature Nanotechn., 3, December issue (2008) [0pt] [4] Adv. Mater. 20, 1467--1473.

de Boer, Bert

2009-03-01

84

Electrical conductivity of metal powders under pressure  

NASA Astrophysics Data System (ADS)

A model for calculating the electrical conductivity of a compressed powder mass consisting of oxide-coated metal particles has been derived. A theoretical tool previously developed by the authors, the so-called `equivalent simple cubic system', was used in the model deduction. This tool is based on relating the actual powder system to an equivalent one consisting of deforming spheres packed in a simple cubic lattice, which is much easier to examine. The proposed model relates the effective electrical conductivity of the powder mass under compression to its level of porosity. Other physically measurable parameters in the model are the conductivities of the metal and oxide constituting the powder particles, their radii, the mean thickness of the oxide layer and the tap porosity of the powder. Two additional parameters controlling the effect of the descaling of the particle oxide layer were empirically introduced. The proposed model was experimentally verified by measurements of the electrical conductivity of aluminium, bronze, iron, nickel and titanium powders under pressure. The consistency between theoretical predictions and experimental results was reasonably good in all cases.

Montes, J. M.; Cuevas, F. G.; Cintas, J.; Urban, P.

2011-12-01

85

Electrical conductivity of acidic sulfate solution  

NASA Astrophysics Data System (ADS)

The electrical conductivities of the aqueous solution system of H2SO4-MSO4 (involving ZnSO4, MgSO4, Na2SO4, and (NH4)2SO4), reported by Tozawa et al., were examined in terms of a (H2O) and H+ ion concentration. The equations to compute the concentrations of various species in aqueous sulfuric acid solutions containing metal sulfates were derived for a typical example of the H2SO4-ZnSO4-MgSO4-(Na2SO4)-H2O system. It was found that the H+ ion concentrations in concentrated sulfuric acid solutions corresponding to practical zinc electrowinning solutions are very high and remain almost constant with or without the addition of metal sulfates. The addition of metal sulfates to aqueous sulfuric acid solution causes a decrease in electrical conductivity, and this phenomenon is attributed to a decrease in water activity, which reflects a decrease in the amount of free water. The relationship between conductivity and water activity at a constant H+ ion concentration is independent of the kind of sulfates added. On the other hand, any increase in H+ ion concentration results in an increase in electrical conductivity. A novel method for the prediction of electrical conductivity of acidic sulfate solution is proposed that uses the calculated data of water activity and the calculated H+ ion concentration. Also, the authors examined an extension of the Robinson-Bower equation to calculate water activity in quarternary solutions based on molarity instead of molality, and found that such calculated values are in satisfactory agreement with those determined experimentally by a transpiration method.

Majima, Hiroshi; Peters, Ernest; Awakura, Yasuhiro; Park, Sung Kook

1987-03-01

86

The electrical conductivity of sodium polysulfide melts  

SciTech Connect

The electrical conductivities of sodium polysulfide melts, Na{sub 2}S{sub 4} and Na{sub 2}S{sub 5}, were measured as a function of temperature between 300 and 360 C. Due to the viscous nature of the sodium polysulfide melts, the conductance cells are axisymmetric cylindrical cells with a microelectrode, instead of capillary cells. The values of the Arrhenius activation energy derived from the experimental conductivity data are about 33 kJ/mol. The macroscopic model of sodium polysulfide melts has described the melts as composed of sodium cations, monosulfide anions, and neutral sulfur solvent. For this model, the binary interaction coefficients quantifying the interaction between sodium cations and monosulfide anions were calculated from the experimental conductivity data and literature data for the transference number, diffusion coefficient, activity coefficient, and density.

Wang, M.H.; Newman, J. [Lawrence Berkeley Lab., CA (United States). Energy and Environment Division]|[Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering

1995-03-01

87

Electric conductance of highly selective nanochannels  

NASA Astrophysics Data System (ADS)

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

Schnitzer, Ory; Yariv, Ehud

2013-05-01

88

Electrically conductive palladium containing polyimide films  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

89

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

90

Electrical conductivity of Co doped cuprous oxide  

Microsoft Academic Search

The solubility limit of metals in cuprous oxide is very low and it is therefore difficult to form solid solutions of metal\\u000a oxides with cuprous oxide. In an on going research looking for such solid solutions and their properties we have prepared\\u000a Co doped Cu2O. We report here on measurements of the electrical conductivity of Co doped Cu2O as a

Y. Tsur; I. Riess

1995-01-01

91

Damage Detection in Electrically Conductive Structures  

NASA Astrophysics Data System (ADS)

High-technology systems are in need of structures that perform with increased functionality and a reduction in weight, while simultaneously maintaining a high level of performance and reliability. To accomplish this, structural elements must be designed more efficiently and with increased functionality, thereby creating multifunctional structures (MFS). Through the addition of carbon fibers, nanotubes, or particles, composite structures can be made electrically conductive while simultaneously increasing their strength and stiffness to weight ratios. Using the electrical properties of these structures for the purpose of damage detection and location for health and usage monitoring is of particular interest for aerospace structures. One such method for doing this is Electrical Impedance Tomography (EIT). With EIT, an electric current is applied through a pair of electrodes and the electric potential is recorded at other monitoring electrodes around the area of study. An inverse solution of the governing Maxwell equations is then required to determine the conductivities of discrete areas within the region of interest. However, this method is nearly ill-posed and computationally intensive as it focuses on imaging small changes in conductivity within the region of interest. For locating damage in a medium with an otherwise homogeneous conductivity, an alternative approach is to search for parameters such as the damage location and size. Towards those ends, this study develops an Artificial Neural Network (ANN) to determine the state of an electrically conductive region based on applied reference current and electrical potentials at electrodes around the periphery of the region. A significant benefit of the ANN approach is that once trained, the solution of an inverse problem does not require costly computations of the inverse problem. This method also takes advantage of the pattern recognition abilities of neural networks and is a robust solution method in the presence of signal noise. The network is based on a two-tier approach where the coarse location of the damage is first located within given regions using a Learning Vector Quantization (LVQ) network. Once the approximate location is known, the second step is to apply a more refined feed-forward back-propagation (FFBP) ANN that utilizes the current and electric potential electrodes that focus on that region. In this manner, the resolution of the prediction scheme is increased. To train both the LVQ and FFBP networks, instead of time consuming and perhaps for large space structures, unfeasible experiments, a computational model is developed. The training function for the ANN is based on a finite element solution of the region and the applied boundary conditions. The inputs to the network are thus the location of the current electrodes and the corresponding electric potential values around the periphery and the network targets are the damage location and size. Future work will focus on the further development of the two-tier ANN, extension of the scheme for plural defects, and on the experimental validation of the computational training model for materials with isotropic and anisotropic conductivity.

Anderson, Todd A.

2002-12-01

92

The electrical conductivity of sodium polysulfide melts  

SciTech Connect

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

Meihui Wang.

1992-06-01

93

Electrical Noise in Individual Conducting Polymer Nanowires  

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

94

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

95

Electric conductivity of hafnium-containing fluoride-chloride melts  

SciTech Connect

This paper presents the results of an investigation of the specific electric conductivity of melts of the potassium, hafnium-containing fluoride-chloride ternary reciprocal system which is of practical interest because fluoride-chloride melts containing hafnium can be used as electrolytes in the preparation of metallic hafnium. Experimental results depend largely on the purity of the salts that are used, so much attention was paid to problems of preparation and storage of the pure anhydrous salts. To obtain potassium fluorides, the authors used cp KF.2H/sub 2/O which was dried and then melted with continuous vacuum treatment. The specific electric conductivity was measured by a relative capillary method at a frequency of 50 kHz with an R-568 alternatingcurrent bridge. The lines of equal specific electric conductivity of the melts investigated at 1000/sup 0/C show that the conductivity of the melts was determined mainly by the hafnium tetrafluoride content, namely, the increase of its concentration in the melt caused a decrease of the electric-conductivity values.

Darienko, S.E.; Chervinskii, Yu.F.; Katyshev, S.F.; Nichkov, I.F.

1985-08-01

96

Finite Element Model of Cardiac Electrical Conduction.  

NASA Astrophysics Data System (ADS)

In this thesis, we develop mathematical models to study electrical conduction of the heart. One important pattern of wave propagation of electrical excitation in the heart is reentry which is believed to be the underlying mechanism of some dangerous cardiac arhythmias such as ventricular tachycardia and ventricular fibrillation. We present in this thesis a new ionic channel model of the ventricular cardiac cell membrane to study the microscopic electrical properties of myocardium. We base our model on recent single channel experiment data and a simple physical diffusion model of the calcium channel. Our ionic channel model of myocardium has simpler differential equations and fewer parameters than previous models. Further more, our ionic channel model achieves better results in simulating the strength-interval curve when we connect the membrane patch model to form a one dimensional cardiac muscle strand. We go on to study a finite element model which uses multiple states and non-nearest neighbor interactions to include curvature and dispersion effects. We create a generalized lattice randomization to overcome the artifacts generated by the interaction between the local dynamics and the regularities of the square lattice. We show that the homogeneous model does not display spontaneous wavefront breakup in a reentrant wave propagation once the lattice artifacts have been smoothed out by lattice randomization with a randomization scale larger than the characteristic length of the interaction. We further develop a finite 3-D 3-state heart model which employs a probability interaction rule. This model is applied to the simulation of Body Surface Laplacian Mapping (BSLM) using a cylindrical volume conductor as the torso model. We show that BSLM has a higher spatial resolution than conventional mapping methods in revealing the underlying electrical activities of the heart. The results of these studies demonstrate that mathematical modeling and computer simulation are very useful tools to study the electrical conduction of the heart. Our new ionic channel model can be used in future higher dimensional model study of cardiac electrical conduction. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-5668; Fax 617-253-1690.).

Yin, John Zhihao

1994-01-01

97

[The electrical conductivity of triggered lightning channel].  

PubMed

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

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

2007-10-01

98

Numerical recovery of certain discontinuous electrical conductivities  

NASA Technical Reports Server (NTRS)

The inverse problem of recovering an electrical conductivity of the form Gamma(x) = 1 + (k-1)(sub Chi(D)) (Chi(D) is the characteristic function of D) on a region omega is a subset of 2-dimensional Euclid space from boundary data is considered, where D is a subset of omega and k is some positive constant. A linearization of the forward problem is formed and used in a least squares output method for approximately solving the inverse problem. Convergence results are proved and some numerical results presented.

Bryan, Kurt

1991-01-01

99

Electrically-conducting thermal-control coating  

NASA Technical Reports Server (NTRS)

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

Shai, M. C.

1978-01-01

100

Electrically conductive polyurethanes for biomedical applications  

NASA Astrophysics Data System (ADS)

Electrical interfacing with neural tissue poses significant problems due to host response to the material. This response generally leads to fibrous encapsulation and increased impedance across the electrode. In neural electrodes such as cochlear implants, an elastomeric material like silicone is used as an insulator for the metal electrode. This project ultimately aims to produce a polymer electrode with elastomeric mechanical properties, metal like conductivity and capability. The approach taken was to produce a nanocomposite elastomeric material based on polyurethane (PU) and carbon nanotubes. Carbon nanotubes are ideal due to their high aspect ratio as well as being a ballistic conductor. The choice of PU is based on its elastomeric properties, processability and biocompatibility. Multi-walled nanotubes (MWNTs) were dispersed ultrasonically in various dispersive solutions before being added at up to 20wt% to a 5wt% PU (Pellethane80A) in Dimethylacetamide (DMAc). Films were then solvent cast in a vacuum oven overnight. The resulting films were tested for conductivity using a two-probe technique and mechanically tested using an Instron tensiometer. The percolation threshold (p) of the PU/MWNT films occurred at loadings of between 7 and 10 wt% in this polymer system. Conductivity of the films (above p) was comparable to those for similar systems reported in the literature at up to approximately 7x10-2 Scm-1. Although PU stiffness increased with increased %loading of nanotubes, all composites were highly flexible and maintained elastomeric properties. From these preliminary results we have demonstrated electrical conductivity. So far it is evident that a superior percolation threshold is dependent on the degree of dispersion of the nanotubes. This has prompted work into investigating other preparations of the films, including melt-processing and electrospinning.

Williams, Charles M.; Nash, M. A.; Poole-Warren, Laura A.

2005-02-01

101

Local Electrical Conductivity of Multiferroic Domain Walls  

NASA Astrophysics Data System (ADS)

There is an intense interest in magnetoelectric coupling between electric and magnetic due to its potential to the revolutionary of device architectures. Single-phase multiferroics - materials that show spontaneous magnetization and polarization simultaneously at ambient conditions remain elusive as most systems (such as the manganites) exhibit multiferroicity only at low temperatures. Alternatively, multiferroics can be synthesized as a composite system, e.g. as a product property of a composite phase consisting of a magnetostrictive and a piezoelectric material. One multiferroic material, however, has played a key role in rejuvenating the field after a report of large ferroelectric polarization combined with interesting magnetic properties - BiFeO3. Here we provide evidence of a unique property of single domain walls in multiferroic BiFeO3. Unlike other multiferroic materials, e.g. PbTiO3, on which the electronic properties of the domain walls are not significantly different from the domain area, we observe a finite electric conductivity at room temperature along such a wall using conductive atomic force microscopy. This intrinsic property of the domain wall is attributed to a changed crystallographic structure as revealed by high resolution transmission electron microscopy. Additionally, optical absorption measurements confirm a change in bandstructure at domain walls in BiFeO3.

He, Qing; Seidel, Jan; Martin, Lane; Chu, Ying-Hao; Zhan, Qian; Wang, Feng; Ramesh, Ramamoorthy

2008-03-01

102

Induction heating of electrically conductive porous asphalt concrete  

Microsoft Academic Search

In this research, an electrically conductive porous asphalt concrete, used for induction heating, was prepared by adding electrically conductive filler (steel fibers and steel wool) to the mixture. The main purpose of this paper is to examine the electrical conductivity and the indirect tensile strength of this conductive porous asphalt concrete and prove that it can be heated via induction

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

2010-01-01

103

The deep lunar electrical conductivity profile - Structural and thermal inferences  

NASA Technical Reports Server (NTRS)

Simultaneous lunar surface and orbital magnetometer records are reexamined, to ascertain intervals which may be suitable for measuring lunar inductive response in the solar wind and terrestrial magnetosheath. Power spectral estimates of the response tangent to the lunar surface, defined in terms of transfer and gain functions, are obtained for the 0.0001-0.01 Hz frequency range. The maximum consistency of estimates from different time intervals is found when the initial analysis is limited to the tangential direction of maximum incident power, or that direction in which the ratio of signal to background noise is greatest. Spherically symmetric plasma confinement theory is used in the interpretation of transfer function data, by way of forward model calculations, under the assumption of continuous electrical conductivity increase with depth. Results are presented for internal electrical conductivity profile, metallic core radius, and selenotherm limits.

Hood, L. L.; Herbert, F.; Sonett, C. P.

1982-01-01

104

System for Measuring the Local Electrical Conductivity of Plasma.  

National Technical Information Service (NTIS)

The system for measuring the local electrical conductivity of the plasma of products of combustion (SILYeP) is intended for investigation of the distribution of electrical conductivity of the ionized gas flows (plasma) and the determination of the electri...

N. A. Balashov I. M. Gaponov G. P. Malyuzhonok Y. S. Mikhailov F. M. Oberman

1975-01-01

105

Electrical Conductance of Liquid Propellants: Theory and Results.  

National Technical Information Service (NTIS)

An overview of the development of the theory of electrical conductance of electrolytes is presented. Conditions where ion-pairing can occur is emphasized. Electrical conductance versus both concentration and temperature is reported for aqueous hydroxylamm...

J. A. Vanderhoff P. M. Donmoyer S. W. Bunte

1986-01-01

106

Levitation characteristics of magnetically suspended vehicles utilizing continuous conductive sheets  

Microsoft Academic Search

In a magnetically levitated railway system with superconducting vehicular magnetic coil, short-circuiting ground coil, and a loop-type track, the magnetic field produced by ground coils is not uniform and therefore the lift force fluctuates as the train moves and the magnetic flux of the superconducting magnet fluctuates with time. The sheet-type track consists of continuous conductive sheets of aluminum or

Takao Takahashi

1976-01-01

107

Electrical conductivity of thermally hydrogenated nanodiamond powders  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

108

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

109

Chapter A6. Section 6.3. Specific Electrical Conductance  

USGS Publications Warehouse

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

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

2005-01-01

110

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

111

Continuous polyelectrolyte adsorption under an applied electric potential  

PubMed Central

Interactions between charged macromolecules (e.g., proteins, nucleic acids, polyelectrolytes) and charged surfaces govern many natural and industrial processes. We investigate here the influence of an applied electric potential on the adsorption of charged polymers, and report the following significant result: the adsorption of certain amine side chain-containing polycations may become continuous, i.e., asymptotically linear (or nearly linear) in time over hours, upon the application of a modest anodic potential. Employing optical waveguide lightmode spectroscopy (OWLS) and an indium tin oxide (ITO) substrate, we show that asymptotic kinetics, and the adsorbed mass at the onset of the asymptotic regime, depend sensitively on polymer chemistry (in particular, side chain volume and charge location), increase with applied potential and ionic strength (conditions favoring a thicker initial layer), and are independent of bulk polymer concentration (suggesting postadsorption events to be rate limiting). X-ray photoelectron spectra reveal a suppressed polymer charge within layers formed via continuous adsorption, but no evidence of electrochemical reactions. We propose a mechanism based on polymer–polymer binding within the adsorbed layer, enabled by suppressed electrostatic repulsion and/or enhanced ionic correlations near the conducting surface, and stabilized by short-range attractive interactions. Continuous adsorption under an applied electric potential offers the possibility of nanoscale films of tailored polymer content realized in a single step.

Ngankam, A. Pascal; Van Tassel, Paul R.

2007-01-01

112

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

113

Magnetic flowmeter for electrically conductive liquid  

DOEpatents

A magnetic flowmeter includes first and second tube sections each having walls 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. Two magnets are provided in matched pairs spaced 180/sup 0/ 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, S.B.; Raue, D.J.

1980-08-18

114

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

115

Electric Field in Materials, Containing Conductive Nanofibers  

Microsoft Academic Search

Concentrated electric field and its energy in materials, containing nanofibers, are discussed. It is shown that the electric field in the vicinity of the end of a fiber is proportional to the external applied field and to the fiber length, whilst it is inversely proportional to the fiber diameter. Specific electrostatic energy of a fiber in a sample under the

Yuri Kornyushin

2010-01-01

116

Spin state dependence of electrical conductivity of spin crossover materials.  

PubMed

We studied the spin state dependence of the electrical conductivity of the spin crossover compound [Fe(Htrz)(2)(trz)](BF(4)) (Htrz = 1H-1,2,4-triazole) by means of dc electrical measurements. The low spin state is characterized by higher conductance and lower thermal activation energy of the conductivity, when compared to the high spin state. PMID:22466531

Rotaru, Aurelian; Gural'skiy, Il'ya A; Molnár, Gábor; Salmon, Lionel; Demont, Philippe; Bousseksou, Azzedine

2012-05-01

117

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

118

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.

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

2012-01-01

119

Electrical conductivity of nitride carbon films with different nitrogen content  

NASA Astrophysics Data System (ADS)

The electrical conductivity of nitride carbon (DLC: N) films has been studied. It is found that the electrical conductivity of the deposited films increases slowly with increasing nitrogen content, however, it decreases after the nitrogen content in the film reaches a certain value of 12.8 at%. Thermal treatment results show that the electrical conductivity of the lowly nitrogen doped DLC film increases rapidly, while that of the heavily doped film decreases after annealing at 300 °C for 30 min. Raman and XPS spectra results show that when the nitrogen content in the films reaches a certain value, there appears nonconductive phases. Therefore the electrical conductivity of the heavily doped films decreases. FTIR spectra analysis results show that the nitrogen atom as an impurity center undergoes an 'activation' process during the thermal treatment, which leads to the increase of the electrical conductivity. Therefore, the nitrogen in these two kinds of films has different effects on the electrical conductivity.

Zhang, Weili; Xia, Yiben; Ju, Jianhua; Wang, Linjun; Fang, Zhijun; Zhang, Minglong

2003-04-01

120

Gas-Tolerant Device Senses Electrical Conductivity of Liquid  

NASA Technical Reports Server (NTRS)

The figure depicts a device for measuring the electrical conductivity of a flowing liquid. Unlike prior such devices, this one does not trap gas bubbles entrained in the liquid. Usually, the electrical conductivity of a liquid is measured by use of two electrodes immersed in the liquid. A typical prior device based on this concept contains large cavities that can trap gas. Any gas present between or near the electrodes causes a significant offset in the conductivity reading and, if the gas becomes trapped, then the offset persists. Extensive tests on two-phase (liquid/ gas) flow have shown that in the case of liquid flowing along a section of tubing, gas entrained in the liquid is not trapped in the section as long as the inner wall of the section is smooth and continuous, and the section is the narrowest tubing section along the flow path. The design of the device is based on the foregoing observation: The electrodes and the insulators separating the electrodes constitute adjacent parts of the walls of a tube. The bore of the tube is machined to make the wall smooth and to provide a straight flow path from the inlet to the outlet. The diameter of the electrode/insulator tube assembly is less than the diameter of the inlet or outlet tubing. An outer shell contains the electrodes and insulators and constitutes a leak and pressure barrier. Any gas bubble flowing through this device causes only a momentary conductivity offset that is filtered out by software used to process the conductivity readings.

O'Connor, Edward W.

2005-01-01

121

Method of forming an electrically conductive cellulose composite  

DOEpatents

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

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

2011-11-22

122

Electrical conductivity and Paleo-Proterozoic foredeeps  

NASA Astrophysics Data System (ADS)

Sedimentary facies associated with Paleo-Proterozoic foredeeps are apparently highly conductive. The conductive lithology appears to be a euxinic carbonaceous shale deposited on preforedeep continental margin facies. The shale is overlaid by axial turbidites and often incorporated into the succeeding fold and thrust belt. Carbonaceous shales can be made highly conducting if graphitized by exposure to temperatures exceeding 400°C. Although foredeep facies develop diachronously, the most conductive unit is usually found in the core of the fold and thrust belt, suggesting that deformation may be essential for the complete graphitization of the carbon. The foredeep hypothesis offers an attractive explanation for several highly conductive features detected in the upper and middle crust in Laurentia, and possibly throughout the world. The euxinic facies represent highly specific, tectonic marker horizons that are readily delineated by using electromagnetic methods.

Boerner, D. E.; Kurtz, R. D.; Craven, J. A.

1996-06-01

123

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

124

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

125

Local Electrical Conductivity of Multiferroic Domain Walls  

Microsoft Academic Search

There is an intense interest in magnetoelectric coupling between electric and magnetic due to its potential to the revolutionary of device architectures. Single-phase multiferroics - materials that show spontaneous magnetization and polarization simultaneously at ambient conditions remain elusive as most systems (such as the manganites) exhibit multiferroicity only at low temperatures. Alternatively, multiferroics can be synthesized as a composite system,

Qing He; Jan Seidel; Ying-Hao Chu; Qian Zhan; Feng Wang; Ramamoorthy Ramesh

2008-01-01

126

Electrical conductivity measurements from the STRATCOM 8 experiment  

NASA Technical Reports Server (NTRS)

A blunt probe experiment for measuring electrical conductivity was flown with the STRATCOM 8 instrument package. Data were obtained by the instrument throughout the entire measurement period. A preliminary analysis of the data indicates an enhancement in conductivity associated with the krypton discharge ionization lamp, particularly in negative conductivity. The conductivity values and their altitude dependence are consistent with previous balloon and rocket results.

Mitchell, J. D.; Ho, K. J.; Half, L. C.; Croskey, C. L.; Olsen, R. O.

1978-01-01

127

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

NASA Technical Reports Server (NTRS)

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

Zimmer, Hans

1993-01-01

128

Continuously Variable Transmission: Assessment of Applicability to Advance Electric Vehicles.  

National Technical Information Service (NTIS)

A brief historical account of the evolution of continuously variable transmissions (CVT) for automotive use is given. The CVT concepts which are potentially suitable for application with electric and hybrid vehicles are discussed. The arrangement and func...

R. J. Parker S. H. Loewenthal

1981-01-01

129

Continuously Variable Transmission: Assessment of Applicability to Advanced Electric Vehicles.  

National Technical Information Service (NTIS)

A brief historical account of the evolution of continuously variable transmissions (CVT) for automotive use is given. CVT concepts which are potentially suitable for application with electric and hybrid vehicles are discussed. The arrangement and function...

S. H. Loewenthal R. J. Parker

1981-01-01

130

Advanced Continuously Variable Transmissions for Electric and Hybrid Vehicles.  

National Technical Information Service (NTIS)

A brief survey of past and present continuously variable transmissions (CVT) which are potentially suitable for application with electric and hybrid vehicles is presented. Discussion of general transmission requirements and benefits attainable with a CVT ...

S. H. Loewenthal

1980-01-01

131

Design Studies of Continuously Variable Transmissions for Electric Vehicles.  

National Technical Information Service (NTIS)

Preliminary design studies were performed on four continuously variable transmission (CVT) concepts for use in advanced electric vehicles. A 1700 kg (3750 lb) vehicle with an energy storage flywheel was specified. Requirements of the CVTs were a maximum t...

R. J. Parker S. H. Loewenthal G. K. Fischer

1981-01-01

132

High pressure electrical conductivity studies of acid doped polybenzimidazole  

Microsoft Academic Search

Electrical conductivity studies of acid doped poplybenzimidazole (PBI) and 85% phosphoric acid have been carried out. The PBI contained about 600mol% of 85% phosphoric acid and the electrical conductivity was deduced from complex impedance studies which were made at frequencies from 10 to 107Hz. Measurements were made at pressures up to 0.25 GPa and temperatures of about 25, 50 and

J. J Fontanella; M. C Wintersgill; J. S Wainright; R. F Savinell; M Litt

1998-01-01

133

Evaluation of contact resistance for isotropic electrically conductive adhesives  

Microsoft Academic Search

Electrically conductive adhesives are discussed and studied with ever-increasing interest as an alternative to solder interconnection in microelectronics circuit packaging. A similar level of scrutiny that is used to evaluate contact resistance performance for interconnections made with solder and separable connectors is necessary for electrically conductive adhesives. Experience with solder interconnection and separable connectors shows low initial contact resistance of

Michael A. Gaynes; Russell H. Lewis; R. F. Saraf; Judith M. Roldan

1995-01-01

134

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

135

Continuous and scalable fabrication of transparent conducting carbon nanotube films.  

PubMed

We report an industrially scalable, fast, and simple process for the large scale fabrication of optically transparent and electrically conducting thin films of single-walled carbon nanotubes (SWNT). Purified, pristine HiPco SWNTs were dispersed in water at high concentrations with the help of surfactants, rod-coated into uniform thin films, and doped by various acids. We show how to combine different surfactants to make uniform dispersions with high concentration of SWNTs and optimal rheological behavior for coating and drying, including preventing dewetting and film rupture that has plagued earlier attempts. Doping by fuming sulfuric acid yielded the films with best performance (sheet resistance of 100 and 300 Omega/sq for respective transparency of 70% and 90%). We use a figure of merit (FOM) plot for an immediate evaluation and comparison of the performance and microstructure of CNT films produced by different methods. Further scientific engineering will pave the way to the deployment of CNT films in commercial applications. PMID:19354279

Dan, Budhadipta; Irvin, Glen C; Pasquali, Matteo

2009-04-28

136

Structural and Electrical Study of Conducting Polymers  

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

137

Electrically Conductive Multiphase Polymer Blend Carbon-Based Composites  

NASA Astrophysics Data System (ADS)

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

Brigandi, Paul James

138

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

139

Excitation of discrete and continuous spectrum for a surface conductivity model of graphene  

NASA Astrophysics Data System (ADS)

Excitation of the discrete (surface-wave/plasmon propagation mode) and continuous (radiation modes) spectrum by a point current source in the vicinity of graphene is examined. The graphene is represented by an infinitesimally thin, local, and isotropic two-sided conductivity surface. The dynamic electric field due to the point source is obtained by complex-plane analysis of Sommerfeld integrals, and is decomposed into physically relevant contributions. Frequencies considered are in the GHz through mid-THz range. As expected, the TM discrete surface wave (surface plasmon) can dominate the response along the graphene layer, although this depends on the source and observation point location and frequency. In particular, the TM discrete mode can provide the strongest contribution to the total electric field in the upper GHz and low THz range, where the surface conductivity is dominated by its imaginary part and the graphene acts as a reactive (inductive) sheet.

Hanson, George W.; Yakovlev, Alexander B.; Mafi, Arash

2011-12-01

140

Aircraft observations of electrical conductivity in warm clouds  

NASA Astrophysics Data System (ADS)

Aircraft observations of electrical conductivity and cloud microphsical, dynamical and other electrical parameters were made in warm stratocumulus and cumulus clouds forming during the summer monsoon seasons (June-September) of 1983 and 1985 in the Deccan Plateau region, India. A Gerdien type cylindrical condenser was used for the measurement of electrical conductivity. The variations in the electrical conductivity are observed to be closely associated with the updrafts and downdrafts in the cloud, liquid water content, cloud droplet charge and corona discharge current. The value of electrical conductivity in warm clouds is found to be in the order of 10-12 ohm-1 m-1 which is two orders higher than that observed in clear-air at cloud-base levels in some regions by other investigators. Classical static electricity concepts predict reduced conductivity values inside clouds. Cloud electrical conductivity measurements, particularly in warm clouds are few and the results are contradictory. The recently identified mechanism of vertical mixing in clouds lends support to convective charge separation mechanism with inherent larger than clear-air values for cloud electrical conductivity and therefore consistent with the measurements reported herein.

Raj, P. Ernest; Devara, P. C. S.; Selvam, A. M.; Murty, A. S. R.

1993-02-01

141

Variable anisotropic brain electrical conductivities in epileptogenic foci.  

PubMed

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

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

2010-09-01

142

Synthesis of cross-linked electrically conductive polymers  

Microsoft Academic Search

We report attempts to improve the intrinsic conductivity of electrically conductive polymers by crosslinking them with conjugated linkages, thus providing physical pathways for charge transport. Conductive polymers were crosslinked by palladium catalyzed cross-coupling reactions of the type developed by Suzuki and Stille. Crosslinked polymers included derivatives of poly(thiophene), and poly(?-thiophenediyl)benzylidene. Changes in the physical and electrical properties are reported.

K. Davidson; A. M. Ponsonby

1999-01-01

143

Calibration-Free Electrical Conductivity Measurements for Highly Conductive Slags;Metallurgical Transactions B.  

National Technical Information Service (NTIS)

This research involves the measurement of the electrical conductivity (k) for the ESR (electroslag remelting) slag (60 wt.% CaF2 - 20 wt.% CaO - 20 wt.% Al2O3) used in the decontamination of radioactive stainless steel. The electrical conductivity is meas...

Macdonald Gao Pal Van Den Avyle Melgaard

2000-01-01

144

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

145

Ultraviolet-laser-induced permanent electrical conductivity in polyimide  

Microsoft Academic Search

When polyimide (Kapton) is irradiated by a krypton fluoride (KrF) laser, an increase of the electrical conductivity of up to 16 orders of magnitude is observed. In the high conduction regime, the resistivity is about 0.1 O cm, the current voltage characteristic is ohmic and the contacts of gold and silver with the irradiated conducting polymer are also ohmic. The

T. Feurer; R. Sauerbrey; M. C. Smayling; B. J. Story

1993-01-01

146

Ultraviolet-laser-induced permanent electrical conductivity in polyimide  

Microsoft Academic Search

When polyimide (Kapton) is irradiated by a krypton fluoride (KrF) laser, an increase of the electrical conductivity of up to 16 orders of magnitude is observed. In the high conduction regime, the resistivity is about 0.1 Omega cm, the current voltage characteristic is ohmic and the contacts of gold and silver with the irradiated conducting polymer are also ohmic. The

T. Feurer; R. Sauerbrey; M. C. Smayling; B. J. Story

1993-01-01

147

Electrical Conductivity in a Mixed-Species Biofilm  

PubMed Central

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

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

2012-01-01

148

Thermal and Electrical Conductivity Probe (TECP) for Phoenix  

Microsoft Academic Search

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

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

2009-01-01

149

Electric Pulp Tester Conductance Through Various Interface Media  

Microsoft Academic Search

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

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

2006-01-01

150

Assembly for electrical conductivity measurements in the piston cylinder device  

DOEpatents

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

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

2012-06-05

151

Thermal and electrical conductivities of silver-indium-tin alloys  

NASA Astrophysics Data System (ADS)

The variations of thermal conductivity with temperature for the Ag-[x] wt% Sn-20 wt% In alloys (x=8, 15, 35, 55 and 70) were measured using a radial heat flow apparatus. From the graphs of thermal conductivity versus temperature, the thermal conductivities of solid phases at their melting temperature for the Ag-[x] wt% Sn-20 wt% In alloys (x=8, 15, 35, 55 and 70) were found to be 46.9±3.3, 53.8±3.8, 61.2±4.3, 65.1±4.6 and 68.1±4.8 W/Km, respectively. The variations of electrical conductivity of solid phases versus temperature for the same alloys were determined from the Wiedemann-Franz equation using the measured values of thermal conductivity. From the graphs of electrical conductivity versus temperature, the electrical conductivities of the solid phases at their melting temperatures for the Ag-[x] wt% Sn-20 wt% In alloys (x=8, 15, 35, 55 and 70) alloys were obtained to be 0.036, 0.043, 0.045, 0.046 and 0.053 (×108/?m), respectively. Dependencies of the thermal and electrical conductivities on the composition of Sn in the Ag-Sn-In alloys were also investigated. According to present experimental results, the thermal and electrical conductivities for the Ag-[x] wt% Sn-20 wt% In alloys linearly decrease with increasing the temperature and increase with increasing the composition of Sn.

Aksöz, Sezen; Mara?l?, Necmettin

2012-07-01

152

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

153

Conductivity  

NSDL National Science Digital Library

Students make a simple conductivity tester using a battery and light bulb. They learn the difference between conductors and insulators of electrical energy as they test a variety of materials for their ability to conduct electricity.

Integrated Teaching And Learning Program

154

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

155

Electrical conduction and breakdown properties of silicon nitride films  

Microsoft Academic Search

The electrical conduction properties of ion-plated silicon nitride films in the form of aluminium-silicon nitride-aluminium structures have been studied in the temperature range 300 K to 470 K. The results obtained in the d.c. Conduction studies have been explained on the basis of the Poole-Frenkel conduction mechanism. The a.c. conduction studies in the frequency range 500 Hz to 30 kHz

D. Mangalaraj; M. Radhakrishnan; C. Balasubramanian

1982-01-01

156

“SIGMELTS”: A web portal for electrical conductivity calculations in geosciences  

NASA Astrophysics Data System (ADS)

Electrical conductivity measurements in the laboratory are critical for interpreting geoelectric and magnetotelluric profiles of the Earth's crust and mantle. In order to facilitate access to the current database on electrical conductivity of geomaterials, we have developed a freely available web application (SIGMELTS) dedicated to the calculation of electrical properties. Based on a compilation of previous studies, SIGMELTS computes the electrical conductivity of silicate melts, carbonatites, minerals, fluids, and mantle materials as a function of different parameters, such as composition, temperature, pressure, water content, and oxygen fugacity. Calculations on two-phase mixtures are also implemented using existing mixing models for different geometries. An illustration of the use of SIGMELTS is provided, in which calculations are applied to the subduction zone-related volcanic zone in the Central Andes. Along with petrological considerations, field and laboratory electrical data allow discrimination between the different hypotheses regarding the formation and rise from depth of melts and fluids and quantification of their storage conditions.

Pommier, A.; Le-Trong, E.

2011-09-01

157

Improving electrical conductivity in polycarbonate nanocomposites using highly conductive PEDOT/PSS coated MWCNTs.  

PubMed

We describe a strategy to design highly electrically conductive polycarbonate nanocomposites by using multiwalled carbon nanotubes (MWCNTs) coated with a thin layer of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate), a conductive polymer. We found that this coating method improves the electrical properties of the nanocomposites in two ways. First, the coating becomes the main electrical conductive path. Second, the coating promotes the formation of a percolation network at a low filler concentration (0.3 wt %). To tailor the electrical properties of the conductive polymer coating, we used a polar solvent ethylene glycol, and we can tune the final properties of the nanocomposite by controlling the concentrations of the elementary constituents or the intrinsic properties of the conductive polymer coating. This very flexible technique allows for tailoring the properties of the final product. PMID:23758203

Zhou, Jian; Lubineau, Gilles

2013-07-10

158

Electrical conductivity of rocks at high pressures and temperatures  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

159

Proton Abstraction as a Route to Electrically Conductive Polymers.  

National Technical Information Service (NTIS)

Proton abstraction with strong base from relatively acidic coubly allylic and/or benzylic methylene moieties spaced along an otherwise all-conjugated polymer chain has been demonstrated as an alternate route to electrically conductive polymers. Poly(p-phe...

B. Gordon L. F. Hancock

1987-01-01

160

Electrical conductivity of rocks in the heating and cooling cycle  

Microsoft Academic Search

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

Marcela Lastovicková; F. Janák

1978-01-01

161

Corrosion-Protective Coatings from Electrically Conducting Polymers.  

National Technical Information Service (NTIS)

In a joint effort between NASA Kennedy and LANL, electrically conductive polymer coatings were developed as corrosion protective coatings for metal surfaces. At NASA Kennedy, the launch environment consist of marine, severe solar, and intermittent high ac...

K. G. Thompson C. J. Bryan B. C. Benicewicz D. A. Wrobleski

1991-01-01

162

Corrosion-protective coatings from electrically conducting polymers.  

National Technical Information Service (NTIS)

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...

K. G. Thompson C. J. Bryan B. C. Benicewicz D. A. Wrobleski

1991-01-01

163

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.

Mphale, Kgakgamatso; Heron, Mal

2008-01-01

164

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

165

Metallization and electrical conductivity of hydrogen in Jupiter  

SciTech Connect

Electrical conductivities of molecular hydrogen in Jupiter were calculated by scaling electrical conductivities measured at shock pressures in the range of 10 to 180 gigapascals (0.1 to 1.8 megabars) and temperatures to 4000 kelvin, representative of conditions inside Jupiter. Jupiter`s magnetic field is caused by convective dynamo motion of electrically conducting fluid hydrogen. The data imply that Jupiter should become metallic at 140 gigapascals in the fluid, and the electrical conductivity in the jovian molecular envelope at pressures up to metallization is about an order of magnitude larger than expected previously. The large magnetic field is produced in the molecular envelope closer to the surface than previously thought. 30 refs., 3 figs.

Nellis, W.J.; Weir, S.T.; Mitchell, A.C. [Lawrence Livermore National Laboratory, CA (United States)

1996-08-16

166

Metallization and electrical conductivity of hydrogen in Jupiter.  

PubMed

Electrical conductivities of molecular hydrogen in Jupiter were calculated by scaling electrical conductivities measured at shock pressures in the range of 10 to 180 gigapascals (0.1 to 1.8 megabars) and temperatures to 4000 kelvin, representative of conditions inside Jupiter. Jupiter's magnetic field is caused by convective dynamo motion of electrically conducting fluid hydrogen. The data imply that Jupiter should become metallic at 140 gigapascals in the fluid, and the electrical conductivity in the jovian molecular envelope at pressures up to metallization is about an order of magnitude larger than expected previously. The large magnetic field is produced in the molecular envelope closer to the surface than previously thought. PMID:8688072

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

1996-08-16

167

Electrically Conductive Resinous Bond and Method of Manufacture.  

National Technical Information Service (NTIS)

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 ...

T. M. Snowden B. J. Wells

1985-01-01

168

Electrical Circuit Analogues of Thermal Conduction and Diffusion  

ERIC Educational Resources Information Center

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

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

1978-01-01

169

Electrical Conductivities of Liquid Egg Products and Fruit Juices Exposed to High Pulsed Electric Fields  

Microsoft Academic Search

Electrical conductivity can be used to monitor important changes in a food product during pulsed electric field (PEF) processing. Electrical conductivities of selected fruit juices (namely apple, orange, and pineapple juices) and liquid egg products (namely whole egg, yolk, and egg white) were determined online during a PEF treatment. The property was measured at broad processing temperatures ranging from 5

Malek Amiali; Michael O. Ngadi; Vijaya G. S. Raghavan; D. H. Nguyen

2006-01-01

170

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

171

DC electrical conductivity of silicon carbide ceramics and composites for flow channel insert applications  

NASA Astrophysics Data System (ADS)

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

Katoh, Y.; Kondo, S.; Snead, L. L.

2009-04-01

172

Effect of volatile components on electrical conductivity of mantle materials  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

173

Estimating Soil Salinity from Saturated Soil-Paste Electrical Conductivity  

Microsoft Academic Search

A method is presented for estimating the electrical conductivity of the saturated soil-paste extract (EC,) from measurement of the electrical conductivity of the saturated soil-paste (EC,) and esti- mated saturated soil-paste water content (SP), for purposes of soil salinity appraisal. The method is suitable for both field and labo- ratory applications. Empirical relations are provided to estimate val- ues of

J. D. Rhoades; Nahid A. Manteghi; P. J. Shouse; W. J. Alves

1989-01-01

174

Manipulating connectivity and electrical conductivity in metallic nanowire networks.  

PubMed

Connectivity in metallic nanowire networks with resistive junctions is manipulated by applying an electric field to create materials with tunable electrical conductivity. In situ electron microscope and electrical measurements visualize the activation and evolution of connectivity within these networks. Modeling nanowire networks, having a distribution of junction breakdown voltages, reveals universal scaling behavior applicable to all network materials. We demonstrate how local connectivity within these networks can be programmed and discuss material and device applications. PMID:23062152

Nirmalraj, Peter N; Bellew, Allen T; Bell, Alan P; Fairfield, Jessamyn A; McCarthy, Eoin K; O'Kelly, Curtis; Pereira, Luiz F C; Sorel, Sophie; Morosan, Diana; Coleman, Jonathan N; Ferreira, Mauro S; Boland, John J

2012-11-14

175

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

176

Ultraviolet-laser-induced permanent electrical conductivity in polyimide  

NASA Astrophysics Data System (ADS)

When polyimide (Kapton) is irradiated by a krypton fluoride (KrF) laser, an increase of the electrical conductivity of up to 16 orders of magnitude is observed. In the high conduction regime, the resistivity is about 0.1 ? cm, the current voltage characteristic is ohmic and the contacts of gold and silver with the irradiated conducting polymer are also ohmic. The conduction mechanism is phonon-assisted variable range hopping, evident from the observed temperature and electric field dependence of the resistivity at low conductivities. The laser-induced conductivity depends on the ambient atmosphere during irradiation. Transmission spectroscopy in the visible region and infrared Fourier transform spectroscopy have been used to characterize the material. A thermal mechanism is proposed for the formation of conducting polyimide, by excimer-laser irradiation.

Feurer, T.; Sauerbrey, R.; Smayling, M. C.; Story, B. J.

1993-03-01

177

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

178

Electrically conductive nanocomposites made from cellulose nanofibrils and polyaniline.  

PubMed

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

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

2009-05-01

179

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

180

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

National Technical Information Service (NTIS)

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 ...

S. G. Liter J. R. Torczynski K. A. Shollenberger S. L. Ceccio

2002-01-01

181

Extended thermodynamics of a relativistic plasma with finite electric conductivity  

NASA Astrophysics Data System (ADS)

A system of equations for relativistic m.h.d, with finite electric conductivity and no heat flux is proposed, starting from the properties of the systems of conservation laws compatible with a supplementary balance law (entropy balance) with convex density ( symmetric-hyperbolic systems). The electric current density is treated as a new field variable which contributes to non equilibrium entropy density ( extended thermodynamics). The result is a theory in which only one new constitutive function, representing entropy increment respect to equilibrium, is necessary to characterize the properties of the medium related to electric conductivity.

Strumia, A.

1991-03-01

182

Scaling of the electrical conductivity of granular media  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

183

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

184

ION AND TEMPERATURE DEPENDENCE OF ELECTRICAL CONDUCTANCE FOR NATURAL WATERS  

EPA Science Inventory

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

185

Distinguishability of Conductivities by Electric Current Computed Tomography  

Microsoft Academic Search

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

David Isaacson

1986-01-01

186

Conductance imaging AFM and electrical properties of carbon nanotubes  

Microsoft Academic Search

This thesis reports the development of a new method for measuring electrical of nanoscale objects, called conductance imaging atomic force microscopy (CIAFM), and reports the results of measurements performed on carbon nanotube networks and nanotube junctions. We introduce CIAFM, a method that combines atomic force microscopy and local conductance measurements. The method is implemented by using a tuning fork as

Michael Stadermann

2004-01-01

187

Liquid Additives to Improve Conductivity in Electric Contacts  

Microsoft Academic Search

Electric contacts generally have high contact resistances because of the relatively small number of conducting contact spots and correspondingly small area through which to transfer current. Liquid metals have been used in the past to provide complete coverage in the contact region but generally require protective atmospheres to prevent corrosion of the liquid metal. Adding an atmospherically stable, non-consumable, conductive

W. A. Lynch; N. A. Sondergaard

2009-01-01

188

Electrical conduction of XLPE with vacuum degassed semiconductive electrodes  

Microsoft Academic Search

It has been found that the electrical conduction characteristics of polyethylene are influenced strongly by the vacuum treatment of cross-linked polyethylene (XLPE) and\\/or semiconductive electrodes. The major changes due to the vacuum treatment of these materials are the suppression in the rate of change of current density at some field range and the change of conduction mechanisms from the SCLC

K. S. Suh; C. R. Lee; Min-Koo Han

1992-01-01

189

Electrical conductivity of amphibole-bearing rocks: influence of dehydration  

NASA Astrophysics Data System (ADS)

We investigated the electrical conductivity of amphibole-bearing rocks under the conditions of the middle to lower crust. Alternating current measurements were performed in the frequency range of 10-106 Hz in a cubic-anvil high-pressure apparatus at 0.5-1.0 GPa and 373-873 K. The electrical conductivity of these rocks is weakly temperature dependent below ~800 K with modest anisotropy and relatively low conductivity (~5 × 10-3 S/m at ~750 K with the activation enthalpy of 64-67 kJ/mol). However, the electrical conductivity starts to increase with temperature more rapidly above ~800 K (activation enthalpy of 320-380 kJ/mol). The infrared spectroscopy observations indicate that dehydration occurs in this high temperature regime. The observed high activation enthalpy and the reproducibility suggest that the enhanced conductivity is not due to the direct effect caused by the generation of conductive fluids. Dehydration of amphibole is associated with the oxidation of iron (from ferrous to ferric), and we suggest that the increased conductivity associated with dehydration is caused by oxidation. This effect may explain high electrical conductivity observed in some regions of the continental crust.

Wang, Duojun; Guo, Yingxing; Yu, Yingjie; Karato, Shun-ichiro

2012-07-01

190

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

191

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

192

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

193

Electric field enhanced conductivity in strongly coupled dense metal plasma  

NASA Astrophysics Data System (ADS)

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

Stephens, J.; Neuber, A.

2012-06-01

194

A Simulation Study of Electrical Fiber Composite Conductivity  

NASA Astrophysics Data System (ADS)

Percolation concept has been used in this study to estimate the amount of conductive fibers embedded in polymeric matrix, necessary to establish conduction in this kind of composites. The resistance of composite materials is calculated by simulating composite samples with different size, containing conductive fibers with various lengths Calculation is based on detecting conductive pathways through the insulating matrix, these pathways are assumed to be resistances in parallel. Electrical resistance curves showed a percolative behavior of the samples versus volume fraction of filler. Lower conduction thresholds are obtained for fiber aspect ratio of 20 and sample size of 100. The electrical resistivity and the conduction thresholds of the carbon fiber reinforced polycarbonate composites have been characterized. Simulation results are in good agreement with an experimental result found in the literature.

Mezdour, D.; Sahli, S.

2008-11-01

195

An Expansion Theorem for the Elecric Conductivity of Metals. I Electric Conductivity for Longitudinal Electric Field  

Microsoft Academic Search

A systematic diagram representation in a composite 4-dimensional space is developed for Kubo's response function which describes the electric response currents of metals for longitudinal electric fields. Proper diagrams are defined as the Feynman type linked diagrams which cannot be decomposed into simpler diagrams connected only by one Coulomb line. The greatest care is exercised with reference to the fact

Takeo Izuyama

1961-01-01

196

Numerical study on electrical conductivity of spin-fermion models  

NASA Astrophysics Data System (ADS)

The DC electrical conductivity is studied numerically in finite-size spin-fermion models with antiferromagnetic couplings between localized spins by a direct numerical estimation of the Kubo formula. In contrast with an ordinary magnetoresistance, in a system where the localized spins form an antiferromagnetically coupled two-leg ladder, conductivity shows an anomalous non-monotonic field dependence. It is attributed to a spin configuration where two spins on the ladder rung dimerize into a spin singlet. In addition, we study conductivity of a square lattice and observe the direction dependence of conductivity. We obtained remarkable and qualitative differences in behavior of conductivity depending on the direction of current.

Ogasahara, Akira; Kusakabe, Koichi

2005-04-01

197

The electrical conductivity of the oceanic upper mantle  

Microsoft Academic Search

SUMMARY Previous inversions of sea-floor magnetotelluric (MT) sounding data have predicted upper mantle electrical conductivities which are more than an order of magnitude higher than laboratory measurements of the conductivity of olivine would suggest, and controlled source-field electromagnetic (CSEM) soundings require a lithos- pheric mantle conductivity of 3 x lop5 Sm-', which is so low that the electromag- netic (EM)

Graham Heinson; Steven Constable

1992-01-01

198

Detection of temperature distribution via recovering electrical conductivity in MREIT  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

199

Detection of temperature distribution via recovering electrical conductivity in MREIT.  

PubMed

In radiofrequency (RF) ablation or hyperthermia, internal temperature measurements and tissue property imaging are important to control their outputs and assess the treatment effect. Recently, magnetic resonance electrical impedance tomography (MREIT), as a non-invasive imaging method of internal conductivity distribution using an MR scanner, has been developed. Its reconstruction algorithm uses measured magnetic flux density induced by injected currents. The MREIT technique has the potential to visualize electrical conductivity of tissue with high spatial resolution and measure relative conductivity variation according to the internal temperature change based on the fact that the electrical conductivity of biological tissues is sensitive to the internal temperature distribution. In this paper, we propose a method to provide a non-invasive alternative to monitor the internal temperature distribution by recovering the electrical conductivity distribution using the MREIT technique. To validate the proposed method, we design a phantom with saline solution and a thin transparency film in a form of a hollow cylinder with holes to create anomalies with different electrical and thermal conductivities controlled by morphological structure. We first prove the temperature maps with respect to spatial and time resolution by solving the thermal conductivity partial differential equation with the real phantom experimental environment. The measured magnetic flux density and the reconstructed conductivity distributions using the phantom experiments were compared to the simulated temperature distribution. The relative temperature variation of two testing objects with respect to the background saline was determined by the relative conductivity contrast ratio (rCCR,%). The relation between the temperature and conductivity measurements using MREIT was approximately linear with better accuracy than 0.22 °C. PMID:23552880

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

2013-04-21

200

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

NSDL National Science Digital Library

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

201

Investigation of thermal and electrical conductivity of graphene based nanofluids  

NASA Astrophysics Data System (ADS)

We report for the first time, the synthesis of highly stable exfoliated graphene based nanofluids with water and ethylene glycol as base fluids with out any surfactant and the subsequent studies on their thermal and electrical conductivities. Graphene was synthesized by thermal exfoliation of graphene oxide at 1050 °C in Ar atmosphere. The as-synthesized graphene has been suitably functionalized and further dispersed it in the base fluids without any surfactant. Thermal and electrical conductivities of these nanofluids were measured for varying volume fractions and at different temperatures. An enhancement in thermal conductivity by about 14% has been achieved at 25 °C with deionized water (DI) as base fluid at a very low volume fraction of 0.056% which increases to about 64% at 50 °C. Electrical conductivity measurements for these nanofluids indicate an enormous enhancement at 25 °C for a volume fraction of 0.03%in DI water.

Baby, Tessy Theres; Ramaprabhu, S.

2010-12-01

202

DC electrical conductivity of silicon carbide ceramics and composites for flow channel insert applications  

Microsoft Academic Search

High purity chemically vapor-deposited silicon carbide (SiC) and 2D continuous SiC fiber, chemically vapor-infiltrated SiC matrix composites with pyrocarbon interphases were examined. Specifically, temperature dependent (RT to 800°C) electrical conductivity and the influence of neutron irradiation were measured. The influence of neutron irradiation on electrical properties appeared very strong for the SiC of this study, typically resulting in orders lower

Yutai Katoh; Sosuke Kondo; Lance Lewis Snead

2009-01-01

203

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

204

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

Microsoft Academic Search

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

Jan Räthel; Mathias Herrmann; Wieland Beckert

2009-01-01

205

Electrical Conductivity of HgTe at High Temperatures  

NASA Technical Reports Server (NTRS)

The electrical conductivity of HgTe was measured using a rotating magnetic field method from 300 K to the melting point (943 K). A microscopic theory for electrical conduction was used to calculate the expected temperature dependence of the HgTe conductivity. A comparison between the measured and calculated conductivities was used to obtain the estimates of the temperature dependence of Gamma(sub 6)-Gamma(sub 8) energy gap from 300 K to 943 K. The estimated temperature coefficient for the energy gap was comparable to the previous results at lower temperatures (less than or equal to 300 K). A rapid increase in the conductivity just above 300 K and a subsequent decrease at 500 K is attributed to band crossover effects. This paper describes the experimental approach and some of the theoretical calculation details.

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

2004-01-01

206

Electrical conductivity of stishovite as a function of water content  

NASA Astrophysics Data System (ADS)

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

Yoshino, Takashi; Shimojuku, Akira; Li, Danyang

2014-02-01

207

Measurement of Electrical Conductivity into Tomato Cultivation Beds using Small Insertion Type Electrical Conductivity Sensor Designed for Agriculture  

NASA Astrophysics Data System (ADS)

Our group has studied on-site monitoring sensor for agricultural field. An electrical conductivity (EC) sensor had been fabricated using Si integrated circuit technology. EC information of solutions shows ion concentrations dissolving in water, and can be used as the index of nutrient concentration for plants. So, it is important to measure EC in real time and on site. Because our EC sensor (5mm×5mm in size) is smaller than other commercial ones (several centimeters), it is easy to insert and achieve measurement in rock wool. In this study, our sensor measured long term EC values in tomato cultivation soil and rock wool medium. At first, we calibrated a relationship between output voltages and EC values on the sensor. The sensor was confirmed about enough EC measurement range from 8 to 969mS/m. In long period measurement, the sensor was confirmed about continuous operation for over five months, and intermittent measurement for over a year. In measurement in the cultivation soil, the sensor indicated that water was kept and diffused in the soil. In contrast, it was found that water diffused without keeping in it in rock wool medium. We confirmed our small EC sensor is useful for on-site monitoring and analysis of solution concentration distribution in several kinds of cultivation bed in real time.

Kawashima, Kazuko; Futagawa, Masato; Ban, Yoshihiro; Asano, Yoshiyuki; Sawada, Kazuaki

208

Electrical conductivity of polypropylene fibers with dispersed carbon fillers  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

209

Electrical and thermal conductivity of hybrid nanocomposites with giant strain  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

210

Measurements of the vertical atmospheric electric field and of the electrical conductivity with stratospheric balloons  

NASA Technical Reports Server (NTRS)

Measurements of the atmospheric (vertical) electric field with balloons in the stratosphere are reported. The atmospheric electrical conductivity is also measured and the current density inferred. The average vertical current shows the expected variation with universal time and is also seen to be influenced by external (magnetospheric) electric fields.

Iversen, I. B.; Madsen, M. M.; Dangelo, N.

1985-01-01

211

Monitoring pH and electric conductivity in an EBPR sequencing batch reactor.  

PubMed

This paper presents laboratory-scale experimentation carried out to study enhanced biological phosphorus removal. Two anaerobic aerobic (A/O) sequencing batch reactors (SBR) have been operated during more than one year to investigate the information provided by monitoring pH and electric conductivity under stationary and transient conditions. Continuous measurements of these parameters allow detecting the end of anaerobic phosphorus release, of aerobic phosphorus uptake and of initial denitrification, as well as incomplete acetic acid uptake. These results suggest the possibility of using pH and electric conductivity as control parameters to determine the length of both anaerobic and aerobic phases in an A/O SBR. More valuable information provided by monitoring pH and electric conductivity is the relation between the amount of phosphorus released and the conductivity increase observed during the anaerobic stages and which group of bacteria (heterotrophic or polyphosphate accumulating) is carrying out the denitrification process. PMID:15656307

Serralta, J; Borrás, L; Blanco, C; Barat, R; Seco, A

2004-01-01

212

Contamination from electrically conductive silicone tubing during aerosol chemical analysis  

SciTech Connect

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

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

2009-06-01

213

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.

214

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

215

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

216

Electrical conductivity measurements on silicate melts using the loop technique  

NASA Technical Reports Server (NTRS)

A new method is described for measurement of the electrical conductivity of silicate melts under controlled oxygen partial pressure at temperatures to 1550 C. The melt samples are suspended as droplets on platinum-rhodium loops, minimizing iron loss from the melt due to alloying with platinum, and providing maximum surface exposure of the melt to the oxygen-buffering gas atmosphere. The latter provides extremely rapid equilibration of the melt with the imposed oxygen partial pressure. The loop technique involves a minimum of setup time and cost, provides reproducible results to within + or - 5% and is well suited to electrical conductivity studies on silicate melts containing redox cations.

Waff, H. S.

1976-01-01

217

Electrically conductive doped block copolymer of polyacetylene and polyisoprene  

DOEpatents

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

Aldissi, Mahmoud (Los Alamos, NM)

1985-01-01

218

Corrosion-protective coatings from electrically conducting polymers  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

219

Rubber-like electrically conductive polymeric materials with shape memory  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

220

Electrically Joining Mixed Conducting Oxides for High Temperature Applications  

SciTech Connect

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

Weil, K. Scott; Hardy, John S.

2003-01-06

221

Electrical conductivity of albite melts at high pressures  

NASA Astrophysics Data System (ADS)

High electrical conductivity observed from magnetotelluric/geomagnetic depth sounding is probably associated with the presence of silicate melts. We investigated electrical conductivity of albite melts, both anhydrous and hydrous with 2.0-5.4 wt% H2O, at 300-1500°C and 0.9-1.8 GPa in a piston-cylinder apparatus. Anhydrous glass was synthesized by fusing oxides and carbonates in 1-bar furnace, and hydrous glasses were prepared by fusing the mixture of glass powder and water in a TZM vessel. A glass cylinder was enclosed between a platinum rod as inner electrode and a Pt-Rh capsule as outer electrode. Platinum wires were used to connect both electrodes to a Solartron 1260 impedance analyzer for conductivity measurements at 3M to 3 HZ. A type-S thermocouple, which was separated from the conductivity circuit, was used to monitor temperature. Furthermore, a Mo foil was employed to reduce the interference from heating circuit. Experimental results demonstrate that the electrical conductivity of albite melt follows an Arrhenius relationship in both glass (<700°C) and liquid (>1100°C) region. In both cases, electrical conductivity increases with water content but decreases with pressure. In the glass region, electrical conductivity can be modelled as log? = 3.5734 + 0.25534C - (4264+160.43P)/T, where ? is conductivity in S/m, C is water content in wt%, P is pressure in GPa, and T is temperature in K. The above expression implies an activation energy of 82 kJ/mol and an activation volume of 3.1 cc/mol. In the liquid region, electrical conductivity can be modelled as log? = 2.6906 + 0.065915C - (2339+371.97P)/T, which implies an activation energy of 45 kJ/mol and an activation volume of 7.1 cc/mol. The dominating conduction mechanism in albite melts is suggested to be the motion of sodium cation.

Ni, H.; Keppler, H.

2009-12-01

222

Porosity effect on the electrical conductivity of sintered powder compacts  

Microsoft Academic Search

A new equation for calculating the electrical conductivity of sintered powder compacts is proposed. In this equation, the\\u000a effective resistivity of porous compacts is a function of the fully dense material conductivity, the porosity of the compact\\u000a and the tap porosity of the starting powder. The new equation is applicable to powder sintered compacts from zero porosity\\u000a to tap porosity.

J. M. Montes; F. G. Cuevas; J. Cintas

2008-01-01

223

Ionic Conduction at High Electric Field Strengths in Tantalum Pentoxide  

Microsoft Academic Search

Polarization of the cell Ta|Ta2O5|Solution|Pt sets up a very high electric field strength in the oxide and ionic conduction (resulting in growth of the oxide film) occurs with negligible electronic conduction. With this cell measurements of field strength and current density have been made in the temperature range -63 to + 90°C. These results are incompatible with single barrier control

A. R. Bray; P. W. M. Jacobs; L. Young

1958-01-01

224

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

225

Electrical conductivity in shaly sands with geophysical applications  

NASA Astrophysics Data System (ADS)

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 porosity ?. For the cations, the situation is different. At high salinities, the dominant paths for the electromigration of the cations are located in the interconnected pore space, and the tortuosity for the transport of cations is therefore the bulk tortuosity. As the salinity decreases, the dominant paths for transport of the cations shift from the pore space to the mineral water interface and consequently are subject to different tortuosities. This shift occurs at salinities corresponding to ?/t(+)f ˜ 1, where ? is the ratio between the surface conductivity of the grains and the electrolyte conductivity, and t(+)f is the Hittorf transport number for cations in the electrolyte. The electrical conductivity of granular porous media is determined as a function of pore fluid salinity, temperature, water and gas saturations, shale content, and porosity. The model provides a very good explanation for the variation of electrical conductivity with these parameters. Surface conduction at the mineral water interface is described with the Stern theory of the electrical double layer and is shown to be independent of the salinity in shaly sands above 10-3 mol L-1. The model is applied to in situ salinity determination in the Gulf Coast, and it provides realistic salinity profiles in agreement with sampled pore water. The results clearly demonstrate the applicability of the equations to well log interpretation of shaly sands.

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

1998-10-01

226

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

NASA Astrophysics Data System (ADS)

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

Guo, Xinzhuan; Yoshino, Takashi

2013-05-01

227

Relating Relative Hydraulic Conductivity and Electrical Conductivity in the Unsaturated Zone  

NASA Astrophysics Data System (ADS)

Monitoring flow in the unsaturated zone is an important task, especially for overseeing managed aquifer recharge, tracking contaminant transport, and optimizing agricultural operations. Geophysical data can provide in-situ unsaturated subsurface information with much higher temporal and spatial resolution over a larger areal extent than traditional hydrologic methods. The measurement of electrical conductivity is a geophysical technique of particular interest in the vadose zone because the geophysical parameter that is obtained is highly correlated with saturation. Changes in saturation can then be used to make qualitative inferences on the rate of fluid motion within the unsaturated zone. However, quantitative information on infiltration rates and unsaturated flow rates via saturation is typically hard to find and usually requires a cumbersome hydrologic inversion that cannot be done in real-time. In this work, we used numerical simulations to find a relationship that relates electrical conductivity not to saturation, but to relative hydraulic conductivity, which has been shown to be a useful proxy for direct estimation of infiltration and unsaturated flow rates even under transient conditions. We obtained this relationship through numerical modeling by generating pore-scale soil structures, partially saturating them through morphological operations according to both wetting and draining schemes and calculating their hydraulic and electrical conductivities at a range of saturations. We found that a power law relationship exists between relative hydraulic conductivity (hydraulic conductivity divided by saturated conductivity) and relative electrical conductivity for each of the sixteen tested media. The power law exponent in the relationship changes depending on whether the medium is being wetted or drained as would be expected as hysteresis is evident in both unsaturated hydraulic and electrical conductivity. Parameters that are typically seen to be related to both saturated conductivities, such as tortuosity, porosity and surface area to volume ratio were calculated for each sphere pack and plotted against the exponent. No correlation was seen between the exponent and these parameters for either the wetting or draining curves. However, the exponent was well constrained for the wetting curve to between 2.45 and 3 and the draining curve to between 1.6 and 2.2. The error introduced by using values within these bounds to estimate the hydraulic conductivity of any of the numerical soil packs using electrical conductivity was negligible, meaning that mean values of 2.75 and 1.8 could be used to estimate the hydraulic conductivity for any pack. These results are applicable to media with minimal surface conduction. We went on to analyze the effects of surface conduction via mineralogy and clay on the power law relationship between electrical and hydraulic conductivity via a number of approaches. We found that the power law relationship between hydraulic and electrical conductivity breaks down when clay content exceeds 5%. However, for media with less clay, use of the relationship with the mean values for exponents found for the clean medium results in less than ten percent error.

Mawer, C. M.; Knight, R. J.; Kitanidis, P. K.

2013-12-01

228

Electrical Conductivity of milk: ability to predict mastitis status  

Microsoft Academic Search

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

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

2004-01-01

229

Using Soil Electrical Conductivity to Improve Nutrient Management  

Microsoft Academic Search

ECa could be used to measure the available nutrient content of the soil, eliminating the need for time-consum- While site-specific nutrient management has the potential for im- ing and expensive soil sample acquisition and analysis. proving crop yields, the cost of intensive soil sampling is usually greater Apparent soil electrical conductivity consists of two than the benefits gained. Apparent soil

Ronnie W. Heiniger; Robert G. McBride; David E. Clay

2003-01-01

230

Electrical conduction in polyethylene terephthalate and polyethylene films  

Microsoft Academic Search

Electrical conduction is studied in polyethylene terephthalate and to a limited extent in polyethylene over a range of fields up to 1·2×106 V cm?1. In common with previous investigations, it is found that the current decays with time according to an inverse power law, but this can be obviated by a conditioning procedure which then allows steady values of current

D M Taylor; T J Lewis

1971-01-01

231

Resistance welding of metals with high electrical and thermal conductivity  

Microsoft Academic Search

A simple device for welding metals with high electrical and thermal conductivity is described. The use of the device, which was adapted from a commercially available carbon deposition unit, for welding 0.0127 and 0.0507-cm-diam Ag, Au, and Pt wires is discussed.

R. Ekern; A. W. Czanderna

1977-01-01

232

Structure and electrical conduction properties of phthalocyanine thin films  

Microsoft Academic Search

The structure and the dc and ac electrical conduction properties of evaporated phthalocyanine thin films are critically reviewed.Results of various structural studies on phthalocyanine single crystals and thin films performed using X-ray diffraction methods are described, and reported unit cell dimensions are given for several phthalocyanines in both the metastable ? and the stable ? forms: reported unit cell dimensions

R. D. Gould

1996-01-01

233

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

234

Prediction of electrical contact resistance for anisotropic conductive adhesive assemblies  

Microsoft Academic Search

Anisotropic conductive adhesive (ACA) assembly is emerging as one of the most flexible and cost effective packaging interconnect methods in the microelectronics industry. One of the major impediments to the full realization of the fine pitch (<200 ?m) capabilities of this assembly method is accurate prediction and control of electrical contact resistance. This paper presents a detailed review and direct

Melida Chin; Kaushik A. Iyer; S. Jack Hu

2004-01-01

235

Ion induced electrical conductivity versus chemical doping in polyaniline (PANI)  

Microsoft Academic Search

The effect of ion implantation on the electrical conducting behavior of neutral polyaniline (EB) has been studied and this is compared with the result of chemical doping (ES). The damage caused by ion implantation was analyzed with 4He+ Rutherfold backscattering spectroscopy. The experimental results indicate that the value of the resistivity in the carbon-rich layer of EB resulted from the

Zhi Shen Tong; Mei Zhen Wu; Jiu Long Ding; Qun Hua Hu; Min Zhu; Lei Chen; Xing Long Xu; Mei Xiang Wan; Huai Xia Zhou

1992-01-01

236

Electrical conductivity of silicon carbide composites and fibers  

Microsoft Academic Search

The electrical conductivity, ?, of silicon carbide (SiC) composites and fibers was measured for temperatures between 20 and 1000 °C in order to estimate the magnitude of magnetohydrodynamic effects for liquid metal blankets and a SiC composite structure. Two types of composites were tested: the first type had a matrix made by chemical vapor infiltration (CVI), the second type had

R. Scholz; F. dos Santos Marques; B. Riccardi

2002-01-01

237

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

238

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

239

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.

Kato, Souichiro; Hashimoto, Kazuhito; Watanabe, Kazuya

2012-01-01

240

Electrical conduction and polarization of calcite single crystals  

NASA Astrophysics Data System (ADS)

The electrical conductivity and polarization properties of calcite single crystals with three orientations, namely, a (00.1) plane perpendicular to the crystallographic c axis (10.0) plane parallel to the crystallographic c axis, and a (10.4) cleavage plane, were studied by both complex impedance and thermally stimulated depolarization current (TSDC) measurements. Conductivities for (00.1)-, (10.0)-, and (10.4)-oriented single calcite crystals at 400-600 °C were 1.16 × 10-7 - 1.05 × 10-5, 7.40 × 10-8 - 4.27 × 10-6, and 4.27 × 10-7 - 2.86 × 10-5 ?-1 m-1, respectively, and the activation energies for conduction were 112, 103, and 101 kJ mol-1, respectively. The TSDC spectra verified the electrical polarizability of calcite crystals. The activation energy for depolarization, estimated from TSDC spectra, of the (00.1)-, (10.0)-, and (10.4)-oriented calcite substrates were 112, 119, and 114 kJ mol-1, respectively. Considering the correlation between the processes of conduction and electric polarization, we proposed the mechanisms of conduction and polarization in calcite on the assumption of oxide ion transport.

Wada, Norio; Horiuchi, Naohiro; Wang, Wei; Hiyama, Tetsuo; Nakamura, Miho; Nagai, Akiko; Yamashita, Kimihiro

2012-10-01

241

Electrical conductivity anomalies associated with circular lunar maria  

NASA Technical Reports Server (NTRS)

A strong anisotropy is observed in magnetic field fluctuations measured by the Lunokhod 2 magnetometer located on the eastern edge of Mare Serenitatis. This anisotropy can be explained by a regional anomaly in the subsurface electrical conductivity distribution associated with the mare similar to the proposed conductivity anomaly associated with Mare Imbrium. The Serenitatis magnetic field anisotropy is compared to the field fluctuation measured by the Apollo 16 magnetometer 1100 km to the south, and this comparison indicates that the subsurface conductivity distribution can be modeled by a nonconducting layer in the lunar lithosphere which is 150 km thick beneath the highlands and 300 km thick beneath Serenitatis. The decrease in electrical conductivity of the upper mantle beneath the mare may result from lower temperatures due to transport of thermal energy and radioactive heat sources to the surface during mare flooding. This proposed anomaly, along with that proposed for Mare Imbrium, strengthens the possibility of regional anomalies in electrical conductivity associated with all circular lunar maria.

Dyal, P.; Daily, W. D.

1979-01-01

242

Electrical insulation and conduction coating for fusion experimental devices  

SciTech Connect

The development of electrical insulation and conduction coating methods that can be applied to large components of fusion experimental devices has been investigated. A thermal spraying method is used to coat the insulation or conduction materials on the structural components because of its applicability for large surfaces. The insulation material chosen was Al{sub 2}O{sub 3}, while Cr{sub 3}C{sub 2}-NiCr and WC-NiCr were chosen as conduction materials. These materials were coated on stainless steel substrates to examine the basic characteristics of the coated layers, such as their adhesive strength to the substrate, thermal shock resistance, electrical resistance, dielectric breakdown voltage, and thermal conductivity. It was found that they have sufficient electrical insulation and conduction properties, respectively. In addition, the sliding tests of the coated layers showed adequate frictional properties. The spraying method was tested on a 100- x 1000-mm surface and found to be applicable for large surfaces of experimental fusion devices. 9 refs., 6 figs., 15 tabs.

Onozuka, Masanori; Tsujimura, Seiji; Toyoda, Masahiko; Inoue, Masahiko [Mitsubishi Heavy Industries, Ltd., Yokohama (Japan); Abe, Tetsuya; Murakami, Yoshio [Japan Atomic Energy Research Inst., Naka (Japan)

1996-01-01

243

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

PubMed

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. PMID:23387698

Maeda, Nobuo

2013-01-01

244

The mechanical and the electrical properties of conducting polypyrrole fibers  

NASA Astrophysics Data System (ADS)

The mechanical and the electrical properties of polypyrrole (PPy) fibers and electrochemically deposited PPy films were studied. It was found that the PPy fibers showed a significantly higher strength than the PPy films due to better orientation of the molecular structure. The electrochemically prepared PPy films had a higher electrical conductivity than that of the fibers at high temperature. At low temperature, the PPy fibers showed the higher conductivity. The conductivity results were analyzed in the frame of the three-dimensional variable range hopping model. The results showed that at room temperature the average hopping distance for the fibers was about 4 A? while for the films it increases to about 5.7 A?. This corresponds to about 1 and 2 monomer units in length for the fiber and film samples, respectively.

Foroughi, J.; Ghorbani, S. R.; Peleckis, G.; Spinks, G. M.; Wallace, G. G.; Wang, X. L.; Dou, S. X.

2010-05-01

245

Unconventional approaches to combine optical transparency with electrical conductivity  

NASA Astrophysics Data System (ADS)

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

Medvedeva, J. E.

2007-10-01

246

Unconventional approaches to combine optical transparency with electrical conductivity  

NASA Astrophysics Data System (ADS)

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

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

2007-10-01

247

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

NASA Astrophysics Data System (ADS)

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

Vollrath, Fritz; Edmonds, Donald

2013-12-01

248

Electrical conductivity beneath the volcanoes of the NW Argentinian Puna  

NASA Astrophysics Data System (ADS)

The detection of a high conductivity anomaly below the northern (Bolivian) part of the Altiplano-Puna plateau motivated a new analysis of magnetotelluric (MT) data which were formerly collected further south in NW Argentina. After appropriate dimensionality analysis from a profile located in the magmatic arc and backarc of the south-central Andean subduction zone, two-dimensional (2-D) electrical conductivity modelling of the crust and upper mantle in the eastern sector could be performed, i.e., in the eastern Puna and backarc zone. The 2-D conductivity models show a conductive zone beneath the eastern Puna shoshonitic volcanoes and nearby Tuzgle volcano, which reaches from the upper crust to the upper mantle. We suggest that this conductor is related to the Puna volcanism of enriched mantle composition. Whether the western Puna is also characterized by anomalous conductivities at crust-mantle depths, is still an open question.

Lezaeta, Pamela; Brasse, Heinrich

249

Optimization and Testing of Electrically Conductive Spacecraft Coatings  

NASA Technical Reports Server (NTRS)

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

Mell, Richard J.

2001-01-01

250

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

USGS Publications Warehouse

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

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

2012-01-01

251

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

252

High performance electrically conductive adhesives (ECAs) for leadfree interconnects  

NASA Astrophysics Data System (ADS)

Electrically conductive adhesives (ECAs) are one of the lead-free interconnect materials with the advantages of environmental friendliness, mild processing conditions, fewer processing steps, low stress on the substrates, and fine pitch interconnect capability. However, some challenging issues still exist for the currently available ECAs, including lower electrical conductivity, conductivity fatigue in reliability tests, limited current-carrying capability, poor impact strength, etc. The interfacial properties is one of the major considerations when resolving these challenges and developing high performance conductive adhesives. Surface functionalization and interface modification are the major approaches used in this thesis. Fundamental understanding and analysis of the interaction between various types of interface modifiers and ECA materials and substrates are the key for the development of high performance ECA for lead-free interconnects. The results of this thesis provide the guideline for the enhancement of interfacial properties of metal-metal and metal-polymer interactions. Systematic investigation of various types of ECAs contributes to a better understanding of materials requirements for different applications, such as surface mount technology (SMT), flip chip applications, flat panel display modules with high resolution, etc. Improvement of the electrical, thermal and reliability of different ECAs make them a potentially ideal candidate for high power and fine pitch microelectronics packaging option.

Li, Yi

253

Thermal and Electrical Conductivity Probe for Phoenix Mars Lander  

NASA Technical Reports Server (NTRS)

NASA's Phoenix Mars Lander will assess how heat and electricity move through Martian soil from one spike or needle to another of a four-spike electronic fork that will be pushed into the soil at different stages of digging by the lander's Robotic Arm.

The four-spike tool, called the thermal and electrical conductivity probe, is in the middle-right of this photo, mounted near the end of the arm near the lander's scoop (upper left).

In one type of experiment with this tool, a pulse of heat will be put into one spike, and the rate at which the temperature rises on the nearby spike will be recorded, along with the rate at which the heated spike cools. A little bit of ice can make a big difference in how well soil conducts heat. Similarly, soil's electrical conductivity -- also tested with this tool -- is a sensitive

indicator of moisture in the soil. This device adapts technology used in soil-moisture gauges for irrigation-control systems. The conductivity probe has an additional role besides soil analysis. It will serve as a hunidity sensor when held in the air.

2007-01-01

254

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

255

Electrical Conductivity of Cadmium Oxide in High-Frequency Electrical Fields.  

National Technical Information Service (NTIS)

Results are given of an investigation into the electrical conductivity of polycrystalline samples of cadmium oxide using the non-electrode method in the frequency range (7 to 8.9) x 10 to the 9th power cps. (Author)

R. A. Baltrushaitis P. P. Brazdzhyunas

1967-01-01

256

Electrical conductivity in lipid bilayer membranes induced by pentachlorophenol.  

PubMed Central

Electrical conductivity induced in thin lipid bilayer membranes by pentachlorophenol has been studied. The membranes were formed from phosphatidyl choline, phosphatidyl ethanolamine, or phosphatidyl glycerol and various amounts of cholesterol. The position and the magnitude of the maximum of the conductivity vs. pH curve depend on the type of lipids and cholesterol content. At low pentachlorophenol concentrations and low pH the concentration dependence of conductivity is quadratic and becomes linear at higher pH. Above 10(-5) M of pentachlorophenol the concentration dependence of the membrane conductivity tends to saturate. Presence of pentachlorophenol enhances membrane transport of nonactin-K+ complex. Increase of cholesterol content increases pentachlorophenol induced conductivity in all membranes and shifts the conductivity toward lower pH. For phosphatidyl choline the largest rate of change of membrane conductivity with cholesterol occurs at 1:1 phospholipid to cholesterol molar ratio. Pentachlorophenol is found to be a class II uncoupler and the experimental results are consistent with the hypothesis that the membrane permeable species are dimers formed by combination of neutral and dissociated pentachlorophenol molecules. Several schemes of membrane conduction, including dimer formation in the aqueous phase as well as at the membrane-water interface have been considered. Arguments are given in favor of the formation of dimers within the membrane surface.

Smejtek, P; Hsu, K; Perman, W H

1976-01-01

257

Effect of orientation anisotropy on calculating effective electrical conductivities  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

258

Evolving concepts on the electrical conductivity of the continental crust  

NASA Astrophysics Data System (ADS)

Several decades of geophysical research have established that the middle and lower crust are typically much more electrically conductive than the upper crust and orders of magnitude more so than either dry crystalline rocks or rock-forming silicate minerals at similar conditions. The high conductivities at depth were originally ascribed to the presence of saline fluids. Two problems with this view have emerged: hot water is far too reactive with surrounding rocks to remain for long in the deep crust, and the permeability of hot, ductile crust is too low to account for the observed conductivities. Another possibility is that graphitic carbon exerts the primary control on deep crustal conductivity. Graphitic carbon can exist in different habits and abundances and influence conductivity on different scales. Buried organic-rich shales form megascopic layers in which carbon is likely to be interconnected over kilometers, but such layers are not common. Graphitic veins formed during metamorphism are probably more common but much less extensive. Carbon also forms films on microfracture surfaces. These have been observed in many crystalline rocks and appear to be ubiquitous; they are also probably extensive and thus may generally account for the crustal conductivity structure. The microcrack network need not be completely interconnected to impart high electrical conductivity. It can exist in series with conductive minor phases such as oxides or sulfides, and it also reduces the size of regions of high resistivity. Regardless of mode of occurrence, that carbonaceous rocks are more abundant in the Phanerozoic than Precambrian records explains why the deep Phanerozoic crust is more conductive than old shield regions. The control of rock conductivity by carbon in the microfracture network implies that conductivity is in part controlled by microstructure and microfabric and by the chemical state of carbon. Observations of rocks from the KTB borehole indicate that microcrack carbon at the bottom of the hole (9.1 km depth) is relatively pure but at shallower levels contains a higher proportion of hydrocarbon. With uplift of the host rocks, carbon may react with fluids to form less conductive hydrocarbons. This retrograde metamorphism of microcrack carbon may be one reason that shallow crust can be less conductive than deep crust.

Mathez, E. A.

2002-12-01

259

Correlations of electrical conductivity to slag composition and temperature  

NASA Astrophysics Data System (ADS)

The electrical conductivity of slags is an important factor in the design of electric smelting furnaces. Although there are many experimental studies on this subject, as yet there are no quantitative correlations of conductivity to slag composition and temperature. The objective of this work was to develop such correlations, on the basis of the experimental data by various other authors. The results show that in the concentration range of industrial-type SiO2-CaO-MgO-MnO slags the slag conductivity can be expressed as a linear function of the molar concentrations of the basic oxides; in the concentration range of industrial nonferrous slags, where the iron oxide content is usually over 20 pct, the slag conductivity can be expressed as an exponential function of the molar concentrations of the iron and basic oxides. The effect of temperature on slag conductivity, in the industrial range of interest, can be accounted for by means of an Arrhenius-type of equation.

Jiao, Q.; Themelis, N. J.

1988-02-01

260

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

261

Electrical conductivity of the roof of electric arc steel melting furnaces  

SciTech Connect

The authors test for the relationship between temperature and electrical conductivity in the refractory liners of arc furnaces used by the steel industry in the Soviet Union in order to minimize the degradation of these refractories by electrical and thermal processes, to maximize their service life, and to optimize their insulating properties and the consequent efficiency of the furnaces in which they are utilized.

Osipenko, V.D.; Garbuz, S.S.; Khromov, A.P.

1987-01-01

262

Orbital dynamics of two electrically charged conducting spheres  

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

263

Single-photon heat conduction in electrical circuits  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

264

Electrical conductivity of tissue at frequencies below 1 MHz  

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

265

Electrical conductivity of two-phase composite material  

SciTech Connect

It is a long standing problem to predict the effective electrical conductivity of binary mixtures or two-phase composites. The early history of this problem is often connected with the names of Clausius, Mossotti, Lorenz, and Lorentz. Currently, the general effective media (GEM) equation, proposed by McLachlan, seems to explain different results of experimental studies over an entire composition range. The GEM equation consists of electrical conductivity of constituent phases, their volume fractions and two free parameters. As has been pointed out by Boccaccini the free parameters of the GEM equation do not have yet a clear correlation with the real features of the microstructure. In this paper the author discusses such correlation using connections among the GEM equation, percolation theory and effective medium theory.

Kovacik, J. [Slovak Academy of Sciences, Bratislava (Slovakia). Inst. of Materials and Machine Mechanics] [Slovak Academy of Sciences, Bratislava (Slovakia). Inst. of Materials and Machine Mechanics

1998-06-12

266

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

267

Electrical conductivity and total dissolved solids in urine  

Microsoft Academic Search

The objective of this paper is to study the relevance of electrical conductivity (EC) and total dissolved solids (TDS) in\\u000a early morning and random samples of urine of urinary stone patients; 2,000 urine samples were studied. The two parameters\\u000a were correlated with the extent of various urinary concrements. The early morning urine (EMU) and random samples of the patients\\u000a who

Y. M. Fazil Marickar

2010-01-01

268

The Electrical Conductivity of Packed Beds Containing Macroporous Cation Exchanger  

Microsoft Academic Search

The electrical conductivity of packed beds containing macroporous Duolite C-25 polystyrene sulfonate cation exchanger equilibrated with aqueous solutions of a single electrolyte (NaCl or HCl) has been measured over a range of electrolyte concentrations. The results are interpreted in terms of a two-phase model for the resin particle involving (1) the resin matrix, with the conventional properties of polystyrene sulfonate

Darryl G. Howery; Sugihiko Tada

1969-01-01

269

Nonlinear dc and ac conductivity in electrically insulating composites  

Microsoft Academic Search

The non-linear electrical behavior of zinc oxide, used to practical advantage in surge arresters on distribution power systems, has been replicated in epoxy resin, which has been filled with an appropriate volume fraction of this intrinsically semi-conducting material. Comparison has been made with epoxy resin containing a similar volume fraction of aluminum oxide in order to establish that the non-linearity

K. P. Donnelly; B. R. Varlow

2003-01-01

270

Electric conductivity of hafnium-containing fluoride-chloride melts  

Microsoft Academic Search

This paper presents the results of an investigation of the specific electric conductivity of melts of the potassium, hafnium-containing fluoride-chloride ternary reciprocal system which is of practical interest because fluoride-chloride melts containing hafnium can be used as electrolytes in the preparation of metallic hafnium. Experimental results depend largely on the purity of the salts that are used, so much attention

S. E. Darienko; Yu. F. Chervinskii; S. F. Katyshev; I. F. Nichkov

1985-01-01

271

STATUS OF SOIL ELECTRICAL CONDUCTIVITY STUDIES BY CENTRAL STATE RESEARCHERS  

Microsoft Academic Search

Practical tools are needed to identify and advance sustainable management practices to optimize economic return, conserve soil, and minimize negative off-site environmental effects. The objective of this article is to review current research in non-saline soils of the central U.S. to consider bulk soil electrical conductivity (EC a) as an assessment tool for: (1) tracking N dynamics, (2) identifying management

C. K. Johnson; R. A. Eigenberg; J. W. Doran; B. J. Wienhold; B. Eghball; B. L. Woodbury

272

Influence of oxygen fugacity on the electrical conductivity of hydrous olivine: Implications for the mechanism of conduction  

NASA Astrophysics Data System (ADS)

Various mechanisms of hydrogen-assisted electrical conductivity predict different dependence of conductivity on oxygen fugacity. If a majority of hydrogen-related defects (i.e., two protons at M-site) carries the electrical current, then the conductivity will be independent of oxygen fugacity, whereas if a minority defect such as free proton carries the electrical conductivity, then the electrical conductivity will decrease with oxygen fugacity. We have determined the dependence of hydrogen-assisted electrical conductivity on oxygen fugacity in hydrous olivine. We found that the hydrogen-assisted electrical conductivity in olivine decreases with oxygen fugacity. This result supports a model where hydrogen-related defect with minor concentration (e.g., free proton or one hydrogen at M-site) carries most of the electric charge.

Dai, Lidong; Karato, Shun-ichiro

2014-07-01

273

On the electrical conductivity of Ti-implanted alumina  

SciTech Connect

Ion implantation of metal species into insulators provides a tool for the formation of thin, electrically conducting, surface layers with experimenter-controlled resistivity. High energy implantation of Pt and Ti into alumina accelerator components has been successfully employed to control high voltage surface breakdown in a number of cases. In the work described here we have carried out some basic investigations related to the origin of this phenomenon. By comparison of the results of alumina implanted with Ti at 75 keV with the results of prior investigations of polymers implanted with Pt at 49 eV and Au at 67 eV, we describe a physical model of the effect based on percolation theory and estimate the percolation parameters for the Ti-alumina composite. We estimate that the percolation dose threshold is about 4 x 10{sup 16} cm{sup -2} and the maximum dose for which the system remains an insulator-conductor composite is about 10 x 10{sup 16} cm{sup -2}. The saturation electrical conductivity is estimated to be about 50 S/m. We conclude that the observed electrical conductivity properties of Ti-implanted alumina can be satisfactorily described by percolation theory.

Salvadori, M. C.; Teixeira, F. S.; Cattani, M. [Institute of Physics, University of Sao Paulo, C.P. 66318, CEP 05315-970, Sao Paulo S.P. (Brazil); Nikolaev, A.; Savkin, K. P.; Oks, E. M. [High Current Electronics Institute, Russian Academy of Sciences, Tomsk 634055 (Russian Federation); Park, H.-K.; Phillips, L. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States); Yu, K. M.; Brown, I. G. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2012-03-15

274

On the electrical conductivity of Ti-implanted alumina  

NASA Astrophysics Data System (ADS)

Ion implantation of metal species into insulators provides a tool for the formation of thin, electrically conducting, surface layers with experimenter-controlled resistivity. High energy implantation of Pt and Ti into alumina accelerator components has been successfully employed to control high voltage surface breakdown in a number of cases. In the work described here we have carried out some basic investigations related to the origin of this phenomenon. By comparison of the results of alumina implanted with Ti at 75 keV with the results of prior investigations of polymers implanted with Pt at 49 eV and Au at 67 eV, we describe a physical model of the effect based on percolation theory and estimate the percolation parameters for the Ti-alumina composite. We estimate that the percolation dose threshold is about 4 × 1016 cm-2 and the maximum dose for which the system remains an insulator-conductor composite is about 10 × 1016 cm-2. The saturation electrical conductivity is estimated to be about 50 S/m. We conclude that the observed electrical conductivity properties of Ti-implanted alumina can be satisfactorily described by percolation theory.

Salvadori, M. C.; Teixeira, F. S.; Cattani, M.; Nikolaev, A.; Savkin, K. P.; Oks, E. M.; Park, H.-K.; Phillips, L.; Yu, K. M.; Brown, I. G.

2012-03-01

275

Electrical conductivity of disordered semi-infinite systems  

NASA Astrophysics Data System (ADS)

Employing the Kubo-Greenwood formula the electrical conductivity of disordered semi-infinite systems is formulated in terms of the (Screened) KKR method and the Coherent Potential Approximation. It is shown that by neglecting vertex corrections in the same manner as in the bulk case, the elements of the electrical conductivity tensor can be described in terms of ''layer-diagonal''- and ''layer-off-diagonal'' contributions. In order to discuss effects of the underlying electronic structure on the electrical conductivity, but also to point out particular contributions to it, Bloch spectral functions are formulated. A spin-polarized (relativistic) application of the present theory to non-collinear disordered magnetic multilayers allows to discuss giant magnetoresistance (GMR) on an ab-inito level in quite a general context. --This paper was financially supported by the CMS, Vienna, the Hungarian National Scientific Research Foundation (OTKA F014378), from the Office of Naval Research (N00014-91-J-1695), and a grant from NATO, CGR. 890599.

Weinberger, P.; Szunyogh, L.; Ujfalussy, B.; Levy, P. M.; Banhart, J.

1996-03-01

276

Electrical studies on silver based fast ion conducting glassy materials  

NASA Astrophysics Data System (ADS)

Among all the available fast ion conductors, silver based glasses exhibit high conductivity. Further, glasses containing silver iodide enhances fast ion conducting behavior at room temperature. Glasses of various compositions of silver based fast ion conductors in the AgI-Ag2O-[(1-x)B2O3-xTeO2] (x=0 to1 mol% in steps of 0.2) glassy system have been prepared by melt quenching method. The glassy nature of the compounds has been confirmed by X-ray diffraction. The electrical conductivity (AC) measurements have been carried out in the frequency range of 1 KHz-3MHz by Impedance Analyzer in the temperature range 303-423K. The DC conductivity measurements were also carried out in the temperature range 300-523K. From both AC and DC conductivity studies, it is found that the conductivity increases and activation energy decreases with increasing the concentration of TeO2 as well as with temperature. The conductivity of the present glass system is found to be of the order of 10-2 S/cm at room temperature. The ionic transport number of these glasses is found to be 0.999 indicating that these glasses can be used as electrolyte in batteries.

Rao, B. Appa; Kumar, E. Ramesh; Kumari, K. Rajani; Bhikshamaiah, G.

2014-04-01

277

Determination of Electric Conductivity and Local SAR Via B1 Mapping  

Microsoft Academic Search

The electric conductivity can potentially be used as an additional diagnostic parameter, e.g., in tumor diagnosis. Moreover, the electric conductivity, in connection with the electric field, can be used to estimate the local SAR distribution during MR measurements. In this study, a new approach, called electric properties tomography (EPT) is presented. It derives the patient's electric conductivity, along with the

Ulrich Katscher; Tobias Voigt; Christian Findeklee; Peter Vernickel; Kay Nehrke; Olaf Dössel

2009-01-01

278

Theoretical Study on the Electronic and Electrical Properties of p-Type Transparent Conducting Metal Oxides  

Microsoft Academic Search

Transparent conducting oxides (TCOs) continue to be in high demand because of their immediate applications. In addition to good quality n-type TCOs, there is increasing demand for good p-type TCOs. In the present study, we reported a theoretical study on the electronic and electrical properties for p-type TCO, Zn-doped In2O3 (IZO). The geometries of IZO were optimized using the density

Chen Lv; Agalya Govindasamy; Hideyuki Tsuboi; Michihisa Koyama; Akira Endou; Hiromitsu Takaba; Momoji Kubo; Carlos A. Del Carpio; Akira Miyamoto

2007-01-01

279

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

280

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

281

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

282

An Overview of Earth's Global Electric Circuit and Atmospheric Conductivity  

NASA Astrophysics Data System (ADS)

The Earth’s global atmospheric electric circuit depends on the upper and lower atmospheric boundaries formed by the ionosphere and the planetary surface. Thunderstorms and electrified rain clouds drive a DC current (˜1 kA) around the circuit, with the current carried by molecular cluster ions; lightning phenomena drive the AC global circuit. The Earth’s near-surface conductivity ranges from 10-7 S m-1 (for poorly conducting rocks) to 10-2 S m-1 (for clay or wet limestone), with a mean value of 3.2 S m-1 for the ocean. Air conductivity inside a thundercloud, and in fair weather regions, depends on location (especially geomagnetic latitude), aerosol pollution and height, and varies from ˜10-14 S m-1 just above the surface to 10-7 S m-1 in the ionosphere at ˜80 km altitude. Ionospheric conductivity is a tensor quantity due to the geomagnetic field, and is determined by parameters such as electron density and electron-neutral particle collision frequency. In the current source regions, point discharge (coronal) currents play an important role below electrified clouds; the solar wind-magnetosphere dynamo and the unipolar dynamo due to the terrestrial rotating dipole moment also apply atmospheric potential differences. Detailed measurements made near the Earth’s surface show that Ohm’s law relates the vertical electric field and current density to air conductivity. Stratospheric balloon measurements launched from Antarctica confirm that the downward current density is ˜1 pA m-2 under fair weather conditions. Fortuitously, a Solar Energetic Particle (SEP) event arrived at Earth during one such balloon flight, changing the observed atmospheric conductivity and electric fields markedly. Recent modelling considers lightning discharge effects on the ionosphere’s electric potential (˜+250 kV with respect to the Earth’s surface) and hence on the fair weather potential gradient (typically ˜130 V m-1 close to the Earth’s surface. We conclude that cloud-to-ground (CG) lightning discharges make only a small contribution to the ionospheric potential, and that sprites (namely, upward lightning above energetic thunderstorms) only affect the global circuit in a miniscule way. We also investigate the effects of mesoscale convective systems on the global circuit.

Rycroft, Michael J.; Harrison, R. Giles; Nicoll, Keri A.; Mareev, Evgeny A.

2008-06-01

283

Using High Resolution Complex Electrical Conductivity Measurements of Heterogeneous Rocks  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

284

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

285

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

SciTech Connect

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

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

2013-06-30

286

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

SciTech Connect

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

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

2012-04-17

287

Determinantal quantum theory of d.c. electrical conductivity  

NASA Astrophysics Data System (ADS)

the quantum calculation of the d.c. electrical conductivity for an electron system is reconsidered by using an improved form of the long-time solution of the density matrix. The starting time-evolution equation which is written as a linear system in the Liouville space of discrete quantum states, is first solved in terms of Cramer's determinants and next suitably adapted to tranport problems. The calculation of the statistical average of the many-body current density, in the presence of scattering potential, is carried out in the thermodynamic limit, using a characteristic property of collision matrices introduced earlier by van Hove as the so-called ?-singularity. In contrast to previous methods based on kinetic equations solved by perturbations, Kubo's theory, or Mori type memory functions, the resolution of an integral equation, initially included in Cramer's formulae, is no longer required. Among its major advantages, the method succeeds in overcoming the well known zero frequency divergent behaviour of the conductivity. It also yields an explicit expression of an effective relaxation time which is just constructed out of those diagonal transition sequences responsible for self-energy effects in van Hove's theory. This expression which only assumes the randomization of phases of initial states can be used to get tractable expansions in powers of the collision potential. Its range of validity is limited by the effect of collisions on equilibrium statistics, which is shown to be negligible within the Peierls criterion, hbar / tau ll ?, tau being the relaxation time and ? the Fermi energy. Finally, the comparison of the present approach with the elementary transport theory reveals that the relaxation time is close to the standard expression, even though the latter would be exactly recovered, in lowest order of collisions, only on disregarding divergent terms arising beyond second order. Le calcul quantique de la conductivité en courant continu d'un système d'électrons est reconsidéré à l'aide d'une solution améliorée pour la matrice densité. L'équation d'évolution utilisée est d'abord écrite comme un système linéaire dans l'espace de Liouville des états quantiques discrets, résolue à l'aide de déterminants de Cramer et convenablement adaptée ensuite aux problèmes de transport. Le calcul de la moyenne statistique de la densité de courant, en présence d'un potentiel de diffusion, est effectué à la limite thermodynamique, en utilisant une propriété caractéristique des matrices de collision, initialement introduite par van Hove sous le nom de singularité ?. Contrairement aux méthodes précédentes, basées sur les équations cinétiques résolues par perturbations, la théorie de Kubo, ou l'utilisation de fonctions mémoire de type Mori, la résolution d'une équation intégrale, déjà incluse dans les formules de Cramer, n'est plus nécessaire. Parmi ses autres avantages majeurs, la méthode est capable de résoudre la divergence bien connue de la conductivité lorsque la fréquence tend vers zéro. Elle fournit aussi une expression explicite d'un temps de relaxation effectif, construite précisément à partir des séquences de transitions diagonales responsables des effets de self-énergie dans la théorie de van Hove. Cette expression qui ne suppose que la distribution de phase aléatoire des états d'équilibre initiaux, peut être utilisée pour obtenir des développements maniables en puissances du potentiel de collision. Son domaine de validité n'est limité que par l'effet des collisions sur la statistique d'équilibre, qui se révèle négligeable dans les limites du critère de Peierls hbar / tau ll ?, où tau est le temps de relaxation et ? l'énergie de Fermi. Finalement, la comparaison avec la théorie élémentaire montre que le temps de relaxation est proche de l'expression classique, mais ne pourrait s'y identifier complètement, à l'ordre le plus bas des collisions, qu'en ignorant les divergences apparaissant au-delà du second ordre.

Fortini, A.

1992-05-01

288

Testing and Optimization of Electrically Conductive Spacecraft Coatings  

NASA Technical Reports Server (NTRS)

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

Mell, R. J.; Wertz, G. E.; Edwards, D. L. (Technical Monitor)

2001-01-01

289

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

NASA Astrophysics Data System (ADS)

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

Heo, Cheol; Chang, Jin-Hae

2013-10-01

290

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

291

Electrically conductive biodegradable polymer composite for nerve regeneration: electricity-stimulated neurite outgrowth and axon regeneration.  

PubMed

Normal and electrically stimulated PC12 cell cultures and the implantation of nerve guidance channels were performed to evaluate newly developed electrically conductive biodegradable polymer composites. Polypyrrole (PPy) doped by butane sulfonic acid showed a significantly higher number of viable cells compared with PPy doped by polystyrenesulfonate after a 6-day culture. The PC12 cells were left to proliferate for 6 days, and the PPy-coated membranes, showing less initial cell adherence, recorded the same proliferation rate as did the noncoated membranes. Direct current electricity at various intensities was applied to the PC12 cell-cultured conductive membranes. After 7 days, the greatest number of neurites appeared on the membranes with a current intensity approximating 1.7-8.4 microA/cm. Nerve guidance channels made of conductive biodegradable composite were implanted into rats to replace 8 mm of sciatic nerve. The implants were harvested after 2 months and analyzed with immunohistochemistry and transmission electron microscopy. The regenerated nerve tissue displayed myelinated axons and Schwann cells that were similar to those in the native nerve. Electrical stimulation applied through the electrically conductive biodegradable polymers therefore enhanced neurite outgrowth in a current-dependent fashion. The conductive polymers also supported sciatic nerve regeneration in rats. PMID:17209956

Zhang, Ze; Rouabhia, Mahmoud; Wang, Zhaoxu; Roberge, Christophe; Shi, Guixin; Roche, Phillippe; Li, Jiangming; Dao, Lê H

2007-01-01

292

Ionospheric electrical conductances produced by auroral proton precipitation  

NASA Astrophysics Data System (ADS)

From incoherent scatter radar observations and space-borne particle detector data, it appears that energetic proton precipitation can sometimes, for some locations, be a major source of ionization in the auroral ionosphere and contribute significantly to the electrical conductances. Here we propose a simple parameterization for the Pedersen and Hall conductances produced by proton precipitation. The derivation is based on a proton transport code for computing the electron production rate and on an effective recombination coefficient for deducing the electron density. The atmospheric neutral densities and temperatures and the geomagnetic-field strength are obtained from standard models. The incident protons are assumed to have a Maxwellian distribution in energy with a mean energy in the 2-40 keV range and an energy flux Q0. The parameterized Pedersen and Hall conductances are functions of and Q0, as well as of the geomagnetic-field strength. The dependence on these quantities is compared with those obtained for electron precipitation and for solar EUV radiation. To add the contribution of proton precipitation to the total conductances for electrodynamic studies in auroral regions, the conductances produced by electron and proton precipitations can be combined by applying a root-sum-square approximation.

Galand, Marina; Richmond, Arthur D.

2001-01-01

293

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

294

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

295

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

PubMed

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

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

2011-07-01

296

Electrical Conductivity Imaging Using Controlled Source Electromagnetics for Subsurface Characterization  

NASA Astrophysics Data System (ADS)

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

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

2004-05-01

297

Electrical Conductivity of Interacting Fermions. I. General Formulation  

NASA Astrophysics Data System (ADS)

Electrical conductivity ?(?,T)of a lattice electron system due only to mutual Coulomb interaction is studied on the basis of the Fermi liquid theory, ? and T being the external frequency and the temperature, respectively. Based on the Kubo formula to respect the consistency between the selfenergyand the vertex corrections, a formulation of ?(?,T)is given in terms of memory function which is extended to the matrix form.In this formulation, it is explicitly demonstrated that,in the absence of Umklapp processes, T2-term in the resistivity vanishesas it should in spite of the fact that the total current is not conserved.

Maebashi, Hideaki; Fukuyama, Hidetoshi

1997-11-01

298

Sinterability and electrical conductivity of calcium-doped lanthanum chromites  

Microsoft Academic Search

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

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

1990-01-01

299

Design studies of continuously variable transmissions for electric vehicles  

NASA Technical Reports Server (NTRS)

Preliminary design studies were performed on four continuously variable transmission (CVT) concepts for use with a flywheel equipped electric vehicle of 1700 kg gross weight. Requirements of the CVT's were a maximum torque of 450 N-m (330 lb-ft), a maximum output power of 75 kW (100 hp), and a flywheel speed range of 28,000 to 14,000 rpm. Efficiency, size, weight, cost, reliability, maintainability, and controls were evaluated for each of the four concepts which included a steel V-belt type, a flat rubber belt type, a toroidal traction type, and a cone roller traction type. All CVT's exhibited relatively high calculated efficiencies (68 percent to 97 percent) over a broad range of vehicle operating conditions. Estimated weight and size of these transmissions were comparable to or less than equivalent automatic transmission. The design of each concept was carried through the design layout stage.

Parker, R. J.; Loewenthal, S. H.; Fischer, G. K.

1981-01-01

300

Measurements of middle-atmosphere electric fields and associated electrical conductivities  

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

301

Electrical Modulation of the Local Conduction at Oxide Tubular Interfaces  

SciTech Connect

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

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

2013-01-01

302

Electrical modulation of the local conduction at oxide tubular interfaces.  

PubMed

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

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

2013-10-22

303

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

304

Stimulation of neurite outgrowth using an electrically conducting polymer  

PubMed Central

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

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

1997-01-01

305

Stimulation of neurite outgrowth using an electrically conducting polymer.  

PubMed

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

Schmidt, C E; Shastri, V R; Vacanti, J P; Langer, R

1997-08-19

306

Stimulation of Neurite Outgrowth Using an Electrically Conducting Polymer  

NASA Astrophysics Data System (ADS)

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

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

1997-08-01

307

Simultaneous monitoring of electrical conductance and light transmittance during red blood cell aggregation.  

PubMed

The electrical properties of red blood cell (RBC) suspensions are influenced by flow conditions, and prior studies indicate that electrical properties may reflect the kinetics of RBC aggregation. Changes of conductance and capacitance were monitored and had a time course resembling a "syllectogram" (i.e., temporal change of light reflectance from an RBC suspension after sudden cessation of flow). In the present study, both AC electrical conductance (EC) across and light transmission (LT) through a 1 mm ID glass tube were recorded simultaneously after a sudden stoppage of flow for RBC at various hematocrits in plasma or in isotonic saline (PBS). Preliminary results indicate that EC and LT signals for RBC in plasma have similar time courses, both increasing after an initial decrement of a few seconds duration. Aggregation indexes and aggregation half times calculated using LT and EC showed a similar dependence on hematocrits between 30-50%. Interestingly, RBC in PBS also exhibited a syllectogram time course for conductance, whereas LT continued to decrease after an initial decline reflecting RBC shape recovery. These results suggest that electrical conductance in aggregating and non-aggregating suspensions may be sensitive to phenomena other than RBC aggregation. PMID:19581730

Baskurt, O K; Uyuklu, M; Meiselman, H J

2009-01-01

308

Proton conduction related electrical dipole and space charge polarization in hydroxyapatite  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HAp), well known as a biomaterial, is also known as a proton conductor. Its electrical properties are related strongly to its stability and surface properties. In particular, persistent electrical polarization related to proton conductivity of hydroxyapatite has a substantial influence on hydroxyapatite surface properties. The origins of polarizations were investigated in proton-defect-induced HAp ceramics using thermally stimulated depolarization current (TSDC) measurements. Two peaks were observed, indicating that the persistent polarization comprises polarization elements of two kinds. The TSDC response as a function of the applied electric field in polarization treatments indicated that the persistent polarization is dipole polarization and space charge polarization. The former, dipole polarization, increased continuously with increased defect concentration. The activation energies were 0.67-0.86 eV, which are comparable to proton conduction activation energy. Results show that dipole polarization consists of electrical dipoles of the defect pairs, which are formed through proton conduction. The activation energies of 1.01 +/- 0.01 eV for space charge polarization are independent of the defect concentration, suggesting that these originated from protons trapped at the grain boundaries as a result of long-range proton conduction. The polarization of two different types is expected to exert different effects on the HAp surface properties.

Horiuchi, N.; Nakamura, M.; Nagai, A.; Katayama, K.; Yamashita, K.

2012-10-01

309

Conductance imaging AFM and electrical properties of carbon nanotubes  

NASA Astrophysics Data System (ADS)

This thesis reports the development of a new method for measuring electrical of nanoscale objects, called conductance imaging atomic force microscopy (CIAFM), and reports the results of measurements performed on carbon nanotube networks and nanotube junctions. We introduce CIAFM, a method that combines atomic force microscopy and local conductance measurements. The method is implemented by using a tuning fork as cantilever and a solid metal tip. It excels at taking large amounts of measurements at high data density, making it equally suitable to analyze transitions on the nanometer scale or large systems such as networks. The method is thoroughly characterized. CIAFM is applied to measure the local conductances of a carbon nanotube network on the nanometer scale to characterize current paths through the network. The extent of metallic connections is investigated and found to be the principal contributor to current flow on the macroscopic scale. Finally, we analyze the length scale of conductance decay around carbon nanotube junctions. We find indication for ballistic current and exponential decay of ballistic current over a distance of several microns.

Stadermann, Michael

310

DNA-templated nanowires: morphology and electrical conductivity.  

PubMed

DNA-templating has been used to create nanowires from metals, compound semiconductors and conductive polymers. The mechanism of growth involves nucleation at binding sites on the DNA followed by growth of spherical particles and then, under favourable conditions, a slow transformation to a smooth nanowire. The final transformation is favoured by restricting the amount of templated material per unit length of template and occurs most readily for materials of low surface tension. Electrical measurements on DNA-templated nanowires can be facilitated using three techniques: (i) standard current-voltage measurements with contact electrodes embedded in a dielectric so that there is a minimal step height at the dielectric/electrode boundary across which nanowires may be aligned by molecular combing, (ii) the use of a dried droplet technique and conductive AFM to determine contact resistance by moving the tip along the length of an individual nanowire and (iii) non-contact assessment of conductivity by scanned conductance microscopy on Si/SiO2 substrates. PMID:24614835

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

2014-04-21

311

Hopping conduction from multiple scattering theory and continuous time random walk to the coherent medium approximation  

Microsoft Academic Search

A random-walk in a random environment is studied in connection with hopping conduction in doped semiconductors and with the dynamical percolation problem. A brief review is given of linear response theory, the continuous time random walk method, multiple scattering theory and the coherent medium approximation. The ac hopping conductivity in doped semiconductors is obtained in the coherent medium approximation and

M. Lax; T. Odagaki

1984-01-01

312

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

313

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

314

Low-drag electrical contact arrangement for maintaining continuity between horizontally movable members  

DOEpatents

This invention is a low-drag electrical contact arrangement for establishing continuity between upper and lower spaced members which are subject to relative horizontal movement. In one aspect, the invention comprises an electrical commutating arrangement which includes a horizontally disposed linear electrical commutator. A horizontally movable electrically conductive pedestal is positioned below the commutator and defines a clearance therewith. The pedestal is formed with a cavity confronting the commutator. In the cavity is a bead of electrical conductive liquid, the bead being characterized by an upwardly convex meniscus portion which extends across the clearance and contacts the commutator. The surface tension of the bead is sufficient to maintain the bead intact when the commutator and pedestal are displaced horizontally at speeds from zero to at least twelve inches a minute. This arrangement provides a significant advance in highly precise machining processes, such as diamond-turning, where precision is limited by the drag imposed by conventional commutators of the carbon-brush type.

Brown, R. Jack (Clinton, TN); Gerth, Howard L. (Knoxville, TN); Robinson, Samuel C. (Clinton, TN)

1982-01-01

315

Acidosis slows electrical conduction through the atrio-ventricular node  

PubMed Central

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.

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

316

Electrical conduction of carbon nanotube forests through sub-nanometric films of alumina  

NASA Astrophysics Data System (ADS)

We report both the growth of carbon nanotube forests and electrical conduction on W, Ti, and TiN substrates coated with an ultra-thin Al2O3 support layer. Varying the Al2O3 thickness, a good electrical contact and high nanotube density is possible for a 0.5 nm Al2O3 layer as such an ultra-thin film allows tunnelling. X-ray photoelectron spectroscopy shows that, when using these non-continuous Al2O3 films, Fe catalyst diffuses into the conducting substrates, eventually causing growth to stop. Forests grown on ultra-thin Al2O3 are potentially useful for applications as interconnects, supercapacitors, and heat spreaders.

Esconjauregui, Santiago; Xie, Rongsi; Guo, Yuzheng; Pfaendler, Sieglinde M.-L.; Fouquet, Martin; Gillen, Roland; Cepek, Cinzia; Castellarin-Cudia, Carla; Eslava, Salvador; Robertson, John

2013-03-01

317

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

318

Experimental Analysis of Mechanical and Electrical Characteristics of Metal-Coated Conductive Spheres for Anisotropic Conductive Adhesives (ACAs) Interconnection  

Microsoft Academic Search

An accurate characterization for the deformation behavior of conductive particles is important: 1) to understand the anisotropic conductive adhesive (ACA) interconnection and 2) to optimize the ACA bonding parameter. This paper introduces an experimental technique, which has been developed to allow continuous monitoring of deformation characteristics of a single conductive particle. The load-deformation curve of a single conductive particle is

Woon-Seong Kwon; Kyung-Wook Paik

2006-01-01

319

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

NASA Astrophysics Data System (ADS)

The power supplied to the geodynamo, measured by the heat-flux at the core-mantle boundary (CMB), places constraints on the evolution of Earth's core. 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. Recently, we computed these conductivities at core conditions for liquid iron mixtures that fit the seismologically-determined core density and inner-core boundary density jump. Both conductivities were found to be 2-3 times higher than estimates in current use. Here we describe a reassessment of the power requirements for the geodynamo based on the revised conductivity values and new estimates of the mass diffusion coefficients for individual components of the mixtures. The adiabatic heat-flux at the CMB is found to be 15-16 TW at the CMB, higher than present estimates of CMB heat-flux based on mantle convection. A thermally stratified layer beneath the CMB appears unavoidable unless a very high present-day CMB heat-flux can be maintained, which requires a rapid CMB cooling rate and an inner core that is only a few hundred years old. We estimate stable layer thicknesses by computing the radial variation of thermal and compositional gradients for a range of plausible CMB heat-flux values and assuming that the base of the layer is defined by the condition for neutral buoyancy. Thermally stable layers spanning hundreds of kilometres are found for all cases except those where the inner core is very young. These calculations also suggest that compositional buoyancy may not be sufficient to overcome the large stabilising thermal gradient; any convection in the upper core must be driven by dynamical instabilities arising from convection deeper inside the core, or by lateral variations in CMB heat flow.

Davies, C. J.; Pozzo, M.; Gubbins, D.; Alfe, D.

2012-12-01

320

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

321

Spectroscopic and Electrical Conductivity Studies of Some Semicarbazide Hydrochloride Complexes  

NASA Astrophysics Data System (ADS)

The infrared and electronic absorption spectra of semicarbazide hydrochloride and its complexes with anthracene, tetracyanoquinodimethane TCNQ, Na-fluorescein and cupferron were recorded in the regions 200-4000cm-1 and 200-400nm. The new bands that appeared in the complex spectra were assigned. The effect of the complex formation on the frequency and intensity of the active vibrational bands was also studied. The internal energy changes of the complexes were calculated in a new line of calculation to give a clear insight about the stability of the investigated complexes. The electrical conductivity of the complexes was measured in the temperature range 25-130°C. The activation energy E was calculated and discussed on the basis of the spectroscopic information.

Fadly, M.; El-Manakhly, H.

1998-11-01

322

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

323

Formulation of electrically conductive thermal-control coatings  

NASA Technical Reports Server (NTRS)

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

Shai, M. C.

1978-01-01

324

Polymeric salt bridges for conducting electric current in microfluidic devices  

DOEpatents

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

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

2009-11-17

325

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

326

Thermal effects of electrically conductive deposits in melter  

SciTech Connect

The radioactive waste processed by the Defense Waste Processing Facility melter at the Savannah river Site contains noble metal fission-products. Operation of waste-glass melters treating commercial power reactor wastes indicates that accumulation of noble metals on melter floors can lead to distortion of electric heating patterns, loss of power, and possible electrode damage. Changes in melter geometry have been developed in Japan and Germany to minimize these effects. The two existing melters for the US Department of Energy`s Defense Waste Processing Facility were designed in 1982, before this effect was known or had been characterized. Modeling and pilot scale tests are being conducted in the Integrated DWPF melter system to determine if the effect is significant for melters processing defense wastes, and if the effect can be diagnosed and corrected without significant damage or changes to the melter design. This document provides a discussion of these tests.

Choi, I.G.; Bickford, D.F.; Carter, J.T.

1992-07-01

327

Thermal effects of electrically conductive deposits in melter  

SciTech Connect

The radioactive waste processed by the Defense Waste Processing Facility melter at the Savannah river Site contains noble metal fission-products. Operation of waste-glass melters treating commercial power reactor wastes indicates that accumulation of noble metals on melter floors can lead to distortion of electric heating patterns, loss of power, and possible electrode damage. Changes in melter geometry have been developed in Japan and Germany to minimize these effects. The two existing melters for the US Department of Energy's Defense Waste Processing Facility were designed in 1982, before this effect was known or had been characterized. Modeling and pilot scale tests are being conducted in the Integrated DWPF melter system to determine if the effect is significant for melters processing defense wastes, and if the effect can be diagnosed and corrected without significant damage or changes to the melter design. This document provides a discussion of these tests.

Choi, I.G.; Bickford, D.F.; Carter, J.T.

1992-01-01

328

Facile synthesis of boron nitride nanotubes and improved electrical conductivity.  

PubMed

A layer of catalyst film on substrate is usually required during the vapor-liquid-solid (VLS) growth of one-dimensional (1D) nanomaterials. In this work, however, a novel approach for synthesizing high-purity bamboo-like boron nitride (BN) nanotubes directly on commercial stainless steel foils was demonstrated. Synthesis was realized by heating boron and zinc oxide (ZnO) powders at 1200 degrees C under a mixture gas flow of nitrogen and hydrogen. The stainless steel foils played an additional role of catalyst besides the substrate during the VLS growth of the nanotubes. In addition, the electrical conductivity of the BN nanotubes was efficiently improved in a simple way by coating with Au and Pd nanoparticles. The decorated BN nanotubes may find potential applications in catalysts, sensors and nanoelectronics. PMID:20352730

Chen, Yongjun; Luo, Lijie; Zhou, Longchang; Mo, Libin; Tong, Zhangfa

2010-02-01

329

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

330

Lower mantle electrical conductivity based on measurements of Al,?Fe-bearing perovskite under lower mantle conditions  

NASA Astrophysics Data System (ADS)

Laboratory measurements of the electrical conductivities of minerals provide important constraints on the chemistry and structure of the Earth's interior. We have measured the electrical conductivity of Al, Fe-bearing perovskite (Pv), the most abundant lower mantle phase, using a laser-heated diamond-anvil cell (LHDAC). The sample with composition Mg0.83Fe0.21Al0.06Si0.91O3 (Fe3+/?Fe ratio ? 0.4) was synthesized at 26 GPa and 2073 K using a multianvil press. Sample resistance was measured in situ at high pressure and high temperature up to 82 GPa and 2000 K, respectively. Results show a continuous increase in electrical conductivity with increasing pressure, in contrast to some previous studies of (Mg, Fe)SiO3 perovskite and a pyrolite assemblage where a decrease in conductivity was observed at higher pressure. Our results suggest that (1) incorporation of aluminum in Pv has a strong effect on its electrical conductivity and evolution with pressure; (2) spin crossover of Fe3+ does not occur or its effect on the conductivity is small in Al, Fe-bearing Pv, and (3) the contribution of ferropericlase to the electrical conductivity of pyrolite may be significant. The electrical conductivity profile of the Earth's lower mantle derived from geomagnetic data can be better explained by a pyrolitic bulk chemical composition rather than a non-pyrolitic model such as one based solely on perovskite.

Sinmyo, R.; Pesce, G.; Greenberg, E.; McCammon, C.; Dubrovinsky, L.

2014-05-01

331

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

332

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

333

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

334

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

335

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

336

High pressure-temperature electrical conductivity of magnesiowustite as a function of iron oxide concentration  

NASA Technical Reports Server (NTRS)

The electrical conductivity of (Mg, Fe)O magnesiowustite containing 9 and 27.5 mol pct FeO has been measured at simultaneously high pressures (30-32 GPa) and temperatures using a diamond anvil cell heated with a continuous wave Nd:YAG laser and an external resistance heater. The conductivity depends strongly on the FeO concentration at both ambient and high pressures. At the pressures and temperatures of about 30 GPa and 2000 K, conditions expected in the lower mantle, the magnesiowustite containing 27.5 percent FeO is 3 orders of magnitude more conductive than that containing 9 percent FeO. The activation energy of magnesiowustite decreases with increasing iron concentration from 0.38 (+ or - 0.09) eV at 9 percent FeO to 0.29 (+ or - 0.05) eV at 27.5 percent FeO.

Li, Xiaoyuan; Jeanloz, Raymond

1990-01-01

337

Soil electrical conductivity: Effects of soil properties and application to soil salinity appraisal  

Microsoft Academic Search

A model is discussed which relates bulk soil electrical conductivity (ECa) to volumetric water content (?W), electrical conductivity of the soil water (ECW), volumetric content of the solid phase (?S) and average electrical conductivity of the soil particles (ECS). Within the model a distinction is made between the water and dissolved salt present in the “immobile”; (fine pores) and “mobile”;

J. D. Rhoades; D. L. Corwin

1990-01-01

338

Use of the electrical conductivity method for investigation of the thermal stability of metal-coating systems  

SciTech Connect

The authors propose a method of measuring the ac electrical resistance with the use of an automatic compensator in the audible range of frequencies. This makes it possible to record the continuous relationships of electrical resistance to the temperature and time of conduct of the experiment used for investigation of the phase transformations in a metal-coating system directly during heat treatment. The capabilities and sensitivity of the method used have been shown using niobium with an aluminum coating as an example.

Fedorov, V.V.; Pohkmurskii, V.I.; Sokolovskii, O.R.; Lizun, O.Ya.

1986-09-01

339

EFFECT OF NEUTRON IRRADIATION ON DC ELECTRICAL CONDUCTIVITY OF SILICON CARBIDE CERAMICS AND COMPOSITES FOR FUSION FLOW CHANNEL INSERT APPLICATIONS—Y. Katoh, S  

Microsoft Academic Search

SUMMARY 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 800ºC) 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

L. L. Snead

340

Parametric instability of the surface of conducting liquid in variable electric field  

SciTech Connect

The authors investigate the parametric pumping and instabilities of a planar surface of a viscous conducting liquid metal under simultaneous application of constant and variable electric fields. The model takes into account the Maxwell relaxation of the viscosity of the liquid for the purpose of describing the dispersive interaction of the surface with the variable field whose period of oscillation is commensurable with the characteristic relaxation time of the shear stress in the liquid. Liquid flow is described by Navier-Stokes and continuity equations.

Aliev, I.N.

1987-10-01

341

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

NASA Astrophysics Data System (ADS)

The electrical parameters such as ion mobility, small ion number density, and conductivity are important for understanding the electrical nature of the atmosphere. The small ions consisting of aggregates of a few molecules practically determine the electrical conductivity over the region. The number density of these ions is controlled by ionizing mechanisms for the production of ions and electrons, and the loss processes for these charged species. Ion - production is chiefly due to radioactive substances present in the Earth's crust and the cosmic rays coming from the extra - terrestrial origin, and the resulting electrons and positive ions rapidly undergo hydration reactions which lead to the formation of negative and positive molecular ion clusters referred to as ‘small ions'. Only singly charged ions are important since the cross section for the production of multiply charged ions by particle impact are smaller than those for the production of singly charged ions by an order of magnitude or more. Further, the multiply charged ions that are formed will rapidly undergo charge transfer reaction with neutral molecules to result in singly charged ions. The small ions have mobilities large enough to move appreciably under the influence of electric field and thus determine the electrical conductivity of the atmosphere. The equilibrium density of small ions (positive or negative) is governed by the equations of continuity for the production and loss of these ions, where the gain and loss due to transport are negligible. The effective recombination of small ions is altered in the presence of aerosols, since these aerosols interact with the ions through various attachment and recombination processes. The attachment of small ions to neutral aerosols produces charged aerosols referred to as ‘large ions', which are less mobile than the smaller molecular ions. The subsequent recombination of charged aerosols with ions as well as the oppositely charged aerosols would result in the depletion of small ion concentration more rapidly than in the absence of aerosols. Thus, the formation of less mobile aerosol ions and the reduction of more mobile molecular ions alter the electrical conductivity of atmosphere. Thus, the pollution due to aerosols/dust in the atmosphere can considerably reduce the atmospheric conductivity. Hence, the atmospheric pollution level can be monitored through electrical conductivity measurements and conductivity is used as index of air pollution. In an experimental programme at Pune (18N, 74E), India measurements of radon and its progeny, aerosol number density and atmospheric conductivity are measured over a period of time covering different seasons. Using the ionization rate, ambient aerosol density and meteorological parameters such as temperature, pressure and relative humidity, the small ion concentration and hence the conductivity of the atmosphere is estimated from an Ion-aerosol model. Model computed conductivity of the atmosphere is used to validate the measured conductivity from a Gerdien condenser setup. Also estimated from the model is the reduction in small ion concentration and hence the conductivity of the atmosphere for varying levels of aerosols. It is seen that for an increase of aerosols by 3 fold the percent reduction in conductivity is 7 %, and for an increase of aerosols by 6 fold the reduction in conductivity is 10 % from the pollution free atmosphere. These results are presented in the paper.

Kamsali, Nagaraja; Datta, Jayati; Prasad, Bsn

342

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

343

Electrical modification of a conductive polymer using a scanning probe microscope  

Microsoft Academic Search

We have demonstrated the electrical modification of a conductive polymer for data storage using a scanning probe microscope (SPM). A blend of polyaniline and polymethyl-methacrylate as the conductive polymer was spun on a silicon substrate to make a test specimen. The tip of a conductive SPM probe was placed in contact with the conductive polymer and electrical modification was carried

Takahito Ono; Shinya Yoshida; Masayoshi Esashi

2003-01-01

344

Hopping conduction in high electric fields: three issues  

SciTech Connect

Three issues concerning phonon-assisted hopping in molecularly doped polymers are considered. The first issue is whether Arrhenius jump rates in the vicinity of room temperature arise from single- phonon or small-polaronic hopping. It is concluded that Arrhenius hopping only occurs above low temperatures through small-polaronic hopping. Second, hopping in molecularly doped polymers is compared with small- polaronic hopping of other systems. Small-polaronic hopping typically occurs between similar chemical structures whose energies are relatively insensitive to their surroundings. Thus, disorder energies experienced by carriers are often modest, values of several hundredths of an eV are common. Nonetheless, the effects of large electric fields on carrier mobilities differ significantly among disordered systems. Data reported for molecularly doped polymers is unlike that for either transition- metal-oxide or chalcogenide glasses. In no case is high-field transport well understood. Finally, I stress that steady-state flow is driven by differences in sites` quasielectrochemical potentials (QECPs). With disorder, differences of QECPs are not simply related to the driving emf. Solution of the (nonlinear) stochastic equations for the QECPs shows that bottlenecks produced by disorder result in nonohmic conduction. Solving the linearized stochastic (disordered resistor network) equations underestimates bottleneck effects. Linearization is inappropriate when interest differences in the QECPs exceed [kappa]T.

Emin, D.

1996-10-01

345

Effect of Electric Field on Conductivity and Vickers Hardness of an Al-Li Alloy  

NASA Astrophysics Data System (ADS)

Static electric fields were applied on an aluminium-lithium alloy during solution treatment. The conductivity and Vickers hardness of the quenched Al-Li alloy is changed with the effect of electric field. The Vickers hardness increases with the applied electric field for a certain solutionizing time but decreases with the time under an electric field. In the absence of the electric field, the Vickers hardness and the conductivity increase synchronously, while reversed after electric field treatment. Positive and negative electric fields had the similar effect. The change of the local electron density in alloy caused by electric field is presented to explain the effect.

Liu, Bing; Chen, Da-Rong; Chen, Zheng; Wang, Yong-Xin; Li, Xiao-Ling

2003-11-01

346

High-strength carbon nanotube fibre-like ribbon with high ductility and high electrical conductivity.  

PubMed

Macroscopic fibres made up of carbon nanotubes exhibit properties far below theoretical predictions and even much lower than those for conventional carbon fibres. Here we report improvements of mechanical and electrical properties by more than one order of magnitude by pressurized rolling. Our carbon nanotubes self-assemble to a hollow macroscopic cylinder in a tube reactor operated at high temperature and then condense in water or ethanol to form a fibre, which is continually spooled in an open-air environment. This initial fibre is densified by rolling under pressure, leading to a combination of high tensile strength (3.76-5.53?GPa), high tensile ductility (8-13%) and high electrical conductivity ((1.82-2.24) × 10(4)?S?cm(-1)). Our study therefore demonstrates strategies for future performance maximization and the very considerable potential of carbon nanotube assemblies for high-end uses. PMID:24964266

Wang, J N; Luo, X G; Wu, T; Chen, Y

2014-01-01

347

Fracture criterion for conductive cracks in soda-lime glass under combined mechanical and electrical loading  

Microsoft Academic Search

Fracture tests of electrically conductive cracks on pre-notched four-point bending soda-lime glass samples were conducted\\u000a under combined mechanical and electrical loading. The experimental results show that the critical stress intensity factor\\u000a at fracture is reduced if an electric field is applied, thereby indicating that the electric field makes contributions to\\u000a the fracture of conductive cracks. Base on the charge-free zone

Dong-Jun Yan; Hai-You Huang; Chi-Wai Cheung; Tong-Yi Zhang

2010-01-01

348

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

349

Electrochemical mineral scale prevention and removal on electrically conducting carbon nanotube--polyamide reverse osmosis membranes.  

PubMed

The electrochemical prevention and removal of CaSO4 and CaCO3 mineral scales on electrically conducting carbon nanotube - polyamide reverse osmosis membrane was investigated. Different electrical potentials were applied to the membrane surface while filtering model scaling solutions with high saturation indices. Scaling progression was monitored through flux measurements. CaCO3 scale was efficiently removed from the membrane surface through the intermittent application of a 2.5 V potential to the membrane surface, when the membrane acted as an anode. Water oxidation at the anode, which led to proton formation, resulted in the dissolution of deposited CaCO3 crystals. CaSO4 scale formation was significantly retarded through the continuous application of 1.5 V DC to the membrane surface, when the membrane was operated as an anode. The continuous application of a sufficient electrical potential to the membrane surface leads to the formation of a thick layer of counter-ions along the membrane surface that pushed CaSO4 crystal formation away from the membrane surface, allowing the formed crystals to be carried away by the cross-flow. We developed a simple model, based on a modified Poisson-Boltzmann equation, which qualitatively explained our observed experimental results. PMID:24563026

Duan, Wenyan; Dudchenko, Alexander; Mende, Elizabeth; Flyer, Celeste; Zhu, Xiaobo; Jassby, David

2014-05-28

350

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

351

Electrical conductivities of three-phase emulsions. 1. Strongly wetting middle phase  

SciTech Connect

Electrical conductivities of steady-state, three-phase (macro)emulsions formed by the top (T), middle (M), and bottom (B) phases of the amphiphile/oil/[open quotes]water[close quotes] (i.e., aqueous 10 mM NaCl) system C[sub 4]H[sub 9]OC[sub 2]H[sub 4]OH/n-decane/water have been measured and compared with the predictions of equations from the literature or that we have proposed. In all cases the continuous phase could be deduced from the combination of experiment and theory, but less information was obtained about dispersed-phase structures. Three new conductivity equations and two new three-phase dispersion morphologies have been proposed. 30 refs., 8 figs., 2 tabs.

Smith, D.H. (Morgantown Energy Technology Center, WV (United States) Univ. of Oklahoma, Norman, OK (United States)); Johnson, G.K. (Morgantown Energy Technology Center, WV (United States)); Wang, Y.H.C.; Lim, K.H. (WASC, Inc., Morgantown, WV (United States))

1994-08-01

352

Bisphenol A Exposure and Cardiac Electrical Conduction in Excised Rat Hearts  

PubMed Central

Background: Bisphenol A (BPA) is used to produce polycarbonate plastics and epoxy resins that are widely used in everyday products, such as food and beverage containers, toys, and medical devices. Human biomonitoring studies have suggested that a large proportion of the population may be exposed to BPA. Recent epidemiological studies have reported correlations between increased urinary BPA concentrations and cardiovascular disease, yet the direct effects of BPA on the heart are unknown. Objectives: The goal of our study was to measure the effect of BPA (0.1–100 ?M) on cardiac impulse propagation ex vivo using excised whole hearts from adult female rats. Methods: We measured atrial and ventricular activation times during sinus and paced rhythms using epicardial electrodes and optical mapping of transmembrane potential in excised rat hearts exposed to BPA via perfusate media. Atrioventricular activation intervals and epicardial conduction velocities were computed using recorded activation times. Results: Cardiac BPA exposure resulted in prolonged PR segment and decreased epicardial conduction velocity (0.1–100 ?M BPA), prolonged action potential duration (1–100 ?M BPA), and delayed atrioventricular conduction (10–100 ?M BPA). These effects were observed after acute exposure (? 15 min), underscoring the potential detrimental effects of continuous BPA exposure. The highest BPA concentration used (100 ?M) resulted in prolonged QRS intervals and dropped ventricular beats, and eventually resulted in complete heart block. Conclusions: Our results show that acute BPA exposure slowed electrical conduction in excised hearts from female rats. These findings emphasize the importance of examining BPA’s effect on heart electrophysiology and determining whether chronic in vivo exposure can cause or exacerbate conduction abnormalities in patients with preexisting heart conditions and in other high-risk populations. Citation: Posnack NG, Jaimes R III, Asfour H, Swift LM, Wengrowski AM, Sarvazyan N, Kay MW. 2014. Bisphenol A exposure and cardiac electrical conduction in excised rat hearts. Environ Health Perspect 122:384–390;?http://dx.doi.org/10.1289/ehp.1206157

Jaimes, Rafael; Asfour, Huda; Swift, Luther M.; Wengrowski, Anastasia M.; Sarvazyan, Narine; Kay, Matthew W.

2014-01-01

353

Enhanced Electrically Conductive Polypropylene\\/Nano Carbon Black Composite  

Microsoft Academic Search

In this work, a porous polypropylene (PP)\\/nano carbon black (CB) composite was facilely fabricated via immiscible co-continuous polymer blend and subsequent dissolution process. The porous structure was generated from co-continuous polymer blend, which was exploited as the substrate for depositing nano CB. The interconnected micro pores of the co-continuous polymer blend and nano pores derived from agglomerated CB resulted in

Guang Xiu Mao; An Feng Zhu

2012-01-01

354

The electrically detected magnetic resonance microscope: Combining conductive atomic force microscopy with electrically detected magnetic resonance  

NASA Astrophysics Data System (ADS)

We present the design and implementation of a scanning probe microscope, which combines electrically detected magnetic resonance (EDMR) and (photo-)conductive atomic force microscopy ((p)cAFM). The integration of a 3-loop 2-gap X-band microwave resonator into an AFM allows the use of conductive AFM tips as a movable contact for EDMR experiments. The optical readout of the AFM cantilever is based on an infrared laser to avoid disturbances of current measurements by absorption of straylight of the detection laser. Using amorphous silicon thin film samples with varying defect densities, the capability to detect a spatial EDMR contrast is demonstrated. Resonant current changes as low as 20 fA can be detected, allowing the method to realize a spin sensitivity of 8 × 10^6spins/?Hz at room temperature.

Klein, Konrad; Hauer, Benedikt; Stoib, Benedikt; Trautwein, Markus; Matich, Sonja; Huebl, Hans; Astakhov, Oleksandr; Finger, Friedhelm; Bittl, Robert; Stutzmann, Martin; Brandt, Martin S.

2013-10-01

355

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

Microsoft Academic Search

\\u000a Proximal ground conductivity sensors produce high spatial resolution maps that integrate the bulk electrical conductivity\\u000a (ECa) of the soil profile. For meaningful interpretation, variability in conductivity maps must either be inverted to profile\\u000a conductivity or be directly calibrated to profile properties. Penetrating apparent electrical conductivity (ECa–P) sensors produce high depth resolution data at relatively fewer spatial locations. The objectives of

D. B. Myers; N. R. Kitchen; K. A. Sudduth; S. Grunwald; R. J. Miles; E. J. Sadler; R. P. Udawatta

356

Continuous glucose monitoring microsensor with a nanoscale conducting matrix and redox mediator  

NASA Astrophysics Data System (ADS)

The major limiting factor in kidney clinical transplantation is the shortage of transplantable organs. The current inability to distinguish viability from non-viability on a prospective basis represents a major obstacle in any attempt to expand organ donor criteria. Consequently, a way to measure and monitor a relevant analyte to assess kidney viability is needed. For the first time, the initial development and characterization of a metabolic microsensor to assess kidney viability is presented. The rate of glucose consumption appears to serve as an indicator of kidney metabolism that may distinguish reversible from irreversible kidney damage. The proposed MetaSense (Metabolic Sensor) microdevice would replace periodic laboratory diagnosis tests with a continuous monitor that provides real-time data on organ viability. Amperometry, a technique that correlates an electrical signal with analyte concentration, is used as a method to detect glucose concentrations. A novel two-electrode electrochemical sensing cell design is presented. It uses a modified metallic working electrode (WE) and a bare metallic reference electrode (RE) that acts as a pseudo-reference/counter electrode as well. The proposed microsensor has the potential to be used as a minimally invasive sensor for its reduced number of probes and very small dimensions achieved by micromachining and lithography. In order to improve selectivity of the microdevice, two electron transfer mechanisms or generations were explored. A first generation microsensor uses molecular oxygen as the electron acceptor in the enzymatic reaction and oxidizes hydrogen peroxide (H2O2) to get the electrical signal. The microsensor's modified WE with conductive polymer polypyrrole (PPy) and corresponding enzyme glucose oxidase (GOx) immobilized into its matrix, constitutes the electrochemical detection mechanism. Photoluminescence spectroscopic analysis confirmed and quantified enzyme immobilized concentrations within the matrix. In vitro testing for glucose shows increasing current with increasing analyte concentration. Testing the glucose microsensor with known concentrations of glucose over a period of 48 hours demonstrated both the potential durability and sensitivity of the device. Unknown/blind in vitro glucose experiments showed the reproducibility and accuracy of the microsensor to detect various glucose levels. Thinner polymer matrix films lead to better sensing performance during in vitro tests (0.6nA/mM lower limit sensitivity and 0.2nA/mM upper limit sensitivity). In vitro experiments using electroactive ascorbic acid (AA) and uric acid (UA) showed the selectivity of the sensor for glucose. In an effort to reduce the sensor's oxidation potential (0.7V) and noise, a second generation electron transfer approach was developed by incorporating into a modified Platinum WE with a nanoscale PPy and GOx matrix, a redox mediator. Ferrocene (Fc) was selected as the artificial electron carrier, substituting molecular oxygen in the enzymatic reaction. The incorporation of Fc into the polymer matrix is done by a simple electrochemical synthesis. Modifications in the microsensor design, materials and fabrication process are presented. Experiments with the new sensor generation resulted in higher sensitivity values (22.8nA/mM lower limit sensitivity and 12.5nA/mM upper limit sensitivity) for glucose and noise was further eliminated by operating the sensor at a lower oxidation potential (0.3V). The final experimental work consisted of preliminary ex vivo tests with the MetaSense microdevice on bovine kidney samples, which showed a qualitatively correlation between glucose consumption trend profile during preservation and viability histology outcome.

Pesantez, Daniel

357

Preparation and characterization of highly electrically and thermally conductive polymeric nanocomposites  

Microsoft Academic Search

The conducting polymers and polymeric composites have attracted considerable attention in recent years because of their potential applications in advanced technologies, for example, in antistatic coatings, electromagnetic shielding. The introduction of electrically conductive fillers such as graphite, carbon black, metal and metal oxide powders into the polymeric matrix is a promising approach to fabricate electrically conductive polymeric materials. The recent

Volkan Çeçen; I. Özdemir; Alparslan Turgut; Igor Krupa; Maria Omastova; Igor Novak

358

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

359

Mechanism of electrical conductivity in an irradiated polyimide  

NASA Technical Reports Server (NTRS)

A polyimide was exposed to 1.0 MeV electron radiation. The radiation-induced radical density and dc conductivity were measured at various post-irradiation times. The radiation-induced radical density was found to be correlated to the increased dc conductivity through a hopping model of conductivity. The post-irradiation radical species were identified.

Ries, H. R.; Harries, W. L.; Long, S. A. T.; Long, E. R., Jr.

1989-01-01

360

20 CFR 404.1589 - We may conduct a review to find out whether you continue to be disabled.  

Code of Federal Regulations, 2013 CFR

...SOCIAL SECURITY ADMINISTRATION FEDERAL OLD-AGE, SURVIVORS AND DISABILITY INSURANCE (1950- ) Determining Disability and Blindness Continuing Or Stopping Disability § 404.1589 We may conduct a review to find out whether you continue to be...

2013-04-01

361

20 CFR 416.989 - We may conduct a review to find out whether you continue to be disabled.  

Code of Federal Regulations, 2013 CFR

...SUPPLEMENTAL SECURITY INCOME FOR THE AGED, BLIND, AND DISABLED Determining Disability and Blindness Continuing Or Stopping Disability Or Blindness § 416.989 We may conduct a review to find out whether you continue to be...

2013-04-01

362

Investigation of a High Temperature Electrical Conductivity Device for Use with Thermal Image Heating.  

National Technical Information Service (NTIS)

The 'double-clamshell' imaging system has been successfully used to measure electrical conductivity of single crystal and polycrystalline aluminum oxide and pyrolytic boron nitride in the absence of impressed electric and magnetic fields. A furnace with a...

P. S. Schaffer H. A. Hobbs R. C. Folweiler

1964-01-01

363

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

National Technical Information Service (NTIS)

Measurements of fluid thermal properties using the transient hot-wire technique are described. When bare hot wires are used in electrically conducting fluids there are additional measurement uncertainties due to the formation of electric double layers on ...

R. A. Perkins

1994-01-01

364

Electrical-stress-induced conductivity increase in SrTiO3 films  

Microsoft Academic Search

The charge transport of polycrystalline SrTiO3 films doped with Cr is investigated by means of temperature- and electric-field-dependent current measurements. In particular, the effect of electrical stress on the conduction mechanism is analyzed to understand the forming process of samples exhibiting resistance-switching phenomena. The temperature dependence of the conductivity can be described with the variable-range hopping model. The electrical-stress-induced conductivity

S. Karg; G. I. Meijer; D. Widmer; J. G. Bednorz

2006-01-01

365

Intercomponent momentum transport and electrical conductivity of collisionless plasma  

NASA Technical Reports Server (NTRS)

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

Wilhelm, H. E.

1973-01-01

366

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

367

Continuous microbial fuel cells convert carbohydrates to electricity.  

PubMed

Microbial fuel cells which are operated in continuous mode are more suitable for practical applications than fed batch ones. Three influent types containing carbohydrates were tested, i.e. a glucose medium, a plant extract and artificial wastewater. The anode reactor compartment yielding the best results was a packed bed reactor containing graphite granules. While in non-mediated batch systems power outputs up to 479 W m(-3) of anode compartment could be attained; in continuous mode the power outputs were limited to 49W m(-3). Cyclic voltammetry was performed to determine the potential of the in-situ synthesized bacterial redox mediators. Addition of mediators with a potential similar to the bacterial potential did not significantly alter the MFC power output, indicating a limited influence of soluble mediators for continuous microbial fuel cells. Maximum coulombic and energy conversion efficiencies were, for the continuous microbial fuel cell operating on plant extract at a loading rate of 1 kg COD m(-3) of anode compartment per day, 50.3% and 26.0% respectively. PMID:16180472

Rabaey, I; Ossieur, W; Verhaege, M; Verstraete, W

2005-01-01

368

Electrical conductivity of diopside: evidence for oxygen vacancies  

USGS Publications Warehouse

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

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

1988-01-01

369

Preparation of Electrically Conductive Polystyrene/Carbon Nanofiber Nanocomposite Films  

ERIC Educational Resources Information Center

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

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

2008-01-01

370

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

371

Breakdown Characteristics of an Isolated Conducting Object in a Uniform Electric Field.  

National Technical Information Service (NTIS)

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. Gr...

M. G. Grothaus T. F. Trost

1986-01-01

372

Changes During Storage of Electrically Conductive Blends Polyaniline–Poly(Ethylene?co?vinyl Acetate)  

Microsoft Academic Search

The electrical conductivity behavior of polyaniline–poly(ethylene?co?vinyl acetate) (PANI–EVA) blends was variable and dynamic during their storage. It was shown that the apparent concentration of the intrinsically conductive polymer at which a conductivity jump of the blends occurs (?c) is not a constant value over time. The electrical conductivity of the films of low PANI content (below 2.5 wt.%) increased by several

T. Tsanov; P. Mokreva; D. Tsocheva; L. Terlemezyan

2004-01-01

373

Investigation of DC electrical conductivity of chalcogenide glasses  

NASA Astrophysics Data System (ADS)

The various Se-S-Zn chalcogenide glasses have been prepared by the standard melt-quenching technique. Their amorphous state was verified by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The temperature dependence of DC conductivity was measured in the temperature range 323-358K, in order to identify the conduction mechanism and to observe the doping effect of Zn on Se-S. In this temperature range, DC conductivity increases from 10-8 to 10-7 S/m with an increase in Zn concentration.

Sanjay; Kishore, N.; Kundu, R. S.; Agarwal, A.; Dhankhar, S.

2013-02-01

374

Magnetospheric and ionospheric signals in magnetic observatory monthly means: Electrical conductivity of the deep mantle  

NASA Technical Reports Server (NTRS)

First differences of magnetic observatory monthly means for 1963-1982 were analyzed using techniques of spherical harmonics analysis and power spectral analysis. The external source signal is shown to be primarily zonal in geomagnetic coordinates. Prominent peaks are present in the power spectrum at frequencies of 1.0 cycle/yr and 2.0 cycles/yr. The annual signal is largest on the degree 2 external zonal spherical harmonic, while the semiannual signal is largest on the degree 1 and degree 3 external zonal spherical harmonics. The presence of the semiannual signal on odd-degree spherical harmonics and of the annual signal on even-degree spherical harmonics was predicted from symmetry considerations and the annual cycle of solar inclination. These signals are all modulated by the sunspot frequency and its harmonics. The degree 1 term is believed to be due mainly to magnetopause and ring currents while the degree 2 and degree 3 terms are believed to be due mainly to ionospheric currents. The degree 1 external zonal harmonic has a continuous spectrum in addition to the semiannual spectral peak. A corresponding degree 1 internal term is due to electromagnetic induction. The degree 1 continuous spectrum is useful for study of the electrical conductivity of the deep mantle. A global geomagnetic response function consistent with a mantle conductivity of about 10 S/m at the core-mantle boundary has been derived.

Mcleod, Malcolm G.

1994-01-01

375

Electrochemical intercalation and electrical conductivity of graphite fibers  

NASA Technical Reports Server (NTRS)

Lamellar compounds of graphite fibers were prepared by electrochemical intercalation. The dependence of the electrical resistance on the intercalate concentration was determined by a quasi simultaneous method. A factor 30 decrease of the relative fiber resistance was obtained with fluorosulfuric acid.

Besenhard, J. O.; Fritz, H. P.; Moehwald, H.; Nickl, J. J.

1982-01-01

376

Surface Electrical Conductivity of Single Crystal Spinel in Cesium Vapour.  

National Technical Information Service (NTIS)

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 Pr...

P. Agnew J. L. Ing

1995-01-01

377

High frequency electrical conduction block of the pudendal nerve  

Microsoft Academic Search

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

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

2006-01-01

378

Electrical Conductance of Bolted Copper Joints for Cryogenic Applications  

NASA Astrophysics Data System (ADS)

We present the results of electric contact resistance measurements at low temperatures on copper-to-copper bolted joints. Our accurate and systematic data display a rather small dispersion, and may be a useful tool for cryogenic applications like pulse-tubes, dilution refrigerators and nuclear refrigerators.

Blondelle, F.; Sultan, A.; Collin, E.; Godfrin, H.

2014-06-01

379

Electrical and Optical Properties of Conducting Polymer - Fullerene and Conducting Polymer - Carbon Nanotube Composites  

Microsoft Academic Search

Various novel photo-physical properties such as a drastic photoluminescence quenching and photoconductivity enhancement and a photo-induced enhancement of low-field microwave absorption due to a highly effective photo-induced electron transfer have been observed in various conducting polymers doped with fullerenes and also acceptor-type molecules and conducting polymers. New types of junction devices utilizing effective charge separation at the interface of conducting

Katsumi Yoshino; Hirotake Kajii; Hisashi Araki; Tooru Sonoda; Hiroyoshi Take; Sergey Lee

1999-01-01

380

Thermal characterisation of electrically conductive adhesive flip-chip joints  

Microsoft Academic Search

In this paper, we present simulation results of the thermal characteristics of epoxy-based anisotropically conductive adhesive (ACA) flip-chip joints. The results are compared with the thermal characteristics of isotropically conductive adhesive (ICA) flip-chip joints, soldered flip-chip modules and wire bonded modules. The simulated thermal parameters are the overall thermal resistance from the active chip surface down to the substrate as

Anders Sihlbom; Johan Liu

1998-01-01

381

Enhancement of Electrical Conductivity in Plasticized Chitosan Based Membranes  

Microsoft Academic Search

Plasticized natural macromolecules-based polymer electrolyte samples were prepared and characterized. The plasticization of chitosonium acetate with glycerol increased the ionic conductivity value from 3.0 × 10 S\\/cm to 1.1 × 10 S\\/cm. The conductivity temperature relationship of the samples exhibits either VTF or Arrhenius type depending on the glycerol concentration in the sample. The dielectric studies evidencing the relaxation process

R. I. Mattos; E. Raphael; S. R. Majid; A. K. Arof; A. Pawlicka

2012-01-01

382

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

Microsoft Academic Search

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

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

1998-01-01

383

Electrical Conductance Cell Assembly for Precise Measurements with Carbonates, Oxides, and Fluorides up to 1000°C  

Microsoft Academic Search

A conductance cell assembly is reported of the capillary design with a cell constant sufficiently high to permit precise electrical conductance measurements with the standard type precision conductance bridge circuits. Important features are the use of single crystal grade MgO for construction of the capillaries that determine the resistance for the electrolyte in the conductance cell, and the use of

George J. Janz; Max R. Lorenz

1961-01-01

384

Physical property and electrical conductivity of electroless Ag-plated carbon fiber-reinforced paper  

Microsoft Academic Search

The addition of a large amount of conductive filler to paper in order to increase electrical conductivity adversely affects some physical properties of the paper. Hence, it is desirable that conductive paper can be manufactured by adding only a small amount of conductive filler. Reinforced paper was manufactured by adding (1) electroless Ag-plated carbon fiber or (2) activated carbon fiber

Joon Jang; Seung Kon Ryu

2006-01-01

385

Measurements of the Electrical Conductivities of Air over Hot Water.  

NASA Astrophysics Data System (ADS)

Measurements of the conduction current between two electrodes in air over recently boiled water have been interpreted by Carlon as indicating that the humidified air became highly conductive and that large numbers of ions were produced in the air after it was saturated with water vapor. These interpretations have been questioned because it is possible that the insulators used in the high-humidity experiments allowed leakage currents to flow and these were treated as though they were conduction currents through the air.We repeated these measurements with the use of a conventional, Gerdien cylinder conductivity-measuring apparatus that had insulators heated to temperatures above the dew point of the water vapor in the air being measured so that the insulators maintained high resistances. The results from the heated Gerdien cylinder experiments contradict the suggestions of high conductivities in humid air, for the measured conductivities of air were repeatedly observed to decrease by about 50% when recently boiled, hot water was brought in contact with the air.

Moore, C. B.; Vonnegut, B.

1988-03-01

386

Electrical conductivity in directionally solidified lead-9 and -20 wt pct copper alloys  

NASA Technical Reports Server (NTRS)

Composites consisting of aligned copper dendrites in a lead matrix have been produced by directional solidification processing for potential application as grids in lead-acid batteries. To promote a uniform composite of aligned copper dendrites in a protective lead matrix, two alloy compositions, Pb-9 and -20 wt pct Cu, have been directionally solidified through a temperature gradient of 4.5 K/mm at constant growth velocities which ranged from 1 to 100 micron/s. With slow growth rates (below about 10 microns/s), the copper dendrites were generally columnar and continuous along the sample length; at higher velocities (above 60 microns/s), they assumed an intricate and equiaxed morphology. In accordance with copper content and growth rate, the electrical conductivity of the directionally solidified composites was found to be as much as a 2.5 times that of pure lead. The results are compared with that predicted by a model based on a geometrical dendrite.

Kim, Shinwoo; Flanagan, W. F.; Lichter, B. D.; Grugel, R. N.

1993-01-01

387

Electrical conductivity in directionally solidified lead-9 and -20 wt pct copper alloys  

NASA Astrophysics Data System (ADS)

Composites consisting of aligned copper dendrites in a lead matrix have been produced by directional solidification processing for potential application as grids in lead-acid batteries. To promote a uniform composite of aligned copper dendrites in a protective lead matrix, two alloy compositions, Pb-9 and -20 wt pct Cu, have been directionally solidified through a temperature gradient, G l of 4.5 Kmm-1 at constant growth velocities which ranged from 1 to 100 µm s-1. With slow growth rates (?10 µm s-1 ), the copper dendrites were generally columnar and continuous along the sample length; at higher velocities (?60 µm s-1), they assumed an intricate and equiaxed morphology. In accordance with copper content and growth rate, the electrical conductivity of the directionally solidified composites was found to be as much as a 2.5 times that of pure lead. The results are compared with that predicted by a model based on a geometrical dendrite.

Kim, Shinwoo; Flanagan, W. F.; Lichter, B. D.; Grugel, R. N.

1993-04-01

388

Simultaneous measurements of thermal conductivity and electrical conductivity of micro-machined Silicon films  

NASA Astrophysics Data System (ADS)

The in-plane effective thermal conductivity of free-standing Si thin films with periodic micropores was measured at -100 to 0 °C. The Si thin films with micropores were prepared from silicon-on-insulator (SOI) wafers by standard microfabrication processes. The dimensions of the free-standing Si thin films were 200?m×150?m×2 ?m, with staggered 4 ?m pores having an average pitch of 4 mm. The Si thin film serves both as a heater and thermometer. The average temperature rise of the thin film is a function of its in-plane thermal conductivity. The effective thermal conductivity was calculated using a simple one-dimensional heat conduction model. The measured thermal conductivity was much lower than that expected based on classical model evaluations. A significant phonon size effect was observed even in the microsized structures, and the mean free path for phonons is very long even at the room temperature.

Hagino, H.; Kawahara, Y.; Goto, A.; Miyazaki, K.

2012-02-01

389

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

390

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

391

A review of laboratory measurements of the electrical conductivity of rocks and minerals  

Microsoft Academic Search

The use of laboratory measurements of electrical conductivity for rocks and minerals at high temperatures and pressures helps us to interpret magnetotelluric measurements and allows us to obtain further information about various physical and mineralogical properties of the Earth's interior. A survey of recent laboratory measurements of electrical conductivity of rocks and minerals at high temperatures and pressures is outlined.

Marcela Latoviková

1991-01-01

392

Polyaniline\\/zeolite LTA composites and electrical conductivity response towards CO  

Microsoft Academic Search

Electrical conductivity response of polyaniline\\/zeolite composites towards CO is investigated in terms of dopant type, dopant concentration, zeolite LTA content and zeolite pore size. Both MA and HCl doped polyanilines respond with comparable magnitudes towards CO; the latter responses are slightly smaller for the same doping level. Addition of zeolite 4A reduces the electrical conductivity response but improves the sensitivity

C. Chuapradit; L. Ruangchuay Wannatong; D. Chotpattananont; Piyanoot Hiamtup; A. Sirivat; J. Schwank

2005-01-01

393

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

Microsoft Academic Search

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

Wenge Zheng; Shing-Chung Wong

2003-01-01

394

Electrical Conductivity Of Diamond Up To 1,200 Degrees C  

NASA Technical Reports Server (NTRS)

Report discusses measurements of electrical conductivities of two synthetic diamond films, three synthetic diamondlike films, and two natural type IIa diamonds at temperatures from ambient to 1,200 degrees C. Measurements performed to compare electrical conductivities of state-of-the-art diamond films with those of natural insulating diamond, particularly at temperatures above 700 degrees C.

Vandersande, Jan W.; Zoltan, Leslie D.

1993-01-01

395

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

396

Electrical Conductivity of Solid Oxides. Xi. La2O3-CaO System.  

National Technical Information Service (NTIS)

In view of the previously investigated electrical conductivity of a solid solution with the fluorite-type lattice, the subject of this study was to determine the effect of the change of the crystal structure of the electrolyte on electrical conductivity. ...

S. F. Palguev Z. S. Volchenkova

1968-01-01

397

Comparison of Electromagnetic Induction and Direct Sensing of Soil Electrical Conductivity  

Microsoft Academic Search

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

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

2003-01-01

398

Electrical Conductivity during XPS of Heated PMMA: Detection of Core Line and Valence Band Tacticity Effects.  

National Technical Information Service (NTIS)

Electrical conductivity during the XPS of approximately 100 nm thick films of PMMA on silicon was induced by heating to above 100 degrees C. Rapid x-ray induced depolymerization set in at about the same temperature. The electrical conductivity allowed acq...

G. Beamson D. T. Clark D. S. L. Law

1998-01-01

399

Thermal conductivity of KH2PO4 in an applied electric field  

Microsoft Academic Search

The thermal conductivity of single-crystal KH2PO4 has been measured from 10 K to room temperature in an applied electric field. The applied field causes a small increase in the thermal conductivity at temperatures close to the ferroelectric-to-paraelectric transition. The results are compared with the dielectric polarization KH2PO4 in an applied electric field.

Fengqi Lin; Da-Ming Zhu

1994-01-01

400

Thermal conductivity of KH2PO4 in an applied electric field  

NASA Astrophysics Data System (ADS)

The thermal conductivity of single-crystal KH2PO4 has been measured from 10 K to room temperature in an applied electric field. The applied field causes a small increase in the thermal conductivity at temperatures close to the ferroelectric-to-paraelectric transition. The results are compared with the dielectric polarization KH2PO4 in an applied electric field.

Lin, Fengqi; Zhu, Da-Ming

1994-06-01

401

Electrical conductivity measurements of a high-pressure seeded air plasma  

Microsoft Academic Search

The magnetohydrodynamic (MHD) accelerator has been considered as a device for augmenting the performance of hypersonic test facilities. A requirement for operating an MHD accelerator is that the gas must have sufficient electrical conductivity to allow current flow at reasonable applied electrode voltage. Therefore, knowledge of flow properties such as the electrical conductivity, electron density and current discharge characteristics in

Hsuan-Cheng Liu

1998-01-01

402

Electrical behaviour of conducting silicon rubber under short high current stress  

Microsoft Academic Search

The conducting silicon rubber was highly stressed by means of voltage impulses in order to investigate the electric behaviour of this material. A specific value of electric load-carrying capacity was observed. Below this value material exhibits resistive character and constant electrical properties, however, above this value the material is damaged and can not be used in practical application. The explanation

A. Napierala

2010-01-01

403

Local electrical conduction in polycrystalline La-doped BiFeO? thin films.  

PubMed

Local electrical conduction behaviors of polycrystalline La-doped BiFeO3 thin films have been investigated by combining conductive atomic force microscopy and piezoelectric force microscopy. Nanoscale current measurements were performed as a function of bias voltage for different crystal grains. Completely distinct conducting processes and resistive switching effects were observed in the grain boundary and grain interior. We have revealed that local electric conduction in a grain is dominated by both the grain boundary and ferroelectric domain, and is closely related to the applied electric field and the as-grown state of the grain. At lower voltages the electrical conduction is dominated by the grain boundary and is associated with the redistribution of oxygen vacancies in the grain boundary under external electric fields. At higher voltages both the grain boundary and ferroelectric domain are responsible for the electrical conduction of grains, and the electrical conduction gradually extends from the grain boundary into the grain interior due to the extension of the ferroelectric domain towards the grain interior. We have also demonstrated that the conduction dominated by the grain boundary exhibits a much small switching voltage, while the conduction of the ferroelectric domain causes a much high switching voltage in the grain interior. PMID:23637078

Zhou, Ming-Xiu; Chen, Bo; Sun, Hai-Bin; Wan, Jian-Guo; Li, Zi-Wei; Liu, Jun-Ming; Song, Feng-Qi; Wang, Guang-Hou

2013-06-01

404

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

405

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

SciTech Connect

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. [Physics Department, Technion, Haifa 32000 (Israel)

2011-09-15

406

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

PubMed

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

407

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.

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

2011-01-01

408

Relationship between microstructure, hardness and electrical conductivity of 2219 aluminium  

Microsoft Academic Search

A TEM study of unstretched, heat-treated aluminium alloy 2219 was performed with the aim of correlating the microstructure with hardness (H) and eddy current conductivity (C) data. Recently Chihoski has developed a new method of evaluating heat treatments of aluminium alloys by constructing in an H-C field a “sail” formed by a network of curved coordinate lines of quenching and

M. Natan; R. A. Chihoski

1983-01-01

409

Atrioventricular conduction in mammalian species: Hemodynamic and electrical scaling  

Microsoft Academic Search

OBJECTIVES The purpose of this study was to investigate scaling of the duration of late diastolic left ventricular (LV) filling in relation to AV conduction time (delay) (PR interval on the ECG) in mammals.\\u000aBACKGROUND From mouse to whale, AV delay increases 10-fold, whereas body mass increases one million-fold. The apparent \\

Frits L. Meijler; Jacques Billette; José Jalife; Marja J. L. Kik; Johan H. C. Reiber; Arnold A. Stokhof; Jos J. M. Westenberg; Claes Wassenaar; Jan Strackee

2005-01-01

410

Electric Conduction in n-Type Germanium and Cadmium Sulfide.  

National Technical Information Service (NTIS)

The impurity conduction of n-type Ge and CdS is calculated via a previously developed theory for impurity bands in doped semiconductors. Rough agreement with experimental data over a wide range of impurity concentration is found. The comparison with AMO-M...

D. A. Ferreira I. C. Dacunhalima M. Fabbri

1980-01-01

411

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

412

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

413

Highly Electrically Conductive Nanocomposites Based on PolymerInfused Graphene Sponges  

PubMed Central

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

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

2014-01-01

414

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

PubMed

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

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

2011-01-01

415

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

PubMed Central

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

2011-01-01

416

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

417

Improving the electrical and mechanical behavior of electrically conductive paint by partial replacement of silver by carbon black  

Microsoft Academic Search

Partial replacement of silver particles by carbon black (low cost) in electrically conductive paint was found to decrease\\u000a the electrical resistivity and increase the scratch resistance of the resulting thick film, which is for use in electrical\\u000a interconnections. An effective carbon black content is 0.055 of the total filler volume. By using a total solid volume fraction\\u000a of 0.1969 and

Chia-Ken Leong; D. D. L. Chung

2006-01-01

418

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

419

Electrical Conductivity of 2D-SiCf/CVI-SiC  

SciTech Connect

Electrical conductivity (EC) data for several plate forms of two-dimensional, silicon carbide composite made with chemical vapor infiltration matrix and with Hi Nicalon{trademark} type S fibers (2D-SiCf/CVI-SiC) were acquired. The composite fibers were coated with pyrocarbon (PyC) of various thicknesses (50 to 310 nm) and an outer thin ({approx}60 {mu}m) SiC 'seal coat' was applied by CVD to the infiltrated plates. The EC was highly anisotropic in the transverse and in-plane directions. In-plane EC ranged from {approx}150 to 1600 S/m, increased slowly with increasing temperature, and depended primarily on the total PyC thickness. High in-plane EC-values occur because it is dominated by conduction along the numerous, continuous PyC fiber coating pathways. Transverse EC ranged from {approx}1 to 60 S/m, and increased strongly with increasing temperature up to 800 C. The transverse EC is controlled by conduction through the interconnections of the carboncoating network within and between fiber bundles, especially at moderate temperatures ({approx}300 to 700 C). Below {approx}300 C, the electrical resistance of the pure SiC seal coat becomes increasingly more important as temperatures are further lowered. Importantly, a '3-layer series' model predicts that transverse EC-values for a standard seal-coated 2DSiCf/ CVI-SiC with a monolayer PyC fiber coating of {approx}50-nm thickness will be <20 S/m for all temperatures up to 800 C, as desired for a flow channel insert in a fusion reactor blanket component.

Youngblood, Gerald E.; Thomsen, Edwin C.; Shinavski, Robert J.

2011-07-11

420

Effective Thermal Conductivity of Continuous Matrix-spherical Dispersed Phase Composite with Single-point Interfacial Thermal Contact: Free Molecular Gas Conduction in the Gap  

Microsoft Academic Search

Analytical solutions are presented for the lower bound of the effective thermal conductivity of a continuous matrix composite for the limiting case of fully debonded spherical inclusions in single-point contact with the matrix, with heat conduction across the interfacial gap occurring by gaseous heat transfer in the free-molecular regime. Imposed temperature gradients parallel and perpendicular to the diameter through the

J. R. Thomas; D. P. H. Hasselman

2007-01-01

421

Electrical Conductivity Images of South African Continental Collision Zones  

Microsoft Academic Search

Within the framework of the German-South African geo-scientific research initiative Inkaba yeAfrica several magnetotelluric (MT) field experiments were conducted along the Agulhas-Karoo transect in South Africa. This 600km long transect is designed to cross the Cape Fold Belt, the Namaqua-Natal Mobile Belt (NNMB), the Karoo Basin and the transition into the Kaapvaal Craton. At the same time, the transect crosses

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

2008-01-01

422

Modeling the Time-dependent Changes in Electrical Conductivity of Basaltic Melts With Redox State  

Microsoft Academic Search

The electrical conductivity sigma is an efficient probe of mass transfer processes within silicate melts and magmas. Little attention has been given to the influence of redox state (fO2) on the melts conductivity. We present an experimental setup allowing electrical conductivity measurements for basaltic melts under variable fO2. We demonstrate a significant dependence of sigma with fO2, allowing to characterize

A. Pommier; F. Gaillard; M. Pichavant

2008-01-01

423

Space charge and electrical conduction in maleic anhydride-grafted polyethylene  

Microsoft Academic Search

The space charge behavior such as charge distribution and electrical conduction of maleic anhydride grafted LDPE (LDPE-g-MAH) was investigated. Heterocharge was found in LDPE and it decreased with increasing MAH graft ratio in LDPE-g-MAH. Conduction currents also decreased with increasing MAH graft ratio. The relationship between the space charge behavior and the electrical conduction characteristics in LDPE-g-MAH is discussed

Seung Hyung Lee; Jung-Ki Park; Jae Hong Han; Kwang S. Suh

1995-01-01

424

Measurement of Complex Electrical Conductivity of Metallic Powders in a Sealed Tube  

Microsoft Academic Search

We studied the method of complex-electrical-conductivity measurement for powders placed in a sealed tube at microwave and millimeter-wave frequencies, using a cavity perturbation technique. We applied this technique to a molecular superconductor K3C60, whose electrical conduction is well known in single crystals, and reproduced the metallic conductivity with the magnitude of 0.5-1.2 mOmegacm at 20 K which is in good

Atsutaka Maeda; Ryoji Matsuo; Ryotaro Inoue; Haruhisa Kitano; Taishi Takenobu; Yoshihiro Iwasa; Tadaoki Mitani

2000-01-01

425

Electrical conductivity and chemical diffusion coefficient of Sr-doped lanthanum chromites  

Microsoft Academic Search

The electrical conductivity and chemical diffusion coefficient of Sr-doped lanthanum chromites were measured as a function of oxygen partial pressure (Po2) and temperature, and the results were discussed in light of defect chemistry. The electrical conductivity was independent of Po2 and in proportion to the Sr-content at high Po2, while at low Po2, the conductivity decreased exponentially with decrease of

I. Yasuda; M. Hishinuma

1995-01-01

426

Deterministic and stochastic dynamic modeling of continuous manufacturing systems using analogies to electrical systems  

Microsoft Academic Search

A dynamic system model of continuous manufacturing systems has been developed based on analogies with electrical systems. This model has the capability to model both deterministic and stochastic systems. The model provides physically meaningful governing equations to describe both the steady state and transient responses of continuous manufacturing systems. For stochastic solutions, the model is not limited to any specific

Bashar H. Sader; Carl D. Sorensen

2003-01-01

427

Bisphenol a exposure and cardiac electrical conduction in excised rat hearts.  

PubMed

Background: Bisphenol A (BPA) is used to produce polycarbonate plastics and epoxy resins that are widely used in everyday products, such as food and beverage containers, toys, and medical devices. Human biomonitoring studies have suggested that a large proportion of the population may be exposed to BPA. Recent epidemiological studies have reported correlations between increased urinary BPA concentrations and cardiovascular disease, yet the direct effects of BPA on the heart are unknown.Objectives: The goal of our study was to measure the effect of BPA (0.1-100 ?M) on cardiac impulse propagation ex vivo using excised whole hearts from adult female rats.Methods: We measured atrial and ventricular activation times during sinus and paced rhythms using epicardial electrodes and optical mapping of transmembrane potential in excised rat hearts exposed to BPA via perfusate media. Atrioventricular activation intervals and epicardial conduction velocities were computed using recorded activation times.Results: Cardiac BPA exposure resulted in prolonged PR segment and decreased epicardial conduction velocity (0.1-100 ?M BPA), prolonged action potential duration (1-100 ?M BPA), and delayed atrioventricular conduction (10-100 ?M BPA). These effects were observed after acute exposure (? 15 min), underscoring the potential detrimental effects of continuous BPA exposure. The highest BPA concentration used (100 ?M) resulted in prolonged QRS intervals and dropped ventricular beats, and eventually resulted in complete heart block.Conclusions: Our results show that acute BPA exposure slowed electrical conduction in excised hearts from female rats. These findings emphasize the importance of examining BPA's effect on heart electrophysiology and determining whether chronic in vivo exposure can cause or exacerbate conduction abnormalities in patients with preexisting heart conditions and in other high-risk populations.Citation: Posnack NG, Jaimes R III, Asfour H, Swift LM, Wengrowski AM, Sarvazyan N, Kay MW. 2014. Bisphenol A exposure and cardiac electrical conduction in excised rat hearts. Environ Health Perspect 122:384-390;?http://dx.doi.org/10.1289/ehp.1206157. PMID:24487307

Posnack, Nikki Gillum; Jaimes, Rafael; Asfour, Huda; Swift, Luther M; Wengrowski, Anastasia M; Sarvazyan, Narine; Kay, Matthew W

2014-04-01

428

Re-evaluation of electrical conductivity of anhydrous and hydrous wadsleyite  

NASA Astrophysics Data System (ADS)

Recent laboratory electrical conductivity measurements of the main mantle constituent minerals have represented considerable efforts to determine the effects of water content on electrical conductivity. However, there are large discrepancies between the results of Yoshino et al. (2008a) and those of Dai and Karato (2009a) on hopping conduction and the effects of water on the electrical conductivity of wadsleyite. To investigate the cause of these discrepancies, the electrical conductivity of anhydrous and hydrous wadsleyite were newly measured under low and high temperature conditions by impedance spectroscopy. The conductivity values of dry wadsleyite aggregates with less than 2 ppm H2O by weight were similar to those for hopping conduction reported by Yoshino et al. (2008a) and distinctly higher than those of Dai and Karato (2009a). For hydrous wadsleyite, at temperatures below 1000 K, the electrical conductivity in an Arrhenius plot was repeatable along the heating-cooling paths and was similar to the results of Yoshino et al. (2008a). The impedance spectrum in the complex impedance plane of hydrous wadsleyite showed a semicircular shape, and the infrared spectrum did not show any shape change after the conductivity measurements. In contrast, when the temperature exceeds 1000 K, the electrical conductivity in an Arrhenius plot showed higher activation enthalpy. The impedance spectra were greatly distorted and the impedance arc contained at least two relaxation processes. This shape is similar to those reported by Dai and Karato (2009a) who measured the conductivity above 1000 K. The infrared spectra showed a large contribution from molecular water after conductivity measurements, suggesting significant dehydration during the conductivity measurements. In summary, the results obtained from conductivity measurements at higher temperatures (>1000 K) do not represent the proton conduction in the grain interior.

Yoshino, Takashi; Katsura, Tomoo

2012-07-01

429

Carbon nanotube grease with enhanced thermal and electrical conductivities  

Microsoft Academic Search

A stable and homogeneous grease based on carbon nanotubes (CNTs, single-wall and multi-wall) in polyalphaolefin oil has been\\u000a produced without using a chemical surfactant. For example, for a 11 wt% (7 vol%) single-wall CNT (diameter 1–2 nm, length\\u000a 0.5–40 ?m) loading, the thermal conductivity (TC) of the grease shows a 60–70% increase compared to that for no nanotube loading.\\u000a In addition, the grease is

Haiping Hong; Dustin Thomas; Andy Waynick; Wenhua Yu; Pauline Smith; Walter Roy

2010-01-01

430

Tunable single-photon heat conduction in electrical circuits  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

431

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

432

Simple Method for Estimating the Electrical Conductivity of Oxide Melts with Optical Basicity  

NASA Astrophysics Data System (ADS)

The electrical conductivity of oxide melts is an important physicochemical property for designing the electric smelting furnaces. Although the data of many slag systems have been measured, the quantitative relationships of electrical conductivity to slag composition and temperature are still limited. In this article, a model is proposed based on the optical basicity corrected for the cations required for the charge balance of {{AlO}}_{ 4}^{ 5- } , in which Arrhenius Law is used to describe the relationship between electrical conductivity and temperature. In this model, the activation energy is expressed as a linear function of the corrected optical basicity. Successful applications to CaO-MgO-Al2O3-SiO2 and CaO-Al2O3-SiO2 systems indicate that this model can work well in the electrical conductivity estimation.

Zhang, Guo-Hua; Chou, Kuo-Chih

2010-02-01

433

Electrostatic interaction of two unequal conducting spheres in uniform electric field  

Microsoft Academic Search

An image dipole method is employed to calculate the induced dipole moments of a pair of unequal-size conducting spheres subjected to a uniform electric field. Expressions for the dipole moments are given, involving the size ratio and separation of the spheres. Two typical cases are analyzed; two similar conducting spheres and two unequal conducting spheres with remarkable difference in size.

Zehui Jiang

2003-01-01

434

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

NASA Astrophysics Data System (ADS)

The electrical conductivity of rocks results from conduction through the bulk solution occupying the pores and from surface conduction occurring at the fluid/grain interface. The nature of the surface electrical conductivity of shaly and clean sands and sandstones is examined. Surface conduction is characterized by the specific surface conductance which is the sum of three contributions: (i) Conduction within the electrical diffuse layer, which makes a negligible contribution to the total specific surface conductance, (ii) Conduction in the Stern layer, which is shown to vary significantly with the salinity of the pore fluid at low salinities (10-6 to 10-3 mol 1-1), but becomes independent of salinity at higher salinities, (iii) A mechanism operating directly on the mineral surface, independent of salinity, and perhaps associated with proton transfer. At salinities higher than 10-3 mol 1-1 and at 25°C, the specific surface conductance of quartz and clays is equal to 8.9×10-9 S and 2.5×10-9 S respectively. Equations describing the influence of surface conductivity and microstructure upon the macroscopic electrical conductivity of sands, sandstones, and shales are also developed.

Revil, A.; Glover, P. W. J.

435

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

436