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Sample records for apparent electrical conductivity

  1. Estimating depth to argillic soil horizons using apparent electrical conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  3. Predicting saturated hydraulic conductivity in a sandy grassland using proximally sensed apparent electrical conductivity

    NASA Astrophysics Data System (ADS)

    Rezaei, Meisam; Saey, Timothy; Seuntjens, Piet; Joris, Ingeborg; Boënne, Wesley; Van Meirvenne, Marc; Cornelis, Wim

    2016-03-01

    Finding a correspondence between soil hydraulic properties, such as saturated hydraulic conductivity (Ks) and apparent electrical conductivity (ECa) as an easily measurable parameter, may be a way forward to estimate the spatial distribution of hydraulic properties at the field scale. In this study, the spatial distributions of Ks, of soil ECa measured by a DUALEM-21S sensor and of soil physical properties were investigated in a sandy grassland. To predict field scale Ks, the statistical relationship between co-located soil Ks, and EMI-ECa was evaluated. Results demonstrated the large spatial variability of all studied properties with Ks being the most variable one (CV = 86.21%) followed by ECa (CV ≥ 53.77%). A significant negative correlation was found between ln-transformed Ks and ECa (r = 0.83; P ≤ 0.01) at two depths of exploration (0-50 and 0-100 cm). This site-specific relation between ln Ks and ECa was used to predict saturated hydraulic conductivity over 0-50 cm depth for the whole field. The empirical relation was validated using an independent dataset of measured Ks. The statistical results demonstrate the robustness of this empirical relation with mean estimation error MEE = 0.46 (cm h- 1), root-mean-square estimation errors RMSEE = 0.74 (cm h- 1), coefficient of determination r2 = 0.67 and coefficient of model efficiency Ce = 0.64. The relationship was then used to produce a detailed map of Ks for the whole field. The result will allow model predictions of spatially distributed water content in view of irrigation management.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  5. REPEATABILITY OF SOIL APPARENT ELECTRICAL CONDUCTIVITY MEASURED BY THE VERIS 3100 SENSOR

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Repeatability of a measurement can be assessed by characterizing the variation between successive measurements of the same quantity. Apparent electrical conductivity (ECa) offers advantages for mapping soil variability because detailed data can be colleted easily and inexpensively using on-the-go EC...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  7. APPARENT ELECTRICAL CONDUCTIVITY AS A TOOL FOR DELINEATING SPATIAL PATTERNS IN INHERENT SOIL PROPERTIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil properties affecting crop yield exhibit spatial variability. Apparent electrical conductivity (ECa) can be economically measured and is well correlated with many soil properties. Methods for processing ECa survey data and determining the relationship between ECa and soil properties are needed. ...

  8. REPEATABILITY OF SOIL APPARENT ELECTRICAL CONDUCTIVITY MEASURED BY A COULTER SENSOR

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Repeatability of a measurement can be assessed by characterizing the variation between successive measurements of the same quantity. Apparent electrical conductivity (ECa) measured using an on-the-go coulter sensor offers advantages for mapping soil variability because detailed data can be colleted ...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    SciTech Connect

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

    2015-03-14

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  13. Characterisation of soil texture variability using the apparent soil electrical conductivity at a highly variable site

    NASA Astrophysics Data System (ADS)

    Heil, K.; Schmidhalter, U.

    2012-02-01

    The characterisation of the spatial distribution of clay, silt, and sand/gravel is one of the main objectives of soil surveys. Researchers as well as producers have an interest in characterising soil texture variability. The objective of our study was the development of models to derive the clay, silt, and sand/gravel content from the variables apparent electrical conductivity (EC a), the boundary depth between Quaternary and Tertiary sediments, the terrain parameters, and the cultivation (organic vs integrated and type of fertiliser). The investigation site made it possible to include a wide range of soil types within the geological area under investigation. The apparent electrical conductivity and the soil properties texture and digital terrain attributes were densely mapped onto approximately 17 ha. Soil sampling was carried out in a 50*50-m grid. Clay and sand/gravel were most closely related to the EC a, whereas silt showed a stronger dependency on the boundary depth. R2 values ranged between 0.67 and 0.76 in this hilly landscape. However, some weaknesses of the applied procedure were observed: on layered soils with clay lenses covered with sandy, gravelly material, too much clay, and too little sand/gravel were predicted. In some subareas with distinct differences at the field boundaries, breaks in the EC a were observed. The latter was likely due to fertilising effects that caused enhanced EC a levels. In conclusion, the EC a, in combination with the boundary depth between Quaternary and Tertiary sediments, the elevation, the terrain aspect, and the cultivation parameters represent a useful and robust surveying technique to predict soil texture for the Tertiary hill country in southern Germany.

  14. Soil Properties Assessment using Apparent Electric Conductivity (ECa) in semi-arid Environments of Northern Tanzania

    NASA Astrophysics Data System (ADS)

    Mrker, M.; Qunherv, G.

    2012-04-01

    Semi-arid environments such as in Northern Tanzania are characterized by a variety of degradation processes due to long dry periods and short but intensive rainfall events. High potential evaporation, high run-off rates, and low water holding capacities are typical for the present soils. The area is mainly covered by semi-arid savannah, the dominating crop is maize and extensive grazing is conducted. Soil properties and their spatial distribution play a critical role for hydrologic processes. To assess the spatial distribution of these soil properties we utilized a Electromagnetic Induction (EMI) device that induce an electromagnetic field into the soil, creating an electric current. The strength of a resulting secondary electromagnetic field is recorded as the apparent electric conductivity (ECa), measured in mS/m. ECa can provide an indirect indicator of important soil properties. Factors that influence ECa include soil salinity, clay content and cation exchange capacity (CEC), clay mineralogy, soil pore size and distribution, soil moisture content, and temperature. However, in non-saline soils, conductivity variations are primarily a function of soil texture, moisture content, and CEC. There are few studies, related to EMI measurements, conducted in semi-arid environments. In this study we conducted field measurements with the GSSI Profiler EMP-400. Soil physical characteristics were also measured in field on typical soil profiles to get the respective calibration data, validation was done by lab analysis. We analyzed the spatial pattern of the soil ECa maps to determine relationships with soil properties, with a focus on soil texture. The regionalization was carried out using stochastic models. In this study we tested classification and regression trees as well as advanced stochastic gradient boosting methods.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  16. Spatial interpolation of soil organic carbon using apparent electrical conductivity as secondary information

    NASA Astrophysics Data System (ADS)

    Martinez, G.; Vanderlinden, K.; Ordez, R.; Muriel, J. L.

    2009-04-01

    Soil organic carbon (SOC) spatial characterization is necessary to evaluate under what circumstances soil acts as a source or sink of carbon dioxide. However, at the field or catchment scale it is hard to accurately characterize its spatial distribution since large numbers of soil samples are necessary. As an alternative, near-surface geophysical sensor-based information can improve the spatial estimation of soil properties at these scales. Electromagnetic induction (EMI) sensors provide non-invasive and non-destructive measurements of the soil apparent electrical conductivity (ECa), which depends under non-saline conditions on clay content, water content or SOC, among other properties that determine the electromagnetic behavior of the soil. This study deals with the possible use of ECa-derived maps to improve SOC spatial estimation by Simple Kriging with varying local means (SKlm). Field work was carried out in a vertisol in SW Spain. The field is part of a long-term tillage experiment set up in 1982 with three replicates of conventional tillage (CT) and Direct Drilling (DD) plots with unitary dimensions of 15x65m. Shallow and deep (up to 0.8m depth) apparent electrical conductivity (ECas and ECad, respectively) was measured using the EM38-DD EMI sensor. Soil samples were taken from the upper horizont and analyzed for their SOC content. Correlation coefficients of ECas and ECad with SOC were low (0.331 and 0.175) due to the small range of SOC values and possibly also to the different support of the ECa and SOC data. Especially the ECas values were higher in the DD plots. The normalized ECa difference (?ECa), calculated as the difference between the normalized ECas and ECad values, distinguished clearly the CT and DD plots, with the DD plots showing positive ?ECa values and CT plots ?ECa negative values. The field was stratified using fuzzy k-means (FKM) classification of ?ECa (FKM1), and ECas and ECad (FKM2). The FKM1 map mainly showed the difference between CT and DD plots, while the FKM2 map showed both differences between CT and DD and topography-associated features. Using the FKM1 and FKM2 maps as secondary information accounted for 30% of the total SOC variability, whereas plot and management average SOC explained 44 and 41%, respectively. Cross validation of SKlm using FKM2 reduced the RMSE by 8% and increased the efficiency index almost 70% as compared to Ordinary Kriging. This work shows how ECa can improve the spatial characterization of SOC, despite its low correlation and the small size of the plots used in this study.

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

    PubMed Central

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

    2014-01-01

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

  18. Spatial and temporal patterns of apparent electrical conductivity: DUALEM vs. Veris sensors for monitoring soil properties.

    PubMed

    Serrano, Joo; Shahidian, Shakib; Silva, Jos Marques da

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    PubMed Central

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

    2014-01-01

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

  3. Using multivariate geostatistics to assess patterns of spatial dependence of apparent soil electrical conductivity and selected soil properties.

    PubMed

    Siqueira, Glcio Machado; Dafonte, Jorge Dafonte; Valcrcel Armesto, Montserrat; Frana e Silva, nio Farias

    2014-01-01

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

  4. A Novel Low-Cost Instrumentation System for Measuring the Water Content and Apparent Electrical Conductivity of Soils.

    PubMed

    Rêgo Segundo, Alan Kardek; Martins, José Helvecio; Monteiro, Paulo Marcos de Barros; de Oliveira, Rubens Alves; Freitas, Gustavo Medeiros

    2015-01-01

    The scarcity of drinking water affects various regions of the planet. Although climate change is responsible for the water availability, humanity plays an important role in preserving this precious natural resource. In case of negligence, the likely trend is to increase the demand and the depletion of water resources due to the increasing world population. This paper addresses the development, design and construction of a low cost system for measuring soil volumetric water content (θ), electrical conductivity (σ) and temperature (T), in order to optimize the use of water, energy and fertilizer in food production. Different from the existing measurement instruments commonly deployed in these applications, the proposed system uses an auto-balancing bridge circuit as measurement method. The proposed models to estimate θ and σ and correct them in function of T are compared to the ones reported in literature. The final prototype corresponds to a simple circuit connected to a pair of electrode probes, and presents high accuracy, high signal to noise ratio, fast response, and immunity to stray capacitance. The instrument calibration is based on salt solutions with known dielectric constant and electrical conductivity as reference. Experiments measuring clay and sandy soils demonstrate the satisfactory performance of the instrument. PMID:26445049

  5. A Novel Low-Cost Instrumentation System for Measuring the Water Content and Apparent Electrical Conductivity of Soils

    PubMed Central

    Rêgo Segundo, Alan Kardek; Martins, José Helvecio; Monteiro, Paulo Marcos de Barros; de Oliveira, Rubens Alves; Freitas, Gustavo Medeiros

    2015-01-01

    The scarcity of drinking water affects various regions of the planet. Although climate change is responsible for the water availability, humanity plays an important role in preserving this precious natural resource. In case of negligence, the likely trend is to increase the demand and the depletion of water resources due to the increasing world population. This paper addresses the development, design and construction of a low cost system for measuring soil volumetric water content (θ), electrical conductivity (σ) and temperature (T), in order to optimize the use of water, energy and fertilizer in food production. Different from the existing measurement instruments commonly deployed in these applications, the proposed system uses an auto-balancing bridge circuit as measurement method. The proposed models to estimate θ and σ and correct them in function of T are compared to the ones reported in literature. The final prototype corresponds to a simple circuit connected to a pair of electrode probes, and presents high accuracy, high signal to noise ratio, fast response, and immunity to stray capacitance. The instrument calibration is based on salt solutions with known dielectric constant and electrical conductivity as reference. Experiments measuring clay and sandy soils demonstrate the satisfactory performance of the instrument. PMID:26445049

  6. Electrical Conductivity.

    ERIC Educational Resources Information Center

    Allen, Philip B.

    1979-01-01

    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)

  7. Electrical Conductivity.

    ERIC Educational Resources Information Center

    Hershey, David R.; Sand, Susan

    1993-01-01

    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)

  8. Analysis of the Representation of Soil Map Units using a Common Apparent Electrical Conductivity Sampling Scheme for the Mapping of Soil Properties

    NASA Astrophysics Data System (ADS)

    Brevik, E. C.

    2012-04-01

    The introduction of new technologies such as GIS and GPS has led to demands for more detailed and accurate soils information than is available in traditional soil surveys. One of the common ways this more detailed soils information has been pursued is through apparent electrical conductivity (ECa) surveys conducted by slowly pulling ECa equipment through fields along transects and collecting georeferenced ECa data. This study investigated how well the data collected from these transect surveys represents soil map units (SMUs) established by Order 1 soil surveys. On the whole, the transect surveys did a good job of representing the field SMUs. However, SMUs that were only present in a small percentage (<5% by area) of the fields studied tended to be represented fairly poorly. SMUs that were present over more than 5% of the field area tended to be represented well by the transect surveys.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  10. Using soil apparent electrical conductivity to optimize sampling of soil penetration resistance and to improve the estimations of spatial patterns of soil compaction.

    PubMed

    Machado Siqueira, Glcio; Dafonte Dafonte, Jorge; Bueno Lema, Javier; Valcrcel Armesto, Montserrat; Frana e Silva, nio Farias

    2014-01-01

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

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

    PubMed Central

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

    2014-01-01

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

  12. The Apparent Thermal Conductivity of Pozzolana Concrete

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

    Aura, Pedrera,; De Vijver, Ellen, Van; Karl, Vanderlinden,; Sergio, Martos-Rosillo; Meirvenne, Marc, Van; Espejo-Prez, Antonio, J.; Encarnacin V., Taguas,; Girldez, Juan, V.

    2013-04-01

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

  14. An Apparent Anomaly in Peanut Leaf Conductance

    PubMed Central

    Pallas, James E.

    1980-01-01

    Conductance to gaseous transfer is normally considered to be greater from the abaxial than from the adaxial side of a leaf. Measurements of the conductance to water vapor of peanut leaves (Arachis hypogaea L.) under well watered and stress conditions in a controlled environment, however, indicated a 2-fold higher conductance from the adaxial side of the leaf than from the abaxial. Studies of conductance as light level was varied showed an increase in conductance from either surface with increasing light level, but conductance was always greater from the adaxial surface at any given light level. In contrast, measurements of soybean (Glycine max [L.] Merr.) and snapbean (Phaseolus vulgaris L.) leaf conductance showed an approximate 2-fold greater conductance from the abaxial surface than from the adaxial. Approximately the same number of stomata were present on both peanut leaf surfaces and stomatal size was similar. Electron microscopic examination of peanut leaves did not reveal any major structural differences between stomata on the two surfaces that would account for the differences in conductance. Light microscope studies of leaf sections revealed an extensive network of bundle sheaths with achloraplastic bundle sheath extensions; the lower epidermis was lined with a single layer of large achloraplastic parenchyma cells. Measurements of net photosynthesis made on upper and lower leaf surfaces collectively and individually indicated that two-thirds of the peanut leaf's total net photosynthesis can be attributed to diffusion of CO2 through the adaxial leaf surface. Possibly the high photosynthetic efficiency of peanut cultivars as compared with certain other C3 species is associated with the greater conductance of CO2 through their upper leaf surfaces. Images PMID:16661294

  15. Electrically conductive cellulose composite

    DOEpatents

    Evans, Barbara R.; O'Neill, Hugh M.; Woodward, Jonathan

    2010-05-04

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  18. Electrically conductive diamond electrodes

    DOEpatents

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

    2009-05-19

    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.

  19. Polymers that Conduct Electricity.

    ERIC Educational Resources Information Center

    Edelson, Edward

    1983-01-01

    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…

  20. Polymers that Conduct Electricity.

    ERIC Educational Resources Information Center

    Edelson, Edward

    1983-01-01

    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

  1. Electrically conductive composite material

    DOEpatents

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

    1989-01-01

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

  2. Electrically conductive composite material

    DOEpatents

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

    1988-06-20

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

  3. Electrically conductive composite material

    DOEpatents

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

    1989-05-23

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

  4. Electrically conductive material

    DOEpatents

    Singh, Jitendra P.; Bosak, Andrea L.; McPheeters, Charles C.; Dees, Dennis W.

    1993-01-01

    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.

  5. Electrically conductive material

    DOEpatents

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

    1993-09-07

    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.

  6. Electrical Conductivity in Insulator

    NASA Astrophysics Data System (ADS)

    Sinha, Anil Kumar

    2003-03-01

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

  7. Electrical Conductivity in Textiles

    NASA Technical Reports Server (NTRS)

    2006-01-01

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

  8. Electrically Conductive Porous Membrane

    NASA Technical Reports Server (NTRS)

    Burke, Kenneth Alan (Inventor)

    2014-01-01

    The present invention relates to an electrically conductive membrane that can be configured to be used in fuel cell systems to act as a hydrophilic water separator internal to the fuel cell, or as a water separator used with water vapor fed electrolysis cells, or as a water separator used with water vapor fed electrolysis cells, or as a capillary structure in a thin head pipe evaporator, or as a hydrophobic gas diffusion layer covering the fuel cell electrode surface in a fuel cell.

  9. Electrically conductive alternating copolymers

    DOEpatents

    Aldissi, M.; Jorgensen, B.S.

    1987-08-31

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

  10. Influence of surface conductivity on the apparent zeta potential of calcite.

    PubMed

    Li, Shuai; Leroy, Philippe; Heberling, Frank; Devau, Nicolas; Jougnot, Damien; Chiaberge, Christophe

    2016-04-15

    Zeta potential is a physicochemical parameter of particular importance in describing the surface electrical properties of charged porous media. However, the zeta potential of calcite is still poorly known because of the difficulty to interpret streaming potential experiments. The Helmholtz-Smoluchowski (HS) equation is widely used to estimate the apparent zeta potential from these experiments. However, this equation neglects the influence of surface conductivity on streaming potential. We present streaming potential and electrical conductivity measurements on a calcite powder in contact with an aqueous NaCl electrolyte. Our streaming potential model corrects the apparent zeta potential of calcite by accounting for the influence of surface conductivity and flow regime. We show that the HS equation seriously underestimates the zeta potential of calcite, particularly when the electrolyte is diluted (ionic strength⩽0.01M) because of calcite surface conductivity. The basic Stern model successfully predicted the corrected zeta potential by assuming that the zeta potential is located at the outer Helmholtz plane, i.e. without considering a stagnant diffuse layer at the calcite-water interface. The surface conductivity of calcite crystals was inferred from electrical conductivity measurements and computed using our basic Stern model. Surface conductivity was also successfully predicted by our surface complexation model. PMID:26852350

  11. Electrically conductive anodized aluminum coatings

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  12. Measurement of Apparent Thermal Conductivity and Laser Absorptivity of Individual Carbon Fibers

    NASA Astrophysics Data System (ADS)

    Liu, Jin-hui; Wang, Hai-dong; Hu, Yu-dong; Ma, Wei-gang; Zhang, Xing

    2015-11-01

    The apparent thermal conductivity (ATC) and laser absorptivity (α ) are important properties of miro/nano materials but a challenge to measure due to their small size. In this paper, a simple and effective method employing Raman spectroscopy together with electrical heating is developed to measure thermal properties of micro/nano wires. The sample used in the experiment is very simple and easy to fabricate. The ATC is obtained by measuring the temperature difference induced by changing the electrical heating power; the laser heating power is neither neglected nor needed. Using the laser heating temperature rise and the measured ATC, the absorbed laser power can be calculated. Three individual carbon fibers were studied using the presented method.

  13. Autonomic restoration of electrical conductivity.

    PubMed

    Blaiszik, Benjamin J; Kramer, Sharlotte L B; Grady, Martha E; McIlroy, David A; Moore, Jeffrey S; Sottos, Nancy R; White, Scott R

    2012-01-17

    Self-healing of an electrical circuit is demonstrated with nearly full recovery of conductance less than one millisecond after damage. Crack damage breaks a conductive pathway in a multilayer device, interrupting electron transport and simultaneously rupturing adjacent microcapsules containing gallium-indium liquid metal (top). The released liquid metal flows to the area of damage, restoring the conductive pathway (bottom). PMID:22183927

  14. Electrically Conductive Anodized Aluminum Surfaces

    NASA Technical Reports Server (NTRS)

    Nguyen, Trung Hung

    2006-01-01

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

  15. Electrical conductivity of compressed argon

    SciTech Connect

    Bauer, R.; Windl, W.; Collins, L.; Kress, J.; Kwon, I.

    1997-10-01

    The authors report calculations of the electrical conductivity of solid argon as a function of compression within the density functional local density approximation formulation for a norm-conserving pseudopotential using both electron-phonon coupling and molecular dynamics techniques.

  16. Electrical conduction in polymer dielectrics

    NASA Technical Reports Server (NTRS)

    Cotts, D. B.

    1985-01-01

    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.

  17. Electrical Conductivity of Cryolite Melts

    NASA Astrophysics Data System (ADS)

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

    1985-11-01

    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.

  18. Electrically conductive polymer concrete coatings

    DOEpatents

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

    1990-01-01

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

  19. Electrically conductive polymer concrete coatings

    DOEpatents

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

    1988-05-26

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

  20. Electrically conductive polymer concrete coatings

    DOEpatents

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

    1990-03-13

    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.

  1. Electrically conductive polymer concrete overlays

    NASA Astrophysics Data System (ADS)

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

    1984-08-01

    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.

  2. Electrical Conductivity in Transition Metals

    ERIC Educational Resources Information Center

    Talbot, Christopher; Vickneson, Kishanda

    2013-01-01

    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…

  3. Electrically conductive rigid polyurethane foam

    DOEpatents

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

    1983-12-08

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

  4. Electrically conductive rigid polyurethane foam

    DOEpatents

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

    1985-03-19

    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.

  5. Electrical Conductivity in Transition Metals

    ERIC Educational Resources Information Center

    Talbot, Christopher; Vickneson, Kishanda

    2013-01-01

    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

  6. Electric conductivity of plasma in solar wind

    NASA Technical Reports Server (NTRS)

    Chertkov, A. D.

    1995-01-01

    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.

  7. Electrical conductivity of ice VII.

    PubMed

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

    2014-01-01

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

  8. Electrical conductivity of ice VII

    PubMed Central

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

    2014-01-01

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

  9. Electrically conductive thermal control coatings

    NASA Technical Reports Server (NTRS)

    Shai, M. C. (inventor)

    1978-01-01

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

  10. Electrical conduction through DNA molecule.

    PubMed

    Abdalla, S

    2011-09-01

    Several disorder parameters, inside the DNA molecule, lead to localization of charge carriers inside potential wells in the lowest unoccupied and highest occupied molecular orbits (LUMO and HOMO) which affects drastically the electrical conduction through the molecule, and demonstrates that the band carriers play an essential role in the conduction mechanism. So, a model is presented to shed light on the role of electrons of the LUMO in the electrical conduction through the DNA molecule. DC-, AC-conductivity and dielectric permittivity experimental data are well fitted with the presented model giving evidence that the free carriers in the LUMO and HOMO are responsible to make the DNA molecule conductor, insulator or semiconductor. The obtained results show that the localized charge carriers in the DNA molecule are characterized by four different types of relaxation phenomena which are thermally activated by corresponding four activation energies at 0.56 eV, 0.33 eV, 0.24 eV, and 0.05 eV respectively. Moreover, the calculations after the model, at room temperature, show that the time of the relaxation times of the current carriers are in the order of 5 10(-2)s, 1.74 10(-4)s, 5 10(-7)s, and 1.6 10(-10)s, respectively. PMID:21396395

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

    NASA Technical Reports Server (NTRS)

    Yuan, Zeng-Guang; Kleinhenz, Julie E.

    2011-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Yuan, Zeng-Guang; Kleinhenz, Julie E.

    2011-01-01

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

  13. Electric Conductivity of the QGP

    NASA Astrophysics Data System (ADS)

    Puglisi, Armando; Plumari, Salvatore; Greco, Vincenzo

    2015-05-01

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

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

    EPA Science Inventory

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

  15. INCREASING INFORMATION WITH MULTIPLE SOIL ELECTRICAL CONDUCTIVITY DATASETS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Maps of apparent electrical conductivity (ECa) of the soil profile are widely used in precision agriculture practice and research. Because ECa is often strongly related to clay content, soil water holding capacity, and other soil physical properties that also relate to crop productivity, ECa maps ca...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  17. Electrical Conductivity of Ferritin Proteins by Conductive AFM

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

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

  19. Electrically conductive fibers thermally isolate temperature sensor

    NASA Technical Reports Server (NTRS)

    De Waard, R.; Norton, B.

    1966-01-01

    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.

  20. Preparation of Electrically Conductive Polymeric Membranes

    NASA Astrophysics Data System (ADS)

    Encinas, J. C.; Castillo-Ortega, M. M.; Rodríguez, F.; Castaño, V. M.

    2015-10-01

    Cellulose acetate porous membranes, coated with polyaniline, were chemically modified with polyelectrolytes to produce films of varying and controlled porosity and electrical conductivity. The highest electrical conductivity was obtained in membranes prepared with poly(styrene sulfonate) with large pore sizes. The electrical properties as well as scanning electron microscopy (SEM) images are discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  2. Electrical conductivity of pyrolyzed polyacrylonitrile

    SciTech Connect

    Teoh, H.; Metz, P.D.; Wilhelm, W.G.

    1981-01-01

    Using ultrapure samples of polyacrylonitrile (PAN) of 485,000 or 150,000 average molecular weight solution cast in dimethylformamide, the dc conductivity (sigma) of pyrolyzed PAN (PANP) films has been studied for pyrolysis temperatures (T/ sub p/) of 280 to 435/sup 0/C. Conductivity measurements made during pyrolysis indicate the onset of a dramatic increase in sigma for T/sub p/ of 390 to 435/sup 0/C. Conductivities as high as 5 (ohm-cm)/sup -1/ have been observed for T/sub p/ < 435/sup 0/C.

  3. Calibration-free electrical conductivity measurements for highly conductive slags

    SciTech Connect

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

    2000-05-01

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

  4. Electrically conductive polyimides containing silver trifluoroacetylacetonate

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  5. Electrically conducting polymers for aerospace applications

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Gaier, James R.; Good, Brian S.; Sharp, G. R.; Meador, Michael A.

    1991-01-01

    Current research on electrically conducting polymers from 1974 to the present is reviewed focusing on the development of materials for aeronautic and space applications. Problems discussed include extended pi-systems, pyrolytic polymers, charge-transfer systems, conductive matrix resins for composite materials, and prospects for the use of conducting polymers in space photovoltaics.

  6. Electrical and thermal conductivities in dense plasmas

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  7. Electrical Conductivity of Shock Compressed Xenon

    NASA Astrophysics Data System (ADS)

    Mintsev, V. B.; Ternovoi, V. Ya.; Gryaznov, V. K.; Pyalling, A. A.; Fortov, V. E.

    1999-06-01

    The results on measurements of electrical conductivity of shock compressed gaseous and liquid xenon are discussed. Thermodynamic parameters of xenon are calculated in the frame of plasma chemical model. Semi-empirical equation of state was constructed for the liquid range of densities. To estimate the electrical conductivity the modified Ziman theory was used. A reasonable agreement between experimental and theoretical data on equation of state and transport properties is shown in a wide range of parameters: from gas to liquid densities, pressures 10-140 GPa and temperatures >5000K. New experimental data on measurements of equation of state and electrical conductivity of xenon under multiple shock compression are presented.

  8. Electrically Conductive Polyimide Films Containing Gold Surface

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  9. Electrical and thermal conductivities in dense plasmas

    SciTech Connect

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

    2014-09-15

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

  10. Electrically conductive proppant and methods for detecting, locating and characterizing the electrically conductive proppant

    SciTech Connect

    Cannan, Chad; Bartel, Lewis; Palisch, Terrence; Aldridge, David

    2015-01-13

    Electrically conductive proppants and methods for detecting, locating, and characterizing same are provided. The electrically conductive proppant can include a substantially uniform coating of an electrically conductive material having a thickness of at least 500 nm. The method can include injecting a hydraulic fluid into a wellbore extending into a subterranean formation at a rate and pressure sufficient to open a fracture therein, injecting into the fracture a fluid containing the electrically conductive proppant, electrically energizing the earth at or near the fracture, and measuring three dimensional (x, y, and z) components of electric and magnetic field responses at a surface of the earth or in an adjacent wellbore.

  11. Electrically Conductive White Thermal-Control Paint

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

  12. [Myocardial infarction after conduction electrical weapon shock].

    PubMed

    Ben Ahmed, H; Bouzouita, K; Selmi, K; Chelli, M; Mokaddem, A; Ben Ameur, Y; Boujnah, M R

    2013-04-01

    Controversy persists over the safety of conducted electrical weapons, which are increasingly used by law enforcement agencies around the world. We report a case of 33-year-old man who had an acute inferior myocardial infarction after he was shot in the chest with an electrical weapon. PMID:22551781

  13. Electrical conductivity of nickel nanostrand polymer composites

    NASA Astrophysics Data System (ADS)

    Hansen, Nathan D.

    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.

  14. Electrically conductive connection for an electrode

    DOEpatents

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

    1986-09-02

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

  15. Electrically conductive and thermally conductive materials for electronic packaging

    NASA Astrophysics Data System (ADS)

    Liu, Zongrong

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

  16. Electrical conductivity of shock compressed xenon

    NASA Astrophysics Data System (ADS)

    Mintsev, Victor B.; Ternovoi, Vladimir Ya.; Gryaznov, Victor K.; Pyalling, Alexei A.; Fortov, Vladimir E.; Iosilevskii, Igor L.

    2000-04-01

    The results on measurements of electrical conductivity of shock compressed gaseous and liquid xenon are discussed. Thermodynamical parameters of xenon are calculated in frames of plasma chemical model. To estimate electrical conductivity modified Ziman theory is used. A reasonable agreement between experimental and theoretical data on equation of state and transport properties is shown in a wide range of parameters from gas to liquid densities, pressures 10-140 GPa and temperatures >5000 K. New experimental data on measurements of equation of state and conductivity of xenon under multiple shock compression are presented.

  17. Making Complex Electrically Conductive Patterns on Cloth

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

  18. Soil permittivity response to bulk electrical conductivity for selected soil water sensors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bulk electrical conductivity can dominate the low frequency dielectric loss spectrum in soils, masking changes in the real permittivity and causing errors in estimated water content. We examined the dependence of measured apparent permittivity (Ka) on bulk electrical conductivity in contrasting soil...

  19. Electrical conductivity of an arbitrarily dense plasma

    SciTech Connect

    Rinker, G.

    1984-01-01

    This is the first of a series of papers concerning the electrical and thermal transport properties of dense plasmas. Temperatures and densities considered range from zero to 2/sup 13/ eV and 2/sup -13/ to 2/sup 13/ times compressed. In the present work we describe theoretical calculations of electrical conductivities using the t-matrix version of the Ziman theory with various self-consistent ionic potential models. The theoretical basis is described and illustrative results are given.

  20. Electrically conductive containment vessel for molten aluminum

    DOEpatents

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

    1985-01-01

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

  1. Electrically conductive containment vessel for molten aluminum

    DOEpatents

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

    1984-06-25

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

  2. Electrical conductivity and impedance behaviour of hydrogels

    NASA Astrophysics Data System (ADS)

    Warren, Holly; in het Panhuis, Marc

    2014-08-01

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

  3. Thermal and electrical contact conductance studies

    NASA Technical Reports Server (NTRS)

    Vansciver, S. W.; Nilles, M.

    1985-01-01

    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.

  4. Electrical conduction of a XLPE nanocomposite

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  5. Electrical conduction through linear porphyrin arrays.

    PubMed

    Yoon, Dae Hwan; Lee, Sun Bae; Yoo, K-H; Kim, Jinhee; Lim, Jong Kuk; Aratani, Naoki; Tsuda, Akihiko; Osuka, Atsuhiro; Kim, Dongho

    2003-09-10

    Electrical conduction measurements were made on two extreme types of directly linked porphyrin arrays by using nanoelectrodes. One type is the directly linked Zn(II)porphyrin arrays, consisting of 48 Zn(II)porphyrin moieties (Z48), and the other type is the completely flat, tape-shaped Zn(II)porphyrin arrays, consisting of eight Zn(II)porphyrin units (T8). The I-V curve for Z48 exhibits the diode-like behavior and the hysteresis depending on the voltage sweep direction presumably due to the conformational heterogeneity arising from the dihedral angle distribution in Z48. On the other hand, the I-V curve for T8 is nearly symmetric without any hysteresis, leading to the higher conductivity and the smaller band gap. These results illustrate that the stronger pi-electron conjugation in T8, as compared with that of Z48, results in better electrical conduction. PMID:12952488

  6. Time resolved strain dependent morphological study of electrically conducting nanocomposites

    NASA Astrophysics Data System (ADS)

    Khan, Imran; Mitchell, Geoffrey; Mateus, Artur; Kamma-Lorger, Christina S.

    2015-10-01

    An efficient and reliable method is introduced to understand the network behaviour of nano-fillers in a polymeric matrix under uniaxial strain coupled with small angle x-ray scattering measurements. The nanoparticles (carbon nanotubes) are conductive and the particles form a percolating network that becomes apparent source of electrical conduction and consequently the samples behave as a bulk conductor. Polyurethane based nanocomposites containing 2% w/w multiwall carbon nanotubes are studied. The electrical conductivity of the nanocomposite was (3.28×10-5s/m).The sample was able to be extended to an extension ratio of 1.7 before fracture. A slight variation in the electrical conductivity is observed under uniaxial strain which we attribute to the disturbance of conductive pathways. Further, this work is coupled with in- situ time resolved small angle x-ray scattering measurements using a synchrotron beam line to enable its measurements to be made during the deformation cycle. We use a multiscale structure to model the small angle x-ray data. The results of the analysis are interpreted as the presence of aggregates which would also go some way towards understanding why there is no alignment of the carbon nanotubes.

  7. Study of electrical conductivity in magnetorheological elastomers

    NASA Astrophysics Data System (ADS)

    Wang, Xiaojie; Ghafoorianfar, Nima; Gordaninejad, Faramarz

    2011-03-01

    In this study, the electrical conductivity and magnetoresistance of magnetorheological elastomers (MREs) are experimentally investigated. The electrical resistivity of MREs is measured as a function of particle volume fraction, under different applied magnetic fields. In addition, the strain of the samples is measured simultaneously in order to evaluate the magnetoresistance and piezoresistance of MREs. It is observed that both magnetoresistance and piezoresistance in MREs are independent of the applied magnetic field and pre-compression force; and only depend on the particle concentration and mechanical strain.

  8. Electrical conductivity of a strongly coupled plasma

    SciTech Connect

    Rinker, G.A.

    1985-04-01

    This is the first in a series of papers concerning the electrical and thermal transport properties of dense plasmas. Temperatures and densities considered range approximately from room temperature to 10/sup 4/ eV and from 10/sup -4/ to 10/sup 4/ times compressed. In the present work they describe theoretical calculations of electrical conductivities using the t-matrix version of the Ziman theory with various self-consistent ionic potential models and realistic structure factors. The theoretical basis is described, and illustrative results are given.

  9. Electrically Conductive Porous Metal-Organic Frameworks.

    PubMed

    Sun, Lei; Campbell, Michael G; Dinc?, Mircea

    2016-03-01

    Owing to their outstanding structural, chemical, and functional diversity, metal-organic frameworks (MOFs) have attracted considerable attention over the last two decades in a variety of energy-related applications. Notably missing among these, until recently, were applications that required good charge transport coexisting with porosity and high surface area. Although most MOFs are electrical insulators, several materials in this class have recently demonstrated excellent electrical conductivity and high charge mobility. Herein we review the synthetic and electronic design strategies that have been employed thus far for producing frameworks with permanent porosity and long-range charge transport properties. In addition, key experiments that have been employed to demonstrate electrical transport, as well as selected applications for this subclass of MOFs, will be discussed. PMID:26749063

  10. Electrically conductive palladium containing polyimide films

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  11. Liquid crystallinity in electrically conducting polymers

    SciTech Connect

    Levon, K.

    1996-10-01

    The order formation of electrically conducting polymers is essential for achieving the optimal conditions for the functionality of these polymers. As three dimensional crystallinity has been shown to maximize the conductivity, the solubility with bulky counter-ion dopants has been important for the improved processing. These two desired properties combined would indicate the existence of liquid crystallinity. As the alkylated stiff conjugated polymers resemble the traditional anisotropic hairy rods, we have investigated the possible liquid crystallinity in polyalkyl thiophenes. Presently, we have expanded our studies to polyaniline when doped with amphiphilic dopants. Results on the anisotropic ordering on the both systems will be reported.

  12. Electrically conducting polyimide film containing tin complexes

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  13. Damage Detection in Electrically Conductive Structures

    NASA Astrophysics Data System (ADS)

    Anderson, Todd A.

    2002-12-01

    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.

  14. The electrical conductivity of sodium polysulfide melts

    SciTech Connect

    Meihui Wang.

    1992-06-01

    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.

  15. Electrical conductivity of warm expanded aluminum

    NASA Astrophysics Data System (ADS)

    Faussurier, G.; Blancard, C.; Renaudin, P.; Silvestrelli, P. L.

    2006-05-01

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

  16. Electrical conductivity of warm expanded aluminum

    NASA Astrophysics Data System (ADS)

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

    2006-03-01

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

  17. Electrical conductivity of warm expanded Al

    NASA Astrophysics Data System (ADS)

    Faussurier, G.; Blancard, C.; Renaudin, P.; Silvestrelli, P. L.

    2006-02-01

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

  18. Electrical conductivity of warm expanded Al

    SciTech Connect

    Faussurier, G.; Blancard, C.; Renaudin, P.

    2006-02-15

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

  19. Inductive Measurement of Plasma Jet Electrical Conductivity

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  20. Apparent thermal conductivity of polyurethane foam insulation, containing various HCFC blends, from 125 to 335 K

    SciTech Connect

    Smith, D.R.

    1993-01-01

    The specimens contain several different blends of HCFC 123 and HCFC 141b as fill gases. Effects of thickness on conductivity and, indirectly, on aging were studied by repeating measurements of conductivity of one specimen whose thickness was reduced in 6-mm steps from 25 to 6 mm. The effect of aging was directly studied by repeating conductivity measurements, after a lapse of time, on two different specimens. The conductivities of all specimens rise linearly with temperature over the lowest (125 to 220 K) and the highest (280 to 335 K) range of temperature, but pass through a local maximum at about 225 K and a local minimum at about 2735 K. The slopes of the two linear portions are approximately equal. For all specimens the conductivity functions below the local maximum practically coincide. The position of the local minimum is independent of fill gas species or mixture, while the location and height of the local maximum depends on fill gas species and on effects of aging. Functional relationships between the conductivity and temperature are obtained for each specimen in the form of ratios of cubic polynomials, the simplest form that accurately models the temperature dependence of conductivity over the whole range studied.

  1. Electrical Conductivity Beneath Slave Craton (Canada) From Laboratory Experiments

    NASA Astrophysics Data System (ADS)

    Bagdassarov, N. S.; Eichert, S.; Kopylova, M.

    2004-12-01

    The electrical conductivity beneath Slave craton in North Canada has been characterized on the base of the laboratory measurements of peridotite sample resistance, which have been studied mineralogically in previous works (Kopylova & Russel, 2000; Kopylova & Garo, 2004). The chemical composition of peridotites representing differing depths beneath the Slave craton has been chosen as follows, for the depth from 36 to 100 km spinel peridotite (40-16), from 100 to 140 km low-T spinel-garnet perodotite (41-4), from 140 to 160 km low-T garnet peridotite (8-7), from 160- to 260 km high-T garnet peridotite (40-9). The conductivity of samples were determined in piston-cylinder apparatus at 1 and 2 GPa and in the temperature interval from 600 to 1150 C. The electrical measurements were conducted in the frequency range from 100 kHz to 10 mHz in a measuring cell having a coaxial capacitor geometry with a geometric factor c. 5-6 cm. The temperature dependence of electrical conductivity follows the Arrhenius dependence with the activation energy varying from 1.94 (sample 40-9) to 1.77 eV (sample 8-7). The pressure increase from 1 GPa to 2 GPa results ina a small increase of the activation energy for 0.1 eV. Using the temperature profile beneath Slave craton based on thermobarometry of mantle xenolithes from Jericho pipe (Kopylova et al. 1999) the depth profile of the electrical conductivity has been constructed. The magneto-telluric response of these model has been compared with the field MT observations (Jones et al., 2003) with a satisfactory agreement for phase and apparent resistivity in the frequency range 10-2 to 102 Hz.

  2. [The electrical conductivity of triggered lightning channel].

    PubMed

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

    2007-10-01

    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

  3. Numerical recovery of certain discontinuous electrical conductivities

    NASA Technical Reports Server (NTRS)

    Bryan, Kurt

    1991-01-01

    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.

  4. Kinetic theory of electrical conductivity in plasmas

    SciTech Connect

    Boercker, D.B.

    1981-04-01

    A recently developed quantum kinetic theory for time-correlation functions is applied to the calculation of the electrical conductivity in dense, strongly coupled plasmas. In the weak-collision limit the theory generalizes the Ziman expression to finite temperatures while, for strong collisions, it generalizes the result of Gould and of Williams and DeWitt to include strong ion coupling. Numerical results which compare the effects that strong ion coupling, bound (core) electrons, and strong collisions have upon the collision frequency are also presented.

  5. Electrical Conductivity Calculations from the Purgatorio Code

    SciTech Connect

    Hansen, S B; Isaacs, W A; Sterne, P A; Wilson, B G; Sonnad, V; Young, D A

    2006-01-09

    The Purgatorio code [Wilson et al., JQSRT 99, 658-679 (2006)] is a new implementation of the Inferno model describing a spherically symmetric average atom embedded in a uniform plasma. Bound and continuum electrons are treated using a fully relativistic quantum mechanical description, giving the electron-thermal contribution to the equation of state (EOS). The free-electron density of states can also be used to calculate scattering cross sections for electron transport. Using the extended Ziman formulation, electrical conductivities are then obtained by convolving these transport cross sections with externally-imposed ion-ion structure factors.

  6. Electrically-conducting thermal-control coating

    NASA Technical Reports Server (NTRS)

    Shai, M. C.

    1978-01-01

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

  7. NOVEL GRAPHITE SALTS AND THEIR ELECTRICAL CONDUCTIVITIES

    SciTech Connect

    Bartlett, N.; McCarron, E.M.; McQuillan, B.W.; Thompson, T.E.

    1980-02-01

    A set of novel first stage graphite salts of general formula C{sub 8}{sup +}MF{sub 6}{sup -} has been prepared (M = Os, Ir, As). Single crystal X-ray diffraction studies indicate that these salts are hexagonal with a {approx} 4.9 and c {approx} 8.1 {angstrom}. The unit cell volume indicates that the anions are closely packed in the galleries. Platinum hexafluoride, which is the most powerful oxidizer of the third transition series, forms a first stage compound, which analytical, structural, and magnetic studies establish as C{sub 12}{sup 2+}PtF{sub 6}{sup 2-}. In this salt the anions are not close packed, but the electron withdrawal from the graphite planes is greater than for the C{sub 8}{sup +}MF{sub 6}{sup -} series. The variation in the electrical conductivity (in the a-b plane), as a function of composition, has been investigated with the OsF{sub 6}, IrF{sub 6}, PtF{sub 6} and AsF{sub 5} intercalates. For OsF{sub 6} and IrF{sub 6}, the conductance per plane of graphite is found to be a maximum at approximately C{sub 24}MF{sub 6} (second stage); the conductivity being an order of magnitude greater than that of the parent material. Intercalation beyond C{sub 24}MF{sub 6} leads to a marked decrease in conductivity. C{sub 8}MF{sub 6} is comparable in conductivity with the parent graphite. This behavior contrasts with the graphite/AsF{sub 5} system in which a steady increase in conductance per graphite plane with increasing AsF{sub 5} content is observed. For the PtF{sub 6} system, the second as well as the first stage materials are poorly conducting.

  8. Electrical conductivities for hot, dense hydrogen

    SciTech Connect

    Kwon, I.; Collins, L.; Kress, J.; Troullier, N.

    1996-09-01

    We report electrical conductivities for a hydrogen plasma at temperatures between a few tenths to a few tens of electron volts and densities ranging from 0.3 to 3 g/cm{sup 3}. The ac conductivities were determined within the Kubo-Greenwood formulation based on eigenstates from a finite-temperature density functional calculation at selected time steps along a lengthy molecular-dynamics (MD) simulation trajectory. Density functional, tight-binding, and effective pair potentials were employed in the MD simulations for samples of 50 to 250 atoms within a periodically replicated reference cell. We compare with other techniques and discuss trends with density and temperature. Good agreement results at the higher temperatures and densities with generalized Ziman forms. {copyright} {ital 1996 The American Physical Society.}

  9. Electrically conductive polyurethanes for biomedical applications

    NASA Astrophysics Data System (ADS)

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

    2005-02-01

    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.

  10. Electrical-conductivity testing of latex gloves

    SciTech Connect

    Stampfer, J.F.; Salazar, J.A.; Trujillo, A.G.; Harris, T.; Berardinelli, S.P.

    1994-11-01

    There is an increasing awareness in the healthcare field that gloves worn for protection from hazards associated with body fluids do not always afford the protection desired. Gloves may have defects, such as holes, as they come from the manufacturer or distributor, or they may become defective during storage or use. While the numbers vary widely, failure rates for new gloves, defined as detectable holes in gloves prior to use, for unused examination gloves are reported as high as 58%. Rates as high as 7% have been reported for sterile latex gloves. Incidences of breaching the latex barrier during use vary with procedure but have been reported as high as 50%. In recent years, a number of devices have been developed to detect holes in latex gloves as they are being worn. Detection of increased electrical conductivity that takes place through the holes in the gloves is used to activate an audible alarm. The primary purpose of this research was to investigate the validity of this method for hole detection. This evaluation was accomplished with both basic laboratory equipment and commercially available instruments. We did not evaluate or critically compare the individual devices. We also investigated the use of electrical conductivity as a quality assurance (QA) procedure, and the degradation of latex gloves due to storage and exposure to laboratory atmospheres and disinfectants.

  11. Signatures in flowing fluid electric conductivity logs

    SciTech Connect

    Doughty, Christine; Tsang, Chin-Fu

    2003-06-02

    Flowing fluid electric conductivity logging provides a meansto determine hydrologic properties of fractures, fracture zones, or otherpermeable layers intersecting a borehole in saturated rock. The methodinvolves analyzing the time-evolution of fluid electric conductivity(FEC) logs obtained while the well is being pumped and yields informationon the location, hydraulic transmissivity, and salinity of permeablelayers. The original analysis method was restricted to the case in whichflows from the permeable layers or fractures were directed into theborehole (inflow). Recently, the method was adapted to permit treatmentof both inflow and outflow, including analysis of natural regional flowin the permeable layer. A numerical model simulates flow and transport inthe wellbore during flowing FEC logging, and fracture properties aredetermined by optimizing the match between simulation results andobserved FEC logs. This can be a laborious trial-and-error procedure,especially when both inflow and outflow points are present. Improvedanalyses methods are needed. One possible tactic would be to develop anautomated inverse method, but this paper takes a more elementary approachand focuses on identifying the signatures that various inflow and outflowfeatures create in flowing FEC logs. The physical insight obtainedprovides a basis for more efficient analysis of these logs, both for thepresent trial and error approach and for a potential future automatedinverse approach. Inflow points produce distinctive signatures in the FEClogs themselves, enabling the determination of location, inflow rate, andion concentration. Identifying outflow locations and flow rates typicallyrequires a more complicated integral method, which is also presented inthis paper.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  13. Electrical conductivity and thermopower of metallic helium

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  14. Photovoltaic device having light transmitting electrically conductive stacked films

    DOEpatents

    Weber, Michael F.; Tran, Nang T.; Jeffrey, Frank R.; Gilbert, James R.; Aspen, Frank E.

    1990-07-10

    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.

  15. Chapter A6. Section 6.3. Specific Electrical Conductance

    USGS Publications Warehouse

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

    2005-01-01

    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.

  16. New method for electrical conductivity temperature compensation.

    PubMed

    McCleskey, R Blaine

    2013-09-01

    Electrical conductivity (?) measurements of natural waters are typically referenced to 25 C (?25) using standard temperature compensation factors (?). For acidic waters (pH < 4), this can result in a large ?25 error (??25). The more the sample temperature departs from 25 C, the larger the potential ??25. For pH < 4, the hydrogen ion transport number becomes substantial and its mode of transport is different from most other ions resulting in a different ?. A new method for determining ? as a function of pH and temperature is presented. Samples with varying amounts of H2SO4 and NaCl were used to develop the new ?, which was then applied to 65 natural water samples including acid mine waters, geothermal waters, seawater, and stream waters. For each sample, the ? and pH were measured at several temperatures from 5 to 90 C and ?25 was calculated. The ??25 ranged from -11 to 9% for the new method as compared to -42 to 25% and -53 to 27% for the constant ? (0.019) and ISO-7888 methods, respectively. The new method for determining ? is a substantial improvement for acidic waters and performs as well as or better than the standard methods for circumneutral waters. PMID:23895179

  17. Magnetic flowmeter for electrically conductive liquid

    DOEpatents

    Skladzien, S.B.; Raue, D.J.

    1980-08-18

    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.

  18. Magnetic flowmeter for electrically conductive liquid

    DOEpatents

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

    1982-01-01

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

  19. Electrically conductive, immobilized bioanodes for microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Ganguli, R.; Dunn, B.

    2012-07-01

    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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  2. Development of an angular scanning system for sensing vertical profiles of soil electrical conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Apparent soil electrical conductivity (EC**a**) is typically mapped to define soil spatial variability within an agricultural field. Knowledge of the vertical variability of EC**a** is desired to define site-specific behavior of the soil profile. A Pneumatic Angular Scanning System (PASS) was develo...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  6. Relating relative hydraulic and electrical conductivity in the unsaturated zone

    NASA Astrophysics Data System (ADS)

    Mawer, Chloe; Knight, Rosemary; Kitanidis, Peter K.

    2015-01-01

    Numerical modeling was used to generate pore-scale structures with different structural properties. They were partially saturated according to wetting and drainage regimes using morphological operations for a range of saturations. The hydraulic and electrical conductivities of the resulting partially saturated grain packs were numerically computed to produce relative hydraulic conductivity versus saturation and relative electrical conductivity versus saturation curves. The relative hydraulic conductivities were then compared to the relative electrical conductivities for the same saturations and it was found that relative hydraulic conductivity could be expressed as relative electrical conductivity to a power law exponent, ?. This exponent ? was not correlated to porosity, specific surface area, or tortuosity. It did change according to whether the soil was wetting or draining. However, a ? value of 2.1 reproduced relative hydraulic conductivity from relative electrical conductivity with little added error. The effects of surface conduction on the observed power law relationship due to either low fluid electrical conductivity or increased clay content were analyzed. The relationship was found to hold for fluid conductivities typical of groundwater and for clay content of less than 5% if the clays were layered perpendicular to electrical flow. The relationship breaks down for electrical flow parallel to clay layers, which makes the choice of electrode arrangement important in cases where clay may be present. This relationship can be used with secondary pressure or saturation data to characterize a soil's hydraulic conductivity curve.

  7. Linear Electrical Conductivity of a Bipolar Semiconductor: Heating and Recombination

    NASA Astrophysics Data System (ADS)

    Lashkevych, Igor; Gurevich, Yuri G.

    2016-01-01

    The linear electrical conductivity of a nondegenerate bipolar semiconductor, with metal contacts at both sides, is investigated for small values of the thermal conductivity in a general case, i.e., when both nonequilibrium charge carriers (electrons and holes) and nonequilibrium temperature are present. It must be emphasized that both concentration and energy nonequilibria arise automatically when an electric current flows, even in a linear approximation with respect to perturbation. The expression for the electrical conductivity is obtained. This expression depends on electrical conductivities of electrons and holes, the thermal conductivity, the bandgap, the lifetime of charge carriers, and the surface recombination rate at the contacts of a semiconductor with a metal.

  8. Synthesis and electrical conductivity of multilayer silicene

    SciTech Connect

    Vogt, P. E-mail: bruno.grandidier@isen.iemn.univ-lille1.fr; Bruhn, T.; Capiod, P.; Berthe, M.; Grandidier, B. E-mail: bruno.grandidier@isen.iemn.univ-lille1.fr; Resta, A.; De Padova, P.; Le Lay, G.

    2014-01-13

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

  9. Radiation Fluence dependent variation in Electrical conductivity of Cu nanowires

    SciTech Connect

    Gehlawat, Devender; Chauhan, R. P.; Sonkawade, R. G.

    2011-07-15

    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.

  10. Role of Dislocation Movement in the Electrical Conductance of Nanocontacts

    PubMed Central

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

    2012-01-01

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

  11. Method of forming an electrically conductive cellulose composite

    DOEpatents

    Evans, Barbara R.; O'Neill, Hugh M.; Woodward, Jonathan

    2011-11-22

    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.

  12. Predicting plot-scale water infiltration using the correlation between soil apparent electrical resistivity and various soil properties

    NASA Astrophysics Data System (ADS)

    Chaplot, Vincent; Jewitt, Graham; Lorentz, Simon

    The identification of runoff source areas is essential for Integrated Water and Resources Management (IWRM). Although direct methods for the determination of steady-state water infiltration in soils ( Inf) do exist, these are tedious and time-consuming. Geophysical techniques offer an alternative, however, geophysical data are often misinterpreted, especially in terms of the inter-relationships between soil apparent electrical resistivity ( Rho) and Inf and several other soil physical or chemical properties. This paper evaluates the magnitude of the extend Rho measurements might allow prediction of Inf. This study was conducted in the Kwazulu-Natal province of South Africa where surface runoff arising from the steep slopes has a large impact in land degradation. Measurements of Rho with an RM-15 resistance meter were taken within a 10 30 m plot showing similar sandy-loam Acrisols but different proportions of soil surface coverage by plants (from 0-5% to 75-100%), depth to the clayey Bw horizon ( D2B), top-soil (0-0.1 m) water content ( ?) and bulk density ( BD). There was a low correlation between Rho and Inf obtained under controlled conditions of rainfall (30 mm h -1during 45 min) at fifteen 1 m 2 micro-plots ( r2 = 0.30). However, the correlation with the normalized Rho ( Rho n) as if D2B, ?, and BD were constant over the study plot and equal to their average value, was much higher ( r2 = 0.66), pointing out the need to consider the complex and multiple correlations between soil properties and Rho in an attempt to map the spatial variations of Inf. Finally, the use of Rho n as a co-kriging co-variate appeared to significantly improve the short range spatial prediction of water infiltration in soils and thus IWRM implementation.

  13. Non-Contact Electrical Conductivity Measurement Technique for Molten Metals

    NASA Technical Reports Server (NTRS)

    Rhim, W. K.; Ishikawa, T.

    1998-01-01

    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.

  14. Wet method for measuring starch gelatinization temperature using electrical conductivity.

    PubMed

    Morales-Sanchez, E; Figueroa, J D C; Gaytan-Martnez, M

    2009-09-01

    The objective of the present study was to develop a method for obtaining the gelatinization temperature of starches by using electrical conductivity. Native starches from corn, rice, potato, and wheat were prepared with different proportions of water and heated from room temperature to 90 degrees C, in a device especially designed for monitoring the electrical conductivity as a function of temperature. The results showed a linear trend of the electrical conductivity with the temperature until it reaches the onset gelatinization temperature. After that point, the electrical conductivity presented an increment or decrement depending on the water content in the sample and it was related to starch swelling and gelatinization phenomena. At the end gelatinization temperature, the conductivity becomes stable and linear, indicating that there are no more changes of phase. The starch gelatinization parameter, which was evaluated in the 4 types of starches using the electrical conductivity, was compared with those obtained by using differential scanning calorimeter (DSC). The onset temperature at which the electrical conductivity increased or decreased was found to be similar to that obtained by DSC. Also, the final temperature at which the electrical conductivity returned to linearity matched the end gelatinization temperature of the DSC. Further, a wet method for measuring the onset, peak, and end gelatinization temperatures as a function of temperature using the electrical conductivity curves is presented for a starch-water suspension. PMID:19895467

  15. Apparent cooperativity of amino acid transport in Halobacterium halobium - Effect of electrical potential

    NASA Technical Reports Server (NTRS)

    Lanyi, J. K.

    1978-01-01

    Active serine accumulation in cell envelope vesicles from Halobacterium halobium proceeds by co-transport with Na(+) and can be induced by either transmembrane electrical potential or transmembrane Na(+) concentration difference. It was shown earlier that in the former case the initial transport rate is a fourth-power function of the magnitude of the electrochemical potential difference of sodium ions, and in the latter, a second-power function. A possible interpretation of this finding is cooperativity of sodium-transporting sites in the transport carrier. When both kinds of driving force are imposed simultaneously on the vesicles, fourth-power dependence on the total potential difference of sodium ions is obtained, suggesting that the transport carrier is regulated by the electrical potential. Heat treatment of the vesicles at 48 C partially inactivates transport and abolishes this effect of the electrical potential.

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Zimmer, Hans

    1993-01-01

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

  18. Variable Anisotropic Brain Electrical Conductivities in Epileptogenic Foci

    PubMed Central

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

    2010-01-01

    Source localization models assume brain electrical conductivities are isotropic at about 0.33 S/m. These assumptions have not been confirmed ex vivo in humans. This study determined bidirectional electrical conductivities from pediatric epilepsy surgery patients. Electrical conductivities perpendicular and parallel to the pial surface of neocortex and subcortical white matter (n=15) were measured using the 4-electrode technique and compared with clinical variables. Mean (SD) electrical conductivities were 0.100.01S/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

  19. Estimation of CI-based soil compaction status from soil apparent electrical conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Regionalization of soil properties is very important for successful site-specific field management. Soil compaction is a critical issue to be detected and managed due to its effects on crop growth. Soil compaction has been conventionally quantified as cone index (CI) measured by an ASABE-standard co...

  20. Simulation of partial discharges in conducting and non-conducting electrical tree structures

    NASA Astrophysics Data System (ADS)

    Champion, J. V.; Dodd, S. J.

    2001-04-01

    Electrical treeing is of interest to the electrical generation, transmission and distribution industries as it is one of the causes of insulation failure in electrical machines, switchgear and transformer bushings. Previous experimental investigations of electrical treeing in epoxy resins have found evidence that the tree structures formed were either electrically conducting or non-conducting, depending on whether the epoxy resin was in a flexible state (above its glass transition temperature) or in the glassy state (below its glass transition temperature). In this paper we extend an existing model, of partial discharges within an arbitrarily defined non-conducting electrical tree structure, to the case of electrical conducting trees. With the inclusion of tree channel conductivity, the partial discharge model could simulate successfully the experimentally observed partial discharge activity occurring in trees grown in both the flexible and glassy epoxy resins. This modelling highlights a fundamental difference in the mechanism of electrical tree growth in flexible and glassy epoxy resins. The much lower resistivities of the tree channels grown in the glassy epoxy resins may be due to conducting decomposition (carbonized) products condensing on the side walls of the existing channels, whereas, in the case of non-conducting tree channels, subsequent discharges within the main branches lead to side-wall erosion and a consequent widening of the tubules. The differing electrical characteristics of the tree tubules also have consequences for the development of diagnostic tools for the early detection of pre-breakdown phenomena.

  1. Anisotropy of the electrical conductivity of lithium heptagermanate crystals

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

  2. Sintering, Microstructure, and Electrical Conductivity of Zirconia-Molybdenum Cermet

    NASA Astrophysics Data System (ADS)

    Guo, Yanling; Tang, Lei; Zhang, Jieyu

    2015-08-01

    Monolithic zirconia-molybdenum ( m-ZrO2/Mo) cermets of different compositions (5-40 vol.% Mo) and different initial Mo particles sizes (0.08-13 ?m) were prepared by traditional powder metallurgy process. The influences of metal content and initial particle sizes on the densification behavior, microstructure, and electrical conductivity of the cermets were studied. A percolation threshold value was obtained about 17.1 vol.% molybdenum fraction, above which a sharp increase in the electrical conductivity was observed. The temperature dependence of the electrical conductivity of cermets was studied. The cermet containing 5 vol.% Mo showed the ionic nature of the conductivity, while the metallic nature was observed in the samples of Mo fraction up to 16 vol.%. The activation of conductivity for ionic type of conductivity and the temperature coefficient of resistivity as well as the effect of porosity on electronic type conductivity are discussed.

  3. Direct quantification of apparent binding indices from quinidine-induced in vivo conduction delay in canine myocardium.

    PubMed Central

    Haugland, F N; Johnson, S B; Packer, D L

    1994-01-01

    To characterize quantitatively the quinidine (QUIN)-induced conduction delay (CD) in vivo, canine ventricular activation times were examined with an epicardial mapping technique. A high-resolution index of normalized (N) QUIN CD, derived from all 56 recording sites, was used to quantify QUIN effect. Repetitive stimulation elicited monoexponential increases in CD(N), the rates of which were a linear function of interpulse recovery interval, tr. Steady-state CD(N) was also linearly related to an exponential function of tr and drug uptake rates. The frequency-dependent properties of QUIN in 14 dogs were characterized by apparent binding and unbinding rates of ka = 7.1 +/- 3.5 x 10(6) M-1 s-1, la = 81 +/- 51 s-1 for activated, and kr = 12.6 +/- 11.3 x 10(3) M-1 s-1, lr = 0.51 +/- 0.26 s-1 for resting states. ka and la were similar to values previously derived in canine Purkinje fibers. Drug unbinding at resting potentials was faster in vivo than previously observed in vitro. The time constant of recovery from QUIN block extracted from the interpulse recovery rate was also identical to that determined from post-mature stimulus diastolic scanning. As predicted by the two-state model, similar binding rates were also derived from declining CD(N) elicited by step decreases in heart rate. These findings represent a complete quantitative description of use-dependent QUIN CD in vivo and provide a firm foundation for characterizing antiarrhythmic drug action under physiologic and pathologic conditions. PMID:8163679

  4. Assembly for electrical conductivity measurements in the piston cylinder device

    DOEpatents

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

    2012-06-05

    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.

  5. Electrical Conductivity in a Mixed-Species Biofilm

    PubMed Central

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

    2012-01-01

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

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

    PubMed Central

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

    2014-01-01

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

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

    SciTech Connect

    Agnew, P.; Ing, J.L.

    1995-04-02

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

  8. Electrical conductivity of wadsleyite at high temperatures and high pressures

    NASA Astrophysics Data System (ADS)

    Dai, Lidong; Karato, Shun-ichiro

    2009-09-01

    The electrical conductivity of wadsleyite aggregates has been determined under the broad range of thermodynamic conditions using the impedance spectroscopy for a frequency range of 10 - 2 to 10 6 Hz. Two branches are observed in the complex impedance, one (at high frequency range) showing a half circle originated at Z' (real part of impedance) = Z? (imaginary part of impedance) = 0 in the Z'- Z? plot, and another branch in the low frequency range. The results from high frequency semi-circles correspond to the electric properties of a sample, whereas the results from a low frequency branch correspond to the electrode effects. From the analysis of the results from the semi-circles, we have identified two distinct mechanisms of electrical conduction having different activation enthalpies and different sensitivity to oxygen fugacity and water content. One mechanism dominating at water-poor condition has a high activation enthalpy (~ 147 kJ/mol) and the conductivity increases with oxygen fugacity. We suggest that electrical conduction in this regime is due to charge transfer involving ferric iron ("polaron" conduction). Under water-rich conditions, electrical conductivity increases with water content but decreases with oxygen fugacity, and the activation enthalpy is smaller (~ 88 kJ/mol). We infer that electrical conduction in this regime is due to protons. The activation enthalpy in this regime is insensitive to water content and the conductivity is proportional to water content, CW, as ? ? Cwr with r~ 0.72. The value of r is smaller than one suggests that minority defects such as H M' or H ? are responsible for electrical conduction. Our results show that a completely dry transition zone is incompatible with most of the geophysical observations on the mantle transition zone, and some water (~ 0.1-0.3 wt.% in the Pacific) is required to explain the observed electrical conductivity.

  9. Electrical conductivity of porous silver made from sintered nanoparticles

    NASA Astrophysics Data System (ADS)

    Zuruzi, Abu Samah; Siow, Kim S.

    2015-03-01

    Electrical conductivity of open cell porous silver (Ag) with sub-micrometer features was studied. Porous Ag was formed from annealing Ag nanoparticles at 150C up to 5 minutes. Porous Ag is a network of cylindrical ligaments joined at their ends to spherical vertices. Electrical conductivity of porous Ag was ~20% of bulk value after 5 mins annealing. Kelvin cells (truncated octahedrons) with cylindrical ligaments and spherical vertices (CLSV) were used to compute electrical conductivity which is in agreement with experimental data, without any fitting parameter. Results of the CLSV model are also in agreement with the well-established Koh-Fortini empirical relation. [Figure not available: see fulltext.

  10. Electrical conductivity and magnetic permeability measurement of case hardened steels

    NASA Astrophysics Data System (ADS)

    Tian, Yong

    2015-03-01

    For case carburized steels, electrical conductivity and magnetic permeability profiles are needed to develop model-based case depth characterization techniques for the purpose of nondestructive quality control. To obtain fast and accurate measurement of these material properties, four-point potential drop approaches are applied on circular-shaped discs cut from steel rings with different case depths. First, a direct current potential drop (DCPD) approach is applied to measure electrical conductivity. Subsequently, an alternating current potential drop (ACPD) approach is used to measure magnetic permeability. Practical issues in measurement design and implementation are discussed. Depth profiles of electrical conductivity and magnetic permeability are reported.

  11. Ultrahigh strength and high electrical conductivity in copper.

    PubMed

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

    2004-04-16

    Methods used to strengthen metals generally also cause a pronounced decrease in electrical conductivity, so that a tradeoff must be made between conductivity and mechanical strength. We synthesized pure copper samples with a high density of nanoscale growth twins. They showed a tensile strength about 10 times higher than that of conventional coarse-grained copper, while retaining an electrical conductivity comparable to that of pure copper. The ultrahigh strength originates from the effective blockage of dislocation motion by numerous coherent twin boundaries that possess an extremely low electrical resistivity, which is not the case for other types of grain boundaries. PMID:15031435

  12. Using electrical impedance tomography to map subsurface hydraulic conductivity

    DOEpatents

    Berryman, James G.; Daily, William D.; Ramirez, Abelardo L.; Roberts, Jeffery J.

    2000-01-01

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

  13. SIGMELTS: A web portal for electrical conductivity calculations in geosciences

    NASA Astrophysics Data System (ADS)

    Pommier, A.; Le-Trong, E.

    2011-09-01

    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.

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

    PubMed

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

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

    PubMed Central

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

    2015-01-01

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

  17. Electrical Circuit Analogues of Thermal Conduction and Diffusion

    ERIC Educational Resources Information Center

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

    1978-01-01

    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)

  18. Temperature-dependent electrical conductivity of soda-lime glass

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  19. Electrical conductivity of rocks at high pressures and temperatures

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  20. Metallization and electrical conductivity of hydrogen in Jupiter.

    PubMed

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

    1996-08-16

    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

  1. Thermal conductivity and electrical resistivity of porous materials

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    Process for determining thermal conductivity and electrical resistivity of porous materials is described. Characteristics of materials are identified and used in development of mathematical models. Limitations of method are examined.

  2. Measurement of Electrical Conductivity for a Biomass Fire

    PubMed Central

    Mphale, Kgakgamatso; Heron, Mal

    2008-01-01

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

  3. Software optimization for electrical conductivity imaging in polycrystalline diamond cutters

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  4. Software optimization for electrical conductivity imaging in polycrystalline diamond cutters

    SciTech Connect

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

    2014-02-18

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

  5. Manipulating connectivity and electrical conductivity in metallic nanowire networks.

    PubMed

    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

    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

  6. Cardiac fibrillation risks with TASER conducted electrical weapons.

    PubMed

    Panescu, Dorin; Kroll, Mark; Brave, Michael

    2015-08-01

    The TASER() conducted electrical weapon (CEW) delivers electrical pulses that can temporarily incapacitate subjects. We analyzed the cardiac fibrillation risk with TASER CEWs. Our risk model accounted for realistic body mass index distributions, used a new model of effects of partial or oblique dart penetration and used recent epidemiological CEW statics. PMID:26736265

  7. Electrical conductivity of the burning surface of ammonium perchlorate

    SciTech Connect

    Ivashchenko, Yu.S.; Sadyrin, A.L.; Pavlenko, V.L.

    1987-01-01

    The authors perform experimental measurements of the electrical conductivity of the surface of ammonium perchlorate during its combustion in order to gain insight into its combustion kinetics. Samples with additions of 5% copper salicylate and sodium salicylate were also investigated. Both additives were found to substantially increase the combustion rate. Electrical conductivity was found to depend heavily on temperature and pressure. Ionized combustion products are also analyzed. A full description of the experimental method and instrumentation is given.

  8. Electrical conductivity of (an-)isotropic quark gluon plasma

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    In this article, we have calculated one of the transport coefficient viz. electrical conductivity of the quark gluon plasma (QGP) phase which exhibits an anisotropy in the momentum space. Relativistic Boltzmann's kinetic equation has been solved in the relaxation-time approximation to obtain the electrical conductivity. We have used the quasiparticle description to define the basic properties of QGP through the distribution functions of partons.

  9. Development of electrically/thermally conducting polymer-matrix composites

    SciTech Connect

    Li, Lin

    1993-12-31

    Polymer-matrix composites that are (i) electrically conducting or (ii) thermally conducting but electrically insulating were developed. A goal was to enhance the conductivity, while maintaining good mechanical properties. An in-situ technology for forming an electrically conducting network in a polymer-matrix composite during composite fabrication was developed. One variation of this technology involved the use of a particulate filler that melted at fabrication temperature and hot pressing the filler-polymer mixture at a temperature above the T{sub g} of the polymer, so that the filler particles became flakes that were partially interconnected. Another variation involved adding a small proportion of metal particles as a second filler to a fiber composite. In the second category of the composites (ii), a bridge technology was developed. With a mixture of AlN particles and a small proportion of less conductive SiC whiskers, the thermal conductivity and the flexural toughness were enhanced from the values of the composite containing AlN particles only. The viscosity of the polymer was found to affect the formation of quasi-continuous electrically conducting paths in discontinuous composites made by compression molding of a polymer-filler particulate mixture with the filler in the segregated packing arrangement. Polymers with a high viscosity above their T{sub g} resulted in improved electrical properties. The combination of aluminum flakes and PES and that of nickel particles and PISO gave composites of good electrical and mechanical properties. The use of a silane coupling agent was found to decrease the CTE of AlN polyimide-matrix composites and increase the tensile strength. The use of Cu-coated PES particles in a single layer not touching one another in a PISO matrix provided conducting paths along the z-axis. The average electrical resistivity were 0.05 ohm.cm and 2 ohm-cm (overall composite film). The conducting path density was 10{sup 3}/cm{sup 2}.

  10. Simulation of Electrical Conduction in Geomaterials by SPICE

    NASA Astrophysics Data System (ADS)

    Yeung, Albert T.; Akhtar, Anwar S.

    2008-05-01

    Electrical responses of the subsurface can be used to identify geologic strata, locate anomalies, detect and delineate contamination, among many other applications. All these applications depend on the spatial variations of electrical properties in the subsurface and the resulting flow pattern of electric current. Due to the heterogeneity of the subsurface and complex boundary conditions, three-dimensional electric current flow problems are not easy to analyze, in particular when the response is frequency- and/or time-dependent. In this paper, a method of electric circuit analogy is proposed to simulate the electrical responses of geomaterials using the circuit simulator SPICE. The technique will allow simulation of more complex electrical conduction behavior of geomaterials without much extra effort. The excellent agreement between simulated results and analytical solutions developed for surface geophysical techniques establishes the viability of the method. Limitations of the approach and potential solutions to relax these limitations, and other potential applications of the technique in geosciences are also discussed.

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

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

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

  12. Thermal and Electrical Conductivity Measurements of Cda 510 Phosphor Bronze

    NASA Astrophysics Data System (ADS)

    Tuttle, J.; Canavan, E.; DiPirro, M.

    2010-04-01

    Many cryogenic systems use electrical cables containing phosphor bronze wire. While phosphor bronze's electrical and thermal conductivity values have been published, results vary 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). These harnesses dominate the heat conducted into the JWST instrument stage, and approximately half of the harness conductance is due to the phosphor bronze wires. Since the JWST radiators are expected to 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 that measured its electrical and thermal conductivity between 4 and 295 Kelvin.

  13. Ultraviolet-laser-induced permanent electrical conductivity in polyimide

    NASA Astrophysics Data System (ADS)

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

    1993-03-01

    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.

  14. Electrostatic Discharge Sensitivity and Electrical Conductivity of Composite Energetic Materials

    SciTech Connect

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

    2013-02-01

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

  15. Scaling of the electrical conductivity of granular media

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  16. Electrically conductive resinous bond and method of manufacture

    DOEpatents

    Snowden, Jr., Thomas M.; Wells, Barbara J.

    1987-01-01

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

  17. Electrically conductive resinous bond and method of manufacture

    DOEpatents

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

    1985-01-01

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

  18. Mechanically stiff, electrically conductive composites of polymers and carbon nanotubes

    DOEpatents

    Worsley, Marcus A.; Kucheyev, Sergei O.; Baumann, Theodore F.; Kuntz, Joshua D.; Satcher, Jr., Joe H.; Hamza, Alex V.

    2015-07-21

    Using SWNT-CA as scaffolds to fabricate stiff, highly conductive polymer (PDMS) composites. The SWNT-CA is immersing in a polymer resin to produce a SWNT-CA infiltrated with a polymer resin. The SWNT-CA infiltrated with a polymer resin is cured to produce the stiff and electrically conductive composite of carbon nanotube aerogel and polymer.

  19. 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...

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  1. Measuring the local electrical conductivity of human brain tissue

    NASA Astrophysics Data System (ADS)

    Akhtari, M.; Emin, D.; Ellingson, B. M.; Woodworth, D.; Frew, A.; Mathern, G. W.

    2016-02-01

    The electrical conductivities of freshly excised brain tissues from 24 patients were measured. The diffusion-MRI of the hydrogen nuclei of water molecules from regions that were subsequently excised was also measured. Analysis of these measurements indicates that differences between samples' conductivities are primarily due to differences of their densities of solvated sodium cations. Concomitantly, the sample-to-sample variations of their diffusion constants are relatively small. This finding suggests that non-invasive in-vivo measurements of brain tissues' local sodium-cation density can be utilized to estimate its local electrical conductivity.

  2. UV-induced surface electrical conductivity jump of polymer nanocomposites

    SciTech Connect

    Chen Guangxin; Miyauchi, Masahiro; Shimizu, Hiroshi

    2008-05-19

    A method of improving the electrical conductivity of polymer nanocomposites under UV irradiation was described. An anatase TiO{sub 2}-grafted carbon nanotube could function as a conductive filler and a photocatalyst when it compounds with a poly(L-lactide) to produce a composite. After UV irradiation, the decomposition of the polymer only occurred on the surface of a poly(L-lactide)/TiO{sub 2} grafted carbon nanotube composite and not on bulk, resulting in an electrical conductivity jump as high as six orders of magnitude.

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

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

    SciTech Connect

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

    2012-04-17

    A combination 2/4-probe method was used to measure electrical resistances across a pure, monolithic CVD-SiC disc sample with contact resistance at the SiC/metallic electrode interfaces. By comparison of the almost simultaneous 2/4-probe measurements, the specific contact resistance and its temperature dependence were determined for two types (sputtered gold and porous nickel) electrodes from RT to ~700C. 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 700C. 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.

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

    SciTech Connect

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

    2013-06-30

    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 ?110 ? 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%.

  6. A Structural Electrical Conductivity Model for Oxide Melts

    NASA Astrophysics Data System (ADS)

    Thibodeau, Eric; Jung, In-Ho

    2016-02-01

    A structural electrical conductivity model for oxide melts was developed based on the Nernst-Einstein relationship of ionic conductivity. In the description of ionic conductivity, the effective diffusivities of cations in oxide slags were described as a function of the polymerization of the melt. The polymerization of oxide melts was calculated from the Modified Quasichemical Model, taking into account the short-range ordering in slags. The parameters of this conductivity model were fixed to reproduce the electrical conductivity data in unary and binary melts, and the model can well predict the conductivity data in ternary and higher order system without any additional model parameters. The model is successfully applied to the CaO-MgO-MnO-PbO-Al2O3-SiO2 system.

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

    PubMed

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

    2013-04-21

    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

  8. Electric and thermal conductivities of quenched neutron star crusts

    NASA Technical Reports Server (NTRS)

    Ogata, Shuji; Ichimaru, Setsuo

    1990-01-01

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

  9. Thermal conductivity and electrical resistivity of porous material

    NASA Technical Reports Server (NTRS)

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

    1971-01-01

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

  10. Electrical conductance across self-assembled lipid bilayers

    NASA Astrophysics Data System (ADS)

    Guha, Ingrid; Kedzierski, Jakub; Abedian, Behrouz

    2013-02-01

    This study investigates electrical conduction across lipid bilayers that self-assemble in oil between a water drop and a hafnium oxide surface. Morphology and electrical properties of two bilayers formed from equal molar concentrations of sorbitan monooleate (Span 80) and sorbitan trioleate (Span 85) in dodecane are quantified and compared. The molecular structures of the two surfactants are quite similar, except that sorbitan monooleate contains one unsaturated lipid tail per molecule, whereas sorbitan trioleate contains three. We find that the leakage current density across both bilayers increases exponentially with electric field. The relative leakage current densities across the two bilayers scale with the packing density of lipid tails in the bilayers. This correlation provides evidence that the lipid tail interactions through thermal fluctuations provide a pathway of electrical conduction across the membrane.

  11. Fabrication of highly conductive carbon nanotube fibers for electrical application

    NASA Astrophysics Data System (ADS)

    Guo, Fengmei; Li, Can; Wei, Jinquan; Xu, Ruiqiao; Zhang, Zelin; Cui, Xian; Wang, Kunlin; Wu, Dehai

    2015-09-01

    Carbon nanotubes (CNTs) have great potential for use as electrical wires because of their outstanding electrical and mechanical properties. Here, we fabricate lightweight CNT fibers with electrical conductivity as high as that of stainless steel from macroscopic CNT films by drawing them through diamond wire-drawing dies. The entangled CNT bundles are straightened by suffering tension, which improves the alignment of the fibers. The loose fibers are squeezed by the diamond wire-drawing dies, which reduces the intertube space and contact resistance. The CNT fibers prepared by drawing have an electrical conductivity as high as 1.6 × 106 s m-1. The fibers are very stable when kept in the air and under cyclic tensile test. A prototype of CNT motor is demonstrated by replacing the copper wires with the CNT fibers.

  12. Electrical conductivity of stishovite as a function of water content

    NASA Astrophysics Data System (ADS)

    Yoshino, Takashi; Shimojuku, Akira; Li, Danyang

    2014-02-01

    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.

  13. Multi-rate flowing Wellbore electric conductivity logging method

    SciTech Connect

    Tsang, Chin-Fu; Doughty, Christine

    2003-04-22

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

  14. Electrical conductivity of rigid polyurethane foam at high temperature

    NASA Astrophysics Data System (ADS)

    Johnson, R. T., Jr.

    1982-08-01

    The electrical conductivity of rigid polyurethane foam, used for electronic encapsulation, was measured during thermal decomposition to 3400 C. At higher temperatures the conductance continues to increase. With pressure loaded electrical leads, sample softening results in eventual contact between electrodes which produces electrical shorting. Air and nitrogen environments show no significant dependence of the conductivity on the atmosphere over the temperature range. The insulating characteristics of polyurethane foam below approx. 2700 C are similar to those for silicone based materials used for electronic case housings and are better than those for phenolics. At higher temperatures (greater than or equal to 2700 C) the phenolics appear to be better insulators to approx. 5000 C and the silicones to approx. 6000 C. It is concluded that the Sylgard 184/GMB encapsulant is a significantly better insulator at high temperature than the rigid polyurethane foam.

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

    PubMed

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

    1996-12-01

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

  16. Thermal and Electrical Conductivities of Porous Si Membranes

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  17. High Temperature, Electrically Conductive Graphite Composites For Space Nuclear Power.

    NASA Astrophysics Data System (ADS)

    Lake, M. L.; Woollam, J. A.; Dillon, R. O.; Ahmed, A.; Brito, K. K.

    1988-04-01

    Space nuclear power systems require materials with low density, high thermal conductivity, and high electrical conductivity at elevated temperatures. Vapor grown carbon fiber (VGCF) is a novel material which is a good candidate for these structures. VGCF has been shown to have combined characteristics of thermal conductivity, strength and modulus which exceed values for PAN and pitch-based fibers, and has an electrical conductivity comparable to single crystal graphite. Major thrusts of the current research are to explore growth and processing of vapor grown fibers, and to study the effect of boron doping on the electrical properties of VGCF. Doping of graphite is known to change the distribution of electrons between energy levels in carbon, to enhance graphitization, and to modify the chemical composition of the surface of carbon fibers. Measurements of electrical resistivity as a function of temperature from 4 K to 2700 K have been obtained. The product of resistivity times density of annealed VGCF has been observed to be substantially lower than that of refractory metals at temperatures exceeding 1000 K, suggesting the utility of this unique material as an electrical conductor in space nuclear power thermionic conversion and other high temperature applications.

  18. Rubber-like electrically conductive polymeric materials with shape memory

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    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.

  19. Instrumentation development for electrical conductivity imaging in polycrystalline diamond cutters

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

  20. Corrosion-protective coatings from electrically conducting polymers

    SciTech Connect

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

    1991-12-31

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

  1. Electrically conductive doped block copolymer of polyacetylene and polyisoprene

    DOEpatents

    Aldissi, Mahmoud (Los Alamos, NM)

    1985-01-01

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

  2. Corrosion-protective coatings from electrically conducting polymers

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

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

    SciTech Connect

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

    2009-06-01

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

  4. Electrical conductivity measurements on silicate melts using the loop technique

    NASA Technical Reports Server (NTRS)

    Waff, H. S.

    1976-01-01

    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.

  5. Electrically conducting porphyrin and porphyrin-fullerene electropolymers

    DOEpatents

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

    2014-03-11

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

  6. Direct current electrical conduction block of peripheral nerve.

    PubMed

    Bhadra, Niloy; Kilgore, Kevin L

    2004-09-01

    Electrical currents can be used to produce a block of action potential conduction in whole nerves. This block has a rapid onset and reversal. The mechanism of electrical nerve conduction block has not been conclusively determined, and inconsistencies appear in the literature regarding whether the block is produced by membrane hyperpolarization, depolarization, or through some other means. We have used simulations in a nerve membrane model, coupled with in vivo experiments, to identify the mechanism and principles of electrical conduction block. A nerve simulation package (Neuron) was used to model direct current (dc) block in squid, frog, and mammalian neuron models. A frog sciatic nerve/gastrocnemius preparation was used to examine nerve conduction block in vivo. Both simulations and experiments confirm that depolarization block requires less current than hyperpolarization block. Dynamic simulations suggest that block can occur under both the real physical electrode as well as adjacent virtual electrode sites. A hypothesis is presented which formulates the likely types of dc block and the possible block current requirements. The results indicate that electrical currents generally produce a conduction block due to depolarization of the nerve membrane, resulting in an inactivation of the sodium channels. PMID:15473193

  7. Self-healable electrically conducting wires for wearable microelectronics.

    PubMed

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

    2014-09-01

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

  8. Carbonatite melts and electrical conductivity in the asthenosphere.

    PubMed

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

    2008-11-28

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

  9. Electrical conductivity of albite melts at high pressures

    NASA Astrophysics Data System (ADS)

    Ni, H.; Keppler, H.

    2009-12-01

    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 300-1500C 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 (<700C) and liquid (>1100C) 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.

  10. Tuning Electrical Conductivity of Inorganic Minerals with Carbon Nanomaterials.

    PubMed

    Kovalchuk, Anton A; Tour, James M

    2015-12-01

    Conductive powders based on Barite or calcium carbonate with chemically converted graphene (CCG) were successfully synthesized by adsorption of graphene oxide (GO) or graphene oxide nanoribbons (GONRs) onto the mineral surfaces and subsequent chemical reduction with hydrazine. The efficient adsorption of GO or GONRs on the surface of Barite and calcium carbonate-based mineral particles results in graphene-wrapped hybrid materials that demonstrate a concentration dependent electrical conductivity that increases with the GO or GONR loading. PMID:26544547

  11. Apparent thermal conductivity of polyurethane foam insulation, containing various HCFC blends, from 125 to 335 K. [Final report

    SciTech Connect

    Smith, D.R.

    1993-05-01

    The specimens contain several different blends of HCFC 123 and HCFC 141b as fill gases. Effects of thickness on conductivity and, indirectly, on aging were studied by repeating measurements of conductivity of one specimen whose thickness was reduced in 6-mm steps from 25 to 6 mm. The effect of aging was directly studied by repeating conductivity measurements, after a lapse of time, on two different specimens. The conductivities of all specimens rise linearly with temperature over the lowest (125 to 220 K) and the highest (280 to 335 K) range of temperature, but pass through a local maximum at about 225 K and a local minimum at about 2735 K. The slopes of the two linear portions are approximately equal. For all specimens the conductivity functions below the local maximum practically coincide. The position of the local minimum is independent of fill gas species or mixture, while the location and height of the local maximum depends on fill gas species and on effects of aging. Functional relationships between the conductivity and temperature are obtained for each specimen in the form of ratios of cubic polynomials, the simplest form that accurately models the temperature dependence of conductivity over the whole range studied.

  12. Analytical study on two-phase MHD flow of electrically conducting magnetic fluid

    SciTech Connect

    Okubo, Masaaki; Ishimoto, Jun; Nishiyama, Hideya; Kamiyama, Shinichi

    1994-01-01

    An energy conversion system using magnetic fluids proposed by Resler and Rosensweig was based on the principle that the magnetization of magnetic fluids changes with temperature. However, significant results have not been obtained up to the present. To overcome this limit and to increase the acceleration of fluid flow the authors have contributed a new energy conversion system using two-phase flow produced by heat addition. This idea came from the two-phase liquid-metal MHD power generation system proposed by Petrick and Branover. If temperature sensitive magnetic fluids are used, such a system can produce a larger force than conventional systems because the properties of apparent magnetization change not only by temperature rise but also by gas inclusion. In the present paper, an analytical study is extended to the case of electrically conducting magnetic fluid as a basic study for demonstrating the possibility of application of electrically conducting magnetic fluid to working fluid in a liquid-metal MHD power generation system. Electrically conducting magnetic fluid is usually prepared by dispersing fine iron particles into a liquid metal such as mercury. To prevent a solidification of particles and keep a homogeneous dispersion, a thin film of tin is attached to the particle`s surface. Thus the electrically conducting liquid behaves as fluid itself having magnetization. The equations governing a one-dimensional boiling two-phase duct flow of such an electrically conducting magnetic fluid in a traverse magnetic field are numerically solved. The analytical results of the two-phase flow characteristics of the magnetic fluid are compared with ones of an electrically conducting nonmagnetic fluid.

  13. Osteoblast function on electrically conductive electrospun PLA/MWCNTs nanofibers.

    PubMed

    Shao, Shijun; Zhou, Shaobing; Li, Long; Li, Jinrong; Luo, Chao; Wang, Jianxin; Li, Xiaohong; Weng, Jie

    2011-04-01

    The electrospinning process was utilized successfully to fabricate the random oriented and aligned electrically conductive nanofibers of biodegradable poly-DL-lactide (PLA) in which multiwalled carbon nanotubes (MWCNTs) were embedded. The topographical features of the composite nanofibers were characterized by SEM. The dispersion and alignment of MWCNTs in nanofiber matrix were observed by TEM. The in vitro degradation was characterized in terms of the morphological change, the mass loss and the reduction of polymer molecular weight as well as the decrease of pH value of degradation media. In particular, these conductive nanofiber meshes offered a unique system to study the synergistic effect of topographic cues and electrical stimulation on osteoblasts outgrowth as a way of exploring their potential application in bone tissue engineering. The results of obsteoblasts assay unstimulated showed that the aligned nanofibers as topographic cues could enhance the extension and direct the outgrowth of obsteoblasts better than random fibers. In the presence of direct current (DC) of 100 ?A, the obsteoblasts on all samples grew along the electrical current direction. The cellular elongation and proliferation were mainly dependent on the electrical stimulation whereas the topographical features played a minor role in them. Therefore, electrical stimulation with an appropriate DC value imparted on conductive substrate had great potential in application of bone tissue engineering. PMID:21292320

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  15. Electrically conductive polycrystalline diamond and particulate metal based electrodes

    DOEpatents

    Swain, Greg M.; Wang, Jian

    2005-04-26

    An electrically conducting and dimensionally stable diamond (12, 14) and metal particle (13) electrode produced by electrodepositing the metal on the diamond is described. The electrode is particularly useful in harsh chemical environments and at high current densities and potentials. The electrode is particularly useful for generating hydrogen, and for reducing oxygen and oxidizing methanol in reactions which are of importance in fuel cells.

  16. VLF waves at satellite altitude to investigate Earth electrical conductivity

    NASA Astrophysics Data System (ADS)

    Leye, P. O.; Tarits, P.

    2015-03-01

    At and near the Earth surface, electromagnetic (EM) fields radiated from VLF transmitters are commonly used in geological exploration to determine the shallow Earth conductivity structure. Onboard satellites such as DEMETER, the electric and magnetic sensors detect the VLF signal in altitude. While we know for surface measurement that the VLF EM field recorded at some distance from the transmitter is a function of the ground conductivity, we do not know how this relationship changes when the field is measured at satellite altitude. Here we study the electromagnetic field radiated by a vertical electric dipole located on the Earth surface in the VLF range and measured at satellite altitude in a free space. We investigate the EM field as function of distance from the source, the height above the Earth surface, and the electrical conductivity of the Earth. The mathematical solution in altitude has more severe numerical complications than the well-known solutions at or near the Earth surface. We test most of the solutions developed for the latter case and found that direct summation was best at several hundred kilometers above the Earth. The numerical modeling of the EM field in altitude shows that the field remains a function of Earth conductivity. The dependence weakens with altitude and distance from the transmitter. It remains more important for the electric radial component.

  17. MULTIPLEXER-INDUCED INTERFERENCE ON TDR MEASUREMENTS OF ELECTRICAL CONDUCTIVITY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The possibility of automated multiple readings of water content and bulk soil electrical conductivity represents a major benefit in soil research, and is one of the most attractive characteristics of the time domain reflectometry (TDR) technique. Coaxial multiplexers are commonly employed to monitor...

  18. Soil water sensor response to bulk electrical conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  19. Electrical conductivity of rigid polyurethane foam at high temperature

    SciTech Connect

    Johnson, R.T. Jr.

    1982-08-01

    The electrical conductivity of rigid polyurethane foam, used for electronic encapsulation, has been measured during thermal decomposition to 340/sup 0/C. The conductivity below approx. 150/sup 0/C is < 10/sup -13/ (ohm-cm)/sup -1/ but increases dramatically to approx. 10/sup -9/ (ohm-cm)/sup -1/ as the temperature is increased to 260 to 270/sup 0/C. At higher temperatures the conductance continues to increase, but some of this increase is due to sample softening and changes in sample geometry. With pressure-loaded electrical leads, sample softening results in eventual contact between electrodes (at approx. 340/sup 0/C) producing electrical shorting. Experiments in air and nitrogen environments showed no significant dependence of the conductivity on the atmosphere over the temperature range examined. The insulating characteristics of polyurethane foam below approx. 270/sup 0/C are similar to those for silicone-based (glass-fabric reinforcing) materials used for electronic case (or support structure) housings and are better than those for phenolics (glass-fabric reinforced). At higher temperatures (greater than or equal to 270/sup 0/C) the phenolics appear to be better insulators (combined physical and electrical characteristics) to approx. 500/sup 0/C and the silicones to approx. 600/sup 0/C. The Sylgard 184/GMB encapsulant is a significantly better insulator at high temperature than the rigid polyurethane foam.

  20. Microstructured polymer composites with enhanced thermal and electrical conduction capabilities

    NASA Astrophysics Data System (ADS)

    Moeller, Daniel K.; Shkel, Yuri M.

    2004-07-01

    This paper introduces polymer composites with locally micro-tailored electric and thermal conductive properties. We concentrate on specially designed orthotropic composites that have modified thermal properties in one preferable direction. This preferable direction can vary from region to region in the composite part to fulfill design objectives. Required local micro-tailoring and optimization of structure for given thermal applications is achieved by exposing liquid polymer suspensions to an electric field and then curing the obtained structure. We present testing results for epoxy resin with various fillers including graphite, silica etc. Obtained orthotropic composites are tested for mechanical and thermal and electrical properties. Elastic modulus, thermal expansion, and thermal conduction are measured for various compositions, directions and degree of orthotropy. The potential of obtained materials for electronic, aerospace and automotive applications are briefly discussed.

  1. High temperature electrical conductivity of rigid polyurethane foam

    SciTech Connect

    Johnson, R.T. Jr.

    1984-03-01

    The temperature dependence of the electrical conductivity of three rigid polyurethane foams prepared using different formulations has been measured to approx. 320/sup 0/C. The materials exhibit similar conductivity characteristics, showing a pronounced increase in conductivity with increasing temperature. The insulating characteristics to approx. 200/sup 0/C are better than that for phenolic materials (glass fabric reinforced), and are similar to those for silicone materials (glass microsphere reinforced). At higher temperatures (500 to 600/sup 0/C), the phenolics and silicones are better insulators.

  2. Relating Relative Hydraulic Conductivity and Electrical Conductivity in the Unsaturated Zone

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  3. Composite yarns of multiwalled carbon nanotubes with metallic electrical conductivity.

    PubMed

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

    2010-08-16

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

  4. On the question of the interrelation between variations in crustal electrical conductivity and geodynamical processes

    NASA Astrophysics Data System (ADS)

    Bataleva, E. A.; Batalev, V. Yu.; Rybin, A. K.

    2013-05-01

    The behavior of the variations in the crustal electrical conductivity in a wide range of periods is studied from the data of magnetotelluric soundings (MTS) during the Kambarata experiment (a strong industrial explosion to construct the blast-fill dam on the Naryn river), as well as at Aksu, a stationary geophysical monitoring point. The concept of the interrelation between the stress-strain state of the medium and the change in the apparent electrical resistivity, which is based on the idea of the redistribution of mineralized solutions between the crack networks, is confirmed experimentally. A procedure of azimuthal monitoring is developed, which allowed us not only to identify the anomalous changes in the module and phase of apparent resistivity but also to establish the directions of their maximum increases and decreases (the axes of compression and tension). For 34 points of deep MTS in the territory of Central Tien Shan, the depth intervals in the upper crust that are most sensitive to the changes in the stress-strain state of the medium are established. The variations in the electrical conductivity are compared with the solar-lunar tidal impacts. It is shown that by analyzing the recorded time series, it is possible to recognize the characteristic signs of the changes in the stress-strain state of the medium that are caused by seismic events.

  5. Electric fields in the presence of conducting objects

    NASA Astrophysics Data System (ADS)

    Marrero, Jos Luis Rodrguez

    2010-06-01

    When a conducting object is placed in a region where there is an electric field, charges are induced on its surface. We seek the unique surface charge density that produces an electric field that cancels the original field inside the conductor. When the external sources are point charges or uniform fields, it is easy to determine the field that the induced charges must produce inside the conducting object. Up to a constant, this field gives the potential on the conducting surface, which suffices to determine the potential function outside the conductor. The perturbing field produced by the induced charges is obtained from this potential, and a simple boundary condition gives us the induced surface charge density.

  6. Evaluation of electrical transverse conductivity of the unidirectional CFRP

    NASA Astrophysics Data System (ADS)

    Khebbab, Mohamed; Feliachi, Mouloud; El Hadi Latreche, M.

    2016-01-01

    In this paper, a technique for the calculation of the electrical transverse conductivity of unidirectional carbon fiber reinforced polymer (CFRP), based on Markov chains, is proposed. Inspired by the microscopic cross-sectional structure of CFRP, an electrical percolation system is constructed. The effective transverse conductivity is derived from an equivalent conductance of the percolation network. To achieve such a determination, a notion of escape probability associated to absorbing Markov chains is applied. The obtained results are compared with those given by percolation theory; and also with published experimental data. Our results are shown to be in good agreement with the references. Contribution to the topical issue "Numelec 2015 - Elected submissions", edited by Adel Razek

  7. Electrical conductivity and dielectric property of fly ash geopolymer pastes

    NASA Astrophysics Data System (ADS)

    Hanjitsuwan, Sakonwan; Chindaprasirt, Prinya; Pimraksa, Kedsarin

    2011-02-01

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

  8. Electric field in the vicinity of long thin conducting rods

    NASA Astrophysics Data System (ADS)

    Rezinkina, M. M.; Rezinkin, O. L.; Svetlichnaya, E. E.

    2015-09-01

    We report on the results of numerical and analytical calculations of distributions of potentials and electric fields in the vicinity of thin conducting rods that model the leader channel of lightning and lightning rods. We consider rods represented in the form of a uniformly charged filament, a conducting ellipsoid with a free charge on its surface, as well an ellipsoid or a cylinder in a uniform external electric field. The effect of parameters of conducting rods modeling the leader channel of lightning and lightning rods, as well as the region containing a space charge around the tip of the leader channel, on the distribution of potentials and field strengths are analyzed. The conditions for the propagation of the counter leader from the lightning rod are specified.

  9. Durable Microstructured Surfaces: Combining Electrical Conductivity with Superoleophobicity.

    PubMed

    Pan, Zihe; Wang, Tianchang; Sun, Shaofan; Zhao, Boxin

    2016-01-27

    In this study, electrically conductive and superoleophobic polydimethylsiloxane (PDMS) has been fabricated through embedding Ag flakes (SFs) and Ag nanowires (SNWs) into microstructures of the trichloroperfluorooctylsilane (FDTS)-blended PDMS elastomer. Microstructured PDMS surfaces became conductive at the percolation surface coverage of 3.0 × 10(-2) mg/mm(2) for SFs; the highest conductivity was 1.12 × 10(5) S/m at the SFs surface coverage of 6.0 × 10(-2) mg/mm(2). A significant improvement of the conductivity (increased 3 times at the SNWs fraction of 11%) was achieved by using SNWs to replace some SFs because of the conductive pathways from the formed SNWs networks and its connections with SFs. These conductive fillers bonded strongly with microstructured FDTS-blended PDMS and retained surface properties under the sliding preload of 8.0 N. Stretching tests indicated that the resistance increased with the increasing strains and returned to its original state when the strain was released, showing highly stretchable and reversible electrical properties. Compared with SFs embedded surfaces, the resistances of SFs/SNWs embedded surfaces were less dependent on the strain because of bridging effect of SNWs. The superoleophobicity was achieved by the synergetic effect of surface modification through blending FDTS and the microstructures transferred from sand papers. The research findings demonstrate a simple approach to make the insulating elastomer to have the desired surface oleophobicity and electrical conductivity and help meet the needs for the development of conductive devices with microstructures and multifunctional properties. PMID:26714207

  10. Electrically conducting novel polymer films containing pi-stacks

    NASA Astrophysics Data System (ADS)

    Duan, Robert Gang

    1997-12-01

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

  11. Electrical conductivity in two mixed-valence liquids.

    PubMed

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

    2015-06-01

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

  12. Electrical conductivity of doped polyacrylonitrile (PAN). [Halogen doped polyacrylonitrile

    SciTech Connect

    Teoh, H.; MacInnes, D.; Metz, P.D.

    1982-01-01

    The electrical conductivity and optical absorption spectra of halogen doped PAN have been investigated. When films of PAN previously heated in vacuum to 280/sup 0/C are exposed to bromine or iodine vapor the conductivity rises suddenly. The conductivity is reduced by pumping off the vapor, but upon subsequent reheating the conductivity increases dramatically, with a transition occurring at about 270/sup 0/C. Undoped samples were previously reported to undergo a similar transition above 390/sup 0/C. All samples obey sigma ..cap alpha.. T/sup -1/4/ behavior, suggesting 3-dimensional variable range hopping as the conduction mechanism. The optical and infrared absorption spectra of doped PAN are compared to those previously reported for the undoped material. The stability of doped PAN in air is also discussed. 7 figures.

  13. Optimization and Testing of Electrically Conductive Spacecraft Coatings

    NASA Technical Reports Server (NTRS)

    Mell, Richard J.

    2001-01-01

    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.

  14. Effect of electrically conducting walls on rotating magnetoconvection

    NASA Astrophysics Data System (ADS)

    Zhang, Keke; Weeks, Mark; Roberts, Paul

    2004-06-01

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

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

    NASA Technical Reports Server (NTRS)

    Li, Xiaoyuan; Jeanloz, Raymond

    1991-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Sarvi, Ali

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

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

    SciTech Connect

    Gupta, Sapna; Mahapatra, Manoj K.; Singh, Prabhakar

    2013-09-01

    Graphical abstract: - Highlights: Orthorhombic and rhombohedral phases co-exist at ?260 C and cubic above 1000 C. Polymorphic changes with temperature in air and Ar3%H{sub 2} are observed. Lattice volume change in Ar3%H{sub 2} atmosphere corresponds to Cr{sup 4+} ? Cr{sup 3+} transition. Change in valence state of Cr{sup 4+} to Cr{sup 3+} results in lower electrical conductivity. Experimental evidence is provided for poor densification of LaCrO{sub 3} in air. - Abstract: This paper addresses discrepancies pertaining to structural, thermal and electrical properties of lanthanum chromite. Experimental evidence is provided to support the hypothesis for poor densification in air as well as reduction in electrical conductivity in reducing atmosphere. Sintering condition for the synthesis of LaCrO{sub 3} was optimized to 1450 C and 10 h. Thermo-analytical (differential scanning calorimetry DSC) and high temperature X-ray diffraction (HT-XRD) studies show that orthorhombic lanthanum chromite transforms into rhombohedral structure at ?260 C and cubic structure above 1000 C. Co-existence of the structural phases and the variation in each polymorph with temperature in both air and 3%H{sub 2}Ar atmosphere is reported. Presence and absence of Cr-rich phase at inter-particle neck are observed in oxidizing and reducing atmospheres respectively. The linear thermal expansion co-efficient was calculated to be 10.8 0.2 10{sup ?6} C{sup ?1} in the temperature range of RT1400 C. Electrical conductivity of lanthanum chromite was found to be 0.11 S/cm in air. A decrease in electrical conductivity (0.02 S/cm at 800 C) of LaCrO{sub 3}, as observed in reducing atmosphere (3%H{sub 2}Ar), corresponds to lattice volume change as indicated by peak shift in HT-XRD results.

  18. Facile synthesis of degradable and electrically conductive polysaccharide hydrogels.

    PubMed

    Guo, Baolin; Finne-Wistrand, Anna; Albertsson, Ann-Christine

    2011-07-11

    Degradable and electrically conductive polysaccharide hydrogels (DECPHs) have been synthesized by functionalizing polysaccharide with conductive aniline oligomers. DECPHs based on chitosan (CS), aniline tetramer (AT), and glutaraldehyde were obtained by a facile one-pot reaction by using the amine group of CS and AT under mild conditions, which avoids the multistep reactions and tedious purification involved in the synthesis of degradable conductive hydrogels in our previous work. Interestingly, these one-pot hydrogels possess good film-forming properties, electrical conductivity, and a pH-sensitive swelling behavior. The chemical structure and morphology before and after swelling of the hydrogels were verified by FT-IR, NMR, and SEM. The conductivity of the hydrogels was tuned by adjusting the content of AT. The swelling ratio of the hydrogels was altered by the content of tetraaniline and cross-linker. The hydrogels underwent slow degradation in a buffer solution. The hydrogels obtained by this facile approach provide new possibilities in biomedical applications, for example, biodegradable conductive hydrogels, films, and scaffolds for cardiovascular tissue engineering and controlled drug delivery. PMID:21574634

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

    PubMed

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

    2014-12-28

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  1. Rearrangement of 1D conducting nanomaterials towards highly electrically conducting nanocomposite fibres for electronic textiles.

    PubMed

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

    2015-01-01

    Nanocarbon-based conducting fibres have been produced using solution- or dry-spinning techniques. Highly conductive polymer-composite fibres containing large amounts of conducting nanomaterials have not been produced without dispersants, however, because of the severe aggregation of conducting materials in high-concentration colloidal solutions. Here we show that highly conductive (electrical conductivity ~1.5 10(5) S m(-1)) polymer-composite fibres containing carbon nanotubes and silver nanowires can be fabricated via a conventional solution-spinning process without any other treatment. Spinning dopes were fabricated by a simple mixing of a polyvinyl alcohol solution in dimethylsulfoxide with a paste of long multi-walled carbon nanotubes dispersed in organic solvents, assisted by quadruple hydrogen-bonding networks and an aqueous silver nanowire dispersion. The high electrical conductivity of the fibre was achieved by rearrangement of silver nanowires towards the fibre skin during coagulation because of the selective favourable interaction between the silver nanowires and coagulation solvents. The prepared conducting fibres provide applications in electronic textiles such as a textile interconnector of light emitting diodes, flexible textile heaters, and touch gloves for capacitive touch sensors. PMID:25792333

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

    PubMed Central

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

    2015-01-01

    Nanocarbon-based conducting fibres have been produced using solution- or dry-spinning techniques. Highly conductive polymer-composite fibres containing large amounts of conducting nanomaterials have not been produced without dispersants, however, because of the severe aggregation of conducting materials in high-concentration colloidal solutions. Here we show that highly conductive (electrical conductivity ~1.5 105?S m?1) polymer-composite fibres containing carbon nanotubes and silver nanowires can be fabricated via a conventional solution-spinning process without any other treatment. Spinning dopes were fabricated by a simple mixing of a polyvinyl alcohol solution in dimethylsulfoxide with a paste of long multi-walled carbon nanotubes dispersed in organic solvents, assisted by quadruple hydrogen-bonding networks and an aqueous silver nanowire dispersion. The high electrical conductivity of the fibre was achieved by rearrangement of silver nanowires towards the fibre skin during coagulation because of the selective favourable interaction between the silver nanowires and coagulation solvents. The prepared conducting fibres provide applications in electronic textiles such as a textile interconnector of light emitting diodes, flexible textile heaters, and touch gloves for capacitive touch sensors. PMID:25792333

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    SciTech Connect

    Hurd, Joseph A.; Van Sciver, Steven W.

    2014-01-29

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

  5. Thermal and Electrical Conductivity Probe for Phoenix Mars Lander

    NASA Technical Reports Server (NTRS)

    2007-01-01

    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.

  6. Inflow and outflow signatures in flowing wellbore electrical conductivity logs

    SciTech Connect

    Doughty, Christine; Tsang, Chin-Fu

    2002-08-28

    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.

  7. Electrical Conductivity Measurements on Hydrous Carbonate Melts at Mantle Pressure

    NASA Astrophysics Data System (ADS)

    Sifre, D.; Gaillard, F.

    2012-04-01

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

  8. Effect of orientation anisotropy on calculating effective electrical conductivities

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

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

    PubMed

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

    2014-09-01

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

  10. Variations in electrical conductivity of rocks above metamorphic conditions

    NASA Astrophysics Data System (ADS)

    Fuji-ta, Kiyoshi; Katsura, Tomoo; Ichiki, Masahiro; Matsuzaki, Takuya; Kobayashi, Tomoyuki

    2011-05-01

    This study of the electrical conductivity of metamorphic rocks as a function of temperature highlights the importance of conductivity variations associated with dehydration. We observed conductivity changes for anhydrous rocks and hydrous amphibolites up to 1100 K at 0.5 GPa. Our experimental results revealed that dehydration takes place and that there is a non-linear variation above metamorphic temperatures. To evaluate the observed changes in conductivity after dehydration, numerical calculations were conducted. The calculation results showed that the bulk conductivity of rock plus pure water cannot account for the conductivity values of reacted rocks if the crust dehydrates. However, the data for 0.1 m NaCl solutions are consistent with those for amphibolites between 530 and 1100 K. In this temperature range, the estimated volume fractions of dewatered saline solutions vary between 0.04 and 0.36 vol.%. These results show that although dehydration is insignificant, and only small amounts of high-salinity fluids are formed in the crust, the total conductivity of amphibolites is high after dehydration.

  11. Single-photon heat conduction in electrical circuits

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    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.

  12. Temperature dependence of the electrical conductivity of imidazolium ionic liquids.

    PubMed

    Leys, Jan; Wübbenhorst, Michael; Preethy Menon, Chirukandath; Rajesh, Ravindran; Thoen, Jan; Glorieux, Christ; Nockemann, Peter; Thijs, Ben; Binnemans, Koen; Longuemart, Stéphane

    2008-02-14

    The electrical conductivities of 1-alkyl-3-methylimidazolium tetrafluoroborate ionic liquids and of 1-hexyl-3-methylimidazolium ionic liquids with different anions were determined in the temperature range between 123 and 393 K on the basis of dielectric measurements in the frequency range from 1 to 10(7) Hz. Most of the ionic liquids form a glass and the conductivity values obey the Vogel-Fulcher-Tammann equation. The glass transition temperatures are increasing with increasing length of the alkyl chain. The fragility is weakly dependent on the alkyl chain length but is highly sensitive to the structure of the anion. PMID:18282058

  13. Temperature dependence of the electrical conductivity of imidazolium ionic liquids

    NASA Astrophysics Data System (ADS)

    Leys, Jan; Wübbenhorst, Michael; Preethy Menon, Chirukandath; Rajesh, Ravindran; Thoen, Jan; Glorieux, Christ; Nockemann, Peter; Thijs, Ben; Binnemans, Koen; Longuemart, Stéphane

    2008-02-01

    The electrical conductivities of 1-alkyl-3-methylimidazolium tetrafluoroborate ionic liquids and of 1-hexyl-3-methylimidazolium ionic liquids with different anions were determined in the temperature range between 123 and 393K on the basis of dielectric measurements in the frequency range from 1to107Hz. Most of the ionic liquids form a glass and the conductivity values obey the Vogel-Fulcher-Tammann equation. The glass transition temperatures are increasing with increasing length of the alkyl chain. The fragility is weakly dependent on the alkyl chain length but is highly sensitive to the structure of the anion.

  14. Electrical conductivity and cationic mobility of some refining slags

    NASA Astrophysics Data System (ADS)

    Basov, A. V.; Magidson, I. A.; Smirnov, N. A.

    2015-12-01

    The electrical conductivity and mobility of cations in slag melts are studied. The slag melts are obtained by the partial replacement of silica by sodium oxide in the basic slag charge designed for steel refining without deoxidation with aluminum in a ladle-furnace unit (LFU). The results are analyzed in the framework of a cationic model of conduction and are similar, on the whole, to the earlier obtained results for slags of the same design but when alumina in a charge is replaced by sodium oxide.

  15. Compensation Effect in Electrical Conduction Process: Effect of Substituent Group

    NASA Astrophysics Data System (ADS)

    Mitra, Bani; Misra, T. N.

    1987-05-01

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

  16. Electrical conductivity of tissue at frequencies below 1 MHz

    NASA Astrophysics Data System (ADS)

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

    2009-08-01

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

  17. Thermal and Electrical Conductivity Probe (TECP) for Phoenix

    NASA Astrophysics Data System (ADS)

    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

    2009-03-01

    The Thermal and Electrical Conductivity Probe (TECP) is a component of the Microscopy, Electrochemistry and Conductivity Analyzer (MECA) payload on the Phoenix Lander. TECP will measure the temperature, thermal conductivity, and volumetric heat capacity of the regolith. It will also detect and quantify the population of mobile H2O molecules in the regolith, if any, throughout the polar summer, by measuring the electrical conductivity of the regolith as well as the dielectric permittivity. In the vapor phase, TECP is capable of measuring the atmospheric H2O vapor abundance as well as augmenting 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.

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

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

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

  19. Influence of natural time-dependent variations of electrical conductivity on DC resistivity measurements

    NASA Astrophysics Data System (ADS)

    Rein, Arno; Hoffmann, Ruth; Dietrich, Peter

    2004-01-01

    Long-term direct current (DC) resistivity monitoring surveys are carried out to investigate structures and processes in the subsurface which are coupled to changes in electrical conductivity. Examples would be leaching tests in the unsaturated zone or the observation of a salt tracer spreading in the saturated zone. As these investigations usually take some hours to weeks, natural time-dependent background variations of electrical conductivity have to be considered. Parameters influencing the electrical conductivity are temperature changes, variable water contents in soil due to precipitation or changing groundwater levels, and natural fluctuations of the ionar content in groundwater. Measurements over different time periods (one month to one year) at different test sites demonstrated daily and seasonal trends of electrical conductivity and temperature of groundwater, surface temperatures and groundwater levels. Variable water saturation and changing soil temperatures (in the uppermost soil) are estimated to influence the electrical conductivity most significantly, followed by changing water temperatures and varying ionar content. To verify these conclusions, multi-electrode DC resistivity monitoring has been performed at two test sites for 16 and 22 days. The results reflect natural characteristics and processes in the subsurface. With mean values and standard deviations of apparent resistivities plotted in pseudosections, different areas of the subsurface with different ranges of resistivity variations have been specified. In the area of variable groundwater level (varying water saturation) and in the uppermost soil (strong temperature and moisture changes), especially high resistivity variations are obvious (up to 26%). In the saturated zone, variations are low (predominately below 1%). Concerning resistivity measurements, we conclude that electrodes positioned below the groundwater level (e.g. for salt tracer tests) or between the uppermost meter of subsurface and the area of variable groundwater level (e.g. for leaching tests in the unsaturated zone) should be used to avoid strong influences of background variations.

  20. On the electrical conductivity of Ti-implanted alumina

    SciTech Connect

    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.

    2012-03-15

    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.

  1. Electric conductivity of metallic oblate or prolate nanoparticles

    NASA Astrophysics Data System (ADS)

    Grigorchuk, N. I.; Tomchuk, P. M.

    2007-04-01

    The kinetic method is used to study the electric conductivity of a metallic nanometer-size particle with the shape of an oblate or prolate ellipsoid of revolution at frequencies above and below the characteristic free transit rate of an electron between the walls of the particle. The boundary condition chosen for this problem is diffusive reflection of an electron from the inner surface of the particle. Analytical expressions for the dependence of the electric conductivity on the degree of prolateness or oblateness of the particle and its orientation with respect to the direction of the incident radiation are obtained for the case where the incident wavelength is long compared to the characteristics dimensions of the particle. The dependence of the transverse and longitudinal components of the electric conductivity on the dimensions of the particle and on the frequency of the electromagnetic radiation is investigated. For a particle with large eccentricity these components are found to be in correspondence with known results for thin films and thin wires.

  2. The electrical conduction of conjugated molecular CAMs studied by a conductive atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shin-ichi; Ogawa, Kazufumi

    2006-09-01

    Monomolecular layers containing pyrrolyl groups between two parallel Pt electrodes on a glass substrate by a chemical adsorption technique using N-[11-(trichlorosilyl)undecyl] pyrrole (PNN) were studied. Polymerization with pure water by applying a DC voltage of 10 V between the two Pt electrodes was carried out, and several electric paths were formed between the two Pt electrodes were identified. Conductive probe of an atomic force microscopy (AFM) was used to examine the electrical polymerized paths through the surface of the polypyrrolyl group in a chemically adsorbed monomolecular layer. With a measurement volume of about 0.2 nm (thickness of the monomolecular layer) × 100 μm (the average width of an electric path) × 100 μm (the distance between the Pt electrode and the Au-covered AFM tip), the resistance at room temperature of one electric path was 5 kΩ under ambient conditions. From the results conducted in an atmosphere, the conductivity of a super-long conjugated polypyrrolyl group without any dopant in a lateral direction was ohmically estimated to be at least 5.0 × 10 5 s/m.

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

    DOEpatents

    Tsang, K.L.; Chen, Y.

    1984-02-09

    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.

  4. Electrical studies on silver based fast ion conducting glassy materials

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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.

  5. Electrical studies on silver based fast ion conducting glassy materials

    SciTech Connect

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

    2014-04-24

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

  6. Electrical conductivity of p-type BiOCl nanosheets.

    PubMed

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

    2015-02-14

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

  7. Miniaturization of Electrical Conductivity Sensors for a Multimodal Smart Microchip

    NASA Astrophysics Data System (ADS)

    Futagawa, Masato; Iwasaki, Taichi; Noda, Toshihiko; Takao, Hidekuni; Ishida, Makoto; Sawada, Kazuaki

    2009-04-01

    A new electrical conductivity (EC) sensor with Pt electrodes on a Si substrate was proposed for use in agricultural applications. The complementary metal oxide semiconductor (CMOS) logic technology-compatible sensor was successfully fabricated with a small chip (area, 25 mm2). This sensor was used for an alternating voltage, owing to the polarization of the Pt electrode and its best operation at 10 kHz frequency. Measurements were conducted on water with electrical conductivities ranging from 10-2 to 101 S/m, which shows sufficient linearity for use as a sensor for agriculture applications. It was also possible to be miniaturized. In an agricultural application, measurements were carried out with the sensor inserted in the rock wools, which was confirmed by the linearity of the values obtained using the sensor. In addition, successful real-time measurements using the sensor were conducted by inserting the sensor into the compost in the vicinity of the roots of a tomato seedling. This sensor provides a promising solution for an EC sensor for broad fields of agricultural applications.

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

    NASA Astrophysics Data System (ADS)

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

    2008-06-01

    The Earths 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 Earths 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 Earths surface show that Ohms 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 ionospheres electric potential (+250 kV with respect to the Earths surface) and hence on the fair weather potential gradient (typically 130 V m-1 close to the Earths 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.

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

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

  10. Electrical Conductivity of Water at 70-220 GPa

    NASA Astrophysics Data System (ADS)

    Chau, R.; Mitchell, A. C.; Nellis, W. J.; Minich, R.

    1999-06-01

    Electrical conductivities of water were measured in the pressure range 70-220 GPa using a reverberating shock wave obtained by the impact of a planar projectile onto a sample held between two stiff anvils. The planar projectile was accerlerated to velocities up to 7 km/s using a two-stage light gas gun. The conductivity of water varies from 40 to 200 ?-1 cm-1 between 70 GPa and 220 GPa. Our results are consistent with a purely protonic conduction mechanism at these conditions and are in agreement with recent ab-initio molecular dynamics calculations(C. Cavazzoni, G. L. Chiarotti, S. Scandolo, E. Tosatti, M. Bernasconi, and M. Parrinello, Science (in press)). The data will be compared to recent results for fluid hydrogen which undergoes a transition from a semiconducting to metallic fluid in the same pressure range and CH2 which is an insulator.

  11. Flake Electrical Conductivity of Few-Layer Graphene

    PubMed Central

    2014-01-01

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

  12. The effect of electrical conductivity on pore resistance and electroporation

    NASA Astrophysics Data System (ADS)

    Li, Jianbo; Lin, Hao

    2008-11-01

    Electroporation is an elegant means to gain access to the cytoplasm, and to deliver molecules into the cell while simultaneously maintaining viability and functionality. In this technique, an applied electric pulse transiently permeabilizes the cell membrane, through which biologically active agents such as DNA, RNA, and amino acids can enter the cell, and perform tasks such as gene and cancer therapy. Despite wide applications, current electroporation technologies fall short of desired efficiency and reliability, in part due to the lack of fundamental understanding and quantitative modeling tools. This work focuses on the modeling of cell membrane conductance due to the formation of aqueous conducting pores. An analytical expression is developed to determine effective pore resistance as a function of the membrane thickness, pore size, and intracellular and extracellular conductivities. The availability of this expression avoids empirical or ad hoc specification of the conductivity of the pore-filling solution which was adopted in previous works. Such pore resistance model is then incorporated into a whole-cell electroporation simulation to investigate the effect of conductivity ratio on membrane permeabilization. The results reveal that the degree of permeabilization strongly depends on the specific values of the extracellular and intracellular conductivities.

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

    PubMed

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

    2015-06-01

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

  14. Testing and Optimization of Electrically Conductive Spacecraft Coatings

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  15. Electric conductivity from the solution of the relativistic Boltzmann equation

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  16. The bedrock electrical conductivity structure of Northern Ireland

    NASA Astrophysics Data System (ADS)

    Beamish, David

    2013-08-01

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

  17. The use of electrical conductivity measurements in the prediction of hydraulic conductivity of unsaturated soils

    NASA Astrophysics Data System (ADS)

    Niu, Qifei; Fratta, Dante; Wang, Yu-Hsing

    2015-03-01

    Statistical models have been widely used in soil science, hydrogeology and geotechnical engineering to predict the hydraulic conductivity of unsaturated soils. However, no effective method is available yet for the determination of the associated model parameters such as the tortuosity factor q. Considering the analogy between water flow and electrical current flow in a porous medium, in this study, we proposed to improve the predictive capability of statistical models by determining the tortuosity factor q using electrical conductivity (EC) measurements. We first developed a theoretical hydraulic-electrical conductivity (K-EC) relationship for unsaturated soils based on the bundle of capillary tubes model. This K-EC relationship was then used to form a new unsaturated soil EC model, which was verified using published experimental data. The tortuosity factor q can then be determined by fitting the new EC model to soil EC measurements. Experimental data of six soils were used to test the effectiveness of this method and it was shown that the prediction was significantly improved when compared with the one using the commonly suggested value q = 0.5. The associated root-mean-square-deviation (RMSD) between measurements and predictions is only 0.28 when q is obtained by using our proposed method. In contrast, the RMSD is 0.97 when q is simply assumed as 0.5.

  18. Miniatuization of the flowing fluid electric conductivity loggingtec hnique

    SciTech Connect

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

    2005-10-19

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

  19. Modeling electrical conductivities of nanocomposites with aligned carbon nanotubes.

    PubMed

    Bao, W S; Meguid, S A; Zhu, Z H; Meguid, M J

    2011-12-01

    We have developed an improved three-dimensional (3D) percolation model to investigate the effect of the alignment of carbon nanotubes (CNTs) on the electrical conductivity of nanocomposites. In this model, both intrinsic and contact resistances are considered, and a new method of resistor network recognition that employs periodically connective paths is developed. This method leads to a reduction in the size effect of the representative cuboid in our Monte Carlo simulations. With this new technique, we were able to effectively analyze the effects of the CNT alignment upon the electrical conductivity of nanocomposites. Our model predicted that the peak value of the conductivity occurs for partially aligned rather than perfectly aligned CNTs. It has also identified the value of the peak and the corresponding alignment for different volume fractions of CNTs. Our model works well for both multi-wall CNTs (MWCNTs) and single-wall CNTs (SWCNTs), and the numerical results show a quantitative agreement with existing experimental observations. PMID:22071680

  20. Multifunctional conducting fibres with electrically controlled release of ciprofloxacin.

    PubMed

    Esrafilzadeh, Dorna; Razal, Joselito M; Moulton, Simon E; Stewart, Elise M; Wallace, Gordon G

    2013-08-10

    We hereby present a new method of producing coaxial conducting polymer fibres loaded with an antibiotic drug that can then be subsequently released (or sustained) in response to electrical stimulation. The method involves wet-spinning of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) fibre, which served as the inner core to the electropolymerised outer shell layer of polypyrrole (Ppy). Ciprofloxacin hydrochloride (Cipro) was selected as the model drug and as the dopant in the Ppy synthesis. The release of Cipro in phosphate buffered saline (PBS) from the fibres was controlled by switching the redox state of Ppy.Cipro layer. Released Cipro under passive and stimulated conditions were tested against Gram positive (Streptococcus pyogenes) and Gram negative (Escherichia coli) bacteria. Significant inhibition of bacterial growth was observed against both strains tested. These results confirm that Cipro retains antibacterial properties during fibre fabrication and electrochemically controlled release. In vitro cytotoxicity testing utilising the neural B35 cell line confirmed the cytocompatibility of the drug loaded conducting fibres. Electrical conductivity, cytocompatibility and tuning release profile from this flexible fibre can lead to promising bionic applications such as neuroprosthetics and localised drug delivery. PMID:23379995

  1. Electrically conductive nano graphite-filled bacterial cellulose composites.

    PubMed

    Erbas Kiziltas, Esra; Kiziltas, Alper; Rhodes, Kevin; Emanetoglu, Nuri W; Blumentritt, Melanie; Gardner, Douglas J

    2016-01-20

    A unique three dimensional (3D) porous structured bacterial cellulose (BC) can act as a supporting material to deposit the nanofillers in order to create advanced BC-based functional nanomaterials for various technological applications. In this study, novel nanocomposites comprised of BC with exfoliated graphite nanoplatelets (xGnP) incorporated into the BC matrix were prepared using a simple particle impregnation strategy to enhance the thermal properties and electrical conductivity of the BC. The flake-shaped xGnP particles were well dispersed and formed a continuous network throughout the BC matrix. The temperature at 10% weight loss, thermal stability and residual ash content of the nanocomposites increased at higher xGnP loadings. The electrical conductivity of the composites increased with increasing xGnP loading (attaining values 0.75 S/cm with the addition of 2 wt.% of xGnP). The enhanced conductive and thermal properties of the BC-xGnP nanocomposites will broaden applications (biosensors, tissue engineering, etc.) of BC and xGnP. PMID:26572457

  2. DNA sequencing using electrical conductance measurements of a DNA polymerase

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  3. Transparent electrical conducting films by activated reactive evaporation

    DOEpatents

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

    1982-01-01

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

  4. Bio-electric conductivity potentials in experimental skin grafts.

    PubMed

    Angrist, R C; Gonnering, R S; Dortzbach, R K; Crawford, K

    1987-01-01

    Prior investigations have established that changes in bio-electric potentials accompany the processes of wound creation and healing. In order to investigate these changes in an experimental full-thickness skin graft model, grafts were harvested from the dorsa of eight albino rabbits. Changes in potential were recorded over a period of 32 days, using silver-silver chloride electrodes and a recording polygraph. The potential measured across the skin graft became increasingly more electropositive until, between days 1 and 2, the potential abruptly reversed polarity. This negative potential lasted until day 4, when the conductivity again became positive, with a slow return to baseline measurements by day 32. Although these observations may indicate a bio-electric counterpart to the cellular events of wound healing, more study is needed. PMID:3154591

  5. Transparent electrical conducting films by activated reactive evaporation

    DOEpatents

    Bunshah, R.; Nath, P.

    1982-06-22

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

  6. Development of Tailorable Electrically Conductive Thermal Control Material Systems

    NASA Technical Reports Server (NTRS)

    Deshpande, M. S.; Harada, Y.

    1998-01-01

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

  7. Gas-Tolerant Device Senses Electrical Conductivity of Liquid

    NASA Technical Reports Server (NTRS)

    O'Connor, Edward W.

    2005-01-01

    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.

  8. Electrical Conductivity in Polymer Blends/ Multiwall Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

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

    2008-10-01

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

  9. Electrical Conductivity in Polymer Blends/ Multiwall Carbon Nanotubes

    SciTech Connect

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

    2008-10-23

    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.

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

    PubMed

    Kim, Howon; Hasegawa, Yukio

    2015-05-22

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

  11. Improving the Electrical Conductivity of Polyaniline Through Molecular Control

    NASA Astrophysics Data System (ADS)

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

    2009-03-01

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

  12. Electrical conduction in chalcogenide glasses of phase change memory

    NASA Astrophysics Data System (ADS)

    Nardone, M.; Simon, M.; Karpov, I. V.; Karpov, V. G.

    2012-10-01

    Amorphous chalcogenides have been extensively studied over the last half century due to their application in rewritable optical data storage and in non-volatile phase change memory devices. Yet, the nature of the observed non-ohmic conduction in these glasses is still under debate. In this review, we consolidate and expand the current state of knowledge related to dc conduction in these materials. An overview of the pertinent experimental data is followed by a review of the physics of localized states that are peculiar to chalcogenide glasses. We then describe and evaluate twelve relevant transport mechanisms with conductivities that depend exponentially on the electric field. The discussed mechanisms include various forms of Poole-Frenkel ionization, Schottky emission, hopping conduction, field-induced delocalization of tail states, space-charge-limited current, field emission, percolation band conduction, and transport through crystalline inclusions. Most of the candidates provide more or less satisfactory fits of the observed non-linear IV data. Our analysis calls upon additional studies that would enable one to discriminate between the various alternative models.

  13. Characterization of electrically conductive transition metal dichalcogenide lubricant films

    NASA Astrophysics Data System (ADS)

    Waghray, Harish C.

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

  14. Pore connectivity, electrical conductivity, and partial water saturation: Network simulations

    NASA Astrophysics Data System (ADS)

    Li, M.; Tang, Y. B.; Bernabé, Y.; Zhao, J. Z.; Li, X. F.; Bai, X. Y.; Zhang, L. H.

    2015-06-01

    The electrical conductivity of brine-saturated rock is predominantly dependent on the geometry and topology of the pore space. When a resistive second phase (e.g., air in the vadose zone and oil/gas in hydrocarbon reservoirs) displaces the brine, the geometry and topology of the pore space occupied by the electrically conductive phase are changed. We investigated the effect of these changes on the electrical conductivity of rock partially saturated with brine. We simulated drainage and imbibition as invasion and bond percolation processes, respectively, in pipe networks assumed to be perfectly water-wet. The simulations included the formation of a water film in the pipes invaded by the nonwetting fluid. During simulated drainage/imbibition, we measured the changes in resistivity index as well as a number of relevant microstructural parameters describing the portion of the pore space saturated with water. Except Euler topological number, all quantities considered here showed a significant level of "universality," i.e., insensitivity to the type of lattice used (simple cubic, body-centered cubic, or face-centered cubic). Hence, the coordination number of the pore network appears to be a more effective measure of connectivity than Euler number. In general, the simulated resistivity index did not obey Archie's simple power law. In log-log scale, the resistivity index curves displayed a substantial downward or upward curvature depending on the presence or absence of a water film. Our network simulations compared relatively well with experimental data sets, which were obtained using experimental conditions and procedures consistent with the simulations. Finally, we verified that the connectivity/heterogeneity model proposed by Bernabé et al. (2011) could be extended to the partial brine saturation case when water films were not present.

  15. Measurements of middle-atmosphere electric fields and associated electrical conductivities

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    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.

  16. Electrical Modulation of the Local Conduction at Oxide Tubular Interfaces

    SciTech Connect

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

    2013-01-01

    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.

  17. Electrical conduction in nanodomains in congruent lithium tantalate single crystal

    SciTech Connect

    Cho, Yasuo

    2014-01-27

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

  18. Electrical conductivity of condensed molecular hydrogen in the giant planets

    NASA Technical Reports Server (NTRS)

    Smoluchowski, R.

    1972-01-01

    Theoretical interpretation of several phenomena concerning Jupiter and Saturn depends upon the electrical conductivity of molecular hydrogen which, according to present models, forms the outermost layer of both planets. The layer starts at the transition pressure between the metallic and the molecular form of hydrogen, that is around 1 Mbar, and extends to the outside limits of the atmosphere. Whether at the highest pressures (and temperatures) this layer is a solid or a dense fluid is not certain. In any case, the fluid is in supercritical condition so that there is only a gradual transition from dense liquid to a gaseous form. The two theories which require specific values of the conductivity of the condensed molecular hydrogen are those pertaining to the generation of a magnetic field in the liquid hydrogen rather than in the deep metallic interior (HIDE, 1967), and those concerned with the electromagnetic coupling and exchange of angular momentum between the liquid core and the solid molecular hydrogen mantle.

  19. Grain consolidation and electrical conductivity in porous media

    NASA Astrophysics Data System (ADS)

    Roberts, James N.; Schwartz, Lawrence M.

    1985-05-01

    A simple geometrical model is proposed for diagenesis. Diagenesis is the process by which granular systems evolve geologically from unconsolidated, high-porosity packings toward more consolidated, less porous, materials. We find that the relation between the electrical conductivity σ and the porosity φ can be approximated by a nontrivial power law over a wide range of porosity for both ordered and disordered lattice configurations. The most realistic model is generated from a dense disordered packing. This leads to a problem involving both short-range structural disorder and correlated percolation. In comparison with experiment, our calculations (on both ordered and disordered systems) are shown to reproduce the qualitative trends found in recent data on the conductivity of systems comprised of fused glass beads.

  20. Electrical conductivity of quasi-two-dimensional foams.

    PubMed

    Yazhgur, Pavel; Honorez, Clément; Drenckhan, Wiebke; Langevin, Dominique; Salonen, Anniina

    2015-04-01

    Quasi-two-dimensional (quasi-2D) foams consist of monolayers of bubbles squeezed between two narrowly spaced plates. These simplified foams have served successfully in the past to shed light on numerous issues in foam physics. Here we consider the electrical conductivity of such model foams. We compare experiments to a model which we propose, and which successfully relates the structural and the conductive properties of the foam over the full range of the investigated liquid content. We show in particular that in the case of quasi-2D foams the liquid in the nodes needs to be taken into account even at low liquid content. We think that these results may provide different approaches for the characterization of foam properties and for the in situ characterization of the liquid content of foams in confining geometries, such as microfluidics. PMID:25974485

  1. Electrical conductivity of a boron plasma through the OCP crystallization

    NASA Astrophysics Data System (ADS)

    Lambert, F.; Mazevet, S.; Clrouin, J.

    2009-06-01

    We calculate the DC conductivity of a boron plasma along the 1 eV isotherm up to 25 times the normal density. We use both the quantum and Thomas Fermi molecular dynamics coupled with, respectively, the Kubo-Greenwood formulation and the semi-classical Ziman theory. We find that the DC conductivity obtained using a full quantum mechanical treatment exhibits a significant jump at the one component plasma phase transition - specifically the OCP crystallization of the ions - that is not reproduced using the semi-classical Ziman description. This difference - reaching up to a factor of four - remains well beyond the phase transition and up to the highest density explored. This shows that a full quantum mechanical treatment of the optical and electrical quantities is required in this regime even if semi-classical theories are reliable to obtain both the thermodynamical, and the ionic dynamical and structural properties.

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

    PubMed

    Zhu, Dandan; Lu, Xuemin; Lu, Qinghua

    2014-04-29

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

  3. Correlation Between Viscosity and Electrical Conductivity of Aluminosilicate Melts

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Hua; Chou, Kuo-Chih

    2012-08-01

    The linear relations between logarithm of viscosity and logarithm of electrical conductivity deduced in our previous paper for MO-SiO2 (M = Mg, Ca, Sr, Ba) and M2O-SiO2 (Li, Na, K) melts are extended in this study. It is found that the linear law for MO-SiO2 system is also followed for the melts of FeO-SiO2 and MnO-SiO2 (when electronic conduct can be neglected relative to ionic conduct). The relation between viscosity and electrical conductivity is mainly dependent on the valences of cations of basic oxides. For the sum {{{M}}x {{O-SiO}}2 } melt containing several basic oxides, there are two situations: In the case where all cations are divalent (or univalent), the relation is the same as that of MO-SiO2 melt (or M2O-SiO2 melt); in the case of existing both divalent and univalent cations, the coefficients for the linear relation can be calculated based on the coefficients of MO-SiO2 and M2O-SiO2 melts, with the weight factors from the renormalized mole fractions of sum {{MO}} and sum {{{M}}_{ 2} {{O}}} . It is also found that Al2O3 has little effect on the relation, and the law for sum {{{M}}_{{x}} {{O-SiO}}_{ 2} } melt can be approximately applied to sum {{{M}}_{{x}} {{O-Al}}_{ 2} {{O}}_{ 3} {{-SiO}}_{ 2} } melt.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  5. Changes in Electrical Conductance of Rhodopsin on Photolysis

    PubMed Central

    Hara, Reiko

    1963-01-01

    The change in electrical conductance of rhodopsin solutions was studied with flash-photolysis techniques. The whole pattern of the conductance change on illumination consists of three different processes: (I) the initial decrease, (II) the increase, and (III) the slow decrease, which are in decreasing order of reaction rate. The processes I, II, and III can be most distinctly recognized on flash illumination of acid, slightly acid, and alkaline rhodopsins, respectively. On the other hand, the bleaching of rhodopsin also shows at least three successive phases of different rates, but none of them corresponds in reaction rate to any of the processes of the conductance change. The conductance change may be related to conformational changes of opsin following photoisomerization of retinene, being due to hydrogen or hydroxyl ions and some other inorganic electrolytes. The amount of the change, especially the initial decrease, is proportional to the amount of rhodopsin bleached, even when the photochemical back reaction towards rhodopsin and isorhodopsin occurs in the chromophore depending on the intensity of illumination. Of the three processes, the slow decrease is most severely affected by aging, but the initial decrease and increase are slightly affected. These two processes promptly caused by illumination are connected closely to the conformational changes during the conversion of rhodopsin to metarhodopsin, and perhaps to the initial stage of excitation of rod cells. PMID:14085016

  6. Electric pulp tester conductance through various interface media.

    PubMed

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

    2006-12-01

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

  7. Magnetoresistance, electrical conductivity, and Hall effect of glassy carbon

    SciTech Connect

    Baker, D.F.

    1983-02-01

    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.

  8. Synthesis and electrical conductivity of nanocrystalline tetragonal FeS

    NASA Astrophysics Data System (ADS)

    Zeng, Shu-Lin; Wang, Hui-Xian; Dong, Cheng

    2014-08-01

    A convenient method for synthesis of tetragonal FeS using iron powder as iron source, is reported. Nanocrystalline tetragonal FeS samples were successfully synthesized by reacting metallic iron powder with sodium sulfide in acetate buffer solution. The obtained sample is single-phase tetragonal FeS with lattice parameters a = 0.3767 nm and c = 0.5037 nm, as revealed by X-ray diffraction. The sample consists of flat nanosheets with lateral dimensions from 20 nm up to 200 nm and average thickness of about 20 nm. We found that tetragonal FeS is a fairly good conductor from the electrical resistivity measurement on a pellet of the nanosheets. The temperature dependence of conductivity of the pellet was well fitted using an empirical equation wherein the effect of different grain boundaries was taken into consideration. This study provides a convenient, economic way to synthesize tetragonal FeS in a large scale and reports the first electrical conductivity data for tetragonal FeS down to liquid helium temperature.

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  10. Printability and Electrical Conductivity of UV Curable MWCNT Ink

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  11. Synthesis and applications of electrically conducting polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Ku, Bon-Cheol

    This research focuses on the synthesis and applications of electrically conducting polymer nanocomposites through molecular self-assembly. Two different classes of polymers, polyaniline (PANI) and polyacetylenes have been synthesized by biomimetic catalysis and spontaneous polymerization method. For gas barrier materials, commercially available polymers, poly(allylamine hydrochloride) (PAH) and poly (acrylic acid) (PAA), have also been used and thermally cross-linked. The morphological, optical and electrical properties of amphiphilic polyacetylenes have been studied. Furthermore, barrier properties, permselectivity, pervaporation properties of polyacetylenes/aluminosilicate nanocomposites have been investigated. For processability and electrical properties of carbon nanotube and conducting polymers, substituted ionic polyacetylenes (SIPA) have been covalently incorporated onto single-walled carbon nanotubes (SWNT) using the "grafting-from" technique. In the first study, a nanocomposite film catalyst has been prepared by electrostatic layer-by-layer (ELBL) self-assembly of a polyelectrolyte and a biomimetic catalyst for synthesis of polyaniline. Poly(dimethyl diallylammonium chloride) (PDAC) and hematin have been used as polycation and counter anions, respectively. The absorption spectra by UV-vis-NIR spectroscopy showed that conductive form polyaniline was formed not only as a coating on the surface of the ELBL composites but was also formed in solution. Furthermore, it was found that the reaction rate was affected by pH and concentration of hematin in the multilayers. The feasibility of controlled desorption of hematin molecules from the LBL assembly was explored and demonstrated by changing the pH and hematin concentration. The polymerization rate of aniline in solution was enhanced with decreasing pH of the solutions due to increased desorption of hematin nanoparticles from the multilayers. These ELBL hematin assemblies demonstrated both a way to functionalize surfaces with conductive polyaniline and a potential method of reusability of the catalyst for improved cost effectiveness. For fabrication of multifunctional nanocomposite membranes, (P2EPy-R/Saponite) n on NafionRTM substrate was demonstrated by electrostatic layer-by layer assembly technique. (Abstract shortened by UMI.)

  12. Spatial and Temporal Variations in Electrical Conductivity in North Mississippi Loamy Soils

    NASA Astrophysics Data System (ADS)

    Aufman, M. S.; Holt, R. M.

    2005-05-01

    The use of electromagnetic induction (EM) to characterize and quantify spatial and temporal variations in soil properties is appealing due to low operational costs, rapid measurements, and device mobility. EM methods are sensitive to soil electrical conductivity, which can vary with soil moisture, clay content, soil salinity, and the presence of electrically conductive minerals. We are evaluating the controls on EM response in loamy soils present at the University of Mississippi (UM) Soil Moisture Observatory (SMO). The 5 acre SMO is located in a former agricultural field at the UM Field Station, a 740 acre tract of land located 11 miles from the UM campus in Oxford, Mississippi. EM responses were surveyed along transects and randomly chosen locations using a Geonics EM38. The apparent electrical conductivity (EC) of the soil was determined in both a vertical and horizontal dipole position, which correspond to deep (~1m) and shallow (~0.5) measurements, respectively. We find that EC is primarily controlled by soil physical and chemical properties under moderately dry conditions. Under wetter conditions, EC shows good correlation with soil moisture content. EC variograms show similar spatial structures at different times. However, EC variability increases under wet conditions. These results imply that pore surface conduction dominates under dry conditions, while pore water conduction becomes more important under wet conditions. Variogram similarity suggests that spatial variations in EC are strongly influenced by spatial variations in soil properties regardless of soil moisture conditions. These relationships may allow the development of a predictive model for soil moisture based on EC measurements in North Mississippi loamy soils.

  13. Electrical Conductivity and Dielectric Studies of Hydraulic Cements

    NASA Astrophysics Data System (ADS)

    Pena, Marianela Perez

    Electrical properties of portland cements and other non-portland cementitious materials have been studied at two different stages of hydration. The following relationships have been observed:. Higher water/cement (w/c) ratio (0.5 compared to 0.4) resulted in an increase of the relative permittivity and electrical conductivity of early stage hydrating materials. The relative permittivity values were close to 10('7). The phenomena giving rise to changes in electrical conductivity have been related to the heat of hydration. Higher alkali ion concentration resulted in higher electrical conductivity and relative permittivity values in cement pastes. Cations of inorganic admixtures were found to increase maximum peak of electrical conductivity and relative permittivity in the order: Ca('++) > Mg('++) > Sr('++) and K('+) (TURNEQ) Na('+) > Li('+). Dielectric properties of pressed hardened materials cured over water for 1 day with w/c = 0.20 and heat treated to 500(DEGREES)C prepared with type I, type III, and a microfine calcium silicate (MC500) cement have been compared as a function of temperature and frequency. The relative permittivity for type I hardened materials at 30(DEGREES)C was found to range from 12.5 to 9.4 at frequencies from 1 KHz to 2 MHz. The dissipation factor was found to range from 0.122 to 0.014. The relative permittivity and dissipation factors for type III hardened materials were found to range from 17.8 to 13.0 and from 0.035 to 0.071, respectively, and for MC500 hardened materials were determined to range from 7.6 to 6.9 and from 0.033 to 0.002, respectively. The activation energies determined from Arrhenius plots for the relaxation mechanism operating in these materials correspond to 0.33, 0.30, and 0.46 eV for type I, type III, and MC500 densified hardened materials, respectively. Cement/polymer composites have been prepared using 1.76 wt.% methyl cellulose polymer and a w/c ratio of 0.17. The relative permittivity and loss factor the samples cured over water range from 7.5 to 7.3 and from 0.001 to 0.005, respectively, at frequencies from 10 KHz to 1 MHz, while for the materials cured under sealed conditions, the values range from 5.6 to 5.4 and from 0.007 to 0.004. The heat-treated hardened MC500 cement based materials containing 60 vol.% silica microspheres have the lowest relative permittivity when compared to other materials prepared. The relative permittivity and loss factor of these materials ranged from 5.4 to 5.1 and from 0.035 to 0.012.

  14. Gellan gum-graft-polyaniline-An electrical conducting biopolymer.

    PubMed

    Karthika, J S; Vishalakshi, B; Naik, Jagadish

    2016-01-01

    Grafting of polyaniline (PANI) on to gellan gum (GG) was carried out in the presence of catalytic amount of ammonium peroxydisulfate (APS) as oxidant/initiator under mild acidic conditions by microwave irradiation technique. The grafting condition was optimized by varying the microwave power, exposure time and the composition of the reaction mixture. The graft copolymer GG-g-PANI was characterized by FTIR, TGA, UV/vis, (1)H NMR and SEM techniques. The characteristic peaks at 1506, 1462, 1070 and 830cm(-1) in the IR spectrum and signals at 7.3, 7.2, 7.1 and 4.0 δ in the (1)H NMR spectrum confirms the grafting process. The TGA data reveals GG-g-PANI to be thermally less stable than GG. The optimum grafting was observed when the reaction mixture containing 0.066mmol APS, 0.1M aniline, 1M hydrochloric acid and 0.1g/dL GG was exposed to 80W microwave power for 40s. The DC and AC conductivity of the GG-g-PANI were measured using the 'Two-point probe' method based on which the dielectric properties were evaluated. GG-g-PANI exhibited appreciable electrical conductivity, which increased with the extent of grafting. The results indicate threefold increase in DC conductivity of graft copolymer as compared to GG. PMID:26526174

  15. Oxygen non-stoichiometry, electrical conductivity, and oxygen transport property in mixed conducting perovskite oxides

    NASA Astrophysics Data System (ADS)

    Yoo, Jiho

    2002-01-01

    The experimental results from solid-state coulometric titrations and electrical conductivity relaxation measurements on SrFeO3-delta are described. In coulometric titration experiments, two-phase behavior at T ? 850C was observed as hysteresis in the oxygen non-stoichiometry (delta) isotherms. The p to n transition in the electrical conductivity (sigmatot) isotherms is found to occur at the composition, SrFeO2.505 at 950C and SrFeO2.508 at 900C, respectively. Values of vacancy diffusion coefficient ( Dnu) for SrFeO3-delta is ?1.55 times smaller than for the La1-xSrxFeO3-delta series probably due to stronger defect interactions. Values of oxygen ion diffusion coefficient ( DO2- ) and surface exchange coefficient (kex) for SrFeO3-delta are much greater than for the La 1-xSrxFeO3-delta series, because of its higher delta-values. Electrical conductivity data for La0.2Sr0.8Cr 0.2Fe0.8O3-delta were obtained at 752 ? T ? 1055C and at 10-18 ? pO2 ? 0.5 atm. The slope of a plot of log sigma vs. log pO2 is 1/5 in the p-type region. At T ? 940C, a plateau in the conductivity isotherms indicates the presence of a two-phase region most probably corresponding to a mixture of perovskite and an oxygen vacancy ordered phases. Electrical conductivity relaxation measurements were performed to investigate the kinetics of oxygen transport at 800 ? T ? 1000C and at 0.01 ? pO2 ? 1 atm, having values of Dchem = 1.62 x 10 -4 3.10 x 10-4 cm2/s at 950C with an activation energy (Ea) of 84 +/- 14 kJ/mol. The oxygen ion diffusion coefficient ( DO2- ) and surface exchange coefficient (kex) of La0.2Sr0.8Cr0.2Fe0.8O 3-delta are relatively high because of high oxygen vacancy concentration. The experimental results of electrical conductivity measurements and solid-state coulometric titrations on La0.5Sr0.5Ga 0.2Fe0.8O3-delta are reported. The effect of oxygen partial pressure (pO2) on electrical conductivities of La0.5Sr0.5Ga0.2Fe0.8O3-delta was investigated at 750 ? T ? 1050C and at 10-17 ? pO2 ? 0.5 atm. At 10-5 ? pO2 ? 0.1 atm the log sigmatot is almost proportional to log (pO2) with a slope of ? slope. At T ? 850C, a plateau and a rapid increase in the conductivity isotherms indicate a presence of a two-phase region. In a plot of log pO 2 vs. oxygen non-stoichiometry discontinuity appears at T ? 900C and at the pO2 region where the two-phase region was observed from the conductivity results. The p to n transition in the conductivity isotherms occurs at the composition, La0.5Sr0.5Ga0.2Fe 0.8O2.7492.750 at 850C and La0.5Sr 0.5Ga0.2Fe0.8O2.7482.749 at 900C, respectively. The oxygen transport kinetics in La0.5Sr0.5FeO 3-delta were investigated using the electrical conductivity relaxation technique at 788 ? T ? 943C and at 0.03 ? pO 2 ? 1 atm. (Abstract shortened by UMI.)

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

    PubMed

    Lehmann-Horn, J A; Walbrecker, J O

    2012-07-01

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

  17. Electrically Conductive Multiphase Polymer Blend Carbon-Based Composites

    NASA Astrophysics Data System (ADS)

    Brigandi, Paul James

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  19. Electrical Conduction and Dielectric Properties of Biodegradable Plastics

    NASA Astrophysics Data System (ADS)

    Shinyama, Katsuyoshi; Fujita, Shigetaka

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

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  1. System and method for determining velocity of electrically conductive fluid

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    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.

  2. Electrically Conductive and Optically Active Porous Silicon Nanowires

    PubMed Central

    Qu, Yongquan; Liao, Lei; Li, Yujing; Zhang, Hua; Huang, Yu; Duan, Xiangfeng

    2009-01-01

    We report the synthesis of vertical silicon nanowire array through a two-step metal-assisted chemical etching of highly doped n-type silicon (100) wafers in a solution of hydrofluoric acid and hydrogen peroxide. The morphology of the as-grown silicon nanowires is tunable from solid nonporous nanowires, nonporous/nanoporous core/shell nanowires, and entirely nanoporous nanowires by controlling the hydrogen peroxide concentration in the etching solution. The porous silicon nanowires retain the single crystalline structure and crystallographic orientation of the starting silicon wafer, and are electrically conductive and optically active with visible photoluminescence. The combination of electronic and optical properties in the porous silicon nanowires may provide a platform for the novel optoelectronic devices for energy harvesting, conversion and biosensing. PMID:19807130

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

    DOEpatents

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

    2009-11-17

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

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

    NASA Technical Reports Server (NTRS)

    Parkin, C. W.

    1978-01-01

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

  5. Formulation of electrically conductive thermal-control coatings

    NASA Technical Reports Server (NTRS)

    Shai, M. C.

    1978-01-01

    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.

  6. Electrical Conductivities and Optical Reflectivities of Dense Aluminum Plasmas

    NASA Astrophysics Data System (ADS)

    Blancard, C.; Desjarlais, M. P.; Faussurier, G.; Recoules, V.; Renaudin, P.

    2004-10-01

    We present a model to describe the thermodynamic and transport properties of dense plasmas. The electronic and ionic structures are determined self-consistently using finite temperature density functional theory and the Gibbs-Bogolyubov inequality. The main thermodynamic quantities, i.e., internal energy, pressure, entropy, and sound speed are obtained by numerical differentiation of the plasma total Helmholtz free energy. Electronic electrical and thermal conductivities are calculated from the Ziman approach. Ionic transport coefficients are estimated using those of a hard-sphere system and the Rosenfeld semi-empirical "universal" correspondence between excess entropy and dimensionless transport coefficients of dense fluids. Numerical results and comparisons with quantum molecular dynamics calculations and experiments are presented and discussed.

  7. Electrical Conductivities and Optical Reflectivities of Dense Aluminum Plasmas

    SciTech Connect

    Blancard, C.; Faussurier, G.; Recoules, V.; Renaudin, P.

    2004-10-20

    We present a model to describe the thermodynamic and transport properties of dense plasmas. The electronic and ionic structures are determined self-consistently using finite temperature density functional theory and the Gibbs-Bogolyubov inequality. The main thermodynamic quantities, i.e., internal energy, pressure, entropy, and sound speed are obtained by numerical differentiation of the plasma total Helmholtz free energy. Electronic electrical and thermal conductivities are calculated from the Ziman approach. Ionic transport coefficients are estimated using those of a hard-sphere system and the Rosenfeld semi-empirical 'universal' correspondence between excess entropy and dimensionless transport coefficients of dense fluids. Numerical results and comparisons with quantum molecular dynamics calculations and experiments are presented and discussed.

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

    NASA Astrophysics Data System (ADS)

    Laumonier, Mickael; Gaillard, Fabrice; Sifre, David

    2015-04-01

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

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

    NASA Technical Reports Server (NTRS)

    Duba, AL

    1987-01-01

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

  10. Development of Tailorable Electrically Conductive Thermal Control Material Systems

    NASA Technical Reports Server (NTRS)

    Deshpande, M. S.; Harada, Y.

    1997-01-01

    The optical characteristics of surfaces on spacecraft are fundamental parameters in controlling its temperature. Passive thermal control coatings with designed solar absorptance and infrared emittance properties have been developed and have been in use for some time. In this total space environment, the coating must be stable and maintain its desired optical properties as well as mechanical properties for the course of the mission lifetime. The mission lifetimes are increasing and in our quest to save weight, newer substrates are being integrated which limit electrical grounding schemes. All of this has added to already existing concerns about spacecraft charging and related spacecraft failures or operational failures. The concern is even greater for thermal control surfaces that are very large. One way of alleviating such concerns is to design new thermal control material systems (TCMS) that can help to mitigate charging via providing charge leakage paths. The objective of this program was to develop two types of passive electrically conductive TCMS. The first was a highly absorbing/emitting black surface and the second was a low (alpha(sub s)/epsilon(sub N)) type white surface. The surface resistance goals for the black absorber was 10(exp 4) to 10(exp 9) Omega/square, and for the white surfaces it was 10(exp 6) to 10(exp 10) Omega/square. Several material system concepts were suggested and evaluated for space environment stability and electrical performance characterization. Our efforts in designing and evaluating these material systems have resulted in several developments. New concepts, pigments and binders have been developed to provide new engineering quality TCMS. Some of these have already found application on space hardware, some are waiting to be recognized by thermal designers, and some require further detailed studies to become state-of-the-art for future space hardware and space structures. Our studies on baseline state-of-the-art materials and conductive concepts have resulted in several important findings that are of interest to all thermal designers and systems integrators.

  11. DNA origami metallized site specifically to form electrically conductive nanowires.

    PubMed

    Pearson, Anthony C; Liu, Jianfei; Pound, Elisabeth; Uprety, Bibek; Woolley, Adam T; Davis, Robert C; Harb, John N

    2012-09-01

    DNA origami is a promising tool for use as a template in the design and fabrication of nanoscale structures. The ability to engineer selected staple strands on a DNA origami structure provides a high density of addressable locations across the structure. Here we report a method using site-specific attachment of gold nanoparticles to modified staple strands and subsequent metallization to fabricate conductive wires from DNA origami templates. We have modified DNA origami structures by lengthening each staple strand in select regions with a 10-base nucleotide sequence and have attached DNA-modified gold nanoparticles to the lengthened staple strands via complementary base-pairing. The high density of extended staple strands allowed the gold nanoparticles to pack tightly in the modified regions of the DNA origami, where the measured median gap size between neighboring particles was 4.1 nm. Gold metallization processes were optimized so that the attached gold nanoparticles grew until gaps between particles were filled and uniform continuous nanowires were formed. Finally, electron beam lithography was used to pattern electrodes in order to measure the electrical conductivity of metallized DNA origami, which showed an average resistance of 2.4 kΩ per metallized structure. PMID:22578334

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

    NASA Astrophysics Data System (ADS)

    Jault, Dominique

    2015-07-01

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

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

    PubMed

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

    2012-05-17

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

  14. Electrical conductivity of majorite garnet and its implications for electrical structure in the mantle transition zone

    NASA Astrophysics Data System (ADS)

    Yoshino, Takashi; Nishi, Masayuki; Matsuzaki, Takuya; Yamazaki, Daisuke; Katsura, Tomoo

    2008-11-01

    Electrical conductivities of majorite garnet with compositions of pyrolite minus olivine (pyrolite majorite) and mid-ocean ridge basalt (MORB majorite) were measured under physical conditions of the mantle transition zone (18 and 23 GPa and temperatures up to 2000 K) in a Kawai-type multi-anvil apparatus. The samples with MORB composition are mainly composed of majorite, which has higher Fe and Al contents, and contain a small amount of stishovite. The conductivity of the MORB majorite is more than twice higher than those of the pyrolite majorite at the same temperature. The activation energies of these majorites are both 1.4 eV at temperature of 1000-1600 K suggesting that the dominant mechanism of charge transportation is Fe 2+-Fe 3+ hopping (small polaron) conduction. At higher temperatures (>1600 K), corresponding to temperature conditions of the transition zone, conduction mechanism of the pyrolite majorite would change from small polaron to ionic conduction. The pyrolite majorite has only slightly higher and lower conductivity than dry wadsleyite and ringwoodite, respectively, and will not largely change the conductivity-depth profile predicted for the dry mantle transition zone. The laboratory-based conductivity profile of the mantle transition zone with pyrolitic composition can explain well the current semi-global conductivity-depth profile obtained from electromagnetic study beneath Pacific. On the other hand, the garnetite originating from the oceanic crust has remarkably higher conductivity than the surrounding mantle because the conductivity of MORB majorite is significantly higher than those of wadsleyite and ringwoodite. Conductivity values of MORB majorite agree with those of the stagnant slab beneath the northeastern China.

  15. EFFECTS OF TRITIUM GAS EXPOSURE ON ELECTRICALLY CONDUCTING POLYMERS

    SciTech Connect

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

    2009-12-16

    Effects of beta (tritium) and gamma irradiation on the surface electrical conductivity of two types of conducting polymer films are documented to determine their potential use as a sensing and surveillance device for the tritium facility. It was shown that surface conductivity was significantly reduced by irradiation with both gamma and tritium gas. In order to compare the results from the two radiation sources, an approximate dose equivalence was calculated. The materials were also sensitive to small radiation doses (<10{sup 5} rad), showing that there is a measurable response to relatively small total doses of tritium gas. Spectroscopy was also used to confirm the mechanism by which this sensing device would operate in order to calibrate this sensor for potential use. It was determined that one material (polyaniline) was very sensitive to oxidation while the other material (PEDOT-PSS) was not. However, polyaniline provided the best response as a sensing material, and it is suggested that an oxygen-impermeable, radiation-transparent coating be applied to this material for future device prototype fabrication. A great deal of interest has developed in recent years in the area of conducting polymers due to the high levels of conductivity that can be achieved, some comparable to that of metals [Gerard 2002]. Additionally, the desirable physical and chemical properties of a polymer are retained and can be exploited for various applications, including light emitting diodes (LED), anti-static packaging, electronic coatings, and sensors. The electron transfer mechanism is generally accepted as one of electron 'hopping' through delocalized electrons in the conjugated backbone, although other mechanisms have been proposed based on the type of polymer and dopant [Inzelt 2000, Gerard 2002]. The conducting polymer polyaniline (PANi) is of particular interest because there are extensive studies on the modulation of the conductivity by changing either the oxidation state of the main backbone chain, or by protonation of the imine groups [de Acevedo, 1999]. There are several types of radiation sensors commercially available, including ionization chambers, geiger counters, proportional counters, scintillators and solid state detectors. Each type has advantages, although many of these sensors require expensive electronics for signal amplification, are large and bulky, have limited battery life or require expensive materials for fabrication. A radiation sensor constructed of a polymeric material could be flexible, light, and the geometry designed to suit the application. Very simple and inexpensive electronics would be necessary to measure the change in conductivity with exposure to radiation and provide an alarm system when a set change of conductivity occurs in the sensor that corresponds to a predetermined radiation dose having been absorbed by the polymer. The advantages of using a polymeric sensor of this type rather than those currently in use are the flexibility of sensor geometry and relatively low cost. It is anticipated that these sensors can be made small enough for glovebox applications or have the ability to monitor the air tritium levels in places where a traditional monitor cannot be placed. There have been a few studies on the changes in conductivity of polyaniline specifically for radiation detection [de Acevedo, 1999; Lima Pacheco, 2003], but there have been no reports on the effects of tritium (beta radiation) on conducting polymers, such as polyaniline or polythiophene. The direct implementation of conducting polymers as radiation sensor materials has not yet been commercialized due to differing responses with total dose, dose rate, etc. Some have reported a large increase in the surface conductivity with radiation dose while others report a marked decrease in conductive properties; these differing observations may reflect the competing mechanisms of chain scission and cross-linking. However, it is clear that the radiation dose effects on conducting polymers must be fully understood before these materials can be used as sensing devices. This report presents the results of irradiations of two conductive polymers: polyaniline and polythiophene. Samples of doped polyaniline and polythiophene were coated onto polyester (polyethyleneterephalate, PET) substrates and were exposed to both tritium gas (beta irradiation) and {sup 60}Co gamma irradiation. The samples were subsequently characterized after various total doses. Infrared spectroscopy was utilized to characterize the gamma-exposed samples post-irradiation. Although the sources of radiation are different in kind (charged particle versus photon) and their energies differ, there will be great value in using noncontaminating gamma irradiation to model the effects of tritium beta radiation.

  16. Detection of Wheat Kernels with Hidden Insect Infestations Using an Electrically Conductive Roller Mill

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A laboratory roller mill system was modified to measure and analyze the electrical conductance of wheat as it was crushed. The electrical conductance of normal wheat kernels is normally low and fairly constant. In contrast, the electrical conductance of wheat kernels infested with live insects is su...

  17. Laboratory derived constraints on electrical conductivity beneath Slave craton

    NASA Astrophysics Data System (ADS)

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

    2007-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Kole, Madhusree; Dey, T. K.

    2013-02-01

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

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

    TOXLINE Toxicology Bibliographic Information

    Kaith BS; Sharma R; Kalia S

    2015-04-01

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

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

    PubMed

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

    2015-04-01

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

  1. Electrical conductivity of milk: ability to predict mastitis status.

    PubMed

    Norberg, E; Hogeveen, H; Korsgaard, I R; Friggens, N C; Sloth, K H M N; Løvendahl, P

    2004-04-01

    Electrical conductivity (EC) of milk has been introduced 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 traits were investigated for their association with udder health. In total, 322 cows with 549 lactations were included in the study. Cows were classified as healthy or clinically or subclinically infected, and EC was measured repeatedly during milking on each quarter. Four EC traits were defined; the inter-quarter ratio (IQR) between the highest and lowest quarter EC values, the maximum EC level for a cow, IQR between the highest and lowest quarter EC variation, and the maximum EC variation for a cow. Values for the traits were calculated for every milking throughout the entire lactation. All EC traits increased significantly (P < 0.001) when cows were subclinically or clinically infected. A simple threshold test and discriminant function analysis was used to validate the ability of the EC traits to distinguish between cows in different health groups. Traits reflecting the level rather than variation of EC, and in particular the IQR, performed best to classify cows correctly. By using this trait, 80.6% of clinical and 45.0% of subclinical cases were classified correctly. Of the cows classified as healthy, 74.8% were classified correctly. However, some extra information about udder health status was obtained when a combination of EC traits was used. PMID:15259246

  2. Strong and Electrically Conductive Graphene Based Composite Fibers and Laminates

    DOE PAGESBeta

    Vlassiouk, Ivan V.; Polyzos, Georgios; Cooper, Ryan C.; Ivanov, Ilia N.; Keum, Jong Kahk; Paulauskas, Felix L.; Datskos, Panos G.; Smirnov, Sergei

    2015-04-28

    Graphene is an ideal candidate for lightweight, high-strength composite materials given its superior mechanical properties (specific strength of 130 GPa and stiffness of 1 TPa). To date, easily scalable graphene-like materials in a form of separated flakes (exfoliated graphene, graphene oxide, and reduced graphene oxide) have been investigated as candidates for large-scale applications such as material reinforcement. These graphene-like materials do not fully exhibit all the capabilities of graphene in composite materials. In this study, we show that macro (2 inch × 2 inch) graphene laminates and fibers can be produced using large continuous sheets of single-layer graphene grown bymore » chemical vapor deposition. The resulting composite structures have potential to outperform the current state-of-the-art composite materials in both mechanical properties and electrical conductivities (>8 S/cm with only 0.13% volumetric graphene loading and 5 × 103 S/cm for pure graphene fibers) with estimated graphene contributions of >10 GPa in strength and 1 TPa in stiffness.« less

  3. Strong and Electrically Conductive Graphene Based Composite Fibers and Laminates

    SciTech Connect

    Vlassiouk, Ivan V.; Polyzos, Georgios; Cooper, Ryan C.; Ivanov, Ilia N.; Keum, Jong Kahk; Paulauskas, Felix L.; Datskos, Panos G.; Smirnov, Sergei

    2015-04-28

    Graphene is an ideal candidate for lightweight, high-strength composite materials given its superior mechanical properties (specific strength of 130 GPa and stiffness of 1 TPa). To date, easily scalable graphene-like materials in a form of separated flakes (exfoliated graphene, graphene oxide, and reduced graphene oxide) have been investigated as candidates for large-scale applications such as material reinforcement. These graphene-like materials do not fully exhibit all the capabilities of graphene in composite materials. In this study, we show that macro (2 inch × 2 inch) graphene laminates and fibers can be produced using large continuous sheets of single-layer graphene grown by chemical vapor deposition. The resulting composite structures have potential to outperform the current state-of-the-art composite materials in both mechanical properties and electrical conductivities (>8 S/cm with only 0.13% volumetric graphene loading and 5 × 103 S/cm for pure graphene fibers) with estimated graphene contributions of >10 GPa in strength and 1 TPa in stiffness.

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

    PubMed

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

    2002-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2007-01-01

    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 15C and 40C. 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 40C, due to the low hygrothermal stability of epoxy. Graphite colloid is even less durable than silver epoxy, due to its being water based.

  6. The Wilkes subglacial basin eastern margin electrical conductivity anomaly

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    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 (5mm5mm 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.

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

    PubMed

    Kruglikov, Ilja L

    2015-01-01

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

  9. Microstructural Inhomogeneity of Electrical Conductivity in Subcutaneous Fat Tissue

    PubMed Central

    Kruglikov, Ilja L.

    2015-01-01

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

  10. SOIL MICROBIAL BIOMASS RELATIONSHIPS WITH ORGANIC MATTER FRACTIONS IN A NEBRASKA CORN FIELD MAPPED USING APPARENT ELECTRICAL CONDUCTIVITY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soils vary within a field and this variation effects crop yield, crop residue decomposition, and nutrient and water availability. Variation in soil depth, and amounts of sand, silt, and clay do not change quickly with time and spatial patterns within a field in these properties are stable. These st...

  11. Materials and methods for autonomous restoration of electrical conductivity

    SciTech Connect

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

    2014-03-25

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  13. The electrically detected magnetic resonance microscope: combining conductive atomic force microscopy with electrically detected magnetic resonance.

    PubMed

    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

    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 810(6)spins/?Hz at room temperature. PMID:24182133

  14. High thermal conductivity connector having high electrical isolation

    DOEpatents

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

    1995-01-01

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

  15. Electrical conductivity model of Al-bearing bridgmanite with implications for the electrical structure of the Earth's lower mantle

    NASA Astrophysics Data System (ADS)

    Yoshino, Takashi; Kamada, Seiji; Zhao, Chengcheng; Ohtani, Eiji; Hirao, Naohisa

    2016-01-01

    Electrical conductivity measurements of bridgmanite with various Al contents and a constant Mg# of 90 were performed at temperatures ranging from room temperature up to 2000 K at pressures of 26-28 GPa in a Kawai-type multianvil apparatus by impedance spectroscopy analysis. The incorporation of Al into bridgmanite raises its electrical conductivity significantly, but it is a small conductivity variation with respect to the quantity of Al. Synchrotron Mössbauer spectroscopy of recovered samples showed significant amounts of ferric iron in aluminous bridgmanite. The mobility of the charge carriers in bridgmanite was calculated based on the conductivity and the Fe3+/ΣFe ratio. The relationship between the logarithm of the electrical conductivity and the reciprocal temperature is consistent with Fe2+-Fe3+ electron hopping (small polarons) as the dominant conduction mechanism at low temperatures (<1400 K) and ionic conduction at higher temperatures (>1600 K). By taking various conduction mechanisms into account, we develop an electrical conductivity model for aluminous bridgmanite as a function of the Al and Fe contents. The small polaron conduction model indicates that the electrical conductivity of aluminous bridgmanite has a maximum at around 0.06 Al atoms per formula unit, and any further increase in the Al content in bridgmanite reduces the conductivity. In contrast, the ionic conduction model indicates that the electrical conductivity simply increases with increasing Al content. The resulting conductivity of Al-bearing bridgmanite first increases up to 0.06 Al atoms per formula unit and then remains constant or increases with increasing Al content at higher temperatures. The increase in conductivity observed in the uppermost part of the lower mantle by electromagnetic studies can be explained by the gradual decomposition of majorite garnet. The deeper lower mantle conductivity would be controlled by small polaron conduction because of the large positive activation volume required for ionic conduction.

  16. 76 FR 70122 - Plan for Conduct of 2012 Electric Transmission Congestion Study

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-10

    ... relief (TLR) actions. Historic energy flows. Current and projected electric supply and generation plans... for Conduct of 2012 Electric Transmission Congestion Study AGENCY: Office of Electricity Delivery and... Energy (Department or DOE) to complete a study of electric transmission congestion every three years....

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

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

    NASA Technical Reports Server (NTRS)

    Khusid, B.; Acrivos, A.

    1999-01-01

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

  19. Heat Conduction through Surface Structures and Mixtures using Electric Circuits as Analogs

    NASA Astrophysics Data System (ADS)

    Huebner, W. F.; Boice, D. C.; Green, J. R.

    1998-09-01

    We present a mathematical model using electric analogs to simulate vertical and lateral conductive heat flow in surface layers of planetary bodies with topography. The model can also be used to determine average electric and thermal conductivities of small-scale granular mixtures (as opposed to molecular mixtures). The algorithm is general and applicable to complex compositions. Analogies between thermal and electric conductivities are basic and well known. The model uses Kirchhoff's rules for electric networks. If a temperature difference is maintained across a solid body, the thermal energy transported per unit time and unit area, (the vector heat current per unit area, Q), is proportional to the negative temperature gradient, such that Q = - kappa nabla T. Here kappa is the heat (or thermal) conductivity of the material. For the electric analogy we use Ohm's law. If a potential difference is maintained in a resistive (ohmic) body, the electric charge transported per unit time and unit area (the vector current density, i) is proportional to the electric field, such that i = sigma E = - sigma nabla V. Here sigma is the electric conductivity (or specific conductance) of the material and V is the electric potential. With i replacing Q and V replacing T the parallel nature of thermal and electric conductivity is established. The thermal conductivity, kappa , is a direct analog to the electric conductivity, sigma . The model will be used to verify heat flow measured through porous mixtures of ice and dust as an analog of comet matter in the laboratory. Heat flow is simulated by electric currents through a three-dimensional network of resistors with emfs representing temperatures at boundaries. We illustrate our model, for simplicity, with a two-dimensional network. Each type of material with given conductivity is represented by a corresponding value for the electric resistance. The number of each type of resistor is proportional to the relative abundance of each material type. For mixtures, resistors are selected randomly.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

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

    PubMed

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

    2014-11-01

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

  2. The Electrical Conductivity Of Partly Ionized Helium Plasma

    SciTech Connect

    Sreckovic, Vladimir A.; Ignjatovic, Ljubinko; Mihajlov, A. A.

    2007-04-23

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

  3. Preparation of Electrically Conductive Polystyrene/Carbon Nanofiber Nanocomposite Films

    ERIC Educational Resources Information Center

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

    2008-01-01

    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…

  4. Electrical conductivity of diopside: evidence for oxygen vacancies

    USGS Publications Warehouse

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

    1988-01-01

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

  5. Preparation of Electrically Conductive Polystyrene/Carbon Nanofiber Nanocomposite Films

    ERIC Educational Resources Information Center

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

    2008-01-01

    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

  6. Different Clinical Electrodes Achieve Similar Electrical Nerve Conduction Block

    PubMed Central

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

    2015-01-01

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

  7. Different clinical electrodes achieve similar electrical nerve conduction block

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

  9. Study of AC electrical conduction mechanisms in an epoxy polymer

    NASA Astrophysics Data System (ADS)

    Jilani, Wissal; Mzabi, Nissaf; Gallot-Lavallée, Olivier; Fourati, Najla; Zerrouki, Chouki; Zerrouki, Rachida; Guermazi, Hajer

    2015-11-01

    The AC conductivity of an epoxy resin was investigated in the frequency range 10^{-1} - 106 Hz at temperatures ranging from -100 to 120 °C. The frequency dependence of σ_{ac} was described by the law: σ_{ac}=ω \\varepsilon0\\varepsilon^''_{HN}+Aωs. The study of temperature variation of the exponent (s) reveals two conduction models: the AC conduction dependence upon temperature is governed by the small polaron tunneling mechanism (SPTM) at low temperature (-100 -60 °C) and the correlated barrier hopping (CHB) model at high temperature (80-120 °C).

  10. Effect of plasma treatment on electrical conductivity and Raman spectra of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Lee, Szetsen; Peng-Wei, Jr.

    2011-09-01

    Multi-walled carbon nanotubes (MWCNTs) were treated with a radio-frequency discharge. We found that MWCNTs showed opposite trends in electrical conductivity when treated with oxygen and hydrogen plasmas. MWCNTs showed enhanced electrical conductivity when placed at cathode with oxygen plasma treatment, whereas MWCNTs treated at positive column did not show such a trend. In contrast, the conductivity of MWCNTs dropped sharply with hydrogen plasma treatment. The measured conductivity trends of MWCNTs are correlated with observed Raman spectral shift. The possible mechanisms of the change in electrical conductivity in plasma-treated MWCNTs are discussed.

  11. Anisotropy of synthetic quartz electrical conductivity at high pressure and temperature

    NASA Astrophysics Data System (ADS)

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

    2010-09-01

    AC measurements of the electrical conductivity of synthetic quartz along various orientations were made between 0.1 and 1 MHz, at 8551601 K and at 1.0 GPa. In addition, the electrical conductivity of quartz along the c axis has been studied at 1.0-3.0 GPa. The impedance arcs representing bulk conductivity occur in the frequency range of 103-106 Hz, and the electrical responses of the interface between the sample and the electrode occur in the 0.1103 Hz range. The pressure has a weak effect on the electrical conductivity. The electrical conductivity experiences no abrupt change near the ? - ? phase transition point. The electrical conductivity of quartz is highly anisotropic; the electrical conductivity along the c axis is strongest and several orders of magnitude larger than in other directions. The activation enthalpies along various orientations are determined to be 0.6 and 1.2 eV orders of magnitude, respectively. The interpretation of the former is based on the contribution of alkali ions, while the latter effect is attributed to additional unassociated aluminum ions. Comparison of determined anisotropic conductivity of quartz determined with those from field geophysical models shows that the quartz may potentially provide explanations for the behavior of electrical conductivity of anisotropy in the crust that are inferred from the transverse magnetic mode.

  12. Effect of electrical double layer on electric conductivity and pressure drop in a pressure-driven microchannel flow

    PubMed Central

    Ban, Heng; Lin, Bochuan; Song, Zhuorui

    2010-01-01

    The effect of an electrical double layer (EDL) on microchannel flow has been studied widely, and a constant bulk electric conductivity is often used in calculations of flow rate or pressure drop. In our experimental study of pressure-driven micropipette flows, the pipette diameter is on the same order of magnitude as the Debye length. The overlapping EDL resulted in a much higher electric conductivity, lower streaming potential, and lower electroviscous effect. To elucidate the effect of overlapping EDL, this paper developed a simple model for water flow without salts or dissolved gases (such as CO2) inside a two-dimensional microchannel. The governing equations for the flow, the Poisson, and Nernst equations for the electric potential and ion concentrations and the charge continuity equation were solved. The effects of overlapping EDL on the electric conductivity, velocity distribution, and overall pressure drop in the microchannel were quantified. The results showed that the average electric conductivity of electrolyte inside the channel increased significantly as the EDL overlaps. With the modified mean electric conductivity, the pressure drop for the pressure-driven flow was smaller than that without the influence of the EDL on conductivity. The results of this study provide a physical explanation for the observed decrease in electroviscous effect for microchannels when the EDL layers from opposing walls overlap. PMID:20644673

  13. Electrical and Hydraulic Properties of Humified Bog Peat as a Function of Pore-fluid Conductivity

    NASA Astrophysics Data System (ADS)

    Comas, X.; Slater, L.

    2003-12-01

    The electrical properties of organic sediments and their relationship to physical properties are poorly understood. A simple approach to relate electrical properties to physical properties commonly applied to inorganic sediments is to model the electrolytic conductivity and the surface conductivity as parallel conduction paths. Low-frequency electrical measurements were made in conjunction with hydraulic conductivity measurements on peat samples from an 11 m section collected in a large freshwater peatland. The electrical and hydraulic measurements were made as a function of NaCl concentration and depth of burial. In all cases, the electrical conductivity of the peat was not well modeled by the parallel conduction path model, with the model yielding formation factor values close to one. Sample measurements along the section suggest a slight increase in the formation factor and surface conductivity values with depth. Hydraulic conductivity measured by constant head method shows a marked increase with increasing NaCl concentration, which we believe results from expansion of macropore porosity by chemical dilation as proposed by others. Attempts to return the samples to their original conditions by decreasing the salinity only partially restored the hydraulic conductivity values, indicating a permanent disruption of the hydraulic properties of the peat. The increase of surface electrical conductivity and hydraulic conductivity with depth may indicate a close correlation with the high cation exchange capacity of organic matter and its tendency for chemical dilation as decomposition of organic matter increases with depth. We propose that the electrical conductivity of peat cannot be modeled by an electrolytic and a surface conduction path in parallel. The increase in the electrolytic conduction causes ionic accumulation and dispersion processes, expanding the macropore porosity and hence inducing a decrease in the formation factor values. A proper electrical model for organic materials such as peat needs to include this pore dilation effect caused by the increase in electrolytic conduction.

  14. Relating bulk electrical conduction to litho-textural properties and pore-fluid conductivity within porous alluvial aquifers

    NASA Astrophysics Data System (ADS)

    Mele, M.; Giudici, M.; Inzoli, S.; Cavalli, E.; Bersezio, R.

    2012-04-01

    The estimate of hydraulic conductivity from Direct Current methods represents a powerful tool in aquifer characterization as both electrical and hydraulic conductivities depend on connected pore volumes and connected pore surface areas. A crucial, intermediate stage of this process is the assessment of sediments' textures and lithology from DC electrical conductivity as the electrical response of the aquifers' basic building blocks (i.e., hydrofacies) is controlled by the prevailing process of electrical conduction, electrolytic (σEL; pore-volume dominated) vs. "shale" (σSH; pore-surface dominated), determined by pore-space structure, clay distribution and electrical properties of pore fluids (σW). In this work laboratory experiments were conducted and the results were interpreted through the analysis i) of a volume-averaged, macroscopic litho-textural property of alluvial hydrofacies', the coarse-to-fine ratio (C/F), as a "proxy" of the process of electrical conduction within each samples on the basis of the volume proportion between nonconductive, coarse-grained and conductive, shaly textures and ii) of the surface conduction component, produced in fresh-to-salt water environment by clay materials. 8 hydrofacies' samples were collected with an hand-auger within the outcropping alluvial aquifers of the Quaternary meander river belt of the southernmost Lodi plain (northern Italy), represented by loose gravelly-sands to sands (6 samples), fine and sandy-silty clays (2 samples). As a first step, laboratory measurements of the bulk electrical conductivity (σB) of representative sub-samples, totally saturated with water with different salinity (σW from 125 to 1100 μs/cm), were performed. The experimental apparatus was made up by a series of polycarbonate, cylindrical cells (9cm x 12cm) equipped with external, copper plates as current electrodes and internal, copper squared-grids as potential electrodes. Electrical conductivity of each sample was obtained averaging time-repeated measures during 48 h after the samples' assemblage with a DC resistivity meter. As a second step, texture analysis was performed in order to obtain the textures' volume fractions of each hydrofacies subsamples; C/F threshold equal to 1 identifies coarse-grained litho-textural association (gravelly-sands to sands samples) and fine-grained litho-textural association. Plot of σB vs. C/F generally shows an increasing conductivity with decreasing C/F ratio and increasing σW, that is consistent with previous studies perform on field-scale electrical conductivity datasets obtained through DC resistivity soundings calibrated on sediments outcropping the alluvial basin. The distributions of σB vs. C/F are fitted with a power-law regressions, showing a decreasing R2 with increasing σW. A conduction model which takes into account C/F and σW and considers σB as the sum of two terms, σEL (pore-volume dominated) and σSH (pore-surface dominated), where surface conduction is treated as an equivalent shale volume conduction, was adopted. Values of σEL and σSH were computed for each sample and for increasing σW.

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

    SciTech Connect

    Sheftman, D.; Krasik, Ya. E.

    2011-09-15

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  17. Electrical Characterization and Morphological Studies of Conducting Polymer Nanofibers

    NASA Technical Reports Server (NTRS)

    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

    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.

  18. Sea salt dependent electrical conduction in polar ice

    SciTech Connect

    Moore, J.; Paren, J. ); Oerter, H. )

    1992-12-10

    A 45 m length of ice core from Dolleman Island, Antarctic Peninsula has been dielectrically analyzed at 5 cm resolution using the dielectric profiling (DEP) technique. The core has also been chemically analyzed for major ionic impurities. A statistical analysis of the measurements shows that the LF (low frequency) conductivity is determined both by neutral salt and acid concentrations. The statistical relationships have been compared with results from laboratory experiments on ice doped with HF (hydrogen fluoride). Salts (probably dispersed throughout the ice fabric) determine the dielectric conductivity. The salt conduction mechanism is probably due to Bjerrum L defects alone, created by the incorporation of chloride ions in the lattice. Samples of ice from beneath the Filchner-Ronne Ice Shelf were also measured and display a similar conduction mechanism below a solubility limit of about 400 [mu]M of chloride. The temperature dependence of the neutral salt, acid and pure ice contributions to the LF conductivity of natural ice between [approximately] 70[degrees]C and 0[degrees]C is discussed. These results allow a comprehensive comparison of dielectric and chemical data from natural ice.

  19. 76 FR 75875 - Plan for Conduct of 2012 Electric Transmission Congestion Study

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-05

    ... regional workshops and request for written comments in connection with the preparation of a study of electric transmission congestion pursuant to section 216(a)(1) of the Federal Power Act (76 FR 70122). This... for Conduct of 2012 Electric Transmission Congestion Study AGENCY: Office of Electricity Delivery...

  20. Intrinsic electrical conductivity of nanostructured metal-organic polymer chains

    PubMed Central

    Hermosa, Cristina; Vicente Álvarez, Jose; Azani, Mohammad-Reza; Gómez-García, Carlos J.; Fritz, Michelle; Soler, Jose M.; Gómez-Herrero, Julio; Gómez-Navarro, Cristina; Zamora, Félix

    2013-01-01

    One-dimensional conductive polymers are attractive materials because of their potential in flexible and transparent electronics. Despite years of research, on the macro- and nano-scale, structural disorder represents the major hurdle in achieving high conductivities. Here we report measurements of highly ordered metal-organic nanoribbons, whose intrinsic (defect-free) conductivity is found to be 104 S m−1, three orders of magnitude higher than that of our macroscopic crystals. This magnitude is preserved for distances as large as 300 nm. Above this length, the presence of structural defects (~ 0.5%) gives rise to an inter-fibre-mediated charge transport similar to that of macroscopic crystals. We provide the first direct experimental evidence of the gapless electronic structure predicted for these compounds. Our results postulate metal-organic molecular wires as good metallic interconnectors in nanodevices. PMID:23591876

  1. Intrinsic electrical conductivity of nanostructured metal-organic polymer chains.

    PubMed

    Hermosa, Cristina; Vicente Álvarez, Jose; Azani, Mohammad-Reza; Gómez-García, Carlos J; Fritz, Michelle; Soler, Jose M; Gómez-Herrero, Julio; Gómez-Navarro, Cristina; Zamora, Félix

    2013-01-01

    One-dimensional conductive polymers are attractive materials because of their potential in flexible and transparent electronics. Despite years of research, on the macro- and nano-scale, structural disorder represents the major hurdle in achieving high conductivities. Here we report measurements of highly ordered metal-organic nanoribbons, whose intrinsic (defect-free) conductivity is found to be 10(4) S m(-1), three orders of magnitude higher than that of our macroscopic crystals. This magnitude is preserved for distances as large as 300 nm. Above this length, the presence of structural defects (~ 0.5%) gives rise to an inter-fibre-mediated charge transport similar to that of macroscopic crystals. We provide the first direct experimental evidence of the gapless electronic structure predicted for these compounds. Our results postulate metal-organic molecular wires as good metallic interconnectors in nanodevices. PMID:23591876

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  3. Electrical Conductivity Of Diamond Up To 1,200 Degrees C

    NASA Technical Reports Server (NTRS)

    Vandersande, Jan W.; Zoltan, Leslie D.

    1993-01-01

    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.

  4. Experimental study of critical exponents of electrical conductivity in a two-dimensional continuum percolation system

    PubMed

    Okazaki; Horibe; Maruyama; Miyazima

    2000-06-01

    In this paper an experimental study is presented for critical exponents of electrical conductivity in an inverse Swiss-cheese model. Filled circles are drawn on random positions of square paper in drawing ink with an X-Y plotter, and electrical resistance between both opposite sides is measured automatically by the use of general purpose interface bus system. Electrical conductivity is obtained from the inverse of the electrical resistance. Electrical conductivity in a bond process is also measured with the same system. It is confirmed that the critical exponent of electrical conductivity of a continuum two-dimensional inverse Swiss-cheese model is different from that of a discrete one. PMID:11088294

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

  6. Transparent electrically conducting thin films for spacecraft temperature control applications

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  7. High temperature biowaste resistojets using electrically conducting ceramic heaters.

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    Description of the experimental characteristics of a heater for advanced biowaste resistojets, potentially operable to material temperatures of 2400 K in the presence of all of the biowaste gases, with or without oxygen, or in a vacuum. A conservative operating chamber temperature of 2000 K is being considered to ensure a lifetime of thousands of hours. In the small biowaste resistojet sized for 25-mlb (.11 N) of thrust, specific impulses of 200 sec on CO2 and 275 sec on H2O are possible. Typical characteristics for 150 watts of electrical power are 120 V AC at 1.25 A, providing direct adaptability to the space station power systems.

  8. An electrical conductivity inspection methodology of polycrystalline diamond cutters

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

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

  9. Electrically Conductive Bulk Composites through a Contact-Connected Aggregate

    PubMed Central

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

    2013-01-01

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

  10. Electrically-conductive Low-Permeability Pressure Seal

    NASA Technical Reports Server (NTRS)

    Krieg, H. C.

    1982-01-01

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

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

    PubMed

    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

    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

  12. Local electrical conduction in polycrystalline La-doped BiFeO3 thin films

    NASA Astrophysics Data System (ADS)

    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

    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.

  13. Electrical conductivity and physical properties of surimi-potato starch under ohmic heating.

    PubMed

    Pongviratchai, P; Park, J W

    2007-11-01

    Electrical conductivities of Alaska pollock surimi mixed with native and pregelled potato starch at different concentrations (0%, 3%, and 9%) were measured at different moisture contents (75% and 81%) using a multifrequency ohmic heating system. Surimi-starch paste was tested up to 80 degrees C at frequencies from 55 Hz to 20 KHz and at alternating currents of 4.3 and 15.5 V/cm voltage gradient. Electrical conductivity increased when moisture content, applied frequency, and applied voltage increased, but decreased when starch concentration increased. Electrical conductivity was correlated linearly with temperature (R(2) approximately 0.99). Electrical conductivity pattern (magnitude) changed when temperature increased, which was clearly seen after 55 degrees C in the native potato starch system, especially at high concentration. This confirms that starch gelatinization that occurred during heating affects the electrical conductivity. Whiteness and texture properties decreased with an increase of starch concentration and a decrease of moisture content. PMID:18034719

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

    PubMed Central

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

    2011-01-01

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

  15. High performance heat curing copper-silver powders filled electrically conductive adhesives

    NASA Astrophysics Data System (ADS)

    Cui, Hui-Wang; Jiu, Jin-Ting; Sugahara, Tohru; Nagao, Shijo; Suganuma, Katsuaki; Uchida, Hiroshi

    2015-03-01

    In this study, high performance electrically conductive adhesives were fabricated from a vinyl ester resin, a thermal initiator, silver coated copper powders, and pure silver powders, without using any other coupling agent, dispersing agent, and reducing agent. The heat cured copper-silver powders filled electrically conductive adhesives presented low bulk resistivity (e.g., 4.53 10-5 ?cm) due to the silver powders that had given high electrical conductivity to the adhesives, and high shear strength (e.g., 16.22 MPa) provided by the crosslinked structures of vinyl ester resin. These high performance copper-silver powders filled electrically conductive adhesives have lower cost than those filled by pure silver powders, which can be well used in the electronic packaging and can enlarge the application prospects of electrically conductive adhesives. [Figure not available: see fulltext.

  16. Electrical conduction of LiF interlayers in organic diodes

    SciTech Connect

    Bory, Benjamin F.; Janssen, René A. J.; Meskers, Stefan C. J.; Gomes, Henrique L.; Leeuw, Dago M. de

    2015-04-21

    An interlayer of LiF in between a metal and an organic semiconductor is commonly used to improve the electron injection. Here, we investigate the effect of moderate bias voltages on the electrical properties of Al/LiF/poly(spirofluorene)/Ba/Al diodes by systematically varying the thickness of the LiF layer (2-50 nm). Application of forward bias V below the bandgap of LiF (V < E{sub g} ∼ 14 V) results in reversible formation of an electrical double layer at the LiF/poly(spirofluorene) hetero-junction. Electrons are trapped on the poly(spirofluorene) side of the junction, while positively charged defects accumulate in the LiF with number densities as high as 10{sup 25}/m{sup 3}. Optoelectronic measurements confirm the built-up of aggregated, ionized F centres in the LiF as the positive trapped charges. The charged defects result in efficient transport of electrons from the polymer across the LiF, with current densities that are practically independent of the thickness of the LiF layer.

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

    PubMed Central

    2011-01-01

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

  18. Electrical and surface properties of clay-conducting polymer composites

    NASA Astrophysics Data System (ADS)

    Eastman, M. P.; Hagerman, M. E.; Porter, T. L.; Parnell, R. A.; Attuso, J. L.; Bradley, M.; Thompson, D.

    1997-08-01

    Organic guests such as aniline, pyrrole and thiophene polymerize on the surface and in the intergallery regions of smectite clays which contain exchangeable transition metal cations such as Cu2+ and Fe3+. We monitor these reactions in thin films of smectite clays using electron spin resonance (ESR) and impedance spectroscopies. Polymers that form on the surface and in the interlayer region are studied by scanning force microscopy (SFM). ESR studies have shown that the transition metal ions are reduced during the polymerization process. Impedance measurements indicate that the formation of conducting polymer in the interlayer region of dry, Cu2+ exchanged hectorite thin films results in a dramatic reduction in observed impedance. SFM scans indicate that the conducting polymers can adopt a variety of morphologies on the surfaces of the films and within the intergalleries of the host framework. These studies have applications in the development of advanced materials including microsensors and novel nanocomposites.

  19. Electrical conductivity of cobalt-titanium substituted SrCaM hexaferrites

    NASA Astrophysics Data System (ADS)

    Eraky, M. R.

    2012-03-01

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

  20. Structural and electrical properties of conducting diamond nanowires.

    PubMed

    Sankaran, Kamatchi Jothiramalingam; Lin, Yen-Fu; Jian, Wen-Bin; Chen, Huang-Chin; Panda, Kalpataru; Sundaravel, Balakrishnan; Dong, Chung-Li; Tai, Nyan-Hwa; Lin, I-Nan

    2013-02-01

    Conducting diamond nanowires (DNWs) films have been synthesized by N?-based microwave plasma enhanced chemical vapor deposition. The incorporation of nitrogen into DNWs films is examined by C 1s X-ray photoemission spectroscopy and morphology of DNWs is discerned using field-emission scanning electron microscopy and transmission electron microscopy (TEM). The electron diffraction pattern, the visible-Raman spectroscopy, and the near-edge X-ray absorption fine structure spectroscopy display the coexistence of sp diamond and sp graphitic phases in DNWs films. In addition, the microstructure investigation, carried out by high-resolution TEM with Fourier transformed pattern, indicates diamond grains and graphitic grain boundaries on surface of DNWs. The same result is confirmed by scanning tunneling microscopy and scanning tunneling spectroscopy (STS). Furthermore, the STS spectra of current-voltage curves discover a high tunneling current at the position near the graphitic grain boundaries. These highly conducting regimes of grain boundaries form effective electron paths and its transport mechanism is explained by the three-dimensional (3D) Mott's variable range hopping in a wide temperature from 300 to 20 K. Interestingly, this specific feature of high conducting grain boundaries of DNWs demonstrates a high efficiency in field emission and pave a way to the next generation of high-definition flat panel displays or plasma devices. PMID:23327783

  1. Electrical Conductivity Studies on Proton Conducting Polymer Electrolytes Based on Poly (vinyl Acetate)

    NASA Astrophysics Data System (ADS)

    Arun Kumar, D.; Savitha, T.; Selvasekarapandian, S.; Baskaran, R.

    2006-06-01

    Proton conducting polymer electrolytes based on Poly (vinyl acetate) (PVAc) and perchloric acid (HClO4) has been prepared by solution casting technique with various compositions. FTIR spectra analysis reveals the interaction between proton and ester oxygen of Poly (vinyl acetate) (PVAc). Ac impedance spectroscopy reveals that 75m%PVAc:25m%HClO4 exhibits maximum conductivity, 6.210-2 Scm-1 at room temperature (303K). The increase in conductivity with increase in dopant concentration and temperature may be attributed to the enhanced mobility of the polymer chains, number of charge carriers and rotations of side chains. The temperature dependence of conductivity shows non-arrhenius behaviour at higher temperatures. Dielectric loss spectra show two relaxations ? (high temperature) and ? (low temperature) relaxations in low and high frequency range respectively

  2. Highly Electrically Conductive Nanocomposites Based on PolymerInfused Graphene Sponges

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2014-01-01

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

  4. Structural states and electrical conductivity of oxidized niobium nanopowders

    NASA Astrophysics Data System (ADS)

    Shamrai, V. F.; Blagoveshchenski, Yu. V.; Gordeev, A. S.; Mitin, A. V.; Drobinova, I. A.

    2007-08-01

    The structure of niobium nanopowders (particle size 0.03 0.07 ?m) oxidized in air is studied by X-ray diffraction. The nanopowder particles have a significant fraction of an amorphous phase. The amorphous component is likely to block the well-known mechanism of niobium oxidation Nb ? Nbs.s ? Nb6O ? NbO ? NbOx, which was proposed on the basis of the results of studying the oxidation of niobium powders at high temperatures. Here, Nbs.s is the solid solution of oxygen in niobium and NbOx are the higher niobium oxides NbO2 and Nb2O5. The amorphization of the surface of niobium nanopowders oxidized at 20C can be one of the main causes of a rather high electrical resistivity (? ? 108 ? cm) of the samples compacted from these powders.

  5. Lorentz force sigmometry: a novel technique for measuring the electrical conductivity of solid and liquid metals

    NASA Astrophysics Data System (ADS)

    Alkhalil, Shatha; Kolesnikov, Yurii; Thess, André

    2015-11-01

    In this paper, a novel method to measure the electrical conductivity of solid and molten metals is described. We term the method ‘Lorentz force sigmometry’, where the term ‘sigmometry’ refers to the letter sigma σ, often used to denote the electrical conductivity. The Lorentz force sigmometry method is based on the phenomenon of eddy currents generation in a moving conductor exposed to a magnetic field. Based on Ampere’s law, the eddy currents in turn generate a secondary magnetic field; as a result, the Lorentz force acts to brake the conductor. Owing to Newton’s third law, a measurable force, which is equal to the Lorentz force and is directly proportional to the electrical conductivity of the conductive fluid or solid, acts on the magnet. We present the results of the measurements performed on solids along with the initial measurements on fluids with a eutectic alloy composition of Ga67In20.5Sn12.5; detailed measurements on molten metals are still in progress and will be published in the future. We conducted a series of experiments and measured the properties of known electrical conductive metals, including aluminum and copper, to compute the calibration factor of the device, and then used the same calibration factor to estimate the unknown electrical conductivity of a brass bar. The predicted electrical conductivity of the brass bar was compared with the conductivity measured with a commercial device called ‘SigmaTest’ the observed error was less than 0.5%.

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

    SciTech Connect

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

    1998-07-01

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

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

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Hua; Chou, Kuo-Chih

    2010-02-01

    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.

  8. Electrical conductivity anisotropy of deformed talc rocks and serpentinites at 3 GPa

    NASA Astrophysics Data System (ADS)

    Guo, Xinzhuan; Yoshino, Takashi; Katayama, Ikuo

    2011-09-01

    The electrical conductivity anisotropy of deformed natural talc rocks and serpentinites was investigated using a Kawai-type multi-anvil press in the temperature range of 500-1000 K at 3 GPa. The electrical conductivities of the samples were measured by an impedance analyzer with a frequency range of 10 -3-10 6 Hz along three sample directions: the direction parallel to the lineation of oriented minerals ( x direction), the direction perpendicular to the lineation on the foliation plane ( y direction), and the direction perpendicular to the foliation ( z direction). For both rock types, electrical conductivities parallel to the x and the z directions were the highest and the lowest, respectively. Electrical conductivities of talc rocks and serpentinites were at least two orders of magnitude lower than previous reports. Electrical conductivities of the serpentinites were higher than those of the talc rocks. Electrical conductivity anisotropy for the talc rocks was stronger than that for the serpentinites at the same oxygen buffer condition. Electrical conductivity and its anisotropy of the serpentinites become higher with higher oxygen fugacity. The activation enthalpy of talc rocks was the lowest (0.59 eV) in the x direction and highest (0.68 eV) in the z direction. The activation enthalpies of the serpentinites in different directions show similar values: about 0.74 eV and 0.68 eV for the experiments using Mo and Ni electrodes, respectively. Impedance spectra for both rock types show the presence of two conduction paths: grain interior and grain boundary conductions. The total electrical conductivities were reduced by grain boundary conduction. Electrical conductivities of hydrous minerals show strong dependence on hydrogen concentration and hydrogen mobility. The conduction mechanism probably was proton migration through extrinsic vacancies derived from a presence of ferric iron perpendicular to the c axis of the crystals and through interstitial mechanisms parallel to the c axis. In both warm and cold subduction zones, high electrical conductors (10 -1.5 S/m) cannot be explained by the presence of talc or serpentinites. The electrical conductivity anisotropy in a subduction zone would be inconspicuously small (within one order) unless we consider other well aligned high conductive phases.

  9. High frequency electrical conduction block of the pudendal nerve

    NASA Astrophysics Data System (ADS)

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

    2006-06-01

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

  10. Enhanced Electrical Conductivity of Aluminum by Carbon Nanotube Hybrid Dilution

    NASA Astrophysics Data System (ADS)

    Stigers, Shelby; Savadelis, Alexader; Carruba, Kathryn; Johns, Kiley; Adu, Kofi

    2015-03-01

    Carbon nanotubes (CNTs) have been recognized as potential candidate for reinforcements in lightweight metals. A composite consisting of CNTs embedded in an Al-matrix might work as an ultra-low-resistive material with the potential of having a room-temperature resistivity far below Al, Cu and Ag. While several advances have been made in developing Al-CNT composites, three major challenges: (1) interfacial bond strength between CNT and the Al matrix, (2) homogeneous dispersion of the CNTs in the Al matrix and impurity (CNTs) scattering centers, continue to limit progress in Al-CNT composites. Several conventional methods including powder metallurgy, melting and solidification, thermal spray and electrochemical deposition have been used to process Al and CNT to form composites. We present preliminary results that address these challenges and demonstrate the fabrication of easily drawable Al-CNT composites into wires of diameter <= 1.0mm with ~ 18% +/- 2% reduction in the electrical resistivity of Al-CNT composite using CNT-hybrid as reinforcement and an inductive melting technique that takes advantage of the induced eddy current in the melt to provide in-situ stirring. This Work is Supported by Penn State Altoona Undergraduate Research Sponsored Program and Penn State Materials Research Institute, University Park.

  11. Electrical Charging of Aerosols and Conductivity of Titan's Atmosphere

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    We have used recent data on graphitic cloud particles in the atmosphere of Titan to compute the electrical charging of the particles (radii ranging from 0.01 microns to 0.26 microns). The charging on the nightside was rather similar to that obtained earlier except that charge distributions on the particles are now computed and recently obtained cloud particle sizes and density distributions were employed. The negative charge on particles of 0.26 microns peaked at 9 at 150 km altitude. The computations were repeated for the dayside with the addition of photoelectron emission by the particles as a result of the absorption of solar UV radiation. Particles (except the very smallest) now became positively charged with particles of radius 0.26 microns being charged up to +47. Next, very small particles (radii approx. 3 x 10 (sup -4) microns) of polycyclic aromatic hydrocarbons (PAHs) were introduced and treated as sources of negative ions since they could be either neutral or carry one negative charge. Moreover, they are mobile so that they had to be treated like molecular size negative ions although much more massive. They had the effect of substantially reducing the electron densities in the altitude range 190 to 310 km to values less than the negative PAH densities and increasing the peak electron charge on the larger particles. Particles of radius 0.26 microns bore peak charges of approx. +47 at altitudes of approx. 250 km. The simulated effect of PAHs on the nightside proved to be much less pronounced; at the peak negative PAH density, it was less than the electron density. The physics governing these results will be discussed.

  12. Influence of pressure and temperature on the electrical conductivity of dolomite

    NASA Astrophysics Data System (ADS)

    Ono, Shigeaki; Mibe, Kenji

    2015-10-01

    The electrical conductivity of dolomite, (Mg, Ca)CO3, was investigated under conditions of 650-1000 K and 3-6 GPa with a multi-anvil press and an impedance spectroscopy analyzer with a frequency range of 0.05-106 Hz. As pressure increased, an increase in the electrical conductivity and a decrease in the calculated activation enthalpy were observed. The negative activation volume observed in this study suggests that the hopping of polarons is the dominant mechanism for the electrical conductivity across the pressure and temperature range investigated. This mechanism is the same as that of magnesite, MgCO3, which has the similar structure of dolomite. In contrast, the mechanism of the ionic conduction was reported in aragonite, CaCO3. These results indicate that the mechanism for the electrical conductivity of carbonate minerals varies because of a crystallographic difference between the calcite- and the aragonite-type structure.

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

    USGS Publications Warehouse

    McCleskey, R. Blaine

    2011-01-01

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

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

    SciTech Connect

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

    2009-01-01

    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.

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

    SciTech Connect

    Islamgaliev, R. K. Nesterov, K. M.; Bourgon, J.; Champion, Y.; Valiev, R. Z.

    2014-05-21

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

  16. Dynamic electrical conduction in p-type CuIn3Se5

    NASA Astrophysics Data System (ADS)

    Essaleh, L.; Marín, G.; Wasim, S. M.; Alimoussa, A.; Bourial, A.

    2016-04-01

    In this work, ac electrical conductivity measurements were studied for the first time in p type bulk ternary semiconductor compound CuIn3Se5. The dynamic electrical conductivity is analyzed in the frequency range 20 Hz to 1 MHz and temperature from 308 K to 500 K. The relaxation times for the grain and grain boundaries were studied from the second derivative of electric modulus versus frequency at various temperatures. The relaxation time is found to decrease with increasing temperature and to obey the Arrhenius relationship. The values of activation energies for conduction and relaxation times are obtained.

  17. Effect of gamma irradiation on DC electrical conductivity of ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Swaroop, K.; Naveen C., S.; Jayanna H., S.; Somashekarappa H., M.

    2015-06-01

    The temperature dependent dc electrical conductivity of gamma irradiated Zinc oxide (ZnO) nanoparticles is presented in this paper. The X-ray diffraction (XRD) pattern shows hexagonal wurtzite structure of ZnO. Fourier Transform Infrared Spectroscopy (FTIR) confirms Zn-O stretching vibrations. UV-Visible spectroscopy studies show that the energy band gap (Eg) of the prepared ZnO nanoparticles increases with respect to gamma irradiation dose, which can be related to room temperature dc electrical conductivity. The result shows significant variation in the high temperature dc electrical conductivity of ZnO nanoparticles due to gamma irradiation.

  18. Electrical-stress-induced conductivity increase in SrTiO3 films

    NASA Astrophysics Data System (ADS)

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

    2006-08-01

    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 increase of SrTiO3:Cr films is accompanied by a change of the temperature dependence corresponding to a significant increase of the density of localized states.

  19. Electrical conductivity measurements of bacterial nanowires from Pseudomonas aeruginosa

    NASA Astrophysics Data System (ADS)

    Maruthupandy, Muthusamy; Anand, Muthusamy; Maduraiveeran, Govindhan; Sait Hameedha Beevi, Akbar; Jeeva Priya, Radhakrishnan

    2015-12-01

    The extracellular appendages of bacteria (flagella) that transfer electrons to electrodes are called bacterial nanowires. This study focuses on the isolation and separation of nanowires that are attached via Pseudomonas aeruginosa bacterial culture. The size and roughness of separated nanowires were measured using transmission electron microscopy (TEM) and atomic force microscopy (AFM), respectively. The obtained bacterial nanowires indicated a clear image of bacterial nanowires measuring 16 nm in diameter. The formation of bacterial nanowires was confirmed by microscopic studies (AFM and TEM) and the conductivity nature of bacterial nanowire was investigated by electrochemical techniques. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which are nondestructive voltammetry techniques, suggest that bacterial nanowires could be the source of electrons—which may be used in various applications, for example, microbial fuel cells, biosensors, organic solar cells, and bioelectronic devices. Routine analysis of electron transfer between bacterial nanowires and the electrode was performed, providing insight into the extracellular electron transfer (EET) to the electrode. CV revealed the catalytic electron transferability of bacterial nanowires and electrodes and showed excellent redox activities. CV and EIS studies showed that bacterial nanowires can charge the surface by producing and storing sufficient electrons, behave as a capacitor, and have features consistent with EET. Finally, electrochemical studies confirmed the development of bacterial nanowires with EET. This study suggests that bacterial nanowires can be used to fabricate biomolecular sensors and nanoelectronic devices.

  20. Ignition Sensitivity and Electrical Conductivity of a Composite Energetic Material with Conductive Nanofillers

    SciTech Connect

    Eric S. Collins; Brandon R. Skelton; Michelle L. Pantoya; Fahmida Irin; Micah J. Green; Michael A. Daniels

    2014-12-01

    The safe handling of powdered composite energetic materials requires an understanding of their response to electrostatic ignition stimuli. A binary composite comprised of Al and polytetrafluoroethylene (PTFE) was tailored for ESD ignition sensitivity with varied concentrations of highly conductive nanofillers. The goal was to control the ESD ignition response of the Al+PTFE with small concentrations of nanofillers that may not significantly affect the overall combustion performance of the mixture. The nanofillers examined include carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs). Adding CNTs created percolation at a lower volumetric percentage than GNPs and were found to be the controlling nanofiller, creating percolation for the mixture containing both CNTs and GNPs. Various mixing methods were examined. Ignition was achieved only for adding nanofillers at a volumetric percentage and mixing method that led to a bulk conductivity of approximately 5x10-3 ?S/cm.

  1. Rate dependence of electrical and mechanical properties of conductive polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Foley, J. R.; Stilson, C. L.; Smith, K. K. G.; McKinion, C. M.; Chen, C.; Ganguli, S.; Roy, A. K.

    2015-09-01

    Conductive polymer nanocomposites with enhanced electrical and thermal properties show promise as an alternative solution for electronic materials. For example, electronic interconnect materials will have comparable electrical and thermal conductivity to solder with an increased operating range of strain and temperature. This paper documents the fabrication and experimental evaluation of a prototype conductive polymer nanocomposite. Material selection, fabrication processes, and initial characterization of a low Tg polymer with a high fill ratio of carbon nanotubes is presented. The electrical and thermal properties of the composite are measured and compared with predictions. The mechanical properties are measured using dynamic mechanical analysis (DMA) over a wide temperature range. The mechanical and electrical responses of the conductive polymer composite are simultaneously measured at higher strain rates using a modified split Hopkinson pressure bar (SHPB) apparatus. The dynamic stress-strain response is obtained using traditional analytic methods (e.g., two- and three-wave analysis). The electrical response is observed using constant current excitation with high bandwidth (>500 kHz) instrumentation. The dynamic compression data implies the change in electrical resistance is solely a function of the material deformation, i.e., the material exhibits constant electrical conductivity and is insensitive to the applied loads. DMA and SHPB dynamic data are used to estimate the parameters in a Mulliken-Boyce constitutive model, and the resulting behavior is critically evaluated. Finally, progress towards improving the polymer composite's mechanical, electrical, and thermal properties are discussed.

  2. Synthesis and electric conductivity of a NASICON-type electrolyte

    SciTech Connect

    Bukun, N.G.; Domashnev, I.A.; Moskvina, E.I.; Ukshe, E.A.

    1988-08-01

    The purpose of this work was to study the sequence of solid-phase reactions in the synthesis of the solid electrolyte, corresponding to the stoichiometric composition Na/sub 3/Zr/sub 2/Si/sub 2/PO/sub 12/. The solid-phase reaction of the mixture ZrO(NO/sub 3/)/sub 2/ x 2H/sub 2/O, Na/sub 2/CO/sub 3/, NH/sub 4/H/sub 2/PO/sub 4/ and amorphous SiO/sub 2/ proceeds through the stage of dehydration of zirconium oxide-nitrate, decomposition of ammonium dihydrophosphate, and formation and decomposition of ammonium and sodium nitrates. The intermediate products of the reaction are sodium and zirconium phosphates, and part of the ZrO/sub 2/ participates in the reaction in the form of an amorphous or metastable tetragonal modification, while part transforms into a stable monoclinic modification. The formation of NASICON starts near 1000/sup 0/C, and in addition silicon dioxide, which can first transform from the amorphous state into the mixture of tridymite and ..cap alpha..-cristobalite, participates in the reaction only at this stage. After annealing at 1230/sup 0/C the single-phase solid electrolyte Na/sub 3/Zr/sub 2/Si/sub 2/PO/sub 12/, having a conductivity of 0.14 S/cm at 300/sup 0/C and 0.00028 S/cm at 25/sup 0/C, is obtained.

  3. Mechanical tension and electrical conductivity of liquid crystal filaments

    NASA Astrophysics Data System (ADS)

    Kress, Oliver H.

    During the NSF funded IRES internship at the Otto-von-Geuricke Univeristy in Magdeburg, Germany, I studied the optical properties and mechanical behavior in the form of line tension of bent-core liquid crystal fiber bundles and verified previously published tension values and temperature dependent behavior. Then, carbon nanotubes were added and it as found that the tension in the fibers decreased by a factor of two instead of increasing as was hoped. A new device for pulling fibers and measuring tension by deflection due to the adhesion of glass beads was built at the LCI. The device was meant to improve upon the device used at O.v.G. Improvements included a smaller heating chamber with better insulation, temperature control, large viewing windows, more stable mounting interface, easier disassembly and the option to quickly modify the device in order to perform a variety of other experiments such as observing behavior due to acoustic driving (based on previous literature), observing optical behavior under a polarizing microscope and introducing probes to measure the electrical properties of fibers. The platform remains modular and makes the addition of new components for carrying out new experiments very simple and straightforward. The addition of carbon nanotubes has scattered results regarding the modulation of fiber tension. It seems that the addition of CNTs to BLC1571 may slightly be decreasing tension while the addition to BLC1688 may be increasing it. In both mesogens, 10wt% CNT yielded the highest tension value above the theoretical surface tension contribution. A reversal of temperature dependence was observed for fibers containing CNT; their tension increased with temperature instead of decreased. A driving rod attached to a speaker was used to acoustically drive a filament of pure BLC1571 in an attempt to replicate the tension values in a different way. The movement of the fiber and the driving rod were captured using a high-speed camera and MATLAB code was written to extract the phase between the rod and the fiber as well as measured their amplitude across a frequency sweep between 40 Hz and 800 Hz. The tension and elastic modulus of fibers was extracted from the fundamental frequency of the fiber and matched the values observed in the bead-hanging experiments. This research is part of a larger study in which results and observations from the work of several group members under the guidance of Dr. Antal Jakli are continuously being combined in order to further understand the nature of self-assembling liquid crystal filaments. A paper on the rupture dynamics of BLC fibers made of the same mesogens studied here is in the process of being published and further experiments and results on the topics studied in this thesis are expected to produce future publications. After graduating with my M.Sc. from Kent, I will move to Gottingen, Germany where I have joined the group of Dr. Stephan Herminghaus at the Max Planck Institute for Dynamics and Self-Organization and will work towards receiving my Ph,D from the University of Gottingen. I will be continuing my work on liquid crystal filaments and look forward to maintaining an open collaboration with Dr. Jakli's group at the LCI. (Abstract shortened by UMI.).

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

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  8. A promising structure for fabricating high strength and high electrical conductivity copper alloys

    NASA Astrophysics Data System (ADS)

    Li, Rengeng; Kang, Huijun; Chen, Zongning; Fan, Guohua; Zou, Cunlei; Wang, Wei; Zhang, Shaojian; Lu, Yiping; Jie, Jinchuan; Cao, Zhiqiang; Li, Tingju; Wang, Tongmin

    2016-02-01

    To address the trade-off between strength and electrical conductivity, we propose a strategy: introducing precipitated particles into a structure composed of deformation twins. A Cu-0.3%Zr alloy was designed to verify our strategy. Zirconium was dissolved into a copper matrix by solution treatment prior to cryorolling and precipitated in the form of Cu5Zr from copper matrix via a subsequent aging treatment. The microstructure evolutions of the processed samples were investigated by transmission electron microscopy and X-ray diffraction analysis, and the mechanical and physical behaviours were evaluated through tensile and electrical conductivity tests. The results demonstrated that superior tensile strength (602.04 MPa) and electrical conductivity (81.4% IACS) was achieved. This strategy provides a new route for balancing the strength and electrical conductivity of copper alloys, which can be developed for large-scale industrial application.

  9. A promising structure for fabricating high strength and high electrical conductivity copper alloys.

    PubMed

    Li, Rengeng; Kang, Huijun; Chen, Zongning; Fan, Guohua; Zou, Cunlei; Wang, Wei; Zhang, Shaojian; Lu, Yiping; Jie, Jinchuan; Cao, Zhiqiang; Li, Tingju; Wang, Tongmin

    2016-01-01

    To address the trade-off between strength and electrical conductivity, we propose a strategy: introducing precipitated particles into a structure composed of deformation twins. A Cu-0.3%Zr alloy was designed to verify our strategy. Zirconium was dissolved into a copper matrix by solution treatment prior to cryorolling and precipitated in the form of Cu5Zr from copper matrix via a subsequent aging treatment. The microstructure evolutions of the processed samples were investigated by transmission electron microscopy and X-ray diffraction analysis, and the mechanical and physical behaviours were evaluated through tensile and electrical conductivity tests. The results demonstrated that superior tensile strength (602.04 MPa) and electrical conductivity (81.4% IACS) was achieved. This strategy provides a new route for balancing the strength and electrical conductivity of copper alloys, which can be developed for large-scale industrial application. PMID:26856764

  10. Numerical solution of an inverse electrocardiography problem for a medium with piecewise constant electrical conductivity

    NASA Astrophysics Data System (ADS)

    Denisov, A. M.; Zakharov, E. V.; Kalinin, A. V.; Kalinin, V. V.

    2010-07-01

    A numerical method is proposed for solving an inverse electrocardiography problem for a medium with a piecewise constant electrical conductivity. The method is based on the method of boundary integral equations and Tikhonov regularization.

  11. Electrical conductivity of double stranded DNA measured with ac impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Jiaxiong

    2008-12-01

    The electrical conductivity of double stranded DNA is investigated with ac impedance spectroscopy. Atomic force microscopy is used to provide images of the DNA molecules stretched over some gap electrodes through a flow cell. More stretched DNA molecules result in smaller charge-transfer resistances in the ac impedance spectra. The DNA molecules stretched across the electrode gaps can be degraded with the enzyme DNase, which generates larger charge-transfer resistances or results in capacitive behavior. The distorted DNA molecules filled in the electrode gaps rather than stretched over the gap electrodes do not exhibit the electrical conduction in the ac impedance spectra. The present work suggests the double stranded DNA to be a one-dimensional semiconductor. It also suggests that the ac impedance spectroscopy may be a more effective method than a dc one to measure the electrical conduction of double stranded DNA. The electrical and ionic conductivities of DNA molecules are extensively discussed.

  12. The effect of temperature on the electric conductivity of poly(dimethyl siloxane) ferromagnetic gel

    NASA Astrophysics Data System (ADS)

    Kubisz, L.; Skumiel, A.; Hornowski, T.; Szlaferek, A.; Pankowski, E.

    2008-05-01

    In this paper the influence of temperature on the electrical conductivity of a ferromagnetic gel is investigated. The material used was poly(dimethyl siloxane) (PDMS) gel which contained randomly distributed magnetite nanosized particles. The electrical conductivity was measured by means of the two-point dc method. During the heating of the PDMS in the temperature range of 295-460 K the electrical conductivity increased from about 2 10-12 to 2 10-8 S m-1. A study of the current-temperature dependence obtained during subsequent heating runs revealed two subranges of temperature characterized by different activation energies. The presence of these subranges could be explained either by the liberation of two different types of charge carrier or by the increase in the degree of polymer cross-linking. In the upper temperature subrange (420-460 K) both types of charge carrier probably contribute to the electrical conductivity of PDMS ferromagnetic gel.

  13. The effect of temperature on the electric conductivity of poly(dimethyl siloxane) ferromagnetic gel.

    PubMed

    Kubisz, L; Skumiel, A; Hornowski, T; Szlaferek, A; Pankowski, E

    2008-05-21

    In this paper the influence of temperature on the electrical conductivity of a ferromagnetic gel is investigated. The material used was poly(dimethyl siloxane) (PDMS) gel which contained randomly distributed magnetite nanosized particles. The electrical conductivity was measured by means of the two-point dc method. During the heating of the PDMS in the temperature range of 295-460K the electrical conductivity increased from about 2 10(-12) to 2 10(-8)Sm(-1). Astudy of the current-temperature dependence obtained during subsequent heating runs revealed two subranges of temperature characterized by different activation energies. The presence of these subranges could be explained either by the liberation of two different types of charge carrier or by the increase in the degree of polymer cross-linking. In the upper temperature subrange (420-460K) both types of charge carrier probably contribute to the electrical conductivity of PDMS ferromagnetic gel. PMID:21694247

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

    EPA Science Inventory

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

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

    PubMed

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

    2013-07-01

    We herein report on the preparation of epoxy nanocomposites, which had enhanced thermal conductivities but were still electrical insulators, incorporating hybrid nanosheets (NSs) with sandwich structures composed of thermally reduced graphene oxide (TRGO) and silica. The silica layer covered the surface of the TRGO, hindering electrical conduction and effectively forming a 3D phonon transport channel that had a unique effect on the electrical and thermal properties of the epoxy matrix. A 1 wt% TRGO-silica NS epoxy nanocomposite maintained an electrical resistivity of 2.96 10(11)? cm, and its thermal conductivity was 0.322 W m(-1) K(-1), which is 61% higher than the conductivity of an epoxy nanocomposite without TRGO-silica NSs (0.2 W m(-1) K(-1)). PMID:23695448

  16. The electrical conductivity of CuCrZr alloy after SPD processing

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  17. A promising structure for fabricating high strength and high electrical conductivity copper alloys

    PubMed Central

    Li, Rengeng; Kang, Huijun; Chen, Zongning; Fan, Guohua; Zou, Cunlei; Wang, Wei; Zhang, Shaojian; Lu, Yiping; Jie, Jinchuan; Cao, Zhiqiang; Li, Tingju; Wang, Tongmin

    2016-01-01

    To address the trade-off between strength and electrical conductivity, we propose a strategy: introducing precipitated particles into a structure composed of deformation twins. A Cu-0.3%Zr alloy was designed to verify our strategy. Zirconium was dissolved into a copper matrix by solution treatment prior to cryorolling and precipitated in the form of Cu5Zr from copper matrix via a subsequent aging treatment. The microstructure evolutions of the processed samples were investigated by transmission electron microscopy and X-ray diffraction analysis, and the mechanical and physical behaviours were evaluated through tensile and electrical conductivity tests. The results demonstrated that superior tensile strength (602.04 MPa) and electrical conductivity (81.4% IACS) was achieved. This strategy provides a new route for balancing the strength and electrical conductivity of copper alloys, which can be developed for large-scale industrial application. PMID:26856764

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  19. Characteristics of convection of an electrically conducting liquid in an additional external force field

    SciTech Connect

    Mikel'son, A.E.; Karklin, Ya.Kh.

    1987-07-01

    The authors analyze, theoretically and experimentally, the combined effects of gravitational and electric fields along with inertial forces on convective heat and mass transfer in liquid metals undergoing vortex flow in the presence of constant magnetic fields. The experimental data are derived for a eutectic indium-gallium-tin alloy. The flow model incorporates electrical conductivity and Hartmann number as well as other properties.

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

    DOEpatents

    Tran, Nang T.; Gilbert, James R.

    1992-08-04

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

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

    PubMed

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

    2014-10-01

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

  2. Electrical conductivity distribution during detonation of a TATB-based explosive

    NASA Astrophysics Data System (ADS)

    Satonkina, N. P.; Rubtsov, I. A.

    2016-01-01

    The distribution of electrical conductivity upon detonation of a TATB-based explosive (C6H6N6O6) is obtained for two densities (1.3 and 1.8 g/cc). A peak of width of about 0.1 µs detected in all profiles is in good agreement with the duration of the chemical reaction zone known from the literature. An extended electrical conductivity region is observed in the Taylor wave.

  3. Velocity, temperature, and electrical conductivity profiles in hydrogen-oxygen MHD duct flows

    NASA Technical Reports Server (NTRS)

    Greywall, M. S.; Pian, C. C. P.

    1978-01-01

    Two-dimensional duct flow computations for radial distributions of velocity, temperature, and electrical conductivity are reported. Calculations were carried out for the flow conditions representative of a hydrogen-oxygen combustion driven MHD duct. Results are presented for: profiles of developing flow in a smooth duct, and for profiles of fully developed pipe flow with a specified streamwise shear stress distribution. The predicted temperature and electrical conductivity profiles for the developing flows compare well with available experimental data.

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

    SciTech Connect

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

    1987-07-01

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

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

    PubMed

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

    2009-11-01

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

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

    PubMed

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

    2015-02-01

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

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

    NASA Astrophysics Data System (ADS)

    Guo, Wenchuan; Liu, Yi; Zhu, Xinhua; Zhuang, Hong

    2011-08-01

    In order to predict the water content in honey, electrical conductivity was measured on blossom honey types milk-vetch, jujube and yellow-locust with the water content of 18-37% between 5 and 40 °C. The regression models of electrical conductivity were developed as functions of water content and temperature. The results showed that increases in either water content or temperature resulted in an increase in the electrical conductivity of honey with greater changes at higher water content and/or higher temperature. The linear terms of water content and temperature, a quadratic term of water content, and the interaction effect of water content and temperature had significant influence on the electrical conductivity of honey (p < 0.0001). Regardless of blossom honey type, the linear coefficient of the determination of measured and calculated electrical conductivities was 0.998 and the range error ratio was larger than 100. These results suggest that the electrical conductivity of honey might be used to develop a detector for rapidly predicting the water content in blossom honey.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    PubMed Central

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

    2008-01-01

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

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

    PubMed Central

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

    2010-01-01

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

  11. Melt processed electrically conductive binary and ternary immiscible polymer/polyaniline blends

    SciTech Connect

    Zilberman, M.; Siegmann, A.; Narkis, M.

    1998-07-01

    In the present study, conductive binary and ternary blends of PANI with thermoplastic polymers were prepared by melt processing. The binary blends' investigation focused on the morphology and on the resulting electrical conductivity. Generally, the level of interaction between the doped PANI and the matrix polymer determines the blend morphology, and thus, its electrical conductivity. The morphology of a conductive network is described by a primary structure of small dispersed polyaniline particles, interconnected by secondary short range fine fibrillar structure. In blends containing a semicrystalline matrix the doped PANI network locates within the amorphous regions, leading to a reduction of the percolation concentration. The ternary blends' investigation focused on a system containing two co-continuous immiscible thermoplastic polymers and PANI. The PANI is preferably located in one of the matrix polymers. This concentration effects enables high electrical conductivities at low PANI contents.

  12. Independent control of electrical and heat conduction by nanostructure designing for Si-based thermoelectric materials

    PubMed Central

    Yamasaka, Shuto; Watanabe, Kentaro; Sakane, Shunya; Takeuchi, Shotaro; Sakai, Akira; Sawano, Kentarou; Nakamura, Yoshiaki

    2016-01-01

    The high electrical and drastically-low thermal conductivities, a vital goal for high performance thermoelectric (TE) materials, are achieved in Si-based nanoarchitecture composed of Si channel layers and epitaxial Ge nanodots (NDs) with ultrahigh areal density (~1012 cm−2). In this nanoarchitecture, the ultrasmall NDs and Si channel layers play roles of phonon scattering sources and electrical conduction channels, respectively. Electron conductivity in n-type nanoacrhitecture shows high values comparable to those of epitaxial Si films despite the existence of epitaxial NDs. This is because Ge NDs mainly scattered not electrons but phonons selectively, which could be attributed to the small conduction band offset at the epitaxially-grown Si/Ge interface and high transmission probability through stacking faults. These results demonstrate an independent control of thermal and electrical conduction for phonon-glass electron-crystal TE materials by nanostructure designing and the energetic and structural interface control. PMID:26973092

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  14. Improving the electrical conductivity of PEDOT:PSS films by binary secondary doping

    NASA Astrophysics Data System (ADS)

    Zhu, Zhengyou; Liu, Congcong; Xu, Jingkun; Jiang, Qinglin; Shi, Hui; Liu, Endou

    2016-01-01

    In this work, the electrical conductivity of poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) films was effectively enhanced by binary secondary doping. Initially, doping with 5 vol.% dimethyl sulfoxide (DMSO) improved the electrical conductivity from 0.3 S cm-1 to 437 S cm-1 and a further increase to 950 S cm-1 was achieved by adding LiClO4. The conductivity value we report here is one of the highest reported for pretreated PEDOT:PSS films. The obtained maximum electrical conductivity is almost 3000 times higher than that shown by pristine PEDOT:PSS films. The increase in the electrical conductivity is ascribed to the synergistic effect of the two dopants. Fourier transform infrared spectra indicated the absence of any changes to the chemical structure of PEDOT:PSS. Atomic force microscopy images demonstrate an increased surface roughness and suggest the occurrence of conformational changes of PEDOT chains from the coiled to coil-extended one, which is the key reason for the electrical conductivity enhancement. The pretreatments we propose here are rapid, simple and effective for the large-scale preparation of high-conductivity PEDOT:PSS films. [Figure not available: see fulltext.

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

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  16. The electrical, thermal conductivity, microstructure and mechanical properties of Al-Sn-Pb ternary alloys

    NASA Astrophysics Data System (ADS)

    Alper Billur, C.; Gerekcioglu, E.; Bozoklu, M.; Saati, B.; Ari, M.; Nair, F.

    2015-08-01

    The structural, thermal, electrical and mechanical properties and micro-hardness of four different samples of Al-Sn-Pb ternary alloys (Al-[x] wt. % Sn-10 wt. % Pb) (x = 40, 30, 20 and 10) with constant lead concentrations were investigated for four different samples. Electrical resistivity and conductivity were measured by using (four-point probe measurement techniques) 4PPT techniques. The variations of thermal conductivity were determined by Wiedemann-Franz law (W-F) and Smith-Palmer (S-P) equation using the data obtained from electrical properties. The mechanical properties of the same alloys were obtained by the tensile test and the Vickers micro-hardness test.

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

    NASA Astrophysics Data System (ADS)

    Binbin, Jie; Chihtang, Sah

    2014-04-01

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

  18. dc and ac characterizations of electrical conducting nanoporous carbon structures based on resorcinol-formaldehyde

    NASA Astrophysics Data System (ADS)

    Najeh, I.; Ben Mansour, N.; Dahman, H.; Alyamani, A.; El Mir, L.

    2012-06-01

    Structural, electrical and morphological properties of electrical conducting nanoporous carbon structures, prepared at different pyrolysis temperatures by sol-gel method, were investigated. The effect of the measurement temperature on the electrical properties of the obtained sample pyrolysed at 675 C was studied. The imaginary and real parts of the sample impedance versus frequency, in the range of 40 Hz-100 MHz, are investigated. The Nyquist diagrams were used to identify an equivalent circuit and the fundamental parameters of the circuit are determined at different temperatures with the aim to study the contributions of the grains and boundary grains to the conductivity.

  19. Estimates of olivine-basaltic melt electrical conductivity using a digital rock physics approach

    NASA Astrophysics Data System (ADS)

    Miller, Kevin J.; Montési, Laurent G. J.; Zhu, Wen-lu

    2015-12-01

    Estimates of melt content beneath fast-spreading mid-ocean ridges inferred from magnetotelluric tomography (MT) vary between 0.01 and 0.10. Much of this variation may stem from a lack of understanding of how the grain-scale melt geometry influences the bulk electrical conductivity of a partially molten rock, especially at low melt fraction. We compute bulk electrical conductivity of olivine-basalt aggregates over 0.02 to 0.20 melt fraction by simulating electric current in experimentally obtained partially molten geometries. Olivine-basalt aggregates were synthesized by hot-pressing San Carlos olivine and high-alumina basalt in a solid-medium piston-cylinder apparatus. Run conditions for experimental charges were 1.5 GPa and 1350 °C. Upon completion, charges were quenched and cored. Samples were imaged using synchrotron X-ray micro-computed tomography (μ-CT). The resulting high-resolution, 3-dimensional (3-D) image of the melt distribution constitutes a digital rock sample, on which numerical simulations were conducted to estimate material properties. To compute bulk electrical conductivity, we simulated a direct current measurement by solving the current continuity equation, assuming electrical conductivities for olivine and melt. An application of Ohm's Law yields the bulk electrical conductivity of the partially molten region. The bulk electrical conductivity values for nominally dry materials follow a power-law relationship σbulk = Cσmeltϕm with fit parameters m = 1.3 ± 0.3 and C = 0.66 ± 0.06. Laminar fluid flow simulations were conducted on the same partially molten geometries to obtain permeability, and the respective pathways for electrical current and fluid flow over the same melt geometry were compared. Our results indicate that the pathways for flow fluid are different from those for electric current. Electrical tortuosity is lower than fluid flow tortuosity. The simulation results are compared to existing experimental data, and the potential influence of volatiles and melt films on electrical conductivity of partially molten rocks is discussed.

  20. Measurements of atmospheric electric field and conductivity in the locality of a gas well flame

    NASA Astrophysics Data System (ADS)

    Gopalakrishnan, V.; Deshpande, C. G.; Kamra, A. K.

    Measurements of the atmospheric electric field and conductivity of both polarities are made at the Earth's surface 1.5 kms from a very large flame produced due to a gas well blowout. The results show a single periodic diurnal variation of electric field with a maximum in the afternoons and very low values of electric field during nights. The observation is explained with the help of Vonnegut et al.'s [1995] results that a flame burning under the influence of the fair weather electric field releases negative charge into the atmosphere. Possible implication of the results in explaining the development of inverted dipole in forest fire clouds is discussed.

  1. Conduction of Electrical Current to and Through the Human Body: A Review

    PubMed Central

    Fish, Raymond M.; Geddes, Leslie A.

    2009-01-01

    Objective: The objective of this article is to explain ways in which electric current is conducted to and through the human body and how this influences the nature of injuries. Methods: This multidisciplinary topic is explained by first reviewing electrical and pathophysiological principles. There are discussions of how electric current is conducted through the body via air, water, earth, and man-made conductive materials. There are also discussions of skin resistance (impedance), internal body resistance, current path through the body, the let-go phenomenon, skin breakdown, electrical stimulation of skeletal muscles and nerves, cardiac dysrhythmias and arrest, and electric shock drowning. After the review of basic principles, a number of clinically relevant examples of accident mechanisms and their medical effects are discussed. Topics related to high-voltage burns include ground faults, ground potential gradient, step and touch potentials, arcs, and lightning. Results: The practicing physician will have a better understanding of electrical mechanisms of injury and their expected clinical effects. Conclusions: There are a variety of types of electrical contact, each with important characteristics. Understanding how electric current reaches and travels through the body can help the clinician understand how and why specific accidents occur and what medical and surgical problems may be expected. PMID:19907637

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

    NASA Astrophysics Data System (ADS)

    Jang, Sung-Hwan; Yin, Huiming

    2015-04-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    Graphite fluoride fibers can be produced by fluorinating pristine or intercalated graphite fibers. The higher the degree of graphitization of the fibers, the higher the temperature needed to reach the same degree of fluorination. Structural damage during high temperature fluorination can be reduced or eliminated by pretreating the fibers with bromine and/or fluorine. The electrical resistivity of the fibers was in the 0.01 to 10 to the 11th ohm-cm range. The thermal conductivity of these fibers ranged from 5 to 75 W/m-K, which is much larger than the thermal conductivity of glass (1.1 W/m-K), the commonly used fiber in epoxy composites. A composite made from graphite fluoride fibers and epoxy or PTFE may be highly thermally conducting and electrically insulating or semiconducting. The electrically insulating product may be used as heat sinks for electrical or electronic instruments.

  4. Study on a Haptic Sensor Using MCF (Magnetic Compound Fluid) Electric Conductive Rubber

    NASA Astrophysics Data System (ADS)

    Zheng, Yaoyang; Shimada, Kunio

    To provide a new composite material having a high degree of sensitivity regarding both electrical conduction and temperature for the field of robotics or sensing, we have developed magnetic rubber that contains a network-like magnetic cluster. We compared the temperature response of MCF rubber with others rubbers made under various experimental conditions, allowing us to find an optimum condition for making MCF rubber. The temperature response was obtained by an experimental equation. We also compared the electric conductivity of MCF rubber with that of ordinary electric conductive rubber and found that its electric sensitivity was lower at a small deformation, but increased at larger deformations. Therefore, MCF rubber has proven itself effective as a switching sensor when a small deformation is applied.

  5. Dual percolation behaviors of electrical and thermal conductivity in metal-ceramic composites

    NASA Astrophysics Data System (ADS)

    Sun, K.; Zhang, Z. D.; Qian, L.; Dang, F.; Zhang, X. H.; Fan, R. H.

    2016-02-01

    The thermal and electrical properties including the permittivity spectra in radio frequency region were investigated for copper/yttrium iron garnet (Cu/YIG) composites. Interestingly, the percolation behaviors in electrical and thermal conductivity were obtained due to the formation of copper particles' networks. Beyond the electrical percolation threshold, negative permittivity was observed and plasmon frequency was reduced by several orders of magnitude. With the increase in copper content, the thermal conductivity was gradually increased; meanwhile, the phonon scattering effect and thermal resistance get enhanced, so the rate of increase in thermal conductivity gradually slows down. Hopefully, Cu/YIG composites with tunable electrical and thermal properties have great potentials for electromagnetic interference shielding and electromagnetic wave attenuation.

  6. High electrical conductivity in out of plane direction of electrodeposited Bi2Te3 films

    NASA Astrophysics Data System (ADS)

    Rojo, Miguel Muoz; Manzano, Cristina V.; Granados, Daniel; Osorio, M. R.; Borca-Tasciuc, Theodorian; Martn-Gonzlez, Marisol

    2015-08-01

    The out of plane electrical conductivity of highly anisotropic Bi2Te3 films grown via electro-deposition process was determined using four probe current-voltage measurements performed on 4.6 - 7.2 ?m thickness Bi2Te3 mesa structures with 80 - 120 ?m diameters sandwiched between metallic film electrodes. A three-dimensional finite element model was used to predict the electric field distribution in the measured structures and take into account the non-uniform distribution of the current in the electrodes in the vicinity of the probes. The finite-element modeling shows that significant errors could arise in the measured film electrical conductivity if simpler one-dimensional models are employed. A high electrical conductivity of (3.2 0.4) ? 105 S/m is reported along the out of plane direction for Bi2Te3 films highly oriented in the [1 1 0] direction.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    USGS Publications Warehouse

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

    1995-01-01

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

  9. Electrical conductivity of strongly degenerate plasma with the account of electron-electron scattering

    NASA Astrophysics Data System (ADS)

    Karakhtanov, V. S.

    2014-08-01

    The influence of electron-electron scattering on the strongly degenerate plasma conductivity is investigated with a linear response theory. In the present work the temperature dependence of the electron-electron scattering term of the electrical conductivity and further modification of the Ziman formula are discussed.

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

    NASA Astrophysics Data System (ADS)

    Maeda, Nobuo

    2013-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

  12. Effect of temperature-dependent electrical conductivity on transport processes in magnetosolidmechanics

    NASA Technical Reports Server (NTRS)

    Craig, G. T.; Arnas, O. A.

    1975-01-01

    The effect of temperature-dependent electrical conductivity on transport processes for a solid block is analyzed on the basis of a one-dimensional steady-state model under specified thermal boundary conditions. Assumptions are that the solid has an infinitely segmented electrode configuration, the magnetic field (By) may be resolved into a constant applied field and an induced field, the gradient of the electrochemical potential is equal to the electrostatic potential, a constant potential difference is applied externally across each pair of opposite electrodes, and all material properties except electrical conductivity are constant. Conductivity is expressed in normalized form in terms of a baseline conductivity and a constant for the material. The application of the assumptions of the model to the general phenomenological relations yields the governing equations. Solution of these equations gives the distribution of temperature, electric current density, and magnetic field strength along the length of the solid. It is shown that significant differences exist between the case for constant electrical conductivity and the case where electrical conductivity is temperature dependent.

  13. Controlling the shapes and electrical conductivities of polyaniline-wrapped MWCNTs.

    PubMed

    Lee, Byong-Wook; Park, Chang-Hyun; Song, Jae Hee; Kim, Yeong-Joon

    2011-07-01

    Nanocomposites of carbon nanotubes with polyaniline (PANI) constitute promising conducting nanomaterials, due to their ease of synthesis, electrical conductivity, and environmental stability. Variously shaped multi-walled carbon nanotube (MWCNT)-PANI nanocomposites were synthesized, and their electrical conductivities were compared. This study shows that new synthetic methods were able to control the shapes and electrical conductivities of MWCNT-PANI nanocomposites. The shapes of the MWCNT-PANI nanocomposites were changed by altering the reactant concentrations and the sequence of adding the initiator, ammonium persulfate (APS). The use of surface-modified MWCNTs instead of pristine MWCNTs is also an important factor determining the shapes of the nanocomposites. It was found that the electrical conductivity is strongly dependent on the shape and PANI content. The electrical conductivities of the MWCNT-PANI nanocomposites increased when the PANI/MWCNT ratio was decreased. The nanocomposites were characterized via field emission transmission electron microscopy (FE-TEM), Fourier-transform infrared (FT-IR) and ultraviolet-visible (UV-Vis) spectroscopy, and elementary analysis of the MWCNT-PANI nanocomposites. PMID:22121664

  14. Effects of a radially varying electrical conductivity on 3D numerical dynamos

    NASA Astrophysics Data System (ADS)

    Gómez-Pérez, Natalia; Heimpel, Moritz; Wicht, Johannes

    2010-07-01

    The transition from liquid metal to silicate rock in the cores of the terrestrial planets is likely to be accompanied by a gradient in the composition of the outer core liquid. The electrical conductivity of a volatile-enriched liquid alloy can be substantially lower than a light-element-depleted fluid found close to the inner core boundary. In this paper, we investigate the effect of radially variable electrical conductivity on planetary dynamo action using an electrical conductivity that decreases exponentially as a function of radius. We find that numerical solutions with continuous, radially outward decreasing electrical conductivity profiles result in strongly modified flow and magnetic field dynamics, compared to solutions with homogeneous electrical conductivity. The force balances at the top of the simulated fluid determine the overall character of the flow. The relationship between Coriolis, and Lorentz forces near the outer core boundary controls the flow and magnetic field intensity and morphology of the system. Our results imply that a low conductivity layer near the top of Mercury's liquid outer core is consistent with its weak magnetic field.

  15. Electrical conductivity of lawsonite and dehydrating fluids at high pressures and temperatures

    NASA Astrophysics Data System (ADS)

    Manthilake, Geeth; Mookherjee, Mainak; Bolfan-Casanova, Nathalie; Andrault, Denis

    2015-09-01

    Lawsonite is a calcium-aluminum bearing hydrous silicate mineral with CaAl2Si2O7(OH)2.H2O stoichiometry. It is thermodynamically stable in the hydrated oceanic crust. Low-velocity anomalies observed in the cold subducted slabs have been related to the unusual shear wave velocities of lawsonite eclogite. However, electrical conductivity of lawsonite at high pressure and temperature remains unknown. In this study, we measured the electrical conductivity of lawsonite at 7 GPa, and temperatures ranging from 298 K-1320 K. At 1173 K, the electrical conductivity of lawsonite is around 10-1 S/m. A sharp increase of electrical conductivity is observed at temperatures exceeding the dehydration ~1258 K. The high electrical conductivity up to 101 S/m observed in our experiments is due to the presence of highly conductive fluid and could explain the low resistivity observed at 150-250 km depths in subduction zone settings such as NE Japan, northern, and central Chile.

  16. Increasing the electrical conductivity of poly(vinylidene fluoride) by KrF excimer laser irradiation

    SciTech Connect

    Ji Yaling; Jiang Yijian

    2006-11-27

    This letter describes the increase in electrical conductivity of poly(vinylidene fluoride) induced by excimer laser irradiation with {lambda}=248 nm. The electrical conductivity was found to increase from 10{sup -13} to 10{sup -4} {omega}{sup -1} cm{sup -1}. As a result, experiments produced a transition in the property of the material from an insulator to a conductor. Optimal conditions for laser irradiation were determined in terms of the laser energy density, the repetition frequency, and the total number of laser shots. This letter also discusses the micromechanics of increasing conductivity in the light of Raman spectroscopy and x-ray photoelectron spectroscopy.

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

    SciTech Connect

    Sheftman, D.; Krasik, Ya. E.

    2010-11-15

    The results of experiments and magnetohydrodynamic simulations of nanosecond time scale underwater electrical explosions of Al, Cu, and W wires are presented. Experiments were performed using a nanosecond pulsed generator with a {approx}30 kA amplitude and {approx}60 ns rise time current pulse. The electrical conductivity of the tested materials in the density and temperature ranges of 0.1-20 g/cm{sup 3} and 0.03-8 eV, respectively, is presented. It is shown that for the physical conditions obtained in these experiments, the equation of state data used in the SESAME tables must be modified in order to reproduce the experimental results. Also, it was shown that the electrical conductivity of the metals does not consistently fit over the entire range of experimental conditions with either of the transport models presented.

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

    SciTech Connect

    Wittekind, W.D., Westinghouse Hanford

    1996-05-23

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

  19. Understanding Electrical Conduction States in WO3 Thin Films Applied for Resistive Random-Access Memory

    NASA Astrophysics Data System (ADS)

    Ta, Thi Kieu Hanh; Pham, Kim Ngoc; Dao, Thi Bang Tam; Tran, Dai Lam; Phan, Bach Thang

    2016-02-01

    The electrical conduction and associated resistance switching mechanism of top electrode/WO3/bottom electrode devices [top electrode (TE): Ag, Ti; bottom electrode (BE): Pt, fluorine-doped tin oxide] have been investigated. The direction of switching and switching ability depended on both the top and bottom electrode material. Multiple electrical conduction mechanisms control the leakage current of such switching devices, including trap-controlled space-charge, ballistic, Ohmic, and Fowler-Nordheim tunneling effects. The transition between electrical conduction states is also linked to the switching (SET-RESET) process. This is the first report of ballistic conduction in research into resistive random-access memory. The associated resistive switching mechanisms are also discussed.

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

    PubMed Central

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

    2014-01-01

    Direct printing nanoparticle-based conductive inks onto paper substrates has encountered difficulties e.g. the nanoparticles are prone to penetrate into the pores of the paper and become partially segmented, and the necessary low-temperature-sintering process is harmful to the dimension-stability of paper. Here we prototyped the paper-based circuit substrate in combination with printed thermoplastic electrically conductive adhesives (ECA), which takes the advantage of the capillarity of paper and thus both the conductivity and mechanical robustness of the printed circuitsweredrastically improved without sintering process. For instance, the electrical resistivity of the ECA specimen on a pulp paper (6 × 10−5Ω·cm, with 50 wt% loading of Ag) was only 14% of that on PET film than that on PET film. This improvement has been found directly related to the sizing degree of paper, in agreement with the effective medium approximation simulation results in this work. The thermoplastic nature also enables excellent mechanical strength of the printed ECA to resist repeated folding. Considering the generality of the process and the wide acceptance of ECA technique in the modern electronic packages, this method may find vast applications in e.g. circuit boards, capacitive touch pads, and radio frequency identification antennas, which have been prototyped in the manuscript. PMID:25182052