An analysis of electrical conductivity model in saturated porous media

NASA Astrophysics Data System (ADS)

Cai, J.; Wei, W.; Qin, X.; Hu, X.

2017-12-01

Electrical conductivity of saturated porous media has numerous applications in many fields. In recent years, the number of theoretical methods to model electrical conductivity of complex porous media has dramatically increased. Nevertheless, the process of modeling the spatial conductivity distributed function continues to present challenges when these models used in reservoirs, particularly in porous media with strongly heterogeneous pore-space distributions. Many experiments show a more complex distribution of electrical conductivity data than the predictions derived from the experiential model. Studies have observed anomalously-high electrical conductivity of some low-porosity (tight) formations compared to more- porous reservoir rocks, which indicates current flow in porous media is complex and difficult to predict. Moreover, the change of electrical conductivity depends not only on the pore volume fraction but also on several geometric properties of the more extensive pore network, including pore interconnection and tortuosity. In our understanding of electrical conductivity models in porous media, we study the applicability of several well-known methods/theories to electrical characteristics of porous rocks as a function of pore volume, tortuosity and interconnection, to estimate electrical conductivity based on the micro-geometrical properties of rocks. We analyze the state of the art of scientific knowledge and practice for modeling porous structural systems, with the purpose of identifying current limitations and defining a blueprint for future modeling advances. We compare conceptual descriptions of electrical current flow processes in pore space considering several distinct modeling approaches. Approaches to obtaining more reasonable electrical conductivity models are discussed. Experiments suggest more complex relationships between electrical conductivity and porosity than experiential models, particularly in low-porosity formations. However, the available theoretical models combined with simulations do provide insight to how microscale physics affects macroscale electrical conductivity in porous media.

Effect of pH on the electrical properties and conducting mechanism of SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Periathai, R. Sudha; Abarna, S.; Hirankumar, G.; Jeyakumaran, N.; Prithivikumaran, N.

2017-03-01

Semiconductor nanoparticles have attracted more interests because of their size-dependent optical and electrical properties.SnO2 is an oxygen-deficient n-type semiconductor with a wide band gap of 3.6 eV (300 K). It has many remarkable applications as sensors, catalysts, transparent conducting electrodes, anode material for rechargeable Li- ion batteries and optoelectronic devices. In the present work, the role of pH in determining the electrical and dielectric properties of SnO2 nanoparticles has been studied as a function of temperature ranging from Room temperature (RT) to 114 °C in the frequency range of 7 MHz to 50 mHz using impedance spectroscopic technique. The non linear behavior observed in the thermal dependence of the conductance of SnO2 nanoparticles is explained by means of the surface property of SnO2 nanoparticles where proton hopping mechanism is dealt with. Jonscher's power law has been fitted for the conductance spectra and the frequency exponent ("s" value) gives an insight about the ac conducting mechanism. The temperature dependence of electrical relaxation phenomenon in the material has been observed. The complex electric modulus analysis indicates the possibility of hopping conduction mechanism in the system with non-exponential type of conductivity relaxation.

Electrical conductivity measurement of granulite under mid- to lower crustal pressure-temperature conditions

NASA Astrophysics Data System (ADS)

Fuji-ta, K.; Katsura, T.; Tainosho, Y.

2004-04-01

We have developed a technique to measure electrical conductivity of crustal rocks with relatively low conductivity and complicated mineral components in order to compare with results given by magneto-telluric (MT) measurements. A granulite from Hidaka metamorphic belt (HMB) in Hokkaido, Japan at high temperature and pressure conditions was obtained. The granulite sample was ground and sintered under the conditions similar to those of mid- to lower crust. We have observed smooth and reversible change of conductivity with temperature up to about 900 K at 1 GPa. The results were consistent with the electrical conductivity structures suggested by the MT data analysis. Considering pore fluid conduction mechanism or the role of accessory minerals in the rock, the mechanisms of electrical conductivity paths in dry or basic rocks should be reconsidered.

Soil water sensor response to bulk electrical conductivity

USDA-ARS?s Scientific Manuscript database

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...

Dual percolation behaviors of electrical and thermal conductivity in metal-ceramic composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, K.; Zhang, Z. D.; Qian, L.

2016-02-08

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 thermalmore » properties have great potentials for electromagnetic interference shielding and electromagnetic wave attenuation.« less

Disordered Nuclear Pasta, Magnetic Field Decay, and Crust Cooling in Neutron Stars

NASA Astrophysics Data System (ADS)

Horowitz, C. J.; Berry, D. K.; Briggs, C. M.; Caplan, M. E.; Cumming, A.; Schneider, A. S.

2015-01-01

Nuclear pasta, with nonspherical shapes, is expected near the base of the crust in neutron stars. Large-scale molecular dynamics simulations of pasta show long lived topological defects that could increase electron scattering and reduce both the thermal and electrical conductivities. We model a possible low-conductivity pasta layer by increasing an impurity parameter Qimp . Predictions of light curves for the low-mass x-ray binary MXB 1659-29, assuming a large Qimp, find continued late time cooling that is consistent with Chandra observations. The electrical and thermal conductivities are likely related. Therefore, observations of late time crust cooling can provide insight on the electrical conductivity and the possible decay of neutron star magnetic fields (assuming these are supported by currents in the crust).

Disordered nuclear pasta, magnetic field decay, and crust cooling in neutron stars.

PubMed

Horowitz, C J; Berry, D K; Briggs, C M; Caplan, M E; Cumming, A; Schneider, A S

2015-01-23

Nuclear pasta, with nonspherical shapes, is expected near the base of the crust in neutron stars. Large-scale molecular dynamics simulations of pasta show long lived topological defects that could increase electron scattering and reduce both the thermal and electrical conductivities. We model a possible low-conductivity pasta layer by increasing an impurity parameter Q_{imp}. Predictions of light curves for the low-mass x-ray binary MXB 1659-29, assuming a large Q_{imp}, find continued late time cooling that is consistent with Chandra observations. The electrical and thermal conductivities are likely related. Therefore, observations of late time crust cooling can provide insight on the electrical conductivity and the possible decay of neutron star magnetic fields (assuming these are supported by currents in the crust).

Investigation of Transport Properties of a New Biomaterials - GUM Mangosteen

NASA Astrophysics Data System (ADS)

Pradhan, Sourav S.; Sarkar, A.

2006-06-01

Biomaterial has occupied leading position in material science for various scientific and technological applications. This present work is carried out over a natural gum extracted from raw fruit of Mangosteen, an east Indian tree (Gercinia Mangostana) following extraction and purification process. Solid specimen of the said gum is developed following sol-gel like process. AC and DC electrical analysis on the dried solid specimen of the gum were carried out and showed high electrical conduction with σ ~ 1 E-03 S/cm, of which ionic and electronic contributions are 70% and 30% respectively. Analysis shows that origin of high electrical conductivity is due to presence of substantial amount of organic acid unit in its polysaccharide background. In fact the observed σ is about 1000 times of that observed in gum Arabica. Optical absorption of this new bio- materials are also studied using UV-VIS analysis. The results show its high absorption co-efficient in UV and blue part of analysed range. A complete electrical characterization of the material have been made. It has also been observed that the electronic conduction can be enhanced to 70% of the total electrical conductivity by forming complex with Iodine and organic (Citric) acid from Lemon fruit. This high potential material is being studied for development of electronic device application.

Electrical conduction hysteresis in carbon black-filled butyl rubber compounds

NASA Astrophysics Data System (ADS)

Alzamil, M. A.; Alfaramawi, K.; Abboudy, S.; Abulnasr, L.

2018-04-01

Temperature and concentration dependence of electrical resistance of butyl rubber filled with GPF carbon black was carried out. Current-voltage (I-V) characteristics at room-temperature were also investigated. The I-V characteristics show that the behavior is linear at small voltages up to approximately 0.15 V and currents up to 0.05 mA indicating that the conduction mechanism was probably due to electron tunneling from the end of conductive path to the other one under the action of the applied electric field. At higher voltages, a nonlinear behavior was noticed. The nonlinearity was attributed to the joule heating effects. Electrical resistance of the butyl/GPF composites was measured as a function of temperature during heating and cooling cycles from 300 K and upward to a specific temperature. When the specimens were heated up, the resistance was observed to increase continuously with the rise of temperature. However, when the samples were cooled down, the resistance was observed to decrease following a different path. The presence of conduction hysteresis behavior in the resistance-temperature curves during the heating and cooling cycles was then verified. The electrical conduction of the composite system is supposed to follow an activation conduction mechanism. Activation energy was calculated at different filler concentrations for both the heating and cooling processes.

Electrical conduction mechanism of LaNi{sub x}Me{sub 1−x}O{sub 3−δ} (Me = Fe, Mn)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niwa, Eiki, E-mail: e-niwa@phys.chs.nihon-u.ac.jp; Department of Integrated Sciences in Physics and Biology, College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156-8550; Maeda, Hiroki

Graphical abstract: Compositional dependence of (a) electrical conductivity and (b) E{sub a} for hopping conduction of LaNi{sub x}Me{sub 1−x}O{sub 3} (Me = Fe, Mn). - Highlights: • Electrical conduction mechanism of LaNi{sub x}Me{sub 1−x}O{sub 3} (Me = Fe, Mn) was investigated. • Hopping conduction model could be applied for conductivity of both specimens. • The difference of E{sub a} due to that of energy level of Fe and Mn was observed. • Hole concentration estimated by iodimetry increases with increasing Ni content. - Abstract: Electrical conduction mechanism of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} expected as Sr-freemore » new cathode material for solid oxide fuel cells was analyzed. Electrical conduction behaviors of both specimens could be well fitted by small polaron hopping conduction model. The electrical conductivity of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} increased with increasing Ni content, showing agreement with decrease of activation energy for hopping conduction. The decrease of electrical conductivity and increase of activation energy of LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} were observed with increasing Ni content for 0.0 ≤ x ≤ 0.4. Further Ni substitution increased electrical conductivity and decreased activation energy for 0.4 ≤ x ≤ 0.6. It was revealed using iodometry that the difference of hole carrier density between LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} was small. It was suspected that the origin of the difference of electrical conduction behavior of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1-x}O{sub 3+δ} was difference of energy level of e{sub g} band composed of Fe 3d or Mn 3d orbitals and their overlapping quantity with O 2p and Ni 3d band.« less

Discretized modeling of beads-on-a-string morphology from electrically driven, conducting, and viscoelastic polymer jets

NASA Astrophysics Data System (ADS)

Divvela, Mounica Jyothi; Joo, Yong Lak

2017-04-01

In this paper, we provide a theoretical investigation of axisymmetric instabilities observed during electrospinning, which lead to beads-on-a-string morphology. We used a discretized method to model the instability phenomena observed in the jet. We considered the fluid to be analogous to a bead-spring model. The motion of these beads is governed by the electrical, viscoelastic, surface tension, aerodynamic drag, and gravitational forces. The bead is perturbed at the nozzle, and the growth of the instability is observed over time, and along the length of the jet. We considered both lower electrical conducting polyisobutylene (PIB)-based Boger fluids and highly electrical conducting, polyethylene oxide (PEO)/water systems. In PIB fluids, the onset of the axisymmetric instability is predominantly based on the capillary mode, and the growth rate of the instability is decreased with the viscoelasticity of the jet. However, in the PEO/water system, the instability is electrically driven, and a significant increase in the growth rate of the instability is observed with the increase in the voltage. Our predictions from the discretized model are in good agreement with the previous linear stability analysis and experimental results. Our results also revealed the non-stationary behavior of the disturbance, where the amplitude of the perturbation is observed to be oscillating. Furthermore, we showed that the discretized model is also used to observe the non-axisymmetric behavior of the jet, which can be further used to study the bending instability in electrospinning.

Electrical Conductivity Measurement of Granulite Under Mid to Lower Crustal Pressure-Temperature Conditions

NASA Astrophysics Data System (ADS)

Fuji-Ta, K.; Katsura, T.; Tainosho, Y.

2003-12-01

We have developed a technique to measure electrical conductivity of crustal rocks with relatively low conductivity and complicated mineral components in order to compare with results given by Magneto-Telluric (MT) measurements. A granulite from Hidaka Metamorphic Belt (HMB) in Hokkaido, Japan at high temperature and pressure conditions was obtained. The granulite sample was ground and sintered under the conditions similar to those of mid to lower crust. We have observed smooth and reversible change of conductivity with temperature up to about 900 K at 1 GPa. Through the qualitative and quantitative evaluations using Electron Probe Micro Analysis (EPMA), microstructures of the sintered sample were inspected. This inspection is essential to confirm the sample was not affected by chemical interaction of minerals. We also examined the role of accessory minerals in the rock, and the mechanisms of electrical conductivity paths in _gdry_h or _gbasic_h rocks should be reconsidered. Finally, results from electrical conductivity measurements were consistent with the electrical conductivity structures suggested by the former MT data analysis.

External electric field driven modification of the anomalous and spin Hall conductivities in Fe thin films on MgO(001)

NASA Astrophysics Data System (ADS)

Pradipto, Abdul-Muizz; Akiyama, Toru; Ito, Tomonori; Nakamura, Kohji

2018-01-01

The effects of applying external electric fields to the anomalous and spin Hall conductivities in Fe thin-film models with different layer thicknesses on MgO(001) are investigated by using first-principles calculations. We observe that, for the considered systems, the application of positive electric field associated with the accumulation of negative charges on the Fe side generally decreases (increases) the anomalous (spin) Hall conductivities. The mapping of the Hall conductivities within the two-dimensional Brillouin zone shows that the electric-field-induced modifications are related to the modification of the band structures of the atoms at the interface with the MgO substrate. In particular, the external electric field affects the Hall conductivities via the modifications of the dx z,dy z orbitals, in which the application of positive electric field pushes the minority-spin states of the dx z,dy z bands closer to the Fermi level. Better agreement with the anomalous Hall conductivity for bulk Fe and a more realistic scenario for the electric field modification of Hall conductivities are obtained by using the thicker layers of Fe on MgO (Fe3/MgO and Fe5/MgO).

Electron transport and electron energy distributions within the wurtzite and zinc-blende phases of indium nitride: Response to the application of a constant and uniform electric field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siddiqua, Poppy; Hadi, Walid A.; Salhotra, Amith K.

2015-03-28

Within the framework of an ensemble semi-classical three-valley Monte Carlo electron transport simulation approach, we critically contrast the nature of the electron transport that occurs within the wurtzite and zinc-blende phases of indium nitride in response to the application of a constant and uniform electric field. We use the electron energy distribution and its relationship with the electron transport characteristics in order to pursue this analysis. For the case of zinc-blende indium nitride, only a peak corresponding to the electrons within the lowest energy conduction band valley is observed, this peak being seen to broaden and shift to higher energiesmore » in response to increases in the applied electric field strength, negligible amounts of upper energy conduction band valley occupancy being observed. In contrast, for the case of wurtzite indium nitride, in addition to the aforementioned lowest energy conduction band valley peak in the electron energy distribution, and its broadening and shifting to higher energies in response to increases in the applied electric field strength, beyond a certain critical electric field strength, 30 kV/cm for the case of this particular material, upper energy conduction band valley occupancy is observed, this occupancy being further enhanced in response to further increases in the applied electric field strength. Reasons for these results are provided. The potential for device consequences is then commented upon.« less

Some notes on hydrogen-related point defects and their role in the isotope exchange and electrical conductivity in olivine

NASA Astrophysics Data System (ADS)

Karato, Shun-ichiro

2015-11-01

Nominally anhydrous minerals such as olivine dissolve hydrogen in a variety of forms including free (or interstitial) proton (Hrad) and two protons trapped at the M-site ((2 H)M×). The strength of chemical bonding between protons and the surrounding atoms are different among different species, and consequently protons belonging to different species likely have different mobility (diffusion coefficients). I discuss the role of diffusion of protons in different species in the isotope exchange and hydrogen-assisted electrical conductivity adding a few notes to the previous work by Karato (2013) including a new way to test the model. I conclude that in the case of isotope exchange, the interaction among these species is strong because diffusion is heterogeneous, whereas there is no strong interaction among different species in electrical conduction where diffusion is homogeneous (in an infinite crystal). Consequently, the slowest diffusing species controls the rate of isotope exchange, whereas the fastest diffusing species controls electrical conductivity leading to a different temperature dependence of activation energy and anisotropy. This model explains the differences in the activation energy and anisotropy between isotope diffusion and electrical conductivity, and predicts that the mechanism of electrical conductivity changes with temperature providing an explanation for most of the discrepancies among different experimental observations at different temperatures except for those by Poe et al. (2010) who reported anomalously high water content dependence and highly anisotropic activation energy. When the results obtained at high temperatures are used, most of the geophysically observed high and highly anisotropic electrical conductivity in the asthenosphere can be explained without invoking partial melting.

Electrical and thermal response of carbon nanotube composites under quasi-static and dynamic loading

NASA Astrophysics Data System (ADS)

O'Connell, Christopher D.

Carbon nanotube (CNT) composites have attracted much interest due to their possible technical applications as conductive polymers and sensory materials. This study will consist of two major objectives: 1.) to investigate the thermal conductivity and thermal response of multi-wall carbon nanotube (MWCNT) composites under quasi-static loading, and 2.) to investigate the electrical response of carboxyl-terminated butadiene (CTBN) rubber-reinforced MWCNT/Epoxy composites under quasi-static and dynamic loading. Similar studies have shown that the electrical conductivity of CNT/Epoxy composites dramatically increases with compressive strains up to 15%. Part 1 seeks to find out if thermal conductivity show a similar response to electrical conductivity under an applied load. Part 2 seeks to investigate how the addition of rubber affects the mechanical and electrical response of the composite subjected to quasi-static and dynamic loading. By knowing how thermal and electrical properties change under a given applied strain, we attempt to broaden the breadth of understanding of CNT/epoxy composites and inqure the microscopic interactions occurring between the two. Electrical experiments sought to investigate the electrical response of rubber-reinforced carbon nanotube epoxy composites under quasi-static and dynamic loading. Specimens were fabricated with CTBN rubber content of 10 parts per hundredth resin (phr), 20 phr, 30 phr and 0 phr for a basis comparison. Both quasi-static and dynamic mechanical response showed a consistent decrease in peak stress and Young's modulus with increasing rubber content. Trends in the electrical response between each case were clearly observed with peak resistance changes ranging from 58% to 73% and with each peak occurring at a higher value with increasing rubber content, with the exception of the rubber-free specimens. It was concluded that among the rubber-embedded specimens, the addition of rubber helped to delay micro-cracking and degradation and thus prolong the electrical response of the specimen to higher strains. Thermal experiments were first established by designing and fabricating an apparatus to determine the thermal conductivity of an unknown material. The principle of the apparatus is a steady-state one-dimensional comparative method where reference materials of known thermal conductivity are used to determine the system heat flux and in turn, the thermal conductivity of a given specimen. A thermal percolation study was conducted in order to determine a possible threshold of thermal transport of the material. The recorded values of thermal conductivity from 0 -- 0.2 wt% showed no such threshold with all specimens of different CNT loadings yielding similar values of thermal conductivity. The apparatus containing the CNT/epoxy specimen was then quasi-statically compressed to observe how the thermal conductivity changes with strains up to 20%. While a small decrease in thermal conductivity was observed under strain, it can mostly be attributed to material degradation and bulging.

Characterization of electrical conductivity of carbon fiber reinforced plastic using surface potential distribution

NASA Astrophysics Data System (ADS)

Kikunaga, Kazuya; Terasaki, Nao

2018-04-01

A new method of evaluating electrical conductivity in a structural material such as carbon fiber reinforced plastic (CFRP) using surface potential is proposed. After the CFRP was charged by corona discharge, the surface potential distribution was measured by scanning a vibrating linear array sensor along the object surface with a high spatial resolution over a short duration. A correlation between the weave pattern of the CFRP and the surface potential distribution was observed. This result indicates that it is possible to evaluate the electrical conductivity of a material comprising conducting and insulating regions.

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

PubMed

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

2006-09-01

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

An upper bound on the electrical conductivity of hydrated oceanic mantle at the onset of dehydration melting

NASA Astrophysics Data System (ADS)

Naif, Samer

2018-01-01

Electrical conductivity soundings provide important constraints on the thermal and hydration state of the mantle. Recent seafloor magnetotelluric surveys have imaged the electrical conductivity structure of the oceanic upper mantle over a variety of plate ages. All regions show high conductivity (0.02 to 0.2 S/m) at 50 to 150 km depths that cannot be explained with a sub-solidus dry mantle regime without unrealistic temperature gradients. Instead, the conductivity observations require either a small amount of water stored in nominally anhydrous minerals or the presence of interconnected partial melts. This ambiguity leads to dramatically different interpretations on the origin of the asthenosphere. Here, I apply the damp peridotite solidus together with plate cooling models to determine the amount of H2O needed to induce dehydration melting as a function of depth and plate age. Then, I use the temperature and water content estimates to calculate the electrical conductivity of the oceanic mantle with a two-phase mixture of olivine and pyroxene from several competing empirical conductivity models. This represents the maximum potential conductivity of sub-solidus oceanic mantle at the limit of hydration. The results show that partial melt is required to explain the subset of the high conductivity observations beneath young seafloor, irrespective of which empirical model is applied. In contrast, the end-member empirical models predict either nearly dry (<20 wt ppm H2O) or slightly damp (<200 wt ppm H2O) asthenosphere for observations of mature seafloor. Since the former estimate is too dry compared with geochemical constraints from mid-ocean ridge basalts, this suggests the effect of water on mantle conductivity is less pronounced than currently predicted by the conductive end-member empirical model.

Enhanced monitoring of hazardous waste site remediation: Electrical conductivity tomography and citizen monitoring of remediation through the EPA's community advisory group program

NASA Astrophysics Data System (ADS)

Hort, Ryan D.

In situ chemical oxidation using permanganate has become a common method for degrading trichloroethene (TCE) in contaminated aquifers. Its effectiveness, however, is dependent upon contact between the oxidant and contaminant. Monitoring permanganate movement after injection is often hampered by aquifer heterogeneity and insufficient well coverage. Time lapse electrical conductivity tomography increases the spatial extent of monitoring beyond well locations. This technique can create two- or three-dimensional images of the electrical conductivity within the aquifer to monitor aquifer chemistry changes caused by permanganate injection and oxidation reactions. In-phase and quadrature electrical conductivity were measured in homogeneous aqueous and porous media samples to determine the effects of TCE and humate oxidation by permanganate on both measures of conductivity. Further effects of clean sand, 10% kaolinite (v/v), and 10% smectite (v/v) on both types of conductivity were studied as well. Finally, in-phase electrical conductivity was measured over time after injecting permanganate solution into two-dimensional tanks containing artificial groundwater with and without TCE to observe the movement of the permanganate plume and its interaction with TCE and to examine the effectiveness of time-lapse conductivity tomography for monitoring the plume's movement. In-phase electrical conductivity after oxidation reactions involving permanganate, TCE, and humate could be accurately modeled in homogeneous batch samples. Use of forward modeling of in-phase conductivity from permanganate concentrations may be useful for improving recovery of conductivity values during survey inversion, but further work is needed combining the chemistry modeling with solute transport models. Small pH-related quadrature conductivity decreases were observed after TCE oxidation, and large quadrature conductivity increases were observed as a result of sodium ion addition; however, quadrature conductivity could not be related to concentrations of permanganate or reaction products. Additionally, EPA Superfund sites participating in the Community Advisory Group (CAG) program were examined to determine how communities may have benefitted from the program. While CAG participation was correlated with slower achievement of EPA cleanup milestones, many CAGs successfully achieved five standardized social goals. CAGs that achieved these social goals varied in composition but were similar in their focus on community outreach and ability to extend their influence beyond CAG meetings.

Low temperature resistivity studies of SmB6: Observation of two-dimensional variable-range hopping conductivity

NASA Astrophysics Data System (ADS)

Batkova, Marianna; Batko, Ivan; Gabáni, Slavomír; Gažo, Emil; Konovalova, Elena; Filippov, Vladimir

2018-05-01

We studied electrical resistance of a single-crystalline SmB6 sample with a focus on the region of the "low-temperature resistivity plateau". Our observations did not show any true saturation of the electrical resistance at temperatures below 3 K down to 70 mK. According to our findings, temperature dependence of the electrical conduction in a certain temperature interval above 70 mK can be decomposed into a temperature-independent term and a temperature-activated term that can be described by variable-range hopping formula for two-dimensional systems, exp [ -(T0 / T) 1 / 3 ]. Thus, our results indicate importance of hopping type of electrical transport in the near-surface region of SmB6.

Electrodynamics of the middle atmosphere: Superpressure balloon program

NASA Technical Reports Server (NTRS)

Holzworth, Robert H.

1987-01-01

In this experiment a comprehensive set of electrical parameters were measured during eight long duration flights in the southern hemisphere stratosphere. These flight resulted in the largest data set ever collected from the stratosphere. The stratosphere has never been electrodynamically sampled in the systematic manner before. New discoveries include short term variability in the planetary scale electric current system, the unexpected observation of stratospheric conductivity variations over thunderstorms and the observation of direct stratospheric conductivity variations following a relatively small solar flare. Major statistical studies were conducted of the large scale current systems, the stratospheric conductivity and the neutral gravity waves (from pressure and temperature data) using the entire data set.

On conductivity changes in shocked potassium chloride

NASA Astrophysics Data System (ADS)

Bourne, N. K.; Townsend, D.; Braithwaite, M.

2005-06-01

A previous work has reported that shock loading of ionic crystals produces an induced polarization and changes in electrical conductivity. However, previous measurements recorded an integrated electrical signal comprising the induced electrical field and that due to current flow. For this reason a differential system was designed to separate these effects that was adapted from that used in the investigation of the conductivity of hydrogen under shock. The measurement removes voltages produced in the shock-induced electrical field, allowing determination of those resulting from resistance changes. Although the mechanical response of potassium chloride to shock has been studied extensively, the electrical response is less studied. Here, experiments are reported in which it is shocked to various stresses in order to observe conductivity changes. The range of stresses induced includes several mechanical thresholds, including the elastic-plastic transition, the B1:B2 phase transformation, and the overdriving of the shock faster than the elastic wave. The behavior observed when single crystal and targets pressed from granular material (to close to full density) are shocked around each of these thresholds is presented. The effects of loading to a particular stress in a single step or in multiple steps are discussed.

In vivo electric conductivity of cervical cancer patients based on B₁⁺ maps at 3T MRI.

PubMed

Balidemaj, E; de Boer, P; van Lier, A L H M W; Remis, R F; Stalpers, L J A; Westerveld, G H; Nederveen, A J; van den Berg, C A T; Crezee, J

2016-02-21

The in vivo electric conductivity (σ) values of tissue are essential for accurate electromagnetic simulations and specific absorption rate (SAR) assessment for applications such as thermal dose computations in hyperthermia. Currently used σ-values are mostly based on ex vivo measurements. In this study the conductivity of human muscle, bladder content and cervical tumors is acquired non-invasively in vivo using MRI. The conductivity of 20 cervical cancer patients was measured with the MR-based electric properties tomography method on a standard 3T MRI system. The average in vivo σ-value of muscle is 14% higher than currently used in human simulation models. The σ-value of bladder content is an order of magnitude higher than the value for bladder wall tissue that is used for the complete bladder in many models. Our findings are confirmed by various in vivo animal studies from the literature. In cervical tumors, the observed average conductivity was 13% higher than the literature value reported for cervical tissue. Considerable deviations were found for the electrical conductivity observed in this study and the commonly used values for SAR assessment, emphasizing the importance of acquiring in vivo conductivity for more accurate SAR assessment in various applications.

Response of ionospheric electric fields at mid-low latitudes during geomagnetic sudden commencements

NASA Astrophysics Data System (ADS)

Takahashi, N.; Kasaba, Y.; Shinbori, A.; Nishimura, Y.; Kikuchi, T.; Ebihara, Y.; Nagatsuma, T.

2014-12-01

Geomagnetic sudden commencements (SCs) are known as one of the distinct magnetospheric disturbance phenomena triggered by solar wind disturbances. Many previous studies have focused on the generation mechanism of SCs by using in-situ observations and simulations. However, the global evolution of ionospheric electric fields has primarily been estimated from the ionospheric current. Although a few studies utilized electric field data from radar observations, the coverage is limited in time, and limited component of the electric field is obtained. In this study, we investigated the response and local time dependence of the ionospheric electric field at mid-low latitudes associated with 203 SCs occurred from 1999 to 2004 by the in-situ observation of the ROCSAT-1 spacecraft. We found that the ionospheric electric field associated with SCs instantaneously responds to geomagnetic fields regardless of spacecraft local time. Our statistical analysis also showed the instantaneous response of the electric field, which indicates the global instant transmission of the electric field from polar region. In contrast, peak times in the preliminary impulse (PI) and main impulse (MI) phases were different between the ionospheric electric field and equatorial geomagnetic field (20 sec in the PI phase). Based on a comparison to the ground-ionosphere waveguide model by Kikuchi [2014], this time lag is suggested to be due to the latitudinal difference of the ionospheric conductivity. After constructing the local time distribution of the SC amplitude, we found that the dayside feature was seen at 18-22 h even the ionospheric conductivity is lower than that at dayside. We performed a magnetohydrodynamic (MHD) simulation for an ideal SC. The result of the simulation showed that the electric potential distribution is asymmetric with respect to the noon-midnight meridian, which is similar to our observational result. It appears to result from the divergence of the Hall current under the non-uniform ionospheric conductivity near the terminator as well as the auroral region.

Disordered nuclear pasta, magnetic field decay, and crust cooling in neutron stars

NASA Astrophysics Data System (ADS)

Horowitz, C. J.; Berry, D. K.; Briggs, C. M.; Caplan, M. E.; Cumming, A.; Schneider, A. S.

2015-04-01

Nuclear pasta, with non-spherical shapes, is expected near the base of the crust in neutron stars. Large scale molecular dynamics simulations of pasta show long lived topological defects that could increase electron scattering and reduce both the thermal and electrical conductivities. We model a possible low conductivity pasta layer by increasing an impurity parameter Qimp. Predictions of light curves for the low mass X-ray binary MXB 1659-29, assuming a large Qimp, find continued late time cooling that is consistent with Chandra observations. The electrical and thermal conductivities are likely related. Therefore observations of late time crust cooling can provide insight on the electrical conductivity and the possible decay of neutron star magnetic fields (assuming these are supported by currents in the crust). This research was supported in part by DOE Grants DE-FG02-87ER40365 (Indiana University) and DE-SC0008808 (NUCLEI SciDAC Collaboration).

Determination of consolidation properties using electrical resistivity

NASA Astrophysics Data System (ADS)

Kibria, Golam; Hossain, Sahadat; Khan, Mohammad Sadik

2018-05-01

Electrical conductivity is an indirect method used to evaluate pore-structures and their influence on macro and microscale behavior of soils. Although this method can provide useful information about the consolidation properties of soil samples, insufficient studies have been conducted to identify correlations between electrical and consolidation properties. The current study presents electrical resistivity responses of clayey samples at different consolidation stages. The consolidation properties of four soil specimens were measured in conjunction with electrical conductivity. Scanning electron microscope (SEM) analyses were performed on soil samples before and after consolidation to identify the changes in fabric morphology due to the application of loads. It was observed that the electrical conductivity of samples decreased with the increase of pressure, and the trends of variations were similar to e vs. logP curves. Although a linear correlation exists between electrical conductivity and void ratio, the relationship depends on the structural changes in clay particles. Therefore, changes in fabric structures were analyzed using SEM images, and results showed that the aspect ratio of the particles increased as much as 18.3% after consolidation. Based on the investigation, the coefficient of consolidations and one-dimensional strain were determined using electrical resistivity measurements.

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.

Influence of Pore-Fluid Pressure on Elastic Wave Velocity and Electrical Conductivity in Water-Saturated Rocks

NASA Astrophysics Data System (ADS)

Higuchi, A.; Watanabe, T.

2013-12-01

Pore-fluid pressure in seismogenic zones can play a key role in the occurrence of earthquakes (e.g., Sibson, 2009). Its evaluation via geophysical observations can lead to a good understanding of seismic activities. The evaluation requires a thorough understanding of the influence of the pore-fluid pressure on geophysical observables like seismic velocity and electrical conductivity. We have studied the influence of pore-fluid pressure on elastic wave velocity and electrical conductivity in water-saturated rocks. Fine grained (100-500μm) biotite granite (Aji, Kagawa pref., Japan) was used as rock samples. The density is 2.658-2.668 g/cm3, and the porosity 0.68-0.87%. The sample is composed of 52.8% plagioclase, 36.0% Quartz, 3.0% K-feldspar, 8.2% biotite. SEM images show that a lot of grain boundaries are open. Few intracrystalline cracks were observed. Following the method proposed by David and Zimmerman (2012), the distribution function of crack aspect ratio was evaluated from the pressure dependence of compressional and shear wave velocities in a dry sample. Cylindrical sample has dimensions of 25 mm in diameter and 30 mm in length, and saturated with 0.01 mol/l KCl aqueous solution. Compressional and shear wave velocities were measured with the pulse transmission technique (PZT transducers, f=2 MHz), and electrical conductivity the two-electrode method (Ag-AgCl electrodes, f=1 Hz-100 kHz). Simultaneous measurements of velocities and conductivity were made using a 200 MPa hydrostatic pressure vessel, in which confining and pore-fluid pressures can be separately controlled. The pore-fluid is electrically insulated from the metal work of the pressure vessel by using a newly designed plastic device (Watanabe and Higuchi, 2013). The confining pressure was progressively increased up to 25 MPa, while the pore-fluid pressure was kept at 0.1 MPa. It took five days or longer for the electrical conductivity to become stationary after increasing the confining pressure. Elastic wave velocities and electrical conductivity showed reproducibly contrasting changes for a small increase in the confining pressure. The elastic wave velocities increased only by 5% as the confining pressure increased from 0.1 MPa to 25 MPa, while the electrical conductivity decreased by an order of magnitude. Based on the SEM examinations, open grain boundaries work as cracks. The changes in elastic wave velocities and electrical conductivity must be caused by the closure of open grain boundaries. Most (˜80%) of the decrease in electrical conductivity occurred below the confining pressure of 5 MPa. As the confining pressure increased from 0.1 MPa to 5 MPa, cracks with the aspect ratio smaller than 7.5×10-5 were closed. The decrease in porosity was only 0.0005%. Such a small change in porosity caused a large change in electrical conductivity. The connectivity of fluid was maintained at the confining pressure of 25 MPa by cracks with the aspect ratio larger than 3.7×10-4. Simultaneous measurements have provided us a lot of information on the microstructure of fluid-bearing rocks.

Transport properties of olivine grain boundaries from electrical conductivity experiments

NASA Astrophysics Data System (ADS)

Pommier, Anne; Kohlstedt, David L.; Hansen, Lars N.; Mackwell, Stephen; Tasaka, Miki; Heidelbach, Florian; Leinenweber, Kurt

2018-05-01

Grain boundary processes contribute significantly to electronic and ionic transports in materials within Earth's interior. We report a novel experimental study of grain boundary conductivity in highly strained olivine aggregates that demonstrates the importance of misorientation angle between adjacent grains on aggregate transport properties. We performed electrical conductivity measurements of melt-free polycrystalline olivine (Fo90) samples that had been previously deformed at 1200 °C and 0.3 GPa to shear strains up to γ = 7.3. The electrical conductivity and anisotropy were measured at 2.8 GPa over the temperature range 700-1400 °C. We observed that (1) the electrical conductivity of samples with a small grain size (3-6 µm) and strong crystallographic preferred orientation produced by dynamic recrystallization during large-strain shear deformation is a factor of 10 or more larger than that measured on coarse-grained samples, (2) the sample deformed to the highest strain is the most conductive even though it does not have the smallest grain size, and (3) conductivity is up to a factor of 4 larger in the direction of shear than normal to the shear plane. Based on these results combined with electrical conductivity data for coarse-grained, polycrystalline olivine and for single crystals, we propose that the electrical conductivity of our fine-grained samples is dominated by grain boundary paths. In addition, the electrical anisotropy results from preferential alignment of higher-conductivity grain boundaries associated with the development of a strong crystallographic preferred orientation of the grains.

Electrical Conductivity of Dense Al, Ti, Fe, Ni, Cu, Mo, Ta, and W Plasmas

DTIC Science & Technology

2011-06-01

for all but tantalum and titanium shows a minimum at approximately 0.01 times solid density, followed by an increase as the density decreases further...internal energy and specific volume. Conductivity is observed to fall as the plasma expands for fixed internal energy, and for all but tantalum and...plasmas formed from elemental metal wires heated rapidly in a water bath by the electric current from discharge of a charged capacitor . Electrical

Time Lapse Electrical Resistivity to Connect Evapotranspiration and Groundwater Fluxes in the Critical Zone

NASA Astrophysics Data System (ADS)

Jarvis, S. K.; Harmon, R. E.; Barnard, H. R.; Randall, J.; Singha, K.

2017-12-01

The critical zone (CZ)—an open system extending from canopy top to the base of groundwater—is a highly dynamic and heterogeneous environment. In forested terrain, trees make up a large component of the CZ. This work aims to quantify the connection between vegetation and subsurface water storage at a hillslope scale within a forested watershed in the H.J. Andrews Experimental Forest, Oregon. To identify the mechanism(s) controlling the connection at the hillslope scale, we observe patterns in electrical conductivity using 2D-time lapse-DC resistivity. To compare inversions through time a representative error model was determined using L-curve criterion. Inverted data show high spatial variability in ground electrical conductivity and variation at both diel and seasonal timescales. These changes are most pronounced in areas corresponding to dense vegetation. The diel pattern in electrical conductivity is also observed in monitored sap flow sensors, water-level gauges, tensiometers, and sediment thermal probes. To quantify the temporal connection between these data over the course of the growing season a cross correlation analysis was conducted. Preliminary data show that over the course of the growing season transpiration becomes decoupled from both groundwater and soil moisture. Further decomposition of the inverted time lapse data will highlight spatial variability in electrical conductivity providing insight into the where, when, and how(s) of tree-modified subsurface storage.

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

PubMed

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

2004-01-01

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

Spin- and valley-dependent electrical conductivity of ferromagnetic group-IV 2D sheets in the topological insulator phase

NASA Astrophysics Data System (ADS)

Hoi, Bui Dinh; Yarmohammadi, Mohsen; Mirabbaszadeh, Kavoos; Habibiyan, Hamidreza

2018-03-01

In this work, based on the Kubo-Greenwood formalism and the k . p Hamiltonian model, the impact of Rashba spin-orbit coupling on electronic band structure and electrical conductivity of spin-up and spin-down subbands in counterparts of graphene, including silicene, stanene, and germanene nanosheets has been studied. When Rashba coupling is considered, the effective mass of Dirac fermions decreases significantly and no significant change is caused by this coupling for the subband gaps. All these nanosheets are found to be in topological insulator quantum phase at low staggered on-site potentials due to the applied perpendicular external electric field. We point out that the electrical conductivity of germanene increases gradually with Rashab coupling, while silicene and stanene have some fluctuations due to their smaller Fermi velocity. Furthermore, some critical temperatures with the same electrical conductivity values for jumping to the higher energy levels are observed at various Rashba coupling strengths. For all structures, a broad peak appears at low temperatures in electrical conductivity curves corresponding to the large entropy of systems when the thermal energy reaches to the difference between the energy states. Finally, we have reported that silicene has the larger has the larger electrical conductivity than two others.

Dipolar resonances in conductive carbon micro-fibers probed by near-field terahertz spectroscopy

DOE PAGES

Khromova, I.; Navarro-Cia, M.; Brener, I.; ...

2015-07-13

In this study, we observe dipole resonances in thin conductive carbon micro-fibers by detecting an enhanced electric field in the near-field of a single fiber at terahertz (THz) frequencies. Time-domain analysis of the electric field shows that each fiber sustains resonant current oscillations at the frequency defined by the fiber's length. Strong dependence of the observed resonance frequency and degree of field enhancement on the fibers' conductive properties enable direct non-contact probing of the THz conductivity in single carbon micro-fibers. We find the conductivity of the fibers to be within the range of 1– 5∙10 4 S/m. This approach ismore » suitable for experimental characterization of individual doped semiconductor resonators for THz metamaterials and devices.« less

Voltage-Induced Nonlinear Conduction Properties of Epoxy Resin/Micron-Silver Particles Composites

NASA Astrophysics Data System (ADS)

Qu, Zhaoming; Lu, Pin; Yuan, Yang; Wang, Qingguo

2018-01-01

The nonlinear conduction properties of epoxy resin (ER)/micron-silver particles (MP) composites were investigated. Under sufficient high intensity applied constant voltage, the obvious nonlinear conduction properties of the samples with volume fraction 25% were found. With increments in the voltage, the conductive switching effect was observed. The nonlinear conduction mechanism of the ER/MP composites under high applied voltages could be attributed to the electrical current conducted via discrete paths of conductive particles induced by the electric field. The test results show that the ER/MP composites with nonlinear conduction properties are of great potential application in electromagnetic protection of electron devices and systems.

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.

Silicon oxide: a non-innocent surface for molecular electronics and nanoelectronics studies.

PubMed

Yao, Jun; Zhong, Lin; Natelson, Douglas; Tour, James M

2011-02-02

Silicon oxide (SiO(x)) has been widely used in many electronic systems as a supportive and insulating medium. Here, we demonstrate various electrical phenomena such as resistive switching and related nonlinear conduction, current hysteresis, and negative differential resistance intrinsic to a thin layer of SiO(x). These behaviors can largely mimic numerous electrical phenomena observed in molecules and other nanomaterials, suggesting that substantial caution should be paid when studying conduction in electronic systems with SiO(x) as a component. The actual electrical phenomena can be the result of conduction from SiO(x) at a post soft-breakdown state and not the presumed molecular or nanomaterial component. These electrical properties and the underlying mechanisms are discussed in detail.

Conductance Effects on Inner Magnetospheric Plasma Morphology: Model Comparisons with IMAGE EUV, MENA, and HENA Data

NASA Technical Reports Server (NTRS)

Liemohn, M.; Ridley, A. J.; Kozyra, J. U.; Gallagher, D. L.; Brandt, P. C.; Henderson, M. G.; Denton, M. H.; Jahn, J. M.; Roelof, E. C.; DeMajistre, R. M.

2004-01-01

Modeling results of the inner magnetosphere showing the influence of the ionospheric conductance on the inner magnetospheric electric fields during the April 17, 2002 magnetic storm are presented. Kinetic plasma transport code results are analyzed in combination with observations of the inner magnetospheric plasma populations, in particular those from the IMAGE satellite. Qualitative and quantitative comparisons are made with the observations from EW, MENA, and HENA, covering the entire energy range simulated by the model (0 to 300 keV). The electric field description, and in particular the ionospheric conductance, is the only variable between the simulations. Results from the data-model comparisons are discussed, detailing the strengths and weaknesses of each conductance choice for each energy channel.

Ambient temperature thermoelectric performance of thermally evaporated p-type Bi-Sb-Te thin films

NASA Astrophysics Data System (ADS)

Singh, Sukhdeep; Singh, Janpreet; Tripathi, S. K.

2018-04-01

Bismuth antimony telluride (BST) compounds have shown a promising performance in low to medium temperature thermoelectric (TE) conversion. One such composition, Bi1.2Sb0.8Te3, was synthesized by melting elemental entities and thin films of the as-synthesized material were deposited by thermal evaporation. X-Ray Diffraction analysis was conducted to study the crystallographic phases and other structural properties. Electrical conductivity and Seebeck coefficient measurements of as-prepared thin films were conducted in the temperature range from 303-363 K with a view to study ambient temperature application of the synthesized material for power generation in which an increasing trend was observed in the Seebeck coefficient. Electrical conductivity displayed a maximum value of 0.22 × 104 Sm-1 that was comparable to other Bi-Sb-Te compositions whereas power factor had its peak at 323 K. These trends observed in electrical properties indicate that synthesized material can be used for room temperature TE module fabrication.

Measured electric field in the vicinity of a thunderstorm system at an altitude of 37 km

NASA Technical Reports Server (NTRS)

Benbrook, J. R.; Kern, J. W.; Sheldon, W. R.

1974-01-01

A balloon-borne experiment to measure the atmospheric electric field was flown from the National Scientific Balloon Facility at Palestine, Texas, on July 10, 1973. The electric field and atmospheric conductivity were measured during ascent and for a 4-hour float period at 37-km altitude. Termination of the flight occurred near a thunderstorm line in west Texas. The perturbing influence of the thunderstorms on the electric field was observed at least 100 km from the storm line. The measured electric field is in reasonable agreement with calculations based on simple models of cloud structure and atmospheric conductivity. Large pulses in the measured electric field are interpreted as being the result of intracloud lightning.

Simultaneously Enhancing the Cohesion and Electrical Conductivity of PEDOT:PSS Conductive Polymer Films using DMSO Additives.

PubMed

Lee, Inhwa; Kim, Gun Woo; Yang, Minyang; Kim, Taek-Soo

2016-01-13

Conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PSS) has attracted significant attention as a hole transport and electrode layer that substitutes metal electrodes in flexible organic devices. However, its weak cohesion critically limits the reliable integration of PSS in flexible electronics, which highlights the importance of further investigation of the cohesion of PSS. Furthermore, the electrical conductivity of PSS is insufficient for high current-carrying devices such as organic photovoltaics (OPVs) and organic light emitting diodes (OLEDs). In this study, we improve the cohesion and electrical conductivity through adding dimethyl sulfoxide (DMSO), and we demonstrate the significant changes in the properties that are dependent on the wt % of DMSO. In particular, with the addition of 3 wt % DMSO, the maximum enhancements for cohesion and electrical conductivity are observed where the values increase by 470% and 6050%, respectively, due to the inter-PEDOT bridging mechanism. Furthermore, when OLED devices using the PSS films are fabricated using the 3 wt % DMSO, the display exhibits 18% increased current efficiency.

A Novel Method for Measuring Electrical Conductivity of High Insulating Oil Using Charge Decay

NASA Astrophysics Data System (ADS)

Wang, Z. Q.; Qi, P.; Wang, D. S.; Wang, Y. D.; Zhou, W.

2016-05-01

For the high insulating oil, it is difficult to measure the conductivity precisely using voltammetry method. A high-precision measurementis proposed for measuring bulk electrical conductivity of high insulating oils (about 10-9--10-15S/m) using charge decay. The oil is insulated and charged firstly, and then grounded fully. During the experimental procedure, charge decay is observed to show an exponential law according to "Ohm" theory. The data of time dependence of charge density is automatically recorded using an ADAS and a computer. Relaxation time constant is fitted from the data using Gnuplot software. The electrical conductivity is calculated using relaxation time constant and dielectric permittivity. Charge density is substituted by electric potential, considering charge density is difficult to measure. The conductivity of five kinds of oils is measured. Using this method, the conductivity of diesel oil is easily measured to beas low as 0.961 pS/m, as shown in Fig. 5.

Visualization of conduit-matrix conductivity differences in a karst aquifer using time-lapse electrical resistivity

NASA Astrophysics Data System (ADS)

Meyerhoff, Steven B.; Karaoulis, Marios; Fiebig, Florian; Maxwell, Reed M.; Revil, André; Martin, Jonathan B.; Graham, Wendy D.

2012-12-01

In the karstic upper Floridan aquifer, surface water flows into conduits of the groundwater system and may exchange with water in the aquifer matrix. This exchange has been hypothesized to occur based on differences in discharge at the Santa Fe River Sink-Rise system, north central Florida, but has yet to be visualized using any geophysical techniques. Using electrical resistivity tomography, we conducted a time-lapse study at two locations with mapped conduits connecting the Santa Fe River Sink to the Santa Fe River Rise to study changes of electrical conductivity during times of varying discharge over a six-week period. Our results show conductivity differences between matrix, conduit changes in resistivity occurring through time at the locations of mapped karst conduits, and changes in electrical conductivity during rainfall infiltration. These observations provide insight into time scales and matrix conduit conductivity differences, illustrating how surface water flow recharged to conduits may flow in a groundwater system in a karst aquifer.

The Role of Additional Pulses in Electropermeabilization Protocols

PubMed Central

Suárez, Cecilia; Soba, Alejandro; Maglietti, Felipe; Olaiz, Nahuel; Marshall, Guillermo

2014-01-01

Electropermeabilization (EP) based protocols such as those applied in medicine, food processing or environmental management, are well established and widely used. The applied voltage, as well as tissue electric conductivity, are of utmost importance for assessing final electropermeabilized area and thus EP effectiveness. Experimental results from literature report that, under certain EP protocols, consecutive pulses increase tissue electric conductivity and even the permeabilization amount. Here we introduce a theoretical model that takes into account this effect in the application of an EP-based protocol, and its validation with experimental measurements. The theoretical model describes the electric field distribution by a nonlinear Laplace equation with a variable conductivity coefficient depending on the electric field, the temperature and the quantity of pulses, and the Penne's Bioheat equation for temperature variations. In the experiments, a vegetable tissue model (potato slice) is used for measuring electric currents and tissue electropermeabilized area in different EP protocols. Experimental measurements show that, during sequential pulses and keeping constant the applied voltage, the electric current density and the blackened (electropermeabilized) area increase. This behavior can only be attributed to a rise in the electric conductivity due to a higher number of pulses. Accordingly, we present a theoretical modeling of an EP protocol that predicts correctly the increment in the electric current density observed experimentally during the addition of pulses. The model also demonstrates that the electric current increase is due to a rise in the electric conductivity, in turn induced by temperature and pulse number, with no significant changes in the electric field distribution. The EP model introduced, based on a novel formulation of the electric conductivity, leads to a more realistic description of the EP phenomenon, hopefully providing more accurate predictions of treatment outcomes. PMID:25437512

Response of ionospheric electric fields at mid-low latitudes during sudden commencements

NASA Astrophysics Data System (ADS)

Takahashi, N.; Kasaba, Y.; Shinbori, A.; Nishimura, Y.; Kikuchi, T.; Ebihara, Y.; Nagatsuma, T.

2015-06-01

Using in situ observations from the Republic of China Satellite-1 spacecraft, we investigated the time response and local time dependence of the ionospheric electric field at mid-low latitudes associated with geomagnetic sudden commencements (SCs) that occurred from 1999 to 2004. We found that the ionospheric electric field variation associated with SCs instantaneously responds to the preliminary impulse (PI) signature on the ground regardless of spacecraft local time. Our statistical analysis also supports the global instant transmission of electric field from the polar region. In contrast, the peak time detected in the ionospheric electric field is earlier than that of the equatorial geomagnetic field (~20 s before in the PI phase). Based on the ground-ionosphere waveguide model, this time lag can be attributed to the latitudinal difference of ionospheric conductivity. However, the local time distribution of the initial excursion of ionospheric electric field shows that dusk-to-dawn ionospheric electric fields develop during the PI phase. Moreover, the westward electric field in the ionosphere, which produces the preliminary reverse impulse of the geomagnetic field on the dayside feature, appears at 18-22 h LT where the ionospheric conductivity beyond the duskside terminator (18 h LT) is lower than on the dayside. The result of a magnetohydrodynamic simulation for an ideal SC shows that the electric potential distribution is asymmetric with respect to the noon-midnight meridian. This produces the local time distribution of ionospheric electric fields similar to the observed result, which can be explained by the divergence of the Hall current under nonuniform ionospheric conductivity.

Electron tunneling as a basis for semiconduction in proteins

NASA Technical Reports Server (NTRS)

Flax, L.; Flood, D.

1971-01-01

Electron tunneling is investigated as a possible mechanism for the conduction of electrical current in solids composed of protein molecules. An intermolecular potential barrier is assumed which takes into account the applied electric field and the possibility of image charge effects. The WKB approximation is used to calculate the net tunneling current density and resulting conductivity. The results suggest that electron tunneling per se is not a suitable mechanism for explaining the observed conductivities in such materials.

Conductive properties of methanogenic biofilms.

PubMed

Li, Cheng; Lesnik, Keaton Larson; Liu, Hong

2018-02-01

Extracellular electron transfer between syntrophic partners needs to be efficiently maintained in methanogenic environments. Direct extracellular electron transfer via electrical current is an alternative to indirect hydrogen transfer but requires construction of conductive extracellular structures. Conductive mechanisms and relationship between conductivity and the community composition in mixed-species methanogenic biofilms are not well understood. The present study investigated conductive behaviors of methanogenic biofilms and examined the correlation between biofilm conductivity and community composition between different anaerobic biofilms enriched from the same inoculum. Highest conductivity observed in methanogenic biofilms was 71.8±4.0μS/cm. Peak-manner response of conductivity upon changes over a range of electrochemical potentials suggests that electron transfer in methanogenic biofilms occurs through redox driven super-exchange. The strong correlation observed between biofilm conductivity and Geobacter spp. in the metabolically diverse anaerobic communities suggests that the efficiency of DEET may provide pressure for microbial communities to select for species that can produce electrical conduits. Copyright © 2017 Elsevier B.V. All rights reserved.

The role of acids in electrical conduction through ice

NASA Astrophysics Data System (ADS)

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

2013-03-01

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

Sulfonated polyaniline-based organic electrodes for controlled electrical stimulation of human osteosarcoma cells.

PubMed

Min, Yong; Yang, Yanyin; Poojari, Yadagiri; Liu, Yidong; Wu, Jen-Chieh; Hansford, Derek J; Epstein, Arthur J

2013-06-10

Electrically conducting polymers (CPs) were found to stimulate various cell types such as neurons, osteoblasts, and fibroblasts in both in vitro and in vivo studies. However, to our knowledge, no studies have been reported on the utility of CPs in stimulation of cancer or tumor cells in the literature. Here we report a facile fabrication method of self-doped sulfonated polyaniline (SPAN)-based interdigitated electrodes (IDEs) for controlled electrical stimulation of human osteosarcoma (HOS) cells. Increased degree of sulfonation was found to increase the SPAN conductivity, which in turn improved the cell attachment and cell growth without electrical stimulation. However, an enhanced cell growth was observed under controlled electrical (AC) stimulation at low applied voltage and frequency (≤800 mV and ≤1 kHz). The cell growth reached a maximum threshold at an applied voltage or frequency and beyond which pronounced cell death was observed. We believe that these organic electrodes may find utility in electrical stimulation of cancer or tumor cells for therapy and research and may also provide an alternative to the conventional metal-based electrodes.

Electrical conductivity studies in (Ag3AsS3)x(As2S3)1-x superionic glasses and composites

NASA Astrophysics Data System (ADS)

Studenyak, I. P.; Neimet, Yu. Yu.; Kranjčec, M.; Solomon, A. M.; Orliukas, A. F.; Kežionis, A.; Kazakevičius, E.; Šalkus, T.

2014-01-01

Compositional, frequency, and temperature studies of impedance and electrical conductivity in (Ag3AsS3)x(As2S3)1-x superionic glasses and composites were performed. Frequency range from 10 Hz to 3 × 109 Hz and temperature interval 300-400 K were used for the measurements. Compositional dependences of electrical conductivity and activation energy are analyzed; the most substantial changes are observed with the transition from (Ag3AsS3)0.4(As2S3)0.6 glass to (Ag3AsS3)0.5(As2S3)0.5 composite. With increase of Ag3AsS3 content, the investigated materials are found to have crystalline inclusions and show the two-phase composite nature. Addition of Ag3AsS3 leads to the increase of electrical conductivity whereas the activation energy decreases.

Optical and Electrical Characteristics of Silver Ion Conducting Nanocomposite Solid Polymer Electrolytes Based on Chitosan

NASA Astrophysics Data System (ADS)

Aziz, Shujahadeen B.; Rasheed, Mariwan A.; Abidin, Zul H. Z.

2017-10-01

Optical and electrical properties of nanocomposite solid polymer electrolytes based on chitosan have been investigated. Incorporation of alumina nanoparticles into the chitosan:silver triflate (AgTf) system broadened the surface plasmon resonance peaks of the silver nanoparticles and shifted the absorption edge to lower photon energy. A clear decrease of the optical bandgap in nanocomposite samples containing alumina nanoparticles was observed. The variation of the direct-current (DC) conductivity and dielectric constant followed the same trend with alumina concentration. The DC conductivity increased by two orders of magnitude, which can be attributed to hindrance of silver ion reduction. Transmission electron microscopy was used to interpret the space-charge and blocking effects of alumina nanoparticles on the DC conductivity and dielectric constant. The ion conduction mechanism was interpreted based on the dependences of the electrical and dielectric parameters. The dependence of the DC conductivity on the dielectric constant is explained empirically. Relaxation processes associated with conductivity and viscoelasticity were distinguished based on the incomplete semicircular arcs in plots of the real and imaginary parts of the electric modulus.

Temperature profiles in the earth of importance to deep electrical conductivity models

NASA Astrophysics Data System (ADS)

Čermák, Vladimír; Laštovičková, Marcela

1987-03-01

Deep in the Earth, the electrical conductivity of geological material is extremely dependent on temperature. The knowledge of temperature is thus essential for any interpretation of magnetotelluric data in projecting lithospheric structural models. The measured values of the terrestrial heat flow, radiogenic heat production and thermal conductivity of rocks allow the extrapolation of surface observations to a greater depth and the calculation of the temperature field within the lithosphere. Various methods of deep temperature calculations are presented and discussed. Characteristic geotherms are proposed for major tectonic provinces of Europe and it is shown that the existing temperatures on the crust-upper mantle boundary may vary in a broad interval of 350 1,000°C. The present work is completed with a survey of the temperature dependence of electrical conductivity for selected crustal and upper mantle rocks within the interval 200 1,000°C. It is shown how the knowledge of the temperature field can be used in the evaluation of the deep electrical conductivity pattern by converting the conductivity-versustemperature data into the conductivity-versus-depth data.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Inhester, B.; Untiedt, J.; Segatz, M.

From two-dimensional ground magnetic and ionospheric electric field observations it should in principle be possible to estimate the two-dimensional distribution of the ionospheric conductance. The authors have developed a method to directly deduce the Hall conductance distribution {Sigma}{sub H} from ground magnetic and ionospheric electric field observations based upon some assumption for the ratio of the Hall to the Pedersen conductivity. In general, the solutions are shown not to be unique because for a specific solution the value of {Sigma}{sub H} on certain parts of the boundary of the two-dimensional domain has to be specified. However, in many situations, especiallymore » in the presence of strong and isolated field-aligned currents, these boundary values become less influential, and the solution can be shown to be practically unique over a large area of the domain. In some cases, a rather restrictive relation between the electric field and the equivalent height-integrated current density is shown to hold that could be used to cross-check the quality of the observations. As a specific example, they apply their formalism to the observation of a Harang discontinuity obtained in northern Scandinavia simultaneously by the STARE coherent radar system and the IMS Scandinavian Magnetometer Array.« less

Electrical conductivity of H2O-NaCl fluids to 10 kbar

NASA Astrophysics Data System (ADS)

Sinmyo, R.; Keppler, H.

2016-12-01

Magnetotelluric studies often reveal zones of elevated electrical conductivity in the mantle wedge above subducting slabs, in the deep crust below fold belts, or below active volcanoes. Since both aqueous fluids and hydrous silivate melts may be highly conductive, they may both account for these observations. Distinguishing between these two posssibilities, however, is difficult. One reason for this problem is that while there are very good conductivity data for silicate melts, such data do not exist for aqueous fluids under the relevant conditions of pressure, temperature and solute concentration. Most crustal and mantle fluids likely contain some NaCl, which greatly enhances conductivity due to its partial dissociation into Na+ and Cl-. We therefore studied the electrical conductivity of 0.01, 0.1 and 1 m NaCl solutions in water to 10 kbar and 600 °C. The measurements were carried out in externally-heated diamond cells containing two gaskets separated by an insulating ring of diamond, following a method described by Ni et al. (2014). The two gaskets were used as electrodes and full impedance spectra were measured from 30 Hz to 10 MHz using a Solartron 1260 impedance analyzer. Electrical conductivity was generally found to increase with pressure temperature, and fluid density. The conductivity increase observed upon variation of NaCl concentration from 0.1m to 1m was smaller than from 0.01m to 0.1m, which reflects the reduced degree of dissociation at high NaCl concentration. In general, the data show that already a very small fraction of NaCl-bearing aqueous fluid is sufficient to enhance bulk conductivities to values that would be expected for a high degree of partial melting. Accordingly, aqueous fluids may be distinguished from hydrous melts by comparing magnetotelluric and seismic data. H2O-NaCl fluids may enhance electrical conductivities with little disturbance of vp or vp/vs ratios.

Overvoltage effect on electrical discharge type in medium-conductivity water in inhomogeneous pulsed electric field

NASA Astrophysics Data System (ADS)

Panov, V. A.; Vasilyak, L. M.; Pecherkin, V. Ya; Vetchinin, S. P.; Son, E. E.

2018-01-01

The transition between thermal and streamer discharges has been observed experimentally in water solution with conductivity 100 μS/cm applying positive voltage pulses to pin-to-rod electrodes. The transition happens at five-fold pulse amplitude. Considering streamer propagation as an ionization wave helped to establish relation between the parameters governing transition from one to another discharge mechanism.

Ionosphere-magnetosphere coupling and convection

NASA Technical Reports Server (NTRS)

Wolf, R. A.; Spiro, R. W.

1984-01-01

The following international Magnetospheric Study quantitative models of observed ionosphere-magnetosphere events are reviewed: (1) a theoretical model of convection; (2) algorithms for deducing ionospheric current and electric-field patterns from sets of ground magnetograms and ionospheric conductivity information; and (3) empirical models of ionospheric conductances and polar cap potential drop. Research into magnetic-field-aligned electric fields is reviewed, particularly magnetic-mirror effects and double layers.

Associating ground magnetometer observations with current or voltage generators

NASA Astrophysics Data System (ADS)

Hartinger, M. D.; Xu, Z.; Clauer, C. R.; Yu, Y.; Weimer, D. R.; Kim, H.; Pilipenko, V.; Welling, D. T.; Behlke, R.; Willer, A. N.

2017-07-01

A circuit analogy for magnetosphere-ionosphere current systems has two extremes for drivers of ionospheric currents: ionospheric electric fields/voltages constant while current/conductivity vary—the "voltage generator"—and current constant while electric field/conductivity vary—the "current generator." Statistical studies of ground magnetometer observations associated with dayside Transient High Latitude Current Systems (THLCS) driven by similar mechanisms find contradictory results using this paradigm: some studies associate THLCS with voltage generators, others with current generators. We argue that most of this contradiction arises from two assumptions used to interpret ground magnetometer observations: (1) measurements made at fixed position relative to the THLCS field-aligned current and (2) negligible auroral precipitation contributions to ionospheric conductivity. We use observations and simulations to illustrate how these two assumptions substantially alter expectations for magnetic perturbations associated with either a current or a voltage generator. Our results demonstrate that before interpreting ground magnetometer observations of THLCS in the context of current/voltage generators, the location of a ground magnetometer station relative to the THLCS field-aligned current and the location of any auroral zone conductivity enhancements need to be taken into account.

STRUCTURE AND PHYSICAL PROPERTIES OF SOLID AND LIQUID VANADIUM PENTOXIDE.

DTIC Science & Technology

The electrical resistivity of near-stoichiometric crystalline V2O5 was measured as a function of crystal orientation and oxygen partial pressure from...25C to 300C. Conductivity is insensitive to ambient atmosphere. The activation energy for conduction is 0.20 ev. Molten V2O5 , however, is...sensitive to oxygen partial pressure. Its conductivity is proportional to P-O2 to the -1/6th power. Anomalously high electrical resistivity was observed for glassy V2O5 films. (Author)

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.

Interface interactions in benzophenone doped by multiwalled carbon nanotubes

NASA Astrophysics Data System (ADS)

Lebovka, N. I.; Goncharuk, A.; Melnyk, V. I.; Puchkovska, G. A.

2009-08-01

The interface interactions were studied by methods of conductometry, low-temperature phosphorescence and differential scanning calorimetry (DSC) in multiwalled carbon nanotubes (MWCNT) and benzophenone (BP) composite. The concentration of MWCNTs was varied within 0-1 wt%. A percolative threshold was found at MWCNT concentrations exceeding 0.1 wt%. The integration of MWCNTs caused melting temperature increase (≈3 K for 1 wt% of MWCNTs). The effect of positive thermal resistively coefficient, as well as substantial hysteretic behaviour of electrical conductivity σ in a heating-cooling cycle, was observed near the melting point of BP ( T m=321.5 K). The activation-type temperature behaviour of electrical conductivity was observed in the temperature range of supercooled BP. The activation energy was decreasing with increase of MWCNT concentration. The observed nonlinear dependencies of electrical conductivity σ vs. applied voltage U reflect the transport mechanism of the charge carriers through amorphous interface films formed near the surface of the MWCNTs. The thermal shifts of phosphorescence spectra measured within the temperature range 5-200 K evidence existence of such interface films of amorphous BP with width of the order of 0.1 μm.

Tunable electrical conductivity of individual graphene oxide sheets reduced at "low" temperatures.

PubMed

Jung, Inhwa; Dikin, Dmitriy A; Piner, Richard D; Ruoff, Rodney S

2008-12-01

Step-by-step controllable thermal reduction of individual graphene oxide sheets, incorporated into multiterminal field effect devices, was carried out at low temperatures (125-240 degrees C) with simultaneous electrical measurements. Symmetric hysteresis-free ambipolar (electron- and hole-type) gate dependences were observed as soon as the first measurable resistance was reached. The conductivity of each of the fabricated devices depended on the level of reduction (was increased more than 10(6) times as reduction progressed), strength of the external electrical field, density of the transport current, and temperature.

Hydrodynamics of spatially inhomogeneous real membranes

NASA Astrophysics Data System (ADS)

Kirii, V. A.; Shelistov, V. S.; Demekhin, E. A.

2017-07-01

Electrokinetic processes in the vicinity of inhomogeneous ion-selective surfaces (electrodes, membranes, microchannels, and nanochannels) consisting of alternating conducting and nonconducting regions in the presence of a normal-to-surface electric current are numerically studied. An increase in the electric current density is observed in the case of some particular alternation of conducting and nonconducting regions of the surface. The current-voltage characteristics of homogeneous and inhomogeneous electric membranes are found to be in qualitative agreement. Various physical phenomena leading to the emergence of a supercritical current in homogeneous and inhomogeneous membranes are detected.

Spin-dependent electrical conduction in a pentacene Schottky diode explored by electrically detected magnetic resonance

NASA Astrophysics Data System (ADS)

Fukuda, Kunito; Asakawa, Naoki

2017-02-01

Reported is the observation of dark spin-dependent electrical conduction in a Schottky barrier diode with pentacene (PSBD) using electrically detected magnetic resonance at room temperature. It is suggested that spin-dependent conduction exists in pentacene thin films, which is explored by examining the anisotropic linewidth of the EDMR signal and current density-voltage (J-V) measurements. The EDMR spectrum can be decomposed to Gaussian and Lorentzian components. The dependency of the two signals on the applied voltage was consistent with the current density-voltage (J-V) of the PSBD rather than that of the electron-only device of Al/pentacene/Al, indicating that the spin-dependent conduction is due to bipolaron formation associated with hole polaronic hopping processes. The applied-voltage dependence of the ratio of intensity of the Gaussian line to the Lorentzian may infer that increasing current density should make conducting paths more dispersive, thereby resulting in an increased fraction of the Gaussian line due to the higher dispersive g-factor.

Effects of strong earthquakes in variations of electrical and meteorological parameters of the near-surface atmosphere in Kamchatka region

NASA Astrophysics Data System (ADS)

Smirnov, S. E.; Mikhailova, G. A.; Mikhailov, Yu. M.; Kapustina, O. V.

2017-09-01

The diurnal variations in electrical (quasistatic electric field and electrical conductivity) and meteorological (temperature, pressure, relative humidity of the atmosphere, and wind speed) parameters, measured simultaneously before strong earthquakes in Kamchatka region (November 15, 2006, M = 8.3; January 13, 2007, M = 8.1; January 30, 2016, M = 7.2), are studied for the first time in detail. It is found that a successively anomalous increase in temperature, despite the negative regular trend in these winter months, was observed in the period of six-seven days before the occurrences of earthquakes. An anomalous temperature increase led to the formation of "winter thunderstorm" conditions in the near-surface atmosphere of Kamchatka region, which was manifested in the appearance of an anomalous, type 2 electrical signal, the amplification of and intensive variations in electrical conductivity, heavy precipitation (snow showers), high relative humidity of air, storm winds, and pressure changes. With the weak flow of natural heat radiation in this season, the observed dynamics of electric and meteorological processes can likely be explained by the appearance of an additional heat source of seismic nature.

An Experience of Teaching for Learning by Observation: Remote-Controlled Experiments on Electrical Circuits

ERIC Educational Resources Information Center

Kong, Siu Cheung; Yeung, Yau Yuen; Wu, Xian Qiu

2009-01-01

In order to facilitate senior primary school students in Hong Kong to engage in learning by observation of the phenomena related to electrical circuits, a design of a specific courseware system, of which the interactive human-machine interface was created with the use of an open-source software called the LabVNC, for conducting online…

Conductivity and power factor enhancement of n-type semiconducting polymers using sodium silica gel dopant

NASA Astrophysics Data System (ADS)

Madan, Deepa; Zhao, Xingang; Ireland, Robert M.; Xiao, Derek; Katz, Howard E.

2017-08-01

This work demonstrates the use of sodium silica gel (Na-SG) particles as a reducing agent for n-type conjugated polymers to improve the conductivity and thermoelectric properties. Substantial increase in the electrical conductivity (σ, from 10-7 to 10-3 S/cm in air) was observed in two naphthalenetetracarboxylic diimide solution-processable n-type polymers, one of which was designed and synthesized in our lab. Systematic investigations of electrical conductivity were done by varying the weight percentage of Na-SG in the polymers. Additional evidence for the reduction process was obtained from electron spin resonance spectroscopy and control experiments involving nonreducing silica particles and non-electron-accepting polystyrene. The Seebeck coefficient S of the highest conductivity sample was measured and found to be in agreement with an empirical model. All the electrical conductivity and Seebeck coefficients measurements were performed in ambient atmosphere.

Electrical resistivity characterization of anisotropy in the Biscayne Aquifer.

PubMed

Yeboah-Forson, Albert; Whitman, Dean

2014-01-01

Electrical anisotropy occurs when electric current flow varies with azimuth. In porous media, this may correspond to anisotropy in the hydraulic conductivity resulting from sedimentary fabric, fractures, or dissolution. In this study, a 28-electrode resistivity imaging system was used to investigate electrical anisotropy at 13 sites in the Biscayne Aquifer of SE Florida using the rotated square array method. The measured coefficient of electrical anisotropy generally ranged from 1.01 to 1.12 with values as high as 1.36 found at one site. The observed electrical anisotropy was used to estimate hydraulic anisotropy (ratio of maximum to minimum hydraulic conductivity) which ranged from 1.18 to 2.83. The largest values generally were located on the Atlantic Coastal Ridge while the lowest values were in low elevation areas on the margin of the Everglades to the west. The higher values of anisotropy found on the ridge may be due to increased dissolution rates of the oolitic facies of the Miami formation limestone compared with the bryozoan facies to the west. The predominate trend of minimum resistivity and maximum hydraulic conductivity was E-W/SE-NW beneath the ridge and E-W/SW-NE farther west. The anisotropy directions are similar to the predevelopment groundwater flow direction as indicated in published studies. This suggests that the observed anisotropy is related to the paleo-groundwater flow in the Biscayne Aquifer. © 2013, National Ground Water Association.

Electrical conductivity of old oceanic mantle in the northwestern Pacific I: 1-D profiles suggesting differences in thermal structure not predictable from a plate cooling model

NASA Astrophysics Data System (ADS)

Baba, Kiyoshi; Tada, Noriko; Matsuno, Tetsuo; Liang, Pengfei; Li, Ruibai; Zhang, Luolei; Shimizu, Hisayoshi; Abe, Natsue; Hirano, Naoto; Ichiki, Masahiro; Utada, Hisashi

2017-08-01

Seafloor magnetotelluric (MT) experiments were recently conducted in two areas of the northwestern Pacific to investigate the nature of the old oceanic upper mantle. The areas are far from any tectonic activity, and "normal" mantle structure is therefore expected. The data were carefully analyzed to reduce the effects of coastlines and seafloor topographic changes, which are significant boundaries in electrical conductivity and thus distort seafloor MT data. An isotropic, one-dimensional electrical conductivity profile was estimated for each area. The profiles were compared with those obtained from two previous study areas in the northwestern Pacific. Between the four profiles, significant differences were observed in the thickness of the resistive layer beyond expectations based on cooling of homogeneous oceanic lithosphere over time. This surprising feature is now further clarified from what was suggested in a previous study. To explain the observed spatial variation, dynamic processes must be introduced, such as influence of the plume associated with the formation of the Shatsky Rise, or spatially non-uniform, small-scale convection in the asthenosphere. There is significant room of further investigation to determine a reasonable and comprehensive interpretation of the lithosphere-asthenosphere system beneath the northwestern Pacific. The present results demonstrate that electrical conductivity provides key information for such investigation.[Figure not available: see fulltext.

Disorder induced magnetism and electrical conduction in La doped Ca2FeMoO6 double perovskite

NASA Astrophysics Data System (ADS)

Poddar, Asok; Bhowmik, R. N.; Muthuselvam, I. Panneer

2010-11-01

We report the magnetism and electrical transport properties of La doped Ca2FeMoO6 double perovskite. Reduction in magnetic moment, nonmonotonic variation in magnetic ordering temperature (TC), increasing magnetic hardness, low temperature resistivity upturn, and loss of metallic conductivity are some of the major changes that we observed due to La doping induced disorder in double perovskite structure. The increase in magnetic disorder in La doped samples and its effect on TC is more consistent with the mean field theory. The modification in electronic band structure due to La doping is understood by establishing a correlation between the temperature dependence of electrical conductivity and thermoelectric power.

Influence of dehydration on the electrical conductivity of epidote and implications for high-conductivity anomalies in subduction zones

NASA Astrophysics Data System (ADS)

Hu, Haiying; Dai, Lidong; Li, Heping; Hui, Keshi; Sun, Wenqing

2017-04-01

The anomalously high electrical conductivities ( 0.1 to 1 S/m) in deep mantle wedge regions extensively detected by magnetotelluric studies are often associated with the presence of fluids released from the progressive dehydration of subducting slabs. Epidote minerals are the Ca-Al-rich hydrous silicates with huge stability fields exceeding those of amphibole (>70-80 km) in subducting oceanic crust, and they may therefore be transported to greater depth than amphibole and release water to the mantle wedge. In this study, the electrical conductivities of epidote were measured at 0.5-1.5 GPa and 573-1273 K by using a Solartron-1260 Impedance/Gain-Phase Analyzer in a YJ-3000t multianvil pressure within the frequency range of 0.1-106 Hz. The results demonstrate that the influence of pressure on electrical conductivity of epidote is relatively small compared to that of temperature. The dehydration reaction of epidote is observed through the variation of electrical conductivity around 1073 K, and electrical conductivity reaches up to 1 S/m at 1273 K, which can be attributed to aqueous fluid released from epidote dehydration. After sample dehydration, electrical conductivity noticeably decreases by as much as nearly a log unit compared with that before dehydration, presumably due to a combination of the presence of coexisting mineral phases and aqueous fluid derived from the residual epidote. Taking into account the petrological and geothermal structures of subduction zones, it is suggested that the aqueous fluid produced by epidote dehydration could be responsible for the anomalously high conductivities in deep mantle wedges at depths of 70-120 km, particularly in hot subduction zones.

Radiofrequency ablation: importance of background tissue electrical conductivity--an agar phantom and computer modeling study.

PubMed

Solazzo, Stephanie A; Liu, Zhengjun; Lobo, S Melvyn; Ahmed, Muneeb; Hines-Peralta, Andrew U; Lenkinski, Robert E; Goldberg, S Nahum

2005-08-01

To determine whether radiofrequency (RF)-induced heating can be correlated with background electrical conductivity in a controlled experimental phantom environment mimicking different background tissue electrical conductivities and to determine the potential electrical and physical basis for such a correlation by using computer modeling. The effect of background tissue electrical conductivity on RF-induced heating was studied in a controlled system of 80 two-compartment agar phantoms (with inner wells of 0.3%, 1.0%, or 36.0% NaCl) with background conductivity that varied from 0.6% to 5.0% NaCl. Mathematical modeling of the relationship between electrical conductivity and temperatures 2 cm from the electrode (T2cm) was performed. Next, computer simulation of RF heating by using two-dimensional finite-element analysis (ETherm) was performed with parameters selected to approximate the agar phantoms. Resultant heating, in terms of both the T2cm and the distance of defined thermal isotherms from the electrode surface, was calculated and compared with the phantom data. Additionally, electrical and thermal profiles were determined by using the computer modeling data and correlated by using linear regression analysis. For each inner compartment NaCl concentration, a negative exponential relationship was established between increased background NaCl concentration and the T2cm (R2= 0.64-0.78). Similar negative exponential relationships (r2 > 0.97%) were observed for the computer modeling. Correlation values (R2) between the computer and experimental data were 0.9, 0.9, and 0.55 for the 0.3%, 1.0%, and 36.0% inner NaCl concentrations, respectively. Plotting of the electrical field generated around the RF electrode identified the potential for a dramatic local change in electrical field distribution (ie, a second electrical peak ["E-peak"]) occurring at the interface between the two compartments of varied electrical background conductivity. Linear correlations between the E-peak and heating at T2cm (R2= 0.98-1.00) and the 50 degrees C isotherm (R2= 0.99-1.00) were established. These results demonstrate the strong relationship between background tissue conductivity and RF heating and further explain electrical phenomena that occur in a two-compartment system.

Electrical Conductivity, Thermal Stability, and Lattice Defect Evolution During Cyclic Channel Die Compression of OFHC Copper

NASA Astrophysics Data System (ADS)

Satheesh Kumar, S. S.; Raghu, T.

2015-02-01

Oxygen-free high-conductivity (OFHC) copper samples are severe plastically deformed by cyclic channel die compression (CCDC) technique at room temperature up to an effective plastic strain of 7.2. Effect of straining on variation in electrical conductivity, evolution of deformation stored energy, and recrystallization onset temperatures are studied. Deformation-induced lattice defects are quantified using three different methodologies including x-ray diffraction profile analysis employing Williamson-Hall technique, stored energy based method, and electrical resistivity-based techniques. Compared to other severe plastic deformation techniques, electrical conductivity degrades marginally from 100.6% to 96.6% IACS after three cycles of CCDC. Decrease in recrystallization onset and peak temperatures is noticed, whereas stored energy increases and saturates at around 0.95-1.1J/g after three cycles of CCDC. Although drop in recrystallization activation energy is observed with the increasing strain, superior thermal stability is revealed, which is attributed to CCDC process mechanics. Low activation energy observed in CCDC-processed OFHC copper is corroborated to synergistic influence of grain boundary characteristics and lattice defects distribution. Estimated defects concentration indicated continuous increase in dislocation density and vacancy with strain. Deformation-induced vacancy concentration is found to be significantly higher than equilibrium vacancy concentration ascribed to hydrostatic stress states experienced during CCDC.

Induction signals from Callisto's ionosphere and their implications on a possible subsurface ocean

NASA Astrophysics Data System (ADS)

Hartkorn, Oliver; Saur, Joachim

2017-11-01

We investigate whether induction within Callisto's electrically conductive ionosphere can explain observed magnetic fields which have previously been interpreted as evidence of induction in a saline, electrically conductive subsurface ocean. Callisto's ionosphere is subject to the flow of time-periodic magnetized plasma of Jupiter's magnetosphere, which induces electric fields and electric currents in Callisto's electrically conductive ionosphere. We develop a simple analytic model for a first quantitative understanding of the effects of induction in Callisto's ionosphere caused by the interaction with a time-variable magnetic field environment. With this model, we also investigate how the associated ionospheric currents close in the ambient magnetospheric plasma. Based on our model, we find that the anisotropic nature of Callisto's ionospheric conductivity generates an enhancement effect on ionospheric loop currents which are driven by the time-variable magnetic field. This effect is similar to the Cowling channel effect known from Earth's ionosphere. Subsequently, we numerically calculate the expected induced magnetic fields due to Jupiter's time-variable magnetic field in an anisotropic conductive ionosphere and compare our results with the Galileo C-3 and C-9 flybys. We find that induction within Callisto's ionosphere is responsible for a significant part of the observed magnetic fields. Ionospheric induction creates induced magnetic fields to some extent similar as expected from a subsurface water ocean. Depending on currently unknown properties such as Callisto's nightside ionosphere, the existence of layers of "dirty ice" and the details of the plasma interaction, a water ocean might be located much deeper than previously thought or might not exist at all.

Electrically conductive borate-based bioactive glass scaffolds for bone tissue engineering applications.

PubMed

Turk, Mert; Deliormanlı, Aylin M

2017-07-01

In this study, electrically conductive, borate-based, porous 13-93B3 bioactive glass composite scaffolds were prepared using a polymer foam replication technique. For this purpose, a slurry containing 40 vol% glass particles and 0-10 wt% graphene nanoplatelets was prepared by dispersing the particles in ethanol in the presence of ethyl cellulose. Composite scaffolds were subjected to a controlled heat treatment, in air atmosphere, to decompose the foam and sinter the glass particles into a dense network. It was found that the applied heat treatment did not influence the structure of graphene in the glass network. Graphene additions did not negatively affect the mechanical properties and enhanced the electrical conductivity of the glass scaffolds. In X-ray diffraction analysis, the crystalline peak corresponding to hydroxyapatite was observed in all the samples suggesting that all of the samples were bioactive after 30 days of immersion in simulated body fluid. However, Fourier transform infrared spectroscopy analysis and scanning electron microscope observations revealed that hydroxyapatite formation rate decreased with increasing graphene concentration especially for samples treated in simulated body fluid for shorter times. Based on the cytotoxicity assay findings, the MC3T3-E1 cell growth was significantly inhibited by the scaffolds containing higher amount of graphene compared to bare glass scaffolds. Best performance was obtained for 5 wt% graphene which yielded an enhancement of electrical conductivity with moderate cellular response and in vitro hydroxyapatite forming ability. The study revealed that the electrically conductive 13-93B3 graphene scaffolds are promising candidates for bone tissue engineering applications.

Research on a haptic sensor made using MCF conductive rubber

NASA Astrophysics Data System (ADS)

Zheng, Yaoyang; Shimada, Kunio

2008-05-01

To provide a new composite material having a high electrical sensitivity in the fields of robotics and sensing, a magnetic rubber having network-like magnetic clusters was developed by utilizing a magnetic compound fluid (MCF). MCF rubber with small deformations can provide an effective sensor. In this paper, we report many experiments in which changes of the MCF rubber's resistance were observed when the rubber was compressed and a deformation was generated; we then made a trial haptic sensor using the MCF conductive rubber and performed many experiments to observe changes of the electrical resistance of the sensor. The results of experiments showed that the proposed sensor made with MCF conductive rubber is useful for sensing small amounts of pressure or small deformations.

Research on a haptic sensor made using MCF conductive rubber.

PubMed

Zheng, Yaoyang; Shimada, Kunio

2008-05-21

To provide a new composite material having a high electrical sensitivity in the fields of robotics and sensing, a magnetic rubber having network-like magnetic clusters was developed by utilizing a magnetic compound fluid (MCF). MCF rubber with small deformations can provide an effective sensor. In this paper, we report many experiments in which changes of the MCF rubber's resistance were observed when the rubber was compressed and a deformation was generated; we then made a trial haptic sensor using the MCF conductive rubber and performed many experiments to observe changes of the electrical resistance of the sensor. The results of experiments showed that the proposed sensor made with MCF conductive rubber is useful for sensing small amounts of pressure or small deformations.

Influence of Electrical and Ionic Conductivities of Organic Electronic Ion Pump on Acetylcholine Exchange Performance

PubMed Central

Abdullayeva, Nazrin; Sankir, Mehmet

2017-01-01

By using an easy and effective method of depositing conjugated polymers (PEDOT:PSS) on flexible substrates, a new design for organic bioelectronic devices has been developed. The purpose was to build up a system that mimics the motion of neurotransmitters in the synaptic cleft by obtaining an electrical to chemical signal transport. Fourier transform infrared (FTIR) spectroscopy and Raman measurements have demonstrated that electrochemical overoxidation region which separates the pristine PEDOT:PSS electrodes and allows ionic conduction has been achieved successfully. The influence of both electrical and ionic conductivities on organic electronic ion pump (OEIP) performances has been studied. The ultimate goal was to achieve the highest equilibrium current density at the lowest applied voltage via enhancing the electrical conductivity of PEDOT:PSS and ionic conductivity of electrochemically overoxidized region. The highest equilibrium current density, which corresponds to 4.81 × 1017 number of ions of acetylcholine was about 41 μA cm−2 observed for the OEIP with the electrical conductivities of 54 S cm−1. This was a threshold electrical conductivity beyond which the OEIP performances were not changed much. Once Nafion™ has been applied for enhancing the ionic conductivity, the equilibrium current density increased about ten times and reached up to 408 μA cm−2. Therefore, it has been demonstrated that the OEIP performance mainly scales with the ionic conductivity. A straightforward method of producing organic bioelectronics is proposed here may provide a clue for their effortless mass production in the near future. PMID:28772946

Electrical Properties of Bismuth/Lithium-Cosubstituted Strontium Titanate Ceramics

NASA Astrophysics Data System (ADS)

Alkathy, Mahmoud. S.; James Raju, K. C.

2018-03-01

Sr(1-x)(Bi,Li) x TiO3 compound was prepared via a solid-state reaction route with microwave heating of the starting materials. X-ray diffraction analysis revealed pure perovskite phase without formation of any secondary phases. The electrical conductivity was studied as a function of temperature and frequency. The experimental results indicate that the alternating-current (AC) conductivity increased with frequency, following the Jonscher power law. To interpret the possible mechanism for electrical conduction, the correlated barrier hopping model was applied. The effect of temperature and the Bi/Li concentration on the electrical resistivity was studied. The results showed that the electrical resistivity decreased with increasing temperature, which could be due to increased thermal energy of electrons. Also, the electrical resistivity decreased with increase in the amount of Bi and Li, which could be due to increased concentration of structural defects, which could increase the number of either electrons or holes available for conduction. A single semicircular arc corresponding to a single relaxation process was observed for all the investigated ceramics, suggesting a grain contribution to the total resistance in these materials. Arrhenius plots were used to obtain the activation energy for the samples.

Electrical Properties of Bismuth/Lithium-Cosubstituted Strontium Titanate Ceramics

NASA Astrophysics Data System (ADS)

Alkathy, Mahmoud. S.; James Raju, K. C.

2018-07-01

Sr(1- x)(Bi,Li) x TiO3 compound was prepared via a solid-state reaction route with microwave heating of the starting materials. X-ray diffraction analysis revealed pure perovskite phase without formation of any secondary phases. The electrical conductivity was studied as a function of temperature and frequency. The experimental results indicate that the alternating-current (AC) conductivity increased with frequency, following the Jonscher power law. To interpret the possible mechanism for electrical conduction, the correlated barrier hopping model was applied. The effect of temperature and the Bi/Li concentration on the electrical resistivity was studied. The results showed that the electrical resistivity decreased with increasing temperature, which could be due to increased thermal energy of electrons. Also, the electrical resistivity decreased with increase in the amount of Bi and Li, which could be due to increased concentration of structural defects, which could increase the number of either electrons or holes available for conduction. A single semicircular arc corresponding to a single relaxation process was observed for all the investigated ceramics, suggesting a grain contribution to the total resistance in these materials. Arrhenius plots were used to obtain the activation energy for the samples.

Transport, electronic, and structural properties of nanocrystalline CuAlO2 delafossites

NASA Astrophysics Data System (ADS)

Durá, O. J.; Boada, R.; Rivera-Calzada, A.; León, C.; Bauer, E.; de la Torre, M. A. López; Chaboy, J.

2011-01-01

This work reports on the effect of grain size on the electrical, thermal, and structural properties of CuAlO2 samples obtained by solid-state reaction combined with ball milling. Electrical characterization made in microcrystalline and nanocrystalline samples shows that the electrical conductivity decreases several orders of magnitude for the nanocrystalline samples, and, in addition, there is a large discrepancy between the activation energies associated to thermoelectric power ES. The study of the Cu K-edge x-ray absorption spectra of the CuAlO2 samples shows that the local structure around Cu is preserved after the sintering process, indicating that the observed behavior of the electrical conductivity is of intrinsic origin. Complex conductivity measurements as a function of frequency allow us to discard grain-boundaries effects on the electrical transport. Thus, the changes in σ(T) and S(T) are interpreted in terms of charge localization in the framework of small polarons. This is in agreement with the analysis of the near-edge region of the absorption spectra, which indicates that sintering favors the Cu-O hybridization. As a consequence, oxygen atoms progressively lose their capability of trapping holes, and the electrical conductivity is also enhanced.

Geoelectrical investigation of oil contaminated soils in former underground fuel base: Borne Sulinowo, NW Poland

NASA Astrophysics Data System (ADS)

Zogala, B.; Dubiel, R.; Zuberek, W. M.; Rusin-Zogala, M.; Steininger, M.

2009-07-01

The survey has been carried out in the area of 0.23 km2 of the former military underground fuel base. The oil derivative products were observed in excavations and the laboratory tests confirmed the occurrence of hydrocarbons (>C12) in soils. The purpose of the survey was to determine the spatial extent of the contamination. The studied area is covered by postglacial sediments: sands, gravels and till. The first water table was observed at a depth of 10-12 m. The detailed electromagnetic measurements with Geonics EM31-MK2 conductivity meter were performed in the whole area of the former fuel base. Obtained results were elaborated statistically and the map of apparent electrical conductivity to a depth of 6 m was created. Many local low conductivity anomalies were observed. The measurements with Geonics EM34-3XL were performed along one A-A' profile and 1D electromagnetic modelling along with this profile was calculated to obtain the electrical conductivity cross-section to a depth of 30 m. Two-dimensional electrical resistivity imaging measurements were carried out along the same profile and the resistivity cross-section to a depth of 20 m was performed. Both conducivity and resistivity cross-sections show anomalous zones. The zones correlate with oil contaminated zones very well.

CNT fibers p-doped with F4TCNQ (2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane)

NASA Astrophysics Data System (ADS)

Lepak, Sandra; Boncel, Sławomir; Jóźwik, Iwona; Jakubowska, Małgorzata; Koziol, Krzysztof; Łekawa-Raus, Agnieszka

2017-08-01

Films and fibers made of carbon nanotubes were found to be promising materials for future electrical and electronic engineering. Despite of many advantages provided by these materials, they are not without problems. The biggest issue is that the macroscopic CNT structures, such as films or fibers, have much lower electrical conductivity values than it is for individual carbon nanotubes. And therefore researchers worldwide try to increase electrical properties of those macroscopic structures. One of the approaches scientists are currently investigating is chemical doping. Despite chemical doping has been already reported there is still a huge list of compounds that are capable to increase the conductivity values and has not been tested yet. In this work one of such compounds has been examined. It is a strong p-dopant 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). The solution of F4TCNQ in three different solvents (chloroform, acetic acid and dimethylsulfoxide) has been prepared and applied on purified CNT films. Both electrical conductivity and specific conductivity was measured. The best electrical conductivity value achieved is 5,24·106 S·m-1. Samples were also observed under SEM.

Melting Inside the Tibetan Crust? Constraint From Electrical Conductivity of Peraluminous Granitic Melt

NASA Astrophysics Data System (ADS)

Guo, Xuan; Zhang, Li; Su, Xue; Mao, Zhu; Gao, Xiao-Ying; Yang, Xiaozhi; Ni, Huaiwei

2018-05-01

Magnetotelluric and seismological studies suggested the presence of partial melts in the middle to lower Himalaya-Tibetan crust. However, the melt fractions inferred by previous work were based on presumed electrical conductivity of melts. We performed measurements on the electrical conductivity of peraluminous granitic melts with 0.16-8.4 wt % H2O (the expected compositions in the Tibetan crust) at 600-1,300°C and 0.5-1.0 GPa. Peraluminous melt exhibits lower electrical conductivity than peralkaline melt at dry condition, but this difference diminishes at H2O > 2 wt %. With our data, the observed electrical anomalies in the Tibetan crust could be explained by 2-33 vol % of peraluminous granitic melts with H2O > 6 wt %. Possible reasons for our inferred melt fractions being higher than seismological constraints include the following: (1) The real melts are more Na and H2O rich, (2) the effect of melt reducing seismic velocities was overestimated, and (3) the anomalies at some locations are due to fluids.

Growth of carbon nanotubes in arc plasma treated graphite disc: microstructural characterization and electrical conductivity study

NASA Astrophysics Data System (ADS)

Nayak, B. B.; Sahu, R. K.; Dash, T.; Pradhan, S.

2018-03-01

Circular graphite discs were treated in arc plasma by varying arcing time. Analysis of the plasma treated discs by field emission scanning electron microscope revealed globular grain morphologies on the surfaces, but when the same were observed at higher magnification and higher resolution under transmission electron microscope, growth of multiwall carbon nanotubes of around 2 nm diameter was clearly seen. In situ growth of carbon nanotube bundles/bunches consisting of around 0.7 nm tube diameter was marked in the case of 6 min treated disc surface. Both the untreated and the plasma treated graphite discs were characterized by X-ray diffraction, energy dispersive spectra of X-ray, X-ray photoelectron spectroscopy, transmission electron microscopy, micro Raman spectroscopy and BET surface area measurement. From Raman spectra, BET surface area and microstructure observed in transmission electron microscope, growth of several layers of graphene was identified. Four-point probe measurements for electrical resistivity/conductivity of the graphite discs treated under different plasma conditions showed significant increase in conductivity values over that of untreated graphite conductivity value and the best result, i.e., around eightfold increase in conductivity, was observed in the case of 6 min plasma treated sample exhibiting carbon nanotube bundles/bunches grown on disc surface. By comparing the microstructures of the untreated and plasma treated graphite discs, the electrical conductivity increase in graphite disc is attributed to carbon nanotubes (including bundles/bunches) growth on disc surface by plasma treatment.

Electron microscopy analyses and electrical properties of the layered Bi{sub 2}WO{sub 6} phase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taoufyq, A.; Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106, Cité Dakhla, Agadir, Maroc; Département d‘Études des Réacteurs, Laboratoire Dosimétrie Capteurs Instrumentation, CEA Cadarache

2013-07-15

The bismuth tungstate Bi{sub 2}WO{sub 6} was synthesized using a classical coprecipitation method followed by a calcination process at different temperatures. The samples were characterized by X-ray diffraction, simultaneous thermogravimetry and differential thermal analysis (TGA/DTA), scanning and transmission electron microscopy (SEM, TEM) analyses. The Rietveld analysis and electron diffraction clearly confirmed the Pca2{sub 1} non centrosymmetric space group previously proposed for this phase. The layers Bi{sub 2}O{sub 2}{sup 2+} and WO{sub 4}{sup 2−} have been directly evidenced from the HRTEM images. The electrical properties of Bi{sub 2}WO{sub 6} compacted pellets systems were determined from electrical impedance spectrometry (EIS) and directmore » current (DC) analyses, under air and argon, between 350 and 700 °C. The direct current analyses showed that the conduction observed from EIS analyses was mainly ionic in this temperature range, with a small electronic contribution. Electrical change above the transition temperature of 660 °C is observed under air and argon atmospheres. The strong conductivity increase observed under argon is interpreted in terms of formation of additional oxygen vacancies coupled with electron conduction. - Graphical abstract: High resolution transmission electron microscopy: inverse fast Fourier transform giving the layered structure of the Bi{sub 2}WO{sub 6} phase, with a representation of the cell dimensions (b and c vectors). The Bi{sub 2}O{sub 2}{sup 2+} and WO{sub 4}{sup 2−} sandwiches are visible in the IFFT image. - Highlights: • Using transmission electron microscopy, we visualize the layered structure of Bi{sub 2}WO{sub 6}. • Electrical analyses under argon gas show some increase in conductivity. • The phase transition at 660 °C is evidenced from electrical modification.« less

Electrical and thermal conductance quantization in nanostructures

NASA Astrophysics Data System (ADS)

Nawrocki, Waldemar

2008-10-01

In the paper problems of electron transport in mesoscopic structures and nanostructures are considered. The electrical conductance of nanowires was measured in a simple experimental system. Investigations have been performed in air at room temperature measuring the conductance between two vibrating metal wires with standard oscilloscope. Conductance quantization in units of G0 = 2e2/h = (12.9 kΩ)-1 up to five quanta of conductance has been observed for nanowires formed in many metals. The explanation of this universal phenomena is the formation of a nanometer-sized wire (nanowire) between macroscopic metallic contacts which induced, due to theory proposed by Landauer, the quantization of conductance. Thermal problems in nanowires are also discussed in the paper.

The effect of defects produced by electron irradiation on the electrical properties of graphene and MoS2

NASA Astrophysics Data System (ADS)

Rodriguez-Manzo, Julio Alejandro; Balan, Adrian; Nayor, Carl; Parkin, Will; Puster, Matthew; Johnson, A. T. Charlie; Drndic, Marija

2015-03-01

We present a study of the effects of the defects produced by electron irradiation on the electrical and crystalline properties of graphene and MoS2 monolayers. We realized back or side gated electrical devices from monolayer MoS2 or graphene crystals (triangles respectively hexagons) suspended on a 50nm SiNx m. The devices are exposed to electron irradiation inside a 200kV transmission electron microscope (TEM) and we perform in situ conductance measurements. The number of defects and the quality of the crystalline lattice obtained by diffraction are correlated with the observed decrease in mobility and conductivity of the devices. We observe a different behavior between MoS2 and graphene, and try to associate this with different models for conduction with defects. Finally, we use the TEM electron beam to tailor the macroscopic layers into ribbons to be used as the sensing element in MoS2 nanoribbon - nanopore devices for DNA detection and sequencing.

ZnGeSb2: a promising thermoelectric material with tunable ultra-high conductivity.

PubMed

Sreeparvathy, P C; Kanchana, V; Vaitheeswaran, G; Christensen, N E

2016-09-21

First principles calculations predict the promising thermoelectric material ZnGeSb 2 with a huge power factor (S 2 σ/τ) on the order of 3 × 10 17 W m -1 K -2 s -1 , due to the ultra-high electrical conductivity scaled by a relaxation time of around 8.5 × 10 25 Ω -1 m -1 s -1 , observed in its massive Dirac state. The observed electrical conductivity is higher than the well-established Dirac materials, and is almost carrier concentration independent with similar behaviour of both n and p type carriers, which may certainly attract device applications. The low range of thermal conductivity is also evident from the phonon dispersion. Our present study further reports the gradual phase change of ZnGeSb 2 from a normal semiconducting state, through massive Dirac states, to a topological semi-metal. The maximum power factor is observed in the massive Dirac states compared to the other two states.

Pulsed Laser Deposition of High Temperature Protonic Films

NASA Technical Reports Server (NTRS)

Dynys, Fred W.; Berger, M. H.; Sayir, Ali

2006-01-01

Pulsed laser deposition has been used to fabricate nanostructured BaCe(0.85)Y(0.15)O3- sigma) films. Protonic conduction of fabricated BaCe(0.85)Y(0.15)O(3-sigma) films was compared to sintered BaCe(0.85)Y(0.15)O(3-sigma). Sintered samples and laser targets were prepared by sintering BaCe(0.85)Y(0.15)O(3-sigma) powders derived by solid state synthesis. Films 1 to 8 micron thick were deposited by KrF excimer laser on porous Al2O3 substrates. Thin films were fabricated at deposition temperatures of 700 to 950 C at O2 pressures up to 200 mTorr using laser pulse energies of 0.45 - 0.95 J. Fabricated films were characterized by X-ray diffraction, electron microscopy and electrical impedance spectroscopy. Single phase BaCe(0.85)Y(0.15)O(3-sigma) films with a columnar growth morphology are observed with preferred crystal growth along the [100] or [001] direction. Results indicate [100] growth dependence upon laser pulse energy. Electrical conductivity of bulk samples produced by solid state sintering and thin film samples were measured over a temperature range of 100 C to 900 C. Electrical conduction behavior was dependent upon film deposition temperature. Maximum conductivity occurs at deposition temperature of 900 oC; the electrical conductivity exceeds the sintered specimen. All other deposited films exhibit a lower electrical conductivity than the sintered specimen. Activation energy for electrical conduction showed dependence upon deposition temperature, it varied

Correlation between magnetic and electric field perturbations in the field-aligned current regions deduced from DE 2 observations

NASA Technical Reports Server (NTRS)

Ishii, M.; Sugiura, M.; Iyemori, T.; Slavin, J. A.

1992-01-01

The satellite-observed high correlations between magnetic and electric field perturbations in the high-latitude field-aligned current regions are investigated by examining the dependence of the relationship between Delta-B and E on spatial scale, using the electric and magnetic field data obtained by DE 2 in the polar regions. The results are compared with the Pedersen conductivity inferred from the international reference ionosphere model and the Alfven wave velocity calculated from the in situ ion density and magnetic field measurements.

Discharge current distribution in stratified soil under impulse discharge

NASA Astrophysics Data System (ADS)

Eniola Fajingbesi, Fawwaz; Shahida Midi, Nur; Elsheikh, Elsheikh M. A.; Hajar Yusoff, Siti

2017-06-01

The mobility of charge particles traversing a material defines its electrical properties. Soil (earth) have long been the universal grounding before and after the inception of active ground systems for electrical appliance purpose due to it semi-conductive properties. The soil can thus be modelled as a single material exhibiting semi-complex inductive-reactive impedance. Under impulse discharge such as lightning strikes to soil this property of soil could result in electric potential level fluctuation ranging from ground potential rise/fall to electromagnetic pulse coupling that could ultimately fail connected electrical appliance. In this work we have experimentally model the soil and lightning discharge using point to plane electrode setup to observe the current distribution characteristics at different soil conductivity [mS/m] range. The result presented from this research indicate above 5% shift in conductivity before and after discharge which is significant for consideration when dealing with grounding designs. The current distribution in soil have also be successfully observed and analysed from experimental result using mean current magnitude in relation to electrode distance and location, current density variation with depth all showing strong correlation with theoretical assumptions of a semi-complex impedance material.

Effect of high energy ions on the electrical and morphological properties of Poly(3-Hexylthiophene) (P3HT) thin film

NASA Astrophysics Data System (ADS)

Sharma, Trupti; Singhal, R.; Vishnoi, R.; Sharma, G. D.; Biswas, S. K.

2018-05-01

The spin-coated thin films of Poly(3-Hexylthiophene) (P3HT) on the glass and Si (double side polished) substrates have been irradiated with 55 MeV Si+4 swift heavy ions (SHI) at fluences in the range from 1 × 1010 to 1 × 1012 ions/cm2. Structural modifications produced by energetic ions are observed by characterization of pristine and irradiated P3HT thin films. Different techniques like high-resolution X-ray diffraction (HR-XRD), micro-Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) were used to analyze the structural changes in the material. A significant increase in crystallinity and room temperature electrical conductivity of P3HT film has been detected on exposure to the heavy ions. The observed increase in the electrical conductivity with increased fluences is explained in the light of improved ordering of polymer chains after irradiation. Mott's variable range hopping model has been used to explain the conduction mechanism in the material in the temperature range of 230-350 K. The modification in surface properties also observed using AFM analysis and contact angle measurement. It is observed that nature of the P3HT thin films remains hydrophobic after irradiation.

Metamaterial Behavior of Polymer Nanocomposites Based on Polypropylene/Multi-Walled Carbon Nanotubes Fabricated by Means of Ultrasound-Assisted Extrusion

PubMed Central

Pérez-Medina, Juan C.; Waldo-Mendoza, Miguel A.; Cruz-Delgado, Víctor J.; Quiñones-Jurado, Zoe V.; González-Morones, Pablo; Ziolo, Ronald F.; Martínez-Colunga, Juan G.; Soriano-Corral, Florentino; Avila-Orta, Carlos A.

2016-01-01

Metamaterial behavior of polymer nanocomposites (NCs) based on isotactic polypropylene (iPP) and multi-walled carbon nanotubes (MWCNTs) was investigated based on the observation of a negative dielectric constant (ε′). It is demonstrated that as the dielectric constant switches from negative to positive, the plasma frequency (ωp) depends strongly on the ultrasound-assisted fabrication method, as well as on the melt flow index of the iPP. NCs were fabricated using ultrasound-assisted extrusion methods with 10 wt % loadings of MWCNTs in iPPs with different melt flow indices (MFI). AC electrical conductivity (σ(AC)) as a function of frequency was determined to complement the electrical classification of the NCs, which were previously designated as insulating (I), static-dissipative (SD), and conductive (C) materials. It was found that the SD and C materials can also be classified as metamaterials (M). This type of behavior emerges from the negative dielectric constant observed at low frequencies although, at certain frequencies, the dielectric constant becomes positive. Our method of fabrication allows for the preparation of metamaterials with tunable ωp. iPP pure samples show only positive dielectric constants. Electrical conductivity increases in all cases with the addition of MWCNTs with the largest increases observed for samples with the highest MFI. A relationship between MFI and the fabrication method, with respect to electrical properties, is reported. PMID:28774042

Dislocation structures and electrical conduction properties of low angle tilt grain boundaries in LiNbO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Furushima, Yuho; Nakamura, Atsutomo, E-mail: nakamura@numse.nagoya-u.ac.jp; Toyoura, Kazuaki

Dislocations in crystalline materials constitute unique, atomic-scale, one-dimensional structure and have a potential to induce peculiar physical properties that are not found in the bulk. In this study, we fabricated LiNbO{sub 3} bicrystals with low angle tilt grain boundaries and investigated the relationship between the atomic structure of the boundary dislocations and their electrical conduction properties. Observations by using transmission electron microscopy revealed that dislocation structures at the (0001) low angle tilt grain boundaries depend on the tilt angle of the boundaries. Specifically, the characteristic dislocation structures with a large Burgers vector were formed in the boundary with the tiltmore » angle of 2°. It is noteworthy that only the grain boundary of 2° exhibits distinct electrical conductivity after reduction treatment, although LiNbO{sub 3} is originally insulating. This unique electrical conductivity is suggested to be due to the characteristic dislocation structures with a large Burgers vector.« less

Electrical modulus and dielectric behavior of Cr3+ substituted Mg-Zn nanoferrites

NASA Astrophysics Data System (ADS)

Mansour, S. F.; Abdo, M. A.

2017-04-01

The dielectric parameters and ac electrical conductivity of Mg0.8Zn0.2CrxFe2-xO4; (0≤x≤0.025) nanoferrites synthesized citrate-nitrate auto-combustion method were studied using the complex impedance technique in the frequency and temperature ranges 4 Hz-5 MHz and 303-873 K respectively. Hopping of charge carriers plus interfacial polarization could interpret the behaviors of dielectric constant (ε‧), dielectric loss tangent (tanδ) and ac electrical conductivity (σac) with frequency, temperatures and composition. The up-normal behavior observed in tanδ trend with temperatures confirms the presence of relaxation loss (dipoles losses). Correlated barrier hopping (CBH) of electron is the conduction mechanism of the investigated nanoferrites. Cole-Cole plots at different temperatures emphasize the main role of grain and grain boundaries in the properties of the investigated nanoferrites. Cr3+ substitution can control the dielectric parameters and ac electrical conductivity of Mg-Zn nanoferrites making it candidates for versatile applications.

Modulation of electrical potential and conductivity in an atomic-layer semiconductor heterojunction

PubMed Central

Kobayashi, Yu; Yoshida, Shoji; Sakurada, Ryuji; Takashima, Kengo; Yamamoto, Takahiro; Saito, Tetsuki; Konabe, Satoru; Taniguchi, Takashi; Watanabe, Kenji; Maniwa, Yutaka; Takeuchi, Osamu; Shigekawa, Hidemi; Miyata, Yasumitsu

2016-01-01

Semiconductor heterojunction interfaces have been an important topic, both in modern solid state physics and in electronics and optoelectronics applications. Recently, the heterojunctions of atomically-thin transition metal dichalcogenides (TMDCs) are expected to realize one-dimensional (1D) electronic systems at their heterointerfaces due to their tunable electronic properties. Herein, we report unique conductivity enhancement and electrical potential modulation of heterojunction interfaces based on TMDC bilayers consisted of MoS2 and WS2. Scanning tunneling microscopy/spectroscopy analyses showed the formation of 1D confining potential (potential barrier) in the valence (conduction) band, as well as bandgap narrowing around the heterointerface. The modulation of electronic properties were also probed as the increase of current in conducting atomic force microscopy. Notably, the observed band bending can be explained by the presence of 1D fixed charges around the heterointerface. The present findings indicate that the atomic layer heterojunctions provide a novel approach to realizing tunable 1D electrical potential for embedded quantum wires and ultrashort barriers of electrical transport. PMID:27515115

Effects of functionalization on thermal properties of single-wall and multi-wall carbon nanotube-polymer nanocomposites.

PubMed

Gulotty, Richard; Castellino, Micaela; Jagdale, Pravin; Tagliaferro, Alberto; Balandin, Alexander A

2013-06-25

Carboxylic functionalization (-COOH groups) of carbon nanotubes is known to improve their dispersion properties and increase the electrical conductivity of carbon-nanotube-polymer nanocomposites. We have studied experimentally the effects of this type of functionalization on the thermal conductivity of the nanocomposites. It was found that while even small quantities of carbon nanotubes (~1 wt %) can increase the electrical conductivity, a larger loading fraction (~3 wt %) is required to enhance the thermal conductivity of nanocomposites. Functionalized multi-wall carbon nanotubes performed the best as filler material leading to a simultaneous improvement of the electrical and thermal properties of the composites. Functionalization of the single-wall carbon nanotubes reduced the thermal conductivity enhancement. The observed trends were explained by the fact that while surface functionalization increases the coupling between carbon nanotube and polymer matrix, it also leads to formation of defects, which impede the acoustic phonon transport in the single-wall carbon nanotubes. The obtained results are important for applications of carbon nanotubes and graphene flakes as fillers for improving thermal, electrical and mechanical properties of composites.

Physics of a novel magnetic resonance and electrical impedance combination for breast cancer diagnosis

NASA Astrophysics Data System (ADS)

Kallergi, Maria; Heine, John J.; Wollin, Ernest

2015-03-01

A new technique is proposed and experimentally validated for breast cancer detection and diagnosis. The technique combines magnetic resonance with electrical impedance measurements and has the potential to increase the specificity of magnetic resonance mammography (MRM) thereby reducing false positive biopsy rates. The new magnetic resonance electrical impedance mammography (MREIM) adds a time varying electric field during a supplementary sequence to a standard MRM examination with an apparatus that is "invisible" to the patient. The applied electric field produces a current that creates an additional magnetic field with a component aligned with the bore magnetic field that can alter the native signal in areas of higher electrical conductivity. The justification for adding the electric field is that the electrical conductivity of cancerous breast tissue is approximately 3-40 times higher than normal breast tissue and, hence, conductivity of malignant tissue represents a known clinical disease biomarker. In a pilot study with custom-made phantoms and experimental protocols, it was demonstrated that MREIM can produce, as theoretically predicted, a detectable differential signal in areas of higher electrical conductivity (tumor surrogate regions); the evidence indicates that the differential signal is produced by the confluence of two different effects at full image resolution without gadolinium chelate contrast agent injection, without extraneous reconstruction techniques, and without cumbersome multi-positioned patient electrode configurations. This paper describes the theoretical model that predicts and explains the observed experimental results that were also confirmed by simulation studies.

Microbial community structure in a shallow hydrocarbon-contaminated aquifer associated with high electrical conductivity

NASA Astrophysics Data System (ADS)

Duris, J. W.; Rossbach, S.; Atekwana, E. A.; Werkema, D., Jr.

2003-04-01

Little is known about the complex interactions between microbial communities and electrical properties in contaminated aquifers. In order to investigate possible connections between these parameters a study was undertaken to investigate the hypothesis that the degradation of hydrocarbons by resident microbial communities causes a local increase in organic acid concentrations, which in turn cause an increase in native mineral weathering and a concurrent increase in the bulk electrical conductivity of soil. Microbial community structure was analyzed using a 96-well most probable number (MPN) method and rDNA intergenic spacer region analysis (RISA). Microbial community structure was found to change in the presence of hydrocarbon contaminants and these changes were consistently observed in regions of high electrical conductivity. We infer from this relationship that geophysical methods for monitoring the subsurface are a promising new technology for monitoring changes in microbial community structure and simultaneous changes in geochemistry that are associated with hydrocarbon degradation.

Direct geoelectrical evidence of mass transfer at the laboratory scale

NASA Astrophysics Data System (ADS)

Swanson, Ryan D.; Singha, Kamini; Day-Lewis, Frederick D.; Binley, Andrew; Keating, Kristina; Haggerty, Roy

2012-10-01

Previous field-scale experimental data and numerical modeling suggest that the dual-domain mass transfer (DDMT) of electrolytic tracers has an observable geoelectrical signature. Here we present controlled laboratory experiments confirming the electrical signature of DDMT and demonstrate the use of time-lapse electrical measurements in conjunction with concentration measurements to estimate the parameters controlling DDMT, i.e., the mobile and immobile porosity and rate at which solute exchanges between mobile and immobile domains. We conducted column tracer tests on unconsolidated quartz sand and a material with a high secondary porosity: the zeolite clinoptilolite. During NaCl tracer tests we collected nearly colocated bulk direct-current electrical conductivity (σb) and fluid conductivity (σf) measurements. Our results for the zeolite show (1) extensive tailing and (2) a hysteretic relation between σf and σb, thus providing evidence of mass transfer not observed within the quartz sand. To identify best-fit parameters and evaluate parameter sensitivity, we performed over 2700 simulations of σf, varying the immobile and mobile domain and mass transfer rate. We emphasized the fit to late-time tailing by minimizing the Box-Cox power transformed root-mean square error between the observed and simulated σf. Low-field proton nuclear magnetic resonance (NMR) measurements provide an independent quantification of the volumes of the mobile and immobile domains. The best-fit parameters based on σf match the NMR measurements of the immobile and mobile domain porosities and provide the first direct electrical evidence for DDMT. Our results underscore the potential of using electrical measurements for DDMT parameter inference.

Direct geoelectrical evidence of mass transfer at the laboratory scale

USGS Publications Warehouse

Swanson, Ryan D.; Singha, Kamini; Day-Lewis, Frederick D.; Binley, Andrew; Keating, Kristina; Haggerty, Roy

2012-01-01

Previous field-scale experimental data and numerical modeling suggest that the dual-domain mass transfer (DDMT) of electrolytic tracers has an observable geoelectrical signature. Here we present controlled laboratory experiments confirming the electrical signature of DDMT and demonstrate the use of time-lapse electrical measurements in conjunction with concentration measurements to estimate the parameters controlling DDMT, i.e., the mobile and immobile porosity and rate at which solute exchanges between mobile and immobile domains. We conducted column tracer tests on unconsolidated quartz sand and a material with a high secondary porosity: the zeolite clinoptilolite. During NaCl tracer tests we collected nearly colocated bulk direct-current electrical conductivity (σb) and fluid conductivity (σf) measurements. Our results for the zeolite show (1) extensive tailing and (2) a hysteretic relation between σf and σb, thus providing evidence of mass transfer not observed within the quartz sand. To identify best-fit parameters and evaluate parameter sensitivity, we performed over 2700 simulations of σf, varying the immobile and mobile domain and mass transfer rate. We emphasized the fit to late-time tailing by minimizing the Box-Cox power transformed root-mean square error between the observed and simulated σf. Low-field proton nuclear magnetic resonance (NMR) measurements provide an independent quantification of the volumes of the mobile and immobile domains. The best-fit parameters based on σf match the NMR measurements of the immobile and mobile domain porosities and provide the first direct electrical evidence for DDMT. Our results underscore the potential of using electrical measurements for DDMT parameter inference.

Electrical conductivity of the plagioclase-NaCl-water system and its implication for the high conductivity anomalies in the mid-lower crust of Tibet Plateau

NASA Astrophysics Data System (ADS)

Li, Ping; Guo, Xinzhuan; Chen, Sibo; Wang, Chao; Yang, Junlong; Zhou, Xingfan

2018-02-01

In order to investigate the origin of the high conductivity anomalies geophysically observed in the mid-lower crust of Tibet Plateau, the electrical conductivity of plagioclase-NaCl-water system was measured at 1.2 GPa and 400-900 K. The relationship between electrical conductivity and temperature follows the Arrhenius law. The bulk conductivity increases with the fluid fraction and salinity, but is almost independent of temperature (activation enthalpy less than 0.1 eV). The conductivity of plagioclase-NaCl-water system is much lower than that of albite-NaCl-water system with similar fluid fraction and salinity, indicating a strong effect of the major mineral phase on the bulk conductivity of the brine-bearing system. The high conductivity anomalies of 10-1 and 100 S/m observed in the mid-lower crust of Tibet Plateau can be explained by the aqueous fluid with a volume fraction of 1 and 9%, respectively, if the fluid salinity is 25%. The anomaly value of 10-1 S/m can be explained by the aqueous fluid with a volume fraction of 6% if the salinity is 10%. In case of Southern Tibet where the heat flow is high, the model of a thin layer of brine-bearing aqueous fluid with a high salinity overlying a thick layer of partial melt is most likely to prevail.

Relationship between electrical conductivity anisotropy and fabric anisotropy in granular materials during drained triaxial compressive tests: a numerical approach

NASA Astrophysics Data System (ADS)

Niu, Qifei; Revil, André; Li, Zhaofeng; Wang, Yu-Hsing

2017-07-01

The anisotropy of granular media and its evolution during shearing are important aspects required in developing physics-based constitutive models in Earth sciences. The development of relationships between geoelectrical properties and the deformation of porous media has applications to the monitoring of faulting and landslides. However, such relationships are still poorly understood. In this study, we first investigate the definition of the electrical conductivity anisotropy tensor of granular materials in presence of surface conductivity of the grains. Fabric anisotropy is related to the components of the fabric tensor. We define an electrical anisotropy factor based on the Archie's exponent second-order symmetric tensor m of granular materials. We use numerical simulations to confirm a relationship between the evolution of electrical and fabric anisotropy factors during shearing. To realize the simulations, we build a virtual laboratory in which we can easily perform synthetic experiments. We first simulate drained compressive triaxial tests of loose and dense granular materials (porosity 0.45 and 0.38, respectively) using the discrete element method. Then, the electrical conductivity tensor of a set of deformed synthetic samples is computed using the finite-difference method. The numerical results show that shear strains are responsible for a measurable anisotropy in the bulk conductivity of granular media. The observed electrical anisotropy response, during shearing, is distinct for dense and loose synthetic samples. Electrical and fabric anisotropy factors exhibit however a unique linear correlation, regardless of the shear strain and the initial state (porosity) of the synthetic samples. The practical implication of this finding confirms the usefulness of the electrical conductivity method in studying the fabric tensor of granular media. This result opens the door in using time-lapse electrical resistivity to study non-intrusively the evolution of anisotropy of soils and granular rocks during deformation, for instance during landslides, and to use the evolution of the conductivity tensor to monitor mechanical properties.

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.

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

PubMed

Lv, Yi; Cui, Jian; Jiang, Zuimin M; Yang, Xinju

2012-11-29

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

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

PubMed Central

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

2014-01-01

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

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

PubMed

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

2014-05-01

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

Improving our understanding of hydraulic-electrical relations: A case study of the surficial aquifer in Emirate Abu Dhabi

USGS Publications Warehouse

Ikard, Scott; Kress, Wade

2016-01-01

Transmissivity is a bulk hydraulic property that can be correlated with bulk electrical properties of an aquifer. In aquifers that are electrically-resistive relative to adjacent layers in a horizontally stratified sequence, transmissivity has been shown to correlate with bulk transverse resistance. Conversely, in aquifers that are electrically-conductive relative to adjacent layers, transmissivity has been shown to correlate with bulk longitudinal conductance. In both cases, previous investigations have relied on small datasets (on average less than eight observations) that have yielded coefficients of determination (R2) that are typically in the range of 0.6 to 0.7 to substantiate these relations. Compared to previous investigations, this paper explores hydraulic-electrical relations using a much larger dataset. Geophysical data collected from 26 boreholes in Emirate Abu Dhabi, United Arab Emirates, are used to correlate transmissivity modeled from neutron porosity logs to the bulk electrical properties of the surficial aquifer that are computed from deep-induction logs. Transmissivity is found to be highly correlated with longitudinal conductance. An R2 value of 0.853 is obtained when electrical effects caused by variations in pore-fluid salinity are taken into consideration.

Tuning conductivity in boron nanowire by edge geometry

NASA Astrophysics Data System (ADS)

Bhuyan, Prabal Dev; Gupta, Sanjeev K.; Sonvane, Yogesh; Gajjar, P. N.

2018-04-01

In present study, we have investigated electronic and temperature dependent transport properties of carbyne like linear chain and ribbon like zigzag structures of Boron (B) nanowire. The linear chain structure showed higher electric and thermal conductivity, as it is sp-hybridized, than its counterpart ribbon (R) structure. However the conductivity of ribbon structure increases with increases in width due to edge geometry effect. The ribbon (3R) structure showed high electric and thermal conductivity of 8.0×1019 1/Ω m s and 0.59×1015 W/ m K respectively. Interestingly we have observed that B linear chain showed higher thermal conductivity of 0.23×1015 W/ m K than its ribbon R and 2R structure above 600K. Because of high Seebeck co-efficient of boron chain and ribbon (R) structures at low temperature, they could find applications in thermoelectric sensors. Our results show that tuning conductivity property of boron nanowire could be of great interest in research for future electric connector in nanodevices.

Relationship of the interplanetary electric field to the high-latitude ionospheric electric field and currents Observations and model simulation

NASA Technical Reports Server (NTRS)

Clauer, C. R.; Banks, P. M.

1986-01-01

The electrical coupling between the solar wind, magnetosphere, and ionosphere is studied. The coupling is analyzed using observations of high-latitude ion convection measured by the Sondre Stromfjord radar in Greenland and a computer simulation. The computer simulation calculates the ionospheric electric potential distribution for a given configuration of field-aligned currents and conductivity distribution. The technique for measuring F-region in velocities at high time resolution over a large range of latitudes is described. Variations in the currents on ionospheric plasma convection are examined using a model of field-aligned currents linking the solar wind with the dayside, high-latitude ionosphere. The data reveal that high-latitude ionospheric convection patterns, electric fields, and field-aligned currents are dependent on IMF orientation; it is observed that the electric field, which drives the F-region plasma curve, responds within about 14 minutes to IMF variations in the magnetopause. Comparisons of the simulated plasma convection with the ion velocity measurements reveal good correlation between the data.

Electrical Transport Properties of Liquid Al-Cu Alloys

NASA Astrophysics Data System (ADS)

Thakore, B. Y.; Khambholja, S. G.; Suthar, P. H.; Jani, A. R.

2010-06-01

Electrical transport properties viz. electrical resistivity, thermoelectric power and thermal conductivity of liquid Al-Cu alloys as a function of Cu concentration have been studied in the present paper. Ashcroft empty core model potential has been used to incorporate the ion-electron interaction. To incorporate the exchange and correlation effects, five different forms of local field correction functions viz. Hartree, Taylor, Ichimaru et al., Farid et al. and Sarkar et al. have been used. The transport properties of binary system have been studied using Faber-Ziman formulation combined with Ashcroft-Langreth (AL) partial structure factor. The computed values of electrical resistivity are compared with experimental data and for low Cu concentration, good agreement has been observed. Further, thermoelectric power and thermal conductivity have also been predicted.

Transport properties of alumina nanofluids.

PubMed

Wong, Kau-Fui Vincent; Kurma, Tarun

2008-08-27

Recent studies have showed that nanofluids have significantly greater thermal conductivity compared to their base fluids. Large surface area to volume ratio and certain effects of Brownian motion of nanoparticles are believed to be the main factors for the significant increase in the thermal conductivity of nanofluids. In this paper all three transport properties, namely thermal conductivity, electrical conductivity and viscosity, were studied for alumina nanofluid (aluminum oxide nanoparticles in water). Experiments were performed both as a function of volumetric concentration (3-8%) and temperature (2-50 °C). Alumina nanoparticles with a mean diameter of 36 nm were dispersed in water. The effect of particle size was not studied. The transient hot wire method as described by Nagaska and Nagashima for electrically conducting fluids was used to test the thermal conductivity. In this work, an insulated platinum wire of 0.003 inch diameter was used. Initial calibration was performed using de-ionized water and the resulting data was within 2.5% of standard thermal conductivity values for water. The thermal conductivity of alumina nanofluid increased with both increase in temperature and concentration. A maximum thermal conductivity of 0.7351 W m(-1) K(-1) was recorded for an 8.47% volume concentration of alumina nanoparticles at 46.6 °C. The effective thermal conductivity at this concentration and temperature was observed to be 1.1501, which translates to an increase in thermal conductivity by 22% when compared to water at room temperature. Alumina being a good conductor of electricity, alumina nanofluid displays an increasing trend in electrical conductivity as volumetric concentration increases. A microprocessor-based conductivity/TDS meter was used to perform the electrical conductivity experiments. After carefully calibrating the conductivity meter's glass probe with platinum tip, using a standard potassium chloride solution, readings were taken at various volumetric concentrations. A 3457.1% increase in the electrical conductivity was measured for a small 1.44% volumetric concentration of alumina nanoparticles in water. The highest value of electrical conductivity, 314 µS cm(-1), was recorded for a volumetric concentration of 8.47%. In the determination of the kinematic viscosity of alumina nanofluid, a standard kinematic viscometer with constant temperature bath was used. Calibrated capillary viscometers were used to measure flow under gravity at precisely controlled temperatures. The capillary viscometers were calibrated with de-ionized water at different temperatures, and the resulting kinematic viscosity values were found to be within 3% of the standard published values. An increase of 35.5% in the kinematic viscosity was observed for an 8.47% volumetric concentration of alumina nanoparticles in water. The maximum kinematic viscosity of alumina nanofluid, 2.901 42 mm(2) s(-1), was obtained at 0 °C for an 8.47% volumetric concentration of alumina nanoparticles. The experimental results of the present work will help researchers arrive at better theoretical models.

Large-deformation electrohydrodynamics of an elastic capsule in a DC electric field

NASA Astrophysics Data System (ADS)

Das, Sudip; Thaokar, Rochish M.

2018-04-01

The dynamics of a spherical elastic capsule, containing a Newtonian fluid bounded by an elastic membrane and immersed in another Newtonian fluid, in a uniform DC electric field is investigated. Discontinuity of electrical properties such as conductivities of the internal and external fluid media as well as capacitance and conductance of the membrane lead to a net interfacial Maxwell stress which can cause the deformation of such an elastic capsule. We investigate this problem considering well established membrane laws for a thin elastic membrane, with fully resolved hydrodynamics in the Stokes flow limit and describe the electrostatics using the capacitor model. In the limit of small deformation, the analytical theory predicts the dynamics fairly satisfactorily. Large deformations at high capillary number though necessitate a numerical approach (Boundary element method in the present case) to solve this highly non-linear problem. Akin to vesicles, at intermediate times, highly nonlinear biconcave shapes along with squaring and hexagon like shapes are observed when the outer medium is more conducting. The study identifies the essentiality of parameters such as high membrane capacitance, low membrane conductance, low hydrodynamic time scales and high capillary number for observation of these shape transitions. The transition is due to large compressive Maxwell stress at the poles at intermediate times. Thus such shape transition can be seen in spherical globules admitting electrical capacitance, possibly, irrespective of the nature of the interfacial restoring force.

Fluorine follows water: Effect on electrical conductivity of silicate minerals by experimental constraints from phlogopite

NASA Astrophysics Data System (ADS)

Li, Yan; Jiang, Haotian; Yang, Xiaozhi

2017-11-01

Fluorine and hydroxyl groups are minor constituents of silicate minerals, and share a lot of similarities concerning their physical and chemical properties. Hydroxyl groups significantly enhance the electrical conductivity of many silicate minerals, and it is expected that fluorine would have a comparable effect. This, however, has never been documented quantitatively. Here we present experimental approaches on this issue, by investigating the electrical conductivity of phlogopite with a wide range of fluorine content (but with broadly similar contents for other major elements). Electrical conductivities of gem-quality single crystal phlogopites, with samples prepared along the same orientation (normal to the (0 0 1) plane), were determined at 1 GPa and 200-650 °C using an end-loaded piston cylinder apparatus and a Solartron-1260 Impedance/Gain Phase Analyzer over the frequency range of 106 to 0.1 Hz. The complex spectra usually show an arc in the high frequency range and a short tail in the low frequency range, which are caused by lattice conduction and electrode effects, respectively. The electrical conductivity increases with increasing fluorine content, and the main charge carriers are fluorine. The activation enthalpies are ∼180 to 200 kJ/mol, nearly independent of fluorine content. The conductivity is linearly proportional to the content of fluorine, with an exponent factor of ∼1. The results demonstrate that conduction by fluorine leads to very high electrical conductivity at high temperatures. The influence of fluorine on electrical conductivity may be compared to that of hydrogen in nominally anhydrous minerals. This, along with the close association of fluorine and hydroxyl groups in silicate minerals and their similar crystal-chemical behaviors, suggests a more general role of fluorine in enhancing the electrical conductivity of many silicate minerals. Fluorine-rich assemblages, e.g., phlogopite and amphibole, could be locally enriched in the upper mantle, and if they form connected networks as observed for some natural samples, regionally high electrical conductivities could be produced. It has been recently proposed that the transition zone is probably a major reservoir for fluorine in the mantle, due to the significant dissolution of fluorine in wadsleyite and ringwoodite and the coupled incorporation with hydroxyl groups. As such, geophysically-resolved high electrical conductivities in the transition zone may be accounted for by fluorine in the dominant minerals, rather than by hydroxyl groups. The results of this work would stimulate a wide scope of future studies on the deep fluorine cycle, the deep water cycle and the geodynamical properties of the mantle.

Equivalent Electromagnetic Constants for Microwave Application to Composite Materials for the Multi-Scale Problem

PubMed Central

Fujisaki, Keisuke; Ikeda, Tomoyuki

2013-01-01

To connect different scale models in the multi-scale problem of microwave use, equivalent material constants were researched numerically by a three-dimensional electromagnetic field, taking into account eddy current and displacement current. A volume averaged method and a standing wave method were used to introduce the equivalent material constants; water particles and aluminum particles are used as composite materials. Consumed electrical power is used for the evaluation. Water particles have the same equivalent material constants for both methods; the same electrical power is obtained for both the precise model (micro-model) and the homogeneous model (macro-model). However, aluminum particles have dissimilar equivalent material constants for both methods; different electric power is obtained for both models. The varying electromagnetic phenomena are derived from the expression of eddy current. For small electrical conductivity such as water, the macro-current which flows in the macro-model and the micro-current which flows in the micro-model express the same electromagnetic phenomena. However, for large electrical conductivity such as aluminum, the macro-current and micro-current express different electromagnetic phenomena. The eddy current which is observed in the micro-model is not expressed by the macro-model. Therefore, the equivalent material constant derived from the volume averaged method and the standing wave method is applicable to water with a small electrical conductivity, although not applicable to aluminum with a large electrical conductivity. PMID:28788395

Study of Dynamic Membrane Behavior in Applied DC Electric Field

NASA Astrophysics Data System (ADS)

Dutta, Prashanta; Morshed, Adnan; Hossan, Mohammad

2017-11-01

Electrodeformation of vesicles can be used as a useful tool to understand the characteristics of biological soft matter, where vesicles immersed in a fluid medium are subjected to an applied electric field. The complex response of the vesicle membrane strongly depends on the conductivity of surrounding fluid, vesicle size and shape, and applied electric field We studied the electrodeformation of vesicles immersed in a fluid media under a short DC electric pulse. An immersed interface method is used to solve the electric field over the domain with conductive or non-conductive vesicles while an immersed boundary scheme is employed to solve fluid flow, fluid-solid interaction, membrane mechanics and vesicle movement. Force analysis on the membrane surface reveals almost linear relation with vesicle size, but highly nonlinear influence of applied field as well as the conductivity ratios inside and outside of the vesicle. Results also point towards an early linear deformation regime followed by an equilibrium stage for the membranes. Moreover, significant influence of the initial aspect ratio of the vesicle on the force distribution is observed across a range of conductivity ratios. Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number R01GM122081.

Electrical conductivity and thermopower of (1 - x) BiFeO(3) - xBi(0.5)K(0.5)TiO3 (x = 0.1, 0.2) ceramics near the ferroelectric to paraelectric phase transition.

PubMed

Wefring, E T; Einarsrud, M-A; Grande, T

2015-04-14

Ferroelectric BiFeO3 has attractive properties such as high strain and polarization, but a wide range of applications of bulk BiFeO3 are hindered due to high leakage currents and a high coercive electric field. Here, we report on the thermal behaviour of the electrical conductivity and thermopower of BiFeO3 substituted with 10 and 20 mol% Bi0.5K0.5TiO3. A change from p-type to n-type conductivity in these semi-conducting materials was demonstrated by the change in the sign of the Seebeck coefficient and the change in the slope of the isothermal conductivity versus partial pressure of O. A minimum in the isothermal conductivity was observed at ∼10(-2) bar O2 partial pressure for both solid solutions. The strong dependence of the conductivity on the partial pressure of O2 was rationalized by a point defect model describing qualitatively the conductivity involving oxidation/reduction of Fe(3+), the dominating oxidation state of Fe in stoichiometric BiFeO3. The ferroelectric to paraelectric phase transition of 80 and 90 mol% BiFeO3 was observed at 648 ± 15 and 723 ± 15 °C respectively by differential thermal analysis and confirmed by dielectric spectroscopy and high temperature powder X-ray diffraction.

Electrical Counting and Sizing of Mammalian Cells in Suspension

PubMed Central

Gregg, E. C.; Steidley, K. David

1965-01-01

A recently developed method of determining the number and size of particles suspended in a conducting solution is to pump the suspension through a small orifice having an immersed electrode on each side to supply electrical current. The current changes due to the passage of particles of resistivity different from that of the solution. Theoretical expressions are developed which relate the current change caused by such particles to their volume and shape. It is found that most biological cells may be treated as dielectric particles whose capacitive effects are negligible. Electrolytic tank measurements on models confirm the theoretical development, and electric field plots of model orifices are used to predict the observed pulse shapes. An equivalent circuit of the orifice-electrode system is analyzed and shows that the current pulse may be made conductivity-independent when observed with a zero input impedance amplifier. PMID:5861698

Experimental results on current-driven turbulence in plasmas - a survey

NASA Astrophysics Data System (ADS)

de Kluiver, H.; Perepelkin, N. F.; Hirose, A.

1991-01-01

The experimental consequences of plasma turbulence driven by a current parallel to a magnetic field and concurrent anomalous plasma heating are reviewed, with an attempt to deduce universalities in key parameters such as the anomalous electrical conductivities observed in diverse devices. It has been found that the nature of plasma turbulence and turbulent heating depends on several parameters including the electric field, current and magnetic fields. A classification of turbulence regimes based on these parameters has been made. Experimental observations of the anomalous electrical conductivity, plasma heating, skin effect, runaway electron braking and turbulent fluctuations are surveyed, and current theoretical understanding is briefly reviewed. Experimental results recently obtained in stellarators (SIRIUS, URAGAN at Kharkov), and in tokamaks (TORTUR at Nieuwegein, STOR-1M at Saskatoon) are presented in some detail in the light of investigating the feasibility of using turbulent heating as a means of injecting a large power into toroidal devices.

Evaluation of the Atmospheric Boundary-Layer Electrical Variability

NASA Astrophysics Data System (ADS)

Anisimov, Sergey V.; Galichenko, Sergey V.; Aphinogenov, Konstantin V.; Prokhorchuk, Aleksandr A.

2017-12-01

Due to the chaotic motion of charged particles carried by turbulent eddies, electrical quantities in the atmospheric boundary layer (ABL) have short-term variability superimposed on long-term variability caused by sources from regional to global scales. In this study the influence of radon exhalation rate, aerosol distribution and turbulent transport efficiency on the variability of fair-weather atmospheric electricity is investigated via Lagrangian stochastic modelling. For the mid-latitude lower atmosphere undisturbed by precipitation, electrified clouds, or thunderstorms, the model is capable of reproducing the diurnal variation in atmospheric electrical parameters detected by ground-based measurements. Based on the analysis of field observations and numerical simulation it is found that the development of the convective boundary layer, accompanied by an increase in turbulent kinetic energy, forms the vertical distribution of radon and its decaying short-lived daughters to be approximately coincident with the barometric law for several eddy turnover times. In the daytime ABL the vertical distribution of atmospheric electrical conductivity tends to be uniform except within the surface layer, due to convective mixing of radon and its radioactive decay products. At the same time, a decrease in the conductivity near the ground is usually observed. This effect leads to an enhanced ground-level atmospheric electric field compared to that normally observed in the nocturnal stably-stratified boundary layer. The simulation showed that the variability of atmospheric electric field in the ABL associated with internal origins is significant in comparison to the variability related to changes in global parameters. It is suggested that vertical profiles of electrical quantities can serve as informative parameters on ABL turbulent dynamics and can even more broadly characterize the state of the environment.

Thermo-structural analysis and electrical conductivity behavior of epoxy/metals composites

NASA Astrophysics Data System (ADS)

Boumedienne, N.; Faska, Y.; Maaroufi, A.; Pinto, G.; Vicente, L.; Benavente, R.

2017-05-01

This paper reports on the elaboration and characterization of epoxy resin filled with metallic particles powder (aluminum, tin and zinc) composites. The scanning electron microscopy (SEM) pictures, density measurements and x-ray diffraction analysis (DRX) showed a homogeneous phase of obtained composites. The differential scanning calorimetry revealed a good adherence at matrix-filler interfaces, confirming the SEM observations. The measured glass transition temperatures depend on composites fillers' nature. Afterwards, the electrical conductivity of composites versus their fillers' contents has been investigated. The obtained results depict a nonlinear behavior, indicating an insulator to conductor phase transition at a conduction threshold; with high contrast of ten decades. Hence, the elaborated materials give a possibility to obtain dielectric or electrically conducting phases, which can to be interesting in the choice of desired applications. Finally, the obtained results have been successfully simulated on the basis of different percolation models approach combined with structural characterization inferences.

Improving the Ionospheric Auroral Conductance in a Global Ring Current Model and the Effects on the Ionospheric Electrodynamics

NASA Astrophysics Data System (ADS)

Yu, Y.; Jordanova, V. K.; McGranaghan, R. M.; Solomon, S. C.

2017-12-01

The ionospheric conductance, height-integrated electric conductivity, can regulate both the ionospheric electrodynamics and the magnetospheric dynamics because of its key role in determining the electric field within the coupled magnetosphere-ionosphere system. State-of-the-art global magnetosphere models commonly adopt empirical conductance calculators to obtain the auroral conductance. Such specification can bypass the complexity of the ionosphere-thermosphere chemistry but on the other hand breaks the self-consistent link within the coupled system. In this study, we couple a kinetic ring current model RAM-SCB-E that solves for anisotropic particle distributions with a two-stream electron transport code (GLOW) to more self-consistently compute the height-dependent electric conductivity, provided the auroral electron precipitation from the ring current model. Comparisons with the traditional empirical formula are carried out. It is found that the newly coupled modeling framework reveals smaller Hall and Pedersen conductance, resulting in a larger electric field. As a consequence, the subauroral polarization streams demonstrate a better agreement with observations from DMSP satellites. It is further found that the commonly assumed Maxwellian spectrum of the particle precipitation is not globally appropriate. Instead, a full precipitation spectrum resulted from wave particle interactions in the ring current accounts for a more comprehensive precipitation spectrum.

Frequency shifts of an electric-dipole resonance near a conducting surface

NASA Technical Reports Server (NTRS)

Holland, W. R.; Hall, D. G.

1984-01-01

The resonance frequency of an electric dipole placed near a conducting surface is shifted by the dipole-surface interaction. The observation and measurement of these shifts at optical frequencies is reported for an experimental system that consists of a metal-island film spaced a distance d from a continuous Ag film. The dependence of the shift in the frequency of the island resonance on d shows good agreement with that predicted by a classical theory of the dipole-surface interaction.

Electrohydrodynamics of a particle-covered drop

NASA Astrophysics Data System (ADS)

Ouriemi, Malika; Vlahovska, Petia

2014-11-01

We study the dynamics of a drop nearly-completely covered with a particle monolayer in a uniform DC electric field. The weakly conducting fluid system consists of a silicon oil drop suspended in castor oil. A broad range of particle sizes, conductivities, and shapes is explored. In weak electric fields, the presence of particles increases drop deformation compared to a particle-free drop and suppresses the electrohydrodynamic flow. Very good agreement is observed between the measured drop deformation and the small deformation theory derived for surfactant-laden drops (Nganguia et al., 2013). In stronger electric fields, where drops are expected to undergo Quincke rotation (Salipante and Vlahovska, 2010), the presence of the particles greatly decreases the threshold for rotation and the stationary tilted drop configuration observed for clean drop is replaced by a spinning drop with either a wobbling inclination or a very low inclination. These behaviors resemble the predicted response of rigid ellipsoids in uniform electric fields. At even stronger electric fields, the particles can form dynamic wings or the drop implodes. The similar behavior of particle-covered and surfactant-laden drops provides new insights into understanding stability of Pickering emulsions. Supported by NSF-CBET 1437545.

Design and construction of high-sensitivity, infrared bolometers for operation at 300 mK

NASA Technical Reports Server (NTRS)

Alsop, D. C.; Inman, C.; Lange, A. E.; Wibanks, T.

1992-01-01

The design and construction of 300-mK composite bolometers developed for millimeter-wave astronomical observations are described. Graphite fibers are used as the electrical leads for the thermistor to reduce the thermal conductance and heat capacity associated with the leads. A mechanical suspension made of Nylon fibers provides the required thermal conductance. Electrical noise equivalent powers below 1 x 10 exp -16 W/sq rt Hz have been achieved for detectors with thermal time constants of 11 ms. The detectors were installed in a millimeter-wave photometer and used to perform observations of the cosmic microwave background from a balloonborne platform. The flight performance was consistent with the measured laboratory properties.

Thermal history effects on electrical relaxation and conductivity for potassium silicate glass with low alkali concentrations

NASA Technical Reports Server (NTRS)

Angel, Paul W.; Hann, Raiford E.; Cooper, Alfred R.

1993-01-01

Electrical response measurements from 10 Hz to 100 kHz between 120 and 540 C were made on potassium-silicate glasses with alkali oxide contents of 2, 3, 5 and 10 mol percent. Low alkali content glasses were chosen in order to try to reduce the Coulombic interactions between alkali ions to the point that frozen structural effects from the glass could be observed. Conductivity and electrical relaxation responses for both annealed and quenched glasses of the same composition were compared. Lower DC conductivity (sigma(sub DC)) activation energies were measured for the quenched compared to the annealed glasses. The two glasses with the lowest alkali contents exhibited a non-Arrhenius concave up curvature in the log(sigma(sub DC)) against 1/T plots, which decreased upon quenching. A sharp decrease in sigma(sub DC) was observed for glasses containing K2O concentrations of 5 mol percent or less. The log modulus loss peak (M'') maximum frequency plots against 1/T all showed Arrhenius behavior for both annealed and quenched samples. The activation energies for these plots closely agreed with the sigma(sub DC) activation energies. A sharp increase in activation energy was observed for both series as the potassium oxide concentration decreased. Changes in the electrical response are attributed to structural effects due to different alkali concentrations. Differences between the annealed and quenched response are linked to a change in the distribution of activation energies (DAE).

Analysis of the Diurnal Variation of the Global Electric Circuit Obtained From Different Numerical Models

NASA Astrophysics Data System (ADS)

Jánský, Jaroslav; Lucas, Greg M.; Kalb, Christina; Bayona, Victor; Peterson, Michael J.; Deierling, Wiebke; Flyer, Natasha; Pasko, Victor P.

2017-12-01

This work analyzes different current source and conductivity parameterizations and their influence on the diurnal variation of the global electric circuit (GEC). The diurnal variations of the current source parameterizations obtained using electric field and conductivity measurements from plane overflights combined with global Tropical Rainfall Measuring Mission satellite data give generally good agreement with measured diurnal variation of the electric field at Vostok, Antarctica, where reference experimental measurements are performed. An approach employing 85 GHz passive microwave observations to infer currents within the GEC is compared and shows the best agreement in amplitude and phase with experimental measurements. To study the conductivity influence, GEC models solving the continuity equation in 3-D are used to calculate atmospheric resistance using yearly averaged conductivity obtained from the global circulation model Community Earth System Model (CESM). Then, using current source parameterization combining mean currents and global counts of electrified clouds, if the exponential conductivity is substituted by the conductivity from CESM, the peak to peak diurnal variation of the ionospheric potential of the GEC decreases from 24% to 20%. The main reason for the change is the presence of clouds while effects of 222Rn ionization, aerosols, and topography are less pronounced. The simulated peak to peak diurnal variation of the electric field at Vostok is increased from 15% to 18% from the diurnal variation of the global current in the GEC if conductivity from CESM is used.

The electrical structure of lithosphere beneath Northeast China —Preliminary results from SinoProbe-01-04

NASA Astrophysics Data System (ADS)

Hui, F.; Qing, Z.; Gengen, Q.; Fagen, P.; Dawei, B.; Baotun, G.; Jingqi, L.; Changwang, L.; Xiaochang, L.; Meixing, H.; Bingrui, D.

2012-12-01

Being constituted by the Seberia, Northern China fossil plate and Pacific Plate, the tectonics of Northeast China are very complicated. In order to study the electrical structure in these areas, the project SinoProbe-01-04 'Experimental study of 'standard monitoring network' of continental EM parameters in Northeast China' have established a 4°×4°regional MT array covering the whole Northeast China(Fig. 1). To make sure that MT data observed on each standard point representatively, a cross profile with the standard point being center and eight auxiliary measuring points around has been designed in practical work, and the same direction of the physical measuring point should have 20 km space, the observation time should be more than 120 hours in standard point and more than 24 hours in each auxiliary station. Both broadband MT equipment (V5-2000) and long-period MT equipment (LEMI-417M) have been used together in standard point, then the ultra-wideband electromagnetic signals at 320HZ-1/10000Hz can be acquired by combining the field data observed by each equipment. Eleven MT standard network control point with total 99 physical measuring points have been finished in 2010, then those works were repeated again in 2011 to make sure observed result reliable. Based on the observed result, this article preliminary analysis the electrical structure of each major tectonic element in Northeast China, which including the regularity of distribution of regional electrical spindle, the distribution characteristics of vertical conductivity, development status of the low resistivity layer in the crust, and the depth of the high conductivity layer in upper mantle. It has been founded that the electrical features of the major tectonic element in Northeast China are different and appear electrical-heterogeneous in cross direction. Fig.1 MT array observed site

On the Induced Flow of an Electrically Conducting Liquid in a Rectangular Duct by Electric and Magnetic Fields of Finite Extent

NASA Technical Reports Server (NTRS)

Rossow, Vernon J.; Jones, William Prichard; Huerta, Robert H.

1961-01-01

Reported here are the results of a systematic study of a model of the direct-current electromagnetic pump. Of particular interest is the motion imparted to the electrically conducting fluid in the rectangular duct by the body forces that result from applied electric and magnetic fields. The purpose of the investigation is to associate the observed fluid motion with the characteristics of the electric and magnetic fields which cause them. The experiments were carried out with electromagnetic fields that moved a stream of copper sulphate solution through a clear plastic channel. Ink filaments injected into the stream ahead of the region where the fields were applied identify the motion of the fluid elements as they passed through the test channel. Several magnetic field configurations were employed with a two-dimensional electric current distribution in order to study and identify the magnitude of some of the effects on the fluid motion brought about by nonuniformities in the electromagnetic fields. A theoretical analysis was used to guide and evaluate the identification of the several fluid motions observed. The agreement of the experimental data with the theoretical predictions is satisfactory. It is found that sizable variations in the velocity profile and pressure head of the output stream are produced by the shape of the electric and magnetic fields.

Interplanetary double-shock ensembles with anomalous electrical conductivity

NASA Technical Reports Server (NTRS)

Dryer, M.

1972-01-01

Similarity theory is applied to the case of constant velocity, piston-driven, shock waves. This family of solutions, incorporating the interplanetary magnetic field for the case of infinite electric conductivity, represents one class of experimentally observed, flare-generated shock waves. This paper discusses the theoretical extension to flows with finite conductivity (presumably caused by unspecified modes of wave-particle interactions). Solutions, including reverse shocks, are found for a wide range of magnetic Reynolds numbers from one to infinity. Consideration of a zero and nonzero ambient flowing solar wind (together with removal of magnetic considerations) enables the recovery of earlier similarity solutions as well as numerical simulations. A limited comparison with observations suggests that flare energetics can be reasonably estimated once the shock velocity, ambient solar wind velocity and density, and ambient azimuthal Alfven Mach number are known.

Long term changes in electrical conductivity in stratosphere over Hyderabad (India), balloon borne results

NASA Astrophysics Data System (ADS)

Gupta, Surya

2012-07-01

The stratospheric conductivity plays important role in coupling processes between lower atmosphere and ionosphere. It is an important parameter of global electric circuit. The conductivity in troposphere and in stratosphere is mainly due to ionization produced by cosmic rays. The conductivity in stratosphere is measured mainly by balloon borne technique. In country-regionIndia, we had a national program IMAP (1982-1994) to measure conductivity and electric field in stratosphere from CityHyderabad (country-regionplaceIndia). Five institutes took part in this program. Namely NPL (CityNew Delhi), PRL (Ahmedabad), CESS (CityTrivandrum), IIG (Mumbai) and TIFR Balloon facility (CityplaceHyderabad). The vertical profiles on Ion Conductivity (both positive and negative) were measured from CityplaceHyderabad using different techniques. The measurements were done during different solar activity period. Measurements were done at float altitude also. It was observed that conductivity values in stratosphere is larger in high solar activity period compared to low solar activity period by 30%. This was a new finding and will be discussed in terms of composition change due to change in U.V. (200-300 nm) radiation intensity with solar activity. Over mid and polar latitude American scientists have conducted such measurements by balloon borne techniques (covering a period of about twenty-five years (1975-2000). Temporal variations of similar nature were also observed at mid-latitudes, while no correlation was seen at polar latitudes. The conductivity results of CityplaceHyderabad were compared with measurements carried out at different latitudes and different longitudes by other workers and will be discussed in this presentation.

Large Enhancement of Thermal Conductivity and Lorenz Number in Topological Insulator Thin Films.

PubMed

Luo, Zhe; Tian, Jifa; Huang, Shouyuan; Srinivasan, Mithun; Maassen, Jesse; Chen, Yong P; Xu, Xianfan

2018-02-27

Topological insulators (TI) have attracted extensive research effort due to their insulating bulk states but conducting surface states. However, investigation and understanding of thermal transport in topological insulators, particularly the effect of surface states, are lacking. In this work, we studied thickness-dependent in-plane thermal and electrical conductivity of Bi 2 Te 2 Se TI thin films. A large enhancement in both thermal and electrical conductivity was observed for films with thicknesses below 20 nm, which is attributed to the surface states and bulk-insulating nature of these films. Moreover, a surface Lorenz number much larger than the Sommerfeld value was found. Systematic transport measurements indicated that the Fermi surface is located near the charge neutrality point (CNP) when the film thickness is below 20 nm. Possible reasons for the large Lorenz number include electrical and thermal current decoupling in the surface state Dirac fluid, and bipolar diffusion transport. A simple computational model indicates that the surface states and bipolar diffusion indeed can lead to enhanced electrical and thermal transport and a large Lorenz number.

The Kubo-Greenwood spin-dependent electrical conductivity of 2D transition-metal dichalcogenides and group-IV materials: A Green's function study

NASA Astrophysics Data System (ADS)

Hoi, Bui Dinh; Yarmohammadi, Mohsen

2018-04-01

The spin-dependent electrical conductivity of counterparts of graphene, transition-metal dichalcogenides (TMDs) and group-IV nanosheets, have investigated by a magnetic exchange field (MEF)-induction to gain the electronic transport properties of charge carriers. We have implemented a k.p Hamiltonian model through the Kubo-Greenwood formalism in order to address the dynamical behavior of correlated Dirac fermions. Tuning the MEF enables one to control the effective mass of carriers in group-IV and TMDs, differently. We have found the Dirac-like points in a new quantum anomalous Hall (QAH) state at strong MEFs for both structures. For both cases, a broad peak in electrical conductivity originated from the scattering rate and entropy is observed. Spin degeneracy at some critical MEFs is another remarkable point. We have found that in the limit of zero or uniform MEFs with respect to the spin-orbit interaction, the large resulting electrical conductivity depends on the spin sub-bands in group-IV and MLDs. Featuring spin-dependent electronic transport properties, one can provide a new scenario for future possible applications.

Evaluation of the electrical contact area in contact-mode scanning probe microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Celano, Umberto, E-mail: celano@imec.be, E-mail: u.celano@gmail.com; Chintala, Ravi Chandra; Vandervorst, Wilfried

The tunneling current through an atomic force microscopy (AFM) tip is used to evaluate the effective electrical contact area, which exists between tip and sample in contact-AFM electrical measurements. A simple procedure for the evaluation of the effective electrical contact area is described using conductive atomic force microscopy (C-AFM) in combination with a thin dielectric. We characterize the electrical contact area for coated metal and doped-diamond tips operated at low force (<200 nN) in contact mode. In both cases, we observe that only a small fraction (<10 nm{sup 2}) of the physical contact (∼100 nm{sup 2}) is effectively contributing to the transportmore » phenomena. Assuming this reduced area is confined to the central area of the physical contact, these results explain the sub-10 nm electrical resolution observed in C-AFM measurements.« less

LASER BIOLOGY AND MEDICINE: Effect of repetitive laser pulses on the electrical conductivity of intervertebral disc tissue

NASA Astrophysics Data System (ADS)

Omel'chenko, A. I.; Sobol', E. N.

2009-03-01

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

Structure and Electrical Properties of Mn-Cu-O Spinels

NASA Astrophysics Data System (ADS)

Bobruk, M.; Durczak, K.; Dąbek, J.; Brylewski, T.

2017-04-01

The study presents the results of structural and electrical conductivity investigations of a Cu1.3Mn1.7O4 spinel obtained using EDTA gel processes. An amorphous gel was synthesized and calcinated for 5 h in air at temperatures of 673, 773, 873, and 973 K. When calcinating the gel at temperatures below 973 K, the obtained powders consisted of two phases—the regular Cu1.5Mn1.5O4 spinel and manganese(III) oxide. At 973 K, Mn2O3 was no longer observed, but a new Mn3O4 phase appeared in addition to the Cu1.5Mn1.5O4 spinel. Green bodies prepared from these powders were sintered for 2 h in air at 1393 K. The obtained sinters had a porosity of around 12% and were composed predominantly of the spinel phase, with minor amounts of Mn3O4 and, in the case of three of four sinters—CuO. Electrical conductivity measurements were taken over the temperature range of 300-1073 K. A change in the character of conductivity of the studied sinters was observed in the range of 400-430 K, and it was associated with an increase in activation energy from 0.20 to 0.56 eV. The electrical conductivity of the studied sinters ranged from 74.8 to 88.4 S cm-1, which makes the Cu1.3Mn1.7O4 material suitable for application as a protective-conducting coating in IT-SOFC ferritic stainless steel interconnects.

Microwave absorption in powders of small conducting particles for heating applications.

PubMed

Porch, Adrian; Slocombe, Daniel; Edwards, Peter P

2013-02-28

In microwave chemistry there is a common misconception that small, highly conducting particles heat profusely when placed in a large microwave electric field. However, this is not the case; with the simple physical explanation that the electric field (which drives the heating) within a highly conducting particle is highly screened. Instead, it is the magnetic absorption associated with induction that accounts for the large experimental heating rates observed for small metal particles. We present simple principles for the effective heating of particles in microwave fields from calculations of electric and magnetic dipole absorptions for a range of practical values of particle size and conductivity. For highly conducting particles, magnetic absorption dominates electric absorption over a wide range of particle radii, with an optimum absorption set by the ratio of mean particle radius a to the skin depth δ (specifically, by the condition a = 2.41δ). This means that for particles of any conductivity, optimized magnetic absorption (and hence microwave heating by magnetic induction) can be achieved by simple selection of the mean particle size. For weakly conducting samples, electric dipole absorption dominates, and is maximized when the conductivity is approximately σ ≈ 3ωε(0) ≈ 0.4 S m(-1), independent of particle radius. Therefore, although electric dipole heating can be as effective as magnetic dipole heating for a powder sample of the same volume, it is harder to obtain optimized conditions at a fixed frequency of microwave field. The absorption of sub-micron particles is ineffective in both magnetic and electric fields. However, if the particles are magnetic, with a lossy part to their complex permeability, then magnetic dipole losses are dramatically enhanced compared to their values for non-magnetic particles. An interesting application of this is the use of very small magnetic particles for the selective microwave heating of biological samples.

Comparing spatial series of soil bulk electrical conductivity as obtained by Time Domain Reflectometry and Electrical Resistivity Tomography

NASA Astrophysics Data System (ADS)

Saeed, Ali; Dragonetti, Giovanna; Comegna, Allessandro; Garre, Sarah; Lamaddalena, Nicola; Coppola, Antonio

2016-04-01

Conventional ground survey of soil root zone salinity by direct soil sampling are time consuming, costly and destructive. Alternatively, soil salinity can be evaluated by measuring the bulk electrical conductivity, σb, in the field. This approach is faster and cheaper, and allows a more intensive surveying. Measurements of σb can be made either in situ or with remote devices. Time domain reflectometry (TDR) sensors allow simultaneous measurements of water content, θ, and σb. They may be calibrated for estimating the electrical conductivity of the soil solution (σw). However, they have a relatively small observation window and thus they are thought to only provide local-scale measurements. The spatial range of the sensors is limited to tens of centimeters and extension of the information to a large area can be problematic. Also, information on the vertical distribution of the σb soil profile may only be obtained by installing sensors at different depths. In this sense, the TDR may be considered as an invasive technique. Compared to the TDR, other geophysical methods based for example on the Electrical Resistivity Tomography (ERT) techniques represent an alternative in respect to those traditional for soil salinity characterization. In order to deduce the actual distribution of the bulk electrical conductivity, σb, in the soil profile, one needs to invert the signal coming from ERT sensors. The latter, in turn, depends on the specific depth distribution of the σb, as well as on the electrical configuration of the sensor used. With these premises, the main aim of this study is to estimate the vertical σb distribution starting from resistivity data series measured using the ERT method under different salinity conditions and using TDR data as ground-truth data for calibration and validation of the ERT sensor. This way, limited measured TDR data may be used for translating extensive ERT apparent electrical conductivity, σa, measurements to estimate depth-distributions of σb. These, in turn, may be translated to many σw values by applying the σw-σb-θ calibration relationship obtained in the laboratory by using the TDR probes. A field experiment was conducted in the Mediterranean Agronomic Institute (MAI) of Valenzano (Bari - Italy). The experiment consisted of three transects 30 m long and 4.2 width, cultivated with green bean and irrigated with three different salinity levels (1 dS/m, 3 dS/m, and 6 dS/m). Each transect consisted of seven rows equipped by a dripper irrigation system, which supplied a water flux of 2 l/h. As for the salt application, CaCl2 were dissolved in tap water, and subsequently siphoned into the irrigation system. For each transect, 24 regularly spaced monitoring sites (1 m apart) were selected for soil measurements, using different equipments: i) a TDR100, ii) an ERT apparatus in the Wenner configuration array. Overall, 17 measurement campaigns were carried out. Monitoring along transects also allowed to evaluate the role of different smaller and larger scale heterogeneities on the electrical conductivity measured by the two different sensors. Because of the different variability patterns and structure of the ERT and TDR data due to the different observation windows, a site-by-site comparison of the corresponding readings may not reveal the actual correlation between the σb values deduced by ERT measurements on one side and the TDR data on the other. In order to make TDR and ERT data actually comparable, we analyzed the effect of the different observation windows of the two sensors on the different spatial and temporal variability observed in the two data series. Specifically, the study assessed the potential of applying a Fourier's analysis to filter the original data series to extract the predominant, high-variance signal after removing the small- scale (high frequency) variance observed in the TDR data series.

Northeastern Pacific mantle conductivity profile from long-period magnetotelluric sounding using Hawaii-to-California submarine cable data

NASA Astrophysics Data System (ADS)

Lizarralde, Daniel; Chave, Alan; Hirth, Greg; Schultz, Adam

1995-09-01

We present results of a long-period magnetotelluric (MT) investigation of the electrical structure beneath the eastern North Pacific. The electric field data consist of ˜2 years of continuously recorded voltages across an unpowered, ˜4000-km-long submarine telephone cable (HAW-1) extending from Point Arena, California, to Oahu, Hawaii. The electric field measurements are coherent to some degree with magnetic field measurements from Honolulu Observatory at periods of 0.1 to 45 days. This coherence is enhanced at long periods over that observed with point electric field sensors due to horizontal averaging of the motional electric fields of spatial scale smaller than the cable length, significantly diminishing their effect. Robust, controlled leverage MT response estimates and their jacknife confidence limits are computed for the HAW-1 to Honolulu data. An equivalent scalar MT response obtained from Honolulu magnetic variations data is used to correct the HAW-1 MT response for static shift and to extend the MT response estimate to periods of 100 days. The composite response function satisfies necessary and sufficient conditions for consistency with a one-dimensional conductivity structure and is most sensitive to structure between 150 and 1000 km. Inversion of the MT response reveals a conductive zone (0.05-0.1 S/m) between 150 and 400 km depth and a positive gradient below 500 km; these observations are consistent with previous MT studies in the North Pacific. This upper mantle conductivity is too high to be explained by solid-state conduction in dry olivine using reasonable mantle geotherms. Calculations based on measurements of hydrogen solubility and diffusivity in olivine indicate that H+ dissolved in olivine, possibly combined with a lattice preferred orientation consistent with measured seismic anisotropy, provide sufficient conductivity enhancement to explain the inversion results. The high conductivity may also be explained by the presence of gravitationally stable partial melt. Comparison of the HAW-1 results with long-period MT studies conducted on land reveals differences in upper mantle conductivity between different tectonic regimes. In particular, the upper mantle beneath the Pacific Ocean is considerably more conductive than that beneath the Canadian shield and similar in conductivity to that beneath the Basin and Range.

Quantitative assessment of passive electrical properties of the cardiac T-tubular system by FRAP microscopy

PubMed Central

Scardigli, M.; Ferrantini, C.; Gabbrielli, T.; Silvestri, L.; Coppini, R.; Tesi, C.; Rog-Zielinska, E. A.; Kohl, P.; Cerbai, E.; Poggesi, C.; Pavone, F. S.; Sacconi, L.

2017-01-01

Well-coordinated activation of all cardiomyocytes must occur on every heartbeat. At the cell level, a complex network of sarcolemmal invaginations, called the transverse-axial tubular system (TATS), propagates membrane potential changes to the cell core, ensuring synchronous and uniform excitation–contraction coupling. Although myocardial conduction of excitation has been widely described, the electrical properties of the TATS remain mostly unknown. Here, we exploit the formal analogy between diffusion and electrical conductivity to link the latter with the diffusional properties of TATS. Fluorescence recovery after photobleaching (FRAP) microscopy is used to probe the diffusion properties of TATS in isolated rat cardiomyocytes: A fluorescent dextran inside TATS lumen is photobleached, and signal recovery by diffusion of unbleached dextran from the extracellular space is monitored. We designed a mathematical model to correlate the time constant of fluorescence recovery with the apparent diffusion coefficient of the fluorescent molecules. Then, apparent diffusion is linked to electrical conductivity and used to evaluate the efficiency of the passive spread of membrane depolarization along TATS. The method is first validated in cells where most TATS elements are acutely detached by osmotic shock and then applied to probe TATS electrical conductivity in failing heart cells. We find that acute and pathological tubular remodeling significantly affect TATS electrical conductivity. This may explain the occurrence of defects in action potential propagation at the level of single T-tubules, recently observed in diseased cardiomyocytes. PMID:28507142

Electrical resistivity tomography as monitoring tool for unsaturated zone transport: an example of preferential transport of deicing chemicals.

PubMed

Wehrer, Markus; Lissner, Heidi; Bloem, Esther; French, Helen; Totsche, Kai Uwe

2014-01-01

Non-invasive spatially resolved monitoring techniques may hold the key to observe heterogeneous flow and transport behavior of contaminants in soils. In this study, time-lapse electrical resistivity tomography (ERT) was employed during an infiltration experiment with deicing chemical in a small field lysimeter. Deicing chemicals like potassium formate, which frequently impact soils on airport sites, were infiltrated during snow melt. Chemical composition of seepage water and the electrical response was recorded over the spring period 2010. Time-lapse electrical resistivity tomographs are able to show the infiltration of the melt water loaded with ionic constituents of deicing chemicals and their degradation product hydrogen carbonate. The tomographs indicate early breakthrough behavior in parts of the profile. Groundtruthing with pore fluid conductivity and water content variations shows disagreement between expected and observed bulk conductivity. This was attributed to the different sampling volume of traditional methods and ERT due to a considerable fraction of immobile water in the soil. The results show that ERT can be used as a soil monitoring tool on airport sites if assisted by common soil monitoring techniques.

Electroporation of the photosynthetic membrane: structural changes in protein and lipid-protein domains.

PubMed Central

Rosemberg, Y; Rotenberg, M; Korenstein, R

1994-01-01

A biological membrane undergoes a reversible permeability increase through structural changes in the lipid domain when exposed to high external electric fields. The present study shows the occurrence of electric field-induced changes in the conductance of the proton channel of the H(+)-ATPase as well as electric field-induced structural changes in the lipid-protein domain of photosystem (PS) II in the photosynthetic membrane. The study was carried out by analyzing the electric field-stimulated delayed luminescence (EPL), which originates from charge recombination in the protein complexes of PS I and II of photosynthetic vesicles. We established that a small fraction of the total electric field-induced conductance change was abolished by N,N'-dicyclohexylcarbodiimide (DCCD), an inhibitor of the H(+)-ATPase. This reversible electric field-induced conductance change has characteristics of a small channel and possesses a lifetime < or = 1 ms. To detect electric field-induced changes in the lipid-protein domains of PS II, we examined the effects of phospholipase A2 (PLA2) on EPL. Higher values of EPL were observed from vesicles that were exposed in the presence of PLA2 to an electroporating electric field than to a nonelectroporating electric field. The effect of the electroporating field was a long-lived one, lasting for a period > or = 2 min. This effect was attributed to long-lived electric field-induced structural changes in the lipid-protein domains of PS II. PMID:7811916

Impact of monovalent cations on soil structure. Part I. Results of an Iranian soil

NASA Astrophysics Data System (ADS)

Farahani, Elham; Emami, Hojat; Keller, Thomas; Fotovat, Amir; Khorassani, Reza

2018-01-01

This study investigated the impact of monovalent cations on clay dispersion, aggregate stability, soil pore size distribution, and saturated hydraulic conductivity on agricultural soil in Iran. The soil was incubated with treatment solutions containing different concentrations (0-54.4 mmol l-1) of potassium and sodium cations. The treatment solutions included two levels of electrical conductivity (EC=3 or 6 dS m-1) and six K:Na ratios per electrical conductivity level. At both electrical conductivity levels, spontaneously dispersible clay increased with increasing K concentration, and with increasing K:Na ratio. A negative linear relationship between percentage of water-stable aggregates and spontaneously dispersible clay was observed. Clay dispersion generally reduced the mean pore size, presumably due to clogging of pores, resulting in increased water retention. At both electrical conductivity levels, hydraulic conductivity increased with increasing exchangeable potassium percentage at low exchangeable potassium percentage values, but decreased with further increases in exchangeable potassium percentage at higher exchangeable potassium percentage. This is in agreement with earlier studies, but seems in conflict with our data showing increasing spontaneously dispersible clay with increasing exchangeable potassium percentage. Our findings show that clay dispersion increased with increasing K concentration and increasing K:Na ratio, demonstrating that K can have negative impacts on soil structure.

The advantages of the high voltage solar array for electric propulsion

NASA Technical Reports Server (NTRS)

Sater, B. L.

1973-01-01

The high voltage solar array offers improvements in efficiency, weight, and reliability for the electric propulsion power system. Conventional power processes and problems associated with ion thruster operation using SERT 2 experience are discussed and the advantages of the HVSA concept for electric propulsion are presented. Tests conducted operating the SERT 2 thruster system in conjunction with HVSA are reported. Thruster operation was observed to be normal and in some respects improved.

Visualization of Electrical Field of Electrode Using Voltage-Controlled Fluorescence Release

PubMed Central

Jia, Wenyan; Wu, Jiamin; Gao, Di; Wang, Hao; Sun, Mingui

2016-01-01

In this study we propose an approach to directly visualize electrical current distribution at the electrode-electrolyte interface of a biopotential electrode. High-speed fluorescent microscopic images are acquired when an electric potential is applied across the interface to trigger the release of fluorescent material from the surface of the electrode. These images are analyzed computationally to obtain the distribution of the electric field from the fluorescent intensity of each pixel. Our approach allows direct observation of microscopic electrical current distribution around the electrode. Experiments are conducted to validate the feasibility of the fluorescent imaging method. PMID:27253615

Medium's conductivity and stage of growth as crucial parameters for efficient hydrocarbon extraction by electric field from colonial micro-algae.

PubMed

Guionet, Alexis; Hosseini, Bahareh; Akiyama, Hidenori; Hosano, Hamid

2018-04-25

The green algae Botryococcus braunii produces a high amount of extracellular hydrocarbon, making it a promising algae in the field of bio-fuels production. As it mainly produces squalene like hydrocarbons, cosmetic industries are also interested in its milking. Pulsed electric fields (PEF) are an innovative method allowing oil extraction from micro-algae. In common algae accumulating hydrocarbon inside cytoplasm (Chlorella vulgaris, Nannochloropsis sp., etc), electric fields can destroy cell membranes, allowing the release of hydrocarbon. However, for B.braunii, hydrocarbons adhere to the cell wall outside of cells as a matrix. In a previous article we reported that electric fields can unstick cells from a matrix, allowing hydrocarbon harvesting. In this work, we deeper investigated this phenomenon of cell hatching by following 2 parameters: the conductivity of the medium and the cultivation duration of the culture. Cell hatching is accurately evaluated by both microscopic and macroscopic observations. For high conductivity and a short time of cultivation, almost no effect is observed even after up to 1000 PEF pulses are submitted to the cells. While lower conductivity and a longer cultivation period allow strong cell hatching after 200 PEF pulses are applied to the cells. We identify 2 new crucial parameters, able to turn the method from inefficient to very efficient. It might help companies to save energy and money in case of mass production. Copyright © 2018. Published by Elsevier B.V.

Electrical and mechanical behavior of polymethyl methacrylate/cadmium sulphide composites

NASA Astrophysics Data System (ADS)

Kaur, Rajdeep; Samra, Kawaljeet Singh

2018-06-01

In the present investigation, electrical and mechanical behavior of cadmium sulphide (CdS) doped polymethyl methacrylate (PMMA) have been studied using different techniques. Dip casting technique was used for preparing free standing films of pristine and CdS doped PMMA at different compositions (i.e. 1 and 5 wt%). Optical absorbance as a function of wavelength was studied, by UV-visible spectroscopy, to find the impact of CdS doping on the optical band gap of synthesized PMMA/CdS composite. DC and AC conductivities were measured as a function of dopant concentration and temperature. Considerable increase in electrical conductivity was observed with the increase of CdS contents in polymer matrix. Overall electrical conduction mechanism in PMMA/CdS composites was attributed to movement of electrons through the uniformly distributed CdS aggregates within the matrix of PMMA. Mechanical properties, such as Young's modulus, tensile strength, elongation and ductility, of PMMA/CdS composites were determined and relevant responsible phenomena were discussed.

Proton-Induced Conductivity Enhancement in AlGaN/GaN HEMT Devices

NASA Astrophysics Data System (ADS)

Lee, In Hak; Lee, Chul; Choi, Byoung Ki; Yun, Yeseul; Chang, Young Jun; Jang, Seung Yup

2018-04-01

We investigated the influence of proton irradiation on the AlGaN/GaN high-electron-mobility transistor (HEMT) devices. Unlike previous studies on the degradation behavior upon proton irradiation, we observed improvements in their electrical conductivity and carrier concentration of up to 25% for the optimal condition. As we increased the proton dose, the carrier concentration and the mobility showed a gradual increase and decrease, respectively. From the photoluminescence measurements, we observed a reduction in the near-band-edge peak of GaN ( 366 nm), which correlate on the observed electrical properties. However, neither the Raman nor the X-ray diffraction analysis showed any changes, implying a negligible influence of protons on the crystal structures. We demonstrated that high-energy proton irradiation could be utilized to modify the transport properties of HEMT devices without damaging their crystal structures.

Anisotropic electrical conduction and reduction in dangling-bond density for polycrystalline Si films prepared by catalytic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Niikura, Chisato; Masuda, Atsushi; Matsumura, Hideki

1999-07-01

Polycrystalline Si (poly-Si) films with high crystalline fraction and low dangling-bond density were prepared by catalytic chemical vapor deposition (Cat-CVD), often called hot-wire CVD. Directional anisotropy in electrical conduction, probably due to structural anisotropy, was observed for Cat-CVD poly-Si films. A novel method to separately characterize both crystalline and amorphous phases in poly-Si films using anisotropic electrical conduction was proposed. On the basis of results obtained by the proposed method and electron spin resonance measurements, reduction in dangling-bond density for Cat-CVD poly-Si films was achieved using the condition to make the quality of the included amorphous phase high. The properties of Cat-CVD poly-Si films are found to be promising in solar-cell applications.

Electrical properties of dispersions of graphene in mineral oil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monteiro, O. R., E-mail: othon.monteiro@bakerhughes.com

2014-02-03

Dispersions of graphene in mineral oil have been prepared and electrical conductivity and permittivity have been measured. The direct current (DC) conductivity of the dispersions depends on the surface characteristics of the graphene platelets and followed a percolation model with a percolation threshold ranging from 0.05 to 0.1 wt. %. The difference in DC conductivities can be attributed to different states of aggregation of the graphene platelets and to the inter-particle electron transfer, which is affected by the surface radicals. The frequency-dependent conductivity (σ(ω)) and permittivity (ε(ω)) were also measured. The conductivity of dispersions with particle contents much greater than themore » percolation threshold remains constant and equal to the DC conductivity at low frequencies ω with and followed a power-law σ(ω)∝ ω{sup s} dependence at very high frequencies with s≈0.9. For dispersions with graphene concentration near the percolation threshold, a third regime was displayed at intermediate frequencies indicative of interfacial polarization consistent with Maxwell-Wagner effect typically observed in mixtures of two (or more) phases with very distinct electrical and dielectric properties.« less

The sub-auroral electric field as observed by DMSP and the new SuperDARN mid-latitude radars

NASA Astrophysics Data System (ADS)

Talaat, E. R.; Sotirelis, T.; Hairston, M. R.; Ruohoniemi, J. M.; Greenwald, R. A.; Lester, M.

2008-12-01

In this paper we present analyses of the sub-auroral electric field environment as observed from both space and ground. We discuss the dependency of the configuration and strength of the sub-auroral electric field on IMF and geomagnetic activity, longitudinal, seasonal, and solar cycle variability. Primarily, e use ~20 years of electric field measurement dataset derived from the suite of DMSP ion drift meters. A major component of our analysis is correctly specifying the aurora boundary, as the behavior and magnitude of these fields will be drastically different away from the high-conductance auroral oval. As such, we use the coincident particle flux measurements from the DMSP SSJ4 monitors. We also present the solar minimum observations of the sub-auroral flow newly available from the mid-latitude SuperDARN radars at Wallops and Blackstone in Virginia. Preliminary comparisons between these flows and the DMSP climatology are discussed.

Flexible, transparent electrodes using carbon nanotubes

PubMed Central

2012-01-01

We prepare thin single-walled carbon nanotube networks on a transparent and flexible substrate with different densities, using a very simple spray method. We measure the electric impedance at different frequencies Z(f) in the frequency range of 40 Hz to 20 GHz using two different methods: a two-probe method in the range up to 110 MHz and a coaxial (Corbino) method in the range of 10 MHz to 20 GHz. We measure the optical absorption and electrical conductivity in order to optimize the conditions for obtaining optimum performance films with both high electrical conductivity and transparency. We observe a square resistance of 1 to 8.5 kΩ for samples showing 65% to 85% optical transmittance, respectively. For some applications, we need flexibility and not transparency: for this purpose, we deposit a thick film of single-walled carbon nanotubes on a flexible silicone substrate by spray method from an aqueous suspension of carbon nanotubes in a surfactant (sodium dodecyl sulphate), thereby obtaining a flexible conducting electrode showing an electrical resistance as low as 200 Ω/sq. When stretching up to 10% and 20%, the electrical resistance increases slightly, recovering the initial value for small elongations up to 10%. We analyze the stretched and unstretched samples by Raman spectroscopy and observe that the breathing mode on the Raman spectra is highly sensitive to stretching. The high-energy Raman modes do not change, which indicates that no defects are introduced when stretching. Using this method, flexible conducting films that may be transparent are obtained just by employing a very simple spray method and can be deposited on any type or shape of surface. PMID:23074999

Performance of fuel cell using calcium phosphate hydrogel membrane prepared from waste incineration fly ash and chicken bone powder.

PubMed

Fukui, Kunihiro; Arimitsu, Naoki; Jikihara, Kenji; Yamamoto, Tetsuya; Yoshida, Hideto

2009-09-15

Waste incineration fly ash and bone powder could be successfully recycled to calcium phosphate hydrogel, a type of fast proton conductor. The electric conductivity of the crystallized hydrogel from them was compared with that from calcium carbonate reagent. It was found that the conductivity of the hydrogel from bone powder is almost equal to that from calcium carbonate reagent, which is higher than that from incineration fly ash. Because the crystallized hydrogel from incineration ash has a lower crystallinity than that from bone powder and calcium carbonate reagent. However, the difference of the conductivity among them can be hardly observed above 100 degrees C. The fuel cell with membrane electrode assembly (MEA) using the calcium phosphate hydrogel membrane prepared from incineration fly ash and bone powder was observed to generate electricity. The performance of fuel cells having the hydrogel membrane obtained from all raw materials increases with the cell temperature, and the fuel cell containing the hydrogel membrane from incineration fly ash has the highest dependence of the fuel cell performance. For this reason, the difference in the cell performance among them can be hardly observed above 120 degrees C. This tendency agrees with the change in the electric conductivity with the temperature. Further, the performance of all fuel cells with the hydrogel membrane is superior to that of the fuel cell with perfluorosulfonic polymer membrane at temperatures greater than approximately 85 degrees C.

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

NASA Astrophysics Data System (ADS)

Farges, Thomas; Garcia, Geraldine; Blanc, Elisabeth

2010-05-01

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

Self-organized composites of multiwalled carbon nanotubes and nematic liquid crystal 5CB: optical singularities and percolation behavior in electrical conductivity

NASA Astrophysics Data System (ADS)

Ponevchinsky, V. V.; Goncharuk, A. I.; Vasil'ev, V. I.; Lebovka, N. I.; Soskin, M. S.

2009-10-01

This work discusses optical singularities and electrical conductivity behavior in a thin electrooptical cell filled with composites including multi-walled carbon nanotubes (MWCNTs) and nematic liquid crystal (LC). The MWCNTs with high aspect ratio L/d~300 ÷ 1000 and nematic LC 5CB (4-pentyl-40-cyanobiphenyl) were used. The composites were prepared by introduction of MWCNTs (0.0001÷0.1% wt) into LC solvent with subsequent sonication. The increase of MWCNT concentration (between 0.005÷0.05 % wt) resulted in self-organization of MWCNTs and formation of micronsized aggregates with fractal boundaries. The visually observed formation of spanning MWCNT networks near the percolation threshold at ~0.025 % wt was accompanied with transition from non-conductive to conductive state and generation of optical singularities. The observed effects were explained by the strong interactions between MWCNTs and LC medium and planar orientation of 5CB molecules near the lateral surface of MWCNTs. It was speculated that optical singularities arose as a results of interaction of an incident laser beam with LC perturbed interfacial shells covering the MWCNT clusters. Behavior of the interfacial shell thickness in external electric field and in the vicinity of the nematic to isotropic transition was discussed.

High field conduction in Pb doped amorphous Se-Te system

NASA Astrophysics Data System (ADS)

Anjali, Patial, Balbir Singh; Thakur, Nagesh

2018-05-01

In the present study, DC conductivity measurements of as-Se80-xTe20Pbx (x = 0, 1 and 2) glassy alloys are made in the temperature range 298-318 K and in the voltage range 0-180 V. Current-voltage (I-V) characteristics point toward ohmic behavior at low electric field and non-ohmic is observed at high electric field. The variation of ln(I/V) against V are nearly found straight curves but slope of these curves does not decrease linearly with temperature indicates that the space charge limited conduction (SCLC) is absent. Instead the linear relation between ln(I) and V1/2 confirms that the conduction is either Poole-Frenkel type or Schottky emission. A detailed analysis shows that the dominant mechanism is Poole-Frenkel type conduction.

Electrical conductivity of Icelandic deep geothermal reservoirs: insight from HT-HP laboratory experiments

NASA Astrophysics Data System (ADS)

Nono, Franck; Gibert, Benoit; Loggia, Didier; Parat, Fleurice; Azais, Pierre; Cichy, Sarah

2016-04-01

Although the Icelandic geothermal system has been intensively investigated over the years, targeting increasingly deeper reservoirs (i.e. under supercritical conditions) requires a good knowledge of the behaviour of physical properties of the host rock in order to better interpret large scale geophysical observations. In particular, the interpretation of deep electrical soundings remains controversial as only few studies have investigated the influence of altered minerals and pore fluid properties on electrical properties of rocks at high temperature and pressure. In this study, we investigate the electrical conductivity of drilled samples from different Icelandic geothermal fields at elevated temperature, confining pressure and pore pressure conditions (100°C < T < 600°C, confining pressure up to 100 MPa and pore pressure up to 35 MPa). The investigated rocks are composed of hyaloclastites, dolerites and basalts taken from depths of about 800 m for the hyaloclastites, to almost 2500 m for the dolerites. They display different porosity structures, from vuggy and intra-granular to micro-cracked porosities, and have been hydrothermally alterated in the chlorite to amphibolite facies. Electrical conductivity measurements are first determined at ambient conditions as a function of pore fluid conductivity in order to establish their relationships with lithology and pore space topology, prior to the high pressure and temperature measurements. Cementation factor varies from 1.5 for the dolerites to 2.83 for the basalt, reflecting changes in the shape of the conductive channels. The surface conductivities, measured at very low fluid conductivity, increases with the porosity and is correlated with the cation exchange capacity. At high pressure and temperature, we used the two guard-ring electrodes system. Measurements have been performed in dry and saturated conditions as a function of temperature and pore pressure. The supercritical conditions have been investigated and temperature cycles have been performed systematically. Dry electrical conductivity measurements show for most of the samples irreversible changes when temperatures exceed 500°C. These changes are interpreted as destabilization/dehydration of alteration minerals that could lead to the presence of a conductive fluid phase in the samples. Very low and high salinity (NaCl) electrical conductivity measurements have been performed as a function of temperature. At supercritical conditions, electrical conductivity at low salinity is not pore pressure dependent and surface conduction is preponderant. At saturated conditions, the rock's electrical conductivity increases linearly (as a function of T-1) until 350°C. Above 350°C, the conductivity decreases. All rock types exhibit the same increasing rate. This work was funded by the of the EC project IMAGE (Integrated Methods for Advanced Geothermal Exploration, grant agreement No. 608553).

Electrical and dielectric properties of PVdF-HFP - PMMA - (PC + DEC)- LiClO4 based gel polymer electrolyte

NASA Astrophysics Data System (ADS)

Gohel, Khushbu; Kanchan, D. K.; Maheshwaran, C.

2018-04-01

In the present paper, AC impedance studies have been measured to evaluate ion conduction behavior of (PVdF-HFP - PMMA) + (PC-DEC) + LiClO4 gel polymer electrolyte system prepared by solution casting method. Structural characterization and morphology has been carried out using XRD and SEM respectively. The AC conductivity and dielectric permittivity, electric modulus and relaxation mechanism have been studied. The variation of ac conductivity with frequency obeys Jonscher power law. Maximum value of dielectric constant ɛ' in the lower frequency region has been observed for the gel polymer electrolyte containing 7.5 wt% LiClO4. The highest conducting sample shows the shortest relaxation time.

Anisotropy of electrical conductivity in dc due to intrinsic defect formation in α-Al2O3 single crystal implanted with Mg ions

NASA Astrophysics Data System (ADS)

Tardío, M.; Egaña, A.; Ramírez, R.; Muñoz-Santiuste, J. E.; Alves, E.

2016-07-01

The electrical conductivity in α-Al2O3 single crystals implanted with Mg ions in two different crystalline orientations, parallel and perpendicular to c axis, was investigated. The samples were implanted at room temperature with energies of 50 and 100 keV and fluences of 1 × 1015, 5 × 1015 and 5 × 1016 ions/cm2. Optical characterization reveals slight differences in the absorption bands at 6.0 and 4.2 eV, attributed to F type centers and Mie scattering from Mg precipitates, respectively. DC electrical measurements using the four and two-point probe methods, between 295 and 490 K, were used to characterize the electrical conductivity of the implanted area (Meshakim and Tanabe, 2001). Measurements in this temperature range indicate that: (1) the electrical conductivity is thermally activated independently of crystallographic orientation, (2) resistance values in the implanted region decrease with fluence levels, and (3) the I-V characteristic of electrical contacts in samples with perpendicular c axis orientation is clearly ohmic, whereas contacts are blocking in samples with parallel c axis. When thin layers are sequentially removed from the implanted region by immersing the sample in a hot solution of nitric and fluorhydric acids the electrical resistance increases until reaching the values of non-implanted crystal (Jheeta et al., 2006). We conclude that the enhancement in conductivity observed in the implanted regions is related to the intrinsic defects created by the implantation rather than to the implanted Mg ions (da Silva et al., 2002; Tardío et al., 2001; Tardío et al., 2008).

Passive safety device and internal short tested method for energy storage cells and systems

DOEpatents

Keyser, Matthew; Darcy, Eric; Long, Dirk; Pesaran, Ahmad

2015-09-22

A passive safety device for an energy storage cell for positioning between two electrically conductive layers of the energy storage cell. The safety device also comprising a separator and a non-conductive layer. A first electrically conductive material is provided on the non-conductive layer. A first opening is formed through the separator between the first electrically conductive material and one of the electrically conductive layers of the energy storage device. A second electrically conductive material is provided adjacent the first electrically conductive material on the non-conductive layer, wherein a space is formed on the non-conductive layer between the first and second electrically conductive materials. A second opening is formed through the non-conductive layer between the second electrically conductive material and another of the electrically conductive layers of the energy storage device. The first and second electrically conductive materials combine and exit at least partially through the first and second openings to connect the two electrically conductive layers of the energy storage device at a predetermined temperature.

Electrical studies of D%AgI-(100-D)%[0.667Ag2O- 0.333{(0.4)B2O3-(0.6)TeO2}] fast ion conducting glasses

NASA Astrophysics Data System (ADS)

Kumar, E. Ramesh; Nageswar Rao, P.; Appa Rao, B.

2016-09-01

Super ion conducting glasses of composition D%AgI-(100-D)%[MAg2O-F{(F1)B2O3- (F2)TeO2}]; D=10.0 to 60.0 in steps of 10.0 for a fixed values of F1 (0.4), F2 (0.6) which are glass network formers, fixed values of modifier M(0.667), F (0.333) and D is dopant salt which was varied. These glasses were prepared by melt quenching technique. XRD spectra taken for all the samples. Electrical characterization was done in terms of AC and DC conductivities. DC and AC conductivities at room temperature increased from 10-5 to 10-1 scm-1 and DC activation energy (Edc) found to decrease from 0.36 to 0.19eV with increase in D% ratio. Measurements are performed over the frequency range 1 kHz to 3 MHz at different temperatures. From the impedance spectroscopy real and imaginary parts of impedances (Z', Z"), conductivities were calculated and plotted, and equivalent R-C circuit parameters were obtained from Cole-Cole plots. With the increase in D%, AC conductivity is observed to increase whereas the AC activation energy (Eac) is observed to decrease from 0.23 to 0.14 eV. The quantitative analysis of these results indicates that the electrical conductivity of silver borate glasses is enhanced with increase in D% ratio. Based on conductivity values these glasses are ionic conductors, in which conduction is by hopping mechanism. An attempt is made to understand the charge transportation process.

Electrically tunable spatially variable switching in ferroelectric liquid crystal/water system

NASA Astrophysics Data System (ADS)

Choudhary, A.; Coondoo, I.; Prakash, J.; Sreenivas, K.; Biradar, A. M.

2009-04-01

An unusual switching phenomenon in the region outside conducting patterned area in ferroelectric liquid crystal (FLC) containing about 1-2 wt % of water has been observed. The presence of water in the studied heterogeneous system was confirmed by Fourier transform infrared spectroscopy. The observed optical studies have been emphasized on the "spatially variable switching" phenomenon of the molecules in the nonconducting region of the cell. The observed phenomenon is due to diffusion of water between the smectic layers of the FLC and the interaction of the curved electric field lines with the FLC molecules in the nonconducting region.

Micromechanical and Electrical Properties of Monolithic Aluminum Nitride at High Temperatures

NASA Technical Reports Server (NTRS)

Goldsby, Jon C.

2000-01-01

Micromechanical spectroscopy of aluminum nitride reveals it to possess extremely low background internal friction at less than 1x10(exp-4) logarithmic decrement (log dec) from 20 to 1200 T. Two mechanical loss peaks were observed, the first at 350 C approximating a single Debye peak with a peak height of 60x10(exp-4) log dec. The second peak was seen at 950 'C with a peak height of 20x 10' log dec and extended from 200 to over 1200 C. These micromechanical observations manifested themselves in the electrical behavior of these materials. Electrical conduction processes were predominately intrinsic. Both mechanical and electrical relaxations appear to be thermally activated processes, with activation energies of 0.78 and 1.32 eV respectively.

Micromechanical and Electrical Properties of Monolithic Aluminum Nitride at High Temperatures

NASA Technical Reports Server (NTRS)

Goldsby, Jon C.

2001-01-01

Micromechanical spectroscopy of aluminum nitride reveals it to possess extremely low background internal friction at less than 1 x 10 (exp -4) logarithmic decrement (log dec.) from 20 to 1200 C. Two mechanical loss peaks were observed, the first at 350 C approximating a single Debye peak with a peak height of 60 x 10 (exp -4) log dec. The second peak was seen at 950 C with a peak height of 20 x 10 (exp -4) log dec. and extended from 200 to over 1200 C. These micromechanical observations manifested themselves in the electrical behavior of these materials. Electrical conduction processes were predominately intrinsic. Both mechanical and electrical relaxations appear to be thermally activated processes, with activation energies of 0.78 and 1.32 eV respectively.

Construction of conductive multilayer films of biogenic triangular gold nanoparticles and their application in chemical vapour sensing

NASA Astrophysics Data System (ADS)

Singh, Amit; Chaudhari, Minakshi; Sastry, Murali

2006-05-01

Metal nanoparticles are interesting building blocks for realizing films for a number of applications that include bio- and chemical sensing. To date, spherical metal nanoparticles have been used to generate functional electrical coatings. In this paper we demonstrate the synthesis of electrically conductive coatings using biologically prepared gold nanotriangles as the building blocks. The gold nanotriangles are prepared by the reduction of aqueous chloroaurate ions using an extract of the lemongrass plant (Cymbopogon flexuosus) which are thereafter assembled onto a variety of substrates by simple solution casting. The conductivity of the film shows a drastic fall upon mild heat treatment, leading to the formation of electrically conductive thin films of nanoparticles. We have also investigated the possibility of using the gold nanotriangle films in vapour sensing. A large fall in film resistance is observed upon exposure to polar molecules such as methanol, while little change occurs upon exposure to weakly polar molecules such as chloroform.

Molecular modeling of diffusion coefficient and ionic conductivity of CO2 in aqueous ionic solutions.

PubMed

Garcia-Ratés, Miquel; de Hemptinne, Jean-Charles; Bonet Avalos, Josep; Nieto-Draghi, Carlos

2012-03-08

Mass diffusion coefficients of CO(2)/brine mixtures under thermodynamic conditions of deep saline aquifers have been investigated by molecular simulation. The objective of this work is to provide estimates of the diffusion coefficient of CO(2) in salty water to compensate the lack of experimental data on this property. We analyzed the influence of temperature, CO(2) concentration,and salinity on the diffusion coefficient, the rotational diffusion, as well as the electrical conductivity. We observe an increase of the mass diffusion coefficient with the temperature, but no clear dependence is identified with the salinity or with the CO(2) mole fraction, if the system is overall dilute. In this case, we notice an important dispersion on the values of the diffusion coefficient which impairs any conclusive statement about the effect of the gas concentration on the mobility of CO(2) molecules. Rotational relaxation times for water and CO(2) increase by decreasing temperature or increasing the salt concentration. We propose a correlation for the self-diffusion coefficient of CO(2) in terms of the rotational relaxation time which can ultimately be used to estimate the mutual diffusion coefficient of CO(2) in brine. The electrical conductivity of the CO(2)-brine mixtures was also calculated under different thermodynamic conditions. Electrical conductivity tends to increase with the temperature and salt concentration. However, we do not observe any influence of this property with the CO(2) concentration at the studied regimes. Our results give a first evaluation of the variation of the CO(2)-brine mass diffusion coefficient, rotational relaxation times, and electrical conductivity under the thermodynamic conditions typically encountered in deep saline aquifers.

Influence Of The Redox State On The Electrical Conductivity Of Basaltic Melts

NASA Astrophysics Data System (ADS)

Pommier, A.; Gaillard, F.; Pichavant, M.

2007-12-01

The electrical conductivity is an efficient probe of mass transfer processes within silicate melts and magmas. Previous studies have established that the electrical conductivity is sensitive to parameters such as temperature, melt composition and pressure. In contrast to what is known for Fe-bearing minerals, little attention has been given to the influence of redox state on the electrical conductivity of melts. Experiments were performed on tephritic and basaltic compositions respectively from Mt. Vesuvius and Pu'u 'O'o. Measurements were carried out on cylindrical glass samples (OD: 6 mm, ID: 1 mm, L: 8 mm) drilled from glass obtained by fusing each rock sample at 1400°C in air. A two-electrode configuration was adopted, with the electrical impedance being radially measured. A Pt wire was used as the internal electrode whereas a Pt tube served as the external electrode. Experiments were conducted at 1 atm in a vertical furnace between 1200°C and 1300°C, both in air and in a CO-CO2 atmosphere at a fO2 corresponding to NNO+1. Both reduction and oxidation experiments were performed. In reduction experiments (pure CO2 then CO-CO2 gas mixture), electrical conductivities progressively increase with time. The reverse is observed in oxidation experiments (CO-CO2 gas mixture then pure CO2). These variations of electrical conductivities are correlated with modifications of the Fe2+/Fe3+ ratio in the melt, and are consistent with the respective structural roles of Fe2+ and Fe3+. In both types of experiments, a minimum of about 400 mn is necessary before a plateau is reached, interpreted to reflect the kinetics of attainment of the equilibrium Fe2+/Fe3+ ratio in the melt. Differences between plateau and initial values are typically of a few ohms, much higher than the sensitivity of our measurements (better than 0.1 ohm). When increasing temperature, the time required for reaching plateau values decreases. At NNO+1, the electrical activation energy (Ea) was determined for both compositions: Ea=137 kJ/mol (tephrite) and 73 kJ/mol (basalt). Further experiments are necessary to quantify the influence of redox state on electrical conductivity, especially at fO2 below NNO+1.

Polarization-coupled tunable resistive behavior in oxide ferroelectric heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gruverman, Alexei; Tsymbal, Evgeny Y.; Eom, Chang-Beom

2017-05-03

This research focuses on investigation of the physical mechanism of the electrically and mechanically tunable resistive behavior in oxide ferroelectric heterostructures with engineered interfaces realized via a strong coupling of ferroelectric polarization with tunneling electroresistance and metal-insulator (M-I) transitions. This report describes observation of electrically conductive domain walls in semiconducting ferroelectrics, voltage-free control of resistive switching and demonstration of a new mechanism of electrical control of 2D electron gas (2DEG) at oxide interfaces. The research goals are achieved by creating strong synergy between cutting-edge fabrication of epitaxial single-crystalline complex oxides, nanoscale electrical characterization by scanning probe microscopy and theoretical modelingmore » of the observed phenomena. The concept of the ferroelectric devices with electrically and mechanically tunable nonvolatile resistance represents a new paradigm shift in realization of the next-generation of non-volatile memory devices and low-power logic switches.« less

Hydrothermal temperature effect on crystal structures, optical properties and electrical conductivity of ZnO nanostructures

NASA Astrophysics Data System (ADS)

Dhafina, Wan Almaz; Salleh, Hasiah; Daud, Mohd Zalani; Ghazali, Mohd Sabri Mohd; Ghazali, Salmah Mohd

2017-09-01

ZnO is an wide direct band gap semiconductor and possess rich family of nanostructures which turned to be a key role in the nanotechnology field of applications. Hydrothermal method was proven to be simple, robust and low cost among the reported methods to synthesize ZnO nanostructures. In this work, the properties of ZnO nanostructures were altered by varying temperatures of hydrothermal process. The changes in term of morphological, crystal structures, optical properties and electrical conductivity were investigated. A drastic change of ZnO nanostructures morphology and decreases of 002 diffraction peak were observed as the hydrothermal temperature increased. The band gap of samples decreased as the size of ZnO nanostructure increased, whereas the electrical conductivity had no influence on the band gap value but more on the morphology of ZnO nanostructures instead.

Crystal growth and electrical properties of CuFeO 2 single crystals

NASA Astrophysics Data System (ADS)

Dordor, P.; Chaminade, J. P.; Wichainchai, A.; Marquestaut, E.; Doumerc, J. P.; Pouchard, M.; Hagenmuller, P.; Ammar, A.

1988-07-01

Delafossite-type CuFeO 2 single crystals have been prepared by a flux method: crystals obtained in a Cu crucible with LiBO 2 as flux are n-type whereas those prepared in a Pt crucible with a Cu 2O flux are p-type. Electrical measurements have revealed that n-type crystals exhibit weak anisotropic conductivities with large activation energies and small mobilities (r.t. values perpendicular and parallel to the c-axis: μ⊥ = 5 × 10 -5 and μ‖ = 10 -7 cm -2 V -1 sec -1). p-type crystals, less anisotropic, are characterized by low activation energies and higher mobilities ( μ⊥ = 34 and μ‖ = 8.9 cm 2 V -1 sec -1). A two -conduction-band model is proposed to account for the difference observed between the energy gap value deduced from photoelectrochemical measurements and the activation energy of the electrical conductivity in the intrinsic domain.

Structure, Raman, dielectric behavior and electrical conduction mechanism of strontium titanate

NASA Astrophysics Data System (ADS)

Trabelsi, H.; Bejar, M.; Dhahri, E.; Graça, M. P. F.; Valente, M. A.; Khirouni, K.

2018-05-01

Strontium titanate was prepared by solid-state reaction method. According to the XRD, it was single phase and has a cubic perovskite structure. The Raman spectroscopic investigation was carried out at room-temperature, and the second-order Raman modes were observed. By employing impedance spectroscopy, the dielectric relaxation and electrical properties were investigated over the temperature range of 500-700 K at various frequencies. The activation energies evaluated from dielectric and modulus studies are in good agreement and these values are attributed to the bulk relaxation. The impedance data were well fitted to an (R1//C1)-(R2//CPE1) equivalent electrical circuit. It could be concluded that the grain boundaries are more resistive and capacitive than the grains. The ac conductivity was found to follow the Jonscher's universal dynamic law ωS and the correlated barrier hopping model (CBH) has been proposed to describe the conduction mechanism.

Effect of Aspect Ratio on Electrical, Rheological and Glass Transition Properties of PC/MWCNT Nanocomposites.

PubMed

Cruz, Heidy; Son, Younggon

2018-02-01

Since the discovery of carbon nanotubes (CNT), significant research works have focused on the application of CNT as conductive filler to polymer nanocomposites which can be used in several fields such as electrostatic dissipation (ESD), electrostatic painting and electromagnetic interference shielding (EMI-shielding). However, the main challenge in the large-scale manufacturing of this technology is the poor electrical conductivity of polymer nanocomposites produced by injection molding process. This study aims to investigate the effect of CNT aspect ratio in improving the electrical conductivity of injection molded nanocomposites. In this work, three types of multiwall carbon nanotubes with different lengths were melt-mixed with polycarbonate in a twin screw extruder followed by injection and compression molding. Results show that nanocomposites with higher CNT aspect ratio exhibit higher electrical conductivity. Longer nanotubes form a stronger conductive network during secondary agglomeration which can withstand the high shear forces during injection molding. Higher melt viscosity and storage modulus were observed in nanocomposites with higher CNT aspect ratio which is attributed to the effective constriction of polymer chains by longer nanotubes. It was also found that Tg of the composites increased with nanotube aspect ratio and the addition of CNT causes degradation which leads to the general Tg depression of polycarbonate.

Downhole transmission system

DOEpatents

Hall, David R [Provo, UT; Fox, Joe [Spanish Fork, UT

2008-01-15

A transmission system in a downhole component comprises a data transmission element in both ends of the downhole component. Each data transmission element houses an electrically conducting coil in a MCEI circular trough. An electrical conductor connects both the transmission elements. The electrical conductor comprises at least three electrically conductive elements insulated from each other. In the preferred embodiment the electrical conductor comprises an electrically conducting outer shield, an electrically conducting inner shield and an electrical conducting core. In some embodiments of the present invention, the electrical conductor comprises an electrically insulating jacket. In other embodiments, the electrical conductor comprises a pair of twisted wires. In some embodiments, the electrical conductor comprises semi-conductive material.

Convective Electrokinetic Instability With Conductivity Gradients

NASA Astrophysics Data System (ADS)

Chen, Chuan-Hua; Lin, Hao; Lele, Sanjiva; Santiago, Juan

2003-11-01

Electrokinetic flow instability has been experimentally identified and quantified in a glass T-junction microchannel system with a cross section of 11 um x 155 um. In this system, buffers of different conductivities were electrokinetically driven into a common mixing channel by a DC electric field. A convective instability was observed with a threshold electric field of 0.45 kV/cm for a 10:1 conductivity ratio. A physical model has been developed which consists of a modified Ohmic model formulation for electrolyte solutions and the Navier-Stokes equations with an electric body force term. The model and experiments show that bulk charge accumulation in regions of conductivity gradients is the key mechanism of such instabilities. A linear stability analysis was performed in a convective framework, and Briggs-Bers criteria were applied to determine the nature of instability. The analysis shows the instability is governed by two key parameters: the ratio of molecular diffusion to electroviscous time scale which governs the onset of instability, and the ratio of electroviscous to electroosmotic velocity which governs whether the instability is convective or absolute. The model predicted critical electric field, growth rate, wavelength, and phase speed which were comparable to experimental data.

Swelling kinetics and electrical charge transport in PEDOT:PSS thin films exposed to water vapor.

PubMed

Sarkar, Biporjoy; Jaiswal, Manu; Satapathy, Dillip K

2018-06-06

We report the swelling kinetics and evolution of the electrical charge transport in poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS) thin films subjected to water vapor. Polymer films swell by the diffusion of water vapor and are found to undergo structural relaxations. Upon exposure to water vapor, primarily the hygroscopic PSS shell, which surrounds the conducting PEDOT-rich cores, takes up water vapor and subsequently swells. We found that the degree of swelling largely depends on the PEDOT to PSS ratio. Swelling driven microscopic rearrangement of the conducting PEDOT-rich cores in the PSS matrix strongly influences the electrical charge transport of the polymer film. Swelling induced increase as well as decrease of electrical resistance are observed in polymer films having different PEDOT to PSS ratio. This anomalous charge transport behavior in PEDOT:PSS films is reconciled by taking into account the contrasting swelling behavior of the PSS and the conducting PEDOT-rich cores leading to spatial segregation of PSS in films with PSS as a minority phase and by a net increase in mean separation between conducting PEDOT-rich cores for films having abundance of PSS.

Swelling kinetics and electrical charge transport in PEDOT:PSS thin films exposed to water vapor

NASA Astrophysics Data System (ADS)

Sarkar, Biporjoy; Jaiswal, Manu; Satapathy, Dillip K.

2018-06-01

We report the swelling kinetics and evolution of the electrical charge transport in poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS) thin films subjected to water vapor. Polymer films swell by the diffusion of water vapor and are found to undergo structural relaxations. Upon exposure to water vapor, primarily the hygroscopic PSS shell, which surrounds the conducting PEDOT-rich cores, takes up water vapor and subsequently swells. We found that the degree of swelling largely depends on the PEDOT to PSS ratio. Swelling driven microscopic rearrangement of the conducting PEDOT-rich cores in the PSS matrix strongly influences the electrical charge transport of the polymer film. Swelling induced increase as well as decrease of electrical resistance are observed in polymer films having different PEDOT to PSS ratio. This anomalous charge transport behavior in PEDOT:PSS films is reconciled by taking into account the contrasting swelling behavior of the PSS and the conducting PEDOT-rich cores leading to spatial segregation of PSS in films with PSS as a minority phase and by a net increase in mean separation between conducting PEDOT-rich cores for films having abundance of PSS.

Water-Enabled Healing of Conducting Polymer Films.

PubMed

Zhang, Shiming; Cicoira, Fabio

2017-10-01

The conducting polymer polyethylenedioxythiophene doped with polystyrene sulfonate (PEDOT:PSS) has become one of the most successful organic conductive materials due to its high air stability, high electrical conductivity, and biocompatibility. In recent years, a great deal of attention has been paid to its fundamental physicochemical properties, but its healability has not been explored in depth. This communication reports the first observation of mechanical and electrical healability of PEDOT:PSS thin films. Upon reaching a certain thickness (about 1 µm), PEDOT:PSS thin films damaged with a sharp blade can be electrically healed by simply wetting the damaged area with water. The process is rapid, with a response time on the order of 150 ms. Significantly, after being wetted the films are transformed into autonomic self-healing materials without the need of external stimulation. This work reveals a new property of PEDOT:PSS and enables its immediate use in flexible and biocompatible electronics, such as electronic skin and bioimplanted electronics, placing conducting polymers on the front line for healing applications in electronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel Electrospun Dual-Layered Composite Nanofibrous Membrane Endowed with Electricity-Magnetism Bifunctionality at One Layer and Photoluminescence at the Other Layer.

PubMed

Wang, Zijiao; Ma, Qianli; Dong, Xiangting; Li, Dan; Xi, Xue; Yu, Wensheng; Wang, Jinxian; Liu, Guixia

2016-10-05

Dual-layered composite nanofibrous membrane equipped with electrical conduction, magnetism and photoluminescence trifunctionality is constructed via electrospinning. The composite membrane consists of a polyaniline (PANI)/Fe 3 O 4 nanoparticles (NPs)/polyacrylonitrile (PAN) tuned electrical-magnetic bifunctional nanofibrous layer at one side and a Eu(TTA) 3 (TPPO) 2 /polyvinylpyrrolidone (PVP) photoluminescent nanofibrous layer at the other side, and the two layers are tightly combined face-to-face together into the novel dual-layered composite membrane with trifunctionality. The electric conductivity and magnetism of electrical-magnetic bifunctionality can be respectively tunable via modulating the respective PANI and Fe 3 O 4 NPs contents, and the highest electric conductivity approaches the order of 1 × 10 -2 S cm -1 . Predominant red emission at 615 nm can be obviously observed in the photoluminescent layer under 366 nm excitation. Moreover, the luminescent intensity of photoluminescent layer is almost unaffected by the electrical-magnetic bifunctional layer because of the fact that the photoluminescent materials have been successfully isolated from dark-colored PANI and Fe 3 O 4 NPs. The novel dual-layered composite nanofibrous membrane with trifunctionality has potentials in many fields. Furthermore, the design philosophy and fabrication method for the dual-layered multifunctional membrane provide a new and facile strategy toward other membranes with multifunctionality.

Conduction in In 2O 3/YSZ heterostructures: Complex interplay between electrons and ions, mediated by interfaces

DOE PAGES

Veal, B. W.; Eastman, J. A.

2017-03-01

Thin film In 2O 3/YSZ heterostructures exhibit significant increases in electrical conductance with time when small in-plane electric fields are applied. Contact resistances between the current electrodes and film, and between current electrodes and substrate are responsible for the behavior. With an in-plane electric field, different field profiles are established in the two materials, with the result that oxygen ions can be driven across the heterointerface, altering the doping of the n-type In 2O 3. Furthermore, a low frequency inductive feature observed in AC impedance spectroscopy measurements under DC bias conditions was found to be due to frequency-dependent changes inmore » the contact resistance.« less

Crustal-scale electrical conductivity anomaly beneath inflating Lazufre volcanic complex, Central Andes

NASA Astrophysics Data System (ADS)

Budach, Ingmar; Brasse, Heinrich; Díaz, Daniel

2013-03-01

Large-scale surface deformation was observed at Lazufre volcanic center in the Central Andes of Northern Chile/Northwestern Argentina by means of Interferometric Synthetic Aperture Radar (InSAR). Uplift started there after 1998 and increased dramatically in the following years up to a rate of 3 cm/a. Lazufre is now one of the largest deforming volcano systems on Earth, but the cause for uplift - likely influx of magmatic material into the crust - is still poorly understood. In the beginning of 2010 a magnetotelluric survey was conducted to delineate the electrical conductivity distribution in the area. Several long-period magnetotelluric (LMT) sites and two broadband magnetotelluric (BBMT) sites were set up on an EW trending profile crossing the volcanic center; furthermore some LMT sites were arranged circularly around Lazufre complex and adjacent Lastarria volcano. Data were processed using an algorithm for robust and remote reference transfer function estimation. Electrical strike directions were estimated and induction arrows were derived. Although electrical strike is rather ambiguous, in a first step a 2-D resistivity model was calculated. The most prominent feature of this model is a well conducting structure rising from the upper mantle to the shallow crust beneath the center of elevation. This can be interpreted as partial melts ascending from the asthenospheric wedge and feeding a potential magma reservoir beneath Lazufre volcanic center. An improved model is finally achieved by 3-D inversion, supporting this feature. We assume that these rising melts are the source of the observed uplift at Lazufre complex.

In-Situ Wire Damage Detection System

NASA Technical Reports Server (NTRS)

Jolley, Scott T. (Inventor); Gibson, Tracy L. (Inventor); Medelius, Pedro J. (Inventor); Roberson, Luke B. (Inventor); Tate, Lanetra C. (Inventor); Smith, Trent M. (Inventor); Williams, Martha K. (Inventor)

2014-01-01

An in-situ system for detecting damage in an electrically conductive wire. The system includes a substrate at least partially covered by a layer of electrically conductive material forming a continuous or non-continuous electrically conductive layer connected to an electrical signal generator adapted to delivering electrical signals to the electrically conductive layer. Data is received and processed to identify damage to the substrate or electrically conductive layer. The electrically conductive material may include metalized carbon fibers, a thin metal coating, a conductive polymer, carbon nanotubes, metal nanoparticles or a combination thereof.

Structural and Electrical Characteristics of Carbon Nanowalls Synthesized on the Polyimide Film.

PubMed

Kwon, Seok Hun; Kim, Hyung Jin; Choi, Won Seok; Kang, Hyunil

2018-09-01

In this study, the structural and electrical characteristics of carbon nanowalls (CNWs) synthesized on polyimide films were investigated. CNWs were synthesized on polyimide films as various growth times. The cross-section and surface of the CNWs synthesized were examined using FE-SEM. The growth and defects of CNWs were observed by raman spectrum. The hall measurement system was used to analyzed sheet resistance, resistivity and conductivity. The CNWs synthesized at 40 minutes showed outstanding structural and electrical characterizations than another growth times.

Current characteristics of λ-DNA molecules/polystyrene nanoparticles in TBE buffer solution through micro/nanofluidic capillaries under DC electric field

NASA Astrophysics Data System (ADS)

Duan, Yifei; Zhao, Wei; Xue, Jing; Sun, Dan; Wang, Kaige; Wang, Guiren; Li, Junjie; Bai, Jintao; Gu, Changzhi

2017-03-01

In practical applications of biochips and bio-sensors, electrokinetic mechanisms are commonly employed to manipulate single bio-molecules and analyze their characteristics. To accurately and flexibly control the movement of single-molecule within micro/nanofluidic channels which are the basic components of Lab-chips, the current signals in micro/nanocapillaries filled with solutions of DNA molecules or polystyrene (PS) nanoparticles are systematically studied. Experimental results indicate that the current response along the micro/nanocapillaries can be significantly influenced by the diameter of the capillaries and the pH value of the solutions. Specifically, when there is only a pure (TBE) solution, the electric conductance does not monotonically decrease with decreasing the diameter of the capillaries, but slightly increases with decreasing the capillary diameter. When λ-DNA molecules or PS nanoparticles are added into the TBE buffer, the size effect on the electric conductance of the solutions are quite different. Although in the former, the electric conductance behaves differently from that in the pure TBE solution and decreases with the decreasing diameter, in the latter, the change is similar to that in the pure TBE solution. Besides, an abnormal ‘falling’ of the electric conductance is observed in a capillary with diameter of 200 nm. The investigation will significantly enhance the understanding on the electric properties of the solutions of biomolecules and particles in micro/nanofluidics. This is especially helpful for designing functional Lab-chip devices.

Gigantic jets between a thundercloud and the ionosphere.

PubMed

Su, H T; Hsu, R R; Chen, A B; Wang, Y C; Hsiao, W S; Lai, W C; Lee, L C; Sato, M; Fukunishi, H

2003-06-26

Transient luminous events in the atmosphere, such as lighting-induced sprites and upwardly discharging blue jets, were discovered recently in the region between thunderclouds and the ionosphere. In the conventional picture, the main components of Earth's global electric circuit include thunderstorms, the conducting ionosphere, the downward fair-weather currents and the conducting Earth. Thunderstorms serve as one of the generators that drive current upward from cloud tops to the ionosphere, where the electric potential is hundreds of kilovolts higher than Earth's surface. It has not been clear, however, whether all the important components of the global circuit have even been identified. Here we report observations of five gigantic jets that establish a direct link between a thundercloud (altitude approximately 16 km) and the ionosphere at 90 km elevation. Extremely-low-frequency radio waves in four events were detected, while no cloud-to-ground lightning was observed to trigger these events. Our result indicates that the extremely-low-frequency waves were generated by negative cloud-to-ionosphere discharges, which would reduce the electrical potential between ionosphere and ground. Therefore, the conventional picture of the global electric circuit needs to be modified to include the contributions of gigantic jets and possibly sprites.

Relationship between anisotropies of permeability, electrical conductivity, and dielectric permittivity, with application to the Ellenburger dolomite reservoir analog

NASA Astrophysics Data System (ADS)

Kutemi, Titilope F.

The steady-state flow technique was employed to measure the flow rate of clean dry air through thirty core plugs (approximately 1" diameter) of the Ellenburger dolomite, drilled normal and parallel to the dominant fractures. Porosity was estimated by the method of imbibition. Electrical parameters (electrical conductivity and dielectric permittivity) were calculated from electrical resistance and capacitance measured as a function of frequency (100 Hz, 120 Hz, 1 KHz, and 10 KHz) and saturation (dry/ambient and brine saturated conditions). Another set of permeability data obtained by the method of pressure decay on similar samples was used for correlation. Anisotropies of permeability and electromagnetic parameters were established. Empirical relations between porosity (phi), permeability (k), electrical conductivity (sigma), and dielectric permittivity (epsilon) were defined via cross-plots and linear regressions. Prediction of k from sigma and epsilon was attempted; k from sigma was modeled from a combination of the Archie's relation and the Carman-Kozeny relation. Anisotropic EM responses are sensitive to saturation. Anisotropies of conductivity and permeability were observed to be controlled by the pore micro-structure. Although the rock is fractured, the fracture density appears insufficient to dominate the effects of primary structures in these samples of the Ellenburger dolomite. Model-based prediction of permeability from conductivity is generally unreliable, and is attributed to the underlying assumptions of the models, which are not consistent with the properties of the samples used for this study. Permeability was not predictable from dielectric permittivity.

Soil salinisation and irrigation management of date palms in a Saharan environment.

PubMed

Haj-Amor, Zied; Ibrahimi, Mohamed-Khaled; Feki, Nissma; Lhomme, Jean-Paul; Bouri, Salem

2016-08-01

The continuance of agricultural production in regions of the world with chronic water shortages depends upon understanding how soil salinity is impacted by irrigation practises such as water salinity, irrigation frequency and amount of irrigation. A two-year field study was conducted in a Saharan oasis of Tunisia (Lazala Oasis) to determine how the soil electrical conductivity was affected by irrigation of date palms with high saline water. The study area lacked a saline shallow water table. Field results indicate that, under current irrigation practises, soil electrical conductivity can build up to levels which exceed the salt tolerance of date palm trees. The effects of irrigation practises on the soil electrical conductivity were also evaluated using model simulations (HYDRUS-1D) of various irrigation regimes with different frequencies, different amounts of added water and different water salinities. The comparison between the simulated and observed results demonstrated that the model gave an acceptable estimation of water and salt dynamics in the soil profile, as indicated by the small values of root mean square error (RMSE) and the high values of the Nash-Sutcliffe model efficiency coefficient (NSE). The simulations demonstrated that, under field conditions without saline shallow groundwater, saline irrigation water can be used to maintain soil electrical conductivity and soil water content at safe levels (soil electrical conductivity <4 dS m(-1) and soil water content >0.04 cm(3) cm(-3)) if frequent irrigations with small amounts of water (90 % of the evapotranspiration requirements) were applied throughout the year.

Saline tracer visualized with three-dimensional electrical resistivity tomography: Field-scale spatial moment analysis

USGS Publications Warehouse

Singha, Kamini; Gorelick, Steven M.

2005-01-01

Cross-well electrical resistivity tomography (ERT) was used to monitor the migration of a saline tracer in a two-well pumping-injection experiment conducted at the Massachusetts Military Reservation in Cape Cod, Massachusetts. After injecting 2200 mg/L of sodium chloride for 9 hours, ERT data sets were collected from four wells every 6 hours for 20 days. More than 180,000 resistance measurements were collected during the tracer test. Each ERT data set was inverted to produce a sequence of 3-D snapshot maps that track the plume. In addition to the ERT experiment a pumping test and an infiltration test were conducted to estimate horizontal and vertical hydraulic conductivity values. Using modified moment analysis of the electrical conductivity tomograms, the mass, center of mass, and spatial variance of the imaged tracer plume were estimated. Although the tomograms provide valuable insights into field-scale tracer migration behavior and aquifer heterogeneity, standard tomographic inversion and application of Archie's law to convert electrical conductivities to solute concentration results in underestimation of tracer mass. Such underestimation is attributed to (1) reduced measurement sensitivity to electrical conductivity values with distance from the electrodes and (2) spatial smoothing (regularization) from tomographic inversion. The center of mass estimated from the ERT inversions coincided with that given by migration of the tracer plume using 3-D advective-dispersion simulation. The 3-D plumes seen using ERT exhibit greater apparent dispersion than the simulated plumes and greater temporal spreading than observed in field data of concentration breakthrough at the pumping well.

Drude conductivity exhibited by chemically synthesized reduced graphene oxide

NASA Astrophysics Data System (ADS)

Younas, Daniyal; Javed, Qurat-ul-Ain; Fatima, Sabeen; Kalsoom, Riffat; Abbas, Hussain; Khan, Yaqoob

2017-09-01

Electrical conductance in graphene layers having Drude like response due to massless Dirac fermions have been well explained theoretically as well as experimentally. In this paper Drude like electrical conductivity response of reduced graphene oxide synthesized by chemical route is presented. A method slightly different from conventional methods is used to synthesize graphene oxide which is then converted to reduced graphene oxide. Various analytic techniques were employed to verify the successful oxidation and reductions in the process and were also used to measure various parameters like thickness of layers and conductivity. Obtained reduced graphene oxide has very thin layers of thickness around 13 nm on average and reduced graphene oxide has average thickness below 20 nm. Conductivity of the reduced graphene was observed to have Drude like response which is explained on basis of Drude model for conductors.

Heat Coulomb blockade of one ballistic channel

NASA Astrophysics Data System (ADS)

Sivre, E.; Anthore, A.; Parmentier, F. D.; Cavanna, A.; Gennser, U.; Ouerghi, A.; Jin, Y.; Pierre, F.

2018-02-01

Quantum mechanics and Coulomb interaction dictate the behaviour of small circuits. The thermal implications cover fundamental topics from quantum control of heat to quantum thermodynamics, with prospects of novel thermal machines and an ineluctably growing influence on nanocircuit engineering. Experimentally, the rare observations thus far include the universal thermal conductance quantum and heat interferometry. However, evidence for many-body thermal effects paving the way to markedly different heat and electrical behaviours in quantum circuits remains wanting. Here we report on the observation of the Coulomb blockade of electronic heat flow from a small metallic circuit node, beyond the widespread Wiedemann-Franz law paradigm. We demonstrate this thermal many-body phenomenon for perfect (ballistic) conduction channels to the node, where it amounts to the universal suppression of precisely one quantum of conductance for the transport of heat, but none for electricity. The inter-channel correlations that give rise to such selective heat current reduction emerge from local charge conservation, in the floating node over the full thermal frequency range (<~temperature × kB/h). This observation establishes the different nature of the quantum laws for thermal transport in nanocircuits.

Thermal and ac electrical properties of N-methylanthranilic acid below room temperature

NASA Astrophysics Data System (ADS)

Abdel-Kader, M. M.; Basha, M. A. F.; Ramzy, G. H.; Aboud, A. I.

2018-06-01

In this study, we investigated the thermal and alternating current (ac) electrical properties of N-methylanthranilic acid. Based on data obtained by differential scanning calorimetry, we detected two endothermic transitions at ≈ 213 K and ≈265.41 K. The weakening of hydrogen bonds as the temperature increased appeared to be the main cause of these phase transitions. We also recorded the melting point at about 475.5 K. Both the ac conductivity (σac) and complex dielectric constant (ε∗ = ε ' - jε ' ') were studied as functions of temperature over the frequency range from 1 kHz to 100 kHz. We observed significant variations in the thermal and electrical properties before and after the transition temperature at 265.41 K. The conduction mechanism responsible for the ac electrical properties before this transition was due to overlapping large polarons. These novel results are expected to have impacts on the application of organic semiconductors and dielectrics.

Dr. Alexander Garden, a Linnaean in colonial America, and the saga of five "electric eels".

PubMed

Finger, Stanley

2010-01-01

Alexander Garden (1730-1791) was born in Scotland, where he trained in medicine before settling in South Carolina in 1752. With a passion for collecting and a love of nature, he sent specimens to Linnaeus and his associates in Europe. In 1774, Garden observed and conducted electrical experiments on some "eels" that had survived the trip from Surinam to Charleston. His detailed observations and reasons for believing they emit electricity were read before the Royal Society of London and subsequently published. He also advised the sea captain who owned the eels on how to preserve them and where to deliver their bodies if they died en route to London. Although they did die en route, John Hunter of the Royal Society was able to provide excellent descriptions of their electric organs because they were so well preserved. The sequence of events that followed led to other live eels surviving the voyage to London, where they were observed to spark in darkness in 1776. This was a critical piece of evidence in favor of fish electricity and eventually for the more revolutionary idea that even human nerves and muscles might function electrically.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tooker, Angela C.; Felix, Sarah H.; Pannu, Satinderpall S.

A neural interface includes a first dielectric material having at least one first opening for a first electrical conducting material, a first electrical conducting material in the first opening, and at least one first interconnection trace electrical conducting material connected to the first electrical conducting material. A stiffening shank material is located adjacent the first dielectric material, the first electrical conducting material, and the first interconnection trace electrical conducting material.

Product formulation for ohmic heating: blanching as a pretreatment method to improve uniformity in heating of solid-liquid food mixtures.

PubMed

Sarang, S; Sastry, S K; Gaines, J; Yang, T C S; Dunne, P

2007-06-01

The electrical conductivity of food components is critical to ohmic heating. Food components of different electrical conductivities heat at different rates. While equal electrical conductivities of all phases are desirable, real food products may behave differently. In the present study involving chicken chow mein consisting of a sauce and different solid components, celery, water chestnuts, mushrooms, bean sprouts, and chicken, it was observed that the sauce was more conductive than all solid components over the measured temperature range. To improve heating uniformity, a blanching method was developed to increase the ionic content of the solid components. By blanching different solid components in a highly conductive sauce at 100 degrees C for different lengths of time, it was possible to adjust their conductivity to that of the sauce. Chicken chow mein samples containing blanched particulates were compared with untreated samples with respect to ohmic heating uniformity at 60 Hz up to 140 degrees C. All components of the treated product containing blanched solids heated more uniformly than untreated product. In sensory tests, 3 different formulations of the blanched product showed good quality attributes and overall acceptability, demonstrating the practical feasibility of the blanching protocol.

Thermoelectric Properties of Highly Conductive Poly(3,4-ethylenedioxythiophene) Polystyrene Sulfonate Printed Thin Films.

PubMed

Beretta, Davide; Barker, Alex J; Maqueira-Albo, Isis; Calloni, Alberto; Bussetti, Gianlorenzo; Dell'Erba, Giorgio; Luzio, Alessandro; Duò, Lamberto; Petrozza, Annamaria; Lanzani, Guglielmo; Caironi, Mario

2017-05-31

Organic conductors are being evaluated for potential use in waste heat recovery through lightweight and flexible thermoelectric generators manufactured using cost-effective printing processes. Assessment of the potentiality of organic materials in real devices still requires a deeper understanding of the physics behind their thermoelectric properties, which can pave the way toward further development of the field. This article reports a detailed thermoelectric study of a set of highly conducting inkjet-printed films of commercially available poly(3,4-ethylenedioxythiophene) polystyrene sulfonate formulations characterized by in-plane electrical conductivity, spanning the interval 10-500 S/cm. The power factor is maximized for the formulation showing an intermediate electrical conductivity. The Seebeck coefficient is studied in the framework of Mott's relation, assuming a (semi-)classical definition of the transport function. Ultraviolet photoelectron spectroscopy at the Fermi level clearly indicates that the shape of the density of states alone is not sufficient to explain the observed Seebeck coefficient, suggesting that carrier mobility is important in determining both the electrical conductivity and thermopower. Finally, the cross-plane thermal conductivity is reliably extracted thanks to a scaling approach that can be easily performed using typical pump-probe spectroscopy.

Variations of magnetic and electrostatic atmospheric parameters and dynamics of the heart rate in mHz range

NASA Astrophysics Data System (ADS)

Nagorskiy, Petr; Zenchenko, Tatiana; Breus, Tamara; Smirnov, Sergey

The objective of this work was to study the degree of synchronization of heart rate (HR) of healthy volunteers with magnetic variations and various weather conditions in mHz - frequency range. Experimental results for synchronic registration of physiological variations, atmospheric electrical and meteorological parameters with a time resolution of 0.5-1 min are presented. The experiment was conducted in a building of IMCES SB RAS (Tomsk). 15 experiments of 60 minutes each were conducted, and four volunteers of all ages in a state of rest were examined. Meteorological parameters (atmospheric pressure, relative air humidity and temperatureas well as a wind speed) were measured using standard meteorological devices located on the roof of the same building and also on the open area. Data on geomagnetic activity on the nearest magnetic station Klyichi were obtained from the site http://ottawa.intermagnet.org/apps/download/index-eng.php # view. The electric field intensity was recorded the following way: in the room (5-storey panel ferroconcrete building) by the autonomous fluxmeter CS110 at a distance of 1.5 meters from the investigated volunteers, and on the open test - area by the stationary electric fluxmeter "Field 2". Data analysis techniques were: cross-correlation analysis, spectral analysis (Fourier transform and the calculation of the coherence function) and wavelet analysis. It was found that the dependence of the heart rate variation dynamics from the X-component of the Earth magnetic field magnitude was observed in 53% of cases, from the relative humidity - in 33%, from the atmospheric pressure, the wind speed and intensity of the electric field in an open area - in 20%, from the intensity the electric field in the room of the experiment - in 7% of cases. It was found not only coincidence of observed values of oscillation periods in physiological and geophysical series lasting 5-30 minutes, but also moments of approximate synchronicity in their appearance and disappearance. The highest degree of synchronization of HR with the variations of the geomagnetic field (in all four conducted experiments in this day) was observed in the most geomagnetically quiet day - 04.10.12 (Ap = 1), while the lowest one - in the day of the geomagnetic disturbances - 01.10.12 (Ap = 32). The characteristics of the electric field variations in the time-frequency domain in the experiments conducted indoors and outdoors differ fundamentally.

Double-Wall Nanotubes and Graphene Nanoplatelets for Hybrid Conductive Adhesives with Enhanced Thermal and Electrical Conductivity.

PubMed

Messina, Elena; Leone, Nancy; Foti, Antonino; Di Marco, Gaetano; Riccucci, Cristina; Di Carlo, Gabriella; Di Maggio, Francesco; Cassata, Antonio; Gargano, Leonardo; D'Andrea, Cristiano; Fazio, Barbara; Maragò, Onofrio Maria; Robba, Benedetto; Vasi, Cirino; Ingo, Gabriel Maria; Gucciardi, Pietro Giuseppe

2016-09-07

Improving the electrical and thermal properties of conductive adhesives is essential for the fabrication of compact microelectronic and optoelectronic power devices. Here we report on the addition of a commercially available conductive resin with double-wall carbon nanotubes and graphene nanoplatelets that yields simultaneously improved thermal and electrical conductivity. Using isopropanol as a common solvent for the debundling of nanotubes, exfoliation of graphene, and dispersion of the carbon nanostructures in the epoxy resin, we obtain a nanostructured conducting adhesive with thermal conductivity of ∼12 W/mK and resistivity down to 30 μΩ cm at very small loadings (1% w/w for nanotubes and 0.01% w/w for graphene). The low filler content allows one to keep almost unchanged the glass-transition temperature, the viscosity, and the curing parameters. Die shear measurements show that the nanostructured resins fulfill the MIL-STD-883 requirements when bonding gold-metalized SMD components, even after repeated thermal cycling. The same procedure has been validated on a high-conductivity resin characterized by a higher viscosity, on which we have doubled the thermal conductivity and quadrupled the electrical conductivity. Graphene yields better performances with respect to nanotubes in terms of conductivity and filler quantity needed to improve the resin. We have finally applied the nanostructured resins to bond GaN-based high-electron-mobility transistors in power-amplifier circuits. We observe a decrease of the GaN peak and average temperatures of, respectively, ∼30 °C and ∼10 °C, with respect to the pristine resin. The obtained results are important for the fabrication of advanced packaging materials in power electronic and microwave applications and fit the technological roadmap for CNTs, graphene, and hybrid systems.

Structural, optical and ac electrical characterization of CBD synthesized NiO thin films: Influence of thickness

NASA Astrophysics Data System (ADS)

Das, M. R.; Mukherjee, A.; Mitra, P.

2017-09-01

We have studied the electrical conductivity, dielectric relaxation mechanism and impedance spectroscopy characteristics of nickel oxide (NiO) thin films synthesized by chemical bath deposition (CBD) method. Thickness dependent structural, optical and ac electrical characterization has been carried out and deposition time was varied to control the thickness. The material has been characterized using X-ray diffraction and UV-VIS spectrophotometer. Impedance spectroscopy analysis confirmed enhancement of ac conductivity and dielectric constant for films deposited with higher deposition time. Decrease of grain size in thicker films were confirmed from XRD analysis and activation energy of the material for electrical charge hopping process was increased with thickness of the film. Decrease in band gap in thicker films were observed which could be associated with creation of additional energy levels in the band gap of the material. Cole-Cole plot shows contribution of both grain and grain boundary towards total resistance and capacitance. The overall resistance was found to decrease from 14.6 × 105 Ω for 30 min deposited film ( 120 nm thick) to 2.42 × 105 Ω for 120 min deposited film ( 307 nm thick). Activation energy value to electrical conduction process evaluated from conductivity data was found to decrease with thickness. Identical result was obtained from relaxation time approach suggesting hopping mechanism of charge carriers.

Electronic conductivity of solid and liquid (Mg, Fe)O computed from first principles

NASA Astrophysics Data System (ADS)

Holmström, E.; Stixrude, L.; Scipioni, R.; Foster, A. S.

2018-05-01

Ferropericlase (Mg, Fe)O is an abundant mineral of Earth's lower mantle and the liquid phase of the material was an important component of the early magma ocean. Using quantum-mechanical, finite-temperature density-functional theory calculations, we compute the electronic component of the electrical and thermal conductivity of (Mg0.75, Fe0.25)O crystal and liquid over a wide range of planetary conditions: 0-200 GPa, 2000-4000 K for the crystal, and 0-300 GPa, 4000-10,000 K for the liquid. We find that the crystal and liquid are semi-metallic over the entire range studied: the crystal has an electrical conductivity exceeding 103 S/m, whereas that of the liquid exceeds 104 S/m. Our results on the crystal are in reasonable agreement with experimental measurements of the electrical conductivity of ferropericlase once we account for the dependence of conductivity on iron content. We find that a harzburgite-dominated mantle with ferropericlase in combination with Al-free bridgmanite agrees well with electromagnetic sounding observations, while a pyrolitic mantle with a ferric-iron rich bridgmanite composition yields a lower mantle that is too conductive. The electronic component of thermal conductivity of ferropericlase with XFe = 0.19 is negligible (<1 W/m/K). The electrical conductivity of the crystal and liquid at conditions of the core-mantle boundary are similar to each other (3 ×104 S/m). A crystalline or liquid ferropericlase-rich layer of a few km thickness thus accounts for the high conductance that has been proposed to explain anomalies in Earth's nutation. The electrical conductivity of liquid ferropericlase exceeds that of liquid silica by more than an order of magnitude at conditions of a putative basal magma ocean, thus strengthening arguments that the basal magma ocean could have produced an ancient dynamo.

Internal Electric Field Modulation in Molecular Electronic Devices by Atmosphere and Mobile Ions.

PubMed

Chandra Mondal, Prakash; Tefashe, Ushula M; McCreery, Richard L

2018-06-13

The internal potential profile and electric field are major factors controlling the electronic behavior of molecular electronic junctions consisting of ∼1-10 nm thick layers of molecules oriented in parallel between conducting contacts. The potential profile is assumed linear in the simplest cases, but can be affected by internal dipoles, charge polarization, and electronic coupling between the contacts and the molecular layer. Electrochemical processes in solutions or the solid state are entirely dependent on modification of the electric field by electrolyte ions, which screen the electrodes and form the ionic double layers that are fundamental to electrode kinetics and widespread applications. The current report investigates the effects of mobile ions on nominally solid-state molecular junctions containing aromatic molecules covalently bonded between flat, conducting carbon surfaces, focusing on changes in device conductance when ions are introduced into an otherwise conventional junction design. Small changes in conductance were observed when a polar molecule, acetonitrile, was present in the junction, and a large decrease of conductance was observed when both acetonitrile (ACN) and lithium ions (Li + ) were present. Transient experiments revealed that conductance changes occur on a microsecond-millisecond time scale, and are accompanied by significant alteration of device impedance and temperature dependence. A single molecular junction containing lithium benzoate could be reversibly transformed from symmetric current-voltage behavior to a rectifier by repetitive bias scans. The results are consistent with field-induced reorientation of acetonitrile molecules and Li + ion motion, which screen the electrodes and modify the internal potential profile and provide a potentially useful means to dynamically alter junction electronic behavior.

Attenuated geophysical signatures associated with ongoing remediation efforts at Wurtsmith Air Force Base, Oscoda, Michigan

NASA Astrophysics Data System (ADS)

Che-Alota, V.; Atekwana, E. A.; Sauck, W. A.; Nolan, J. T.; Slater, L. D.

2007-12-01

Previous geophysical investigations (1996, 1997, 2003, and 2004) conducted at the decommissioned Wurtsmith Air Force Base former Fire Training Cell (FT-02) showed a clearly defined high conductivity anomaly associated with hydrocarbon contaminants in the vadose zone and ground water near the source area. The source of the geophysical anomalies was attributed to biogeochemical modifications of the contaminated zone resulting from intrinsic bioremediation. During these previous surveys, ground penetrating radar (GPR) data showed a zone of attenuated GPR reflections extending from the vadose zone to below the water table. Self potential data (SP) data defined a positive anomaly coincident with the hydrochemically defined plume, while electrical resistivity data showed anomalously high conductivity within the zone of impact. In 2007, another integrated geophysical study of the site was conducted. GPR, SP, electrical resistivity, and induced polarization surveys were conducted with expectations of achieving similar results as the past surveys. However, preliminary assessment of the data shows a marked decrease in electrical conductivity and SP response over the plume. GPR data still showed the attenuated signals, but the zone of attenuation was only observed below the water table. We attribute the attenuation of the observed geophysical anomalies to ongoing soil vapor extraction initiated in 2003. Significant removal of the contaminant mass by the vapor extraction system has altered the subsurface biogeochemical conditions and these changes were documented by the 2007 geophysical and geochemical data. The results of this study show that the attenuation of the contaminant plume is detectable with geophysical methods.

Apparatus for detecting alpha radiation in difficult access areas

DOEpatents

Steadman, Peter; MacArthur, Duncan W.

1997-09-02

An electrostatic alpha radiation detector for measuring alpha radiation emitted from inside an enclosure comprising an electrically conductive expandable electrode for insertion into the enclosure. After insertion, the electrically conductive expandable electrode is insulated from the enclosure and defines a decay cavity between the electrically conductive expandable electrode and the enclosure so that air ions generated in the decay cavity are electrostatically captured by the electrically conductive expandable electrode and the enclosure when an electric potential is applied between the electrically conductive expandable electrode and the enclosure. Indicator means are attached to the electrically conductive expandable electrode for indicating an electrical current produced by generation of the air ions generated in the decay cavity by collisions between air molecules and the alpha particles emitted from the enclosure. A voltage source is connected between the indicator means and the electrically conductive enclosure for creating an electric field between the electrically conductive expandable electrode and the enclosure.

A study on lithium/air secondary batteries-Stability of NASICON-type glass ceramics in acid solutions

NASA Astrophysics Data System (ADS)

Shimonishi, Y.; Zhang, T.; Johnson, P.; Imanishi, N.; Hirano, A.; Takeda, Y.; Yamamoto, O.; Sammes, N.

The stability of a NASICON-type lithium ion conducting solid electrolyte, Li 1+ x+ yTi 2- xAl xP 3- ySi yO 12 (LTAP), in acetic acid and formic acid solutions was examined. XRD patterns of the LTAP powders immersed in 100% acetic acid and formic acid at 50 °C for 4 months showed no change as compared to the pristine LTAP. However, the electrical conductivity of LTAP drastically decreased. On the other hand, no significant electrical conductivity change of LTAP immersed in lithium formate saturated formic acid-water solution was observed, and the electrical conductivity of LTAP immersed in lithium acetate saturated acetic acid-water increased. Cyclic voltammogram tests suggested that acetic acid was stable up to a high potential, but formic acid decomposed under the decomposition potential of water. The acetic acid solution was considered to be a candidate for the active material in the air electrode of lithium-air rechargeable batteries. The cell reaction was considered as 2Li + 2 CH 3COOH + 1/2O 2 = 2CH 3COOLi + H 2O. The energy density of this lithium-air system is calculated to be 1477 Wh kg -1 from the weights of Li and CH 3COOH, and an observed open-circuit voltage of 3.69 V.

MO-F-CAMPUS-I-01: EIT Imaging to Monitor Human Salivary Gland Functionality: A Feasibility Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kohli, K; Karvat, A; Liu, J

Purpose: Clinically, there exists a need to develop a non-invasive technique for monitoring salivary activity. In this study, we investigate the feasibility of a using the electrical conductivity information from Electrical Impedance Tomography (EIT) to monitor salivary flow activity. Methods: To acquire EIT data, eight Ag/AgCl ECG electrodes were placed around the mandible of the subject. An EIT scan was obtained by injecting current at 50 KHz, 0.4 mA through each pair of electrodes and recording voltage across other electrode pairs. The functional conductivity image was obtained through reconstruction of the voltage data, using Electrical Impedance Tomography and Diffuse Opticalmore » Tomography Reconstruction Software (EIDORS) in Matlab. In using EIDORS, forward solution was obtained using a user-defined finite element model shape and inverse solution was obtained using one-step Gaussian solver. EIT scans of volunteer research team members were acquired for three different physiological states: pre-stimulation, stimulation and post-stimulation. For pre-stimulation phase, data were collected in intervals of 5 minutes for 15 minutes. The salivary glands were then stimulated in the subject using lemon and the data were collected immediately. Post-stimulation data were collected at 4 different timings after stimulation. Results: Variations were observed in the electrical conductivity patterns near parotid regions between the pre- and post-stimulation stages. The three images acquired during the 15 minute pre-stimulation phase showed no major changes in the conductivity. Immediately after stimulation, electrical conductivity increased near parotid regions and 15 minutes later slowly returned to pre-stimulation level. Conclusion: In the present study involving human subjects, the change in electrical conductivity pattern shown in the EIT images, acquired at different times with and without stimulation of salivary glands, appeared to be consistent with the change in salivary gland activity. The conductivity changes imaged through EIT are potentially useful for the purpose of salivary monitoring.« less

Stacking fault induced tunnel barrier in platelet graphite nanofiber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lan, Yann-Wen, E-mail: chiidong@phys.sinica.edu.tw, E-mail: ywlan@phys.sinica.edu.tw; Chang, Yuan-Chih; Chang, Chia-Seng

A correlation study using image inspection and electrical characterization of platelet graphite nanofiber devices is conducted. Close transmission electron microscopy and diffraction pattern inspection reveal layers with inflection angles appearing in otherwise perfectly stacked graphene platelets, separating nanofibers into two domains. Electrical measurement gives a stability diagram consisting of alternating small-large Coulomb blockade diamonds, suggesting that there are two charging islands coupled together through a tunnel junction. Based on these two findings, we propose that a stacking fault can behave as a tunnel barrier for conducting electrons and is responsible for the observed double-island single electron transistor characteristics.

The neutral wind 'flywheel' as a source of quiet-time, polar-cap currents

NASA Technical Reports Server (NTRS)

Lyons, L. R.; Walterscheid, R. L.; Killeen, T. L.

1985-01-01

The neutral wind pattern over the summer polar cap can be driven by plasma convection to resemble the convection pattern. For a north-south component of the interplanetary magnetic field Bz directed southward, the wind speeds in the conducting E-region can become approximately 25 percent of the electric field drift speeds. If convection ceases, this neutral wind distribution can drive a significant polar cap current system for approximately 6 hours. The currents are reversed from those driven by the electric fields for southward Bz, and the Hall and field-aligned components of the current system resemble those observed during periods of northward Bz. The current magnitudes are similar to those observed during periods of small, northward Bz; however, observations indicate that electric fields often contribute to the currents as much as, or more than, the neutral winds.

Modulation of structural, electrical, and magnetic features with dilute Zr substitution in Bi0.8La0.2Fe1-xZrxO3 system

NASA Astrophysics Data System (ADS)

Usama, Hasan M.; Akter, Ayesha; Zubair, M. A.

2017-12-01

A significant structural modification and enhancement of the electrical and magnetic properties with dilute substitution of Zr (≤1 mol. %) in the Bi0.8La0.2Fe1-xZrxO3 system has been reported. A mixture of rhombohedral and orthorhombic phases was detected in these conventionally sintered ceramics. Transition from a leaky state to an insulating state was observed upon Zr substitution. This is the first time that a drop in the electrical conductivity as large as 6 orders of magnitude for doping as small as 0.25 mol. % in bismuth ferrite systems has been reported. An investigation on the nature of this abrupt transition revealed the dominant role of defects. A proper consideration of possible defect reactions taking place during and after sintering satisfactorily accounts for the observed modulation in the electrical properties. Both AC and DC measurements indicate that, before Zr substitution, p-type hopping conduction prevails with an activation energy as low as ˜0.57 eV, whereas the Zr substitution makes oxide ion migration the central mechanism for conduction with the activation energy of ˜0.96-1.08 eV. In contrast to that, the magnetic properties of the compounds experience a more subtle effect; a gradual modification of saturation magnetization and coercivity with Zr substitution is observed. Curve fitting of the magnetic hysteresis loops not only allowed extraction of three separate contributions from the magnetic response but also helped to explain the effects of Zr on the magnetic properties. Modifications of structural characteristics and magnetic anisotropy of the samples are believed to be the primary driving force behind the improvement in the magnetic properties.

Electrical image of passive mantle upwelling beneath the northern East Pacific Rise.

PubMed

Key, Kerry; Constable, Steven; Liu, Lijun; Pommier, Anne

2013-03-28

Melt generated by mantle upwelling is fundamental to the production of new oceanic crust at mid-ocean ridges, yet the forces controlling this process are debated. Passive-flow models predict symmetric upwelling due to viscous drag from the diverging tectonic plates, but have been challenged by geophysical observations of asymmetric upwelling that suggest anomalous mantle pressure and temperature gradients, and by observations of concentrated upwelling centres consistent with active models where buoyancy forces give rise to focused convective flow. Here we use sea-floor magnetotelluric soundings at the fast-spreading northern East Pacific Rise to image mantle electrical structure to a depth of about 160 kilometres. Our data reveal a symmetric, high-conductivity region at depths of 20-90 kilometres that is consistent with partial melting of passively upwelling mantle. The triangular region of conductive partial melt matches passive-flow predictions, suggesting that melt focusing to the ridge occurs in the porous melting region rather than along the shallower base of the thermal lithosphere. A deeper conductor observed east of the ridge at a depth of more than 100 kilometres is explained by asymmetric upwelling due to viscous coupling across two nearby transform faults. Significant electrical anisotropy occurs only in the shallowest mantle east of the ridge axis, where high vertical conductivity at depths of 10-20 kilometres indicates localized porous conduits. This suggests that a coincident seismic-velocity anomaly is evidence of shallow magma transport channels rather than deeper off-axis upwelling. We interpret the mantle electrical structure as evidence that plate-driven passive upwelling dominates this ridge segment, with dynamic forces being negligible.

Nighttime observations of thunderstorm electrical activity from a high altitude airplane

NASA Technical Reports Server (NTRS)

Brook, M.; Vonnegut, B.; Orville, R. E.; Vaughan, O. H., Jr.

1984-01-01

Nocturnal thunderstorms were observed from above and features of cloud structure and lightning which are not generally visible from the ground are discussed. Most, lightning activity seems to be associated with clouds with strong convective cauliflower tops. In both of the storms lightning channels were visible in the clear air above the cloud. It is shown that substances produced by thunderstorm electrical discharges can be introduced directly into the stratosphere. The cause and nature of the discharges above the cloud are not clear. They may be produced by accumulations of space charge in the clear air above the cloud. The discharges may arise solely because of the intense electric fields produced by charges within the cloud. In the latter case the ions introduced by these discharges will increase the electrical conductivity of the air above the cloud and increase the conduction current that flows from the cloud to the electrosphere. More quantitative data at higher resolution may show significant spectral differences between cloud to ground and intracloud strokes. It is shown that electric field change data taken with an electric field change meter mounted in an airplane provide data on lightning discharges from above that are quite similar to those obtained from the ground in the past. The optical signals from dart leaders, from return strokes, and from continuing currents are recognizable, can be used to provide information on the fine structure of lightning, and can be used to distinguish between cloud to ground and intracloud flashes.

Enhancing electrical conductivity of room temperature deposited Sn-doped In2O3 thin films by hematite seed layers

NASA Astrophysics Data System (ADS)

Lohaus, Christian; Steinert, Céline; Deyu, Getnet; Brötz, Joachim; Jaegermann, Wolfram; Klein, Andreas

2018-04-01

Hematite Fe2O3 seed layers are shown to constitute a pathway to prepare highly conductive transparent tin-doped indium oxide thin films by room temperature magnetron sputtering. Conductivities of up to σ = 3300 S/cm are observed. The improved conductivity is not restricted to the interface but related to an enhanced crystallization of the films, which proceeds in the rhombohedral phase.

Low resistance thin film organic solar cell electrodes

DOEpatents

Forrest, Stephen [Princeton, NJ; Xue, Jiangeng [Piscataway, NJ

2008-01-01

A method which lower the series resistance of photosensitive devices includes providing a transparent film of a first electrically conductive material arranged on a transparent substrate; depositing and patterning a mask over the first electrically conductive material, such that openings in the mask have sloping sides which narrow approaching the substrate; depositing a second electrically conductive material directly onto the first electrically conductive material exposed in the openings of the mask, at least partially filling the openings; stripping the mask, leaving behind reentrant structures of the second electrically conductive material which were formed by the deposits in the openings of the mask; after stripping the mask, depositing a first organic material onto the first electrically conductive material in between the reentrant structures; and directionally depositing a third electrically conductive material over the first organic material deposited in between the reentrant structures, edges of the reentrant structures aligning deposition so that the third electrically conductive material does not directly contact the first electrically conductive material, and does not directly contact the second electrically conductive material.

Flexible neural interfaces with integrated stiffening shank

DOEpatents

Tooker, Angela C.; Felix, Sarah H.; Pannu, Satinderpall S.; Shah, Kedar G.; Sheth, Heeral; Tolosa, Vanessa

2016-07-26

A neural interface includes a first dielectric material having at least one first opening for a first electrical conducting material, a first electrical conducting material in the first opening, and at least one first interconnection trace electrical conducting material connected to the first electrical conducting material. A stiffening shank material is located adjacent the first dielectric material, the first electrical conducting material, and the first interconnection trace electrical conducting material.

The Effect of Precipitating Electrons and Ions on Ionospheric Conductance and Inner Magnetospheric Electric Fields 142106

NASA Astrophysics Data System (ADS)

Chen, M.; Lemon, C.; Hecht, J. H.; Evans, J. S.; Boyd, A. J.

2016-12-01

We investigate how scattering of electrons by waves and of ions by field-line curvature in the inner magnetosphere affect precipitating energy flux distributions and how the precipitating particles modify the ionospheric conductivity and electric potentials during magnetic storms. We examine how particle precipitation in the evening sector affects the development of the Sub-Auroral Polarization Stream (SAPS) electric field that is observed at sub-auroral latitudes in that sector as well as the electric field in the morning sector. Our approach is to use the magnetically and electrically self-consistent Rice Convection Model - Equilibrium (RCM-E) of the inner magnetosphere to simulate the stormtime precipitating particle distributions and the electric field. We use parameterized rates of whistler-generated electron pitch-angle scattering from Orlova and Shprits [JGR, 2014] that depend on equatorial radial distance, magnetic activity (Kp), and magnetic local time (MLT) outside the simulated plasmasphere. Inside the plasmasphere, parameterized scattering rates due to hiss [Orlova et al., GRL, 2014] are employed. Our description for the rate of ion scattering is more simplistic. We assume that the ions are scattered at a fraction of strong pitch-angle scattering where the fraction is scaled by epsilon, the ratio of the gyroradius to the field-line radius of curvature, when epsilon is greater than 0.1. We compare simulated trapped and precipitating electron/ion flux distributions with measurements from Van Allen Probes/MagEIS, POES and DMSP, respectively, to validate the particle loss models. DMSP observations of electric fields are compared with the simulation results. We discuss the effect of precipitating electrons and ions on the SAPS and the inner magnetospheric electric field through the data-model comparisons.

Role of dielectric constant in electrohydrodynamics of conducting fluids

NASA Technical Reports Server (NTRS)

Rhodes, Percy H.; Snyder, Robert S.; Roberts, Glyn O.

1992-01-01

Electrohydrodynamic (EHD) flows are driven by the interaction of an electric field with variations in electric conductivity or dielectric constant. In reported EHD experiments on the deformation of drops of immiscible dielectric fluids, the role of conductivity has tended to overshadow the role of dielectric constant. Often, large conductivity contrasts were convenient because the conductivities of the dielectric fluid were relatively uncertain. As a result, the observed effects were always qualitatively the same as if there had been no contrast in dielectric constant. Our early experiments studying the EHC deformations of cylindrical streams readily showed the conductivity effect but the dielectric constant effect was not discernible. We have modified our flow chamber and improved our method of observation and can now see an unequivocal dielectric constant effect which is in agreement with the prior theory. In this paper we first give a brief description of the physics of charge buildup at the interface of an immersed spherical drop or flowing cylindrical sample stream and then show how these charge distributions lead to interface distortions and accompanying viscous flows which constitute EHD. We next review theory and experiment describing the deformation of spherical drops. We show that in the reported drop deformation experiments, the contrast in dielectric constant was never sufficient to reverse the deformation due to the conductivity contrast. We review our work describing the deformation of a cylindrical stream of one fluid flowing in a parallel flow of another, and we compare the deformation equations with those for spherical drops. Finally, we show a definite experimental dielectric constant effect for cylindrical stream of aqueous polystyrene latex suspension. The dielectric constant varies with the frequency of the imposed electric field, and the associated EHD flow change is very apparent.

Field-induced dielectric response saturation in $o$ -TaS 3

DOE PAGES

Ma, Yongchang; Lu, Cuimin; Wang, Xuewei; ...

2016-08-03

The temperature and electric field dependent conductivity spectra of o-TaS 3 sample with 10 μm 2 in cross section were measured. Besides the classical electric threshold E T₋Cl, we observed another novel threshold E T₋N at a larger electric field, where an S-shaped I-V relation revealed. The appearance of E T₋N may be due to the establishment of coherence among small charge-density- wave domains. Under a stable field E > E T-N, a sharp dispersion emerged below kHz. At a fixed temperature, the scattering rate of the charged condensate was extremely small and decreased with increasing field. With decreasing temperature,more » the scattering Fröhlic-mode conductivity would be consistent with the meta-stable state.« less

Thermodynamic and electrical properties of laser-shocked liquid deuterium

NASA Astrophysics Data System (ADS)

He, Zhiyu; Jia, Guo; Zhang, Fan; Luo, Kui; Huang, Xiuguang; Shu, Hua; Fang, Zhiheng; Ye, Junjian; Xie, Zhiyong; Xia, Miao; Fu, Sizu

2018-01-01

Liquid deuterium at high pressure and temperature has been observed to undergo significant electronic structural changes. Reflectivity and temperature measurements of liquid deuterium up to around 70 GPa were obtained using a quartz standard. The observed specific heat of liquid deuterium approaches the Dulong-Petit limit above 1 eV. Discussions on specific heat indicate a molecular dissociation below 1 eV and fully dissociated above 1.5 eV. Also, the electrical conductivity of deuterium estimated from reflectivity reaches 1.3 × 105 (Ωṡm)-1, proving that deuterium in this condition is a conducting degenerate liquid metal and undergo an insulator-metal transition. The results from specific heat, carrier density and conductivity agreed well with each other, which might be a reinforcement of the insulator-metal transition and the molecular dissociation. In addition, a new correction method of reflectivity in temperature calculation was proposed to improve the accuracy of temperature results. A new "dynamic calibration" was introduced in this work to make the experiments simpler and more accurate.

Quadratic Electro-optic Effect in a Novel Nonconjugated Conductive Polymer, iodine-doped Polynorbornene

NASA Astrophysics Data System (ADS)

Narayanan, Ananthakrishnan; Thakur, Mrinal

2009-03-01

Quadratic electro-optic effect in a novel nonconjugated conductive polymer, iodine-doped polynorbornene has been measured using field-induced birefringence at 633 nm. The electrical conductivity^1 of polynorbornene increases by twelve orders of magnitude to about 0.01 S/cm upon doping with iodine. The electro-optic measurement has been made in a film doped at the medium doping-level. The electro-optic modulation signal was recorded using a lock-in amplifier for various applied ac voltages (4 kHz) and the quadratic dependence of the modulation on the applied voltage was observed. A modulation of about 0.01% was observed for an applied electric field of 3 V/micron for a 100 nm thick film The Kerr coefficient as determined is about 1.77x10-11m/V^2. This exceptionally large quadratic electro-optic effect has been attributed to the confinement of this charge-transfer system within a sub-nanometer dimension. 1. A. Narayanan, A. Palthi and M. Thakur, J. Macromol. Sci. -- PAC, accepted.

Crystalline-like temperature dependence of the electrical characteristics in amorphous Indium-Gallium-Zinc-Oxide thin film transistors

NASA Astrophysics Data System (ADS)

Estrada, M.; Hernandez-Barrios, Y.; Cerdeira, A.; Ávila-Herrera, F.; Tinoco, J.; Moldovan, O.; Lime, F.; Iñiguez, B.

2017-09-01

A crystalline-like temperature dependence of the electrical characteristics of amorphous Indium-Gallium-Zinc-Oxide (a-IGZO) thin film transistors (TFTs) is reported, in which the drain current reduces as the temperature is increased. This behavior appears for values of drain and gate voltages above which a change in the predominant conduction mechanism occurs. After studying the possible conduction mechanisms, it was determined that, for gate and drain voltages below these values, hopping is the predominant mechanism with the current increasing with temperature, while for values above, the predominant conduction mechanism becomes percolation in the conduction band or band conduction and IDS reduces as the temperature increases. It was determined that this behavior appears, when the effect of trapping is reduced, either by varying the density of states, their characteristic energy or both. Simulations were used to further confirm the causes of the observed behavior.

Apparatus for detecting alpha radiation in difficult access areas

DOEpatents

Steadman, P.; MacArthur, D.W.

1997-09-02

An electrostatic alpha radiation detector for measuring alpha radiation emitted from inside an enclosure comprising an electrically conductive expandable electrode for insertion into the enclosure is disclosed. After insertion, the electrically conductive expandable electrode is insulated from the enclosure and defines a decay cavity between the electrically conductive expandable electrode and the enclosure so that air ions generated in the decay cavity are electrostatically captured by the electrically conductive expandable electrode and the enclosure when an electric potential is applied between the electrically conductive expandable electrode and the enclosure. Indicator means are attached to the electrically conductive expandable electrode for indicating an electrical current produced by generation of the air ions generated in the decay cavity by collisions between air molecules and the alpha particles emitted from the enclosure. A voltage source is connected between the indicator means and the electrically conductive enclosure for creating an electric field between the electrically conductive expandable electrode and the enclosure. 4 figs.

Electrical Conductivity of Charged Particle Systems and Zubarev's Nonequilibrium Statistical Operator Method

NASA Astrophysics Data System (ADS)

Röpke, G.

2018-01-01

One of the fundamental problems in physics that are not yet rigorously solved is the statistical mechanics of nonequilibrium processes. An important contribution to describing irreversible behavior starting from reversible Hamiltonian dynamics was given by D. N. Zubarev, who invented the method of the nonequilibrium statistical operator. We discuss this approach, in particular, the extended von Neumann equation, and as an example consider the electrical conductivity of a system of charged particles. We consider the selection of the set of relevant observables. We show the relation between kinetic theory and linear response theory. Using thermodynamic Green's functions, we present a systematic treatment of correlation functions, but the convergence needs investigation. We compare different expressions for the conductivity and list open questions.

Soil and groundwater VOCs contamination: How can electrical geophysical measurements help assess post-bioremediation state?

NASA Astrophysics Data System (ADS)

Kessouri, P.; Johnson, T. C.; Day-Lewis, F. D.; Slater, L. D.; Ntarlagiannis, D.; Johnson, C. D.

2016-12-01

The former Brandywine MD (Maryland, USA) Defense Reutilization and Marketing Office (DRMO) was designated a hazardous waste Superfund site in 1999. The site was used as a storage area for waste and excess government equipment generated by several U.S. Navy and U.S. Air Force installations, leading to soil and groundwater contamination by volatile organic compounds (VOCs). Active bioremediation through anaerobic reductive dehalogenation was used to treat the groundwater and the aquifer unconsolidated materials in 2008, with electrical geophysical measurements employed to track amendment injections. Eight years later, we used spectral induced polarization (SIP) and time domain induced polarization (TDIP) on 2D surface lines and borehole electrical arrays to assess the long term impact of active remediation on physicochemical properties of the subsurface. Within the aquifer, the treated zone is more electrically conductive, and the phase shift describing the polarization effects is higher than in the untreated zone. Bulk conductivity and phase shift are also locally elevated close to the treatment injection well, possibly due to biogeochemical transformations associated with prolonged bacterial activity. Observed SIP variations could be explained by the presence of biofilms coating the pore space and/or by-products of the chemical reactions catalyzed by the bacterial activity (e.g. iron sulfide precipitation). To investigate these possibilities, we conducted complementary well logging measurements (magnetic susceptibility [MS], nuclear magnetic resonance [NMR], gamma-ray) using 5 boreholes installed at both treated and untreated locations of the site. We also collected water and soil samples on which we conducted microbiological and chemical analyses, along with geophysical observations (SIP, MS and NMR), in the laboratory. These measurements provide further insights into the physicochemical transformations in the subsurface resulting from the treatment and highlight the possibility of long term monitoring of treatment-impacted zones using electrical geophysics.

3D conductive nanocomposite scaffold for bone tissue engineering

PubMed Central

Shahini, Aref; Yazdimamaghani, Mostafa; Walker, Kenneth J; Eastman, Margaret A; Hatami-Marbini, Hamed; Smith, Brenda J; Ricci, John L; Madihally, Sundar V; Vashaee, Daryoosh; Tayebi, Lobat

2014-01-01

Bone healing can be significantly expedited by applying electrical stimuli in the injured region. Therefore, a three-dimensional (3D) ceramic conductive tissue engineering scaffold for large bone defects that can locally deliver the electrical stimuli is highly desired. In the present study, 3D conductive scaffolds were prepared by employing a biocompatible conductive polymer, ie, poly(3,4-ethylenedioxythiophene) poly(4-styrene sulfonate) (PEDOT:PSS), in the optimized nanocomposite of gelatin and bioactive glass. For in vitro analysis, adult human mesenchymal stem cells were seeded in the scaffolds. Material characterizations using hydrogen-1 nuclear magnetic resonance, in vitro degradation, as well as thermal and mechanical analysis showed that incorporation of PEDOT:PSS increased the physiochemical stability of the composite, resulting in improved mechanical properties and biodegradation resistance. The outcomes indicate that PEDOT:PSS and polypeptide chains have close interaction, most likely by forming salt bridges between arginine side chains and sulfonate groups. The morphology of the scaffolds and cultured human mesenchymal stem cells were observed and analyzed via scanning electron microscope, micro-computed tomography, and confocal fluorescent microscope. Increasing the concentration of the conductive polymer in the scaffold enhanced the cell viability, indicating the improved microstructure of the scaffolds or boosted electrical signaling among cells. These results show that these conductive scaffolds are not only structurally more favorable for bone tissue engineering, but also can be a step forward in combining the tissue engineering techniques with the method of enhancing the bone healing by electrical stimuli. PMID:24399874

3D conductive nanocomposite scaffold for bone tissue engineering.

PubMed

Shahini, Aref; Yazdimamaghani, Mostafa; Walker, Kenneth J; Eastman, Margaret A; Hatami-Marbini, Hamed; Smith, Brenda J; Ricci, John L; Madihally, Sundar V; Vashaee, Daryoosh; Tayebi, Lobat

2014-01-01

Bone healing can be significantly expedited by applying electrical stimuli in the injured region. Therefore, a three-dimensional (3D) ceramic conductive tissue engineering scaffold for large bone defects that can locally deliver the electrical stimuli is highly desired. In the present study, 3D conductive scaffolds were prepared by employing a biocompatible conductive polymer, ie, poly(3,4-ethylenedioxythiophene) poly(4-styrene sulfonate) (PEDOT:PSS), in the optimized nanocomposite of gelatin and bioactive glass. For in vitro analysis, adult human mesenchymal stem cells were seeded in the scaffolds. Material characterizations using hydrogen-1 nuclear magnetic resonance, in vitro degradation, as well as thermal and mechanical analysis showed that incorporation of PEDOT:PSS increased the physiochemical stability of the composite, resulting in improved mechanical properties and biodegradation resistance. The outcomes indicate that PEDOT:PSS and polypeptide chains have close interaction, most likely by forming salt bridges between arginine side chains and sulfonate groups. The morphology of the scaffolds and cultured human mesenchymal stem cells were observed and analyzed via scanning electron microscope, micro-computed tomography, and confocal fluorescent microscope. Increasing the concentration of the conductive polymer in the scaffold enhanced the cell viability, indicating the improved microstructure of the scaffolds or boosted electrical signaling among cells. These results show that these conductive scaffolds are not only structurally more favorable for bone tissue engineering, but also can be a step forward in combining the tissue engineering techniques with the method of enhancing the bone healing by electrical stimuli.

Can We Probe the Conductivity of the Lithosphere and Upper Mantle Using Satellite Tidal Magnetic Signals?

NASA Technical Reports Server (NTRS)

Schnepf, N. R.; Kuvshinov, A.; Sabaka, T.

2015-01-01

A few studies convincingly demonstrated that the magnetic fields induced by the lunar semidiurnal (M2) ocean flow can be identified in satellite observations. This result encourages using M2 satellite magnetic data to constrain subsurface electrical conductivity in oceanic regions. Traditional satellite-based induction studies using signals of magnetospheric origin are mostly sensitive to conducting structures because of the inductive coupling between primary and induced sources. In contrast, galvanic coupling from the oceanic tidal signal allows for studying less conductive, shallower structures. We perform global 3-D electromagnetic numerical simulations to investigate the sensitivity of M2 signals to conductivity distributions at different depths. The results of our sensitivity analysis suggest it will be promising to use M2 oceanic signals detected at satellite altitude for probing lithospheric and upper mantle conductivity. Our simulations also suggest that M2 seafloor electric and magnetic field data may provide complementary details to better constrain lithospheric conductivity.

Electric transport coefficients in highly epitaxial LaBaCo{sub 2}O{sub 5 + δ} films with “p-to-n” transition induced by oxygen deficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaibo, J.; Zhang, Q. Y., E-mail: qyzhang@dlut.edu.cn; Hu, H. C.

2016-08-14

Electric transport coefficients such as carrier type, density, and mobility are the important physical parameters in designing functional devices. In this work, we report the study on the electric transport coefficients of the highly epitaxial LaBaCo{sub 2}O{sub 5 + δ} (LBCO) films, which were discussed as a function of electric conductivity for the first time and compared with the results calculated by the theory for mixed conduction. The mobility in the LBCO films was determined to be ∼0.85 and ∼40 cm{sup 2}/V s for holes and electrons, respectively, and the density of p-type carriers strongly depends on the oxygen deficiency. Solid evidence ismore » presented to demonstrate that the oxygen deficiency cannot make LBCO materials changed from p- to n-type. The n-type conduction observed in experiment is a counterfeit phenomenon caused by the deficiency in Hall measurement, rather than a realistic transition induced by oxygen deficiency. In addition, the temperature-dependent conductivity was discussed using the differential coefficients, which might be useful in the study of the samples with magnetic transition.« less

Robust Neurite Extension Following Exogenous Electrical Stimulation within Single Walled Carbon Nanotube-Composite Hydrogels

PubMed Central

Koppes, A. N.; Keating, K. W.; McGregor, A. L.; Koppes, R. A.; Kearns, K. R.; Ziemba, A. M.; McKay, C. A.; Zuidema, J. M.; Rivet, C. J.; Gilbert, R. J.; Thompson, D. M.

2016-01-01

The use of exogenous electrical stimulation to promote nerve regeneration has achieved only limited success. Conditions impeding optimized outgrowth may arise from inadequate stimulus presentation due to differences in injury geometry or signal attenuation. Implantation of an electrically-conductive biomaterial may mitigate this attenuation and provide a more reproducible signal. In this study, a conductive nanofiller (single-walled carbon nanotubes [SWCNT]) was selected as one possible material to manipulate the bulk electrical properties of a collagen type I-10% Matrigel™ composite hydrogel. Neurite outgrowth within hydrogels (SWCNT or nanofiller-free controls) was characterized to determine if: 1) nanofillers influence neurite extension and 2) electrical stimulation of the nanofiller composite hydrogel enhances neurite outgrowth. Increased SWCNT loading (10–100-μg/ml) resulted in greater bulk conductivity (up to 1.7-fold) with no significant changes to elastic modulus. Neurite outgrowth increased 3.3-fold in 20-μg/mL SWCNT loaded biomaterials relative to the nanofiller-free control. Electrical stimulation promoted greater outgrowth (2.9-fold) within SWCNT-free control. The concurrent presentation of electrical stimulation and SWCNT-loaded biomaterials resulted in a 7.0-fold increase in outgrowth relative to the unstimulated, nanofiller-free controls. Local glia residing within the DRG likely contribute, in part, to the observed increases in outgrowth; but it is unknown which specific nanofiller properties influence neurite extension. Characterization of neuronal behavior in model systems, such as those described here, will aid the rational development of biomaterials as well as the appropriate delivery of electrical stimuli to support nerve repair. PMID:27167609

FT-MIR supported Electrical Impedance Spectroscopy based study of sugar adulterated honeys from different floral origin.

PubMed

Das, Chirantan; Chakraborty, Subhadip; Acharya, Krishnendu; Bera, Nirmal Kumar; Chattopadhyay, Dipankar; Karmakar, Anupam; Chattopadhyay, Sanatan

2017-08-15

This study sought to detect the presence of sucrose as an adulterant in selected honey varieties from different floral origins by employing Electrical Impedance Spectroscopy (EIS) technique which has been simultaneously supported by Fourier Transform-Mid Infrared Spectroscopy (FT-MIR) measurements to provide a rapid, robust yet simple platform for honey quality evaluation. Variation of electrical parameters such as impedance, capacitance and conductance for 10%, 20%, 30%, 40%, 50%, 60% and 70% (w/w) sucrose syrup (SS) adulterated honey samples are analyzed and their respective current-voltage (I-V) characteristics are studied. Capacitance, conductance and net current flowing through the system are observed to decrease linearly whereas system impedance has been found to increase similarly with the increase in adulterant content. Also, FT-MIR measurements in the spectral region between 1800cm -1 and 650cm -1 reveal the increment of absorbance values due to the addition of SS. Full-Width-at-Half-Maximum (FWHM) is estimated from the spectral peak 1056cm -1 for all pure and adulterated honey samples and is observed to be linearly increasing with increase in adulterant content. Finally, the coefficient of sensitivity has been extracted for all varieties of honey considered in terms of the measured conductance values. Copyright © 2017 Elsevier B.V. All rights reserved.

Evaluation of PVA biodegradable electric conductive membranes for nerve regeneration in axonotmesis injuries: the rat sciatic nerve animal model.

PubMed

Ribeiro, Jorge; Caseiro, Ana Rita; Pereira, Tiago; Armada-da-Silva, Paulo Alexandre; Pires, Isabel; Prada, Justina; Amorim, Irina; Leal Reis, Inês; Amado, Sandra; Santos, José Domingos; Bompasso, Simone; Raimondo, Stefania; Varejão, Artur Severo Proença; Geuna, Stefano; Luís, Ana Lúcia; Maurício, Ana Colette

2017-05-01

The therapeutic effect of three polyvinyl alcohol (PVA) membranes loaded with electrically conductive materials - carbon nanotubes (PVA-CNTs) and polypyrrole (PVA-PPy) - were tested in vivo for neuro-muscular regeneration after an axonotmesis injury in the rat sciatic nerve. The membranes electrical conductivity measured was 1.5 ± 0.5 × 10 -6 S/m, 579 ± 0.6 × 10 -6 S/m, and 1837.5 ± 0.7 × 10 -6 S/m, respectively. At week-12, a residual motor and nociceptive deficit were present in all treated groups, but at week-12, a better recovery to normal gait pattern of the PVA-CNTs and PVA-PPy treated groups was observed. Morphometrical analysis demonstrated that PVA-CNTs group presented higher myelin thickness and lower g-ratio. The tibialis anterior muscle, in the PVA-PPy and PVA-CNTs groups showed a 9% and 19% increase of average fiber size area and a 5% and 10% increase of the "minimal Feret's diameter," respectively. No inflammation, degeneration, fibrosis or necrosis were detected in lung, liver, kidneys, spleen, and regional lymph nodes and absence of carbon deposits was confirmed with Von Kossa and Masson-Fontana stains. In conclusion, the membranes of PVA-CNTs and PVA-PPy are biocompatible and have electrical conductivity. The higher electrical conductivity measured in PVA-CNTs membrane might be responsible for the positive results on maturation of myelinated fibers. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1267-1280, 2017. © 2017 Wiley Periodicals, Inc.

Enhanced Electrical Conductivity of Molecularly p-Doped Poly(3-hexylthiophene) through Understanding the Correlation with Solid-State Order

PubMed Central

2017-01-01

Molecular p-doping of the conjugated polymer poly(3-hexylthiophene) (P3HT) with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) is a widely studied model system. Underlying structure–property relationships are poorly understood because processing and doping are often carried out simultaneously. Here, we exploit doping from the vapor phase, which allows us to disentangle the influence of processing and doping. Through this approach, we are able to establish how the electrical conductivity varies with regard to a series of predefined structural parameters. We demonstrate that improving the degree of solid-state order, which we control through the choice of processing solvent and regioregularity, strongly increases the electrical conductivity. As a result, we achieve a value of up to 12.7 S cm–1 for P3HT:F4TCNQ. We determine the F4TCNQ anion concentration and find that the number of (bound + mobile) charge carriers of about 10–4 mol cm–3 is not influenced by the degree of solid-state order. Thus, the observed increase in electrical conductivity by almost 2 orders of magnitude can be attributed to an increase in charge-carrier mobility to more than 10–1 cm2 V–1 s–1. Surprisingly, in contrast to charge transport in undoped P3HT, we find that the molecular weight of the polymer does not strongly influence the electrical conductivity, which highlights the need for studies that elucidate structure–property relationships of strongly doped conjugated polymers. PMID:29093606

Electrokinetic instability in microchannel ferrofluid/water co-flows

PubMed Central

Song, Le; Yu, Liandong; Zhou, Yilong; Antao, Asher Reginald; Prabhakaran, Rama Aravind; Xuan, Xiangchun

2017-01-01

Electrokinetic instability refers to unstable electric field-driven disturbance to fluid flows, which can be harnessed to promote mixing for various electrokinetic microfluidic applications. This work presents a combined numerical and experimental study of electrokinetic ferrofluid/water co-flows in microchannels of various depths. Instability waves are observed at the ferrofluid and water interface when the applied DC electric field is beyond a threshold value. They are generated by the electric body force that acts on the free charge induced by the mismatch of ferrofluid and water electric conductivities. A nonlinear depth-averaged numerical model is developed to understand and simulate the interfacial electrokinetic behaviors. It considers the top and bottom channel walls’ stabilizing effects on electrokinetic flow through the depth averaging of three-dimensional transport equations in a second-order asymptotic analysis. This model is found accurate to predict both the observed electrokinetic instability patterns and the measured threshold electric fields for ferrofluids of different concentrations in shallow microchannels. PMID:28406228

Room-temperature coupling between electrical current and nuclear spins in OLEDs

NASA Astrophysics Data System (ADS)

Malissa, H.; Kavand, M.; Waters, D. P.; van Schooten, K. J.; Burn, P. L.; Vardeny, Z. V.; Saam, B.; Lupton, J. M.; Boehme, C.

2014-09-01

The effects of external magnetic fields on the electrical conductivity of organic semiconductors have been attributed to hyperfine coupling of the spins of the charge carriers and hydrogen nuclei. We studied this coupling directly by implementation of pulsed electrically detected nuclear magnetic resonance spectroscopy in organic light-emitting diodes (OLEDs). The data revealed a fingerprint of the isotope (protium or deuterium) involved in the coherent spin precession observed in spin-echo envelope modulation. Furthermore, resonant control of the electric current by nuclear spin orientation was achieved with radiofrequency pulses in a double-resonance scheme, implying current control on energy scales one-millionth the magnitude of the thermal energy.

3D printable highly conductive and mechanically strong thermoplastic-based nanocomposites

NASA Astrophysics Data System (ADS)

Tabiai, Ilyass; Therriault, Daniel

Highly conductive 3D printable inks can be used to design electrical devices with various functionalities and geometries. We use the solvent evaporation assisted 3D-printing method to create high resolution structures made of poly(lactid) acid (PLA) reinforced with multi-walled carbon nanotube (MWCNTs). We characterize fibers with diameters ranging between 100 μm to 330 μm and reinforced with MWCNTs from 0.5 up to 40wt% here. Tensile test, shrinkage ratio, density and electrical conductivity measurements of the printed nanocomposite are presented. The material's electrical conductivity is strongly improved by adding MWCNTs (up to 3000S/m), this value was found to be higher than any 3D-printable carbon based material available in the literature. It is observed that MWCNTs significantly increase the material's strength and stiffness while reducing its ductility. The ink's density was also higher while still being in the range of polymers' densities. The presented nanocomposite is light weight, highly conductive, has good mechanical properties and can be printed in a freeform fashion at the micro scale. A myriad of low power consumption with less resistive heating sensors and devices can potentially be designed using it and integrated into other 3D printable products.

Cole-cole analysis and electrical conduction mechanism of N{sup +} implanted polycarbonate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chawla, Mahak; Shekhawat, Nidhi; Aggarwal, Sanjeev, E-mail: write2sa@gmail.com

2014-05-14

In this paper, we present the analysis of the dielectric (dielectric constant, dielectric loss, a.c. conductivity) and electrical properties (I–V characteristics) of pristine and nitrogen ion implanted polycarbonate. The samples of polycarbonate were implanted with 100 keV N{sup +} ions with fluence ranging from 1 × 10{sup 15} to 1 × 10{sup 17} ions cm{sup −2}. The dielectric measurements of these samples were performed in the frequency range of 100 kHz to 100 MHz. It has been observed that dielectric constant decreases whereas dielectric loss and a.c. conductivity increases with increasing ion fluence. An analysis of real and imaginary parts of dielectric permittivity has beenmore » elucidated using Cole-Cole plot of the complex permittivity. With the help of Cole-Cole plot, we determined the values of static dielectric constant (ε{sub s}), optical dielectric constant (ε{sub ∞}), spreading factor (α), average relaxation time (τ{sub 0}), and molecular relaxation time (τ). The I–V characteristics were studied using Keithley (6517) electrometer. The electrical conduction behaviour of pristine and implanted polycarbonate specimens has been explained using various models of conduction.« less

The Bulk Lunar Electrical Conductivity. Ph.D. Thesis. Final Report; [from Explorer 35 satellite and the Apollo 12 flight

NASA Technical Reports Server (NTRS)

Leavy, Donald Lucien

1975-01-01

The electrical conductivity structure was studied of a spherically layered moon consistent with the very low frequency magnetic data collected on the lunar surface and by Explorer 35. In order to obtain good agreement with the lunar surface magnetometer observations, the inclusion of a void cavity behind the moon requires a conductivity at shallow depths higher than that of models having the solar wind impinging on all sides. By varying only the source parameters, a conductivity model can be found that yields a good fit to both the tangential response upstream and the radial response downstream. This model also satisfies the dark side tangential response in the frequency range above 0.006 Hz, but the few data points presently available below this range do not seem to agree with the theory.

A dielectrophoresis-impedance method for protein detection and analysis

NASA Astrophysics Data System (ADS)

Mohamad, Ahmad Sabry; Hamzah, Roszymah; Hoettges, Kai F.; Hughes, Michael Pycraft

2017-01-01

Dielectrophoresis (DEP) has increasingly been used for the assessment of the electrical properties of molecular scale objects including proteins, DNA, nanotubes and nanowires. However, whilst techniques have been developed for the electrical characterisation of frequency-dependent DEP response, biomolecular study is usually limited to observation using fluorescent markers, limiting its applicability as a characterisation tool. In this paper we present a label-free, impedance-based method of characterisation applied to the determination of the electrical properties of colloidal protein molecules, specifically Bovine Serum Albumin (BSA). By monitoring the impedance between electrodes as proteins collect, it is shown to be possible to observe multi-dispersion behaviour. A DEP dispersion exhibited at 400 kHz is attributable to the orientational dispersion of the molecule, whilst a second, higher-frequency dispersion is attributed to a Maxwell-Wagner type dispersion; changes in behaviour with medium conductivity suggest that this is strongly influenced by the electrical double layer surrounding the molecule.

Dynamics of vesicles in electric fields

NASA Astrophysics Data System (ADS)

Vlahovska, Petia; Gracia, Ruben

2007-11-01

Electromechanical forces are widely used for cell manipulation. Knowledge of the physical mechanisms underlying the interaction of cells and external fields is essential for practical applications. Vesicles are model cells made of a lipid bilayer membrane. They are examples of ``soft'' particles, i.e., their shape when subjected to flow or electric field is not given a priori but it is governed by the balance of membrane, fluid and electrical stresses. This generic ``softness'' gives rise to a very complex vesicle dynamics in external fields. In an AC electric field, as the frequency is increased, vesicles filled with a fluid less conducting than the surrounding fluid undergo shape transition from prolate to oblate ellipsoids. The opposite effect is observed with drops. We present an electro- hydrodynamic theory based on the leaky dielectric model that quantitatively describes experimental observations. We compare drops and vesicles, and show how their distinct behavior stems from different interfacial properties.

Electrical detection of nuclear spins in organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Malissa, H.; Kavand, M.; Waters, D. P.; Lupton, J. M.; Vardeny, Z. V.; Saam, B.; Boehme, C.

2014-03-01

We present pulsed combined electrically detected electron paramagnetic and nuclear magnetic resonance experiments on MEH-PPV OLEDs. Spin dynamics in these structures are governed by hyperfine interactions between charge carriers and the surrounding hydrogen nuclei, which are abundant in these materials. Hyperfine coupling has been observed by monitoring the device current during coherent spin excitation. Electron spin echoes (ESEs) are detected by applying one additional readout pulse at the time of echo formation. This allows for the application of high-resolution spectroscopy based on ESE detection, such as electron spin echo envelope modulation (ESEEM) and electron nuclear double resonance (ENDOR) available for electrical detection schemes. We conduct electrically detected ESEEM and ENDOR experiments and show how hyperfine interactions in MEH-PPV with and without deuterated polymer side groups can be observed by device current measurements. We acknowledge support by the Department of Energy, Office of Basic Energy Sciences under Award #DE-SC0000909.

Is the ;Earth-ionosphere capacitor; a valid component in the atmospheric global electric circuit?

NASA Astrophysics Data System (ADS)

Haldoupis, Christos; Rycroft, Michael; Williams, Earle; Price, Colin

2017-11-01

This paper examines whether the Earth-ionosphere capacitor (EIC) model is correct, by comparing observed atmospheric electrical properties with those expected for a spherical capacitor, as defined in electrostatics. The comparisons suggest that the EIC concept cannot be reconciled with, and hence cannot account for, the observations, particularly the rapid reduction of the atmospheric electric field with height that is measured. This means that the spherical EIC concept is incorrect by being too simplistic; it is thus misleading. The reason for this flawed concept is simple: the model disregards the non-uniform conductivity of the atmosphere which requires the presence of a net positive charge in the lower atmosphere that equals in magnitude the Earth's negative charge. This positive charge shields the action of the Earth's negative charge from polarizing the ionosphere positively. Thus, the lower D region ionosphere remains electrically neutral, which makes the EIC concept inappropriate.

Surface electrical properties of stainless steel fibres: An AFM-based study

NASA Astrophysics Data System (ADS)

Yin, Jun; D'Haese, Cécile; Nysten, Bernard

2015-03-01

Atomic force microscopy (AFM) electrical modes were used to study the surface electrical properties of stainless steel fibres. The surface electrical conductivity was studied by current sensing AFM and I-V spectroscopy. Kelvin probe force microscopy was used to measure the surface contact potential. The oxide film, known as passivation layer, covering the fibre surface gives rise to the observation of an apparently semiconducting behaviour. The passivation layer generally exhibits a p-type semiconducting behaviour, which is attributed to the predominant formation of chromium oxide on the surface of the stainless steel fibres. At the nanoscale, different behaviours are observed from points to points, which may be attributed to local variations of the chemical composition and/or thickness of the passivation layer. I-V curves are well fitted with an electron tunnelling model, indicating that electron tunnelling may be the predominant mechanism for electron transport.

Electric Vehicle Preparedness: Task 1, Assessment of Fleet Inventory for Marine Corps Base Camp Lejeune

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schey, Stephen; Francfort, Jim

2015-01-01

Several U.S. Department of Defense-based studies were conducted to identify potential U.S. Department of Defense transportation systems that are strong candidates for introduction or expansion of plug-in electric vehicles (PEVs). Task 1 included a survey of the inventory of non-tactical fleet vehicles at the Marine Corps Base Camp Lejeune (MCBCL) to characterize the fleet. This information and characterization will be used to select vehicles for monitoring that takes place during Task 2. This monitoring involves data logging of vehicle operation in order to identify the vehicle’s mission and travel requirements. Individual observations of these selected vehicles provide the basis formore » recommendations related to PEV adoption. It also identifies whether a battery electric vehicle or plug-in hybrid electric vehicle (collectively referred to as PEVs) can fulfill the mission requirements and provides observations related to placement of PEV charging infrastructure.« less

Deformation and Rotation of a Drop in a Uniform Electric Field

NASA Astrophysics Data System (ADS)

Salipante, Paul; Hanna, James; Vlahovska, Petia

2009-11-01

Drop deformation in uniform electric fields is a classic problem. The pioneering work of G.I.Taylor demonstrated that for weakly conducting media, the drop fluid undergoes a toroidal flow and the drop adopts a prolate or oblate spheroidal shape, the flow and shape being axisymmetrically aligned with the applied field. However, recent studies have revealed a nonaxisymmetric rotational mode for drops of lower conductivity than the surrounding medium, similar to the rotation of solid dielectric particles observed by Quincke in the 19th century. We will present an experimental and theoretical study of this phenomenon in DC fields. The critical electric field, drop inclination angle, and rate of rotation are measured. For small, high viscosity drops, the threshold field strength is well approximated by the Quincke rotation criterion. Reducing the viscosity ratio shifts the onset for rotation to stronger fields. The drop inclination angle increases with field strength. The rotation rate is approximately given by the inverse Maxwell-Wagner polarization time. We also observe a hysteresis in the tilt angle for low-viscosity drops. The effects of AC fields and surfactants are also explored.

High Thermal Conductive BBL/Graphene Nanocomposite System

DTIC Science & Technology

2011-09-02

properties. Composite materials employing carbon -based materials such as carbon - nanotube (CNT), graphene, and fullerene have been explored. However, at...fraction as low as 0.1 vol %, comparable to those observed in carbon nanotube -based composites1c and a conductivity of 0.1 Sm-1, sufficient for many...in both poly(benzimidazobenzophenanthroline) (BBL) and the carbon sheets of the graphene so that the electrical-conductivity levels of the composites

A Modeling Study of the Spatial Structure of Electric Fields Generated by Electrified Clouds with Screening Layers

NASA Astrophysics Data System (ADS)

Biagi, C. J.; Cummins, K. L.

2015-12-01

The growing possibility of inexpensive airborne observations of electric fields using one or more small UAVs increases the importance of understanding what can be determined about cloud electrification and associated electric fields outside cloud boundaries. If important information can be inferred from carefully selected flight paths outside of a cloud, then the aircraft and its instrumentation will be much cheaper to develop and much safer to operate. These facts have led us to revisit this long-standing topic using quasi-static, finite-element modeling inside and outside arbitrarily shaped clouds with a variety of internal charge distributions. In particular, we examine the effect of screening layers on electric fields outside of electrified clouds by comparing modeling results for charged clouds having electrical conductivities that are both equal to and lower than the surrounding clear air. The comparisons indicate that the spatial structure of the electric field is approximately the same regardless of the difference in the conductivities between the cloud and clear air and the formation of a screening layer, even for altitude-dependent electrical conductivities. This result is consistent with the numerical modeling results reported by Driscoll et al [1992]. The similarity of the spatial structure of the electric field outside of clouds with and without a screening layer suggests that "bulk" properties related to cloud electrification might be determined using measurements of the electric field at multiple locations in space outside the cloud, particularly at altitude. Finally, for this somewhat simplified model, the reduction in electric field magnitude outside the cloud due to the presence of a screening layer exhibits a simple dependence on the difference in conductivity between the cloud and clear air. These results are particularly relevant for studying clouds that are not producing lightning, such as developing thunderstorms and decaying anvils associated with mature storm systems.Driscoll K.T., R.J. Blakeslee, M.E. Baginski, 1992, A modeling study of the time-averaged electric currents in the vicinity of isolated thunderstorms, J. Geophys. Res., 97, D11, pp 11535-11551.

Pressure-Induced Amorphization in Single-Crystal Ta2O5 Nanowires: A Kinetic Mechanism and Improved Electrical Conductivity

NASA Astrophysics Data System (ADS)

Lu, Xujie; Hu, Qingyang; Yang, Wenge; Bai, Ligang; Sheng, Howard; Wang, Lin; Huang, Fuqiang; Wen, Jianguo; Miller, Dean; Zhao, Yusheng

2014-03-01

Pressure-induced amorphization (PIA) in single-crystal Ta2O5 nanowires is observed at 19 GPa and the obtained amorphous Ta2O5 nanowires show significant improvement in electrical conductivity. The phase transition process is unveiled by monitoring structural evolution with in-situ synchrotron XRD, PDF, Raman spectroscopy and TEM. The first principles calculations reveal the phonon modes softening during compression at particular bonds, and the analysis on the electron localization function also shows bond strength weakening at the same positions. Based on the experimental and theoretical results, a kinetic PIA mechanism is proposed and demonstrated systematically that amorphization is initiated by the disruption of connectivity between polyhedra at the particular weak-bonding positions along the a-axis in the unit cell. The one-dimensional morphology is well preserved for the pressure-induced amorphous Ta2O5 and the electrical conductivity is improved by an order of magnitude compared to traditional amorphous forms.

Monitoring Damage Propagation in Glass Fiber Composites Using Carbon Nanofibers.

PubMed

Al-Sabagh, Ahmed; Taha, Eman; Kandil, Usama; Nasr, Gamal-Abdelnaser; Reda Taha, Mahmoud

2016-09-10

In this work, we report the potential use of novel carbon nanofibers (CNFs), dispersed during fabrication of glass fiber composites to monitor damage propagation under static loading. The use of CNFs enables a transformation of the typically non-conductive glass fiber composites into new fiber composites with appreciable electrical conductivity. The percolation limit of CNFs/epoxy nanocomposites was first quantified. The electromechanical responses of glass fiber composites fabricated using CNFs/epoxy nanocomposite were examined under static tension loads. The experimental observations showed a nonlinear change of electrical conductivity of glass fiber composites incorporating CNFs versus the stress level under static load. Microstructural investigations proved the ability of CNFs to alter the polymer matrix and to produce a new polymer nanocomposite with a connected nanofiber network with improved electrical properties and different mechanical properties compared with the neat epoxy. It is concluded that incorporating CNFs during fabrication of glass fiber composites can provide an innovative means of self-sensing that will allow damage propagation to be monitored in glass fiber composites.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schey, Steve

Several U.S. Department of Defense based studies have been conducted to identify potential U.S. Department of Defense transportation systems that are strong candidates for introduction or expansion of plug-in electric vehicles (PEVs). Task 2 involved identifying daily operational characteristics of select vehicles and initiating data logging of vehicle movements in order to characterize the vehicle’s mission. Individual observations of these selected vehicles provide the basis for recommendations related to PEV adoption and whether a battery electric vehicle or plug-in hybrid electric vehicle (collectively referred to as PEVs) can fulfill the mission requirements and provide observations related to placement of PEVmore » charging infrastructure. This report provides the results of the data analysis and observations related to replacement of current vehicles with PEVs. This fulfills part of the Task 3 requirements. Task 3 also includes an assessment of the charging infrastructure required to support this replacement, which is the subject of a separate report.« less

Electrically rotating suspended films of polar liquids

NASA Astrophysics Data System (ADS)

Shirsavar, R.; Amjadi, A.; Tonddast-Navaei, A.; Ejtehadi, M. R.

2011-02-01

Controlled rotation of a suspended soap water film, simply generated by applying an electric field, has been reported recently. The film rotates when the applied electric field exceeds a certain threshold. In this study, we investigate the phenomenon in films made of a number of other liquids with various physical and chemical properties. Our measurements show that the intrinsic electrical dipole moments of the liquid molecules seems to be vital for the corresponding film rotation. All the investigated rotating liquids have a molecular electric dipole moment of above 1 Debye, while weakly polar liquids do not rotate. However, the liquids investigated here cover a wide range of physical parameters (e.g. viscosity, density, conductivity, etc.). So far, no significant correlation has been observed between the electric field thresholds and macroscopic properties of the liquids.

High conductance surge cable

DOEpatents

Murray, M.M.; Wilfong, D.H.; Lomax, R.E.

1998-12-08

An electrical cable for connecting transient voltage surge suppressors to electrical power panels. A strip of electrically conductive foil defines a longitudinal axis, with a length of an electrical conductor electrically attached to the metallic foil along the longitudinal axis. The strip of electrically conductive foil and the length of an electrical conductor are covered by an insulating material. For impedance matching purposes, triangular sections can be removed from the ends of the electrically conductive foil at the time of installation. 6 figs.

Shot noise at the quantum point contact in InGaAs heterostructure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nishihara, Yoshitaka; Nakamura, Shuji; Ono, Teruo

2013-12-04

We study the shot noise at a quantum point contact (QPC) fabricated in an InGaAs/InGaAsP heterostructure, whose conductance can be electrically tuned by the gate voltages. Shot noise suppression is observed at the conductance plateau of N(2e{sup 2}/h) (N = 4,5,and 6), which indicates the coherent quantized channel formation in the QPC. The electron heating effect generated at the QPC explains the deviation of the observed Fano factor from the theory.

Electrical power generation by mechanically modulating electrical double layers.

PubMed

Moon, Jong Kyun; Jeong, Jaeki; Lee, Dongyun; Pak, Hyuk Kyu

2013-01-01

Since Michael Faraday and Joseph Henry made their great discovery of electromagnetic induction, there have been continuous developments in electrical power generation. Most people today get electricity from thermal, hydroelectric, or nuclear power generation systems, which use this electromagnetic induction phenomenon. Here we propose a new method for electrical power generation, without using electromagnetic induction, by mechanically modulating the electrical double layers at the interfacial areas of a water bridge between two conducting plates. We find that when the height of the water bridge is mechanically modulated, the electrical double layer capacitors formed on the two interfacial areas are continuously charged and discharged at different phases from each other, thus generating an AC electric current across the plates. We use a resistor-capacitor circuit model to explain the results of this experiment. This observation could be useful for constructing a micro-fluidic power generation system in the near future.

Method of Fault Detection and Rerouting

NASA Technical Reports Server (NTRS)

Gibson, Tracy L. (Inventor); Medelius, Pedro J. (Inventor); Lewis, Mark E. (Inventor)

2013-01-01

A system and method for detecting damage in an electrical wire, including delivering at least one test electrical signal to an outer electrically conductive material in a continuous or non-continuous layer covering an electrically insulative material layer that covers an electrically conductive wire core. Detecting the test electrical signals in the outer conductive material layer to obtain data that is processed to identify damage in the outer electrically conductive material layer.

An electrical-heating and self-sensing shape memory polymer composite incorporated with carbon fiber felt

NASA Astrophysics Data System (ADS)

Gong, Xiaobo; Liu, Liwu; Liu, Yanju; Leng, Jinsong

2016-03-01

Shape memory polymers (SMPs) have the ability to adjust their stiffness, lock a temporary shape, and recover the permanent shape upon imposing an appropriate stimulus. They have found their way into the field of morphing structures. The electrically Joule resistive heating of the conductive composite can be a desirable stimulus to activate the shape memory effect of SMPs without external heating equipment. Electro-induced SMP composites incorporated with carbon fiber felt (CFF) were explored in this work. The CFF is an excellent conductive filler which can easily spread throughout the composite. It has a huge advantage in terms of low cost, simple manufacturing process, and uniform and tunable temperature distribution while heating. A continuous and compact conductive network made of carbon fibers and the overlap joints among them was observed from the microscopy images, and this network contributes to the high conductive properties of the CFF/SMP composites. The CFF/SMP composites can be electrical-heated rapidly and uniformly, and its’ shape recovery effect can be actuated by the electrical resistance Joule heating of the CFF without an external heater. The CFF/SMP composite get higher modulus and higher strength than the pure SMP without losing any strain recovery property. The high dependence of temperature and strain on the electrical resistance also make the composite a good self-sensing material. In general, the CFF/SMP composite shows great prospects as a potential material for the future morphing structures.

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

DOEpatents

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.

Electrical transport properties of nanoplates shaped tungsten oxide embedded poly(vinyl-alcohol) film

NASA Astrophysics Data System (ADS)

Das, Amit Kumar; Chatterjee, Piyali; Meikap, Ajit Kumar

2018-04-01

Tungsten oxide (WO3) nanoplates have been synthesized via hydrothermal method. The average crystallite size of the nanoplates is 28.9 ± 0.5 nm. The direct and indirect band gap of WO3 is observed. The AC conductivity of PVA-WO3 composite film has been observed and carrier transport mechanism follows correlated barrier hopping model. The maximum barrier height of the composite film is 0.1 eV. The electric modulus reflects the non-Debye type behaviour of relaxation time which is simulated by Kohlrausch-Willims-Watts (KWW) function.

Magnetotellurics with geomagnetic observatory data influenced by the ocean effect: upper mantle conductivity under the islands of Gan and Tristan da Cunha

NASA Astrophysics Data System (ADS)

Morschhauser, A.; Grayver, A.; Kuvshinov, A. V.; Samrock, F.; Matzka, J.

2017-12-01

The electric conductivity of the oceanic lithosphere and upper mantle is not well constrained, mainly due to logistical challenges in oceanic surveys. However, electric field measurements can easily be added to geomagnetic observatories on islands.Currently, such measurements are available for Tristan da Cunha in the Atlantic Ocean and Gan on the Maldives in the Indian Ocean, and we derive tippers, impedances, and phase tensors for those observatories. The main challenge is that these transfer functions are severely affected by the conductivity contrast between seawater and land, which results in a three-dimensional (3-D) behaviour of the responses. We use an adaptive finite-element MT forward solver in order to properly account for this 3-D effect by including the available bathymetry and topography data into the model. Then, different transfer functions are individually inverted for upper mantle conductivities using a stochastic approach. We observe that tippers are mostly sensitive down to depths of approx. 100 km, and that additional electric field measurements improve the resolution for 100 to 200 km depth. The obtained 1-D conductivity profiles indicate a normal oceanic mantle below GAN and an anomalously conductive mantle below TDC, which may be related to the presence of melt below the island.

Electric-field control of conductance in metal quantum point contacts by electric-double-layer gating

NASA Astrophysics Data System (ADS)

Shibata, K.; Yoshida, K.; Daiguji, K.; Sato, H.; , T., Ii; Hirakawa, K.

2017-10-01

An electric-field control of quantized conductance in metal (gold) quantum point contacts (QPCs) is demonstrated by adopting a liquid-gated electric-double-layer (EDL) transistor geometry. Atomic-scale gold QPCs were fabricated by applying the feedback-controlled electrical break junction method to the gold nanojunction. The electric conductance in gold QPCs shows quantized conductance plateaus and step-wise increase/decrease by the conductance quantum, G0 = 2e2/h, as EDL-gate voltage is swept, demonstrating a modulation of the conductance of gold QPCs by EDL gating. The electric-field control of conductance in metal QPCs may open a way for their application to local charge sensing at room temperature.

The effect of longitudinal conductance variations on the ionospheric prompt penetration electric fields

NASA Astrophysics Data System (ADS)

Sazykin, S.; Wolf, R.; Spiro, R.; Fejer, B.

Ionospheric prompt penetration electric fields of magnetospheric origin, together with the atmospheric disturbance dynamo, represent the most important parameters controlling the storm-time dynamics of the low and mid-latitude ionosphere. These prompt penetration fields result from the disruption of region-2 field-aligned shielding currents during geomagnetically disturbed conditions. Penetration electric fields con- trol, to a large extent, the generation and development of equatorial spread-F plasma instabilities as well as other dynamic space weather phenomena in the ionosphere equatorward of the auroral zone. While modeling studies typically agree with average patterns of prompt penetration fields, experimental results suggest that longitudinal variations of the ionospheric con- ductivities play a non-negligible role in controlling spread-F phenomena, an effect that has not previously been modeled. We present first results of modeling prompt pene- tration electric fields using a version of the Rice Convection Model (RCM) that allows for longitudinal variations in the ionospheric conductance tensor. The RCM is a first- principles numerical ionosphere-magnetosphere coupling model that solves for the electric fields, field-aligned currents, and particle distributions in the ionosphere and inner/middle magnetosphere. We compare these new theoretical results with electric field observations.

Chern structure in the Bose-insulating phase of Sr2RuO4 nanofilms

NASA Astrophysics Data System (ADS)

Nobukane, Hiroyoshi; Matsuyama, Toyoki; Tanda, Satoshi

2017-01-01

The quantum anomaly that breaks the symmetry, for example the parity and the chirality, in the quantization leads to a physical quantity with a topological Chern invariant. We report the observation of a Chern structure in the Bose-insulating phase of Sr2RuO4 nanofilms by employing electric transport. We observed the superconductor-to-insulator transition by reducing the thickness of Sr2RuO4 single crystals. The appearance of a gap structure in the insulating phase implies local superconductivity. Fractional quantized conductance was observed without an external magnetic field. We found an anomalous induced voltage with temperature and thickness dependence, and the induced voltage exhibited switching behavior when we applied a magnetic field. We suggest that there was fractional magnetic-field-induced electric polarization in the interlayer. These anomalous results are related to topological invariance. The fractional axion angle Θ = π/6 was determined by observing the topological magneto-electric effect in the Bose-insulating phase of Sr2RuO4 nanofilms.

Enhancement of electrical conductivity by changing phase morphology for composites consisting of polylactide and poly(ε-caprolactone) filled with acid-oxidized multiwalled carbon nanotubes.

PubMed

Xu, Zhaohua; Zhang, Yaqiong; Wang, Zhigang; Sun, Ning; Li, Heng

2011-12-01

Composites consisting of polylactide (PLA) and poly(ε-caprolactone) (PCL) filled with acid-oxidized multiwalled carbon nanotubes (A-MWCNTs) were prepared through melt compounding. Phase morphologies of PLA/PCL/A-MWCNT composites with different contents of filled A-MWCNTs and PCL compositions were mainly observed by scanning electron microscope. The results show that A-MWCNTs are selectively dispersed in the PCL phase, regardingless of PCL phase domain sizes. For PLA/PCL/A-MWCNT composites with fixed PLA/PCL ratio of 95/5, the dispersed PCL phase domain sizes in the PLA matrix decrease even though a small content of A-MWCNTs is added, compared with PLA/PCL blend with the same composition, indicating that A-MWCNTs effectively prevent from coalescence of the dispersed PCL phase domains. With filling of 1.0 wt % A-MWCNTs, an interesting change of electrical conductivity for PLA/PCL/A-MWCNT composites is observed, in which the maximum conductivity is observed for PLA/PCL/A-MWCNT composite with PLA/PCL ratio of 60/40. The result is well-explained by the formed cocontinuous phase morphology and effective A-MWCNT content. © 2011 American Chemical Society

Electrical conductivity modeling in fractal non-saturated porous media

NASA Astrophysics Data System (ADS)

Wei, W.; Cai, J.; Hu, X.; Han, Q.

2016-12-01

The variety of electrical conductivity in non-saturated conditions is important to study electric conduction in natural sedimentary rocks. The electrical conductivity in completely saturated porous media is a porosity-function representing the complex connected behavior of single conducting phases (pore fluid). For partially saturated conditions, the electrical conductivity becomes even more complicated since the connectedness of pore. Archie's second law is an empirical electrical conductivity-porosity and -saturation model that has been used to predict the formation factor of non-saturated porous rock. However, the physical interpretation of its parameters, e.g., the cementation exponent m and the saturation exponent n, remains questionable. On basis of our previous work, we combine the pore-solid fractal (PSF) model to build an electrical conductivity model in non-saturated porous media. Our theoretical porosity- and saturation-dependent models contain endmember properties, such as fluid electrical conductivities, pore fractal dimension and tortuosity fractal dimension (representing the complex degree of electrical flowing path). We find the presented model with non-saturation-dependent electrical conductivity datasets indicate excellent match between theory and experiments. This means the value of pore fractal dimension and tortuosity fractal dimension change from medium to medium and depends not only on geometrical properties of pore structure but also characteristics of electrical current flowing in the non-saturated porous media.

Electrical and optical transport properties of single layer WSe2

NASA Astrophysics Data System (ADS)

Tahir, M.

2018-03-01

The electronic properties of single layer WSe2 are distinct from the famous graphene due to strong spin orbit coupling, a huge band gap and an anisotropic lifting of the degeneracy of the valley degree of freedom under Zeeman field. In this work, band structure of the monolayer WSe2 is evaluated in the presence of spin and valley Zeeman fields to study the electrical and optical transport properties. Using Kubo formalism, an explicit expression for the electrical Hall conductivity is examined at finite temperatures. The electrical longitudinal conductivity is also evaluated. Further, the longitudinal and Hall optical conductivities are analyzed. It is observed that the contributions of the spin-up and spin-down states to the power absorption spectrum depend on the valley index. The numerical results exhibit absorption peaks as a function of photon energy, ℏ ω, in the range ∼ 1.5 -2 eV. Also, the optical response lies in the visible frequency range in contrast to the conventional two-dimensional electron gas or graphene where the response is limited to terahertz regime. This ability to isolate carriers in spin-valley coupled structures may make WSe2 a promising candidate for future spintronics, valleytronics and optical devices.

FAST TRACK COMMUNICATION: Mechanical, electrical and micro-structural properties of La0.6Sr0.4Co0.2Fe0.8O3 perovskite-based ceramic foams

NASA Astrophysics Data System (ADS)

Gupta, Ravindra K.; Kim, Eun Yi; Noh, Ho Sung; Whang, Chin Myung

2008-02-01

Mechanical, electrical and micro-structural properties of new electronic conducting ceramic foams are reported. Ceramic foams are prepared using the slurry of La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) by the polymeric sponge method, which is followed by spray coating for increasing the number of coatings-sinterings on polyurethane foams of 30, 45 and 60 ppi (pores per linear inch). An increase in the number of coatings-sinterings and ppi improved the compressive strength, density and electrical conductivity by decreasing the porosity to ~76%, as also observed by the SEM study. The three-times coated-sintered ceramic foams (60 ppi) exhibited optimum values of compressive strength of ~1.79 MPa and relative density of ~0.24 at 25 °C and electrical conductivity of ~22 S cm-1 at 600 °C with an activation energy of ~0.22 eV indicating its suitability as a solid oxide fuel cell current collector. The experimental results are discussed in terms of the Gibson and Ashby theoretical model.

Synthesis and Characterization of Molybdenum Doped ZnO Thin Films by SILAR Deposition Method

NASA Astrophysics Data System (ADS)

Radha, R.; Sakthivelu, A.; Pradhabhan, D.

2016-08-01

Molybdenum (Mo) doped zinc oxide (ZnO) thin films were deposited on the glass substrate by Successive Ionic Layer Adsorption and Reaction (SILAR) deposition method. The effect of Mo dopant concentration of 5, 6.6 and 10 mol% on the structural, morphological, optical and electrical properties of n-type Mo doped ZnO films was studied. The X-ray diffraction (XRD) results confirmed that the Mo doped ZnO thin films were polycrystalline with wurtzite structure. The field emission scanning electron microscopy (FESEM) studies shows that the surface morphology of the films changes with Mo doping. A blue shift of the optical band gap was observed in the optical studies. Effect of Mo dopant concentration on electrical conductivity was studied and it shows comparatively high electrical conductivity at 10 mol% of Mo doping concentration.

Electrical study on Carboxymethyl Cellulose-Polyvinyl alcohol based bio-polymer blend electrolytes

NASA Astrophysics Data System (ADS)

Saadiah, M. A.; Samsudin, A. S.

2018-04-01

The present work deals with the formulation of bio-materials namely carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA) for bio-polymer blend electrolytes (BBEs) system which was successfully carried out with different ratio of polymer blend. The biopolymer blend was prepared via economical & classical technique that is solution casting technique and was characterized by using impedance spectroscopy (EIS). The ionic conductivity was achieved to optimum value 9.12 x 10-6 S/cm at room temperature for sample containing ratio 80:20 of CMC:PVA. The highest conducting sample was found to obey the Arrhenius behaviour with a function of temperature. The electrical properties were analyzed using complex permittivity ε* and complex electrical modulus M* for BBEs system and it shows the non-Debye characteristics where no single relaxation time has observed.

Joule heating effects on particle immobilization in insulator-based dielectrophoretic devices

PubMed Central

Gallo-Villanueva, Roberto C.; Sano, Michael B.; Lapizco-Encinas, Blanca H.; Davalos, Rafael V.

2014-01-01

In this work, the temperature effects due to Joule heating obtained by application of a DC electric potential were investigated for a microchannel with cylindrical insulating posts employed for insulator based dielectrophoresis (iDEP). The conductivity of the suspending medium, the local electric field, and the gradient of the squared electric field, which directly affect the magnitude of the dielectrophoretic force exerted on particles, were computationally simulated employing COMSOL Multiphysics. It was observed that a temperature gradient is formed along the microchannel which redistributes the conductivity of the suspending medium leading to an increase of the dielectrophoretic force towards the inlet of the channel while decreasing towards the outlet. Experimental results are in good agreement with simulations on the particle trapping zones anticipated. This study demonstrates the importance of considering Joule heating effects when designing iDEP systems. PMID:24002905

Direct Observation of Surface Potential Distribution in Insulation Resistance Degraded Acceptor-Doped BaTiO3 Multilayered Ceramic Capacitors

NASA Astrophysics Data System (ADS)

Hong, Kootak; Lee, Tae Hyung; Suh, Jun Min; Park, Jae-Sung; Kwon, Hyung-Soon; Choi, Jaeho; Jang, Ho Won

2018-05-01

Insulation resistance (IR) degradation in BaTiO3 is a key issue for developing miniaturized multilayer ceramic capacitors (MLCCs) with high capacity. Despite rapid progress in BaTiO3-based MLCCs, the mechanism of IR degradation is still controversial. In this study, we demonstrate the Al doping effect on IR degradation behavior of BaTiO3 MLCCs by electrical measurements and scanning Kelvin probe microscopy (SKPM). As the Al doping concentration in BaTiO3 increases, IR degradation of MLCCs seems to be suppressed from electrical characterization results. However, SKPM results reveal that the conductive regions near the cathode become lager with Al doping after IR degradation. The formation of conducting regions is attributed to the migration of oxygen vacancies, which is the origin of IR degradation in BaTiO3, in dielectric layers. These results imply that acceptor doping in BaTiO3 solely cannot suppress the IR degradation in MLCC even though less asymmetric IR characteristics and IR degradation in MLCCs with higher Al doping concentration are observed from electrical characterization. Our results strongly suggest that observing the surface potential distribution in IR degraded dielectric layers using SKPM is an effective method to unravel the mechanism of IR degradation in MLCCs.

Study of dielectric relaxation and AC conductivity of InP:S single crystal

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Ali, H. A. M.; El-Shazly, E. A.

2012-07-01

The dielectric relaxation and AC conductivity of InP:S single crystal were studied in the frequency range from 100 to 5.25 × 105 Hz and in the temperature range from 296 to 455 K. The dependence of the dielectric constant (ɛ1) and the dielectric loss (ɛ2) on both frequency and temperature was investigated. Since no peak was observed on the dielectric loss, we used a method based on the electric modulus to evaluate the activation energy of the dielectric relaxation. Scaling of the electric modulus spectra showed that the charge transport dynamics is independent of temperature. The AC conductivity (σAC) was found to obey the power law: Aωs. Analysis of the AC conductivity data and the frequency exponent showed that the correlated barrier hopping (CBH) model is the dominant mechanism for the AC conduction. The variation of AC conductivity with temperature at different frequencies showed that σAC is a thermally activated process.

Hopping conduction in zirconium oxynitrides thin film deposited by reactive magnetron sputtering

NASA Astrophysics Data System (ADS)

Guo, Jie; Zhan, Guanghui; Liu, Jingquan; Yang, Bin; Xu, Bin; Feng, Jie; Chen, Xiang; Yang, Chunsheng

2015-10-01

Zirconium oxynitrides thin film thermometers were demonstrated to be useful temperature sensors. However, the basic conduction mechanism of zirconium oxynitrides films has been a long-standing issue, which hinders the prediction and optimization of their ultimate performance. In this letter, zirconium oxynitrides films were grown on sapphire substrates by magnetron sputtering and their electric transport mechanism has been systemically investigated. It was found that in high temperatures region (>150 K) the electrical conductivity was dominated by thermal activation for all samples. In the low temperatures range, while Mott variable hopping conduction (VRH) was dominated the transport for films with relatively low resistance, a crossover from Mott VRH conduction to Efros-Shklovskii (ES) VRH was observed for films with relatively high resistance. This low temperature crossover from Mott to ES VRH indicates the presence of a Coulomb gap (~7 meV). These results demonstrate the competing and tunable conduction mechanism in zirconium oxynitrides thin films, which would be helpful for optimizing the performance of zirconium oxynitrides thermometer.

ALTUS Cumulus Electrification Study (ACES)

NASA Technical Reports Server (NTRS)

Kim, Tony; Blakeslee, Richard; Russell, Larry W. (Technical Monitor)

2002-01-01

The ALTUS Cumulus Electrification Study (ACES) is an uninhabited aerial vehicle (UAV)-based project that will investigate thunderstorms in the vicinity of the Florida Everglades in August 2002. ACES is being conducted to both investigate storm electrical activity and its relationship to storm morphology, and validate Tropical Rainfall Measurement Mission (TRMM) satellite measurements. In addition, as part of NASA's UAV-based science demonstration program, this project will provide a scientifically useful demonstration of the utility and promise of UAV platforms for Earth science and applications observations. Part of the demonstration involves getting approvals from the Federal Aviation Administration and the NASA airworthiness flight safety review board. ACES will employ the ALTUS II aircraft, built by General Atomics - Aeronautical Systems, Inc. Key science objectives simultaneously addressed by ACES are to: (1) investigate lightning-storm relationships, (2) study storm electrical budgets, and (3) provide Lightning Imaging Sensor validation. The ACES payload, already developed and flown on ALTUS, includes electrical, magnetic, and optical sensors to remotely characterize the lightning activity and the electrical environment within and around thunderstorms. ACES will contribute important electrical and optical measurements not available from other sources. Also, the high altitude vantage point of the UAV observing platform (up to 55,000 feet) offers a useful 'cloud-top' perspective. By taking advantage of its slow flight speed (70 to 100 knots), long endurance, and high altitude flight, the ALTUS will be flown near, and when possible, above (but never into) thunderstorms for long periods of time, allowing investigations to be conducted over entire storm life cycles. In addition, concurrent ground-based observations will enable the UAV measurements to be more completely interpreted and evaluated in the context of the thunderstorm structure, evolution, and environment.

Analytical solution of electromagnetic radiation by a vertical electric dipole inside the earth and the effect of atmospheric electrical conductivity inhomogeneity

NASA Astrophysics Data System (ADS)

Mosayebidorcheh, Taha; Hosseinibalam, Fahimeh; Hassanzadeh, Smaeyl

2017-11-01

In this paper, the effect of atmospheric electrical conductivity on the electromagnetic waves radiated by a vertical electric dipole located in the earth, near the surface of the earth, is investigated. As far as electrical conductivity is concerned, the atmosphere is divided into three areas, in which the electrical conductivity changes with altitude. The Maxwell equations in these areas are investigated as well. Using the differential transform method, the differential equation is solved in a way that atmospheric electrical conductivity is variable. Solving the problem in these areas indicates that electrical conductivity in the middle and lower areas of atmosphere may be ignored. However, in the upper areas of atmosphere, the magnitude of the magnetic field in the ionosphere at a frequency of 10 kHz at night is five times smaller when electrical conductivity is considered compared to when it is neglected.

Electric double-layer capacitors based on highly graphitized nanoporous carbons derived from ZIF-67.

PubMed

Torad, Nagy L; Salunkhe, Rahul R; Li, Yunqi; Hamoudi, Hicham; Imura, Masataka; Sakka, Yoshio; Hu, Chi-Chang; Yamauchi, Yusuke

2014-06-23

Nanoporous carbons (NPCs) have large specific surface areas, good electrical and thermal conductivity, and both chemical and mechanical stability, which facilitate their use in energy storage device applications. In the present study, highly graphitized NPCs are synthesized by one-step direct carbonization of cobalt-containing zeolitic imidazolate framework-67 (ZIF-67). After chemical etching, the deposited Co content can be completely removed to prepare pure NPCs with high specific surface area, large pore volume, and intrinsic electrical conductivity (high content of sp(2) -bonded carbons). A detailed electrochemical study is performed using cyclic voltammetry and galvanostatic charge-discharge measurements. Our NPC is very promising for efficient electrodes for high-performance supercapacitor applications. A maximum specific capacitance of 238 F g(-1) is observed at a scan rate of 20 mV s(-1) . This value is very high compared to previous works on carbon-based electric double layer capacitors. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Piezoelectric effect on the thermal conductivity of monolayer gallium nitride

NASA Astrophysics Data System (ADS)

Zhang, Jin

2018-01-01

Using molecular dynamics and density functional theory simulations, in this work, we find that the heat transport property of the monolayer gallium nitride (GaN) can be efficiently tailored by external electric field due to its unique piezoelectric characteristic. As the monolayer GaN possesses different piezoelectric properties in armchair and zigzag directions, different effects of the external electric field on thermal conductivity are observed when it is applied in the armchair and zigzag directions. Our further study reveals that due to the elastoelectric effect in the monolayer GaN, the external electric field changes the Young's modulus and therefore changes the phonon group velocity. Also, due to the inverse piezoelectric effect, the applied electric field induces in-plane stress in the monolayer GaN subject to a length constraint, which results in the change in the lattice anharmonicity and therefore affects the phonon mean free path. Furthermore, for relatively long GaN monolayers, the in-plane stress may trigger the buckling instability, which can significantly reduce the phonon mean free path.

The electrical and dielectric properties of the Au/Ti/HfO2/n-GaAs structures

NASA Astrophysics Data System (ADS)

Karabulut, Abdulkerim; Türüt, Abdulmecit; Karataş, Şükrü

2018-04-01

In this work, temperature dependent electrical and dielectric properties of the Au/Ti/HfO2/n-GaAs structures were investigated using capacitance-voltage (C-V) and conductance-voltage (G-V) measurements in the temperature range of 60-320 K by steps of 20 K at 1 MHz. The dielectric constant (ε‧), dielectric loss (ε″), dielectric loss tangent (tanδ) and ac electrical conductivities (σac) have been calculated as a function of temperature. These values of the ε‧, ε″, tanδ and σac have been found to be 2.272, 5.981, 2.631 and 3.32 × 10-6 (Ω-1cm-1) at 80 K, respectively, 1.779, 2.315, 1.301 and 1.28 × 10-6 (Ω-1cm-1), respectively at 320 K. These decrease of the dielectric parameters (ε‧, ε″, tanδ and σac) have been observed at high temperatures. The experimental results show that electrical and dielectric properties are strongly temperature and bias voltage dependent.

Conduction at domain walls in insulating Pb(Zr0.2 Ti0.8)O3 thin films.

PubMed

Guyonnet, Jill; Gaponenko, Iaroslav; Gariglio, Stefano; Paruch, Patrycja

2011-12-01

Domain wall conduction in insulating Pb(Zr(0.2) Ti(0.8))O(3) thin films is demonstrated. The observed electrical conduction currents can be clearly differentiated from displacement currents associated with ferroelectric polarization switching. The domain wall conduction, nonlinear and highly asymmetric due to the specific local probe measurement geometry, shows thermal activation at high temperatures, and high stability over time. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Supercritical fluid in the mantle transition zone deduced from H-D interdiffusion of wadsleyite

NASA Astrophysics Data System (ADS)

Sun, Wei; Yoshino, Takashi; Sakamoto, Naoya; Yurimoto, Hisayoshi

2018-02-01

Knowledge of the distribution of water in the Earth's mantle is key to understanding the mantle convection and geochemical evolution of the Earth. As wadsleyite and ringwoodite can incorporate large amounts of water in their crystal structures, proton conduction has been invoked to account for the widespread conductive anomalies observed in the mantle wedge, where descending slab stagnates at the transition zone. However, there is a lot of controversy on whether proton conduction by itself is able to explain such anomalies, because of large discrepancy in the extent of the water effect deduced from previous electrical conductivity measurements on hydrous polycrystalline wadsleyite and ringwoodite. Here we report the hydrogen self-diffusion coefficient obtained from H-D interdiffusion experiments in wadsleyite single-crystal couples. Our results demonstrate that the effect of water on the electrical conductivity of wadsleyite is limited and hydrous wadsleyite by itself is unable to explain conductive anomalies in the transition zone. In contrast, the expected hydrogen effective diffusion does not allow the wide propagation of water between the stagnant slab and surrounding mantle, probably leading to persistence of local water saturation and continuous release of supercritical fluids at the stagnant slab roof on geological time scales. This phenomenon provides an alternative explanation for both the high-conductivity and seismic-velocity anomalies observed in the mantle wedge at the transition-zone depth.

Geophysical constraints on contaminant transport modeling in a heterogeneous fluvial aquifer.

PubMed

Bowling, Jerry C; Zheng, Chunmiao; Rodriguez, Antonio B; Harry, Dennis L

2006-05-05

Approximately 3000 measurements of hydraulic conductivity in over 50 flowmeter boreholes were available at the Macro-Dispersion Experiment (MADE) site in Columbus, Mississippi, USA to quantify the heterogeneity in hydraulic conductivity at the site scale. This high-density measurement approach is perhaps infeasible for time and expense in typical groundwater remediation sites. A natural-gradient tracer experiment from the MADE site was simulated by a groundwater flow and solute transport model incorporating direct-current (DC) resistivity data collected over the observed plume location. Hydraulic conductivity from one borehole collected during the original site characterization was used to calibrate the electrical resistivity data to hydraulic conductivity using a previously derived log-log relationship. Application of this relationship, using site-specific empirical constants determined from the data, transforms the 3D electrical resistivity data into a 3D description of hydraulic conductivity that can be used in groundwater models. The validity of this approach was tested by using the geophysically derived hydraulic conductivity representation in numerical simulations of the natural-gradient tracer experiment. The agreement between the simulated and observed tracer plumes was quantified to gauge the effectiveness of geophysically derived and flowmeter based representations of the hydraulic conductivity field. This study demonstrates that a highly heterogeneous aquifer can be modeled with minimal hydrological data supplemented with geophysical data at least as well as previous models of the site using purely hydrologic data.

Investigations of conjugate MSTIDS over the Brazilian sector during daytime

NASA Astrophysics Data System (ADS)

Jonah, O. F.; Kherani, E. A.; De Paula, E. R.

2017-09-01

This study focuses on the daytime medium-scale traveling ionospheric disturbances (MSTIDs) observed at conjugate hemispheres. It is the first time that the geomagnetical conjugate daytime MSTIDs are observed over the South America sector. To observe the MSTID characteristics, we used detrended total electron content (TEC) derived from Global Navigation Satellite Systems receivers located at Brazilian sector covering the Northern and Southern Hemispheres along the same magnetic meridian. The geographic grid of 1°N to 14°S in latitude and 60°S to 50°S in longitude was selected for this study. The cross-correlation method between two latitudes and longitudes in time was used to observe the propagation of the MSTID waves. The following features are noted: (a) MSTIDs are well developed at both hemispheres; (b) the peak MSTIDs amplitudes vary from one hemisphere to another; hence, we suppose that MSTIDs generated in Southern Hemisphere or Northern Hemisphere mirrored in the conjugate hemisphere; (c) the gravity wave-induced electric fields from one hemisphere map along the field lines and generate the mirrored MSTIDs in the conjugate region. To investigate the hemispheric mapping mechanism, a rough approximation for the integrated field line conductivity ratio of E and F regions is calculated using digisonde E and F region parameters. We noted that during the period of mapping the decrease in E region conductivity results in an increase in total conductivity. This shows that the E region was partially short circuited; hence, electric field generated at F region could map to the conjugate hemisphere during daytime: daytime MSTIDs at conjugate regions; mechanisms responsible for daytime electrified MSTIDs; gravity wave-induced electric field role in daytime MSTIDs.

Improvement and evaluation of thermal, electrical, sealing and mechanical contacts, and their interface materials

NASA Astrophysics Data System (ADS)

Luo, Xiangcheng

Material contacts, including thermal, electrical, seating (fluid sealing and electromagnetic sealing) and mechanical (pressure) contacts, together with their interface materials, were, evaluated, and in some cases, improved beyond the state of the art. The evaluation involved the use of thermal, electrical and mechanical methods. For thermal contacts, this work evaluated and improved the heat transfer efficiency between two contacting components by developing various thermal interface pastes. Sodium silicate based thermal pastes (with boron nitride particles as the thermally conductive filler) as well as polyethylene glycol (PEG) based thermal pastes were developed and evaluated. The optimum volume fractions of BN in sodium silicate based pastes and PEG based pastes were 16% and 18% respectively. The contribution of Li+ ions to the thermal contact conductance in the PEG-based paste was confirmed. For electrical contacts, the relationship between the mechanical reliability and electrical reliability of solder/copper and silver-epoxy/copper joints was addressed. Mechanical pull-out testing was conducted on solder/copper and silver-epoxy/copper joints, while the contact electrical resistivity was measured. Cleansing of the copper surface was more effective for the reliability of silver-epoxy/copper joint than that of solder/copper joint. For sealing contacts, this work evaluated flexible graphite as an electromagnetic shielding gasket material. Flexible graphite was found to be at least comparable to conductive filled silicone (the state of the art) in terms of the shielding effectiveness. The conformability of flexible graphite with its mating metal surface under repeated compression was characterized by monitoring the contact electrical resistance, as the conformability is important to both electromagnetic scaling and fluid waling using flexible graphite. For mechanical contacts, this work focused on the correlation of the interface structure (such as elastic/plastic deformation, oxidation, strain hardening, passive layer damage, fracture, etc.) with the electrical contact resistance, which was measured in real time for contacts under dynamic compression, thus allowing both reversible and irreversible changes to be observed. The materials studied included metals (carbon steel, stainless steel, aluminum and copper), carbon fiber reinforced polymer-matrix composite (nylon-6), ceramic (mortar) and graphite, due to their relevance to fastening, concrete structures, electric brushes and electrical pressure contacts.

High conductance surge cable

DOEpatents

Murray, Matthew M.; Wilfong, Dennis H.; Lomax, Ralph E.

1998-01-01

An electrical cable for connecting transient voltage surge suppressers to ectrical power panels. A strip of electrically conductive foil defines a longitudinal axis, with a length of an electrical conductor electrically attached to the metallic foil along the longitudinal axis. The strip of electrically conductive foil and the length of an electrical conductor are covered by an insulating material. For impedance matching purposes, triangular sections can be removed from the ends of the electrically conductive foil at the time of installation.

Surfactant free graphene nanosheets based nanofluids by in-situ reduction of alkaline graphite oxide suspensions

NASA Astrophysics Data System (ADS)

Jyothirmayee Aravind, S. S.; Ramaprabhu, S.

2011-12-01

Herein we report an entirely different route for the synthesis of graphene nanosheets (GNs) based nanofluids without surfactant or harsh chemical treatments, by reducing the alkaline graphite oxide suspension in ethylene glycol (EG) and de-ionized (DI) water based fluids by a simple thermal treatment. The thermal conductivity measurement after the reduction shows about 6.5 and 13.6% enhancements at 25 °C for the 0.14% volume fraction of GN in EG and DI water, respectively, which is ascribed to the high aspect ratio of the GNs. In addition, a large enhancement in the electrical conductivity of EG and DI water based reduced nanofluids is observed. This interesting result is attributed to the high electrical conductivity of reduced graphene nanosheets suspensions.

Electrical conductivity enhancement in heterogeneously doped scandia-stabilized zirconia

NASA Astrophysics Data System (ADS)

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

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

Apparatus for Use in Determining Surface Conductivity at Microwave Frequencies

NASA Technical Reports Server (NTRS)

Hearn, Chase P. (Inventor)

1995-01-01

An apparatus is provided for use in determining surface conductivity of a flat or shaped conductive material at microwave frequencies. A plate has an electrically conductive surface with first and second holes passing through the plate. An electrically conductive material under test (MUT) is maintained in a spaced apart relationship with the electrically conductive surface of the plate by one or more nonconductive spacers. A first coupling loop is electrically shielded within the first hole while a second coupling loop is electrically shielded within the second hole. A dielectric resonator element is positioned between the first and second coupling loops, while also being positioned closer to the MUT than the electrically conductive surface of the plate. Microwave energy at an operating frequency f is supplied from a signal source to the first coupling loop while microwave energy received at the second coupling loop is measured. The apparatus is capable of measuring the Q-factor of the dielectric resonator situated in the 'cavity' existing between the electrically conductive surface of the plate and the MUT. Surface conductivity of the electrically conductive surface can be determined via interpolation using: 1 ) the measured Q-factor with the electrically conductive surface in place, and 2) the measured Q-factor when the MUT is replaced with reference standards having known surface conductivities.

Increasing strength and conductivity of Cu alloy through abnormal plastic deformation of an intermetallic compound

PubMed Central

Han, Seung Zeon; Lim, Sung Hwan; Kim, Sangshik; Lee, Jehyun; Goto, Masahiro; Kim, Hyung Giun; Han, Byungchan; Kim, Kwang Ho

2016-01-01

The precipitation strengthening of Cu alloys inevitably accompanies lowering of their electric conductivity and ductility. We produced bulk Cu alloys arrayed with nanofibers of stiff intermetallic compound through a precipitation mechanism using conventional casting and heat treatment processes. We then successfully elongated these arrays of nanofibers in the bulk Cu alloys to 400% of original length without breakage at room temperature using conventional rolling process. By inducing such an one-directional array of nanofibers of intermetallic compound from the uniform distribution of fine precipitates in the bulk Cu alloys, the trade-off between strength and conductivity and between strength and ductility could be significantly reduced. We observed a simultaneous increase in electrical conductivity by 1.3 times and also tensile strength by 1.3 times in this Cu alloy bulk compared to the conventional Cu alloys. PMID:27488621

Electric-field-driven phase transition in vanadium dioxide

NASA Astrophysics Data System (ADS)

Wu, B.; Zimmers, A.; Aubin, H.; Ghosh, R.; Liu, Y.; Lopez, R.

2011-12-01

We report on local probe measurements of current-voltage and electrostatic force-voltage characteristics of electric-field-induced insulator to metal transition in VO2 thin film. In conducting AFM mode, switching from the insulating to metallic state occurs for electric-field threshold E˜6.5×107Vm-1 at 300K. Upon lifting the tip above the sample surface, we find that the transition can also be observed through a change in electrostatic force and in tunneling current. In this noncontact regime, the transition is characterized by random telegraphic noise. These results show that electric field alone is sufficient to induce the transition; however, the electronic current provides a positive feedback effect that amplifies the phenomena.

Conductive network formation of carbon nanotubes in elastic polymer microfibers and its effect on the electrical conductance: Experiment and simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cho, Hyun Woo; Kim, Jeongmin; Sung, Bong June, E-mail: jjpark@chonnam.ac.kr, E-mail: bjsung@sogang.ac.kr

We investigate how the electrical conductance of microfibers (made of polymers and conductive nanofillers) decreases upon uniaxial deformation by performing both experiments and simulations. Even though various elastic conductors have been developed due to promising applications for deformable electronic devices, the mechanism at a molecular level for electrical conductance change has remained elusive. Previous studies proposed that the decrease in electrical conductance would result from changes in either distances or contact numbers between conductive fillers. In this work, we prepare microfibers of single walled carbon nanotubes (SWCNTs)/polyvinyl alcohol composites and investigate the electrical conductance and the orientation of SWCNTs uponmore » uniaxial deformation. We also perform extensive Monte Carlo simulations, which reproduce experimental results for the relative decrease in conductance and the SWCNTs orientation. We investigate the electrical networks of SWCNTs in microfibers and find that the decrease in the electrical conductance upon uniaxial deformation should be attributed to a subtle change in the topological structure of the electrical network.« less

Grain size effect on activation energy in spinel CoFe{sub 2}O{sub 4} ceramic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Supriya, Sweety, E-mail: sweety@iitp.ac.in; Kumar, Sunil; Kar, Manoranjan

2016-05-23

Cobalt ferrite of different average crystallites (from nanocrystallite to micro crystallites) has been prepared by the Sol-Gel Method. The X-ray diffraction (XRD) analysis confirms the cubic spinel phase with no trace of impurity phases. The effect of annealing temperature on micro structure and electric transport properties as a function of frequency and temperature has been studied. It is observed that the electric impedance and conductivity are strongly dependent on grain size. The impedance spectroscopic study is employed to understand the electrical transport properties of cobalt ferrite.

The advantages of the high voltage solar array for electric propulsion

NASA Technical Reports Server (NTRS)

Sater, B. L.

1973-01-01

The high voltage solar array (HVSA) offers improvements in efficiency, weight, and reliability for the electric propulsion power system. The basic HVSA technology involves designing the solar array to deliver power in the form required by the ion thruster. This paper delves into conventional power processes and problems associated with ion thruster operation using SERT II experience for examples. In this light, the advantages of the HVSA concept for electric propulsion are presented. Tests conducted operating the SERT II thruster system in conjunction with HVSA are discussed. Thruster operation was observed to be normal and in some respects improved.

Electrohydrodynamic fibrillation governed enhanced thermal transport in dielectric colloids under a field stimulus.

PubMed

Dhar, Purbarun; Maganti, Lakshmi Sirisha; Harikrishnan, A R

2018-05-30

Electrorheological (ER) fluids are known to exhibit enhanced viscous effects under an electric field stimulus. The present article reports the hitherto unreported phenomenon of greatly enhanced thermal conductivity in such electro-active colloidal dispersions in the presence of an externally applied electric field. Typical ER fluids are synthesized employing dielectric fluids and nanoparticles and experiments are performed employing an in-house designed setup. Greatly augmented thermal conductivity under a field's influence was observed. Enhanced thermal conduction along the fibril structures under the field effect is theorized as the crux of the mechanism. The formation of fibril structures has also been experimentally verified employing microscopy. Based on classical models for ER fluids, a mathematical formalism has been developed to predict the propensity of chain formation and statistically feasible chain dynamics at given Mason numbers. Further, a thermal resistance network model is employed to computationally predict the enhanced thermal conduction across the fibrillary colloid microstructure. Good agreement between the mathematical model and the experimental observations is achieved. The domineering role of thermal conductivity over relative permittivity has been shown by proposing a modified Hashin-Shtrikman (HS) formalism. The findings have implications towards better physical understanding and design of ER fluids from both 'smart' viscoelastic as well as thermally active materials points of view.

Power module assembly

DOEpatents

Campbell, Jeremy B [Torrance, CA; Newson, Steve [Redondo Beach, CA

2011-11-15

A power module assembly of the type suitable for deployment in a vehicular power inverter, wherein the power inverter has a grounded chassis, is provided. The power module assembly comprises a conductive base layer electrically coupled to the chassis, an insulating layer disposed on the conductive base layer, a first conductive node disposed on the insulating layer, a second conductive node disposed on the insulating layer, wherein the first and second conductive nodes are electrically isolated from each other. The power module assembly also comprises a first capacitor having a first electrode electrically connected to the conductive base layer, and a second electrode electrically connected to the first conductive node, and further comprises a second capacitor having a first electrode electrically connected to the conductive base layer, and a second electrode electrically connected to the second conductive node.

Synthesis, thermal and electrical properties of Al-doped Bi{sub 4}V{sub 1.8}Cu{sub 0.2}O{sub 10.7}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Essalim, R.; Ammar, A.; Tanouti, B.

2016-08-15

Partial substitution of copper with aluminum in Bi{sub 4}V{sub 1.8}Cu{sub 0.2}O{sub 10.7} has led to the Bi{sub 4}V{sub 1.8}Cu{sub 0.2−x}Al{sub x}O{sub 10.7+x/2} solid solution. X-ray diffraction and thermal analysis have shown that the compounds with x=0.05 and x=0.10 are tetragonal with γ′ form of Bi{sub 4}V{sub 2}O{sub 11}, while the compound with x=0.15 is of β polymorph. The effect of Al{sup 3+} doping on electrical conductivity has been studied using Electrochemical Impedance Spectroscopy. The electrical conductivity of doped samples along with the amount of Al{sup 3+} has been studied by electrochemical impedance spectroscopy in the temperature range 250–700 °C. Themore » slope changes observed in the Arrhenius plots agree with the microstructural transitions occurring in these compounds. The highest ionic conductivity values are obtained for the sample with x=0.05. - Graphical abstract: Arrhenius plots of the electrical conductivity of the of Bi{sub 4}V{sub 1.8}Cu{sub 0.2−x}Al{sub x}O{sub 10.7+x/2} compounds. Display Omitted.« less

Investigating the effects of microbial communities on electrical properties of soils: preliminary results from a pilot scale column experiment

NASA Astrophysics Data System (ADS)

Atekwana, E.; Atekwana, E.; Werkema, D.; Duris, J.; Rossbach, S.; Sauck, W.; Koretsky, C.; Cassidy, D.; Means, J.; Sherrod, L.

2003-04-01

In this study, we describe the results of a mesoscale pilot experiment designed to investigate the influence of biogeochemical processes on electrical conductivity of soils impacted by hydrocarbons. This is an interdisciplinary study integrating geophysics, geochemistry, and microbiology which was undertaken to: 1) verify microbial hydrocarbon degradation by monitoring changes in microbial types, population, and community structure, 2) document temporal changes in the electrical conductivity of soils, and 3) document changes in pore fluid geochemistry using major ions and stable carbon isotopes. We constructed duplicate soil columns as follows: Columns 1 and 2 had no bacteria, no diesel; columns 3 and 4 had diesel and no bacteria; columns 5 and 6 had bacteria and no diesel; and columns 7 and 8 had bacteria and diesel. Soil cores were sampled at 5 cm intervals and analyzed for bacteria using the most probable number (MPN) and the rDNA intergenic spacer region analyses (RISA) techniques. The MPN method showed an increase in the percentage of alkane degraders with time, and accounted for 1.2x (120%) the number of heterotrophic bacteria in colums 7 and 8 compared to less than 15% for the other columns. The RISA analysis of the communities in columns 7 and 8 showed a shift towards less diversity over time in response to the contaminant stress to a composition that is more capable of the utilization of an alkane as a carbon source. These results confirm microbial mineralization of diesel within contaminated columns. Electrical conductivity measurements were made using a Wenner array at 2 cm spacing. The electrical measurements show an initial decrease in conductivity. This is consistent with the diesel replacing the more conductive pore waters and changes in water saturation, especially within the unsaturated zone. However, a slow increase in conductivity was observed in column 7 overtime compared to the other columns. The slight increase in electrical conductivity for the contaminated column may be attributed to microbial degradation of hydrocarbon and secondary weathering of the soil minerals. However, the magnitude in the shift of the pore fluid chemistry does not appear to directly translate to changes in soil electrical conductivity. At present, since the experiment is still ongoing, we expect that as more degradation and mineral weathering occur in the soils columns, we should be able to model the magnitude of the pore fluid chemical change on the soil conductivity.

Electrically-conductive proppant and methods for making and using same

DOEpatents

Cannan, Chad; Roper, Todd; Savoy, Steve; Mitchell, Daniel R.

2016-09-06

Electrically-conductive sintered, substantially round and spherical particles and methods for producing such electrically-conductive sintered, substantially round and spherical particles from an alumina-containing raw material. Methods for using such electrically-conductive sintered, substantially round and spherical particles in hydraulic fracturing operations.

Gamma-Ray Light Curves from Pulsar Magnetospheres with Finite Conductivity

NASA Technical Reports Server (NTRS)

Harding, A. K.; Kalapotharakos, C.; Kazanas, D.; Contopoulos, I.

2012-01-01

The Fermi Large Area Telescope has provided an unprecedented database for pulsar emission studies that includes gamma-ray light curves for over 100 pulsars. Modeling these light curves can reveal and constrain the geometry of the particle accelerator, as well as the pulsar magnetic field structure. We have constructed 3D magnetosphere models with finite conductivity, that bridge the extreme vacuum and force-free solutions used in previous light curves modeling. We are investigating the shapes of pulsar gamma-ray light curves using these dissipative solutions with two different approaches: (l) assuming geometric emission patterns of the slot gap and outer gap, and (2) using the parallel electric field provided by the resistive models to compute the trajectories and . emission of the radiating particles. The light curves using geometric emission patterns show a systematic increase in gamma-ray peak phase with increasing conductivity, introducing a new diagnostic of these solutions. The light curves using the model electric fields are very sensitive to the conductivity but do not resemble the observed Fermi light curves, suggesting that some screening of the parallel electric field, by pair cascades not included in the models, is necessary

Measurements of Ozone, Lightning, and Electric Fields within Thunderstorms over Langmuir Laboratory, New Mexico

NASA Astrophysics Data System (ADS)

Eack, K. B.; Winn, W. P.; Rust, W. D.; Minschwaner, K.; Fredrickson, S.; Kennedy, D.; Edens, H. E.; Kalnajs, L. E.; Rabin, R. M.; Lu, G. P.; Bonin, D.

2008-12-01

A field project was conducted at the Langmuir Laboratory for Atmospheric Research during the summer of 2008 in an effort to better understand the direct production of ozone within electrically active storms. Five balloon flights were successfully launched into thunderstorms during this project. In situ measurements from the balloon instrument package included ozone mixing ratio, electric field strength, meteorological variables, and GPS location and timing. Lightning discharges were identified within each storm using a ground based lightning mapping array. The data show that the instruments ascended through regions of high electric fields within the sampled storms, and in some cases the balloon was in very close proximity to lightning. Relationships between electric field, lightning, and ozone observed during these flights will be discussed.

Significantly enhanced thermal conductivity of indium arsenide nanowires via sulfur passivation.

PubMed

Xiong, Yucheng; Tang, Hao; Wang, Xiaomeng; Zhao, Yang; Fu, Qiang; Yang, Juekuan; Xu, Dongyan

2017-10-16

In this work, we experimentally investigated the effect of sulfur passivation on thermal transport in indium arsenide (InAs) nanowires. Our measurement results show that thermal conductivity can be enhanced by a ratio up to 159% by sulfur passivation. Current-voltage (I-V) measurements were performed on both unpassivated and S-passivated InAs nanowires to understand the mechanism of thermal conductivity enhancement. We observed a remarkable improvement in electrical conductivity upon sulfur passivation and a significant contribution of electrons to thermal conductivity, which account for the enhanced thermal conductivity of the S-passivated InAs nanowires.

Electrical conductivity of the crust in central Baja California, México, based on magnetotelluric observations

NASA Astrophysics Data System (ADS)

Romo, J. M.; Gómez-Treviño, E.; Flores-Luna, C.; García-Abdeslem, J.

2017-12-01

Crustal and sub-crustal structure of northwestern Mexico (peninsular California) resulted from major accretion episodes occurred during the long-lived subduction of the Farallon plate beneath the North American plate, since late Jurassic time. A magnetotelluric profile across central Baja California reveals several electrical conductivity anomalies probably associated to the crustal boundaries of distinct Mezosoic terranes juxtaposed in the current peninsular crust. It is known that electrical conductivity is significantly increased by the pervasive presence of conductive minerals generated during metamorphic processes in highly sheared zones. We interpret a striking sub-horizontal conductivity anomaly reveled in the model as explained by the presence of high-salinity fluids released after dehydration of the subducted Magdalena microplate (Farallon plate?). The presence of fluids at the base of the peninsular crust may produce a zone of weakness, which supports the idea that Baja California lithosphere has not been entirely coupled to the Pacific plate. In addition, crustal thickness is estimated in our model in about 35 km beneath the western Peninsular Ranges batholith (PRB) and 20 km beneath the eastern PRB. This crustal thickness is in good agreement with independent estimations of a thinner crust in the Gulf of California margin and a thicker crust along the axial PRB.

Complex permeability and permittivity spectra of percolated Fe50Co50/Cu granular composites

NASA Astrophysics Data System (ADS)

Massango, Herieta; Tsutaoka, Takanori; Kasagi, Teruhiro; Yamamoto, Shinichiro; Hatakeyama, Kenichi

2017-11-01

Complex permeability and permittivity spectra of Fe50Co50/Cu hybrid granular composite materials have been studied in the RF to microwave frequency range. At low Cu particle content, the Fe50Co50/Cu hybrid sample shows a metallic percolative property with the electrical conductivity value about 0.1 S/cm. However, the low frequency plasmonic (LFP) state with negative permittivity (ENG) spectrum was not observed. An abrupt increase of electrical conductivity takes place at 14 to 16 vol% Cu content where the conductivity becomes above 1.0 S/cm; the Fe50Co50/Cu composite possesses the LFP state with negative permittivity spectrum below a characteristic frequency. The complex permittivity spectra in the LFP state can be described by the Drude model. Magnetic permeability spectrum in the LFP state showed a broad frequency dispersion above 10 MHz; a small negative permeability (MNG) dispersion was observed from 2 to 10 GHz. Consequently, the double negative (DNG) electromagnetic property with MNG and ENG was realized in the microwave range for the Cu content of 26 and 30 vol%.

Theoretical study of the criteria and consequences of hydrodynamic electron flow in graphene.

NASA Astrophysics Data System (ADS)

Adam, Shaffique; Ho, Derek; Yudhistira, Indra; Chakraborty, Nilotpal

Experiments on graphene electrons have succeeded in entering the hydrodynamic regime, as demonstrated by successful observations of Wiedemann-Franz law violations, and evidence for electron vortices. The hydrodynamic regime is expected to occur when electron-electron interactions dominate over all other electron collision mechanisms. We calculate the electron-electron, electron-impurity and electron-phonon scattering rates as a function of temperature, charge doping and disorder (charge puddle) strength. We find that there exists a window in parameter space where electron-electron scattering dominates and hydrodynamic effects become observable. However, we also find that disorder induced carrier density inhomogeneity continues to play an important role in the vicinity of charge neutrality, even in the strongly interacting hydrodynamic regime. For example, although the ratio of thermal conductivity and electrical conductivity show a violation of the Wiedemann-Franz law in the aforementioned experiment, the electrical conductivity as a function of temperature still follows a disorder-driven universal scaling theory first predicted in This work was supported by the National Research Foundation of Singapore (NRF-NRFF2012-01).

Optimizing amorphous indium zinc oxide film growth for low residual stress and high electrical conductivity

NASA Astrophysics Data System (ADS)

Kumar, Mukesh; Sigdel, A. K.; Gennett, T.; Berry, J. J.; Perkins, J. D.; Ginley, D. S.; Packard, C. E.

2013-10-01

With recent advances in flexible electronics, there is a growing need for transparent conductors with optimum conductivity tailored to the application and nearly zero residual stress to ensure mechanical reliability. Within amorphous transparent conducting oxide (TCO) systems, a variety of sputter growth parameters have been shown to separately impact film stress and optoelectronic properties due to the complex nature of the deposition process. We apply a statistical design of experiments (DOE) approach to identify growth parameter-material property relationships in amorphous indium zinc oxide (a-IZO) thin films and observed large, compressive residual stresses in films grown under conditions typically used for the deposition of highly conductive samples. Power, growth pressure, oxygen partial pressure, and RF power ratio (RF/(RF + DC)) were varied according to a full-factorial test matrix and each film was characterized. The resulting regression model and analysis of variance (ANOVA) revealed significant contributions to the residual stress from individual growth parameters as well as interactions of different growth parameters, but no conditions were found within the initial growth space that simultaneously produced low residual stress and high electrical conductivity. Extrapolation of the model results to lower oxygen partial pressures, combined with prior knowledge of conductivity-growth parameter relationships in the IZO system, allowed the selection of two promising growth conditions that were both empirically verified to achieve nearly zero residual stress and electrical conductivities >1480 S/cm. This work shows that a-IZO can be simultaneously optimized for high conductivity and low residual stress.

Thin semi-rigid coaxial cables for cryogenics applications

NASA Astrophysics Data System (ADS)

Kushino, Akihiro; Kasai, Soichi

2013-03-01

We have developed cryogenic coaxial cables for low temperature signal readout from sensitive devices, such as transition edge sensors, superconducting tunnel junctions, and kinetic inductance detectors. In order to reduce heat penetration into cryogenic stages, low thermal conductivity metals were chosen for both center and outer electrical conductors. Various types of coaxial cables, employing stainless-steel, cupro-nickel, brass, beryllium-copper, phosphor-bronze, niobium, and niobium-titanium, were manufactured using drawing dies. Thermal and electrical properties were investigated between 1 and 8 K. Coaxial cables made of copper alloys showed thermal conductance roughly consistent with literature, meanwhile Nb coaxial cable must be affected by the drawing process and thermal conductance was lowered. Attenuation of superconducting Nb and NbTi coaxial cables were observed to be adequately small up to above 10 GHz compared to those of normal conducting coaxial cables, which are subject to the Wiedemann-Franz law. We also measured normal conducting coaxial cables with silver-plated center conductors to improve high frequency performance.

Ba6-3 x Nd8+2 x Ti18O54 Tungsten Bronze: A New High-Temperature n-Type Oxide Thermoelectric

NASA Astrophysics Data System (ADS)

Azough, Feridoon; Freer, Robert; Yeandel, Stephen R.; Baran, Jakub D.; Molinari, Marco; Parker, Stephen C.; Guilmeau, Emmanuel; Kepaptsoglou, Demie; Ramasse, Quentin; Knox, Andy; Gregory, Duncan; Paul, Douglas; Paul, Manosh; Montecucco, Andrea; Siviter, Jonathan; Mullen, Paul; Li, Wenguan; Han, Guang; Man, Elena A.; Baig, Hasan; Mallick, Tapas; Sellami, Nazmi; Min, Gao; Sweet, Tracy

2016-03-01

Semiconducting Ba6-3 x Nd8+2 x Ti18O54 ceramics (with x = 0.00 to 0.85) were synthesized by the mixed oxide route followed by annealing in a reducing atmosphere; their high-temperature thermoelectric properties have been investigated. In conjunction with the experimental observations, atomistic simulations have been performed to investigate the anisotropic behavior of the lattice thermal conductivity. The ceramics show promising n-type thermoelectric properties with relatively high Seebeck coefficient, moderate electrical conductivity, and temperature-stable, low thermal conductivity; For example, the composition with x = 0.27 (i.e., Ba5.19Nd8.54Ti18O54) exhibited a Seebeck coefficient of S 1000K = 210 µV/K, electrical conductivity of σ 1000K = 60 S/cm, and thermal conductivity of k 1000K = 1.45 W/(m K), leading to a ZT value of 0.16 at 1000 K.

Experimental Study on the Electrical Conductivity of Pyroxene Andesite at High Temperature and High Pressure

NASA Astrophysics Data System (ADS)

Hui, KeShi; Dai, LiDong; Li, HePing; Hu, HaiYing; Jiang, JianJun; Sun, WenQing; Zhang, Hui

2017-03-01

The electrical conductivity of pyroxene andesite was in situ measured under conditions of 1.0-2.0 GPa and 673-1073 K using a YJ-3000t multi-anvil press and Solartron-1260 Impedance/Gain-phase analyzer. Experimental results indicate that the electrical conductivities of pyroxene andesite increase with increasing temperature, and the electrical conductivities decrease with the rise of pressure, and the relationship between electrical conductivity ( σ) and temperature ( T) conforms to an Arrhenius relation within a given pressure and temperature range. When temperature rises up to 873-923 K, the electrical conductivities of pyroxene andesite abruptly increase, and the activation enthalpy increases at this range, which demonstrates that pyroxene andesite starts to dehydrate. By the virtue of the activation enthalpy (0.35-0.42 eV) and the activation volume (-6.75 ± 1.67 cm3/mole) which characterizes the electrical properties of sample after dehydration, we consider that the conduction mechanism is the small polaron conduction before and after dehydration, and that the rise of carrier concentration is the most important reason of increased electrical conductivity.

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.

The influence of oxidation time on the properties of oxidized zinc films

NASA Astrophysics Data System (ADS)

Rambu, A. P.

2012-09-01

The effect of oxidation time on the structural characteristics and electronic transport mechanism of zinc oxide thin films prepared by thermal oxidation, have been investigated. Zinc metallic films were deposited by thermal evaporation under vacuum, the subsequent oxidation of Zn films being carried out in open atmosphere. XRD and AFM analysis indicate that obtained films posses a polycrystalline structure, the crystallites having a preferential orientation. Structural analysis reveals that microstructure of the films (crystallite size, surface roughness, internal stress) is depending on the oxidation time of metallic films. The electrical behavior of ZnO films was investigated, during a heat treatment (two heating/cooling cycles). It was observed that after the first heating, the temperature dependences of electrical conductivity become reversible. Mott variable range hopping model was proposed to analyze the temperature dependence of the electrical conductivity, in low temperature ranges. Values of some characteristic parameters were calculated.

Joule heating effects on particle immobilization in insulator-based dielectrophoretic devices.

PubMed

Gallo-Villanueva, Roberto C; Sano, Michael B; Lapizco-Encinas, Blanca H; Davalos, Rafael V

2014-02-01

In this work, the temperature effects due to Joule heating obtained by application of a direct current electric potential were investigated for a microchannel with cylindrical insulating posts employed for insulator-based dielectrophoresis. The conductivity of the suspending medium, the local electric field, and the gradient of the squared electric field, which directly affect the magnitude of the dielectrophoretic force exerted on particles, were computationally simulated employing COMSOL Multiphysics. It was observed that a temperature gradient is formed along the microchannel, which redistributes the conductivity of the suspending medium leading to an increase of the dielectrophoretic force toward the inlet of the channel while decreasing toward the outlet. Experimental results are in good agreement with simulations on the particle-trapping zones anticipated. This study demonstrates the importance of considering Joule heating effects when designing insulator-based dielectrophoresis systems. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exploring Carbon Nanotubes for Nanoscale Devices

NASA Technical Reports Server (NTRS)

Han, Jie; Dai; Anantram; Jaffe; Saini, Subhash (Technical Monitor)

1998-01-01

Carbon nanotubes (CNTs) are shown to promise great opportunities in nanoelectronic devices and nanoelectromechanical systems (NEMS) because of their inherent nanoscale sizes, intrinsic electric conductivities, and seamless hexagonal network architectures. I present our collaborative work with Stanford on exploring CNTs for nanodevices in this talk. The electrical property measurements suggest that metallic tubes are quantum wires. Furthermore, two and three terminal CNT junctions have been observed experimentally. We have proposed and studied CNT-based molecular switches and logic devices for future digital electronics. We also have studied CNTs based NEMS inclusing gears, cantilevers, and scanning probe microscopy tips. We investigate both chemistry and physics based aspects of the CNT NEMS. Our results suggest that CNT have ideal stiffness, vibrational frequencies, Q-factors, geometry-dependent electric conductivities, and the highest chemical and mechanical stabilities for the NEMS. The use of CNT SPM tips for nanolithography is presented for demonstration of the advantages of the CNT NEMS.

Microstructure factor and mechanical and electronic properties of hydrogenated amorphous and nanocrystalline silicon thin-films for microelectromechanical systems applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mouro, J.; Gualdino, A.; Chu, V.

2013-11-14

Thin-film silicon allows the fabrication of MEMS devices at low processing temperatures, compatible with monolithic integration in advanced electronic circuits, on large-area, low-cost, and flexible substrates. The most relevant thin-film properties for applications as MEMS structural layers are the deposition rate, electrical conductivity, and mechanical stress. In this work, n{sup +}-type doped hydrogenated amorphous and nanocrystalline silicon thin-films were deposited by RF-PECVD, and the influence of the hydrogen dilution in the reactive mixture, the RF-power coupled to the plasma, the substrate temperature, and the deposition pressure on the structural, electrical, and mechanical properties of the films was studied. Three differentmore » types of silicon films were identified, corresponding to three internal structures: (i) porous amorphous silicon, deposited at high rates and presenting tensile mechanical stress and low electrical conductivity, (ii) dense amorphous silicon, deposited at intermediate rates and presenting compressive mechanical stress and higher values of electrical conductivity, and (iii) nanocrystalline silicon, deposited at very low rates and presenting the highest compressive mechanical stress and electrical conductivity. These results show the combinations of electromechanical material properties available in silicon thin-films and thus allow the optimized selection of a thin silicon film for a given MEMS application. Four representative silicon thin-films were chosen to be used as structural material of electrostatically actuated MEMS microresonators fabricated by surface micromachining. The effect of the mechanical stress of the structural layer was observed to have a great impact on the device resonance frequency, quality factor, and actuation force.« less

Experimental observation of Lorenz chaos in the Quincke rotor dynamics.

PubMed

Peters, François; Lobry, Laurent; Lemaire, Elisabeth

2005-03-01

In this paper, we report experimental evidence of Lorenz chaos for the Quincke rotor dynamics. We study the angular motion of an insulating cylinder immersed in slightly conducting oil and submitted to a direct current electric field. The simple equations which describe the dynamics of the rotor are shown to be equivalent to the Lorenz equations. In particular, we observe two bifurcations in our experimental system. Above a critical value of the electric field, the cylinder rotates at a constant rate. At a second bifurcation, the system becomes chaotic. The characteristic shape of the experimental first return map provides strong evidence for Lorenz-type chaos.

Experimental observation of Lorenz chaos in the Quincke rotor dynamics

NASA Astrophysics Data System (ADS)

Peters, François; Lobry, Laurent; Lemaire, Elisabeth

2005-03-01

In this paper, we report experimental evidence of Lorenz chaos for the Quincke rotor dynamics. We study the angular motion of an insulating cylinder immersed in slightly conducting oil and submitted to a direct current electric field. The simple equations which describe the dynamics of the rotor are shown to be equivalent to the Lorenz equations. In particular, we observe two bifurcations in our experimental system. Above a critical value of the electric field, the cylinder rotates at a constant rate. At a second bifurcation, the system becomes chaotic. The characteristic shape of the experimental first return map provides strong evidence for Lorenz-type chaos.

Heating the sun's lower transition region with fine-scale electric currents

NASA Technical Reports Server (NTRS)

Rabin, D.; Moore, R.

1984-01-01

Analytical and observational data are presented to show that the lower transition zone, a 100 km thick region at 10,000-200,000 K between the solar chromosphere and corona, is heated by local electric currents. The study was spurred by correlations between the enhanced atmospheric heating and magnetospheric flux in the chromospheric network and active regions. Field aligned current heated flux loops are asserted to mainly reside in and make up most of the transition region. It is shown that thermal conduction from the sides of hot gas columns generated by the current dissipation is the source of the observed temperature distribution in the transition regions.

Electrical transport properties in indium tin oxide films prepared by electron-beam evaporation

NASA Astrophysics Data System (ADS)

Liu, X. D.; Jiang, E. Y.; Zhang, D. X.

2008-10-01

Amorphous and polycrystalline indium tin oxide films have been prepared by electron-beam evaporation method. The amorphous films exhibit semiconductor behavior, while metallic conductivity is observed in the polycrystalline samples. The magnetoconductivities of the polycrystalline films are positive at low temperatures and can be well described by the theory of three-dimensional weak-localization effect. In addition, the electron phase-breaking rate is proportional to T3/2. Comparing the experimental results with theory, we find that the electron-electron scattering is the dominant destroyer of the constructive interference in the films. In addition, the Coulomb interaction is the main contribution to the nontrivial corrections for the electrical conductivity at low temperatures.

Applications of Electrified Dust and Dust Devil Electrodynamics to Martian Atmospheric Electricity

NASA Astrophysics Data System (ADS)

Harrison, R. G.; Barth, E.; Esposito, F.; Merrison, J.; Montmessin, F.; Aplin, K. L.; Borlina, C.; Berthelier, J. J.; Déprez, G.; Farrell, W. M.; Houghton, I. M. P.; Renno, N. O.; Nicoll, K. A.; Tripathi, S. N.; Zimmerman, M.

2016-11-01

Atmospheric transport and suspension of dust frequently brings electrification, which may be substantial. Electric fields of 10 kV m-1 to 100 kV m-1 have been observed at the surface beneath suspended dust in the terrestrial atmosphere, and some electrification has been observed to persist in dust at levels to 5 km, as well as in volcanic plumes. The interaction between individual particles which causes the electrification is incompletely understood, and multiple processes are thought to be acting. A variation in particle charge with particle size, and the effect of gravitational separation explains to, some extent, the charge structures observed in terrestrial dust storms. More extensive flow-based modelling demonstrates that bulk electric fields in excess of 10 kV m-1 can be obtained rapidly (in less than 10 s) from rotating dust systems (dust devils) and that terrestrial breakdown fields can be obtained. Modelled profiles of electrical conductivity in the Martian atmosphere suggest the possibility of dust electrification, and dust devils have been suggested as a mechanism of charge separation able to maintain current flow between one region of the atmosphere and another, through a global circuit. Fundamental new understanding of Martian atmospheric electricity will result from the ExoMars mission, which carries the DREAMS (Dust characterization, Risk Assessment, and Environment Analyser on the Martian Surface)—MicroARES ( Atmospheric Radiation and Electricity Sensor) instrumentation to Mars in 2016 for the first in situ electrical measurements.

Applications of Electrified Dust and Dust Devil Electrodynamics to Martian Atmospheric Electricity

NASA Technical Reports Server (NTRS)

Harrison, R. G.; Barth, E.; Esposito, F.; Merrison, J.; Montmessin, F.; Aplin, K. L.; Borlina, C.; Berthelier, J J.; Deprez, G.; Farrell, William M.;

Experimental analysis of electrical properties of composite materials

NASA Astrophysics Data System (ADS)

Fiala, L.; Rovnaník, P.; Černý, R.

2017-02-01

Dry cement-based composites are electrically non-conductive materials that behave in electric field like dielectrics. However, a relatively low amount of electrically conductive admixture significantly increases the electrical conductivity which extends applicability of such materials in practice. Therefore, they can be used as self-monitoring sensors controlling development of cracks; as sensors monitoring moisture content or when treated by an external electrical voltage as heat sources used for deicing of material's surface layer. Alkali-activated aluminosilicates (AAA), as competing materials to cement-based materials, are intensively investigated in the present due to their superior durability and environmental impact. Whereas the electrical properties of AAA are similar to those cement-based, they can be enhanced in the same way. In both cases, it is crucial to find a reasonable amount of electrically conductive phase to design composites with a sufficient electrical conductivity at an affordable price. In this paper, electrical properties of composites based on AAA binder and electrically conductive admixture represented by carbon nanotubes (CNT) are investigated. Measurements of electrical properties are carried out by means of 2-probes DC technique on nine types of samples; reference sample without the conductive phase and samples with CNT admixture in amount of 0.1 % - 2.5 % by vol. A significant increase of the electrical conductivity starts from the amount of 0.5 % CNT admixture and in case of 2.5 % CNT is about three orders of magnitude higher compared to the reference sample.

Modeling an Excitable Biosynthetic Tissue with Inherent Variability for Paired Computational-Experimental Studies.

PubMed

Gokhale, Tanmay A; Kim, Jong M; Kirkton, Robert D; Bursac, Nenad; Henriquez, Craig S

2017-01-01

To understand how excitable tissues give rise to arrhythmias, it is crucially necessary to understand the electrical dynamics of cells in the context of their environment. Multicellular monolayer cultures have proven useful for investigating arrhythmias and other conduction anomalies, and because of their relatively simple structure, these constructs lend themselves to paired computational studies that often help elucidate mechanisms of the observed behavior. However, tissue cultures of cardiomyocyte monolayers currently require the use of neonatal cells with ionic properties that change rapidly during development and have thus been poorly characterized and modeled to date. Recently, Kirkton and Bursac demonstrated the ability to create biosynthetic excitable tissues from genetically engineered and immortalized HEK293 cells with well-characterized electrical properties and the ability to propagate action potentials. In this study, we developed and validated a computational model of these excitable HEK293 cells (called "Ex293" cells) using existing electrophysiological data and a genetic search algorithm. In order to reproduce not only the mean but also the variability of experimental observations, we examined what sources of variation were required in the computational model. Random cell-to-cell and inter-monolayer variation in both ionic conductances and tissue conductivity was necessary to explain the experimentally observed variability in action potential shape and macroscopic conduction, and the spatial organization of cell-to-cell conductance variation was found to not impact macroscopic behavior; the resulting model accurately reproduces both normal and drug-modified conduction behavior. The development of a computational Ex293 cell and tissue model provides a novel framework to perform paired computational-experimental studies to study normal and abnormal conduction in multidimensional excitable tissue, and the methodology of modeling variation can be applied to models of any excitable cell.

Estimating the power-law distribution of Earth electrical conductivity from low-frequency, controlled-source electromagnetic responses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beskardes, G. D.; Weiss, Chester J.; Everett, M. E.

Electromagnetic responses reflect the interaction between applied electromagnetic fields and heterogeneous geoelectrical structures. Here by quantifying the relationship between multi-scale electrical properties and the observed electromagnetic response is therefore important for meaningful geologic interpretation. Furthermore, we present here examples of near-surface electromagnetic responses whose spatial fluctuations appear on all length scales, are repeatable and fractally distributed, suggesting that the spatial fluctuations may be considered as “geologic noise”.

Estimating the power-law distribution of Earth electrical conductivity from low-frequency, controlled-source electromagnetic responses

DOE PAGES

Beskardes, G. D.; Weiss, Chester J.; Everett, M. E.

2016-11-30

Electromagnetic responses reflect the interaction between applied electromagnetic fields and heterogeneous geoelectrical structures. Here by quantifying the relationship between multi-scale electrical properties and the observed electromagnetic response is therefore important for meaningful geologic interpretation. Furthermore, we present here examples of near-surface electromagnetic responses whose spatial fluctuations appear on all length scales, are repeatable and fractally distributed, suggesting that the spatial fluctuations may be considered as “geologic noise”.

Studies on Structural, Optical, Thermal and Electrical Properties of Perylene-Doped p-terphenyl Luminophors.

PubMed

Desai, Netaji K; Mahajan, Prasad G; Bhopate, Dhanaji P; Dalavi, Dattatray K; Kamble, Avinash A; Gore, Anil H; Dongale, Tukaram D; Kolekar, Govind B; Patil, Shivajirao R

2018-01-01

A simple solid state reaction technique was employed for the preparation of polycrystalline luminophors of p-terphenyl containing different amounts of perylene followed by spectral characterization techniques viz. XRD, SEM, TGA-DSC, UV-Visible spectroscopy, thermo-electrical conductivity, fluorescence spectroscopy, fluorescence life time spectroscopy and temperature dependent fluorescence. X-ray diffraction profiles of the doped p-terphenyl reveal well-defined and sharp peaks indicate homogeneity and crystallinity. The SEM micrograph of pure p-terphenyl exhibit flakes like grains and then compact and finally gets separately with perylene amounts. The observed results indicate that closed packed crystal structures of doped p-terphenyl during crystal formation. The band gaps estimated from UV-visible spectroscopy decreased from 5.20 to 4.10 eV, while thermo-electrical conductivity increases with perylene content. The fluorescence spectra showed partial quenching of p-terphenyl fluorescence and simultaneously sensitization of perylene fluorescence at the excitation wavelength of p-terphenyl (290 nm) due to excitation energy transfer from p-terphenyl to perylene. The observed sensitization results are in harmony with intense blue color seen in fluorescence microscopy images and has high demand in scintillation process.

Electrical characterization of Bi1.50-xYxZn0.92Nb1.5O6.92 varactors

NASA Astrophysics Data System (ADS)

Qasrawi, A. F.; Muis, Khalil O. Abu; Rob, Osama H. Abu Al; Mergen, A.

2014-05-01

The electrical properties of yttrium doped bismuth zinc niobium oxide (BZN) pyrochlore ceramics are explored by means of temperature dependent electrical conductivity dielectric constant and capacitance spectra in the frequency range of 0-3 GHz. It is observed that the doped BZN exhibit a conductivity type conversion from intrinsic to extrinsic as the doping content increased from 0.04 to 0.06. The thermal energy bandgap of the intrinsic type is 3.45 eV. The pyrochlore is observed to exhibit a dielectric breakdown at 395 K. In addition, a negative capacitance (NC) spectrum with main resonance peak position of 23.2 MHz is detected. The NC effect is ascribed to the increased polarization and the availability of more free carriers in the device. When the NC signal amplitude is attenuated in the range of 0-20 dBm at 50 MHz and 150 MHz, wide tunability is monitored. Such characteristics of the Y-doped BZN are attractive for using them to cancel the positive parasitic capacitance of electronic circuits. The canceling of parasitic capacitance improves the high frequency performance of filter inductors and reduces the common mode noise of the resonance signal.

Effectiveness of a worker-worn electric-field sensor to detect power-line proximity and electrical-contact.

PubMed

Zeng, Shengke; Powers, John R; Newbraugh, Bradley H

2010-06-01

Construction workers suffer the most electrocutions among all industries. Currently, there are no electrical contact warning devices on the market to protect workers. This paper proposes a worker-worn electric-field sensor. As the worker is in proximity to, or in contact with, a live power-circuit, the sensor sets off an audible/visual warning alarm. The sensor also has the potential to wirelessly trip a wireless-capable circuit breaker, and to trigger a wireless transmitter to notify emergency response of an electrical contact. An experiment was conducted to measure electric-field variation on simulated human-wrists (10 defrosted hog-legs) in various proximities and in electrical-contact to a simulated power-circuit. The purpose of these tests was to determine the feasibility of developing a worker-worn electric-field detection sensor for use in protecting workers from contact with energized electrical conductors. This study observed a significant electric-field-magnitude increase as a hog-leg approaches the live-circuit, and the distinct electric-field-magnitude jump as the leg contacts with the live-circuit. The observation indicates that this sensor can be an effective device to warn the workers of electrical hazards. Additionally, the sensor has the potential to wirelessly trip a wireless-capable circuit-breaker and trigger a wireless transmitter (such as a cell phone) to notify an emergency response. The prompt notification prevents the worker from further injury caused by postponed medical-care. Widespread use of this sensor could lower electrocution and electrically related injury rates in the construction industry. (c) 2010 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakayama, T.; Kubo, O.; Shingaya, Y.

the research of advanced materials based on nanoscience and nanotechnology, it is often desirable to measure nanoscale local electrical conductivity at a designated position of a given sample. For this purpose, multiple-probe scanning probe microscopes (MP-SPMs), in which two, three or four scanning tunneling microscope (STM) or atomic force microscope (AFM) probes are operated independently, have been developed. Each probe in an MP-SPM is used not only for observing high-resolution STM or AFM images but also for forming an electrical contact enabling nanoscale local electrical conductivity measurement. The world's first double-probe STM (DP-STM) developed by the authors, which was subsequentlymore » modified to a triple-probe STM (TP-STM), has been used to measure the conductivities of one-dimensional metal nanowires and carbon nanotubes and also two-dimensional molecular films. A quadruple-probe STM (QP-STM) has also been developed and used to measure the conductivity of two-dimensional molecular films without the ambiguity of contact resistance between the probe and sample. Moreover, a quadruple-probe AFM (QP-AFM) with four conductive tuning-fork-type self-detection force sensing probes has been developed to measure the conductivity of a nanostructure on an insulating substrate. A general-purpose computer software to control four probes at the same time has also been developed and used in the operation of the QP-AFM. These developments and applications of MP-SPMs are reviewed in this paper.« less

Method of forming an electrically conductive cellulose composite

DOEpatents

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

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.

Local time distribution of the SSC-associated HF-Doppler frequency shifts

NASA Technical Reports Server (NTRS)

Kikuchi, T.; Sugiuchi, H.; Ishimine, T.

1985-01-01

The HF-Doppler frequency shift observed at the storm's sudden commencement is composed of a frequency increase (+) and decrease (-), and classified into four types, SCF(+ -), SCF(- +), SCF(+) and SCF(-). Since the latter two types are special cases of the former two types, two different kinds of electrical field exist in the F region and cause the ExB drift motion of plasma. HUANG (1976) interpreted the frequency increase of SCF(+ -) as due to the westward induction electric field proportional to delta H/ delta t and the succeeding frequency decrease due to the eastward conduction electric field which produces ionospheric currents responsible for the magnetic increase on the ground. In spite of his success in interpreting the SCF(+ -), some other interpretations are needed for the explanation of the whole set of SCF's, particularly SCF(- +). Local time distributions of the SCF's are derived from 41 SCF's which are observed on the HF standard signal (JJY) as received in Okinawa (path length =1600 km) and Kokubunji (60 km). It is shown that the SCF(+ -) appears mainly during the day, whereas the SCF(- +) is observed during the night. The results indicate that the preliminary frequency shift (+) of SCF(+ -) and (-) of SCF(- +) is caused by a westward electric field in the dayside hemisphere, while by an eastward electric field in the nightside hemisphere. The main frequency shift (-) of SCF(+ -) and (+) of SCF(- +) is caused by the reversed electric field. Consequently, the preliminary frequency shift is caused by the dusk-to-dawn electric field, while the main frequency shift by the dawn-to-dusk electric field.

Risk of neurological diseases among survivors of electric shocks: a nationwide cohort study, Denmark, 1968-2008.

PubMed

Grell, Kathrine; Meersohn, Andrea; Schüz, Joachim; Johansen, Christoffer

2012-09-01

Several studies suggest a link between electric injuries and neurological diseases, where electric shocks may explain elevated risks for neuronal degeneration and, subsequently, neurological diseases. We conducted a retrospective cohort study on the risk of neurological diseases among people in Denmark who had survived an electric accident in 1968-2008. The cohort included 3,133 people and occurrences of neurological diseases were determined by linkage to the nationwide population-based Danish National Register of Patients. The numbers of cases observed at first hospital contact in the cohort were compared with the respective rates of first hospital contacts for neurological diseases in the general population. We observed significantly increased risks for peripheral nerve diseases (standardized hospitalization ratio (SHR), 1.66; 95% confidence interval (CI), 1.22-2.22), for migraine (SHR, 1.80; 95% CI, 1.23-2.54), for vertigo (SHR, 1.60; 95% CI, 1.22-2.05), and for epilepsy (SHR, 1.45; 95% CI, 1.11-1.85). Only small numbers of cases of other neurological diseases were found, making the risk estimates unstable. These findings suggest an association between a single electric shock and increased risks for peripheral nerve diseases, migraines, vertigo, and epilepsy, but confirmation of these observations is needed. Copyright © 2012 Wiley Periodicals, Inc.

Monitoring the ground water level change during the pump test by using the Electric resistivity tomography

NASA Astrophysics Data System (ADS)

Hsu, H.; Chang, P. Y.; Yao, H. J.

2017-12-01

For hydrodynamics study of the unconfined aquifer in gravel formation, a pumping test was established to estimate the hydraulic conductivity in the midstream of Zhoushui River in Taiwan. The hydraulic parameters and the cone of depression could be estimated by monitoring the groundwater drawdown in an observation well which was in a short distance far from the pumping well. In this study we carried out the electric resistivity image monitoring during the whole pumping test. The electric resistivity data was measured with the surface and downhole electrodes which would produce a clear subsurface image of groundwater level through a larger distance than the distance between pumping and observation wells. The 2D electric image could also describe how a cone of depression truly created at subsurface. The continuous records could also show the change of groundwater level during the whole pumping test which could give a larger scale of the hydraulic parameters.

Preparation of monodisperse microbubbles using an integrated embedded capillary T-junction with electrohydrodynamic focusing.

PubMed

Parhizkar, Maryam; Stride, Eleanor; Edirisinghe, Mohan

2014-07-21

This work investigates the generation of monodisperse microbubbles using a microfluidic setup combined with electrohydrodynamic processing. A basic T-junction microfluidic device was modified by applying an electrical potential difference across the outlet channel. A model glycerol air system was selected for the experiments. In order to investigate the influence of the electric field strength on bubble formation, the applied voltage was increased systematically up to 21 kV. The effect of solution viscosity and electrical conductivity was also investigated. It was found that with increasing electrical potential difference, the size of the microbubbles reduced to ~25% of the capillary diameter whilst their size distribution remained narrow (polydispersity index ~1%). A critical value of 12 kV was found above which no further significant reduction in the size of the microbubbles was observed. The findings suggest that the size of the bubbles formed in the T-junction (i.e. in the absence of the electric field) is strongly influenced by the viscosity of the solution. The eventual size of bubbles produced by the composite device, however, was only weakly dependent upon viscosity. Further experiments, in which the solution electrical conductivity was varied by the addition of a salt indicated that this had a much stronger influence upon bubble size.

The effect of different surfactants/plastisizers on the electrical behavior of CNT nano-modified cement mortars

NASA Astrophysics Data System (ADS)

Dalla, P. T.; Alafogianni, P.; Tragazikis, I. K.; Exarchos, D. A.; Dassios, K.; Barkoula, N.-M.; Matikas, T. E.

2015-03-01

Cement-based materials have in general low electrical conductivity. Electrical conductivity is the measure of the ability of the material to resist the passage of electrical current. The addition of a conductive admixture such as Multi-Walled Carbon Nanotubes (MWCNTs) in a cement-based material increases the conductivity of the structure. This research aims to characterize nano-modified cement mortars with MWCNT reinforcements. Such nano-composites would possess smartness and multi-functionality. Multifunctional properties include electrical, thermal and piezo-electric characteristics. One of these properties, the electrical conductivity, was measured using a custom made apparatus that allows application of known D.C. voltage on the nano-composite. In this study, the influence of different surfactants/plasticizers on CNT nano-modified cement mortar specimens with various concentrations of CNTs (0.2% wt. cement CNTs - 0.8% wt. cement CNTs) on the electrical conductivity is assessed.

BRNBOX v.1.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aldridge, David F.

Program BRNBOX conducts a systematic search through a pre-defined 3D volume of candidate sub-surface Born scattering points in order to identify the particular point that minimizes the misfit between predicted (i.e., calculated) and observed electromagnetic (EM) data. This global minimum misfit point is interpreted as the location where electrically conductive proppant is injected into a sub-surface petroleum reservoir in a hydraulic fracturing experiment.

Low damage electrical modification of 4H-SiC via ultrafast laser irradiation

NASA Astrophysics Data System (ADS)

Ahn, Minhyung; Cahyadi, Rico; Wendorf, Joseph; Bowen, Willie; Torralva, Ben; Yalisove, Steven; Phillips, Jamie

2018-04-01

The electrical properties of 4H-SiC under ultrafast laser irradiation in the low fluence regime (<0.50 J/cm2) are presented. The appearance of high spatial frequency laser induced periodic surface structures is observed at a fluence near 0.25 J/cm2 and above, with variability in environments like in air, nitrogen, and a vacuum. In addition to the formation of periodic surface structures, ultrafast laser irradiation results in possible surface oxidation and amorphization of the material. Lateral conductance exhibits orders of magnitude increase, which is attributed to either surface conduction or modification of electrical contact properties, depending on the initial material conductivity. Schottky barrier formation on ultrafast laser irradiated 4H-SiC shows an increase in the barrier height, an increase in the ideality factor, and sub-bandgap photovoltaic responses, suggesting the formation of photo-active point defects. The results suggest that the ultrafast laser irradiation technique provides a means of engineering spatially localized structural and electronic modification of wide bandgap materials such as 4H-SiC with relatively low surface damage via low temperature processing.

Characterization and electrical properties of V 2O 5-CuO-P 2O 5 glasses

NASA Astrophysics Data System (ADS)

Al-Assiri, M. S.

2008-08-01

Characterization and electrical properties of vanadium-copper-phosphate glasses of compositions xV 2O 5-(40- x)CuO-60P 2O 5 have been reported. X-ray diffraction (XRD) confirms the amorphous nature of these glasses. It was observed that, the density ( d) decreases gradually while the molar volume ( Vm) increases with the increase of the vanadium oxide content in such glasses. This may be due to the effect of the polarizing power strength, PPS, which is a measure of ratio of the cation valance to its diameter. The dc conductivity increases while the activation energy decreases with the increase of the V 2O 5 content. The dc conductivity in the present glasses is electronic and depends strongly upon the average distance, R, between the vanadium ions. Analysis of the electrical properties has been made in the light of small polaron hopping model. The parameters obtained from the fits of the experimental data to this model are reasonable and consistent with glass composition. The conduction is attributed to non-adiabatic hopping of small polaron.

Electrode Models for Electric Current Computed Tomography

PubMed Central

CHENG, KUO-SHENG; ISAACSON, DAVID; NEWELL, J. C.; GISSER, DAVID G.

2016-01-01

This paper develops a mathematical model for the physical properties of electrodes suitable for use in electric current computed tomography (ECCT). The model includes the effects of discretization, shunt, and contact impedance. The complete model was validated by experiment. Bath resistivities of 284.0, 139.7, 62.3, 29.5 Ω · cm were studied. Values of “effective” contact impedance z used in the numerical approximations were 58.0, 35.0, 15.0, and 7.5 Ω · cm2, respectively. Agreement between the calculated and experimentally measured values was excellent throughout the range of bath conductivities studied. It is desirable in electrical impedance imaging systems to model the observed voltages to the same precision as they are measured in order to be able to make the highest resolution reconstructions of the internal conductivity that the measurement precision allows. The complete electrode model, which includes the effects of discretization of the current pattern, the shunt effect due to the highly conductive electrode material, and the effect of an “effective” contact impedance, allows calculation of the voltages due to any current pattern applied to a homogeneous resistivity field. PMID:2777280

Electrode models for electric current computed tomography.

PubMed

Cheng, K S; Isaacson, D; Newell, J C; Gisser, D G

1989-09-01

This paper develops a mathematical model for the physical properties of electrodes suitable for use in electric current computed tomography (ECCT). The model includes the effects of discretization, shunt, and contact impedance. The complete model was validated by experiment. Bath resistivities of 284.0, 139.7, 62.3, 29.5 omega.cm were studied. Values of "effective" contact impedance zeta used in the numerical approximations were 58.0, 35.0, 15.0, and 7.5 omega.cm2, respectively. Agreement between the calculated and experimentally measured values was excellent throughout the range of bath conductivities studied. It is desirable in electrical impedance imaging systems to model the observed voltages to the same precision as they are measured in order to be able to make the highest resolution reconstructions of the internal conductivity that the measurement precision allows. The complete electrode model, which includes the effects of discretization of the current pattern, the shunt effect due to the highly conductive electrode material, and the effect of an "effective" contact impedance, allows calculation of the voltages due to any current pattern applied to a homogeneous resistivity field.

Electrical conductivity of graphite oxide nanoplatelets obtained from bamboo: Effect of the deoxidation degree

NASA Astrophysics Data System (ADS)

Gross, K.; Prias-Barragan, J. J.; Sangiao, S.; de Teresa, J. M.; Lajaunie, L.; Arenal, R.; Ariza-Calderón, H.; Prieto, P.

Given the high interest in the fabrication and application of carbon-based materials, we present a new and cost-effective method for the synthesis of graphite oxide nanoplatelets (GONP) using bamboo pyroligneous acid (BPA) as source. GONP-BPA present lateral dimensions of 5-100 micro-meter and thickness less than 80 nm, as confirmed by TEM. EEL spectra show that locally the carbon is mainly in sp2 bonding configuration and confirm a short/medium range crystalline order. Elemental analysis by EDX confirms the presence of oxygen in an atomic percentage ranging from 17 to 5%. For electrical characterization, single platelets were contacted by focused-ion-beam-induced deposition of Pt nanowires. The four-point probe electrical conductivity shows a direct correlation with the oxygen percentage. Three orders of magnitude conductivity rise is observed by the oxygen reduction, reaching a value of 2.3x103 S/m at the final deoxidation degree. The results suggest that GONP-BPA could be used in the development of advanced devices and sensors.

Solution processed aluminum paper for flexible electronics.

PubMed

Lee, Hye Moon; Lee, Ha Beom; Jung, Dae Soo; Yun, Jung-Yeul; Ko, Seung Hwan; Park, Seung Bin

2012-09-11

As an alternative to vacuum deposition, preparation of highly conductive papers with aluminum (Al) features is successfully achieved by the solution process consisting of Al precursor ink (AlH(3){O(C(4)H(9))(2)}) and low temperature stamping process performed at 110 °C without any serious hydroxylation and oxidation problems. Al features formed on several kinds of paper substrates (calendar, magazine, and inkjet printing paper substrates) are less than ~60 nm thick, and their electrical conductivities were found to be as good as thermally evaporated Al film or even better (≤2 Ω/□). Strong adhesion of Al features to paper substrates and their excellent flexibility are also experimentally confirmed by TEM observation and mechanical tests, such as tape and bending tests. The solution processed Al features on paper substrates show different electrical and mechanical performance depending on the paper type, and inkjet printing paper is found to be the best substrate with high and stable electrical and mechanical properties. The Al conductive papers produced by the solution process may be applicable in disposal paper electronics.

Negative differential photoconductance in gold nanoparticle arrays in the Coulomb blockade regime.

PubMed

Mangold, Markus A; Calame, Michel; Mayor, Marcel; Holleitner, Alexander W

2012-05-22

We investigate the photoconductance of gold nanoparticle arrays in the Coulomb blockade regime. Two-dimensional, hexagonal crystals of nanoparticles are produced by self-assembly. The nanoparticles are weakly coupled to their neighbors by a tunneling conductance. At low temperatures, the single electron charging energy of the nanoparticles dominates the conductance properties of the array. The Coulomb blockade of the nanoparticles can be lifted by optical excitation with a laser beam. The optical excitation leads to a localized heating of the arrays, which in turn gives rise to a local change in conductance and a redistribution of the overall electrical potential in the arrays. We introduce a dual-beam optical excitation technique to probe the distribution of the electrical potential in the nanoparticle array. A negative differential photoconductance is the direct consequence of the redistribution of the electrical potential upon lifting of the Coulomb blockade. On the basis of our model, we calculate the optically induced current from the dark current-voltage characteristics of the nanoparticle array. The calculations closely reproduce the experimental observations.

Thermoelectric properties of the ceramic oxide Sr1- x La x TiO3

NASA Astrophysics Data System (ADS)

Mahmud, Iqbal; Yoon, Man-Soon; Kim, Il-Ho; Choi, Moon-Kwan; Ur, Soon-Chul

2016-01-01

The effect of lanthanum on the electric and the thermoelectric properties of the ceramic oxide Sr1- x La x TiO3 (where x = 0.0, 0.04, 0.06, 0.08 and 0.12 mole) have been studied. La-doped SrTiO3 was prepared by using the conventional mixed-oxide reaction method. XRD patterns indicated that almost all the La atoms incorporated into the SrTiO3 crystal provided charge carriers. The lattice parameter increases with increasing La doping content. The relative densities of all the samples varied from 89.6% to 94.8%. The electrical conductivity increased with La doping up to 0.08 moles and then decreased as the content of La was increased above 0.08 moles. The thermal conductivity decreased with increasing La content. The largest absolute value of the Seebeck coefficient, 394 μVK-1 at 973 K, was observed at x = 0.04. The Sr0.92La0.08TiO3 sample showed its maximum electrical conductivity at 773 K and its largest ZT value of 0.20 at 973 K.

Effect of direct electric current on contaminants removal from the peat water with continuous system

NASA Astrophysics Data System (ADS)

Amri, I.; Azis, A.; Drastinawati

2018-04-01

This research was analysed the essentially of treat peat water using an electric current. Initially, the characterization of peat water was determined including of three parameters they are pH, colour, and conductivity solution exhibited values that exceeded the water standard limit. There are two factors influencing the electric coagulation such as electric current and voltage that were observed in the continous study. The results obtained indicated that the majority of the an electric current were very effective for removing TDS, and pH. The research variable for the voltage from 23,5 to 42,5 volt and the electric current from 2,2 to 4,1. The optimum electric current and voltage was found around 1,5 Ampere and 25 volt, it was exhibited at 4 L/minute. In unit study, continous electric reactor showed that the optimal reduction on the 20 minutes treatment were found pH = 7, 256 ppm. It was meet to the minimum standard government permition.

Structural, Transport and Electrochemical Properties of LiFePO4 Substituted in Lithium and Iron Sublattices (Al, Zr, W, Mn, Co and Ni)

PubMed Central

Molenda, Janina; Kulka, Andrzej; Milewska, Anna; Zając, Wojciech; Świerczek, Konrad

2013-01-01

LiFePO4 is considered to be one of the most promising cathode materials for lithium ion batteries for electric vehicle (EV) application. However, there are still a number of unsolved issues regarding the influence of Li and Fe-site substitution on the physicochemical properties of LiFePO4. This is a review-type article, presenting results of our group, related to the possibility of the chemical modification of phosphoolivine by introduction of cation dopants in Li and Fe sublattices. Along with a synthetic review of previous papers, a large number of new results are included. The possibility of substitution of Li+ by Al3+, Zr4+, W6+ and its influence on the physicochemical properties of LiFePO4 was investigated by means of XRD, SEM/EDS, electrical conductivity and Seebeck coefficient measurements. The range of solid solution formation in Li1−3xAlxFePO4, Li1−4xZrxFePO4 and Li1−6xWxFePO4 materials was found to be very narrow. Transport properties of the synthesized materials were found to be rather weakly dependent on the chemical composition. The battery performance of selected olivines was tested by cyclic voltammetry (CV). In the case of LiFe1−yMyPO4 (M = Mn, Co and Ni), solid solution formation was observed over a large range of y (0 < y ≤ 1). An increase of electrical conductivity for the substitution level y = 0.25 was observed. Electrons of 3d metals other than iron do not contribute to the electrical properties of LiFe1−yMyPO4, and substitution level y > 0.25 leads to considerably lower values of σ. The activated character of electrical conductivity with a rather weak temperature dependence of the Seebeck coefficient suggests a small polaron-type conduction mechanism. The electrochemical properties of LiFe1−yMyPO4 strongly depend on the Fe substitution level. PMID:28809235

Electromagnetic interference filter for automotive electrical systems

DOEpatents

Herron, Nicholas Hayden; Carlson, Douglas S; Tang, David; Korich, Mark D

2013-07-02

A filter for an automotive electrical system includes a substrate having first and second conductive members. First and second input terminals are mounted to the substrate. The first input terminal is electrically connected to the first conductive member, and the second input terminal is electrically connected to the second conductive member. A plurality of capacitors are mounted to the substrate. Each of the capacitors is electrically connected to at least one of the first and second conductive members. First and second power connectors are mounted to the substrate. The first power connector is electrically connected to the first conductive member, and the second power connector is electrically connected to the second conductive member. A common mode choke is coupled to the substrate and arranged such that the common mode choke extends around at least a portion of the substrate and the first and second conductive members.

Ultrahigh Oxidation Resistance and High Electrical Conductivity in Copper-Silver Powder.

PubMed

Li, Jiaxiang; Li, Yunping; Wang, Zhongchang; Bian, Huakang; Hou, Yuhang; Wang, Fenglin; Xu, Guofu; Liu, Bin; Liu, Yong

2016-12-22

The electrical conductivity of pure Cu powder is typically deteriorated at elevated temperatures due to the oxidation by forming non-conducting oxides on surface, while enhancing oxidation resistance via alloying is often accompanied by a drastic decline of electrical conductivity. Obtaining Cu powder with both a high electrical conductivity and a high oxidation resistance represents one of the key challenges in developing next-generation electrical transferring powder. Here, we fabricate a Cu-Ag powder with a continuous Ag network along grain boundaries of Cu particles and demonstrate that this new structure can inhibit the preferential oxidation in grain boundaries at elevated temperatures. As a result, the Cu-Ag powder displays considerably high electrical conductivity and high oxidation resistance up to approximately 300 °C, which are markedly higher than that of pure Cu powder. This study paves a new pathway for developing novel Cu powders with much enhanced electrical conductivity and oxidation resistance in service.

Investigation of the electrical characteristics of electrically conducting yarns and fabrics

NASA Astrophysics Data System (ADS)

Akbarov, R. D.; Baymuratov, B. H.; Akbarov, D. N.; Ilhamova, M.

2017-11-01

Electro-conductive textile materials and products are used presently giving solutions to the problems, related to static electricity, electromagnetic shielding and electromagnetic radiation. Thus a study of their electro-physical characteristics, character of conductivity, possibility of forecasting of electric parameters etc has a substantial value. This work shows the possibility of production electro-conducting textile materials with stable anti-static properties by introduction of electro-conducting yarn into the structure of fabrics. The results of the research, directed to the study of the electro-physical characteristics of electroconducting yarn and fabrics, are influenced by the frequent washing of polyester fabrics containing the different amounts of electro-conducting filaments in the composition. This article reviews the results of the related research, of the electrical characteristics of the yarn and fabric, of the effect of multiple water treatments on the electrical properties of polyester fabrics, containing in their composition different amounts of electrically conductive yarns.

Monitoring electrical properties for improving the lithological and hydrological characterization of landslides

NASA Astrophysics Data System (ADS)

Malet, J. P.; Gance, J.; Lajaunie, M.; Gallistl, J.; Denchik, N.; Flores Orozco, A.; Ottowitz, D.; Supper, R.; Sailhac, P.; Gautier, S.; Schmutz, M.

2017-12-01

Imaging water flows in landslides is of critical importance as the distribution of pore-fluid pressures controls the dynamics (acceleration, deceleration) of the material. Detecting and imaging water is a difficult task, not only because of the complex topography and the small dimensions of the geological structures, but also because the landslide material consists of unsaturated porous and heterogeneous fractured media, leading to multi-scale water-flow properties. Further, these properties can change in time, in relation to temperature, rainfall and biological forcings. Electrical properties are relevant proxies of the sub-surface hydrological properties. In order to image water in landslide bodies, we propose to combine multi-frequency electrical and electromagnetic measurements using campaigns or permanent instruments, and surface/boreole investigations, installed on several unstable slopes in France. To evaluate the information gained from electrical properties for different geological conditions, we discuss electrical and electro-magnetic imaging results for data collected at four different landslides located in France (Super-Sauze and La Valette in the South East Alps, Lodève lin the southern border of the Massif Central Massif, and Séchilienne in the North French Alps). Time-lapse electrical DC resistivity observations, complex electrical conductivity (conduction and polarization/chargeability) measured by IP imaging methods, and controlled-source electromagnetic (CS-AMT) methods are discussed. Imaging results demonstrate an improved lithological characterization of the landslide structures (delineation of the sliding planes, identification of the fractures, discrimination of clay lenses with enhanced resolution); further, water infiltration within the soil matrix and/or the fractures is discriminated allowing better modelling of the hydrological regime of the landslides at the slope scale. This research is conducted in the frame of the project HYDROSLIDE - Hydrogeophysical Monitoring of Clay-Rich Landslides funded by the Austrian Science Fund (FWF) and the French Research Agency (ANR).

Substorm Birkeland currents and Cowling channels in the ionosphere

NASA Astrophysics Data System (ADS)

Fujii, R.

2016-12-01

Field-aligned current (FAC) connects electromagnetically the ionosphere with the magnetosphere and plays important roles on dynamics and energetics in the magnetosphere and the ionosphere. In particular, connections between FACs in the ionosphere give important information on various current sources in the magnetosphere and the linkage between them, although the connection between FACs in the ionosphere does not straightforwardly give that in the magnetosphere. FACs in the ionosphere are closed to each other through ionospheric currents determined with the electric field and the Hall and Pedersen conductivities. The electric field and the conductivities are not independently distributed, but rather they are harmonized with each other spatially and temporarily in a physically consistent manner to give a certain FAC. In particular, the divergence of the Hall current due to the inhomogeneity of the Hall conductivity either flows in/out to the magnetosphere as a secondary FAC or accumulates excess charges that produce a secondary electric field. This electric field drives a current circuit connecting the Hall current with the Pedersen current; a Cowling channel current circuit. The FAC (the electric field) we observe is the sum of the primary and secondary FACs (electric fields). The talk will present characteristics of FACs and associated electric field and auroras during substorms, and the ionospheric current closures between the FACs. A statistical study has shown that the majority of region 1 currents are connected to their adjacent region 2 or region 0 currents, indicating the Pedersen current closure rather than the Hall current closure is dominant. On the other hand, the Pedersen currents associated with surge and substorm-related auroras often are connected to the Hall currents, forming a Cowling channel current circuit within the ionosphere.

Surface Charge Effects on the Electro-Orientation of Insulating Nanotubes in Aqueous Electrolytes

NASA Astrophysics Data System (ADS)

Cetindag, Semih; Tiwari, Bishnu; Zhang, Dongyan; Yap, Yoke Khin; Kim, Sangil; Shan, Jerry W.

2017-11-01

While the alignment of electrically conductive nanowires and nanotubes by electric fields in liquid solution has been well studied, much less is known about the electro-orientation of insulating 1D particles, such as boron-nitride nanotubes (BNNTs). Here, we demonstrate for the first time the electro-orientation of individual insulating BNNTs in aqueous KCl solutions under AC fields. Comparison to theory indicates that the observed frequency response is not related to the crossover for Maxwell-Wagner interfacial polarization. Instead, the cross-over frequency in the low-frequency regime scales as the square root of solution conductivity, indicating that alignment is associated with the formation and motion of an electrical double layer (EDL), much like induced-charge electro-osmosis for a conducting particle. However, the mechanism for the formation of the EDL is presumably different for insulating particles like BNNTs as compared to conductors. By varying the surface charge of the particle by changing pH, we show that the alignment rate increases with increasing surface charge, and is likely a result of counter-ion migration and EDL polarization under the influence of applied electric field. Thus, particle surface charge (large Dukhin number) is believed to play a vital role in the electro-orientation of insulating particles in aqueous solutions. NSF CBET-1604931 and NSF DMR-1261910.

Frequency Dependent Electrical and Dielectric Properties of Au/P3HT:PCBM:F4-TCNQ/n-Si Schottky Barrier Diode

NASA Astrophysics Data System (ADS)

Taşçıoğlu, İ.; Tüzün Özmen, Ö.; Şağban, H. M.; Yağlıoğlu, E.; Altındal, Ş.

2017-04-01

In this study, poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester: 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (P3HT:PCBM:F4-TCNQ) organic film was deposited on n-type silicon (n-Si) substrate by spin coating method. The electrical and dielectric analysis of Au/P3HT:PCBM:F4-TCNQ/n-Si Schottky barrier diode was conducted by means of capacitance-voltage ( C- V) and conductance-voltage ( G/ ω- V) measurements in the frequency range of 10 kHz-2 MHz. The C- V- f plots exhibit fairly large frequency dispersion due to excess capacitance caused by the presence of interface states ( N ss). The values of N ss located in semiconductor bandgap at the organic film/semiconductor interface were calculated by Hill-Coleman method. Experimental results show that dielectric constant ( ɛ') and dielectric loss ( ɛ″) decrease with increasing frequency, whereas loss tangent (tan δ) remains nearly the same. The decrease in ɛ' and ɛ″ was interpreted by the theory of dielectric relaxation due to interfacial polarization. It is also observed that ac electrical conductivity ( σ ac) and electric modulus ( M' and M″) increase with increasing frequency.

Low power consumption resistance random access memory with Pt/InOx/TiN structure

NASA Astrophysics Data System (ADS)

Yang, Jyun-Bao; Chang, Ting-Chang; Huang, Jheng-Jie; Chen, Yu-Ting; Tseng, Hsueh-Chih; Chu, Ann-Kuo; Sze, Simon M.; Tsai, Ming-Jinn

2013-09-01

In this study, the resistance switching characteristics of a resistive random access memory device with Pt/InOx/TiN structure is investigated. Unstable bipolar switching behavior is observed during the initial switching cycle, which then stabilizes after several switching cycles. Analyses indicate that the current conduction mechanism in the resistance state is dominated by Ohmic conduction. The decrease in electrical conductance can be attributed to the reduction of the cross-sectional area of the conduction path. Furthermore, the device exhibits low operation voltage and power consumption.

Electric field modulated ferromagnetism in ZnO films deposited at room temperature

NASA Astrophysics Data System (ADS)

Bu, Jianpei; Liu, Xinran; Hao, Yanming; Zhou, Guangjun; Cheng, Bin; Huang, Wei; Xie, Jihao; Zhang, Heng; Qin, Hongwei; Hu, Jifan

2018-04-01

The ZnO film deposited at room temperature, which is composed of the amorphous-phase background plus a few nanograins or nanoclusters (about 1-2 nm), exhibits room temperature ferromagnetism (FM). Such FM is found to be connected with oxygen vacancies. For the Ta/ZnO/Pt device based on the medium layer ZnO deposited at room temperature, the saturation magnetization not only is modulated between high and low resistive states by electric voltage with DC loop electric current but also increases/decreases through adjusting the magnitudes of positive/negative DC sweeping voltage. Meanwhile, the voltage-controlled conductance quantization is observed in Ta/ZnO/Pt, accompanying the voltage-controlled magnetization. However, the saturation magnetization of the Ta/ZnO/Pt device becomes smaller under positive electric voltage and returns in some extent under negative electric voltage, when the DC loop electric current is not applied.

Interhemispheric Poynting Flux Associated with Postsunset Equatorial Plasma Depletions as Observed by Swarm

NASA Astrophysics Data System (ADS)

Rodriguez-Zuluaga, J.; Stolle, C.; Park, J.

2017-12-01

By using simultaneous measurements of electric and magnetic fields gathered by the Swarm constellation, the direction of both Poynting flux and field-aligned currents (FACs) associated with topside equatorial plasma depletions (EPDs) is derived. Contrary to expectations, FACs are found to flow at the walls of EPDs from one magnetic hemisphere to the other rather than flowing away from and towards the dip equator, as has been suggested so far. In turn, an interhemispheric Poynting flux is observed to flow into the E region of the hemisphere with larger ionospheric conductivity when eastward polarisation electric field is present across the depletion. However, also westward electric field is often observed but without a change in the FACs orientation, that would preserve the direction of the Poynting flux. The interhemispheric flows show seasonal, longitudinal and local time dependence. Empirical models are used to substantiate the conclusions of this study. After these new findings, the question about the location of a generator and load in terms of electromagnetic energy flow remains open.

Observations of subauroral ion drift (SAID) occurrence statistics and associated ionospheric conditions measured by the Defense Meteorological Satellite Program (DMSP) and Dynamics Explorer 2 (DE-2).

NASA Astrophysics Data System (ADS)

Landry, R. G.; Anderson, P. C.

2017-12-01

Subauroral ion drifts (SAID) are a phenomenon sometimes observed in the subauroral ionosphere in dusk to post-midnight magnetic local time sectors during magnetically active periods characterized by strong poleward electric fields that drive westward ion drifts greater than 1 km/s. SAIDs typically will span 1-2 degrees magnetic latitude and several hours in magnetic local time. SAIDs are often observed colocated with the midlatitude trough. The strong electric field can act to reduce the ionospheric conductivity further through enhanced recombination and vertical transport. The theory that SAIDs are generated by ionospheric Pedersen currents fed by ring current driven field-aligned currents (FAC) requires the decreased conductance associated with the midlatitude trough to produce the latitudinally narrow, large amplitude SAID electric field. Using Dynamics Explorer 2 (DE 2) plasma measurements of SAIDs from altitudes of 200 to 1000 km, we investigate the statistical variation of the ionospheric composition, temperature, and vertical ion drifts as a function of altitude. Using Defense Meteorological Satellite Program (DMSP) measurements from 1987-2012, we extend the empirical study at the DMSP altitude of 830 km to investigate how season, longitude, and any ionospheric preconditioning before SAID formation affect the likelihood of SAID occurrence and coincidence with FACs and ion density troughs.

Quantized Majorana conductance

NASA Astrophysics Data System (ADS)

Zhang, Hao; Liu, Chun-Xiao; Gazibegovic, Sasa; Xu, Di; Logan, John A.; Wang, Guanzhong; van Loo, Nick; Bommer, Jouri D. S.; de Moor, Michiel W. A.; Car, Diana; Op Het Veld, Roy L. M.; van Veldhoven, Petrus J.; Koelling, Sebastian; Verheijen, Marcel A.; Pendharkar, Mihir; Pennachio, Daniel J.; Shojaei, Borzoyeh; Lee, Joon Sue; Palmstrøm, Chris J.; Bakkers, Erik P. A. M.; Sarma, S. Das; Kouwenhoven, Leo P.

2018-04-01

Majorana zero-modes—a type of localized quasiparticle—hold great promise for topological quantum computing. Tunnelling spectroscopy in electrical transport is the primary tool for identifying the presence of Majorana zero-modes, for instance as a zero-bias peak in differential conductance. The height of the Majorana zero-bias peak is predicted to be quantized at the universal conductance value of 2e2/h at zero temperature (where e is the charge of an electron and h is the Planck constant), as a direct consequence of the famous Majorana symmetry in which a particle is its own antiparticle. The Majorana symmetry protects the quantization against disorder, interactions and variations in the tunnel coupling. Previous experiments, however, have mostly shown zero-bias peaks much smaller than 2e2/h, with a recent observation of a peak height close to 2e2/h. Here we report a quantized conductance plateau at 2e2/h in the zero-bias conductance measured in indium antimonide semiconductor nanowires covered with an aluminium superconducting shell. The height of our zero-bias peak remains constant despite changing parameters such as the magnetic field and tunnel coupling, indicating that it is a quantized conductance plateau. We distinguish this quantized Majorana peak from possible non-Majorana origins by investigating its robustness to electric and magnetic fields as well as its temperature dependence. The observation of a quantized conductance plateau strongly supports the existence of Majorana zero-modes in the system, consequently paving the way for future braiding experiments that could lead to topological quantum computing.

Quantized Majorana conductance.

PubMed

Zhang, Hao; Liu, Chun-Xiao; Gazibegovic, Sasa; Xu, Di; Logan, John A; Wang, Guanzhong; van Loo, Nick; Bommer, Jouri D S; de Moor, Michiel W A; Car, Diana; Op Het Veld, Roy L M; van Veldhoven, Petrus J; Koelling, Sebastian; Verheijen, Marcel A; Pendharkar, Mihir; Pennachio, Daniel J; Shojaei, Borzoyeh; Lee, Joon Sue; Palmstrøm, Chris J; Bakkers, Erik P A M; Sarma, S Das; Kouwenhoven, Leo P

2018-04-05

Majorana zero-modes-a type of localized quasiparticle-hold great promise for topological quantum computing. Tunnelling spectroscopy in electrical transport is the primary tool for identifying the presence of Majorana zero-modes, for instance as a zero-bias peak in differential conductance. The height of the Majorana zero-bias peak is predicted to be quantized at the universal conductance value of 2e 2 /h at zero temperature (where e is the charge of an electron and h is the Planck constant), as a direct consequence of the famous Majorana symmetry in which a particle is its own antiparticle. The Majorana symmetry protects the quantization against disorder, interactions and variations in the tunnel coupling. Previous experiments, however, have mostly shown zero-bias peaks much smaller than 2e 2 /h, with a recent observation of a peak height close to 2e 2 /h. Here we report a quantized conductance plateau at 2e 2 /h in the zero-bias conductance measured in indium antimonide semiconductor nanowires covered with an aluminium superconducting shell. The height of our zero-bias peak remains constant despite changing parameters such as the magnetic field and tunnel coupling, indicating that it is a quantized conductance plateau. We distinguish this quantized Majorana peak from possible non-Majorana origins by investigating its robustness to electric and magnetic fields as well as its temperature dependence. The observation of a quantized conductance plateau strongly supports the existence of Majorana zero-modes in the system, consequently paving the way for future braiding experiments that could lead to topological quantum computing.

Electrical contact arrangement for a coating process

DOEpatents

Kabagambe, Benjamin; McCamy, James W; Boyd, Donald W

2013-09-17

A protective coating is applied to the electrically conductive surface of a reflective coating of a solar mirror by biasing a conductive member having a layer of a malleable electrically conductive material, e.g. a paste, against a portion of the conductive surface while moving an electrodepositable coating composition over the conductive surface. The moving of the electrodepositable coating composition over the conductive surface includes moving the solar mirror through a flow curtain of the electrodepositable coating composition and submerging the solar mirror in a pool of the electrodepositable coating composition. The use of the layer of a malleable electrically conductive material between the conductive member and the conductive surface compensates for irregularities in the conductive surface being contacted during the coating process thereby reducing the current density at the electrical contact area.

Dynamical electrical conductivity of graphene.

PubMed

Rani, Luxmi; Singh, Navinder

2017-06-28

For graphene (a Dirac material) it has been theoretically predicted and experimentally observed that DC resistivity is proportional to T 4 when the temperature is much less than Bloch-Grüneisen temperature ([Formula: see text]) and T-linear in the opposite case ([Formula: see text]). Going beyond this case, we investigate the dynamical electrical conductivity in graphene using the powerful method of the memory function formalism. In the zero frequency regime, we obtain the above mentioned behavior which was previously obtained using the Bloch-Boltzmann kinetic equation. In the finite frequency regime, we obtain several new results: (1) the generalized Drude scattering rate, in the zero temperature limit, shows [Formula: see text] behavior at low frequencies ([Formula: see text]) and saturates at higher frequencies. We also observed the Holstein mechanism, however, with different power laws from that in the case of metals; (2) at higher frequencies, [Formula: see text], and higher temperatures [Formula: see text], we observed that the generalized Drude scattering rate is linear in temperature. In addition, several other results are also obtained. With the experimental advancement of this field, these results should be experimentally tested.

Chern structure in the Bose-insulating phase of Sr2RuO4 nanofilms

PubMed Central

Nobukane, Hiroyoshi; Matsuyama, Toyoki; Tanda, Satoshi

2017-01-01

The quantum anomaly that breaks the symmetry, for example the parity and the chirality, in the quantization leads to a physical quantity with a topological Chern invariant. We report the observation of a Chern structure in the Bose-insulating phase of Sr2RuO4 nanofilms by employing electric transport. We observed the superconductor-to-insulator transition by reducing the thickness of Sr2RuO4 single crystals. The appearance of a gap structure in the insulating phase implies local superconductivity. Fractional quantized conductance was observed without an external magnetic field. We found an anomalous induced voltage with temperature and thickness dependence, and the induced voltage exhibited switching behavior when we applied a magnetic field. We suggest that there was fractional magnetic-field-induced electric polarization in the interlayer. These anomalous results are related to topological invariance. The fractional axion angle Θ = π/6 was determined by observing the topological magneto-electric effect in the Bose-insulating phase of Sr2RuO4 nanofilms. PMID:28112269

Concentration and Mobility of Electrically-Conducting Defects in Olivine

NASA Astrophysics Data System (ADS)

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

2002-12-01

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

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 ˜855˜1601 K and at 1.0 GPa. In addition, the electrical conductivity of quartz along the c axis has been studied at 1.0-3.0 GPa. The impedance arcs representing bulk conductivity occur in the frequency range of 103-106 Hz, and the electrical responses of the interface between the sample and the electrode occur in the 0.1˜103 Hz range. The pressure has a weak effect on the electrical conductivity. The electrical conductivity experiences no abrupt change near the α - β 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.

Sintering temperature effect on electrical and thermal properties of Zn1-xAlxO as thermoelectric material candidate

NASA Astrophysics Data System (ADS)

Fajarin, Rindang; Rahel, Amelthia; Widyastuti

2018-04-01

Thermoelectric is a device to convert residual heat energy into electricity. Electrical and thermal properties of constituent material determine thermoelectric efficiency. One of metal oxides, namely zinc oxide (ZnO), is highly stable in a large temperature range, non-toxic, low cost and eco-friendly, has potential application as thermoelectric at high temperature. The aims of this study are to synthesize Zn0.98Al0.02O by coprecipitation method using ZnO and Al2O3 powders as raw materials, and to investigate the effect of sintering temperatures (at 700, 800, 900, and 950°C) on the electrical and thermal properties of the material. The sample products were analyzed by x-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive x-ray (EDX) measurements to identify phase content, to observe particle morphology and to analyze distribution of elements in the sample, respectively. LCR meter was conducted to study electrical measurements of the samples. Further, thermal properties of the samples were analyzed by TGA measurements. The data show that Al3+ ions have been successfully doped into ZnO crystal lattice and they tend to increase the electrical conductivity of the samples. The sintered Zn0.98Al0.02O sample at 900°C has the highest conductivity value (4.53 × 10-4 S/m) compared to the others. It is relatively stable at high temperature, and thus, it can be used as one promising candidate for thermoelectric material at high temperature.

Conductivity detection for monitoring mixing reactions in microfluidic devices.

PubMed

Liu, Y; Wipf, D O; Henry, C S

2001-08-01

A conductivity detector was coupled to poly(dimethylsiloxane)-glass capillary electrophoresis microchips to monitor microfluidic flow. Electroosmotic flow was investigated with both conductivity detection (CD) and the current monitoring method. No significant variation was observed between these methods, but CD showed a lower relative standard deviation. Gradient mixing experiments were employed to investigate the relationship between the electrolyte conductivity and the electrolyte concentration. A good linear response of conductivity to concentration was obtained for solutions whose difference in concentrations were less than 27 mM. The new system holds great promise for precision mixing in microfluidic devices using electrically driven flows.

Capillary zone electrophoresis-mass spectrometer interface

DOEpatents

D'Silva, Arthur

1996-08-06

A device for providing equal electrical potential between two loci unconnected by solid or liquid electrical conducts is provided. The device comprises a first electrical conducting terminal, a second electrical conducting terminal connected to the first terminal by a rigid dielectric structure, and an electrically conducting gas contacting the first and second terminals. This device is particularly suitable for application in the electrospray ionization interface between a capillary zone electrophoresis apparatus and a mass spectrometer.

An electrical method for the measurement of the thermal and electrical conductivity of reduced graphene oxide nanostructures.

PubMed

Schwamb, Timo; Burg, Brian R; Schirmer, Niklas C; Poulikakos, Dimos

2009-10-07

This paper introduces an electrical four-point measurement method enabling thermal and electrical conductivity measurements of nanoscale materials. The method was applied to determine the thermal and electrical conductivity of reduced graphene oxide flakes. The dielectrophoretically deposited samples exhibited thermal conductivities in the range of 0.14-2.87 W m(-1) K(-1) and electrical conductivities in the range of 6.2 x 10(2)-6.2 x 10(3) Omega(-1) m(-1). The measured properties of each flake were found to be dependent on the duration of the thermal reduction and are in this sense controllable.

DC conductivity of twisted bilayer graphene: Angle-dependent transport properties and effects of disorder

NASA Astrophysics Data System (ADS)

Andelković, M.; Covaci, L.; Peeters, F. M.

2018-03-01

The in-plane dc conductivity of twisted bilayer graphene is calculated using an expansion of the real-space Kubo-Bastin conductivity in terms of Chebyshev polynomials. We investigate within a tight-binding approach the transport properties as a function of rotation angle, applied perpendicular electric field, and vacancy disorder. We find that for high-angle twists, the two layers are effectively decoupled, and the minimum conductivity at the Dirac point corresponds to double the value observed in monolayer graphene. This remains valid even in the presence of vacancies, hinting that chiral symmetry is still preserved. On the contrary, for low twist angles, the conductivity at the Dirac point depends on the twist angle and is not protected in the presence of disorder. Furthermore, for low angles and in the presence of an applied electric field, we find that the chiral boundary states emerging between AB and BA regions contribute to the dc conductivity, despite the appearance of localized states in the AA regions. The results agree qualitatively with recent transport experiments in low-angle twisted bilayer graphene.

Modeling conduction in host-graft interactions between stem cell grafts and cardiomyocytes.

PubMed

Chen, Michael Q; Yu, Jin; Whittington, R Hollis; Wu, Joseph C; Kovacs, Gregory T A; Giovangrandi, Laurent

2009-01-01

Cell therapy has recently made great strides towards aiding heart failure. However, while transplanted cells may electromechanically integrate into host tissue, there may not be a uniform propagation of a depolarization wave between the heterogeneous tissue boundaries. A model using microelectrode array technology that maps the electrical interactions between host and graft tissues in co-culture is presented and sheds light on the effects of having a mismatch of conduction properties at the boundary. Skeletal myoblasts co-cultured with cardiomyocytes demonstrated that conduction velocity significantly decreases at the boundary despite electromechanical coupling. In an attempt to improve the uniformity of conduction with host cells, differentiating human embryonic stem cells (hESC) were used in co-culture. Over the course of four to seven days, synchronous electrical activity was observed at the hESC boundary, implying differentiation and integration. Activity did not extend far past the boundary, and conduction velocity was significantly greater than that of the host tissue, implying the need for other external measures to properly match the conduction properties between host and graft tissue.

Multiple electrical phase transitions in Al substituted barium hexaferrite

NASA Astrophysics Data System (ADS)

Kumar, Sunil; Supriya, Sweety; Kar, Manoranjan

2017-12-01

Barium hexaferrite is known to be a very good ferromagnetic material. However, it shows very good dielectric properties, i.e., the dielectric constant is comparable to that of the ferroelectric material. However, its crystal symmetry does not allow it to be a ferroelectric material. Hence, the electrical properties have revived the considerable research interest on these materials, not only for academic interest, but also for technological applications. There are a few reports on temperature dependent dielectric behavior of these materials. However, the exact cause of dielectric as well as electrical conductivity is yet to be established. Hence, Al (very good conducting material) substituted barium hexaferrite (BaFe12-xAlxO19, x = 0.0-4.0) has been prepared by following the modified sol-gel method to understand the ac and DC electrical properties of these materials. The crystal structure and parameters have been studied by employing the XRD and FTIR techniques. There are two transition temperatures, which have been observed in the temperature dependent ac dielectric and DC resistivity measurement. The response of dielectric behaviors to temperature is similar to that of the ferroelectric material; however, the dielectric polarization is due to the polaron hopping, which is evident from the DC resistivity analysis. Hence, the present observations lead to understand the electrical properties of barium hexaferrite. The frequency dependent dielectric dispersion can be understood by the modified Debye model. More interestingly, the dielectric constant decreases and DC resistivity increases with the increase in the Al concentration, which has the correlation between bond length modifications in the crystal due to substitution.

Azobenzenes as light-controlled molecular electronic switches in nanoscale metal-molecule-metal junctions.

PubMed

Mativetsky, Jeffrey M; Pace, Giuseppina; Elbing, Mark; Rampi, Maria A; Mayor, Marcel; Samorì, Paolo

2008-07-23

Conductance switching associated with the photoisomerization of azobenzene-based (Azo) molecules was observed in nanoscopic metal-molecule-metal junctions. The junctions were formed by using a conducting atomic force microscope (C-AFM) approach, where a metallic AFM tip was used to electrically contact a gold-supported Azo self-assembled monolayer. The measured 30-fold increase in conductance is consistent with the expected decrease in tunneling barrier length resulting from the conformational change of the Azo molecule.

Enhancement of optical transmittance and electrical resistivity of post-annealed ITO thin films RF sputtered on Si

NASA Astrophysics Data System (ADS)

Ali, Ahmad Hadi; Hassan, Zainuriah; Shuhaimi, Ahmad

2018-06-01

This paper reports on the enhancement of optical transmittance and electrical resistivity of indium tin oxide (ITO) transparent conductive oxides (TCO) deposited by radio frequency (RF) sputtering on Si substrate. Post-annealing was conducted on the samples at temperature ranges of 500-700 °C. From X-ray diffraction analysis (XRD), ITO (2 2 2) peak was observed after post-annealing indicating crystallization phase of the films. From UV-vis measurements, the ITO thin film shows highest transmittance of more than 90% at post-annealing temperature of 700 °C as compared to the as-deposited thin films. From atomic force microscope (AFM), the surface roughness becomes smoother after post-annealing as compared to the as-deposited. The lowest electrical resistivity for ITO sample is 6.68 × 10-4 Ω cm after post-annealed at 700 °C that are contributed by high carrier concentration and mobility. The improved structural and surface morphological characteristics helps in increasing the optical transmittance and reducing the electrical resistivity of the ITO thin films.

Influence of Carbon Nanotube Clustering on Mechanical and Electrical Properties of Cement Pastes

PubMed Central

Jang, Sung-Hwan; Kawashima, Shiho; Yin, Huiming

2016-01-01

Given the continued challenge of dispersion, for practical purposes, it is of interest to evaluate the impact of multi-walled carbon nanotubes (MWCNTs) at different states of clustering on the eventual performance properties of cement paste. This study evaluated the clustering of MWCNTs and the resultant effect on the mechanical and electrical properties when incorporated into cement paste. Cement pastes containing different concentrations of MWCNTs (up to 0.5% by mass of cement) with/without surfactant were characterized. MWCNT clustering was assessed qualitatively in an aqueous solution through visual observation, and quantitatively in cement matrices using a scanning electron microscopy technique. Additionally, the corresponding 28-day compressive strength, tensile strength, and electrical conductivity were measured. Results showed that the use of surfactant led to a downward shift in the MWCNT clustering size distribution in the matrices of MWCNT/cement paste, indicating improved dispersion of MWCNTs. The compressive strength, tensile strength, and electrical conductivity of the composites with surfactant increased with MWCNT concentration and were higher than those without surfactant at all concentrations. PMID:28773348

Ba doped Fe3O4 nanocrystals: Magnetic field and temperature tuning dielectric and electrical transport

NASA Astrophysics Data System (ADS)

Dutta, Papia; Mandal, S. K.; Nath, A.

2018-05-01

Nanocrystalline BaFe2O4 has been prepared through low temperature pyrophoric reaction method. The structural, dielectric and electrical transport properties of BaFe2O4 are investigated in detail. AC electrical properties have been studied over the wide range of frequencies with applied dc magnetic fields and temperatures. The value of impedance is found to increase with increase in magnetic field attributing the magnetostriction property of the sample. The observed value of magneto-impedance and magnetodielectric is found to ∼32% and ∼33% at room temperature. Nyquist plots have been fitted using resistance-capacitor circuits at different magnetic fields and temperatures showing the dominant role of grain and grain boundaries of the sample. Metal-semiconductor transition ∼403 K has been discussed in terms of delocalized and localized charge carrier.We have estimated activation energy using Arrhenius relation indicating temperature dependent electrical relaxation process in the system. Ac conductivity follow a Jonscher’s single power law indicating the large and small polaronic hopping conduction mechanism in the system.

Fourier analysis of polar cap electric field and current distributions

NASA Technical Reports Server (NTRS)

Barbosa, D. D.

1984-01-01

A theoretical study of high-latitude electric fields and currents, using analytic Fourier analysis methods, is conducted. A two-dimensional planar model of the ionosphere with an enhanced conductivity auroral belt and field-aligned currents at the edges is employed. Two separate topics are treated. A field-aligned current element near the cusp region of the polar cap is included to investigate the modifications to the convection pattern by the east-west component of the interplanetary magnetic field. It is shown that a sizable one-cell structure is induced near the cusp which diverts equipotential contours to the dawnside or duskside, depending on the sign of the cusp current. This produces characteristic dawn-dusk asymmetries to the electric field that have been previously observed over the polar cap. The second topic is concerned with the electric field configuration obtained in the limit of perfect shielding, where the field is totally excluded equatorward of the auroral oval. When realistic field-aligned current distributions are used, the result is to produce severely distorted, crescent-shaped equipotential contours over the cap. Exact, analytic formulae applicable to this case are also provided.

Electrical condition monitoring method for polymers

DOEpatents

Watkins, Jr., Kenneth S.; Morris, Shelby J [Hampton, VA; Masakowski, Daniel D [Worcester, MA; Wong, Ching Ping [Duluth, GA; Luo, Shijian [Boise, ID

2008-08-19

An electrical condition monitoring method utilizes measurement of electrical resistivity of an age sensor made of a conductive matrix or composite disposed in a polymeric structure such as an electrical cable. The conductive matrix comprises a base polymer and conductive filler. The method includes communicating the resistivity to a measuring instrument and correlating resistivity of the conductive matrix of the polymeric structure with resistivity of an accelerated-aged conductive composite.

Carbon-Nanotube Conductive Layers for Thin-Film Solar Cells

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A.

2005-01-01

Thin, transparent layers comprising mats of carbon nanotubes have been proposed for providing lateral (that is, inplane) electrical conductivities for collecting electric currents from the front surfaces of the emitter layers of thin-film solar photovoltaic cells. Traditionally, thin, semitransparent films of other electrically conductive materials (usually, indium tin oxide, zinc oxide, or cadmium sulfide) have been used for this purpose. As in the cases of the traditional semitransparent conductive films, the currents collected by the nanotube layers would, in turn, be further collected by front metal contact stripes. Depending on details of a specific solar-cell design, the layer of carbon nanotubes would be deposited in addition to, or instead of, a semitransparent layer of one of these traditional conductive materials (see figure). The proposal is expected to afford the following advantages: The electrical conductivity of the carbon- nanotube layer would exceed that of the corresponding semitransparent layer of traditional electrically conductive material. The greater electrical conductivity of the carbon-nanotube layer would make it possible to retain adequate lateral electrical conductivity while reducing the thickness of, or eliminating entirely, the traditional semitransparent conductive layer. As a consequence of thinning or elimination of the traditional semitransparent conductive layer, less light would be absorbed, so that more of the incident light would be available for photovoltaic conversion. The greater electrical conductivity of the carbon-nanotube layer would make it possible to increase the distance between front metal contact stripes, in addition to (or instead of) thinning or eliminating the layer of traditional semitransparent conductive material. Consequently, the fraction of solar-cell area shadowed by front metal contact stripes would be reduced again, making more of the incident light available for photovoltaic conversion. The electrical conductivities of individual carbon nanotubes can be so high that the mat of carbon nanotubes could be made sparse enough to be adequately transparent while affording adequate lateral electrical conductivity of the mat as a whole. The thickness of the nanotube layer would be chosen so that the layer would contribute significant lateral electrical conductivity, yet would be as nearly transparent as possible to incident light. A typical thickness for satisfying these competing requirements is expected to lie between 50 and 100 nm. The optimum thickness must be calculated by comparing the lateral electrical conductivity, the distance between front metal stripes, and the amount of light lost by absorption in the nanotube layer.

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.

Electrical conductivity of the Cascadia subduction zone and implications for the plate interface

NASA Astrophysics Data System (ADS)

Livelybrooks, D.; Bedrosian, P.; Egbert, G. D.; Key, K.; Schultz, A.; Parris, B. A.; Yang, B.; Bowles-martinez, E.

2016-12-01

The Magnetotelluric Observations of Cascadia using a Huge Array (MOCHA) experiment resulted in the collection of 146 amphibious, long-period magnetotelluric stations acquired between 2012 and 2014. These data, supplemented with the previously-acquired CAFÉ, EMSLAB, SWORMT and EarthScope (MT) Transportable Array stations, have been interpreted to provide electrical conductivity models of Cascadia spanning from the trench eastward through the Cascades, and extending to about 150km depth. We have a particular interest in understanding the roles electrically-conductive, aqueous fluids play in Cascadia subduction processes at or near the plate interface, thus inversions of data are predisposed to accommodate an initially-resistive (McCrory et al. 2014) slab. Beginning at the mantle wedge corner, 3-D inversions reveal significant, latitudinal variation in the conductivity, with enhanced conductivity at 47oN and south at 42oN. Two-dimensional inversions at 44.5oN allowing for a step discontinuity at the Moho give two distinct zones of conductance, one at the MWC tip (c.f. Furukowa, 2009) and another further down-dip, with a conductivity `plume' directed eastwards. At depths of between 20-25km we image a latitudinally-discontinuous resistive lower crust immediately overlying resistive subducted slab. This implies a lack of free fluids near the plate interface. Krogstad et al. (2016) have analyzed historic uplift data and can model the presence of an inboard `secondary locked zone' near 44.5oN. One explanation for both observations—a down-dip, `pinned interface' that is shielding the traditionally-modeled off-shore locked zone from stress accumulation, would explain the paucity of seismicity observed off the north-central Oregon coast during the four-year Cascadia Initiative. At coastal longitudes a narrow, supra-slab conductive zone is imaged at 22km depth with a southern termination at 45oN. It is notable that some researchers place the inboard boundary of the (mostly off-shore) seismogenic zone as moving eastward and on-shore beginning north of 45oN. The thinner Coast Range crust is imaged as generally more conductive north of 46oN, which is consistent with higher permeabilities ascribed to the Crescent formation.

Origin of temperature dependent conduction of current from n-4H-SiC into silicon dioxide films at high electric fields

NASA Astrophysics Data System (ADS)

Xiang, An; Xu, Xingliang; Zhang, Lin; Li, Zhiqiang; Li, Juntao; Dai, Gang

2018-02-01

The conduction of current from n-4H-SiC into pyrogenic and dry oxidized films is studied. Anomalous current conduction was observed at a high electric field above 8 MV/cm for dry oxidized metal-oxide-semiconductor (MOS) capacitors, which cannot be interpreted in the framework of pure Fowler-Nordheim tunneling. The temperature-dependent current measurement and density of interface trap estimated from the hi-lo method for the SiO2/4H-SiC interface revealed that the combined current conduction of Fowler-Nordheim and Poole-Frenkel emission is responsible for the current conduction in both pyrogenic and dry oxidized MOS capacitors. Furthermore, the origin of temperature dependent current conduction is the Poole-Frenkel emission via the carbon pair defect trap level at 1.3 eV below the conduction band edge of SiO2. In addition, with the dry oxidized capacitors, the enhanced temperature dependent current above 8 MV/cm is attributed to the PF emission via a trap level at 1.47 eV below the conduction band edge of SiO2, which corresponds to another configuration of a carbon pair defect in SiO2 films.

Quasi-ballistic Electronic Thermal Conduction in Metal Inverse Opals.

PubMed

Barako, Michael T; Sood, Aditya; Zhang, Chi; Wang, Junjie; Kodama, Takashi; Asheghi, Mehdi; Zheng, Xiaolin; Braun, Paul V; Goodson, Kenneth E

2016-04-13

Porous metals are used in interfacial transport applications that leverage the combination of electrical and/or thermal conductivity and the large available surface area. As nanomaterials push toward smaller pore sizes to increase the total surface area and reduce diffusion length scales, electron conduction within the metal scaffold becomes suppressed due to increased surface scattering. Here we observe the transition from diffusive to quasi-ballistic thermal conduction using metal inverse opals (IOs), which are metal films that contain a periodic arrangement of interconnected spherical pores. As the material dimensions are reduced from ∼230 nm to ∼23 nm, the thermal conductivity of copper IOs is reduced by more than 57% due to the increase in surface scattering. In contrast, nickel IOs exhibit diffusive-like conduction and have a constant thermal conductivity over this size regime. The quasi-ballistic nature of electron transport at these length scales is modeled considering the inverse opal geometry, surface scattering, and grain boundaries. Understanding the characteristics of electron conduction at the nanoscale is essential to minimizing the total resistance of porous metals for interfacial transport applications, such as the total electrical resistance of battery electrodes and the total thermal resistance of microscale heat exchangers.

Accelerated test design

NASA Technical Reports Server (NTRS)

Mcdermott, P. P.

1980-01-01

The design of an accelerated life test program for electric batteries is discussed. A number of observations and suggestions on the procedures and objectives for conducting an accelerated life test program are presented. Equations based on nonlinear regression analysis for predicting the accelerated life test parameters are discussed.

Branching Patterns and Stepped Leaders in an Electric-Circuit Model for Creeping Discharge

NASA Astrophysics Data System (ADS)

Hidetsugu Sakaguchi,; Sahim M. Kourkouss,

2010-06-01

We construct a two-dimensional electric circuit model for creeping discharge. Two types of discharge, surface corona and surface leader, are modeled by a two-step function of conductance. Branched patterns of surface leaders surrounded by the surface corona appear in numerical simulation. The fractal dimension of branched discharge patterns is calculated by changing voltage and capacitance. We find that surface leaders often grow stepwise in time, as is observed in lightning leaders of thunder.

Hydroxyapatite Nanowire-Based All-Weather Flexible Electrically Conductive Paper with Superhydrophobic and Flame-Retardant Properties.

PubMed

Chen, Fei-Fei; Zhu, Ying-Jie; Xiong, Zhi-Chao; Dong, Li-Ying; Chen, Feng; Lu, Bing-Qiang; Yang, Ri-Long

2017-11-15

How to survive under various harsh working conditions is a key challenge for flexible electronic devices because their performances are always susceptible to environments. Herein, we demonstrate the novel design and fabrication of a new kind of the all-weather flexible electrically conductive paper based on ultralong hydroxyapatite nanowires (HNs) with unique combination of the superhydrophobic surface, electrothermal effect, and flame retardancy. The superhydrophobic surface with water repellency stabilizes the electrically conductive performance of the paper in water. For example, the electrical current through the superhydrophobic paper onto which water droplets are deposited shows a little change (0.38%), and the electrical performance is steady as well even when the paper is immersed in water for 120 s (just 3.65% change). In addition, the intrinsic electrothermal effect of the electrically conductive paper can efficiently heat the paper to reach a high temperature, for example, 224.25 °C, within 10 s. The synergistic effect between the electrothermal effect and superhydrophobic surface accelerates the melting and removal of ice on the heated electrically conductive paper. Deicing efficiency of the heated superhydrophobic electrically conductive paper is ∼4.5 times that of the unheated superhydrophobic electrically conductive paper and ∼10.4 times that of the heated superhydrophilic paper. More importantly, benefiting from fire-resistant ultralong HNs, thermally stable Ketjen black, and Si-O backbone of poly(dimethylsiloxane), we demonstrate the stable and continuous service of the as-prepared electrically conductive paper in the flame for as long as 7 min. The electrical performance of the electrically conductive paper after flame treatment can maintain as high as 90.60% of the original value. The rational design of the electrically conductive paper with suitable building materials and structure demonstrated here will give an inspiration for the development of new kinds of all-weather flexible electronic devices that can work under harsh conditions.

Evaluation of Soft Tissue Sarcoma Tumors Electrical Conductivity Anisotropy Using Diffusion Tensor Imaging for Numerical Modeling on Electroporation.

PubMed

Ghazikhanlou-Sani, K; Firoozabadi, S M P; Agha-Ghazvini, L; Mahmoodzadeh, H

2016-06-01

There is many ways to assessing the electrical conductivity anisotropy of a tumor. Applying the values of tissue electrical conductivity anisotropy is crucial in numerical modeling of the electric and thermal field distribution in electroporation treatments. This study aims to calculate the tissues electrical conductivity anisotropy in patients with sarcoma tumors using diffusion tensor imaging technique. A total of 3 subjects were involved in this study. All of patients had clinically apparent sarcoma tumors at the extremities. The T1, T2 and DTI images were performed using a 3-Tesla multi-coil, multi-channel MRI system. The fractional anisotropy (FA) maps were performed using the FSL (FMRI software library) software regarding the DTI images. The 3D matrix of the FA maps of each area (tumor, normal soft tissue and bone/s) was reconstructed and the anisotropy matrix was calculated regarding to the FA values. The mean FA values in direction of main axis in sarcoma tumors were ranged between 0.475-0.690.  With assumption of isotropy of the electrical conductivity, the FA value of electrical conductivity at each X, Y and Z coordinate axes would be equal to 0.577. The gathered results showed that there is a mean error band of 20% in electrical conductivity, if the electrical conductivity anisotropy not concluded at the calculations. The comparison of FA values showed that there is a significant statistical difference between the mean FA value of tumor and normal soft tissues (P<0.05). DTI is a feasible technique for the assessment of electrical conductivity anisotropy of tissues.  It is crucial to quantify the electrical conductivity anisotropy data of tissues for numerical modeling of electroporation treatments.

Pulsed Laser Deposition of BaCe(sub 0.85)Y(sub 0.15)0(sub 3) FILMS

NASA Technical Reports Server (NTRS)

Dynys, F. W.; Sayir, A.

2006-01-01

Pulsed laser deposition has been used to grow nanostructured BaCe(sub 0.85)Y(sub 0.15)0(sub 3) films. The objective is to enhance protonic conduction by reduction of membrane thickness. Sintered samples and laser targets were prepared by sintering BaCe(sub 0.85)Y(sub 0.15)O(sub 3) powders derived by solid state synthesis. Films 2 to 6 m thick were deposited by KrF excimer laser on Si and porous Al2O3 substrates. Nanocrystalline films were fabricated at deposition temperatures of 600-800 C deg at O2 pressure of 30 mTorr and laser fluence of 1.2 J/cm square. Films were characterized by x-ray diffraction, scanning electron microscopy and electrical impedance spectroscopy. Dense single phase BaCe(sub 0.85)Y((sub 0.15) 0(sub 3) films with a columnar growth morphology is observed, preferred crystal growth was found to be dependent upon deposition temperature and substrate type. Electrical conductivity of bulk samples produced by solid state sintering and thin film samples were measured over a temperature range of 100 C deg to 900 C deg in moist argon. Electrical conduction of the fabricated films was 1 to 4 orders of magnitude lower than the sintered bulk samples. With respect to the film growth direction, activation energy for electrical conduction is 3 times higher in the perpendicular direction than the parallel direction.

Grain boundary dominated electrical conductivity in ultrananocrystalline diamond

NASA Astrophysics Data System (ADS)

Wiora, Neda; Mertens, Michael; Brühne, Kai; Fecht, Hans-Jörg; Tran, Ich C.; Willey, Trevor; van Buuren, Anthony; Biener, Jürgen; Lee, Jun-Sik

2017-10-01

N-type electrically conductive ultrananocrystalline diamond (UNCD) films were deposited using the hot filament chemical vapor deposition technique with a gas mixture of H2, CH4 and NH3. Depending on the deposition temperature and ammonia feed gas concentration, which serves as a nitrogen source, room temperature electrical conductivities in the order of 10-2 to 5 × 101 S/cm and activation energies in the meV range were achieved. In order to understand the origin of the enhanced electrical conductivity and clarify the role of ammonia addition to the process gas, a set of UNCD films was grown by systematically varying the ammonia gas phase concentration. These samples were analyzed with respect to their morphology and electrical properties as well as their carbon and nitrogen bonding environments. Temperature dependent electrical conductivity measurements (300-1200 K) show that the electrical conductivity of the samples increases with temperature. The near edge x-ray absorption fine structure measurements reveal that the electrical conductivity of the UNCD films does not correlate directly with ammonia addition, but depends on the total amount of sp2 bonded carbon in the deposited films.

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-π' 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-π' interactions in achieving low electrical percolation in PA6/ABS+MWNT composites.

Effect of the mechanical deformation on the electrical properties of the polymer/CNT fiber

NASA Astrophysics Data System (ADS)

Cho, Hyun Woo; Sung, Bong June; Nano-Bio Computational Chemistry Laboratory Team

2014-03-01

We elucidate the effect of the mechanical deformation on the electrical properties of the polymer/CNT fiber. The conductive polymer fiber has drawn a great attention for its potential application to a stretchable electronics such as wearable devices and artificial muscles, etc. However, the electrical conductivity of the polymer-based stretchable electronics decreases significantly during the deformation, which may limit the applicability of the polymer/CNT fiber for the stretchable electronics. Moreover, its physical origin for the decrease in electrical conductivity has not been explained clearly. In this work, we employ a coarse-grained model for the polymer/CNT fiber, and we calculate the electric conductivity using global tunneling network (GTN) model. We show that the electric conductivity decreases during the elongation of the polymer/CNT fiber. We also find using critical path approximation (CPA) that the structure of the electrical network of the CNTs changes collectively during the elongation of the fiber, which is strongly responsible for the reduction of the electrical conductivity of the polymer/CNT fiber.

Hot wire needle probe for thermal conductivity detection

DOEpatents

Condie, Keith Glenn; Rempe, Joy Lynn; Knudson, Darrell lee; Daw, Joshua Earl; Wilkins, Steven Curtis; Fox, Brandon S.; Heng, Ban

2015-11-10

An apparatus comprising a needle probe comprising a sheath, a heating element, a temperature sensor, and electrical insulation that allows thermal conductivity to be measured in extreme environments, such as in high-temperature irradiation testing. The heating element is contained within the sheath and is electrically conductive. In an embodiment, the heating element is a wire capable of being joule heated when an electrical current is applied. The temperature sensor is contained within the sheath, electrically insulated from the heating element and the sheath. The electrical insulation electrically insulates the sheath, heating element and temperature sensor. The electrical insulation fills the sheath having electrical resistance capable of preventing electrical conduction between the sheath, heating element, and temperature sensor. The control system is connected to the heating element and the temperature sensor.

Maximum on the Electrical Conductivity Polytherm of Molten TeCl4

NASA Astrophysics Data System (ADS)

Salyulev, Alexander B.; Potapov, Alexei M.

2017-05-01

The electrical conductivity of molten TeCl4 was measured up to 761K, i.e. 106 degrees above the normal boiling point of the salt. For the first time it was found that TeCl4 electrical conductivity polytherm has a maximum. It was recorded at 705K (κmax=0.245 Sm/cm), whereupon the conductivity decreases as the temperature rises. The activation energy of electrical conductivity was calculated.

Low-frequency electrical properties of peat

NASA Astrophysics Data System (ADS)

Comas, Xavier; Slater, Lee

2004-12-01

Electrical resistivity/induced polarization (0.1-1000 Hz) and vertical hydraulic conductivity (Kv) measurements of peat samples extracted from different depths (0-11 m) in a peatland in Maine were obtained as a function of pore fluid conductivity (σw) between 0.001 and 2 S/m. Hydraulic conductivity increased with σw (Kv ∝ σw0.3 between 0.001 and 2 S/m), indicating that pore dilation occurs due to the reaction of NaCl with organic functional groups as postulated by previous workers. Electrical measurements were modeled by assuming that "bulk" electrolytic conduction through the interconnected pore space and surface conduction in the electrical double layer (EDL) at the organic sediment-fluid interface act in parallel. This analysis suggests that pore space dilation causes a nonlinear relationship between the "bulk" electrolytic conductivity (σel) and σw (σel ∝ σw1.3). The Archie equation predicts a linear dependence of σel on σw and thus appears inappropriate for organic sediments. Induced polarization (IP) measurements of the imaginary part (σ″surf) of the surface conductivity (σ*surf) show that σ″surf is greater and more strongly σw-dependent (σ″surf ∝ σw0.5 between 0.001 and 2 S/m) than observed for inorganic sediments. By assuming a linear relationship between the real (σ'surf) and the imaginary part (σ″surf) of the surface conductivity, we develop an empirical model relating the resistivity and induced polarization measurements to σw in peat. We demonstrate the use of this model to predict (a) σw and (b) the change in Kv due to an incremental change in σw from resistivity and induced polarization measurements on organic sediments. Our study has implications for noninvasive geophysical characterization of σw and Kv with potential to benefit studies of carbon cycling and greenhouse gas fluxes as well as nutrient supply dynamics in peatlands.

Fractional calculus applied to the analysis of spectral electrical conductivity of clay-water system.

PubMed

Korosak, Dean; Cvikl, Bruno; Kramer, Janja; Jecl, Renata; Prapotnik, Anita

2007-06-16

The analysis of the low-frequency conductivity spectra of the clay-water mixtures is presented. The frequency dependence of the conductivity is shown to follow the power-law with the exponent n=0.67 before reaching the frequency-independent part. When scaled with the value of the frequency-independent part of the spectrum the conductivity spectra for samples at different water content values are shown to fit to a single master curve. It is argued that the observed conductivity dispersion is a consequence of the anomalously diffusing ions in the clay-water system. The fractional Langevin equation is then used to describe the stochastic dynamics of the single ion. The results indicate that the experimentally observed dielectric properties originate in anomalous ion transport in clay-water system characterized with time-dependent diffusion coefficient.

Reliability Studies of Ceramic Capacitors.

DTIC Science & Technology

1984-10-01

Virginia Polytechnic BaTiO 3 Ispecimens with variable composition, density and grain size to be used to make carrier concentration, mobility, thermoelectric ...low fields, observed steady-state electrical behavior will be controlled by the bulk properties of the insulator, the second phase of the conduction...carrier mobility E =applied field Note that bulk properties of the Insulator control the conduction process. From this equation it can be seen that a

Dielectric properties of metallic alloy FeCoZr-dielectric ceramic PZT nanostructures prepared by ion sputtering in vacuum conditions

NASA Astrophysics Data System (ADS)

Boiko, O.

2018-05-01

The main objective of the research was investigation of dielectric properties of (FeCoZr)x(PZT)(100-x) granular nanocomposites and determination the influence of isochronous annealing in temperatures of 398 K-573 K on them. The impedance spectroscopy methodology was used. The measurements of electrical parameters, such as: phase shift angle φ, dielectric loss factor tgδ, capacity C and conductivity σ of (FeCoZr)x(PZT)(100-x) nanocomposites have been performed. Frequency dependencies of these parameters were obtained for the ambient temperature range 98 K-373 K for the frequencies ranging from 50 Hz to 105 Hz. It was established, that the conductivity σ of the tested materials before the percolation threshold demonstrates non-linear dependence on frequency. Furthermore, it increases when the ambient temperature is increasing, which indicates a dielectric type of the material. The two types of electrical conduction: capacitive (phase shift angle φ takes negative values) and inductive (φ takes positive values) have been observed. It was concluded that the hopping conductivity dominated in the nanocomposites. Voltage and current resonances phenomena are observed in the materials. The isochronous annealing intensifies the dielectric properties of (FeCoZr)x(PZT)(100-x) nanocomposites.

Effect of particle size on band gap and DC electrical conductivity of TiO2 nanomaterial

NASA Astrophysics Data System (ADS)

Avinash, B. S.; Chaturmukha, V. S.; Jayanna, H. S.; Naveen, C. S.; Rajeeva, M. P.; Harish, B. M.; Suresh, S.; Lamani, Ashok R.

2016-05-01

Materials reduced to the Nano scale can exhibit different properties compared to what they exhibit on a micro scale, enabling unique applications. When TiO2 is reduced to Nano scale it shows unique properties, of which the electrical aspect is highly important. This paper presents increase in the energy gap and decrease in conductivity with decrease in particle size of pure Nano TiO2 synthesized by hydrolysis and peptization of titanium isopropoxide. Aqueous solution with various pH and peptizing the resultant suspension will form Nano TiO2 at different particle sizes. As the pH of the solution is made acidic reduction in the particle size is observed. And it is confirmed from XRD using Scherer formula and SEM, as prepared samples are studied for UV absorbance, and DC conductivity from room temperature to 400°C. From the tauc plot it was observed, and calculated the energy band gap increases as the particle size decreases and shown TiO2 is direct band gap. From Arrhenius plot clearly we encountered, decrease in the conductivity for the decrease in particle size due to hopping of charge carriers and it is evident that, we can tailor the band gap by varying particle size.

Complex quantum transport in a modulation doped strained Ge quantum well heterostructure with a high mobility 2D hole gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morrison, C., E-mail: c.morrison.2@warwick.ac.uk; Casteleiro, C.; Leadley, D. R.

The complex quantum transport of a strained Ge quantum well (QW) modulation doped heterostructure with two types of mobile carriers has been observed. The two dimensional hole gas (2DHG) in the Ge QW exhibits an exceptionally high mobility of 780 000 cm{sup 2}/Vs at temperatures below 10 K. Through analysis of Shubnikov de-Haas oscillations in the magnetoresistance of this 2DHG below 2 K, the hole effective mass is found to be 0.065 m{sub 0}. Anomalous conductance peaks are observed at higher fields which deviate from standard Shubnikov de-Haas and quantum Hall effect behaviour due to conduction via multiple carrier types. Despite this complex behaviour,more » analysis using a transport model with two conductive channels explains this behaviour and allows key physical parameters such as the carrier effective mass, transport, and quantum lifetimes and conductivity of the electrically active layers to be extracted. This finding is important for electronic device applications, since inclusion of highly doped interlayers which are electrically active, for enhancement of, for example, room temperature carrier mobility, does not prevent analysis of quantum transport in a QW.« less

In-situ Observation of Size and Irradiation Effects on Thermoelectric Properties of Bi-Sb-Te Nanowire in FIB Trimming

PubMed Central

Chien, Chia-Hua; Lee, Ping-Chung; Tsai, Wei-Han; Lin, Chien-Hung; Lee, Chih-Hao; Chen, Yang-Yuan

2016-01-01

In this report, the thermoelectric properties of a Bi0.8Sb1.2Te2.9 nanowire (NW) were in-situ studied as it was trimmed from 750 down to 490 and 285 nm in diameter by a focused ion beam. While electrical and thermal conductivities both indubitably decrease with the diameter reduction, the two physical properties clearly exhibit different diameter dependent behaviors. For 750 and 490 nm NWs, much lower thermal conductivities (0.72 and 0.69 W/m-K respectively) were observed as compared with the theoretical prediction of Callaway model. The consequence indicates that in addition to the size effect, extra phonon scattering of defects created by Ga ion irradiation was attributed to the reduction of thermal conductivities. As the NW was further trimmed down to 285 nm, both the electrical and thermal conductivities exhibited a dramatic reduction which was ascribed to the formation of amorphous structure due to Ga ion irradiation. The size dependence of Seebeck coefficient and figure of merit (ZT) show the maximum at 750 nm, then decrease linearly with size decrease. The study not only provides the thoroughly understanding of the size and defect effects on the thermoelectric properties but also proposes a possible method to manipulate the thermal conductivity of NWs via ion irradiation. PMID:27030206

Ultrahigh Oxidation Resistance and High Electrical Conductivity in Copper-Silver Powder

PubMed Central

Li, Jiaxiang; Li, Yunping; Wang, Zhongchang; Bian, Huakang; Hou, Yuhang; Wang, Fenglin; Xu, Guofu; Liu, Bin; Liu, Yong

2016-01-01

The electrical conductivity of pure Cu powder is typically deteriorated at elevated temperatures due to the oxidation by forming non-conducting oxides on surface, while enhancing oxidation resistance via alloying is often accompanied by a drastic decline of electrical conductivity. Obtaining Cu powder with both a high electrical conductivity and a high oxidation resistance represents one of the key challenges in developing next-generation electrical transferring powder. Here, we fabricate a Cu-Ag powder with a continuous Ag network along grain boundaries of Cu particles and demonstrate that this new structure can inhibit the preferential oxidation in grain boundaries at elevated temperatures. As a result, the Cu-Ag powder displays considerably high electrical conductivity and high oxidation resistance up to approximately 300 °C, which are markedly higher than that of pure Cu powder. This study paves a new pathway for developing novel Cu powders with much enhanced electrical conductivity and oxidation resistance in service. PMID:28004839

System and method for evaluating a wire conductor

DOEpatents

Panozzo, Edward; Parish, Harold

2013-10-22

A method of evaluating an electrically conductive wire segment having an insulated intermediate portion and non-insulated ends includes passing the insulated portion of the wire segment through an electrically conductive brush. According to the method, an electrical potential is established on the brush by a power source. The method also includes determining a value of electrical current that is conducted through the wire segment by the brush when the potential is established on the brush. The method additionally includes comparing the value of electrical current conducted through the wire segment with a predetermined current value to thereby evaluate the wire segment. A system for evaluating an electrically conductive wire segment is also disclosed.

Modifications of structural, chemical, and electrical characteristics of Er2O3/Si interface under Co-60 gamma irradiation

NASA Astrophysics Data System (ADS)

Kaya, Senol; Yilmaz, Ercan

2018-03-01

This paper reports the influences of gamma radiation on the structural, electrical, and chemical characteristics of erbium oxide (Er2O3) thin films and the possible mechanisms underlying these irradiation-induced effects. The crystallographic and morphological modifications under gamma irradiation were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively, while radiation influences on electrochemical characteristics were analyzed by X-ray photoelectron spectroscopy (XPS). Furthermore, changes in electrical characteristics were analyzed on the basis of capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements. The XRD results demonstrated that small atomic displacement was observed and that the grain size of the nanostructure slightly increased. Improvements in surface roughness were observed in AFM measurements. The observed variations in the XRD and AFM measurements can be attributed to the radiation-induced local heating and microscopic atomic mobility. In addition, the XPS analysis obviously demonstrated that the oxygen vacancies increased with irradiation dose because of the breaking of Er2O3 and ErxOy bonds. Significant influences of the generated oxygen vacancies on the electrical measurements were observed, and the radiation-induced hole traps, which caused large flat band shifts, can be attributed to the generated oxygen vacancies. The results show that radiation does not degrade the physical characteristics significantly, but the generation of oxygen vacancies considerably increases the electrical sensitivity of the Er2O3 dielectric.

Quantification of the effect of electrical and thermal parameters on radiofrequency ablation for concentric tumour model of different sizes.

PubMed

Jamil, Muhammad; Ng, E Y K

2015-07-01

Radiofrequency ablation (RFA) has been increasingly used in treating cancer for multitude of situations in various tissue types. To perform the therapy safely and reliably, the effect of critical parameters needs to be known beforehand. Temperature plays an important role in the outcome of the therapy and any uncertainties in temperature assessment can be lethal. This study presents the RFA case of fixed tip temperature where we've analysed the effect of electrical conductivity, thermal conductivity and blood perfusion rate of the tumour and surrounding normal tissue on the radiofrequency ablation. Ablation volume was chosen as the characteristic to be optimised and temperature control was achieved via PID controller. The effect of all 6 parameters each having 3 levels was quantified with minimum number of experiments harnessing the fractional factorial characteristic of Taguchi's orthogonal arrays. It was observed that as the blood perfusion increases the ablation volume decreases. Increasing electrical conductivity of the tumour results in increase of ablation volume whereas increase in normal tissue conductivity tends to decrease the ablation volume and vice versa. Likewise, increasing thermal conductivity of the tumour results in enhanced ablation volume whereas an increase in thermal conductivity of the surrounding normal tissue has a debilitating effect on the ablation volume and vice versa. With increase in the size of the tumour (i.e., 2-3cm) the effect of each parameter is not linear. The parameter effect varies with change in size of the tumour that is manifested by the different gradient observed in ablation volume. Most important is the relative insensitivity of ablation volume to blood perfusion rate for smaller tumour size (2cm) that is also in accordance with the previous results presented in literature. These findings will provide initial insight for safe, reliable and improved treatment planning perceptively. Copyright © 2015 Elsevier Ltd. All rights reserved.

External electric field driving the ultra-low thermal conductivity of silicene.

PubMed

Qin, Guangzhao; Qin, Zhenzhen; Yue, Sheng-Ying; Yan, Qing-Bo; Hu, Ming

2017-06-01

The manipulation of thermal transport is in increasing demand as heat transfer plays a critical role in a wide range of practical applications, such as efficient heat dissipation in nanoelectronics and heat conduction hindering in solid-state thermoelectrics. It is well established that the thermal transport in semiconductors and insulators (phonons) can be effectively modulated by structure engineering or materials processing. However, almost all the existing approaches involve altering the original atomic structure of materials, which would be hindered due to either irreversible structure change or limited tunability of thermal conductivity. Motivated by the inherent relationship between phonon behavior and interatomic electrostatic interaction, we comprehensively investigate the effect of external electric field, a widely used gating technique in modern electronics, on the lattice thermal conductivity (κ). Taking two-dimensional silicon (silicene) as a model, we demonstrate that by applying an electric field (E z = 0.5 V Å -1 ) the κ of silicene can be reduced to a record low value of 0.091 W m -1 K -1 , which is more than two orders of magnitude lower than that without an electric field (19.21 W m -1 K -1 ) and is even comparable to that of the best thermal insulation materials. Fundamental insights are gained from observing the electronic structures. With an electric field applied, due to the screened potential resulting from the redistributed charge density, the interactions between silicon atoms are renormalized, leading to phonon renormalization and the modulation of phonon anharmonicity through electron-phonon coupling. Our study paves the way for robustly tuning phonon transport in materials without altering the atomic structure, and would have significant impact on emerging applications, such as thermal management, nanoelectronics and thermoelectrics.

Electrical signaling, stomatal conductance, ABA and Ethylene content in avocado trees in response to root hypoxia

PubMed Central

Gurovich, Luis; Schaffer, Bruce; García, Nicolás; Iturriaga, Rodrigo

2009-01-01

Avocado (Persea americana Mill.) trees are among the most sensitive of fruit tree species to root hypoxia as a result of flooded or poorly drained soil. Similar to drought stress, an early physiological response to root hypoxia in avocado is a reduction of stomatal conductance. It has been previously determined in avocado trees that an extracellular electrical signal between the base of stem and leaves is produced and related to reductions in stomatal conductance in response to drought stress. The current study was designed to determine if changes in the extracellular electrical potential between the base of the stem and leaves in avocado trees could also be detected in response to short-term (min) or long-term (days) root hypoxia, and if these signals could be related to stomatal conductance (gs), root and leaf ABA and ACC concentrations, ethylene emission from leaves and leaf abscission. In contrast to previous observations for drought-stressed trees, short-term or long-term root hypoxia did not stimulate an electrical potential difference between the base of the stem and leaves. Short-term hypoxia did not result in a significant decrease in gs compared with plants in the control treatment, and no differences in ABA concentration were found between plants subjected to hypoxia and control plants. Long-term hypoxia in the root zone resulted in a significant decrease in gs, increased leaf ethylene and increased leaf abscission. The results indicate that for avocado trees exposed to root hypoxia, electrical signals do not appear to be the primary root-to-shoot communication mechanism involved in signaling for stomatal closure as a result of hypoxia in the root zone. PMID:19649181

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

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

PubMed

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

2011-01-01

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

Depositing bulk or micro-scale electrodes

DOEpatents

Shah, Kedar G.; Pannu, Satinderpall S.; Tolosa, Vanessa; Tooker, Angela C.; Sheth, Heeral J.; Felix, Sarah H.; Delima, Terri L.

2016-11-01

Thicker electrodes are provided on microelectronic device using thermo-compression bonding. A thin-film electrical conducting layer forms electrical conduits and bulk depositing provides an electrode layer on the thin-film electrical conducting layer. An insulating polymer layer encapsulates the electrically thin-film electrical conducting layer and the electrode layer. Some of the insulating layer is removed to expose the electrode layer.

Can Direct Current Electrotherapy Be Used for Patients With Orthopedic Implants?

PubMed Central

Thaler, Evangeline; Korte, Holger

2017-01-01

Introduction: Although electrotherapy appears to have particularly interesting applications in the field of postoperative orthopedic rehabilitation, relatively little scientifically based research has been conducted in the area of electrotherapy with regard to safety involving patients with orthopedic implants. Method: Three electrotherapy forms were tested, such as high-volt stimulation (HVS), transcutaneous electric nerve stimulation (TENS), and galvanic current (GAL), using a model system containing a metal implant plate to evaluate whether heating in excess of 3°C would occur. Results: All changes in temperature for HVS, GAL, and TENS therapeutic electrical currents observed in our model system fall below the predefined 3°C. Conclusion: To the best of our knowledge, this is the first experimental based observation that prolonged exposure to a direct electrical current at therapeutic strength does not result in heating of metal titanium plates. PMID:28255511

Variable Anisotropic Brain Electrical Conductivities in Epileptogenic Foci

PubMed Central

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

2010-01-01

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

Electric property measurement of free-standing SrTiO3 nanoparticles assembled by dielectrophoresis

NASA Astrophysics Data System (ADS)

Budiman, Faisal; Kotooka, Takumi; Horibe, Yoichi; Eguchi, Masanori; Tanaka, Hirofumi

2018-06-01

Free-standing strontium titanate (SrTiO3/STO) nanoparticles (NPs) were synthesized by the sol–gel method. X-ray diffractometry revealed that the required minimum annealing temperature to synthesize pure and highly crystalline STO NPs was 500 °C. Moreover, morphological observation by field emission scanning electron microscopy showed that the STO NPs have a spherical structure and their size depended on annealing condition. Electrical properties were measured using a low-temperature probing system. Here, an electrode was fabricated by electron beam lithography and the synthesized STO NPs were aligned at the electrodes by dielectrophoresis. The conductance of a sample was proportional to temperature. Two conduction mechanisms originating from hopping and tunneling appeared in the Arrhenius plot.

Coated carbon nanotube array electrodes

DOEpatents

Ren, Zhifeng; Wen, Jian; Chen, Jinghua; Huang, Zhongping; Wang, Dezhi

2006-12-12

The present invention provides conductive carbon nanotube (CNT) electrode materials comprising aligned CNT substrates coated with an electrically conducting polymer, and the fabrication of electrodes for use in high performance electrical energy storage devices. In particular, the present invention provides conductive CNTs electrode material whose electrical properties render them especially suitable for use in high efficiency rechargeable batteries. The present invention also provides methods for obtaining surface modified conductive CNT electrode materials comprising an array of individual linear, aligned CNTs having a uniform surface coating of an electrically conductive polymer such as polypyrrole, and their use in electrical energy storage devices.

Coated carbon nanotube array electrodes

DOEpatents

Ren, Zhifeng [Newton, MA; Wen, Jian [Newton, MA; Chen, Jinghua [Chestnut Hill, MA; Huang, Zhongping [Belmont, MA; Wang, Dezhi [Wellesley, MA

2008-10-28

The present invention provides conductive carbon nanotube (CNT) electrode materials comprising aligned CNT substrates coated with an electrically conducting polymer, and the fabrication of electrodes for use in high performance electrical energy storage devices. In particular, the present invention provides conductive CNTs electrode material whose electrical properties render them especially suitable for use in high efficiency rechargeable batteries. The present invention also provides methods for obtaining surface modified conductive CNT electrode materials comprising an array of individual linear, aligned CNTs having a uniform surface coating of an electrically conductive polymer such as polypyrrole, and their use in electrical energy storage devices.

Quantized edge modes in atomic-scale point contacts in graphene

NASA Astrophysics Data System (ADS)

Kinikar, Amogh; Phanindra Sai, T.; Bhattacharyya, Semonti; Agarwala, Adhip; Biswas, Tathagata; Sarker, Sanjoy K.; Krishnamurthy, H. R.; Jain, Manish; Shenoy, Vijay B.; Ghosh, Arindam

2017-07-01

The zigzag edges of single- or few-layer graphene are perfect one-dimensional conductors owing to a set of gapless states that are topologically protected against backscattering. Direct experimental evidence of these states has been limited so far to their local thermodynamic and magnetic properties, determined by the competing effects of edge topology and electron-electron interaction. However, experimental signatures of edge-bound electrical conduction have remained elusive, primarily due to the lack of graphitic nanostructures with low structural and/or chemical edge disorder. Here, we report the experimental detection of edge-mode electrical transport in suspended atomic-scale constrictions of single and multilayer graphene created during nanomechanical exfoliation of highly oriented pyrolytic graphite. The edge-mode transport leads to the observed quantization of conductance close to multiples of G0 = 2e2/h. At the same time, conductance plateaux at G0/2 and a split zero-bias anomaly in non-equilibrium transport suggest conduction via spin-polarized states in the presence of an electron-electron interaction.

Streamer discharges as advancing imperfect conductors: inhomogeneities in long ionized channels

NASA Astrophysics Data System (ADS)

Luque, A.; González, M.; Gordillo-Vázquez, F. J.

2017-12-01

A major obstacle for the understanding of long electrical discharges is the complex dynamics of streamer coronas, formed by many thin conducting filaments. Building macroscopic models for these filaments is one approach to attain a deeper knowledge of the discharge corona. Here, we present a one-dimensional, macroscopic model of a propagating streamer channel with a finite and evolving internal conductivity. We represent the streamer as an advancing finite-conductivity channel with a surface charge density at its boundary. This charge evolves self-consistently due to the electric current that flows through the streamer body and within a thin layer at its surface. We couple this electrodynamic evolution with a field-dependent set of chemical reactions that determine the internal channel conductivity. With this one-dimensional model, we investigate the formation of persisting structures in the wake of a streamer head. In accordance with experimental observations, our model shows that a within a streamer channel some regions are driven towards high fields that can be maintaned for tens of nanoseconds.

Electric conductance of a mechanically strained molecular junction from first principles: Crucial role of structural relaxation and conformation sampling

NASA Astrophysics Data System (ADS)

Nguyen, Huu Chuong; Szyja, Bartłomiej M.; Doltsinis, Nikos L.

2014-09-01

Density functional theory (DFT) based molecular dynamics simulations have been performed of a 1,4-benzenedithiol molecule attached to two gold electrodes. To model the mechanical manipulation in typical break junction and atomic force microscopy experiments, the distance between two electrodes was incrementally increased up to the rupture point. For each pulling distance, the electric conductance was calculated using the DFT nonequilibrium Green's-function approach for a statistically relevant sample of configurations extracted from the simulation. With increasing mechanical strain, the formation of monoatomic gold wires is observed. The conductance decreases by three orders of magnitude as the initial twofold coordination of the thiol sulfur to the gold is reduced to a single S-Au bond at each electrode and the order in the electrodes is destroyed. Independent of the pulling distance, the conductance was found to fluctuate by at least two orders of magnitude depending on the instantaneous junction geometry.

Topological transport from a black hole

NASA Astrophysics Data System (ADS)

Melnikov, Dmitry

2018-03-01

In this paper the low temperature zero-frequency transport in a 2 + 1-dimensional theory dual to a dyonic black hole is discussed. It is shown that transport exhibits topological features: the transverse electric and heat conductivities satisfy the Wiedemann-Franz law of free electrons; the direct heat conductivity is measured in units of the central charge of CFT2+1, while the direct electric conductivity vanishes; the thermoelectric conductivity is non-zero at vanishing temperature, while the O (T) behavior, controlled by the Mott relation, is subleading. Provided that the entropy of the black hole, and the dual system, is non-vanishing at T = 0, the observations indicate that the dyonic black hole describes a ħ → 0 limit of a highly degenerate topological state, in which the black hole charge measures the density of excited non-abelian quasiparticles. The holographic description gives further evidence that non-abelian nature of quasiparticles can be determined by the low temperature behavior of the thermoelectric transport.

Quantized edge modes in atomic-scale point contacts in graphene.

PubMed

Kinikar, Amogh; Phanindra Sai, T; Bhattacharyya, Semonti; Agarwala, Adhip; Biswas, Tathagata; Sarker, Sanjoy K; Krishnamurthy, H R; Jain, Manish; Shenoy, Vijay B; Ghosh, Arindam

2017-07-01

The zigzag edges of single- or few-layer graphene are perfect one-dimensional conductors owing to a set of gapless states that are topologically protected against backscattering. Direct experimental evidence of these states has been limited so far to their local thermodynamic and magnetic properties, determined by the competing effects of edge topology and electron-electron interaction. However, experimental signatures of edge-bound electrical conduction have remained elusive, primarily due to the lack of graphitic nanostructures with low structural and/or chemical edge disorder. Here, we report the experimental detection of edge-mode electrical transport in suspended atomic-scale constrictions of single and multilayer graphene created during nanomechanical exfoliation of highly oriented pyrolytic graphite. The edge-mode transport leads to the observed quantization of conductance close to multiples of G 0  = 2e 2 /h. At the same time, conductance plateaux at G 0 /2 and a split zero-bias anomaly in non-equilibrium transport suggest conduction via spin-polarized states in the presence of an electron-electron interaction.

The influence of reduced graphene oxide on electrical conductivity of LiFePO{sub 4}-based composite as cathode material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arifin, Muhammad; Aimon, Akfiny Hasdi; Winata, Toto

2016-02-08

LiFePO{sub 4} is fascinating cathode active materials for Li-ion batteries application because of their high electrochemical performance such as a stable voltage at 3.45 V and high specific capacity at 170 mAh.g{sup −1}. However, their low intrinsic electronic conductivity and low ionic diffusion are still the hindrance for their further application on Li-ion batteries. Therefore, the efforts to improve their conductivity are very important to elevate their prospecting application as cathode materials. Herein, we reported preparation of additional of reduced Graphene Oxide (rGO) into LiFePO{sub 4}-based composite via hydrothermal method and the influence of rGO on electrical conductivity of LiFePO{sub 4}−basedmore » composite by varying mass of rGO in composition. Vibration of LiFePO{sub 4}-based composite was detected on Fourier Transform Infrared Spectroscopy (FTIR) spectra, while single phase of LiFePO{sub 4} nanocrystal was observed on X-Ray Diffraction (XRD) pattern, it furthermore, Scanning Electron Microscopy (SEM) images showed that rGO was distributed around LiFePO4-based composite. Finally, the 4-point probe measurement result confirmed that the optimum electrical conductivity is in additional 2 wt% rGO for range 1 to 2 wt% rGO.« less

Systems Characterization of Temperature, Ph and Electrical Conductivity in Aerobic Biodegradation of Wheat Biomass at Differing Mixing Rates

NASA Technical Reports Server (NTRS)

Calhoun, M.; Trotman, A.; Aglan, H.

1998-01-01

The purpose of this preliminary study is to observe and relate the rate of mixing to pH and electrical conductivity in an aerobic, continuously stirred bioreactor. The objective is to use data collected from successive experiments as a means of a system characterization. Tests were conducted to obtain these data using a continuously stirred 20 L Cytostir glass reaction vessel as a bioreactor operated without built-in temperature or pH control. The tests were conducted on the lab bench at ambient temperatures. The substrate in the bioreactor was ground wheat biomass obtained from the Biomass Production Chamber at NASA Kennedy Space Center. In this study, the data reflect characteristics of the native (uninoculated) systems as well as inoculated systems. In the native systems, it was found that pi levels became stable after approximately 2 to 3 days. The electrical conductivity levels for the native systems tended to decrease over time. In contrast, ion activity was increased after the introduction of bacteria into the system. This could be correlated with the release of nutrients, due to the activity of the bacteria. Also, there were slight increases in pH in the inoculated system, a result which is expected for a system with no active pr controls. The data will be used to test a mathematical model in an automated system.

The Influence of Vesicle Shape and Medium Conductivity on Possible Electrofusion under a Pulsed Electric Field

PubMed Central

Liu, Linying; Mao, Zheng; Zhang, Jianhua; Liu, Na; Liu, Qing Huo

2016-01-01

The effects of electric field on lipid membrane and cells have been extensively studied in the last decades. The phenomena of electroporation and electrofusion are of particular interest due to their wide use in cell biology and biotechnology. However, numerical studies on the electrofusion of cells (or vesicles) with different deformed shapes are still rare. Vesicle, being of cell size, can be treated as a simple model of cell to investigate the behaviors of cell in electric field. Based on the finite element method, we investigate the effect of vesicle shape on electrofusion of contact vesicles in various medium conditions. The transmembrane voltage (TMV) and pore density induced by a pulsed field are examined to analyze the possibility of vesicle fusion. In two different medium conditions, the prolate shape is observed to have selective electroporation at the contact area of vesicles when the exterior conductivity is smaller than the interior one; selective electroporation is more inclined to be found at the poles of the oblate vesicles when the exterior conductivity is larger than the interior one. Furthermore, we find that when the exterior conductivity is lower than the internal conductivity, the pulse can induce a selective electroporation at the contact area between two vesicles regardless of the vesicle shape. Both of these two findings have important practical applications in guiding electrofusion experiments. PMID:27391692

Degenerate p-type conductivity in wide-gap LaCuOS1-xSex (x=0-1) epitaxial films

NASA Astrophysics Data System (ADS)

Hiramatsu, Hidenori; Ueda, Kazushige; Ohta, Hiromichi; Hirano, Masahiro; Kamiya, Toshio; Hosono, Hideo

2003-02-01

Epitaxial films of LaCuOS1-xSex (x=0-1) solid solution were grown on MgO (001) substrates and their electrical and optical properties were examined. Sharp emission due to room-temperature exciton with binding energy of ˜50 meV is observed for all x values. Hall mobility becomes large with an increase in the Se content and it reaches 8.0 cm2V-1s-1 in LaCuOSe, a comparable value to that of p-type GaN:Mg. Doping of Mg2+ ions at La3+ sites enhances a hole concentration up to 2.2×1020 cm-3, while maintaining the Hall mobility as large as 4.0 cm2V-1s-1. Consequently, a degenerate p-type electrical conduction with a conductivity of 140 S cm-1 was achieved.

The time and temperature dependence of the thermoelectric properties of silicon-germanium alloy

NASA Technical Reports Server (NTRS)

Raag, V.

1975-01-01

Experimental data on the electrical resistivity and Seebeck coefficient of n-type and p-type silicon-germanium alloys are analyzed in terms of a solid-state dopant precipitation model proposed by Lifshitz and Slyozov (1961). Experimental findings on the time and temperature dependence of the thermal conductivity of these two types of alloy indicate that the thermal conductivity of silicon-germanium alloys changes with time, contrary to previous hypothesis. A preliminary model is presented which stipulates that the observed thermal conductivity decrease in silicon-germanium alloys is due partly to dopant precipitation underlying the electrical property changes and partly to enhanced alloying of the material. It is significant that all three properties asymptotically approach equilibrium values with time. Total characterization of these properties will enable the time change to be fully compensated in the design of a thermoelectric device employing silicon-germanium alloys.

Ceramic substrate including thin film multilayer surface conductor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolf, Joseph Ambrose; Peterson, Kenneth A.

2017-05-09

A ceramic substrate comprises a plurality of ceramic sheets, a plurality of inner conductive layers, a plurality of vias, and an upper conductive layer. The ceramic sheets are stacked one on top of another and include a top ceramic sheet. The inner conductive layers include electrically conductive material that forms electrically conductive features on an upper surface of each ceramic sheet excluding the top ceramic sheet. The vias are formed in each of the ceramic sheets with each via being filled with electrically conductive material. The upper conductive layer includes electrically conductive material that forms electrically conductive features on anmore » upper surface of the top ceramic sheet. The upper conductive layer is constructed from a stack of four sublayers. A first sublayer is formed from titanium. A second sublayer is formed from copper. A third sublayer is formed from platinum. A fourth sublayer is formed from gold.« less

Electrostatic force microscopy on oriented graphite surfaces: coexistence of insulating and conducting behaviors.

PubMed

Lu, Yonghua; Muñoz, M; Steplecaru, C S; Hao, Cheng; Bai, Ming; Garcia, N; Schindler, K; Esquinazi, P

2006-08-18

We present measurements of the electric potential fluctuations on the surface of highly oriented pyrolytic graphite using electrostatic force and atomic force microscopy. Micrometric domainlike potential distributions are observed even when the sample is grounded. Such potential distributions are unexpected given the good metallic conductivity of graphite because the surface should be an equipotential. Our results indicate the coexistence of regions with "metalliclike" and "insulatinglike" behaviors showing large potential fluctuations of the order of 0.25 V. In lower quality graphite, this effect is not observed. Experiments are performed in Ar and air atmospheres.

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.

High-pressure Seebeck coefficients and thermoelectric behaviors of Bi and PbTe measured using a Paris-Edinburgh cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baker, Jason; Kumar, Ravhi S.; Park, Changyong

2016-01-01

A new sample cell assembly design for the Paris-Edinburgh type large-volume press for simultaneous measurements of X-ray diffraction, electrical resistance, Seebeck coefficient and relative changes in the thermal conductance at high pressures has been developed. The feasibility of performing in situ measurements of the Seebeck coefficient and thermal measurements is demonstrated by observing well known solid–solid phase transitions of bismuth (Bi) up to 3 GPa and 450 K. A reversible polarity flip has been observed in the Seebeck coefficient across the Bi-I to Bi-II phase boundary. Also, successful Seebeck coefficient measurements have been performed for the classical high-temperature thermoelectric materialmore » PbTe under high pressure and temperature conditions. In addition, the relative change in the thermal conductivity was measured and a relative change in ZT, the dimensionless figure of merit, is described. Furthermore, this new capability enables pressure-induced structural changes to be directly correlated to electrical and thermal properties.« less

High-pressure Seebeck coefficients and thermoelectric behaviors of Bi and PbTe measured using a Paris-Edinburgh cell.

PubMed

Baker, Jason; Kumar, Ravhi; Park, Changyong; Kenney-Benson, Curtis; Cornelius, Andrew; Velisavljevic, Nenad

2016-11-01

A new sample cell assembly design for the Paris-Edinburgh type large-volume press for simultaneous measurements of X-ray diffraction, electrical resistance, Seebeck coefficient and relative changes in the thermal conductance at high pressures has been developed. The feasibility of performing in situ measurements of the Seebeck coefficient and thermal measurements is demonstrated by observing well known solid-solid phase transitions of bismuth (Bi) up to 3 GPa and 450 K. A reversible polarity flip has been observed in the Seebeck coefficient across the Bi-I to Bi-II phase boundary. Also, successful Seebeck coefficient measurements have been performed for the classical high-temperature thermoelectric material PbTe under high pressure and temperature conditions. In addition, the relative change in the thermal conductivity was measured and a relative change in ZT, the dimensionless figure of merit, is described. This new capability enables pressure-induced structural changes to be directly correlated to electrical and thermal properties.

The Altus Cumulus Electrification Study (ACES): A UAV-Based Science Demonstration

NASA Technical Reports Server (NTRS)

Blakeslee, R. J.; Croskey, C. L.; Desch, M. D.; Farrell, W. M.; Goldberg, R. A.; Houser, J. G.; Kim, H. S.; Mach, D. M.; Mitchell, J. D.; Stoneburner, J. C.

2003-01-01

The Altus Cumulus Electrification Study (ACES) is an unmanned aerial vehicle (UAV)- based project that investigated thunderstorms in the vicinity of the Florida Everglades in August 2002. ACES was conducted to investigate storm electrical activity and its relationship to storm morphology, and to validate satellite-based lightning measurements. In addition, as part of the NASA sponsored UAV-based science demonstration program, this project provided a scientifically useful demonstration of the utility and promise of UAV platforms for Earth science and applications observations. ACES employed the Altus II aircraft, built by General Atomics - Aeronautical Systems, Inc. Key science objectives simultaneously addressed by ACES are to: (1) investigate lightning-storm relationships, (2) study storm electrical budgets, and provide Lightning Imaging Sensor validation. The ACES payload included electrical, magnetic, and optical sensors to remotely characterize the lightning activity and the electrical environment within and around thunderstorms. ACES contributed important electrical and optical measurements not available from other sources. Also, the high altitude vantage point of the UAV observing platform (up to 55,000 feet) provided cloud-top perspective. By taking advantage of its slow flight speed (70 to 100 knots), long endurance, and high altitude flight, the Altus was flown near, and when possible, over (but never into) thunderstorms for long periods of time that allowed investigations to be conducted over entire storm life cycles. An innovative real time weather system was used to identify and vector the aircraft to selected thunderstorms and safely fly around these storms, while, at the same time monitor the weather near our base of operations. In addition, concurrent ground-based observations that included radar (Miami and Key West WSRBD, NASA NPOL), satellite imagery, and lightning (NALDN and Los Alamos EDOT) enable the UAV measurements to be more completely interpreted and evaluated in the context of the thunderstorm structure, evolution, and environment.

A novel application of ADC/K-foaming agent-loaded NBR rubber composites as pressure sensor

NASA Astrophysics Data System (ADS)

Mahmoud, W. E.; El-Eraki, M. H. I.; El-Lawindy, A. M. Y.; Hassan, H. H.

2006-02-01

Nitrile butadiene rubber (NBR) structure foam of different apparent densities was obtained by using different concentrations of foaming agent, azodicarbonamide, ADC/K. The true stress-strain characteristics, in case of compression, of foamed samples were measured. It was found that the theoretical values predicted from the simple blending model are in more agreement with the experimental results than those from the square-relationship model. The effect of cyclic loading-unloading and dissipation energy of rubber foams was studied. The results also indicated that foams with low density exhibited a small hysteresis. The electrical properties were found dependent on the foaming agent concentration. This study was assisted by Mott and Gurney equation. The effect of compressive strain on the electrical conductivity of rubber foams was studied. The free current carrier mobility and the equilibrium concentration of charge carrier in the conduction band were produced as functions of compressive strain. The results also indicate that there is a linear variation between pressure and conductivity for all samples, which means that these samples can be used as a pressure sensor. At a certain concentration of foaming agent (5 phr) a change of electrical conductivity by more than three orders is observed at 20% compression strain.

Preparation and Dielectric Properties of SiC/LSR Nanocomposites for Insulation of High Voltage Direct Current Cable Accessories

PubMed Central

Shang, Nanqiang; Chen, Qingguo; Wei, Xinzhe

2018-01-01

The conductivity mismatch in the composite insulation of high voltage direct current (HVDC) cable accessories causes electric field distribution distortion and even insulation breakdown. Therefore, a liquid silicone rubber (LSR) filled with SiC nanoparticles is prepared for the insulation of cable accessories. The micro-morphology of the SiC/LSR nanocomposites is observed by scanning electron microscopy, and their trap parameters are characterized using thermal stimulated current (TSC) tests. Moreover, the dielectric properties of SiC/LSR nanocomposites with different SiC concentrations are tested. The results show that the 3 wt % SiC/LSR sample has the best nonlinear conductivity, more than one order of magnitude higher than that of pure LSR with improved temperature and nonlinear conductivity coefficients. The relative permittivity increased 0.2 and dielectric loss factor increased 0.003, while its breakdown strength decreased 5 kV/mm compared to those of pure LSR. Moreover, the TSC results indicate the introduction of SiC nanoparticles reduced the trap level and trap density. Furthermore, the SiC nanoparticles filling significantly increased the sensitivity of LSR to electric field stress and temperature changes, enhancing the conductivity and electric field distribution within the HVDC cable accessories, thus improving the reliability of the HVDC cable accessories. PMID:29518054

Electrical properties and oxygen functionalities in ethanol-treated and thermally modified graphene oxide

NASA Astrophysics Data System (ADS)

Scalese, S.; Baldo, S.; D'Angelo, D.; Filice, S.; Bongiorno, C.; Reitano, R.; Fazio, E.; Conoci, S.; La Magna, A.

2017-04-01

Graphene-based materials are among the most innovative and promising materials for the development of high-performance sensing devices, mainly due to the large surface area and the possibility to modify their reactivity by suitable functionalization. In the field of sensing applications, the peculiarities of innovative materials can be exploited only if chemical and physical properties are fully understood and correlated with each other. To this aim, in this work, graphene oxide (GO) and ethanol-treated GO (GOEt) were investigated from chemical and structural points of view. Electrical characterization was performed by depositing GO and GOEt between two electrodes by dielectrophoresis. All the investigations were repeated on GO materials after thermal treatment in a low temperature range (60 °C-300 °C). Furthermore, the electrical conductivity of GO was investigated by changing the temperature and the environment (air or N2) during the characterization: an increase in the conductivity of the as-deposited GO was observed when the device is cooled down and this effect is reversible with the temperature. GOEt and the thermally treated GO and GOEt show an opposite trend, confirming the key role of the oxygen functionalities in the conduction mechanisms and, therefore, in the conductivity of the GO layers.

Electroosmotic flow and ionic conductance in a pH-regulated rectangular nanochannel

NASA Astrophysics Data System (ADS)

Sadeghi, Morteza; Saidi, Mohammad Hassan; Sadeghi, Arman

2017-06-01

Infinite series solutions are obtained for electrical potential, electroosmotic velocity, ionic conductance, and surface physicochemical properties of long pH-regulated rectangular nanochannels of low surface potential utilizing the double finite Fourier transform method. Closed form expressions are also obtained for channels of large height to width ratio for which the depthwise variations vanish. Neglecting the Stern layer impact, the effects of EDL (Electric Double Layer) overlap, multiple ionic species, and association/dissociation reactions on the surface are all taken into account. Moreover, finite-element-based numerical simulations are conducted to account for the end effects as well as to validate the analytical solutions. We show that, with the exception of the migratory ionic conductivity, all the physicochemical parameters are strong functions of the channel aspect ratio. Accordingly, a slit geometry is not a good representative of a rectangular channel when the width is comparable to the height. It is also observed that the distribution of the electrical potential is not uniform over the surface of a charge-regulated channel. In addition, unlike ordinary channels for which an increase in the background salt concentration is always accompanied by higher flow rates, quite the opposite may be true for a pH-regulated duct at higher salt concentrations.

Preparation and Dielectric Properties of SiC/LSR Nanocomposites for Insulation of High Voltage Direct Current Cable Accessories.

PubMed

Shang, Nanqiang; Chen, Qingguo; Wei, Xinzhe

2018-03-08

The conductivity mismatch in the composite insulation of high voltage direct current (HVDC) cable accessories causes electric field distribution distortion and even insulation breakdown. Therefore, a liquid silicone rubber (LSR) filled with SiC nanoparticles is prepared for the insulation of cable accessories. The micro-morphology of the SiC/LSR nanocomposites is observed by scanning electron microscopy, and their trap parameters are characterized using thermal stimulated current (TSC) tests. Moreover, the dielectric properties of SiC/LSR nanocomposites with different SiC concentrations are tested. The results show that the 3 wt % SiC/LSR sample has the best nonlinear conductivity, more than one order of magnitude higher than that of pure LSR with improved temperature and nonlinear conductivity coefficients. The relative permittivity increased 0.2 and dielectric loss factor increased 0.003, while its breakdown strength decreased 5 kV/mm compared to those of pure LSR. Moreover, the TSC results indicate the introduction of SiC nanoparticles reduced the trap level and trap density. Furthermore, the SiC nanoparticles filling significantly increased the sensitivity of LSR to electric field stress and temperature changes, enhancing the conductivity and electric field distribution within the HVDC cable accessories, thus improving the reliability of the HVDC cable accessories.

Electrical Spin-Injection into Silicon and Spin FET

DTIC Science & Technology

2010-02-18

differential conductance ( NDC ), which saw the limelight with the realization of the Esaki tunneling diode, had been predicted and observed to occur in a...collector current of a tunneling emitter bipolar transistor, i.e., negative differential transconductance NDTC. Gate controlled NDC had been observed in...measurement and simulation results are relevant as well for other NDC geometries such as FET style tunnel transistors since they offer crucial

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.

Electric moisture meters for wood

Treesearch

William L. James

1988-01-01

Electric moisture meters for wood measure electric conductance (resistance) or dielectric properties, which vary fairly consistently with moisture content when it is less than 30 percent. The two major classes of electric moisture meters are the conductance (resistance) type and the dielectric type. Conductance-t ype meters use penetrating electrodes that measure in a...

Iodine doping effects on the lattice thermal conductivity of oxidized polyacetylene nanofibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bi, Kedong, E-mail: lishi@mail.utexas.edu, E-mail: kedongbi@seu.edu.cn; Department of Mechanical Engineering, University of Texas at Austin, Austin, Texas 78712; Weathers, Annie

2013-11-21

Thermal transport in oxidized polyacetylene (PA) nanofibers with diameters in the range between 74 and 126 nm is measured with the use of a suspended micro heater device. With the error due to both radiation and contact thermal resistance corrected via a differential measurement procedure, the obtained thermal conductivity of oxidized PA nanofibers varies in the range between 0.84 and 1.24 W m{sup −1} K{sup −1} near room temperature, and decreases by 40%–70% after iodine doping. It is also found that the thermal conductivity of oxidized PA nanofibers increases with temperature between 100 and 350 K. Because of exposure to oxygen during sample preparation, themore » PA nanofibers are oxidized to be electrically insulating before and after iodine doping. The measurement results reveal that iodine doping can result in enhanced lattice disorder and reduced lattice thermal conductivity of PA nanofibers. If the oxidation issue can be addressed via further research to increase the electrical conductivity via doping, the observed suppressed lattice thermal conductivity in doped polymer nanofibers can be useful for the development of such conducting polymer nanostructures for thermoelectric energy conversion.« less

Electrically-Conductive Polyaramid Cable And Fabric

NASA Technical Reports Server (NTRS)

Orban, Ralph F.

1988-01-01

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

Effect of process parameters on microstructure and electrical conductivity during FSW of Al-6101 and Pure Copper

NASA Astrophysics Data System (ADS)

Sharma, Nidhi; Khan, Zahid A.; Siddiquee, Arshad Noor; Shihab, Suha K.; Atif Wahid, Mohd

2018-04-01

Copper (Cu) is predominantly used material as a conducting element in electrical and electronic components due to its high conductivity. Aluminum (Al) being lighter in weight and more conductive on weight basis than that of Cu is able to replace or partially replace Cu to make lighter and cost effective electrical components. Conventional methods of joining Al to Cu, such as, fusion welding process have many shortcomings. Friction Stir Welding (FSW) is a solid state welding process which overcomes the shortcoming of the fusion welding. FSW parameters affect the mechanical and electrical properties of the joint. This study aims to evaluate the effect of different process parameters such as shoulder diameter, pin offset, welding and rotational speed on the microstructure and electrical conductivity of the dissimilar Al-Cu joint. FSW is performed using cylindrical pin profile, and four process parameters. Each parameter at different levels is varied according to Taguchi’s L18 standard orthogonal array. It is found that the electrical conductivity of the FSWed joints are equal to that of aluminum at all the welded sections. FSW is found to be an effective technique to join Al to Cu without compromising with the electrical properties. However, the electrical conductivity gets influenced by the process parameters in the stir zone. The optimal combination of the FSW parameters for maximum electrical conductivity is determined. The analysis of variance (ANOVA) technique applied on stir zone suggests that the rotational speed and tool pin offset are the significant parameters to influence the electrical conductivity.

System to measure accurate temperature dependence of electric conductivity down to 20 K in ultrahigh vacuum.

PubMed

Sakai, C; Takeda, S N; Daimon, H

2013-07-01

We have developed the new in situ electrical-conductivity measurement system which can be operated in ultrahigh vacuum (UHV) with accurate temperature measurement down to 20 K. This system is mainly composed of a new sample-holder fixing mechanism, a new movable conductivity-measurement mechanism, a cryostat, and two receptors for sample- and four-probe holders. Sample-holder is pushed strongly against the receptor, which is connected to a cryostat, by using this new sample-holder fixing mechanism to obtain high thermal conductivity. Test pieces on the sample-holders have been cooled down to about 20 K using this fixing mechanism, although they were cooled down to only about 60 K without this mechanism. Four probes are able to be touched to a sample surface using this new movable conductivity-measurement mechanism for measuring electrical conductivity after making film on substrates or obtaining clean surfaces by cleavage, flashing, and so on. Accurate temperature measurement is possible since the sample can be transferred with a thermocouple and∕or diode being attached directly to the sample. A single crystal of Bi-based copper oxide high-Tc superconductor (HTSC) was cleaved in UHV to obtain clean surface, and its superconducting critical temperature has been successfully measured in situ. The importance of in situ measurement of resistance in UHV was demonstrated for this HTSC before and after cesium (Cs) adsorption on its surface. The Tc onset increase and the Tc offset decrease by Cs adsorption were observed.

Unexpected low thermal conductivity and large power factor in Dirac semimetal Cd3As2

NASA Astrophysics Data System (ADS)

Cheng, Zhang; Tong, Zhou; Sihang, Liang; Junzhi, Cao; Xiang, Yuan; Yanwen, Liu; Yao, Shen; Qisi, Wang; Jun, Zhao; Zhongqin, Yang; Faxian, Xiu

2016-01-01

Thermoelectrics has long been considered as a promising way of power generation for the next decades. So far, extensive efforts have been devoted to the search of ideal thermoelectric materials, which require both high electrical conductivity and low thermal conductivity. Recently, the emerging Dirac semimetal Cd3As2, a three-dimensional analogue of graphene, has been reported to host ultra-high mobility and good electrical conductivity as metals. Here, we report the observation of unexpected low thermal conductivity in Cd3As2, one order of magnitude lower than the conventional metals or semimetals with a similar electrical conductivity, despite the semimetal band structure and high electron mobility. The power factor also reaches a large value of 1.58 mW·m-1·K-2 at room temperature and remains non-saturated up to 400 K. Corroborating with the first-principles calculations, we find that the thermoelectric performance can be well-modulated by the carrier concentration in a wide range. This work demonstrates the Dirac semimetal Cd3As2 as a potential candidate of thermoelectric materials. Project supported by the National Young 1000 Talent Plan China, the Pujiang Talent Plan in Shanghai, China, the National Natural Science Foundation of China (Grant Nos. 61322407 and 11474058), the Fund for Fostering Talents in Basic Science of the National Natural Science Foundation of China (Grant No. J1103204), and the National Basic Research Program of China (Grant No. 2011CB921803).

Graphene-Decorated Nanocomposites for Printable Electrodes in Thin Wafer Devices

NASA Astrophysics Data System (ADS)

Bakhshizadeh, N.; Sivoththaman, S.

2017-12-01

Printable electrodes that induce less stress and require lower curing temperatures compared to traditional screen-printed metal pastes are needed in thin wafer devices such as future solar cells, and in flexible electronics. The synthesis of nanocomposites by incorporating graphene nanopowders as well as silver nanowires into epoxy-based electrically conductive adhesives (ECA) is examined to improve electrical conductivity and to develop alternate printable electrode materials that induce less stress on the wafer. For the synthesized graphene and Ag nanowire-decorated ECA nanocomposites, the curing kinetics were studied by dynamic and isothermal differential scanning calorimetry measurements. Thermogravimetric analysis on ECA, ECA-AG and ECA/graphene nanopowder nanocomposites showed that the temperatures for onset of decomposition are higher than their corresponding glass transition temperature ( T g) indicating an excellent thermal resistance. Printed ECA/Ag nanowire nanocomposites showed 90% higher electrical conductivity than ECA films, whereas the ECA/graphene nanocomposites increased the conductivity by over two orders of magnitude. Scanning electron microscopy results also revealed the effect of fillers morphology on the conductivity improvement and current transfer mechanisms in nanocomposites. Residual stress analysis performed on Si wafers showed that the ECA and nanocomposite printed wafers are subjected to much lower stress compared to those printed with metallic pastes. The observed parameters of low curing temperature, good thermal resistance, reasonably high conductivity, and low residual stress in the ECA/graphene nanocomposite makes this material a promising alternative in screen-printed electrode formation in thin substrates.

Coupling behaviors of graphene/SiO2/Si structure with external electric field

NASA Astrophysics Data System (ADS)

Onishi, Koichi; Kirimoto, Kenta; Sun, Yong

2017-02-01

A traveling electric field in surface acoustic wave was introduced into the graphene/SiO2/Si sample in the temperature range of 15 K to 300 K. The coupling behaviors between the sample and the electric field were analyzed using two parameters, the intensity attenuation and time delay of the traveling-wave. The attenuation originates from Joule heat of the moving carriers, and the delay of the traveling-wave was due to electrical resistances of the fixed charge and the moving carriers with low mobility in the sample. The attenuation of the external electric field was observed in both Si crystal and graphene films in the temperature range. A large attenuation around 190 K, which depends on the strength of external electric field, was confirmed for the Si crystal. But, no significant temperature and field dependences of the attenuation in the graphene films were detected. On the other hand, the delay of the traveling-wave due to ionic scattering at low temperature side was observed in the Si crystal, but cannot be detected in the films of the mono-, bi- and penta-layer graphene with high conductivities. Also, it was indicated in this study that skin depth of the graphene film was less than thickness of two graphene atomic layers in the temperature range.

Comparing bulk electrical conductivities spatial series obtained by Time Domain Reflectometry and Electromagnetic Induction sensors

NASA Astrophysics Data System (ADS)

Saeed, Ali; Ajeel, Ali; dragonetti, giovanna; Comegna, Alessandro; Lamaddalena, Nicola; Coppola, Antonio

2016-04-01

The ability to determine and monitor the effects of salts on soils and plants, are of great importance to agriculture. To control its harmful effects, soil salinity needs to be monitored in space and time. This requires knowledge of its magnitude, temporal dynamics, and spatial variability. Conventional ground survey procedures by direct soil sampling are time consuming, costly and destructive. Alternatively, soil salinity can be evaluated by measuring the bulk electrical conductivity (σb) directly in the field. Time domain reflectometry (TDR) sensors allow simultaneous measurements of water content, θ, and σb. They may be calibrated for estimating the electrical conductivity of the soil solution (σw). However, they have a relatively small observation window and thus they are thought to only provide local-scale measurements. The spatial range of the sensors is limited to tens of centimeters and extension of the information to a large area can be problematic. Also, information on the vertical distribution of the σb soil profile may only be obtained by installing sensors at different depths. In this sense, the TDR may be considered as an invasive technique. Compared to the TDR, other geophysical methods based for example on Electromagnetic Induction (EMI) techniques are non-invasive methods and represent a viable alternative to traditional techniques for soil characterization. The problem is that all these techniques give depth-weighted apparent electrical conductivity (σa) measurements, depending on the specific depth distribution of the σb, as well as on the depth response function of the sensor used. In order to deduce the actual distribution of the bulk electrical conductivity, σb, in the soil profile, one needs to invert the signal coming from EMI. Because of their relatively lower observation window, TDR sensors provide quasi-point values and do not adequately integrate the spatial variability of the chemical concentration distribution in the soil solution (and of the water content) induced by natural soil heterogeneity. Thus, the variability of TDR readings is expected to come from a combination of smaller and larger-scale variations. By contrast, an EMI sensor reading partly smoothes the small-scale variability seen by a TDR probe. As a consequence, the variability revealed by profile-integrated EMI and local (within a given depth interval) TDR readings may have completely different characteristics. In this study, a comparison between the variability patterns of σb revealed by TDR and EMI sensors was carried out. The database came from a field experiment conducted in the Mediterranean Agronomic Institute (MAI) of Valenzano (Bari). The soil was pedologically classified as Colluvic Regosol, consisting of a silty loam with an average depth of 60 cm on a shallow fractured calcareous rock. The experimental field (30m x 15.6 m; for a total area of 468 m2) consisted of three transects of 30 m length and 4.2 width, cultivated with green bean and irrigated with three different salinity levels (1 dS/m, 3dS/m, 6dS/m). Each transect consisted of seven crop rows irrigated by a drip irrigation system (dripper discharge q=2 l/h.). Water salinity was induced by adding CaCl2 to the tap water. All crop-soil measurements were conducted along the middle row at 24 monitoring sites, 1m apart. The spatial and temporal evolution of bulk electrical conductivity (σb) of soil was monitored by i) an Electromagnetic Induction method (EM38-DD) and ii) Time Domain Reflectometry (TDR). Herein we will focus on the methodology we used to elaborate the database of this experiment. Mostly, the data elaboration was devoted to make TDR and EMI data actually comparable. Specifically, we analysed the effect of the different observation windows of TDR and EMI sensors on the different spatial and temporal variability observed in the data series coming from the two sensors. After exploring the different patterns and structures of variability of the original EMI and TDR data series the study assessed the potential of applying a Fourier's analysis to filter the original data series to extract the predominant, high-variance signal after removing the small- scale (high frequency) variance observed in the TDR data series.

Minimizing radiation damage in nonlinear optical crystals

DOEpatents

Cooke, D.W.; Bennett, B.L.; Cockroft, N.J.

1998-09-08

Methods are disclosed for minimizing laser induced damage to nonlinear crystals, such as KTP crystals, involving various means for electrically grounding the crystals in order to diffuse electrical discharges within the crystals caused by the incident laser beam. In certain embodiments, electrically conductive material is deposited onto or into surfaces of the nonlinear crystals and the electrically conductive surfaces are connected to an electrical ground. To minimize electrical discharges on crystal surfaces that are not covered by the grounded electrically conductive material, a vacuum may be created around the nonlinear crystal. 5 figs.

Optical and electrical properties of indium tin oxide films near their laser damage threshold [Electrical and optical properties of indium tin oxide films under multi-pulse laser irradiation at 1064 nm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoo, Jae -Hyuck; Lange, Andrew; Bude, Jeff

In this paper, we investigated whether the optical and electrical properties of indium tin oxide (ITO) films are degraded under laser irradiation below their laser ablation threshold. While performing multi-pulse laser damage experiments on a single ITO film (4.7 ns, 1064 nm, 10 Hz), we examined the optical and electrical properties in situ. A decrease in reflectance was observed prior to laser damage initiation. However, under sub-damage threshold irradiation, conductivity and reflectance of the film were maintained without measurable degradation. This indicates that ITO films in optoelectronic devices may be operated below their lifetime laser damage threshold without noticeable performancemore » degradation.« less

Optical and electrical properties of indium tin oxide films near their laser damage threshold [Electrical and optical properties of indium tin oxide films under multi-pulse laser irradiation at 1064 nm

DOE PAGES

Yoo, Jae -Hyuck; Lange, Andrew; Bude, Jeff; ...

2017-02-10

In this paper, we investigated whether the optical and electrical properties of indium tin oxide (ITO) films are degraded under laser irradiation below their laser ablation threshold. While performing multi-pulse laser damage experiments on a single ITO film (4.7 ns, 1064 nm, 10 Hz), we examined the optical and electrical properties in situ. A decrease in reflectance was observed prior to laser damage initiation. However, under sub-damage threshold irradiation, conductivity and reflectance of the film were maintained without measurable degradation. This indicates that ITO films in optoelectronic devices may be operated below their lifetime laser damage threshold without noticeable performancemore » degradation.« less

Correction of contaminated yaw rate signal and estimation of sensor bias for an electric vehicle under normal driving conditions

NASA Astrophysics Data System (ADS)

Zhang, Guoguang; Yu, Zitian; Wang, Junmin

2017-03-01

Yaw rate is a crucial signal for the motion control systems of ground vehicles. Yet it may be contaminated by sensor bias. In order to correct the contaminated yaw rate signal and estimate the sensor bias, a robust gain-scheduling observer is proposed in this paper. First of all, a two-degree-of-freedom (2DOF) vehicle lateral and yaw dynamic model is presented, and then a Luenberger-like observer is proposed. To make the observer more applicable to real vehicle driving operations, a 2DOF vehicle model with uncertainties on the coefficients of tire cornering stiffness is employed. Further, a gain-scheduling approach and a robustness enhancement are introduced, leading to a robust gain-scheduling observer. Sensor bias detection mechanism is also designed. Case studies are conducted using an electric ground vehicle to assess the performance of signal correction and sensor bias estimation under difference scenarios.

Microstructure and Precipitate's Characterization of the Cu-Ni-Si-P Alloy

NASA Astrophysics Data System (ADS)

Zhang, Yi; Tian, Baohong; Volinsky, Alex A.; Sun, Huili; Chai, Zhe; Liu, Ping; Chen, Xiaohong; Liu, Yong

2016-04-01

Microstructure of the Cu-Ni-Si-P alloy was investigated by transmission electron microscopy (TEM). The alloy had 551 MPa tensile strength, 226 HV hardness, and 36% IACS electrical conductivity after 80% cold rolling and aging at 450 °C for 2 h. Under the same aging conditions, but without the cold rolling, the strength, hardness, and electrical conductivity were 379 MPa, 216 HV, and 32% IACS, respectively. The precipitates identified by TEM characterization were δ-Ni2Si. Some semi-coherent spherical precipitates with a typical coffee bean contrast were found after aging for 48 h at 450 °C. The average diameter of the observed semi-coherent precipitates is about 5 nm. The morphology of the fracture surface was observed by scanning electron microscopy. All samples showed typical ductile fracture. The addition of P refined the grain size and increased the nucleation rate of the precipitates. The precipitated phase coarsening was inhibited by the small additions of P. After aging, the Cu-Ni-Si-P alloy can gain excellent mechanical properties with 804 MPa strength and 49% IACS conductivity. This study aimed to optimize processing conditions of the Cu-Ni-Si-P alloys.

Characterization and frequency-thermal response of electrical properties of Cu nanoferrite prepared by sol-gel method

NASA Astrophysics Data System (ADS)

Moghadasi, Fatemeh S.; Daadmehr, Vahid; Kashfi, Monire

2016-10-01

In this paper, we have synthesized copper ferrite nanocrystals using sol-gel method. X-ray diffraction (XRD) analysis confirms that the ferrite has cubic spinal structure and shows Jahn-Teller effect. Also, scan electron microscope (SEM) image demonstrates that grains are nano size order. We showed that the dielectric properties are compatible with the Maxwell-Wagner model and phenomenological Koop's theory. Loss tangent and conductivity of the ferrite have been measured to have small values of 2.4 and 2×10-7 S/m, respectively at room temperature and at 12 Hz. Conductivity has been investigated in terms of localized hopping mechanism and good obedience of Jonscher's law was observed. Variation of activation energy was studied and showed a transition temperature of 443 °K. The electrical modulus shows relaxation of interfacial polarization with relaxation time of 0.318 ms at 24 °C and 15.9 μs at 72 °C. In Impedance spectroscopy, we observed the effects of grain and grain boundary. By increasing temperature, capacity and conduction would increase which show easier polarization process and a semiconducting behavior. Also, relaxation times are shifted to smaller values to represent increasing the electrons mobility.

Complex capacitance in the representation of modulus of the lithium niobate crystals

NASA Astrophysics Data System (ADS)

Alim, Mohammad A.; Batra, A. K.; Bhattacharjee, Sudip; Aggarwal, M. D.

2011-03-01

The lithium niobate (LiNbO 3 or LN) single crystal is grown in-house. The ac small-signal electrical characterization is conducted over a temperature range 35 ≤T≤150 °C as a function of measurement frequency (10 ≤f≤10 6 Hz). Meaningful observation is noted only in a narrow temperature range 59 ≤T≤73 °C. These electrical data when analyzed via complex plane formalisms revealed single semicircular relaxation both in the complex capacitance ( C*) and in the modulus ( M*) planes. The physical meaning of this kind of observation is obtained on identifying the relaxation type, and then incorporating respective equivalent circuit model. The simplistic non-blocking nature of the equivalent circuit model obtained via M*-plane is established as the lumped relaxation is identified in the C*-plane. The feature of the eventual equivalent circuit model allows non-blocking aspect for the LN crystal attributing to the presence of the operative dc conduction process. Identification of this leakage dc conduction via C*-plane is portrayed in the M*-plane where the blocking nature is removed. The interacting interpretation between these two complex planes is successfully presented.

Landscape scale assessment of soil and water salinization processes in agricultural coastal area.

NASA Astrophysics Data System (ADS)

Elen Bless, Aplena; Follain, Stéphane; Coiln, François; Crabit, Armand

2017-04-01

Soil salinization is among main land degradation process around the globe. It reduces soil quality, disturbs soil function, and has harmful impacts on plant growth that would threaten agricultural sustainability, particularly in coastal areas where mostly susceptible on land degradation because of pressure from anthropogenic activities and at the same time need to preserve soil quality for supporting food production. In this presentation, we present a landscape scale analysis aiming to assess salinization process affecting wine production. This study was carried out at Serignan estuary delta in South of France (Languadoc Roussillon Region, 43˚ 28'N and 3˚ 31'E). It is a sedimentary basin near coastline of Mediterranean Sea. Field survey was design to characterize both space and time variability of soil and water salinity through water electrical conductivity (ECw) and soil 1/5 electrical conductivity (EC1/5). For water measurements, Orb River and groundwater salinity (piezometers) were determined and for soil 1737 samples were randomly collected from different soil depths (20, 50, 80, and 120 cm) between year 2012 and 2016 and measured. In order to connect with agricultural practices observations and interviews with farmers were conducted. We found that some areas combining specific criteria presents higher electrical conductivity: positions with lower elevation (a.s.l), Cambisols (Calcaric) / Fluvisols soil type (WRB) and dominated clay textures. These observations combined with geochemical determination and spatial analysis confirm our first hypothesis of sea salt intrusion as the main driven factor of soil salinity in this region. In this context, identification of salinization process, fine determination of pedological specificities and fine understanding of agricultural practices allowed us to proposed adaptation strategies to restore soil production function. Please fill in your abstract text. Key Words: Salinity, Coastal Agriculture, Landscape, Soil, Water

Nano silver diffusion behaviour on conductive polymer during doping process for high voltage application

NASA Astrophysics Data System (ADS)

Mohammad, A.; Mahmood, A.; Chin, K. T.; Danquah, M. K.; van Stratan, S.

2017-06-01

Conductive polymer had opened a new era of engineering for microelectronics and semiconductor applications. However, it is still a challenge for high voltage applications due to lower electrical conductivity compare to metals. This results tremendous energy losses during transmission and restricts its usage. In order to address such problem a novel method was investigated using nano silver particle doped iodothiophene since silver is the highest electrical conductive material. The experiments were carried out to study the organometallic diffusion behaviour of nanosilver doped iodothiophene with different concentration of iodothiophene. Five different mixing ratio between nanosilver and the solution of iodothiophene dissolved in diethyl ether were used which are 1:1.25, 1:1.5, 1:2.5, 1:3 and l:5. It was revealed that there is an effective threshold concentration of which the nano silver evenly distributed and there was no coagulation observed. These parameters laid the foundation of better doping process between the nano silver and the polymer significantly which would contribute developing conductive polymer towards high voltage application for industries that are vulnerable to corrosive environment.

Effect of silicide/silicon hetero-junction structure on thermal conductivity and Seebeck coefficient.

PubMed

Choi, Wonchul; Park, Young-Sam; Hyun, Younghoon; Zyung, Taehyoung; Kim, Jaehyeon; Kim, Soojung; Jeon, Hyojin; Shin, Mincheol; Jang, Moongyu

2013-12-01

We fabricated a thermoelectric device with a silicide/silicon laminated hetero-structure by using RF sputtering and rapid thermal annealing. The device was observed to have Ohmic characteristics by I-V measurement. The temperature differences and Seebeck coefficients of the proposed silicide/silicon laminated and bulk structure were measured. The laminated thermoelectric device shows suppression of heat flow from the hot to cold side. This is supported by the theory that the atomic mass difference between silicide and silicon creates a scattering center for phonons. The major impact of our work is that phonon transmission is suppressed at the interface between silicide and silicon without degrading electrical conductivity. The estimated thermal conductivity of the 3-layer laminated device is 126.2 +/- 3.7 W/m. K. Thus, by using the 3-layer laminated structure, thermal conductivity is reduced by around 16% compared to bulk silicon. However, the Seebeck coefficient of the thermoelectric device is degraded compared to that of bulk silicon. It is understood that electrical conductivity is improved by using silicide as a scattering center.

Percolation-induced plasmonic state and double negative electromagnetic properties of Ni-Zn Ferrite/Cu granular composite materials

NASA Astrophysics Data System (ADS)

Massango, Herieta; Kono, Koji; Tsutaoka, Takanori; Kasagi, Teruhiro; Yamamoto, Shinichiro; Hatakeyama, Kenichi

2018-05-01

Complex permeability and permittivity spectra of Ni-Zn Ferrite/Cu hybrid granular composite materials have been studied in the RF to microwave frequency range. The electrical conductivity σ shows insulating properties in the volume fraction of Cu particles below φ = 0.14. A large jump in conductivity was observed between φ = 0.14 and 0.24 indicating that the Cu particles make metallic conduction between this interval. Hence, the percolation threshold φC, was estimated to be 0.14. A percolation-induced low frequency plasmonic state with negative permittivity spectrum was observed from φ = 0.14-0.24. Meanwhile the negative permeability was observed at φ = 0.16, 0.19 and 0.24. Hence the DNG characteristic was realized in these Cu volume content in the frequency range from 105 MHz to 2 GHz.

Effect of Precipitating Electrons on Stormtime Inner Magnetospheric Electric Fields during the 17 March 2013 Storm

NASA Astrophysics Data System (ADS)

Chen, M.; Lemon, C. L.; Sazykin, S. Y.; Wolf, R.; Hecht, J. H.; Walterscheid, R. L.; Boyd, A. J.; Turner, D. L.

2015-12-01

We investigate how scattering of electrons by waves in the plasma sheet and plasmasphere affects precipitating energy flux distributions and how the precipitating electrons modify the ionospheric conductivity and electric potentials during the large 17 March 2013 magnetic storm. Of particular interest is how electron precipitation in the evening sector affects the development of the Sub-auroral Polarization Stream (SAPS) electric field that is observed at sub-auroral latitudes in that sector. Our approach is to use the magnetically and electrically self-consistent Rice Convection Model - Equilibrium (RCM-E) of the inner magnetosphere to simulate the stormtime precipitating electron distributions and the electric field. We use parameterized rates of whistler-generated electron pitch-angle scattering from Orlova and Shprits [JGR, 2014] that depend on equatorial radial distance, magnetic activity (Kp), and magnetic local time (MLT) outside the simulated plasmasphere. Inside the plasmasphere, parameterized scattering rates due to hiss [Orlova et al., GRL, 2014] are used. We compare simulated trapped and precipitating electron flux distributions with measurements from Van Allen Probes/MagEIS, POES/TED and MEPED, respectively, to validate the electron loss model. Ground-based (SuperDARN) and in-situ (Van Allen Probes/EFW) observations of electric fields are compared with the simulation results. We discuss the effect of precipitating electrons on the SAPS and inner magnetospheric electric field through the data-model comparisons.

Nature of Dielectric Properties, Electric Modulus and AC Electrical Conductivity of Nanocrystalline ZnIn2Se4 Thin Films

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Attia, A. A.; Ali, H. A. M.; Salem, G. F.; Ismail, M. I.

2018-02-01

The structural characteristics of thermally deposited ZnIn2Se4 thin films were indexed utilizing x-ray diffraction as well as scanning electron microscopy techniques. Dielectric properties, electric modulus and AC electrical conductivity of ZnIn2Se4 thin films were examined in the frequency range from 42 Hz to 106 Hz. The capacitance, conductance and impedance were measured at different temperatures. The dielectric constant and dielectric loss decrease with an increase in frequency. The maximum barrier height was determined from the analysis of the dielectric loss depending on the Giuntini model. The real part of the electric modulus revealed a constant maximum value at higher frequencies and the imaginary part of the electric modulus was characterized by the appearance of dielectric relaxation peaks. The AC electrical conductivity obeyed the Jonscher universal power law. Correlated barrier hopping model was the appropriate mechanism for AC conduction in ZnIn2Se4 thin films. Estimation of the density of states at the Fermi level and activation energy, for AC conduction, was carried out based on the temperature dependence of AC electrical conductivity.

Grain boundary dominated electrical conductivity in ultrananocrystalline diamond

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiora, Neda; Mertens, Michael; Bruhne, Kai

Here, N-type electrically conductive ultrananocrystalline diamond (UNCD) films were deposited using the hot filament chemical vapor deposition technique with a gas mixture of H 2, CH 4 and NH 3. Depending on the deposition temperature and ammonia feed gas concentration, which serves as a nitrogen source, room temperature electrical conductivities in the order of 10 –2 to 5 × 10 1S/cm and activation energies in the meV range were achieved. In order to understand the origin of the enhanced electrical conductivity and clarify the role of ammonia addition to the process gas, a set of UNCD films was grown bymore » systematically varying the ammonia gas phase concentration. These samples were analyzed with respect to their morphology and electrical properties as well as their carbon and nitrogen bonding environments. Temperature dependent electrical conductivity measurements (300–1200 K) show that the electrical conductivity of the samples increases with temperature. The near edge x-ray absorption fine structure measurements reveal that the electrical conductivity of the UNCD films does not correlate directly with ammonia addition, but depends on the total amount of sp2 bonded carbon in the deposited films.« less

Grain boundary dominated electrical conductivity in ultrananocrystalline diamond

DOE PAGES

Wiora, Neda; Mertens, Michael; Bruhne, Kai; ...

2017-10-09

Here, N-type electrically conductive ultrananocrystalline diamond (UNCD) films were deposited using the hot filament chemical vapor deposition technique with a gas mixture of H 2, CH 4 and NH 3. Depending on the deposition temperature and ammonia feed gas concentration, which serves as a nitrogen source, room temperature electrical conductivities in the order of 10 –2 to 5 × 10 1S/cm and activation energies in the meV range were achieved. In order to understand the origin of the enhanced electrical conductivity and clarify the role of ammonia addition to the process gas, a set of UNCD films was grown bymore » systematically varying the ammonia gas phase concentration. These samples were analyzed with respect to their morphology and electrical properties as well as their carbon and nitrogen bonding environments. Temperature dependent electrical conductivity measurements (300–1200 K) show that the electrical conductivity of the samples increases with temperature. The near edge x-ray absorption fine structure measurements reveal that the electrical conductivity of the UNCD films does not correlate directly with ammonia addition, but depends on the total amount of sp2 bonded carbon in the deposited films.« less

Gasket Assembly for Sealing Mating Surfaces

NASA Technical Reports Server (NTRS)

Bryant, Melvin A., III (Inventor)

2003-01-01

A pair of substantially opposed mating surfaces are joined to each other and sealed in place by means of an electrically-conductive member which is placed in proximity to the mating surfaces. The electrically-conductive member has at least one element secured thereto which is positioned to contact the mating surfaces, and which softens when the electrically-conductive member is heated by passing an electric current therethrough. The softened element conforms to the mating surfaces, and upon cooling of the softened element the mating surfaces are joined together in an effective seal. Of particular significance is an embodiment of the electrically-conductive member which is a gasket having an electrically-conductive gasket base and a pair of the elements secured to opposite sides of the gasket base. This embodiment is positioned between the opposed mating surfaces to be joined to each other. Also significant is an embodiment of the electrically-conductive member which is an electrically-conductive sleeve having an element secured to its inner surface. This embodiment surrounds cylindrical members the bases of which are the substantially opposed mating surfaces to be joined, and the element on the inner surface of the sleeve contacts the outer surfaces of the cylindrical members.

Low temperature synthesis and enhanced electrical properties by substitution of Al3+ and Cr3+ in Co-Ni nanoferrites

NASA Astrophysics Data System (ADS)

Pervaiz, Erum; Gul, I. H.

2013-10-01

Aluminum and chromium substituted Co-Ni spinel nanoferrites were prepared by sol-gel auto combustion method. Structural parameters along with electrical and magnetic properties have been investigated in the present work. Crystallite sizes of nano ferrite estimated from the peak (311) lies in the range of 13-21 nm ±2 nm and compared with crystallite sizes calculated from Williamsons-Hall plots. DC electrical resistivity variations due to the concentration of aluminum and chromium in the host ferrite have been measured from 368 K to 573 K. Increase in the room temperature DC electrical resistivity was observed up to a concentration x=0.2 and then decreases for x >0.2. Dielectric parameters (real and imaginary part of complex permittivity, dielectric loss tangent) were studied as a function of frequency (20 Hz-5 MHz) and a decrease in the dielectric parameters was observed due to substitution of nickel, aluminum and chromium ions in cobalt nanoferrites. AC conductivity, complex impedance and complex electrical modulus were studied as a function of frequency for the conduction and relaxation mechanisms in the present ferrite system. Saturation magnetization, coercivity, canting angles and magneto crystalline anisotropy variations with composition were observed and presented for the present ferrites under an applied magnetic field of 10 kOe at room temperature. It was found that both magnetization and coercivity decreases with increase in the concentration of aluminum and chromium along with a decrease in the anisotropy parameters. High DC resistivity with low dielectric parameters of the present nanoferrites make them suitable for high frequency and electromagnetic wave absorbing devices. High purity mixed Co-Ni-Al-Cr nanoferrites have been prepared by sol-gel auto combustion method. DC electrical resistivity increases due to substitution of Al3+ and Cr3+. Complex permittivity decrease for Co-Ni-Al-Cr nanoferrites. Detailed AC response analysis has been presented for mixed Co-Ni-Al-Cr nanoferrites. Magnetization and coercively reduces for Al3+ and Cr3+ doped Co-Ni ferrite nanoparticles showing that material is becoming soft magnetic.

Anisotropic electrical and thermal conductivity in Bi2AE2Co2O8+δ [AE = Ca, Sr1-xBax (x = 0.0, 0.25, 0.5, 0.75, 1.0)] single crystals

NASA Astrophysics Data System (ADS)

Dong, Song-Tao; Zhang, Bin-Bin; Xiong, Ye; Lv, Yang-Yang; Yao, Shu-Hua; Chen, Y. B.; Zhou, Jian; Zhang, Shan-Tao; Chen, Yan-Feng

2015-09-01

Bi2AE2Co2O8+δ (AE represents alkaline earth), constructed by stacking of rock-salt Bi2AE2O4 and triangle CoO2 layers alternatively along c-axis, is one of promising thermoelectric oxides. The most impressive feature of Bi2AE2Co2O8+δ, as reported previously, is their electrical conductivity mainly lying along CoO2 plane, adjusting Bi2AE2O4 layer simultaneously manipulates both thermal conductivity and electrical conductivity. It in turn optimizes thermoelectric performance of these materials. In this work, we characterize the anisotropic thermal and electrical conductivity along both ab-plane and c-direction of Bi2AE2Co2O8+δ (AE = Ca, Sr, Ba, Sr1-xBax) single crystals. The results substantiate that isovalence replacement in Bi2AE2Co2O8+δ remarkably modifies their electrical property along ab-plane; while their thermal conductivity along ab-plane only has a slightly difference. At the same time, both the electrical conductivity and thermal conductivity along c-axis of these materials also have dramatic changes. Certainly, the electrical resistance along c-axis is too high to be used as thermoelectric applications. These results suggest that adjusting nano-block Bi2AE2O4 layer in Bi2AE2Co2O8+δ cannot modify the thermal conductivity along high electrical conductivity plane (ab-plane here). The evolution of electrical property is discussed by Anderson localization and electron-electron interaction U. And the modification of thermal conductivity along c-axis is attributed to the microstructure difference. This work sheds more light on the manipulation of the thermal and electrical conductivity in the layered thermoelectric materials.

Conductivity studies of Chitosan doped with different ammonium salts: Effect of ion size

NASA Astrophysics Data System (ADS)

Mohan, C. Raja; Senthilkumar, M.; Jayakumar, K.

2015-06-01

In the present investigation influence of ion size on the electrical properties of various ammonium salts of various concentrations doped with Chitosan liquid electrolyte has been studied. The attachment of ammonium salts with Chitosan has been confirmed through FTIR Spectrum. Polarizability is calculated from the refractive index data. Addition of ammonium salts increases the conductivity. It is also observed that increase in ion size, increases the ionic conductivity due to increase in amorphous nature of the material. Increase in concentration leads to increase in conductivity due to the presence of more number of free ions.

Effective conductivity and permittivity of unsaturated porous materials in the frequency range 1 mHz–1GHz

PubMed Central

Revil, A

2013-01-01

A model combining low-frequency complex conductivity and high-frequency permittivity is developed in the frequency range from 1 mHz to 1 GHz. The low-frequency conductivity depends on pore water and surface conductivities. Surface conductivity is controlled by the electrical diffuse layer, the outer component of the electrical double layer coating the surface of the minerals. The frequency dependence of the effective quadrature conductivity shows three domains. Below a critical frequency fp, which depends on the dynamic pore throat size Λ, the quadrature conductivity is frequency dependent. Between fp and a second critical frequency fd, the quadrature conductivity is generally well described by a plateau when clay minerals are present in the material. Clay-free porous materials with a narrow grain size distribution are described by a Cole-Cole model. The characteristic frequency fd controls the transition between double layer polarization and the effect of the high-frequency permittivity of the material. The Maxwell-Wagner polarization is found to be relatively negligible. For a broad range of frequencies below 1 MHz, the effective permittivity exhibits a strong dependence with the cation exchange capacity and the specific surface area. At high frequency, above the critical frequency fd, the effective permittivity reaches a high-frequency asymptotic limit that is controlled by the two Archie's exponents m and n like the low-frequency electrical conductivity. The unified model is compared with various data sets from the literature and is able to explain fairly well a broad number of observations with a very small number of textural and electrochemical parameters. It could be therefore used to interpret induced polarization, induction-based electromagnetic methods, and ground penetrating radar data to characterize the vadose zone. PMID:23576823

Infection Risk From Conducted Electrical Weapon Probes: What Do We Know?

PubMed

Kroll, Mark W; Ritter, Mollie B; Guilbault, Richard A; Panescu, Dorin

2016-11-01

Concern has been raised over the infection risk of the TASER electrical weapon since the probes penetrate the skin. The manufacturing process produces unsterilized probes with a 5% rate of Staphylococcus aureus contamination. Voluntary recipients (n = 208) of probe exposures were surveyed and there were no self-observations of infection. With over 3.3 million probe landings, there have been 10 case reports of penetrations of sensitive tissue with no reported infections. The electrical field was modeled and found that the electrical pulses generate a field of over 1200 V/mm on the dart portion. This is sufficient to sterilize the dart via electroporation. Electrical weapon probes appear to have a very low (possibly zero) rate of infection. The factors leading to this low infection rate appear to be a manufacturing process producing a low rate of bacterial contamination and the pulses sterilizing the dart via electroporation. © 2016 American Academy of Forensic Sciences.

Assembly of 1D nanofibers into a 2D bi-layered composite nanofibrous film with different functionalities at the two layers via layer-by-layer electrospinning.

PubMed

Wang, Zijiao; Ma, Qianli; Dong, Xiangting; Li, Dan; Xi, Xue; Yu, Wensheng; Wang, Jinxian; Liu, Guixia

2016-12-21

A two-dimensional (2D) bi-layered composite nanofibrous film assembled by one-dimensional (1D) nanofibers with trifunctionality of electrical conduction, magnetism and photoluminescence has been successfully fabricated by layer-by-layer electrospinning. The composite film consists of a polyaniline (PANI)/Fe 3 O 4 nanoparticle (NP)/polyacrylonitrile (PAN) tuned electrical-magnetic bifunctional layer on one side and a Tb(TTA) 3 (TPPO) 2 /polyvinylpyrrolidone (PVP) photoluminescent layer on the other side, and the two layers are tightly combined face-to-face together into the novel bi-layered composite film of trifunctionality. The brand-new film has totally different characteristics at the double layers. The electrical conductivity and magnetism of the electrical-magnetic bifunctional layer can be, respectively, tunable via modulating the PANI and Fe 3 O 4 NP contents, and the highest electrical conductivity can reach up to the order of 10 -2 S cm -1 , and predominant intense green emission at 545 nm is obviously observed in the photoluminescent layer under the excitation of 357 nm single-wavelength ultraviolet light. More importantly, the luminescence intensity of the photoluminescent layer remains almost unaffected by the electrical-magnetic bifunctional layer because the photoluminescent materials have been successfully isolated from dark-colored PANI and Fe 3 O 4 NPs. By comparing with the counterpart single-layered composite nanofibrous film, it is found that the bi-layered composite nanofibrous film has better performance. The novel bi-layered composite nanofibrous film with trifunctionality has potential in the fields of nanodevices, molecular electronics and biomedicine. Furthermore, the design conception and fabrication technique for the bi-layered multifunctional film provide a new and facile strategy towards other films of multifunctionality.

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.

Morphology, structure, optical, and electrical properties of AgSbO3

NASA Astrophysics Data System (ADS)

Yi, Z. G.; Liu, Y.; Withers, R. L.

2010-07-01

The morphology of defect pyrochlore-type, AgSbO3 microparticle/nanoparticles obtained via solid state reaction evolve from irregular to Fullerene-like polyhedra before finally decomposing into metal-organic framework-5 like particles with increase in sintering temperature. The defect pyrochlore-type AgSbO3 particles are slightly Ag deficient while the valence of the antimony ion is shown to be +5 giving rise to a probable stoichiometry of Ag1-xSbVO3-x/2, with x˜0.01-0.04. A highly structured diffuse intensity distribution observed via electron diffraction is interpreted in terms of correlated displacements of one-dimensional (1D) silver ion chains along ⟨110⟩ directions. A redshifting in the absorption edges in UV-visible absorption spectra is observed for samples prepared at sintering temperatures higher than 1000 °C and attributed to the surface plasma resonance effect associated with small amounts of excess metallic Ag on the Ag1-xSbVO3-x/2 particles. An electrical properties investigation of the silver antimonate samples via dielectric, conductivity, and electric modulus spectroscopy shows a prominent dielectric relaxation associated with grain boundaries. The silver ion conductivity is associated with correlated displacements of 1D silver ion chains along ⟨110⟩ directions.

Novel Electronically Conducting Tellurium Oxides

NASA Astrophysics Data System (ADS)

Subramanian, Mas; Siritanon, Theerunan; Sleight, Arthur

2010-03-01

Tellurium oxides seldom show measurable electronic conductivity. Tellurium oxides that appear to have Te^5+ contain Te^4+ and Te^6+ in two distinct crystallographic sites and are electronic insulators. Here we report on the synthesis and characterization of several new tellurium rich oxides of the general formula, CsMxTe2-xO6, crystallizing in modified pyrochlore structure. Most of the compounds reported here are black in color with some exhibiting good electronic conductivities (2 S/cm) and Seebeck measurements indicate all are n-type. The observation of high electronic conductivities in compounds like CsGe0.5Te1.5O6, CsAl0.33Te1.67O6 confirms that observed conductivity is arising from doping of electrons into the empty 5s orbitals of Te^6+. This reduction is apparently accompanied with some small deviation from the ideal formula: oxygen content and/or ratio of cations on octahedral sites. This is in consistent with single-crystal X-ray as well as powder neutron diffraction structure refinements and the observed sign of the Seebeck coefficient. To our knowledge, this is a first observance of high electrical conductivity in mixed valent tellurium oxides.

Solar wind: Internal parameters driven by external source

NASA Technical Reports Server (NTRS)

Chertkov, A. D.

1995-01-01

A new concept interpreting solar wind parameters is suggested. The process of increasing twofold of a moving volume in the solar wind (with energy transfer across its surface which is comparable with its whole internal energy) is a more rapid process than the relaxation for the pressure. Thus, the solar wind is unique from the point of view of thermodynamics of irreversible processes. The presumptive source of the solar wind creation - the induction electric field of the solar origin - has very low entropy. The state of interplanetary plasma must be very far from the thermodynamic equilibrium. Plasma internal energy is contained mainly in non-degenerate forms (plasma waves, resonant plasma oscillations, electric currents). Microscopic oscillating electric fields in the solar wind plasma should be about 1 V/m. It allows one to describe the solar wind by simple dissipative MHD equations with small effective mean free path (required for hydrodynamical description), low value of electrical conductivity combined with very big apparent thermal conductivity (required for observed solar wind acceleration). These internal parameters are interrelated only due to their origin: they are externally driven. Their relation can change during the interaction of solar wind plasma with an obstacle (planet, spacecraft). The concept proposed can be verified by the special electric field measurements, not ruining the primordial plasma state.

40 CFR 60.52Da - Recordkeeping requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... (CONTINUED) STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES Standards of Performance for Electric Utility... opacity field data sheets; (2) For each performance test conducted using Method 22 of appendix A-4 of this... performance test; (iii) Copies of all visible emission observer opacity field data sheets; and (iv...

Contact-independent electrical conductance measurement

DOEpatents

Mentzel, Tamar S.; MacLean, Kenneth; Kastner, Marc A.; Ray, Nirat

2017-01-24

Electrical conductance measurement system including a one-dimensional semiconducting channel, with electrical conductance sensitive to electrostatic fluctuations, in a circuit for measuring channel electrical current. An electrically-conductive element is disposed at a location at which the element is capacitively coupled to the channel; a midpoint of the element aligned with about a midpoint of the channel, and connected to first and second electrically-conductive contact pads that are together in a circuit connected to apply a changing voltage across the element. The electrically-conductive contact pads are laterally spaced from the midpoint of the element by a distance of at least about three times a screening length of the element, given in SI units as (K.di-elect cons..sub.0/e.sup.2D(E.sub.F)).sup.1/2, where K is the static dielectric constant, .di-elect cons..sub.0 is the permittivity of free space, e is electron charge, and D(E.sub.F) is the density of states at the Fermi energy for the element.

Lunisolar Tides Influence on Electrical Conductivity of the Earth's Crust in the Territory of Kola Peninsula

NASA Astrophysics Data System (ADS)

Zhamaletdinov, A. A.; Shevtsov, A. N.; Korotkova, T. G.

2018-05-01

The results of studying the influence of lunisolar tides on the electrical conductivity of the Earth's crust in the territory of the Kola Peninsula are presented. Along with the results obtained by the authors, the data of other researchers are also considered. All the studies are based on the analysis of the field produced by the Zevs facility transmitting extremely low frequency (ELF) signals at 82-83 Hz. The measurements were carried out in different years at the Avva-Guba (1998), Lovozero (2009), and Imandra-Varzuga polygon (IVP) monitoring sites (2013) located 180, 90, and 160 km from the transmitter, respectively. The negative correlation between the tides and crustal electrical resistivity is revealed at all the points. This means that tidal rises of the Earth's surface are accompanied by a decrease in resistivity and vice versa. The overview shows that the higher the resistivity of separate Earth's crustal blocks the higher the relative amplitudes of the corresponding tidal responses that are observed.

The fabrication of highly conductive and flexible Ag patterning through baking Ag nanosphere-nanoplate hybrid ink at a low temperature of 100 °C

NASA Astrophysics Data System (ADS)

Han, Y. D.; Zhang, S. M.; Jing, H. Y.; Wei, J.; Bu, F. H.; Zhao, L.; Lv, X. Q.; Xu, L. Y.

2018-04-01

With the aim of developing highly conductive ink for flexible electronics on heat-sensitive substrates, Ag nanospheres and nanoplates were mixed to synthesize hybrid inks. Five kinds of hybrid ink and two types of pure ink were written to square shape on Epson photo paper using rollerball pens, and sintered at a low temperature (100 °C). The microstructure, electrical resistivity, surface porosity, hardness and flexibility of silver patterns were systematically investigated and compared. It was observed that the optimal mixing ratio of nanospheres and nanoplates was 1:1, which equipped the directly written pattern with excellent electrical and mechanical properties. The electrical resistivity was 0.103 μΩ · m, only 6.5 times that of bulk silver. The enhancement compared to pure silver nanospheres or nanoplates based ink was due to the combined action of nanospheres and nanoplates. This demonstrates a valuable way to prepare Ag nanoink with good performance for printed/written electronics.

The fabrication of highly conductive and flexible Ag patterning through baking Ag nanosphere-nanoplate hybrid ink at a low temperature of 100 °C.

PubMed

Han, Y D; Zhang, S M; Jing, H Y; Wei, J; Bu, F H; Zhao, L; Lv, X Q; Xu, L Y

2018-02-12

With the aim of developing highly conductive ink for flexible electronics on heat-sensitive substrates, Ag nanospheres and nanoplates were mixed to synthesize hybrid inks. Five kinds of hybrid ink and two types of pure ink were written to square shape on Epson photo paper using rollerball pens, and sintered at a low temperature (100 °C). The microstructure, electrical resistivity, surface porosity, hardness and flexibility of silver patterns were systematically investigated and compared. It was observed that the optimal mixing ratio of nanospheres and nanoplates was 1:1, which equipped the directly written pattern with excellent electrical and mechanical properties. The electrical resistivity was 0.103 μΩ · m, only 6.5 times that of bulk silver. The enhancement compared to pure silver nanospheres or nanoplates based ink was due to the combined action of nanospheres and nanoplates. This demonstrates a valuable way to prepare Ag nanoink with good performance for printed/written electronics.

Solar-terrestrial coupling through atmospheric electricity

NASA Technical Reports Server (NTRS)

Roble, R. G.; Hays, P. B.

1979-01-01

There are a number of measurements of electrical variations that suggest a solar-terrestrial influence on the global atmospheric electrical circuit. The measurements show variations associated with solar flares, solar magnetic sector boundary crossings, geomagnetic activity, aurorae, differences between ground current and potential gradients at high and low latitudes, and solar cycle variations. The evidence for each variation is examined. Both the experimental evidence and the calculations made with a global model of atmospheric electricity indicate that there is solar-terrestrial coupling through atmospheric electricity which operates by altering the global electric current and field distribution. A global redistribution of currents and fields can be caused by large-scale changes in electrical conductivity, by alteration of the columnar resistance between thunderstorm cloud tops and the ionosphere, or by both. If the columnar resistance is altered above thunderstorms, more current will flow in the global circuit, changing the ionospheric potential and basic circuit variables such as current density and electric fields. The observed variations of currents and fields during solar-induced disturbances are generally less than 50% of mean values near the earth's surface.

Giant magmatic water reservoirs at mid-crustal depth inferred from electrical conductivity and the growth of the continental crust

NASA Astrophysics Data System (ADS)

Laumonier, Mickael; Gaillard, Fabrice; Muir, Duncan; Blundy, Jon; Unsworth, Martyn

2017-01-01

The formation of the continental crust at subduction zones involves the differentiation of hydrous mantle-derived magmas through a combination of crystallization and crustal melting. However, understanding the mechanisms by which differentiation occurs at depth is hampered by the inaccessibility of the deep crust in active continental arcs. Here we report new high-pressure electrical conductivity and petrological experiments on hydrated andesitic melt from Uturuncu volcano on the Bolivian Altiplano. By applying our results to regional magnetotelluric data, we show that giant conductive anomalies at mid-crustal levels in several arcs are characterized by relatively low amounts of intergranular andesitic partial melts with unusually high dissolved water contents (≥8 wt.% H2O). Below Uturuncu, the Altiplano-Puna Magma Body (APMB) displays an electrical conductivity that requires high water content (up to 10 wt.%) dissolved in the melt based on crystal-liquid equilibria and melt H2O solubility experiments. Such a super-hydrous andesitic melt must constitute about 10% of the APMB, the remaining 90% being a combination of magmatic cumulates and older crustal rocks. The crustal ponding level of these andesites at around 6 kbar pressure implies that on ascent through the crust hydrous magmas reach their water saturation pressure in the mid-crust, resulting in decompression-induced crystallization that increases magma viscosity and in turn leads to preferential stalling and differentiation. Similar high conductivity features are observed beneath the Cascades volcanic arc and Taupo Volcanic Zone. This suggests that large amounts of water in super-hydrous andesitic magmas could be a common feature of active continental arcs and may illustrate a key step in the structure and growth of the continental crust. One Sentence Summary: Geophysical, laboratory conductivity and petrological experiments reveal that deep electrical conductivity anomalies beneath the Central Andes, Cascades and Taupo Volcanic Zone image the ponding of super-hydrous andesitic melts which contributes to the growth of continental crust.

Against the grain: The physical properties of anisotropic partially molten rocks

NASA Astrophysics Data System (ADS)

Ghanbarzadeh, S.; Hesse, M. A.; Prodanovic, M.

2014-12-01

Partially molten rocks commonly develop textures that appear close to textural equilibrium, where the melt network evolves to minimize the energy of the melt-solid interfaces, while maintaining the dihedral angle θ at solid-solid-melt contact lines. Textural equilibrium provides a powerful model for the melt distribution that controls the petro-physical properties of partially molten rocks, e.g., permeability, elastic moduli, and electrical resistivity. We present the first level-set computations of three-dimensional texturally equilibrated melt networks in rocks with an anisotropic fabric. Our results show that anisotropy induces wetting of smaller grain boundary faces for θ > 0 at realistic porosities ϕ < 3%. This was previously not thought to be possible at textural equilibrium and reconciles the theory with experimental observations. Wetting of the grain boundary faces leads to a dramatic redistribution of the melt from the edges to the faces that introduces strong anisotropy in the petro-physical properties such as permeability, effective electrical conductivity and mechanical properties. Figure, on left, shows that smaller grain boundaries become wetted at relatively low melt fractions of 3% in stretched polyhedral grains with elongation factor 1.5. Right plot represents the ratio of melt electrical conductivity to effective conductivity of medium (known as formation factor) as an example of anisotropy in physical properties. The plot shows that even slight anisotropy in grains induces considerable anisotropy in electrical properties.

Resolving the deep electrical resistivity structure at Central Pontides, Northern Turkey by three-dimensional magnetotelluric modeling

NASA Astrophysics Data System (ADS)

Özaydın, Sinan; Bülent Tank, Sabri; Karaş, Mustafa; Sandvol, Eric

2017-04-01

Wide-band magnetotelluric (MT) (360 Hz - 1860 sec) data were acquired at 25 sites along a north - south aligned profile cutting across the Central Pontides, which are made up of highly metamorphosed formations and their tectonic boundaries including: a Lower Cretaceous-aged turbidite sequence, Central Pontides Metamorphic Supercomplex (CPMS), North Anatolian Fault Zone (NAFZ) and Izmir-Ankara-Erzincan Suture Zone (IAESZ). Dimensionality analyses over all observation points demonstrated high electrical anisotropy, which indicates complex geological and tectonic structures. This dimensional complexity and presence of the electrically conductive Black Sea augmented the requirement for a three-dimensional analysis. Inverse modeling routines, ModEM (Egbert and Kelbert, 2012) and WSINV3DMT (Siripunvaraporn et al., 2005) were utilized to reveal the geo-electrical implications over this unusually complicated region. Interpretations of the resultant models are summarized as follows: (i) Çangaldaǧ and Domuzdaǧ complexes appear as highly resistive bodies bounded by north dipping faults. (ii) Highly conductive Tosya Basin sediments overlain the ophiolitic materials as a thin cover located at the south of the NAFZ. (iii) North Anatolian Fault and some auxiliary faults within the system exhibit conductive-resistive interfaces that reach to lower crustal levels. (iv) IAESZ is a clear feature marked by the resistivity contrast between NAFZ-related sedimentary basins and Neo-Tethyan ophiolites.

Annealing effects on electrical behavior of gold nanoparticle film: Conversion of ohmic to non-ohmic conductivity

NASA Astrophysics Data System (ADS)

Ebrahimpour, Zeinab; Mansour, Nastaran

2017-02-01

This paper reports on the electrical behavior of self-assembled gold nanoparticle films before and after high-temperature annealing in ambient environment. These films are made by depositing gold nanoparticles from a colloidal solution on glass substrates using centrifuge deposition technique. The current-voltage (I-V) characteristics of these films exhibits ohmic and non-ohmic properties for un-annealed and annealed films respectively. As the annealing time duration increases, the onset of non-ohmic behavior occurs at higher voltages. To understand the underlying mechanisms for the observed electrical conduction behavior in these films and how electrical conduction is effected by film morphology and structural properties before and after annealing, systematic comparative studies based on scanning electron microscopy (SEM), UV-vis absorption spectroscopy and X-ray photoelectron spectroscopy (XPS) have been performed. The morphology of the films shows that the assembled gold nanoparticles are distributed on the substrate in a random way before annealing. After 2 h annealing gold nanoparticles exhibit a higher filling fraction when examined by SEM, which means that they coalesce, upon annealing, with respect to un-annealed films. The UV-vis absorption spectra of the films show that there is a red-shift and broadening in the absorption band for the annealed films. The observed phenomenon is related to the plasmon near-field coupling effect and suggests that the nanoparticle ensembles interspacing has decreased. The structural and crystallinity of the films exhibit amorphous structure before annealing and pure crystalline phases with a preferential growth direction along the (111) plane after annealing. The XPS analysis further suggests the existence of the stable thin oxide layer in the phase of Au2O3 in the annealed films. The I-V characteristics have been described by Simmons' model for tunnel transport through metal-insulator-metal (MIM) junctions. The Fowler-Nordheim (F-N) plots show the transition of the in-plane charge transport mechanism from direct tunneling to field emission in annealed films. Our results suggest that, the formation of a thin layer of Au2O3 , the proximity of the nanoparticles as well as their higher filling fraction are important parameters related with the tunneling process enhancement. The observed non-ohmic conductivity property can make these self-assembled gold nanoparticle films very useful structures in different applications such as sensing, resistors and other nanoelectronic applications.

Mechanisms of Electrical Activation and Conduction in the Gastrointestinal System: Lessons from Cardiac Electrophysiology

PubMed Central

Tse, Gary; Lai, Eric Tsz Him; Yeo, Jie Ming; Tse, Vivian; Wong, Sunny Hei

2016-01-01

The gastrointestinal (GI) tract is an electrically excitable organ system containing multiple cell types, which coordinate electrical activity propagating through this tract. Disruption in its normal electrophysiology is observed in a number of GI motility disorders. However, this is not well characterized and the field of GI electrophysiology is much less developed compared to the cardiac field. The aim of this article is to use the established knowledge of cardiac electrophysiology to shed light on the mechanisms of electrical activation and propagation along the GI tract, and how abnormalities in these processes lead to motility disorders and suggest better treatment options based on this improved understanding. In the first part of the article, the ionic contributions to the generation of GI slow wave and the cardiac action potential (AP) are reviewed. Propagation of these electrical signals can be described by the core conductor theory in both systems. However, specifically for the GI tract, the following unique properties are observed: changes in slow wave frequency along its length, periods of quiescence, synchronization in short distances and desynchronization over long distances. These are best described by a coupled oscillator theory. Other differences include the diminished role of gap junctions in mediating this conduction in the GI tract compared to the heart. The electrophysiology of conditions such as gastroesophageal reflux disease and gastroparesis, and functional problems such as irritable bowel syndrome are discussed in detail, with reference to ion channel abnormalities and potential therapeutic targets. A deeper understanding of the molecular basis and physiological mechanisms underlying GI motility disorders will enable the development of better diagnostic and therapeutic tools and the advancement of this field. PMID:27303305

The electrical conductivity of in vivo human uterine fibroids.

PubMed

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

2011-01-01

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

Penetration of Nonstationary Ionospheric Electric Fields into Lower Atmospheric Layers in the Global Electric Circuit Model

NASA Astrophysics Data System (ADS)

Morozov, V. N.

2018-01-01

The problem of the penetration of nonstationary ionospheric electric fields into the lower atmospheric layers is considered based on the model of the global electric circuit in the Earth's atmosphere. For the equation of the electric field potential, a solution that takes into account exponential variation in the electrical conductivity with height has been obtained. Analysis of the solution made it possible to reveal three cases of the dependence of the solution on height. The first case (the case of high frequencies) corresponds to the Coulomb approximation, when the electrical conductivity of the atmosphere can be neglected. In the case of low frequencies (when the frequency of changes in the ionosphere potential is less than the quantity reciprocal to the time of electric relaxation of the atmosphere), a quasi-stationary regime, in which the variation in the electric potential of the atmosphere is determined by the electric conduction currents, occurs. In the third case, due to the increase in the electrical conductivity of the atmosphere, two spherical regions appear: with the Coulomb approximation in the lower region and conduction currents in the upper one. For these three cases, formulas for estimating the electric field strength near the Earth's surface have been obtained.

Electrical properties of a novel 1,3-bis-(p-iminobenzoic acid) indane Langmuir-Blodgett films containing ZnS nanoparticles.

PubMed

Sari, H; Uzunoglu, T; Capan, R; Serin, N; Serin, T; Tarimci, C; Hassan, A K; Namli, H; Turhan, O

2007-08-01

ZnS nanoparticles have been formed in a newly synthesized 1,3-bis-(p-iminobenzoic acid) indane (IBI) by exposing Zn2+ doped multilayered Langmuir-Blodgett (LB) film to H2S gas after the growth. The formation of ZnS nanoparticles in the LB film structure was verified by measuring UV-Visible absorption spectra. DC electrical measurements were carried out for thin films of IBI prepared in a metal/LB films/metal sandwich structure with and without ZnS nanoparticles. It was observed that ZnS nanoparticles in the LB films cause a blue-shift in the absorption spectra as well as a decrease in both capacitance and conductivity values. By analysing I-V curves and assuming a Schottky conduction mechanism the barrier height was found to be about 1.13 eV and 1.21 eV for IBI LB films without and with ZnS nanoparticles, respectively. It is thought that the presence of ZnS nanoparticles influences the barrier height at the metal-organic film interface and causes a change in electrical conduction properties of LB films.

Properties of carbon composite paper derived from coconut coir as a function of polytetrafluoroethylene content

NASA Astrophysics Data System (ADS)

Destyorini, Fredina; Indriyati; Indayaningsih, Nanik; Prihandoko, Bambang; Zulfia Syahrial, Anne

2018-03-01

The carbon composite papers were produced by utilizing carbon materials from coconut coir. In the present work, carbon composite papers (CCP) were prepared by mixing carbon materials in the form of powder and fibre with polymer (ethylene vinyl acetate and polyethylene glycol) in xylene at 100°C. Then, polytetrafluoroethylene (PTFE) with different content was used to treat the surface of CCP. The properties of PTFE-coated CCP were analysed by means of contact angle measurement, tensile testing, porosity, density, and electrical conductivity measurements. As expected, all CCP’s surfaces treated with PTFE were found to be hydrophobic with contact angle >120° and relatively constant during 60 minutes measurement. Furthermore, water contact angle, density, and mechanical properties of CCP generally increase with increasing PTFE content. However, the porosity and electrical conductivity of CCP decrease slightly as the PTFE content increased from 0 wt% to 30 wt%. Based on the observation and analysis, the optimum PTFE content on CCP was 20 %, in which the mechanical properties and hydrophobicity behaviour were improved significantly, but it was only caused a very small drop in porosity and electrical conductivity

Reactive conductors for increased efficiency of exploding foil initiators and other detonators

DOEpatents

Morris, Christopher J.; Wilkins, Paul; May, Chadd; Zakar, Eugene

2015-05-05

Provided among other things are reactive energetic material systems used for conductors in detonators for increased efficiencies. According to an embodiment, a detonator may include: a conductor including at least two constituents including (i) an electrically conductive constituent, and (ii) an electrically non-conductive constituent, that when subjected to sufficient electrical energy, result in an exothermic reaction; and a flyer plate having a non-conductive surface in contact with said conductor. When the sufficient electrical energy is supplied to said conductor, rapid heating and vaporization of at least a portion of the conductor occurs so as to explosively drive at least a portion of the flyer plate away from said conductor. In an embodiment, a multilayer conductor may be formed of alternating layers of at least one electrically conductive layer, and at least one electrically non-conductive layer, that when subjected to sufficient electrical energy, result in an exothermic reaction.

Picosecond Electric-Field-Induced Threshold Switching in Phase-Change Materials.

PubMed

Zalden, Peter; Shu, Michael J; Chen, Frank; Wu, Xiaoxi; Zhu, Yi; Wen, Haidan; Johnston, Scott; Shen, Zhi-Xun; Landreman, Patrick; Brongersma, Mark; Fong, Scott W; Wong, H-S Philip; Sher, Meng-Ju; Jost, Peter; Kaes, Matthias; Salinga, Martin; von Hoegen, Alexander; Wuttig, Matthias; Lindenberg, Aaron M

2016-08-05

Many chalcogenide glasses undergo a breakdown in electronic resistance above a critical field strength. Known as threshold switching, this mechanism enables field-induced crystallization in emerging phase-change memory. Purely electronic as well as crystal nucleation assisted models have been employed to explain the electronic breakdown. Here, picosecond electric pulses are used to excite amorphous Ag_{4}In_{3}Sb_{67}Te_{26}. Field-dependent reversible changes in conductivity and pulse-driven crystallization are observed. The present results show that threshold switching can take place within the electric pulse on subpicosecond time scales-faster than crystals can nucleate. This supports purely electronic models of threshold switching and reveals potential applications as an ultrafast electronic switch.