Dispersive and directional electrical conductivity and dielectric permittivity of conductive-mineral-bearing samples derived from multifrequency tensor electromagnetic induction measurements

Geophysics ◽  
2017 ◽  
Vol 82 (4) ◽  
pp. D211-D223 ◽  
Author(s):  
Siddharth Misra ◽  
Carlos Torres-Verdín ◽  
Dean Homan ◽  
John Rasmus
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Permittivity ◽  
Glass Bead ◽  
Frequency Dispersion ◽  
Source Rocks ◽  
Relative Dielectric Permittivity ◽  
Electrically Conductive ◽  
Mineral Inclusions ◽  
Em Field ◽  
Graphite Inclusions

Organic-rich mudrocks, hydrocarbon-bearing conventional formations, and source rocks generally contain pyrite, rutile, graphite, graphitic precursors, and other electrically conductive minerals in the form of veins, laminations, flakes, and grains. Under redox-inactive subsurface conditions, when an external electromagnetic (EM) field is applied to geomaterials containing conductive mineral inclusions, ions in pore-filling brine and charge carriers (electrons and holes) in electrically conductive mineral inclusions migrate, accumulate/deplete, and diffuse around impermeable host-inclusion interfaces. These EM-field-induced phenomena are referred to as perfectly polarized interfacial polarization (PPIP) phenomena, and they alter the effective electrical conductivity [Formula: see text] and effective relative dielectric permittivity [Formula: see text] of geomaterials. In addition, the relaxation process associated with such polarization phenomena and the time required to fully develop and dissipate the EM-field-induced polarization gives rise to frequency dispersion of [Formula: see text] and [Formula: see text] of geomaterials containing conductive mineral inclusions. A laboratory-based EM apparatus, referred to as a whole-core EM induction tool, was used to measure the directional, multifrequency EM response of brine-saturated 4 in diameter (10.16 cm diameter), 2 ft long (0.61 m long), glass-bead packs containing uniformly distributed pyrite and graphite inclusions. We then implemented a semianalytic (SA) EM forward model, referred to as the SA model, to compute the [Formula: see text] and [Formula: see text] of these conductive-mineral-bearing glass-bead packs. The estimated [Formula: see text] and [Formula: see text] of conductive-mineral-bearing packs exhibit directional and frequency dispersive characteristics, which can be explained using the theory of PPIP phenomena. Relative variations in [Formula: see text] and [Formula: see text] due to frequency dispersion were as large as [Formula: see text] and [Formula: see text], respectively, between the values estimated at 20 and 260 kHz. Computed values of [Formula: see text] of conductive-mineral-bearing packs were unusually large in the range of 103–106, whereas the corresponding values of [Formula: see text] exhibited strong dependence on volume content, size, and metallic nature of conductive mineral inclusions, brine salinity, and frequency. Furthermore, packs containing uniformly distributed pyrite and graphite inclusions exhibited conductivity and permittivity anisotropy in the range of one to two.

Influence of graphene–carbon nanotubes and processing parameters on electrical and dielectric properties of polypropylene nanocomposites

2021 ◽  
pp. 002199832110067
Author(s):  
UO Uyor ◽  
API Popoola ◽  
OM Popoola ◽  
VS Aigbodion
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Dielectric Permittivity ◽  
Graphene Nanosheets ◽  
Processing Parameters ◽  
Melt Processing ◽  
Future Research ◽  
Relative Dielectric Permittivity ◽  
Melt Compounding ◽  
Fabrication Parameters

In this study, the effect of carbon nanotubes (CNTs) and graphene nanosheets (GNs) on the microstructure, electrical conductivity and relative dielectric permittivity of polypropylene (PP) nanocomposites were investigated in relation to the melt compounding parameters. Although CNTs/GNs can significantly improve the conductivity and permittivity of PP nanocomposites, more significant results can be obtained by using optimal fabrication parameters. For optimal melt processing parameters using Taguchi optimization method, electrical conductivity and relative dielectric permittivity of about 3.08 × 10−5 S/m and 158.97 were achieved, whereas only about 1.34 × 10−11 S/m and 2.02 were measured for pure PP respectively. Therefore, this study showcased optimal melt compounding process parameters for the endless future research on PP-CNTs/GNs nanocomposites for various advanced engineering applications. This will also guide future research on the uniform use of melt fabrication parameters for proximity in comparison of results published on PP-CNTs/GNs nanocomposites.

Interfacial polarization of disseminated conductive minerals in absence of redox-active species — Part 1: Mechanistic model and validation

Geophysics ◽  
2016 ◽  
Vol 81 (2) ◽  
pp. E139-E157 ◽  
Author(s):  
S. Misra ◽  
C. Torres-Verdín ◽  
A. Revil ◽  
J. Rasmus ◽  
D. Homan
Keyword(s):  
Electrical Conductivity ◽  
Mechanistic Model ◽  
Interfacial Polarization ◽  
Active Species ◽  
Surface Conductance ◽  
Electrically Conductive ◽  
Mineral Inclusions ◽  
Redox Active ◽  
Polarization Phenomena ◽  
Complex Valued

Electrically conductive mineral inclusions are commonly present in organic-rich mudrock and source-rock formations such as veins, laminations, rods, grains, flakes, and beds. Laboratory and subsurface electromagnetic (EM) measurements performed on geomaterials containing electrically conductive inclusions generally exhibit frequency dispersion due to interfacial polarization phenomena at host-inclusion interfaces. In the absence of redox-active species, surfaces of electrically conductive mineral inclusions are impermeable to the transport of charge carriers, inhibit the exchange of charges and behave as perfectly polarized (PP) interfaces under the influence of an externally applied EM field. Interfacial polarization phenomena involving charge separation, migration, accumulation/depletion, and relaxation around PP interfaces is referred to as PP interfacial polarization; it influences the magnitude and direction of the electric field and charge carrier migration in the geomaterial. We have developed a mechanistic model to quantify the complex-valued electrical conductivity response of geomaterials containing electrically conductive mineral inclusions, such as pyrite and magnetite, uniformly distributed in a fluid-filled, porous matrix made of nonconductive grains possessing surface conductance, such as silica and clay grains. The model first uses a linear approximation of the Poisson-Nernst-Planck equations of dilute solution theory to determine the induced dipole moment of a single isolated conductive inclusion and that of a single isolated nonconductive grain surrounded by an electrolyte. A consistent effective-medium formulation was then implemented to determine the effective complex-valued electrical conductivity of the geomaterial. Model predictions were in good agreement with laboratory measurements of multifrequency complex-valued electrical conductivity, relaxation time, and chargeability of mixtures containing electrically conductive inclusions.

Interfacial polarization of disseminated conductive minerals in absence of redox-active species — Part 2: Effective electrical conductivity and dielectric permittivity

Geophysics ◽  
2016 ◽  
Vol 81 (2) ◽  
pp. E159-E176 ◽  
Author(s):  
S. Misra ◽  
C. Torres-Verdín ◽  
A. Revil ◽  
J. Rasmus ◽  
D. Homan
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Permittivity ◽  
Electric Field ◽  
Relative Permittivity ◽  
Effective Conductivity ◽  
Interfacial Polarization ◽  
Surface Conductance ◽  
Frequency Dependent ◽  
Mineral Inclusions ◽  
Effective Electrical Conductivity

Hydrocarbon-bearing conventional formations, mudrock formations, and source-rock formations generally contain clays, pyrite, magnetite, graphitelike carbon, and/or other electrically conductive mineral inclusions. Under redox-inactive conditions, these inclusions give rise to perfectly polarized interfacial polarization (PPIP) when subjected to an external electric field. Effective electrical conductivity and dielectric permittivity of geomaterials containing such inclusions are frequency-dependent properties due to the electric-field-induced interfacial polarization and associated charge relaxation around host-inclusion interfaces. Existing resistivity interpretation techniques do not account for PPIP phenomena, and hence they can lead to inaccurate estimation of water saturation, total organic content, and conductivity of formation water based on subsurface galvanic resistivity, electromagnetic (EM) induction, and EM propagation measurements in the presence of conductive mineral inclusions. In the first paper of our two-part publication series, we derived a mechanistic electrochemical model, the PPIP model, and we validated a coupled model that integrates the PPIP model with a surface-conductance-assisted interfacial polarization (SCAIP) model to quantify the frequency-dependent electrical complex conductivity of geomaterials. We have used the PPIP-SCAIP model to evaluate the dependence of effective complex-valued conductivity of geologic mixtures on (1) frequency, (2) conductivity of the host medium, and (3) material, size, and the shape of inclusions. Notably, we have used the PPIP-SCAIP model to identify rock conditions that give rise to significant differences in effective conductivity and effective relative permittivity of conductive-inclusion-bearing mixtures from those of conductive-inclusion-free homogeneous media. For a mixture containing as low as a 5% volume fraction of disseminated conductive inclusions, the low-frequency effective conductivity of the mixture is in the range of [Formula: see text] to [Formula: see text] with respect to the host conductivity for frequencies between 100 Hz and 100 kHz. Further, the high-frequency effective relative permittivity of that mixture is in the range of [Formula: see text] to [Formula: see text] with respect to the host relative permittivity for frequencies between 100 kHz and 10 MHz.

Conductivity behavior of n-type semiconducting ferrites from hydrothermal powders

1998 ◽  
Vol 13 (8) ◽  
pp. 2190-2194 ◽  
Author(s):  
Anderson Dias ◽  
Roberto Luiz Moreira
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Permittivity ◽  
Temperature Dependence ◽  
Sintering Temperature ◽  
Frequency Dispersion ◽  
Ferrous Ions ◽  
Electron Hopping ◽  
Before And After ◽  
Very High ◽  
Conductivity Behavior

The frequency and temperature dependencies of the dielectric permittivity and of the electrical conductivity of excess ferrous ions hydrothermal NiZn ferrites were analyzed before and after sintering. A decreasing tendency with frequency of the dielectric responses was observed, but the high permittivities attained (ε′ ≈ 105) masked any relaxation in these materials. This behavior is characteristic of n-type semiconducting ferrites, where electron hopping between Fe+2 and Fe+3 ions leads to very high conductivity values. The temperature dependence of the dielectric permittivities revealed the existence of broader peaks. The electron hopping mechanism leads to a frequency dispersion of the temperature where the permittivities attain their maxima. The electrical conductivity variations with temperature exhibited Arrhenius-type behaviors, with activation energies ranging from 0.34 eV (hydrothermal powder) to 0.16 eV (for the highest sintering temperature). These results were correlated to the variations in Fe+2 concentration and microstructure.

scholarly journals Estimating Pore Water Electrical Conductivity of Sandy Soil from Time Domain Reflectometry Records Using a Time-Varying Dynamic Linear Model

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4403 ◽  
Author(s):  
Basem Aljoumani ◽  
Jose Sanchez-Espigares ◽  
Gerd Wessolek
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Permittivity ◽  
Linear Relationship ◽  
Linear Model ◽  
Pore Water ◽  
Sandy Soil ◽  
Time Domain ◽  
Time Domain Reflectometry ◽  
Relative Dielectric Permittivity ◽  
Time Varying

Despite the importance of computing soil pore water electrical conductivity (σp) from soil bulk electrical conductivity (σb) in ecological and hydrological applications, a good method of doing so remains elusive. The Hilhorst concept offers a theoretical model describing a linear relationship between σb, and relative dielectric permittivity (εb) in moist soil. The reciprocal of pore water electrical conductivity (1/σp) appears as a slope of the Hilhorst model and the ordinary least squares (OLS) of this linear relationship yields a single estimate ( 1 / σ p ^ ) of the regression parameter vector (σp) for the entire data. This study was carried out on a sandy soil under laboratory conditions. We used a time-varying dynamic linear model (DLM) and the Kalman filter (Kf) to estimate the evolution of σp over time. A time series of the relative dielectric permittivity (εb) and σb of the soil were measured using time domain reflectometry (TDR) at different depths in a soil column to transform the deterministic Hilhorst model into a stochastic model and evaluate the linear relationship between εb and σb in order to capture deterministic changes to (1/σp). Applying the Hilhorst model, strong positive autocorrelations between the residuals could be found. By using and modifying them to DLM, the observed and modeled data of εb obtain a much better match and the estimated evolution of σp converged to its true value. Moreover, the offset of this linear relation varies for each soil depth.

Polypyrrole/PU hybrid hydrogels: electrically conductive and fast self-healing for the potential application in body-monitor sensor

2021 ◽  
Author(s):  
Zhanyu Jia ◽  
Guangyao Li ◽  
Juan Wang ◽  
shouhua Su ◽  
Jie Wen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Electrical Conductivity ◽  
Potential Application ◽  
Self Healing ◽  
Electrically Conductive ◽  
Sensor Application ◽  
Hybrid Hydrogels ◽  
Health Monitor

Conductivity, self-healing and moderate mechanical properties are necessary for multifunctional hydrogels which have great potential in health-monitor sensor application. However, the combination of electrical conductivity, self-healing and good mechanical properties...

scholarly journals Electrically Conductive Networks from Hybrids of Carbon Nanotubes and Graphene Created by Laser Radiation

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1875
Author(s):  
Alexander Yu. Gerasimenko ◽  
Artem V. Kuksin ◽  
Yury P. Shaman ◽  
Evgeny P. Kitsyuk ◽  
Yulia O. Fedorova ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Conductivity ◽  
Laser Irradiation ◽  
Flexible Electronics ◽  
Threshold Energy ◽  
Wavelength Region ◽  
Hybrid Nanostructures ◽  
Graphene Sheets ◽  
Electrically Conductive ◽  
Walled Carbon Nanotubes

A technology for the formation of electrically conductive nanostructures from single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), and their hybrids with reduced graphene oxide (rGO) on Si substrate has been developed. Under the action of single pulses of laser irradiation, nanowelding of SWCNT and MWCNT nanotubes with graphene sheets was obtained. Dependences of electromagnetic wave absorption by films of short and long nanotubes with subnanometer and nanometer diameters on wavelength are calculated. It was determined from dependences that absorption maxima of various types of nanotubes are in the wavelength region of about 266 nm. It was found that contact between nanotube and graphene was formed in time up to 400 fs. Formation of networks of SWCNT/MWCNT and their hybrids with rGO at threshold energy densities of 0.3/0.5 J/cm2 is shown. With an increase in energy density above the threshold value, formation of amorphous carbon nanoinclusions on the surface of nanotubes was demonstrated. For all films, except the MWCNT film, an increase in defectiveness after laser irradiation was obtained, which is associated with appearance of C–C bonds with neighboring nanotubes or graphene sheets. CNTs played the role of bridges connecting graphene sheets. Laser-synthesized hybrid nanostructures demonstrated the highest hardness compared to pure nanotubes. Maximum hardness (52.7 GPa) was obtained for MWCNT/rGO topology. Regularity of an increase in electrical conductivity of nanostructures after laser irradiation has been established for films made of all nanomaterials. Hybrid structures of nanotubes and graphene sheets have the highest electrical conductivity compared to networks of pure nanotubes. Maximum electrical conductivity was obtained for MWCNT/rGO hybrid structure (~22.6 kS/m). Networks of nanotubes and CNT/rGO hybrids can be used to form strong electrically conductive interconnections in nanoelectronics, as well as to create components for flexible electronics and bioelectronics, including intelligent wearable devices (IWDs).

Complex dielectric permittivity, electric modulus and electrical conductivity analysis of Au/Si3N4/p-GaAs (MOS) capacitor

2021 ◽  
Author(s):  
Sema Türkay ◽  
Adem Tataroğlu
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Permittivity ◽  
Electric Modulus ◽  
Arrhenius Equation ◽  
Rf Magnetron Sputtering ◽  
Oxide Semiconductor ◽  
Complex Dielectric Permittivity ◽  
Mos Capacitor ◽  
Universal Power Law ◽  
Complex Electrical Conductivity

AbstractRF magnetron sputtering was used to grow silicon nitride (Si3N4) thin film on GaAs substrate to form metal–oxide–semiconductor (MOS) capacitor. Complex dielectric permittivity (ε*), complex electric modulus (M*) and complex electrical conductivity (σ*) of the prepared Au/Si3N4/p-GaAs (MOS) capacitor were studied in detail. These parameters were calculated using admittance measurements performed in the range of 150 K-350 K and 50 kHz-1 MHz. It is found that the dielectric constant (ε′) and dielectric loss (ε″) value decrease with increasing frequency. However, as the temperature increases, the ε′ and ε″ increased. Ac conductivity (σac) was increased with increasing both temperature and frequency. The activation energy (Ea) was determined by Arrhenius equation. Besides, the frequency dependence of σac was analyzed by Jonscher’s universal power law (σac = Aωs). Thus, the value of the frequency exponent (s) were determined.

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