Effects of material texture and packing density on the interfacial polarization of granular soils

Geophysics ◽  
2021 ◽  
pp. 1-58
Author(s):  
Hang Chen ◽  
Qifei Niu
Keyword(s):  
Electrical Conductivity ◽  
Packing Density ◽  
Characteristic Frequency ◽  
Effective Permittivity ◽  
Scale Up ◽  
Interfacial Polarization ◽  
Granular Soils ◽  
Geologic Materials ◽  
Effective Electrical Conductivity ◽  
Material Texture

Many electrical and electromagnetic (EM) methods operate at MHz frequencies, at which the interfacial polarization occurring at the solid-liquid interface in geologic materials may dominate the electrical signals. To correctly interpret electrical/EM measurements, it is therefore critical to understand how the interfacial polarization influences the effective electrical conductivity and permittivity spectra of geologic materials. We have used pore-scale simulation to study the role of material texture and packing in interfacial polarization in water-saturated granular soils. Synthetic samples with varying material textures and packing densities are prepared with the discrete element method. The effective electrical conductivity and permittivity spectra of these samples are determined by numerically solving the Laplace equation in a representative elementary volume of the samples. The numerical results indicate that the effective permittivity of granular soils increases as the frequency decreases due to the polarizability enhancement from the interfacial polarization. The induced permittivity increment is mainly influenced by the packing state of the samples, increasing with the packing density. Material textures such as the grain shape and size distribution may also affect the permittivity increment, but their effects are less significant. The frequency characterizing the interfacial polarization (i.e., the characteristic frequency) is mainly related to the electrical contrast of the solid and water phases. The model based on the traditional differential effective medium (DEM) theory significantly underestimates the permittivity increment by a factor of more than two and overestimates the characteristic frequency by approximately 1 MHz. These inaccurate predictions are due to the fact that the electrical interactions between neighboring grains are not considered in the DEM theory. A simple empirical equation is suggested to scale up the theoretical depolarization factor of grains entering the DEM theory to account for the interaction of neighboring grains in granular soils.

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.

Preparation and Characterization of Porous Si-Coated SiC Fiber Media

2004 ◽  
Vol 449-452 ◽  
pp. 233-236 ◽  
Author(s):  
Jun Suh Yu ◽  
B.S. Lee ◽  
Sung Churl Choi ◽  
Ji Hun Oh ◽  
Jae Chun Lee
Keyword(s):  
Electrical Conductivity ◽  
Silicon Content ◽  
Porous Si ◽  
Electrically Conductive ◽  
Electrode Distance ◽  
Sic Fiber ◽  
Effective Electrical Conductivity ◽  
The One ◽  
Fiber Preforms

Electrically conductive porous Si/SiC fiber media were prepared by infiltration of liquid silicon into porous carbon fiber preforms. The series rule of mixture for the effective electrical conductivity was applied to the disc shaped samples to estimate their silicon content, effective electrical conductivity and porosity. The electrical conductivity was estimated by assuming the disc sample as a plate of equivalent geometry, i.e., same thickness, electrode distance and volume. As the volumetric content of silicon in a sample increases from 0.026% to 0.97%, the estimated electrical conductivity increases from 0.17 S/cm to 2.09 S/cm. The porosity of the samples measured by Archimedes principle was in the range of 75~83% and 1~4% less than the one estimated by the series rule of mixture for the effective electrical conductivity.

Packing Density and Overconsolidation Ratio Effects on the Mechanical Response of Granular Soils

2019 ◽  
Vol 38 (1) ◽  
pp. 723-742 ◽  
Author(s):  
Youcef Mahmoudi ◽  
Abdellah Cherif Taiba ◽  
Leila Hazout ◽  
Mostefa Belkhatir ◽  
Wiebke Baille
Keyword(s):  
Packing Density ◽  
Mechanical Response ◽  
Granular Soils ◽  
Overconsolidation Ratio

Analysis of Clustering and Interphase Region Effects on the Electrical Conductivity of Carbon Nanotube-Polymer Nanocomposites via Computational Micromechanics

2008 ◽  
Author(s):  
Gary D. Seidel ◽  
Kelli L. Boehringer ◽  
Dimitris C. Lagoudas
Keyword(s):  
Electrical Conductivity ◽  
Polymer Nanocomposites ◽  
Effective Conductivity ◽  
Interphase Layer ◽  
Finite Element Software ◽  
Interphase Region ◽  
Effective Electrical Conductivity ◽  
Wide Range ◽  
Electrical Conductivities ◽  
Computational Micromechanics

In the present work, computational micromechanics techniques are applied towards predicting the effective electrical conductivities of polymer nanocomposites containing aligned bundles of SWCNTs at wide range of volume fractions. Periodic arrangements of well-dispersed and clustered/bundled SWCNTs are studied using the commercially available finite element software COMSOL Multiphysics 3.4. The volume averaged electric field and electric flux obtained are used to calculate the effective electrical conductivity of nanocomposites in both cases, therefore indicating the influence of clustering on the effective electrical conductivity. In addition, the influence of the presence of an interphase region on the effective electrical conductivity is considered in a parametric study in terms of both interphase thickness and conductivity for both the well dispersed case and for the clustered arrangements. Comparing the well-dispersed case with an interphase layer to the same arrangement without the interphase layer allows for the assessment of the influence of the interphase layer on the effective electrical conductivities, while similar comparisons for the clustered arrangements yield information about the combined effects of clustering and interphase regions. Initial results indicate that there is very little influence of the interphase layer on the effective conductivity prior to what is identified as the interphase percolation concentration, and that there is an appreciable combined effect of clustering in the presence of interphase regions which leads to increases in conductivity larger than the sum of the two effects independently.

scholarly journals Morphology and Electrical Conductivity of Carbon Nanocoatings Prepared from Pyrolysed Polymers

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Marcin Molenda ◽  
Michał Świętosławski ◽  
Marek Drozdek ◽  
Barbara Dudek ◽  
Roman Dziembaj
Keyword(s):  
Electrical Conductivity ◽  
Electrode Materials ◽  
Lithium Iron Phosphate ◽  
Solid Phase ◽  
Scale Up ◽  
Iron Phosphate ◽  
Battery Cell ◽  
Pyromellitic Acid ◽  
Specific Morphology ◽  
Precursor Composition

Conductive carbon nanocoatings (conductive carbon layers—CCL) were formed onα-Al2O3model support using three different polymer precursors and deposition methods. This was done in an effort to improve electrical conductivity of the material through creating the appropriate morphology of the carbon layers. The best electrical properties were obtained with use of a precursor that consisted of poly-N-vinylformamide modified with pyromellitic acid (PMA). We demonstrate that these properties originate from a specific morphology of this layer that showed nanopores (3-4 nm) capable of assuring easy pathways for ion transport in real electrode materials. The proposed, water mediated, method of carbon coating of powdered supports combines coating from solution and solid phase and is easy to scale up process. The optimal polymer carbon precursor composition was used to prepare conductive carbon nanocoatings on LiFePO4cathode material. Charge-discharge tests clearly show that C/LiFePO4composites obtained using poly-N-vinylformamide modified with pyromellitic acid exhibit higher rechargeable capacity and longer working time in a battery cell than standard carbon/lithium iron phosphate composites.

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