Tailoring the frequency-dependent electrical conductivity and dielectric permittivity of CNT-polymer nanocomposites with nanosized particles

2019 ◽  
Vol 142 ◽  
pp. 1-19 ◽  
Author(s):  
Xiaodong Xia ◽  
George J. Weng ◽  
Dan Hou ◽  
Weibin Wen
Geophysics ◽  
2016 ◽  
Vol 81 (2) ◽  
pp. E159-E176 ◽  
Author(s):  
S. Misra ◽  
C. Torres-Verdín ◽  
A. Revil ◽  
J. Rasmus ◽  
D. Homan

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.


2019 ◽  
Vol 8 (3) ◽  
pp. 7928-7932

Aluminum nitride (AlN) is ceramic material. It has very high thermal and low electrical conductivity. The Variation of Various Electrical Parameters viz. Impedance (Z), Admittance (Y), Dielectric Permittivity ('), Relative Loss (''), Electrical Conductivity (), and Loss Tangent (Tan ) with frequency Dependence of Aluminum Nitride (AlN) Nano powder were studied. Scanning electron microscopy (SEM); Raman Spectroscopy; and X-ray diffraction (XRD) were used to analyse the surfaces and structures of aluminum nirtride nanopowder. It has been found that the particle size is of 36.15 nm and the crystallographic structure is amorphous. The surface morphology of the studied compound has been investigated by Scanning Election Microscopy (SEM) indicating the particles are in nanosize and characteristic range of diameters are in nanoscale. The electrical studies of the studied compound have been examined in order to acquire the electrical parameters (mainly dielectric permittivity, loss, conductivity, loss-tangent, impedance, and admittance). Small rise in the conductivity (with frequency dependent) has been observed due to the decrease in the particle size of the material.it is also observed that the relative permittivity ('), relative loss '') and dissipation factor (Tan ) decreases with increase in frequency. The Raman shift variation with the intensity which shows the peaks of the compound are obtained at 506 cm-1 , 615 cm-1 656 cm-1 , 873 cm-1 , 882 cm-1 , 949 cm-1 , and 974 cm-1 using laser at 785 nm.


2004 ◽  
Vol 37 (24) ◽  
pp. 9048-9055 ◽  
Author(s):  
Fangming Du ◽  
Robert C. Scogna ◽  
Wei Zhou ◽  
Stijn Brand ◽  
John E. Fischer ◽  
...  

2021 ◽  
pp. 108128652110214
Author(s):  
Xiaodong Xia ◽  
George J. Weng

Recent experiments have revealed two distinct percolation phenomena in carbon nanotube (CNT)/polymer nanocomposites: one is associated with the electrical conductivity and the other is with the electromagnetic interference (EMI) shielding. At present, however, no theories seem to exist that can simultaneously predict their percolation thresholds and the associated conductivity and EMI curves. In this work, we present an effective-medium theory with electrical and magnetic interface effects to calculate the overall conductivity of a generally agglomerated nanocomposite and invoke a solution to Maxwell’s equations to calculate the EMI shielding effectiveness. In this process, two complex quantities, the complex electrical conductivity and complex magnetic permeability, are adopted as the homogenization parameters, and a two-scale model with CNT-rich and CNT-poor regions is utilized to depict the progressive formation of CNT agglomeration. We demonstrated that there is indeed a clear existence of two separate percolative behaviors and showed that, consistent with the experimental data of poly-L-lactic acid (PLLA)/multi-walled carbon nanotube (MWCNT) nanocomposites, the electrical percolation threshold is lower than the EMI shielding percolation threshold. The predicted conductivity and EMI shielding curves are also in close agreement with experimental data. We further disclosed that the percolative behavior of EMI shielding in the overall CNT/polymer nanocomposite can be illustrated by the establishment of connective filler networks in the CNT-poor region. It is believed that the present research can provide directions for the design of CNT/polymer nanocomposites in the EMI shielding components.


Author(s):  
Sema Türkay ◽  
Adem Tataroğlu

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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