Analysis of the complex dielectric permittivity behavior of porous Al2O3–SiC composites in the 1 MHz to 18 GHz frequency range

2007 ◽  
Vol 22 (12) ◽  
pp. 3292-3302 ◽  
Author(s):  
J. Battat ◽  
J.P. Calame
Keyword(s):  
Dielectric Permittivity ◽  
Dielectric Response ◽  
Porous Alumina ◽  
Complex Dielectric Permittivity ◽  
Polymer Precursor ◽  
Frequency Range ◽  
Subsequent Step ◽  
Infusion Method ◽  
Sic Composites ◽  
Scanning Electron

The complex dielectric permittivity of electrically lossy, porous Al2O3–SiC composites was measured as a function of frequency over the range of 0.001 to 18 GHz. These composites were fabricated by an infusion method of incorporating SiC polymer precursor into porous alumina disks. Repeat polymer infusions and pyrolysis steps to 1000 °C were carried out, with some samples undergoing an additional air fire prior to each subsequent step. Generally, it was found that for non-air-fired samples, moderate, controllable losses were attainable over a broad frequency range. By contrast, the dielectric loss attainable for air-fired samples was generally very low. For all samples, various aspects of the variation of permittivity components ϵ′ and ϵ″ with frequency were analyzed, with a view to determine the various factors contributing to dielectric response. Microstructure analysis using scanning electron microscopy was also performed.

National Primary Standard for the Units of Complex Dielectric Permittivity in the Frequency Range from 1 to 178.4 Ghz

2014 ◽  
Vol 57 (1) ◽  
pp. 1-7 ◽  
Author(s):  
V. N. Egorov ◽  
M. V. Kashchenko ◽  
V. L. Masalov ◽  
E. Yu. Tokareva ◽  
Nong Quoc Quang
Keyword(s):  
Dielectric Permittivity ◽  
Primary Standard ◽  
Complex Dielectric Permittivity ◽  
Frequency Range ◽  
National Primary Standard

The Arctic soils dielectric characteristics

2021 ◽  
pp. 127-134
Author(s):  
K.N. Suslov ◽  
A.S. Yashchenko ◽  
S.V. Krivaltsevich
Keyword(s):  
Dielectric Permittivity ◽  
Arctic Region ◽  
The State ◽  
The Arctic ◽  
Underlying Surface ◽  
Complex Dielectric Permittivity ◽  
Frequency Range ◽  
Near Surface ◽  
Laboratory Conditions ◽  
The Arctic Region

The state of the underlying surface has a noticeable effect on the process of emission and propagation of radio waves. The state of the underlying surface is dependent on the value of the complex dielectric permittivity. Usually, the underlying surface is understood as soil or ground medium. The Dobson model is recommended by the International Telecommunication Union (ITU) for calculating the dielectric permittivity of moist soils over a wide frequency range. However, this model was developed based on experimental data obtained at frequencies above 1 GHz for soils of the temperate climatic zone. This paper presents the results of measuring the complex dielectric permittivity of the Arctic region soils sample at the frequency range from 1 MHz to 8 GHz. Also, we compared the dielectric permittivity data measured in laboratory conditions and calculated by the Dobson model. It was found that the Arctic soil dielectric permittivity data measured under laboratory conditions and calculated using the Dobson model differ markedly from each other, which indicates the impossibility of using the Dobson model for calculating soil dielectric permittivity of the Arctic region. The data obtained in the laboratories case may be used to estimate the directional characteristics of near-surface emissivity systems, as well as of the ground wave propagation prediction in the Arctic region.

scholarly journals A Study on the Dielectric Behaviour of Epoxy/Hafnium Oxide Nanopowder Composites

2011 ◽  
Vol 20 (5) ◽  
pp. 096369351102000 ◽  
Author(s):  
S.N. Georga
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Permittivity ◽  
High Temperatures ◽  
High Frequency ◽  
Dielectric Response ◽  
Hafnium Oxide ◽  
Filler Concentration ◽  
High Frequency Range ◽  
Frequency Range ◽  
Low Frequencies

The dielectric response of 10 and 15phr epoxy/HfO2 nanocomposite systems has been studied in a wide frequency and temperature range. The experimental results show an enhancement of the dielectric permittivity with increasing filler concentration. The dielectric spectra reveal the presence of α-relaxation and a weak MWS effect. In the high frequency range the real part of the electrical conductivity obeys the Universal Dielectric Response (UDR), whereas at low frequencies and high temperatures DC conductivity is observed. VFT (Vogel-Fulcher-Tamann) parameters are calculated for all measured specimens.

scholarly journals The effect of shape and sizes of particles of wet quartz powders on complex dielectric permittivity in the frequency range of 10 kHz – 10 GHz

2021 ◽  
Vol 2140 (1) ◽  
pp. 012004
Author(s):  
P P Bobrov ◽  
E S Kroshka ◽  
O V Rodionova
Keyword(s):  
Dielectric Permittivity ◽  
High Frequency ◽  
Experimental Studies ◽  
Low Frequency ◽  
Dielectric Permeability ◽  
Complex Dielectric Permittivity ◽  
Particle Sizes ◽  
Frequency Range ◽  
High Concentration ◽  
River Sand

Abstract The results of experimental studies of complex dielectric permeability of river sand and powders of granules of fused quartz with narrow distributions of particles in size at the frequencies from 10 kHz to 10 GHz are presented. The granule particles are spheres and the sand particles are irregularly shaped. The samples were moistened with distilled water and NaCl salt solution with conductivity of 0.1 and 0.77 S/m. It has been shown that the shape of the particles affects the complex dielectric permittivity (CDP) in the low frequency part of the range only when proportion of the solution is small and its concentration is weak. At full saturation of the samples with the solution and its high concentration, as well as in all cases at frequencies above 100 MHz, the influence of the particle shape is small. In the mid-frequency part of the range (from units to tens of megahertz) in a sample of quartz granules with small particles, there is a strong relaxation process, leading to a significant increase in the real part of the CDP. A similar, but slight increase is observed in samples of sand with larger particles. In the high-frequency range, the effect of the shape and particle sizes is very weak.

Combined vector network analyzer and impedance analyzer for broadband determination of complex permittivity spectrum of glass beads with talc

2020 ◽  
Author(s):  
Justyna Szerement ◽  
Hironobu Saito ◽  
Kahori Furuhata ◽  
Shin Yagihara ◽  
Agnieszka Szypłowska ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Soil Moisture ◽  
Dielectric Permittivity ◽  
Glass Beads ◽  
Vector Network Analyzer ◽  
Complex Dielectric Permittivity ◽  
Network Analyzer ◽  
Frequency Range ◽  
Impedance Analyzer ◽  
Permittivity Spectrum

<p>Soil complex dielectric permittivity is frequency dependent. At low frequencies soil dielectric spectrum exhibits relaxation effects mainly due to interfacial phenomena caused by water strongly bounded to solid phase particles surfaces, double-layer effects and Maxwell-Wagner effect. At frequencies of several GHz and above, the influence of dielectric dispersion of free water dipoles can be observed.  Since dielectric soil moisture meters operate at frequencies from kHz up to several GHz, their output can be affected by these phenomena.</p><p>Currently, there is a variety of commercial sensors that operate at various frequencies from kHz up to several GHz. Most popular are TDR sensors with frequency band up to 1-2 GHz and capacitance/impedance sensors that operate at a single frequency usually from the range <br>1-150 MHz. Therefore, the knowledge of the broadband complex dielectric permittivity spectrum can help to improve the existing and develop new methods and devices for soil moisture and salinity estimation. Also, accurate characterization of complex dielectric permittivity spectrum of porous materials in the broadband frequency range is required for modeling of dielectric properties of materials in terms of moisture, salinity, density, mineralogy etc.</p><p>The aim of the study was to measure the complex dielectric permittivity of glass beads with 5% talc moistened with distilled water and saline water (electrical conductivity of 500, 1000, 1500 mS/m). The experiment was carried out using a seven-rod probe connected to an impedance analyzer (IA) and a vector network analyzer (VNA) using a multiplexer in the frequency range from 40Hz to 110MHz (IA) and 10MHz to 500MHz (VNA). The glass beads (90-106 µm, Fuji Manufacturing Industries, Japan) with 5% talc (Sigma Aldrich) in 4 different moisture and 4 different salinity values were examined. The results obtained from the IA and the VNA were combined and modeled with complex conductivity and dielectric permittivity model. The influence of water content and electrical conductivity on broadband complex dielectric spectra and the fitted model parameters was examined.</p><p> </p><p>The work has been supported by the National Centre for Research and Development, Poland, BIOSTRATEG3/343547/8/NCBR/2017.</p>

Complex Dielectric Permittivity of Sandy Loam as a Function of Salinity and Biomass at Microwaves

2013 ◽  
Vol 209 ◽  
pp. 116-120 ◽  
Author(s):  
Arun Sharma ◽  
K.C. Pancholi ◽  
S.P. Bhatnagar
Keyword(s):  
Soil Moisture ◽  
Dielectric Permittivity ◽  
Sandy Loam ◽  
Strong Dependence ◽  
Normal Incidence ◽  
Complex Dielectric Permittivity ◽  
Network Analyzer ◽  
Frequency Range ◽  
Moisture Contents ◽  
Loam Soil

Real and Imaginary parts of Complex Dielectric Permittivity (ε’ and ε” ) of Sandy Loam soil have been measured in the frequency range 150 MHz – 2.4 GHz using a Vector Network Analyzer at varied Moisture contents, Salinity and Biomass. The Emissivity of the soil for normal incidence was also calculated from measured values of Complex Permittivity. The measured permittivity data show strong dependence on moisture content. Salinity causes higher permittivity and dielectric loss. Biomass appears to enhance the permittivity data due to increase in porosity of the soil. The emissivity of the soil was observed to decrease with increasing soil moisture and soil salinity, but it increases with biomass.

Numerical Modeling of Multi-Frequency Complex Dielectric Permittivity Dispersion of Clay-Rich Rocks

Geophysics ◽  
2021 ◽  
pp. 1-70
Author(s):  
Artur Posenato Garcia ◽  
Zoya Heidari
Keyword(s):  
Spatial Distribution ◽  
Dielectric Permittivity ◽  
Mineralogical Composition ◽  
Exchange Capacity ◽  
Complex Dielectric Permittivity ◽  
Frequency Range ◽  
Volumetric Concentration ◽  
New Equation ◽  
Permittivity Measurements ◽  
The Impact

Interpretation of complex dielectric permittivity measurements is challenging in clay-rich rocks, such as shaly sands and organic-rich mudrocks, due to complex rock fabric and mineralogical composition, which are overlooked by conventional interpretation models. For instance, the impact of fabric features (e.g., laminations, structural/dispersed shale) and diverse constitution (e.g., clay, kerogen, pyrite, brine) to the broadband complex permittivity is not well understood. Therefore, the main objective of this work is to develop a framework capable of reliably quantifying the impact of different minerals and their corresponding spatial distribution on the multi-frequency complex dielectric permittivity measurements in clay-rich rocks.To achieve the aforementioned objective, we introduce a numerical algorithm to compute the dielectric dispersion in 3D pore-scale images of clay-rich rocks. We numerically solve the quasi-electrostatic approximation to Maxwell's equations in the frequency domain through the finite volume method. The clay particles are often sub-resolution in most imaging methods. Therefore, we introduce a workflow to calculate the effective admittance of the clay network. Furthermore, we derive a new equation to incorporate the induced polarization effect into the effective admittance of pyrite particles. Finally, we perform a sensitivity analysis of the complex dielectric permittivity of clay-rich rocks in the frequency range from 100 Hz to 1 GHz to the volumetric concentration and spatial distribution of clays, cation exchange capacity (CEC), volumetric concentration of pyrite, and the orientation of the electric field. Results showed that clays can enhance or diminish electrical conductivity values at different frequencies depending on their intrinsic properties and spatial distribution. Laminations, for instance, significantly enhance dielectric permittivity in the sub-MHz frequency range, but their effect is imperceptible at 1 GHz. Furthermore, the impact of the variation of CEC on permittivity is approximately proportional at 100Hz but negligible at 1 GHz.

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