Solid Permittivity Research Articles

A Sixteenth-Mode Substrate Integrated Waveguide Sensor Loaded With CCRR Resonator Used for Solid Permittivity Measurement

A Sixteenth-Mode Substrate Integrated Waveguide Sensor Loaded With CCRR Resonator Used for Solid Permittivity Measurement

A Solid Concentration Measurement Method With Online Calibration of Solid Permittivity

A Solid Concentration Measurement Method With Online Calibration of Solid Permittivity

Solid Permittivity Measurement Sensor Based With IDE-ELC Substrate Integrated Waveguide Resonator

Solid Permittivity Measurement Sensor Based With IDE-ELC Substrate Integrated Waveguide Resonator

Effect of Nonzero Solid Permittivity on the Electrical Repulsion between Charged Surfaces.

The electrical repulsion between two charged solid surfaces separated by an electrolyte is studied as a function of the permittivity ϵs of the solid in the limit in which potentials are small, and the gap between the plane solid surfaces is small compared to the Debye length κ-1 within the electrolyte. The solid surfaces are uniformly charged in a central region |x|< L outside which they are uncharged. When ϵs = 0, ions from the charge cloud between the charged surfaces spill out into regions of length O(κ-1) beyond x = ± L, thereby reducing the pressure between the surfaces from that predicted by Derjaguin-Landau-Verwey-Overbeek theory for infinite, uniformly charged surfaces. When ϵs>0, ions spill out over much larger O(L) regions, thereby reducing still further both the electrical potential between the solid surfaces and the repulsive force between them. However, this reduction becomes smaller as κL becomes large.

Effect of Microgeometry on Modeling Accuracy of Fluid-Saturated Rock Using Dielectric Permittivity

A common practice for estimating subsurface constituents from remote sensing methods is to use analytical effective medium models relating effective dielectric permittivity to properties of the targeted region. These models suggest that the effective permittivity depends on the volumetric fraction and phase property of each constituent of the composite. Most effective medium models are based on idealized approximations of the composite’s geometry. Some studies have shown that the analytical mixing rule may underestimate or overestimate the effective property when there are geometrical variations. In this paper, we use numerical experiments to compute the effective dielectric permittivity of composites with different microgeometries having varying amounts of internal interfaces. By comparing the numerical results with the classic analytical mixing rules, we quantify the discrepancy with a diagram that indicates the high deviation region. The study is carried out by using various fluid–solid permittivity contrasts to suit a wide range of applications.

On AC-Field-Induced Nonlinear Electroosmosis next to the Sharp Corner-Field-Singularity of Leaky Dielectric Blocks and Its Application in on-Chip Micro-Mixing.

Induced-charge electroosmosis has attracted lots of attention from the microfluidic community over the past decade. Most previous researches on this subject focused on induced-charge electroosmosis (ICEO) vortex streaming actuated on ideally polarizable surfaces immersed in electrolyte solutions. Starting from this point, we conduct herein a linear asymptotic analysis on nonlinear electroosmotic flow next to leaky dielectric blocks of arbitrary electrical conductivity and dielectric permittivity in harmonic AC electric fields, and theoretically demonstrate that observable ICEO fluid motion can be generated at high field frequencies in the vicinity of nearly insulating semiconductors, a very low electrical conductivity, of which can evidently increase the double-layer relaxation frequency (inversely proportional to the solid permittivity) to be much higher than the typical reciprocal RC time constant for induced double-layer charging on ideally polarizable surfaces. A computational model is developed to study the feasibility of this high-frequency vortex flow field of ICEO for sample mixing in microfluidics, in which the usage of AC voltage signal at high field frequencies may be beneficial to suppress electrochemical reactions to some extent. The influence of various parameters for developing an efficient mixer is investigated, and an integrated arrangement of semiconductor block array is suggested for achieving a reliable mixing performance at relatively high sample fluxes. Our physical demonstration with high-frequency ICEO next to leaky dielectric blocks using a simple channel structure offers valuable insights into the design of high-throughput micromixers for a variety of lab-on-a-chip applications.

On the size-effect in the dielectric permittivity of solids

Reducing the grain size in a powder should enhance its dielectric permittivity, as unpaired electrons on the grain surface create a double electric layer, the effect of which increases together with the specific surface area of the powder.

A novel measurement method of a single dust particle permittivity at a microwave frequency band as I/P to accurate scattering computations. Part I

In electromagnetic scattering computation the scattering properties of a single particle can be evaluated if the solid permittivity of its constituent material is known. If the material is not homogeneous (e.g. water layer on the particle surface) both the structure and the permittivity of the different parts must be known. However, it is possible (at least at microwave frequencies) to define an equivalent homogeneous permittivity $$\left( {\bar \varepsilon } \right)$$ which would produce the same scattering properties for a homogeneous particle of the same outer shape as the real one. In this work a novel measurement method of a single particle scattering for evaluating the dielectric properties of dust is derived. Results are compared with another work on bulk/scaled measurement (Part II) of dust permittivity at the same frequency band (X-band) gave matched results.

Electro-osmotic flows over highly polarizable dielectric surfaces

A thin-Debye-layer macroscale model is developed and analyzed for electrokinetic flows about dielectric surfaces, wherein solid polarization modifies the zeta-potential distribution. The harmonic electric potential within the solid is governed by a nonlinear boundary condition, which constitutes a generalization of the linear Robin-type condition of Yossifon et al. [Phys. Fluids 19, 068105 (2007)] to voltages comparable with the thermal scale. The resulting polarization model is demonstrated in the classical context of spherical-particle electrophoresis, where the electrophoretic mobility—now a function of applied-field magnitude and solid permittivity—is evaluated using both eigenfunction series expansions and asymptotic approximations. For strong polarization, the mobility saturates at a field-dependent value which is lower than the comparable Smoluchowski slope. At strongly applied fields, the mobility diminishes at a rate that corresponds to a logarithmic increase of particle velocity with applied-field magnitude.

Density-Permittivity Relationships for Powdered and Granular Materials

Relationships between the permittivities of powdered or granular solid materials and their bulk densities (density of the air-particle mixture) are discussed. Linear relationships between functions of the permittivity and bulk density are identified that are useful in determining permittivity of solids from measurements of the permittivity of pulverized samples. The usefulness of several dielectric mixture equations for calculating solid material permittivity from measured permittivity of pulverized samples is also discussed. Results of testing linear extrapolation techniques and dielectric mixture equations on pulverized coal, limestone, plastics, and granular wheat and flour are presented. Recommendations are provided for reliable estimation of solid material permittivities or changes in permittivities of powdered and granular materials as a result of changes in their bulk densities.

A method for measuring the solid particle permittivity or electrical conductivity of rocks, sediments, and granular materials

Measurement of the effective dielectric permittivity of porous media provides an elegant method of estimating both the porosity and water content of soils, sediments, and rocks. Obtaining accurate estimates of water content can only be achieved if the models relating the measured permittivity to water content work well. One of the difficulties with testing physical models describing two‐ and three‐phase dielectric mixtures (saturated and unsaturated systems) is obtaining an accurate value for the permittivity of the mineral matrix. No direct measurement method has been presented for rocks and soils, so the solid permittivity value is often an estimate of 5, essentially remaining a fitting parameter. We present a measurement method requiring no preassumed theoretical model. The method requires the measurement of the effective permittivity of a granular material immersed in fluids of differing permittivity and interpolation between the range of data points. Measurements of the permittivity of the mineral matrix of a number of materials are presented, including glass beads (7.6), quartz sand (4.7), calcareous seashell fragments (8.9), hematite ore (18.1), tuff (6.0), and a sandy loam soil (5.1). Estimates based on using mixing models to obtain the solid permittivity are demonstrated to underestimate the permittivity of hematite ore by between 0% and 45%, depending on the model and packing. The method is also suitable for measuring the electrical conductivity of granular minerals by changing the electrical conductivity of the bathing solution. Results for the electrical conductivity of hematite ore (0.040 dS m−1) and carborundum (10.9 dS m−1) are presented.

The effective permittivity of dense packings of glass beads, quartz sand and their mixtures immersed in different dielectric backgrounds

Dielectric methods, which measure the effective dielectric permittivity of granular materials, e.g., rocks, sediments and soils are often applied to estimate water or oil content. To test physically based models requires that the permittivity values of all phases are known. Measurements of the solid permittivity of glass spheres, quartz sand grains and their mixtures are made using an immersion method. The results obtained are tested against several classical models including the Maxwell Garnett, the symmetric effective medium approximation (SEMA) and the non-SEMA. The results demonstrate inadequate predictions between these models and the measured data. However, the Maxwell Garnett model comes close to predicting the effective permittivity of the media. Divergence between this model and the measurements is known to be due to interaction effects between grains that is not accounted for by a model based simply on the mixing of volumetric fractions of the components. With water as the background (contrast of 10 for glass) the Maxwell Garnett model overestimates the effective permittivity ∼5% as the contrast reduces this error decreases. For contrasts <4 the error for the permittivity estimate using the Maxwell Garnett formula was <3%. The modeling is simply used to demonstrate that the permittivity of the inclusions, for practical purposes, can be considered a linear function of the volumetric fraction times its respective permittivity.

Complex Permittivity of Solid, Liquid and Granular Materials using a four layer boundary cell

The four boundary cell is an important arrangement for the measurement of complex permittivity of bulk solids and liquids. Transcendental equations for reflection and transmission are derived and previous errors in the literature are noted. This measurement method is extended to granular samples where a compression technique is introduced to minimize the dispersion in S-parameter measurements associated with interface problems.

Estimating the Permittivity of Solids from Measurements on Granular or Pulverized Materials

ABSTRACTA procedure is outlined for determining the complex permittivity components of solid materials of known densities from those properties of granular or pulverized samples measured at a few different bulk densities. Properties of the solid are obtained by extrapolation of functions of the dielectric constant and loss factor that are linearly related to the bulk density of the air-particle mixture. Examples are given for whole-kernel wheat, ground white rice, and pulverized goethite.

Q band interferometer for high temperature measurements

A Q band interferometer for determining the complex permittivity of solids and liquids between 20°C and 1300°C has been developed. The Roberts and Von Hippel standing-wave method was used. The technique involves the utilization of a computer-assisted digital voltmeter for data acquisition and treatment. Results for a 67SiO2−33Na2O within the temperature range 20–400°C and in the liqid state (950°C) are presented.

Novel technique for determining the relative permittivity of solids at millimetre wavelengths

A technique for determining the relative permittivity of solids from measurements made on a.lower-density sample prepared from the same material is demonstrated. Data presented for three different solids at 70GHz illustrate the potential of the technique implemented with conventional short-circuit or waveguide-bridge instrumentation.