Separation and extraction of non-thermal effects of strong microwave electric field on dielectric properties of materials based on time modulation and cavity perturbation method

Recently, a laboratory setup for microwave-based characterization of powder samples at elevated temperatures and different gas atmospheres was presented. The setup is particularly interesting for operando investigations on typical materials for exhaust gas aftertreatment. By using the microwave cavity perturbation method, where the powder is placed inside a cavity resonator, the change of the resonant properties provides information about changes in the dielectric properties of the sample. However, determining the exact complex permittivity of the powder samples is not simple. Up to now, a simplified microwave cavity perturbation theory had been applied to estimate the bulk properties of the powders. In this study, an extended approach is presented which allows to determine the dielectric properties of the powder materials more correctly. It accounts for the electric field distribution in the resonator, the depolarization of the sample and the effect of the powder filling. The individual method combines findings from simulations and recognized analytical approaches and can be used for investigations on a wide range of materials and sample geometries. This work provides a more accurate evaluation of the dielectric powder properties and has the potential to enhance the understanding of the microwave behavior of storage materials for exhaust gas aftertreatment, especially with regard to the application of microwave-based catalyst state diagnosis.

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Measurement of the Dielectric Constant and Loss Tangent of Polyester / Walnut Shells by the Cavity Perturbation Method at the Microwave X-band Frequencies

NeuroQuantology ◽

10.14704/nq.2021.19.3.nq21024 ◽

2021 ◽

Vol 19 (3) ◽

pp. 26-31

Author(s):

Ahmed R. Mathloom

Keyword(s):

Dielectric Constant ◽

Dielectric Properties ◽

Perturbation Method ◽

Loss Tangent ◽

Dominant Mode ◽

Walnut Shells ◽

Microwave Engineering ◽

Dielectric Constant And Loss ◽

X Band ◽

Cavity Perturbation

In this paper, the cavity perturbation method was used to measure the dielectric properties of materials that are important for understanding the response to microwave waves, in terms of the ability of these materials to store energy and dissipate it as heat, respectively. Compounds (polyester / walnut shells) were prepared, and for different weight concentrations of walnut shells (WS) additive, the proportions ranged between (0% - 25%). The used cavity is rectangular in shape with a theoretically resonance frequency of around (9.9978 GHz) and exiting the dominant mode (TE101). The study shows the highest values of each dielectric constant with a weight concentration (25%) of the walnut shells, and the loss tangent without any material change to the sample. These compounds have been found to be useful in applications of electromagnetic materials such as microwave engineering and protection from biological influences when exposed to the field of microwaves, which is why it is very important to test their dielectric properties.

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Application of a cavity perturbation method to the measurement of the complex microwave impedance of thin super- or normal conducting films

Journal de Physique III ◽

10.1051/jp3:1994174 ◽

1994 ◽

Vol 4 (5) ◽

pp. 917-927 ◽

Cited By ~ 8

Author(s):

G. Schaumburg ◽

H. W. Helberg

Keyword(s):

Perturbation Method ◽

Cavity Perturbation

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Effects of tissue dielectric properties on the electric field induced in tDCS: A sensitivity analysis

2012 Annual International Conference of the IEEE Engineering in Medicine and Biology Society ◽

10.1109/embc.2012.6346049 ◽

2012 ◽

Cited By ~ 7

Author(s):

R. Salvador ◽

F. Ramirez ◽

M. V'yacheslavovna ◽

P. C. Miranda

Keyword(s):

Sensitivity Analysis ◽

Dielectric Properties ◽

Electric Field

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Electrostatic Forces on Particles Floating Within the Interface Between Two Immiscible Fluids

Volume 8: Heat Transfer, Fluid Flows, and Thermal Systems, Parts A and B ◽

10.1115/imece2007-44095 ◽

2007 ◽

Author(s):

Nadine Aubry ◽

Pushpendra Singh

Keyword(s):

Dielectric Properties ◽

Field Strength ◽

Electric Field ◽

Electric Field Strength ◽

External Electric Field ◽

Capillary Force ◽

Electrostatic Force ◽

Immiscible Fluids ◽

Electrostatic Forces ◽

Dipole Interactions

The objective of this paper is to study the dependence of the electrostatic force that act on a particle within the interface between two immiscible fluids on the parameters such as the dielectric properties of the fluids and particles, the particle’s position within the interface, and the electric field strength. It is shown that the component of electrostatic force normal to the interface varies as a2, where a is the particle radius, and since in equilibrium it is balanced by the vertical capillary force, the interfacial deformation caused by the particle changes when an external electric field is applied. In addition, there are lateral electrostatic forces among the particles due to the dipole-dipole interactions which, when the distance between two particles is O(a), vary as a2, and remain significant for submicron sized particles.

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