Dielectric Permittivity of Polymers Containing Conductive Inclusions

Kolesnicov, A.N.; Lagarkov, A. N.; Matitsin, S.M.; Novogrudskiy, L.N.; Rozanov, Konstantin N.; Sarychev, Andrey K.

doi:10.1557/proc-214-113

Cited by 4 publications

(3 citation statements)

References 1 publication

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“…It is well known that a structure composed of a periodic mesh of metallic thin wires, behaves as a homogeneous material with a low plasma frequency [6][7][8]. The behavior of this metamaterial was further investigated when its characteristic dimensions (period, section of the wires) are small in comparison to the wavelength [9][10][11].…”

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confidence: 99%

“…We note that the last three terms with boundary integrals are some penalty terms enforcing the boundary conditions ( 2)-( 4) as D and D(1 − ν) are strictly positive constants. These terms can be simplified as in (5) and (6).…”

mentioning

confidence: 99%

“…Last but not least, it should be mentioned that in the case of a microvawe application the design of an omni-directive antenna with a source placed inside a metamaterial with an effective refractive index close to zero [6,7,12] is partly spoiled due to losses that widen the directivity diagram. This effect would be even more pronounced at higher frequencies (e.g.…”

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confidence: 99%

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High directivity and confinement of flexural waves through ultra-refraction in thin perforated plates

Farhat¹,

Guenneau²,

Enoch³

2010

EPL

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We propose a design of a periodically perforated thin plate leading to omni-directivity and confinement of bending waves via ultra-refraction. We first analyze the band spectrum of the bi-harmonic operator for an array of freely vibrating square voids arranged in a checkerboard fashion using finite elements: the spectrum displays nearly flat bands associated with slow flexural waves shown to be associated with resonances of square cells with stress-free boundary conditions. We find some point in the reciprocal space where the curvature of the dispersion diagram vanishes. We then demonstrate that a concentrated point force generating a bending wave within a finite array of 221 perforations displays an enhanced local density of states and radiates a flexural wave mostly in the direction perpendicular to the checkerboard slab. We next propose a simple reconstruction of the effective density associated with the platonic crystal by comparison of local density of states. This also allows us to quantify the confinement of elastic energy with the platonic crystal. We finally produce the emission diagram which demonstrates that the radiative device acts as an omni-directive super-antenna.

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High directivity and confinement of flexural waves through ultra-refraction in thin perforated plates

Farhat¹,

Guenneau²,

Enoch³

2010

EPL

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Microwave characterization and modelization of magnetic granular materials

Olmedo¹,

Chateau²,

Deleuze³

et al. 1993

Journal of Applied Physics

107

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The use of dispersion techniques for development of microwave absorbers is a convenient way of realization of coatings with good attenuation characteristics in the 1- to 20-GHz range. Particularly, elastomer mixing is a very good technique for dispersion and individualization of each grain up to 60% volume. A first generation of materials, developed with ferrite powders, has been extensively studied. It was found possible to predict properties of composites with classical mixture laws using intrinsic properties of filler and matrix. When using conductive ferromagnetic fillers, the inability to measure intrinsic magnetic properties does not permit prediction of behavior of composites. Therefore, a method of inverse calculation has been developed which, from (ε, μ) parameters measured on composites, allows inferrence of intrinsic properties of each filler (iron, cobalt, permalloy,...). It is shown that this method, employed for several amounts of filler, gives significant accuracy on (μ′, μ″) with intermediate concentrations (typically 25% vol. to 45% vol. with spheres). For permittivity, this method is satisfying in the case of nonpercolating systems. Also studied was the effect of morphology on properties of granular materials, particularly in the case of sphericity and grain size of iron and cobalt particles. Permittivity level is directly correlated to sphericity, and magnetic relaxation frequency to grain size. It is also shown that the chemical nature, particularly for ex-carbonyl origin of iron, does not play a significant role in composite material properties.

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Electromagnetic composites: From effective medium theories to metamaterials

Qin

Peng

Estévez

et al. 2022

Journal of Applied Physics

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Electromagnetic (EM) composites have stimulated tremendous fundamental and practical interests owing to their flexible electromagnetic properties and extensive potential engineering applications. Hence, it is necessary to systematically understand the physical mechanisms and design principles controlling EM composites. In this Tutorial, we first provide an overview of the basic theory of electromagnetism about electromagnetic constitutive parameters that can represent the electromagnetic properties of materials. We show how this corpus allows a consistent construction of effective medium theories and allows for numerical simulation of EM composites to deal with structure–property relationships. We then discuss the influence of spatial dispersion of shaped inclusions in the material medium on the EM properties of composites, which has not been systematically illustrated in the context of this interdisciplinary topic. Next, artificial composites or metamaterials with peculiar properties not readily available in nature are highlighted with particular emphasis on the control of the EM interaction with composites. We conclude by discussing appropriate methods of electromagnetic measurement and practical aspects for implementing composites for specific applications are described. Overall, this Tutorial will serve the purpose of introducing the basics and applications of electromagnetic composites to newcomers in this field. It is also anticipated that researchers from different backgrounds including materials science, optics, and electrical engineering can communicate to each other with the same language when dealing with this interdisciplinary subject and further push forward this advancement from fundamental science to technological applications.

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Dielectric Permittivity of Polymers Containing Conductive Inclusions

Cited by 4 publications

References 1 publication

High directivity and confinement of flexural waves through ultra-refraction in thin perforated plates

High directivity and confinement of flexural waves through ultra-refraction in thin perforated plates

Microwave characterization and modelization of magnetic granular materials

Electromagnetic composites: From effective medium theories to metamaterials

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