Electromagnetic Properties Of Composite Materials Research Articles

Effective thermal and electromagnetic properties of composite materials containing ellipsoidal-coated fillers oriented randomly

This study aims to derive explicit solutions for the effective thermal and electromagnetic properties of composite materials containing coated fillers oriented randomly. In this study, the coated fillers are modeled as double inhomogeneous inclusions with anisotropic properties and ellipsoidal shapes, without loss of generality. This model is analyzed by combining the double inclusion method with the self-consistent method or the Mori–Tanaka method. The derived solutions for the effective properties are expressed in explicit form by the physical properties of constituents and the difference in shape between the inner and outer regions of the coated fillers, and confirmed to be consistent in the limit of no coating layer. In addition, the solutions of effective properties are also derived for composite materials containing many kinds of coated fillers with different shapes and physical properties. The solutions allow the prediction of thermal conductivity, permittivity, electrical conductivity, and magnetic permeability of a wide range of composite materials by analogy with thermal and electromagnetic properties. These solutions are applied to the following two composites: diamond fillers coated with TiC/Al, and Co fillers coated with Co 3 O 4/Mg. The effect of the thickness of the coating layer on the effective thermal conductivity of these materials is investigated. As a result, our analytical results for these composite materials generally agree with the experimental results. Moreover, from the viewpoint of maximizing the thermal conductivity of diamond fillers coated with TiC/Al, the optimal combinations of the thickness of the coating layer and the shape of the diamond fillers are identified. For Co coated with Co 3 O 4/Mg, we find that the shape of Co fillers should be long fibrous from the viewpoint of giving high magnetic permeability while maintaining high thermal conductivity due to Mg. Thus, the analytical solutions are demonstrated to be powerful tools for designing composite materials containing coated fillers.

Electromagnetic Properties of Composite Materials Based on Nd-Compound Modified Fe-Si-Al Alloy

The investigation of microstructure, optical and electromagnetic properties of powder prepared from Nd-compound doped Al6Si9Fe85 (Alsifer) alloy. The result of energy-dispersive X-ray spectroscopy is an evidence that the complementary Nd-containing Nd-Fe phase is on the surface of Alsifer particles. The magnetic particles distribution histogram in powder after mechanical treatment was plotted and analyzed. The electromagnetic properties (components magnetic permeability and dielectric permittivity) for produced composites with Nd-compound doped Alsifer powder with 50-90% (wt.) was studied. The nonlinear concentration dependence of magnetic and dielectric permittivity versus concentration Nd-compound doped Alsifer particles was observed. The magnetic resonance in composites was detected that shifted in low frequencies with increased magnetic filler concentration. The resonance field, absorption linewidth, g-factor and microwave absorption ability of Nd-compound doped Alsifer powder were determined from FMR experiment.

Electromagnetic characteristics of composite materials based on hexaferrite powders and a silicone binder

This article studies the electromagnetic properties of composite materials based on hexaferrite powders and a silicone binder. The results of this study are presented. Samples of radiomaterials based on hexaferrite powders Z-, W-, M-type and silicone binder were made. The measurements were carried out in a frequency range from 100 MHz to 18 GHz. The frequency dependencies of complex permittivity and permeability are shown. Based on the data obtained, the electromagnetic response for composites of various thicknesses located in free space and on the metal was calculated. The composite located on the metal, which contains 80 wt.% BaCo0.6Zn1.4Fe16O27 and has a thickness of 2 mm, can reduce the level of reflected radiation by more than 100 times in the frequency range from 12.5 to 18 GHz. A composite material containing 80 wt.% BaCo2.4Ti0.4Fe23.2O41 is effective narrowband absorber (reduces reflection by more than 100,000 times) at a frequency of 11.6 GHz, at a thickness of 2.6 mm.

Electromagnetic Properties of Composite Materials Based on ABS Plastic with Carbon Nanotubes Obtained by the Additive Technology in the SHF and EHF Bands

The results of study of the electromagnetic characteristics of polymer composite materials containing multiwall carbon nanotubes are presented. New radio filaments for 3D printing with MWCNTs have been created. Experimental samples were obtained from composite filaments by 3D printing. Also investigated is the ABS plastic brand Conductive with carbon fibers. Studies of electromagnetic characteristics were carried out in the SHF and EHF ranges. The frequency dependences of the complex permittivity for these materials are shown. The results show that ABS Conductive plastic has the best absorbing properties on microwave frequency, and composite plastics with MWCNTs of 2% or more on EHF.

Modular Analysis of Arbitrary Dipolar Scatterers

Within the paradigm of metamaterials and metasurfaces, electromagnetic properties of composite materials can be engineered by shaping or modulating their constituents, so-called meta-atoms. Synthesis and analysis of complex-shape meta-atoms with general polarization properties is a challenging task. In this paper, we demonstrate that the most general response can be conceptually decomposed into a set of basic, fundamental polarization phenomena, which enables immediate all-direction characterization of electromagnetic properties of arbitrary linear metamaterials and metasurfaces. The proposed platform of modular characterization (called "materiatronics") is tested on several examples of bianisotropic and nonreciprocal meta-atoms. As a demonstration of the potential of the modular analysis, we use it to design a single-layer metasurface of vanishing thickness with unitary circular dichroism. The analysis approach developed in this paper is supported by a ready-to-use computational code and can be further extended to meta-atoms engineered for other types of wave interactions, such as acoustics and mechanics.

Micromechanical Analysis for Electro-Magnetic Properties of Composite Materials Containing Clusters of Reinforcements

Micromechanical Analysis for Electro-Magnetic Properties of Composite Materials Containing Clusters of Reinforcements

Terahertz absorption in graphite nanoplatelets/polylactic acid composites

The electromagnetic properties of composite materials based on poly(lactic) acid (PLA) filled with graphite nanoplatelets (GNP) were investigated in the microwave (26–37 GHz) and terahertz (0.2–1 THz) frequency ranges. The maximum of the imaginary part of the dielectric permittivity was observed close to 0.6 THz for composites with 1.5 and 3 wt.% of GNP. The experimental data of complex dielectric permittivity of GNP/PLA composites was modelled using the Maxwell-Garnett theory. The effects of fine dispersion, agglomeration, and percolation in GNP-based composites on its electromagnetic constitutive parameters, presence, and position of THz absorption peak are discussed on the basis of the modeling results and experimental data. The unique combination of conductive and geometrical parameters of GNP embedded into the PLA matrix below the percolation threshold allow us to obtain the THz-absorptive material, which may be effectively used as a 3D-printing filament.

Micromechanical Analysis for Electro-Magnetic Properties of Composite Materials Containing Clusters of Reinforcements

Micromechanical Analysis for Electro-Magnetic Properties of Composite Materials Containing Clusters of Reinforcements

Shielding properties of composite materials based on epoxy resin with graphene nanoplates in the microwave frequency range

Analysis of the electromagnetic properties of composite materials based on epoxy resin with the addition of 0.5 wt % graphene nanoplates in the frequency range of 26–37 GHz is performed. The influence of types of epoxy resin with different viscosities and the type of solvent used (ethanol, acetone) on the electromagnetic response in this frequency range are determined. It is established that the least viscous epoxy resin, Epikote 828, and solvent ethanol are most effective for creation of a shielding covering in the microwave range. Composite materials with optimal composition provide attenuation of the electromagnetic signal at a level at least 10 dB in power for a film thickness of 1.1 mm.

Research of Electromagnetic Properties of Composite Materials on the Basis of MWNTs in Microwave Range

In this paper electromagnetic properties of composite materials based on polymethylmethacrylate and multiwall carbon nanotubes (MWCNTs) are investigated. Carbon nanotubes are received with application of various types of catalysts and have various structural parameters. Calculation of dielectric permeability of the synthesised materials is carried out. Dependence of electromagnetic properties of composite materials on concentration and structure used multilayer carbon nanotubes is shown.

Electromagnetic properties of composite materials for the electrical power device.

The current-voltage characteristics and the mechanism of memorized magnetic effect of a BiSrCaCuO superconductor were studied to develop a superconductor device. An external magnetic field produced an out-put voltage across the superconducting sample which increased with increasing the applied magnetic flux. The out-put voltage was not completely disappeared after removal of the magnetic field at a temperature. The appearance of the voltage was ascribed to the trapping of magnetic flux. The magnetic effect arose from the interaction between a trapped magnetic flux and a weak link of the superconducting bulk. The type and distribution of second phases are important factors to control magnetic pinning effect for a precisely controlled device.

Effective Permittivity of Shielding Composite Materials for Microwave Frequencies

Due to mass constraints, composite materials are possible candidates to replace metal alloys for electromagnetic shielding applications. The design of standard metallic shielding enclosures often relies on finite-element calculations. But in the case of composite materials, the strong dependence on the shielding properties to the microstructure makes the finite-element approach almost impossible. Indeed meshing the microstructure would imply a huge number of elements, incompatible with usual computational resources. We propose in this paper to develop homogenization tools to define the effective electromagnetic properties of composite materials at microwave frequencies. The ratio between the characteristic size of the microstructure and the wavelength is shown to be a key parameter in the homogenization process. The effective properties can then be used as an input for electromagnetic compatibility standard tools, designed for homogeneous media.

Anisotropy of composite materials with inclusion with orientation preference

In this paper, the quasicrystalline model and the differential evolution strategy are applied to analyze the effective electromagnetic properties of composite materials with aligned nonspherical inclusions. The relationship between the effective wave number, volume concentration, direction of wave propagation vector, and aspect ratio of the inclusion particle are numerically studied. It is found that composite materials with small inclusion particles behave like uniaxial material. In addition, we observed general effective anisotropy in composite materials with larger inclusion particles.

Synthesis and electromagnetic properties of ferroelectric–ferromagnetic composite material

Ferroelectric–ferromagnetic composite materials which possess both capacitive and inductive properties for suppressing electromagnetic interference (EMI) were synthesized by usual ceramic technology. These composite materials have relatively high dielectric constant ( ε r = 70 ) and high relaxation frequency ( f r>1.8 GHz). The influences of different composition on the electromagnetic properties of composite materials were investigated. The microstructures of the sintered ceramics were observed and analyzed by SEM. It was found that the average grain size of sintered ceramics was smaller than 5 μm and the densities ranged from 4.9 to 5.3 g/cm 3.

Microwave signal rectification using artificial composite materials composed of diode-loaded electrically small dipole antennas

The electromagnetic properties of composite materials composed of dipole or loop antennas (also called molecules) loaded with different linear passive electronic circuits are summarized. These molecules are extended to those molecules whose loads contain some basic nonlinear elements. Several examples are discussed. The simplest nonlinear load is the clamping circuit: a diode and a resistor are connected in series to an electrically small dipole antenna. This is generalized to a more complicated molecule based on a diode bridge. Numerical results generated with a finite-difference time-domain (FDTD) simulator demonstrate how an incident narrow-bandwidth pulse interacts with these materials and can be transformed into a baseband, rectified signal, or a signal containing selected harmonics of the fundamental frequency. Potential applications of these artificial material-based signal convertors include target identification and signal modulation.

Maxwell Garnett approach for nonlinear dilute particulate composites with bi-isotropic host media

Homogenization theories foster understanding of the electromagnetic properties of composite materials formed by dispersing electrically small inclusions made of various types of homogeneous media in a homogeneous host medium. In this paper, the Maxwell Garnett approach is applied to homogenize a broad class of nonlinear composites. While the host is a linear bi-isotropic medium, the inclusions are made of a nonlinear anisotropic dielectric medium. Bloembergen's formalism, originally developed for nonlinear isotropic dielectric inclusions dispersed in a linear isotropic dielectric host medium, is employed for the estimation of local fields; and its applicabillity for this considerably more general problem is critically examined and contextualized. The homogenized composite displays a rich behaviour due to the chirality of the host medium, and novel optical applications are therefore anticipated.