Broadband Electromagnetic Absorbers Using Carbon Nanostructure-Based Composites

Abstract

Abstract\ud \ud In this paper, we present the design of nanostructured multilayer absorbers, carried out with the aid of a genetic algorithm (GA). Waveguide measurements are performed to recover the dielectric properties of micrographite single-walled carbon nanotube, micrographite walled carbon nanotube, carbon nanofiber, and fullerene-based composite materials. Conductive fillers are uniformly dispersed in an epoxy resin at different weight percentages (1, 3, 5 wt.%). The electromagnetic (EM) analysis is performed embedding the forward/backward propagation matrix formalism in an in-house GA, thus able to carry out optimization upon oblique incidence over a finite angular range. Developed code minimizes both the reflection and the transmission coefficients under the thickness minimization constraint. Comparison between micrographite and nanopowders absorbers is presented and discussed, when a broadband quasi-perfect absorber is achieved among the X-band combining the two filler families, i.e., exhibiting a loss factor greater than 90% in most of the band, for a thickness of about 1 cm. It is demonstrated that the nanofillers with higher aspect ratio mainly contribute to the EM absorption. Findings are of interest in both radar-absorbing material and shielding structures

Absorbing Cross Section in Reverberation Chamber: Experimental and Numerical Results

“…Materials are often used to produce absorbing foam sheets or objects with complex geometry (pyramidal absorbers for example), to be used to minimize the radar cross section (RCS) of targets or to assemble anechoic chambers. In this cases, reflection measurements are carried out on large samples, or directly on-site measurement are done [4][5][6][7][8]. Although, permittivity and permeability are intrinsic properties of the materials, absorption properties of large panels or walls depend also on geometry, incoming wave polarization and direction of incidence.…”

Enhanced Polarization in Tadpole-Shaped (Ni, Al)/Aln Nanoparticles and Microwave Absorption at High Frequencies

“…The magnetic loss is in such a low value at 17 GHz and cannot be the reason for the strong RL. The impedance matching condition requires the intrinsic wave impedances of the absorber (η) equivalent to that of air (Z 0 ), which can be computed by [42]: η = µ 0 /ε 0 µ r /ε r = Z 0 µ r /ε r , where Z 0 = 377 Ω and ε r , µ r are the complex permittivity and complex permeability of the absorber. According to the equation, the impedance matching condition can be satisfied when µ r equals to ε r .…”

Design and Optimization of Multilayered Electromagnetic Shield Using a Real-Coded Genetic Algorithm

“…This is evident from the results reported in various tables of this paper. Reference [10] suggests a new direction for further research towards experimental realization and measurement of such multilayer composites. However, the differences lie in the achievable "thickness" of the composite material (where it varies from 1 mm single layer to 1 cm multilayer) and our predicted results for three-layered composite (varies from ∼ 177 µm to ∼ 725 µm for 40 dB and ∼ 333.2 µm to ∼ 725 µm for 80 dB) considering all cases.…”

“…To achieve minimum reflection coefficient of the multilayered compound from the predefined database of various materials, the selection of materials is obtained by employing genetic algorithm (GA) [6]. Similar approach has been adopted to optimize the selection of material by formulating different objective functions, such as SE, reflection or absorption from the given set of materials to achieve minimum thickness by several other groups [7][8][9][10]. In place of selecting materials from the predefined database, researchers in [3] optimize the material parameters from the given range (upper and lower bounds) to achieve the desired shielding efficiency of the multilayered compound for a given application using the binary-coded GA.…”