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Recent Advances in Microwave and Millimeter Wave Nanocomposite Absorbers for EMI Applications

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A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "A：Physics".

Deadline for manuscript submissions: closed (30 November 2020) | Viewed by 12898

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Special Issue Editor

Prof. Dr. Isabelle Huynen

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Institute of Information and Communication Technologies, Electronics and Applied Mathematics (ICTEAM), Université Catholique de Louvain, Place du Levant 3, 1348 Louvain-la-Neuve, Belgium
Interests: microwave and millimeter wave; nanotechnotechnology; modeling; simulation; measurement; broadband nanodevices
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In the present urban, domestic, and working place environments, electromagnetic (EM) waves are omnipresent. The major trends towards wideband wireless communication, on one hand, and ever increasing density of electronic devices, on the other, generate a growing issue with electromagnetic interference (EMI), which can occur between devices or between subcomponents of devices. The consequences are at best annoying but can be very dangerous for health- or security-related applications. Classical broadband EMI shielding is based on electromagnetic reflectors, usually metal foils or coatings, acting as Faraday cages. These methods are less and less satisfactory in the present environment, because the interfering EM signal is simply reflected back to the environment without significant loss. This explains the renewed popularity of EM absorbers, which truly eliminate the EM signal in directions or locations where it is unwanted.

The present Special Issue aims to focus on absorbers operating at microwave and/or millimeter waves and based on nanocomposite materials that may contain various kinds of nano inclusions such as carbon nanotubes, graphene nanoplatelets, metallic nanoparticles, etc. Various aspects can be covered, such as design, fabrication, and modeling of novel nanocomposite absorbers having performances competing with the state-of-the art.

Prof. Isabelle Huynen
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Micromachines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Nanocomposite
Absorber
Microwaves
Millimeter waves
Nanostructures
Magnetic losses
Dielectric losses
Absorption mechanism

Related Special Issue

Nanodevices for Microwave and Millimeter Wave Applications in Micromachines (8 articles)

Published Papers (4 papers)

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Research

18 pages, 6599 KiB

Open AccessArticle

Long Carbon Fibers for Microwave Absorption: Effect of Fiber Length on Absorption Frequency Band

by Hanadi Breiss, Aicha El Assal, Ratiba Benzerga, Chloé Méjean and Ala Sharaiha

Micromachines 2020, 11(12), 1081; https://doi.org/10.3390/mi11121081 - 06 Dec 2020

Cited by 13 | Viewed by 2668

Abstract

This work presents lightweight epoxy foams loaded with very low weight percentages (≤0.5 wt.%) of carbon fibers (CFs) with different lengths (3 mm, 6 mm, and 12 mm) as broadband microwave absorbing materials for anechoic chamber application. The effect of CF length on microwave absorption, especially on the absorption frequency band, is investigated for frequencies between 1 and 15 GHz. For the elaboration of composites, three different methods—spatula, shear mixing, and ultrasounds—are used for the dispersion of CFs. The observation of these CFs, after the dispersion step, shows a high fiber breakage rate when shear mixing is used, unlike when spatula or ultrasounds methods are used. On the other hand, the characterization of the elaborated composites highlights a correlation between the mixing methods, hence the fiber brakeage, and the measured reflection coefficient (reflection loss) of the composites. As a result, the minimum value of the reflection coefficient is shifted toward the high frequencies when the fiber breakage is observed, suggesting that short CFs absorb at high frequencies while long CFs absorb at low frequencies. Dielectric properties, extracted from the measurement in free space, of composites elaborated with different fiber lengths (3 mm, 6 mm, and 12 mm) confirm that short CFs (3 mm) show maximum losses at high frequencies (around 15 GHz) while long CFs (12 mm) show maximum dielectric losses at low frequencies (below 4 GHz). However, no significant variation is observed on the real part of the relative permittivity, as a function of fiber length, for these porous composites loaded with very low CF rates. A hybrid composite, with a mix of different CF lengths, is prepared and characterized. The simulation of the absorption performance of a pyramidal absorber, based on this hybrid composite, is compared to the one of pyramidal absorber based on composites loaded with a single length of carbon fibers. The pyramidal absorber-based hybrid composite predicts the best absorption performance, especially at the low frequency band. The simulated reflection coefficient of this absorber is less than −12 dB in all the studied frequency range, and less than −40 dB for frequencies higher than 3 GHz. This result confirms the interest of using a mix of carbon fiber lengths to achieve a broadband microwave absorber. Full article

(This article belongs to the Special Issue Recent Advances in Microwave and Millimeter Wave Nanocomposite Absorbers for EMI Applications)

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16 pages, 4327 KiB

Open AccessArticle

Toward an Ultra-Wideband Hybrid Metamaterial Based Microwave Absorber

by Aicha El Assal, Hanadi Breiss, Ratiba Benzerga, Ala Sharaiha, Akil Jrad and Ali Harmouch

Micromachines 2020, 11(10), 930; https://doi.org/10.3390/mi11100930 - 13 Oct 2020

Cited by 16 | Viewed by 3924

Abstract

In this paper, we propose a novel design of an ultra-wideband hybrid microwave absorber operating in the frequency range between 2 GHz and 18 GHz. This proposed hybrid absorber is composed of two different layers that integrate a multiband metamaterial absorber and a lossy dielectric layer. The metamaterial absorber consists of a periodic pattern that is composed of an arrangement of different scales of coupled resonators and a metallic ground plane, and the dielectric layer is made of epoxy foam composite loaded with low weight percentage (0.075 wt.%) of 12 mm length carbon fibers. The numerical results show a largely expanded absorption bandwidth that ranges from 2.6 GHz to 18 GHz with incident angles between 0° and 45° and for both transverse electric and transverse magnetic waves. The measurements confirm that absorption of this hybrid based metamaterial absorber exceeds 90% within the above-mentioned frequency range and it may reach an absorption rate of 99% for certain frequency ranges. The proposed idea offers a further step in developing new electromagnetic absorbers, which will impact a broad range of applications. Full article

(This article belongs to the Special Issue Recent Advances in Microwave and Millimeter Wave Nanocomposite Absorbers for EMI Applications)

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13 pages, 5625 KiB

Open AccessArticle

Investigation of Microwave Absorption Performance of CoFe₂O₄/NiFe₂O₄/Carbon Fiber Composite Coated with Polypyrrole in X-Band Frequency

by Rozhin Sadeghi, Abbas Sharifi, Marta Orlowska and Isabelle Huynen

Micromachines 2020, 11(9), 809; https://doi.org/10.3390/mi11090809 - 26 Aug 2020

Cited by 10 | Viewed by 2315

Abstract

The current research reports the preparation of a microwave absorber containing CoFe₂O₄/NiFe₂O₄/Carbon fiber (H/S/CF) coated with polypyrrole polymer (PPy@H/S/CF) through sol-gel and in-situ polymerization processes. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM), and a vector network analyzer (VNA) are utilized to evaluate the features of the prepared composite. The microstructure analysis results revealed carbon fibers well decorated with submicron-size particles having hard/soft magnetic phases and thoroughly coated with polymer. The paraffin-based microwave absorber sample filled with 45 wt.% of PPy@H/S/CF has simultaneously both magnetic and dielectric losses in the 8.2–12.4 GHz frequency range. The absorber is used in a Salisbury screen configuration aiming at reducing the radar cross-section of objects. A minimum reflection loss of −55 dB at 10.6 GHz frequency with 5 GHz bandwidth is obtained for the sample with a 2 mm thickness. Different mechanisms, such as interfacial polarization, ferromagnetic resonance, and electron hopping, are the main factors for achieving such an appropriate microwave absorption. These results suggest that the PPy@H/S/CF composite is an ideal candidate for microwave absorption applications requiring high performance and low thickness. Full article

(This article belongs to the Special Issue Recent Advances in Microwave and Millimeter Wave Nanocomposite Absorbers for EMI Applications)

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17 pages, 2591 KiB

Open AccessArticle

Simulation and Optimization of Electromagnetic Absorption of Polycarbonate/CNT Composites Using Machine Learning

by Lakhdar Sidi Salah, Mohamed Chouai, Yann Danlée, Isabelle Huynen and Nassira Ouslimani

Micromachines 2020, 11(8), 778; https://doi.org/10.3390/mi11080778 - 15 Aug 2020

Cited by 13 | Viewed by 3481

Abstract

Electronic devices that transmit, distribute, or utilize electrical energy create electromagnetic interference (EMI) that can lead to malfunctioning and degradation of electronic devices. EMI shielding materials block the unwanted electromagnetic waves from reaching the target material. EMI issues can be solved by using a new family of building blocks constituted of polymer and nanofillers. The electromagnetic absorption index of this material is calculated by measuring the “S-parameters”. In this article, we investigated the use of artificial intelligence (AI) in the EMI shielding field by developing a new system based on a multilayer perceptron neural network designed to predict the electromagnetic absorption of polycarbonate-carbon nanotubes composites films. The proposed system included 15 different multilayer perception (MLP) networks; each network was specialized to predict the absorption value of a specific category sample. The selection of appropriate networks was done automatically, using an independent block. Optimization of the hyper-parameters using hold-out validation was required to ensure the best results. To evaluate the performance of our system, we calculated the similarity error, precision accuracy, and calculation time. The results obtained over our database showed clearly that the system provided a very good result with an average accuracy of 99.7997%, with an overall average calculation time of 0.01295 s. The composite based on polycarbonate−5 wt.% carbon nanotube was found to be the ultimate absorber over microwave range according to Rozanov formalism. Full article

(This article belongs to the Special Issue Recent Advances in Microwave and Millimeter Wave Nanocomposite Absorbers for EMI Applications)

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