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10 pages, 2838 KiB

Open AccessArticle

Numerical Study of Angle-Insensitive and Tunable Dual-Band THz Absorber Using Periodic Cross-Shaped Graphene Arrays

by Tian Sang, Jian Gao, La Wang, Honglong Qi, Xin Yin and Yueke Wang

Materials 2019, 12(13), 2063; https://doi.org/10.3390/ma12132063 - 27 Jun 2019

Cited by 9 | Viewed by 2255

A dual-band terahertz (THz) absorber using the periodic cross-shaped graphene arrays is presented. It is shown that the dual-band light absorption enhancement of graphene results from the edge graphene plasmon (EGP) resonance, and the locations of the two absorption peaks can be precisely [...] Read more.

A dual-band terahertz (THz) absorber using the periodic cross-shaped graphene arrays is presented. It is shown that the dual-band light absorption enhancement of graphene results from the edge graphene plasmon (EGP) resonance, and the locations of the two absorption peaks can be precisely estimated by using the Fabry-Pérot (F-P) cavity model. Slight residual reflection remains at the two absorption peaks because the input impedance of the cross-arm cannot be perfectly matched with the free space impedance. In addition, the locations of the two absorption bands can be simultaneously tuned by changing the Fermi level of graphene, and they can be independently tuned by changing the width or the length of the cross-arm of graphene. Excellent angle-insensitivity dual-band absorption enhancement of graphene can be maintained for both the transverse electric (TE) and transverse magnetic (TM) polarizations. Full article

(This article belongs to the Special Issue Carbon Based Functional Microwave Shields)

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11 pages, 6499 KiB

Open AccessArticle

Percolative Composites with Carbon Nanohorns: Low-Frequency and Ultra-High Frequency Response

by Olga V. Sedelnikova, Kseniya I. Baskakova, Artem V. Gusel’nikov, Pavel E. Plyusnin, Lyubov G. Bulusheva and Alexander V. Okotrub

Materials 2019, 12(11), 1848; https://doi.org/10.3390/ma12111848 - 06 Jun 2019

Cited by 7 | Viewed by 2585

Abstract

We systematically studied the electromagnetic properties of carbon nanohorns (CNHs) and polystyrene composites filled with CNHs in static regime, low frequency and microwave regions. CNHs were synthesized using the direct current arc-discharge method using solid graphite rods and graphite rods filled by melamine [...] Read more.

We systematically studied the electromagnetic properties of carbon nanohorns (CNHs) and polystyrene composites filled with CNHs in static regime, low frequency and microwave regions. CNHs were synthesized using the direct current arc-discharge method using solid graphite rods and graphite rods filled by melamine mixed with graphite powder. Transmission electron microscopy and thermo-gravimetric analysis showed that CNH agglomerates are the main product, while the addition of melamine promotes the formation of graphite balls. Graphitic contamination causes the internal leakage of inter-agglomerate capacity, lowering the permittivity and enhancing the conductivity of composites. The permittivity of CNH/polystyrene composites increases with the filler fraction, and near the dielectric threshold electromagnetic characteristics of the composites exhibit critical behaviour. Our results suggest that CNHs with relatively high values of permittivity and contact resistance could be used as high-k materials. Full article

(This article belongs to the Special Issue Carbon Based Functional Microwave Shields)

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8 pages, 3092 KiB

Open AccessFeature PaperArticle

Improved Electromagnetic Interference Shielding Properties Through the Use of Segregate Carbon Nanotube Networks

by Sung-Hoon Park and Ji-Hwan Ha

Materials 2019, 12(9), 1395; https://doi.org/10.3390/ma12091395 - 29 Apr 2019

Cited by 23 | Viewed by 3392

Abstract

We report the enhanced electromagnetic interference (EMI) shielding properties of hybrid carbon nanotube (CNT) composites consisting of more than two kinds of fillers through the use of segregate conducting networks. An excluded volume was created by micro-sized silica particles that concentrate the CNT [...] Read more.

We report the enhanced electromagnetic interference (EMI) shielding properties of hybrid carbon nanotube (CNT) composites consisting of more than two kinds of fillers through the use of segregate conducting networks. An excluded volume was created by micro-sized silica particles that concentrate the CNT network, resulting in improved electrical conductivity and microwave properties. To achieve the optimal dispersion of CNTs and silica particles, high shear force was applied to the pre-cured composite mixture via three-roll milling. Depending on the micro-silica content ratio, we observed improved electrical conductivity and EMI shielding properties. For a quantitative comparison to observe the excluded-volume effects, a CNT composite without micro-silica was measured in parallel with the other sample. Full article

(This article belongs to the Special Issue Carbon Based Functional Microwave Shields)

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10 pages, 4537 KiB

Open AccessFeature PaperArticle

Ultra-Light Reduced Graphene Oxide Based Aerogel/Foam Absorber of Microwave Radiation

by Artyom Plyushch, Tianliang Zhai, Hesheng Xia, Chiara Santillo, Letizia Verdolotti, Marino Lavorgna and Polina Kuzhir

Materials 2019, 12(2), 213; https://doi.org/10.3390/ma12020213 - 10 Jan 2019

Cited by 8 | Viewed by 4779

Abstract

We present the polarization-dependent highly absorptive in Ka-band composition of conventional polyurethane foam filled with in situ synthesized aerogel coated by reduced graphene oxide (rGO). The rGO-based aerogel was in situ prepared into the open-cell polyurethane foam (PUF) skeleton through a bidirectional freeze-drying [...] Read more.

We present the polarization-dependent highly absorptive in Ka-band composition of conventional polyurethane foam filled with in situ synthesized aerogel coated by reduced graphene oxide (rGO). The rGO-based aerogel was in situ prepared into the open-cell polyurethane foam (PUF) skeleton through a bidirectional freeze-drying process. The aerogel is composed of the flat lamellas stacks, possessing the anisotropic structure and unique electromagnetic properties. Further improvement of the electromagnetic shielding ability was possible by the rGO coating introduction as a coupling layer between PUF and rGO-based aerogel. This enhances the overall conductivity of the resulting composites: 1.41 + 3.33i S/m vs. 0.9 + 2.45i S/m for PUF loaded with in situ synthesized aerogel without rGO coating.With this mechanically robust plane easy to process coating one could achieve −20 dB by power with the record light structure (0.0462 g/cm²). That could compete in view of the weight per cm² even with graphene-based absorbers comprising either dielectric matching elements or back metal reflectors, or both. Full article

(This article belongs to the Special Issue Carbon Based Functional Microwave Shields)

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11 pages, 5499 KiB

Open AccessArticle

Tunable Perfect THz Absorber Based on a Stretchable Ultrathin Carbon-Polymer Bilayer

by Alesia Paddubskaya, Marina Demidenko, Konstantin Batrakov, Gintaras Valušis, Tommi Kaplas, Yuri Svirko and Polina Kuzhir

Materials 2019, 12(1), 143; https://doi.org/10.3390/ma12010143 - 04 Jan 2019

Cited by 22 | Viewed by 3559

Abstract

By exploring the Salisbury screen approach, we propose and demonstrate a thin film absorber of terahertz (THz) radiation. The absorber is comprised of a less than 100 nm thick layer of pyrolytic carbon deposited on a stretchable polydimethylsiloxane (PDMS) film followed by the [...] Read more.

By exploring the Salisbury screen approach, we propose and demonstrate a thin film absorber of terahertz (THz) radiation. The absorber is comprised of a less than 100 nm thick layer of pyrolytic carbon deposited on a stretchable polydimethylsiloxane (PDMS) film followed by the metal film. We demonstrate that being overall less than 200 microns thick, such a sandwich structure absorbs resonantly up to 99.9%of the incident THz radiation, and that the absorption resonance is determined by the polymer thickness, which can be adjusted by stretching. Full article

(This article belongs to the Special Issue Carbon Based Functional Microwave Shields)

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8 pages, 3180 KiB

Open AccessArticle

Graphene Based Controllable Broadband Terahertz Metamaterial Absorber with Transmission Band

by Qihui Zhou, Song Zha, Peiguo Liu, Chenxi Liu, Li-an Bian, Jihong Zhang, Hanqing Liu and Liang Ding

Materials 2018, 11(12), 2409; https://doi.org/10.3390/ma11122409 - 29 Nov 2018

Cited by 28 | Viewed by 4731

Abstract

A graphene-based controllable broadband terahertz metamaterial absorber with transmission band is presented in this paper. It consists of a graphene-SiO₂-frequency selective surface (FSS) sandwich structure. The sinusoidal graphene layer supports continuous plasmonic resonances, forming a broad electric-tuning absorbing band. Bandpass FSS [...] Read more.

A graphene-based controllable broadband terahertz metamaterial absorber with transmission band is presented in this paper. It consists of a graphene-SiO₂-frequency selective surface (FSS) sandwich structure. The sinusoidal graphene layer supports continuous plasmonic resonances, forming a broad electric-tuning absorbing band. Bandpass FSS constructs a transmission window outside the absorbing band. The simulation results indicate that the absorption from 0.5 THz to 1 THz can be tuned continuously from 0.4 to 0.9 with angle and polarization independence. A transparent window peaking at 1.65 THz maintains high transmittance over 0.7. The metamaterial absorber has potential applications for detection, stealth, filtering, and electromagnetic compatibility. Full article

(This article belongs to the Special Issue Carbon Based Functional Microwave Shields)

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14 pages, 7709 KiB

Open AccessArticle

Effects of the Carbon Fiber-Carbon Microcoil Hybrid Formation on the Effectiveness of Electromagnetic Wave Shielding on Carbon Fibers-Based Fabrics

by Hyun-Ji Kim, Sung-Hoon Kim and Sangmoon Park

Materials 2018, 11(12), 2344; https://doi.org/10.3390/ma11122344 - 22 Nov 2018

Cited by 18 | Viewed by 3688

Abstract

Carbon fiber-carbon microcoil (CF-CMC) hybrids were formed on carbon fiber (CF)-based fabric. The morphologies of CF-based fabrics and CF-CMC hybridized fabrics were investigated. The electrical conductivities of the CF-CMC hybridized fabrics were examined and compared with those of native CF-based fabrics. Furthermore, the [...] Read more.

Carbon fiber-carbon microcoil (CF-CMC) hybrids were formed on carbon fiber (CF)-based fabric. The morphologies of CF-based fabrics and CF-CMC hybridized fabrics were investigated. The electrical conductivities of the CF-CMC hybridized fabrics were examined and compared with those of native CF-based fabrics. Furthermore, the electromagnetic wave shielding effectiveness (SE) of the CF-CMC hybridized fabrics was investigated across operating frequencies in the 8.0–12.0 GHz range, and the results were compared with those for native CF-based fabrics. For the CF-based nonwoven fabrics, the SE values were improved by the CF-CMC hybridization reaction, although the electrical conductivities of the nonwoven fabric were reduced by the CF-CMC hybrid formation. For the CF-based woven fabrics, the SE values were improved by more than twofold throughout the entire range of frequencies, owing to the CF-CMC hybrid formation. This dramatic improvement was partly ascribed to the enhanced electrical conductivity, particularly in the transverse direction to the individual CFs. Owing to the increased thickness of the woven or nonwoven fabrics after the CF-CMC hybrid formation and the intrinsic characteristics of CMCs, the absorption mechanism for the SE was determined for the main factor that contributed to the improvement of the SE values. Full article

(This article belongs to the Special Issue Carbon Based Functional Microwave Shields)

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10 pages, 2505 KiB

Open AccessArticle

Gamma Irradiation-Induced Preparation of Graphene–Ni Nanocomposites with Efficient Electromagnetic Wave Absorption

by Youwei Zhang, Hui-Ling Ma, Ke Cao, Liancai Wang, Xinmiao Zeng, Xiuqin Zhang, Lihua He, Pinggui Liu, Zhiyong Wang and Maolin Zhai

Materials 2018, 11(11), 2145; https://doi.org/10.3390/ma11112145 - 31 Oct 2018

Cited by 21 | Viewed by 3107

Abstract

A facile and environmentally friendly method is proposed to prepare reduced graphene oxide–nickel (RGO–Ni) nanocomposites using γ-ray irradiation. Graphene oxide (GO) and Ni²⁺ are reduced by the electrons which originated from the gamma radiolysis of H₂O. The structure and morphology [...] Read more.

A facile and environmentally friendly method is proposed to prepare reduced graphene oxide–nickel (RGO–Ni) nanocomposites using γ-ray irradiation. Graphene oxide (GO) and Ni²⁺ are reduced by the electrons which originated from the gamma radiolysis of H₂O. The structure and morphology of the obtained RGO–Ni nanocomposites were analyzed using X-ray diffraction (XRD) and Raman spectroscopy. The results show that Ni nanoparticles were dispersed uniformly on the surface of the RGO nanosheets. As expected, the combination of RGO nanosheets and Ni nanoparticles improved the electromagnetic wave absorption because of the better impedance matching. RGO–Ni nanocomposites exhibited efficient electromagnetic wave absorption performance. The minimum reflection loss (RL) of RGO–Ni reached −24.8 dB, and the highest effective absorption bandwidth was up to 6.9 GHz (RL < −10 dB) with a layer thickness of 9 mm. Full article

(This article belongs to the Special Issue Carbon Based Functional Microwave Shields)

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12 pages, 4555 KiB

Open AccessArticle

Decorating MOF-Derived Nanoporous Co/C in Chain-Like Polypyrrole (PPy) Aerogel: A Lightweight Material with Excellent Electromagnetic Absorption

by Xiaodong Sun, Xuliang Lv, Mingxu Sui, Xiaodi Weng, Xiaopeng Li and Jijun Wang

Materials 2018, 11(5), 781; https://doi.org/10.3390/ma11050781 - 11 May 2018

Cited by 37 | Viewed by 4910

Abstract

To clear away the harmful effects of the increment of electromagnetic pollution, high performance absorbers with appropriate impedance matching and strong attenuation capacity are strongly desired. In this study, a chain-like PPy aerogel decorated with MOF-derived nanoporous Co/C (Co/C@PPy) has been successfully prepared [...] Read more.

To clear away the harmful effects of the increment of electromagnetic pollution, high performance absorbers with appropriate impedance matching and strong attenuation capacity are strongly desired. In this study, a chain-like PPy aerogel decorated with MOF-derived nanoporous Co/C (Co/C@PPy) has been successfully prepared by a self-assembled polymerization method. With a filler loading ratio of 10 wt %, the composite of Co/C@PPy could achieve a promising electromagnetic absorption performance both in intensity and bandwidth. An optimal reflection loss value of −44.76 dB is achieved, and the effective bandwidth (reflection loss lower than −10 dB) is as large as 6.56 GHz. Furthermore, a composite only loaded with 5 wt % Co/C@PPy also achieves an effective bandwidth of 5.20 GHz, which is even better than numerous reported electromagnetic absorption (EA) materials. The result reveals that the as-fabricated Co/C@PPy—with high absorption intensity, broad bandwidth, and light weight properties—can be utilized as a competitive absorber. Full article

(This article belongs to the Special Issue Carbon Based Functional Microwave Shields)

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7 pages, 1729 KiB

Open AccessLetter

A New Broadband and Strong Absorption Performance FeCO₃/RGO Microwave Absorption Nanocomposites

by Wei Huang, Shicheng Wei, Yujiang Wang, Bo Wang, Yi Liang, Yuwei Huang and Binshi Xu

Materials 2019, 12(13), 2206; https://doi.org/10.3390/ma12132206 - 09 Jul 2019

Cited by 19 | Viewed by 2737

Abstract

A novel composite of FeCO₃ nanoparticles, which are wrapped with reduced graphene oxide (RGO), is fabricated using a facile one-spot solvothermal method. The composite consists of a substrate of RGO and FeCO₃ nanoparticles that are embedded in the RGO layers. The [...] Read more.

A novel composite of FeCO₃ nanoparticles, which are wrapped with reduced graphene oxide (RGO), is fabricated using a facile one-spot solvothermal method. The composite consists of a substrate of RGO and FeCO₃ nanoparticles that are embedded in the RGO layers. The experimental results for the FeCO₃/RGO composite reveal a minimum refection loss (−44.5 dB) at 11.9 GHz when the thickness reaches 2.4 mm. The effective bandwidth is 7.9 GHz between 10.1 and 18 GHz when the refection loss was below −10 dB. Compared to GO and RGO, this type of composite shows better microwave absorption thanks to improved impedance matching. Overall, this thin and lightweight FeCO₃/RGO composite is a promising candidate for absorbers that require both strong and broad absorption. Full article

(This article belongs to the Special Issue Carbon Based Functional Microwave Shields)

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