High-performance Microwave Absorption Research Articles

Independently regulating the electric and magnetic properties of flaky FeSiAl powder based composites for high-performance microwave absorber

Independently regulating the electric and magnetic properties of flaky FeSiAl powder based composites for high-performance microwave absorber

Laser irradiation induced CoNi@carbon composites as high-performance microwave absorbers

Metal-organic-frameworks (MOFs) derivatives, known for their lightweight and high-performance properties, are highly sought after as microwave absorbers. However, most reported MOFs derived absorbers are pyrolyzed in tube furnaces, which is time-consuming and difficult to finely tune the microstructure due to the low heating-quenching process. In this study, laser irradiation was used as a heat source to pyrolyze CoNi ZIF. By controlling the irradiation power (30 mW, 50 mW), Co/C composites were obtained in just a few seconds, with Co nanocrystals ranging from 10 to 50 nm. The presence of Ni could modulate the microstructure and electric-magnetic parameters of Co/C composites. The effects of Ni content and irradiation power on the electromagnetic absorption properties of Co/C were analyzed. Considering the enhanced dipolar/interfacial polarization, matched impedance, and strong magnetic coupling network, a minimum reflection loss of −45 dB with the effective absorption bandwidth of 6 GHz can be achieved by Co/C at the thickness of 2 mm. Additionally, the laser irradiation was performed in air atmosphere, providing an effective way for industrial production of high-efficiency and broadband wave-absorbing materials.

Polypyrrole modified MIL-101-Fe-derived Fe/Fe3O4@C composites for high-performance microwave absorber

Carbon-based microwave absorbing composites with magnetic-dielectric properties and multiple loss mechanism are considered to be an effective choice for solving electromagnetic pollution. In this paper, the PPy/Fe/Fe3O4@C composite was synthesized from MIL-101-Fe derivatives and subsequently coated polypyrrole (PPy) by combining hydrothermal, high-temperature pyrolysis and oxidative polymerization. The effects of pyrolysis temperature and PPy loading on components, microstructures and electromagnetic parameters were investigated. The results showed that the PPy/Fe/Fe3O4@C composite consisted of two-dimensional carbon flakes modified by magnetic particles and laminated conductive polymers. When the PPy loading is moderate, the composite reaches a minimum reflection loss (RLmin) of −61.38 dB at a 3.1 mm thickness and effective absorption bandwidth (EAB) of 5.81 GHz at the thickness of 2.2 mm. After pyrolysis, the unique three-dimensional structure of carbon sheet stacking, as well as the heterogeneous interface and conductive networks generated by the modification of magnetic particles Fe and Fe3O4 and conductive PPy, are beneficial to improve the dielectric and magnetic losses to optimize the impedance matching. These conductive polymer-modified magnetic-dielectric composites have potential for development and application in microwave absorption.

Enhanced microwave absorption in graphene-based composites: A study on the synergistic effect of ferrite integration and electromagnetic coupling

Graphene integration with magnetic particles demonstrates a synergistic enhancement in dielectric and magnetic loss properties, facilitating the realization of absorbing materials that are strong, broadband, lightweight, and thin. This study achieved uniform dispersion of ferrite on the surface of in-situ synthesized high-conductivity graphene, utilizing an economical liquid glucose precursor and cobalt ferrite sintering process. An interface consisting of iron carbide and cobalt-iron alloy forms between the graphene and cobalt ferrite, significantly enhancing the samples’ microwave absorption performance. Furthermore, the magnetic loss is notably enhanced through the coupling of soft and hard magnetic materials. Consequently, a composite material consisting of Graphene/Fe3C/CoFe2/CoFe2O4, with a minimal thickness of 1.85 mm, demonstrated an impressive minimum reflection loss of −48.8 dB and a notable absorption bandwidth extending over 4.04 GHz. This research will offer an effective approach for developing high-performance microwave absorption materials using graphene-based composite magnetic materials.

Facile and scalable preparation of Ni/NiO/SiO2@porous carbon network with strong and wide bandwidth microwave absorption

Researchers are exploring high-performance electromagnetic wave absorbing materials to mitigate electromagnetic interference, focusing on minimizing surface reflection and enhancing attenuation capability. However, one single component and structure struggle to meet the aforementioned requirements. Here, a Ni/NiO/SiO2@porous carbon network (Ni/NiO/SiO2@PCN) with porous structures is synthesized via a pyrolysis process. The magnetic Ni/NiO and dielectric SiO2 nanoparticles are uniformly dispersed within the PCN matrix. The absorption capability of the material can be controlled by adjusting the SiO2 content in Ni/NiO/SiO2@PCN. Particularly, when the SiO2 loading is 0.5 wt%, the resulting Ni/NiO/SiO2@PCN-0.05 demonstrates outstanding EMW absorption properties, exhibiting strong broadband absorption attributed to its 3D porous architectures, the hybrid composition of Ni/C, NiO/C, and SiO2/C, and good impedance matching. At a filler loading of 20 wt%, the Ni/NiO/SiO2@PCN-0.05 achieves remarkable EMW absorption performance, with a minimal reflection loss reaching −71.42 dB at 2.6 mm and 11.18 GHz, and an effective absorption band extending over 6.24 GHz within the frequency range of 11.52 to 18.0 GHz at a thickness of 2.25 mm, effectively covering the entire Ku band. This study introduces a cost-effective and efficient fabrication approach for producing high-performance microwave absorbers, thereby offering promising prospects for applications in the field of microwave telecommunications.

Temperature regulated Fe3Si@SiC@carbon core-shell structure with high-performance microwave absorption

Developing high-performance microwave absorbing materials (MAMs) to address the electromagnetic wave pollution is still a huge challenge. Multi-interface core-shell structure with magnetic and dielectric loss components have been attracting extensive attention as MAMs for the enhanced interfacial polarization and impedance matching. In this work, magnetic loss core and dielectric loss bi-shell structure Fe3Si@SiC@C (FSC) composite was synthesized through hydrothermal, self-polymerizing coating and high temperature thermolysis. The thermal treatment temperature has a great effect on the morphology structure and electromagnetic properties of FSC. The results indicated that the FSC exhibited an effective absorption bandwidth (EAB) of 4.24 GHz at a thickness of 1.4 mm, and an EAB of 12.4 GHz with the absorber thickness varied from 1 mm to 3 mm. Furthermore, the microwave attenuation mechanism of the FSC composite were investigated in detail. The integration of magnetic core with multiple dielectric shells provides a design deliberation and reference for further high-performance MAMs fabrication.

High-performance NiTi-C nanofibers microwave absorbent prepared by electrospinning

Carbon nanofibers embedded with magnetic NiTi nanoparticles have been synthesized using electro-spinning technique, followed by one-step carbonization. By using NiTi-CFs as filler with 7.5%content, the sample achieved a very high effective absorption bandwidth(EAB) of 6.1 GHz (11.4–17.5 GHz)at the thickness of 1.97 mm. The effective absorption coverage of different microwave bands can be achieved by adjusting the thickness of the material. Adjusting the thickness of the material at 1.35 mm to 5 mm can achieve coverage from 3.7 GHz to 18 GHz. The superior properties might be due to the great impedance matching, rich dielectric loss and magnetic loss basis, excellent 1/4 λ space structure. This work presents a facile and promising method to produce high performance microwave absorption materials with thin thickness, light weight and strong absorption, as well as a detailed study of its wave absorbing basis.

Composites of Zn-Co spinel ferrites and PANI: Structural, magnetic, microwave absorption characterization in 18–40 GHz

The present research work deals with the fabrication of composites containing spinel ferrites and polyaniline as high-performance microwave absorbers. The composites were prepared by the inter-mixing of Zn-Co spinel ferrites and PANI polymer in a 4:1 M ratio using the mechanical blending technique. The sol–gel citrate route was employed to synthesize Zn-Co spinel ferrites, while the oxidative polymerization method was used to synthesize PANI. The structural, morphological, magnetic, and microwave absorption properties of the composite samples were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM), and vector network analyzer (VNA), respectively. The X-ray diffraction patterns indicated the crystalline nature of spinel ferrites and the amorphous nature of PANI. The magnetic properties revealed that saturation magnetization (Ms) increased significantly with the addition of spinel ferrites into PANI owing to its magnetic nature. The microwave absorption results showed that the minimum reflection loss (RL) reached up to −26.63 dB at 20.72 GHz with the effective bandwidth of 5.95 GHz in the K-band and −39.16 dB at 35.68 GHz with the effective bandwidth of 8.1 GHz in the Ka-band for composition NZP. This study indicated that the prepared SF/PANI composites can be proposed as a promising absorbent in the K-band and Ka-band.

Lightweight titanium dioxide/carbon nanotube composites prepared by atomic layer deposition for broad-band microwave absorption

The microwave absorbing material with appropriate impedance matching and excellent attenuation ability can be applied to resist electromagnetic radiation. In this work, carbon nanotubes were modified by titanium dioxide via the atomic layer deposition method, to prepare lightweight composites with high microwave absorption performance. The impedance matching and attenuation ability of titanium dioxide/carbon nanotube (TiO2/CNT) composites could be precisely controlled by adjusting the number of titanium dioxide deposition cycles. The relationship between the microstructure and microwave absorption performance of the composite was analyzed in detail. When the number of TiO2 deposition cycles was 100, the composite displayed outstanding microwave absorption performance, due to appropriate impedance matching and strong attenuation ability. The maximum effective absorption bandwidth of the composite reached 5.19 GHz (1.6 mm), which almost covered the Ku band. The microwave attenuation mechanism of the composite has also been investigated. This work provided a new idea for fabricating lightweight microwave absorption materials.

Multidimensional and hierarchical design of biomass-derived carbon nanofiber networks for efficient microwave absorption

Carbon materials have gained significant attention for their potential as highly efficient microwave absorbers. However, it remains a challenge to attain a perfect integration of thin thickness, wide frequency bandwidth, lightweight and strong absorption through structural design of carbon materials. Herein, we design multidimensional and hierarchical carbon nanofiber networks consisting of core-shell carbon nanofibers wrapped by hollow carbon nanoparticles, named CPDA@RCNFs. CPDA@RCNFs which are derived from cellulose and polydopamine (PDA) were prepared by electrostatic spinning, deacetylation, self-polymerization, and carbonization, successively. Thanks to the cooperation of three-dimensional conductive networks, core-shell/hollow/porous structures, as well as doped nitrogen and oxygen heteroatoms, CPDA@RCNFs exhibit excellent comprehensive microwave absorption performance. Specifically, an ultra-strong reflection loss value of −63.31 dB and a wide frequency bandwidth of 5.60 GHz (12.32–17.92 GHz) are achieved at a very thin thickness of 1.8 mm with an ultra-low filler loading of 5 wt%. This work provides a new insight into the structural design of advanced high-performance microwave absorption carbon materials.

Highly enhanced microwave absorption of carbon nanotube/nickel/styrene-butadiene-styrene composite with segregated structure

High-performance microwave absorption (MA) polymer composites are highly required in electromagnetic protection. Although the desirable MA performance of many MA absorbers is obtained, its loading of obtaining optimal MA performance still is too high, which is not beneficial to the mechanical properties of polymer composites. In this work, based on the concept of segregated structure, the selective distribution of carbon nanotube/nickel (CNT/Ni) particles was successfully achieved in the styrene-butadiene-styrene (SBS) matrix via hot-compression molding. The CNT/Ni/SBS composites with segregated structure present an excellent MA performance when the filler content is only 5 wt%, including the minimum reflection loss (RLmin) of −42.7 dB and effective absorption bandwidth (EAB) of 6.6 GHz, which shows 27.3 % and 8.2 % increases in comparison to the optimal MA performance of the composites with randomly dispersed structure (10 wt%). In addition, the elongation at break and tensile strength of CNT/Ni/SBS composites can reach 1222 % and 14.3 MPa, respectively, showing great application potential as flexible MA materials. The efficient method provides a promising way to improve the function efficiency of MA absorbers and develop high-performance MA polymer composites with low filler loading in the future.

Dielectric-magnetic synergistic construction of 2D FeCo/Co8FeS8/C composites for efficient electromagnetic wave capture

Nowadays, the issue of electromagnetic pollution has become increasingly prominent, underscoring the critical importance of developing high-performance microwave absorbers. This study put forwards the synthesis process of two-dimensional (2D) FeCo/Co8FeS8/C carbon nanosheets, wherein CoSO4 and FeCl3 serve as inorganic salt templates, and dopamine functions as the carbon source. FeCo alloy nanoparticles and Co8FeS8 nanoparticles are loaded on the surface of the carbon layer. 2D structure forms the conductive network, which proves advantages in establishing efficient electronic channels and minimizing conduction losses. The carbon component increases the dielectric constant of the composite and improves its impedance matching, and the FeCo alloy provides a certain ML. The synergistic effect between these components significantly contributes to the exceptional microwave absorption performance of the composites. Accordingly, the minimum reflection loss (RLmin) of FeCo/Co8FeS8/C composite reaches −47.4 dB, its effective absorption bandwidth (EAB) reaches 5.3 GHz. In particular, CST confirms that radar cross-section reduction value of FeCo/Co8FeS8/C composite can reach 20.2 dB m2 in the range of −90° < phi< 90°, indicating a high microwave attenuation ability. The study introduces a novel strategy for advancing the development of two-dimensional carbon-based absorption materials.

A novel high-temperature FeSiAl/CaO–B2O3–SiO2 microwave absorption coating prepared via atmospheric plasma spraying

In this paper, CaO–B2O3–SiO2 (CBS) is utilized as matrix material of microwave coating for the first time to achieve high-performance microwave absorption under high-temperature. A series of FeSiAl (FSA)/CBS composite coatings were prepared via atmospheric plasma spraying. The impact of spraying power on the microstructure, electromagnetic properties, and high-temperature stability of as-sprayed coatings were studied. The experimental results reveal that CBS could effectively suppress the formation of the lamellar structure of FSA as the low initial melting temperature, also form unexpected Fe2SiO4 structure with FSA during the spraying process. The increase in complex permittivity of the coating is primarily attributed to enhanced coating density and the development of Fe-rich regions within the CBS matrix. Furthermore, the dense coating prevents the oxidation of FSA and exhibits high-temperature stability. Our coating of 1 mm thickness has a reflection loss below −5 dB with frequency range of 7–14.8 GHz at 500 °C.

CoNi/MXene@CoNi/MXene microsphere/silicone rubber multilayered composites for ultra-broadband microwave absorption

2D transition metal carbide/nitride (MXene) nanomaterials have prospective applications in high-performance microwave absorption (MA). However, the excessively high permittivity, absence of magnetic loss, and susceptible oxidizability of MXene severely hinder the enhancement of its MA properties. Here, we used a facile organic solution–phase thermal decomposition method to prepare dielectric–magnetic MXene@CoNi nanocomposites with heterojunctions, which can effectively prevent the oxidation of MXene. Subsequently, the MXene@CoNi nanocomposites were integrated with magnetic CoNi alloys, MXene microspheres (MXene MPs), and a silicon rubber (SR) matrix to construct multilayered CoNi/MXene@CoNi/MXene MPs/SR composites by casting and curing. Benefiting from the multilayered structure and complementary effects of the dielectric and magnetic components, the multilayered CoNi/MXene@CoNi/MXene MPs/SR composites composed of matching, absorbing, and reflective layers showed a remarkable minimum reflection loss of −53.3 dB and an ultra-broad effective absorption bandwidth up to 11.12 GHz at a thickness of 2.96 mm. These results demonstrated the developed multilayered composites are promising candidates for high-performance MA. Our study provides new insights into the development of ultra-broadband MXene-based absorbent materials.

Efficient Synthesis of Fe3O4/PPy Double-Carbonized Core-Shell-like Composites for Broadband Electromagnetic Wave Absorption.

Ever-increasing electromagnetic pollution largely affects human health, sensitive electronic equipment, and even military security, but current strategies used for developing functional attenuation materials cannot be achieved in a facile and cost-effective way. Here, a unique core-shell-like composite was successfully synthesized by a simple chemical approach and a rapid microwave-assisted carbonization process. The obtained composites show exceptional electromagnetic wave absorption (EMWA) properties, including a wide effective absorption band (EAB) of 4.64 GHz and a minimum reflection loss (RLmin) of -26 dB at 1.6 mm. The excellent performance can be attributed to the synergistic effects of conductive loss, dielectric loss, magnetic loss, and multiple reflection loss within the graphene-based core-shell-like composite. This work demonstrates a convenient, rapid, eco-friendly, and cost-effective method for synthesizing high-performance microwave absorption materials (MAMs).

Large-Scale Fabrication of Customized, Tunable, Ultrathin, and Flexible Metamaterial Absorbers Based on Laser-induced Graphene

Developing various 3D graphene microwave absorbers is a hotspot strategy to address the issue of continuous electromagnetic pollution, but remains great challenges in realizing high-performance microwave absorption capability at thin thickness. Herein, a series of flexible metamaterial absorbers (MAs) composed of periodical laser-induced graphene (LIG) surface, dielectric substrate and metallic ground fabric from top to bottom are fabricated. The LIG meta-surface is customized by means of regulating parameters including laser power density (LPD), laser engraving rate (LER) and input patterns to well balance impedance matching and electromagnetic loss. LIG MAs exhibit minimum reflection loss (RL) of −39.7 dB (with effective absorption bandwidth (EAB) of 5.5 GHz) and maximum EBA of 12.1 GHz (with RL of −18.9 dB) at thickness less than 1.1 mm, and the simulated and experimental results are highly consistent. In addition, radar cross section (RCS) simulation of LIG MA with multi-angles endows its potential for prospective applications in in-orbit satellites electromagnetic protection.

EVA copolymer loaded with PAni/CNT/GNP hybrids: A flexible and lightweight material with high microwave absorption

AbstractMicrowave‐absorbing materials are widely used for electromagnetic interference shielding and stealth technology. However, most existing materials are heavy, rigid, and expensive, limiting their practical applications. Therefore, there is a need to develop new materials that are flexible, lightweight, and cost effective. This study aimed to synthesize and characterize a novel ternary composite material based on polyaniline (PAni), carbon nanotubes (CNTs), and graphene nanoplatelets (GNPs) in an ethylene‐vinyl acetate (EVA) copolymer matrix. PAni‐based ternary composites were prepared by in situ polymerization of aniline in toluene dispersion of CNT/GNP hybrids and EVA. The microwave absorption properties were evaluated using a vector network analyzer in the frequency range of 8.2–18 GHz. The presence of as little as 0.8 wt% of CNT/GNP hybrid with appropriate mass ratio increased the conductivity by more than four orders of magnitude compared to the EVA@PAni blend. The minimum reflection loss corresponded to −40.55 dB at 16.31 GHz for the system containing CNT/GNP = 0.3:0.7, whereas those with CNT/GNP = 0.0:1.0 and 0.7:0.3 presented the widest effective absorption bandwidths (RL &lt; −10 dB), covering almost the entire Ku‐band. Due to the excellent flexibility, low weight, and high microwave absorption performance, these composites are potential candidates for microwave absorption applications.

1-bit encoding optimized transparent ultra-wideband microwave absorber

This work is dedicated to designing high-performance microwave absorbers that meet the pressing needs for advanced stealth materials, which are controllable, ultra-thin, transparent, and ultra-wideband. Consequently, we propose two transparent ultra-wideband microwave absorbers based on 1-bit encoded optimization in this study. We analyze the absorption mechanisms of these two coded absorbers, emphasizing their complementary bandwidth properties. Among them, the Chinese character "Mi" structure encoded absorber achieves an absorption rate exceeding 90 % within the frequency range of 15.7 to 49.4 GHz, with a fractional bandwidth being only 0.07 times its upper cutoff wavelength. This absorber demonstrates remarkable stability under varying incident angles and maintains polarization insensitivity. It sustains an approximate 80 % absorption rate as the incident angle varies from 0°–60°. Finally, fabricated test samples exhibit absorption performance consistent with simulations across the 10–40 GHz frequency range, thereby validating the effectiveness of the proposed design.

Superior microwave absorption properties of carbon-coated FeSiCr micro flakes

Carbon-coated ferromagnetic alloys can protect from microwave radiation due to their tunable electromagnetic parameters and multiple loss mechanisms. We prepared carbon-coated flaky FeSiCr (FFSC@C) powders by the encapsulation and thermal decomposition of epoxy resin. The crystallization degree and thickness of carbon coating were tuned to optimize the microwave absorption of FFSC@C. The phase composition, morphology, magnetic properties, electromagnetic parameters, and microwave absorption properties of FFSC@C were comprehensively investigated. The oriented flaky FeSiCr possessed strong attenuation capacity, the amorphous carbon improved the impedance matching of flaky FeSiCr. The sample carbonized at 500 ℃, with the epoxy addition amount of 45 wt% exhibited a broad effective absorption bandwidth of 5.60 GHz at a thickness of 2.4 mm. Compared with other absorbents, the FFSC@C exhibited stronger absorption capacity at a lower thickness and filler loading in the X-band (8−12 GHz). This work demonstrated the facile fabrication of a high-performance carbon-coated ferromagnetic microwave absorber.

Compositional and Hollow Engineering of Silicon Carbide/Carbon Microspheres as High-Performance Microwave Absorbing Materials with Good Environmental Tolerance

HighlightsHollow SiC/C microspheres with controllable composition have been successfully synthesized by simultaneously implementing compositional and structural engineering.The optimum dielectric properties (i.e., conductivity loss and polarization loss) and impedance matching characteristics can achieve outstanding microwave absorption performance.Broadband wave absorption (5.1 GHz with only 1.8 mm thickness), high efficiency loss (− 60.8 dB at 10.4 GHz) combined with good environmental tolerance, demonstrate their bright prospects in practice.