Electromagnetic Wave Absorption Materials Research Articles

Regulating the Electronic Structure of MAX Phases Based on Rare Earth Element Sc to Enhance Electromagnetic Wave Absorption.

MAX phases are highly promising materials for electromagnetic (EM) wave absorption because of their specific combination of metal and ceramic properties, making them particularly suitable for harsh environments. However, their higher matching thickness and impedance mismatching can limit their ability to attenuate EM waves. To address this issue, researchers have focused on regulating the electronic structure of MAX phases through structural engineering. In this study, we successfully synthesized a ternary MAX phase known as Sc2GaC MAX with the rare earth element Sc incorporated into the M-site sublayer, resulting in exceptional conductivity and impressive stability at high temperatures. The Sc2GaC demonstrates a strong reflection loss (RL) of -47.7 dB (1.3 mm) and an effective absorption bandwidth (EAB) of 5.28 GHz. It also achieves effective absorption of EM wave energy across a wide frequency range, encompassing the X and Ku bands. This exceptional performance is observed within a thickness range of 1.3 to 2.1 mm, making it significantly superior to other Ga-MAX phases. Furthermore, Sc2GaC exhibited excellent absorption performance even at elevated temperatures. After undergoing oxidation at 800 °C, it achieves a minimum RL of -28.3 dB. Conversely, when treated at 1400 °C under an argon atmosphere, Sc2GaC demonstrates even higher performance, with a minimum RL of -46.1 dB. This study highlights the potential of structural engineering to modify the EM wave absorption performance of the MAX phase by controlling its intrinsic electronic structure.

Optimization of electromagnetic absorption properties based on graphene, carbon nanotubes, and Fe3O4 multidimensional composites

AbstractExcellent electromagnetic wave loss and impedance matching are typical characteristics of superior‐performance electromagnetic wave (EMW) absorption materials. Changing the component ratios and multidimensional combinations of various absorbing materials is one of the best methods to improve absorption performance. This work used a convenient physical mixing approach to combine three wave‐absorbing materials with various dimensions to successfully prepare Graphene/carbon nanotubes/Fe3O4 (G/C/Fe3O4)/paraffin composites. One‐dimensional (1D) tube carbon nanotubes (CNTs) pierced two‐dimensional (2D) sheet graphene to form a strong three‐dimensional (3D) conductive network, enhancing interfacial polarization without introducing zero‐dimensional (0D) magnetic Nano‐Fe3O4. Nevertheless, because of their significant dielectric characteristics, the graphene/carbon nanotube (G/C) paraffin composites displayed low impedance matching and electromagnetic wave absorption properties. At a mass ratio of 1:1, the G/C/paraffin composites achieved an ideal reflection loss (RL) of −11.99 db and an impedance matching value of 0.59. Adding Fe3O4 improved the impedance matching and electromagnetic wave loss performance and promoted the formation of a non‐homogeneous interface, improving interfacial polarization and reflection. The G/C/Fe3O4/paraffin composite, with a mass ratio of 1:1:6 and a filler ratio of 20%, achieved an optimum reflection loss of −37.2 dB and an effective absorption bandwidth of 4.16 GHz. This work optimized and improved the performance of EMW materials practically and rapidly, providing a research method for the widespread application of superior‐performance electromagnetic wave absorption materials.Highlights The EMW absorption materials with various architectures. 1D CNTs pierced 2D sheet graphene to form a strong 3D conductive network. Adding Fe3O4 promoted the formation of a non‐homogeneous interface. Electromagnetic synergies and different structural combinations It achieved excellent impedance matching and electromagnetic loss performance.

Hierarchically three-dimensional ZrO2/Fe3O4/C nanocomposites with Janus structure for high-efficiency electromagnetic wave absorption

Hierarchically three-dimensional (3D) materials present a pivotal challenge and opportunity in achieving effective microwave absorption with synergistic effects. In this work, α-Fe2O3@ZrO2 with core-shell structure were fabricated in-situ on aramid nanofibers by a solvothermal method. Following calcination, 3D ZrO2/Fe3O4/C nanocomposites with Janus structure have been successfully synthesized. By controlling the lattice match and mismatch in both processes, a core-shell structure of α-Fe2O3@ZrO2 and Janus structure of ZrO2/Fe3O4 have been well-define performed. The composite material ZrO2/Fe3O4/C-700 has a minimum reflection loss (RLmin) of −67.4 dB at a thickness of 2.0 mm. The effective absorption bandwidth (EAB) at a thickness of 2.4 mm is 6.0 GHz (11.0–17.0 GHz). This study provides a novel strategy for fabricating high-efficiency electromagnetic wave absorption materials with dual synergistic effects in nanosized scale.

IIIA-IIB multicomponent perovskite rare earth ferrites with promising electromagnetic wave absorption properties

Perovskite-type rare-earth ferrites (REFeO3) are promising materials for absorbing electromagnetic (EM) wave pollution. However, insufficient dielectric loss and poor impedance matching are key factors that limit the broader implementation of REFeO3. Herein, a series of multicomponent perovskite-type ferrites with strong EM wave absorption capabilities was prepared. Through the synergistic effect of chemical constitution regulation and entropy regulation, optimization of the dielectric loss and impedance matching is achieved by strengthening the structural defect mechanism, thus further adjusting the EM wave absorption performance. Compared with (LaGdSmNdBa)FeO3 (HE-1) and (LaGdPrSmNdBa)FeO3 (HE-2), (LaGdBa)FeO3 (ME-1) and (LaGdSmBa)FeO3 (ME-2) exhibit favorable performance, with optimal minimum reflection loss (RLmin) of −56.35 dB (at 11.12 GHz) and −63.25 dB (at 7.22 GHz) and effective absorption bandwidth (EAB) of 4.46 and 4.72 GHz, respectively. This multicomponent design provides a new strategy for the development of EM wave absorption materials.

MXene‐Based Ultrathin Electromagnetic Wave Absorber with Hydrophobicity, Anticorrosion, and Quantitively Classified Electrical Losses by Intercalation Growth Nucleation Engineering

AbstractMXene, a highly regarded material, has garnered significant attention within the electromagnetic wave (EMW) absorption field. However, the practical application of MXene is limited in harsh environments. Herein, a magic technique strategy of intercalation growth nucleation engineering is employed to prepare multifunctional MXene‐based EMW absorption materials. By regularly introducing different metal ions between the layers of MXene, an ultrathin absorber can be achieved by annealing after reacting in specific positions. The synthesized MCFC‐69‐8 shows hydrophobicity properties and exhibits a large charge‐transfer resistance of 18112 Ω cm2 with a low corrosion rate and corrosion rate, indicating a good anti‐corrosion property. Through applying a series of mathematical methods, MCFC‐69‐8 shows 25% relaxation polarization loss and 75% conduction loss, and its relaxation time is linked with the specific type of relaxation polarization loss, resulting in an effective absorption bandwidth (EAB) of 4.9 GHz with an ultra‐thin optimal matching thickness of 1.48 mm. Finally, an absorber is built using CST to attain an ultrabroad EAB covering 2–18 GHz. This engineering not only simplifies the intercalation process but also achieves a high‐performance and anti‐corrosion EMW absorber, providing a valuable perception for realizing thinner MXene‐based EMW absorbers in the future.

Lightweight broadband electromagnetic wave absorption achieved by a like-clustered CNTs spheres modified SiC nanowires

Developing lightweight, broadband, and highly absorptive electromagnetic (EM) wave absorption materials by effectively utilizing the agglomeration effect of one-dimensional nanowires is challenging. In this work, a SiCnws/CNTs aerogel with a like-clustered CNTs sphere-modified SiCnws structure was prepared via simple freeze-drying and heat treatment techniques, where the CNTs content was controlled to adjust the quantity and volume of the CNTs spheres. This allows for effective regulation of the impedance matching characteristics and dielectric loss capability. Specifically, the SiCnws/CNTs aerogel exhibited remarkable dissipation of EM waves through the enhancement of the interface and dipole polarization, achieved by significantly increasing the presence of multiple interfaces and defects. Moreover, the aerogel structure induces conduction loss and amplifies multiple reflections and scattering, facilitating efficient dissipation of EM wave energy across multiple levels. The minimum reflection loss (RLmin) of the SiCnws/CNTs aerogel (SN-3 sample) achieves −43.4 dB at 11.2 GHz with a matching thickness of 2.6 mm. Its effective absorption bandwidth (EAB) spans from the C band to the Ku band (7.4–18 GHz) at thicknesses ranging from 2.1 to 4.4 mm. Additionally, when the matching thickness is 3.4 mm, the broadened EAB extends up to 9.8 GHz (covering the whole X and Ku bands). Furthermore, CST simulations clearly demonstrate a remarkable suppression of the incident EM wave by the samples under real-world conditions, with a substantial reduction of 42.5 dBm2 in the RCS. Considering this, SiCnws/CNTs aerogel materials pave the way for new opportunities in lightweight, broadband, and high-absorption materials.

Sodium alginate derived SiC-carbon composite aerogel for effective microwave absorption

Biomass-derived carbon aerogels are expected to be ideal candidates for electromagnetic wave (EMW) absorption due to their extensive sources, cheap cost, low density and abundant porosity. Herein, using the natural polymer sodium alginate (SA) as the carbon-based precursor and SiC nano-whiskers (SiCw) as the reinforcing material, a series of three-dimensional (3D) SiCw@C composite aerogels doped with different metal ions (Fe, Ni, Al) were designed and studied for lightweight and effective EMW absorption. The emergence of metal ions and three-dimensional conductive carbon networks enriches the loss mechanism of the composites. The results show that the SiCw@C-Al exhibits a considerable minimum reflection loss (RLmin) value at 1.5 mm thickness (-28.7 dB) and a broad effective absorption bandwidth (EAB, RL < -10 dB) of 4.1 GHz. Meanwhile, SiCw@C-Fe has good wave absorption performance at a thickness of 2 mm, RLmin is −49.2 dB, and EAB is 3.6 GHz. By adjusting the matching thickness of the Al3+ and Fe3+ crosslinked composite aerogel from 1.5 mm to 3.5 mm, the integrated EAB can cover the Ku-band, X-band and even C-band. The SA derived 3D SiCw@C composite aerogels open a new path for the design of lightweight and effective EMW absorption materials used in multi-frequency.

Carbon microspheres/carbon sheets as efficient electromagnetic wave absorbers

To address the issue of weak absorption intensity and narrow frequency band in pure dielectric electromagnetic wave (EMW) absorbing materials, this study adopts a simple method to successfully prepare a pure dielectric EMW absorption material by modifying acrylonitrile–methylmethacrylate copolymer carbon microspheres (co-AN-MMA@CS) with capsaicin-like 3,5-dimethylphenol derivative (DMPD). The introduction of DMPD into the carbon microspheres increases the heteroatoms (N, O) in the carbon material, thus resulting in functional groups (-C-N, –NO, and C–O) that enable energy loss through dipole polarization. Additionally, the special morphology of carbon microspheres attached or embedded in carbon sheets derived from DMPD increases the inhomogeneous interfaces, thereby increasing the interface polarization relaxation and further attenuating EMWs. The resulting carbon material with the optimal structure (denoted as CNO-2) exhibits superior EMW absorption properties. At a thickness of 2.50 mm, the minimum reflection loss (RLmin) reaches −63.10 dB at 13.14 GHz, whereas the maximum effective absorption bandwidth (EABmax) reaches 6.81 GHz (8.95–15.76 GHz). CNO-2 has excellent EMW absorption capabilities due to the controllable complex dielectric constant and multiple attenuation mechanisms, including interfacial polarization, dipole polarization, and conduction loss. The CNO absorbers prepared in this study can be used as efficient microwave absorbers for electromagnetic protection applications.

Synthesis of Co@N-doped carbon with yolk–shell heterostructures for efficient electromagnetic wave absorption

Regulating the composition and microstructure of nanomaterials is a major challenge in the development of high-performance materials for electromagnetic wave (EMW) absorption. This paper introduces a new lightweight EMW-absorbing material Co@N/C with a yolk–shell structure and compositions of ferromagnetic metal and carbon materials. The minimum reflection loss (RLmin) of the as-designed Co@N/C nanospheres with a filler loading of 25 wt% reaches −67.68 dB and the effective absorption bandwidth of a 1.9 mm thickness is 5.3 GHz. The exceptional absorption performance of the EMW absorption is primarily achieved through the synergistic effect between the Co–carbonaceous material and the yolk–shell structure, which optimizes the impedance matching. The polarization loss, conductivity loss, magnetic loss, and multiple scattering mainly contribute to the excellent EMW-absorption ability of the materials. The proposed method for regulating the structure and morphology of Co@N/C can efficiently construct high-performance EMW absorbers.

Symmetric sandwich microcellular (SSM) structure design for multifunctional carbon nanotubes/polymethylmethacrylate composites foam with broadband electromagnetic wave absorption

The ingenious acquisition of lightweight, thin thickness and wide absorption bandwidth electromagnetic wave absorbing (EMWA) materials remains a significant challenge, the architecture design of the absorber is critical. In this study, symmetric sandwich microcellular (SSM) structures made of polymethylmethacrylate (PMMA) and carbon nanotubes (CNTs)/PMMA are developed, and their EMWA behavior is detailed investigated. The optimal effective absorbing bandwidth reaches 3.00 GHz and optimal specific reflection loss value achieves -48.53 dB·g/cm3 over the X-band at 2.5 mm for resulting composite foam with 6 wt.% of CNTs loading, showing a distinct improvement of EMWA performance comparing with normal single-layered sample. The dramatic improved performances mainly ascribe to the better impedance matching and multiple relaxation polarization behaviors derived from SSM structure. Such SSM structure effectively blocks heat conduction, resulting in a lower thermal conductivity (0.092 W/mK), which empowers the material to fulfill dual microwave-infrared stealth meanwhile, it is expected to be a EMWA absorber with the characteristics of “lightweight, multifunction and comprehensiveness”.

Enhancing electromagnetic wave absorption performance through construction of three-dimensional multilayered SiCw/Y3Si2C2/Ni0.5Zn0.5Fe2O4 composites

In this study, three-dimensional (3D) multilayer electromagnetic wave absorbing (EMWA) materials SiCw/Y3Si2C2/Ni0.5Zn0.5Fe2O4 were fabricated for the first time. A two-dimensional (2D) Y3Si2C2 coating was synthesized onto the one-dimensional (1D) SiCw surface by the molten salt method. Subsequently, one layer of zero-dimensional (0D) Ni0.5Zn0.5Fe2O4 nanoparticles was deposited onto the Y3Si2C2 coating surface via hydrothermal reaction. The microstructure and electromagnetic wave absorption mechanism of SiCw/Y3Si2C2/Ni0.5Zn0.5Fe2O4 were systematically investigated. The introduction of 2D Y3Si2C2 and 0D Ni0.5Zn0.5Fe2O4 enhanced impedance matching and provided abundant heterogeneous interfaces, thus leading to interface polarization loss. Owing to the promoted impedance matching and superb attenuation capacity, 3D multilayered SiCw/Y3Si2C2/Ni0.5Zn0.5Fe2O4 composites exhibit superior EMWA performance in comparison with origin SiCw. For the SiCw/Y3Si2C2/Ni0.5Zn0.5Fe2O4 composites, their minimum reflection loss (RLmin) can be achieved −43.95 dB and the effective absorption bandwidth (EAB) is 4.08 GHz when the thickness is 2.12 mm. This study could pave a reference for the investigation of multi-dimensional hybrid structure EMWA material.

Fabrication of Metal–Organic Framework‐Derived LaCo/C‐Decorated Ti3C2Tx Composites with High Electromagnetic Wave Absorption

Thin‐thickness and lightweight electromagnetic wave (EMW) absorption materials are critically needed for stealth technology in the military stealth field. The special structure of a material is important for improving its good EMW absorption. Herein, a series of porous metal–organic framework‐derived LaCo/C‐decorated Ti3C2Tx (LaCo/C/Ti3C2Tx) composites are prepared by carbonization at high temperatures. Impressively, the minimum reflection loss of LaCo/C/Ti3C2Tx–2 is −47.72 dB at 10.26 GHz (thickness 2.3 mm), and the optimal effective absorption bandwidth is 5.45 GHz (thickness 1.9 mm). The excellent EMW absorption properties are due to multiple electromagnetic loss mechanisms, such as polarization loss, magnetic loss, and multiple reflections and scattering. This work provides a new route for the application of Ti3C2Tx‐based derivatives.

Hetero-Interface Engineering on 9.0wt% CoOx-Doped CeO2 Nanorods as Electromagnetic Wave Absorber and Integrated into Multifunctional Aerogel.

Ceria (CeO2) becomes a promising candidate as electromagnetic wave absorbing materials (EWAMs) for their abundant natural source, rich oxygen vacancy, charge conversion, and electron transfer abilities. However, it remains challenging to regulate its nanoscale and atom-scale composition to optimize the absorbing performance and develop high-performance commercial devices. Herein, a facile method to large-scale synthesis CeO2@Co-x% (x = 5, 7, 9, 11, 13) series EWAMs with diverse amounts of decorated CoOx is presented. By modulating the ratio of doped CoOx, a rational hetero-interface is created in CeO2@Co-9% to enhance natural and exchange resonances, improving magnetic loss capability and optimizing impedance matching. Doped CoOx promotes the charge accumulation, interfacial polarization, and multiple scattering of the CeO2 for strengthening the EW absorption and attenuation, which display superb minimum reflective loss (RLmin) of -74.4dB with a wide effective absorbing bandwidth (EAB) of 5.26GHz. Furthermore, a dual crosslinking strategy is employed to fabricate CeO2@Co-9% into an aerogel device with integrated lightweight, heat insulation, compression resistance, and fame-retardant functions. This work presents an excellent example of large-scale fast synthesis of high-performance CeO2-based EWAMs and multiplication 3D devices.

Synergistic effect of nickel selenide‑carbon composites for efficient broadband electromagnetic wave absorption

Novel NiSe2-based composites loaded with carbon nanotubes (CNTs) and graphene (GNs), respectively, were successfully synthesized via a facile hydrothermal reaction, aiming to enhance the electromagnetic wave (EMW) absorption performance. Microstructure, morphology, dielectric properties and EMW absorption performance of as-prepared NiSe2/CNTs and NiSe2/GNs composites were explored. Results showed that both NiSe2/CNTs and NiSe2/GNs composites exhibited improvement in EMW absorption compared to pure NiSe2, especially NiSe2/GNs showed the best EMW absorption performance. NiSe2/GNs composites demonstrated an exceptional minimum reflection loss (RLmin) of −52.10 dB at a thin thickness of merely 1.71 mm, accompanied by a wide effective absorption bandwidth (EAB) of 4.1 GHz. However, the EMW absorbing performance of NiSe2/CNTs composites was slightly lower than that of NiSe2/GNs composites, showing an RLmin of −45.10 dB and an EAB of 3.76 GHz at a thin thickness of 1.60 mm. Such significantly enhanced absorption capability of NiSe2/GNs composites can be attributed to the synergistic interplay of desirable impedance matching and efficient attenuation ability. These findings highlight the potential of NiSe2-based composites loading with carbon conductive fillers as highly promising contenders for high-performance EMW absorption materials.

Construction of three-dimensional porous network Fe-rGO aerogels with monocrystal magnetic Fe3O4@C core-shell structure nanospheres for enhanced microwave absorption

Single dielectric loss material has defects such as strong dielectric properties and impedance mismatch. Hence, developing electromagnetic wave (EMW) absorption materials with both outstanding EMW absorption and favourable impedance matching performances is still a great challenge. A large number of literature have reported that combining dielectric materials with magnetic materials to enhance microwave absorption. However, there is little literature on the effect of crystal structure on the absorbing properties of materials. Owing to the virtues of light weight, low density and thin thickness of aerogel, which has been widely utilized in EMW absorption materials. Herein, Fe-based metal organic framework-reduced graphene oxide (Fe-rGO) aerogel was synthesized via simple hydrothermal method and freeze-drying. Besides, Polyvinyl Pyrrolidone (PVP) was used as a surfactant to endow Fe3O4 nanospheres with uniform size and smooth morphology. Moreover, Fe3O4 nanospheres with different crystal phase (monocrystal and polycrystal) structure were obtained under different carbonization temperatures (600 and 800 °C). Through comparison, the monocrystal Fe3O4 nanospheres show better microwave absorption and impedance matching performance than that of polycrystal Fe3O4 nanospheres. In addition, the electromagnetic parameters can be adjusted by regulating the mass ratio of Fe-based metal organic framework (Fe-MOF) to GO. As a consequence, the prepared 600Fe-rGO 2:1 aerogel achieves the minimum reflection loss (RLmin) of −64.89 dB and a broad effective absorption bandwidth (EAB) of 6.96 GHz with a low filling content of 5 wt%, showing excellent EMW absorption and impedance matching property. In short, the structural design of single crystal magnetic Fe3O4 nanospheres provides inspiration and guidance for future research of enhanced microwave absorption materials.

Thin and ultra-broadband electromagnetic absorption carbonyl iron-based metamaterial via multiscale synergic dielectric-magnetic design

Thin and ultra-broadband electromagnetic wave (EMW) absorption material is essential in the fields of electromagnetic compatibility and radiation protection. Unfortunately, conventional materials are difficult to achieve low frequency EMW absorption such as 2–4 GHz at a limited thickness. Herein, a multiscale design strategy is presented to overcome this shortcoming. Carbonyl iron particle was used as the starting material. Firstly, microstructure modification from spherical morphology (SCIP) to flake one (FCIP) via a ball milling process was used to improve CIP's electromagnetic properties. Afterthat, macroscopic electromagnetic metastructure with the FCIP/polyurethane (PU) composite units was designed and its geometrical configuration was optimized. Through the multiscale design, an effective absorption in 2∼40 GHz was achieved at a thickness of merely 5 mm, surpassing most of the reported metamaterials. The broadband absorption mechanism was deciphered by CST simulation, which includes the synergic low-frequency absorption contributed by the FCIP/PU composite with delicate dielectric/magnetic synergistic property and the optimized impedance matching in broadband frequency caused by the well-designed metastructure. Our study provides valuable insights for the development of thin and ultra-broadband-absorbing material.

Regulating the electromagnetic balance of materials by electron transfer for enhanced electromagnetic wave absorption

The fact that single dielectric loss materials have disadvantages of excessive conductivities and impedance mismatches has given rise to a large effort to develop effective strategies to fabricate electromagnetic wave (EMW) absorbing materials comprised of components that bring about a balance between dielectric loss and magnetic loss. Moreover, little is known about the essential features that regulate EMW absorption propensities. This study focused on the development of a new EMW absorbing material and gaining information about factors that govern EMW absorption abilities. The materials at the center of the effort are light weight and porous cobalt sulfonated phthalocyanine-reduced graphene oxide (CoSPc-rGO) aerogels that were synthesized by using a simple hydrothermal method followed by freeze-drying. The properties of these materials that contribute to the electromagnetic balance between dielectric and magnetic loss were elucidated by first formulating a reasonable hypothesis about how the relative orientation of the components in CoSPc-rGO govern p-conjugation and electron transfer from rGO to CoSPc, which is proposed to be a key factor contributing to the regulation of the electromagnetic balance. Polarization relaxation process of materials was analyzed in detail using a variety of approaches including theoretical calculation, spectroscopic measurements, and experimental and simulation studies. The fabricated CoSPc-rGO aerogels that contain an ultra-low content of 4 % were found to exhibit an extraordinary microwave absorption performance associated with a strong reflection loss of -53.23 dB and a broad effective absorption bandwidth of 8.04 GHz. The results of this study should provide an effective guide for new designs of composite materials for EMW absorption.

Fabrication of hollow Ni/NiO/C/MnO2@polypyrrole core-shell structures for high-performance electromagnetic wave absorption

In response to the increasingly serious problem of electromagnetic wave pollution, there is a growing demand for materials capable of absorbing electromagnetic waves. A crucial strategy involves optimizing the microstructure and composition of these materials. In this study, the Ni/NiO/C/MnO2@PPy (NCMP) composites are successfully fabricated through the combination of hydrothermal method, high-temperature calcination process, chemical method and in situ polymerization. Due to the strong synergistic effect of the dielectric and magnetic components, and good impedance match, the NCMP-40 exhibits excellent electromagnetic wave absorption properties, with an optimal reflection loss (RLmin) of −56.23 dB at a thickness of 3.87 mm, and a high effective absorption bandwidth (EAB) of 6.86 GHz (10.68–17.54 GHz) at a thickness of 1.97 mm covering the entire Ku-band part of the X-band. Moreover, the radar cross section (RCS) attenuation is obtained through a simulation procedure. Compared to the sole perfect electrically conductive (PEC) layer, the PEC layer coated with NCMP-40 achieves an RCS value consistently below −10 dB m2 in the range of −60° < θ < 60°, and an RCS value is −22.0 dB m2 at θ = 0°. The prepared NCMP-40 presented herein shows excellent electromagnetic wave absorption performances. And this study provides a new method for the structural design of electromagnetic wave absorption materials.

Construction of the N, S co-doped C/FeS2 materials for low thickness and high-efficiency microwave absorption

Research into electromagnetic wave-absorbing materials is essential to tackle the growing impact of electromagnetic wave pollution on human health and social advancement. Therefore, a method for synthesizing N,S co-doped C/FeS2 porous carbon composite absorbers (N,S@APCs) with low thickness, low filler content, and high performance is reported. The porous carbon structures were prepared by a high-temperature-hydrothermal two-step method using directly liquefied coal pitch as the carbon source. The successful doping of diatomic N and S at optimal concentrations enhances their impedance matching capacity. At the same time, forming FeS2 through the reaction between S and Fe3+ in the raw material efficiently improves the dielectric loss effect and enhances interfacial and dipole polarization effects. These factors together contribute to the strong absorption performance and low matching thickness of the fabricated N, S@APCs. At a thickness of 1.5 mm, 10 wt% of absorber filling resulted in a strong absorption performance with RLmin=-51.05 dB. Meanwhile, at a thickness of 1.7 mm, an effective absorption bandwidth of 4.76 GHz was achieved. This research offers a novel viewpoint on investigating porous carbon absorbers at low thicknesses. It serves as a reference for later investigations into polyatomic co-doped porous carbon absorbers.

Interface Modulation of CoNi Alloy Decorated with Few-Layer Reduced Graphene Oxide for High-Efficiency Microwave Absorption

Metal-organic frameworks (MOFs)-derived microwave absorbers with tunable components and microstructures show great potential in microwave absorption. Herein, we report a facile thermal reduction approach for synthesizing CoNi alloy/reduced graphene oxide (CoNi/rGO) composites from bimetallic CoNi-MOFs. By tuning the ratio of graphene oxide (GO) in the precursors, the resulting CoNi/rGO-2 composite demonstrates optimal microwave absorption performance with a minimum reflection loss (RLmin) of −66.2 dB at 7.6 GHz in the C band. Moreover, the CoNi/rGO-2 with 50 wt% filler loading achieves a maximum effective absorption bandwidth (EAB) of 6.8 GHz (10.6–17.4 GHz) at a thickness of 2.5 mm, almost spanning the entire Ku band and a portion of the X band. The outstanding performance of CoNi/rGO-2 is ascribed to the high magnetic loss from the CoNi alloy and the incorporation of rGO, which induces interfacial polarization to enhance the dielectric loss and improve the impedance matching of composite. These favorable findings highlight the considerable potential and superiority of the CoNi/rGO-2 composite as an electromagnetic wave absorption material. This work sets forth a viable strategy for designing high-efficiency alloy/rGO absorbers.