Broadband Electromagnetic Wave Absorption Research Articles

Preparation of nitrogen-doped reduced graphene oxide/zinc ferrite@nitrogen-doped carbon composite for broadband and highly efficient electromagnetic wave absorption

Traditionally reduced graphene oxide (RGO)-based electromagnetic wave (EMW) absorbing materials have poor absorption effectiveness due to impedance mismatch caused by skin effect. The introduction of structural defects and the design of heterogeneous interfaces play a crucial role in enhancing the polarization effect of EMW absorbers. In this study, nitrogen-doped reduced graphene oxide/zinc ferrite@nitrogen-doped carbon (NRGO/ZnFe2O4@NC) ternary composite with rich heterogeneous interfaces is constructed by combining solvothermal reaction, in-situ polymerization, annealing treatment with subsequent hydrothermal reaction. The research results have shown that the obtained NRGO/ZnFe2O4@NC ternary composite exhibits a unique core-shell structure and excellent EMW absorption performance. At a thickness of 2.61 mm, the maximum effective absorption bandwidth can reach 7.2 GHz, spanning the entire Ku-band and a portion of the X-band, and the minimum reflection loss is –61.1 dB, which is superior to most reported RGO-based EMW absorbers. The excellent EMW absorbing ability is mainly ascribed to the optimized impedance matching and the enhanced polarization loss caused by the abundant heterogeneous interfaces and structural defects derived from heteroatomic nitrogen doping. Furthermore, the radar cross section in the far field is simulated by a computer simulation technique. This study provides a novel way to prepare core-shell magnetic carbon composites as highly efficient and broadband EMW absorbers.

MOFs-Derived Strategy and Ternary Alloys Regulation in Flower-Like Magnetic-Carbon Microspheres with Broadband Electromagnetic Wave Absorption

HighlightsMetal–organic frameworks-derived CoNiM@C (M = Cu, Zn, Fe, Mn) microspheres were successfully fabricated with custom-built magnetic alloy-carbon heterogeneous interfaces.Flower-like CoNiMn@C microspheres achieve broadband electromagnetic wave absorption with effective absorption bandwidth of 5.8 GHz at only 2.0 mm thickness.Visual interface charge distribution and hierarchical magnetic coupling were observed to elucidate the electromagnetic energy absorption mechanism.

Ultralight Hierarchical Fe3O4/MoS2/rGO/Ti3C2Tx MXene Composite Aerogels for High-Efficiency Electromagnetic Wave Absorption.

Aerogel-based composites, renowned for their three-dimensional (3D) network architecture, are gaining increasing attention as lightweight electromagnetic (EM) wave absorbers. However, attaining high reflection loss, broad effective absorption bandwidth (EAB), and ultrathin thickness concurrently presents a formidable challenge, owing to the stringent demands for precise structural regulation and incorporation of magnetic/dielectric multicomponents with synergistic loss mechanisms within the 3D networks. In this study, we successfully synthesized a 3D hierarchical porous Fe3O4/MoS2/rGO/Ti3C2Tx MXene (FMGM) composite aerogel via directional freezing and subsequent heat treatment processes. Owing to their ingenious structure and multicomponent design, the FMGM aerogels, featured with abundant heterogeneous interface structure and magnetic/dielectric synergism, show exceptional impedance matching characteristics and diverse EM wave absorption mechanisms. After optimization, the prepared ultralight (6.4 mg cm-3) FMGM-2 aerogel exhibits outstanding EM wave absorption performance, achieving a minimal reflection loss of -66.92 dB at a thickness of 3.61 mm and an EAB of 6.08 GHz corresponding to the thickness of 2.3 mm, outperforming most of the previously reported aerogel-based absorbing materials. This research presents an effective strategy for fabricating lightweight, ultrathin, highly efficient, and broad band EM wave absorption materials.

Carbon nanofiber aerogel microspheres with heterogeneous skin-core structure for broadband electromagnetic wave absorption

The advancement in the miniaturization of carbon aerogels into micro-sized spheres represents a significant development in the creation of ultralight, broadband microwave absorbers. Notwithstanding this innovation, there is still a considerable challenge in optimizing microwave absorption (MA) performance through heterointerface engineering within aerogel microspheres. Herein, we have developed skin-core heterogeneous aerogel microspheres by the in situ generation of ZIF-67 nanocrystals on the wet-spun aramid nanofiber (ANF) aerogel microspheres, followed by a high-temperature carbonization process. The resulting Co@C nanoparticle-enshrouded ANF-derived carbon nanofiber aerogel microspheres (Co@C/CNFAMs) demonstrate an exceptional equilibrium between impedance matching and multi-faceted attenuation. Remarkably, the Co@C/CNFAM2 sample attains a maximum effective absorption bandwidth of 8.72 GHz, while maintaining an ultralow filler proportion of 1.5 wt%. Moreover, the Co@C/CNFAM3 sample achieves a minimum reflection loss of −72.34 dB with a filling ratio of 1.2 wt%. Our findings offer a refined approach to the intricate engineering of heterostructures, along with the strategic macrostructural design, paving the way for the development of aerogel-based microwave absorbers that represent the next step in material science innovation.

3D-printed multi-material pyramids for broadband electromagnetic wave absorption

Designing and manufacturing broadband electromagnetic wave-absorbing materials represents one of the significant approaches to address electromagnetic pollution issues. This study utilizes three different PLA-based composite absorbing materials to prepare multilayer pyramid structures employing 3D printing technology. Results indicate that with material composition Z1-GT6-N8, material layer height (h) of 6 mm, and pyramid base length (L) of 36 mm, the fabricated structure achieves a minimum reflection loss of −24.19 dB with an effective absorption bandwidth of 14.21 GHz, demonstrating outstanding absorption performance. It is noteworthy that regardless of the incident angle increasing from 0° to 50°, the equivalent absorption bandwidth (EAB) for both transverse electric (TE) and transverse magnetic (TM) polarizations remains greater than 10 GHz, indicating excellent angle stability. The broadband and efficient electromagnetic wave (EMW) absorption characteristics exhibited by this absorber can be attributed to its outstanding impedance matching performance and the integration of multiscale loss mechanisms.

All-Around Electromagnetic Wave Absorber Based on Ni-Zn Ferrite.

Exploring a convenient, scalable, yet effective broadband electromagnetic wave absorber (EMA) in the gigahertz (GHz) region is of high interest today to quench its expanding demand. Ni-Zn ferrite is considered as a potential EMA; however, their performance study as a scalable effective millimeter-length absorber is still limited. Herein, we investigated EM wave attenuation properties of Ni0.5Zn0.5Fe2O4 (NZF) samples substituting Mn ion in place of Fe3+ as well as Zn2+ within a widely used frequency range of 0.1-9 GHz. Through composition optimization, Ni0.5Zn0.4Mn0.1Fe2O4 (NZM0.1F) EMA demonstrates excellent microwave absorption performance accompanied by simultaneous maximum reflection loss (RL) of -50.2 dB and wide BW of 6.8 GHz (with RL < -10 dB, i.e., attenuation >90%) at an optimum thickness of 6 mm. Moreover, the attenuation constant significantly increases from ∼217 to 301 Np/m with Mn doping. The key contribution arises from magnetic-dielectric properties synergy along with enhanced dielectric and magnetic losses owing to cation chemistry and site occupation in spinel NZF. In addition, porosity is induced in the system by a controlled two-step heat treatment process that promotes total loss with multiple internal reflections of the EM wave. Furthermore, RL is simulated by varying incident EM wave angles for the NZM0.1F sample displaying its angle insensitivity up to 50°. Our results reveal NZM0.1F as a futuristic environment-friendly microwave absorber material that is suitable for practical high-frequency applications.

Construction of CoO/Co9S8/NC composites with low-frequency and broadband electromagnetic wave absorption

Low-frequency electromagnetic wave absorption (EMWA) materials were crucial for addressing electromagnetic pollution and radar stealth. However, achieving low-frequency and broadband absorption still faces challenges. In this work, a succession of CoO/Co9S8/N-doped carbon (NC) composites were fabricated via a partial sulfidation strategy of Co-Prussian blue analogue (Co-PBA). The as-prepared CoO/Co9S8/NC composites featured a porous architecture. The electromagnetic parameters were effectively modulated via varying the sulfidation time. When the sulfidation time was 9 h, the minimum reflection loss (RLmin) value was −50.40 dB at 2.93 mm and a maximum effective absorption bandwidth value was 5.76 GHz (12.24–18.00 GHz) at 1.80 mm. Notably, when the sulfidation time was 12 h, the composites exhibited enhanced EMWA capability in the low-frequency S-band (3.52 GHz) with an RLmin value of −28.91 dB. The superior EMWA performance of composites were primarily attributed to appropriate dielectric constants and optimized impedance matching due to magnetic loss. Moreover, the radar cross section simulation consequences further verified that dissipation capability of electromagnetic wave of the CoO/Co9S8/NC composites in the actual far field. This work afforded novel perspectives into the rational develop of PBA-derived carbon-based EMWA materials with the low-frequency and broadband absorption.

Construction of 1D heterogeneous PPy@FeCo@PPy nanotubes with broadband and strong electromagnetic wave absorption

Developing nanomaterials with efficient electromagnetic wave absorption to eliminate increasingly serious electromagnetic pollution is of great significance. The peculiar electromagnetic characteristics of one-dimensional dielectric-magnetic heterostructures bring a promising strategy for designing high-efficiency absorber. Herein, a hierarchical PPy@FeCo@PPy nanotube was fabricated through a process of oxidative polymerization and electroless plating. In the product, the FeCo nanoparticles are encapsulate in the middle of the polypyrrole (PPy) dual conductive layers, which facilitates the deep construction of heterointerfaces and simultaneously prevents magnetic agglomeration. Furthermore, the hollow structure and suitable dielectric-magnetic component optimize impedance matching. Profiting from the reasonable structural design and the strong synergistic loss mechanism of dielectric-magnetic, the coaxial multi-shell PPy@FeCo@PPy nanotube exhibits prominent electromagnetic wave absorption performance, with a minimum reflection loss of −50.5 dB and the effective absorption bandwidth of 5.7 GHz at 2.0 mm. This work offers a gentle strategy for preparing ideal microwave absorbers by constructing dielectric-magnetic heterogeneous interfaces.

The hollow cubic octahedral structure of Fe3O4 with excellent electromagnetic wave absorption capacity

The unique nanostructure combined with high dielectric and magnetic losses is essential for electromagnetic wave (EMW) attenuation in microwave-absorbing materials (MAM). In this paper, using cubic octahedral Cu2O as a template, we synthesized hollow cubic octahedral Fe(OH)3 at first. After annealing at 450 °C, the hollow cubic octahedral structure Fe3O4 could be obtained. When the filling ratio was 40 %, the minimum reflection loss (RLmin) reached -66.08 dB, and the maximum effective absorption bandwidth (EAB) was 5.38 GHz at a thickness of 1.84 mm, exhibiting improved EMW properties compared with previous works. The hollow cubic octahedral structure of Fe3O4 enhances EMW absorption characteristics, which is attributed to abundant dipole polarization, interface polarization, and good conduction loss. These results indicate that Fe3O4 with the hollow cubic octahedral structure can be used as potential candidates for efficient and broadband EMW absorbers.

Broadband electromagnetic wave absorption properties of RGO cement-based composite

In this study, a cement-based composite was prepared using reduced graphene oxide (RGO) as a raw material via an ethanol liquid-phase mixing pre-dispersion process. The microstructure of cement-based composites with varying RGO contents was discussed, and a systematic investigation was conducted into the electromagnetic wave absorption (EWA) performance of RGO-cement composites within the frequency range of 2–18 GHz. The results indicate that the RGO content significantly impacts its wave absorption performance. Notably, at an RGO content of 3.0 wt%, the wave absorption performance experiences substantial enhancement. For instance, the minimum reflection loss (RLmin) of −48.33 dB at 8.9 GHz with a coating thickness of 2.6 mm is achieved, while an effective absorption bandwidth (EAB) of 5.02 GHz is attained with a thickness of only 1.6 mm, covering nearly the entire Ku-band. The incorporation of high specific surface area RGO into cement materials results in abundant interface polarization losses and additional electromagnetic wave transmission paths, effectively boosting the EWA performance. Consequently, these materials exhibit significant potential for applications in the field of electromagnetic wave shielding.

Ferrite doped sucrose-derived porous carbon composites inspired by Pharaoh's Serpent for broadband electromagnetic wave absorption

This paper presents a straightforward and intriguing approach for designing wide bandwidth, lightweight, and tunable electromagnetic wave (EMW) absorbing materials. Drawing inspiration from the "Pharaoh's Snake", biomass carbon source and sucrose were used to fabricate Fe/Fe3O4@porous carbon (PC) composite materials through combustion experiments. Subsequently, high-temperature calcination was applied to enhance the microwave absorbing properties of the materials. The as-prepared composites demonstrate an impressive 6.62 GHz effective bandwidth and an excellent absorption ability of −51.54 dB at a matched thickness of 2.2 mm. Moreover, by tuning the content of magnetic particles and controlling the thickness of the composite material, comprehensive coverage across C, X, and Ku bands can be achieved. The outstanding performance suggests that the synthesized Fe/Fe3O4@PC porous materials hold significant potential for applications in electromagnetic wave absorption. It opens up a novel, straightforward, and cost-effective approach to acquiring broadband absorbing materials.

Material extrusion 3D printing of large-scale SiC honeycomb metastructure for ultra-broadband and high temperature electromagnetic wave absorption

Electromagnetic (EM) wave absorbing materials have been widely used in various equipment to reduce the interference caused by EM waves. However, current EM wave absorbing materials are limited by narrow absorption bandwidth under high temperatures due to a lack of structural design. Herein, SiC ceramic and large-scale SiC honeycomb metastructure were monolithically fabricated by material extrusion 3D printing. The real permittivity and imaginary permittivity of as-obtained SiC ceramic approached 10 and 2.3 within the frequency of 2–18 GHz. After optimized structure design, the as-obtained SiC honeycomb metastructure exhibited broadband EM performance of −10 dB effective bandwidth from 4.85 to 39.49 GHz (34.64 GHz) when the incident angle was 60° at room temperature. Moreover, the as-obtained SiC honeycomb structure had a stable broadband −10 dB effective bandwidth of above 35 GHz when the incident angle is 60° even after in-situ 1000 °C and ex-situ 1600 °C erosion in the air atmosphere. Broadband EM wave absorption under oblique incident wave was also achieved from 30° to 60° both in transverse electric (TE) polarization and transverse magnetic (TM) polarization. This novel strategy unravels the potential of additive manufacturing of high-performance EM wave absorbers for high temperature environment applications.

Broadband microwave absorption for thin FeSiCr/rGO composites

A series of FeSiCr/reduced graphene oxide composites (FeSiCr/rGO) are successfully prepared by ball milling as a lightweight broadband electromagnetic wave absorbers. The microstructure and absorption properties of the FeSiCr and FeSiCr/rGO composites were compared in detail. The results show that the milled FeSiCr/rGO composite for 1 h can achieve a minimum reflection loss (RLmin) of −15.2 dB at 3.64 GHz with the thickness of 2.0 mm. Whereas, at the thickness of 1 mm, the effective bandwidth is 9.8 GHz when the value of the RL below −5dB. The FeSiCr/rGO composites show better microwave absorption thanks to the improved impedance matching. Furthermore, the peak of RL for FeSiCr/rGO composites, is entirely within the C-band and Ku-band, with a thickness ranging from 1 mm to 2 mm. Overall, this thin and lightweight FeSiCr/rGO composites can meet the requirement of strong and broadband absorber.

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.

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”.

Strong Magnetic–Dielectric Synergistic Gradient Metamaterials for Boosting Superior Multispectral Ultra‐Broadband Absorption with Low‐Frequency Compatibility

AbstractThe construction of 3D porous structures and metamaterials (MMs) is the most promising approaches to achieve broadband electromagnetic wave (EMW) absorption. However, it is still a huge challenge to achieve multispectral ultra‐broadband EMW absorption properties compatible with low‐frequency band (L‐ and S‐band) due to its ultralong wavelength and strong bypass capability. Herein, magnetic–dielectric synergistic gradient MMs (MDSGM) consisting of oriented flaky carbonyl iron (FCI) film and periodical RGO/CNT/CNF aerogel (GTFA) array are demonstrated. Benefiting from the synergistic effect of strong magnetic–dielectric loss, structural loss, and excellent impedance matching, MDSGM harvests an exciting multispectral ultra‐broadband EMW absorption performance with a remarkable effective absorption bandwidth covering the whole measured frequency of 1–40, 50–110 GHz, and 0.1–2.0 THz for the first time. The minimum RL (RLmin) reaches −40.24 dB and average RL is up to −19.3 dB (98.8% EMW being absorbed) in microwave band. Moreover, this multispectral ultra‐broadband EMW absorption property is less affected by the incident angle. This work pioneered realization of multispectral ultra‐broadband EMW absorption compatible with low‐frequency, which provides a great thrust for the development of stealth technology in the upcoming smart era.

A simple co-doping strategy to synthesis of Ni@B/N carbon nanotubes with broadband and low-frequency electromagnetic wave absorption

Development of magnetic composites with rational microstructural design to achieve excellent electromagnetic wave (EMW) absorption in the low-frequency range is necessary and still challenging. Herein, the B/N carbon nanotubes loaded with Ni nanoparticles were successfully synthesized through a homogeneous precursor pyrolysis route. The homogeneity of the micro-magnetic field in the composite architecture is improved by the co-doping of B and N in carbon nanotubes due to the polarization effect, which would enhance the impedance matching and EMW absorption. The Ni@B/N carbon nanotubes exhibit a minimum reflection loss (RLmin) of −56.9 dB at 8.24 GHz with a maximum bandwidth of 7.12 GHz ranging almost all S and C bands (from 3.44 to 10.56 GHz) suggesting that the composite architecture effectively enhances low-frequency EMW absorption properties. The combination of impedance matching and interfacial polarization resulting from the homogeneous Ni nanoparticles and co-doping of B and N in carbon lattice structure is responsible for the enhanced low-frequency EMW absorption properties. This simple co-doping synthesis strategy provides a new design strategy for the preparation of broadband and low-frequency EMW absorbers.

Mechanical metamaterials as broadband electromagnetic wave absorbers: investigating relationships between geometrical parameters and electromagnetic response.

The utilization of low-density and robust mechanical metamaterials rises as a promising solution for multifunctional electromagnetic wave absorbers due to their structured porous structures, which facilitates impedance matching and structural absorption. However, the various geometrical parameters involved in constructing these metamaterials affect their electromagnetic response, necessitating a comprehensive understanding of underlying absorbing mechanisms. Through experimentally validated numerical analysis, this study delves into the influence of geometrical factors on the electromagnetic response of representative low-density, high strength mechanical metamaterials, namely octet-truss and octet-foam. By juxtaposing electromagnetic response under varying volume fractions, cell lengths, and multilayer configurations of octet-truss and octet-foam, distinct absorption mechanisms emerge as geometrical parameters evolve. These mechanisms encompass diminished reflection owing to porous structures, effective medium approximations within subwavelength limits, and transmission-driven or reflection-driven phenomena originating from the interplay of open- and closed-cell structures. Through analyses on these mechanical metamaterials, we demonstrate the viability of employing them as tunable yet scalable structures that are lightweight, robust, and broadband electromagnetic wave absorption.

Robust and flexible composite aerogel films with porous multilayered structures toward broadband electromagnetic wave absorption

Robust composite aerogel films exhibit superior electromagnetic wave absorption performance, owing to multilayered heterostructures assisted by MXene and Ni nanochains.

Preparation of CIP@TiO2 composite with broadband electromagnetic wave absorption properties

Preparation of CIP@TiO2 composite with broadband electromagnetic wave absorption properties