Cotton-derived hierarchical carbon fibers@MnO2@polypyrrole core-shell structures engineered by stepwise modification for enhanced broadband electromagnetic wave absorption and corrosion resistance

Broadband electromagnetic wave absorption using pure carbon aerogel by synergistically modulating propagation path and carbonization degree

Aiming at the demand for structural–functional integrated designs with electromagnetic (EM) wave absorption and lightweight load bearing performances, an oblique corrugated channel sandwich structure (OCCSS) is proposed. The oblique corrugated channel is assembled from oblique corrugations, which are cut obliquely from straight corrugations. For EM wave absorption, glass fiber reinforced plastic (GFRP) and carbon fiber reinforced plastic are used for the face and back sheets, respectively, while the core is formed by GFRP and indium tin oxide (ITO) films. EM simulations and experimental tests indicate that the proposed OCCSS realizes broadband (4–18 GHz), wide-angle (0°–60°), and efficient (>85% absorptivity) EM wave absorption. The EM simulations demonstrate that the concentrated E-fields excited by the oblique corrugated channel enhance the efficiency of the current flow along the ITO films, which results in a 21% increase in the absorptivity of the OCCSS compared with that of a straight channel sandwich structure (SCCSS). The compressive performances of the OCCSS and SCCSS are investigated experimentally. The results show that the energy absorption per unit mass of the OCCSS is 43.2% higher than that of the SCCSS. The OCCSS demonstrates strong potential in engineering applications owing to its excellent EM wave absorption and load bearing performance, as well as potential thermal management capability.

Construction of porous carbon-based magnetic composites derived from iron zinc bimetallic metal-organic framework as broadband and high-efficiency electromagnetic wave absorbers

Synthesis of three-dimensional carbon networks decorated with Fe3O4 nanoparticles as lightweight and broadband electromagnetic wave absorber

Structural modification of mesoporous lanthanum oxide into 3D coral-like and nano needle-like structure for effective broadband microwave absorbing materials☆

Tunable and broad-band electromagnetic wave absorption using W-type Hexaferrites in 1–40 GHz range

Electromagnetic wave (EMW) absorbers with broadband attenuation and long-term stability are important for applications in marine environments. Dielectric ceramics excel in thermal and chemical resistance but offer limited impedance matching, whereas magnetic materials provide strong absorption yet degrade rapidly due to corrosion. Herein, we present an engineering approach for polymer-derived ceramics that utilizes ferric crosslinking to integrate both magnetic functionality and hierarchical structure within a single system. By reacting iron (III) acetylacetonate with Si-H groups in polyborosilazane, the uniformly distributed ferric polymer network is formed. Subsequent pyrolysis drives carbon nanotube growth and Fe_xSi_y phase formation, yielding a distinctive hierarchical “mushroom-like” structure composed of SiBCN matrices, carbon nanotube stems, and carbon-encapsulated Fe_xSi_y caps. This structure promotes EMW absorption via magneto-dielectric synergy, rich interfaces, and multiple scattering, while carbon-encapsulated Fe_xSi_y in the SiBCN matrix provides corrosion resistance. The effective absorption bandwidth (EAB, defined as reflection loss less than -10 dB) of h-SiBCNFe reaches up to 8.16 GHz, while also exhibits a corrosion potential (<em>E</em>_corr) of 0.033 V and an ultralow corrosion current (<em>I</em>_corr) of 0.63 μA·cm^-2. These features highlight a new design strategy for developing advanced EMW absorbers tailored for marine applications.

Rationally engineered porous structures enable lightweight broadband electromagnetic (EM) wave absorbers for countering radar signals or mitigating EM interference between multiple components. However, the scalability of such structures has been hindered by their limited mechanical properties resulting from low density. Herein, an additively manufactured Kelvin foam-based EM wave absorber (KF-EMA) is reported that exhibits multifunctionality, namely EM wave absorption and light-weighted load-bearing structures with constant relative stiffness made possible using bending-dominated lattice structures. Based on tuning design parameters, such as the backbone structures and constituent materials, the proposed KF-EMA features a multilayered 3D-printed design with geometrically optimized KF structures made of carbon black-based backbone composites. The developed KF-EMA demonstrated an absorbance greater than 90% at frequencies ranging from 5.8 to 18GHz (average EM wave absorption rates of 95.89% and maximum of 99.1% at 15.8GHz), while the low-density structures of the absorber (≈200kg m-3 ) still maintained a compression index between the stiffness and relative density (n = 2) under compression. The design strategy paves the way for using metamaterials as mechanically reinforced EM wave absorbers that enable multifunctionality by optimizing unit-cell parameters through a single and low-density structure.

Construction of cobalt zinc metal-organic frameworks derived Co/CoO/C composites toward broadband and high-efficiency electromagnetic wave absorption

Magnetic absorbers with high permeability have significant advantages in low-frequency and broadband electromagnetic wave (EMW) absorption. However, the insufficient magnetic loss and inherent high conductivity of existing magnetic absorbers limit the further expansion of EMW absorption bandwidth. Herein, the spinel (FeCoNiCrCu)3O4 high-entropy oxides (HEO) are successfully constructed on the surface of FeCoNiCr0.4Cu0.2 high-entropy alloys (HEA) through low-temperature oxygen bath treatment. On the one hand, HEO and HEA have different magnetocrystalline anisotropies, which is conducive to achieving continuous natural resonance to improve magnetic loss. On the other hand, HEO with low conductivity can serve as an impedance matching layer, achieving magneto-electric co-modulation. When the thickness is 5mm, the minimum reflection loss (RL) value and absorption bandwidth (RL < - 5dB) of bi-phase high-entropy composites (BPHEC) can reach - 12.8dB and 633MHz, respectively. The RCS reduction value of multilayer sample with impedance gradient characteristic can reach 18.34dB m2. In addition, the BPHEC also exhibits temperature-stable EMW absorption performance, high Curie temperature, and oxidation resistance. The absorption bandwidth maintains between 593 and 691MHz from - 50 to 150°C. This work offers a new and tunable strategy toward modulating the electromagnetic genes for temperature-stable ultra-broadband megahertz EMW absorption.

In this study, the electromagnetic (EM) wave absorption properties of a two-layered structure composed of La0.7Sr0.3MnO3-epoxy (10 wt.%) (LSMO) and SrFe9.5Co1.25Ti1.25O19-epoxy (10 wt.%) (SFCTO), both exhibiting distinct high-frequency magnetic and dielectric properties, were investigated using a High Frequency Simulation Software (HFSS) simulation tool. LSMO had a high dielectric constant (ε' &gt;30) within the measurement range (0.1-18 GHz), indicating that dielectric loss mechanisms primarily contribute to EM wave absorption. In contrast, SFCTO is a material capable of significantly absorbing EM waves near 10 GHz due to ferromagnetic resonance (FMR). The simulations were validated by comparing the measured and simulated reflection losses (RL) of an unpatterned LSMO/SFCTO bilayer. The RL spectra were examined by varying the layer thickness and pattern size in three configurations: a continuous LSMO/SFCTO structure, a cross-patterned LSMO on SFCTO, and a square-patterned LSMO on SFCTO. In the continuous LSMO/SFCTO structure, tunable absorption frequency bands were achieved by adjusting the layer thickness. However, it was difficult to achieve broadband absorption due to the reflective characteristics of the high dielectric LSMO layer. The cross-patterned LSMO structure on SFCTO demonstrated broader bandwidth absorption, with layer thickness being more influential than pattern width. The square-patterned LSMO on SFCTO exhibited the best broadband EM wave absorption (max Δf = 7.39 GHz). These results suggest that broader absorption is achievable by partially covering the high-dielectric layer with patterns on a hexaferrite sheet.

RGO supported bimetallic MOFs-derived Co/MnO/porous carbon composite toward broadband electromagnetic wave absorption

Synthesis of magnetical nanoparticles decorated with reduced graphene oxide as an efficient broad band EM wave absorber

Both morphological structure and chemical composition are the important factors that determine the electromagnetic wave (EMW) absorption properties of EMW absorbers. Herein, hierarchical porous carbon (HPPC) was synthesized by using polyetheretherketone (PEEK) as the starting material via the salt template method combined with KOH activation. Then, taking advantage of the hierarchical porous characteristics of the carbon, a novel EMW absorber (HPPC/CoNi) was synthesized by in situ growth of CoNi bimetallic alloys inside the above porous carbon. The as-synthesized HPPC/CoNi exhibits excellent EMW absorption performance with a minimum reflection loss (RLmin) value of -65.56 dB at 2.00 mm and a maximum effective absorption bandwidth (EAB) of 5.92 GHz at 1.80 mm. The superior EMW absorption property is ascribable to the multiple reflection/scattering induced by the hierarchical porous structure of HPPC, dielectric loss, magnetic loss, and good impedance matching. The results show that HPPC/CoNi is a potential EMW absorber with characteristics of ultra-light weight, ultrathin thickness, broad bandwidth, and strong absorption.

The design method and analysis of novel broadband electromagnetic (EM) wave absorbers is presented in this paper. The proposed absorber is a planar structure based on lossy Electromagnetic Bandgap (EBG) surface with the specific sheet resistance, which replaces conventional resistive layer of Salisbury screen. The absorber performance can be easily controlled by simply modifying the EBG surface. The analysis for the reflectivity response due to the phase variation of the reflection and transmission recognizes electrical characteristics of the proposed absorber. A broadband reflectivity response with about 96% fractional bandwidth below -10 dB is presented. The computational results are presented to verify the functioning of the proposed absorber.