One-step, template-free, scalable fabrication of N/O-co-doped 2D porous carbon/FeCo nanoparticles with ultralow low filler loading for excellent microwave absorption performance

Intelligent electromagnetic functional composites exhibit dynamic electromagnetic parameters, offering potential solutions for electronic devices in complex environments. Traditional methods relying on composites' volume changes often result in structural instability and poor environmental adaptability. Herein, we design an intelligent phase-change composite that mimics the firefly's luminescent "on-off" switching behavior, which consists of a polyacrylonitrile/polyvinyl pyrrolidone/polyvinyl alcohol/carbon nanotubes (3PC) aerogel and polyethylene glycol (PEG). This unique structure features temperature-responsive characteristics, enabling effective modulation of the composite's dielectric constant. Temperature variations induce PEG's phase transition and dynamically alter hydrogen bonding interactions within the composite. 3PC/PEG demonstrates innovative and reversible thermal-responsive switching properties: 3PC/mPEG in the molten state achieves a minimum reflection loss of -23.9 dB, while 3PC/cPEG in the solidified state exhibits a reduced minimum reflection loss of -8.9 dB. This mechanism enables temperature-dependent modulation of the dielectric constant, facilitating controlled microwave absorption and attenuation. Furthermore, the composite achieves switchable microwave absorption performance across different temperature ranges by regulating the molecular weight of the absorbed PEG. It also demonstrates modulatable electromagnetic interference (EMI) shielding properties and exceptional infrared stealth capability. This work advances the development of intelligent electromagnetic functional composites and presents significant potential for practical applications in adaptive electromagnetic management.

To suppress the ever-increasing challenge of electromagnetic radiation pollution and exploit lightweight wave absorbers, enormous attention has been focused on aerogels. Herein, a sequence of Fe3C/Fe/NC aerogels with variable dielectric/magnetic ratios has been successfully synthesized by redox reaction, freeze-drying, and high-temperature calcination. Benefiting from the dielectric-magnetic coupling loss, optimized impedance matching, and structural advantages, the Fe3C/Fe/NC-2/PVDF composite displays optimal microwave absorption performance with a minimum reflection loss (RLmin) value of -59.03 dB at 2.53 mm under an ultralow filler loading of 3 wt %. Meanwhile, the maximum effective absorption bandwidth (EAB) of Fe3C/Fe/NC-3/PVDF composite nearly covers the entire X-band at 2.92 mm. Moreover, the radar cross-section (RCS) simulation results and infrared thermal images respectivelly verify their application potential in radar wave attenuation and the infrared stealth domain. The specific wave absorption mechanism is mainly ascribed to dielectric loss, including conduction loss and polarization loss, magnetic loss containing eddy current loss and exchange resonance, as well as multiple reflections and scattering caused by the porous structure. This study can effectively decouple the impedance matching and microwave dissipating ability by dielectric/magnetic ratio modulation and microstructure design, which is of great significance for the development of lightweight and advanced wave absorbers.

Stimuli-responsive microwave absorbing (MA) materials are highly desirable for next-generation electromagnetic interference protection systems, as they enable adaptive regulation of electromagnetic responses under dynamic service conditions. Herein, a bioinspired temperature-responsive composite based on Ti3C2Tx MXene and poly(N-isopropylacrylamide) (PNIPAAm) is fabricated via in situ polymerization of PNIPAAm within MXene dispersions. Benefiting from the reversible conformational transition of PNIPAAm chains induced by temperature variation, the MXene nanosheets undergo a dynamic bridging-disconnection transformation, analogous to the opening and closing behavior of plant leaf stomata. This microstructural evolution enables adaptive reconstruction of the conductive network, thereby modulating dielectric properties and realizing switchable microwave absorption performance. At 50 °C, the composite delivers a minimum reflection loss of -47.8 dB and a broad effective absorption bandwidth of 5.9 GHz, whereas negligible absorption is observed at 20 °C. This work demonstrates a viable strategy for constructing intelligent, stimuli-responsive MA materials based on MXene@polymer architectures, offering promising prospects for advanced EMI protection and adaptive electromagnetic devices.

Biomass-derived carbon materials are promising for electromagnetic wave (EMW) absorption. However, the inherent structural rigidity of raw biomass severely restricts the microstructural tunability of its carbonized derivatives, limiting their scalable fabrication and high-performance EMW absorption applications. To address this issue, a "cure-in-the-cause" strategy is proposed based on deep eutectic solvent (DES)-mediated redistribution of cork components, with no external additives required. Notably, DES plays a vital role in pore structure regulation by selectively dissolving lignin and part of the suberin from raw cork. The subsequent regeneration of these dissolved components on the cork surface induces controllable shrinkage and deformation of the cork cell lumens, thereby not only constructing a labyrinthine porous structure but also achieving precise modulation of the material's microstructure. After carbonization, the labyrinthine porous structure is well retained, forming a porous carbon framework with tunable pore size, graphitization degree, and nitrogen doping. Benefiting from the well-regulated microstructure, the obtained sample C-R-DLC1000 exhibits superior EMW absorption performance at a thickness of 1.44 mm, with a minimum reflection loss of -77.5 dB and an effective absorption bandwidth of 4.32 GHz (13.12-17.44 GHz), which nearly covers the entire Ku-band. This facile, low-cost "cure-in-the-cause" strategy provides a viable route for the high-value transformation of waste biomass into advanced EMW absorbers and offers a universal pathway strategy for microstructure engineering of biomass-derived functional materials.

Optimizing loss components by phase engineering is crucial for enhancing the microwave absorption performance of magnetic core-dielectric shell composites. In this work, a series of core-shell structured composites (FTR) were elaborately synthesized by high-temperature hydrogen reduction of Fe3O4@TiO2 precursors and the TiO2 shell content was effectively regulated by varying the dosage of tetrabutyl titanate (TBOT). With the increase of TBOT dosage, the phase composition of FTR composites gradually evolves from Fe/Fe2O3@TiO2 (FTR-2.0) to Fe@TiO2 (FTR-2.5) and Fe@FeTiO3/TiO2 (FTR-3.0, FTR-3.5). FTR-2.5 has the highest Fe content (86.24 wt %) and saturation magnetization (141.7 emu·g-1). Low TBOT dosage leads to TiO2 cracks around the magnetic core after hydrogen reduction, but the remaining shell still encapsulates the magnetic core. In contrast, high TBOT dosage promotes the solid-state reaction between Fe and TiO2 shells, generating thick and dense FeTiO3 shells and abundant hollow spheres. Regarding loss components, FTR-2.5 is dominated by magnetic loss due to its highest metallic Fe content, whereas dielectric loss plays a more prominent role in other FTR composites. Notably, polarization loss prevails in the high-frequency range, including interfacial polarization at the heterogeneous interfaces among Fe, Fe2O3, TiO2, and FeTiO3 and dipole polarization enhanced by abundant oxygen vacancies. Benefiting from the synergistic effects of strong magnetic loss, enhanced multiple polarization, and a continuous impedance matching region, FTR-2.5 achieves a maximum effective absorption bandwidth of 5.92 GHz at a thickness of 1.95 mm. This work provides insights into the phase evolution mechanism of Fe3O4@TiO2 during H2 reduction and a reference for improving broadband microwave absorption.

The rapid advances in detection technologies have raised greater demands on microwave-steady materials, particularly for curved surfaces and movable components of aircraft that are highly susceptible to detection. However, electromagnetic wave (EMW) absorbers based on composite metastructures or metal-backed resonant cavities often suffer from intrinsic rigidity, resulting in poor conformability to complex surfaces and consequently compromised microwave-absorption performance. Herein, inspired by the locally segmented deformability of soft-bodied organisms, a deformation-adaptive EGaIn/CIP-TPU nanofibrous absorber is developed through liquid-metal confinement within electrospun nanofibers, which integrates segmented fiber network reconfiguration with EGaIn/CIP-induced dielectric-magnetic synergistic attenuation for flexible microwave absorption. Specifically, the flexible microwave absorber delivers a minimum reflection loss (RL) of -51.4 dB at a matching thickness of 2.2 mm. Meanwhile, these absorbers exhibit elastic recovery ratios above 70% and show stable mechanical responses over 500 compression cycles. This study demonstrates an effective balance between mechanical adaptability and microwave-absorption performance, providing a promising strategy for next-generation flexible EMWA.

Microwave absorption performance of an ultra-thin carbon composite absorber CuFe2O4/Cu/Fe4N/Fe3O4/C

Carbon-based composite materials with high microwave absorption performance: Current research status and prospects

Controllable preparation of 3D porous Co/Mo2C/C aerogels: Synergizing multifunctionality with efficient microwave absorption performance

The development of cost-effective and resource-rich materials is crucial for the practical application of microwave absorbers. This study demonstrates the successful fabrication of core-shell Fe and TiC nanoparticles encapsulated within carbon shells using the arc discharge method. The samples are designated as Fe3Ti1 and Fe1Ti3, where the numbers indicate the Fe-to-Ti mass ratio in the precursor (e.g., Fe1Ti3 = 1:3 by mass). In the arc discharge synthesis mechanism, the mass ratio of Fe to Ti in the raw material was adjusted from 3:1 to 1:3 to optimize the Fe/TiC/C interfaces under a CH4 forming gas atmosphere. TEM analysis reveals spherical and polyhedral nanoparticles with diameters of 30–50 nm and a uniform carbon shell thickness of 3–4 nm. Raman spectroscopy shows that the Fe1Ti3 sample has a higher defect density (ID/IG = 1.13) compared to Fe3Ti1 (0.87), indicating a more disordered carbon structure. Magnetic measurements yield saturation magnetization values of 87 emu/g for Fe3Ti1 and 50 emu/g for Fe1Ti3, with coercivities of 190.72 Oe and 203.65 Oe, respectively. When composited with paraffin at 50 wt% loading, the Fe1Ti3 sample exhibits superior microwave absorption performance, achieving a minimum reflection loss (RL) of −25.22 dB at 8.23 GHz and an effective absorption bandwidth (RL ≤ −10 dB) of 4 GHz (6.5–10.5 GHz) at a thickness of 2.5 mm. This enhanced performance is attributed to the synergistic effect of multiple loss mechanisms, including conduction loss within the three-dimensional core-shell architecture, interfacial polarization at the heterojunctions between the core and the carbon shell, and magnetic loss induced by ferromagnetic behavior associated with defects in both the shell and carbon atomic layers. The magnetic loss in the (Fe/TiC)@C nanocomposites primarily arises from the natural resonance (at ~6.5 GHz) and exchange resonance (at ~12 GHz) of the Fe cores. The dielectric loss is primarily attributed to dipole, interfacial, and space charge polarization from TiC and the carbon shell, as well as multiple scattering effects between nanoparticles. Furthermore, far-field radar cross-section simulations substantiate that the Fe/TiC@C nanocomposite demonstrates excellent radar wave attenuation capability. Further, first principles simulations reveal that introducing Fe at the C/TiC interface induces strong charge redistribution and orbital hybridization, transforming a localized dielectric interface into a highly conductive and electronically coupled C/Fe/TiC system. This interfacial modulation enhances both dielectric loss (via charge transport and polarization) and magnetic loss (via Fe-induced magnetic interactions), thereby enabling optimized dielectric-magnetic synergy for broadband microwave absorption in (Fe/TiC)@C nanocomposites.

Effective absorption in the S-band usually requires relatively thick absorbing materials. However, growing application demands necessitate the development of high-performance materials with subwavelength thickness. This study presents a broadband absorbing metamaterial for the S-band, based on a novel structural design featuring a nested hexagonal metal resonant layer integrated with a carbonyl iron powder (CIP)/charcoal (CH)/epoxy resin (ER) composite slab. This structural innovation enables exceptional S-band absorption within a subwavelength thickness, effectively overcoming the inherent physical limitations of traditional materials. By combining the arch measurement method and simulations over the 2–18 GHz, we demonstrate that the metal resonant layer of the metamaterial plays a key role in controlling the electromagnetic field vector distribution. This work investigates the mechanism for enhancing S-band absorption in metamaterials through the redistribution of electromagnetic field vectors. Additionally, magnetic loss from CIP/CH/ER and dielectric loss from the resonators further enhance absorption performance. The designed absorbing metamaterial exhibits effective absorption at a thickness of only 2.25 mm, with a reflection loss (RL) below −10 dB from 2.2 to 3.8 GHz. Simultaneously, it can maintain a radar cross-section (RCS) below −10 dBm2 in a wide-angle range of ±160°. Furthermore, a superhydrophobic coating with a contact angle of 152° was prepared for absorbing metamaterial. This coating allowed the metamaterial to preserve its microwave absorption performance while imparting self-cleaning capability. This study proposes a multifunctional absorbing metamaterial for efficient absorption in the S-band.

ABSTRACT In this study, (Fe2O3/Y3Fe5O1 2)/MoS2 composites were successfully fabricated using an ultrasonic composite method. By precisely controlling the mass ratios of the constituent components, heterogeneous interfaces were engineered, and the complex dielectric constant was optimized, resulting in enhanced microwave absorption properties of the material. Experimental findings revealed that the YFMo-3 sample achieved a minimum reflection loss (RLmin) of −49.74 dB at 9.76 GHz, corresponding to an electromagnetic wave absorption efficiency of 99.998%. The sample YFMo-2 exhibits a minimum reflection loss (RLmin) of -47.18 dB at the 10.4 GHz frequency band, with an effective absorption bandwidth of 4.03 GHz – covering nearly the entire X-band – and all these performance metrics are achieved at an ultra-thin matching thickness of 3.0 mm. Comparative analyses demonstrated that the microwave absorption performance of YFMo-2 significantly surpassed that of the single-phase Y3Fe5O1 2/MoS2 composite with an equivalent ratio YMo-2. Analysis suggests that this advantage may stem from Fe2O3， increasing both the variety and quantity of heterogeneous interfaces within the composite material, thereby inducing more interface polarization phenomena. The present work offers a novel approach for optimizing yttrium iron garnet-based microwave absorbing materials and holds promise for advancing their practical applications in military-civilian integrated domains, such as electromagnetic stealth technology and electromagnetic compatibility of electronic devices.

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Magnetic porous carbon foams, with low density, strong attenuation, and improved impedance matching, have been introduced as effective microwave absorbers to combat electromagnetic interference. In this study, morphology regulation of CoMn-MOF derived composites anchored on carbon foam were prepared by in situ growth and high-temperature pyrolysis. The pyrolysis temperature significantly influences the structural and chemical properties of the magnetic carbon foams. At a matching thickness of 1.45 mm, the material yielded a wide absorption bandwidth of 4.46 GHz, along with a minimum reflection loss of -51.54 dB at 1.55 mm. The excellent microwave absorption properties were contributed to the conductive loss, dipole polarization, interfacial polarization, natural resonance, exchange resonance, and impedance matching. The prepared magnetic porous carbon foams also integrate thermal insulation property. This work established a promising design strategy for advanced microwave absorbers that combine low density with high absorption efficiency, broadband absorption capabilities, and thermal insulation properties.

Multifunctional ultralight Fe3O4/α-Fe/bamboo composites for high-performance microwave absorption, hydrophobicity, and heat response.

Defect engineering is an effective strategy for tuning the electromagnetic properties of materials to enhance microwave absorption performance. However, the mechanism of the materials by which variations in intrinsic defect type and concentration govern the dielectric behavior has not been fully elucidated. Herein, single-phase Cu2-xS with controllable defect states is successfully synthesized via a facile solvothermal method. A te-mperature-driven defect evolution strategy is employed to systematically investigate the influence of intrinsic defect concentration and distribution on the dielectric properties. It is shown that the concentration of copper vacancies exhibits an increasing and then decreasing trend, while the density of dislocations show a consistent rise with temperatur, which significantly affect the ε values of Cu2-xS. The sample synthesized at 170°C exhibits an optimal synergistic distribution of high-concentration copper vacancies and dislocations, which effectively improves impedance matching and significantly enhances dielectric loss. Consequently, it demonstrates outstanding electromagnetic wave absorption performance, achieving a minimum reflection loss (RLmin) of -51.85dB and an effective absorption bandwidth (EAB) of 4.95GHz (13.05-18GHz) at a thickness of 1.7mm, covering 82.5% in the entire Ku-band. The proposed temperature-driven defect engineering strategy establishes a definitive defect structure and dielectric performance relationship in Cu2-xS.

ABSTRACT Modern electromagnetic wave (EMW) absorbers face challenges in simultaneously achieving high absorption efficiency, robust thermal/chemical stability, and strong environmental adaptability. This study addresses these limitations through the ultrafast synthesis of high‐entropy rare‐earth borides (HERBs) containing five to eight cations (Y, Dy, Gd, Nd, La, Sm, Yb, and Er) via Joule heating. This technique overcomes key drawbacks of conventional methods, such as carbon contamination, strict stoichiometric sensitivity, and severe grain coarsening, by enabling rapid (∼30 s), low‐temperature (1300°C) processing. The octonary HERB (8ReB 4 /8ReB 6 ), namely ((Y 1/8 Dy 1/8 Gd 1/8 Nd 1/8 La 1/8 Sm 1/8 Yb 1/8 Er 1/8 )B 4 /(Y 1/8 Dy 1/8 Gd 1/8 Nd 1/8 La 1/8 Sm 1/8 Yb 1/8 Er 1/8 )B 6 ), achieves a record‐high configurational entropy (2.08 R ), thereby inducing severe lattice distortion, numerous point defects, and significant microstrain. These structural features act as polarization centers, while the abundant heterogeneous interfaces promote interfacial polarization. Defect‐enhanced conduction loss combined with intrinsic magnetic properties optimizes the electromagnetic parameters, yielding exceptional impedance matching and attenuation capability. 8HERB exhibits outstanding microwave absorption performance, with a minimum reflection loss (RL min ) of −46.14 dB at 2.1‐mm thickness and an effective absorption bandwidth (EAB) of 3.52 GHz at 2.2‐mm thickness. Radar cross‐section simulations confirm superior wide‐angle stealth performance, with a maximum reduction of 32.55 dB·m 2 . This work establishes ultrahigh configurational entropy as a pivotal design strategy for enhancing dielectric/magnetic loss mechanisms and demonstrates Joule heating as an efficient, scalable route for developing advanced EMW absorbers with multifunctional stability.

Enhancing the conduction and polarization properties of the emerging two-dimensional carbon material graphdiyne (GDY) represents a crucial step in broadening its application in microwave absorption. A novel strategy was proposed to improve the microwave absorption performance of GDY through precise regulation of single-atom structures. Using three-dimensional spherical GDY as a substrate, Two Fe single-atom absorbers were successfully constructed: one anchored by Fe-N-GDY (FeN2C2) via sp-N/sp-C cooperative coordination, and the other anchored by Fe-GDY (FeC4) via sp-C coordination alone. Combined experimental characterization and theoretical calculations revealed that the FeN2C2 configuration induces stronger charge transfer and dipole polarization. This effect synergistically optimizes both the dielectric loss and impedance matching of the material. Consequently, the optimal sample Fe-N-GDY achieved an effective absorption bandwidth of 5.98GHz at a matched thickness of 2.0mm, with a minimum reflection loss of -51.2dB. The strategy was further extended to multiple 3d transition metals (Cr, Mn, Co, Ni, Cu, and Zn). Results indicate that Group VIII elements (Fe, Co, Ni) exhibit superior performance in practical materials due to their electronic structures that favor balancing polarization and conduction losses. Radar cross section simulations confirm the exceptional attenuation capabilities of this series of absorbers in real-world scenarios. This work not only pioneers new applications for GDY in microwave absorption but also establishes a theoretical foundation for rationally designing atomically precise electromagnetic functional materials by revealing the "single-atom structure-property" correlation.

ABSTRACT The escalating growth in telecommunication technology has led to a surge in electromagnetic pollution due to the increase in electronic devices. This not only impacts the performance of electronic gadgets but also poses risks to human health. To counteract electromagnetic pollution, researchers have extensively investigated microwave absorbers. As communication technologies predominantly operate in the microwave region, demand for efficient microwave‐absorbing materials is rising. Traditional metal‐based microwave absorber materials face limitations in terms of cost, density, corrosiveness, and rigidity, prompting attention to polymer‐based composites, among which polyurethane (PU) composites stand out for their exceptional properties, making them a favorable candidate for microwave absorption applications. This study explores the microwave absorption performance in the X‐band frequency (8.2–12.4 GHz) of PU nanocomposites containing graphene nanoplatelets (GNP) as a conductive filler and magnetite as a magnetic filler. Various loading percentages of GNP and magnetite were incorporated into both rigid polyurethane (RPU) and flexible polyurethane (FPU) matrices. The optimized composition of 2.5% GNP and 2.5% magnetite (1:1 ratio) exhibited superior microwave absorption properties, achieving a minimum reflection loss of −39.2 dB with an effective absorption bandwidth of 1.22 GHz in RPU, and −26.5 dB with an EAB of 1.52 GHz in FPU. These results highlight that the synergistic combination of conductive and magnetic fillers within PU matrices provides an efficient pathway for designing lightweight, cost‐effective, and high‐performance microwave absorbers.