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There is an urgent need to develop microwave absorbing materials with ultra‐broadband absorption and multiband stealth compatibility, but this is difficult to achieve due to the difficulty of perfect electromagnetic impedance matching. Therefore, inspired by the anti‐reflection moth eye model, this article prepares carbonyl iron (CIP)/polyurethane (PU) absorbing materials into three biomimetic structures of cylinder, circular cone, and semi‐ellipsoid structures to optimize the absorption performance, which realizes the effective absorption of 5.13–18 GHz. The simulation models proved that the biomimetic structures can improve the anti‐reflection performance by building gradient impedance inside the materials. Finally, under the synergistic action of multiple reflection and gradient impedance mechanisms, the effective absorption bandwidth (EAB) of the semi‐ellipsoid moth eye biomimetic structure material with a total thickness of 3 mm can reach 6.94 GHz. The material can still achieve the EAB of 6.84 GHz with a low infrared emissivity of 0.242 by constructing the double‐layer structure. This work effectively solves the problem that the EAB of traditional microwave absorbing materials is difficult to be broadened due to impedance mismatch, and puts forward a new idea for optimizing the performance of microwave absorbing materials and compatible stealth. [ABSTRACT FROM AUTHOR]

[Display omitted] The compound eyes of the dragonfly, Pantala flavescens Fabricius, are covered by micro-scaled ocelli capable of sensing polarized light, an attractive property for radar stealth and counterreconnaissance. In this work, we fabricated biomimetic electromagnetic wave absorption materials (EAMs) by analyzing the covert information identifications of biological systems and focusing on the design of metastructures and microstructures. Several bionic metasurfaces with anisotropic double-V meta atoms made up of (FeCoNiSi 8.9 Al 8.9)C 0.2 high-entropy-alloy (HEA) ribbons for multiple-degrees-of-freedom recognition and broadband absorption are presented. The covert phase, amplitude, and angular momentum of electromagnetic waves were controlled and recognized as information by manipulating the rotation angle θ of meta atoms. A vortex wave with a topological charge of 1 was generated to recognize linearly polarization and left- and right-handed circular polarization. In addition, the polarization conversion enhanced absorption. The hierarchical nanostructures of HEA ribbons give rise to suitable electromagnetic loss and a superior impedance match. Finally, inspired by the structure of compound eyes, the designed multilayer metamaterials realized effective absorption (reflection loss (RL) ≤ − 10 dB) within the 4.5–18 GHz regime under 2.8 mm thickness. These materials provide evidence for a new way for integrated EAMs and metamaterials. [ABSTRACT FROM AUTHOR]

Carbon-coated Cu nanocapsules (Cu@C NCs) with controllable graphite-like shells were designed and synthesized for applications in wireless communication, military stealth or electronic devices. A modified arc plasma method was employed to prepare the NCs, where a solid carbon source was used to provide a carbon-saturated atmosphere, resulting in the constitution of core–shell nanostructures with thickness-controllable carbon shells. Formation mechanisms were involved in the nucleation and growth, adsorption–diffusion or secondary growth process. The Cu@C NCs with thicker graphite-like shells demonstrated the enhanced oxidation resistance, thermal stability and excellent electromagnetic absorption performance ranging between 2 and 18 GHz. A mass of hetero-interfaces and defects inside them strengthened dielectric polarizations and achieved impedance matching. The Cu@C NCs exhibited a minimum reflection loss of − 38.4 dB at 4.88 GHz. Benefiting from the structurally controllable core–shell nanostructure, the Cu@C NCs would become a potential candidate material for electromagnetic wave absorption applications. [ABSTRACT FROM AUTHOR]

Despite great efforts in material design and modification, there are still obstacles to improve the effective microwave absorption, which hinders the development of stealth materials. By introducing a magnetically induced Huygens' metasurface with Fibonacci spiral meta‐atom, a hierarchical absorber with carbonyl iron particle coating is designed and prepared, of which the total effective absorption bandwidth (EAB, reflection loss ≤−10 dB) amazingly reaches 9.41 GHz, exceeding 199% of the original coatings', and the absorption peak value declines from −15.91 to −32.12 dB. The overall thickness of the absorber is 7 mm, only 0.17 over the minimum thickness dictated by the causality limit. A conceptual basis for the proposed design is provided, that is, the balance of effective surface current and magnetic current induced simultaneously will enhance the electromagnetic (EM) wave transmission, which contributes to broadening the absorption bandwidth with promising impedance matching. The system is validated numerically and experimentally, suggesting a novel route to obtain high‐performance microwave absorption materials for the EM stealth technology. [ABSTRACT FROM AUTHOR]

Flaky carbonyl iron particles/nano silicon dioxide/Polyurethane (FCIP/SiO2/PU) composites coatings were fabricated. And FCIP were fabricated from sphere carbonyl iron particles (SCIP) by ball milling. The electromagnetic parameters of absorbers (SCIP, FCIP and SiO2) and the reflection loss (RL) of coatings were measured in the frequency range of 2–18 GHz. The results showed that the complex permeability and absorbing properties of FCIP are significantly enhanced compared with SCIP because of its smaller thickness and easy magnetization plane. In addition, as a low dielectric material, SiO2 can build more wave-transmission channels and optimize the impedance matching, making more electromagnetic wave transmitting into the coatings and being attenuated. Due to the addition of SiO2, the absorbing properties and effective absorption bandwidth of coatings are further enhanced. The reflection loss values exceeding − 10 dB can be obtained in the frequency range of 8.5–18 GHz with a thickness of 1 mm. [ABSTRACT FROM AUTHOR]

To design a single-component absorber with optimizing reflections loss and tunable absorption frequency, the unique lightweight MnO 2 microspheres are successfully synthesized by a template-free method. The as-synthesized MnO 2 microspheres are of mesoporous in diverse specific surface area. By controlling the pH value of the reacting solution, the specific surface area of MnO 2 microspheres is adjustable. The maximum specific surface area of MnO 2 microspheres with mesoporous nature being 90.52 m2/g for specimens is obtained from solution of pH = 5. The complex permittivity and permeability of manganese dioxide are tailored to obtain proper impedance matching. Thus, the resultant MnO 2 microspheres exhibit remarkable microwave characteristic in a wax matrix. The minimum reflection loss reaches −31.79 dB at 14.60 GHz, with the effective absorbing bandwidth below −10 dB being 5.78 GHz with a 2 mm thickness. The effective absorption broadband also changes from 10.27 to 13.75 GHz to 12.56–18.00 GHz as the increasing pH value. Such an outstanding microwave absorption performance ascribes to the unique mesoporous structure with designable specific surface area, giving rise to the multiple scattering and reflecting, interfacial polarization, and dielectric relaxation from the abundant interfaces and curved surfaces and impedance matching. Unlabelled Image • Mesoporous MnO 2 microspheres are facilely synthesized instead of tedious process. • Diverse specific surface area is obtained through adjusting pH of reaction system. • Specific surface area controls property and tunable absorption frequency response. • Maximum specific surface area is 90.52 m2/g, pore size concentrates on 4.909 nm. • Minimum reflection loss reaches −31.79 dB with effective bandwidth 5.78 GHz at 2 mm. [ABSTRACT FROM AUTHOR]

Optimizing impedance matching is crucial to achieve high-efficiency electromagnetic wave (EMW) absorption performance. In this work, Hollow CoSe 2 @N-doped Carbon/Carbon Nanotube-x (HCSC/CNTs-x) with unique three-dimensional conduction network was synthesized by using protection etching and high-temperature selenization strategies. The conductivity of HCSC/CNTs-x was regulated by varying the content of CNTs, and the extended three-dimensional electron transport pathway resulted in enhanced conduction and multiple reflection loss, while also optimizing impedance matching. Hollow CoSe 2 @N-doped carbon (HCSC) further facilitates the optimization of impedance matching. The abundant heterogeneous interfaces and defects induce strong interface polarization and dipole polarization, and the multiple loss mechanisms work in concert to confer excellent EMW absorption performance to HCSC/CNTs-x. The RL min of HCSC/CNTs-30 reaches −41.68 dB, and the EAB max is 4.92 GHz at only 2.0 mm. The design strategy of three-dimensional conduction network of HCSC/CNTs-x provides an effective way to achieve the impedance matching optimization of CoSe 2 -based EMW absorption materials. The unique three-dimensional conduction network of HCSC/CNTs-x was successfully synthesized by protected etching and high-temperature selenization. The extended three-dimensional electron transport path not only enhances the conduction loss and multiple reflection loss, but also optimizes the impedance matching to achieve the harmony between impedance matching and electromagnetic loss capability. Attributed to the synergistic effect of multiple loss mechanisms, HCSC/CNTs-30 has excellent electromagnetic wave absorption performance with the RL min up to −41.68 dB and the EAB max is 4.92 GHz only 2.0 mm. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • T-ZnO w can enable FCIPs to show the vertically oriented distribution. • The vertical distribution can significantly improve impedance matching. • The effective bandwidth of T-ZnO w /FCIPs covers the entire X-band over 30–350 °C. Currently, most magnetic high-temperature microwave absorbing materials (MAMs) suffer from the problem of impedance mismatch caused by sudden increase in conductivity along with the changing temperature. Herein, the tetra-needle zinc oxide whisker (T-ZnO w) is used as a structural template to manage the spatial distribution of flake carbonyl iron powders (FCIPs), achieving temperature-stable broadband microwave absorption in the range of 30–350 °C. By adjusting the filling content of T-ZnO w makes FCIPs change from random distribution to a vertically oriented distribution. This distribution provides more stable conductive paths and facilitates low temperature-sensitivity conductance loss. At the same time it provides more transmission channels for the incidence of electromagnetic waves (EMW) and achieves excellent impedance matching. Compatibility of conductance loss and impedance matching is thus achieved. The effective absorption bandwidth (reflection loss (RL) < −10 dB) of T-ZnO w /FCIPs in the range of 30–350 °C could cover entire X-band (8.2–12.4 GHz). This work proposes a simple method to adjust the spatial distribution of absorbers and provides a valuable inspiration for the preparation of temperature-stable broadband MAMs. [ABSTRACT FROM AUTHOR]

FeSiAl powder (FSA)/water-based varnish (WV) microwave-absorbing coatings with discrete structure (DMCs) were fabricated, and the effects of the discrete structure on their impedance matching and absorption performance were investigated. The electromagnetic parameters of FSA were determined in the frequency range 2-18 GHz using transmission/reflection measurements. The microwave absorption (MA) properties of the coatings were determined by measuring the reflection loss using the arch method. The normalized input impedances of the DMCs with different coatings were calculated for the investigation of impedance matching. The results showed that, compared with conventional coatings, the discrete-structure coating has superior impedance matching and delivers clearly enhanced MA performance. When the concentration of FeSiAl is 17 wt%, the absorption peak reaches −12.5 dB from −5.8 dB, and the qualified frequency bandwidth is 2.5 GHz. Furthermore, the effect of the discrete unit size and coating thickness on the impedance matching and absorption performance of the coatings were investigated. [ABSTRACT FROM AUTHOR]

The structural destructive resonance caused by the single resonant thickness of flat microwave absorbers results in narrow absorption, hindering the progress of stealth materials. Multi-scale optimization and metastructure design are effective in the improvement of multiple resonance thickness as well as wavefront transmission, allowing for greater freedom in the realization of broadband. Herein, hierarchical metamaterials constructed from pyramid metastructure composites and Huygens' metasurface on the basis of Fibonacci spiral element are reported here, with effective absorption bandwidth (reflection loss ≤ −10 dB) ranging from 4.8 to 18 GHz in terms of subwavelength thickness. The hybrid absorber also exhibits robustness with incident angle across 0°–50° for transverse magnetic polarization. The gradient impedance model based on pyramid composites comprising spherical carbonyl iron particles and graphene sheets will serve as a driver for the enhancement of the electromagnetic wave transmission and the booster of impedance matching. Huygens' resonance of HMS induces the magnetic field convergence effect due to the simultaneous balance of effective surface current and magnetic current, which facilitates the absorption of lossy composites for further broadening absorption bandwidth. This integrated design could be widely applied to other absorbent materials of choice. [Display omitted] • In the case of the electrical and magnetic response are properly balanced, the field excited by the meta-atom composed of centrosymmetric Fibonacci spirals shows similar dispersion of electric and magnetic polarizabilities, resulting in a negligible reflection of the proposed Huygens' metasurface in the frequency range of 2–18 GHz. • A comprehensive design of hierarchical metamaterials from four perspectives: microscale, mesoscale, macroscale and metamaterials, which provides a rigorous and scientific route for the broadband directional design of microwave absorbing materials. • The effective absorption bandwidth of proposed hierarchical metamaterial ranges from 4.8 to 18 GHz across C, X and Ku-band in terms of subwavelength thickness (0.096 λ 0) which merely 7% over theoretical minimum thickness dictated by the causality limit, and exhibits robustness with incident angle across 0°–50° for transverse magnetic polarization. [ABSTRACT FROM AUTHOR]

Although various absorbers have been developed for electromagnetic-wave absorption materials (EAMs), the uniform composition and microstructure limit the design freedom of the soft magnetic properties, thus resulting in a ceiling of the absorption properties. Herein, we propose a revolutionary concept of C-doped FeCoNiSiAl high-entropy-alloy (HEA) ribbons with hierarchical nanostructures composed of ultrafine grains (400 nm), B2 nanoprecipitates (80 nm), and C@FeNi core–shell nanoparticles (15 nm) to induce superior soft magnetization and absorption. The hierarchical nanostructures resulted in a low coercivity (H C , 589.04 A/m) and a low conductivity (294.1 S/cm) to support the loss effect and impedance matching, and 87% of the saturation magnetization (M S , 135.13 emu/g) was maintained, even at the high temperature of 973 K, corresponding to ultra-stable magnetization. Furthermore, the Curie-temperature was greater than 1000 K. The B2 nanoprecipitates and corresponding interfaces created strong stray magnetic flux lines and magnetic domain vortices, and thus, the metasurfaces innovatively fabricated with HEA ribbons induced a strong absorption peak (−50.88 dB) and effective broadband absorption (reflection loss (RL) ≤ −10 dB within 5.86–18 GHz) due to the strong magnetic coupling. The hierarchical nanostructure is a promising strategy to tailor magnetic HEAs with a new degree of freedom for advanced EAMs. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Hierarchical 2D N-doped graphene@amorphous carbon are designed. • Phase mutation, group delay and resonance response are certified. • Almost perfect impedance-matching (SWR approaching 1) is achieved. • An alternative route for polymers and graphene as promising MAMs is provided. Two dimensional (2D) nitrogen-doped graphene@amorphous carbon was constructed by in-situ polymerization of sandwich-like structured polyaniline/graphene oxide composites then carbonization at 650 °C in vacuum. The results revealed that the as-prepared 2D N-doped graphene@amorphous carbon and N-doped amorphous carbon nanorods have almost the same decomposition degree and crystal structure. However larger defective degree and more polar bonds are conducive to enhance the polarization loss capacity, and larger dielectric constant can contribute to prominent conductive loss potential. The standing-wave ratio at 13.325 GHz of 2D N-doped graphene@amorphous carbon is 1.08426 approaching to 1, almost perfect impedance-matching level achieving. HFSS simulations certify phase mutation, group delay and the resonance response between N-doped graphene@amorphous carbon and testing microwave, as well as the stronger microwave loss capacity and better impedance matching. Both of the above make 2D N-doped graphene@amorphous carbon a promising microwave absorbing material. The minimum reflection loss (RL) of nitrogen-doped graphene@amorphous carbon can reach −29.5 dB and the effective absorbing bandwidth (EAB, RL < −10 dB) can reach 5.355 GHz ranging from 12.56 to 17.915 GHz only at a thickness of 2.25 mm. [ABSTRACT FROM AUTHOR]

As the increasing requirements on microwave absorber resulting from the complex application environment, composites consisting of multiple components have obvious superiority to the pure materials. In order to achieve excellent absorption performance for composites, both composition and microstructure should be properly designed. In this work, a three-phase composite consisting of conductive CNT, magnetic ZnFe 2 O 4 and dielectric ZnO with coating structure is designed to enhance the microwave absorbing performance. The three-phase CNT@ZnFe 2 O 4 @ZnO composites are prepared by a two-step coprecipitation method. The as-prepared composite shows good impedance matching and high attenuation. When the content of ZnFe 2 O 4 is 3 mmol, the composite has a reflection loss of −33.5 dB at 4.4 GHz. The huge interfaces area attributed to both the multi-phase component and multi-layer structure helps to improve the interface polarization, dipole polarization, multiple reflection and scattering. Besides, the synergy of the different loss mechanisms coming from the different materials can also effectively promote the absorption. [Display omitted] • A three-phase CNT@ZnFe 2 O 4 @ZnO composite with coating structure is designed to enhance microwave absorbing performance. • ZnFe 2 O 4 microspheres grow on CNT skeleton over which the ZnO nanoparticle of ~10–20 nm covers uniformly. • The influence of ZnFe 2 O 4 content on the electromagnetic properties of CNT@ZnFe 2 O 4 @ZnO is discussed. • A maximum reflection loss of −33.5 dB at 4.4 GHz is obtained for prepared composite. [ABSTRACT FROM AUTHOR]

Building core@shell nanostructures and doping ions are two important strategies to optimize the performance for the microwave impedance matching and attenuation. In this research, the Ag-doped α-MnO 2 @δ-MnO 2 was successfully synthesized by combining hydrothermal reaction and chemical deposition reaction. Driven by the lowest surface energy principle, all the δ-MnO 2 nanosheets nucleate on the surface of α-MnO 2 nanowires. During this process, the edge of nanosheets attach on the α-MnO 2 nanowire with low lattice mismatch of δ (201)//α (211) (nearly 0) and vertically grow on the nanowires surfaces, then the assembled core-shell composites can be prepared. The core-shell composites exhibit synergistic effect and improved the impedance matching, so that the absorbing performance has been obtained. The composite shows the minimum reflection loss (RL) of −53.67 dB at 13.28 GHz for 1.8 mm thickness, and the broadest effective absorbing bandwidth (RL < −10 dB) is 5.44 GHz as the thickness was 1.9 mm. The excellent performance is come from the preferable impedance matching, the large heterogeneous existence of the interfaces and the numerous transmission paths for microwave. Image 1 [ABSTRACT FROM AUTHOR]

• Co-doped MnO 2 nanowires exhibit excellent electromagnetic absorption performance with the minimal reflection loss is −51.03 dB and effective absorbing bandwidth can reach 7.04 GHz. • The bonds length decreases and bonds energy increase caused by Co doping result in the enhancement of attenuation ability and the impedance matching. • Thinner nanowires supply more surface and interface and improve the multiple polarizations loss. The essence of designing ideal absorption materials is to control the electromagnetic parameters. In this work, doping strategy was adopted to regulate electromagnetic parameters. According to the experimental results and density functional theory calculations, the introduction of Co can make the charge redistribute, distortion increase, bonds length decrease, and bonds energy enhance, which can lead to the reducing of dielectric storage and raising of dielectric loss. Meanwhile, the superfine long nanowires of Co-doped MnO 2 can bring abundant surface and interfaces, which improve the polarization relaxations. These changes result in the enhancement of attenuation and improvement of impedance matching feature at the same time. Therefore, the Co-doped MnO 2 exhibits excellent microwave absorption performance, the minimal reflection loss is -51.03 dB and effective absorbing bandwidth can reach 7.04 GHz. This work offers an effective approach for the design of high-performance microwave absorption materials, which has been validated through experimental and theoretical evidence. [Display omitted] [ABSTRACT FROM AUTHOR]

Difficulty of multicomponent regulation and nanostructure design make it challenging to fabricate high-performance electromagnetic wave (EMW) absorption materials. Herein, pomegranate-like Fe 3 C@graphitic carbon embedded in amorphous carbon matrix (Fe 3 C@GC/AC) is successfully prepared through a viable heating induced self-assembly strategy. By adjusting carbonization temperature, controllable electromagnetic parameters and impedance matching characteristics of Fe 3 C@GC/AC nanocomposites could be acquired. Besides, dielectric loss and magnetic loss are offered by GC and Fe 3 C, while the amorphous carbon not only disperse Fe 3 C@GC nanoparticles well, but also strengthens interface polarization. The detailed analysis show that Fe 3 C@GC/AC nanocomposites exhibit excellent EMW absorption performance under the combined function of unique pomegranate-like nanostructure and various loss mechanisms of multi-components. Moreover, the strongest reflection loss value of optimal sample (RCF-700) is up to −96.3 dB (loss of EMW above 99.99999%) with a matching thickness of 2.08 mm, and the effective absorption bandwidth (EAB, RL < −10 dB) covers 6.38 GHz (11.62–18.0 GHz, covering Ku-band). In addition, the EAB can reach 14.08 GHz with the simulated thickness varies from 1.0 to 5.0 mm, covering 88% of the measured frequency range. The deep exploration of the bio-inspired structure of multi-component system provides a creative and effective way for high-performance EMW absorbers. [ABSTRACT FROM AUTHOR]

Due to the growing harm of electromagnetic radiation, it is extremely urgent to develop high-efficiency microwave absorbers with tunable electromagnetic properties. Herein, a simple strategy for synthesizing hetero-atoms (sulfur) doped carbon-coated FeNi alloy nanocapsules (FeNi@C(S x) NCs) by DC arc-discharge plasma was demonstrated. The hetero-interface between the FeNi alloy core and the graphitic shell induce interfacial polarization was found. Meantime, many defects produced by substitutional sulfur atoms in the graphitic shell facilitated dipole polarization and conduction loss. Besides, the multiple magnetic resonance produced by FeNi magnetic alloys worked together to optimize impedance matching. The excellent microwave absorption performance was attributed to the core-shell structure, dipole and interface polarizations, as well as favorable impedance matching. Importantly, the first-principles calculation was applied to prove the charge transfer and polarization process. The minimum reflection loss (RL) can reach up to −50.3 dB at a thickness of 1.6 mm. [Display omitted] • S-doped graphitic shells coated FeNi obtained by one-step arc discharge method. • S doping into the graphitic shells enhance dipole polarization. • S-doped graphitic shells can improve the conduction loss. • The DFT is applied to prove the charge transfer process. • The RL value reaches up to −50.3 dB with a thickness of 1.6 mm. [ABSTRACT FROM AUTHOR]

Electromagnetic absorbents with peculiarities of light-weight, beneficial structure, broadband, adequate corrosion resistance, and facile synthesis route are always highly practical in the telecom and stealth fields. In this regard, a new type hybird material (SiC/Fe)@C nanowires (NWs) has been effectively synthesized through an in-situ vapor-liquid-solid growth confined at arc-plasma region. A (SiC/Fe)@C NW is composed of a dielectric SiC NW with a magnetic Fe nanoparticle at it tip, both tightly encapsulated by conductive graphene-like carbon nanolayers at the surfaces. Such carbon-coated NWs form a randomly interconnected network, endowing a proper impedance matching to microwave and an anti-corrosion ability. It is found that the composite of (SiC/Fe)@C NWs and paraffin with a 25 wt% loading has shown the lowest reflection loss (RL) of −63.44 dB at 12.4 GHz, with a wide effective absorption band (RL ≤ −10 dB) of 7 GHz in thickness of 1.95 mm. This superb RL is attributed to the synergic outcomes from the balanced dielectric/magnetic losses with an appropriate impedance matching, resulted from the intrinsic physical properties and special structures of the (SiC/Fe)@C NWs. Pseudo percolation threshold, near 30 wt% loading of (SiC/Fe)@C NWs in the electromagnetically transparent matrix, implies the significant efficacy of concentration/distribution of absorbent on RL performances. Image 1 • (SiC/Fe)@C NWs have been fabricated by arc-discharge plasma; formation mechanism well explained by VLS growth. • (SiC/Fe)@C NWs found oxidation resistant up to ∼500 °C, allowing the microwave absorber adaptive in an atrocious condition. • 1D geometry of (SiC/Fe)@C NW synergistically contribute to microwave absorption. • The (SiC/Fe)@C NWs/paraffin composite reveals RL min. of -63.44 dB at 12.4 GHz in 1.95 mm thickness, and EAB of 7 GHz. [ABSTRACT FROM AUTHOR]

Abundant resources, light weight as well as stable physicochemical properties enable carbon nanomaterials promising candidates toward microwave absorption. However, it is still a great challenge for carbon-based absorbers to achieve broad frequency bandwidth and strong absorption, which fundamentally ascribes to the poor impedance matching resulted by their comparatively high electrical conductivities. Herein, a feasible and high-yield method has been employed to the in-situ synthesis of N-doped graphene nanoflakes which can effectively address interfacial impedance mismatching, and realize the majority of microwaves penetration into the interior of absorber. The incorporation of substitutional N atoms into graphene lattices markedly weaken crystallization degree and introduce masses of defects, directly leading to the decline of electric conductivity, meanwhile benefiting the improvement of static magnetization. Our findings indicate that compared with pure graphene nanoflakes, the counterpart containing 4.6 at.% of nitrogen exhibits an excellent absorption capability, in which more than 99% of microwave energy can be quantitatively attenuated at 5–18 GHz. Experimental results coupled with theory calculations further elucidate that such high performance essentially originates from the proper impedance matching constructed in the N-doped graphene nanoflakes. Image 1091 [ABSTRACT FROM AUTHOR]

Abstract To effectively optimize electromagnetic (EM) wave absorption performance and reduce the reflection at the absorbent-air interface, the absorbents coupling magnetic/dielectric loss components to construct heterogeneous interfaces are urgent. Herein, we report a facile method for preparing a unique (TiC/Ni)@C ternary composite. The incorporation of Ni into TiC/C matrix to form heterogeneous interface not only ameliorates impedance matching, but also introduces the additional interface polarization for tuning dielectric loss capacity. Comparing with the weak absorption performance of TiC@C composite, the minimum reflection loss (RL) value of (TiC/Ni)@C composite can reach up to −43.4 dB at 7.0 GHz with the 3.4 mm thickness, and the effective bandwidth of RL below −10 dB can be up to 5.1 GHz at the 1.8 mm thickness. The results reveal that the efficient synergistic effect between magnetic Ni and dielectric TiC/C plays a more important role for the absorption performance, comparing to the merely strong dielectric loss of TiC@C composite. Highlights • (TiC/Ni)@C ternary composite was firstly synthesized by an arc discharging approach. • Dual dielectric loss components (TiC/C) coupling with magnetic Ni is beneficial to achieve a good impedance matching. • The minimum RL values reaches to −43.4 dB at 7.0 GHz with the absorbent thickness of 3.4 mm. [ABSTRACT FROM AUTHOR]

[Display omitted] • The prominent soft magnetic properties are ascribed to their special coherent microstructure. • A short-time ball-milling does not change the coherent BCC/ L2 1 structure of MEA powders. • The prominent soft magnetic and high resistivity, which contributes to the excellent electromagnetic wave-absorbing properties. • Al 1.5 Co 3.5 Fe 3.5 flake powders possess the maximum effective bandwidth of 7.01 GHz with a sample thickness of 1.7 mm. Magnetic alloy powders show a great superiority in the balance of permittivity and permeability for electromagnetic (EM) wave-absorption. However, it is necessary to enhance their effective absorption bandwidth (Δf) and impedance matching due to their insufficient soft-magnetic properties and low resistivity, which would be solved by high/medium-entropy alloys (HEAs/MEAs). In this report, we designed Al 1.5 Co 3.5 Fe 3.5 and Al 1.5 Co 3 Fe 3 Cr MEAs with prominent soft-magnetic property and high resistivity. It is contributed to the special coherent microstructure with ultrafine magnetic body-centered-cubic nanoprecipitates uniformly-distributed into the L2 1 matrix, which could not be changed by ball-milling. Thus, alloy powders possess excellent EM properties, as evidenced by the minimum reflection loss of −42.2 dB at 14.52 GHz and the largest Δf = 7.01 GHz in 5 h-milled Al 1.5 Co 3.5 Fe 3.5 , better than existing alloy powders. The wave-absorbing behavior of MEA powders was discussed from both permittivity and permeability. The current findings offer a useful design strategy for developing high-performance absorbers. [ABSTRACT FROM AUTHOR]

• Novel Cr 3 C 2 @C hexgonal-shaped nanoplatelets were fabricated by arc-discharge plasma. • Anti-oxidation stability up to 350 °C is found in Cr 3 C 2 @C nanoplatelets. • Dielectric and magnetic losses operated synergistically in Cr 3 C 2 @C nanoplatelets. • Cr 3 C 2 @C nanoplatelets exhibited a minimum reflection loss of −36.9 dB at1.6 mm thickness. Core-shell nanomaterials have been considered excellent microwave absorbents due to their unique morphologies and designs. Here, hexagonal-shaped Cr 3 C 2 nanoplatelets coated with carbon shells (Cr 3 C 2 @C) were fabricated by an arc discharge plasma process. In as-synthesized Cr 3 C 2 @C nanoplatelets a weak ferromagnetism is found with an observable coercivity of 38 Oe, a saturation magnetization of 4 × 10−1 emu/g, and along with a suitable conductivity of 9.56 × 102 Ω−1cm−1. The observed suitable electrical conductivity and inductive magnetism of Cr 3 C 2 @C nanoplatelets played a vital role as a magnetic and conductive losses. Intrinsic defect-rich Cr 3 C 2 cores and amorphous carbon shells acted as dielectric polarization centers, wherein the incident electromagnetic wave dissipated through polarization and interfacial losses. The Cr 3 C 2 @C nanoplatelets with 30 wt% loadings in the paraffin matrix exhibited a minimum reflection loss of −36.9 dB at the thickness of 1.6 mm. The excellent refelection loss performance of Cr 3 C 2 @C nanoplatelets was certified to be a result from the synergetic effects of dielectric/magnetic losses and impedance matching. Furthermore, the Cr 3 C 2 @C nanoplatelets exhibited oxidation resistivity at 350 °C endorsing their application in harsh atmospheres. [ABSTRACT FROM AUTHOR]