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This work presents a theoretical analysis of the oscillations of a system of degenerate electrons in metallic submicron clusters, taking into account the presence of a large-scale spatial inhomogeneity caused by quantum shell effects. The analysis was carried out in a model formulation in which the large-scale effect was taken into account by the presence of an effective external field acting on the electrons. Two approaches to the description of electron dynamics were considered: kinetic and hydrodynamic. The results obtained within these approaches are in good qualitative and quantitative agreement with each other and demonstrate that for certain cluster sizes, a spectrum of oscillations of the electronic system appears with frequencies differing by the value Δω ∼ ω0/R20 and localized in the vicinity of plasmon frequency ω0 (R0, radius of cluster). The impact of the large-scale effect on the processes of light and electron scattering by metal clusters is estimated. It is shown that maxima appear in the absorption spectrum of the electromagnetic waves, and they turn out to be shifted from the plasmon frequency by value Δω ∼ ω0/R20. Within the framework of the Born approximation, it is shown that a maximum at kR0 ∼ 4π appears in the cross section of elastic scattering of electrons on a metal cluster. The results obtained are important from the point of view of interpreting experiments on plasmonic structures, in particular, on metal films. [ABSTRACT FROM AUTHOR]

This study presents a novel implementation of vanadium dioxide (VO2) phase change material in an electromagnetic (EM) surface with beam steering capabilities. For the first time, we present the design, fabrication, and measurement of a globally actuated, VO2-based beamforming reflective EM surface. We propose a design featuring complementary unit cells that enable beam steering with a single excitation, marking a pioneering use of low-loss VO2 in creating a complementary EM surface for the mmWave band. The unit cells incorporating VO2 exhibit low-loss characteristics, with −0.92 and −1.9 dB in the hot state and −0.49 and −0.25 dB in the cold state, respectively. We incorporate both positive and negative phase variants alongside two temperature-independent phase unit cells. The complementary design enables us to utilize two beam operating states, effectively exploiting the otherwise unused cold state. We experimentally demonstrated beamforming at ±5° and ±10° from the broadside. In the case of ±10°, the measured gains at 35 GHz in the cold and hot states were 19.4 and 20.3 dB, respectively, which aligned well with the simulated gains of 20.9 and 21.5 dB. Manipulation of the electromagnetic wave direction with a single excitation has the potential for imaging, sensing, and communication applications. The complementary unit cell design methodology can be further adapted for mmWave beamforming, absorbing, and cloaking reconfigurable EM surfaces. Furthermore, the use of VO2 can be extended up to sub-THz frequencies due to the wideband, low-loss characteristics compared with conventional reconfigurable devices, such as PIN diodes or MEMS switches. [ABSTRACT FROM AUTHOR]

The graphene-based electromagnetic wave absorption materials have attracted extensive attention due to their lightweight, strong absorption, broadband, and thin thickness. In this work, graphene hollow microspheres anchored with FeNi-coupled nanocrystal (GHMs@FeNi3/NiFe2O4) were synthesized using water-in-oil (W/O) emulsification and high-temperature calcination. The GHMs@FeNi3/NiFe2O4 microspheres have a homogeneous spherical morphology and a pronounced hollow structure, and the FeNi-coupled nanocrystals are homogeneously embedded in a spongy shell assembled by rGO nanosheets. Owing to the optimized impedance matching and enhanced attenuation, the GHMs@FeNi3/NiFe2O4 composites exhibit outstanding microwave absorption ability, particularly in the Ku band. The minimum reflection loss (RLmin) value can reach −58.96 dB at 14.43 GHz with a matching thickness of 2.25 mm, and the effective absorption bandwidth (lower than −10 dB) is up to 6.29 GHz (11.71–18 GHz) covering the whole Ku band. We believe that our work provides an idea for the design of high-performance absorbing composite materials. [ABSTRACT FROM AUTHOR]

Transparent and flexible metamaterial absorbers can provide solutions for electromagnetic compatibility and electromagnetic radiation pollution. They also play key roles in platforms with optical windows that require low detectability and immunity to electromagnetic interference. Due to the lack of active adaptability to complex electromagnetic environments, early metamaterial absorbers need to be redesigned and manufactured once the application scenarios change. The new two-dimensional material graphene provides a practical technical approach for the realization of transparent tunable absorbers. In this work, we propose a polarization-insensitive dual-tunable microwave absorber based on graphene metasurface. By controlling two separate bias voltages applied to patterned graphene or continuous graphene, independent dynamic regulation of electromagnetic wave absorption frequency and amplitude is achieved. It also possesses the features of optical transparency and flexibility. The measurement results show that the absorption frequency can be shifted from 9.8 to 11.3 GHz, the peak absorption rate at each absorption frequency remains above 99.6%, and the reflection amplitude modulation can be achieved simultaneously at each absorption frequency. The proposed absorber integrates multiple modulation functions for electromagnetic waves, and the overall structure is optically transparent and flexible. Therefore, it can contribute to many practical wave absorbing applications. [ABSTRACT FROM AUTHOR]

Realization of microwave-absorbing materials with "small thickness, light weight, broad bandwidth, and low reflectivity" is an invariable topic. In this paper, Sm2Fe14BHx/polyurethane (SFBH/PU) composites with planar anisotropy were prepared by reduction–diffusion (R/D) and water bath hydrogenation (WBH) process. A minimum reflection loss (RL) value reaches −59.7 dB at the perfect matching frequency of 13.79 GHz with a thickness of only 1.035 mm. Compared with unhydrogenated SFB, the bandwidth and reflectivity are significantly improved. It is mainly attributed to the fact that introduction of hydrogen atoms effectively modulates the electromagnetic parameters and increases the Snoek limit ((μ i − 1) f r) , which leads to the improvement of the high-frequency microwave absorption performance. In addition, the bandwidth equation is derived and simplified from the perspective of the reflected wave at the interface, which is in good agreement with the measured results. [ABSTRACT FROM AUTHOR]

The research and development of absorbing materials with high absorbing capacity, wide effective absorption bandwidth, and lightweight has always been interesting. In this research, a facile hydrothermal method was used to prepare MnFe2O4, and the grain size of MnFe2O4 decreased with increasing hydrothermal temperature. When the size of MnFe2O4 nanoparticles is less than 10 nm, its quantum size effect and surface effect make its electromagnetic microwave absorption performance greatly optimized. When the thickness of MnFe2O4-110 °C is 2.57 mm, the minimum reflection loss (RLmin) is −35.28 dB. Based on this, light porous diatomite and a three-dimensional polyaniline network are introduced. Diatomite is used as the base material to effectively reduce the agglomeration of MnFe2O4 quantum dots. The relatively high surface area introduced by a three-dimensional network of polyaniline promotes the orientation, interfacial polarization, multiple relaxation, and impedance matching, thereby generating further dielectric loss. Additionally, the magnetic properties of manganese ferrite and the strong electrical conductivity of polyaniline play an appropriate complementary role in electromagnetic wave absorption. The RLmin of MnFe2O4/PANI/diatomite is −56.70 dB at 11.12 GHz with an absorber layer thickness of 2.57 mm. The effective frequency bandwidth (RL < −10 dB) ranges from 9.21 to 18.00 GHz. The absorption mechanism indicates that the high absorption intensity is the result of the synergistic effect of impedance matching, conduction losses, polarization losses, and magnetic losses. [ABSTRACT FROM AUTHOR]

The rare earth alloy Y 2 Co 17 − x Ni x was prepared by a low-cost co-precipitation reduction-diffusion process, and its crystal structure, static magnetic properties, and microscopic morphology were systematically characterized. The effects of Ni doping with different contents on the electromagnetic parameters and wave absorption properties of Y 2 Co 17 − x Ni x /polyurethane(PU) compounds were researched in the frequency range of 0.1–18 GHz. The results show that the static magnetic properties and wave absorption properties change significantly with Ni doping, and the maximum reflection loss of Y 2 Co 14 Ni 3 /PU reaches − 89.7 dB at 2.9 mm thickness, and the maximum reflection loss peaks of Y 2 Co 17 /PU and Y 2 Co 16 Ni 1 /PU are at 1.316 and 1.515 GHz, which is at the center frequency of the L-band. With Ni doping, the effective absorption bandwidth of the compounds at a frequency above 3 GHz is greatly increased. The physical factor in the bandwidth calculation was modified, and the effective absorption bandwidth of the material was calculated theoretically, and the error was less than 5 % compared with the experimental value. [ABSTRACT FROM AUTHOR]

With the application of low frequency radar and the demand for stealth of high temperature resistant components, it is increasingly urgent to develop absorbing materials with both low frequency and high temperature resistant properties. Here, we successfully prepared various carbon/polyimide composites as low-frequency electromagnetic wave (EMW) absorbing materials by simple blending method. The well-designed mesh lap structure introduces a large amount of free space, further optimizing the impedance matching of the material. At the same time, the multiple loss mechanism formed by the combination of carbon black dominated polarization and carbon nanotube dominated conductive loss enhances the loss of incident EMW. The results showed that only 10 wt% filler loading of the CB/CNT@PI is achieved in the low frequency range (1–4 GHz) with a minimum reflection loss strength of –18.3 dB, which has obvious advantages compared with other works in recent years. This study provides a way for the design and preparation of resin-based absorbing materials. [ABSTRACT FROM AUTHOR]

This study introduces a cost-effective and eco-efficient method for fabricating an advanced microwave absorber using a layer-by-layer rGO and SiO 2 structure. The rGO/SiO 2 composite, synthesized via modified Hummer's and Stöber methods, demonstrates remarkable microwave absorption properties. The resultant porous structure, characterized by an S BET of 294.89 m2/g, enables multiple reflections and scatterings of electromagnetic waves. At a sample thickness of 3.8 mm, the material achieves a reflection loss (RL) of −47.43 dB at 12.56 GHz and an effective absorption bandwidth (EAB) of 11.04 GHz. For a 6 mm thick sample, an exceptionally high EAB of 12.72 GHz is observed, maintaining a high RL of −42.32 dB. These results demonstrate that the rGO/SiO 2 material is a promising candidate for applications in electromagnetic wave absorption, offering a simple, scalable solution for mitigating electromagnetic pollution and enhancing military stealth technologies. [ABSTRACT FROM AUTHOR]

Strong absorption and large bandwidth are two contributors to material's electromagnetic wave absorbing performance. While spinel ferrite materials have garnered extensive attention in the realm of microwave absorption, their relatively low conductivity remains a practical challenge. In this work, NiCo 2-x Fe x O 4 (x = 0, 0.04, 0.06 and 0.08) precursor was prepared by hydrothermal and after-sintered method. It was found that Fe doping exhibit excellent EM absorption properties. Specially, when the Fe content is 0.08, the maximum reflection loss −48.90 dB at 15.40 GHz and the maximum effective bandwidth 4.20 GHz are achieved. More importantly, the absorption frequency can be broadened from Ku to C band even to S band with proper adjusting Fe content. Doping with Fe enhances conduction loss and make a significant contribution to dielectric loss, as a result, the impedance matching degree of the Fe-NiCo 2 O 4 composite is influenced by the synergistic effect of its dielectric and magnetic properties. This work provides a simple way for enhancing the microwave absorption capabilities of ferrite materials and provides insight into understanding conduction loss in microwave absorption. [ABSTRACT FROM AUTHOR]

Vacancy engineering presents an appealing method for modifying the electronic structure of spinel architectures. However, based on well-defined vacancy concentrations, how to design anionic vacancies to modulate electromagnetic parameters as well as electromagnetic wave absorption (EMA) properties is less studied. Here, NiCo 2 Se 4 spinel structures were prepared using different selenization methods, and the Se vacancy defect concentration was controlled by changing the annealing temperature, thus regulating the EMA properties. Among them, the design of the hollow structure effectively enhanced the EMA performance. Moreover, the increase of Se vacancy concentration increases the conductivity loss while regulating the electronic structure, and also acts as an unsaturated site to induce the formation of dipoles to optimize the polarization loss. The effective absorption bandwidth (EAB) of NiCo 2 Se 4 -130 reaches 8.48 GHz at 2.4 mm at the highest Se vacancy concentration. This work establishes a direct relationship between vacancy concentration and the electromagnetic wave dissipation capability, offering valuable insights for the development of advanced EMA materials. [ABSTRACT FROM AUTHOR]

This study reports on the synthesis and electromagnetic wave-absorbing properties of Ag/Fe 3 O 4 /SiO 2 under various magnetic field intensities. The nanocomposites were prepared via a solvothermal method followed by a Stober proces, during which uniform magnetic fields were applied to induce the formation of one-dimensional nanochain structures. Results indicate that the Ag/Fe 3 O 4 /SiO 2 exhibit enhanced wave-absorbing capabilities under strong magnetic fields. Specifically, at a magnetic field of 600 mT, the composite achieves a minimum reflection loss value of −48.61 dB, accompanied by a broad effective absorption bandwidth. Furthermore, the microwave absorption performance of samples oriented horizontally along the circumference surface during preparation shows a significant improvement compared to non-oriented samples. It is attributed to the optimized electromagnetic wave transmission pathways and improved electrical conductivity and magnetic loss capabilities facilitated by the nanochain structures. Specifically, the nanochains effectively lengthen the wave propagation distance, promote charge migration, and intensify natural and exchange resonance effects. This research not only broadens the design paradigm for electromagnetic wave-absorbing materials but also offers novel strategies for their development. [ABSTRACT FROM AUTHOR]

This paper introduces a broadband electromagnetic wave absorber with characteristics of polarization-independence and wide-angle stability based on resistive films with a three-dimensional (3D) configuration. The absorber consists of a 3D dielectric substrate array covered by a resistive film, which not only broadens the operation frequency band but also improves the absorption with large incidence angles. Simulated results indicate that the absorber achieves wideband absorption with over 90% absorptivity in the frequency range of 5.7–41.8 GHz, corresponding to a relative absorption bandwidth of 152%. Due to the high symmetry of the structure, the absorber is insensitive to polarization angles. Moreover, the presented design maintains wave absorption greater than 90% when incidence angle reaches 70∘ due to its 3D structure that ensures high absorption for wide incidence angles. The mechanism of this structure is investigated through surface current and power consumption distribution, while optimization parameters are analyzed for achieving the desired bandwidth. This absorber has the advantages of wide-band absorption and excellent stability under oblique incidence angles, making it potentially useful in applications such as electromagnetic shielding and energy harvesting. [ABSTRACT FROM AUTHOR]

BaTiO 3 is a promising electromagnetic waves (EMWs) absorption material due to its chemical stability and large dielectric constant. However, the high reflection coefficient of pure BaTiO 3 at high frequencies reduced its EMWs absorption capacity. To resolve the issue, BaTiO 3 /expanded graphite (EG) hybrids were successfully synthesized by high-energy ultrasound assisted heat treatment technology. The combination of BaTiO 3 particles and layered EG formed three-dimensional (3D) heterostructure of BaTiO 3 /EG hybrids, which optimized the impedance matching. Abundant conductive network enhanced interfacial polarization, numerous interface defects and multiple reflections together promoted the attenuation of EMWs. At the molar ratio of 0.2:0.8 between BaTiO 3 and EG, the BaTiO 3 /EG sample with 1.5 mm match thickness displayed −100.6 dB of minimum reflection loss (RL min) and 5.9 GHz of effective absorption bandwidth (EAB). In addition, the ceramic character of BaTiO 3 /EG hybrids endowed them excellent high-temperature stability. [ABSTRACT FROM AUTHOR]

In virtue of mutually exclusive stealth mechanisms, effectively protecting from infrared detection and attenuating microwaves through composition and structure design remains a formidable challenge. To achieve high-efficiency infrared/radar compatible stealth, in this work, 0D magnetic Co nanoparticles were successfully in situ grown onto the renewable biomass chitosan-based 3D porous carbon skeletons via facile liquid reaction, freeze-drying, and calcination method. Herein, the as-prepared Co/C hybrid aerogels exhibit dielectric and magnetic coupling network, and the relevant infrared/radar compatible stealth property can be regulated by adjusting the addition amount of Co salt. The minimum thermal conductivity value reached 0.095 W m−1 K−1 at 60 °C, and the lowest infrared emissivity of 0.717 in the 8–14 μm band was also achieved. Furthermore, the minimum reflection loss (RL min) value of −44.70 dB at a relatively thin thickness of 1.35 mm and the maximum effective absorption bandwidth (EAB) of 5.45 GHz at only 1.5 mm appeared in the optimal Co/C hybrid aerogel with the most appropriate Co content. Compared with perfect conductive layer (PEC), the simulated radar cross section (RCS) signals of Co/C composites covered PEC have been significantly reduced by 18.44 dB m2 at the scanning angle of 80°. This study inspires the exploration of the elaborate design strategy and facile construction method for environment-friendly infrared/radar compatible hybrid aerogels in the future. In this work, dielectric and magnetic coupling network design strategy was proposed to achieve cobalt salt/chitosan derived Co/C hybrid aerogels, providing inspiration and reference for the development of biomass derivatives radar-infrared compatible stealth materials. [Display omitted] [ABSTRACT FROM AUTHOR]

As typical dielectric materials, transition metal compounds have a broad potential in the field of stealth, but their application is still hampered by poor conductivity. In this study, based on the mechanism of electrostatic self-assembly of heteropolyacids and organic ligands, the electrostatic structures obtained after the introduction of different heteropolyacids into the conductive phase pyrrole are carbonized. On the one hand, the as-prepared transition metal compounds/carbon matrix nanocomposites produce synergistic effects and optimize impedance matching, and on the other hand, the formation of the abundant heterogeneous interfaces as well as the doping of the N, P heteroatoms induce the generation of interfacial polarisation and dipole polarisation, all of which provide the opportunities to produce composites with enhanced electromagnetic wave absorption properties. Unsurprisingly, the best synthesised sample, Mo 2 C/W 2 C/NPC, exhibits a significantly improved electromagnetic wave absorption performance, with an effective bandwidth of 5.7 GHz at a matched thickness of 2.5 mm, where the minimum reflection loss value of −54.5 dB is also achieved. The total effective bandwidth of the Mo 2 C/W 2 C/NPC-35 wt% is up to 10.5 GHz (7.3–17.8 GHz) via adjusting the matching thickness in the range of 1.7–3.5 mm. Therefore, this study reflects that dual transition metal compound/carbon based composite wave-absorbing materials provide a new material basis for the construction of high-performance absorption materials. [ABSTRACT FROM AUTHOR]

The advancement of military technology, 5G communication, and electronic equipment has increased the demand for efficient electromagnetic wave absorption materials. Calcium manganate (CaMnO 3) is a commonly used dielectric absorber due to its excellent dielectric polarization effect. However, traditional ceramic materials like CaMnO 3 have low conductivity, making it difficult to achieve impedance matching and electromagnetic loss simultaneously. In this work, to address this issue and create ideal wave-absorbing materials, one-dimensional La-doped CaMnO 3 materials were synthesized using a simple biological template hydrothermal method. By studying the relationship between doping content and electromagnetic parameters, it was found that the La-doped CaMnO 3 material exhibited excellent electromagnetic wave absorption properties, with a minimum reflection loss (RLmin) of −73.62 dB and a maximum effective absorption bandwidth of 3.3 GHz in the X-band. The introduction of La elements, which have different electronegativities from Ca ions, altered the electron cloud distribution in the sample, leading to the formation of electric dipoles that disrupt charge distribution and dissipate electromagnetic waves. The dielectric loss in fibrous La-doped CaMnO 3 is mainly due to interfacial polarization. The fibrous structure allows for increased contact area with the air medium, while the porous structure introduces air bubbles that alter the dielectric properties between the sample and the air medium. This not only enhances impedance characteristics to some extent but also triggers interfacial polarization. Both of these factors help improve the material's ability to absorb electromagnetic waves. The successful creation of this one-dimensional absorbing material opens up possibilities for developing new one-dimensional absorbing materials using a straightforward method. [ABSTRACT FROM AUTHOR]

In order to solve the increasingly serious electromagnetic wave pollution, the preparation of high-performance electromagnetic wave absorbing (EWA) materials has been very urgent. High-entropy ceramics have a good prospect in the field of EWA materials due to the unique effect brought by its multi-component elements. Therefore, in this study, the composition of high-entropy ceramics was designed by utilizing the Goldschmid tolerance factor. Then the high-entropy perovskite Ba(Zn 0.2 Yb 0.2 Ta 0.2 Nb 0.2 V 0.2)O 3 ceramic (BZO) with high EWA performance was prepared by high-temperature solid-phase method. The EWA mechanism of the material was explored based on the phase composition, microstructure and electromagnetic parameters of the samples. Good impedance matching and better attenuation ability were obtained for BZO-1100 due to the crystallographic transition and interface increase. As a result, BZO-1100 achieves excellent EWA performance at a thickness of 2.12 mm, with a minimum reflection loss (RL min) of −54.09 dB and an effective absorption bandwidth (EAB) of 2.81 GHz in the X-band. In addition, the possibility of the practical application of the BZO high-entropy ceramics is verified by electric field distribution simulations and RCS simulations. This study provides a valuable reference for the design of high-performance high-entropy perovskite ceramic absorber materials. [Display omitted] [ABSTRACT FROM AUTHOR]

The construction of a three-dimensional heterojunction interface and chemical modification can significantly enhance the electromagnetic wave absorption capability of composites. In this study, we successfully synthesized a covalently bonded carboxyl functionalized Ti 3 C 2 T x (CFTC) complexed with Amino-Fe 3 O 4 (CFTC-Fe 3 O 4) through an amidation reaction followed by a post-annealing process, resulting in the homogeneous dispersion of NH 2 –Fe 3 O 4 between CFTC layers. The innovative approach establishes a multi-layer heterojunction interface that effectively encapsulates magnetic nanoparticles with CFTC, thereby enhancing both interface polarization, defect polarization and conduction loss. The magnetoelectric synergy between CFTC and NH 2 –Fe 3 O 4 improves impedance matching and endows the composites with exceptional electromagnetic wave absorption capabilities. Notably, the absorbers demonstrate an impressive minimum reflection loss of −50.95 dB at a thickness of 1.56 mm when the mass ratio of CFTC to NH 2 –Fe 3 O 4 is 1:1 (designated as CTNF-2), accompanied by an effective absorption bandwidth of 4.76 GHz (12.32–17.08 GHz). This study presents a novel approach to developing highly efficient MXene-based absorbing materials through chemical modifications. [ABSTRACT FROM AUTHOR]

The pressing need for the enhancement of stealth materials that are harmonious with state-of-the-art military equipment is critical, as it plays a pivotal role in bolstering the survivability and operational capabilities of advanced military technology. This research offers a straightforward approach for fabricating a gradient triple-layer absorber utilizing a Cu 2 O/ h -BN nanocomposite and FeCoNi magnetic compounds, characterized by reduced thickness, designed for X-band wave spectrum attenuation purposes. The primary objective of this study is to examine the electromagnetic wave absorption characteristics of single-layer samples and subsequently develop a triple-layer gradient sample with distinct electromagnetic wave stealth features based on the findings. Optimal performance was observed in the gradient sample, where Cu 2 O/ h -BN nanocomposite with 20 and 10 wt% was incorporated as a matching layer with thicknesses of 0.5 and 0.5 mm, respectively, and FeCoNi with 20 wt% was employed as an absorbing layer with a 0.4 mm thickness, surpassing the performance of the other samples. The optimal sample achieves a dissipation loss of −45.6 dB and a bandwidth of 2.9 GHz, all while maintaining a total thickness of just 1.4 mm. Facilitating multiple heterogeneous interfaces among layers, substances, and the synergistic interaction between constituent elements and layers' thickness and arrangement enable this gradient configuration to demonstrate exceptional performance in radar stealth compatibility. [ABSTRACT FROM AUTHOR]

High-performance SiC aerogels are sought after for their superior thermal insulation and absorption properties, especially in applications such as electromagnetic stealth for aero engines and high-temperature radar stealth. However, achieving SiC aerogel with both temperature resistance and strong wave absorption while controlling their properties remains a significant challenge. This study investigates the influence of reactant concentrations on the structure, thermal insulation, and absorption performance of SiC aerogels synthesized via the sol-gel method. The aerogel synthesized with a n(C):n(Si) ratio of 1:2 showed superior thermal insulation. Additionally, it showed excellent electromagnetic wave absorption, with a minimum reflection loss of −53.80 dB at 6.16 GHz and a maximum effective absorption bandwidth of 3.10 GHz at a thickness of 2.40 mm. Furthermore, the maximum compressive strength of C/SiC@SiC reached 0.98 MPa, a notable improvement of 81.48 % compared to the pristine C/SiC matrix. The maximum effective absorption bandwidth of C/SiC@SiC was increased to 6.06 GHz at 2.35 mm, and the surface center temperature decreased from 183.1 °C for C/SiC to 130.1 °C for C/SiC@SiC. Overall, this study offers valuable insights into the development of advanced absorption and thermal insulation materials, providing a foundation for further research and innovation in this field. [ABSTRACT FROM AUTHOR]

Among magnetic materials, spinel ferrite is regarded as a potentially excellent low-frequency electromagnetic wave (2–8 GHz) absorber with low magnetic resonance frequency. However, spinel ferrite manufactured by conventional methods tends to be shape-isotropic, making the magnetic loss of the absorber quite weak under the Snoek Limit. Accordingly, our work prepares a highly shape-anisotropic Ni 0.5 Mn 0.5 Nd 0.04 Fe 1.96 O 4 ferrite (H-NMNF) with multiple crystal structures (mainly decahedral) via a novel sol-gel method. Compared with the uniformly laminated Ni 0.5 Mn 0.5 Nd 0.04 Fe 1.96 O 4 ferrite prepared by the conventional sol-gel method (C-NMNF), the natural resonance loss of H-NMNF is dramatically improved owing to the enhanced shape-anisotropic effect resulting in the Snoek Limit being breached. The results show that H-NMNF achieves the maximum effective absorption bandwidth (EAB max) of 6.64 GHz (2.96–9.6 GHz) at a thinner matching thickness of 5.1 mm, covering approximately the entire low-frequency band. This study provides methodological guidance for manufacturing magnetic loss materials with high shape-anisotropy and a new strategy for fabricating ultra-broadband, low-frequency magnetic electromagnetic wave absorbers. [ABSTRACT FROM AUTHOR]

Polymer-derived SiBCN ceramic aerogels have attracted extensive attention in recent years due to the excellent electromagnetic wave absorption and thermal insulation properties. With these merits, SiBCN aerogels are promising for the application of high-speed vehicles requiring thermal and electromagnetic shielding. However, the brittleness and poor mechanical property of SiBCN aerogel seriously hinder its practical applications. In this paper, SiBCN/SiBCN nf composite ceramic aerogels with enhanced mechanical property were prepared by combining electrospinning technique with simultaneous pyrolysis process of polyborosilane (PBS) fibers and precursor aerogels. The effect of varying fiber content on the density, mechanical property, thermal insulation as well as microwave absorption performance of the composite aerogel was investigated. In addition, the underlying toughness mechanism of the SiBCN/SiBCN nf composite ceramic aerogel was elucidated. The compressive strength of the SiBCN/SiBCN nf composite aerogel increased from 0.29 MPa to 1.62 MPa. Importantly, while the mechanical strength of the composite aerogel increased by about 5.5 times, SiBCN/SiBCN nf aerogel still exhibits low density of 0.105 g/cm³, low thermal conductivity of 0.048 W/mK and a minimum reflection loss (RL min) of −20 dB. Owing to the integration of electromagnetic wave (EMW) absorption and thermal insulation properties, SiBCN/SiBCN nf aerogels pave the way for the construction of thermal and electromagnetic shielding material for high-speed vehicles. [ABSTRACT FROM AUTHOR]

Decorating the CNTs with dielectric loss material is an effective means of enhancing electromagnetic wave absorption properties. In this work, we synthesized high dielectric loss NiCo 2 O 4 nanoparticles on CNTs through hydrothermal method. By adjusting hydrothermal time, the NiCo 2 O 4 /CNTs with different NiCo 2 O 4 content were obtained. The nucleation and growth of NiCo 2 O 4 nanoparticles would cause a lot of defects and heterogeneous interfaces on CNTs, which influences the conduction loss and polarization loss of CNTs. Therefore, adjusting the content of NiCo 2 O 4 in CNTs is an efficient path to enhance its absorbing performance. When the content of NiCo 2 O 4 is 45.05 wt%, the reflection loss of NiCo 2 O 4 /CNTs reaches −43.2 dB, and the effective absorption bandwidth can be up to 3.3 GHz. It proves that NiCo 2 O 4 /CNTs has potential to be a high quality absorbing agent. [ABSTRACT FROM AUTHOR]

A novel high-temperature resistant calcium aluminate cement-based electromagnetic wave absorption composites were prepared using carbon fibers, Al 2 O 3 hollow spheres, and expanded polystyrene spheres (EPS). EPS, as a pore forming agent, was oxidized as to form pores at high temperatures. The effects of carbon fibers doping levels and various high-temperature treatment on the permittivity of the composites from 0.3 to 18 GHz were investigated in detail. Additionally, a high-temperature resistant porous cone cement-based electromagnetic wave absorption structure was designed, and its microwave absorption mechanism was explored. The findings indicated that the permittivity of electromagnetic wave absorption composites exhibited stability even after undergoing high-temperature treatments below 350 °C, while experiencing a decrease at 500 °C. Following cyclic treatments at temperatures of 200 °C and 350 °C, the cone calcium aluminate porous cement-based composites still exhibited outstanding electromagnetic wave absorption performance, achieving reflection loss (RL) bandwidths below −30 dB of 17.4 GHz and 17.2 GHz, respectively, within the frequency range of 0.3–18 GHz. Furthermore, the RL of the composite from 4 to 18 GHz after 500 °C treatment remained less than −50 dB. Thus, present work associated with the materials and structural design of calcium aluminate porous cone cement-based composites provided a potential insight into the high-temperature electromagnetic wave absorption engineering applications. [Display omitted] • Cone cement-based wave-absorbing composites exhibit excellent broadband absorbing properties. • The cone composites maintain stable electromagnetic properties after cyclic treatment at a temperature of 350 °C. • The cone exhibits a RL below −50 dB in 4–18 GHz after treatment at 500 °C. [ABSTRACT FROM AUTHOR]

Defects and defective technology are considered to be an efficient method for improving electromagnetic wave (EMW) absorption performance. In this study, W-type barium hexaferrite BaCo2Fe16O27 (BCFO) composites with Sm doping were synthesized by a simple ball milling and subsequent annealing process. The phase structure characteristics, magnetic properties, and microwave absorption performance of the BCFO composites were systematically investigated. Specifically, Sm-doped and annealed BCFO composites demonstrated outstanding microwave absorption characteristics because of the efficient interaction between ideal impedance matching and large dielectric loss, specifically, a minimum reflection loss (RL) value of −28.57 dB at 8.5 GHz with 3 mm thickness. Moreover, a broad effective absorption bandwidth reaches 11 GHz, covering the range of 7–18 GHz. It is believed that defects and vacancies induced by Sm doping or annealing in the Ar atmosphere may be an effective means for enhancing microwave absorption, and related mechanisms are discussed in detail. [ABSTRACT FROM AUTHOR]

Metal single‐atoms implanted on nitrogen‐doped carbon matrices (M‐NxCs) can effectively adjust local surface electrons and polarization relaxation through coordination structures to significantly enhance the electromagnetic wave (EMW) absorption properties of the materials. However, the precise construction of the geometric and electronic structures of metal single atoms and the discovery of the structure‐absorption relationship at the atomic level confront a huge challenge. Herein, this work summarizes the latest progress in metal single‐atom engineering of EMW absorbing materials via a comprehensive analysis of M‐NxCs in terms of design principles, modulation strategies, and structure‐performance correlations. Subsequently, it highlights the recent progress of several typical M‐NxCs as the EMW absorbing materials, aiming to achieve a complete understanding of the physical effects and atomic‐level absorption mechanisms. Finally, current key challenge and future directions of M‐NxCs are presented by focusing on the electromagnetic functional materials. This work provides new insights for the development of atomically dispersed absorbing materials for efficient electromagnetic response functionalities. [ABSTRACT FROM AUTHOR]

Thermochemical conversion is a highly effective method for upgrading organic solid wastes into high‐value materials, contributing to carbon neutrality and peak, carbon emission goals. It also serves as a pathway to develop energy‐efficient electromagnetic wave absorbing (EMWA) materials. In this study, fish skin to successfully in situ nitrify Prussian Blue into Fe3N under external thermal driving condition, resulting in high saturation magnetization is utilized. The resulting Fe3N@C demonstrates outstanding EMWA property, achieving a minimum reflection loss of −71.3 dB. Furthermore, by introducing cellulose nanofiber, a portion of the iron nitride is transformed into iron carbide, resulting in Fe3C/Fe3N@C. This composite exhibits enhanced EMWA properties owing to wider local charge redistribution and stronger electronic interactions, achieving an effective absorption bandwidth (EAB) of 6.64 GHz. Electromagnetic simulations and first‐principles calculations further elucidate the EMWA mechanism, and the maximum reduction value of the radar‐cross section reached 37.34 dB·m2. The design of multilayer gradient metamaterials demonstrated an ultra‐broadband EAB of 11.78 GHz. This paper presents an efficient strategy for atomic‐level biomass waste utilization to prepare Fe3N, provides novel insights into the conversion between metal nitrides and metal carbides, and offers a promising direction for the development of advanced EMWA materials. [ABSTRACT FROM AUTHOR]

In this work, N-doped and oxygen vacancy-rich NiCo2O4/NiO/Co3O4 composites are synthesized by the direct calcination method. Noticeably, by changing the additive concentrations of urea dissolved in DMF (N–N dimethylformamide), the electromagnetic wave (EMW) absorption abilities of NiCo2O4/NiO/Co3O4 composite effectively. A maximum reflection loss (RLmax) value at 12.94 GHz for a 2.8 mm thick sheet is −29.76 dB, while its effective absorption bandwidth (RL < −10 dB) reaches 4.21 GHz. In-depth research of possible mechanisms of EMW absorption enhancement. Owing to its simple preparation method and superb EMW absorption properties, the NiCo2O4/NiO/Co3O4 composites have a chance to be suitable candidates for high-property EMW absorbers. [ABSTRACT FROM AUTHOR]

In this work, SiBCN fibers with excellent electromagnetic wave (EMW) absorption performance were fabricated using electrospinning technology, followed by curing, pyrolysis, and heat treatment. Microstructure evolution and EMW absorption performance of SiBCN fibers after heat treatment at 1200–1600 °C were investigated. After heat treatment at 1200 °C, the conductive turbostratic C was precipitated from amorphous SiBCN fibers, resulting in minimum reflection loss (RL min) reaching −63 dB and efficient absorption bandwidth (EAB) reaching 5.2 GHz. While turbostratic C and nano-SiC grains were simultaneously precipitated from SiBCN fibers heat treated at 1400 °C, and the RL min reached −67 dB. The excellent EMW absorption performance of SiBCN fibers was mainly attributed to the synergistic effect of conductive loss, dipole polarization, and interfacial polarization. This work can guide the fabrication of high-performance EMW-absorbing ceramic fibers. [ABSTRACT FROM AUTHOR]

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Telecommunication Engineering is the property of Telecommunication Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights Basalt fibers (BF) are widely used in shipbuilding due to their excellent corrosion resistance. However, basalt fibers do not possess good electromagnetic wave absorption properties, failing to meet the stealth performance requirements of ships. Therefore, this study focuses on basalt fiber composite materials, modifying the matrix by adding different amounts of carbon nanotubes (CNTs). Carbon nanotube‐basalt fiber‐epoxy resin absorptive composite materials are prepared using Vacuum Assisted Resin Transfer Molding (VARTM) technique to investigate the influence of CNT content on the materials. Samples with added CNTs can effectively absorb electromagnetic waves in the low‐frequency range, reducing surface reflectivity. In the high‐frequency range, the impedance matching value of the samples initially increases slowly. When the CNT content reaches 1.5 wt%, at a thickness of 2.5 mm and a frequency of 9.6 GHz, the minimum reflection loss of the sample is −14.40 dB, with an effective absorption bandwidth of 0.7 GHz. Also, CNTs can enhance the mechanical properties of composite materials. With increasing CNT content, both the bending strength and tensile strength of the composite materials are improved. When the CNT content reaches 1.5 wt%, the average tensile fracture strength of the material increases by 21%, and the bending strength increases by 9%. Enhanced low‐frequency electromagnetic wave absorption from CNTs and reduced polarization. Improved impedance matching and attenuation at high frequencies with CNTs. Significant enhancement in flexural and tensile strength due to CNTs and basalt fibers. [ABSTRACT FROM AUTHOR]

Surface modulation strategies have spurred great interest with regard to regulating the morphology, dispersion and flexible processability of materials. Unsurprisingly, customized modulation of surfaces is primed to offer a route to control their electronic functions. To regulate electromagnetic wave (EMW) absorption applications by surface engineering is an unmet challenge. Thanks to pyrolyzing surface-anchored metal-porphyrin, here we report on the surface modulation of four-nitrogen atoms-confined single metal site on a nitrogen-doped carbon layer (sM(N4)@NC, M = Ni, Co, Cu, Ni/Cu) (sM=single metal; NC= nitrogen-doped carbon layer) that registers electromagnetic wave absorption. Surface-anchored metal-porphyrins are afforded by attaching them onto the polypyrrole surface via a prototypical click reaction. Further, sM(N4)@NC is experimentally found to elicit an identical dipole polarization loss mechanism, overcoming the handicaps of conductivity loss, defects, and interfacial polarization loss among the current EMW absorber models. Importantly, sM(N4)@NC is found to exhibit an effective absorption bandwidth of 6.44 and reflection loss of −51.7 dB, preceding state-of-the-art carbon-based EMW absorbers. This study introduces a surface modulation strategy to design EMW absorbers based on single metal sites that enable fine-tunable and controlled absorption mechanism with atomistic precision. In this work, Cheng et al. report a unique electromagnetic wave (EMW) dipole-dominated loss model excluding other redundant EMW loss, opening an avenue for exploring future academic studies and industrially applicable EMW absorbing materials. [ABSTRACT FROM AUTHOR]

2D materials with ultrathin structure, high specific areas, and excellent mechanical properties provide potentials to enhance the electrical, mechanical, and chemical properties of metals. In particular, MXene with different compositions, abundant surface terminations, high electrical conductivity has good affinity with some metals such as Al, Li, Na as well as can be uniformly dispersed in the metals. Moreover, the above unique features enable the MXene–metal hybrids with diversified functions. In this review, the current advanced studies in the topic of MXene–metal hybrids are summarized. The properties of MXenes such as mechanical properties, electrical conductivity, wettability, and surface properties of MXenes are first reviewed. Subsequently, different synthetic approaches including physical, metallurgy, electrochemical, and wet‐chemical routes are screened. By harnessing the above unique features, MXene could enhance the electrical, mechanical, and chemical properties of the hybrids, and their application such as energy storage devices, anticorrosion coating, functional structural materials, electromagnetic wave absorption are highlighted. Finally, an outlook on the in‐operando characterization techniques is provided to clarify the strengthening mechanism of MXenes in metals, tailoration of interface between MXenes and metals, and urgent need for industrial‐scale manufacture of MXene–metal hybrids. [ABSTRACT FROM AUTHOR]

Molybdenum carbide (MoC) integrated into a carbon matrix, known for its robust interfacial polarization, emerges as a promising ultra‐lightweight EM wave absorber. However, the fabrication of such materials remains a formidable challenge. Herein, a facile and scalable strategy for preparing MoC‐incorporated carbon matrix employing ZnMo‐HZIF foam material through ball‐milling foaming and calcination process as a promising electromagnetic wave materials (EWAMs). In detail, the 3D foam structure reaches impedance matching, and heterogeneous interfaces of N‐doped MoC‐incorporated carbon material (MoC/NC) promote the dipolar/interfacial polarization, confirmed by the hologram. Mo defects induced the charge transfers, displaying an enhanced interfacial polarization. At 15 wt.%, the minimum reflection loss of the obtained sample at 2.5 mm reaches −47.56 dB, and the effective absorption bandwidth spans 4.40 GHz, nearly covering the full X band. Additionally, the assembly device testing demonstrates their excellent self‐cleaning, heat‐insulation, flame retardancy, and infrared stealth properties. This work presents a new perspective on the synergistic effect of structure and components on electromagnetic wave absorption performance and provides a new approach for preparing lightweight and high‐performance MOF‐based electromagnetic wave absorbing materials. [ABSTRACT FROM AUTHOR]

In this paper, BaFe12O19/Ni0.5Mn0.5Fe2O4@PANI core‐shell nanocomposites were synthesized with different ferrite/PANI ratios. The Ferrite nanoparticles were prepared by the auto‐combustion sol–gel method. Chemical oxidative polymerization of aniline in acidic solution along with adding ferrite nanoparticles to the composition was used for the synthesis of nanocomposites. The product then was studied by X‐ray diffractometer)XRD(, field emission scanning electron microscope (FE‐SEM), transmission electron microscope (TEM), and Fourier transform infrared spectroscopy (FTIR) analyses. The magnetic properties of samples were investigated with vibrating sample magnetometer (VSM). Also, nanocomposite samples were examined in terms of the ability to absorb microwaves. Using Vector Network Analyzer (VNA). the reflection loss (RL) of nanocomposites was measured at frequencies between 2 and 18 GHz. The minimum reflection loss (RLmin) was obtained at −36.98 dB at the frequency of 13.8 GHz with an effective absorption bandwidth of 4.87 GHz for the sample with the equal ratio of ferrite/PANI. Synthesized nanocomposite as an effective compound has very high reflection loss in a wide frequency range. Highlights: Thermal stability is improved by adding ferrite nanoparticles to polyaniline.The polymer shell reduces the magnetic properties of ferrite nanoparticles.There is a strong exchange coupling between hard and soft ferrite.Ferrite/polymer ratio of 1:1 has the lowest amount of reflection loss.In the X and Ku band, magnetic loss is mainly caused by eddy currents. [ABSTRACT FROM AUTHOR]

Construction of built‐in electric field (BIEF) in nanohybrids has been demonstrated as an efficacious strategy to boost the dielectric loss by facilitating oriented transfer and transition of charges, thus optimizing the electromagnetic wave absorption property. However, the specific influence of BIEF on interface polarization needs to explore thoroughly and the BIEF strength should be further augmented. Herein, several dielectric systems incorporated Mott–Schottky heterojunctions and hollow structures are designed and constructed, where bimetallic zeolitic imidazolate framework are employed to derive Cu‐ZnO Mott–Schottky heterojunctions, and hierarchical structures and BIEF are further enriched by introducing hollow structure and reduced graphene oxide. The well‐established “double” BIEF verified by theoretical calculation and hollow engineering can regulate the conductivity, and enhance the polarization relaxation effectively. Especially, there always coexisted both enhanced charge separation and reversed charge distribution in this “double” BIEF, boosting the interface polarization. Attributing to the synergy of well‐matched impedance and amplified dielectric loss, the obtained hybrids exhibited superior absorption (reflection loss of −46.29 dB and an ultra‐wide effective absorption bandwidth of 7.6 GHz at only 1.6 mm). This work proves an innovative model for dissecting dielectric loss mechanisms and pioneers a novel strategy to explore advanced absorbers through enhancing BIEF. [ABSTRACT FROM AUTHOR]

Highly efficient microwave absorbents and multilayer composite structures are crucial methods for enhancing electromagnetic wave (EMW) absorbent performance and broadening the bandwidth of materials. Herein, Ni-Fe/NBR microwave-absorbing composite sheets were prepared for the first time by uniformly dispersing Ni-Fe alloy fiber absorbers into a nitrile butadiene rubber (NBR) matrix using a mechanical mixing method. By varying the content and length of Ni-Fe fibers, thickness of Ni-Fe/NBR and blowing agent content (AC), a series of composites with low reflectivity and different frequency bands were obtained in the 2–18 GHz frequency. As a result, the single-layer NBR sheet with a Ni-Fe fiber content of 15% and fiber length of 3 mm can reach a minimum reflection loss (RLmin) of − 11.92 dB at a thickness of 2.7 mm. Secondly, it is noteworthy that double-layer stacked single-layer NBR absorbers can broaden the absorption bandwidth and improve the absorption effect. Furthermore, varying the positions of the upper and lower layers of sheet materials can yield disparate outcomes. The double-layer Ni-Fe/NBR absorber can achieve an RLmin of − 38.05 dB. Its effective absorption bandwidth (EAB) is 5.06 GHz in the C band and 3.44 GHz in the Ku band. This work provides new ideas for the design of efficient wave-absorbing flexible composites with structural functionalization. [ABSTRACT FROM AUTHOR]

Electronic equipment brings great convenience to daily life but also causes a lot of electromagnetic radiation pollution. Therefore, there is an urgent demand for electromagnetic wave-absorbing materials with a low thickness, wide bandwidth, and strong absorption. This work obtained a high-performance electromagnetic wave absorption system by adding conductive carbon spheres (CSs) to the CH3NH3PbI3 (MAPbI3) absorber. In this system, MAPbI3, with strong dipole and relaxation polarization, acts dominant to the wave absorber. The carbon spheres provide a free electron transport channel between MAPbI3 lattices and constructs interfacial polarization loss in MAPbI3/CS. By regulating the content of CSs, we speculate that this increased effective absorption bandwidth and reflection loss intensity are attributed to the conductive channel of the carbon sphere and the interfacial polarization. As a result, when the mass ratio of the carbon sphere is 7.7%, the reflection loss intensity of MAPbI3/CS reaches −54 dB at 12 GHz, the corresponding effective absorption bandwidth is 4 GHz (10.24–14.24 GHz), and the absorber thickness is 2.96 mm. This work proves that enhancing conduction loss and interfacial polarization loss is an effective strategy for regulating the properties of dielectric loss-type absorbing materials. It also indicates that organic-inorganic hybrid perovskites have great potential in the field of electromagnetic wave absorption. [ABSTRACT FROM AUTHOR]

Rational heterostructure design can bring interfacial polarization relaxation to significantly enhance the electromagnetic wave (EMW) absorption performance. However, intelligently building a homogeneous heterostructure with superior EMW absorption properties remains a great challenge. Herein, a typical conductive metal–organic framework Cu3(HHTP)2 (hexahydroxytriphenylene, HHTP) is delicately packed onto a polypyrrole (PPy) conductive polymer surface via a one‐step in situ polymerization approach. Results show that Cu3(HHTP)2 is well packed on the PPy surface to form an elegant Cu3(HHTP)2@PPy hybrids interfacial microstructure with a unique superiority regarding EMW absorption compared with single components of PPy and Cu3(HHTP)2. Interestingly, the interfacial microstructure of Cu3(HHTP)2@PPy hybrids can be tuned by adjusting the composition of the PPy and Cu3(HHTP)2, resulting in the improvement of impedance matching, conductive loss, and enhancement of interfacial polarization relaxation, endowing the optimization of the EM wave absorption properties of the Cu3(HHTP)2@PPy. The broad effective absorption bandwidth covers a range as broad as 6.68 GHz (11.00–17.68 GHz), which is higher than most reported metal‐organic frameworks (MOFs) and conductive polymer‐based EM absorbing materials. Herein, new insight for developing highly efficient EMW absorption materials through hybridized interfacial microstructure engineering is provided. [ABSTRACT FROM AUTHOR]

The revolution of millimeter‐wave (mmWave) technologies is prompting a need for absorption‐dominant EMI shielding materials. While conventional shielding materials struggle in the mmWave spectrum due to their reflective nature, this study introduces a novel EMI shielding film with ultralow reflection (<0.05 dB or 1.5%), ultrahigh absorption (>70 dB or 98.5%), and superior shielding (>70 dB or 99.99999%) across triple mmWave frequency bands with a thickness of 400 µm. By integrating a magnetic composite layer (MCL), a conductive patterned grid (CPG), and a double‐walled carbon nanotube film (DWCNTF), specific resonant frequencies of electromagnetic waves are transmitted into the film with minimized reflection, and trapped and dissipated between the CPG and the DWCNTF. The design factors for resonant frequencies, such as the CPG geometry and the MCL refractive index, are systematically investigated based on electromagnetic wave propagation theories. This innovative approach presents a promising solution for effective mmWave EMI shielding materials, with implications for mobile communication, radar systems, and wireless gigabit communication. [ABSTRACT FROM AUTHOR]

Structural design and interface regulation are useful strategies for achieving strong electromagnetic wave absorption (EMWA) and broad effective absorption bandwidth (EAB). Herein, a monomer‐mediated strategy is employed to control the growth of covalent organic framework (COF) wrapping flower‐shaped Gd‐doped FeNi3 (GFN), and a novel raspberry‐like absorbent based on biomimetic design is fabricated by thermal catalysis. Further, a unique dielectric‐magnetic synergistic system is constructed by utilizing the COF‐derived nitrogen‐doped porous carbon (NPC) as the shell and anisotropic GFN as the core. The electromagnetic parameters of the GFN@NPC composites can be tuned by adjusting the proportions of GFN and NPC. Off‐axis electron holography results further clarify the interface polarization and microscale magnetic interactions affecting the EMW loss mechanism. As a result, the GFN@NPC samples exhibit broad EMWA performance. The EAB values of all GFN@NPC composites reach up to 6.0 GHz, with the GFN@NPC‐2 sample showing a minimum reflection loss (RLmin) of −69.6 dB at 1.68 mm. In addition, GFN@NPC‐2 achieves a maximum radar cross–section (RCS) reduction of 29.75 dB·m2. A multi‐layer gradient structure is also constructed using metamaterial simulation to achieve an ultra‐wide EAB of 12.24 GHz. Overall, this work provides a novel bio‐inspired design strategy to develop high‐performance EMWA materials. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

SiC‐based porous ceramic wave‐absorbing materials have attracted much attention due to their excellent properties such as low density, high‐temperature resistance, and oxidation resistance. In this work, the impedance matching of SiC ceramics is improved by introducing Si3N4 wave‐transparent phase, and the dielectric loss capability of SiC ceramics is enhanced by introducing FeSi wave loss phase. To achieve a balance between impedance matching and absorption loss in porous ceramics, different molar contents of Al were introduced into FeSi to tailor electromagnetic parameters. The effects of introducing FeAlxSi1−x on the phase composition, microstructure, dielectric loss, and microwave absorption mechanism of SiC–Si3N4 porous ceramics were systematically investigated. When FeAl0.25Si0.75 is added, the minimum reflection loss of the porous ceramics is as low as −58.02 dB, and the flexural strength is as high as 87.23 MPa. The presence of Al promotes the transformation of the Si3N4 crystal and the generation of Al2O3. The introduction of FeAl0.25Si0.75 into SiC–Si3N4 has constructed "inductor–capacitor–resistance" microcircuit, which enhances polarization loss, conductivity loss, and magnetic loss, and realized the double enhancement of the mechanical and wave‐absorbing properties of porous ceramics. [ABSTRACT FROM AUTHOR]

Three-dimensional network structures of flower-like 1T/2H Molybdenum disulfide nanosheets anchored to carbon fibers were prepared, which exhibited satisfactory electromagnetic wave absorption properties, providing a path for the preparation of electromagnetic wave absorbing materials with wide effective absorption bandwidth. [Display omitted] • 3D 1T/2H MoS 2 /CNFs interconnected network structures were prepared; • Heterogeneous interfaces between CNFs and MoS 2 , 1T and 2H MoS 2 phase was built; • Excellent EM wave absorption with RL min of −42.26 dB and EAB of 6.48 GHz was obtained; • The EM wave absorption performance was proved by radar reflectance cross section simulation. With the wide application of electromagnetic waves in national defense, communication, navigation and home appliances, the electromagnetic pollution problem is becoming more and more prominent. Therefore, high-performance, and low-density composite wave-absorbing materials have attracted much attention. In this paper, three-dimensional (3D) network structures of flower-like 1T/2H Molybdenum disulfide nanosheets anchored to carbon fibers (1T/2H MoS 2 /CNFs) were prepared by electrostatic spinning technique and calcination process. The morphology and electromagnetic wave absorption properties were tuned by changing the content of flower-like MoS 2. The optimized 1T/2H MoS 2 /CNFs composite exhibits superior electromagnetic wave absorption with minimum reflection (RL min) of −42.26 dB and effective absorption bandwidth (EAB) of 6.48 GHz at 2.5 mm. Multi-facts contribute to the super performance. First, the uniquely designed nanosheet and 3D interconnected networks leads to multiple reflection and scattering of electromagnetic waves, which promotes the attenuation of electromagnetic waves. Second, the propriate content of CNFs and MoS 2 with different phase regulates its impedance matching characteristic. Third, Numerous heterogeneous interfaces existed between CNFs and MoS 2 , 1T and 2H MoS 2 phase results in interface polarization. Besides, the 1T/2H MoS 2 rich in defects induces defect polarization, improving the dielectric loss. Furthermore, the electromagnetic wave absorption performance was proved via radar reflectance cross section simulation. This work illustrates 1T/2H MoS 2 /CNFs is a promising material for electromagnetic absorption with wide bandwidth, strong absorption, low density, and high thermal stability. [ABSTRACT FROM AUTHOR]

Ultra-high temperature ceramics (UHTCs) are candidates that can be used in extremely high temperature environments relative to the Si-based ceramic due to their excellent high-temperature performance. However, there are few researches on the electromagnetic wave absorption of the UHTCs themselves. In this work, rod-like ZrB 2 and its composites were prepared by polymer derived method at a lower temperature. The phase composition and electromagnetic wave absorption properties of the ceramics at different pyrolyzed temperatures were analyzed. The rod-like ZrB 2 pyrolyzed at 1500 °C shows a RL min of −54.77 dB at a thickness of 4.7 mm. The rod-like ZrB 2 /SiC has an absorption bandwidth of 5.68 GHz (RL <-10 dB, 7.6–13.28 GHz) at a thickness of 4.25 mm, exceeding the X-band. An absorption bandwidth of 2.24 GHz for RL <-20 dB (99% absorbed) was obtained by the fabricated composites. The strong absorption of rod-like ZrB 2 /SiC composites is due to the strong conductive loss and multiple scattering of electromagnetic wave by the rod-like network structure. The formation of core-shell ZrB 2 /SiC increases the polarization and enhance the electromagnetic wave absorbing properties of the ceramics. The results of this study show that the polymer derived UHTCs have the strong ability to absorb electromagnetic wave. [Display omitted] [ABSTRACT FROM AUTHOR]

There is an urgent need for multifunctional materials that possess high absorption and infrared stealth capabilities to address the increasingly complex and severe electromagnetic pollution. This research explores how the microstructure of components and the design of the absorber impact the stealth performance of electromagnetic and infrared waves. This research involved designing and fabricating a bi-layer sample with a hierarchical structure consisting of FeCoNi magnetic particles as the absorbing layer and Cu 2 O micro-cube/ h -BN nanocomposite as the matching layer. The particular design of the absorber was instrumental in intensifying the synergistic relationship between dielectric and magnetic loss, thereby achieving a superior level of impedance matching and absorption efficacy. The optimized microwave absorption performance was achieved by tuning thickness and arrangement of each layer. It shows that the minimum reflection loss for bilayer sample reaches −38 dB with a total thickness of only 1.2 mm, and effective absorption bandwidth of 4.4 GHz which covers 75 % of the entire ku frequency band. Its excellent electromagnetic and infrared wave stealth performance may be attributed to enhanced heterogeneous interfaces and consequently polarization relaxation along with magnetic loss, which result from multi-component synergy and the unique 3D hierarchical microstructure and interconnection between particles. [ABSTRACT FROM AUTHOR]

Mullite fibers have been widely used in thermal protection materials, but they still face challenges related to inefficient wave absorption performance. SiBCN aerogel has the advantage of tunable dielectric properties, outstanding microwave absorption performance, low density and low thermal conductivity, making it an ideal candidate for enhancing mullite fibers. Herein, a novel SiBCN aerogel/mullite fiber composite (SiBCN/MF composite) was prepared by sol-gel, freeze-drying and high temperature thermal treatment for the first time. By tuning the concentration of polyborosilazane (PBSZ), the density, microwave absorption performance, and thermal insulation properties were regulated. The obtained composites displayed low density (0.151–0.190 g/cm3), excellent microwave absorption performance (the minimum reflection loss as low as −67.83 dB and effective absorption bandwidth of 5.40 GHz) and low thermal conductivity (0.056–0.081 W/(m·K)). The outstanding comprehensive performance of the fabricated composites makes them promising candidates for use in the thermal protection system of aerospace vehicles. [ABSTRACT FROM AUTHOR]

Exploring high-performance electromagnetic wave (EMW) absorption materials holds extraordinary potential for new-generation wireless communication and integrated electronics. Herein, a series of heterogeneous hydrangea-like NiMn-layered double hydroxide (NiMn-LDH)/MXene (denoted as NMM) hybrids were successfully synthesized by facile hydrothermal method and followed electrostatic self-assembly strategy. The EMW absorption performance of NMM hybrids could be flexibly tuned by regulating the ratios of NiMn-LDH to MXene. Benefiting from the synergy of unique structural design and various EMW attenuation mechanisms, the resultant NMM hybrids realize excellent EMW absorption performance. The NMM3 hybrid (the ratio of NiMn-LDH to MXene is 1:1) achieves an optimal reflection loss of −47.7 dB at 13.29 GHz with a thickness of 1.68 mm and a broad effective absorption bandwidth of 4.4 GHz (13.6–18.0 GHz) at a tiny thickness of 1.43 mm. Moreover, the radar cross section simulation is used to intuitively reveal the effectiveness of NMM hybrids as high-performance EMW absorption materials in actual application. This work provides an innovative perspective on the controllable design of highly efficient EMW absorption materials with remarkably practical application value. [ABSTRACT FROM AUTHOR]