Attenuation Of Electromagnetic Waves Research Articles

Constructing FeNi alloy/polydopamine-derived carbon composite for efficient microwave absorption

Facile strategies for constructing efficient absorber with heterointerfaces have attracted considerable attention but still remain challenges. Herein, FeNi/nitrogen-doped carbon (FeNi/NC) composites were synthesized based on NiFe2O4/polydopamine (PDA) composite and carbonization strategy, and the law of electromagnetic wave absorbing (EMWA) property was explored by modulating the components. Particularly, when the mass ratio of PDA to NiFe2O4 was 3:1, the minimum reflection loss value of FeNi/NC composite was − 49.80 dB at a thickness of 4.0 mm, and the effective absorption bandwidth value can reach up to 4.00 GHz (10.72–14.72 GHz) at 2.0 mm. The introduction of FeNi alloy improved the impedance matching, and the heterointerfaces constructed by FeNi alloy and NC promoted to interface polarization. Additionally, the conductive networks formed by NC were beneficial to the dissipation of electromagnetic wave (EMW). The magnetic loss provided by FeNi alloy contributed greatly to the absorption of EMW. In summary, these loss mechanisms together contributed to the attenuation of EMW. This work provides a new prospect for the preparation of high-efficiency EMWA materials.

Preparation of Hollow Porous Carbon Nanofibers and Their Performance and Mechanism of Broadband Microwave Absorption.

Developing microwave absorbing composites with lightweight and wide absorption bands is an essential direction for electromagnetic wave stealth and shielding application. In this article, PAN/PMMA blend fibers and sheath-core blend fibers with PAN/PMMA as the sheath and PMMA as the core were spun by uniaxial and coaxial electrostatic spinning, respectively. Porous carbon nanofiber (PCNF) and hollow porous carbon nanofiber (HPCNF) were obtained after pre-oxidation and carbonization of the corresponding two precursor fibers. The microwave absorption composite samples with PCNF and HPCNF as absorbents and paraffin as matrix were prepared, respectively. Their electromagnetic parameters were investigated by the reflective-transmission network parameter method. The microwave absorption properties of the corresponding composites were calculated based on a model for a single-layer planewave absorber from electromagnetic parameters. The results showed diversity between the microwave absorbing performance of the composites filled with PCNF and HPCNF. HPCNF performs better than PCNF as an absorbent; that is, the lowest reflection loss of composite filled with HPCNF is −20.26 dB and the effective bandwidth (lower than −10 dB) is to 4.56 GHz, while the lowest reflection loss of a composite filled with PCNF is −13.70 dB, and the effective bandwidth (lower than −10 dB) is 2.68 GHz when the absorbent content is 7%, and the thickness is 3 mm. Much lower reflection loss and a wider absorption band could be expected from HPCNF. The presence of a hollow structure in HPCNF, which may increase the degree of polarization and provide more interfaces for the interference phase extinction of reflected electromagnetic waves, might help to improve the attenuation of electromagnetic waves and broaden the absorption band.

Radar Cross-section of a target and attenuation of electromagnetic waves in sandstorms

The sand particles suspended in the atmosphere can cause the attenuation of electromagnetic waves (EWs) and affect the electromagnetic scattering properties of a target during sandstorms. In this study, a theoretical analysis is offered for the prediction of the EWs attenuation and the radar cross section (RCS) of a target in sandstorms. In the model, an equivalent medium approximation is performed by considering the non-uniform charge distribution on the sand particles, and the effect of the charged sand particles on the scattering characteristics of a target is also taken into account. Numerical results show that the RCS of a target is severely affected in sandstorms. Besides, the charged sand particles have a much greater effect on the target's RCS than the case of the uncharged sand particles. It can be found that the average variation value of the target's RCS decreases nearly exponentially with the increase of visibility, and increases nearly linearly with the distance between the target and incident wave source. Finally, an empirical formula is presented to calculate the RCS of an arbitrarily shaped metal target in a homogeneous lossy medium. These investigations will be of significant benefit to radar detection technology in sandstorms.

Monodispersed Co@C nanoparticles anchored on reclaimed carbon black toward high-performance electromagnetic wave absorption

• CB/Co@C nanocomposites composed of sustainable carbon black and anchored Co@C nanoparticles have been successfully synthesized. • As a novel lightweight electromagnetic wave absorber, the optimal RL min and EAB of -53.989 dB and 6.0 GHz were achieved at thin thickness. • A reasonable absorption mechanism was proposed according to various loss mechanism induced by different components. Recently, developing carbon-based hybrid materials loaded with magnetic components has been generally regarded as a promising and practically feasible strategy when it comes to constructing lightweight electromagnetic wave absorbers. In the current work, reclaimed carbon black (CB) nanopowder was firstly produced by simple burning of wheat straw, which was then employed as sustainable carbon-based host materials (carrier) and successfully decorated Co@C nanoparticles via a simple thermal reduction process. Remarkably, both the as-fabricated nanocomposites and corresponding electromagnetic wave absorption performances could be effectively tuned by tailoring the dosage of the Co@C nanoparticles. The minimum reflection loss (RL min ) of –53.989 dB was achieved for CB/Co@C-2# at 2.28 mm thickness, meanwhile, CB/Co@C-3# was featured by a wide effective absorption band (EAB) of 6 GHz (6.72–12.72 GHz) at a 2.73 mm matching thickness, which covered the entire X band, suggesting that the CB/Co@C nanocomposites were an attractive candidate for electromagnetic wave absorber. According to the synergistic influence of dielectric loss and magnetic loss from CB and Co@C, respectively, as well as the properly matched impedance, a reasonable electromagnetic wave attenuation mechanism was illustrated. It is noteworthy that the preparation process of CB is a facile, recycled, and low-cost strategy for achieving nanoscale carbon-based absorbing materials, moreover, the CB/Co@C nanocomposites provide a reference for constructing lightweight dielectric-magnetic products with superb electromagnetic wave absorption performances.

Hollow spherical NiFe-MOF derivative and N-doped rGO composites towards the tunable wideband electromagnetic wave absorption: Experimental and theoretical study

N-doped rGO (N-rGO) based nano materials are considered to be competent candidates for absorbing electromagnetic waves (EMWs), owing to the low filler loading and abundant relaxation polarization losses. With a unique multistage porous structure, NiFe@N–C/rGO, derived from the composite of NiFe-MOF anchoring on GO nanosheeets, was successfully constructed by a facile solvothermal method and high-temperature annealing technique. Adjusting the ratio of GO is an effective strategy to optimize the EMWs absorption performance to a large extent. At a filler loading of 20 wt%, when the content of graphene is 30 mg, the corresponding product NiFe@N–C/rGO-30 is found to have a minimum reflection loss (RLmin) of −72.28 dB at 10.82 GHz, and an effective absorption bandwidth (EAB, RL ≤ −10 dB) is 5.25 GHz (12.43–17.68 GHz) under the matching thickness of 2.46 mm, its EAB dramatically reached 7.14 GHz (9.74–16.88 GHz) when the graphene content was increased to 90 mg at 2.04 mm matching thickness, which covers most of the X and Ku radar frequency band. Combined with the analysis of the electronic and surface structures of NiFe@N–C/rGO composites, the formation energy and dipole moment were calculated to reveal the mechanism of EMWs absorption within them. The results show that the N-doped structure is more stable than the vacancy modification, where the pyridinic-N is the source of dipole relaxation polarization under high-frequency electromagnetic field. The combination of experimental and theoretical research reveals the inherent mechanism of EMWs attenuation in as-prepared composites, paving an inspirational route for controllable high performance absorbing materials.

Magnetic Composite Rapidly Treats Staphylococcus aureus-Infected Osteomyelitis through Microwave Strengthened Thermal Effects and Reactive Oxygen Species.

It is difficult to effectively treat bacterial osteomyelitis using photothermal therapy or photodynamic therapy due to poor penetration of light. Here, a microwave (MW)-excited magnetic composite of molybdenum disulfide (MoS2 ) / iron oxide (Fe3 O4 ) is reported for the treatment of bacteria-infected osteomyelitis. In in vitro and in vivo experiments, MoS2 /Fe3 O4 is shown to effectively eradicate bacteria-infected mouse tibia osteomyelitis, due to MW thermal enhancement and reactive oxygen species (ROS) (1 O2 and ·O2 - ) production under MW radiation. In addition, the mechanism of MW heat generation is proposed by MW network vector analysis. By the density functional theory and finite element method, the ROS generation mechanism is proposed. The synergy or conductive network between dielectric MoS2 and magnetic Fe3 O4 can reach both enhancement of the dielectric and magnetic attenuation capability. In addition, abundant interfaces are generated to enhance the attenuation of electromagnetic waves by MoS2 and Fe3 O4, introducing multiple reflections and interfacial polarization. Therefore, MoS2 /Fe3 O4 has excellent MW absorption ability based on the synergy or conductive network between MoS2 and magnetic Fe3 O4 as well as multiple dielectric reflections and interfacial polarization.

Three-dimensional porous manganese oxide/nickel/carbon microspheres as high-performance electromagnetic wave absorbers with superb photothermal property

Regulating electromagnetic parameters and thus improving impedance matching characteristics by multi-component design is regarded as a prospective approach to obtain highly efficient electromagnetic wave absorption materials. Whereas, it is still challenging to fabricate microwave absorbers with strong absorption capacity and durability in harsh conditions. Based on the above considerations, three-dimensional porous multi-functional manganese oxide/nickel/carbon microspheres had been designed and prepared through a combined approach of facile solvothermal reactions and subsequent carbonization processes. The textural characteristic examinations demonstrated that, numerous manganese oxide and Ni nanoparticles of 15–20 nm in diameter were well dispersed in the carbon-based microspheres of approximately 0.8–1 μm in size. Microwave absorption property evaluation indicated that the minimum reflection loss reached up to −53.6 dB at 9.5 GHz, and effective absorption bandwidth of 3.7 GHz was achieved at matching thickness of merely 2.0 mm. The electromagnetic wave attenuation mechanisms analysis displayed that excellent impedance matching and various dissipation pathways, including magnetic loss, interfacial and dipole polarization relaxation synergistically contributed to the high microwave absorption performances of the porous composites. Radar cross-sectional simulation and photothermal measurements verified that the materials were supposed to have promising foregrounds in complicated circumstances.

Prediction Method of Electromagnetic Wave Propagation on High Sea State Based on P-M Wave Spectrum

In order to realize the near sea surface communication under high sea states, a link-peak diffraction model is proposed. A P-M sea wave model is established based on the bilinear superposition method. The simple single-peak diffraction model is modified and the theoretical calculation is carried out. The steps to correct the simple single-edge peak diffraction model are multi-edge diffraction model, multi-circular peak diffraction model, and link-peak diffraction model. Simulation experiments are carried out on the applicable frequencies of the link-peak diffraction model, and the attenuation of electromagnetic waves at the round peak diffraction is calculated. The link-peak diffraction model not only simplifies the calculation process in the applicable frequency but also shows good agreement with the results of the multi-peak diffraction model, which provides a theoretical basis for the calculation of electromagnetic wave propagation attenuation in high sea states.

Microwave Attenuation Studies of Polypyrrole-SWCNT Nanocomposite Films for Improved EMI Shielding

In the process of finding stable, lightweight, broadband, cost-effective and improved electromagnetic interference (EMI) shielding material, electromagnetic wave attenuation properties of polypyrrole (PPy)—single-walled carbon nanotube (SWCNT) nanocomposite hybrid films were investigated in X-band region (8.2–12.4 GHz) and reported in the present work. The incorporation of SWCNT as a nanofiller in polymer matrix exhibits enhanced EMI shielding performance as compared to pure polymer films. The substantial values of dielectric loss with good impedance matching contribute to improvement in EMI shielding performance. It is found that with an increase of SWCNT loading in polymer matrix from 0 wt% to 5 wt%, nanocomposite films display a gradual increase in AC conductivity and total shielding effectiveness. The maximum total shielding effectiveness of 32.10 dB and minimum reflection loss of −45.54 dB with a wide bandwidth of 3.1 GHz, were obtained for 5 wt% CNT loading. The present results revealed that the prepared nanocomposite films are appropriate materials for lightweight, broadband EMI shields for radar and stealth applications.

Research on Inductively Coupled Low-Temperature Plasma Spectroscopy Diagnosis

The electron density distribution of a closed-cavity inductively coupled plasma (ICP), along the incident direction of electromagnetic waves, is a key factor affecting its electromagnetic wave attenuation effect. Therefore, an investigation of the various parameters of the ICP, including the electron density inside a closed cavity, is of great significance in the advancement of plasma technology. In this study, an ICP generator was used to generate argon plasma, and the radiation intensity and full-width at half-maximum (FWHM) of the spectral line were measured using emission spectroscopy. The electron collision section model was then used to calculate the electron temperature of the plasma, which was found to be above 0.9 eV. In addition, the electron temperature was found to decrease as the pressure increases and increase significantly as the power increases. The Stark broadening method was used to calculate the electron density, where the Doppler broadening of spectral lines was considered, and the Voigt convolution function was introduced. An accurate value for the Stark broadening was obtained through the convolution calculation, which improves the accuracy of the plasma electron density. Subsequently, the FWHM of the 794.82-nm spectral line was used to obtain the electron density of the plasma. The influence of different power levels and pressures on the electron density was analyzed under pure argon conditions. Finally, the distributions of the plasma electron temperature and electron density in the axial and radial directions of the cavity were investigated. In order to verify the accuracy of spectral diagnosis in the current experimental environment, the diagnostic results of Langmuir single probe were used to verify it. The electron density of argon plasma measured by the probe method and spectroscopic method is of the order of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{17}\,\,\text {m}^{-3}$ </tex-math></inline-formula> , and the axial distribution of the electron density and the variation trend with the pressure tend to be consistent. The reliability of spectral diagnosis under the current experimental conditions is verified.

MoSe2 nanosheets decorated Co/C fibrous composite towards high efficiency electromagnetic wave absorption

Electromagnetic wave (EMW) absorption materials have recently received considerable attention due to the increasingly severe EMW pollution. It remains challenging to fabricate a lightweight absorber with high absorption performance and low matching thickness via structure design and composition tuning. Herein, one type of fibrous composite EMW absorber with two-dimensional (2D) nanosheets coating was synthesized by electrospinning, pyrolysis and hydrothermal. The combination of cobalt nanoparticle and carbon nanofiber with decoration of 2D MoSe2 nanosheets on the surface significantly promote the EMW absorption through dielectric/magnetic loss, impedance matching, diverse polarizations and porous structure induced multiple scattering. Owing to the coupling effect of proper combination of multiple components and hierarchical structure, a strong EMW absorption with minimum reflection loss (RL) −62.30 dB at 10.70 GHz, effective absorption bandwidth (EAB) 5.10 GHz (9.30–14.40 GHz) covering most of the X-band was achieved with absorber thickness of 2.05 mm. By adjusting the thickness to 1.60 mm, the EAB can reach 6.00 GHz (12.00–18.00 GHz), covering the whole Ku bands. This composite fibrous absorber with excellent EMW absorption performance is promising to be used in many EMW attenuation applications.

Flower-like MoS2 self-assembled on multiferroic Z-type Sr3Co2Fe24O41 hexaferrite for ultra-wideband microwave absorption

In this work, a rare system of Sr3Co2Fe24O41/MoS2 composites has been successfully prepared via the sol-gel method and following a facile hydrothermal process, from which the flower-like MoS2 was evenly anchored on the surface of Z-type Sr3Co2Fe24O41 microplatelets. It is confirmed that the effective combination of transition metal sulfide MoS2 and multiferroic Sr3Co2Fe24O41 hexaferrite greatly optimizes the dielectric behaviors of the composites. Meanwhile, the unique hierarchical structure further enhances the microwave absorption properties. When the mass ratio of Sr3Co2Fe24O41 to MoS2 is 1:3 in composites, the smallest reflection loss value is − 39.2 dB at the thickness of 2.0 mm, and note that the adequate absorption bandwidth can reach up to 7.6 GHz (10–17.6 GHz) with 2.2 mm. When the mass ratio is adjusted as 1:5, the optimal reflection loss of the composite reaches − 44.5 dB at 9.28 GHz with a thickness of 3.0 mm. The high-efficiency microwave absorption performance of the composites is attributed to the synergistic effect of dielectric materials and multiferroic materials. The calculation results on delta and attenuation constant display that impedance matching degree and attenuation ability of composites are balanced, which not only reduces the reflection of electromagnetic waves on the absorber surface, but also enhances its consumption. At the same time, the flower-shaped MoS2 is stacked on the surface of Sr3Co2Fe24O41 microplatelets which is conductive to the multiple reflections and scattering of electromagnetic waves between layers, greatly promoting the attenuation of electromagnetic waves. This work opens up an updated pathway for the design of magnetic/dielectric microwave absorbers with vigorous absorption and ultra-wideband.

Hollow core–shell structure Co/C@MoSe2 composites for high-performance microwave absorption

To address an increasingly serious electromagnetic radiation problem and the urgent need to develop lightweight, high-efficiency, and strong-attenuation electromagnetic wave absorbing (EMA) materials, a hollow core–shell Co/C@MoSe2 composite structure was prepared. Flower-like MoSe2 was wrapped around the surface of Co/C composites after a hydrothermal reaction. The introduction of MoSe2 and the designed hollow core–shell structure was beneficial for optimizing the electromagnetic characteristics of the composites. Owing to the magnetism of Co/C composites after high-temperature treatment, the composite materials were capable of magnetic dissipation. The introduced multiple-attenuation mechanisms, such as dielectric loss, magnetic loss, and conductive loss, contributed greatly to the incident electromagnetic wave attenuation. Among them, Co/C@MoSe2-4 exhibited excellent electromagnetic wave absorption performance. When the matching thickness was 2.5 mm, the minimum reflection loss was −42 dB, and the effective absorption bandwidth was 5.1 GHz. This work provided a smart strategy for electromagnetic wave absorbers designing and commerical application.

Data Collection from Buried Sensor Nodes by Means of an Unmanned Aerial Vehicle.

The development of Wireless Underground Sensor Networks (WUSNs) is a recent research axis based on sensor nodes buried a few dozen centimeters deep. The communication ranges are, however, highly reduced due to the high attenuation of electromagnetic waves in soil, leading to issues of data collection. This paper proposes to embed a data collector on an Unmanned Aerial Vehicle (UAV) coming close to each buried sensor node. The whole system was developed (sensor nodes, data collector, gateway) and experimentations were carried out in real conditions. In hovering mode, the measurements on the RSSI levels with respect to the position of the UAV highlight the interest in maintaining a high altitude when the UAV is far from the node. In dynamic mode, the experimental results demonstrate the feasibility of carrying out the data collection task while the UAV is moving. The speed of the UAV has, however, to be adapted to the required time to collect the data. In the case of numerous buried sensor nodes, evolutionary algorithms are implemented to plan the trajectory of the UAV optimally. To the best of our knowledge, this paper is the first one that reports experiment results combining WUSN and UAV technologies.

Multilayer Ti3C2Tx: From microwave absorption to electromagnetic interference shielding

Ti3C2Tx MXene has attracted extensive attention in the field of electromagnetic (EM) protection over recent years. Multilayer Ti3C2Tx (M-Ti3C2Tx), as an intermediate product of MXene ultra-thin structure, has potential advantages in the field of EM protection. Herein, the M-Ti3C2Tx was obtained by HCl/LiF etching Ti3AlC2. The microwave absorption (MA) and electromagnetic interference (EMI) shielding performance of Ti3AlC2 and M-Ti3C2Tx were compared. The mechanism research of MA and EMI shielding indicates that the construction of local conductive network plays a leading role in the EM wave attenuation. The sample with 30% M-Ti3C2Tx display RLmin of −50.26 dB, and corresponding bandwidth of 4.64 GHz at the thickness of 1.7 mm. Especially, the metastructure based on the EM parameters of M-Ti3C2Tx/wax exhibits ultra-wide bandwidth (15.54 GHz). Our research will provide a basis for the design of MXene-based EM protection performance.

Enhanced Electromagnetic Wave Absorption by Bi-Layered Nano-Hollow Spheres

To cope with the increasingly serious microwave radiation pollution, an extensive search for efficient microwave absorption materials (MAMs) has attracted great attention recently. Herein, a thin layer of SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> with high dielectric permittivity on the surfaces of MnFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> (MnFO) nano-hollow spheres (NHSs) is found to be an effective strategy to improve electromagnetic (EM) wave attenuation for a larger reflection loss (RL) along with a larger bandwidth (BW) within a widely used frequency range. Larger interfacial area, higher magnetic anisotropy, internal reflections, and scattering from NHS along with higher magnetic permeability of MnFO are responsible for superior absorption properties of MnFO NHS. The MnFO (~550 nm)/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (~35 nm) bi-layered NHS results in a sufficiently high RL ~ −61.02 dB with a composite absorber of a thickness of only 4.40 mm and filler concentration of 20%. The above study on the variation of SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> thickness over MnFO NHSs helps us to optimize for maximum BW and absorption with minimum composite absorber thickness. This study demonstrates the optimized MnFO/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> NHS as a highly promising low-cost and lightweight EM wave absorber suitable for high-frequency applications.

Ternary MXene/MnO2/Ni composites for excellent electromagnetic absorption with tunable effective absorption bandwidth

It is still a great challenge to design and fabricate electromagnetic wave absorbing materials with both excellent attenuation capability and effective absorption bandwidth (EAB). Herein, cooperatively coupling the magnetic nanoparticles with dielectric matrix, ternary MXene/MnO2/Ni composites were synthesized through a facile self-assembly method. The MXene (Ti3C2Tx) was served as backbone to effectively assemble MnO2 nanorods, which was further used to support the Ni nanoparticles. The relationship between Ni content and the electromagnetic wave absorption performance of the MXene/MnO2/Ni composites was discussed to maximize the attenuation and impedance matching. The optimized MXene/MnO2/Ni exhibited a strong reflection loss (RL) of − 54.4 dB at 11.6 GHz and a wide EAB of 6.08 GHz (9.04–15.12 GHz). Importantly, a wide EAB of 12 GHz (6–18 GHz) can be tuned to low frequency range (C band) by the modification of Ni content. The combination of the dielectric loss and magnetic loss attributes to the comprehensively excellent absorption performance. In addition, the Ti3C2Tx matrix and the formation of interface between ternary assemblies will generate the interface polarization and scattering path to favor the attenuation of electromagnetic wave.

Preparation and characterization of porous polyimide fibers with electromagnetic wave absorption properties

AbstractThe porous polyimide (PI) composite fibers, which exhibit high‐efficiency electromagnetic wave adsorption (EMWA) performance, were successfully fabricated by controlling temperature of the coagulation bath during the wet spinning process. The mechanical properties of composite fiber decreased and average radius of micropores increased gradually with the rise of coagulation bath temperature. In addition, carbon nanotubes (CNTs) and nano‐Fe3O4 were introduced into the system by in situ polymerization. CNTs and nano‐Fe3O4 contribute to the attenuation of electromagnetic wave (EMW) through microwave absorption and reflection loss (RL), and the porous structure was able to provide multiple reflection paths for incident EMW and achieved higher attenuation. Particularly, when the temperature of coagulation bath was 50°C, the minimum RL (RLmin) value of the PI/CNTs/nano‐Fe3O4 (PI/C‐Fe) composite fibers was demonstrated to be −54.61 dB with the matching thickness of 2.10 mm. The successful preparation of PI/C‐Fe composite fiber in this study pointed out a new direction for the application of PI‐based fiber materials in structural EMWA materials.

A sustainable and low-cost route to prepare magnetic particle-embedded ultra-thin carbon nanosheets with broadband microwave absorption from biowastes

Two-dimensional (2D) carbon nanomaterials have attracted extensive attention in the field of microwave absorption (MA) owing to their unique layered structure, tailorable atomic layer, tunable active surface, and high dielectric loss. Here, novel porous graphene-like heterostructures are facilely prepared through the carbonization of pomelo peel (PP)/prussian blue (PB) and PP/PB analogues (PBA). The magnetic particles derived from PB and PBA are uniformly distributed in the N-doped carbon (NC) ultra-thin nanosheets, which enhances the magnetic loss and improves the interfacial polarization. The optimized Fe/ZnO/NC-7 sample exhibits a maximum reflection loss (RLmax) of −58.12 dB at 2.05 mm, and an ultrabroad effective bandwidth (RL ≤ −10 dB) of 7.6 GHz is achieved at 1.9 mm, which covers nearly half of the measured frequency range. The superior MA performance of Fe/ZnO/NC-7 composite is ascribed to the unique magnetic particle-embedded carbon nanosheet, which not only optimizes the impedance matching but also enhances the electromagnetic wave (EMW) attenuation ability through 2D conductive networks and multiple polarization processes. Overall, this work offers an environmentally friendly method to prepare low-cost and high-performance microwave absorbers from biowastes, which exhibit superior application potential as compared to other 2D microwave absorbers including graphene and MXene.

Optimized impedance matching of micro-porous silicon dioxide coated graphite nanosheets as remarkable microwave absorber

Despite the high electromagnetic wave (EMW) attenuation capabilities, graphite nanosheets (GNs) are still facing great challenges as absorbing material owing to the strong reflection. Herein, a porous silicon dioxide coated GNs (PSi@GNs) is designed by sol–gel reaction to optimize the impedance matching of GNs. The coated porous SiO2 can not only balance the impedance between GNs and air, preventing the EMW reflection, but also increase the interfacial polarization behavior and benefit polarization loss. As a result, the as-synthesized SiO2/GNs exhibits superior EMW absorption performances with the minimum reflection loss (RL) value of −59.835 dB and effective absorbing bandwidth (EAB) of 3.36 GHz at 3.22 mm (25% filled). The advantages of the PSi@GNs potential applications in military radar, electronic communication, weapons and other fields.