Polarization Relaxation Research Articles

Designing a Microstructure of NiCo-LDH@CNTs@Carbon Foam for Efficient Electromagnetic Wave Absorption and Excellent Environmental Tolerance.

The constantly evolving environment imposes increasingly stringent demands on the mechanical qualities of materials employed for absorbing electromagnetic waves (EMWs). Therefore, there is an urgent need for advanced materials capable of efficiently absorbing EMWs and withstanding harsh electromagnetic conditions. In this study, the electrodeposition method was effectively used to synthesize nickel-cobalt layered double hydroxides (NiCo-LDHs) in a controlled manner on a composite structure of carbon nanotubes and carbon foam, creating an exquisite construction. The manipulation of the electrodeposition time facilitated the regulation of the density of the layered structure within the composite material, thereby significantly enhancing its polarization relaxation performance. Increased defect sites and interface polarization enhance impedance matching and the attenuation constant, resulting in greatly improved absorption performance. The optimized sample demonstrated exceptional wave-absorbing performance in comparative experimental analysis, attaining a maximum reflection loss of -58.18 dB. It also has an effective absorption bandwidth of 5.36 GHz at a wavelength of 2.28 mm. The exceptional isolation effect of LDH, coupled with the outstanding insulation ability of the porous carbon skeleton, confers remarkable corrosion resistance and thermal insulation performance on the composite material. Hence, this discovery offers novel insights into designing environmentally tolerant absorbent materials.

Structural, optical, and morphological properties of PVC-BaTiO3 nanocomposite films

This work aims to fabricate barium titanate (BaTiO3) nanoparticles and study the effect of adding different contents of BaTiO3 nanoparticles on the structural, optical, and electrical properties of PVC polymer matrices. The PVC/BaTiO3 nanocomposite films were characterized by X-ray diffraction, FT-IR spectroscopy, and SEM. In addition, dielectric properties were studied within the frequency range of 0.1 KHz–6 MHZ. The XRD analysis reveals an amorphous nature of pure PVC with two characteristic peaks at 2θ = 17.09° and 2θ = 23.25°, and it reveals that BaTiO3 has sharp and narrow peaks. In PVC/BaTiO3 nanocomposite films, all XRD peaks of BaTiO3 appeared in all the samples with an increase in the average particle size from ∼46 nm to 55 nm. There is no shift of IR position in PVC bands, but the decreased intensity of some bands suggests complexation between PVC and BaTiO3. The UV–visible absorption spectrum of pure PVC has a band at λ = 278 nm. This band was shifted to 252 nm after adding BaTiO3 content. UV–visible transmission spectra demonstrate a decrease in the transmittance as an increase of BaTiO3 content from 89.23 % for pure PVC to 5.23 % for 0.1 wt% of BaTiO3. The values of the optical bandgap decrease with increasing BaTiO3 contents due to defect formation in PVC matrices. The optical parameters of the prepared nanocomposite films were also enhanced. The AC conductivity shows an increase with both frequency and BaTiO3 concentration, leading to enhanced movement of charge carriers and relaxation of interface polarization.

Multifunctional bacterial cellulose‑derived carbon hybrid aerogel for ultrabroad microwave absorption and thermal insulation

Carbon aerogel has gained intense attention as one of the most promising microwave absorption materials. It can overcome severe electromagnetic pollution, thanks to its 3D macroscopic structure and superb conductive loss capacity. However, there is still a big challenge to endow multifunctionality to carbon aerogel while maintaining its good electromagnetic wave absorption (EWA) so as to adapt wide practical application. Herein, a novel carbon-based aerogel consisting of Cu and TiO2 nanoparticles dispersed on carbon nanofiber framework was derived from carbonized bacterial cellulose (CBC) decorated with its mother bacteria via freeze-drying, in situ growth and carbonization strategies. The synthesized carbon-based CBC/Cu/TiO2 aerogel achieved an excellent EWA performance with a broad effective absorption bandwidth (EAB) of 8.32 GHz. It is attributed to the synergistic loss mechanism from multiple scattering, conductive network loss, interfacial polarization loss and dipolar polarization relaxation. Meanwhile, the obtained aerogel also shows an excellent thermal insulation with a 3-mm-thick sample generating a temperature gradient of over 42 °C at 85 °C and a maximum radar cross-section (RCS) reduction of 23.88 dB m2 owing to the cellular structure and synergistic effects of multi-components. Therefore, this study proposes a feasible design approach for creating lightweight, effective, and multifunctional CBC-based EWA materials, which offer a new platform to develop ultrabroad electromagnetic wave absorber under the guidance of RCS simulation.

Synergistic SiC/Co3O4 composites for enhanced microwave-assisted benzene catalytic removal performance

Microwave-assisted catalysis is a promising technique for enhancing catalytic reactions through selective heating, potentially leading to improved reaction rates and energy efficiency. However, understanding the complex interactions between microwave absorption and catalytic performance in composite catalysts remains a challenge. In this study, Cobalt oxide(Co3O4)/silicon carbide(SiC) composite catalysts with varying SiC content were synthesized and characterized to investigate the relationship between their microwave absorption properties and catalytic performance. Quantitative analysis revealed that SiC and Co3O4 absorb microwave energy through relaxation polarization and magnetic loss mechanisms, respectively. Increasing SiC content enhanced the dielectric and magnetic loss capabilities of the composites, with the Co3O4/SiC composite containing 10 wt% SiC (Co3O4/SiC-10) exhibiting a dielectric loss tangent of 3.87 and a minimum reflection loss of −35dB. However, higher SiC content decreased the surface chemically adsorbed oxygen, surface oxygen mobility, and benzene adsorption capacity, weakening the catalytic activity under conventional heating. The Co3O4/SiC-10 sample achieved a significantly better balance between microwave absorption and catalytic performance, significantly outperforming the original Co3O4 sample under microwave irradiation. These founding establishes a quantitative research methodology that correlates dielectric loss tangent, reflection loss, and other crucial parameters with microwave absorption performance and further catalytic properties, providing insights for the rational design of catalysts that optimize both microwave absorption and catalytic activity.

Tailored Magnetic Spatial Confinement with Enhanced Polarization and Magnetic Response for Electromagnetic Wave Absorption.

For materials with coexisting phases, the transition from a random to an ordered distribution of materials often generates new mechanisms. Although the magnetic confinement effect has improved the electromagnetic (EM) performance, the transition from random to ordered magnetic confinement positions remains a synthetic challenge, and the underlying mechanisms are still unclear. Herein, precise control of magnetic nanoparticles is achieved through a spatial confinement growth strategy, preparing five different modalities of magnetic confined carbon fiber materials, effectively inhibiting magnetic agglomeration. Systematic studies have shown that the magnetic confinement network can refine CoNi NPs size and enhance strong magnetic coupling interactions. Compared to CoNi@HCNFs on the hollow carbon fibers (HCNFs) outer surface, HCNFs@CoNi constructed on the inner surface induce stronger spatial charge polarization relaxation at the interface and exhibit stronger magnetic coupling interactions at the inner surface due to the high-density magnetic coupling units at the micro/nanoscale, thereby respectively enhancing dielectric and magnetic losses. Remarkably, they achieve a minimum reflection loss (RLmin) of -64.54dB and an absorption bandwidth of 5.60GHz at a thickness of 1.77mm. This work reveals the microscale mechanism of magnetic confinement-induced different polarization relaxation and magnetic response, providing a new strategy for designing magnetic materials.

Simulation on Critical Frequency of Polymer in Electrostrictive Properties

AbstractThe critical frequency and the relaxation time are analyzed through deformation and displacement during electrostriction which is induced by the electrical field at different frequencies. First, when the frequency is 50 Hz and the field strength is 2.5 kV mm−1, the electrostrictive displacement of polyethylene is 6.72 × 10−4 mm. After the data fitting, it is found that the displacement increases linearly with the square of field strength and that the proportional coefficient of 50 Hz is 1.08 × 10−4. Second, due to the influence of relaxation polarization and power loss, with the increase of frequency, the displacement and the proportional coefficient first increases then decreases, and when the frequency is 10 kHz, the displacement of 2.20 × 10−6 mm and the proportional coefficient of 3.51 × 10−7 have minimum values, which are 99.67% and 99.68% lower than that of 50 Hz, respectively. There is the critical frequency. Finally, based on the characteristic of anomalous dispersion, the relaxation time of polyethylene is 9.19 × 10−6s, which is in the time range of thermionic relaxation polarization and consistent with the actual situation. This analysis confirms the quantitative relationship between electrostrictive characteristics, field strength, and polarization. In addition, the relationship between frequency and strain is discussed, and the critical frequency in polymer and the relaxation time are confirmed.

One‐Pot Synthesis of Conductive Metal–Organic Framework@polypyrrole Hybrids with Enhanced Electromagnetic Wave Absorption Performance

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.

Investigating Enhanced Microwave Absorption of CNTs@Nd0.15-BaM/PE Plate via Low-Temperature Sintering and High-Energy Ball Milling.

Composite plates comprising a blend of rare earth neodymium-(Nd) doped M-type barium ferrite (BaM) with CNTs (carbon nanotubes) and polyethylene WERE synthesized through a self-propagating reaction and hot-pressing treatment. The plates' microscopic characteristics were analyzed utilizing X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FTIR), thermo-gravimetric analysis (TGA), Raman, and scanning electron microscopy (SEM) analytical techniques. Their microwave absorption performance within the frequency range of 8.2 to 18 GHz was assessed using a vector network analyzer. It showed that CNTs formed a conductive network on the surface of the Nd-BaM absorber, significantly enhancing absorption performance and widening the absorption bandwidth. Furthermore, dielectric polarization relaxation was investigated using the Debye theory, analyzing the Cole-Cole semicircle. It was observed that the sample exhibiting the best absorbing performance displayed the most semicircles, indicating that the dielectric polarization relaxation phenomenon can increase the dielectric relaxation loss of the sample. These findings provide valuable data support for the lightweight preparation of BaM-based absorbing materials.

Hollow Co9S8-carbon fiber hierarchical heterojunction with Schottky contacts for tunable microwave absorption

Heterogeneous interface engineering of hollow hierarchical structures with Schottky contacts is an attractive approach for designing light weight and efficient microwave absorption (MA) materials. Herein, hollow Co9S8-carbon fiber (CF) composites were prepared by solvothermal, electrostatic spinning, and pyrolysis methods. CF was used as the main chain and hollow Co9S8 derived from metal-organic frameworks (MOFs) was homogeneously embedded in it, which overcame the difficulties of the traditional template method and effectively avoided the particle agglomeration problem. The interface polarization relaxation process is improved by the construction of Co9S8-CF heterojunction with Schottky contacts, which effectively modulates the dielectric loss. The internal hollow macroporous cavity and CF with lightweight properties enhance the reflection attenuation of the internal cavity. In addition, the electromagnetic characteristics can be flexibly adjusted to achieve the tunable MA performance by varying the reaction parameters. As a result, the Co9S8-CF-3–700 exhibits optimum MA performance, with a reflection loss (RL) of −60.83 dB at 10.85 GHz and a thickness of 2.76 mm. The effective absorption bandwidth (EAB) extends to 5.6 GHz at a thickness of 2.19 mm. This research provides a promising approach to creating light weight and efficient MA materials with potential applications in radar and communication systems.

Polarization loss in rutile TiO2 doped with acceptor ions for microwave absorption

With an increase in electromagnetic (EM) pollution, inducing polarization loss using lattice defects has become one of the main strategies for the design and optimization of a new generation of microwave absorbers. In this study, point defects in TiO2 absorbers are designed and controlled using a sol–gel method. The influences of the electronegativity difference and the ionic valence states of the dopant ions on the microwave absorption (MA) performance of rutile TiO2 composites are investigated. The results show that the defects such as oxygen vacancy (VO∙∙) and Ti3+ can be adjusted continuously at a high-temperature sintering process. Cu2+, which has a larger electronegativity than Ti4+ (Cu2+χ = 1.90 > Ti4+χ = 1.54) promotes the localization of electrons. Furthermore, compared with Ag+, which has a similar electronegativity (Ag+χ = 1.93 ≈ Cu2+χ = 1.90), polyvalent copper ions (Cu2++e→Cu+) enhance the electron-hopping process. The formed electron-pinning defect dipole clusters (TiTi′, VO∙∙, CuTi″, CuTi″′, Ti3+→VO∙∙←Ti3+, Ti3+→VO∙∙←Cu2++e, Cu2++e→Cu+, Ti4++e→Ti3+) produce a stronger polarization relaxation process, which regulates the MA performance of TiO2 absorbers. Therefore, this study provides an essential reference for refining the EM wave attenuation performance of simple oxide absorbers.

Hot-pressing-oriented graphene in Si3N4 composites for enhanced electromagnetic wave absorption in X and Ku bands

In this study, the oriented graphene within graphene/Si3N4 composites was successfully achieved by two-step hot-press sintering. Microstructure analysis revealed that the graphene sheets were well dispersed in the Si3N4 matrix and oriented perpendicular to the applied stress. The composites exhibited effective electromagnetic wave (EMW) absorption capabilities and good mechanical properties. The effective absorption bandwidth (EAB) was 9.63 GHz, nearly covering the entire X and Ku bands (8.2–18 GHz), and the minimum reflect loss (RL) was −24.23 dB when the graphene content reached 7 wt% at a thickness of 2.02 mm. Meanwhile, the oriented graphene/Si3N4 composites demonstrated a bending strength of 576.66 MPa and a fracture toughness of 8.40 MPa·m1/2. The EMW absorption in these composites should be primarily due to polarization relaxation loss and conductivity loss, and the toughening mechanism should involve the graphene pull-out, crack bridging, and crack deflection. The graphene/Si3N4 composites have a promising application in structurally integrated functional materials.

Manipulating polarization attenuation in NbS2–NiS2 nanoflowers through homogeneous heterophase interface engineering toward microwave absorption with shifted frequency bands

Homogeneous heterogeneous (heterophase) interfaces regulated with low energy barriers have a fast response to applied electric fields and could provide a unique interfacial polarization, which facilitate the transport of electrons across the substrate. Such regulation on the interfaces is effective in modulating electromagnetic wave absorbing materials. Herein, we construct NbS2–NiS2 heterostructures with NiS2 nanoparticles uniformly grown in NbS2 hollow nanospheres, and such particular structure enhances the interfacial polarization. The strong electron transfer at the interface promotes electron transport throughout the material, which results in less scattering, promotes conduct ion loss and dielectric polarization relaxation, improves dielectric loss, and results in a good impedance matching of the material. Consequently, the absorbing band may be successful tuned. By regulating the amount of NiS2, the heterogeneous interface is finely alternated so that the overall wave-absorbing performance is shifted to lower frequencies. With a NiS2 content of 15 ​wt% and an absorber thickness of 1.84 ​mm, the minimum reflection loss at 14.56 ​GHz is −53.1 ​dB, and the effective absorption bandwidth is 5.04 ​GHz; more importantly, the minimum reflection loss in different bands is −20 dB, and the microwave energy absorption rate reaches 99% when the thickness is about 1.5–4.5 ​mm. This work demonstrates the construction of homogeneous heterostructures is effective in improving the electromagnetic absorption properties, providing guideline for the synthesis of highly efficient electromagnetic absorbing materials.

A lightweight and efficient hollow sunken carbon@MnO2/reduced graphene oxide composite for high-performance electromagnetic wave absorption

To address the environmental and health issues stemming from electromagnetic pollution, it is crucial to investigate high-performance and practical materials for absorbing electromagnetic waves. Herein, the ternary lightweight SC@MnO2/RGO (SCMR) composites are synthesized by using a special kind of hollow sunken carbon nanoparticles (SC) as a substrate and combining MnO2 nanosheets with 2D reduced graphene oxide (RGO). The investigation results show that the minimum reflection loss (RLmin) of SCMR3 can reach −60.95 dB with a matched thickness of 1.47 mm and a frequency of 13.12 GHz, and the effective absorption bandwidth (EAB) is 4.08 GHz (13.76–17.84 GHz) at the thickness of 1.23 mm. Its excellent performance comes from high dielectric loss capability, multiple reflections, interfacial polarization, and defective polarization relaxation brought by the structure of the composite, which can effectively enable electromagnetic wave absorption and facilitates energy conversion. Furthermore, simulation-based assessment under far-field conditions elucidates the radar stealth effect, demonstrating that the maximum radar cross-section (RCS) attenuation value of SCMR3-coated perfect electrical conductor (PEC) at Phi = 0° and θ = 0° can attain 32.13 dB m2. Ultimately, this study presents a viable design methodology for developing lightweight, efficient, and application-oriented carbon-based electromagnetic wave absorption materials.

Mechanical properties and electromagnetic wave absorption characteristics of solid waste low-carbon cementitious materials

A low-carbon multi-functional cement substitute material has been developed to reduce electromagnetic pollution in building spaces and protect human health. The solid waste electromagnetic absorption cementitious material (SWEACM) is produced by combining steel slag (SS), blast furnace slag (BFS), and phosphogypsum (PG). In this study, the properties of SWEACM were analyzed, including flow, electromagnetic wave absorption, strength, and environmental properties. Additionally, the hydration and electromagnetic wave absorption mechanisms were examined. The results indicate that SS, BFS, and PG content significantly affect the strength and electromagnetic wave absorption properties of SWEACM. S-6 exhibits the best overall performance (SS: BFS: PG = 3:6:1), with the highest strength (28 days compressive strength = 33.5 MPa) and fluidity (19.1 cm). Furthermore, it has excellent electromagnetic absorption performance (RLmin = −45.4 dB), with an adequate absorption bandwidth of up to 10 GHz in the 2–18 GHz range. The excellent electromagnetic wave absorption capability of SWEACM is mainly due to the resonance, polarization relaxation loss, and conduction loss of the magnetic and conductive components in the material. The results show that SWEACM can be used as a multi-functional construction engineering material for electromagnetic protection, combining high levels of high electromagnetic wave absorption, strength performance, and environmental benefits.

High-temperature stability of wave absorption properties for SiC enhanced ZrB2–Al2O3 ceramics

To address the challenge of high-temperature microwave absorbing materials (MAM) for the hot-end components of aircraft, SiC enhanced ZrB2–Al2O3 (ZSA) ceramics are prepared by pressureless sintering. In ZSA ceramics, ZrB2 and SiC are the absorbers and Al2O3 is the matrix. The effect of the content of SiC on microwave absorption properties for the ZSA ceramics are studied. The results show that the addition of SiC enhances the MA properties and high-temperature stability of ZrB2–Al2O3 ceramics. Ceramics with an effective absorption bandwidth (EAB) of 3.9 GHz at a thickness of 1.56 mm; and a minimum reflection loss (RLmin) of −15 dB is obtained. After treatment at 1000 °C for 20 h in an air atmosphere, the EAB reduces to 3.5 GHz at the thickness of 1.56 mm, however, RLmin reaches −21 dB. ZSA ceramics consume microwaves through effect including interfacial polarization relaxation, conductive loss and multiple reflection loss. This work is expected to provide new ideas for the design and development of high-temperature microwave absorbing materials.

Design and Fabrication of Flexible double layer Magneto-dielectric nanocomposite for electromagnetic and infrared wave stealth application

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 Cu2O 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.

Facile Recycling of Waste Biomass for Preparation of Hierarchical Porous Carbon with High-Performance Electromagnetic Wave Absorption.

Hierarchical-porous-structured materials have been widely used in the field of electromagnetic wave (EMW) absorption, playing a critical role in minimizing EMW interference and pollution. High-quality EMW absorbers, characterized by a lower thickness, lighter weight, wider absorption band, and stronger absorption capacity, have been instrumental in reducing damage and preventing malfunctions in the automotive and aviation industries. The utilization of discarded nut shells through recycling can not only alleviate environmental problems but relieve resource constraints. Herein, a facile method for the preparation of hierarchical porous biomass carbon derived from abandoned Xanthoceras Sorbifolium Bunge Shell (XSS) biomass was developed for high-performance EMW absorption. The porous structures of XSS biochar were studied by using different levels of the K2CO3 activator and simple carbonization. The effect of K2CO3 on the EMW parameters, including the complex permittivity, complex permeability, polarization relaxation, and impedance matching, was analyzed. The best EMW absorption performance of the XSS biochar was observed at a mass ratio of activator-to-biomass of 2:1. A minimum reflection loss (RLmin) of -38.9 dB was achieved at 9.12 GHz, and a maximum effective absorption bandwidth (EABmax) of up to 3.28 GHz (14.72~18.0 GHz) could be obtained at a 1.8 mm thickness. These results demonstrated that hierarchical porous XSS carbon was prepared successfully. Simultaneously, the prepared XSS biochar was confirmed as a potential and powerfully attractive EMW-absorbing material. The proposal also provided a simple strategy for the development of a green, low-cost, and sustainable biochar as a lightweight high-performance absorbing material.

Metal Single‐Atoms Toward Electromagnetic Wave‐Absorbing Materials: Insights and Perspective

AbstractMetal 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.

Constructing multiple heterogeneous interfaces in one-dimensional carbon fiber materials for superior electromagnetic wave absorption

Due to impedance mismatch and a single loss mechanism, carbon fiber fails to meet the requirements for efficient absorbers in terms of lightweight construction and broad absorption band. In this study, we have successfully prepared one-dimensional beaded SiO2@SiC@C nanofiber (SSCF) composites with multiple heterogeneous interfaces by employing the electrospinning-carbothermal reduction method. The beaded SSCF composites effectively address the impedance mismatch issue by controlling silicon dioxide and silicon carbide through carbothermal reduction. This optimization enriches the defects and interfaces of carbon fibers composites, consequently enhancing the electromagnetic wave absorption performance. The SSCF composites demonstrate remarkable performance, with a minimum reflection loss of −59.53 dB at a matched thickness of 2.21 mm and a maximum absorption bandwidth of 6 GHz. This outstanding performance is attributed to the synergistic effects of the multi-phase composition, bead structure, and one-dimensional network structure. These features not only optimize impedance matching but also enhance defect loss, interface polarization loss (SiC/SiO2, C/SiO2, SiC/C, C/Air), conduction loss, and relaxation loss of the SSCF composites. Furthermore, radar cross-section analysis utilizing computer simulation technology confirms the excellent attenuation of microwave energy by the SSCF composites under realistic far-field conditions. This study provides valuable insights for designing efficient one-dimensional carbon-based electromagnetic wave absorbers.

Optimizing the electromagnetic wave absorption properties of core-shell Fe/FeN/Fe3C@GN nanoparticles by low-temperature NH3 plasma

Surface modification via low-temperature plasma has an extensive application prospect in different engineering fields due to its comprehensive merits in facilitating the introduction of functional groups and creating more heterogeneous interfaces. Herein, a simple high-temperature plasma method is developed to get novel multiple-phase nanocomposites of core-shell Fe/FeN/Fe3C@GN nanoparticles with bifunctional characteristics of microwave absorption (MA) and anti-corrosion. And then, we further investigate the MA properties of Fe/FeN/Fe3C@GN nanoparticles after low-temperature NH3 plasma etching. It is found that surface modification of Fe/FeN/Fe3C@GN nanoparticles can generate remarkable changes in specific surface areas, Raman features and MA properties of these nanocomposites. The Fe/FeN/Fe3C@GN nanoparticles after NH3 plasma etching possess excellent MA properties with an optimal reflection loss (RL) of −51.0 dB at an ultra-thin thickness of 1.9 mm with a low filling content of 30 wt% and the corresponding effective absorption bandwidth (EAB < −10 dB) up to 4.7 GHz (13.3–18.0 GHz). The fascinating MA properties of etched Fe/FeN/Fe3C@GN nanoparticles may be attributed to the cooperative effect of several points: (i) The NH3 plasma etch introduces a large number of polar functional groups, which can be regarded as the polarization center to produce more polarization loss; (ii) The appropriate dielectric loss and impedance matching achieve a good balance, and the abundant heterogeneous interface significantly enhances the polarization relaxation loss; (iii) The existence of hetero-nanostructure further improves the multiple reflections and scattering of the propagating microwaves. In addition, this work provides a new strategy for the design and fabrication of core-shell MA materials.