Achieving Ultra-Wideband and Elevated Temperature Electromagnetic Wave Absorption via Constructing Lightweight Porous Rigid Structure

Realizing ultra-wideband absorption,desirable attenuation capability at high temperature and mechanical requirements for real-life applications remains a great challenge for microwave absorbing materials.Herein,we have constructed a porous carbon fiber/polymethacrylimide(CP)structure for acquiring promising microwave absorption performance and withstanding both elevated temperature and high strength in a low density.Given the ability of porous structure to induce desirable impedance matching and multiple reflection,the absorption bandwidth of CP composite can reach ultra-wideband absorption of 14 GHz at room temperature and even cover the whole X-band at 473 K.Additionally,the presence of imide ring group in polymethacrylimide and hard bubble wall endows the composite with excellent heat and compressive behaviors.Besides,the lightweight of the CP composite with a density of only 110 mg cm^(−3) coupled with high compressive strength of 1.05 MPa even at 453 K also satisfies the requirements in engineering applica-tions.Compared with soft and compressible aerogel materials,we envision that the rigid porous foam absorbing material is particularly suitable for environmental extremes.

Multi-functional and multi-scenario applications for MXene aerogels with synergistically enhanced asymmetric modules

The development of multifunctional materials and synergistic applications of various functions are important conditions for integrated and miniaturized equipment.Here,we developed asymmetric MXene/aramid nanofibers/polyimides(AMAP)aerogels with different modules using an integrated molding process.Cleverly asymmetric modules(layered MXene/aramid nanofibers section and porous MXene/aramid nanofibers/polyimides section)interactions are beneficial for enhanced performances,resulting in low reflection electromagnetic interference(EMI)shielding(specific shielding effectiveness of 2483(dB·cm^(3))/g and a low R-value of 0.0138),high-efficiency infrared radiation(IR)stealth(ultra-low thermal conductivity of 0.045 W/(m·K)and IR emissivity of 0.32 at 3–5μm and 0.28 at 8–14μm),and excellent thermal management performances of insulated Joule heating.Furthermore,these multifunctional AMAP aerogels are suitable for various application scenarios such as personal and building protection against electromagnetic pollution and cold,as well as military equipment protection against infrared detection and EMI.

Magnetic nanoparticle-modified hollow double-shell SiC@C@FeCo with excellent electromagnetic wave absorption

Integrated micro and nanostructures,heterogeneous components,defects,and interfaces is the way to develop high-performance microwave absorbing materials.However,there still needs to be more precise experimental routes and effective validation.In this work,by a continuous process of vacuum sintering,hydrothermal,and carbon thermal reduction,magnetic FeCo nanoparticles were successfully embedded on the hollow double-shell mesoporous SiC@C surface,thus solving the challenges of a single component loss mechanism.The hollow double-shell nanostructure introduces air to enhance impedance matching while significantly reducing the density of the material.The extensive defects and heterogeneous grain boundaries effectively enhance the polarization loss capacity.The magnetic loss mechanism introduced by the magnetic particles effectively improves the impedance matching properties of the material.The synergy of these multiple advantages has enabled the SCFC_(2)-8(here SiC@C@FeCo is abbreviated to SCFC,2 represents the initial metal ion content,and 8 represents the hydrothermal time)sample to achieve an adequate absorption bandwidth of 6.09 GHz at 2.0 mm.With a minimum reflection loss of-60.56 dB,the absorption bandwidth can cover the entire C,X,and Ku bands by adjusting the matching thickness(1.3–4.0 mm).This work provides a valuable paradigm for the deeper exploitation of microwave absorption potential and guides the development of other high-performance materials.

Magneto-electric integrated design strategy of NiCo@C composites for synergistic absorption and conversion in mid-high frequency microwaves

Achieving synergistic absorption of electromagnetic waves(EMWs)in the mid-high frequency and absorption band conversion is an urgent problem.However,the present solution is usually a straightforward mixture of magnetic component-carbon component.Hereby,we optimize the magnetic properties and electrical relaxation response from a chemical synthesis perspective.Through integrated design,the contents of carbon components and multi-dimensional morphology are controlled by retaining strong magnetic properties.The morphology design and the construction of heterogeneous interfaces will boost the intense response of charge in the surrounding to enhance the polarization effect.The multi-dimensional structure and electromagnetic(EM)properties of the sample after optimized engineering have an extremely powerful absorption conversion effect on EMW energy.NiCo@C particles ultimately achieve synergistic absorption effects at low thickness(d<3.5 mm)at middle frequencies(6–10 GHz)and high frequencies(10.5–18 GHz).Our work establishes a correlation mechanism between the physical and chemical properties of materials and EM parameters.It also provides insight into the synergistic absorption of EMWs in the mid-high frequency and absorption band conversion strategies.

3D printed propeller-like metamaterial for wide-angle and broadband microwave absorption

It is a challenge to design an absorber which can simultaneously satisfy comprehensive demands of broad absorption band,wide incident angle range,and low-profile.In this work,we designed a metamaterial absorber(MMA)based on the antenna reciprocity theory to achieve the above goals.Firstly,a three-dimensional(3D)propeller-like structure with reference to a typical magneto-electric dipole(MED)an-tenna was proposed and analyzed by the characteristic mode(CM)theory to realize near-omnidirectional radiation.Then,the radiation-absorption conversion was realized by introducing lossy materials into this structure,and the absorption performance was further improved by optimizing the dispersion feature of the lossy materials.Finally,the propeller-like metamaterial absorber with a thickness of 0.113λL was manufactured efficiently and integrally through 3D printing technology.Simulation results showed that the proposed absorber can achieve broadband absorption with the efficiency more than 90%in the fre-quency band of 3.4-10 GHz.It also has excellent wide-angle absorption capacity,with Transverse Electric(TE)polarization of 0°to 50°and Transverse Magnetic(TM)polarization of 0°to 80°.With the increase of incident angle,the upper limit of absorption bandwidth can be gradually extended to 18 GHz.Moreover,the effectiveness in the range of 0°to 60°incident angle is verified by measuring the reflectivity of the 3D printed absorber.

Heterogeneous ZnO@CF structures and their excellent microwave absorbing properties with thin thickness and low filling

With the aim to obtain enhanced absorbing performance at small thickness and low filling,a robust strat-egy to fabricate zinc oxide(ZnO)modified carbon fiber(CF)structures have been successfully prepared by using low temperature hydrothermal method.Due to the multi-interface polarization caused by the high specific surface area of the complex heterostructures and the improvement of impedance matching,the composites show excellent electromagnetic wave absorption properties.Under the condition of low filling content(20 wt%)and ultra-thin thickness(1.5 mm),the excellent absorption performance of minimal reflection loss of−34.4 dB and an effective absorption bandwidth(RL≤−10 dB)of 4.94 GHz is achieved.In addition,the effective absorption bandwidth covers the whole 2-18 GHz band with the increase of thickness from 0.5 to 10 mm.This work provides an innovative method for designing the matching layer of carbon-based absorbing materials,and ZnO@CF heterostructure is expected to become a potential absorbing material.