Construction of self-assembled bilayer core-shell V2O3 microspheres as absorber with superior microwave absorption performance

Intelligent Tunable Wave-Absorbing CNTs/VO2/ANF Composite Aerogels Based on Temperature-Driving

The development of new electromagnetic absorbing materials is the main strategy to address electromagnetic radiation. Once traditional electromagnetic wave-absorbing materials are prepared, it is difficult to dynamically change their electromagnetic wave-absorbing performance. Facing the complexity of the information age and the rapid development of modern radar, it is significant to develop intelligent modulation of electromagnetic wave-absorbing materials. Here, CNTs/VO2/ANF composite aerogels with dynamic frequency tunability and switchable absorption on/off were synthesized. Based on the phase change behavior of VO2, the degree of polarization and interfacial effects of multiple heterogeneous interfaces between VO2 and CNTs and aramid nanofibers (ANFs) were modulated at different temperatures. With the increase in temperature (from 25 to 200 °C), the maximum absorption frequency of the frequency tunable aerogel is modulated from 12.24 to 8.56 GHz in the X-band, and the absorption intensity remains stable. The maximum effective switching bandwidth (ΔEAB) of the wave-absorbing switchable aerogel is 3.70 GHz. This study provides insights into intelligent electromagnetic wave absorption performance and paves the way for temperature-driven application of intelligent modulation of electromagnetic absorbers.

In Situ Atomic Reconstruction Engineering Modulating Graphene-Like MXene-Based Multifunctional Electromagnetic Devices Covering Multi-Spectrum

With the diversified development of big data, detection and precision guidance technologies, electromagnetic (EM) functional materials and devices serving multiple spectrums have become a hot topic. Exploring the multispectral response of materials is a challenging and meaningful scientific question. In this study, MXene/TiO2 hybrids with tunable conduction loss and polarization relaxation are fabricated by in situ atomic reconstruction engineering. More importantly, MXene/TiO2 hybrids exhibit adjustable spectral responses in the GHz, infrared and visible spectrums, and several EM devices are constructed based on this. An antenna array provides excellent EM energy harvesting in multiple microwave bands, with |S11| up to - 63.2 dB, and can be tuned by the degree of bending. An ultra-wideband bandpass filter realizes a passband of about 5.4 GHz and effectively suppresses the transmission of EM signals in the stopband. An infrared stealth device has an emissivity of less than 0.2 in the infrared spectrum at wavelengths of 6-14 µm. This work can provide new inspiration for the design and development of multifunctional, multi-spectrum EM devices.

Synergetic dielectric and magnetic losses of melamine sponge-loaded puffed-rice biomass carbon and Ni3ZnC0.7 for optimal effective microwave absorption

Multi-dimensional design and the combination of multiple phases can effectively enhance the dielectric loss properties and multiple reflection effects of absorbers. Herein, a novel multi-dimensional microporous nanostructured composite, melamine sponge (MS) loaded puffed-rice biomass carbon (C) together with bimetallic carbide material Ni3ZnC0.7 (Ni3ZnC0.7-MS/C) was synthesized by simple vacuum filtration and hydrothermal calcination. The result indicates that small Ni3ZnC0.7 particles with little Ni doping uniformly decorated on the surfaces of the three-dimensional (3D) melamine sponge and puffed rice carbons. The Ni3ZnC0.7-MS/C composite mixed with paraffin (weight ratio of 1:2) exhibited the best electromagnetic wave (EMW) absorption performance, and the minimum reflection loss (RLmin) value of the Ni3ZnC0.7-MS/C composite reaches -107.7 dB with a matching thickness of 2.78 mm and the maximum effective absorption bandwidth for RL below -10 dB (EABmax) is adjusted to 9.2 GHz at a matching thickness of 4.0 mm. The dipole polarization effect of the N doping and the different interfaces provided by the 3D structure of the MS carbon enhance the conduction loss and interface polarization, while the positive effects of eddy current and resonance caused by Ni3ZnC0.7 effectively improve the microwave absorption performances. This melamine sponge-loaded bimetallic carbon composite exhibited a magnetic/dielectric loss combination, resulting in a high-performance absorber with lightweight, cost-effective and efficient properties.

Porous Carbonaceous Aerogels Composed of Multiscale Carbon-Based Units for High-Performance Microwave Absorption

Structural engineering is definitely a promising and effective approach to develop excellent microwave absorbing materials with quantities of advantages. Especially, when carbon materials act as the constituents, the fabricated absorbers are available to gain more prominent absorption performance. However, extra high conductivities and the widespread aggregations and stacking of low-dimensional carbon materials always detrimentally affect the impedance matching and weaken the attenuation capacity, inevitably confining their further absorption applications. Herein, by introducing the amorphous chiral carbon nanocoils to overcome the challenges and achieve the strategies of structure optimization and multicomponent recombination, the reduced graphene oxide/carbon nanocoil/carbon nanotube aerogels were successfully synthesized by a successive hydrothermal method and freeze-drying strategy. The as-obtained aerogels possess a porous architecture that contribute to the extraordinary impedance matching and multiple reflections, which integrate the multifarious dielectric loss mechanisms of diverse carbon materials simultaneously. Benefiting from the tricomponent synergistic effect, the ultralight aerogels reach an outstanding microwave absorption property with an extremely low filler content of only 6 wt %. This work provides a helpful approach to design hierarchical absorbers consisted by multidimensional carbon materials for fantastic microwave absorption.

Urchin-like Fe3O4@C hollow spheres with core-shell structure: Controllable synthesis and microwave absorption

The steadily increasing use of microwave stealth materials in aerospace flying vehicles needs the development of lightweight absorbers with low density and high thermal stability for printing or spraying. In that regard, the structural designability of typical microwave absorbers made of Fe₃O₄ seems to be a significant roadmap. In this work, a hollow spherical structure with a uniform carbon shell around the urchin-like Fe₃O₄ core (Fe₃O₄@C) was produced via a two-step hydrothermal method and annealing. The Fe₃O₄@C absorber exhibited a strong minimum reflection loss (RL_min) of -73.5 dB at the matching thickness of 3.23 mm. The maximum effective absorption bandwidth (EAB_max) was 4.78 GHz at 4.55 mm. The proposed urchin-like core-shell structure was shown to provide good impedance matching and electromagnetic loss ability due to the synergistic effect of Fe₃O₄ and C. In particular, the urchin-like structure increases the heterogeneous interfaces and effectively improves their polarization and relaxation. On the other hand, it reduces the density of the absorber and enhances multiple scattering attenuations of electromagnetic waves (EMWs). Therefore, the findings of the present study open up prospects for the design of high-efficiency lightweight microwave absorbers with specialized structures.