Facile Synthesis of Hollow ZnxFe3–xO4@Porous MnO2/rGO Conductive Network Composites for Tunable Electromagnetic Wave Absorption

Recent Advances in Structural Design of Carbon/Magnetic Composites and their Electromagnetic Wave Absorption Applications

Electromagnetic pollution protection and military stealth technologies underscore the urgent need to develop efficient electromagnetic wave-absorbing materials (EWAMs). Traditional EWAMs suffer from single absorption loss mechanisms, poor impedance matching, and weak reflection loss. To date, combining dielectric loss with magnetic loss in EWAMs have proven to be an effective approach to enhancing electromagnetic absorption performance. The structural design of composites plays a pivotal role in improving impedance matching and enhancing the attenuation of electromagnetic waves. It is widely regarded as one of the principal methods for fine-tuning electromagnetic parameters and response mechanisms. Among these, composites of carbon and magnetic materials have become a research hotspot due to their magnetoelectric synergistic effects and versatile microstructure design. Herein, the principles of electromagnetic wave absorption in terms of both the loss mechanism and impedance matching are outlined. The research progress on core-shell, skeleton, and hollow structure of carbon/magnetic composite EWAMs are summarized. The synthesis methods, absorption properties, and attenuation mechanisms of composites with these structures are described in detail. Finally, the limitations of carbon/magnetic composites in electromagnetic wave absorption are discussed, possible solutions are proposed, and future development directions for carbon/magnetic composite EWAMs are envisioned.

Fabrication of the Fe-Doped Corona Schiff Base for Enhanced Microwave Absorption Performance

A corolla-shaped Schiff base polymer was synthesized from terephthalaldehyde (TPAD), glutaraldehyde (GA), and p-phenylenediamine (PPD) by block copolymerization, and Schiff base iron complexes were formed by doping with FeCl3. The microscopic morphology, crystal structure, and elemental valence state were characterized by field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Comparing the change of conductivity before and after Fe3+ doping, it was found that the conductivity did not break away from the category of insulator, and the doped sample is a paramagnetic material. Morphological changes were observed by adjusting the ratio of GA to TPAD, and it was found that the corolla-like structure was most complete when the ratio of GA to TPAD was 2:1, and its Schiff base iron complex absorbed waves better. At a thickness of 3 mm, the absorption effect can reach below -10 dB at 12.44-15.16 GHz, and the maximum absorption value is -45.07 dB at a thickness of 3.8 mm; it is an organic absorbing agent with excellent impedance matching and absorbing properties.

Electromagnetic Wave Absorption and Mechanical Properties of CNTs@GN@Fe3O4/PU Multilayer Composite Foam

With the development of intelligent communications and stealth technology in the military field, electromagnetic wave pollution cannot be ignored, and absorbing materials have entered people's field of vision and gradually become a research hotspot. The ideal absorbing material should have the characteristics of "strong, wide, thin, and light", but a single absorbing material often cannot meet the above conditions. At present, absorbing metal powder combined with two-dimensional carbon nanomaterials (such as carbon nanotubes, graphene, etc.) has became a trend. This article focus on a three-layer composite of Fe3O4, Carbon nanotubes@ Fe3O4, Carbon nanotubes@Graphene nano-platelets@ Fe3O4, which was synthesized by solvothermal method. The results show that the electromagnetic wave absorption performance of the three-layer foam at a thickness of 3.0 mm is more excellent. The minimum of RL can reach -67.0 dB, and the effective bandwidth is above 5.0 GHz. All this is due to the synergy of dielectric and magnetic loss between Fe3O4, CNTs, and GN, the increase of interface polarization and the path of electromagnetic wave reflection and scattering by three-layer foam.

Boosted multi-polarization from silicate-glass@rGO doped with modifier cations for superior microwave absorption

Multi-polarization structural design was proved to be a resultful strategy to achieve superior microwave absorbers but limited by the low dielectric properties. In this work, silicate-glasses (SG) nanoparticles doped with different modifier cations (M) have been synthesized by the sol-gel method. Modified silicate-glasses (M-SG) nanoparticles were loaded on reduce graphene oxide (rGO) nanosheets through hydrothermal possess and high-temperature calcination with adding a silane coupling agent (KH-550). The dielectric loss and impedance matching were improved through the synergistic effect of rGO and M-SG. The microwave absorption (MA) performance of M-SG@rGO has been highly boosted, and the minimum reflection loss (RL) is -69.2 dB with a thickness of 2.8 mm. Meanwhile, the X-band and Ku-band absorption can also be obtained with specific M-SG loading at a particular thickness. The results demonstrate that the effects of dipole polarization and interface polarization all play a vital role in improving the microwave absorption performance of M-SG@rGO absorbers.

Constructing and optimizing hollow ZnxFe3-xO4@polyaniline composites as high-performance microwave absorbers

In this study, a series of hollow Zn_xFe_3-xO₄@polyaniline composites (ZFO@PANI) were synthesized by a facile solvothermal process and followed by in-situ chemical oxidation polymerization method, and then evaluated as microwave absorption (MA) absorbers. The effect of ZFO content on the electrical conductivity, electromagnetic parameters and MA performance of the ZFO@PANI composites was also elaborately investigated. As anticipated, the optimized composites of S2 exhibits the minimum reflection loss (RL_min) of -59.44 dB at 11.04 GHz with a matching thickness of 2.31 mm, and the broadest effective absorption bandwidth (EAB, RL < -10 dB, >90% absorption) of up to 4.65 GHz (13.35-18.0 GHz) at 1.72 mm. Noticeably, by adjusting the thickness from 1.5 to 5.0 mm, it can be observed that its RL_min values are all much lower than -10 dB and the qualified EAB can cover the entire C, X and Ku bands. The enhanced MA performance of S2 is mainly due to the efficient synergistic effect between dielectric loss (PANI) and magnetic loss (ZFO nanosphere), and thus achieving the relative balance of impedance matching (appropriate ZFO content) and attenuation capability. Therefore, it has great prospect to be explored as attractive candidate in practical application.