Magnetoelectric Synergistic Effect for Electromagnetic Wave Absorption Enhancement

Abstract

With the rapid development of communication and radar detection technologies, there is an increasing demand for high-performance electromagnetic wave absorption materials (EAMs) to ensure electromagnetic protection and radar detection in both civilian and military fields. In general, electromagnetic wave (EMW) absorption is mainly realized by converting the absorbed EMW energy into thermal energy or other forms of energy to attenuate the incident EMW through magnetic loss and/or dielectric loss. Over the past three decades, significant progress has been made in the development of EAMs through the exploration of magnetic coupling, dielectric dissipation, and magnetic-dielectric synergy. This special issue on functional materials for absorbing EMW encompasses 18 research articles on the most updated research advances in the magnetoelectric synergistic enhancement of electromagnetic wave absorption conducted by leading researchers in this area. It covers the design and fabrication of innovative EAMs, composition/structure-performance relationships, discussions on the EMW attenuation mechanism, and development trends of high-performance EAMs. Magnetic loss typically arises from domain wall motion, natural resonance, eddy current, and exchange resonance, and is often attributed to the use of magnetic materials, such as magnetic metals and metal oxides, etc. In 2004, magnetic metal nanoparticles were first introduced into carbon nanotubes (CNTs) to optimize their impedance matching and induce magnetic loss.[1] In this context, researchers have pioneered a series of advanced EAMs based on strong magnetic loss. For example, taking advantage of strong magnetic coupling by a novel gradient pore strategy, Wu et al. fabricated metal–organic framework (MOF) derived Fe/Fe3Co7/Co/C composites, exhibiting excellent microwave absorption capabilities, with strong reflection loss (RL) of −64.7 dB and a wide effective absorption band (EAB) of 5.8 GHz at a thickness of 2.5 mm (2413048). Additionally, Cao et al. recently developed a hetero-dimensional structure by assembling 3D spirally grown VS2 with 2D FeCo-LDH, with macroscopic electromagnetic and electrochemical properties precisely manipulated through defect and interface engineering, showing an efficient shielding effectiveness of over 20 dB in the frequency range of 2–18 GHz (2404280). Dielectric loss is generally attributed to conduction loss and polarization loss (including interfacial polarization, defect-induced polarization, dipole/molecular polarization, and others). Commonly used dielectric loss materials include carbon materials, MXene, metal–organic frameworks (MOFs), etc. In 2015, an ultralight and highly compressible graphene foam was creatively proposed that exhibited broadband and tunable high-performance microwave absorption, achieving an EAB of 60.5 GHz at 1.0 mm thickness.[2] This work sparked considerable interest in highly conductive 2D nanomaterials-based EAMs, such as graphene, MXene, and CNTs. Zhang et al. reported a strategy to construct reversible wrinkle structures on fiber substrates with Ti3C2Tx MXenes. The transformable wrinkles significantly reinforced the fibers, completed conductive pathways, and endowed switchable shielding performances (2314425). Koo et al. prepared highly crystalline Ti3C2Tx MXene, demonstrating excellent electromagnetic interference shielding effectiveness of up to 106 dB at 110 GHz at an ultrathin thickness of 10 µm, along with outstanding environmental stability and processability for solution coating and film fabrication. And their shielding performance could be enhanced by increasing the thickness and electrical conductivity of MXene films, and the frequency of the EMWs (2409346). Recently, Ji et al. fabricated CNT films with improved absorption-dominated electromagnetic interference shielding performance by defect engineering strategies, showing a high absorption effectiveness ratio of 86.9% (2402193). Utilizing different dielectric loss mechanisms, researchers have prepared a variety of high-performance EAMs. For instance, Wu et al. reported the molecular intercalation induced two-phase structural transitions of 1T and 2H MS2 (M = Mo, V, W), resulting in enhanced interfacial polarization and conduction losses. The 1T-MoS2/MOF-A composite exhibited excellent EMW absorption performance with a minimum RL of −61.07 dB at a thickness of 3.0 mm and an EAB of 7.2 GHz at 2.3 mm (2405523). Considering the generation of multiple continuous local electric fields and enhanced electric field polarization, Che et al. prepared a CuxS multilevel rod-like heterostructure with overall axial symmetry using a nanostructured epitaxial step-growth technique, effectively addressing the balance between wideband and strong absorption. Experimental evidence and theoretical simulations confirmed that the CuxS nanostructures exhibited broadband EMW absorption performance, with an EAB of 6.3 GHz at a thickness of 2.0 mm (2406137). Moreover, multiscale structure design strategies, spanning from atomic to macroscopic scales, have been proposed to optimize the impedance matching and promote the dissipation of EMWs through the synergistic effect of multiple dielectric losses, and a series of EAMs with unique structures have been fabricated. For example, Kong et al. proposed a novel multiscale metamaterial absorbers and prepared bimetallic (cobalt and copper) semiconductive metal–organic framework (SC-MOF) materials with specific topological spaces, achieving an unparalleled EAB of 11.33 GHz (2402923). Cheng et al. implemented a cross-scale design strategy to construct polymetallic sulfides (PMS). The cross-scale synergy of microwave absorption led to significantly enhanced EM performance of PMS via micro-polarization to macro-conductance, with an RL of -49.92 dB and an EAB larger than 5.4 GHz at a thickness of 2.0 mm (2405643). Lu et al. fabricated MXene/ reduced graphene oxide (rGO)-based aerogels with multilevel hierarchical configurations by a magnetic field-guided strategy, achieving enhanced EMW absorption performance, with a superior RL of −64.6 dB and a broad EAB of 7.0 GHz at a thickness of 1.8 mm, surpassing alternative aerogels with other configurations (2406133). Ding et al. developed an ant-nest-inspired hybrid composite by optimizing conductive polypyrrole nanotubes (PNTs) within a 3D carbonaceous structure. Thanks to the highly efficient conductive network in the biomimetic composite, the conduction loss was significantly enhanced, allowing the composite to achieve remarkable EMW absorption performance, with an EAB of 5.4 GHz and a maximum RL of −67.6 dB at a thickness of 1.6 mm (2407458). To further improve the EAB and RL values of the EAMs, the magnetic-dielectric synergistic loss mechanism has emerged as a highly promising strategy. To take full advantage of magnetic and dielectric losses, researchers have developed a series of unprecedented magnetic-dielectric core–shell composite EAMs. In 2016, Che et al. synthesized a series of novel CoNi@SiO2@TiO2 core–shell and CoNi@Air@TiO2 yolk–shell microspheres. Owing to the combination of strong magnetic loss by CoNi cores and excellent dielectric loss from TiO2 nanosheets shells, the CoNi@SiO2@TiO2 absorbers exhibited significantly enhanced microwave absorption performance with a maximum RL of −58.2 dB and an EAB of 8.1 GHz.[3] In subsequent studies, they constructed the staggered nanoporous magnetic coupling network with a substantial loading of magnetic Co components via the self-sacrificing template method followed by the domain-confined growth of zeolitic imidazolate frameworks (ZIFs). The network exhibited great EM dissipation capability, with a minimum RL of −51.7 dB and a maximum EAB of 4.8 GHz (2314541). Recently, Huang et al. assembled novel strong magnetic-dielectric synergistic gradient metamaterials (MDSGM) consisting of oriented flake carbonyl iron film and rGO/CNT/cellulose nanofibrils (CNF) aerogel Benefiting from the synergistic effect of strong magnetic–dielectric loss, structural loss, and excellent impedance matching, the MDSGM demonstrated an exciting multispectral ultra-broadband EMW absorption performance with a remarkable EAB covering the whole measured frequency of 1–40, 50–110 GHz, and 0.1–2.0 THz (2314046). In addition to the materials’ inherent strong magnetoelectric loss, appropriate structural design of the EAMs, such as necklace-like hollow structure, 3D carbonaceous structure, 1D expanded 2D structure, and multilevel hierarchical structure, is critical for achieving strong EMW absorption. Accordingly, various structural regulation strategies have also been proposed to enhance the magnetic-dielectric synergistic loss of EMWs. For instance, Gu et al. designed necklace-like hollow polyacrylonitrile (PAN)/carbon nanofibers to improve the impedance-matching characteristics and interfacial polarization loss capabilities. The obtained nanofibers exhibited excellent microwave absorbing performance, with an EAB of 6.6 GHz and a maximum RL of −44.73 dB at a thickness of 1.76 mm (2316722). Fan et al. designed a “1D expanded 2D structure” carbon matrix and introduced semiconductor ZnIn2S4 (ZIS) to construct a carbon/ZIS heterostructure. Benefiting from the interface expansion and the increase in Fermi level difference on both sides of the interface, the interfacial polarization loss was enhanced, leading to excellent EM absorption performance with a maximum RL of −67.4 dB and an EAB of 6.0 GHz (2407217). Overall, the EMW absorption performance of composite EAMs is governed by both the intrinsic properties of the materials and the extrinsic micro-/nano-structural effects. The design strategies for EAMs can be classified into three main approaches: 1) engineering dielectric polarization and magnetic resonance through chemical and microstructural modifications, 2) tailoring macroscopic geometric structures to dissipate EMWs along their propagation path, and 3) applying external electric, magnetic, or thermal fields to optimize the EMW absorption performance. Despite substantial efforts that have been devoted to the design and mechanism study of the EAMs, the discovery of these materials mainly relies on the traditional trial-and-error methods. Furthermore, the fundamental mechanisms governing the electric-magnetic coupled absorption process remain unclear due to the dimensional limitations of current simulation approaches. To address these challenges, innovative machine learning (ML)-based forecasting systems have recently gained significant attention for their ability to perform high-throughput screening of optimal EAMs from infinite material space, as well as predict fabrication conditions, which paves a new pathway for discovering high-performance EAMs and provides a great thrust for the advancement of stealth technology in the upcoming smart era. The authors declare no conflict of interest. Renchao Che is both a full professor at the Laboratory of Advanced Materials (2008) and director of the electron microscope center (2025), at Fudan University. In 2003, he earned his Ph.D. in physics from the Institute of Physics (IOP), Chinese Academy of Sciences (CAS), followed by more than two years of postdoctoral research at the National Institute for Materials Science (NIMS) in Tsukuba, Japan. In 2017, he was awarded the National Science Fund for Distinguished Young Scholars of China. His research interests cover microwave absorption materials, in situ Lorentz TEM, magnetic physics, energy storage/conversion materials, and semiconductor superlattices. Yi Huang is a Distinguished Professor and Vice Dean of the School of Materials Science and Engineering, at Nankai University. He received his Ph.D. in Materialogy from Sichuan University in 2001. Following this he spent two years as a postdoc at Tsinghua University. He is selected as a Leading Talent in Science and Technology Innovation in the National High-level Talent Special Support Program (P. R. China). He won the second prize of the National Natural Science Award in 2018. His research interests include novel low-dimensional nanomaterials, high-performance electromagnetic wave absorption/shielding materials, and intelligent polymer composites and devices. Hualiang Lv is a professor at the Institute of Optoelectronics, Fudan University. Since 2013, he has specialized in the field of electromagnetic functional materials. Prof. Lv has authored over 80 peer-reviewed international publications and has been recognized as an ESI Highly Cited Scientist. His research has been published in prominent journals such as Science Advances, Nature Communications, Progress in Materials Science, and Advanced Materials. His influential work has amassed over 10 000 citations, underscoring his significant contributions to the scientific community.

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