Electromagnetic Wave Absorption Materials Research Articles

UV-modification of Ag nanoparticles on α-MoCx for interface polarization engineering in electromagnetic wave absorption.

The design of electromagnetic wave absorbing materials (EWAMs) has aroused great attention with the express development of electromagnetic devices, which pose a severe EM pollution risk to human health. Herein, an Ag-doped MoCx composite was designed and constructed through a UV-light-induced self-reduction process. The UV-reduction time was controlled on the α-MoC polymer for 0.5-2 hours for modifying different amounts of Ag. As a result, α-MoC@Ag-1.5 exhibited the strongest RLmin of -56.51 dB at 8.8 GHz under a thickness of 3.0 mm and the widest EAB of 4.96 GHz (12.16-17.12 GHz) covering a substantial portion of the Ku-band at a thickness of 2.0 mm due to the synergy of the conductivity loss and abundant interfacial polarization sites. Additionally, a new strategy for computer simulation technology was proposed to simulate substantial radar cross-sectional reduction values with real far-field conditions, whereby absorbing coatings with α-MoC@Ag-1.5 were proved to contribute to a remarkable radar cross-sectional reduction of 37.4 dB m2.

Multifunctional core–shell CaSnO3@N-doped carbon coaxial nanocables with excellent lithium storage performance and efficient microwave absorption

It is highly desirable but challenging to design multi-functional materials for energy storage and electromagnetic (EM) wave absorption.

Entropy engineering enhances the electromagnetic wave absorption of high-entropy transition metal dichalcogenides/N-doped carbon nanofiber composites.

Entropy engineering strategies provide a broader platform for exploring the behavior of electromagnetic wave (EMW) absorption materials and their absorption mechanisms on the microscopic scale. In this work, a novel entropy engineering strategy was developed to improve the EMW absorption properties of MoS2. A hierarchical N-doped carbon nanofiber/MoS2 (NCNF/MS) composite was synthesized using the electrospinning and hydrothermal methods. Then, the conformational entropy of MoS2 was increased by sequentially integrating elements such as W, Se, and Te. Although MoS2 maintains a single 2H-phase structure throughout the entropy increase process, it triggers a series of complex changes at the microscopic level, including lattice distortion, ingenious electronic structure adjustments, and an increase in defect density. These changes provide more possibilities for the EMW interaction with the absorber, which significantly enhances the dielectric behavior of the composites, including conduction and polarization losses. Owing to the unique hierarchical structure and rich defect structure, the obtained entropy-increased NCNF/MWSST exhibits excellent EMW absorption performance. The minimum reflection loss reaches -60.7 dB, and the maximum effective absorption bandwidth is 6.48 GHz, which is improved by almost 584% and 810% compared to NCNF/MS. This study provides a new way to design efficient and high-performance MoS2-based absorbers and provides valuable insights for exploring the entropy-increasing strategies to optimize the EMW absorption properties.

N-doped branched metal–organic framework derivatives to boost multiband microwave absorption with ultrathin thickness

CoNi@NPC/NCNTs composites with a rod-like N-doped carbon matrix and branched N-doped CNTs, prepared via melamine-assisted CVD pyrolysis, demonstrate superior dual-band electromagnetic wave absorption (2–18 and 26.5–40 GHz) with ultrathin thickness.

Robust and flexible composite aerogel films with porous multilayered structures toward broadband electromagnetic wave absorption

Robust composite aerogel films exhibit superior electromagnetic wave absorption performance, owing to multilayered heterostructures assisted by MXene and Ni nanochains.

Preparation of MIL-88(Fe)@Fe2O3@FeSiCr double core-shell-structural composites and their wave-absorbing properties.

To tackle the aggravating electromagnetic wave (EMW) pollution issues, high-efficiency EMW absorption materials are being urgently explored. The FeSiCr soft magnetic alloy is one of the more widely used and well-received iron-based soft magnetic alloy materials with high permeability; however, the development of high-performance FeSiCr alloy wave-absorbing materials is still a major challenge. In this study, double core-shell-structured composites of MIL-88(Fe)@Fe2O3@FeSiCr were successfully prepared by the oxidative heat treatment of the flaky FeSiCr obtained after ball milling and then in situ composited with MIL-88(Fe). The heterogeneous interfacial composition and microstructure were regulated to balance the microwave-loss capability and impedance matching of the material, and an enhancement of the composite absorbing performance was achieved. The composite material had a reflection-loss minimization (RLmin) of -72.65 dB, corresponding to a frequency of 6.61 GHz, with an absorbing coating thickness of 2.97 mm and an effective absorbing bandwidth (RL ≤ -10 dB) of 2.38 GHz (5.42-7.80 GHz). The results of this study provide useful ideas for wave-absorbing materials by applying high permeability soft magnetic alloy micropowders.

An equivalent RLC circuit loss mechanism introduced by Fe2O3 nanoneedle arrays towards high-performance electromagnetic wave absorption materials

The introduction of an equivalent RLC circuit loss mechanism realizes strong EMW absorption in a low-filling ratio and even lower thicknesses.

Microwave absorbing properties of Polypyrrole-based 2D Nanocomposites

The growing prevalence of electromagnetic wave pollution, attributed to the advancement of electronic communication technology, has resulted in an increased demand for electromagnetic wave-absorbing materials. Polypyrrole (PPy) stands out as...

Tuning dielectric and electromagnetic absorption properties of SiC fiber by in-situ grown polycrystalline carbon nanowires

Silicon carbide fiber (SiCf) has a promising potential to develop structural electromagnetic wave (EMW) absorption materials. Tuning dielectric properties of SiCf is necessary to obtain excellent EMW absorption performances, which is always realized by the introduction of extra dielectric loss phases. Herein, in-situ grown polycrystalline carbon nanowires (CNW) as novel dielectric fillers, possessing moderate conductivity as well as efficient loss ability, were used to improve the EMW absorption performance of SiCf. When the content of CNW is suited, CNW can interconnect with each other and form a multiporous network on the surface of SiCf. Such a unique network makes a great contribution to good impedance matching as well as strong conductivity loss and polarization loss, which endows SiCf with an effective absorption broadband (EAB) of 4.14 GHz at a thickness of 3.0 mm, demonstrating superior EMW absorption performance than most previously reported SiCf/carbon hybrids.

Structural engineering of rare earth metal-organic frameworks derivatives with high anisotropy for high-efficiency electromagnetic wave absorption

Structural engineering and component design are crucial for conceiving outstanding metal-organic frameworks (MOFs)-based electromagnetic wave (EMW) absorption materials. However, an efficient and direct clarification of the structural influences on the EMW absorption performance of MOF-based absorption materials remains highly challenging and still awaits exploration. To this end, we synthesized a new type of rare earth (RE) MOFs with hexagonal-bipyramidal, snowflake-like, and dendritic structures through facilely controlling the solvent ratios in a scalable coprecipitation approach. The MOF-derived CeO2/Co/C hybrids with the same component content inheriting the morphological structures showcased tunable dielectric property and EMW absorption performance. The dendritic MOF derivatives with the highest anisotropy achieved a superior EMW absorption performance, manifesting a minimum reflection loss value of −71.5 dB at 1.7 mm and an effective absorption bandwidth of 5.2 GHz at 1.6 mm thickness, comparable to those of the best EMW absorbers. This work not only confirmed the high potential of RE MOF derivatives for EMW absorption, but also directly and efficiently unveiled the mechanism of morphological structure on the dielectric property and EMW absorption performance for the MOF-based EMW absorption material.

Synthesis of SiC nanowires wrapped in trimetallic layered double hydroxide nanosheets with core-shell structure via self-assembly growth approach for effective electromagnetic wave absorption

The optimization of microstructure and composition is an important strategy to obtain high-performance electromagnetic wave absorption (EMA) materials. In this study, several fungus-like two-dimensional (2D) trimetallic layered double hydroxide (LDH) nanosheets have been synthesized with tunable metallic ions of Ni2+, Co2+, and Zn2+ by using a compositional genetic strategy from MOF. Thereafter, a series of core-shell composites have been fabricated at room temperature by the self-assembly growth approach, constructed from 2D trimetallic LDH nanosheets wrapped on 1D SiC nanowires. The composition and structure of the samples can be preserved by varying the Co and Zn ratios. The EMA materials were prepared by performing a thermal treatment approach in the air atmosphere based on the synthesized composites described above. A reasonable integration of dielectric and magnetic components and an opportune core-shell structure provide better impedance matching, multiple reflections and scattering, polarization loss, enhancing conduction loss, and magnetic loss. The results show that NiCo2Zn1-LC@SiC exhibits superior EMA performance with the minimum reflection loss (RLmin) of −44.73 dB at a thickness of 1.86 mm and the maximum effective absorption band (EABmax) of 6.12 GHz at 2.12 mm. This work proves the influence of the structure and composition on absorbers and provides ideas for the design and development of high-performance EMA materials in a facile approach.

Multifunctional Carbon Fiber Reinforced C/SiOC Aerogel Composites for Efficient Electromagnetic Wave Absorption, Thermal Insulation, and Flame Retardancy.

Carbon fiber composites have great application prospects as a potential electromagnetic (EM) wave-absorbing material, yet it remains extremely challenging to integrate multiple functions of EM wave absorption, mechanical strength, thermal insulation, and flame retardancy. Herein, a novel carbon fiber reinforced C/SiOC aerogel (CF/CS) composite is successfully prepared by sol-gel impregnation combined with an ambient drying process for the first time. The density of the obtained CF/CS composites can be controlled just by changing sol-gel impregnation cycles (original carbon fiber felt (S0), and samples with one (S1) and two (S2) impregnation cycles are 0.249, 0.324, and 0.402 g cm-3, respectively), allowing for efficient tuning of their properties. Remarkably, S2 displays excellent microwave absorption properties, with an optimal reflection loss of -65.45dB, which is significantly improved than S0 (-10.90dB). Simultaneously, compared with S0 (0.75 and 0.30MPa in the x/y and z directions), the mechanical performance of S2 is dramatically improved with a maximum compressive strength of 10.37 and 4.93MPa in the x/y and z directions, respectively. Moreover, CF/CS composites show superior thermal insulation capability than S0 and obtain good flame-retardant properties. This work provides valuable guidance and inspiration for the development of multifunctional EM wave absorbers.

One-dimensional N-doped Co@C nanowires via a dual-control strategy for excellent electromagnetic absorption at ultralow filler loading

Currently, the preparation of electromagnetic wave absorption (EMWA) materials with low load, thin thickness, strong absorption and wide band remains an important challenge. In this work, one-dimensional (1D) N-doped Co@C nanowires with the excellent EMWA behavior have been synthesized by pyrolyzing cobalt-nitrilotriacetic acid chelate (Co-NTAC) nanowires prepared via a hydrothermal method. Then, the influences of the amount of glucose and annealing temperature on the microstructure and EMWA property of Co@C nanowires have also been investigated. Our results show that Co@C-2 exhibits a strong absorption of – 69.56 dB (absorbing 99.99999 % electromagnetic wave) with an EAB of 7.055 GHz at only 8 wt% filler loading. In addition, CST simulation shows that the maximum radar cross section (RCS) value of Co@C-2 can be reduced by 29.8 dB m2. The outstanding EMWA property is ascribed to the synergistic effect of the dielectric and magnetic loss. Moreover, the unique 1D structure of Co@C nanowires is also benefit for attenuating electromagnetic (EM) wave. Therefore, this study designed an easy dual-control strategy (by adjusting the amount of glucose and annealing temperature) to obtain the high-performance EMWA materials, which can provide an effective method for the synthesis of other absorbers.

Sr(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3: A novel high-entropy perovskite oxide with enhanced electromagnetic wave absorption properties

Perovskite materials (ABO3) possess a wealth of elements selectable and exhibit a diverse range of octahedral transformations. The emergence of high-entropy perovskite ceramics provides a fresh perspective for advancing the field of wave-absorbing materials. In this study, we concentrate on the wet chemical synthesis of a high-entropy perovskite oxide, Sr(Cr0.2Mn0.2Fe0.2Co0.2Ni0.2)O3, and investigate its crystal structure, microstructure, chemical composition, magnetic properties, and microwave absorbing capabilities. The results indicate that when sintered at a temperature of 1,350 °C, the sample achieves a minimum reflection loss of −54.0 dB at a frequency of 9.68 GHz, accompanied by a maximum effective absorption bandwidth (EAB) of 7.44 GHz at the thickness of 1.8 mm. The high-entropy design of the B-site induces distortions of oxygen vacancy and octahedral structure of the perovskite material. This leads to the fine tuning of its dielectric and magnetic properties, thereby endowing perovskite with excellent electromagnetic wave absorption capabilities. Consequently, perovskite emerges as a promising new electromagnetic wave absorption material with significant potential.

Chiral composite metamaterials with gradient phase index for vortex electromagnetic−wave generation and attenuation

The conversion of incoming electromagnetic-waves into vortex waves by electromagnetic-wave absorption materials (EAMs) is expected to improve the absorption properties, but remains elusive that direct conversion of linearly polarized waves into vortex waves to breakthrough the angular momentum mismatch. In this context, we fabricate chiral composite metamaterials with gradient phase index to realize the mentioned conversion. The chiral composite metamaterials generate vortex waves with topological charges of ± 1 and ± 2 within broad bandwidth from linearly polarized waves, and the arrangement of meta-atoms with different geometric phases manipulate the chirality of vortex waves. Vortex zero of the electric field vector appears near the phase singularity, which induces the far-field diffusive nature of the vortices to enhance absorption. The best absorption peak value of − 33.55 dB is achieved with a topological charge of + 1. Optimal effective absorption bandwidth (reflection loss (RL) ≤ −10 dB) appears when the topological charge is + 2, which reaches 10.97 GHz (7.89 −12.21 and 29.31 −35.96 GHz). Present works provide a research path for the development of novel metamaterials and EAMs.

Multi-scale heterostructures of MXene-based composites for adjustable electromagnetic wave absorption

Nowadays, electromagnetic pollution caused by the development of communication technology and electronic equipment has become an urgent problem to be solved. It is an effective solution to design high-performance electromagnetic wave absorption (EWA) materials with wide-band and powerful absorption characteristics for electromagnetic protection. In this work, a multi-scale MXene/carbon nanotube@Fe3O4 composite material with a heterogeneous structure was synthesized by a solvothermal method, and the high/low-frequency EWA operating bands were adjusted by component regulation. The composite material performed excellent EWA performances based on the synergistic effect of polarization loss, conductive and magnetic loss, and three-dimensional heterointerfaces. Its minimum reflection loss reached − 59.95 dB with an effective absorption bandwidth of 4.7 GHz (13.3–18 GHz), which basically covered the Ku band. Therefore, this feasible scheme is expected to provide an effective strategy for controlling military and civil electromagnetic pollution.

The synthesis and efficient electromagnetic wave absorption properties of RE-MOF microcrystals

Electromagnetic interference is considered as a potential crisis for human health and social development. Therefore, the exploration of novel electromagnetic wave absorption (EMWA) materials with the characteristics of “Thinner”, “Wider”, “Lighter”, “Stronger” is desired. Compared with traditional materials, metal organic frameworks (MOFs) as the emerging hybrid materials, can better meet these requirements. Here, two rare-earth metal based MOFs microcrystals with regular octahedral morphology (size about 15–20 µm), namely MOF 1 and MOF 2 were successfully fabricated. The derived carbon materials, which remained stable octahedral morphology were obtained by carbonization of as-synthetized MOFs at 450 °C under the N2 atmosphere, named complex 1 and complex 2. Further investigation manifested that carbonization could effectively enhance the EMWA performance of these MOFs. Complex 1 attained the minimum RL value of − 23.22 dB and a broad effective adsorption bands(EAB) of 5.76 GHz. Similarly, the minimum RL value for complex 2 attained − 22.31 dB under the thickness of 2.5 mm with the broad EAB of 4.16 GHz.

Graphene encapsulated MnO2 nanorods boosts interfacial polarization for microwave absorption

The lightweight and efficient electromagnetic wave (EMW) absorption materials have been a popular research topic. In this work, MnO2 @graphene (MnGr) nanofibers with core-shell structure were synthesized by a one-step hydrothermal method. This one-dimensional linear structure was further self-assembled into a three-dimensional hierarchical MnGr aerogel network structure due to the interlayer forces of graphene sheets. The addition of graphene greatly enhances the interfacial polarization. The significant differences in electronic structure and work function between the outer graphene layer and the inner MnO2 layer greatly enhance the interfacial polarization. The formation of 3D hierarchical MnGr aerogel network structure constructs more fast electron transport channels. With the addition of graphene oxide at 7.5 wt% of the theoretical yield of MnO2, MnGr-7.5 exhibits excellent wave absorption properties. The effective absorption bandwidth (EAB) can reach 6.40 GHz at 2.2 mm. And the minimum reflection loss (RLmin) is − 41.3 dB at 1.8 mm and 17.36 GHz. Finite element physical simulation is used to simulate the response of 3D conductive network to electromagnetic wave. Through calculation, it is found that the inter-lap network structure is beneficial to enhance the loss. The low-cost MnO2 compounded with a small amount of graphene has excellent wave absorption performance and a great application prospect.

CNTs-improved electromagnetic wave absorption performance of Sr-doped Fe3O4/CNTs nanocomposites and physical mechanism

Electromagnetic wave pollution is a serious environmental problem, and it is urgent to develop high-efficiency electromagnetic wave absorption (EMA) materials. In this paper, carbon nanotubes (CNTs) were combined with Sr-doped Fe3O4 nanoparticles to form Sr-doped Fe3O4/CNTs nanocomposites with by hydrothermal method. After the characterization of microstructure and magnetic properties, EMA properties of Sr-doped Fe3O4/CNTs nanocomposites are investigated in detail. The well-dispersed CNTs lead to the uneven average grain size of Sr-doped Fe3O4 nanoparticles and a little decrease of saturation magnetization. While CNTs greatly improve EMA performance, and SFC1 sample exhibits the minimum reflection loss value of −65.64 dB at 6.32 GHz with the thickness of 3 mm. CNTs reduces the natural resonance of magnetic loss while increasing the permittivity, conductivity, and heterogeneous interfaces. As the result, Sr-doped Fe3O4/CNTs nanocomposites exhibit not only better impedance matching but also higher electric dipole polarization relaxation loss, interfacial relaxation loss, conductivity loss, and eddy current loss. In this way, the excellent EMA performance is attributed to the good impedance matching, intense dielectric loss and enhanced eddy current loss for Sr-doped Fe3O4/CNTs nanocomposites.

Transparent electromagnetic absorption film derived from the biomass derivate

Electromagnetic wave absorption materials featuring small thicknesses and wide effective absorption bandwidth (EAB) are highly required for next-generation portable devices, wearable electronics, and blooming military applications. However, traditional EM particle absorbents, such as carbon-based, magnetic metal-based, and MXene-based materials are always visible black, which severely hinders their utilization as microwave-stealth smart window alternatives. Therefore, it is a critical challenge to fabricate flexible windows simultaneously possessing high optical transmittance and excellent EM wave absorption properties. Herein, we prepared a transparent wood composite with an optical transmittance value of more than ∼83% through a delignification and polymer composite immersion method. The delignification process could remove the light-absorbing lignin component, and the transparent woods were realized by immersing the delignified wood into refractive-index-matched pre-polymerized acrylamide (AM) including minor silver nanowires, carbon nanotubes, and reduced graphene oxides. In addition, due to the presence of numerous polarization centers originating from hydrophilic functional groups and conductive fillers, the transparent wood composite showed superior EM absorption performance, and EAB can reach 9.5 GHz, almost occupying the whole X band (8.2–12.4 GHz) and Ku band (12.4–18 GHz) at a thickness of 2.0 mm. Furthermore, the transparent wood presented a great insulative thermal performance with a low thermal conductivity of 0.45 W m−1 K−1 (half of common glass). The developed transparent wood composites offered significant potential as smart energy-efficient windows with the expectation to survive military equipment and alleviate EM pollution.