High-performance Microwave Absorption Research Articles

Core-shell heterogeneous graphene-based aerogel microspheres for high-performance broadband microwave absorption via resonance loss and sequential attenuation

Graphene-based aerogels have been attracted wide attention in microwave absorption (MA) for their lightweight and high-efficient absorption. However, the assembly design of their shape and structure is still lacking, bringing obstacles to the optimization of MA. Herein, we applied coaxial electrospinning to shape aerogel monoliths into aerogel microspheres (AMs) with core–shell bilayer structure, exhibiting distinguishing broadband and tunable high‐performance MA. The composite AMs including reduced oxide graphene/Fe3O4 shell layer and chitosan derived carbon core layer ([email protected]/Fe3O4) can be achieved via coaxial electrospinning-freeze frying followed by calcination. The core–shell structure can make electromagnetic wave sequential entry and attenuate, enhancing the impedance matching and electromagnetic wave propagation. Significantly, with a low loading of 5 wt%, the core–shell AMs exhibit a minimum reflection loss of − 61 dB at 13.84 GHz with the thickness of 2.5 mm, and the effective absorption bandwidth reach 6.88 GHz. More importantly, the corresponding absorption bandwidth is further widened to 7.52 GHz by adjusting the core–shell ratio. Electromagnetic simulation further indicate the core–shell bilayer coupling including electromagnetic wave sequential attenuation and cavity resonance loss can realize the enhanced broadband MA. The core–shell bilayer structure strategy paves a way to achieve graphene-based aerogel absorbers with high‐performance MA.

Enhanced microwave absorption property of ferroferric Oxide: The role of magnetoelectric resonance

• Direct fluorination was applied to decorate Fe 3 O 4 . • Core–shell fluorinated Fe 3 O 4 was fabricated by controlling the fluorination conditions. • The microwave absorption property of Fe 3 O 4 was enhanced after fluorination. • Electromagnetic wave dissipation model of magnetoelectric resonance was proposed. • The in-depth mechanism of magnetoelectric resonance was elucidated. The modification of ferrites can effectively improve their microwave absorption (MA) properties. However, attempts to improve their high-frequency performance were still limited and considerably cumbersome for practical application. Herein, we present a facile method that effectively improves the MA behavior of Fe 3 O 4 through direct fluorination using F 2 /N 2 gas. Specifically, we fabricated core–shell structured fluorinated Fe 3 O 4 (F-Fe 3 O 4 ) with a fluorine-doped shell and an unmodified Fe 3 O 4 core by carefully controlling the F 2 concentration and fluorination temperature. We found a unique ‘magnetoelectric collaborative resonance’ (MDR) effect in F-Fe 3 O 4 , manifested by the co-occurrence of double dielectric and magnetic resonance peaks at 14.8 and 16.6 GHz. Band gap measurements and molecular simulations results indicated that the smaller energy gap derived from fluorine doping facilitates both electron hopping between the mixed-valence Fe 2+ /Fe 3+ states and electron accumulation at the core–shell interface, which induce simultaneous magnetic exchange interactions and the Maxwell–Wagner effect (interface polarization). As a result, the incident electromagnetic wave can be dissipated via magnetic exchange resonance coupled with dielectric resonance, thereby improving the MA properties at the same frequency of MDR. Compared with those of pristine Fe 3 O 4 , the minimum reflection loss of F-Fe 3 O 4 was four times higher, reaching −64.9 dB, and the effective absorption bandwidth was 5.03 GHz, which is almost 1.6 times higher. We believe this facile and effective modification method and the unique loss mechanism of MDR will advance the structural design of high-performance MA materials.

Construction of NiCo2O4 nanosheets-covered Ti3C2Tx MXene heterostructure for remarkable electromagnetic microwave absorption

The development of a high-performance electromagnetic microwave (EMW) absorber is pivotal for the practical realization of EMW pollution issues. However, the design of EMW absorbers with ultra-high reflection loss (RL < −70 dB) at ultrathin matching thickness (<2 mm) still faces daunting challenges. Herein, a NiCo2O4 nanosheets-covered Ti3C2Tx MXene (NiCo2O4 NSs-MXene) heterostructure with multi-layered MXene and vertically grown ultrathin NiCo2O4 nanosheets prepared by detachment process, reflux reaction, and heat-treatment is introduced as a new EMW absorber; this heterostructure enables a shocking EMW absorption performance with RL value of −72.3 dB at a thickness of 1.7 mm. The effective absorption bandwidth (EAB, RL < −10 dB) can also reach a relatively impressive 3.6 GHz. Furthermore, the NiCo2O4 NSs-MXene heterostructure shows large dielectric loss derived from conductive loss, interface polarization, and dipolar polarization. The high magnetic loss in the heterostructure originates from natural resonance and eddy current loss. Hence, the synergistic effect of dielectric loss, magnetic loss, and impedance matching promote the superior EMW absorption performance of NiCo2O4 NSs-MXene heterostructure. This achievement paves the way for the exploitation of heterostructure as an ultrathin and super-strong EMW absorption performance.

N-doped residual carbon from coal gasification fine slag decorated with Fe3O4 nanoparticles for electromagnetic wave absorption

• Fe 3 O 4 @N-doped residual carbon composites were successfully fabricated. • The effective absorption bandwidth reached 4.16 GHz at 1.5 mm thickness. • Strong absorption, broad bandwidth and thin thickness were simultaneously achieved. • The reasons for high-performance microwave absorption are studied. The electromagnetic wave absorption (EMWA) performance of materials is affected by their dielectric and magnetic properties. Here, ferroferric oxide@N-doped residual carbon (Fe 3 O 4 @NRC) composites were successfully fabricated by decorating NRC with Fe 3 O 4 nanoparticles via a facile chemical co-precipitation method. The RC was obtained through acid treatment to remove the inorganic minerals in coal gasification fine slag. The structure, composition, thermal stability, morphology, and related EM parameters of the as-fabricated Fe 3 O 4 @NRC composites were thoroughly tested via analytical techniques. Notably, both the Fe 3 O 4 @NRC-2 and Fe 3 O 4 @NRC-3 composites exhibited superior EMWA capacity. When 40% mass was added, the value of minimal reflection loss ( RL min ) for Fe 3 O 4 @NRC-2 was −37.4 dB, and the effective absorption bandwidth (EAB, RL ≤ −10 dB) reached 4.16 GHz (13.84–18.00 GHz) at a thickness of 1.5 mm. Besides, the value of impedance matching was 1.00 as the RL min was achieved. The results demonstrated that the EMWA performance of the composites could be adjusted by controlling the content of Fe 3 O 4 nanoparticles. The magnetic/carbon composites exhibited superior EMWA performance, thus promoting the resource utilization of residual carbon in coal gasification fine slag from coal gasification. The effective absorption bandwidth of 4.16 GHz and minimal reflection loss of −37.3 dB at 1.5 mm thickness were achieved for the Fe3O4@NRC composites. The dielectric loss originated from dipole plarization and interfacial polarization, conduction loss were beneficial to the enhancement of optimal impedance matching and suitable attenuation capacity. This work can provide a significant guidance for the resource utilization of coal gasification fine slag in the field of electromagnetic wave absorption.

Ultralight and ordered lamellar polyimide-based graphene foams with efficient broadband electromagnetic absorption

• Ordered lamellar polyimide-based graphene foam has been constructed. • More lamellar interfaces are formed inside the foam per unit volume. • Lamellar porous structure promotes the layer-by-layer dissipation for incident EMW. • Microwave absorption can be adjusted via controlling microstructure of the foam. The development of high-performance microwave absorption materials with strong absorption capacity and broad bandwidth is highly desirable in the field of electromagnetic pollution protection. Herein, ultralight polyimide-based graphene foam with ordered lamellar structure is precisely designed and controllably constructed by bidirectional freezing process. More lamellar interfaces formed inside the foam per unit volume effectively facilitate the layer-by-layer dissipation for the vertical incident electromagnetic waves, thereby endowing the foam with efficient broadband electromagnetic absorption performance. More importantly, electromagnetic absorption performance can be controllably adjusted by optimizing impedance distribution and microstructure of skeletons. As a result, the optimized foam with an ultralow density of 9.10 mg/cm 3 presents a minimum reflection loss value of −61.29 dB at 9.25 GHz and an effective absorption bandwidth of 5.51 GHz (7.06–12.57 GHz, covering the whole X band) when the thickness is 4.75 mm.

A novel hierarchical structure comprised of biomass-derived porous carbon and silicon carbide nanowires for highly efficient microwave absorption

Recently, porous carbon-based composites with nano- or micro-pores have been considered as attractive alternatives for microwave absorption. However, the dispersity and uniformity of nanomaterials in the porous carbon is not desirable, inducing poor interfacial compatibility and impedance mismatch. Herein, a novel biomass-derived hierarchically porous C/SiC composite (HPCC) with a two-level structure was successfully fabricated. The first level of microscale porous structure templated from dried apple, while the nanoscale bioinspired structure was constructed by in situ growth of SiC nanowires. The hierarchical structures were conducive to enhancing the microwave absorption performance of HPCC. The reflection loss of HPCC was −44.2 dB at a thickness of 1.5 mm, and the broad effective absorption bandwidth reached 4.2 GHz. The synergistic effects of the hierarchical structure on adjusting the impedance matching and the multiple loss mechanisms were investigated in detail. The results provide valuable guidance for fabricating hierarchical structures with high microwave absorption performance.

Ultralight MOF-Derived Ni3S2@N, S-Codoped Graphene Aerogels for High-Performance Microwave Absorption.

To develop high-performance microwave absorption materials with the features of lightweight, thin thickness, broad bandwidth, and strong absorption, an ultralight Ni3S2@N, S-codoped graphene aerogel with a density of 13.5 mg/cm3 has been fabricated by the use of metal-organic frameworks (MOFs) to directly initiate the gelation of graphene oxide strategy. In such a strategy, dual-functional 1D Ni-MOF nanorods not only act as the gelation agent but also afford the doping elements (N and S) originated from the organic species and the precursor for metal sulfide. Due to the synergistic effects of good impedance matching and multiple losses, the optimal reflection loss (RL) of as-prepared Ni3S2@N, S-codoped graphene aerogel reaches −46.9 dB at 17.1 GHz with only 2.0 mm and ultralow filling content (1.75 wt%). The maximum effective absorption bandwidth (EAB) reaches 6.3 GHz (11.7–18.0 GHz) at 2.38 mm, covering the whole Ku band. Moreover, the value of EAB with the RL less than −30 dB can be tuned to 12.2 GHz (5.8–18 GHz) at the absorber thickness ranging from 1.9 to 5.0 mm. This work provides insight for rational design and fabrication of multicomponent-containing graphene aerogels, showing the potential application in lightweight and high-performance microwave absorption.

Porous composites of vertical graphene sheets and Fe3O4 nanorods grown on Fe/Fe3C particle embedded graphene-structured carbon walls for highly efficient microwave absorption

It is significantly important but remains challenging to prepare high performance microwave absorption materials in civil and military fields. Here, the Fe/Fe3C particles embedded in graphene-structured porous carbon (FGPC) served as a three-dimensional framework is prepared by simple carbothermal reduction, then vertical graphene nanosheets (VGSs) and Fe3O4 nanorods are successively grown on FGPC (FGPC/VGSs and FGPC/VGSs/Fe3O4) by thermal chemical vapor deposition, solution method, and subsequent heat treatment. As for comparison, VGSs and Fe3O4 nanorods grown on GPC without Fe/Fe3C particles (GPC/VGSs and GPC/VGSs/Fe3O4) are also prepared. The microwave absorption properties of them are investigated. Benefiting from the multi-component integration and well-designed structure, the FGPC/VGSs/Fe3O4 exhibits impressive microwave absorption performance with an optimal reflection loss of −64.7 dB at 15.3 GHz, a matching thickness of 1.7 mm, filler loading of 12 wt%, and effective absorption bandwidth of over 4.8 GHz. This results from the balance of impedance match and attenuation capability. In detail, the introduction of magnetic particles and nanorods improves the impedance match. The multiple reflections and scatterings, moderate conductive loss and magnetic loss enhance the attenuation of microwaves. Thus, this work might open an avenue to design a highly efficient and lightweight multi-dimensional multiple component microwave absorbers.

Mixed-dimensional engineering of 3D MXene ultralight hybrid aerogel for anticorrosive and microwave absorption applications

Microwave absorption materials have attracted tremendous attention because of the ubiquitous electromagnetic radiation. Although numerous efforts have been devoted to improving the absorption performance, it is still challenging to design multifunctional microwave absorbers to satisfy versatile applications. Herein, an ultralight three-dimensional aerogel assembled with two-dimensional Ti3C2Tx and one-dimensional Kevlar nanofibers was fabricated via freeze-drying followed by annealing. Owing to the mixed-dimensional engineering strategy, the ultralight aerogel (6.02 mg⋅cm−3) exhibited a broad effective absorption bandwidth of 6.9 GHz at a low loading of 0.79 wt% in the supporting matrix. Moreover, the aerogel had a strong anticorrosive ability. Benefiting from the interconnected porous structure, the aerogel demonstrates excellent comprehensive properties, including temperature-independent anti-compressive performance, strong hydrophobicity, and high absorption capacities for organic liquids. These results suggest that the mixed-dimensional engineering is an effective strategy for designing high-performance multifunctional microwave absorbers.

Corrosion-Resistant Graphene-Based Magnetic Composite Foams for Efficient Electromagnetic Absorption.

Designing and fabricating high-performance microwave absorption materials with efficient electromagnetic absorption and corrosion resistance becomes a serious and urgent concern. Herein, novel corrosion-resistant graphene-based carbon-coated iron (Fe@C) magnetic composite foam is fabricated via self-assembly of iron phthalocyanine/Fe3O4 (FePc hybrid) on the graphene skeletons under solvothermal conditions and then annealing at high temperature. As a result, the rational construction of a hierarchical impedance gradient between graphene skeletons and Fe@C particles can facilitate the optimization in impedance matching and attenuation characteristic of the foam, realizing the efficient dissipation for incident electromagnetic waves. Additionally, the performance of electromagnetic absorption can be controllably regulated by optimizing annealing temperature and/or time. More importantly, the formation of a carbon-coated iron structure substantially improves the corrosion resistance of magnetic particles, endowing the composite foam with excellent stability and durability in microwave absorption performance.

Phase engineering reinforced multiple loss network in apple tree-like liquid metal/Ni-Ni3P/N-doped carbon fiber composites for high-performance microwave absorption

Microscopic manipulation and appropriate multicomponent design are still challenging for keeping up with the future development direction for high-efficient electromagnetic wave (EMW) absorbers with unique structure. In this work, apple tree-like Galinstan/Ni-Ni3P/N-doped carbon fiber composites were successfully fabricated through electroless plating and subsequent pyrolysis process. N-doped carbon fiber, derived from silkworm cocoons, is employed as one-dimensional skeleton to generate conductive network and dipole polarization due to intrinsic existence of amino acids. The phase engineering from amorphous Ni-P to crystalline Ni-Ni3P create countless heterogeneous interfaces, double conductive pathway and enhanced permeability, thus promoting the dielectric/magnetic response with incident EMW. And the introduction of the Galinstan is beneficial to manipulate the permittivity and impedance matching degree. By tailoring pyrolysis temperature, the optimal composite produces outstanding EMW absorption performance at the thickness of only 2.05 mm, whose strongest reflection loss can reach −51.73 dB with an effective absorption bandwidth ranging from 9.7 to 13.5 GHz. Besides, CST simulation also evidently show the suppression (13.7 dBm2) with incident EMW of samples in the actual environment. This thorough exploration of the phase engineering and bio-inspired construction of multicomponent system develops a referable route toward the high-efficient EMW absorbers.

Combustion synthesis of porous Fe3-xZnxO4 powders for high-performance microwave absorbers

Fe3-xZnxO4 (x = 0.1, 0.2, and 0.3) powders were synthesized by facile combustion method using metal nitrates as oxidants and glycine as fuel. The structural, microstructural, magnetic, and microwave absorption properties are characterized as a function of Zn2+ substitution. With the increase of Zn2+ contents, some hematite (α-Fe2O3) phases appeared together with the magnetite (Fe3O4) phase. The transmission and scanning electron microscopy observations showed that the particle size was decreased from 120 to 70 nm, while the amount and size of pores increased with adding Zn2+ cations. The as-synthesized Fe2.9Zn0.1O4 powders had the highest saturation magnetization of 92 emu/g, which decreased to 72 emu/g for the Fe2.7Zn0.3O4 sample. The Fe2.8Zn0.2O4 sample exhibited an intense reflection loss of −53 dB in the Ku band at the matching thickness of 2 mm. Despite the reduction of reflection loss, the effective bandwidth increased up to 5.5 GHz with the Zn content, which is attributed to the better impedance matching and higher contribution of magnetic and dielectric loss mechanisms.

Harvesting yolk-shell nanocomposites from Fe-MIL-101 self-template in NaCl/KCl molten salt environment for high-performance microwave absorber

• The molten salt environment facilitates the construction of yolk-shell structure. • The resulting nanocomposite presents remarkable microwave absorption performance. • The effective absorption bandwidth covers the whole X band. • The synthesis strategy integrates the dielectric-magnetic dual-loss effect. The widespread exposure to electromagnetic radiation makes the development of electromagnetic absorber materials an important research topic. While most of the research effort is devoted to the optimization of material compositions, the construction of microstructures is equally indispensable for the enhancement of microwave absorption performance. In this work, we demonstrate how the microwave absorption performance of Fe@C composites can be improved by adopting Fe-MIL-101 as a precursor and being subsequently converted in a unique yolk-shell microstructure by the one-step carbonization process with the help of the NaCl/KCl molten salt environment. Contributed by both the compositions and the construction, the minimum intensity of reflection loss can be achieved at −45.53 dB at 9.85 GHz at a thickness of 2.5 mm, signifying an absorption ability of more than 99.99% incident microwave. Besides, the effective absorption bandwidth covers the whole X band at this thickness, ranging from 8.2 to 12.5 GHz, demonstrating that the microwave absorber could be applied in protecting objects from military radar detection. By integrating the advancement between the microstructure and the components, we propose a promising strategy catering to improving the microwave absorption performance.

Design of hierarchical core-shell ZnFe2O4@MnO2@RGO composite with heterogeneous interfaces for enhanced microwave absorption

In order to overcome the problems caused by electromagnetic pollution, the design and development of high-performance microwave absorbers is urgently required. In this work, a hierarchical ZnFe 2 O 4 @MnO 2 @RGO composite was successfully fabricated via a facile and rapid hydrothermal method. Its unique core-shell structure and synergistic effect between multiple components are beneficial for electromagnetic wave absorption. The morphology, elemental composition, microstructure and microwave absorption characteristics were systematically studied. With a filler loading of 20 wt%, the composite presents a minimum reflection loss (R Lmin ) of −46.7 dB and an effective absorption bandwidth (EAB) as wide as 5.2 GHz at a thickness of 2.5 mm. The superior absorption ability profits from a special microstructure, good impedance matching, multiple attenuation features, interfacial polarization, and the synergistic effect of dielectric and magnetic loss. Consequently, this work lays a foundation for the design of high-performance electromagnetic wave absorbers with multicomponent heterogeneous structures.

Biomass-derived carbon decorated with Ni0.5Co0.5Fe2O4 particles towards excellent microwave absorption performance

Searching forhigh efficiency microwaveabsorbersis to meet the requirements ofelimination of electromagnetic pollution. Herein, the Ni0.5Co0.5Fe2O4 decorated pomelo peel-carbon microwave absorber with uniform particle size was prepared by a facile physical blending method. The skeleton structure formed by biomass carbon (BC) can not only effectively improve the conductive loss, but also extend the propagation path of electromagnetic waves. Besides, the absorber with a great quantity defects and heterogeneous interfaces delivers interfacial polarization and dipole polarization. Also, the Ni0.5Co0.5Fe2O4 particles with good dispersion on BC are beneficial toward dielectric-magnetic combination, resulting in impedance matching. The minimum reflection loss (RL) reaches −41.6 dB and the effective absorption bandwidth (EAB) (RL < −10 dB) is 4.3 GHz with the thickness of 3 mm. This work will promise a good approach to accomplish high performance of microwave absorption.

Three-dimensional FeMZn (M = Co or Ni) MOFs: Ions coordinated self-assembling processes and boosting microwave absorption

Herein, we construct two metal–organic frameworks (MOFs) composite nanoflowers (NFs) with anisotropic binary assembled structures by a facile one-pot method. Different from the two-step epitaxial growth method, the anisotropic assembly of the binary MOFs (MOF-5 and MIL-88B) in the mixed system can be realized without preparing the template MOFs. The ions coordinated self-assembling behaviors during the formation of the three-dimensional (3D) structure are clarified. The absorbing mechanisms of the derivative absorber are elucidated. The results indicate that the special hierarchical assembled structure endows absorbers with rich heterogeneous interfaces, porous structure, suitable impedance matching and complementary loss mechanisms. The optimized absorbers FeCoZn@C NFs and FeNiZn@C NFs exhibit outstanding microwave absorption performance. Only with a matching thickness of 1.9 mm, the effective absorbing bandwidth (EAB, reflection loss (RL) < −10 dB) of the absorber covers 6.0 GHz (12–18 GHz, the entire Ku band). The minimum reflection loss (RLmin) reaches −53.1 dB (loss of electromagnetic waves above 99.999%). This study might shed light on the preparation of high-performance microwave absorbers with sophisticated structures.

Superhydrophobic nanocomposites of erbium oxide and reduced graphene oxide for high-performance microwave absorption

Engineering of electromagnetic wave absorbing materials featuring long-term durability in harsh outdoor environments (e.g., humidity, acid, and alkali conditions) is meaningful for their effective and sustainable implementation. Herein, morphology-controlled erbium oxide-reduced graphene oxide composites are designed for effective absorption of electromagnetic microwaves either in an acidic or alkaline environment. The engineered nanocomposites with chrysanthemum-like structures display good impedance matching, moderate attenuation constant, exchange resonance, natural resonance, multiple reflections, and polarization relaxations, therefore exhibiting excellent microwave absorption capacity with a minimum reflection loss of −37.18 dB and an effective absorption bandwidth of 5.1 GHz. In addition, the chrysanthemum-like composite also displays self-cleaning property, strong weatherability, and acid- and alkali-resistance, enabling sustained electromagnetic wave absorbing performance even in corrosive conditions (1 M HCl, 1 M NaOH). The findings indicate that, through structural engineering, erbium oxide-reduced graphene oxide composites can serve as a promising microwave absorber in harsh outdoor environments.

Grafting thin N-doped carbon nanotubes on hollow N-doped carbon nanoplates encapsulated with ultrasmall cobalt particles for microwave absorption

It is desirable but challenging to integrate 0D, 1D and 2D materials into 3D nanostructures for the microwave absorption. Herein, short and thin N-doped carbon nanotubes (NCNTs) encapsulated with sub-2-nm magnetic Co particles grafted on hollow nanoplates (HCNP) are fabricated after ZIF-67 nanoplates were annealed at a lower temperature relative to conventional chemical vapor deposition methods. The as-fabricated HCNP/NCNT assembled with 0D, 1D and 2D nanostructures features 3D interconnected open structure, endowing them with abundant interfaces and defects that facilitate its microwave absorption. The minimum reflection loss (RLmin) of −41.08 dB with a thickness of 2 mm and effective absorption bandwidth (EAB) of 4.26 GHz with a thickness of 1.8 mm were achieved by the HCNP/NCNT, superior to the counterparts without NCNTs. Besides its unique structural feature, density functional theory (DFT) calculations demonstrate that the increased microwave absorbability of the HCNP/NCNT is also relevant to the additional dipole polarization and interfacial polarization caused by the NCNTs. Based on the computer simulation technology (CST) results, the HCNP/NCNT can attenuate microwave energy under the actual conditions. The proposed controllable synthesis method may open a new avenue for the reasonable design of high-performance microwave absorbers.

Fabrication of ultralight nitrogen-doped reduced graphene oxide/nickel ferrite composite foams with three-dimensional porous network structure as ultrathin and high-performance microwave absorbers

The development of lightweight and high-performance microwave absorbers is still a challenge in the field of electromagnetic absorption. Graphene foam with three-dimensional (3D) network structure and low bulk density has been considered as an ideal candidate for microwave absorption. In this work, nitrogen-doped reduced graphene oxide/nickel ferrite composite foams were prepared by the solvothermal and hydrothermal two-step method. The as-prepared composite foams had very low bulk density (7.8 ∼ 10.0 mg·cm−3) and a unique 3D porous network structure. Furthermore, results revealed that the microwave absorption performance of attained composite foams could be improved by adjusting the calcination temperature. Significantly, the obtained composite foam exhibited the best microwave absorption performance when calcined at 650.0 °C for 2.0 h. The minimum reflection loss was as large as −60.6 dB at an ultrathin matching thickness of only 1.55 mm, and the effective absorption bandwidth could reach 5.5 GHz with a thin thickness of 1.62 mm. In addition, the possible microwave attenuation mechanisms of attained composite foams were proposed. It was believed that our results could be helpful for developing graphene-based 3D magnetic composites as lightweight and high-performance microwave absorbers.

Facile preparation of C/MnO/Co nanocomposite fibers for High-Performance microwave absorption

The C/MnO/Co nanocomposite fibers were prepared via a facile electrospinning and subsequent carbonization process. Co acting as the magnetic nanoparticles and MnO nanoparticles serving as impedance modulator were introduced, effectively inhibiting the agglomeration of carbon fibers during annealing. This optimizes the microstructure and significantly improves the microwave absorption performance of the nanocomposites with diameters of 250–350 nm and rough surface morphologies. The nanocomposite fibers with equal MnO and Co molar contents exhibited the minimum reflection loss of − 71.7 dB at a frequency of 14.1 GHz and an absorber thickness of 2.3 mm, and the effective absorption bandwidth reached at 6.3 GHz at a thickness of 2.6 mm. The high microwave absorption performance can be attributed to the synergistic coactions of conduction loss, magnetic loss, interfacial polarization, and multiple scatterings derived from the rational design of the constituents and microstructure of the nanocomposites.