Electromagnetic Wave Absorption Ability Research Articles

Magnetic fly ash@carbon microspheres for high-performance electromagnetic wave absorption

Magnetic fly ash (MFA) solid waste used as electromagnetic wave (EMW) absorbers has attracted considerable attention, due to its easy recovery, stable physicochemical property, and magnetic property. However, the single loss mechanism and narrow absorption frequency band of magnetic absorption materials, limit the improvement of absorption performance. In this study, MFA@carbon (MFA@C) microspheres with tunable microstructure are directly synthesized, by adjusting the heart treatment temperature of chemical vapor deposition process. The optimization of the absorption properties is realized, and the absorption mechanism of the MFA@C microspheres is analyzed and discussed. In addition, the optimal reaction temperature of the MFA@C microspheres is 700 °C. When the thickness is 2.9 mm, the reflection loss of the MFA@C microspheres is up to −49.6 dB, and the effective absorption bandwidth is 4.6 GHz. The results show that the excellent EMW absorption ability of the MFA@C microspheres is attributed to the synergistic absorption of carbon and MFA. The unique cluster structure of MFA@C microspheres enhances the multiple reflections and promotes the interfacial polarization.

Morphology modulated defects engineering from MnO2 supported on carbon foam toward excellent electromagnetic wave absorption

Defect engineering exerts a crucial impact on polarization loss and thereby enhances electromagnetic (EM) wave absorption ability. The EM loss mechanism beneath of morphology conversion is usually vaguely considered as the synergism of multiple mechanisms. Morphology induced defects and its dominated polarization loss mechanisms are little focus on. In this work, MnO2/Carbon foam (MCF) composites with tunable morphology were prepared via facile hydrothermal and annealing process. Morphological conversion of MnO2 and its induced defects were achieved by KMnO4 concentration, which contributes to the reduction of conductive loss, optimization of impedance matching, increase of polarization loss and multiple scattering. Therefore, the minimum reflection loss of MCF composite harvests −65.18 dB at 3.19 mm and the broad effective absorption bandwidth covers the entire X band. Despite multiple dissipation mechanisms, the excellent performance is dominated by morphology modulated defects in MCF composites. Besides, the optimal MCF composite displays a high compressive strength of 14.647 MPa. According to the results of computer simulation technology, the MCF composite can attenuate EM energy in the actual condition. This work is expected to offer an inspired understanding of morphology modulated defects toward high-performance of EM wave absorption materials.

Preparation and electromagnetic wave absorption properties of PDC–SiC/Si3N4 composites using selective laser sintering and infiltration technology

Polymer-derived silicon carbide/silicon nitride (PDC–SiC/Si3N4) composites were prepared by additive manufacturing and infiltration technology. The composite green bodies were prepared using selective laser sintering (SLS) three-dimensional (3D) printing technology. Carbon-rich PDC–SiC was generated via precursor infiltration and pyrolysis (PIP) to increase the dielectric constant and enhance the electromagnetic wave (EMW) attenuation ability of the composites. Low-dielectric materials, including Al2O3, TiO2, and AlPO4, were introduced by sol infiltration to improve the impedance-matching characteristics of the composites. The results showed that the EMW absorption ability of the PDC–SiC/Si3N4 composites enhanced after two and four PIP cycles, whereas it degraded with further increasing the PIP cycle number. Among all the samples, the PDC–SiC/Si3N4 composite after four PIP cycles displayed an excellent EMW absorption ability with the minimal reflection loss of −46.79 dB, whereas its effective absorption bandwidth was narrow. Comparing to the sample without infiltration, the effective absorption bandwidth of the samples after the infiltration treatment with TiO2 or Al(H2PO4)3 sol increased from 1.44 GHz to 4.08 GHz and 3.52 GHz, respectively. These results demonstrate that the PIP process and infiltration with TiO2 or Al(H2PO4)3 sol resulted in a 3D-printed PDC–SiC/Si3N4 ceramic that is a promising EMW absorption material suitable for high-temperature environments.

3D flower-like (MoS2/Fe3O4)@rGO nanocomposites with remarkable EMW absorption property

Electromagnetic pollution affects people's health and interferes with the normal operation of large equipment. Herein, a flower-like (MoS2/Fe3O4)@rGO nanocomposite with significant EMW absorption property were synthesized via hydrothermal and chemical precipitation methods. The reasonable combination of magnetic Fe3O4 with rGO and MoS2 optimizes the composite’s electromagnetic parameters and improve the impedance matching. Consequently, the flower-like (MoS2/Fe3O4)@rGO composite has a minimum reflection loss of up to −64.05 dB at 1.83 mm and an effective absorption bandwidth of 7.34 GHz at 2.5 mm. It is believed that the good electromagnetic wave absorption ability of the material originates from the synergistic effect of various loss mechanisms among the different components of MoS2, Fe3O4 and RGO, as well as the magnetic loss induced by Fe3O4.

MOFs derived Fe/Co/C heterogeneous composite absorbers for efficient microwave absorption

Microwave absorbing materials (MAMs) can effectively attenuate microwave energy and avoid the secondary pollution of microwaves, showing great research significance. However, most of the reported MAMs are short of efficient electromagnetic wave absorption ability in low-frequency microbands (such as S-band in 2–4 GHz). Herein, we proposed a "MOF on MOF" design to obtain a Fe/Co/C multicomponent composite through the synthesis of ion-ligand of two MOFs and subsequent high-temperature pyrolysis, realizing the broadband microwave absorption(MA) and superb electromagnetic wave absorption in S band. ZIF-67 was grown in situ on micron-scale spindle NH2-MIL-88B (Fe) as the bearing matrix to obtain the precursor composed of Fe-MOF and Co-MOF. After pyrolysis at high temperature in an inert atmosphere, the organic components are carbonized to form a carbon layer coated with magnetic nanoparticles composed of Fe and Co. The characteristics of a rich heterogeneous interface and large specific surface area enhance the polarization ability of composite absorbent and the conduction dissipation path of electromagnetic wave. Besides, the composite absorbent can cover the absorption demand of 2–18 GHz with an adjustable thickness. We believe that this composite design of multiple MOFs can provide a new reference for the realization of efficient microwave absorption.

Continuous in-situ growth of carbon nanotubes on carbon fibers at various temperatures for efficient electromagnetic wave absorption

Carbon fiber (CF) has rarely been presented as a promising electromagnetic wave (EMW) absorber because of its excessive electrical conductivity. Herein, the continuous preparation of carbon nanotubes/carbon fiber (CNTs/CF) multiscale reinforcements and microwave absorbers was realized by one-step chemical vapor deposition (CVD) at different temperatures. Beneficial from the intertwined CNTs, good graphitization and crystallinity, and satisfactory epoxy resin wettability, CNTs/CF650 and its composites show excellent tensile, interfacial and interlaminar shear strength. Importantly, CNTs/CF650 obtains a high-performance EMW absorption ability with a minimum reflection loss (RL min ) of −56.11 dB at 7.36 GHz, and delivers an effective absorption band (EAB) of 3.6 GHz at an ultrathin thickness of 1.18 mm. Notably, CNTs/CF700 exhibits the widest EAB (4.2 GHz) at merely 1.35 mm, basically covering the entire Ku-band. The superior RL min and boosted EAB stem from the synergistic effects of multiple heterointerfaces, enriched defects, proper electronic conductivity, and rational impedance matching. Therefore, the work demonstrates a facile and efficient strategy to develop strong EMW absorbers based on CF with light weight, thin thickness, and high strength.

Single source precursor derived SiBCNHf ceramic with enhanced high‐temperature microwave absorption and antioxidation

Electromagnetic (EM) wave-absorbing materials with high-temperature-resistance are urgently desirable to eliminate EM interference in extreme conditions. Precursor derived ceramics (PDC) route is being evolved as an effective strategy to solve the puzzle. Herein, a single source hyperbranched polyborosilazane precursor containing hafnium (hb-PBSZ-Hf) is introduced and the SiBCNHf ceramic is obtained by further pyrolysis. The micro-sized tissues including HfC, SiC, HfB2 nanocrystals and segregated carbons are in situ generated during annealing which not only increase EM wave absorption ability (minimum reflection coefficient (RCmin) is -56.71 dB with a thickness of 2.5 mm, effective absorption bandwidth (EAB) is 3.4 GHz), but also improve antioxidation property (less than 2 wt.% mass fluctuation at 1400 °C in air). Theoretical simulation of complex permittivity suggests that SiBCNHf ceramic has an RCmin of less than -5 dB for the whole X-band even at 1100 °C. Such SiBCNHf ceramic with superior high-temperature-resistance and antioxidation performance derived from single source precursors possesses great potential for EM wave absorbing coatings in high-temperature and harsh environments.

Broadband electromagnetic wave absorption of Ni0.5Zn0.5Nd0.04Fe1.96O4 ferrites modified by nano-silver particles

Ferrite materials have the potential to become excellent absorbing materials due to their high magnetic loss and good impedance matching. However, the disadvantages of high density and lack of dielectric loss capability limit its application. Herein, we used the citric acid sol-gel method and the self-propagating combustion method to prepare neodymium-doped nickel-zinc ferrite (NZNF), then the target effect of Sn2+ and an improved electroless silver plating process was used to plate a layer composed of silver nanoparticles (Ag NPs) with strong dielectric loss on the NZNF, and a magnetic/dielectric composite material (NZNF@Ag) with a heterogeneous structure was prepared. The number and particle size of Ag NPs on the surface of NZNF can be precisely controlled, thereby greatly enhancing the dielectric loss capability with little impact on the magnetic loss. The huge difference in conductivity between conductors and semiconductors promotes the occurrence of polarization at the heterogeneous interface and significantly enhances the electromagnetic wave absorption ability of the composite material. In the 2–18 GHz frequency band, the best sample can obtain an effective bandwidth of 6.82 GHz when the matching thickness is 2.1 mm. Combining conductors with semiconductor materials to obtain significantly enhanced interfacial polarization provides a new idea for improving the performance of wave absorbing materials.

Multifunctional carbon nanofibers coated Co-Zn alloy nanoparticles composite for efficient energy conversion and microwave absorption

Considering the energy crisis and environment pollution, it is urgently to develop multifunctional materials to ensure the sustainable development of human society. Core-shell bimetal/carbon composites have attracted great attention in microwave absorption or electrochemical energy conversion devices, and the composite can overcome the deficient performance of pure carbon materials or pure metal materials. In this work, we proposed a simple method to prepare N-doped carbon nanofibers coated CoZn alloy nanoparticle composites (CoZn/N-CNFs) using CoZn(OH)X nanowires and melamine as precursors through pyrolysis process. The prepared CoZn/N-CNFs exhibited outstanding catalytic property for oxygen reduction reaction (ORR, half-wave potential of 0.814 V vs RHE) in alkaline solution. The CoZn/N-CNFs acted as cathode in rechargeable Zn-air batteries (ZABs) exhibited high open circuit voltage (1.33 V), large output power density (223.8 mW cm−2), and robust stability (87 h, 6 cycles), surpassing the commercial Pt/C-based ZABs. In addition, as an excellent performance electromagnetic wave absorber, CoZn/N-CNFs exhibited favorable impedance matching and electromagnetic wave absorption ability, which has the RLmin of − 33.93 dB under a thickness of 2.1 mm, and the effective bandwidth (RL<−10 dB) of 4.56 GHz with the matching thickness of 2.2 mm. This composite is expected to be a desired metal/carbon composite for ZABs and electromagnetic absorption. This work provides a simple method for the development of multifunctional materials.

Tunable design of ZnFe2O4@C@BPC hybrid with rich heterogeneous interfaces as a hydrophobic electromagnetic wave absorber

Environmentally friendly microwave absorbers with superior electromagnetic wave absorption, lightweight and hydrophobic ability have received considerable attention in practical applications. However, addressing the above-mentioned characteristics is simultaneously a tremendous challenge. Along these lines, in this work, a lightweight and efficient hybrid material was fabricated by employing simple self-assembly of core-shell ZnFe2O4@C nanospheres embedded within longan shell-derived honeycomb-like porous carbon. The results display that the carbon skeleton not only improves the conduction loss, but also promotes the reflection and scattering of EM wave. In addition, the core-shell ZnFe2O4@C microspheres are conducive to enhancing the ability of interface polarization and magnetic loss, and further improving the synergistic effect between the dielectric loss and magnetic loss. Furthermore, the unique structure of the ZnFe2O4@[email protected] endows it excellent hydrophobicity and avoids water vapor contamination in practical applications. Precisely, at a thickness of 3.4 mm, the minimum reflection loss (RL) is up to −58.6 dB at 12.9 GHz. Notably, the effective absorption bandwidth (EAB) is as wide as 9.1 GHz (8.9–18.0 GHz), covering almost the entire X and Ku bands. Consequently, this outstanding performance renders the ZnFe2O4@[email protected] composite quite attractive for a broad range of applications in lightweight, hydrophobic microwave absorption materials.

Defect- and Interface-Induced Dielectric Loss in ZnFe2O4/ZnO/C Electromagnetic Wave Absorber.

Controlling defects and interfaces in composite absorbers can effectively regulate electromagnetic (EM) parameters and enhance the electromagnetic wave (EMW) absorption ability, but the mechanism still needs to be further elucidated. In this study, ZnFe2O4/ZnO/C composite was synthesized via the hydrothermal method followed by post-annealing in different atmospheres. Defects and interfaces were characterized by Raman, PL spectroscopy, XPS and TEM, and their relationship with dielectric loss and EMW absorption performance was discussed in detail. Results show that the N2-annealed ZnFe2O4/ZnO/C composite with abundant defects and interfaces as well as an optimized composition exhibits excellent EMW dissipation ability, with a RLmin value of −17.4 dB and an fe of 3.85 GHz at a thickness of 2.28 mm. The excellent EMW absorption performance originates from suitable impedance matching, significant conduction loss and strong dielectric loss (interfacial polarization, diploe polarization and defect polarization) dominated by lattice defects and interfaces. This study provides a view into the relationship between defects, interfaces, EM parameters and EMW absorption ability, and also suggests an effective way to promote EMW dissipation ability of the absorbers by controlling defects and interfaces.

Synthesis of niobium nitride porous nanofibers with excellent microwave absorption properties via reduction nitridation of electrospinning precursor nanofibers with ammonia gas

In order to solve the pressing issue of electromagnetic interactions, such as radar detection, communications, information processing and transport originates from civil and military fields, the niobium nitride porous nanofibers as novel microwave absorption materials have been prepared by electrospinning method followed the ammonia reduction nitriding process in the present work. The chemical composition, phase composition and pore structure of niobium nitride fibers are related with the reduction nitriding temperature. It was found that the phase of as-prepared nanofibers was quadrate Nb 4 N 5 phase and Nb 5 N 6 phase formed with the increase of reduction nitriding temperature. Meanwhile, the O atoms were still existed in the form of NbN x O y solid solution. The XPS results also demonstrate that niobium nitride nanofibers had residual oxygen element and abundant valence state, which were positive to impedance matching and interface polarization. The nitrogen content increased and the oxygen content decreased with the increase of reduction nitriding temperature. It was verified that the fibers were composed of niobium nitride nano-crystallite and a large number of holes. The average size of niobium nitride nanoparticles and the pore diameter in nanofibers increase as the reduction nitriding temperature increases. The as-prepared niobium nitride nanofibers with characteristic porous fibrous structure would provide the outstanding conductivity loss, magnetic loss, Debye relaxation, multiple reflections and scatterings, and suitable impedance matching. Hereby, the niobium nitride porous nanofibers were synthesized at 800 ℃, it exhibited excellent electromagnetic wave absorption ability and its optimal reflection loss value was − 49.5 dB at 8.9 GHz when matching layer thickness was only 2.04 mm. • A novel niobium nitride porous fibers as microwave absorbing materials were synthesized via electrospinning method followed the ammonia reduction nitriding process. • The optimal reflection loss was as high as − 49.5 dB at a thin thickness was 2.04 mm. • The residual oxygen and porous fibrous structure improved the impedance matching, multiple reflections and scatterings, conductivity loss, and Debye relaxation through the synergistic effect.

3D printed porous biomass–derived SiCnw/SiC composite for structure–function integrated electromagnetic absorption

ABSTRACT Ceramic-based absorbing composite is irreplaceable in high-temperature conditions. This work has fabricated a novel biomass–derived porous SiCnw/SiC composite for structure–function integrated electromagnetic wave (EMW) absorption through selective laser sintering (SLS) 3D printing and carbothermal reduction. SLS processed the biomass-derived wood precursor with unique porous microstructures. The structure–function properties were controlled by changing the SiO carbothermal reduction temperatures, which facilitated the growth of SiC nanowires for effective EMW absorption. The 3D printed porous SiCnw/SiC composite shows efficient EMW absorption abilities with a minimum reflection loss of −49.01 dB and an effective absorption bandwidth of 5.1 GHz. The bulk density and flexural strength of porous SiCnw/SiC composite are respectively 0.73 ± 0.001 g/cm3 and 6.21 ± 0.66 MPa. Despite a high open porosity of 75.58 ± 0.31%, the porous SiCnw/SiC composite demonstrates excellent thermal conductivities of 3.21∼4.99 W/(m·K) and superior fire-resistant ability. The 3D printed SiCnw/SiC composite integrates structure and functions, indicating wide applications in specific harsh environments.

Silicone-encapsulated carbonyl iron filler for corrosion-resistant electromagnetic shielding

Carbonyl iron (CI) powder (CIP) is highly considered for use as a microwave absorber because of the high activity as well as the high magnetic permeability and saturation magnetization; yet, CIP is vulnerable to corrosion and aging in harsh conditions, such as salty and humid (e.g. ocean) or acidic environments, which limit the spectrum of its applications. The coatings can efficiently solve this problem. This study presents a novel simple approach for enhancing the electromagnetic wave absorption ability and the corrosion resistance of CI, which involves PDMS (polydimethylsiloxane) coating on the surface of CI particles using glycine (G) as a grafting agent. The properties of the resultant composite powder (G-CI/PDMS), such as thermal stability, corrosion resistance, hydrophobicity, and electromagnetic absorption, were determined. The thermal stability, hydrophobicity, and corrosion resistance of the G-CI/PDMS were enhanced, compared to CIP, ascribed to the barrier effect of PDMS. The electromagnetic parameters were reduced, but its electromagnetic wave absorption capacity was improved at specific frequencies and absorber thicknesses due to impedance matching. The polarization curves showed that the corrosion potential of the G-CI/PDMS was shifted to the positive direction and the corrosion current decreased by two orders of magnitude, compared to CIP.

Low temperature synthesis of high-entropy (Y0.2Yb0.2Sm0.2Eu0.2Er0.2)2O3 nanofibers by a novel electrospinning method

High-entropy ceramics (HECs) show outstanding properties such as amorphous-like thermal conductivities, colossal dielectric constant, superionic conductivity, enhanced electromagnetic wave absorption ability, super hardness and strength, which are promising for structural and functional applications. However, the high synthesis temperature has become the bottleneck that hinders the scale-up production and practical applications of HECs. It is thus appealing to develop a novel low-temperature process for the synthesis of HECs. To demonstrate the feasibility of low-temperature synthesis, herein, an electrospinning method has been utilized, for the first time, for the synthesis of high-entropy (Y0.2Yb0.2Sm0.2Eu0.2Er0.2)2O3 nanofibers. It has been found that after electrospinning from liquid precursors single phase (Y0.2Yb0.2Sm0.2Eu0.2Er0.2)2O3 solid solution with bixbyite structure can be formed by calcining at a temperature as low as 500 °C, which is at least about 1000 °C lower than that used in the solid-state synthesis method. The as-prepared (Y0.2Yb0.2Sm0.2Eu0.2Er0.2)2O3 nanofibers are continuous and uniform with a smooth surface and a small diameter of 150 nm. It is also intriguing that the average grain size of (Y0.2Yb0.2Sm0.2Eu0.2Er0.2)2O3 is only about 10 nm, which is much smaller than that in the solid-state synthesized powders. In addition, all the elements are homogeneously distributed along the nanofibers. This work demonstrates that high-entropy ceramic nanofibers can be synthesized from liquid precursors at low temperatures through a simple, efficient, and low-cost electrospinning method, which opens up a new avenue for the low-temperature synthesis of HECs.

Mixed-dimensional hierarchical configuration of 2D Ni2P nanosheets anchored on 1D silk-derived carbon fiber for extraordinary electromagnetic wave absorption

• Mixed-dimensional hierarchical of 2D Ni 2 P nanosheets anchored on 1D silk-derived carbon fiber composites were prepared. • A minimum reflection loss of −56.9 dB and a broad effective bandwidth of 7.2 GHz with 20 wt% filling ratios were achieved. • Ni 2 P not only shows remarkable dielectric characteristic and EMW absorption ability, but also denote to dual-conductive loss and polarization relaxation loss. Considering a series of electromagnetic pollution problems brought by the development of electronic communication technology, more attention has been paid to the research of electromagnetic wave (EMW) absorbing materials with unique composition and structure. Herein, under the inspiration of mixed-dimensional hierarchical structure, 2D Ni 2 P nanosheets anchored on 1D silk-derived carbon fiber is successfully fabricated as a gratifying resistor-dielectric type absorber. By a controllable pyrolyzation strategy and disproportionated reaction, high-density 2D Ni 2 P nanosheets were grown vertically and cross-linked on the surface of 1D silk-derived carbon fiber. The sample exhibited superior EMW absorption performance with maximum reflection loss value of – 56.9 dB at the thickness of 2.32 mm and the effective absorption bandwidth can reach to 7.2 GHz at the thickness of 1.93 mm. In addition, the pure Ni 2 P shows remarkable dielectric characteristic and EMW absorption ability as well. The integration of dual-conductive loss, enhanced polarization relaxation loss and the multiple scattering in the composites was proved to contribute to the good EMW absorption performance. Therefore, this work confirms the great potentials of Ni 2 P as a high-efficient EMW absorbing materials and light a new way in construction of multidimensional absorber.

Micro-flower like Core-shell structured ZnCo@C@1T-2H-MoS2 composites for broadband electromagnetic wave absorption and photothermal performance

Core-shell structure has been receiving extensive attention to enhance the electromagnetic wave (EMW) absorption performance due to its unique interface effect. In this paper, a micro-flower like ZnCo@C@1T-2H-MoS2 was prepared through MOF self-template method. The introduction 1T-2H-MoS2 shell helps optimize impedance matching of the CoZn@C particles to improve the EMW absorption ability. The minimal reflection loss (RLmin) value of ZnCo@C@1T-2H-MoS2 is −35.83 dB with a thickness of 5.0 mm at 5.83 GHz and the effective absorption (RL < -10 dB) bandwidth up to 4.56 GHz at 2.0 mm thickness. Meanwhile, the overall effective absorption bandwidth (OEAB) can reach up to 13.44 GHz from 4.56 to 18.0 GHz. Moreover, ultrafast photothermal performances are also achieved, which can guarantee the normal functioning of ZnCo@C@1T-2H-MoS2 materials in cold conditions. The excellent EMW absorption and photothermal performance are attributed to the unique structure designed with the core of magnetic ZnCo@C rhombic dodecahedral and the shell of dielectric micro-flower like 1T-2H-MoS2 optimize impedance matching.

Etching engineering and electrostatic self-assembly of N-doped MXene/hollow Co-ZIF hybrids for high-performance microwave absorbers

Exploring high-performance microwave absorbing materials with lightweight, thin thickness and strong electromagnetic wave (EMW) absorption capability is an essential way to solve EMW pollution problems. Herein, layered N-doped MXene (Ti3CNTx) flakes and hollow Co-ZIF particles (HCF) hybrids were successfully fabricated using the controllable cooperative protection etching strategy and the electrostatic self-assembly technology. Remarkably, the microwave absorption hybrids achieved ultrathin (1.43 mm), and strong EMW absorption ability (reflection loss of −55.02 dB) with a rather low filler loading, which is superior to the magnetic–dielectric hybrids with similar components reported in the literatures. The synergistic effect generated by the improvement of dielectric loss, magnetic loss and interface polarization could effectively integrate with the impedance matching to improve the attenuation ability of EMW. Therefore, this simple assembly and etching strategy opens a new platform for designing hollow and layered materials and broadens the desirable candidates for lightweight and high-efficient microwave absorbers.

Construction of excellent electromagnetic wave absorber from multi-heterostructure materials derived from ZnCo2O4 and ZIF-67 composite

Structure and composition of materials have an irreplaceable effect on their electromagnetic wave absorption ability. In this study, a series of heterogeneous interface reconstruction products (ZnCo2O4-CoO@N/C, ZnO-Co@N/C and Co3ZnC-Co@N/C) was obtained by calcining the prepared ZnCo2O4@ZIF-67(MOF) heterogeneous precursor composite material at different temperatures. The results show that, ZnCo2O4-CoO@N/C shows excellent reflection loss (RL) of −17.82 dB with the maximum effective absorption bandwidth (EAB) of 3.77 GHz, ZnO-Co@N/C shows RL of −62.7 dB with EAB of 5.75 GHz and Co3ZnC-Co@N/C shows RL of −67.97 dB with EAB of 5.23 GHz. The results further confirmed that the absorbing materials with multi-heterogeneous interfaces can achieve better impedance matching and reflection loss through multiple reflections and scatterings as well as the synergistic effects of conductive loss, dielectric loss and magnetic loss. The research results also show that the composition of the multi-heterointerface absorbing material has an important influence on its absorption performance. Therefore, this work provides an important thought for the design and preparation of high-performance multi-heterointerface absorbing materials.

Novel bimetallic MOF derived hierarchical Co@C composites modified with carbon nanotubes and its excellent electromagnetic wave absorption properties

In the severe electromagnetic wave pollution situation, the absorbers must meet the requirements of lightweight, strong absorption, thin thickness and wide band. Under such a circumstance, it is of great significance to construct reasonable structure and composition for excellent electromagnetic wave absorption. Therefore, the Co/C composites anchored with carbon nanotubes (Co@CNTs) have been successfully prepared by rationally regulating the growth of bimetallic MOF and subsequent pyrolysis process. It is revealed that the conduction loss and polarization loss caused by the carbon nanotubes with different lengths and densities and the porosity of the composites are together responsible for the attenuation of electromagnetic wave. As expected, the hierarchical Co@CNTs composites showed a strong reflection loss of −76.6 dB and a broad effective absorption bandwidth of 6.2 GHz through the improvement of impedance matching and electromagnetic wave absorption ability. Herein, this work presents a strategy for the development of composites as promising electromagnetic wave absorbent.