Excellent Electromagnetic Absorption Research Articles

A magnetic control reconfigurable coded electromagnetic absorbing metamaterial

Electromagnetic absorbing metamaterial with tunability and reconfigurability arisen as an innovative emerging scientific field has attracted huge interest in a frontier academia. Magnetorheological plastomer (MRP) has excellent electromagnetic absorption performance and magnetic-induced properties, is a suitable candidate for the development of magnetic controlled reconfigurable coded electromagnetic absorbing metamaterials. In this paper, we proposed an electromagnetic absorbing metamaterial based on thermoplastic MRP, in which polycaprolactone (PCL) and carbonyl iron particles (CIPs) are used as phase-change and magnetic absorbing elements, respectively. The arch measurement system is used to test the absorbing performance in the range of 2–18 GHz, and used digital coding to design the unit cells with regulable absorption characteristics. The value of reflection loss (RL) is less than −10 dB in the range of 7.44–12.2 GHz, and the minimum RL can reach −17.96 dB. Meanwhile, combined with the thermoplastic property of MRP, the structure of metamaterials can be rearranged under magnetic field. The results showed that the RL in the range of 7.28–11.60 GHz can be still less than −10 dB after the magnetic control reconfiguration. It is demonstrated that the metamaterial with magnetic control, reconfigurability and coding properties have a promising future in improving the application range and absorption and reducing interference.

Preparation and excellent electromagnetic absorption properties of dendritic structured Fe3O4@PANI composites

Fe3O4, as a typical absorber, its electromagnetic wave (EMW) absorption properties are far from meeting the requirements of practical application due to its poor impedance matching. In this study, three kinds of novel heterogeneous structured composites, dendritic Fe3O4@(HCl doped PANI), Fe3O4@(p-TSA doped PANI) and Fe3O4@(dedoped PANI), were prepared via hydrothermal method combined with thermal reduction and in-situ polymerization, and their phase composition, microscopic morphologies, static magnetic properties, EMW absorption performance and absorption mechanisms were investigated. The results showed that the introduction of different medium doped and dedoped PANI greatly enhanced the EMW absorption performance of Fe3O4. The outstanding advantages of Fe3O4@(HCl doped PANI) were that the widest effective absorption bandwidth (EAB) up to 6.08 GHz in a relatively thin thickness of 2.1 mm. And the Fe3O4@(dedoped PANI) composite achieved strong absorption ability (− 53.08 dB@3.04 GHz) at low frequency in a relatively thin thickness (4.9 mm). The remarkable improvement of EMW absorption performance of dendritic Fe3O4@PANI composites could be attributed to the introduction of dissipation mechanisms, the optimization of impedance matching characteristics and the formation of appropriate conductive network microstructure. The dendritic Fe3O4@PANI composites are promising EMW absorption materials and have great practical application value.

Microwave induced in-situ formation of SiC nanowires on SiCNO ceramic aerogels with excellent electromagnetic wave absorption performance

Electromagnetic absorption (EMA) materials with light weight and harsh environmental robustness are highly desired and crucially important in the stealth of high-speed vehicles. However, meeting these two requirements is always a great challenge, which excluded the most attractive lightweight candidates, such as carbon-based materials. In this study, SiCnw-reinforced SiCNO (SiCnw/SiCNO) composite aerogels were fabricated through the in-situ growth of SiCnw in polymer-derived SiCNO ceramic aerogels by using catalyst-assisted microwave heating at ultra-low temperature and in short time. The phase composition, microstructure, and EMA property of the SiCnw/SiCNO composite aerogels were systematically investigated. The results indicated that the morphology and phase composition of SiCnw/SiCNO composite aerogels can be regulated easily by varying the microwave treatment temperature. The composite aerogels show excellent EMA property with minimum reflection loss of −23.9 dB@13.8 GHz, −26.5 dB@10.9 GHz, and −20.4 dB@14.5 GHz and the corresponding effective bandwidth of 5.2 GHz, 3.2 GHz, and 4.8 GHz at 2.0 mm thickness for microwave treatment at 600 °C, 800 °C, and 1000 °C, respectively, which is much better than that of SiCN ceramic aerogels. The superior EMA performance is mainly attributed to the improved impedance matching, multi-reflection, multi-interfacial polarization, and micro current caused by migration of hopping electrons.

Tailoring electronic properties and polarization relaxation behavior of MoS2 monolayers for electromagnetic energy dissipation and wireless pressure micro-sensor

Electromagnetic radiation has become a severe problem due to the widespread utilization of wireless communications and smart electronic devices. Hence, the development of high-performance electromagnetic wave absorbers to overcome the electromagnetic pollution is of utmost significance. Herein, density functional theory (DFT) calculations are adopted to guide the design of high-performance electromagnetic wave absorbers based on layered MoS2. The results indicate that the electronic properties, the dipole moment and the electric polarization of vertically-aligned MoS2 monolayers on N-doped graphene are significantly tuned compared to horizontally-aligned MoS2 monolayers on N-doped graphene and MoS2 nanosheets, favoring the absorption of electromagnetic waves. Based on theoretical predictions, we have combined vertically-aligned MoS2 monolayers and N-doped graphene nanomesh by the spatial confinement effect of the nanomeshs. The experimental results demonstrate that the MoS2 monolayers on N-doped graphene exhibit excellent electromagnetic wave absorption performance with a minimal reflection loss of –72.83 dB and an effective absorption bandwidth of 4.81 GHz even at a matching thickness below 2.0 mm, remarkably outperforming MoS2 nanosheets. The excellent consistency between theoretical and experimental results highlights that the DFT calculations can be employed as a design tool for high-performance electromagnetic wave absorber. Based on the excellent electromagnetic absorption performance of the MoS2 monolayers, a highly sensitive wireless pressure micro-sensor is designed, which has potential apllication in internet of things.

A breathable and flexible fiber cloth based on cellulose/polyaniline cellular membrane for microwave shielding and absorbing applications

High-performance electromagnetic (EM) wave absorption and shielding materials integrating with flexibility, air permeability, and anti-fatigue characteristics are of great potential in portable and wearable electronics. These materials usually prepared by depositing metal or alloy coatings on fabrics. However, the shortcomings of heavy weight and easy corrosion hamper its application. In this work, the cellulose nanofiber (CF) fabric was prepared by electrospinning technology. Then, conductive polyaniline (PANI) was deposited on the CF surface via a facile in-situ polymerization process. The interweaving cellulose/polyaniline nanofiber (CPF) composite constructs a conductive network, and the electrical conductivity can be adjusted by polymerization time. Benefiting from optimal impedance matching, strong conductive loss, as well as interfacial polarization, the CPF possesses excellent EM absorption performance. The minimum reflection loss (RLmin) value is −49.24 dB, and the effective absorption bandwidth (RL < −10 dB, fe) reaches 6.90 GHz. Furthermore, the CPF also exhibits outstanding electromagnetic interference (EMI) shielding capability with shielding efficiency (SE) of 34.93 dB in the whole X band. Most importantly, the lightweight CPF fabrics have the merits of mechanical flexibility, breathability and wash resistance, which is highly applicable for wearable devices.

Edge selectively oxidized graphene on carbonyl iron composites for microwave absorption and radar cross-section performance at X- and Ku-band

This study examined the microwave absorption properties of graphene oxide-carbonyl iron particle (GOCIP) composites and edge selectively oxidized graphene-CIP (EOGCIP) composites with a variation of graphene contents. Due to the addition of selectively oxidized graphene (EOG) to CIP, the resultant EOGCIP composites revealed excellent electromagnetic (EM) absorption properties. Significantly, the minimum reflection loss (RLmin) of −45.37 dB at 10 GHz with a bandwidth (BW@−10 dB) of 4.08 GHz with a thickness of 1.52 mm observed for EOG (5.0 wt%)CIP (72 wt%) composite. Moreover, the highest value of RLmin reached −69.27 dB at 15 GHz with BW@−10 dB beyond 6.47 GHz with a thickness of only 1.33 mm for EOG (0.5 wt%)CIP (72 wt%) composite. In addition, the EOGCIP composites revealed the most robust reduction in the radar cross-section value of approximately 35 dBsm against that of Al flat plate with the same physical area. The EM absorption properties of EOGCIP composites were enhanced compared to those of GOCIP and CIP composites. The increasing content of EOG tunes the dielectric properties of EOGCIP composites to attain proper impedance matching. Moreover, the unique structure of EOG can induce dipolar and interfacial polarization, which increases the dielectric loss in synchronization with magnetic loss resulting in enhanced EM absorption properties. This study suggests a new approach for controlling the EM absorption properties, essentially in the X-band region, which is worthwhile for radar absorption materials (RAM) applications.

Electromagnetic absorbers with Schottky contacts derived from interfacial ligand exchanging metal-organic frameworks

Various types of polycrystals have been regarded as excellent electromagnetic (EM) microwave absorbents, while differentiated heterointerfaces among grains usually manipulate conductive loss and polarization relaxation, especially interfacial polarization. Herein, polar facets that dominated the optimization of EM attenuation were clarified by carefully designing polycrystalline Schottky junctions with metal–semiconductor contacts for the first time. An ingenious ligand exchange technique was utilized to construct Zn-MOF (ZIF-L) precursors for Fe-ZnO polycrystals, in which Fe-containing Fe(CN)63− etching ligand acted as metallic source in Schottky junctions. By adjusting the Schottky contacts in polycrystals, the enhanced grain boundaries mainly induced stronger interfacial polarization and affected the microcurrent lightly. This is because Schottky barriers can cause local charge accumulation on heterointerfaces for polarization relaxation. Additionally, the coexistence of Zn and O vacancies brought a lot of lattice defects and distortions for dipole polarization. Thus, optimal EM wave absorbability was obtained by polycrystals with 8 h ligand exchange and an effective absorption band reaching 4.88 GHz. This work can provide guidance for designing advanced polycrystalline EM absorption materials and also highlight the mechanism and requirement of Schottky junctions dominating polarization.

Excellent electromagnetic wave absorption properties of the ternary composite ZnFe2O4@PANI-rGO optimized by introducing covalent bonds

The ternary composite material ZnFe2O4@PANI-rGO with a core-shell structure and excellent electromagnetic absorption properties has been prepared by covalently modifying reducing graphene oxide with the binary magnetic material ZnFe2O4@PANI. The ternary composite material ZnFe2O4@PANI/rGO forms a " CO–NH ″ covalent bond between ZnFe2O4@PANI and rGO through hydrothermal routes and mechanical stirring. By comparing the two types of the connection method covalent and non-covalent bonds, it was surprised to find that formed by covalently connecting the binary ZnFe2O4@PANI material and rGO (C-ZPr) to obtain extremely excellent electromagnetic absorption performance. By adjusting the thickness from 1 mm to 4 mm, when the filler ratio is 20%, the minimum reflection loss (RLmin) at 2.1 mm was as low as −49.99 dB at 17.28 GHz and the effective absorption bandwidth (RL < 10 dB) was almost 4.32 GHz. The introduction of covalent bonds becomes a bridge connecting magnetic materials and dielectric materials, adjusting electromagnetic parameters, enhancing reflection loss, and achieving impedance matching and improved electromagnetic absorbing performance. This preparation method is expected to provide new ideas for the preparation of high-performance absorbing materials in the future.

A sheath-core shaped ZrO2-SiC/SiO2 fiber felt with continuously distributed SiC for broad-band electromagnetic absorption

Silicon carbide (SiC), has been considered as one of the most suitable options for high-temperature electromagnetic absorption materials (EAMs), and it’s still a challenge to achieve the broad-band absorption performance for SiC-based EAMs. In this work, according to the impedance matching principle, a kind of ZrO2-SiC/SiO2 fiber felt was prepared by combining chemical vapor infiltration (CVI) and oxidation treatment. SiC, as the electromagnetic (EM) absorber, was deposited continuously along the EM transparent ZrO2 fibers, and the SiO2 covered on SiC surface in the oxidation process, forming the unique sheath-core structure. It can form a large amount of interfaces to enhance the polarization loss, leading to excellent EM absorption performance with the reflection loss (RL) smaller than −8 dB at 4.50–18 GHz. The exploration results provide design inspiration to SiC-based EAMs with wide bandwidth strong absorption performance.

N-doped carbon nanotube arrays on reduced graphene oxide as multifunctional materials for energy devices and absorption of electromagnetic wave

Considering serious exhausted non-renewable energy resources and electromagnetic radiation pollution issues, it is quite urgent to exploit multifunctional material for realizing both the conversion sustainable energy sources and protection of electromagnetic radiation pollution. Herein, we develop a facile and high-yield preparation route to fabricate a multifunctional material consisted of CoFe alloy nanoparticles encapsulated in nitrogen doped carbon nanotubes arrays grown on both sides of reduced graphene oxide (CoFe@N-CNT/rGO). CoFe@N-CNT/rGO displays excellent properties in the field of rechargeable Zn-air battery and electromagnetic wave absorption. CoFe@N-CNT/rGO shows bifunctional electrocatalytic performances toward oxygen reduction reaction and oxygen evolution reaction, favorably comparable to that of commercial catalysts (Pt/C and IrO2). Furthermore, the assembled liquid and all-solid-state rechargeable Zn-air batteries with CoFe@N-CNT/rGO as air cathode display good charging–discharging performance. As electromagnetic wave absorbing material, CoFe@N-CNT/rGO shows the minimal reflection loss of −33.2 dB at 13.3 GHz, superior to reported carbon-based electromagnetic wave absorbing materials. Based on excellent electromagnetic absorption performance, electromagnetic energy conversion device is designed to realize reasonable utilization and conversion of the absorbed electromagnetic energy. These encouraging results lay a solid foundation for development the multifunctional material and provide an effective strategy for simultaneously solving energy crisis and electromagnetic radiation problems.

MOF−Guest complex derived Cu/C nanocomposites with multiple heterogeneous interfaces for excellent electromagnetic waves absorption

Electrical conductivity and interfacial polarization are two crucial factors to design high-performance electromagnetic absorption (EMA) materials, but how to synergistically balance these factors still remains to be difficult. In this work, we report the synthesis of Cu/C nanocomposites via the controlled pyrolysis of a MOF-guest complex. The prepared Cu/C nanocomposites are made up of cross-linked carbon network and various irregular particles. The carbon network provides appropriate electrical conductivity to contribute to the conductance loss. Multiple heterogeneous interfaces, such as Mo2C/C, Mo2C/CuO, CuO/C, Mo2C/Cu, and Cu/C interfaces, have been determined in these Cu/C nanocomposites, resulting in obviously improved polarization loss. As a result, the Cu/C nanocomposite exhibits excellent EMA performance, where the efficient absorption bandwidth reaches 6.8 GHz, and the maximal absorption gets to −52 dB. This research provides new idea to design high-performance EMA nanocomposites by tuning the electrical conductivity and interfacial polarization.

Hierarchical porous hollow graphitized carbon@MoS2 with wideband EM dissipation capability

Core-shell materials are promising broadband electromagnetic (EM) absorption materials since the highly component manipulation performance, interfacial effect etc. Herein, a well-defined core-shell shaped structure constructed by 2-dimensional MoS2 nanosheets-coated porous hollow carbon has been successfully designed with controlled pore-sizes of the core, adjustable shell content, and structure. By effectively optimizing the parameters for these factors, the as-prepared hierarchical porous hollow C@MoS2 sample enables an ultra-width EM absorption ability (covering 11.4–18.0 GHz) at a thickness of only 2.0 mm. The detailed contributions of each component and structure on the excellent EM absorption capability have been investigated. These encouraging results indicate that the development of core-shell composites with multiple controllable physical factors is of great significance for the future ultra-wideband electromagnetic absorbers.

Polyimide-based graphene composite foams with hierarchical impedance gradient for efficient electromagnetic absorption

Excellent electromagnetic absorption performance can be controllably adjusted by optimizing impedance gradient of polyimide-based graphene composite foam with hierarchical structure.

Defect-rich titanium nitride nanoparticle with high microwave-acoustic conversion efficiency for thermoacoustic imaging-guided deep tumor therapy

Pulse microwave excite thermoacoustic (TA) Shockwave to destroy tumor cells in situ. This has promising applications for precise tumor therapy in deep tissue. Nanoparticle (NP) with high microwave-acoustic conversion is the key to enhance the efficiency of therapy. In this study, we firstly developed defect-rich titanium nitride nanoparticles (TiN NPs) for pulse microwave excited thermoacoustic (MTA) therapy. Due to a large number of local structural defects and charge carriers, TiN NPs exhibit excellent electromagnetic absorption through the dual mechanisms of dielectric loss and resistive loss. With pulsed microwave irradiation, it efficiently converts the microwave energy into shockwave via thermocavitation effect, achieving localized mechanical damage of mitochondria in the tumor cell and yielding a precise antitumor effect. In addition to the therapeutic function, the NP-mediated TA process also generates images that provide valuable information, including tumor size, shape, and location for treatment planning and monitoring. The experimental results showed that the TiN NPs could be efficiently accumulated in the tumor via intravenous infusion. With the deep tissue penetration characteristics of microwave, the proposed TiN-mediated MTA therapy effectively and precisely cures tumors in deep tissue without any detectable side effects. The results indicated that defect-rich TiN NPs are promising candidates for tumor therapy.

MXene‐derived TiC/SiBCN ceramics with excellent electromagnetic absorption and high‐temperature resistance

AbstractDemand for high‐performance electromagnetic (EM) wave absorbing materials with high‐temperature resistance is always urgent for application in a harsh environment. In this contribution, two‐dimensional material, Ti3C2Tx MXene, was introduced into a hyperbranched polyborosilazane. After pyrolyzation, the as‐prepared TiC/SiBCN ceramics present excellent EM wave absorption in X‐band. The TiC nanograins appearing after annealing provide multilevel reflection and interface polarization. Dipole polarization formed at interface defects, in company with interfacial polarization, also makes a great contribution to enhanced EM wave absorption. The TiC/SiBCN nanocomplex prepared with 5 wt% Ti3C2Tx MXene possesses a minimum reflection coefficient of −45.44 dB at 10.93 GHz and abroad bandwidth 8.4 and 12.4 GHz, almost covering the entire X‐band. Tuning the thickness in the range of 2.35‐2.54 mm, the effective absorption band can achieve the entire X‐band. And the EM wave absorbing performance has been maintained to a large extent at 600°C with the minimum reflection coefficient of −26.12 dB at 12.13 GHz and the effective absorption bandwidth of 2 GHz. Last but not the least, TiC/SiBCN ceramics offer a good thermal stability in argon as well as in air atmosphere, making it possible to serve in high‐temperature detrimental environments. This study is expected to provide a new perspective for the design of high‐performance absorbing materials that are able to be used in harsh environments, especially in high temperatures.

Conductive polyaniline coated on aluminum substrate as bi-functional materials with high-performance microwave absorption and low infrared emissivity

Sheet aluminum powder was used as the substrate and aniline as the polymer monomer, to design novel Al/PANI composites via in-situ polymerization, which exhibited high electromagnetic wave absorption properties and low infrared emissivity. These unique bifunctional composite were systematically characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscope, IR-2 dual-band emission rate measuring instrument and vector network analyzer. The calculated results showed that the maximum reflection loss value of Al/PANI composite reached −46.09 dB at 14.56 GHz with a film thickness of only 1.0 mm. Meanwhile, the infrared emission rate of the composite was 0.55. The excellent electromagnetic absorption performance may be ascribed to its superior conductivity and unique structure. The merits of as-synthesized composites with high-performance microwave absorbing properties and low infrared emissivity indicate the potential use of Al/PANI composites in the applicable stealth fields.

Constructing γ-MnO2 hollow spheres with tunable microwave absorption properties

Hollow γ-MnO2 sphere was obtained by annealing the precursor at 400 °C with different holding time. The influences of different holding time on the morphology and crystalline structure of final products have been discussed in detail, and the microwave absorption properties of the as-products were also investigated. The results exhibited that finer crystalline feature of the γ-MnO2 and larger pore size in the hollow γ-MnO2 sphere could be obtained with the extended holding time. The MnO2/paraffin composites (50 wt% loading) present extraordinary microwave absorption performance, and the minimum reflection loss (RL) values is −51.3 dB at 4.9 GHz with the thickness of 3.5 mm. The excellent electromagnetic absorption properties can be ascribed to the hollow structure, perfect impedance matching behavior and the multiple interface polarization effect.

3D flower-like Co-based oxide composites with excellent wideband electromagnetic microwave absorption

Transition metal oxides because of their excellent dielectric properties have been population for electromagnetic wave absorption application. In this paper, through two-step synthesis, hollow CoSnO3 was in-situ growth between layers of self-assembled flower-like ZnCo2O4 in the solvothermal process. The multi-layer sheet structure of ZnCo2O4 nanoflowers provides growth space for CoSnO3, which can increase interface polarization and natural resonance. Hybrid structure expands the propagation path of electromagnetic waves and the times of reflections and scattering. By adjusting the content of the growing process of CoSnO3, the maximum reflection loss (RL) at 12.4 GHz was −56.0 dB, and the wide effective absorption bandwidth (EAB) of 6.24 GHz (RL < −10 dB) was obtained at a thin matching thickness of 2.6 mm ZnCo2O4@CoSnO3 composites showed satisfactory impedance matching in the frequency range of 2–18 GHz. Therefore, ZnCo2O4@CoSnO3 composites provides a new research idea for electromagnetic wave absorption in morphology designed.

Fabrication of magnesium ferrite microspheres decorated nitrogen-doped reduced graphene oxide hybrid composite toward high-efficiency electromagnetic wave absorption

In this work, magnesium ferrite (MgFe2O4) microspheres decorated nitrogen-doped reduced graphene oxide (NRGO) hybrid composite was fabricated through a solvothermal and hydrothermal two-step method. Results manifested that the three-dimensional netlike structure consisting of MgFe2O4 microspheres and crumpled NRGO was well constructed in the as-synthesized hybrid composite. Significantly, both hybridization with reduced graphene oxide (RGO) and nitrogen doping had few effects on the size of MgFe2O4 microspheres. Furthermore, the influences of hybridization with RGO, nitrogen doping and filler loadings on the electromagnetic absorption properties were carefully examined. It was found that both hybridization with RGO and nitrogen doping were effective strategies to enhance the electromagnetic absorption capacity of MgFe2O4 microspheres. Remarkably, the as-prepared NRGO/MgFe2O4 hybrid composite presented excellent electromagnetic absorption performance, that was the minimum reflection loss of −48.0 dB at 5.2 GHz, and maximum absorption bandwidth of 4.8 GHz under a low filler loading of 25.0 wt% and a small matching thickness of 2.0 mm. In addition, the potential electromagnetic absorption mechanisms were revealed. Therefore, our results could be beneficial to fabricating graphene-based dielectric/magnetic hybrid composites as high-efficiency electromagnetic absorbers.

Spherical shape Co@Co3O4 core-shell composites grown on surface of graphite nanosheets with ultra-thin and excellent electromagnetic absorption performance

In this work, graphite nanosheets (GNs)/Co composites with excellent electromagnetic (EM) absorption performance was designed by a one-step hydrothermal method, and the surface of Co particles were coated with Co3O4 shell layer by a second hydrothermal method to obtain the expected core-shell GNs/Co@Co3O4 structure, and the microtopography, structure and magnetic properties of core-shell GNs/Co@Co3O4 structure were characterized in detail. EM analysis revealed that core-shell GNs/Co@Co3O4 structure has an excellent EM wave absorption performance. For GNs/Co@Co3O4, the excellent reflection loss (RL) is −55.16 dB with an ultra-thin matching thickness of 1.6 mm, and the effective absorption bandwidth (EAB) is 3.84 GHz (from 14.16 GHz to 18.00 GHz) with the ultra-thin matching thickness of only 1.2 mm. In this work, the two hydrothermal methods replaced the conventional core-shell structure method and obtained EM wave absorption core-shell Co@Co3O4/GNs with ultra-thin thickness, strong EM wave absorption capability, and broad absorption bandwidth.