Microwave Absorption Materials Research Articles

Ultra-Flexible microwave absorber of PEDOT:PSS/Melamine composite film with wide tunable frequency controlled by Self-Strain sensing

The exploration of smart microwave (MW) absorption materials with excellent mechanical properties and wide frequency tuning ability is challenging work. Herein, an ultra-flexible MW absorber with wide frequency modulation by itself strain sensing has been successfully constructed, which is realized by introducing doped conductive poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT:PSS) with dimethyl sulfoxide (DMSO) into three-dimensional melamine foam (MF) network. The formed MF/P-D20 composite itself is a piezoresistive sensor with a high sensitivity. Most importantly, it is found that the absorption frequency band of the MF/P-D20 composite film can be controllably and reversibly modulated in a wide frequency range from S to Ku bands by changing the compression strain monitored by the value of ΔR/R0. Furthermore, theoretical simulations and experimental findings confirm that the variations of pore shape and size after compression serve as a crucial factor responsible for shifting the enhanced electron flux density and MW loss to higher frequency, which consequently induces the shift of impedance matching and sequent MW absorption to higher frequency. The MW absorber also shows excellent properties of mechanical robustness, thermal insulation, electro-thermal conversion and retardant. This study provides insights into the smart and reversible control of MW absorption properties and paves the way for tuning MW absorption frequency in wide frequency.

Modulating multiple interfaces, defects, and dual-scale interlinked frameworks of cotton-derived spiral CF@Ni@CNT fibers for boosted thermal conduction and microwave absorption

Developing dual-functional materials with excellent thermal conduction and microwave absorption has emerged as a critical strategy for addressing increasingly serious electromagnetic pollution and heat dissipation difficulties. While the advancements in these materials are constrained by their high loading and incompatible performance. To develop a thermally conductive and microwave-absorbing material with a low load, this work fabricates a series of cotton-derived spiral fibers, i.e., carbon fibers (CFs), carbon fiber/Ni (CF@Ni) fibers, and carbon fiber/Ni/carbon nanotube (CF@Ni@CNT) fibers, via a freeze-drying calcination method. By controlling the amount of nickel acetate (n) and methylbenzene volume (V), we finely modulated the multiple heterostructure interfaces, dual-scale interconnected network, defects, and magnetic/dielectric-loss of the spiral CF@Ni@CNT fibers. Results show that the comprehensive properties of spiral CF@Ni and CF@Ni@CNT fibers, obtained by combining spiral CFs with magnetic Ni nanoparticles and/or CNTs, are significantly improved. The spiral CF@Ni fibers formed at n = 8.4 mmol exhibit a lower thermal conductivity (TC = 3.64 W/m⋅K) but a wider absorption bandwidth (EAB = 6.4 GHz; 10 wt% load) than CFs. Besides, the spiral CF@Ni@CNT fibers formed at n = 4.2 mmol and V = 2 mL bear a higher TC (4.27 W/m⋅K) and a larger EAB (7.52 GHz/mm) at the same load (10 wt%). The low load could be ascribed to the low percolation threshold of a dual-scale interconnected framework consisting of CFs, CNTs, and Ni0. Additionally, the simultaneous improvement in thermal conduction and microwave absorption of the spiral CF@Ni@CNT fibers is associated with their magnetic-dielectric dual loss, electron-phonon co-transmission, and dual-scale interconnected framework.

Single-atom Zn confined in hierarchical hollow microstructure as an acid/base-resistant microwave absorption materials

Single-atom Zn confined in hierarchical hollow microstructure as an acid/base-resistant microwave absorption materials

Magnetic poly(ionic liquid)/graphene oxide/Fe3O4 composites with multiple loss mechanisms for microwave absorbing

Microwave-absorbing materials are very important to reduce electromagnetic interference and pollution. Combining multi-component materials with multiple loss mechanisms is a practical strategy for enhancing microwave absorption performance. In this work, we synthesize a magnetic poly(ionic liquid) (PVim[FeCl4]) with crosslinkable groups and prepare PVim[FeCl4]/graphene oxide (GO)/Fe3O4 composites by incorporating GO and Fe3O4 to enhance the microwave absorption property of the composites. The synergistic effect of GO and Fe3O4 is studied at different feeding ratios, the PVim[FeCl4]/10%GO/20%Fe3O4 composite shows better microwave absorption performance, with a minimum reflection loss (RLmin) of −49.54 dB at 17.31 GHz and 7.1 mm thickness, along with an effective absorption bandwidth (EAB) of 2.52 GHz. This enhancement can be attributed to the quarter-wavelength matching model, well-matched characteristic impedance, and multiple loss mechanisms originating from PVim[FeCl4], GO, and Fe3O4. The magnetic poly(ionic liquid) composites show promising prospects in microwave absorbing materials.

Plasma Engineering toward Improving the Microwave-Absorbing/Shielding Feature of a Biomass-Derived Material.

During the past decade, ever-increasing electromagnetic pollution has excited a global concern. A sustainable resource, facile experimental scenario, fascinating reflection loss (RL), and broad efficient bandwidth are the substantial factors that intrigue researchers. This research led to the achievement of a brilliant microwave-absorbing material by treating pampas as biomass. The carbon-based microfibers attained by biowaste were treated by plasma under diverse environments to amplify their microwave-absorbing features. Moreover, a pyrolysis scenario was performed to compare the results. The reductive processes were performed by H2 plasma and carbonization. However, the CO2 plasma was performed to regulate the heteroatoms and defects. Interestingly, polystyrene (PS) was applied as a microwave-absorbing matrix. The aromatic rings existing in the absorbing medium establish electrostatic interactions, elevating interfacial polarization, and physical characteristics of PS augment the practical applications of the final product. The manipulated biomasses were characterized by Raman, X-ray diffraction, energy-dispersive spectroscopy, field emission scanning electron microscopy, and diffuse reflection spectroscopy analyses. Eventually, the microwave-absorbing features were estimated by a vector network analyzer. The plasma-treated pampas under H2/Ar blended with PS gained a maximum RL of -90.65 dB at 8.79 GHz and an efficient bandwidth (RL ≤ -10 dB) of 4.24 GHz with a thickness of 3.20 mm; meanwhile, plasma treatment under CO2 led to a maximum RL of 97.99 dB at 14.92 GHz and an efficient bandwidth of 7.74 GHz with a 2.05 mm thickness. Particularly, the biomass plasmolyzed under Ar covered the entire X and Ku bands with a thickness of 2.10 mm. Notably, total shielding efficiencies of the treated bioinspired materials were up to ≈99%, desirable for practical applications.

Temperature regulated Fe3Si@SiC@carbon core-shell structure with high-performance microwave absorption

Developing high-performance microwave absorbing materials (MAMs) to address the electromagnetic wave pollution is still a huge challenge. Multi-interface core-shell structure with magnetic and dielectric loss components have been attracting extensive attention as MAMs for the enhanced interfacial polarization and impedance matching. In this work, magnetic loss core and dielectric loss bi-shell structure Fe3Si@SiC@C (FSC) composite was synthesized through hydrothermal, self-polymerizing coating and high temperature thermolysis. The thermal treatment temperature has a great effect on the morphology structure and electromagnetic properties of FSC. The results indicated that the FSC exhibited an effective absorption bandwidth (EAB) of 4.24 GHz at a thickness of 1.4 mm, and an EAB of 12.4 GHz with the absorber thickness varied from 1 mm to 3 mm. Furthermore, the microwave attenuation mechanism of the FSC composite were investigated in detail. The integration of magnetic core with multiple dielectric shells provides a design deliberation and reference for further high-performance MAMs fabrication.

Manganese oxides/graphene aerogels as lightweight microwave absorbers for extreme environment application

The development of microwave absorbing materials (MAMs) with photothermal and electrothermal properties can satisfy special requirements for MAMs used in extreme environment. Herein, manganese oxide/graphene aerogel (MnOx/GA) composites were successfully fabricated by uniformly growing MnOx on GA through combining the hydrothermal and freeze-drying methods. The MnOx/GA composite exhibits a distinctive three-dimensional network structure with heterogeneous interfaces and lattice defects that can optimize the impedance matching and enhance the interfacial polarization, resulting in improved microwave absorption (MA) performance, including absorption intensity and bandwidth. The MnOx/GA sample prepared in this study exhibits an outstanding MA intensity of −54.70 dB at a frequency of 9.92 GHz, accompanied by an effective absorption bandwidth (EAB) of 5.60 GHz with a sample thickness of 2.60 mm and a filling content of 8.0 wt%. Meanwhile, the simulation of the radar cross section (RCS) further confirms the excellent MA performance and practical application potential of the MnOx/GA material. Additionally, MnOx/GA possesses outstanding electrothermal and photothermal properties, rendering it suitable for application in extreme environments. This work provides an economical, environmentally friendly, and efficient method for preparing lightweight and broadband multi-functional MAMs.

Lightweight Fe-doped MnO2@C hollow nanocubes for ultra-broadband microwave absorption

The rational structural design and compositional merits as well as the synergistic coupling effect can break the properties of single material and broaden the microwave absorption band. Herein, the unique lightweight Fe-doped MnO2@C hollow nanocubes are rationally designed and successfully synthesized via a scalable wet chemical process and polydopamine coating followed by high-temperature calcination. By virtue of the unique structure and compositional merits, the as-obtained Fe-doped MnO2@C hollow nanocubes (Fe–MnO2@C-HNBs) displayed notable microwave absorption performance (MAP), simultaneously achieving ultra-broad absorption bandwidth and strong absorption characteristics at a low thickness of 2.3 mm (the reflection loss of −41.02 dB and the effective absorption bandwidth of 5.86 GHz). Surprisingly, the effective absorption bandwidth (RL < −10 dB) could reach up to 8.08 GHz and the minimum reflection loss (RLmin) was −38.20 dB at the thickness of 2.7 mm. The results further confirmed that the excellent microwave attenuation ability of the as-prepared Fe–MnO2@C-HNBs composites benefitted from the special “air@core-shell” structure and multiple heterointerfaces as well as multi-component recombination. These results demonstrated that the as-obtained Fe–MnO2@C-HNBs composites could be attractive candidates for broadband microwave absorption materials.

The hollow cubic octahedral structure of Fe3O4 with excellent electromagnetic wave absorption capacity

The unique nanostructure combined with high dielectric and magnetic losses is essential for electromagnetic wave (EMW) attenuation in microwave-absorbing materials (MAM). In this paper, using cubic octahedral Cu2O as a template, we synthesized hollow cubic octahedral Fe(OH)3 at first. After annealing at 450 °C, the hollow cubic octahedral structure Fe3O4 could be obtained. When the filling ratio was 40 %, the minimum reflection loss (RLmin) reached -66.08 dB, and the maximum effective absorption bandwidth (EAB) was 5.38 GHz at a thickness of 1.84 mm, exhibiting improved EMW properties compared with previous works. The hollow cubic octahedral structure of Fe3O4 enhances EMW absorption characteristics, which is attributed to abundant dipole polarization, interface polarization, and good conduction loss. These results indicate that Fe3O4 with the hollow cubic octahedral structure can be used as potential candidates for efficient and broadband EMW absorbers.

High-performance NiTi-C nanofibers microwave absorbent prepared by electrospinning

Carbon nanofibers embedded with magnetic NiTi nanoparticles have been synthesized using electro-spinning technique, followed by one-step carbonization. By using NiTi-CFs as filler with 7.5%content, the sample achieved a very high effective absorption bandwidth(EAB) of 6.1 GHz (11.4–17.5 GHz)at the thickness of 1.97 mm. The effective absorption coverage of different microwave bands can be achieved by adjusting the thickness of the material. Adjusting the thickness of the material at 1.35 mm to 5 mm can achieve coverage from 3.7 GHz to 18 GHz. The superior properties might be due to the great impedance matching, rich dielectric loss and magnetic loss basis, excellent 1/4 λ space structure. This work presents a facile and promising method to produce high performance microwave absorption materials with thin thickness, light weight and strong absorption, as well as a detailed study of its wave absorbing basis.

Surfactant assisted tuning of electrical conductivity, electromagnetic interference shielding effectiveness, wetting properties of poly(lactic acid)-expanded graphite-magnetite nanocube hybrid bio-nanocomposites

The study aimed at demonstrating polyvinylpyrrolidone (PVP) amount is critical for tuning electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) of poly(lactic acid)-expanded graphite (ExGr)-magnetite (Fe3O4) nanocube hybrid nanocomposites. An optimum loading of PVP (1 wt.%) was found to disperse the nanofillers resulting in enhanced electrical conductivity and EMI SE in the X-band dominated by the absorption mechanism. The electrical conductivity enhancement in hybrid nanocomposites was not only attributed to the network formation between fillers but also to the thickness of the coated surfactant layer. The inter-junction capacitance and real part of relative permittivity of the hybrid nanocomposites were also enhanced at 1 wt.% PVP addition in comparison to 0 wt.% and 2 wt.% surfactant loading. The water contact angle was found to depend on the surface roughness of the film, which varied with both PVP and ExGr loadings. These PLA-based hybrid nanocomposites can be used as microwave-absorbing material.

Progress and Challenges of Ferrite Matrix Microwave Absorption Materials.

Intelligent devices, when subjected to multiple interactions, tend to generate electromagnetic pollution, which can disrupt the normal functioning of electronic components. Ferrite, which acts as a microwave-absorbing material (MAM), offers a promising strategy to overcome this issue. To further enhance the microwave absorption properties of ferrite MAM, numerous works have been conducted, including ion doping and combining with other materials. Notably, the microstructure is also key factor that affects the microwave absorption properties of ferrite-based MAM. Thus, this article provides a comprehensive overview of research progress on the influence of the microstructure on ferrite-based MAM. MAMs with sheet and layered structures are also current important research directions. For core-shell structure composites, the solid core-shell structure, hollow core-shell structure, yolk-eggshell structure, and non-spherical core-shell structure are introduced. For porous composites, the biomass porous structure and other porous structures are presented. Finally, the development trends are summarized, and prospects for the structure design and preparation of high-performance MAMs are predicted.

Micro-helical Ni3Fe chain encapsulated in ultralight MXene/C aerogel to realize multi-functionality: Radar stealth, thermal insulation, fire resistance, and mechanical properties

Magnetic carbon aerogels with high porosity, ultralow density, and excellent impedance matching are considered to be a promising microwave absorption (MA) material. In this study, ethylene glycol polymerization is used to assemble Ni3Fe particles into a micro-helical chain, which is further wrapped by MXene and then encapsulated in poly-Schiff-base aerogels through the carbonyl–amine condensation reaction. Finally, ultralight TiO2/Ni3Fe/MXene/C (NFMC) aerogels are synthesized through calcination treatment. Benefiting from the electromagnetic synergistic effect of multi-dimensional and multi-component materials, the NFMC-7 aerogel exhibits excellent MA performance with a minimum reflection loss of −61.6 dB at 3.0-mm thickness and an effective absorption bandwidth of 8.16 GHz at 2.77-mm thickness under a low filler loading of 7.6 wt%. Commercial computer simulation technology is used to verify the strong magnetic and dielectric loss characteristics of Ni3Fe chains. At the same time, the NFMC-7 aerogel exhibits excellent radar stealth, heat insulation, compression resistance, and fire resistance performance, which verifies its practical applicability. Overall, this work establishes an effective strategy to fabricate multi-functional magnetic aerogels, which can serve as lightweight, thin, and strong microwave absorbers with broad absorption bandwidth.

Lightweight titanium dioxide/carbon nanotube composites prepared by atomic layer deposition for broad-band microwave absorption

The microwave absorbing material with appropriate impedance matching and excellent attenuation ability can be applied to resist electromagnetic radiation. In this work, carbon nanotubes were modified by titanium dioxide via the atomic layer deposition method, to prepare lightweight composites with high microwave absorption performance. The impedance matching and attenuation ability of titanium dioxide/carbon nanotube (TiO2/CNT) composites could be precisely controlled by adjusting the number of titanium dioxide deposition cycles. The relationship between the microstructure and microwave absorption performance of the composite was analyzed in detail. When the number of TiO2 deposition cycles was 100, the composite displayed outstanding microwave absorption performance, due to appropriate impedance matching and strong attenuation ability. The maximum effective absorption bandwidth of the composite reached 5.19 GHz (1.6 mm), which almost covered the Ku band. The microwave attenuation mechanism of the composite has also been investigated. This work provided a new idea for fabricating lightweight microwave absorption materials.

Enhancing microwave absorption via ion exchange-regulated metal elemental-alloy transition behavior

Metal-organic frameworks (MOFs) are considered as suitable candidates for excellent microwave absorption (MA) materials. However, the influence of the transition behavior from metal to alloy dominated by the metal ion ratio and the accompanying multi-phase coexistence model on the MA mechanism is unclear. This study successfully prepared a series of porous electromagnetic composite materials through ion-exchange in-situ pyrolysis synergistic strategy. The results indicate that the modulation of the Fe/Co ion ratio can easily manipulate the phase transition from Co metal to FeCo alloy-cobalt ferrite and the crystal defects within. The state of metal/alloy coexistence obtained at a low ion exchange degree has the highest concentration of vacancies, which is conducive to wideband absorption (6.03 GHz) and efficient loss (−67.44 dB) of MA performance. In contrast, the MA performance of samples at medium/high ion exchange degrees is not ideal. In addition, the application prospects of this material were demonstrated by simulating the actual absorption situation using radar cross-section. In summary, this work reveals the intrinsic relationship between the phase evolution behavior determined by the ion exchange degree in MOF derivatives and the electromagnetic performance, as well as the MA mechanism, providing a new reference for the preparation and design of outstanding MA materials.

Hollow carbon microsphere embedded with Fe nanoparticles for broadband microwave absorption

Nowadays, Fe-based microwave absorption materials still face crucial problems of poor oxidation resistance, lack of dielectric loss and narrow effective absorption bandwidth. In this work, we developed a feasible way of calcining and etching SiO2 microspheres coated Fe3+ and polydopamine (SiO2@Fe3+-PDA) to confine Fe nanoparticles (12 nm) in the hollow carbon microspheres with a thickness of 17 nm, which provides more interfaces and polarization sites to enhance microwave attenuation. With the increase of Fe content, the microwave absorption performance of the sample is gradually improved. When Fe content is 19.7 wt%, the sample has a minimum reflection loss (RL) of −30.9 dB and a broadband absorption bandwidth (RL ≤ −10 dB) of 11.9 GHz (6.1–18 GHz) at the thickness of 4.0 mm. The ultra-wide effective absorption bandwidth is ascribed to synergetic effect of Fe nanoparticles and carbon layer, which provide magnetic loss and dielectric loss, respectively. Moreover, the hollow structure extends the transmission path and induces the multiple scattering of the incident electromagnetic waves. The novel hollow Fe/C microspheres are promising as high-efficiency microwave absorbers with strong microwave absorption and broad absorption bandwidth.

Simulation‐Guided Design of Gradient Multilayer Microwave Absorber with Tailored Absorption Performance

AbstractFlexible microwave absorber (MAR), vital in advanced applications such as wearable electronics and precision devices, are highly valued for their lightweight, exceptional electromagnetic waves (EWs), and ease of fabrication. However, optimizing the electromagnetic parameters of microwave absorption materials (MAMs) to enhance absorption ability and expand effective absorption broadband (EAB, reflection loss (RL) &lt;−10 dB) is a considerable challenge. Herein, a permittivity‐attenuation evaluation diagram (PAED) is constructed using parameter scanning based on the Materials Genome Initiative to determine the ideal electromagnetic parameters and thickness, optimize absorption efficiency, and obtain highly efficient absorbers. Guided by the PAED, a multilayer MAR consisting of a “matching‐absorption‐reflection layer” and a dielectric loss gradient aligned with the direction of EWs propagation is developed. This design significantly enhances the EWs penetration and ensures effective absorption, attributed to the well‐matched impedance and attenuation characteristics. As anticipated, the microwave absorption of the absorber (density = 0.063 g cm−3) is optimized, with an RL of −34 dB at d = 4 mm and an EAB covering the entire X‐band (8.2–12.4 GHz). This study presents a novel approach for establishing a material database for MAMs and developing high‐performance absorbers characterized by thinness, lightness, broad operational frequency range, and robust absorption capacity.

Preparation of high-performance bitumen carbon-based microwave absorbing materials from different coal bitumens toward efficient treatment of industrial waste bitumen

The increasing development of communication technology and electromagnetic pollution have accelerated the research and optimization of electromagnetic microwave absorbing materials. There are few studies and reports on the creation electromagnetic microwave absorbing materials from industrial waste, despite the abundance and promise of research preparing of microwave absorbing materials utilizing sustainable resources from biomass. Herein, we prepared carbon-based microwave absorbing materials GCB-800, HTCB-800, and CDLB-800 using three different industrial solid waste bitumens, namely, coal direct liquefaction bitumen, high-temperature coal bitumen, and globular coal bitumen, as raw materials by using the thermal activation method. Due to the excellent porous carbon skeleton structure and the Fe2O3 contained in its internal ash after the heat treatment, which enhances the internal dielectric properties, the CDLB-800 was found to perform very well at the filler amount of 10 wt% obtained minimum reflection loss (RLmin) is −52.41 dB at 10 wt% filler and matched thickness d = 2.1 mm, and the effective absorption bandwidth (EAB) is 4.88GHz, with 87.14% absorption for X-band in the 2-18GHz. This work not only promotes the development of the comprehensive utilization of solid waste in this field, effectively reduces the burden of solid waste on the environment, but also points out the direction for the development of microwave absorbing materials in the future.

Metal organic frameworks derived NixSey@NC hollow microspheres with modifiable composition and broadband microwave attenuation

The wide utilization of microwave technology across various sectors such as industrial production, medical treatment and military industry accelerates the development of high-performance microwave absorbing materials (MAMs). In this paper, hollow spherical composites composed of NixSey and nano-porous carbon (NixSey@NC) with abundant selenium vacancies were synthesized via a solvothermal process and high-temperature selenylation. The NixSey@NC composites with varied stoichiometric proportions and adjustable dielectric constants were obtained through manipulation of the pyrolysis temperature and Ni/Se ratios. The presence of abundant selenium vacancies plays a crucial role in improving dipole polarization and the composites demonstrate a minimum reflection loss (RL) of −54 dB (1.8 mm). The optimal absorption bandwidth for the composites could almost cover the whole Ku band with thickness of only 1.67 mm (5.6 GHz, 12.4–18 GHz). Consequently, this research could broaden perspectives and applications of metal selenide for electromagnetic protection.

Synthesis of Ti3C2Tx-MXene/PAN-derived double-loss Co/CeO2/TiO2/CNFs nanocomposites for enhanced microwave absorption performance

With the advancement of wireless communication and electronic equipment, microwave absorption materials (MAMs) have more and more broad applications in related fields. Ti3C2Tx-MXene with unique two-dimensional structure and excellent dielectric properties is often used as a precursor of nano-TiO2, which is a potential MAMs. Carbon nanofibers, as a one-dimensional material, have great electrical conductivity and can form interconnected three-dimensional conductive networks. In this study, Ti3C2Tx-MXene was prepared by in-situ HF etching method, and further combined with the benefits of Co, Ce metals, and carbon nanofibers. Co/CeO2/TiO2/CNFs were prepared via a facile technique for electromagnetic microwave (EM) absorption, exhibiting excellent EM absorption performance due to the synergistic effects of dielectric and magnetic properties. The minimum reflection loss (RLmin) and effective absorption bandwidth (EAB) reache −63.35 dB (11.2 GHz) and 3.6 GHz (9.5–13.1 GHz), with a thickness of only 2.35 mm and a filling rate of 30 wt%, while the maximum EAB reaches 5.4 GHz (12.4–17.8 GHz) with a thickness of 1.82 mm, covering nearly the entire Ku band. By offering a novel strategy to the creation of brand-new, high-performance MAMs based on 1D carbon nanofibers with dielectric/magnetic synergy, this work is believed to support the development of upcoming MAMs.