Microwave Absorption Materials Research Articles

Progress and Challenges of Ferrite Matrix Microwave Absorption Materials

Progress and Challenges of Ferrite Matrix Microwave Absorption Materials

Fixed-Point Atomic Regulation Engineered Low-Thickness Wideband Microwave Absorption.

Atomic doping is widely employed to fine-tune crystal structures, energy band structures, and the corresponding electrical properties. However, due to the difficulty in precisely regulating doping sites and concentrations, establishing a relationship between electricity properties and doping becomes a huge challenge. In this work, a modulation strategy on A-site cation dopant into spinel-phase metal sulfide Co9S8 lattice via Fe and Ni elements is developed to improve the microwave absorption (MA) properties. At the atomic scale, accurately controlling doped sites can introduce local lattice distortions and strain concentration. Tunned electron energy redistribution of the doped Co9S8 strengthens electron interactions, ultimately enhancing the high-frequency dielectric polarization (ɛ' from 10.5 to 12.5 at 12GHz). For the Fe-doped Co9S8, the effective absorption bandwidth (EAB) at 1.7mm increases by 5%, and the minimum reflection loss (RLmin) improves by 26% (EAB = 5.8GHz, RLmin = -46dB). The methodology of atomic-scale fixed-point doping presents a promising avenue for customizing the dielectric properties of nanomaterials, imparting invaluable insights for the design of cutting-edge high-performance microwave absorption materials.

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) <−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.

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.

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 (12nm) in the hollow carbon microspheres with a thickness of 17nm, 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 19.7wt.%, the sample has a minimum reflection loss (RL) of -30.9dB and a broadband absorption bandwidth (RL ≤ -10 dB) of 11.9GHz (6.1-18GHz) at the thickness of 4.0mm. 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.

Tailorable effective microwave absorption bandwidth of chitosan-derived carbon-based aerogel under different compression

Confronted with ever-increasing electromagnetic radiation problems, developing microwave absorbing materials with tunable effective absorption bandwidth (EAB) is in high demand. In this work, chitosan-derived carbon-based aerogel was synthesized by unidirectional freeze-drying and the following high-temperature carbonization process. The dielectric-magnetic coupling effect was facilitated by the construction of the 3D conductive network, along with the decoration of the Co nanoparticles and the doping of heteroatoms within the carbon-based framework. Therefore, the aerogel achieved minimum reflection loss intensity of -44.30 dB at 5.20 GHz when carbonizing the precursor at 800 °C. More significantly, the strain-responsive properties of the aerogel endows it with tailorable electromagnetic response behaviors, thereby controlling the effective absorption bandwidth covering from X band to Ku band. This work paves the way for designing next-generation microwave absorption materials with tunable microwave absorption bandwidth, catering to stringent practical requirements prospectively.

Efficient Synthesis of Fe3O4/PPy Double-Carbonized Core-Shell-like Composites for Broadband Electromagnetic Wave Absorption.

Ever-increasing electromagnetic pollution largely affects human health, sensitive electronic equipment, and even military security, but current strategies used for developing functional attenuation materials cannot be achieved in a facile and cost-effective way. Here, a unique core-shell-like composite was successfully synthesized by a simple chemical approach and a rapid microwave-assisted carbonization process. The obtained composites show exceptional electromagnetic wave absorption (EMWA) properties, including a wide effective absorption band (EAB) of 4.64 GHz and a minimum reflection loss (RLmin) of -26 dB at 1.6 mm. The excellent performance can be attributed to the synergistic effects of conductive loss, dielectric loss, magnetic loss, and multiple reflection loss within the graphene-based core-shell-like composite. This work demonstrates a convenient, rapid, eco-friendly, and cost-effective method for synthesizing high-performance microwave absorption materials (MAMs).

Recent research progress and prospect of graphene-based microwave absorbing materials

With the increasing use of electronic devices, electromagnetic wave pollution has become a hot topic of concern and discussion, and microwave absorption materials play an important role in civil and defense military fields. Therefore, the development of electromagnetic wave absorption materials with low density, thin thickness, wide effective bandwidth, and strong wave absorption performance has become the focus and goal of researchers. Graphene shows a unique two-dimensional structure, lightweight, large specific surface area, high electrical conductivity, and high thermal conductivity, which make it a promising electromagnetic wave-absorbing material. However, pure graphene material cannot meet the needs of practical applications due to bad impedance matching. Therefore, graphene is usually combined with other materials (such as carbon materials, magnetic metal, polymer, ferrite, and ceramic) to improve its wave absorption properties. In this review, we summarize recent research progress of different types of graphene-based microwave absorbing materials. In addition, the challenges and prospects for improving the microwave absorption properties of graphene-based composites are presented, which will be useful for those working in related fields.

Synergistic defense: Compositional regulation and temperature engineering of TMCs for enhanced microwave absorption and corrosion protection

In the context of abundant marine wind energy resources, offshore wind power presents an effective solution to the current energy crisis, however, the challenges of electromagnetic interference and corrosion faced by offshore wind power generation equipment demand urgent resolution. This study addresses these issues by employing a coordination strategy between deprotonated dopamine and transition metal ions, utilizing compositional regulation and temperature engineering to synthesize a series of carbon/transition metal carbides (TMCs) composite materials. Compositional regulation introduces heterojunction interfaces to enhance dielectric loss, while temperature engineering effectively adjusts the material's impedance matching. WM@C, with an extremely thin thickness of 1.66 mm, demonstrates a remarkable effective absorption bandwidth (EAB) reaching 5.52 GHz, accompanied by a maximum reflection loss (RL) of –26.8 dB. Notably, attributed to the outstanding anti-chloride ion pitting ability of TMCs and the stacking effect of dense carbon nanosheets on the surface, the synthesized composite coatings demonstrate excellent corrosion protection capabilities. After 10 consecutive days of salt spray test, the EAB of the WM@C still maintains 5.01 GHz at 1.76 mm, a new idea of dual-function integrated materials for microwave absorption (MA) and corrosion protection has been developed, providing theoretical support for the construction of offshore wind power generation equipment.

Metal Valence State Modulation Strategy to Design Core@shell Hollow Carbon Microspheres@MoSe2/MoOx Multicomponent Composites for Anti-Corrosion and Microwave Absorption.

The exploitation of multicomponent composites (MCCs) has become the main pathway for obtaining advanced microwave absorption materials (MAMs). Herein, a metal valence state modulation strategy is proposed to tune the electromagnetic (EM) parameters and improve microwave absorption performances. Core@shell hollow carbon microspheres@MoSe2 and hollow carbon microspheres@MoSe2/MoOx MCCs with various mixed-valence states content are well-designed and produced by a simple hydrothermal reaction or/and heat treatment process. The results reveal that the thermal treatment of hollow carbon microspheres@MoSe2 in Ar and Ar/H2 leads to the in situ formation of MoOx and multivalence state, respectively, and the enhanced content of Mo4+ in the designed MCCs greatly boosts their impedance matching characteristics, polarization, and conduction loss capacities, which lead to their evidently improved EM wave absorption properties. Amongst, the as-prepared hollow carbon microspheres@MoSe2/MoOx MCCs achieve an effective absorption bandwidth of 5.80 GHz under a matching thickness of 1.97 mm and minimum reflection loss of -21.49 dB. Therefore, this work offers a simple and universal method to fabricate core@shell hollow carbon microspheres@MoSe2/MoOx MCCs, and a novel and feasible metal valence state modulation strategy is proposed to develop high-efficiency MAMs.

Review of Three-Dimensional Graphene and Related Composite Materials for Microwave Absorption

Review of Three-Dimensional Graphene and Related Composite Materials for Microwave Absorption

Compositional and Hollow Engineering of Silicon Carbide/Carbon Microspheres as High-Performance Microwave Absorbing Materials with Good Environmental Tolerance

HighlightsHollow SiC/C microspheres with controllable composition have been successfully synthesized by simultaneously implementing compositional and structural engineering.The optimum dielectric properties (i.e., conductivity loss and polarization loss) and impedance matching characteristics can achieve outstanding microwave absorption performance.Broadband wave absorption (5.1 GHz with only 1.8 mm thickness), high efficiency loss (− 60.8 dB at 10.4 GHz) combined with good environmental tolerance, demonstrate their bright prospects in practice.

Collective orientation of CNT coated magnetic microchains for effective microwave absorption in S and C band

The control of undesired electromagnetic radiation in S- and C-band spectra requires novel microwave absorbing materials (MAMs) having high microwave attenuation capability together with optimal impedance matching. CNTs are conformally coated onto the surface of one-dimensional FeCo-based magnetic microchains via electrostatic self-assembly, and then the magnetic inclusions are collectively oriented in matrices by applying an external magnetic field. The proper incorporation of CNTs with magnetic microchains demonstrates a feasible pathway for effectively absorbing microwaves in the S and C band. MAMs consisting of oriented microchains have anisotropic complex permittivity, of which the real part ranges from 6.1 to 30.4 at 2 GHz. When the electric field is parallel to microchains, the 5-mm-thick MAM has an effective absorbing bandwidth (EAB) in the range of 2.3 to 2.9 GHz, and reduces the radar cross section to be lower than ‒15.9 dB m2 from the vertical to the glancing incidence. When the magnetic field is parallel to microchains, the MAM adsorbs C-band microwaves with an EAB of 1.5 GHz, and achieves maximal reflection loss of ‒46.4 dB. The collective orientation of shape-anisotropic magnetic materials, in addition to the composition and microstructure, is a new variable for the design of effective MAMs.

Structural design in reduced graphene oxide (RGO) metacomposites for enhanced microwave absorption in wide temperature spectrum

High-temperature microwave absorbing materials (MAMs) and structures are increasingly appealing due to their critical role in stealth applications under harsh environments. However, the impedance mismatch caused by increased conduction loss often leads to a significant decline in electromagnetic wave absorption (EMWA) performance at elevated temperatures, which severely restricts their practical application. In this study, we propose a novel approach for efficient electromagnetic wave absorption across a wide temperature range using reduced graphene oxide (RGO)/epoxy resin (EP) metacomposites that integrate both electromagnetic parameters and metamaterial design concepts. Due to the discrete distribution of the units, electromagnetic waves can more easily penetrate the interior of materials, thereby exhibiting stable microwave absorption (MA) performance and impedance-matching characteristics suitable across a wide temperature range. Consequently, exceptional MA properties can be achieved within the temperature range from 298 to 473 K. Furthermore, by carefully controlling the structural parameters in RGO metacomposites, both the resonant frequency and effective absorption bandwidth (EAB) can be optimized based on precise manipulation of equivalent electromagnetic parameters. This study not only provides an effective approach for the rational design of MA performance but also offers novel insights into achieving super metamaterials with outstanding performance across a wide temperature spectrum.

Lightweight, flexible, heat resistant and thermal insulating aramid nanofiber/magnetic carbon nanotube interpenetrating network aerogel for microwave absorption in complex environments

Microwave absorbing (MA) materials used in complex environments not only need efficient MA performance, but also should have comprehensive properties of being lightweight, flexible, heat-resistant and insulating. Here, we grew CoFe2O4 nanoparticles (CFO NPs) in situ on oxidized carbon nanotubes (CNTs) by a wet chemical method. Oxidized CNTs limit the aggregation of CFO NPs and form rich heterogeneous interfaces. Then CNT@CFO was mixed with aramid nanofibers (ANFs) dispersions and prepared lightweight and flexible ANF/CNT@CFO interpenetrating network aerogels through a freeze-drying process. Under the action of multiple loss mechanisms, the ANF/CNT@CFO aerogel shows -53.2 dB of minimum reflection loss, and 4.76 GHz of effective absorption bandwidth (1.59 mm). Meanwhile, the composite aerogel inherits the high heat resistance of each component, with the quality and shape remaining stable below 400°C, and TG5% occurs at 460°C. In addition, effective MA properties can be maintained from room temperature to 300°C. ANF/CNT@CFO is expected to become a MA material that can be used in complex environments.

Facile preparation and broadband microwave absorption of multilayered materials based on thin films of reduced graphene oxide

Microwave absorption (MA) materials have received extensive attention for their wide applications in both civil and military areas. However, many MA materials have a large thickness, high filling ratio, and narrow effective microwave absorption bandwidth (Reflection Loss, RL ≤ −10 dB) (EAB), and are prepared by complex processes. In this work, a reduced graphene oxide (RGO) film is prepared for the first time by an approach involving floating-dipping and chemical reduction. Compared with previous micrometers-thick RGO films, the present 200 nm-thick dense RGO film is critical for improving not only the impedance matching but also the capability of the material to attenuate incident microwaves. Based on such a thin RGO film, a multilayered material with a jaaumann structure is constructed with individual RGO layers alternating between low dielectric polyethylene terephthalate (PET) sheets. With the superb impedance matching, multilayer attenuation, and multi-cavity resonance, the present multilayered material can achieve a wide EAB of 13.75 GHz with a minimum reflection loss of −47.69 dB using only 3 layers of RGO films. This study provides a new and simple strategy for the development of layered materials with a thin thickness, low filling ratio, and strong absorption with a wide EAB.

Robust, Flexible, and Superhydrophobic Fabrics for High-efficiency and Ultrawide-Band Microwave Absorption

Microwave absorption (MA) materials are essential for protecting against harmful electromagnetic radiation. In this study, highly efficient and ultrawide-band microwave-absorbing fabrics with superhydrophobic surface features were developed using a facile dip-coating method involving in situ graphene oxide (GO) reduction, deposition of TiO2 nanoparticles, and subsequent coating of a mixture of polydimethylsiloxane (PDMS) and octadecylamine (ODA) on polyester fabrics. Owing to the presence of hierarchically structured surfaces and low-surface-energy materials, the resultant reduced graphene oxide (rGO)/TiO2-ODA/PDMS-coated fabrics demonstrate superhydrophobicity with a water contact angle of 159° and sliding angle of 5°. Under the synergistic effects of conduction loss, interface polarization loss, and surface roughness topography, the optimized fabrics show excellent microwave absorbing performances with a minimum reflection loss (RLmin) of −47.4 dB and a maximum effective absorption bandwidth (EABmax) of 7.7 GHz at a small rGO loading of 6.9 wt%. In addition, the rGO/TiO2-ODA/PDMS coating was robust, and the coated fabrics could withstand repeated washing, soiling, long-term ultraviolet irradiation, and chemical attacks without losing their superhydrophobicity and MA properties. Moreover, the coating imparts self-healing properties to the fabrics. This study provides a promising and effective route for the development of robust and flexible materials with microwave-absorbing properties.