High-performance Microwave Absorption Research Articles

Porous Carbonaceous Aerogels Composed of Multiscale Carbon-Based Units for High-Performance Microwave Absorption.

Structural engineering is definitely a promising and effective approach to develop excellent microwave absorbing materials with quantities of advantages. Especially, when carbon materials act as the constituents, the fabricated absorbers are available to gain more prominent absorption performance. However, extra high conductivities and the widespread aggregations and stacking of low-dimensional carbon materials always detrimentally affect the impedance matching and weaken the attenuation capacity, inevitably confining their further absorption applications. Herein, by introducing the amorphous chiral carbon nanocoils to overcome the challenges and achieve the strategies of structure optimization and multicomponent recombination, the reduced graphene oxide/carbon nanocoil/carbon nanotube aerogels were successfully synthesized by a successive hydrothermal method and freeze-drying strategy. The as-obtained aerogels possess a porous architecture that contribute to the extraordinary impedance matching and multiple reflections, which integrate the multifarious dielectric loss mechanisms of diverse carbon materials simultaneously. Benefiting from the tricomponent synergistic effect, the ultralight aerogels reach an outstanding microwave absorption property with an extremely low filler content of only 6 wt %. This work provides a helpful approach to design hierarchical absorbers consisted by multidimensional carbon materials for fantastic microwave absorption.

Fabrication of flexible waterborne polyurethane/Fe-doped residual carbon from coal hydrogasification semi-coke composites for high-performance microwave absorption

Fabrication of flexible waterborne polyurethane/Fe-doped residual carbon from coal hydrogasification semi-coke composites for high-performance microwave absorption

Cross-scale construction of SiC–Si3N4 porous ceramics with superior electromagnetic wave absorption performance

A unique ceramic structure, which comprises whiskers in its pores and is capable of high-performance microwave absorption, has been designed by comnlining a sacrificial template method with catalytic nitriding. The influence of α-Si3N4 whisker content on the composition, structure, electromagnetic properties, and absorption properties of ceramics is also studied. The α-Si3N4 whisker content is controlled by changing the catalyst amount (FeCl2·4H2O). After adding 5 wt% FeCl2·4H2O, the highest α-Si3N4 whisker content is 78.06 %. The minimum reflection loss value of SiC–Si3N4 porous ceramics with thickness of 2.7 mm is −74.09 dB, rendering it superior than that of previously reported SiC-based absorbing ceramics. The supreior absorption performance is attributed to the reasonable structural design. The unique “whiskers in its pores” structure optimizes impedance matching, enhances attenuation loss and interference cancellation at three scales. This work provides new insights and ideas for the design and development of high-performance ceramic-based absorbing materials.

Tailored heterogeneous interface based on porous hollow In-Co-C nanorods to construct adjustable multi-band microwave absorber

By rationally controlling the growth of zeolite-imidazolium salt skeleton (ZIF-67) nanoparticles on the hollow indium oxide (In2O3) and the subsequent pyrolysis process, In-Co-C hollow rod-like composites with multiple components were successfully prepared in this work. The synergistic impact of diverse components including In2O3, C, Co3InC0.75, and In not only optimizes impedance matching and improves conductive loss, but also creates significant interfacial polarization. Furthermore, the addition of Co source and pyrolysis temperature was found to have a significant affected on impedance matching and microwave absorption. The optimized In-Co-C sample displayed ultra-broad absorption bandwidth (EAB) of up to 7.12 GHz (10.88–18.0 GHz) at 2.26 mm thickness, which could cover the whole Ku band and part of X-band, outperforming the previously reported MOFs-derived composites. Furthermore, by adjusting the thickness to 2.91 mm and 4.01 mm, the EAB could cover the entire X band and most of the C band. The attenuation mechanisms were systematically investigated through the delta function method and ANSYS high-frequency structure simulator. These findings suggest that the MOFs-derived In-Co-C hollow nanorods could serve as high-performance microwave absorbers with ultra-broad absorption.

Urchin-like Fe3O4@C with core-shell structure modified 2D MXene for high-performance microwave absorption

As a typical two-dimensional material, Ti3C2Tx MXene has been considered a novel potential microwave-absorbing material because of its outstanding metallic-like conductivity and rich surface functional groups. Unfortunately, the microwave absorption performance is constrained by its intrinsic high conductivity and single loss mechanism. Herein, an urchin-like Fe3O4@C hollow sphere with core-shell structure was built by hydrothermal and annealing processes, which was subsequently used to modify MXene via electrostatic self-assembly. The Fe3O4@C/Ti3C2Tx hybrid with 30 wt% Fe3O4@C loading displayed a minimum reflection loss (RLmin) value of –64.0 dB at a thickness of 3.32 mm and a maximum efficient absorption bandwidth (EABmax) of 3.02 GHz at 3.24 mm. The exceptional microwave absorption performance is mainly attributed to the impedance matching brought about by the special urchin-like core-shell structure of Fe3O4@C, as well as the rich interfacial polarization and multiple reflections/scatterings. This work offers a novel idea for the design of efficient MXene-based microwave-absorbing materials.

Multifunctional MnFe2O4/TiO2/Ti3C2Tx composites based on in-situ grown TiO2 for efficient microwave absorption, high hydrophobicity, and heat dissipation properties

Despite the fact that the 2D structure Ti3C2Tx with abundant defects and functional groups contributes to the high microwave absorption (MA) performance, it is difficulty to improve the strength and bandwidth by pursuing higher conductivity or loading more groups due to the limitation of intrinsic properties. Therefore, it is important to ingeniously design efficient Ti3C2Tx based MA composites assembling the features of abundant surface groups, good dispersibility, multiple composition, and precise structure. Inspired by the fact that Ti3C2Tx contains thermodynamically metastable marginal Ti atoms, TiO2 nanoparticles can be grown in-situ on Ti3C2Tx nanosheets uniformly and increase the spacing of Ti3C2Tx layers, and then MnFe2O4 nanoparticles are introduced into the layers of Ti3C2Tx by electrostatic self-assembly method for optimized impedance matching. This designed hierarchical MnFe2O4/TiO2/Ti3C2Tx composites shows excellent MA performance, and the minimum reflection loss (RLmin) reaches −46.91 dB with a thickness of 2.5 mm at frequency of 10.4 GHz. The high MA performance mainly comes from the enhanced interfacial polarization induced by edges location and interface region among TiO2, MnFe2O4, and Ti3C2Tx. In addition, the conduction loss existed in the interior untreated Ti3C2Tx, the dielectric loss generated by multiple composition, the multiple scattering from improved large surface specific area all contribute to the excellent MA performance. Meanwhile, the simple preparation process and good stability storage at room temperature under air atmosphere of the MnFe2O4/TiO2/Ti3C2Tx composites promote its exploration on practical use, and the lab-gown cloth coated with MnFe2O4/TiO2/Ti3C2Tx composites shows better electromagnetic shielding properties, hydrophobicity, and heat transfer ability than pure fabric, showing the potential for practical application.

Hierarchical-Bioinspired MOFs Enhanced Electromagnetic Wave Absorption.

Proteins exhibit complex and diverse multi-dimensional structures, along with a wide range of functional groups capable of binding metal ions. By harnessing the unique characteristics of proteins, it is possible to enhance the synthesis of metal-organic frameworks (MOFs) and modify their morphology. Here, the utilization of biomineralized bovine serum albumin (BSA) protein as a template for synthesizing Mil-100 with superior microwave absorption (MA) properties is investigated. The multi-dimensional structure and abundant functional groups of biomineralized BSA protein make it an ideal candidate for guiding the synthesis of Mil-100 with intricate network structures. The BSA@Mil-100 synthesized using this method exhibits exceptional uniformity and monodispersity of nanocrystals. The findings suggest that the BSA protein template significantly influences the regulation of nanocrystal and microstructure formation of Mil-100, resulting in a highly uniform and monodisperse structure. Notably, the synthesized 2-BSA@Mil-100 demonstrates a high reflection loss value of -58dB at 8.85GHz, along with a maximum effective absorption bandwidth value of 6.79GHz, spanning from 6.01 to 12.8GHz. Overall, this study highlights the potential of utilizing BSA protein as a template for MOF synthesis, offering an effective strategy for the design and development of high-performance MA materials.

Rare earth lanthanum pinning effect for corrosion resistance ultraefficient microwave absorption FeCo@rGO composites

Magnetic metal absorbers exhibit remarkable microwave absorption capacity. However, their practical application is severely limited due to their susceptibility to corrosion, particularly in marine environments. To address this challenge, we propose a novel approach involving the modification and control of FeCo/rGO microwave absorbers using rare earth lanthanum (La). This strategy aims to achieve both high-performance microwave absorption and enhanced resistance to marine corrosion. In this study, we employ a La2O3 modifying control strategy to refine the FeCo magnetic particles and coat them with CoFe2O4 on the surface, leveraging the pinning effect of in situ generated La2O3. This process enhances the interface polarization of the absorbers, thereby improving their electromagnetic performance and marine corrosion resistance. Consequently, the La2O3 modified FeCo@rGO composites exhibit broadband absorption, covering a wide frequency range of 6.11 GHz at 1.55 mm. Notably, the electromagnetic properties of the La2O3 modified FeCo@rGO absorbers remain stable even after prolonged exposure to a 3.5 wt% NaCl solution, simulating marine conditions, for at least 15 days. Furthermore, we perform first-principle calculations on FeCo and FeCoO to validate the corrosion resistance of the La2O3 modified FeCo@rGO composites at the atomic level. This comprehensive investigation explores the control of rare earth lanthanum modification on the size of magnetic metal particles, enabling efficient electromagnetic wave absorption and marine corrosion resistance. The results of this study provide a novel and facile strategy for the control of microwave absorbers, offering promising prospects for future research and development in this field.

MOF-derived multicore-shell Fe3O4@Fe@C composite: An ultrastrong electromagnetic wave absorber

Excessive artificial electromagnetic radiation poses significant health risks and disrupts military equipment. To address this, high-performance microwave absorption materials are urgently required. While ferromagnetic materials have excellent absorption but suffer from high density, limited bandwidth, and perishable properties. Carbon materials, especially metal-organic frameworks (MOFs), offer promise due to low density, chemical stability, and high conductivity. In this study, we synthesized a novel multicore-shell Fe3O4@Fe@C composite via solvothermal and in-situ pyrolysis methods. This composite integrated Zn-MOF-derived porous carbon with core-shell Fe3O4@Fe@C, enabling multiple electromagnetic wave routes, strong interfacial polarization, and magnetic-dielectric synergy. It exhibited exceptional electromagnetic wave absorption, with a −59.1 dB reflection loss at 13.36 GHz and a 5.36 GHz effective absorption bandwidth. Our innovative MOF-core-shell approach holds great promise for highly efficient microwave absorbers to mitigate artificial electromagnetic radiation's adverse effects on health and military equipment.

Molybdenum substituted M‐type hexagonal barium ferrite for high microwave absorption performance

AbstractWith the advancement of electrical and electronic devices, overcoming electromagnetic pollution turns into an urgent problem. In this work, high‐valence molybdenum (Mo6+) was doped into M‐type hexagonal barium ferrite (BaFe12‐xMoxO19) to improve its electromagnetic performance. The relationship between the Mo6+ doping concentration and the crystallographic structure, morphology and electromagnetic properties was studied in detail. Structural characterizations authenticate that the Mo6+ ions prefer the 2b site, increasing the lattice values and grain size, and boosting more Fe3+ conversion into Fe2+. The magnetic hysteresis loops demonstrate a reduction of saturation magnetization and coercivity values with the increase of Mo6+ concentration. While the microwave absorption properties were obviously improved by the doping Mo6+, and obtained the highest RLmin value of ‐56.12 dB@16.1 GHz and effective absorption bandwidth of 4.2 GHz at x = 0.1, displaying a potential role in absorbing material.

Graphite/Epoxy-Coated Flaky FeSiCr Powders with Enhanced Microwave Absorption

Flake-shaped FeSiCr (FFSC) material is expected to be a promising microwave absorbent due to its excellent magnetic properties and environmental resistance. By introducing carbon-based materials through suitable coatings, the electromagnetic parameters and energy loss can be tuned to improve the performance of FFSC. A facile solution-blending method was deployed to prepare graphite- and epoxy resin-encapsulated FFSC (FFSC@G/E) powders with a core–shell structure. FFSC@G2000/E showed excellent performance in the X band (8–12 GHz), a minimum reflection loss (RLmin) of −42.77 dB at a thickness of 3 mm and a maximum effective absorption bandwidth (EABmax, RL < −10 dB) that reached 4.55 GHz at a thickness of 2.7 mm. This work provides a route for the production of novel high-performance microwave absorbers.

High-Performance Microwave Absorption Materials: Theory, Fabrication, and Functionalization

High-Performance Microwave Absorption Materials: Theory, Fabrication, and Functionalization

Excellent electrically insulated, thermal-oxidation resistant and corrosion resistant flaky-FeSiAl/BN core–shell composites for high-performance microwave absorption in harsh environments

Currently, multifunctional microwave absorption (MA) materials have become increasingly important in addressing the serious issue of electromagnetic pollution. In this study, flaky FeSiAl (FFSA)/hexagonal boron nitride (h-BN) composites with a core–shell structure were prepared by plasma-assisted ball milling. The FFSA9BN1 composite, with a mass ratio of 9:1 (FFSA:h-BN), exhibits a minimum reflection loss (RLmin) of −68.18 dB at a thickness of 2.14 mm, because the h-BN shells improve the impedance matching of the composites and produce abundant polarization loss. Additionally, the MA performance of the composites hardly shows a decline even after a thermal oxidation at 500 °C for 12 h due to the dense h-BN shells as oxygen barriers. Simultaneously, the corrosion rate of the FFSA/h-BN composites is 66.5% less than that of the FeSiAl cores. Consequently, plasma-assisted ball milling provides a facile and eco-friendly technology to prepare multifunctional FFSA/h-BN core–shell composites for diverse applications in some extreme environments.

Constructing honeycomb-like hierarchical foam via electromagnetic cooperation strategy for broadband microwave absorption

The application of wireless electronic devices inevitably leads to electromagnetic pollution. Three-dimensional porous foam structures have been shown to be an effective strategy to construct high-performance microwave absorbers. Herein, the honeycomb-like hierarchical foams were fabricated via melamine-formaldehyde (MF) foam as substrate coupled with flaky carbonyl iron (CI)-MXene lamellae. Inside the synthesized composite foam, flaky CI is interlaced into MXene nanosheets to form hierarchical structures, which effectively alleviates the originally self-stacking phenomenon and provides numerous heterogeneous interfaces, resulting in the optimization of impedance matching. In addition, owing to the construction of consecutive electromagnetic networks, the CI-MXene/MF foams exhibit significant dielectric loss and magnetic loss capability. Moreover, the honeycomb-like structure offers multiple reflections/scattering for electromagnetic waves, which effectively prolongs the transmission paths, further improving the microwave attenuation ability. Hence, the synthesized composite foam exhibits superior microwave absorption performance with a minimum refection loss of −61.4 dB and a maximum effective absorption band of 7.18 GHz. The construction of unique microstructure and regulation of electromagnetic components is demonstrated to be feasible strategies for the design of efficient microwave absorbers in future.

Preparation of the urchin-like structured Ti3C2@CNTs for high-performance lithium storage and microwave absorbers

Two-dimensional (2D) MXene-based materials are gained significant attention as a prospective anode in lithium-ion batteries (LIBs) due to their superior metallic conductivity, high volumetric capacitance, and thermal stability. However, the unsatisfactory electrochemical performance of MXene-based anodes essentially restricts their practical use attributed to the prevalent interlayer stacking. The urchin-like Ti3C2 @CNTs involve grafting carbon nanotubes (CNTs) onto the 3D hollow MXene via catalytic growth could promise to overcome this obstacle. As conductive bridges, the CNTs further expedite the exchange of charges at the interface, resulting in improved electrochemical kinetics of the composite, which exhibits a high specific capacity of 286.2 mA h g−1 at 1 A g−1 after 2000 cycles. Beneficial from the well-designed architecture, outstanding microwave absorption was achieved with the optimal reflection loss of −48.1 dB covering the C band. This study proposed a practical strategy for fabricating the Ti3C2 @CNTs composite in high-performance lithium-ion batteries and microwave absorbers.

Honeycomb-like bamboo powders-derived porous carbon with low filler loading, high-performance microwave absorption

Nowadays, the problem posed by electromagnetic wave pollution to electronic devices and biological systems is of serious concern. To create a microwave absorber, component and structural modulation is crucial. Biomass-derived porous carbon is a potential material for microwave absorption applications due to the characteristics of lightweight, high specific surface area, and significant dielectric loss. In this study, by examining the impact of various KOH concentrations on the pore structure, bamboo powders with an 80-mesh size were used as a raw material to create honeycomb-like bamboo powders-derived porous carbon (BPDPC) materials. The activation mechanism of the BPDPC material is also explained. Based on the electromagnetic parameters, the sample BPDPC-4 impregnated with 4 mol/L KOH has a maximum effective absorption bandwidth (RL ≤ −10 dB) of 4.76 GHz at a matching thickness of 2.0 mm, covering 11.54–16.30 GHz and a minimum reflection loss (RLmin) of −40.99 dB at a matching thickness of 2.2 mm at 5 wt% ultra-low filler loading. Due to polarization loss, conduction loss, and the mutually beneficial effects of multiple electromagnetic wave reflection and scattering, the superior wave absorption performance is explained. This work also serves as a reference for investigating porous carbon generated from biomass.

Toward high performance microwave absorber by implanting La0.8CoO3 nanoparticles on rGO

The advent of “intelligent era” brings our life more convenience, but the electromagnetic radiation surrounding us not only greatly threatens human health, also makes information leakage and hidden trouble to national defense security. Hence, it is very urgent to develop novel electromagnetic wave absorption materials with lightweight, strong absorption, tunable absorption frequency and broad band absorption. Herein, a novel electromagnetic wave absorber is obtained by constructing La0.8CoO3-rGO nanocomposite, where La0.8CoO3 nanoparticles are anchored on graphene nanosheets by the electrostatic interaction between GO and La0.8CoO3. The effect of hybridization ratio of La0.8CoO3 and rGO on microwave absorption properties is carefully studied. The optimal reflection loss of La0.8CoO3-rGO nanocomposite can reach -62.34 dB with the maximum effective bandwidth of 6.08 GHz, presenting 48.78% and 245.45% increment compared to bare La0.8CoO3 nanoparticles, respectively. The effective absorption bandwidth covers a broad electromagnetic wave absorption band from Ku band to the C band by tailoring thickness of the absorbers from 2.4 mm to 4.4 mm. The fascinating electromagnetic wave absorption performance is attributed to the synergy effect of La0.8CoO3 and rGO, which integrates magnetic and dielectric loss caused by resonance, conductance, relaxation, and scattering loss. This result confirms that La0.8CoO3-rGO nanocomposite is potential candidates toward high-efficiency microwave absorbers and provides a valuable pathway for designing high-performance microwave attenuation materials in the future.

Spongy ternary nano-composites with optimized impedance matching and synergistic effect for broadband and strong microwave absorption

To counter the negative effects of electromagnetic radiation on the immunity of precision instruments, the stealthiness of military equipment, and human health, the preparation of porous multi-component nano-composites is considered an effective strategy to obtain efficient microwave absorption. In this work, the spongy ternary nano-composites (STC) with large specific surface area (SSA) and pore volume obtained by adjusting the calcination temperature, the porous effectively improves the impedance matching. The ternary composition of FeCo/Fe0.45Ni0.55/C, large SSA and pore volume provide abundant specific surface/interface for polarization and magnetization, the continuous conductive network is established, the strong dielectric and magnetic loss achieve a synergistic effect, realizing strong absorption in the low-frequency, greatly reducing the minimum reflection loss (RLmin, −56.37 dB) and broadening the effective absorption bandwidth (EAB, 7.45 GHz). The microwave absorption mechanism has been analyzed in detail and its great potential for practical applications has been verified by RCS signal simulations. This research provides an effective method for fabricating high-performance ternary nano-composite microwave absorbers.

Temperature-dependent dielectric properties and high-temperature microwave absorption performance of Ti3SiC2/Al2O3-13%TiO2 coatings

Ti3SiC2 exhibits considerable potential for high-temperature microwave absorption due to its relatively high melting point and conductivity. In this study, we successfully prepared Ti3SiC2/Al2O3-13%TiO2 heterogeneous coatings through granulation and plasma spraying techniques. This investigation covered composition, microstructure, oxidation resistance, and a focused analysis of the temperature-dependent permittivity of the coatings. The augmentation in Ti3SiC2 content leads to an escalation in the polarized component, consequently elevating susceptibility to dielectric dispersion. With rising temperature, polarization within the coatings gradually establishes, prompting a transition from polarization relaxation loss to conduction loss as the dominant dielectric loss mechanism. At 5 wt% Ti3SiC2 content, the coating achieves an effective bandwidth of 2.2 GHz at 873 K, with a mere 1.4 mm thickness. Moreover, the coating maintains exceptional oxidation resistance below 700 °C. Ti3SiC2/Al2O3-13%TiO2 coatings manifest as strong contenders for high-temperature microwave absorption applications, and plasma spraying emerges as a promising technique for fabricating high-performance microwave absorption coatings.

Facile design of multifunctional melamine foam with Ni-anchored reduced graphene oxide/MXene as highly efficient microwave absorber

The appropriate multi-component strategies and ingenious microstructure design remain challenging for the development of multifunctional and high-performance electromagnetic wave absorbing materials. Here, magnetic Ni nanoparticles-anchored reduced graphene oxide (RGO)/Ti3C2Tx MXene hybrids were successfully assembled on melamine foam (MF) via electrostatic self-assembly and hydrazine vapor reduction processes, achieving high-performance electromagnetic wave absorption and multifunctionality. Interestingly, the RGO/MXene/Ni-MF achieves high-performance microwave absorption with a minimum reflection loss value of − 61.3 dB and a maximum width effective absorption bandwidth (EAB) of 7.04 GHz. The superior electromagnetic wave absorption stems from a 3D dielectric/magnetic network with satisfactory impedance matching, dielectric/magnetic losses, interface/dipole polarization and multiple reflection scattering. Furthermore, the RGO/MXene/Ni-MF also revealed outstanding hydrophobicity, thermal insulation, infrared shielding and incombustibility. This work opens up novel prospects for developing lightweight, multifunctional microwave absorbers for practical applications.