High-efficiency Microwave Absorption Research Articles

Designing Symmetric Gradient Honeycomb Structures with Carbon-Coated Iron-Based Composites for High-Efficiency Microwave Absorption

HighlightsMIL-88C (Fe) with varying aspect ratios as a precursor was synthesized by regulating oil bath conditions, followed by one-step thermal decomposition to obtain carbon-coated iron-based composites.High-efficiency microwave absorption properties were achieved with RLmin value of -67.4 dB (2.13 mm) and wide effective absorption bandwidth (EAB) of 5.52 GHz (1.90 mm) under the low filler loading.A symmetric gradient honeycomb structure was constructed utilizing the high-frequency structure simulator, achieving an EAB of 14.6 GHz and a RLmin of -59.0 dB.

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.

Constructing core-shell biomass carbon@Fe3O4 composites for enhanced mid-to-low frequency electromagnetic wave absorption

Presently, the escalating issue of electromagnetic pollution, propelled by the rapid advancement in electronic information technology, is attracting heightened attention. This problem is particularly pronounced within the 2–10 GHz frequency range, where electronic devices make a substantial contribution to electromagnetic pollution. Research suggests that carbon-based magnetic composites are a viable solution for mitigating this pollution. In our study, we synthesized magnetic composites composed of Fe3O4 particles and biomass carbon (C) derived from corn silk, using a hydrothermal method. The low conductivity of Fe3O4 particles plays a key role in hindering microcurrent transmission, thus reducing the excessive dielectric properties of the carbon material. Additionally, the formation of multiple heterogeneous interfaces between Fe3O4 particles and biomass carbon significantly enhances interfacial polarization. Importantly, adjusting the Fe3O4 particle content in these composites enables modulation of their dielectric and magnetic properties, thus improving impedance matching and signal attenuation. Notably, at a C to Fe3O4 mass ratio of 1:1, the C@Fe3O4 composites exhibit outstanding wave-absorbing efficiency, characterized by an effective bandwidth of 3.3 GHz at a thickness of 2.13 mm. Most significantly, they achieve a reflection loss of -57.86 dB at 7.36 GHz, representing a considerable breakthrough in high-efficiency microwave absorption.

CoN nanorods anchored on N-doped reduced graphene oxides for high-efficient microwave absorption performance

Nowadays, to solve the related electromagnetic radiation and pollution issues, it is urgent to exploit and design high-efficient microwave absorption materials, which owns the advantages of broad bandwidth, lightweight, thin matching thickness, and strong absorbing capacity. In this work, by anchoring CoN nanorods on the N-doped graphene nanosheets, a high-performance CoN/N-rGO hybrids microwave absorption absorber was fabricated with a two-step hydrothermal-nitridation method. Impressively, compared with the pure CoN nanorods, CoN/N-rGO hybrids present boosting microwave absorption properties which can be modulated by component of graphene. The strongest reflection loss (RL) value of CoN/N-rGO (40) hybrids absorber can reach −67.3 dB at 12.4 GHz with a thin matching thickness of 1.97 mm and the effective absorption bandwidth (RL ≤ −10 dB) of 5 GHz (10.4–15.4 GHz) can be gained at only 1.79 mm. This enhancement of microwave absorption is mainly attributed to the polarization, interface interaction, synergistic effect and optimal impedance matching between N-rGO nanosheets and CoN nanorods. This work provides not only a deep insight into adjusting the microwave absorption property of CoN/N-rGO hybrids, but a new route to design high-efficient nitride-based absorbers.

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.

Flexible microwave absorbing fabrics woven by high-strength graphene-based hybrid fibers with broadband electromagnetic response

Fabrics, a class of carriers, have been pioneered in electromagnetic protection, but their microwave absorbing potential has not been fully explored for a considerable period. Herein, aramid nanofibers (ANFs) enhanced reduced graphene oxide fabrics (ANF/rGO fabrics) were synthesized by wet spinning-chemical reduction. The ANF/rGO fabrics can achieve the minimum reflection loss (RLmin) of −15.8 dB with a thickness of 2.7 mm. On this basis, ANF/rGO fabrics grown with polyaniline (ANF/rGO-PANi fabrics) through in-situ doping polymerization were obtained. Polyaniline compensates for the lack of conductivity of the dielectric fabrics, bringing higher impedance matching and attenuation capability. The corresponding RLmin can reach −52.3 dB under 2.9 mm and the effective absorption bandwidth (EAB) increases to 6 GHz covering the whole Ku band under 2.5 mm. The fabrics woven by high-strength graphene-based hybrid fibers proposed in this study provide a new angle to achieve high-efficiency microwave absorption.

Lightweight, Flexible, and Thermal Insulating Carbon/SiO2 @CNTs Composite Aerogel for High-Efficiency Microwave Absorption.

A complex electromagnetic environment is a formidable challenge in national defense areas. Microwave-absorbing materials are considered as a strategy to tackle this challenge. In this work, lightweight, flexible, and thermal insulating Carbon/SiO2 @CNTs (CSC) aerogel is successfully prepared coupled with outstanding microwave absorbing performance, through freeze-drying and high-temperature annealing techniques. The CSC aerogel shows a strong reflection loss (-55.16dB) as well as wide effective absorbing bandwidth (8.5GHz) in 2-18GHz. It also retains good microwave absorption properties under tension and compression. Radar cross-sectional (RCS) simulation result demonstrates the CSC processing a strong reduction ability of RCS compared with a metal plate. Further exploration shows amazing flexibility and good thermal insulation properties of CSC. The successful preparation of this composite aerogel provides a broad prospect for the design of microwave-absorbing materials.

Insight into lightweight MXene/Polyimide aerogel with high-efficient microwave absorption

Two-dimensional transition metal carbides and nitrides (MXenes) which enriched with surface functional groups, defects, and considerable interlayer spaces, demonstrate promising prospects in microwave absorption due to that significantly contribute to dielectric loss. However, their limited gelation ability in aqueous solutions and propensity for self-stacking restrict their applications. Addressing this, a lightweight Ti3C2Tx MXene/Polyimide (MP) aerogel nanocomposites without magnetic materials has been developed through a straightforward freeze-drying method, where ‘PI chains’ anchor the MXene layers, inhibiting self-stacking and enhancing interactions between the Ti3C2Tx nanosheets. The prepared composite aerogels with different MXene contents exhibit exceptional microwave absorption performance. When the thickness of the MP30% is 1.92 mm, the minimum reflection loss (RLmin) is −49.36 dB at 16.28 GHz, and the effective absorption bandwidth (EAB) reaches 6.9 GHz with a matching thickness of 2.5 mm. At 3.8 mm, MP45% achieves an RLmin of −80.4 dB. Additionally, MP aerogels have a notable role in fire protection and insulation. The microwave absorbing mechanism of lightweight MP aerogels from the perspectives of chemical composition and physical structure was deeply explored, which is helpful to the preparation of MXene/PI based aerogels with better microwave absorbing ability in the future. Furthermore, the radar cross section (RCS) reduction value of the optimized MP30% aerogel is simulated as high as 34.775 dBm2 when the scattering angle is 90o using the computer simulation technology (CST). The prepared MP aerogel with extraordinary radar attenuation ability could potentially be applied as efficient absorber candidates in practical applications.

Construction of the N, S co-doped C/FeS2 materials for low thickness and high-efficiency microwave absorption

Research into electromagnetic wave-absorbing materials is essential to tackle the growing impact of electromagnetic wave pollution on human health and social advancement. Therefore, a method for synthesizing N,S co-doped C/FeS2 porous carbon composite absorbers (N,S@APCs) with low thickness, low filler content, and high performance is reported. The porous carbon structures were prepared by a high-temperature-hydrothermal two-step method using directly liquefied coal pitch as the carbon source. The successful doping of diatomic N and S at optimal concentrations enhances their impedance matching capacity. At the same time, forming FeS2 through the reaction between S and Fe3+ in the raw material efficiently improves the dielectric loss effect and enhances interfacial and dipole polarization effects. These factors together contribute to the strong absorption performance and low matching thickness of the fabricated N, S@APCs. At a thickness of 1.5 mm, 10 wt% of absorber filling resulted in a strong absorption performance with RLmin=-51.05 dB. Meanwhile, at a thickness of 1.7 mm, an effective absorption bandwidth of 4.76 GHz was achieved. This research offers a novel viewpoint on investigating porous carbon absorbers at low thicknesses. It serves as a reference for later investigations into polyatomic co-doped porous carbon absorbers.

Interface Modulation of CoNi Alloy Decorated with Few-Layer Reduced Graphene Oxide for High-Efficiency Microwave Absorption

Metal-organic frameworks (MOFs)-derived microwave absorbers with tunable components and microstructures show great potential in microwave absorption. Herein, we report a facile thermal reduction approach for synthesizing CoNi alloy/reduced graphene oxide (CoNi/rGO) composites from bimetallic CoNi-MOFs. By tuning the ratio of graphene oxide (GO) in the precursors, the resulting CoNi/rGO-2 composite demonstrates optimal microwave absorption performance with a minimum reflection loss (RLmin) of −66.2 dB at 7.6 GHz in the C band. Moreover, the CoNi/rGO-2 with 50 wt% filler loading achieves a maximum effective absorption bandwidth (EAB) of 6.8 GHz (10.6–17.4 GHz) at a thickness of 2.5 mm, almost spanning the entire Ku band and a portion of the X band. The outstanding performance of CoNi/rGO-2 is ascribed to the high magnetic loss from the CoNi alloy and the incorporation of rGO, which induces interfacial polarization to enhance the dielectric loss and improve the impedance matching of composite. These favorable findings highlight the considerable potential and superiority of the CoNi/rGO-2 composite as an electromagnetic wave absorption material. This work sets forth a viable strategy for designing high-efficiency alloy/rGO absorbers.

Morphology-tailored microwave absorption in MOF-derived Co9S8/Co@N, S dual-doped carbon composites via ligand-exchange induced progressive hollow engineering

Flexible manipulations of morphology and composition have been considered as an art to achieve excellent microwave absorption performance for absorbers derived from metal-organic frameworks (MOFs). In this work, a strategy combining ligand-exchange induced hollow engineering and high-temperature one-step sulfuration has been proposed to fabricate the Co9S8/Co@N, S dual-doped carbon-based absorbers with tailored solid, yolk-shelled and entirely hollow polyhedral morphologies. The progressive hollow engineering not only enables composition control in the sulfuration process, but also endows the proposed absorbers with superior microwave absorption capacity due to the enhanced conductivity loss and Maxwell-Wagner polarization as well as optimized impedance matching. The yolk-shelled Co9S8/Co@N, S dual-doped carbon-based composite achieves a broad effective absorption bandwidth of 5.13 GHz at 1.88 mm with 20 wt% loading and realizes a minimum microwave loss of − 51.78 dB @ 11.63 GHz with 2.37 mm. This work reveals that the joint strategy of ligand-exchange induced hollow engineering and gas-solid reactive thermal process is an effective path to construct high-efficient lightweight multi-interfacial microwave absorbers for addressing the electromagnetic pollutions.

Strong microwave absorption performance of simply grinding FAPbI3/CNTs composite absorbers

The distinctive physical and chemical characteristics of organic-inorganic lead halide perovskite make it a promising candidate for microwave absorption applications. However, the high-efficiency microwave absorption of halide perovskite-based composites is concentrated at high frequencies, while electronic equipment operates at low-frequency bands. Exploring simple and efficient methods to achieve optimal microwave absorption efficiency at low frequencies continues to pose a considerable challenge. Here, FAPbI3 was synthesized by a simple solvent-free hand grinding method and mixed with carbon nanotubes (CNTs) to obtain a series of FAPbI3/CNTs (FC) composites. By modulating the mass ratio of the components, FAPbI3 modulates the absorption bands, CNTs can effectively establish a conductive network to enhance both polarization loss and conductive loss and regulate impedance matching. The lower permittivity of FAPbI3 gives FC an advantage in terms of low-frequency microwave absorption. The FC-4 composite exhibits a minimum reflection loss (RLmin) of −55.67 dB at a low frequency of 6.88 GHz with a thickness of 3.5 mm. Meanwhile, microwave absorption performance can reach 99 % covering almost the entire C band when utilizing a thickness ranging from 3 to 5 mm. Additionally, according to adjusting the load of FAPbI3 in the mixture, the FC-3 composite displays the highest microwave absorption value among the composites based on halide perovskites. With a thickness of 1.4 mm, the reflection loss at 17.4 GHz reaches an impressive minimum value of −71.89 dB. This study represents the first research specifically focused on FAPbI3 perovskite in the domain of microwave absorption. FC composites display remarkable capabilities in absorbing microwaves, indicating their promising prospects for advancement within the realm of microwave absorption. This research may provide valuable insights for the design of low-frequency and high-efficiency microwave absorbers.

Ni/Porous Carbon-Based Composite Derived from Poplar Wood with Ultrabroad Band Microwave Absorption Performance

Electromagnetic wave (EMW) absorbers and electromagnetic shielding materials have attracted much attention in recent years. In this paper, Ni/wood-based porous carbon (WPC) composite material was prepared via morphology genetic method by using nickel chloride and poplar as raw material, The experimental results show that the microwave absorbing properties of the materials are related to the pyrolysis temperature, when the pyrolysis temperature settle at 700 °C, the minimum reflection loss of WPC-Ni can reach-60.4 dB with the thickness of 2.93 mm. Moreover, the effective absorption bandwidth has been greatly broadened up to 7.3 GHz when the thickness is 2.63 mm. The reason for such excellent wave absorbing performance is that the introduction of magnetic particles Ni and WPC-Ni regular straight channels improve impedance matching, the heterogeneous interface of Ni/ wood increases the polarization loss of electromagnetic waves. It is believed that this work can provide a new idea for the preparation of low-cost and high-efficiency broadband microwave absorber.

3D Porous NiCo2(CO3)3/Reduced graphene oxide with heterogeneous interfaces for high-efficiency microwave absorption

3D Porous NiCo2(CO3)3/Reduced graphene oxide with heterogeneous interfaces for high-efficiency microwave absorption

Component modulation and integrated multidimensional heterostructures of bimetallic MOFs derived 0D Co3ZnC/Co encapsulated in 2D CNTs-grafted 3D N-doped porous carbon polyhedron for high-efficient microwave absorption

Component modulation and multidimensional structural design are effective strategies to regulate the electromagnetic parameters and impedance matching, resulting in high-efficient microwave absorption. Herein, multidimensional integrated Co3ZnC/Co@C heterostructures compounding of 0D Co and Co3ZnC NCs, 1D CNTs and 3D porous carbon polyhedrons were fabricated by pyrolysis of bimetallic MOFs. Co and Co3ZnC NCs are uniformly encapsulated in CNTs-grafted porous carbon polyhedrons, forming 0D-1D-3D integrated heterostructures. The Co3ZnC/Co@C composites show component-modulated electromagnetic parameters and microwave absorption properties, which can be simply regulated by adjusting the ratio of Co/Zn in the MOFs precursor. With a filling ratio of 30 wt%, the optimal Co3ZnC/Co@C heterostructures show a minimum reflection loss (RL) value of −66.78 dB at 7.43 GHz with a thickness of 4.5 mm, located at the C band. The maximum effective absorption bandwidth (RL≤−10 dB) is up to 4.8 GHz (12.9–17.7 GHz) at only 2.0 mm. The high-efficient microwave absorption performance is attributed to that the multidimensional integrated heterostructures can sufficiently maximize the synergistic effects of each component. The uniformly distributed 0D Co and Co3ZnC NCs can promote magnetic loss and interfacial polarization. 1D CNTs are beneficial to enhance the conductive loss. 3D porous carbon polyhedrons grafted with CNTs are favored to promote the scattering of microwaves and impedance matching. These findings suggest a new insight to achieve high-performance microwave absorption by modulating the component and integrating multidimensional structures.

Regulating N-doping strategies to construct 3D interconnected abundant porous N-doped carbon for polarization loss-enhanced microwave absorbers: Theory, design, and experiments

The widespread proliferation of modern portable electronic devices has necessitated the development of functional materials with high-efficiency microwave absorption properties. In this study, we utilized biomass-derived jujube shells as a carbon source and employed a nitrogen-doping process to modify carbon materials, resulting in the fabrication of outstanding microwave-absorbing biomass-based nitrogen-doped porous carbon. Additionally, we discussed the influence of different nitrogen sources on material structure and microwave absorption performance. These N-doped porous carbon materials exhibited excellent specific surface areas, particularly Org-N, which facilitated the formation of conductive networks and the multi-stage reflection and scattering of microwave. Moreover, N-doping created numerous defect sites and heterogeneous structures, improving impedance matching, thus promoting dipole polarization and interface polarization effects, which accelerated electron migration and interlayer hopping, contributing to the attenuation of microwave energy. The lowest reflection loss for Org-N, Inorg-N, and Mixed-N reached −27.3 dB, −40.9 dB, and −45.6 dB, respectively. Mixed-N exhibited optimal microwave absorption performance at 9.9 GHz with d = 2.4 mm and achieved an effective absorption bandwidth (EAB10) of 3.0 GHz (11.0 GHz–14.0 GHz) at d = 2.0 mm. Additionally, the enhancement of polarization relaxation effects was elucidated by examining the charge density distribution in molecular models featuring various N-doping forms. Consequently, biomass-derived N-doped porous carbon materials emerge as lightweight and highly efficient functional materials for microwave absorption purposes.

Heterostructure design of one-dimensional ZnO@CoNi/C multilayered nanorods for high-efficiency microwave absorption

Dimensional design and heterogeneous interface engineering are promising approaches for the fabrication of superior absorbers with high loss performance and a wide effective bandwidth. Therein, ZnO nanorods were successfully synthesized and combined with CoNi nanosheets by hydrothermal method, and PDA was then encapsulated on the surface of the material to form a unique one dimensional (1D) core-sheath structure. The extensive defects and residual functional groups are present in the calcined material, as well as the multiple heterogeneous interfaces enhance the dielectric loss induced by polarization. Simultaneously, the 1D structure wrapped with PDA offers an efficient pathway for electron transfer, hence facilitating the enhancement of conductive loss. In addition, the CoNi-LDHs sheet layer stacked on the surface not only causes multiple scattering and reflections of electromagnetic waves, but also provides magnetic losses to optimize the impedance matching. Finally, radar cross section (RCS) simulations further reveal that the composite can dissipate electromagnetic energy in practical applications. Consequently, the 1D multilayer ZnO@CoNi/C composite exhibits an optimal reflection loss of −55 dB with a thickness of 2.3 mm and an effective absorption bandwidth (EAB) value of 6.8 GHz when the filling ratio is only 20 wt%. In summary, this paper provides a new direction for the fabrication of 1D multilayer nonhomogeneous interfacial absorbers with excellent performance.

3D porous NiCo2(CO3)3/reduced graphene oxide aerogel with heterogeneous interfaces for high-efficiency microwave absorption

Advanced electromagnetic absorbing materials (EAMs) with strong absorption and a wide effective absorption bandwidth (EAB), using innovative microstructural design and suitable multicomponents remain a persistent challenge. Here, we report the production of a material by the hydrothermal reduction of a mixture of graphene oxide (GO), Ni(NO3)2·6H2O, and Co(NO3)2·6H2O, resulting in reduced GO (RGO) with a self-assembled 3D mesh structure filled with NiCo2(CO3)3. The unique microstructure of this assembly not only solves the problem of NiCo2(CO3)3 particles agglomerating but also changes the electromagnetic parameters, thereby improving the impedance matching and attenuation ability. High electromagnetic wave absorption (EMA) was achieved by combining the 3D interconnected mesh structure and the various interfaces between NiCo2(CO3)3 and RGO. The minimal reflection loss (RLmin) was −58.5 dB at 2.3 mm, and the EAB was 6.5 GHz. The excellent EMA performance of the aerogel can be attributed to the multiple reflection, scattering, and relaxation process of the porous 3D structure as well as the strong polarization of the interfacial matrix.

Structure regulating of metal clusters in carbonized metallic organic frameworks for high-efficient microwave absorption via tuning interaction strength between metals and ligands

Structure regulating of metal clusters in carbonized metallic organic frameworks for high-efficient microwave absorption via tuning interaction strength between metals and ligands

Construction of Ni/C composites with double-shell hollow porous structure toward high-efficiency microwave absorption

Designing structure at the nanoscale of materials has been proved to be an effective way to control electromagnetic parameters and optimize microwave absorption performance. For constructing lightweight microwave absorption materials, abundant studies focus on the preparation of absorbent with hollow, porous or yolk-shell structure. However, it is still a challenge to integrate multiple structures on one material by simple method. In this work, we found that the addition of citric acid in the preparation process played an extremely important role in regulating the structure of Ni-MOF, and developed one-step approach to synthesis double-shell hollow porous Ni-MOF. After the carbonization process, the Ni/C composite was obtained. The controllable morphology of Ni-MOF endowed Ni/C composite adjustable absorbing properties. Under the assistance of citric acid, the Ni/C composite with yolk-shell, porous, as well as double-shell hollow porous structure was also synthesized. The optimal reflection loss was −56.18 dB, the broadest bandwidth was 6.1 GHz at 2.2 mm for double-shell hollow porous Ni/C composite. Particularly, strong reflection loss at C band, X band, and Ku band was realized by regulating the structure of Ni/C composite. This work revealed the mechanism of microstructures regulating the absorbing properties, which could be beneficial to the further development of MOFs derived absorbent.