Lightweight Microwave Absorption Research Articles

The tune of shell numbers of multi-shell hollow mesoporous carbon microspheres for enhanced microwave absorption

The morphology of carbon nanomaterials plays significant effect on the dielectric constant and microwave absorption (MA) capability. Elaborate morphology design would bring about efficient MA performance. In this work, we develop a hollow mesoporous carbon microspheres with different shells (from single to quadruple shells) through a facile template method and layer-by-layer etching process. This multi-shell hollow mesoporous carbon microspheres (MS-HMCMs) can be regarded as a complex composite morphology consisting of hollow, mesoporous and yolk-shell structure, which presents the tunable number of shells for optimal impedance matching, multiple interfacial polarization and the extended microwave transmission path from internal spaces. Thus, the MS-HMCMs demonstrates wide effective absorption bandwidth (EAB) of 6.4 GHz and 5.96 GHz at the thicknesses of 2.5 mm and 3.0 mm. Besides, the complex permittivity and MA properties can be effectively tuned via regulating the shell numbers. This MS-HMCMs with controllable shells may be a promising wideband and lightweight microwave absorber.

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.

Two-phase magnetic nanospheres with magnetic coupling effect encapsulated in porous carbon to achieve lightweight and efficient microwave absorbers

Component selection is crucial for microwave absorbents. Multi-component absorbers are increasingly useful and can be prepared through the rational design and control of various electrical, magnetic, and other auxiliary components. In this paper, Ni3Fe/NiFe2O4 nanospheres with two-phase magnetism were designed for use as a multi-component absorber. Specifically, a Ni3Fe/ NiFe2O4@SPC composite with 3D networks was successfully fabricated by hydrothermal method, high-temperature carbonization for activation, and electrostatic self-assembly. The contact interface and coupling effect between the two magnetic components can promote the attenuation of electromagnetic waves. Moreover, the introduction of porous carbon successfully inhibits the easy aggregation of the magnetic particles. Impressively, with a filling load of 10 wt%, the optimal RL of the prepared Ni3Fe/NiFe2O4@SPC composite reaches −60.6 dB, and the effective absorption bandwidth is 5.2 GHz at 2 mm. The combination of two magnetic components and porous carbon in this multiphase microwave-absorbing composite demonstrates a feasible strategy for designing efficient microwave absorbers in the future.

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 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.

N,S-Codoped Hollow Carbon Nanofiber/Multicomponent Nanoparticle Composites for High-Efficiency Lightweight Microwave Absorbers

N,S-Codoped Hollow Carbon Nanofiber/Multicomponent Nanoparticle Composites for High-Efficiency Lightweight Microwave Absorbers

Effect of metal doping on the microwave absorption performance of multi-element (metal, N, and Cl) doped carbon composites

Multi-element-doped carbons are actively being pursued as efficient lightweight microwave absorbers. In this work, metal, nitrogen and chlorine codoped carbons (metal,N,Cl–C, where metals = Ni, Co, Mn, or Zn) were synthesized through the high-temperature carbonization of polypyrrole doped with hydrochloric acid (PPy-HCl) and prepared in the presence of certain metal chloride salts (NiCl2, CoCl2, MnCl2, or ZnCl2). The dielectric parameters and microwave absorption properties of the metal,N,Cl–C composites could be regulated by simply altering the type of metal salt. Compared with N,Cl–C, it was discovered that Co,N,Cl–C and Ni,N,Cl–C possessed higher graphitization degrees, smaller particle sizes and more surface chemical functional groups (metal−N), which significantly improved the conduction loss and polarization loss effects including interfacial polarization and dipole polarization. At a filler ratio of 9.0 wt%, Ni,N,Cl–C displayed a wide effective absorption bandwidth (EAB, RL ≤ −10 dB) of 7.1 GHz at a thickness of 2.5 mm and a minimum reflection loss (RLmin) of −29.7 dB at 9.7 GHz and 3.5 mm thickness. Similarly, Co,N,Cl–C offered an RLmin value of −48.2 dB at 11.3 GHz and a thickness of 3.0 mm and an EAB of 6.0 GHz at a thickness of 2.5 mm. These results showcase the advantages of metal,N,Cl–C composites as microwave absorbers.

Prussian blue analogue-derived ZnOCo@nitrogen-depleted g-C3N4(ND-CN) for lightweight and efficient electromagnetic wave absorption

The sustainable electromagnetic (EM) environment urgently needs the development of high-performance absorbers. This study involved synthesizing a series of ZnOCo@ND-CN (X) composites through in-situ depositing Prussian blue analogue (Zn3[Co(CN)6]2) on varying amounts of Nitrogen-Depleted g-C3N4 (ND-CN), followed by carbonization. Adjusting the amount of ND-CN in the composites can effectively regulate the dielectric constant. The as-fabricated defective structures with high electrical conductivity and the synergy between ND-CN with ZnOCo particles, as well as the presence of a variety of heterogeneous interfaces, which endow the composites with the impressive EM wave absorption properties. ZnOCo@ND-CN (0.2) simultaneously exhibits a minimum reflection loss value of −51.57 dB and a widest effective absorption bandwidth of 5.70 GHz at the thickness of only 1.7 mm with merely 8 wt% filler. This work provides a scalable strategy for the construction of multicomponent PBA-derived composites for lightweight and high-performance microwave absorption.

Construction of ZIF-67 derived multi-interfacial composites embedded in carbonized pomelo peel for enhanced microwave absorption with 8 wt% filler loading

The development of lightweight, environmentally friendly, and cost-effective microwave absorbers with robust absorption capabilities represents a challenging yet imperative undertaking. Herein, we present a methodology wherein derived ZIF-67 (abbreviated as Co/C) embedded in carbonized pomelo peel (CPP) through a combination of pyrolysis and in-situ growth methods, demonstrates effectiveness in microwave absorption. The Density Functional Theory (DFT) provides a comprehensive analysis of the preparation and operating principles underlying the CPP@Co/C absorber. The modification of CPP with Co/C not only facilitates the creation of numerous multiple interfaces but also mitigates impedance mismatching phenomena associated with CPP. It indicates that CPP@Co/C-150 achieves a remarkable 90% wave radiation within the frequency range of 3.52–18 GHz at a mere 8 wt% loading, covering the entire C, X, and Ku bands. Furthermore, CPP@Co/C-100 exhibits a minimum reflection loss (RLmin) value of −42.5 dB at a thickness of 1.82 mm, with an effective absorption bandwidth (EAB) extending to 5.2 GHz at 2.00 mm. This represents a substantial increase of 340% and 209% compared to CPP absorbers, respectively. The exceptional absorption performance is attributed to favorable impedance matching, conductivity loss, polarization loss, and magnetic loss mechanisms. This study introduces novel strategies and benchmarks for the production of low-cost and environmental-friendly microwave absorbers with a straightforward preparation process.

Facile construction of wide-band electromagnetic wave absorber based on honeycomb-like PU foam embedded with GO-rGO/SmCo5 nanocomposite for stealth application of drone

The utilization of three-dimensional hierarchical porous foam structures has proven to be a successful approach in creating lightweight and wide bandwidth microwave absorbers with superior performance. In this study, a honeycomb-shaped polyurethane (PU) foam was utilized as the substrate for an absorber. It was combined with a new nanocomposite consisting of GO-rGO as the dielectric parts and SmCo5 as the magnetic component. The concept of utilizing a GO-rGO nanocomposite with varying bandgap within the synthesized composite foam led to the creation of multiple heterogeneous interfaces, enhancing interfacial polarization and ultimately achieving optimal impedance matching. Furthermore, the incorporation of GO-rGO nanocomposites in the synthesis of SmCo5 aimed to facilitate the thorough amalgamation of the components, mitigate the self-agglomeration of the magnetic particles, and establish a two-dimensional matrix of aligned magnetic particles, resulting in an improvement in magnetic loss phenomena. Additionally, the 3D hierarchical structure of the porous foam serves to create an intricate network, thereby enhancing the transmission pathways and enabling the activation of a greater number of attenuation phenomena. The findings suggest that the compound presents remarkable abilities in absorbing microwaves, boasting a reflection loss of −32.5 dB at 10.6 GHz and an effective absorption bandwidth of 4 GHz at a 1.4 mm thickness. The outstanding microwave absorption properties can be credited to the activation of a variety of attenuation mechanisms, including interfacial polarization, multiple reflections and scattering of waves, enhanced impedance matching, and resilient magneto dielectric losses.

Reduced graphene oxide/nonwoven fabric filled honeycomb composite structure for broadband microwave absorption

The prevalence of electromagnetic pollution in daily life has led to a rapid escalation in the demand for high-performance electromagnetic absorption and protection materials. Herein, a composite material consisting of reduced graphene oxide (RGO)/nonwoven absorbent was prepared and filled into honeycomb structures. The single-layer nonwoven/honeycomb composite, with a thickness of 5 mm, demonstrates an effective absorption bandwidth (reflection loss ≤ −10 dB) reaching 12.1 GHz (5.9 GHz–18 GHz) and a minimum reflection loss of −37 dB. This is attributed to the synergistic absorption effects of conduction loss, interfacial scattering, dielectric relaxation, and multiple scattering losses. Furthermore, the bilayer composite structure demonstrates the capability to achieve full band absorption of 2 GHz–18 GHz with a thickness of only 10 mm, giving carbon materials a thin and lightweight absorption effect. In addition, the composite materials exhibit excellent mechanical properties. This study presents a new idea for the design and manufacture of broadband, lightweight, and high-performance microwave absorbers, which holds significant potential in the field of electromagnetic pollution prevention and absorption.

Low-Cost and Eco-Friendly Synthesis of CoFe2 Nanoparticles Encapsulated into Porous Carbon Nanofibers as a Lightweight and High-Performance Microwave Absorber

Low-Cost and Eco-Friendly Synthesis of CoFe₂ Nanoparticles Encapsulated into Porous Carbon Nanofibers as a Lightweight and High-Performance Microwave Absorber

Fabrication of nitrogen-doped reduced graphene oxide/tricobalt tetraoxide composite aerogels with high efficiency, broadband microwave absorption, and good compression recovery performance

The fabrication of advanced graphene-based microwave absorbing materials with thin thickness, wide bandwidth, strong absorption strength, and low filling ratio remains a huge challenge. In this paper, nitrogen-doped reduced graphene oxide/tricobalt tetraoxide (NRGO/Co3O4) composite aerogels were synthesized by a three-step method of solvothermal reaction, high-temperature calcination, and hydrothermal self-assembly. The results showed that the attained NRGO/Co3O4 composite aerogels had a unique three-dimensional porous network structure, extremely low bulk density, and good compression recovery. Furthermore, the effect of the addition amounts of flower-like Co3O4 on the complex dielectric constant and microwave absorption properties of NRGO/Co3O4 composite aerogels was investigated. When the addition amount of Co3O4 was equal to 15 mg, the prepared binary composite aerogel showed the strongest absorption strength of –62.78 dB and a wide absorption bandwidth of 5.5 GHz at a thin thickness of 2.13 mm and a low filling ratio of 15 wt.%. It was worth noting that the maximum absorption bandwidth could reach 6.32 GHz (11.68–18 GHz, spanning the entire Ku-band) at a thickness of 2.24 mm. In addition, the possible microwave absorption mechanism of NRGO/Co3O4 composite aerogels was also proposed. Therefore, this paper will provide a new and simple strategy for preparing RGO-based porous nanocomposites as lightweight, efficient, and broadband microwave absorbers.

Constructing graphene-based aerogel with bi-continuous interpenetrating networks as a multi-functional microwave absorber

The design of three-dimensional networks in graphene-based aerogels is an effective strategy for fabricating a lightweight microwave absorber with strong absorption and broad effective bandwidth. Herein, a multi-functional aerogel with bi-continuous interpenetrating networks comprised of reduced graphene oxide (RGO) and cellulose nanofiber (CNF) was developed via an “ice-dissolving” (freezing and solvent exchange) and subsequent annealing strategy. Different from the conventional step-by-step construction of two independent networks, the bi-continuous interpenetrating networks were simultaneously built in a one-step freezing process. Notably, the network structure of the aerogel can be tuned by adjusting the concentration of CNF (CCNF) during the freezing stage. When the CCNF increased from 2 to 8 wt%, the network structure transitioned from a single three-dimensional RGO skeleton to ordered bi-continuous interpenetrating networks, and then to a disordered CNF/RGO mixed network. The mutual contributions from the RGO skeleton and CNF network endowed the aerogel (14.96 mg cm−3) with improved conduct loss and optimized characteristic impedance, leading to an excellent microwave absorption capacity. Consequently, the aerogel achieved a maximum reflection loss of −68.3 dB and an effective bandwidth of 6.9 GHz, respectively. Moreover, the unique network structure also enabled the sample to have superior noise absorbing performance (normalized absorption coefficient of 0.894 in 250–6300 Hz) and good structural stability. This strategy provides a facile avenue for constructing multi-functional aerogels with bi-continuous interpenetrating networks for both microwave absorption and noise absorption applications.

Yolk-shell construction of Co0.7Fe0.3 modified with dual carbon for broadband microwave absorption

The rational and effective combination of multicomponent materials and the design of subtle microstructure for efficient microwave absorption are still challenging. In this study, carbon-coated CoFe with heterogeneous interfaces was space-restricted in the void space of hollow mesoporous carbon spheres through a facile approach involving electrostatic adsorption and annealing, and a high-performance microwave absorber (MAs) (denoted as Co0.7Fe0.3@C@void@C) was successfully prepared. The heterostructure, three-dimensional lightweight porous morphology, and electromagnetic synergy strategy enabled the Co0.7Fe0.3@C@void@C material with yolk-shell structure to exhibit surprising microwave absorption properties. When the annealing temperature and filler loading were 550° C and 15 wt%, respectively, the composites exhibited an effective absorption bandwidth (EAB) of 7.16 GHz at 2.48 mm and a minimum reflection loss of −24.1 dB at 2.11 mm. A maximum EAB of 7.21 GHz at 2.37 mm could be achieved for the composite prepared with an annealing temperature of 650° C. In addition, radar cross-section experiments demonstrated, the potential practical applicability of Co0.7Fe0.3@C@void@C. This work expands a new avenue to develop high-performance and lightweight MAs with ingenious microstructure.

Preparation and investigation of high-efficiency ZIF-67/MoS2-based microwave absorbers

The rational design of hollow-structured composite absorbing materials is emerging as a promising approach for enhancing microwave performance. The present study successfully synthesized a series of ZIF-67/MoS2 composites with adjustable size range using a two-step method and achieved the formation of magnetically responsive Co/C/MoS2 hybrids through high temperature pyrolysis. The findings demonstrated that ZIF-67/MoS2 (1:12) exhibited a wide effective attenuation bandwidth (EAB) (5.60 GHz from 12.40 GHz to 18.0 GHz) with a thickness of 2.4 mm, and minimum reflection loss (−43.46 dB) at 2.1 mm. However, Co/C/MoS2 hybrid possessed the better EAB (5.95 GHz from 11.61 GHz to 17.56 GHz) at 1.2 mm and minimum reflection loss (−51.83 dB) at a thickness of 1.0 mm. The ingeniously synthesized ZIF-67/MoS2 and Co/C/MoS2 composites, hence, unravel themselves as a promising and exceedingly efficient contender for lightweight microwave absorption.

Graphene Oxide Paper as a Lightweight, Thin, and Controllable Microwave Absorber for Millimeter-Wave Applications

Graphene Oxide Paper as a Lightweight, Thin, and Controllable Microwave Absorber for Millimeter-Wave Applications

Fe3C/Fe implanted hierarchical porous carbon foams for lightweight and broadband microwave absorption

Porous carbon materials typically exhibit excellent microwave absorption performance and lightweight characteristics, providing a positive significance for controlling the composites weight. This work employed a one-step method, and in situ growth techniques to fabricate a foam-structure Fe3C/Fe/C with a density of only 0.142 g/cm3. The carbon skeleton encapsulates Fe3C/Fe nanoparticles to slow down its oxidation in the natural environment. Remarkably, the Fe3C/Fe/C composite achieves an impressive effective bandwidth of 5.73 GHz with a 2.2 mm thickness and only 10 wt% filling ratio. The outstanding performance can be ascribed to the enhanced interfacial polarization caused by high porosity. Additional nitrogen doping provides active sites to enhance dipole polarization. Additionally, after in-depth analysis of the various magnetic loss mechanisms present in Fe3C/Fe/C, we have revealed the promotion of introducing magnetic nanoparticles on the microwave absorption performance of foam-like carbon. This work provides an effective reference for reducing the weight of microwave absorbers, simplifying preparation methods, and understanding the mechanisms of magnetic nanoparticles in foam-like carbon.

Encapsulation of metal particles in porous carbon by microarchitectural design for lightweight and efficient microwave absorption

The construction of heterojunctions in carbon materials is an effective means of preparing absorbers, but still faces challenges in practical applications. In this paper, N-doped porous C/Cu composites with three-dimensional highly conductive structures were prepared from sustainable biomass materials using a microarchitectural design strategy. The results of the study show that the porous structure provides more electromagnetic wave reflection sites on the surface of the material. The doping of N atoms and the embedding of Cu microspheres improve the impedance matching as well as the transmission path of the microcurrents, and the presence of relaxation polarization in the heterojunction at the interface of the carbon matrix and Cu microspheres is of great importance for the enhancement of the microwave absorption properties. The sample has a minimum reflection loss of −60.68 dB and has a maximum effective absorption bandwidth of 5.92 GHz. The CST simulation results verify the outstanding microwave absorption performance of N-doped porous C/Cu composites, with RCS reduction values up to 19.14 dBm2 at a scattering angle of 0 °C. This work provides new insights into the preparation and practical application of high-performance microwave absorbing materials.

Heterogeneous interface engineering of N–doped carbon onion nanotube chains toward prominent microwave absorption

Synthesizing lightweight, thin–profile, and high–performance microwave absorbers has emerged as an urgent research topic. A promising strategy for carbon–based materials to achieve these attributes is to rationally construct heterostructures. Herein, 0.89–1.54 at.% nitrogen(N)–doped carbon onion nanotube chains (NCONCs) were produced by blending CONCs harvested from candle combustion with HH4Cl and subjecting them to heating at 300–400 °C for 3 h. The hinge–like NCONCs revealed numerous electron transport paths, facilitating the formation of multi–tiered conduction networks. The N–doping introduced C–N groups and interfaces into the CONCs, which yielded extensive dipole and interfacial polarization. Simultaneously, the 1.14 at.% N–doping endowed NCONC–400 with suitable conductivity, thereby ensuring excellent impedance matching. The resulting synergistic effect of impedance matching and electromagnetic wave attenuation was clearly observed. Specifically, NCONC–400 exhibited exceptional performance with a maximum effective absorption bandwidth of 4.71 GHz and a peak reflection loss of –35.47 dB at 1.4 mm. The radar cross–section reduction demonstrated by NCONC–400 composites reached 21.43 dB cm2. These impressive results prove the distinctive advantages of CONCs in tailoring performance and optimizing impedance matching, which are appealing for lightweight and efficient microwave absorbers.