Wide Effective Absorption Bandwidth Research Articles

In situ deposition of pitaya-like Fe3O4@C magnetic microspheres on reduced graphene oxide nanosheets for electromagnetic wave absorber

Reasonable nanostructure design and composition are conducive to the electromagnetic wave (EM) absorption behavior of absorbers. Herein, Fe3O4@C/reduced graphene oxide (rGO) nanocomposites with layered structure were fabricated by a feasible solvothermal method. By adjusting the amount of graphene oxide (GO), different dielectric characteristics and impedance matching conditions of Fe3O4@C/rGO nanocomposites could be obtained. Moreover, with amorphous carbon as the matching layer, Fe3O4 and rGO provide strong magnetic loss and dielectric loss, respectively. The results exhibit that Fe3O4@C/rGO nanocomposites own salient EM absorption properties under the combined action of various components and three-level layered structure. In addition, the Fe3O4@C/rGO-20 nanocomposites (the addition of GO is 20 mg) are endowed with the best EM absorption performance, which demonstrates a minimum reflection loss (RLmin) value of −59.23 dB at 6.24 GHz with a sample thickness of 3.57 mm and effective absorption bandwidth (EAB) is 6.72 GHz. Moreover, the widest EAB is 8.24 GHz at a thinner thickness of 2.6 mm with the RL value of −25.80 dB at 14 GHz. This work could be a reference for lightweight, broadband, strong absorption composite absorber.

Facile synthesis of N, S-codoped honeycomb-like C/Ni3S2 composites for broadband microwave absorption with low filler mass loading

Manufacturing highly efficient microwave absorbents with powerful absorbing intensity, wide effective absorption bandwidth (RL < −10 dB, it means that 90% of the electromagnetic waves enter the absorber and are dissipated) and light weight at low filling loading is still a challenge. In this work, N, S-codoped honeycomb-like C/Ni3S2 composites were synthesized via a freeze-drying approach and following pyrolysis process under Ar atmosphere, using NaCl and sucrose as template and carbon source, respectively. When evaluated as a microwave absorbent, the as-obtained N, S-codoped honeycomb-like C/Ni3S2 composite pyrolyzed at 700 °C displayed high performance for microwave absorption including high absorption intensity (the maximum reflection loss of −46.8 dB at 13.4 GHz), broad effective absorbing bandwidth (7.0 GHz, 11.0–18.0 GHz) and relative low filling loading in paraffin (only 10 wt%). Such high performance of microwave absorption could be ascribed to the better impedance matching and stronger damping ability induced by unique honeycomb-like structure and suitable pyrolysis temperature. Importantly, our research might provide a facile and engineering strategy to explore other types of microwave absorbing materials to boost their microwave absorption at low filler loading.

Rational construction of hierarchical accordion-like Ni@porous carbon nanocomposites derived from metal-organic frameworks with enhanced microwave absorption

Development of high-performance microwave absorption materials with a thin matching thickness, wide effective absorption bandwidth, low filler loading, and strong absorption capacity has attracted extensive scientific and technological interest and it remains a huge challenge. Here, hierarchical accordion-like Ni@porous carbon (Ni@C) nanocomposites derived from metal-organic frameworks were rationally designed and successfully developed as enhanced microwave absorption materials. It was found that the well-tuned composition (Ni, C and CNTs) and structure (laminated, porous, and core-shell characteristics) of the resultant nanocomposites led to the variation of magnetic properties, graphitization degree, and electromagnetic parameters. As expected, the hierarchical accordion-like Ni@C nanocomposites with a low filler loading of 25 wt% achieved a broad effective absorption bandwidth of 6.6 GHz, a strong reflection loss of −86.9 dB with a thin thickness of 1.8 mm through the optimization of impedance matching and improvement of microwave attenuation ability. The enhanced microwave absorption was attributed to the loss synergistic effect between abundant interfacial and dipole polarization in the hierarchical architecture, to the electronic transport in the three-dimensional conductive network, and to strong magnetic coupling in Ni nanoparticles. Therefore, this work presented a tailored strategy for the development of novel hierarchical nanocomposites as enhanced microwave absorption materials.

Zeolitic imidazolate framework derived Fe-N/C for efficient microwave absorbers

Abstract Three main strategies for designing efficient microwave absorber includes the intrinsic dielectric/magnetic properties, the novel structure and the single atom doping. The Fe-N/C nanocomposites integrate the advantages of above three strategies into one system. In this work, the method for preparing Fe-N/C nanocomposite by calcining the FePc@ZIF-8 precursor under a flowing N2 gas is described. Fe-N/C nanocomposites, displaying respectable dodecahedron-like morphology, have the merits of strong absorption ability, wide effective absorption bandwidth, thin thickness, and excellent microwave absorption efficiency, which are attributed to the synergistic effect of good electromagnetic loss capacity and proper impedance matching originating from intrinsic dielectric/magnetic properties, the novel structure and the single atoms (Fe and N) doping. Fe-N/C-24 composite delivers an optimal reflection loss of −30.98 dB, an effective absorption bandwidth of 5.04 GHz, the microwave absorption capacity of 87.61 dB GHz the absorption efficiency of 51.53 dB GHz/mm at 1.7 mm.

Synthesis of porous carbon embedded with NiCo/CoNiO2 hybrids composites for excellent electromagnetic wave absorption performance

A series of NiCo/CoNiO2@C hybrid composites were successfully prepared by a hydrothermal method and subsequent heat-treatment process. Porous carbon was synthesized through a fabric carbonization process derived from fish skin. The micro-morphology and minor component of NiCo/CoNiO2@C hybrid composites could be tuned by controlling the adjunction amount of Co2+ and Ni2+. The NiCo/CoNiO2@C hybrid composite exhibited strong electromagnetic wave absorption performance when the adjunction amount of Co2+ and Ni2+ was 0.4 mmol and 0.2 mmol. The optimal reflection loss could up to −74.3 dB at the matching thickness of 3.8 mm, while the corresponding widest effective absorption bandwidth (reflection loss values lower than −10 dB) is up to 6.32 GHz covering from 11.78 GHz to 18.0 GHz at the matching thickness of 2.4 mm. Based on the Maxwell-Garnet theory, the pore size of porous carbon materials could influence the dielectric constant which has a great effect on impedance. Previous work has illustrated that porous carbon carbonized at 650 °C processes the proper pore size for excellent impedance matching. Besides, NiCo alloy nanosphere and CoNiO2 nanoflower would provide magnetic loss and interface polarization for attenuating electromagnetic wave energy. Moreover, the conductive loss derived from porous carbon and dipolar loss which originated from the defects are also beneficial to decay electromagnetic energy. This work indicates that the as-prepared NiCo/CoNiO2@C hybrid composites accompanied with excellent electromagnetic wave absorption performance could act as a promising absorber to deal with the increasingly serious electromagnetic pollution.

Strong and Thermostable Boron-Containing Phenolic Resin-Derived Carbon Modified Three-Dimensional Needled Carbon Fiber Reinforced Silicon Oxycarbide Composites with Tunable High-Performance Microwave Absorption Properties

This paper focuses on the preparation of boron-containing phenolic resin (BPR)-derived carbon modified three-dimensional (3D) needled carbon fiber reinforced silicon oxycarbide (SiOC) composites through a simple precursor infiltration and pyrolysis process (PIP), and the influence of PIP cycle numbers on the microstructure, mechanical, high-temperature oxidation resistance. The electromagnetic wave (EMW) absorption properties of the composites were investigated for the first time. The pyrolysis temperature played an important role in the structural evolution of the SiOC precursor, as temperatures above 1400 °C would cause phase separation of the SiOC and the formation of silicon carbide (SiC), silica (SiO2), and carbon. The density and compressive strength of the composites increased as the PIP cycle number increased: the value for the sample with 3 PIP cycles was 0.77 g/cm3, 7.18 ± 1.92 MPa in XY direction and 9.01 ± 1.25 MPa in Z direction, respectively. This composite presented excellent high-temperature oxidation resistance and thermal stability properties with weight retention above 95% up to 1000 °C both under air and Ar atmosphere. The minimal reflection loss (RLmin) value and the widest effective absorption bandwidth (EAB) value of as-prepared composites was −24.31 dB and 4.9 GHz under the optimization condition for the sample with 3 PIP cycles. The above results indicate that our BPR-derived carbon modified 3D needled carbon fiber reinforced SiOC composites could be considered as a promising material for practical applications.

NiCo2O4 constructed by different dimensions of building blocks with superior electromagnetic wave absorption performance

A series of NiCo2O4 absorbers constructed by different building cornerstones were successfully fabricated through precipitation-hydrothermal method. By adjusting the precipitants from NaHCO3, urea, and NaOH to Na2CO3, the NiCo2O4 absorbers assembled through zero-dimensional (0D) nanoparticles, one-dimensional (1D) nanorods and two-dimensional (2D) micro/nanoplates could be obtained. We found that NiCo2O4 absorbers formed by two-dimensional building blocks displayed high dielectric loss capacity but rather poor magnetic loss, resulting in inferior electromagnetic (EM) wave absorption performance. On the contrary, the sphere-like and urchin-like NiCo2O4 EM wave absorbing materials assembled by zero-dimensional nanoparticles and one-dimensional nanorods possess multiple magnetic loss mechanisms, which can achieve a balance with dielectric loss, leading to remarkably promoted EM wave attenuation performance. The effective absorption bandwidth for urchin-like and sphere-like NiCo2O4 is up to 5.84 GHz and 6.08 GHz at thickness of 1.88 mm and 2.06 mm, respectively. Moreover, the minimum reflection loss (RLmin) of sphere-like NiCo2O4 also reaches to −42.8 dB as well. The thin thickness, strong absorption capacity and wide effective absorption bandwidth (fe), which is the widest among the previously reported NiCo2O4-based absorbers so far, is prone to be a competitive candidate as the materials for EM wave absorption devices.

Sodium citrate assisted hydrothermal synthesis of nickel cobaltate absorbers with tunable morphology and complex dielectric parameters toward efficient electromagnetic wave absorption

NiCo2O4 was synthesized by sodium citrate assisted hydrothermal method. Four NiCo2O4 samples were fabricated by changing the ratio between sodium citrate and metal ions (0.5, 1, 1.5 and 2). Morphology evolution from 3-dimensional flower-like structure to 2-dimensional nanosheet structure is observed as the ratio between sodium citrate and metal ions increased from 0.5 to 2. In addition to the morphology, the complex permittivity of NiCo2O4 can also be simply adjusted by regulating the addition amount of sodium citrate. The decent complex permittivity was obtained when the ratios between sodium citrate and metal ions were 0.5, 1 and 1.5. The optimal absorber (sodium citrate: metal ions = 1.5: 1) displays high absorption capacity of −47.9 dB and wide effective absorption bandwidth (EABs) of 4.28 GHz (from 13.72 GHz to 18 GHz) at ultrathin thickness of 1.39 mm. This NiCo2O4 absorber, possessing high absorption capacity as well as wide adsorption bandwidth, is the thinnest pristine NiCo2O4 absorbers currently reported. The high EM wave attenuation performance is ascribed to the well matched impedance originated from the rational design of complex permittivity values, and other dissipation mechanism, including dipole polarization, interfacial polarization and conduction loss, etc. This work may provide us a novel strategy for regulating the effective absorption band of other Co-based spinel structure EM wave absorption materials.

Tunable electromagnetic and enhanced microwave absorption properties in CoFe2O4 decorated Ti3C2 MXene composites

Ti3C2 MXene has demonstrated to be a potential microwave absorber if some difficulties, e.g., poor impedance matching and lack of magnetic loss, can be well-solved. In this paper, laminated Ti3C2 MXene was synthesized using the HF etching method. CoFe2O4 nanoparticles-decorated Ti3C2 MXene (CoFe2O4-Ti3C2) composites were then fabricated via a novel in-situ solvothermal process. The incorporation of CoFe2O4 nanoparticles on the electromagnetic (EM) and microwave absorption properties of Ti3C2 MXene were systematically studied over 2–18 GHz. Interestingly, increased percolation threshold and controlled complex permittivity were well-observed in the CoFe2O4-Ti3C2 composites. Furthermore, additional magnetic loss due to the existence of magnetic CoFe2O4 was easily obtained. Benefiting from tunable electromagnetic properties, the minimum reflection loss (RL) value of the CoFe2O4-Ti3C2-filled absorbing coating achieved −30.9 dB with a matching thickness of only 1.5 mm. A wide effective absorption bandwidth (RL < −10 dB) of 8.5 GHz was correspondingly realized. These results demonstrated that the CoFe2O4-Ti3C2 composites are favorable as a broadband microwave absorbent.

Tailoring electromagnetic absorption performances of TiO2/Co/carbon nanofibers through tuning graphitization degrees

Low density, high stability and strong dielectric loss capacity endow carbon-based nanocomposites with superb microwave dissipation performances. Different from grapheme or carbon nanotubes, the graphitization degrees of carbon-based composites derived from the organic precursor pyrolysis can be accurately regulated by controlling the carbonization temperature. As such, their electromagnetic properties can be easily tuned. In this work, we report the preparation of TiO2/Co/Carbon nanofibers (CNFs) through a combined approach of electrospun and carbonization at different temperatures. The nanofibers with an average diameter of 300 nm were coated by a dense layer of TiO2 and embedded by Co/CoO nanoparticles. The performance evaluation indicated the composite obtained at 700 °C exhibits remarkably strong absorption of −63.2 dB at 9.8 GHz and wide effective absorption bandwidth of 6.4 GHz with a pretty low filling rate of 15 wt%. Further analysis on the electromagnetic behaviors shows that the composite possesses regulable impedance matching characteristic and absorption performances, implying the huge application potential under various demand conditions.

Uniformly coating MnOx nanoflakes onto carbon nanofibers as lightweight and wideband microwave absorbers with frequency-selective absorption

Microwave absorption materials have drawn significant attention due to their potential application in information safety and military stealth. In this work, we report a facile strategy to synthesize carbon nanofiber/MnOx core-shell composites (CNF@MnOx) in order to collaborate their advantage for high-performance microwave absorption application. Through a simple ozone pretreatment process, ultrathin MnOx nanoflakes can be uniformly coated onto CNFs by a hydrothermal method. The mixture of several MnOx forms coexists in CNF@MnOx composites because of the readily available crystalline phase transformation from different manganese oxides. The investigation of microwave absorption properties shows that the absorbing capabilities CNF@MnOx composites have significant improvement compared to the pure CNFs and most of single-phase manganese oxides. The minimum reflection loss for CNF@MnOx can arrive at −47.2 dB at 9.4 GHz with a thickness of 2.8 mm, and the widest effective absorption bandwidth was measured to be 5.0 GHz. Furthermore, polymorphic MnOx endows CNF@MnOx with selective-frequency microwave absorption. The dramatic enhancement of microwave absorption is ascribed to dielectric loss, magnetic loss, impedance matching and geometrical effect. Hence, the present CNF@MnOx may be a capable candidate for strong-absorption, broadband and lightweight microwave absorber.

High-performance electromagnetic wave absorption by designing the multilayer graphene/thermoplastic polyurethane porous composites with gradient foam ratio structure

An excellent electromagnetic wave absorbing material (EWAM) should possess both wider effective absorption bandwidth (EB) and lower minimum reflection loss (RLmin), which depends on good impedance matching between the EWAMs and air and strong attenuation of electromagnetic wave (EW) inside the absorber. In this work, single-layer graphene/thermoplastic polyurethane (TPU) porous composites with different foam ratio and gradient foam ratio multilayer graphene/TPU porous composites with different number of layers were prepared. Not only were the EW-absorbing properties and mechanism of these composites investigated, but the mechanical properties were also examined. Compared to the single-layer samples with the same average foam ratios at the same thickness, the multilayer samples showed wider EB, 5.6, 4.6, 4.4 GHz for 3L, 4L and 5L, respectively. By designing the multilayer structure of gradient foam ratio, it provides a novel path for the preparation of EWAMs with strong absorption capacity, wider EB, light weight and excellent mechanical properties.

Enhanced microwave absorption properties of carbonyl iron/resin composites incorporated with Ti3SiC2 particles

Hybrid Ti3SiC2 and carbonyl iron powders were composited with epoxy and polyamide resin to fabricate thin thickness and wide bandwidth microwave absorption composites. The influences of Ti3SiC2 content and particle size on the complex permittivity, complex permeability and microwave absorption properties were investigated systematically in the frequency range of 8.2–12.4 GHz. It was found that the real and imaginary parts of complex permittivity were improved obviously by increasing Ti3SiC2 content or decreasing Ti3SiC2 particle size, which are ascribed to the enhanced interfacial polarization and conductance loss. By calculating the reflection loss, the composite with 7 vol% Ti3SiC2 content and < 30 μm Ti3SiC2 particle size exhibited a wide effective absorption bandwidth of 3.6 GHz in 8.8–12.4 GHz when the thickness is 1.2 mm.

Designed construction of Ti3C2Tx@PPY composites with enhanced microwave absorption performance

The unique features of 2D layered structure, native defects and abundant functional groups provide special peculiarities for exploring Ti3C2Tx MXenes in microwave absorption field. Nonetheless, both bad conductivity and poor impedance matching of Ti3C2Tx MXenes lead to relatively poor EM absorption performance. Herein, by modifying Ti3C2Tx MXenes with conductive PPy microspheres, a new core-shell like delaminated structure composites were fabricated for significant enhancement of absorption performance. It demonstrated that the obtained Ti3C2Tx@PPy composites showed excellent microwave absorption performance due to synergistic effect between Ti3C2Tx and PPy microspheres. The 10 wt% Ti3C2Tx@PPy composites in wax matrix displayed a minimum reflection loss (RL) of −49.5 dB at 7.6 GHz with 3.6 mm in thickness, and the effective absorption bandwidth was 5.14 GHz from 6.44 to 11.58 GHz. The widest effective absorption bandwidth was 6.63 GHz from 8.55 to 15.18 GHz, the RL reached −42.6 dB in 12.4 GHz at only 2.7 mm matching thickness. More importantly, the composites can cover 4–18 GHz by simply adjusting matching thickness of 2–5.5 mm. The fantastic absorption performance could be ascribed to the unique properties of Ti3C2Tx MXenes and heterojunction in Ti3C2Tx@PPy, which might be a promising material in microwave absorption applied aspects.

Microwave-assisted synthesis of tremella-like NiCo/C composites for efficient broadband electromagnetic wave absorption at 2–40 GHz

Materials incorporating magnetic metal particles into a carbon matrix have drawn tremendous interest as electromagnetic wave (EMW) absorbers. Herein, the tremella-like assemblies of hierarchically porous nickel-cobalt/carbon (NiCo/C) were successfully prepared by a microwave-assisted method, followed by a sintering process. The sintering temperature is a vital factor for formation of carbon matrix and the metal particles. The higher temperature is helpful for the graphitization of carbon matrix and growth of NiCo alloy. The NiCo/C composite obtained at 700 °C displayed the best EMW absorption properties: the minimum reflection loss (RLmin) value reaches −41.6 dB at 8.4 GHz and the widest effective absorption bandwidth is up to 34.33 GHz (3.78–38.11 GHz) by adjusting the layer thickness (1.0–5.5 mm) (EAB, RL ≤ −10 dB). The excellent EMW absorption properties are attributed to the synergistic effect of the multiple components (magnetic NiCo and dielectric C) and hierarchically porous structure.

Continuous SiCN Fibers with Interfacial SiC xN y Phase as Structural Materials for Electromagnetic Absorbing Applications.

SiCN ceramics are one of the most important electromagnetic wave (EMW) absorbing materials for application in harsh environments, but research studies on optimizing phase distribution in SiCN ceramics for excellent EMW absorbing properties are still lacking. Herein, continuous SiCN fibers with an interfacial SiC xN y phase were prepared through nanochannel diffusion-controlled nitridation of polycarbosilane fibers with an NH3 gas flow. The existence of the interfacial SiC xN y phase distributed between the carbon-rich SiC phase and Si3N4 phase can improve the impedance matching and efficiently promote the production of macroscopic dipole moments in the heterointerfaces of SiC xN y-SiC and SiC xN y-Si3N4 for an enhanced multifarious polarization relaxation loss. The EMW absorption properties can be further improved by optimizing the microstructure with a continuous carbon-rich SiC phase for possessing an excellent conductive loss by converting the EMW energy into current flow. Finally, under the synergy of the interfacial SiC xN y phase and the continuous carbon-rich SiC phase, SiCN fibers can present excellent EMW absorption properties with extremely strong absorption ability (reflection loss of -63.7 dB), ultrathin thickness (1.78 mm), and wide effective absorption bandwidth (4.20 GHz). These obtained SiCN fibers also possess excellent mechanical properties with the tensile strength higher than 2.0 GPa and excellent high-temperature stability up to 1500 °C. This work provides a strategic method for optimizing the microstructure of SiCN ceramics for admirable EMW absorption properties, and the obtained SiCN fibers can be used as reinforcements of ceramic matrix composites for stealth applications under harsh environments.

Nanolayered Cobalt@Carbon Hybrids Derived from Metal–Organic Frameworks for Microwave Absorption

High-performance broadband microwave absorbers are greatly required to cope with the increasingly serious microwave radiation pollution. Integration of dielectric and magnetic components is a promising strategy to achieve desirable microwave absorption performance. Herein, we demonstrated a facile and efficient approach to fabricate two-dimensional cobalt@carbon (Co@C) hybrids by solvothermal synthesis of cobalt–metal–organic framework (Co-MOF) nanosheets and subsequent thermal pyrolysis for efficient microwave absorption application. The resultant nanolayered Co@C hybrids inherit the two-dimensional architecture of the Co-MOF nanosheets. During the thermal pyrolysis of Co-MOF, its organic component is carbonized to amorphous carbon while its cobalt ions are carbothermally reduced to cobalt nanoparticles, thus in situ integrating the magnetic metal nanocrystal with the dielectric carbon. Consequently, a wide effective absorption bandwidth of 5.44 GHz at a small thickness of 1.76 mm and a minimum reflectio...

NiS₂@MoS₂ Nanospheres Anchored on Reduced Graphene Oxide: A Novel Ternary Heterostructure with Enhanced Electromagnetic Absorption Property.

For the purposes of strength, military equipment camouflage, and protecting the health of organisms, electromagnetic wave absorbing materials have received a lot of attention and are widely studied. In addition to having a strong absorption intensity and a wide effective absorption bandwidth, materials that are lightweight, thermally stable, and antioxidative are also highly desirable. In this study, we fabricated core–shell structured NiS2@MoS2 nanospheres anchored on reduced graphene oxide (rGO) nanosheets (NiS2@MoS2/rGO) by a simple two-step hydrothermal method. The combination ratio was adjusted to achieve proper impedance matching. The electromagnetic parameters and the absorption performance were investigated in detail. A composite loaded with 30 wt.% of the sample achieved a minimum reflection loss (RL) value of −29.75 dB and the effective bandwidth (RL value of less than −10 dB) ranged from 4.95 GHz to 18.00 GHz (13.05 GHz), with a thickness ranging from 1.5 mm to 4.0 mm. This study proved that the generated significant interfacial polarization and synergetic interaction between components can result in NiS2@MoS2/rGO composites with enhanced electromagnetic absorption performance.

The rambutan-like C@NiCo2O4 composites for enhanced microwave absorption performance

To obtain outstanding electromagnetic microwave absorption (EMWA) properties, the rambutan-like dielectric–magnetic C@NiCo2O4 material was successfully prepared by a simple hydrothermal method, followed by a carbonization process. Benefiting from the unique rambutan-like structure, the dielectric–magnetic C@NiCo2O4 composites showed excellent microwave attenuation ability: minimum reflection loss (RLmin) value of − 39.0 dB at 17.4 GHz and wide effective absorption bandwidth (EAB, reflection loss exceeding − 10 dB) of 4.16 GHz (> 13.84 GHz) with a matching thickness of only 1.5 mm, which were much better than those of pure C and NiCo2O4. The superior properties might be due to multiple synergistic effects: magnetic loss (NiCo2O4), dielectric loss (C, NiCo2O4), the multi-reflections, scattering and interface relaxation resulting from mesoporous rambutan-like structures, and the dipole polarization to get good electromagnetic matching and high attenuation efficiency.

Retracted Article: A versatile strategy for alternately arranging the foam ratio layers of multilayer graphene/thermoplastic polyurethane composite foams towards lightweight and broadband electromagnetic wave absorption.

A broadband electromagnetic wave (EW) absorbing material should possess both wider effective absorption bandwidth and lower minimum reflection loss, depending on good impedance matching between the absorber and air and strong attenuation of EW. In this study, single-layer graphene/thermoplastic polyurethane (TPU) composite foams with different foam ratios and alternating multilayer graphene/TPU composite foams with different numbers of layers were prepared. Not only was the EW-absorbing mechanism of these composite foams examined, but also the relationship between the EW-absorbing properties and the number of layers were investigated. The single-layer sample S-5 with good impedance matching characteristics and S-3 with strong EW attenuation characteristics were selected as the constituent layers to design alternating multilayer graphene/TPU composite foams. Compared to the single-layer sample 4L-C (4L-C is defined as the monolayer sample S-4 with a thickness of 9 mm), the 4L alternating multilayer graphene/TPU composite foams could achieve more than 90% EW absorption in a wide frequency band of 8.5 GHz, and its minimum reflection loss was as low as −37.67 dB, which are very beneficial for its use as a lightweight, flexible electromagnetic wave absorbing material (EWAM) for broadband absorption. More importantly, the absorption of the obtained alternating multilayer composite foams could be simply modulated not only by the absorber thickness, but also by the number of layers to satisfy the applications in different frequency bands.