Multiaxial electrospun generation of hollow graphene aerogel spheres for broadband high-performance microwave absorption

Abstract

Although graphene aerogels (GA) have been attracted great attention, the easy-operation and large-scale production of GA are still challenges. Further, most GA have a monolith-like appearance, limiting their application-specific needs. Herein, we highlight graphene aerogel spheres with controllable hollow structures (HGAS) that are delicately designed and manufactured via coaxial electrospinning coupled with freeze-drying and calcination. The HGAS exhibit a spherical configuration at the macroscale, while the construction elements of graphene on the microscale showing an interconnected radial microchannel structure. Further, ball-in-ball graphene aerogel spheres (BGAS) are obtained by reference to the triaxial electrospinning technology. The as-prepared spheres possess the controllable integrated conductive networks, leading to the effective dielectric loss and impedance matching, thus bringing on high-performance microwave absorption. The as-obtained HGAS shows a minimum reflection loss of −52.7 dB, and a broad effective absorption bandwidth (f E ) of 7.0 GHz with thickness of 2.3 mm. Further, the f E reaches 9.3 GHz for BGAS with thickness of 3.4 mm. Aforementioned superior microwave absorption of HGAS and BGAS confirms combination of multiaxial electrospinning and freeze-drying on the multiscale is an effective strategy for scalable fabrication of advanced microwave absorbing functional graphene aerogel spheres.

MoS2/MXene Aerogel with Conformal Heterogeneous Interfaces Tailored by Atomic Layer Deposition for Tunable Microwave Absorption

“…According to Equation S5, Supporting Information, ε ″ depends mainly on the comprehensive contributions of the polarization loss ( ε p ″) and conductive loss ( ε c ″). The numerical change of ε c ″ and ε p ″ versus the detection frequency can be obtained by a nonlinear least squares fitting method, [ 39 , 60 ] which indicates that ε c ″ is higher than ε p ″ for the samples of MSX series (Figure S8a–e , Supporting Information). Furthermore, the average value of ε p ″ increases slightly while that of ε c ″ decreases dramatically as ALD cycle increases.…”

Achieving Super Broadband Electromagnetic Absorption by Optimizing Impedance Match of rGO Sponge Metamaterials

“…[ 1–3 ] Among the electromagnetic microwave absorbers, [ 4–12 ] reduced graphene oxide (rGO) has been widely investigated due to its excellent tunability in dielectric properties. [ 13–15 ] Graphene oxide (GO) nanosheets could be assembled into ultra‐lightweight 3D solid scaffold (also termed as sponge, aerogel, foam, or network) through freeze‐drying [ 16,17 ] or hydrothermal methods, [ 18–21 ] followed by reducing process. For example, Li and co‐workers [ 17 ] prepared an rGO sponge (GS) by the freeze‐drying method and the effective absorption bandwidth (EAB), where reflection loss (RL) is less than −10 dB could reach 7.47 GHz.…”

Large-scale preparation of Co nanoparticles as an additive in carbon fiber for microwave absorption enhancement in C band

“…As illustrated in Fig. 7e,f, the μ″ and tanδ μ curves of Co/PCNF present strong peaks near 14.5 GHz, and the absorption peak caused by natural resonance and exchange resonance appear in the high-frequency range 44,45,54 .…”