Core-shell heterogeneous graphene-based aerogel microspheres for high-performance broadband microwave absorption via resonance loss and sequential attenuation

Graphene-based aerogels have been attracted wide attention in microwave absorption (MA) for their lightweight and high-efficient absorption. However, the assembly design of their shape and structure is still lacking, bringing obstacles to the optimization of MA. Herein, we applied coaxial electrospinning to shape aerogel monoliths into aerogel microspheres (AMs) with core-shell bilayer structure, exhibiting distinguishing broadband and tunable high-performance MA. The composite AMs including reduced oxide graphene/Fe3O4 shell layer and chitosan derived carbon core layer (Carbon@RGO/Fe3O4) can be achieved via coaxial electrospinning-freeze frying followed by calcination. The core-shell structure can make electromagnetic wave sequential entry and attenuate, enhancing the impedance matching and electromagnetic wave propagation. Significantly, with a low loading of 5 wt%, the core-shell AMs exhibit a minimum reflection loss of -61 dB at 13.84 GHz with the thickness of 2.5 mm, and the effective absorption bandwidth reach 6.88 GHz. More importantly, the corresponding absorption bandwidth is further widened to 7.52 GHz by adjusting the core-shell ratio. Electromagnetic simulation further indicate the core-shell bilayer coupling including electromagnetic wave sequential attenuation and cavity resonance loss can realize the enhanced broadband MA. The core-shell bilayer structure strategy paves a way to achieve graphene-based aerogel absorbers with high-performance MA.