Graphene aerogel microspheres with radial pore channels based on PVA-GO crosslinked carbonization strategy for broadband microwave absorption with ultra-low filler loading

Lightweight-grade graphene aerogels are recognized as a rising star in the field of microwave absorption. Nevertheless, conventional ice-templated graphene aerogels are prone to local structural collapse due to their disordered pores, which seriously weakens the multilevel reflection of electromagnetic waves and the interface polarization loss, limiting their broadband absorption. Herein, in this study, PVA-derived carbon/rGO aerogel microspheres (PGA) with strong interfacial combination and three-dimensional network structure of radial pore channels were prepared by introducing poly(vinyl alcohol) (PVA)-assisted assembly and combining with the spray freeze drying and carbonization method. The dynamic transition of PVA morphology from nanowires to nanosheets was driven by the control of the concentration of PVA to form a continuous heterogeneous interface and optimize the PGA structure. The structure and morphology of the resultant graphene microspheres were characterized by FTIR, XPS, Raman spectroscopy and SEM. Furthermore, the conductivity, and the microwave absorption properties were characterized by an automatic four-point probe resistivity tester and vector network analyser, respectively, and the microwave absorption mechanism was investigated. The results showed that the optimized P5GA microspheres demonstrate exceptional broadband absorption with the effective absorption bandwidth (EAB) of 5.52 GHz and the minimum reflection loss (RL_min) of −50.3 dB containing 2 wt% P5GA.