Bio-inspired micro–macro synergistic engineering of GO@Sn/SnO₂ heterostructures for ultra-broadband microwave absorption

To address the insufficient broadband coverage of conventional microwave absorbing materials, a high-performance absorber is developed through a synergistic strategy integrating microscopic component regulation and macroscopic structural design. Sn particles are uniformly anchored onto graphene oxide (GO) using cetyltrimethylammonium bromide (CTAB) as a charge mediator, constructing pod-like bionic micro-absorbing units. Subsequent heat treatment under an inert atmosphere induces the in-situ formation of a GO@Sn/SnO₂ multi-heterolayer structure. The optimized SG-3 sample exhibits a minimum reflection loss of −59.22 dB and a maximum effective absorption bandwidth of 5.49 GHz. To overcome the bandwidth limits of planar absorbers, a turtle shell-inspired metamaterial superstructure was designed to strengthen multi-reflection and structural resonance. Combining the optimized material with this bio-inspired structure, the composite absorber breaks the bandwidth constraints of the Planck-Rozanov limit and realizes 16 GHz broadband absorption in 2-18 GHz. At r1 = r2 = 6 mm, h1 = 8 mm, h2 = 12 mm, the absorber exhibits a 14.56 GHz effective bandwidth with strong absorption peaks in the S, C, X, and Ku bands, and a maximum reflection loss of −52.88 dB. This work provides a feasible strategy for high-performance broadband microwave absorbers.