Self-assembled RGO/SiO2 gradient coated lightweight honeycomb with superhydrophobicity and ultra-broadband microwave absorption

Conventional honeycomb microwave-absorbing structures cannot simultaneously achieve superhydrophobic protection and electromagnetic impedance matching under harsh service conditions such as high humidity, salt spray, and icing. To address this, the present work proposes a surface-energy-driven self-assembly strategy. RGO/SiO₂ nanostructures are introduced into a phenolic resin matrix to form a gradient architecture, which is then applied to a functionalized aramid paper honeycomb. The self-assembled gradient structure creates a low-surface-energy micro/nanostructured rough interface on the outer surface, endowing the coating with excellent superhydrophobic and anti-icing properties. Meanwhile, it enhances the incidence and dissipation of electromagnetic waves through the synergistic effects of outer-layer impedance buffering, intermediate loss enhancement, and multiple interfacial polarization. The results show that the 3FCPR coating exhibits a water contact angle of 153° and an ice delay time of approximately 8 min 30 s. In terms of electromagnetic performance, the honeycomb structure achieves an effective absorption bandwidth (EAB) of 10.6 GHz with a minimum reflection loss of −31 dB. By adopting a vertical gradient design, the EAB of the functionalized aramid honeycomb (FAH) structure is further broadened to 14.5 GHz, covering the C, X, and Ku bands. The surface-energy-driven self-assembly strategy enables the synergistic integration of superhydrophobicity, anti-icing capability, and microwave absorption while preserving the mechanical properties of the honeycomb itself. This work provides a new route for the multifunctional integrated design of lightweight honeycomb microwave absorption materials.