Interfacial micro-capacitor engineering in CF/hyperbranched polyamide/RGO composites for efficient microwave absorption

Developing lightweight electromagnetic wave absorbers with low filler loading remains challenging. However, carbon materials rarely achieve strong attenuation capability, wide absorption bandwidth, lightweight and thin thickness simultaneously. Herein, a carbon fiber-hyperbranched polyamide-reduced graphene oxide (CF-HP-RGO) interfacial micro-capacitor architecture was rationally constructed through thermal reduction. The incorporation of HP and RGO introduces dual heterogeneous interfaces between carbon fibers and RGO layers, while forming CF-HP-RGO micro-capacitor units that act as dominant polarization centers. Under alternating electromagnetic fields, these micro-capacitor interfaces generate pronounced charge accumulation and interfacial polarization, thereby strengthening dielectric relaxation and polarization loss. Meanwhile, the interconnected RGO network establishes efficient electron-transport pathways, producing additional conductive loss. In addition, the multilayer hierarchical interface enhances multiple scattering, effectively extending electromagnetic propagation paths and improving attenuation efficiency. As a result, the optimized composite delivers a maximum effective absorption bandwidth of 5.24 GHz in the Ku band at an ultrathin thickness of 1.6 mm with a filler loading of only 5 wt.%. This work highlights micro-capacitor-dominated interfacial engineering as a promising route toward lightweight and high-performance electromagnetic wave absorption in carbon materials.