Fluorocarbon-gated multilevel heterointerfaces synergistically drive full X-band microwave absorption in composite foams

The PTFE-rich gated layer enables optimized surface impedance matching and spatial separation of internal dissipation units. • Buried CoO x /CFs interfaces trigger confined charge migration and multi-level polarization. • Porous pathways and discontinuous interfaces coordinate wave entry with internal attenuation. • Spatial partitioning drives full X-band absorption and superior corrosive media barrier. For communication and radar stealth applications, microwave absorbing materials urgently need to achieve efficient attenuation and stable operation within limited thickness. However, while continuous conductive networks or high-load loss phases can enhance attenuation, they are prone to impedance mismatch due to excessively high surface dielectric response; simply using low-polarity polymers for coverage may weaken the internal active interface, making it difficult to coordinate wave entry and energy conversion. To address this, we propose a “fluorocarbon-gating–buried-interface dissipation” strategy to construct polytetrafluoroethylene (PTFE)/poly(vinyl alcohol) (PVA)-based porous composite foams containing short carbon fibers (CFs) and cobalt oxide (CoO x ) domains, hereafter denoted PPCFCs. Following the immobilization of Co 2+ precursors on acidified short carbon fibers, PTFE/PVA foaming, and N 2 /air stepwise thermal reconstruction, the resulting composite exhibits an F-rich surface composition and a low-order carbonaceous matrix containing embedded, locally dispersed CoO x /CFs-related nanocrystalline domains. The fluorocarbon surface helps mitigate impedance abrupt changes at the air/material interface and reduces liquid-phase wetting, while the porous framework extends the propagation path. Internally, non-penetrating CFs microcurrent units and CoO x nanodomains synergistically induce confined charge migration, multi-level polarization relaxation, and auxiliary magnetic response. The optimal PPCFC-3 achieves a minimum reflection loss of −52.61 dB at 2.8 mm and effective X-band coverage at 3.4 mm. Simultaneously, this material exhibits high apparent hydrophobicity and effective barrier against corrosive media penetration. This study provides a spatial partitioning design approach for optimizing porous microwave absorbing materials through the synergistic effect of surface impedance tuning and internal interface dissipation. Co 2+ -loaded CFs were integrated into PTFE/PVA foam and thermally reconstructed into PPCFC-3. Fluorocarbon gating and buried CoO x /CFs interfaces enable X-band absorption, simulated RCS reduction, and electrolyte-barrier potential. Download: Download high-res image (313KB) Download: Download full-size image