Abstract: 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 Co²⁺ precursors on acidified short carbon fibers, PTFE/PVA foaming, and N₂/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.

Key words: Fluorocarbon gating, Buried heterointerfaces, Polarization relaxation, Microwave absorption