Collagen Fiber/Fe₃O₄/Polypyrrole Nanocomposites for Absorption-Type Electromagnetic Interference Shielding and Radar Stealth

Absorption-type shielding materials are significant in protecting humans and sensitive electronic devices against electromagnetic waves (EMWs) reflected from a metal surface. However, achieving high shielding performance with a high absorption contribution remains a challenge. Herein, by designing Fe3O4 nanoparticles (NPs) and conductive polypyrrole (PPy) coating and introducing them onto collagen fibers (CFs), we demonstrated a hierarchical core–shell structural CF/Fe3O4/PPy absorption-type shielding nanocomposite. For the as-prepared CF/Fe3O4/PPy, incident EMW energy can be dissipated by dielectric loss, magnetic loss, and interfacial polarization loss simultaneously. Furthermore, the hierarchically suprafibrillar structure of CFs creating nano- to microscale pores induced multiple reflection and scattering of EMWs, which dramatically improved the EMW attenuation capacity of Fe3O4 NPs and PPy coated onto the CFs by enlarging the transmission routes of EMWs. In this way, the resultant CF/Fe3O4/PPy nanocomposite exhibited an exceptional shielding effectiveness value (SE) of ∼72.0 dB with a high absorption contribution of 85.8%, and the corresponding specific SE was 360 dB cm2 g–1. Remarkably, the as-prepared CF/Fe3O4/PPy nanocomposite showed excellent radar-stealth performance (e.g., 8.2–11.5 GHz with reflection loss exceeding −10.0 dB and up to −23.7 dB of reflection loss) by adjusting the proportion of Fe3O4 NPs and PPy coated onto CFs. Overall, this work offers a promising approach to designing high-performance absorption-type shielding materials based on CFs.