Enhanced Microwave Absorption of Shape Anisotropic Fe3O4 Nanoflakes and Their Composites

As a widely applied microwave absorbing material, Fe 3 O 4 with various nanostructures has been extensively studied to further satisfy the practical applications. Herein, uniform Fe 3 O 4 nanoflakes (FNFs) are synthesized by electrospinning and subsequent thermal treatment. The absorbers filled with 30 wt% FNFs (thickness: 1.5 mm) show superior reflection loss ( R L ) of −60.26 dB at 15.20 GHz due to the hierarchically cross‐linked conductive network and shape anisotropy. Furthermore, the FNFs composited with carbon nanotube (FNFs/CNT) and coated with polypyrrole (FNF@PPy) are prepared by direct mixing and vapor‐phase polymerization, respectively, to optimize the microwave absorption. Fast carrier mobility and enlarged interfacial area are realized to enhance electrical conductance and polarization loss. FNFs/CNT present multiple R L peaks of −50.9, −54.3, and −45.1 dB at 3.38, 6.70, and 12.65 GHz, respectively. Meanwhile, FNF@PPy shows wider effective absorbing bandwidths at low‐frequency of C‐band (2.32 GHz, 5.68–8.0 GHz) and S‐band (1.02 GHz, 2.79–3.81 GHz). This study confirms the considerable microwave absorbing performances of FNFs and their composites, and provides candidates for different potential applications in microwave absorption.