Enhanced Microwave Absorption of Shape Anisotropic Fe₃O₄ Nanoflakes and Their Composites

Abstract

As a widely applied microwave absorbing material, Fe3O4 with various nanostructures has been extensively studied to further satisfy the practical applications. Herein, uniform Fe3O4 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 (RL) 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 RL 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.

Synthesis of Conductive Polyaniline Composites for Superior Electromagnetic Wave Absorption with Lightweight and Broad Bandwidth

“…Generally, ε′ is mainly correlated with several polarization processes, such as ion polarization, electronic polarization, interfacial polarization, and electric dipolar polarization. [ 4 ] From PS‐0.20 mL to PS‐0.35 mL, more PANI would be attached to the surface of the SBA‐15 matrix, leading to more interfaces and stronger interfacial polarization. In this way, the real part of permittivity has a rising trend.…”

“…The information technology progress in electronic communications has brought great convenience to our everyday life, while it simultaneously gives rise to critical electromagnetic interference and pollution that have to be solved urgently. [ 1–6 ] Meanwhile, advanced reconnaissance and precision strike systems in modern warfare also anxiously push forward the stealth requirements for weapons and equipment. [ 7 ] Hence, it urgently calls for the electromagnetic (EM) absorbing materials which should be provided with a thin thickness, lightweight, broad bandwidth, and strong absorption.…”

Ultra‐wideband electromagnetic interference shielding properties of parallel expanded graphite/Fe3O4 composites

“…4,7 For example, the 30 wt% Fe 3 O 4 nanoflakes in paraffin wax exhibit an excellent microwave attenuation property. 8 With a thickness of 1.5 mm, the minimum reflection loss reaches −60.26 dB at 15.20 GHz, and the effective adsorption band achieves 4.25 GHz. The magnetic loss caused by eddy current, hysteresis, and multiple resonances plays a significant role in efficient EM wave absorption.…”

“…Ferrite materials are highly desirable as microwave absorbers due to their high magnetization and low cost 4,7 . For example, the 30 wt% Fe 3 O 4 nanoflakes in paraffin wax exhibit an excellent microwave attenuation property 8 . With a thickness of 1.5 mm, the minimum reflection loss reaches −60.26 dB at 15.20 GHz, and the effective adsorption band achieves 4.25 GHz.…”

Hierarchical dandelion-like CoS2 hollow microspheres: self-assembly and controllable microwave absorption performance

“…Many studies have conrmed that the microwave absorption performance (MAP) depends mainly on the electromagnetic parameters (including complex permittivity and complex permeability) and impedance-matching properties, which are closely related to the microstructures, components, and geometry of the absorbing materials. 7,8 Compared to conventional absorbents, various nanomaterials with diverse morphologies and structures such as nanowires, 9 nanoakes, 10 and nanospheres 11 always exhibit moderate microwave absorption performance. Therefore, tremendous research efforts have been devoted to designing and developing advanced and efficient absorbing materials.…”