Magnetite hollow microspheres with a broad absorption bandwidth of 11.9 GHz: toward promising lightweight electromagnetic microwave absorption

Abstract

High-performance magnetite-based hollow spheres with the advantages of low density and low loading content are promising as an ideal lightweight electromagnetic (EM) wave absorption candidate. However, the effective preparation methods for these hollow spheres are still limited, and as a result, materials design and practical applications based on their size-dependent EM microwave attenuation properties are poorly accessible. In this study, high quality magnetite hollow spheres were successfully prepared by a simple, fast, one-step, and scalable plasma dynamic method with sole use of inexpensive precursors (oxygen and mild steel). The experimental results reveal that the as-prepared products are hollowed multiple-component magnetite spheres and have a very wide size distribution with a diameter of several tens of nanometers to hundreds of micrometers, which can be further separated into three fractions with different particle size distributions (0-30 μm, 30-100 μm, and >100 μm) by a simple magnetic separation method. The EM wave absorption results demonstrate that the hollow microspheres can exhibit excellent absorption ability with an effective absorption bandwidth (reflection loss ≤-10 dB) of 11.9 GHz from 3.7 to 15.6 GHz for an only 2 mm thick test absorber (50 wt% filler) and a maximum RL value of -36 dB at ∼8.2 GHz. Moreover, the positions of these resonant absorption peaks strongly depend on the sphere sizes and can be regulated at the L + C band, X band, and Ku band. Strikingly, differing from the nearly negligible microwave absorption for the ground powders, the dominating absorption mechanism for the hollow microspheres could be ascribed to the enhanced magnetic loss and multiple scattering due to the novel hollow magnetic structures, which are beneficial for the attenuation ability and improvements to their permeability and impedance matching.

Investigation of the Broadband Microwave Absorption of Citric Acid Coated Fe3O4/PVDF Composite Using Finite Element Method

“…2019, 9, 3877 2 of 17 attracted much interest in the field of EM wave absorption. However, Fe 3 O 4 as an absorptive material have some limitations such as the rapid decrease in permeability value at microwave frequency, large density, ease of oxidation and mismatch of impedance which impedes its performance as an ideal MAM [6,7].Recently, several research efforts have been geared towards improving the microwave absorption performance (MAP) of Fe 3 O 4 . For example, Mingxu et al [8] fabricated hollow Fe 3 O 4 nanoparticles via solvothermal route, with the aim of reducing its density while retaining good magnetic properties for efficient MAP.…”

“…2019, 9, 3877 2 of 17 attracted much interest in the field of EM wave absorption. However, Fe 3 O 4 as an absorptive material have some limitations such as the rapid decrease in permeability value at microwave frequency, large density, ease of oxidation and mismatch of impedance which impedes its performance as an ideal MAM [6,7].…”

Graphene-wrapped pine needle-like cobalt nanocrystals constructed by cobalt nanorods for efficient microwave absorption performance

“…In recent decades, magnetic materials such as ferrites, magnetic oxides and magnetic metals have been extensively applied in the EM wave absorption area as they possess simultaneous dielectric and magnetic losses. For instance, Shanenkov et al 9 synthesized the hollow ferritic microspheres via the plasma dynamic method. Their experimental results demonstrated that the hollow magnetic microspheres exhibited a minimum reflection loss (RL) value of −36 dB and ultra-wide effective absorption bandwidth of 11.9 GHz at only 2 mm.…”

Multilayer-Structured Wood Electroless Cu–Ni Composite Coatings for Electromagnetic Interference Shielding

“…However, the derived electromagnetic wave pollution and electromagnetic interface problem have seriously restricted their further development [1,2]. Depending on the electromagnetic loss theory, a feasible way to solve such problems is to develop high performance absorption materials [3]. The shielding effectiveness of the electromagnetic shielding materials based on wood due to low cost-effective, lightweight and easy to manufacture, indicating that it had broad prospects.…”