Microwave absorption characterization of hollow and porous rGO-FeCoNiCrMn/EC/EP composite microsphere materials

Abstract

Multi-material composite can effectively realize the lightweight, broadband and strong absorption requirements of microwave-absorbing materials. In this paper, hollow porous rGO-FeCoNiCrMn/EC/EP composite microwave-absorbing microspheres were prepared by the microemulsion method. EC and EP refer to ethyl cellulose and epoxy resin, respectively, which are mainly used as wall skeleton and core material in the formation of composite microspheres.The rGO-FeCoNiCrMn/EC/EP composite microspheres have abundant hollow porous structures, which provide good impedance-matching properties for the microwave-absorbing materials, and are favorable for enhancing the multiple reflection and scattering of microwaves. The multi-material composite constructs abundant dielectric/magnetic heterogeneous interfaces, which is conducive to increasing the microwave-absorbing properties of the materials. The excellent microwave-absorbing properties of composites stem from the fact that the materials possess a wealth of EM loss mechanisms, such as dipole polarization, interfacial polarization, conductive loss, natural resonance, exchange resonance, and eddy current loss. The effective absorption bandwidth of the composite microspheres reached 5.2 GHz (10.4∼15.6 GHz) at 2.5 mm thickness when the rGO content was 2.8 wt%. The composite microspheres with rGO content of 5.4 wt% and thickness of 2.5 mm achieve a minimum reflection loss of -50.46 dB at 10.08 GHz, and an effective absorption bandwidth of 3.6 GHz (11.2∼14.8 GHz) at a thickness of 1.5 mm. Variations in material thickness in the range of 1∼5 mm allow effective absorption of electromagnetic(EM) microwaves in the 4∼18 GHz band, i.e. almost the entire C, X and Ku bands. Finally, the rGO-FeCoNiCrMn/EC/EP composite microspheres were tested by RCS simulation. The simulation results show that the rGO-FeCoNiCrMn/EC/EP composite microspheres have the wide-angle absorption characteristics of EM microwave. The composites with rGO content of 5.4 wt% can realize the RCS below -10 dBm² over the whole range when the incidence angle of EM microwaves varies in the range of -90° < θ < 90°, and the composites with rGO content of 6.7 wt% and 7.9 wt% can realize the RCS below -10 dBm² in the range of 95.5% of the incidence angle. In this paper, the preparation and microwave-absorbing mechanism of rGO-FeCoNiCrMn/EC/EP composites is investigated, which provides a new solution for the preparation of highly efficient broadband EM microwave-absorbing materials with a wide range of application prospects.