Reduced graphene oxide-wrapped Fe–Fe3O4@mSiO2 hollow core–shell composites with enhanced electromagnetic wave absorption properties

Abstract

The Fe/Fe₃O₄ nanocomposite with mesoporous silica (mSiO₂ for short) shell was successfully prepared by solvothermal reaction combined with hydrogen-thermal annealing (550 °C). Further, reduced graphene oxide (RGO) was introduced to obtain Fe–Fe₃O₄@mSiO₂@RGO hollow core–shell composites with hollow structure by an aerogel method utilizing home-made equipment. The introduction of mSiO₂ on the surface of Fe₃O₄ created a ventilated framework, which maintained the dispersion of fine Fe particles emerging from the reduction process. The transformation from Fe₃O₄ to Fe nanoparticles enhanced the ferromagnetic loss, while the introduction of high conductivity RGO also enhanced the polarization relaxation and conductivity loss. Meanwhile, the unique hollow structure of the core–shell structure effectively reduced the density of the ferromagnetic composites (Fe–Fe₃O₄@mSiO₂) without sacrificing the contact between RGO and nanoparticles, adding more surfaces/interfaces. Fe–Fe₃O₄@mSiO₂@RGO exhibited excellent electromagnetic wave absorption properties. The coating using Fe–Fe₃O₄@mSiO₂@RGO as fillers exhibited a minimum reflection loss of −66.24 dB with an effective absorption bandwidth of 5.31 GHz with a sample thickness of only 1.79 mm. The hollow core–shell structure of RGO-wrapped Fe–Fe₃O₄@mSiO₂ demonstrates a promising approach for the design of lightweight and high-performance electromagnetic absorption materials.