Fe/Fe₃O₄@mSiO₂ Core–Shell Nanostructures for Broad-Band Microwave Absorption

Abstract

Fe/Fe3O4 composite particles with mesoporous silica (mSiO2) shells were successfully prepared via solvothermal reaction combined with hydrogen-thermal reduction. The introduction of mSiO2 on the surfaces of Fe3O4 constructs a ventilated frame and thereafter sustains the dispersion of the fine Fe particles that emerge from the reduction reaction. The conversion of Fe3O4 to Fe nanoparticles enhances the ferromagnetic loss, while the Fe3O4/Fe/mSiO2 interfaces induce an intensified dielectric loss. Fe/Fe3O4@mSiO2-500 (FFm-500) presents excellent electromagnetic wave-absorbing performances. The coating using FFm-500 as fillers presents a minimum reflection loss of −26.81 dB, together with an effective absorption bandwidth of 6.66 GHz. The results revealed the key role of mSiO2 in the synthesis of Fe/Fe3O4 nanostructures and the unique potential of Fe/Fe3O4@mSiO2 as broad-band EMA fillers.