Synthesis and microwave absorption characterization of SiO2 coated Fe3O4–MWCNT composites

Abstract

This study investigated the microwave absorption properties of core–shell composites containing; iron oxide decorated carbon nanotubes (CNTs) and silica (SiO₂@Fe₃O₄–MWCNTs) with various thicknesses of silica shells (7, 20 and 50 nm). Transmission electron microscopy (TEM) and X-ray diffraction results confirmed the formation of these core–shell structures. Microwave absorption characterization of the samples at the ranging band under consideration (the X-band) showed increased absorption and shifting of the peaks to lower frequencies compared to the uncoated sample (Fe₃O₄–MWCNTs). The minimum reflection loss decreased with increasing SiO₂ thickness. The minimum reflection loss of the composite with an optimized thickness of the silica shell (7 nm) exceeded −41 dB at 8.7–9 GHz.