Silica-coated iron nanocubes: Preparation, characterization and application in microwave absorption

Silica-coated iron nanocubes exhibited improved magnetic properties, oxidation resistance and microwave absorption performance as compared with the iron cubes without silica coating. Novel cubic nanocapsules consisting of metallic iron core and amorphous silica shell were fabricated through a simple chemical reduction route followed by a Stöber process. Thus-prepared Fe@SiO2 nanocubes were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectrometer (XPS), Fourier transform infrared spectrometer (FTIR), thermogravimetry-differential thermal analysis (TG-DTA), vibrating sample magnetometer (VSM) and scalar network analysis (SNA). Comparing with that of pure iron counterparts, silica-coated iron nanocubes exhibited improved magnetic properties, oxidation resistance and microwave absorption performance. A reflection loss (RL) exceeding −12dB was obtained in the frequency range of 8–14GHz for an absorber thickness of 2mm, with an optimal RL of −18.2dB at 9GHz. Mechanism of the improved microwave absorption properties of the Fe@SiO2 composite was discussed based on their magnetic properties and electromagnetic theory.