Core-shell structured iron-containing ceramic nanoparticles: Facile fabrication and excellent electromagnetic absorption properties

In this work, novel core-shell structured Fe₃Si@C/SiC/Fe₃O₄/SiO₂ nanoparticles were fabricated via a polymer-derived ceramic approach, starting from sol-like polycarbosilane-encapsulated polynuclear carbonyl iron nanoparticles and with pitch as an isolator to avoid aggregation during polymer-to-ceramic transformation. Elemental analysis, X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscope, vibrating sample magnetometer and vector network analyzer were employed to investigate the composition, nano/microstructure, morphology, and dielectric/magnetic properties. The results show that the size of obtained Fe₃Si@C/SiC/Fe₃O₄/SiO₂ nanoparticles is in the range of 2-200 nm. And the unique core-shell structure with the hetero-interface combined with simultaneous dielectric and magnetic loss endow Fe₃Si@C/SiC/Fe₃O₄/SiO₂ nanoparticles outstanding electromagnetic (EM) wave absorbing performance. With a sample thickness of 4.5 mm, the minimum reflection coefficient (RC) of the composites Fe₃Si@C/SiC/Fe₃O₄/SiO₂ mixed with paraffin wax reaches ?44.7 dB, indicating that more than 99.99% EM waves can be attenuated by the composites. By adjusting the sample thicknesses, the effective bandwidth (the bandwidth of RC values lower than ?10 dB) amounts 9.5 GHz (from 2.5 to 12.0 GHz), covering the whole C and X bands.