Novel yolk–shell Fe₃O₄@void@SiO₂@PPy nanochains toward microwave absorption application

A growing number of core–shell structured microwave absorbents have been reported; nevertheless, there are few studies accessible about one-dimensional core–shell electromagnetic nanocomposites as microwave absorption materials. In this work, we have developed two kinds of novel electromagnetic nanocomposites, namely yolk–shell Fe₃O₄@void@SiO₂ nanochains and Fe₃O₄@void@SiO₂@PPy nanochains. Their components and morphologies have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectra, scanning electron microscope and transmission electron microscope. The N₂ adsorption–desorption isotherms have demonstrated their specific surface areas and porosity, and the magnetic properties have been recorded by the vibrating sample magnetometer. Investigation of microwave absorbing properties manifests that Fe₃O₄@void@SiO₂@PPy nanochains have stronger absorption capability and broader effective absorption bandwidth than Fe₃O₄@void@SiO₂ nanochains, which is caused by the introduction of polypyrrole shells, giving rise to the addition of conductive loss and the enhancement of dipole polarizations, interfacial polarizations, multiple reflection and absorption. Specifically, the minimum reflection loss value is − 54.2 dB (17.70 GHz) and the maximum effective absorption bandwidth can reach 5.90 GHz (11.49–17.39 GHz); thus, Fe₃O₄@void@SiO₂@PPy nanochains will become promising microwave absorption candidates. This research once more demonstrates that necklace-like core–shell magnetic–dielectric complex benefit to enhancement of microwave absorption performance, and establishes a good foundation for exploiting the high-effective microwave absorbing materials.