Facile Preparation of Core–Shell Fe3O4@Polypyrrole Composites with Superior Electromagnetic Wave Absorption Properties

Core–shell Fe3O4@polypyrrole (PPy) composites with excellent electromagnetic wave absorption properties have been prepared by a sequential process of etching, polymerization, and replication. Templating from pre-prepared Fe3O4 microspheres, ferric ions were released from the skin layer of the microspheres by acid etching and initiated the oxidative polymerization of pyrrole in suit. The morphological and textural evolution of core–shell Fe3O4@PPy composites depending on etching time was investigated by scanning and transmission electron microscope. A maximum reflection loss of as much as −41.9 dB (>99.99% absorption) at 13.3 GHz with a matching layer thickness of 2.0 mm was achieved when the etching time was 5 min. In comparison with other conductive polymer-based core–shell composites reported previously, the Fe3O4@PPy composites in this study not only possess better reflection loss performance but also demonstrate a wider effective absorption bandwidth (<−10.0 dB) over the entire Ku band (12.0–18.0 GHz). The excellent electromagnetic wave absorption properties of the core–shell Fe3O4@PPy composites are mainly attributed to the enhanced dielectric loss from the PPy shell.