Promising broadband and enhanced microwave absorption of polypyrrole decorated hollow porous ZnO microspheres

The design of hollow porous microstructure and the selection of reasonable dielectric composition are effective ways to obtain microwave absorbing (MWA) materials with outstanding performance. In this paper, polypyrrole decorated ZnO hollow porous composites (ZnO@PPy HPC) with improved MWA performance were successfully prepared by an in situ polymerization method. The results showed that PPy was uniformly loaded on the surface of ZnO hollow porous microspheres (ZnO HPM) to build a hierarchically core-shell hollow structure. The addition and proportion regulation of PPy can effectively improve the dielectric properties, generate interfacial polarization effect and achieve good impedance matching, leading to enhanced MWA characteristics of composite materials. ZnO@PPy HPC exhibited promising broadband microwave absorption properties. The minimum reflection loss (RL _min) reached −48.5 dB at 14.5 GHz with broad effective bandwidth (less than −10 dB) of 6.2 GHz when the matching thickness was 2.2 mm. This study provides guidance for the development on a new type of microwave absorbing materials composed of hollow porous structure and conductive polymer.