Polypyrrole Decorated Flower-like and Rod-like ZnO Composites with Improved Microwave Absorption Performance

In this study, zinc oxide (ZnO)/polypyrrole (PPy) composites with flower- and rod-like structures were successfully fabricated by in situ polymerization and the hydrothermal method and used as microwave absorption (MWA) materials. The surface morphologies, crystal structures, and electromagnetic features of the as-prepared samples were measured by field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and vector network analyzer (VNA). The results show that the conductive polymer PPy was successfully decorated on the surface of ZnO substrates. The MWA ability of flower- and rod-like ZnO/PPy composites is significantly enhanced after introduction of PPy. Rod-like ZnO/PPy composites exhibited superior MWA properties than those of flower-like ZnO/PPy. The former achieved a minimum reflection loss (RLmin) of −59.7 dB at 15.8 GHz with a thickness of 2.7 mm, and the effective absorption bandwidth (EAB, RL < −10 dB) covered 6.4 GHz. PPy addition and stacked structure of rod-like ZnO/PPy composites can effectively improve the dielectric properties, form multiple reflections of incident electromagnetic waves, and generate an interfacial polarization effect, resulting in improved MWA properties of composite materials.