Hollow porous Fe2O3 microspheres wrapped by reduced graphene oxides with high-performance microwave absorption

Benefiting from the assistance of an organic ligand, porous Fe2O3 microspheres tightly wrapped by reduced graphene oxides (Fe2O3@RGO) were synthesized via a facile one-step hydrothermal method. The assembled Fe2O3 microspheres with different morphologies and sizes can be effectively regulated by controlling the addition of the iron source. The as-synthesized Fe2O3 spheres gradually changed from solid, hollow to a final solid ball with decreasing sizes from 800 nm to 200 nm. Intrinsic dielectric properties and charge density distribution were characterized by vector network analysis (VNA) and off-axis electron holography. Owing to their unique structure design, better electron transport behavior and enhanced dielectric and interfacial polarization, RGO wrapped hollow Fe2O3 microspheres exhibit the best electromagnetic energy conversion ability. The maximum reflection loss can reach -48.1 dB and the effective absorption bandwidth cover is 5.28 GHz (10.48-15.76 GHz) at 2.5 mm. Tuning the thickness from 1 to 5 nm, the strongest reflection loss peaks can shift from high to low frequency, showing adjusting absorption properties.