RGO-supported core-shell SiO2@SiO2/carbon microsphere with adjustable microwave absorption properties

RGO-supported core-shell SiO2@SiO2/carbon microsphere hybrid was synthesized by combining solution blending and annealing treatment. The SEM and TEM characterization indicate that the core-shell SiO2@SiO2/carbon microspheres adhere entirely to reduced graphene oxide (RGO) nanosheets, forming porous and bridged structure, which decreases the density of the hybrid effectively. The dielectric properties and microwave absorption performance can be tuned by adjusting the reduction temperature and the weight ratio of the hybrid. The minimum reflection coefficient (RCmin) reaches -24.1 dB at 9.7 GHz with a thickness of 2.8 mm (S-900, 30 wt.%), and the effective absorption bandwidth (EAB) reaches 2.8 GHz with a thickness of 2.0 mm (S-500, 50 wt.%) and 2.7 GHz with 2.7 mm (S-900, 30 wt.%). Importantly, the various interface of the hybrid existed at the interface between RGO and core-shell SiO2@SiO2/carbon microsphere contributed to the enhanced interfacial polarization loss. Besides, the entirely wrapped structure between the core-shell SiO2@SiO2/carbon microsphere and the graphene sheets increase the number of reflections and transmission path to enhance the loss of microwave energy. This work supplies a reliable design method to tune the dielectric properties and microwave absorption performance of RGO based materials.