In situ preparation of Co3O4/CF flexible composites with core-shell structure as high-performance microwave absorbers

This study obtained cobalt nitrate (Co 3 O 4 )/carbon fibers (CF) composites with a core-shell structure using in situ Co 3 O 4 growth on lightweight and flexible hydrophilic CF through a hydrothermal synthesis method and simple heat treatment to improve the attenuation of microwaves and their absorption properties. The urea content was adjusted to tune the needle-like morphology of Co 3 O 4 . The results showed that sample S3 had excellent microwave absorption (MA) performance with a minimum reflection loss ( RL min ) of −61.55 dB at a thickness of 4.75 mm. However, the thickness corresponding to the maximum effective absorption bandwidth (EAB, RL<-10 dB) of 4.72 GHz was only 1.88 mm, covering almost the entire Ku band. CF, as the core of structures, significantly impact microwave reflection. However, the Co 3 O 4 shell coating dominated the dielectric loss of the Co 3 O 4 /CF composite, and its MA performance improved with the refinement of the Co 3 O 4 structures. This study provided a practical solution for preparing lightweight and efficient transition metal oxide and carbon-based MA composites.