Hierarchically porous carbon sheets/Co nanofibers derived from corncobs for enhanced microwave absorbing properties

In order to obtain a microwave absorbing material with strong absorption, broad bandwidth, and light weight, the hierarchically porous carbon sheets/Co nanofibers composites were prepared by using corncobs as precursors in this paper. The electromagnetic parameters of the C/Co composites can be well adjusted by changing the loading amount of Co nanofibers, and then an increased attenuation capability and impedance matching can be obtained. Benefiting from the hierarchically porous architectures and the optimized electromagnetic parameters, the C/Co0.4 absorber with a filler loading of only 20 wt% in paraffin possesses a minimum reflection loss of - 64.50 dB at 13.76 GHz with a thickness of 2.60 mm, and a very large effective bandwidth of 8.40 GHz (9.6-18.0 GHz) at the thickness of 2.90 mm. The strong absorption, broad effective bandwidth and lightweight indicate that the C/Co composites can be employed as a high-performance microwave absorber.