Confinement engineering to enhance broadband microwave absorption of hierarchically magnetic carbon tubular composite

The development of carbon materials remains challenging due to a single loss mechanism and an electromagnetic impedance mismatch. Confinement engineering has been shown to provide a chemical microenvironment for the formation of confined object materials in order to regulate the physical and chemical properties of nanomaterials. In this study, we choose lightweight one-dimensional biomass carbon microtubes as the base, for the first time cleverly using the transition metal nickel only on the inner surface of carbon microtubes with an ultra-small CNT array, and construct a composite with a hierarchically magnetic carbon tubular structure (HMCT-I) on the basis of the theoretical analysis of electromagnetic parameters. Thanks to enhanced magnetic loss and the synergy of multiple polarization losses, HMCT-I ultimately shows encouraging microwave-absorption performance, with an ultra-wide effective absorption bandwidth of 8.44 GHz and an ultra-low reflection loss of −77.7 dB. In addition, the reasonable design makes HMCT-I have superior environmental stability, broadening the way for developing practical broadband carbon-based composite absorbers. This work also provides theoretical guidance and innovative ideas for the design of broadband and efficient microwave absorbers.