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 ultrasmall 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.