Hierarchical structure with dielectric/magnetic network from Kapok fiber with enhanced microwave attenuation capacity

Construction of hierarchical structures with dielectric and magnetic lossy blocks is a robust approach for fabricating functional materials with strong attenuation capacity over a broad range of frequencies. Herein, ultralight three-dimensional (3D) architecture with zero -dimensional (0D) cobalt ferrite-anchored two-dimensional (2D) carbon microtube (CoFe2O4 @CMT) was fabricated from Kapok fibers via facile solvothermal and subsequent pyrolysis methods. Such hierarchical structures with CMT as dielectric components and CoFe2O4 as magnetic blocks provide hybrids with improved microwave-absorbing capability. CoFe2O4 @CMT hybrid with a CoFe2O4/CMT mass ratio of 1:1 demonstrates a minimum reflection loss (RL) of - 66.78 dB at the thickness of 4.6 mm together with an effective absorption bandwidth (RL <= -10 dB) of 4.80 GHz. Moreover, over 90% of the electromagnetic energy ranging from 3.04 GHz to 18.00 GHz can be dissipated by expediently adjusting the thickness. Detailed investigation reveals that hierarchical structures with synergetic effects from dielectric CMT and magnetic CoFe2O4 efficiently tune impedance matching and attenuation capacity of the resulting CoFe2O4 @CMT, affording high microwave absorption performances. This work promises great potential in developing microwave absorbers starting from sustainable natural hollow templates.