Fe3C-coated nitrogen-doped CNT/cattail-derived carbon microtube composites for efficient microwave absorption

• Fe3C@NCNTs/CMTs composites derived from biomass cattail exhibit a hierarchical structure with Fe3C-coated nitrogen-doped carbon nanotubes, achieving a minimum reflection loss of –35.8 dB and an effective absorption bandwidth of 7.02 GHz at 1.7 mm thickness with only 10% filler loading. • Calcination temperature critically tunes the crystallinity and microwave absorption performance, with 800 °C yielding optimal results covering the entire Ku band and part of the X band. • The superior absorption is attributed to synergistic effects of enhanced magnetic loss from Fe3C nanoparticles and multiple dielectric polarization mechanisms from nitrogen doping and hierarchical carbon structures. • This work provides a sustainable and cost-effective strategy for designing biomass-derived carbon-based broadband microwave absorbing materials for advanced electromagnetic interference mitigation.