Phragmites-derived magnetic carbon fiber with hollow assembly architecture toward full-covered effective bandwidth at Ku band

Lightweight and efficient electromagnetic wave absorption (EMA) materials are in high demand, and magnetic carbon fiber composites show potential. However, impedance matching issues make achieving full coverage of the Ku band challenging, hindering improvements in effective absorption bandwidth. This study proposes innovative compositional and structural designs coupling magnetic carbon fibers to balance electromagnetic attenuation and impedance matching. We assemble 1D phragmites-derived hollow carbon fibers (PCF) with 3D CoFe2O4 (CFO) hollow nanoparticles to create a composite with two different dimensions and mechanisms of loss. CFO hollow nanoparticles uniformly distributed on the PCF conductively lose energy and enable multiple reflections. Furthermore, by designing the thermal decomposition temperature and magnetic components, high-frequency electromagnetic parameters can be controllably adjusted. Notably, PCF7-CFO exhibits excellent reflection loss of −57.8 dB at 14.8 GHz with a filling ratio of 20 wt% and matching thickness of 2.0 mm, with an effective absorption bandwidth reaching 5.9 GHz, almost covering the entire Ku band. The hollow-assembly structure balances impedance matching and high-frequency attenuation, achieving full-Ku-band coverage for developing efficient electromagnetic wave absorbers with biomass-derived carbon materials.