Lightweight porous cobalt-encapsulated Nitrogen-Doped Carbon nanotubes for tunable, efficient and stable electromagnetic waves absorption

To eliminate the hazards of electromagnetic radiation, lightweight and efficient electromagnetic waves absorbing (EWA) materials with long-term stability are highly desired. Herein, novel bamboo-like carbon nanotubes wrapped with controllable-sized Co magnetic nanoparticles (Co@CNT) are successfully prepared via a simple calcination strategy. The terminal EWA properties can be effectively tuned by adjusting filler loading, calcination temperature and template usage. Specifically, via controlling the calcination temperature, strong absorption capabilities located at X, C and Ku bands can be achieved. Finally, the optimized Co@CNT displays a superior EWA performance with −53.5 dB absorption intensity and 5.64 GHz effective bandwidth under 1.85 mm thin thickness and 6 wt% low filler loading, being in line with the development of innovative EWs absorber. This remarkable performance is attributed to dielectric loss, magnetic loss, multiple reflections, and moderate impedance matching. Furthermore, through hydrophobic modification by methyltrimethoxysilane (MTMS), it exhibits a significant improvement in stability and still keeps a strong absorption of −59.05 dB after acidic solution immersion. This work sheds a light on the design and synthesis of advanced EWA materials with lightweight, strong absorption, hydrophobicity, and stability merits.