Porous CoNi nanoalloy@N-doped carbon nanotube composite clusters with ultra-strong microwave absorption at a low filler loading

Abstract

Microwave absorption materials with ultra-strong absorption ability at low filler loadings are urgently needed but remain a huge challenge. Herein, porous N-doped carbon nanotube (NCNT) clusters encapsulated with CoNi nanoalloys (50–200 nm) have been fabricated via a facile coordination and carbonization process without toxic solvents and complex conditions. This special composite cluster exhibited a hierarchical microstructure (including 0D CoNi nanoparticles, 1D N-doped carbon nanotubes, and 3D porous networks), high surface areas (143.5–205.8 m² g⁻¹), and excellent thermal oxidation stabilities (≥350 °C). Benefitting from these features, the optimized CoNi@NCNT composite exhibited ultra-strong MA performances with a minimum RL value of up to −64.5 dB (absorbing 99.9999% microwaves) at a low filler loading of 10 wt%, which is much superior to previous ones. The microwave absorption mechanism investigation revealed that the moderate dielectric loss and weak magnetic loss accompanied by a porous structure in the composite clusters together contributed to improving the impedance matching and microwave attenuation ability. This work may pave the way for fabricating low-cost lightweight materials with ultra-strong microwave absorption at low filler loadings.