Temperature induced transformation of Co@C nanoparticle in 3D hierarchical core-shell nanofiber network for enhanced electromagnetic wave adsorption

Developing high-performance electromagnetic wave absorbing materials (EWAMs) with tunable nano-microstructures is of great significance for solving increased electromagnetic radiation pollution. Three-dimensional hierarchical networks within magnetic metal nanoparticles are promising candidates with the great balance of enhanced electromagnetic wave attenuation and impedance matching, but hard to construct. Herein, a two-step electrospinning/in-situ self-assembly strategy was employed, successfully synthesizing a 3D hierarchical core-shell NC@Co/NC nanofiber network (NC@Co/NC-900). The N-doped Carbon (NC) core fibers (diameter of ∼250 nm) built a 3D-conductive network, while the Co@C nanoparticles (diameter of ∼20 nm) embedded into N-doped Carbon (Co/NC) shell (thickness of ∼50 nm) enhanced the polarization loss and magnetic loss. More importantly, the controlled transformation of Co@C nanoparticles in the shell was realized by modulating the calcination temperature at 900 °C, showing an optimal homogeneously dispersion in a narrow particle size distribution in the range of 15–25 nm. Uniformly multiple reflection in core-shell NC@Co/NC-900 fiber network enhanced the electromagnetic wave attenuation with the optimal impedance matching, displaying excellent RLmin of −55.82 dB at 11.60 GHz and wide EAB of 7.44 GHz in a low filler loading of 15 wt %. The whole X and Ku bands could be fully covered in different thickness of 4.0 and 3.0 mm. This work presents a superior nano-micro structural design strategy on 3D hierarchical networks with multiple reflections.