Controllable seeding of nitrogen-doped carbon nanotubes on three-dimensional Co/C foam for enhanced dielectric loss and microwave absorption characteristics

Carbon-based composites with three-dimensional (3D) foam structure are widely considered as a kind of prospective functional materials, and more and more researchers are focusing on their application in the field of microwave absorption. Herein, we demonstrate a controllable seeding of nitrogen-doped carbon nanotubes (NCNTs) on the surface of Co/C foams through in-situ growth. By manipulating the weight ratio of melamine to pre-prepared Co/C foams, the chemical composition and electromagnetic (EM) properties of these samples can be easily controlled. EM analysis reveals that NCNTs will create sufficient polarization effects and induce multiple reflection of incident EM waves. Moreover, the migration of electrons along NCNTs also promotes conductive loss significantly. The optimized sample with moderate NCNTs loading (ca. 23.5 wt%) exhibits a wide effective absorption bandwidth (EAB) of 6.3 GHz and the strongest reflection loss (RL) intensity of -97.3 dB at 16.2 GHz, which are superior to those of pristine Co/C foam and many other common magnetic metal/carbon composites. The unique composition and microstructure ensure that such a composite can produce good microwave absorption performance under a low filling content (15 wt%). It is believed that this study may inspire the fabrication and function enhancement of microwave absorbing materials (MAMs) based on carbon foam.