Dandelion-like carbon nanotube assembly embedded with closely separated Co nanoparticles for high-performance microwave absorption materials.

Enhancing the magnetic loss capacity by microstructure design remains a considerable challenge in the microwave absorption field. Herein, a high-performance microwave absorbent is developed by dispersing a considerable amount of magnetic nanoparticles within the dandelion-like carbon nanotube assembly. A controllable fabrication method is further exploited to adjust the distribution feature of these embedded nanomagnets. In such a hierarchical composite, parts of the interaction network among the coupled closely spaced nanomagnets can be frequently broken and rebuilt to intensively dissipate the microwave energy, which is confirmed by electron holography and micromagnetic simulation for the first time. By virtue of this dynamic magnetic coupling network mechanism, the hierarchical C/Co composite acquires the first-rate microwave absorption performance. The maximum reflection loss value reaches as much as -52.9 dB (absorbance >0.99999) and the effective absorption bandwidth (absorbance >0.9) occupies the entire X band. It is believed that the above insightful mechanism provides a new opportunity to lower the density of the magnet-based microwave absorbent as much as possible. Besides, the unique method for dispersing magnetic nanoparticles also broadens the pathway to assemble the hierarchical architecture.