Ni/C-Carbon Nanotube Multidimensional Heterospheres for Highly Efficient Microwave Absorbers

For microwave absorbers, it is still a tremendous challenge to efficiently construct multidimensional heterostructures for achieving the synergy of multicomponent and multiloss modes. Herein, a kind of cocklebur-like Ni/C-CNT multidimensional heterosphere was obtained by a simple method with graphitic carbon nitride (g-C3N4) and nickel oxide (NiO) as precursors. During the decomposition of g-C3N4 at high temperatures, the vertical CNTs and amorphous carbon were produced on the surface of Ni nanoparticles reduced from NiO. It was found that the conductive network consisting of CNTs and heterospheres not only increased the conduction loss but also facilitated multiple reflection absorption. Moreover, the cocklebur-like heterostructures had many defects and interfaces, effectively realizing the synergistic effect of various loss mechanisms including conduction loss, interface polarization, and dipole polarization. In addition, this cocklebur-like multidimensional heterostructure was beneficial to improve the impedance matching of materials. Accordingly, with a filler loading of 30 wt %, the minimum reflection loss of Ni/C-CNT heterospheres was up to −41.60 dB, and the effective absorption bandwidth reached 4.1 GHz when the matching thickness was 2.4 mm. This work proposed a strategy for fabricating carbon nanotube-based composites with multidimensional heterostructures as efficient microwave absorbers.