1D superstructure assembled from 2D carbon nanosheets for microwave absorption

Hierarchical superstructures in nano/microsize are showing great potential in electromagnetic (EM) absorption. Herein, a templated strategy is presented for the synthesis of one-dimensional (1D) carbon superstructure, where the external surface of carbon nanotubes is composed of periodically aligned two-dimensional (2D) nanosheets. It is found that the formation of 2D nanosheets can effectively prevent the aggregation of carbon nanotubes during high-temperature pyrolysis process (even 900 °C) due to reduced size, and thus the obtained sheet-stacked carbon tube superstructure (SCTS) exhibits larger Brunauer–Emmett–Teller surface area, which is confirmed to be favorable for desirable impedance matching. In addition, 2D nanosheets forming the external surface of carbon nanotubes can not only create sufficient heterogeneous interfaces but also promote multiple reflections of incident EM waves. The former induces sufficient interfacial polarization, and the latter intensifies the dissipation of EM energy. By manipulating the pyrolysis temperature, the optimal SCTS produces excellent EM absorption performance, whose strongest reflection loss can reach up to 66.0 dB, and the effective absorption bandwidth is as broad as 5.5 GHz with the absorber thickness of only 1.5 mm. Such a performance is superior to that of most of the reported structured carbon materials. This study provides a new strategy for the construction of low-dimensional carbon superstructures and may inspire the design of pure carbon composites with excellent EM functions.