Absorption frequency band switchable intelligent electromagnetic wave absorbing carbon composite by cobalt confined catalysis

The dielectric loss of carbon materials is closely related to the microstructure and the degree of crystallization, and the microstructure modulation of electromagnetic wave absorbing carbon materials is the key to enhancing absorption properties. In this work, a porous elastic Co@CNF-PDMS composite was prepared by freeze-drying and confined catalysis. The graphitization degree and conductivity loss of carbon nanofibers (CNFs) were regulated by heat treatment temperature and Co catalyst content. The construction of a heterointerface between Co and C enhances the interfacial polarization loss. The Co@CNF-PDMS composite with 4.5 mm achieves the minimum reflection loss (RL_min) of –81.0 dB at 9.9 GHz and RL no higher than –12.1 dB in the whole of the X-band. After applying a load of up to 40 % strain and 100 cycles to Co@CNF-PDMS, the dielectric properties of the composite remain stable. With the increase of compression strain, the distribution density of the absorbent increases, and the CNF sheet layer extrusion contact forms a conductive path, which leads to the conductive loss increase, finally, the absorption band moves to a high frequency. The absorption band can be bi-directionally regulated by loading and strain with good stability, which provides a new strategy for the development of intelligent electromagnetic wave absorbing materials.