Consecutively Strong Absorption from Gigahertz to Terahertz Bands of a Monolithic Three-Dimensional Fe₃O₄/Graphene...

With the booming microwave and terahertz technology for communication, detection, and healthcare, the consequently increasingly complicated electromagnetic environment is in urgent need of high-performance microwave and terahertz absorption materials. However, it is still a huge challenge to achieve consecutively strong absorption in both microwave and terahertz regimes. Herein, an ultra-broadband and highly efficient absorber for both microwave and terahertz bands based on the monolithic three-dimensional cross-linked Fe₃O₄/graphene material (3DFG) is first reported. The 3DFG shows an incredible wide qualified absorption bandwidth (with reflection loss less than -10 dB) from 3.4 GHz to 2.5 THz, which is the best result in this area by far. Furthermore, the remarkable absorption performance can be maintained under oblique incidence, different compressive strains, and even after 200 compression/release cycles. The designed highly porous structure for minimizing surface reflection combined with the micro-macro integrated high lossy framework results in the excellent absorptivity, as verified by the terahertz time-domain spectroscopy technique. With these, the 3DFG achieves an unprecedentedly average absorption intensity of 38.0 dB, which is the maximum value among the broadband absorbers. In addition, its specific average microwave and terahertz absorption value is over 2 orders of magnitude higher than other kinds of reported materials. The results provide new insights for developing novel ultra-broadband absorbers with stronger reflection loss and wider absorption bandwidth.