Electrostatically Self‐Assembled MXene@CIP for Structural Functional Absorber Spanning Microwave to Terahertz Bands

ABSTRACT The developments of wireless communication, radio astronomy, and deep‐space exploration create an urgent demand for ultra‐broadband electromagnetic absorbing materials (EAMs) covering the frequency range from microwave to terahertz (THz). In this study, an elegant electrostatic self‐assembly process is proposed to synthesize a core‐shell structured absorbing agent, in which magnetic CIP microspheres are encapsulated by few‐layer MXene nanosheets. Owing to the negative electrostatic repulsion between MXene sheets, these MXene‐encapsulated CIP (MC) not only feature precisely‐controlled shell thickness but also exhibit excellent dispersibility in aqueous solutions and resins, both of which facilitate the development of structural and coating materials with superior absorption properties. A structured absorber (MCRC) with gradient impedance characteristics is designed, leveraging the multiple synergies of dielectric and magnetic losses of the MC. It achieves an effective absorption bandwidth ( EAB ) covering from 7.95 GHz to 4 THz, accompanied by an average reflection loss ( RL ave ) of ‐35.92 dB. Furthermore, a 6‐inch blackbody calibration source is demonstrated by coating 1–1.5 mm thick MC coating on the pyramidal metal array, whose emissivity is higher than 0.9998 in the 75–220 GHz range. This work offers a new strategy for the development of structure‐functional EAMs with ultra‐broadband absorption spanning microwave to THz bands.