Abstract: Microwave-absorbing materials (MAMs) play an important role in reducing electromagnetic pollution. However, achieving a balance between low filler loading, low minimum reflection loss (RL_min) and wide effective absorption bandwidth (EAB) for efficient absorption of microwaves remains challenging. In this work, an innovative method of using CO₂ atmosphere annealed Ti₃C₂T_x MXene (C/TiO₂) combined with nickel nanowires (NiNW) via ultrasonic treatment was performed to yield C/TiO₂/NiNW (CTN) composites with abundant NiNW/TiO₂ contacts. The electromagnetic (EM) parameters of the as-synthesized composites were closely studied through a series of experiments and computed theoretical calculations. Through the establishment of built-in electric fields (BIEFs) at the NiNW/TiO₂ interface, the derived CTN composite demonstrated improved dielectric properties and impedance matching characteristics that are clearly reflected on the microwave absorption performance of our as-synthesized MAMs, with RL_min improving by 127.9 % from -31.93 dB to -72.77 dB, and widest EAB increasing by 25.9 % from 4.25 GHz to 5.35 GHz, at a low filler loading of 10 wt.%. This work investigates the mechanisms by which BIEFs influence EM parameters, providing critical insights into improving microwave absorption performance via BIEF structural design.

Key words: Built-in electric field, Electromagnetic parameters, Heterointerface, Microwave absorption