Electrically aligned Ti3C2Tx MXene composite with multilayered gradient structure for broadband microwave absorption

High-performance electromagnetic microwave (EM) absorbers demand not only wide effective absorption bandwidth (EAB) and strong absorption capability, but also lightweight and small thickness. In this work, a new strategy was developed to simultaneously strengthen the lossy capacity and reduce the inclusion loading by designing the orientation of inclusions and constructing multilayered gradient structures. Accordingly, Ti3C2Tx MXene fillers were aligned in the same chains by the electric field-assisted alignment technique, forming a parallel-plate structure, throughout epoxy matrix resulting in strong lossy capacity. The widest EAB of aligned 16 wt% MXene/epoxy composite reached 5.08 GHz with a thickness of 1.34 mm. By comparison, the random 16 wt% MXene/epoxy composite exhibited an EAB of only 0.96 GHz with a thickness of 1.96 mm. Further, the impedance matching was optimized by designing multilayered gradient structures based on aligned MXene/epoxy composites. The trilayered gradient structure with an equivalent filler content of 10.97 wt% illustrated the best EAB of 6.01 GHz at only 1.53 mm thickness. In addition, the synergistic effect of the multiple loss mechanisms was also discussed. Overall, the proposed method demonstrates the effectiveness of coupling the alignment of inclusions with gradient structural design to prepare lightweight, thin, and high-performance EM absorbing materials.