Effect of Crystal Transformation on the Intrinsic Defects and the Microwave Absorption Performance of Mo₂TiC₂T_x/RGO Microspheres

The nitrides and carbides of transition metals are highly favored due to their excellent physical and chemical properties, among which MXene is a hot research topic for microwave absorption. Herein, the controlled preparation of 3D Mo₂TiC₂T_x-based microspheres toward microwave absorption is reported for the first time. With the merits of the performances of both reduced graphite oxide (RGO) and MXene sufficiently considered, the influence of carbonization temperature on the internal crystal structure and the effective microwave-material interaction surface of the prepared Mo₂TiC₂T_x/RGO is systematically investigated. The structure–activity relationships relating the apparent morphology and crystal structure to the microwave absorption performance are deeply explored, and the wave absorption mechanism is put forward as well. The results show that the Mo₂TiC₂T_x/RGO-700 product obtained after heating treatment at 700 °C exhibits excellent microwave absorption performance, with the RL_min being up to −55.1 dB@2.1 mm@13.8 GHz, and the corresponding effective absorption bandwidth covering 5.7 GHz. The outstanding microwave absorption characteristics are attributed to the appropriate impedance matching, high specific surface area, rich intrinsic defects, desirable conductivity, and strong multipolarization capabilities. This work enriches the types of MXene-based composite absorbers and provides a new strategy for controlled preparation of high-performance 3D composite absorbers.