Effect of Ti₃AlC₂ precursor and processing conditions on microwave absorption performance of resultant Ti₃C₂T_x MXene

Ti₃C₂T_x MXene prepared by the removal of Al from the Ti₃AlC₂ precursor is an attractive 2D material with attractive physical and chemical properties. However, the measured properties of Ti₃C₂T_x, especially the microwave absorption (MA) properties, vary greatly in the literature. To illustrate the influence of the dominant factors on the MA property differences of Ti₃C₂T_x, different sized Ti₃AlC₂ precursors and processing conditions were investigated. The Ti₃AlC₂ precursors were synthesized by pressureless sintering a Ti/Al/graphite mixture at 1450 °C for 30 min, 60 min and 120 min, respectively. Ti₃C₂T_x flakes having various lateral dimensions and thicknesses were obtained after etching the Ti₃AlC₂ precursors in 40% HF solution for 2 h. The MA test showed the largest Ti₃C₂T_x flakes by etching of the 120 min-prepared Ti₃AlC₂ demonstrated the minimum reflection loss (RL) value of − 28.11 dB at 10.24 GHz, indicating the larger Ti₃C₂T_x flakes, the richer in surface terminations which dissipate more microwave energy. The etching times from 0.5 h to 20 h was adopted to enrich the surface functional groups which contribute to the enhanced MA properties. However, the prolonged etching time up to 20 h caused the poor MA performance. Furthermore, surface chemistry of Ti₃C₂T_x affected the MA behavior. Annealing Ti₃C₂T_x at 750 °C removed some surface groups, thus deteriorating the MA property. This work is conductive to the practical applications of MXenes.