Effect of Ti3AlC2 precursor and processing conditions on microwave absorption performance of resultant Ti3C2Tx MXene

Ti3C2Tx 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 Ti3C2Tx, 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 Ti3C2Tx, 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. Ti3C2Tx 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 Ti3C2Tx 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 Ti3C2Tx 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 Ti3C2Tx affected the MA behavior. Annealing Ti3C2Tx at 750 °C removed some surface groups, thus deteriorating the MA property. This work is conductive to the practical applications of MXenes.