The effect of ball-milling parameters on the structures of Ti3AlC2 MAX phase and resultant Ti3C2Tx MXene

In this work, the effects of ball-milling parameters on the structure of the Ti3AlC2 MAX-phase, the precursor of Ti3C2Tx MXene, is investigated. To clarify this effect, three approaches with different milling parameters were used to synthesize Ti3AlC2 MAX-phase. In all approaches, the initial elements with the proportion of 3Ti:1.3Al:1.9C were milled at different milling times, intervals, and rotating speeds. The resulting powders were sintered in a SPS furnace with the sintering temperature of 1000-1150 °C.  According to our observation, emerging intermediate Ti and Al compounds in the milling process is the key point for forming the final Ti3AlC2 since such compounds would assist the formation of MAX-phase in the SPS process. Moreover, the temperature increment during the milling process is necessary for the formation of such intermediate compounds. This condition can be achieved when the ratio of intervals to milling times in each milling step is low enough (5 min per 30 min) or the rotating speed is high enough (around 600 rpm). The Al layers in Ti3AlC2 MAX-phase obtained in each approach are etched by HF solution to reveal the difference between the resultant Ti3C2Tx MXene nanolayers. Our characterization suggests that ball-milling at 400 rpm for 18 hours with 5-minute intervals produces the highest quality MAX-phase and MXene.