The purity evolution of Ti3AlC2 MAX phase synthesized by mechanochemical route: The effect of Al content and high-temperature annealing

This study explores the effects of excess Al and annealing at high temperature on the purity of Ti3AlC2 MAX phase synthesized by the mechanochemical route. In this regard, a constant stoichiometric ratio of Ti: Al: C = 3: 1: 2 along with three blends of nonstoichiometric ratios with excess Al (Ti: Al: C = 3: X: 2, X = 1.1, 1.2, and 1.5) were ball milled. Then, to examine the annealing at high-temperature effects, the compacted ball-milled powders were heated at 900 and 1200 degrees C for 1 h. The phase identification revealed that 10 h of ball milling caused a reaction between the elemental powders, and Ti3AlC2 and TiC were formed. The mechanism of the reaction during the high-energy ball milling process is assigned to a mechanically induced self-propagating reaction. Addition of excess Al to primary powders caused to increase the purity of Ti3AlC2 significantly. Furthermore, annealing at high temperature leading to complete reactions of the ball-milled powders and increased Ti3AlC2 purity. The maximum Ti3AlC2 content of 88% was obtained of initial powder of Ti: Al: C = 3: 1.2: 2 ratio after annealing at 1200 degrees C.