In Situ High-Temperature Diffraction Study of the Thermal Dissociation of Ti3AlC2 in Vacuum

In this paper, the effect of high-temperature vacuum annealing on the dynamic phase stability and phase transition of Ti3AlC2 at up to 1550 degrees C was studied using in situ neutron diffraction. The decomposition of Ti3AlC2 into TiCx at an elevated temperature was observed to occur through the continuous sublimation of Al and Ti species in a dynamic environment of high vacuum. The rate of decomposition decreased with increasing temperature, resulting in negative apparent activation energy (i.e., -71.9 kJ/mol). Depth profiling of vacuum-annealed Ti3AlC2 by grazing-synchrotron radiation diffraction has revealed a graded composition of TiCx at the near-surface.