Isothermal Oxidation of Ta ₂ AlC in Air

The oxidation behavior, in air, of bulk polycrystalline Ta 2 AlC samples was studied in the 600°–900°C temperature range. A protective, essentially X‐ray amorphous, oxide layer—which does not appear to be resistant to thermal cycling—forms at 600°C. This layer is comprised of Ta, Al, and O. At 700°C and above, it is compositionally quite uniform, but porous and highly cracked. No phase separation was observed at the micrometer scale. The oxide layers consisted of the crystalline phases, Ta 2 O 5 and TaAlO 4 , and an X‐ray amorphous phase. In the 700°–900°C temperature range, the oxidation kinetics were found to be linear.