Isothermal Oxidation of Ta₂AlC in Air

Abstract

The oxidation behavior, in air, of bulk polycrystalline Ta2AlC 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, Ta2O5 and TaAlO4, and an X‐ray amorphous phase. In the 700°–900°C temperature range, the oxidation kinetics were found to be linear.

Synthesis and oxidation of Ti2InC, Zr2InC, (Ti0.5,Zr0.5)2InC and (Ti0.5,Hf0.5)2InC in air

“…This paper is a continuation of our efforts to understand the oxidation kinetics of the MAX phases [10][11][12][13][14][15][16][17]. Since this is the first report on the oxidation of the ternary compounds considered herein, there are no previous results to review.…”

Synthesis and Characterization of Novel Al-Matrix Composites Reinforced with Ti3SiC2 Particulates

“…The MAX phases are highly damage tolerant, thermal shock resistant, creep resistant, lubricious, readily machinable, and with Vickers hardness values of 2-8 GPa, are anomalously soft for transition metal carbides and nitrides (Ref [1][2][3][4][5][6][7]14). Some of them are also oxidation resistant ( Ref 8,[10][11][12][13]. Due to the above mentioned properties, there is a huge potential that MAX Phases can be used for different structural applications.…”

“…The M n+1 AX n (MAX) phases (over 60+ phases) are thermodynamically stable nanolaminates displaying unusual, and sometimes unique, properties (Ref [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. These novel phases possess a M n+1 AX n chemistry, where n is 1, 2, or 3, M is an early transition metal element, A is an A-group element and X is C or N. MAX phases are layered hexagonal (space group D4 6 h-P63/mmc) with two formula units per cell.…”

Phase Formation of Nanolaminated Transition Metal Carbide Thin Films

“…Therefore, the oxidation behavior of the MAX phases is significantly depending on whether or not the scale is capable of retarding O penetration and M/A-element out-diffusion at a given temperature. Most combinations of the M and A elements are oxidation protective only up to a temperature range of 400 -500 °C, such as M2O5-Al2O3 in M2AlC (M = Nb, Ta) [198,199], Ti2O3-In2O3 in Ti2InC [200], Nb2O5-SnO/SnO2 in Nb2SnC [201], and rutile TiO2 in Ti2SC [202]. Further increase the temperature or the time interval result in linear oxidizing kinetics and the oxidation in the bulk materials due to, e.g., formation of nonprotective oxide species [198][199][200], microcracks/pores [198][199][200][201][202], and volatile oxide species [202], or spallation of the scale [202].…”

“…Most combinations of the M and A elements are oxidation protective only up to a temperature range of 400 -500 °C, such as M2O5-Al2O3 in M2AlC (M = Nb, Ta) [198,199], Ti2O3-In2O3 in Ti2InC [200], Nb2O5-SnO/SnO2 in Nb2SnC [201], and rutile TiO2 in Ti2SC [202]. Further increase the temperature or the time interval result in linear oxidizing kinetics and the oxidation in the bulk materials due to, e.g., formation of nonprotective oxide species [198][199][200], microcracks/pores [198][199][200][201][202], and volatile oxide species [202], or spallation of the scale [202]. Contrarily, Ti2AlC and Ti3AlC2 exhibits less oxidation resistance at temperature lower than ~700 °C [18,[203][204][205] but an improved oxidation resistance at temperature higher than 1000 °C, which can be described with cubic oxidation kinetics [206].…”