Isothermal oxidation of bulk Zr₂Al₃C₄ at 500 to 1000 °C in air

Abstract

The isothermal oxidation behavior of Zr 2 Al 3 C 4 in the temperature range of 500 to 1000°C for 20 h in air has been investigated. The oxidation kinetics follow a parabolic law at 600 to 800°C and a linear law at higher temperatures. The activation energy is determined to be 167.4 and 201.2 kJ/mol at parabolic and linear stages, respectively. The oxide scales have a monolayer structure, which is a mixture of ZrO 2 and Al 2 O 3 . As indicated by x-ray diffraction and Raman spectra, the scales formed at 500 to 700°C are amorphous, and at higher temperatures are ␣-Al 2 O 3 and t-ZrO 2 nanocrystallites. The nonselective oxidation of Zr 2 Al 3 C 4 can be attributed to the strong coupling between Al 3 C 2 units and ZrC blocks in its structure, and the close oxygen affinity of Zr and Al.

Thermal oxidation of amorphous Al0.44Zr0.56 alloys

“…The Zr-O bond strength is much higher than the Al-O bond strength, 4 which suggests a lower energy of the amorphous-alloy/t-ZrO 2 interface as compared to the amorphous-alloy/c-Al 2 O 3 interface (for a similar density of O at the two interface boundary planes [27]). It is thus concluded that the observed exclusive nucleation of t-ZrO 2 is ruled by interface energetics, in accordance with previously reported studies on the oxidation of pure crystalline Zr metal and (crystalline/amorphous) Zr-based alloys [58][59][60]. It has long been recognized that t-ZrO 2 nanocrystallites can be stabilized by their lower surface energy (as compared to the monoclinic phase) up to a critical crystallite size of $10 nm [61,62].…”

Corrosion behavior of Ti3AlC2 in molten KOH at 700 °C

“…In recent decades, a significant number of literatures have reported the oxidation of MAX phases at high temperature [3][4][5][6][7][8][9][10][11][12]. For example, Ti 3 AlC 2 has excellent oxidation resistance, which is attributed to the formation of two-layer dense and adherent passivating films.…”

Synthesis and DFT investigation of new bismuth-containing MAX phases

“…Nevertheless, to our knowledge, there are no reports on the synthesis and thereby on the actual existence of Zr 2 AlC. It can be argued that other non-MAX phase ternary layered carbides such as Zr 2 Al 3 C 4 could be suitable15, however the reported oxidation resistance of these carbides is insufficient16.…”