Early stages of oxidation of Ti3AlC2 ceramics

The nucleation and growth of oxide scale at the early stages of oxidation of Ti3AlC2 ceramics was studied via oxidizing at 1100 degrees C in air for short times (<= 900 s). The nucleation of nanosized Al2O3 particles mainly occurs at the ledges of the fractured lamellar Ti3AlC2 grains as well as on the {0001} basal surfaces. The Al2O3 nuclei mainly grow along these ledges to form oxide strings, and then spread on the terraces and the {0001} basal surfaces. An oxide layer consisting predominantly of nanosized alpha-Al2O3 forms after oxidizing for 180 s. The formation of lenticular hexagonal pores in Ti3AlC2 grains is attributed to the faster consumption of Ti, Al and C atoms along < 11 (2) over bar0 > direction than along < 0001 > direction. With further oxidation, rutile-TiO2 particles form on top of the alpha-Al2O3 layer, and grow to form a rutile-TiO2 layer. Further oxidation leads to the formation of pores underneath the primary alpha-Al2O3 layer. In this porous layer both Al2O3 and TiO2 were present with a preference for Al2O3 to stay adjacent to the inward moving interface of Ti3AlC2 substrate. (C) 2008 Elsevier B.V. All rights reserved.