TiO2 nanoparticles-assisted α-Al2O3 direct thermal growth on nickel aluminide intermetallics: Template effect of the oxide with the hexagonal oxygen sublattice

Abstract An experimental observation was reported that TiO 2 nanoparticles promote α-Al 2 O 3 direct growth on nickel aluminide by skipping the metastable-to-stable alumina transformation during the oxidation process. Mechanically, this direct growth of α-Al 2 O 3 can be attributed to the fact that both α-Al 2 O 3 and rutile-TiO 2 nanoparticles share the well-matching sublattice of oxygen among their energetically favorable interfaces of (0 1 ¯ 0)TiO 2 //(000 1 ¯ )Al 2 O 3 , (0 1 ¯ 0)TiO 2 //( 1 ¯ 2 1 ¯ 0)Al 2 O 3 and (001)TiO 2 //(10 1 ¯ 0)Al 2 O 3 . The work paves a new route to the controlling direct thermal growth of α-Al 2 O 3 on the substrates of M x Al y ( M  = Ni, Co, Fe)-based alloys by spreading the seed of a selected oxide which possesses the well-matching oxygen sublattice to α-Al 2 O 3 .