One-dimensional γ-Al2O3 growth from the oxidation of NiAl

We report an oxide nanowire growth phenomenon that morphologically resembles the vapor-liquid-solid process but with a fundamentally different mechanism. This is demonstrated with the high-temperature NiAl oxidation that results in the unidirectional γ-Al ₂O ₃ growth with a NiO nanoparticle at the nanowire tip. The NiO nanoparticle surface serves as the active site for dissociative O ₂ adsorption that produces an inward flux of atomic oxygen toward the γ-Al ₂O ₃/NiAl interface for γ-Al ₂O ₃ growth by reacting with bottom-up diffusing Al ³⁺ cations. The nanowire lengthening follows the parabolic kinetics with the upward lattice diffusion of Al ³⁺ cations in the γ-Al ₂O ₃ nanowires as the rate-limiting factor.