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 gamma-Al2O3 growth with a NiO nanoparticle at the nanowire tip. The NiO nano-particle surface serves as the active site for dissociative O2 adsorption that produces an inward flux of atomic oxygen toward the gamma-Al2O3/NiAl interface for gamma-Al2O3 growth by reacting with bottom-up diffusing Al3+ cations. The nanowire lengthening follows the parabolic kinetics with the upward lattice diffusion of Al3+ cations in the gamma-Al2O3 nanowires as the rate-limiting factor.