Formation of Nickel oxide nanotubes with uniform wall thickness by low-temperature thermal oxidation through understanding the limiting effect of vacancy diffusion and the kirkendall phenomenon

Abstract

In this work, the step-wise oxidation mechanism of nickel (Ni) nanowires is elucidated. Rapid vacancy diffusion plays a signifi cant role at low temperatures in forming heterostructures of nickel oxide (NiO) nanotubes with Ni nanowires. Subsequent investigations of Ni nanowire oxidation at higher temperatures and faster temperature ramp rates show that it is diffi cult to bypass this rapid vacancy diffusion stage, which affects the formation of the fi nal structure. Therefore, it is unlikely to form solid NiO nanowires or NiO nanotubes with uniform wall thickness through the conventional annealing/ oxidation process of Ni nanowires. Instead, a step-wise oxidation process by combining low temperature oxidation with a chemical etching step is utilized to produce for the fi rst time NiO nanotubes with uniform wall thickness from Ni nanowires. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.