An Array of Concentric Composite Nanostructure of Metal Nanowires Encapsulated in Zirconia Nanotubes: Preparation, Characterization, and Magnetic Properties

An array of highly ordered ZrO 2 nanotubes has been prepared by a simple sol−gel method using the alumina membrane as a template. Furthermore, with use of this nanotube array with an alumina membrane support as a “second-order template”, the novel composite nanostructures of metal nickel- or copper-filled ZrO 2 nanotubes have been synthesized by electrodeposition. TEM images show that these encapsulated metals present as continuous and uniform nanowires in each and all ZrO 2 nanotubes. It is more important that the wall thickness of the ZrO 2 tubules, and the different morphologies of the encapsulated metals (metal nanowires or nanoparticles) can be controlled by the template used and synthesis conditions. Magnetic measurements on the ordered array of a concentric composite of ZrO 2 nanotubes/Ni nanowires reveal that the coercivities are Hc ∥ ∼ 237 Oe and Hc ⊥ ∼ 138 Oe, respectively, which exhibits enhanced coercivities by comparison with that of the bulk Ni.