Controlled synthesis and magnetic properties of Ni nanotubes and nanowires

Ni nanotubes and nanowires with an average diameter of about 140 nm are synthesized by a template assisted sol-gel autocombustion method. using nickel nitrate, citric acid and ammonia as the starting materials. The anodic aluminum oxide templates are prepared by a facile anodizing method. By adjusting the experimental conditions in the sol-gel process, the final products having tubular or wire-like morphologies can be perfectly controlled. Transmission electron microscope characterization indicates that the Ni nanotubes are very friable and can be easily broken into pieces of short nanotubes, but the Ni nanowires are compact and have very high aspect ratios. Magnetic measurements indicate that both the Ni nanowires and the Ni nanotubes possess superparamagnetism at room temperature. (C) 2017 Elsevier Ltd. All rights reserved.