AIN Nanotube:Round or Faceted?

摘要

The unusual properties and wide potential applications of carbon nanotubes (CNTs),resulting from their unique tubular nanostruc-tures,have been stimulating extensive explorations of nanotubes of various materials for over a decade.For quite a long time,the nanotube formation is generally limited in layered materials,which is easy to understand when regarding nanotube as the cylindric form rolled from the corresponding sheet,analogous to the case for CNTs.The weak van der Waals forces between the molecular layers and the strong intralayer bonds are suggested to be necessary for the formation of these nanotubes.As for the nonlayered materials with strong interlayer interactions,template confinement is needed to obtain the corresponding nanotubes.Very recently,the hexagonal AIN nanotubes with nonlayered structure have been synthesized without template.We found that the A1N nanotubes are different from the nanotubes of layered materials and show the faceted geometry with hexagonal cross sections.Actually,similar features also exist in the few recently reported nanotubes of other nonlayered materials using template-free approaches,which could be inferred from the electronic micrographs there,although such a geometrical specialty is often ignored in the literature.