Morphology, structure and growth of WS2 nanotubes

The morphological and structural features of WS2 nanotubes, generated from WOx (x congruent to 2.7) needles, by an in-situ heating process, have been studied by electron microscopy and X-ray diffraction (XRD), in conjunction with computer simulation. The results show that these inorganic fullerene n anotubes exhibit interesting differences when compared with carbon nanotube s (CNTs). In some cases the tube tips or segments are open. Occasionally th e tube walls may be uneven. The sulfur distribution within the tubes is uni form, except for the edge layers which appear to contain less sulfur. Defec ts are often observed, particularly in the outer shells, which may be due t o defective encapsulated WOx phases. Octagonal and square-like defects appe ar to be associated with the closure of tube caps. Electron diffraction (ED ) reveals that nearly half of the non-helical WS2 nanotubes are of the armc hair-type. A mechanism has been proposed to account for the extended inorga nic nanotube growth.