Growth, morphology, and structure of boron nitride nanotubes

Multiwalled BN nanotubes were synthesized via a chemical vapor deposition ( CVD) route from a B4N3O2H precursor. Their morphological and structural fea tures have been studied. It was suggested that the tips encapsulate boron o xynitride nanoclusters, which incorporate silicon, aluminum, and calcium an d serve as the effective promoters for CVD growth of the BN nanotubes. An a lternative open-end growth mechanism is also applied for the occasional for mation of nanotubes with open or flat tip ends. Local three-dimensional ord ering in the nanotube shell assembly was often observed. BN nanotubes synth esized in the current CVD process exhibit a dominant near zigzag arrangemen t and a rhombohedral (r-BN) stacking order. The results of initial efforts to grow arrays of aligned BN nanotubes are also described.