Structures of boron nitride nanotubes with single-layer and multilayers produced by arc discharge

Nanoscale materials created from boron nitride (BN) by are discharge between ZrB2 electrodes in an N-2 atmosphere have been investigated by electron microscopy. BN nanotubes were formed together with Zr-compound nanoparticles encapsulated in BN cages. Most of the tubes were multilayered and had diameters from 3 to 40 nm and lengths on the order of 100 nm. Single-layer tubes with diameters of 2 to 5 nm were also formed as a minority. Concerning the helical structures of BN tubes, a variety of chiral angles, including the zigzag and the armchair types, were observed. The morphology of the tube tips suggests the presence of pentagons and heptagons which are energetically less favorable compared with squares (four-membered rings).