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

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