A new route to the successful arc-discharge synthesis of pure boron nitride (BN) nanotubes is presented. The carbon-free plasma is established between ${\mathrm{HfB}}_2$ electrodes in a nitrogen atmosphere. This technique leads to the formation of BN nanotubes with very few layers including single- and double-layer tubes. Electron-energy-loss spectroscopy yields a B:N ratio of approximately 1. Most tube ends are closed by flat layers perpendicular to the tube axis. A closure by a triangular facet, resulting from three 120° disclinations, is proposed to account for this specific shape.

• Received 18 March 1996

DOI:https://doi.org/10.1103/PhysRevLett.76.4737