Production of zigzag-type BN nanotubes and BN cones by thermal annealing

Boron nitride nanotubes (BNT) and boron nitride cones (BN cones) were produced by thermal annealing of a mixed powder of β-rhombohedral boron and hexagonal boron nitride (h-BN) at 1200°C under lithium vapor. The BNTs were found to grow from the edge of h-BN particles along one of 〈1010〉 directions of the particles. The BNTs consist of zigzag-type layers whose 〈1010〉 direction is parallel to the tube axis. The BN cones with an apex angle of about 20° were discovered. It was revealed that the BN cones were not formed by a helically wound conical BN layer but by a pile of monolayer BN cones.