Fine structure of boron nitride nanotubes produced from carbon nanotubes by a substitution reaction

Here we report on the precise structural investigation of multiwalled boron nitride (BN) nanotubes by means of high-resolution transmission electron m icroscopy and electron energy loss spectroscopy. The nanotubes were produce d from carbon nanotubes by applying a recently discovered technique: a subs titution chemical reaction [W. Han, Y. Bando, K. Kurashima, and T. Sato, Ap pl. Phys. Lett. 73, 3085 (1998)]. It is found that in contrast to the start ing carbon nanotubes, which exhibited large number of shells (typically > 1 0), a significant proportion of buckled and corrugated graphene-like sheets , poor degree of graphitization, and wide distribution of helicities, the r esultant BN nanotubes revealed perfectly straight shapes, limited number of shells (typically 2-6), and remarkable ordering of the graphene-like sheet s in the so-called nonhelical "zig-zag" fashion with the [10(1) over bar 0] direction parallel to the tube axis. (C) 1999 American Institute of Physic s. [S0021-8979(99)07516-7].