Unique morphologies of boron nitride nanotubes

Unusual morphological features of boron nitride nanotubes produced via meta l-oxide-promoted high-temperature syntheses from carbon nanotubes, boron ox ide, and nitrogen were observed using high-resolution transmission electron microscopy. The tubes normally displayed open ends and preferentially two or four tubular layers as revealed by statistical analysis of 600 nanotubes . In addition, the total amount of tubes with even number of shells (61% oc currence) markedly prevailed over that with odd number of shells (39%). All three characteristics are exceptional for BN compared to other layered mat erials which may be assembled in tubules. (C) 2001 American Institute of Ph ysics.