Transformation of BxCyNz nanotubes to pure BN nanotubes

We demonstrate that multiwalled BxCyNz nanotubes can be efficiently converted to BN multiwalled nanotubes via an oxidation treatment. The microstructure and composition of the precursors and final products have been characterized by high-resolution transmission electron microscopy, electron energy-loss spectroscopy, and energy dispersive x-ray spectroscopy. The conversion process is monitored by thermogravimetric analysis. Carbon layers of BxCyNz nanotubes start to oxidize at 550 degreesC, thereby transforming BxCyNz nanotubes into pure BN nanotubes. The remarkable thermal stability of pure BN nanotubes in an oxidizing environment is also established. (C) 2002 American Institute of Physics.