Mechanosynthesis of Boron Nitride Nanotubes1

Boron nitride nanotubes (BN-NTs) with pure hexagonal BN phase have been synthesized by heating ball-milled boron powders in flowing ammonia gas at a temperature of 1200°C. The as-synthesized products were characterized by X-ray powder diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and electron energy loss spectroscopy (EELS). The diameters of nanotubes are in the rage of 40–120nm and the lengths are more than 10μm. EELS result identifies that the ratio of boron and nitrogen is almost 1:1. The growth temperature is a crucial growth parameter in controlling the structure and crystalline of BN-NTs. The nanotubes grown at 1100°C possesses of a bamboo-like structure, while as the temperature increased to 1200°C, most of the nanotubes exhibited a cylindrical structure. In addition, changing the heating time can control the size of the nanotubes. The gas atmosphere has influence on the yield of BN-NTs during heating process. When heating atmosphere was replaced by nitrogen, the yield of nanotubes was remarkably decreased.