Solid-state formation of carbon and boron nitride nanotubes

Both carbon and boron nitride (BN) nanotubes have been produced by first ball milling of graphite and boron nitride powders at room temperature and then by isothermal annealing at temperatures less than 1500 °C. Ball milling creates the nuclei for nanotubes and the subsequent isothermal annealing is responsible for nanotube growth. Because the annealing temperatures are far below the melting points of both graphite and boron nitride, there are no vapor phases during the growth process. In contrast, x-ray diffraction and transmission electron microscopy reveal that the nanotubes grow from the ball milled powder clusters via solid-state crystal growth.