Synthesis of boron nitride nanotubes from boron oxide by ball milling and annealing process

Boron nitride nanotubes were synthesized from boron oxide by high-energy ball milling and annealing method. The diameter of the nanotubes is in the range of 20–200 nm. The nanotubes show a bamboo-like structure and cylindrical-like structure under low magnification. The shorter bamboo nodes with distinct knots were observed for the bamboo-like nanotubes with larger diameters and the knots can also occasionally be observed in the cylindrical-like BN nanotubes with smaller diameters under high magnification. Al and Si were found to be catalytic materials responsible for the formation of BN nanotubes besides the metallic particles containing Fe, Ni and Cr.