Synthesis of boron nitride nanotubes at low temperatures using reactive ball milling

Boron nitride (BN) nanotubes have been produced by thermal annealing at 1000°C of elemental boron powders which were previously ball milled in ammonia gas for 150 h at room temperature. High-energy ball milling induces nitriding reactions between the boron powder and the ammonia gas. A metastable material is formed consisting of disordered BN and nanocrystalline boron. BN nanotubes then grow out from this metastable and chemically activated structure during heat treatment in the presence of nitrogen gas. This novel process for forming BN nanotubes is distinctly different from arc discharge and laser-heating processes.