TECHNICAL DESCRIPTION

The general principle of this invention is based on CO2 laser bombardment of a hexagonal boron nitride powder under a low nitrogen pressure (100-500 mbar).
The laser beam causes locally a high enough temperature to achieve sublimation of boron nitride sample. This dissociation also creates a hole partially filled with melted boron at the sample's surface. When the temperature gradient is stabilized, the sample is cooled before the opening of the chamber.
This results in a nanostructure growth at the sample's surface. In the case of a 100mbar nitrogen pressure, a powdery product growth (made up of NB fibers) around the hole is obtained. If pressure increases, fibers thickness also increases. A little further from the hole, the sample's surface is covered by nanostructures such as a coloured powder of BN Onions.
BN nanotubes obtained with such method can have lengths of about 50µm.

Advantages of this method are speed and simplicity of the process and good quality and quantity of the BN nanotubes produced.