Catalyst-free synthesis of nanotubes and whiskers in an optical furnace and a gaseous model for their formation and growth

In this contribution recent results on catalyst-free synthesis of new structures consisting of boron nitride (BN) and carbon-boron nitride (C-BN) are presented. Light-induced heating of fine grained graphite-like h-BN powders and a h-BN-lamp black composite was performed. The new structures of BN and C-BN were produced in a flow of dried and purified nitrogen in an optical furnace. The structure and phase composition were studied by transmission electron microscopy, scanning electron microscopy, optical microscopy and X-ray diffraction. It was shown that the BN whiskers obtained consist of multiwalled nanotubes covered by a polycrystalline shell. The processes of synthesis, formation and growth of the nanostructures in an optical furnace were analyzed. A qualitative model of the formation and growth of BN nanotubes and whiskers based on the release of gas from the powders and evolution of bubbles is proposed.