Properties of nanostructures after effect of concentrated light

Solar energy is a promising alternative energy source for nanotechnology because this energy is one of cleanest energy sources available. A xenon high-flux optical simulator (also artificial sun) that provides illumination approximating natural sunlight in controllable indoor tests under laboratory conditions is a good model of this source. Optical simulator has numerous advantages. Its versatility, rapid heating and cooling rates, ability to adjust temperature profile along each axes, maximum operating temperatures and environmental adaptability stand out among others. Moreover, this technique can also be suitable for both conducting and non-conducting materials. The results of study of the effect of concentrated light energy on transformation of boron nitride and boron powders with different additives named in a xenon high-flux optical furnace in a flow of nitrogen is presented. It is considered the heating under concentrated light energy, which lead to the formation of the melt, the process of boiling, evaporation of the melt, the formation of nanostructures in conditions of the corresponding temperature gradients and their deposition on the surrounding surfaces. Main driving force, which contributes to the formation and growth of nanostructures of different morphology,is analyzed. Properties of produced powders are presented and analysed. Formation nanotubes, fullerene-like and graphene-like structures is considered as a result of composition of initial powders and heating conditions. It is demonstrated that grain size of boron nitride powder produced direct synthesis of initial boron powders of different sizes does not have a direct correlation with grain size of the starting boron powder. The incorporation of the catalyst to boron powder provides a nanostructures and fibrous BN structures formation regardless starting powder grain size under proper conditions of temperature gradient distribution. The presence of the OH group in nitrogen and additives of silicon, tantalum and indium in boron powder results in a change of chemical, phase and elemental composition, and also, the morphology of the obtained fine powders by increasing the number of nanostructured oxides and the new compounds in the phase composition of the material. SEM and TEM investigations have shown preferential formation of two dimentional BN nanostructures along with equiaxed or plate nanostructures due to presence of H₂O during heating. ''Gaseous theory'' which was developed for explanation of nanotubes formation and growth based on evolution of the bubble has found its confirmation in formation of two-dimensional BN nanostructures. Bursting of bubble, which easily formed in the presence of H₂O leads to this. (author)