Formation and atomic structure of hierarchical boron nitride nanostructures

Abstract

"We report a combined experimental and theoretical study of boron nitride (BN) nanostructures synthesized by ball milling methodology. The BN nanostructures were obtained using h-BN powder under low-vacuum conditions and steel balls of different sizes. The HRTEM images of our samples show the formation of spheroidal BN nanoparticles with diameters as small as 7 nm which self-assemble into different hierarchical nanostructures such as two-dimensional layered materials, spheroidal configurations, and one-dimensional solid BN chains. The Raman spectra reveal an intense absorption band in the 300-600 cm1 region, which is absent in the spectra of BN nanotubes, previously synthesized BN nanoparticles, and in all bulk boron nitride polymorphs. Density functional theory calculations show that the Raman spectra are consistent with the formation of fullerene-like BN particles which also exhibit an intense absorption band in the 200-800 cm1 range dominated by a complex mixture of tangential, stretching, and radial breathing modes. Finally, by means of electron-beam irradiation experiments additional structural transformations can be induce on our hierarchical BN particles consisting in the formation of nanoholes of the order of 5 nm. Our here-reported BN nanostructures might lead to a wide range of potential applications."