Growth and characterization of boron nitride nanotubes having novel morphologies using mechanothermal process

We report an effective approach to synthesize boron nitride (BN) nanotubes having novel morphologies employing a mechanothermal process. In this process, a precursor containing B–N–O–Fe was first synthesized by ball milling a 1:1 mixture of elemental boron (B) and hexagonal boron nitride (hBN) and iron oxide (about 6 wt%) for about 36 h in the presence of ammonia gas. BN nanotubes were grown by annealing this precursor in ammonia gas atmosphere at 1,250–1,350 °C for about 3 h. The nanotubes produced using this technique were found to evolve structures having Y-junctions and bamboo-like morphology with an average diameter of about 30–100 nm and length several microns. A few nanotubes with partially folded in diameter were also found to co-exist along with other nanotubes. These nanotubes were characterized using various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and Raman spectroscopy. The growth mechanism for the formation of these novel morphologies in BN nanotubes is also discussed.