Syntheses of Boron Nitride Nanotubes from Borazine and Decaborane Molecular Precursors by Catalytic Chemical Vapor Deposition with a Floating Nickel Catalyst

Multi- and double-walled boron nitride nanotubes (BNNTs) have been synthesized with the aid of a floating nickel catalyst via the catalytic chemical vapor deposition (CCVD) of either the amine-borane borazine (B3N3H6) or the polyhedral-borane decaborane (B10H14) molecular precursors in ammonia atmospheres. Both sets of BNNTs were crystalline with highly ordered structures. The BNNTs grown at 1200 °C from borazine were mainly double-walled, with lengths up to 0.2 μm and ∼2 nm diameters. The BNNTs grown at 1200–1300 °C from decaborane were double- and multiwalled, with the double-walled nanotubes having ∼2 nm inner diameters and the multiwalled nanotubes (∼10 walls) having ∼4–5 nm inner diameters and ∼12–14 nm outer diameters. BNNTs grown from decaborane at 1300 °C were longer, averaging ∼0.6 μm, whereas those grown at 1200 °C had average lengths of ∼0.2 μm. The BNNTs were characterized using scanning and transmission electron microscopies (SEM and TEM), and electron energy loss spectroscopy (EELS). The floating catalyst method provides a catalytic and potentially scalable route to BNNTs with low defect density from safe and commercially available precursor compounds.