Boron nitride nanotube growth via boron oxide assisted chemical vapor transport-deposition process using LiNO3 as a promoter
boron nitride nanotubes, CVD, lithium nitrate, lithium borate, BNNT growth mechanism
High-purity straight and discrete multiwalled boron nitride nanotubes (BNNTs) were grown via a boron oxide vapor reaction with ammonia using LiNO3 as a promoter. Only a trace amount of boron oxide was detected as an impurity in the BNNTs by energy-dispersive X-ray (EDX) and Raman spectroscopies. Boron oxide vapor was generated from a mixture of B, FeO, and MgO powders heated to 1,150 °C, and it was transported to the reaction zone by flowing ammonia. Lithium nitrate was applied to the upper side of a BN bar from a water solution. The bar was placed along a temperature gradient zone in a horizontal tubular furnace. BNNTs with average diameters of 30–50 nm were mostly observed in a temperature range of 1,280–1,320 °C. At higher temperatures, curled polycrystalline BN fibers appeared. Above 1,320 °C, the number of BNNTs drastically decreased, whereas the quantity and diameter of the fibers increased. The mechanism of BNNT and fiber growth is proposed and discussed.
Tsinghua University Press
Andrei T. Matveev,Konstantin L. Firestein,Alexander E. Steinman,Andrey M. Kovalskii,Oleg I. Lebedev,Dmitry V. Shtansky,Dmitri Golberg, Boron nitride nanotube growth via boron oxide assisted chemical vapor transport-deposition process using LiNO3 as a promoter. NanoRes.2015, 8(6): 2063–2072