The effect of iron oxide on the formation of boron nitride nanotubes

Boron nitride (BN) nanotubes with different yield and structure were synthesized on stainless-steel substrates, by heating mixture powders of amorphous boron and iron oxide (Fe2O3) at 1300 °C in flowing ammonia atmosphere. It was found that Fe2O3 could affect the yield and structure of BN nanotubes dramatically through its adding amount in the starting materials. When the Fe2O3/B molar ratio was small, pure but low-yield BN nanotubes were obtained. Nearly no particle was observed in the product. Meanwhile, the nanotubes were generally hollow with very few B–O–Si–Mn species filled within the tube cavity or enwrapped in the walls. The yield of nanotubes obviously rose with the increase of Fe2O3/B ratio. However, the amounts of B–N–O–Si–Mn particles in the product (from which nanotubes grew in a radial pattern) and B–O–Si–Mn species within the cavity or the walls of the nanotubes also increased. The growth mechanism of the BN nanotubes was believed to be in the framework of vapor–liquid–solid (VLS) model.

► It is the first time to report the synthesis of BN nanotubes on stainless-steel foils by using precursors of B and Fe2O3, the foils act as both the substrate and catalyst for the growth of BN nanotubes.
► It is the first time to study systematically the influence of metal oxide on the formation of BN nanotubes.
► The nanotubes were fully characterized by SEM, TEM, HRTEM, EDX, EELS and elemental mapping. The growth mechanism was also discussed in detail.