Boron nitride nanotubes (BNNTs) can be grown on stainless steel by annealing a mixture of diboron trioxide (B2O3) and boron (B) at 1200-1300 degrees C under ammonia (NH3). In previously reported boron oxide chemical vapor deposition methods for the synthesis of BNNTs, diboron dioxide (B2O2) is generated in situ by the reaction of boron and metal oxides. In this study, we directly used a mixture of B2O3 and boron as boron sources, thereby, avoiding the use of metal containing species in the starting material. The concentration of B2O3 significantly influenced the formation, quality and quantity of BNNTs. (C) 2017 Elsevier B.V. All rights reserved.