Synthesis of boron nitride nanotubes in thermal plasma with continuous injection of boron under atmospheric pressure

Highly crystalline and small-diameter boron nitride nanotubes (BNNTs) are synthesized using a triple DC thermal plasma jet with continuous injection of boron feedstock at atmospheric pressure. The reaction pathway to BN phase is analyzed with thermodynamic equilibrium analysis. It is founded that BN formation through a reaction between nitrogen ion and boron is more thermodynamically favorable than recombination of nitrogen ion with electron. Nitrogen ions formed in the strong electric field of the plasma torches actively react with the boron feedstock, resulted in the formation of BN phase. As a result, the high production rate for BNNTs approaching at 22 g/h is achieved. Input power and total gas flow rate about production rate are 3.4 MJ/g and 120 L/g, resulting in the energy cost superior to those reported to date. Consequently, these findings suggest the industrial-scale production of BNNTs through an atmospheric pressure DC thermal plasma reactor. Graphical abstract