Conversion from carbon nanotubes to boron nitride nanotubes and boron nitride-carbon nanotubes

Abstract

Boron nitride nanotubes (BNNTs) have excellent mechanical, thermal properties as well as large bandgap and high oxidation resistance. Based on these properties, BNNTs are proposed to be candidate for diverse applications including reinforcement, field emitter, biological sensor and polyer wrapping. Owing to the remarkable properties of BNNTs and the many applications that such nanotubes might enable, the growth methodology of high quality BNNTs is a critical subject studied by many in the past two decades. Due to the similarities with carbon nanotubes (CNTs), many of the BNNTs synthesis techniques were adopted from its carbon counterparts, such as arc-discharge method, chemical vapor deposition, laser ablation, ball milling and carbon nanotube-substitution reaction methods. However, these methods often encounter various drawbacks such as high temperature growth and insufficient yield, restricting many of its potential applications. In the M.Eng program, a relatively low temperature method (900 Celsius degrees) to convert carbon nanotubes (CNTs) into their BNNTs equivalent was developed. This conversion technique preserves the geometrical structure of the nanotubes and produces the longest vertically aligned BNNTs arrays to date (4mm in height). Additionally hybrid boron nitride-carbon nanotubes (BNCNTs) and cone-stacking structured BNNTs were successfully synthesized. Moreover, the mechanism of the conversion process and discussed the differences in formation of multi-wall vs cone-stacking BNNTs structure have also been examined. Lastly, the optical bandgap of converted boron nitride-carbon nanotubes has successfully been tuned. This work thus demonstrates a simple synthesis method to explore the combination of both CNTs as well as BNNTs and will be of great interest to many in the field.