Facile Synthesis of Millimeter-Scale Vertically Aligned Boron Nitride Nanotube Forests by Template-Assisted Chemical Vapor Deposition

There is an increasing amount of research interest in synthesizing boron nitride nanotubes (BNNTs) as well as BN coatings to be used for various applications due to their outstanding mechanical, electrical, and thermal properties. However, vertically aligned (VA) BNNTs are difficult to synthesize and the longest VA-BNNTs achieved to date are up to several tens of microns. Here, we report the synthesis of over millimeters long multiwalled BN coated carbon nanotubes (BN/CNT) and BNNT forests via a facile and effective two-step route involving template-assisted chemical vapor deposition at a relatively low temperature of 900 °C and a subsequent annealing process. The as-prepared BN/CNTs and BNNTs retain the highly ordered vertically aligned structures of the CNT templates as identified by scanning electron microscopy. The structure and composition of the resulting products were studied using transmission electron microscopy, electron energy-loss spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. This versatile BN coating technique and the synthesis of millimeter-scale BN/CNTs and BNNTs pave the way for new applications especially where the aligned geometry of the NTs is essential such as for field-emission, interconnects, and thermal management.