BNNT, LLC tubes are synthesized using the high temperature/high pressure (HTP) method, also called the pressurized vapor/condenser (PVC) method. This method produces highly flexible, high aspect ratio BNNTs with high crystallinity. They are few to single walled tubes with 2 and 3 walls being the most common morphology. The as-grown material has a cotton-like appearance with an unusually low tap density.
The basic specifications of our as-grown material are summarized in the following table:
|Purity||~50% BNNT by mass|
|Number of Walls||1 to 5 walls typical, 2 or 3 walls most common|
|Tube Length||up to 200 microns by SEM measurement|
|Surface Area||212 m2/g via multipoint BET|
|Bundles||many isolated tubes, bundles up to 5 tubes across, by TEM|
|Band Gap||5.7 eV direct measurement by low energy EELS spectroscopy|
|Residual Impurities||hBN and amorphous particles; approximately 15% micro-droplets of elemental boron; no catalyst impurities|
|Tap Density||about 0.5 g/cm3|
|Boron-10||Natural boron at 20% Boron-10. 96% Boron-10 BNNT being included in neutron detectors under development|
Click the thumbnail to open a TEM of HTP-grown BNNTs on a lacey carbon grid.
Click to open a high resolution TEM of an isolated 3- wall HTP-grown BNNT self-tensioned by electrostatic forces across the gap of a lacey carbon grid.
Unlike carbon nanotubes, BNNTs have polar bonds and so can be analyzed with FTIR. Below is an ATR FTIR of our as-grown nanotubes, showing the dominant BN peak around 1360 cm-1.
Click the thumbnail to open the figure, excerpted in whole from ‘Boron Nitride Nanotube: Synthesis and Applications,’ Amanda L. Tiano et al. (Proc. of SPIE Vol. 9060, 2014), contains additional TEMs of BNNTs grown by the HTP method. EELs spectra show the elemental composition, and low energy EELS spectra show a direct measurement of the band gap.
Read the full "Boron Nitride Nanotube: Synthesis and Applications" paper.