posted on 2020-03-24, 13:36authored byBenjamin
J. Mapleback, Narelle Brack, Liam Thomson, Michelle J. S. Spencer, Dale A. Osborne, Sagar Doshi, Erik T. Thostenson, Andrew N. Rider
Boron nitride nanotubes
(BNNTs) represent a relatively new class
of materials that provides alternative electrical and thermal properties
to the carbon analogue. The high chemical and thermal stability and
large band gap combined with high electrical resistance make BNNTs
desirable in several thin-film applications. In this study, stable
BNNT and hexagonal boron nitride (hBN) particle dispersions have been
developed using environmentally friendly advanced oxidation processing
(AOP) that can be further modified for electrophoretic deposition
(EPD) to produce thin films. The characterization of the dispersions
has revealed how the hydroxyl radicals produced in AOP react with
BNNT/hBN and contaminant boron nanoparticles (BNPs). While the radicals
remove the carbon contaminant present on BNNT/hBN and increase dispersion
stability, they also oxidize the BNPs and the boron oxide produced,
which, conversely, reduces the dispersion stability. The use of high-
or low-powered ultrasonication in combination with the AOP affects
the rate of the competing reactions, with low-powered sonication and
AOP providing the best combination for producing stable dispersions
with high concentrations. BNNT/hBN dispersions were functionalized
with polyethyleneimine to facilitate EPD, where films of several micrometer
thickness were readily deposited onto stainless steel and glass-fiber
fabrics. BNNT/hBN films produced on glass fabrics by EPD exhibited
a consistent through-thickness macroporosity that was facilitated
by platelet and nanotube stacking. The film macroporosity present
on the coated fabrics was suitable for use as separator layers in
supercapacitors and provided improved device robustness with a minimal
impact on electrochemical performance.