Improved oxidation resistance of boron nitride nanotubes with protective alumina nano-coatings

Boron nitride nanotubes (BNNTs) are gaining interest for high temperature applications due to their thermal stability at elevated temperatures. Although BNNT temperature limits are well studied, there remains a gap in quantifying the high temperature failure mechanisms and oxidation kinetics. This s...

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Bibliographic Details
Published in:	Ceramics international Vol. 50; no. 22; pp. 48620 - 48627
Main Authors:	Davis, Cole R., Nuwayhid, R. Blake, Campbell, Caroline A., Mills, Sara C., Backman, Lavina, Estevez, Joseph E., Schaeffer, Manda R.
Format:	Journal Article
Language:	English
Published:	Elsevier Ltd 15-11-2024
Subjects:	Aluminum oxide Atomic layer deposition (ALD) Boron nitride nanotubes (BNNTs) Oxidation kinetics Oxidation kinetics Boron nitride nanotubes (BNNTs) Atomic layer deposition (ALD) Aluminum oxide
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Summary:	Boron nitride nanotubes (BNNTs) are gaining interest for high temperature applications due to their thermal stability at elevated temperatures. Although BNNT temperature limits are well studied, there remains a gap in quantifying the high temperature failure mechanisms and oxidation kinetics. This study characterizes the oxidation mechanisms and kinetics of BNNTs and Al2O3-coated BNNTs, via atomic layer deposition (ALD), at temperatures between 850 and 1000 °C. ALD Al2O3 surface coatings improved BNNT oxidation resistance by over an order of magnitude for coating thicknesses between 7 and 56 nm. However, the improved oxidation resistance of Al2O3-coated BNNTs decayed after prolonged exposure to oxygen at elevated temperatures, gradually reaching the same extent of oxidation as uncoated BNNTs after approximately 200 min at 900 °C. This behavior is attributed to the crystallization of as-deposited amorphous Al2O3 coatings at elevated temperatures leading to densification, cracking, and exposure of BNNTs to the oxidizing environment. While Al2O3 coatings did not completely prevent oxidation, a significant improvement in oxidation resistance was observed, extending the thermal stability of BNNTs.
ISSN:	0272-8842
DOI:	10.1016/j.ceramint.2024.09.211