Boron Nitride Nanotubes potential material for future hypersonic planes

Boron nitride nanotubes could be used to make hypersonic planes.

NASA has one of the few facilities in the world able to produce quality Boron Nitride Nanotubes BNNTs. Carbon nanotubes can stay stable at temperatures up to 400 degrees Celsius but BNNTs can withstand up to 900 degrees Celsius. BNNTs are also able to handle high amounts of stress and are extremely lightweight.

While the study has brought new light to the strength and stability of BNNTs, their use on planes may not be a reality for another five to 10 years. “Right now, BNNTs cost about $1,000 per gram. It would be impractical to use a product that expensive,” said Ke. But, that does not mean it will never happen. Carbon nanotubes were about the same price 20 years ago. As more studies indicated the usefulness of carbon nanotubes, the production rates increased and prices went down to the current rate, between $10 and $20 per gram. Ke sees the same fate coming down the line for BNNTs.

Ke plans to continue this type of research on BNNTs. He has worked with the U.S. Air Force on several research projects and in 2010 was chosen for the U.S. Air Force’s Young Investigator Research Program, a prestigious program with fewer than 20 percent of applicants accepted. While the advances of BNNTs will probably be used first in fighter jets, Ke said he can see this type of technology trickling down to commercial flights. In 10 to 20 years, air travel could be drastically different from what we experience today.

Scientific Reports – Quantitative Characterization of Structural and Mechanical Properties of Boron Nitride Nanotubes in High Temperature Environments

Abstract

The structural stability and mechanical integrity of boron nitride nanotubes (BNNTs) in high temperature environments are of importance in pursuit of their applications that are involved with extreme thermal processing and/or working conditions, but remain not well understood. In this paper, we perform an extensive study of the impacts of high temperature exposure on the structural and mechanical properties of BNNTs with a full structural size spectrum from nano- to micro- to macro-scale by using a variety of in situ and ex situ material characterization techniques. Atomic force microscopy (AFM) and high resolution transmission electron microscopy measurements reveal that the structures of individual BNNTs can survive at up to 850 °C in air and capture the signs of their structural degradation at 900 °C or above. In situ Raman spectroscopy measurements reveal that the BN bonds in BNNT micro-fibrils undergo substantial softening at elevated temperatures of up to 900 °C. The AFM-based nanomechanical compression measurements demonstrate that the mechanical integrity of individual BNNTs remain intact after being thermally baked at up to 850 °C in air. The studies reveal that BNNTs are structurally and mechanically stable materials in high temperature environments, which enables their usages in high temperature applications.

Conclusion

In this paper, the impacts of high temperature exposure on the structural and mechanical properties of BNNTs were investigated by using a variety of in situ and ex situ material characterization techniques. In situ Raman and optical spectroscopy measurements reveal that BNNT micro fibrils can largely survive at temperatures of up to 1000 °C in air even with substantial thermal-induced BN bond strength weakening. AFM and HRTEM imaging measurements reveal that the structures of individual BNNTs can survive at temperatures of up to 850 °C in air, and also capture the signs of their structural degradation at 900 °C or above. The AFM-based nanomechanical compression measurements demonstrate that the mechanical integrity of individual BNNTs remain intact after being thermally annealed at up to 850 °C in air. The findings are useful to better understand the structural stability and mechanical integrity of BNNTs, especially in the pursuit of their high temperature applications