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Radio Frequency Plasma Synthesis of Boron Nitride Nanotubes (BNNTs) for Structural ApplicationsBoron nitride nanotubes (BNNTs) are more thermally and chemically compatible with metal- and ceramic-matrix composites than carbon nanotubes (CNTs). The lack of an abundant supply of defect-free, high-aspect-ratio BNNTs has hindered development as reinforcing agents in structural materials. Recent activities at the National Research Council - Canada (NRC-C) and the University of California - Berkeley (UC-B) have resulted in bulk synthesis of few-walled, small diameter BNNTs. Both processes employ induction plasma technology to create boron vapor and highly reactive nitrogen species at temperatures in excess of 8000 K. Subsequent recombination under controlled cooling conditions results in the formation of BNNTs at a rate of 20 g/hr and 35 g/hr, respectively. The end product tends to consist of tangled masses of fibril-, sheet-, and cotton candy-like materials, which accumulate within the processing equipment. The radio frequency plasma spray (RFPS) facility at NASA Langley (LaRC), developed for metallic materials deposition, has been re-tooled for in-situ synthesis of BNNTs. The NRC-C and UC-B facilities comprise a 60 kW RF torch, a reactor with a stove pipe geometry, and a filtration system. In contrast, the LaRC facility has a 100 kW torch mounted atop an expansive reaction chamber coupled with a cyclone separator. The intent is to take advantage of both the extra power and the equipment configuration to simultaneously produce and gather BNNTs in a macroscopic form amenable to structural material applications.
Document ID
20160006524
Document Type
Technical Publication (TP)
Authors
Hales, Stephen J. (NASA Langley Research Center Hampton, VA, United States)
Alexa, Joel A. (Analytical Mechanics Associates, Inc. Hampton, VA, United States)
Jensen, Brian J. (NASA Langley Research Center Hampton, VA, United States)
Date Acquired
May 24, 2016
Publication Date
May 1, 2016
Subject Category
Nonmetallic Materials
Report/Patent Number
NF1676L-24198
NASA/TP-2016-219194
L-20695
Funding Number(s)
WBS: WBS 432938.09.01.07.92
Distribution Limits
Public
Copyright
Public Use Permitted.

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