Rapid Fabrication of Boron Nitride Fine Fibers
Materials and Coatings
Rapid Fabrication of Boron Nitride Fine Fibers (LEW-TOPS-172)
Innovative method offers high yield, low-cost, and safe production
Overview
Hexagonal boron nitride (h-BN) nanofibers have become an area of significant interest to industry given their combination of unique characteristics including excellent thermal conductivity, high electrical resistivity, chemical inertness, light weight, and mechanical strength. Potential applications for h-BN nanofibers include their use as an additive to polymers and other composites to improve material properties, high voltage cable insulation, re-entry shielding, radiation shielding, electric vehicle thermal dissipation, and much more. However, manufacturing of h-BN nanofibers is costly, difficult at scale, and could pose respiratory hazards resulting from their small scale (< 100nm). This has limited the commercial availability of h-BN nanofibers. High-cost BN nanosheets are available, but their use is limited as the form factor is already established and they are difficult to disperse.
h-BN nanofibers could be a critical technology enabling the development of advanced multifunctional materials not just for space systems, but also for a variety of terrestrial applications. So, innovators at NASA’s Glenn Research Center (GRC) developed a polymer derived ceramic (PDC) process utilizing forcespinning technology that enables the rapid, low-cost fabrication of h-BN fibers. Fibers generated using the process have larger diameters (≥ 200nm), mitigating respiratory hazard risk.
The Technology
Polymer derived ceramics (PDCs) refers to ceramic materials formed through the pyrolysis of a pre-ceramic polymer. The use of the PDC process enables the fabrication of complex, lightweight, mechanically robust shapes that are too difficult to machine otherwise. The PDC process also allows for granular control over the chemistry, resulting in better fiber homogeneity and allowing for application-specific tailoring.
NASA’s PDC process to rapidly fabricate multifunctional h-BN nanofibers entails the following steps. First a liquid-based polymer precursor solution containing boron and nitrogen is made. Next, the precursor undergoes a forcespinning process, which causes the solvent to evaporate, leaving behind only polymeric nanofiber preforms. These preforms are then cured via UV exposure or other means to link the polymer chains to one another. Finally, the crosslinked polymers are heat treated under specific conditions to convert the polymer fibers into ceramics.
This NASA innovation offers the ability to make low-cost, layered h-BN fiber mats or weaved fabrics of flexible h-BN from spun yarns at scale. The size of the fibers (> 200 nm) makes them easier to handle and disperse relative to nanotubes or nanosheets and mitigates respiratory hazards. The process offers high yields relative to alternative fabrication processes such as electrospinning. The resulting h-BN nanofibers have a broad range of potential applications and are poised to enable the development of new, multifunctional materials.
![](https://technology.nasa.gov/t2media/tops/img/LEW-TOPS-172/20087-front-image.jpg)
![An image of the forcespinning process generating polymeric nanofiber preforms. An image of the forcespinning process generating polymeric nanofiber preforms.](https://technology.nasa.gov/t2media/tops/img/LEW-TOPS-172/20087-back-image.jpg)
Benefits
- High yield, low-cost fabrication: NASA’s PDC forcespinning fabrication process offers significantly higher yields relative to alternative methods such as electrospinning, reducing manufacturing cost and enabling production at scale. This could make the commercial production of h-BN nanofibers feasible.
- Excellent material properties: NASA’s h-BN fibers offer the beneficial material properties inherent to h-BN, including light weight and high strength, electrical resistivity, and thermal conductivity.
- Mitigates safety hazards: Because NASA’s process yields yarns with large diameters (≥ 200nm), respiratory hazards associated with their inhalation is mitigated.
- Ease of dispersion: h-BN nanofibers are easier to handle and disperse as a polymer composite additive relative to boron nitride nanosheets with established form factors.
- Enables development of new, multifunctional materials: This low-cost, high yield method to produce h-BN nanofibers is poised to enable the development of new, unique, multifunctional materials with high temperature and voltage performance.
Applications
- Space: Components requiring high temperature and/or voltage capabilities (e.g., re-entry shielding, radiation shielding, lightweight structural components, sensors, electrical component packaging)
- Electronics packaging: Due to enhanced thermal management capabilities and excellent dielectric properties, h-BN nanofibers could be useful when incorporated into materials used in electronics packaging.
- Electric vehicles: Power electronics heat sinks / cooling solutions, battery barrier layers, structural components, thermal management systems, electrical insulation for high-voltage cables
- Structural power: Structural energy storage devices
- Nuclear: Radiation shielding materials
- Composite additives: Improving composite and ceramic composite properties without introducing significant additional weight
- High-voltage cable insulation: Cable insulation for hybrid-electric aircraft, energy infrastructure, etc.
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