References

Thermal management – Thermally-conductive and electrically-insulating plastics (electronics)

BNNT can increase thermal conductivity of polymers >10x and climbing – BNNT powders have been incorporated into thermoplastic polymers (polyamide, polyethylene, etc.), and self-supporting BNNT sheets have been infused with epoxy              (>3 W/mK and climbing).  They show promise of manufacturable, electrically-insulating, thermally-conductive packaging and coatings for enhanced passive cooling of electronic components, high-performance batteries, and heat / flame-resistant, high-strength cabling.

- M. B. Jakubinek, J. F. Niven, M. B. Johnson, B. Ashrafi, K. S. Kim, B. Simard and M. A. White, Thermal conductivity of bulk boron nitride nanotube sheets and their epoxy-impregnated composites, Physics Status Solidi A, 1–6, 2016.
- T. Terao, C. Zhi, Y. Bando, M. Mitome, C. Tang, D. Golberg, Alignment of boron nitride nanotubes in polymeric composite films for thermal conductivity improvement, Journal of Physical Chemistry C, 114 (10), 4340–4344, 2010.
- C. Zhi, Y. Bando, T. Terao, C. Tang, H. Kuwahara, D. Golberg, Towards thermoconductive, electrically insulating polymeric composites with boron nitride nanotubes as fillers, Advanced Functional Materials, 19 (12) 1857-1862, 2009.

Higher-strength, lighter-weight, higher-temperature composite structures (aerospace, wind-turbines)

BNNTs are renowned for stiffness and strength (1.1 TPa and 61 GPa, respectively) - over 30 times stronger than bullet-stopping Kevlar.  BNNTs have higher interfacial forces to polymers than CNTs because of their local polarity.  When mixed with lightweight polymers such as thermoplastics, polyimides, and epoxies, the long tubes reinforce the material, promising lighter-weight and stronger materials.  Potential applications include aerospace, automotive, and sports equipment, transparent or translucent armor, and thin protective coatings.  Keeping their strength to over 800 °C in air, far beyond CNT or Kevlar         (400 °C), BNNTs are also projected to be an optimal filler for a new generation of lightweight ceramic composites with a wide range of high–temperature applications in systems such as jet engines or gas turbines.

- P. Arenal, M-S. Wang, Z. Xu, A. Loiseau and D. Golberg, Young modulus, mechanical and electrical properties of isolated individual and bundled single-walled boron nitride nanotubes, Nanotechnology, 22(26):265704, 2011.
- X. Chen, L. Zhang, C. Park, C. C. Fay, X. Wang, C. Ke, Mechanical strength of boron nitride nanotube-polymer interfaces. Applied Physics Letters, 107 (25): 253105, 2015.
- P. Nautiyal, C. Rudolf, A. Loganathan, C. Zhang, B. Boesl and A. Agarwal, Directionally aligned ultra-long boron nitride nanotube induced strengthening of aluminum-based sandwich composite, Advanced Engineering Materials, 2016.

EMI shielding and multi-functional materials

Noble metals (Au, Pt, Pd, and Ag) or ferromagnetic materials can be introduced inside the hollow cores of BNNTs for applications such as electromagnetic shielding composites, where some inductance may be required while maintaining the insulating properties of BNNTs.  Moreover, metal-filled BNNTs find promising applications in hydrogen storage, plasmonic devices, and memory devices.

- T. Pham, A. Fathalizadeh, B. Shevitski, S. Turner, S. Aloni, Alex Zettl, A universal wet–chemistry route to metal- filling of boron nitride nanotubes, ACS Nanoletters, 2015.
- X. Hong, D. Wang, D.D.L. Chung, Boron nitride nanotube mat as a low-k dielectric material with relative dielectric constant ranging from 1.0 to 1.1, Journal of Electronic Materials, 2016.

Neutron radiation detection and shielding

BNNTs are more stable than CNTs at high temperatures and better absorb neutron radiation, both advantageous in extreme environments like outer space.  BNNT can also be used for ultra violet (UV) shielding, such as long-duration high-altitude applications and window filler material. 10BNNT (made with pure B-10) can be used as a neutron sensing element in a solid-state neutron detector with 100% suggested efficiency.

- M. Ghazizadeh, J. E. Estevez, A. D. Kelkar, Boron nitride nanotubes for space radiation shielding, International Journal of Nano Studies & Technology, 4. 1-2, 2015.
- P. Ahmad, M. U. Khandaker, Y. M. Amin, Synthesis of highly crystalline multilayers structures of 10BNNTs as a potential neutron sensing element, Ceramics International, 41 (3), 4544-4548, 2015.

Ultra-clean vacuum applications (cryopumps)

BNNTs have high surface area and low service temperature – uniquely suited as cryosorbent in ultra-high & extremely-high vacuums (UHV & XHV) that limit thermal conductance and hence pumping speed of ion or turbo pumps.  This means ultra-clean (no adhesives or other hydrocarbons), deep, faster-pumping vacuum, faster regeneration, and longer lifetime. 

- M. Stutzman, P. Adderley, V. Over, M. Poelker, Investigations of cryopumping for extreme high vacuum systems, 77th IUVSTA Workshop, 2016. 
Vibration damping

Mats of BNNTs are highly viscoelastic, enable efficient vibration damping down to cryogenic temperatures (2 °K) and up to high temperatures (~800 °C), can cycle from low to high temperatures repeatedly, and maintain that viscoelasticity under loads.  Among other uses, this might passively dampen the vibrations which can severely limit performance and reliability of superconducting RF (SRF) cavities.

- R. Agrawal, A. Nieto, H. Chen, A. Agarwal, Nanoscale damping characteristics of boron nitride nanotubes and carbon nanotubes reinforced polymer composites, ACS Applied Materials & Interfaces 5(22):12052-12057, 2013.
- Xinghua Hong, Daojun Wang, D.D.L.  Chung, Strong viscous behavior discovered in nanotube mats, as observed in boron nitride nanotube mats, Composites Part B, 2016.

Piezoelectric materials for sensing and actuation

BNNT composite sheets exhibit piezoelectric and electrostrictive properties, so can generate electric charge when deformed.  This means the material could offer energy harvesting, as well as sensing and actuation capabilities when embedded in a polymer (e.g. for robotics).  Space exploration requires sensors and devices capable of stable operation in harsh environments of high thermal fluctuation, atomic oxygen, and high-energy ionizing radiation.  While conventional and state-of-the-art electrostrictive materials have limitations on use in those extreme applications, BNNT composites show promising piezoelectric and electrostrictive properties.

- J. H. Kang, G. Sauti, C. Park, V. I. Yamakov, K. E. Wise, S. E. Lowther, C. C. Fay, S. A. Thibeault and R. G. Bryant, Multifunctional electroactive nanocomposites based on piezoelectric boron nitride nanotubes, ACS Nano, 2016.
- A. Salehi-Khojin, N. Jalili, Buckling of boron nitride nanotube reinforced piezoelectric polymeric composites subject to combined electro-thermo-mechanical loadings, Composites Science and Technology, 68 (6), 1489-1501, 2008.

Efficient catalytic reaction

BNNTs can improve efficiency and selectivity of important catalytic reactions to produce polyolefin feedstocks.  Preliminary studies indicate boron nitride catalysts are nontoxic, do not contain precious metals, and reduce activation energy of reactions, saving energy and reagents.
- J. T. Grant, C. A. Carrero, F. Goeltl, J. Venegas, P. Mueller, S. P. Burt, S. E. Specht, W. P. McDermott, A. Chieregato, I. Hermans, Selective oxidative dehydrogenation of propane to propene using boron nitride catalysts, Science, 2016.
- G. Elumalai, H. Noguchi, K. Uosaki, Electrocatalytic activity of various types of h-BN for the oxygen reduction reaction, Physical Chemistry Chemical Physics, 16, 13755-13761, 2014.

Optics and photonics applications

BNNTs are superior to CNTs in exhibiting semiconducting properties independent of chirality and diameter, with a wide band gap typically measured near 6 eV.  Potential applications include light-emitting diodes and photo detectors able to provide narrow selectivity in wavelength of emission and detection of light and fine tuning through the nanotube structure.
BNNTs have been used for quantum dots, which will lead to electronic devices such as transistors, solar cells, or diode lasers.

- A. Pierret, L. Schue, F. Fossard, J. Barjon, O. Ersen, S. Moldovan, F. Ducastelle, A. Loiseau, Optical and structural properties of facetted boron nitride nanotubes, European Microscopy Congress 2016: Proceedings, 476-477, 2016.
- J. S. Lauret, R. Arenal, F. Ducatelle, A. Loiseau, M. Cau, B. Attal-Tretout, E. Rosencher, L. Goux-Capes, Optical transitions in single-wall boron nitride nanotubes, Physical Review Letter, 94, 037405, 2005.

Biomedical applications and 3D printing

Preliminary research indicates BNNT is not cytotoxic at concentrations of interest for biologic applications.  BNNT can be applied as nano-textured cellular scaffolding for nerve and bone tissue regeneration, nanoscale drug vectors and delivery structures, and electroporation-based oncology (cancer) therapies.  BNNTs can be incorporated in ceramic composites to improve strength and toughness.  Efficient 3D printing of ceramic composites can be applied in dentistry.

- V. Raffa, C. Riggio, M. W. Smith, K. C. Jordan, W. Cao, A. Cuschieri, BNNT-mediated irreversible electroporation: Its potential on cancer cells, Technology in Cancer Research and Treatment, 2012.
- G. Ciofani, V. Raffa, A. Menciassi, A. Cuschieri, Boron nitride nanotubes: An innovative tool for nanomedicine, Nanotoday, 4 (1), 8-10, 2009.

Super-hydrophobic & anti-corrosion applications

BNNT polymer composites exhibiting super-hydrophobic behavior can be applied as water-repellent textiles, self-cleaning glasses, coatings to help combat corrosion of metal substrates, and coatings to prevent icing of machines and structures.  BNNT-coated mesh could be a highly-efficient filtration membrane for separation of oil from water in oil-polluted water, benefiting the environment and human health.

- L. H. Li, Y. Chen, Superhydrophobic properties of nonaligned boron nitride nanotube films, Langmuir, 26(7), 5135–5140, 2010.
- Y. Yu, H. Chen, Y. Liu, V. Craig, L. H. Li, and Y. Chen, Superhydrophobic and superoleophilic boron nitride nanotube-coated stainless steel meshes for oil and water separation, Advanced Materials Interfaces, 1, 1300002, 2014.