Conversion of Single-walled Carbon nanotubes to Single-walled Boron Nitride Nanotubes

Boron Nitride Nanotubes (BNNT) have a similar structure to carbon nanotubes (CNT). This offers few similar properties to CNT such as mechanical property and thermal conductivity. In terms of electrical property, BNNT showcases insulating property due to its wide bandgap (5- 6 eV)[1].

BNNT can be synthesized via chemical vapour deposition, arc discharge method, laser heating process, etc. But achieving high yield, high purity, single wall and small diameter BNNT is very difficult[2]. The substitution reaction can be used to convert CNT to BNNT. With this process, the yield can be increased but produced material can also have B and N doped CNT[3], [4].

B2O3 + 3C(CNTs) + N2 -> 2BN(BNNTs) + 3CO

To convert the CNT to BNNT, the CNT has to be functionalized with a hydroxyl group. -OH functionalization can be achieved by treating nanotubes with nitric and sulfuric acid followed by reduction process, treating them with hydrogen peroxide, plasma process [5], [6]. The functionalization process must not affect the structure. Because the structure of CNT is very important for the substitution reaction.

Boron acid is used as a boron source placed outside the furnace and heated to 500°C and ammonia gas used as nitrogen source flowed at 5 sccm keeping furnace temperature at 830°C. Slowly the temperature is increased to 900°C. After the conversion, the black nanotubes will convert to white in colour [7].

NoPo Nanotechnology offers a very small diameter of 0.6 to 1 nm HiPCO® single-walled carbon nanotubes (SWCNT). This SWCNT can be functionalized with -OH and can be converted into Small diameter BNNT. This offers a new path to explore the properties of small diameter single-walled BNNT for various applications.

References:

[1] J. H. Kim, T. V. Pham, J. H. Hwang, C. S. Kim, and M. J. Kim, “Boron nitride nanotubes: synthesis and applications,” Nano Converg., vol. 5, no. 1, p. 17, Jun. 2018. [2] D. Golberg et al., “Boron Nitride Nanotubes and Nanosheets,” ACS Nano, vol. 4, no. 6, pp. 2979–2993, Jun. 2010.[3] S. Kalay, Z. Yilmaz, O. Sen, M. Emanet, E. Kazanc, and M. Çulha, “Synthesis of boron nitride nanotubes and their applications,” Beilstein J. Nanotechnol., vol. 6, no. 1, pp. 84–102, Jan. 2015. [4] D. Golberg, Y. Bando, W. Han, K. Kurashima, and T. Sato, “Single-walled B-doped carbon, B/N-doped carbon and BN nanotubes synthesized from single-walled carbon nanotubes through a substitution reaction,” Chem. Phys. Lett., vol. 308, no. 3, pp. 337–342, Jul. 1999. [5] S. Chen et al., “Enhanced dispersion and durability of Pt nanoparticles on a thiolated CNT support,” Chem. Commun., vol. 47, no. 39, pp. 10984–10986, Sep. 2011. [6] E. J. Weydemeyer, A. J. Sawdon, and C.-A. Peng, “Controlled cutting and hydroxyl functionalization of carbon nanotubes through autoclaving and sonication in hydrogen peroxide,” Chem. Commun., vol. 51, no. 27, pp. 5939–5942, Mar. 2015. [7] M. Wei, “Conversion from carbon nanotubes to boron nitride nanotubes and boron nitride-carbon nanotubes,” Thesis, 2015 (https://repository.ntu.edu.sg/handle/10356/65392).