Chemical Sharpening, Shortening, and Unzipping of Boron Nitride Nanotubes

Abstract

Boron nitride nanotubes (BNNTs), the one-dimensional member of the boron nitride nanostructure family, are generally accepted to be highly inert to oxidative treatments and can only be covalently modifi ed by highly reactive species. Conversely, it is discovered that the BNNTs can be chemically dispersed and their morphology modifi ed by a relatively mild method: simply sonicating the nanotubes in aqueous ammonia solution. The dispersed nanotubes are significantly corroded, with end-caps removed, tips sharpened, and walls thinned. The sonication treatment in aqueous ammonia solution also removes amorphous BN impurities and shortened BNNTs, resembling various oxidative treatments of carbon nanotubes. Importantly, the majority of BNNTs are at least partially longitudinally cut, or "unzipped". Entangled and freestanding BN nanoribbons (BNNRs), resulting from the unzipping, are found to be ∼5-20 nm in width and up to a few hundred nanometers in length. This is the fi rst chemical method to obtain BNNRs from BNNT unzipping. This method is not derived from known carbon nanotube unzipping strategies, but is unique to BNNTs because the use of aqueous ammonia solutions specifi cally targets the B-N bond network. This study may pave the way for convenient processing of BNNTs, previously thought to be highly inert, toward controlling their dispersion, purity, lengths, and electronic properties.

Sonication-assisted alcoholysis of boron nitride nanotubes for their sidewalls chemical peeling

“…3). On the other hand, the peaks assigned to B-N vibration bands parallel and perpendicular to the tube axes were noted at 1368 cm À1 and 798 cm À1 , respectively, 26 indicating the presence of the original hexagonal BN structures. 8,20,[32][33][34] These new peaks were also observed for the samples in EtOH.…”

“…24 In contrast to peculiar chemical stability of BNNTs reported so far, 5,8 unzipping of BNNTs during nanotube synthesis was reported. 26 However, the methods producing BNNRs without special treatments and equipments are still limited. 26 However, the methods producing BNNRs without special treatments and equipments are still limited.…”

Facile synthesis, microstructure and photophysical properties of core-shell nanostructured (SiCN)/BN nanocomposites

“…Figure 2b showed the structural evolution during the annealing of the Co-PSBN1 at different temperatures, in which the lattice vibration modes are caused by the stretching among the silicon, carbon, nitrogen and boron atoms. Strong bands centered at 1375 and 815 cm −1 can be assigned to in-plane ring vibration (E 1u mode) of the BNNSs and B−N the in-plane stretching vibration, respectively41. Moreover, the SiCN nanoparticles were also evidenced by the strong absorption bands centered at 902 and 1160 cm −1 corresponded to Si−C and Si−N, respectively.…”

Fire‐Resistant Structural Material Enabled by an Anisotropic Thermally Conductive Hexagonal Boron Nitride Coating

“…Densification has been proven to be effective in enhancing the fire‐retardant performance of wood by self‐forming a wood char layer upon exposure to a flame, which serves as an effective thermal and oxygen barrier . In addition, unlike other inorganic flame retardant nanomaterials, the 2D h‐BN sheets are known to form a layered structure with anisotropic thermal properties (i.e., high in‐plane and low through‐plane thermal conductivities), as well as display good dimensional stability, desirable corrosion resistance, and antioxidant behavior, which are attractive in fire protection of wood, not only for reducing the HRR, but also for enhancing the ignition properties. As reported in the literature, the thermal conductivities of h‐BN in the in‐plane and through‐plane directions are 390 and 2 W m −1 K −1 , respectively.…”