A mini-review on dispersion and functionalization of boron nitride nanotubes

Abstract

Boron nitride nanotubes (BNNTs) are of intense scientific interest due to their unrivaled physicochemical characteristics, extraordinary thermal, electronic, mechanical, optical properties and prospective applications in various nanotechnologies. Therefore, they are particular candidates for the development of new materials potentially applied in abundant applications. However, obtaining homogenous composite materials requires a good dispersion of BNNTs, as well in solvents or in the matrix, which still has remained challenging. The preparation of effective dispersions of BNNTs presents a major impediment to the extension and utilization of BNNTs. BNNTs intrinsically tend to bundle and/or aggregate. The prevention of such behavior has been explored by testing various techniques to improve the dispersibility of BNNTs in a variety of solvents. There are mainly two approaches to obtain a good quality dispersion; chemical functionalization and physical interactions. The chemical functionalization technique has been found effective, but deteriorates the intrinsic properties of BNNTs through the introduction of defects on the wall. Physical blending approaches with the ultrasound and high-speed shearing have been proven capable of debundling BNNTs and stabilizing individual BNNTs while maintaining their integrity and intrinsic properties. Attention has been brought to the study of the dispersion of BNNTs in aqueous media and most attention is paid to molecular dynamics simulation techniques and other physical techniques, as well as to the use of various surfactants and polymers.

Beyond Percolation Threshold Loading of Polyacrylonitrile Electrospun Nanofibers with Boron Nitride Nanotubes for Use in High-Temperature Composites

“…However, there are some difficulties associated with integrating BNNTs into a practical electrospinning solution. Successful electrospinning solutions and useable nanocomposite systems both are highly dependent on a homogeneous nanomaterial dispersion, which in an electrospun solution is often limited to nanomaterial loadings of <10 wt %. − Facilitating dispersion of nanofiller materials via surface modification or addition of surface functional groups is possible but comes at the expense of material property degradation from harsh chemicals or plasmas employed in the process. − Conversely, conventional mixing techniques such as sonication or mechanical shear mixing are incapable of breaking up large agglomerations of high surface energy nanomaterials. This significantly limits their effectiveness for a high weight percentage of unfunctionalized nanomaterials, as high weight percentage is desirable to dramatically change the materials’ properties and enable the development of advanced composite materials.…”

“…This significantly limits their effectiveness for a high weight percentage of unfunctionalized nanomaterials, as high weight percentage is desirable to dramatically change the materials’ properties and enable the development of advanced composite materials. While the polar nature of the boron and nitrogen bond in BNNTs presents a potential interface for bonding without the need for surface modification or functionalization, it can also make BNNTs more difficult to disperse . This further emphasizes the importance of determining appropriate mixing techniques for the material.…”

“…While the polar nature of the boron and nitrogen bond in BNNTs presents a potential interface for bonding without the need for surface modification or functionalization, it can also make BNNTs more difficult to disperse. 36 This further emphasizes the importance of determining appropriate mixing techniques for the material.…”

Dielectric properties of polymer‐derived ceramic reinforced with boron nitride nanotubes

“…30,31 BNNTs also show significant superiority in thermal and chemical stability compared to CNTs in air. 18,32,33 Especially, BNNTs possesses perfect electrical insulation [34][35][36] and superb oxidation resistance, 37 which can be used to adjust the real relative permittivity and dielectric loss tangent of materials. 38 BNNTs therefore are excellent candidates 39 for reinforcing polymers, 38,[40][41][42][43][44][45] ceramics, 18,36,[46][47][48][49] and metals.…”