Fabrication processes and applications of boron nitride nanosheets and BNNS/polymer nanocomposites

Abstract

Boron nitride (BN) low-dimensional materials are among the most promising inorganic nanosystems explored so far. It closely resembles elemental carbon structures by sharing the same total number of electrons between the neighboring atoms. Boron nitride has various dimensional forms (i.e. BN fullerenes, BN nanotubes, and BN nanosheets) and low density ($2.1 g/cm^{3}$), high mechanical strength (Modulus: 800-850 GPa), superior thermal (stable up to 1000°C under atmospheric condition) and chemical stabilities, and intrinsic electrical insulation when it is in the form of atomically few layers. In spite of these advantages, the applications of BN nanosheets are still limited due to their high surface area of BN nanosheets and strong van der Waals interaction between them causes irreversible aggregation. In addition, the exfoliation of h-BN can be achieved mechanically on a small scale, synthesis by deposition techniques on substrates, limiting their large scale production. Simple and scalable exfoliation methods are required for many applications. In this research, we developed fabrication process of two-dimensional hexagonal boron nitride nanosheets (BNNSs) and their polymer nanocomposites. Simple and scalable exfoliation methods are designed for many applications such as novel hybrid and nanocomposite materials. However, high surface area of BNNSs and strong van der Waals interaction between them cause irreversible aggregation restricting their applications. This problem was addressed by noncovalent functionalization chemical modification. Noncovalently functionalized BNNSs facilitate manipulation via various processes that involve mixing, blending, and/or dispersion in a polymer matrix. The influence of surface modification on the properties of BNNS reinforced polymer nanocomposites was investigated. The new concept of fabricating heterostructure film by graphene and BNNSs using a simple wet chemistry route is demonstrated. The alternatively stacked heterostructure film of graphene and BNNSs is prepared by mixing the BNNSs dispersion with that of graphene. In order to alternative stacking of two materials, the BNNSs and graphene are surface modified with different charge. This approach allows for the formation of different heterostructures built from 2D building blocks of various compositions alternatively assembled via a simple chemical route. It is promising that these alternatively stacked heterostructure film could have fascinating properties due to the large number of interfaces between electronically dissimilar, flat, atomic layers bound.