Mechanical properties of atomically thin boron nitride and the role of interlayer interactions

Aleksey Falin,Rodney S Ruoff,Elton J.G Santos,Kenji Watanabe,Zhi Yang,Shaoming Huang,Dong Qian,Ying Chen,Qiran Cai,Matthew R Barnett,Declan Scullion,Rui Zhang,Takashi Taniguchi,Lu Hua Li

doi:10.1038/ncomms15815

Abstract

Atomically thin boron nitride (BN) nanosheets are important two-dimensional nanomaterials with many unique properties distinct from those of graphene, but investigation into their mechanical properties remains incomplete. Here we report that high-quality single-crystalline mono- and few-layer BN nanosheets are one of the strongest electrically insulating materials. More intriguingly, few-layer BN shows mechanical behaviours quite different from those of few-layer graphene under indentation. In striking contrast to graphene, whose strength decreases by more than 30% when the number of layers increases from 1 to 8, the mechanical strength of BN nanosheets is not sensitive to increasing thickness. We attribute this difference to the distinct interlayer interactions and hence sliding tendencies in these two materials under indentation. The significantly better interlayer integrity of BN nanosheets makes them a more attractive candidate than graphene for several applications, for example, as mechanical reinforcements.

Highlights

Thin boron nitride (BN) nanosheets are important two-dimensional nanomaterials with many unique properties distinct from those of graphene, but investigation into their mechanical properties remains incomplete
BN nanosheets, which are composed of atomically thin hexagonal boron nitride, have a structure similar to graphene but possess many distinguished properties[30]
We experimentally measured the mechanical properties of high-quality 1–9L BN nanosheets using atomic force microscopy (AFM)

Summary

Introduction

Thin boron nitride (BN) nanosheets are important two-dimensional nanomaterials with many unique properties distinct from those of graphene, but investigation into their mechanical properties remains incomplete. From the aspect of theoretical calculations, the mechanical properties of few-layer BN have never been theoretically investigated, the Young’s modulus of 1L BN was predicted to be 0.716–0.977 TPa (that is, E2D 1⁄4 239–326 N m À 1 with an effective thickness of 0.334 nm), while its breaking strength fell in the wide range of 68–215 GPa (that is, 23–72 N m À 1)[42,43,44,45,46,47,48,49,50,51]. The monolayer BN is found to have a Young’s modulus of 0.865±0.073 TPa, and fracture strength of 70.5±5.5 GPa. In contrast to graphene, whose strength decreases dramatically with an increase in thickness, few-layer BN nanosheets (at least up to 9L) have a strength similar to that of 1L BN. This study suggests that BN nanosheets are one of the strongest insulating materials, and more importantly, the strong interlayer interaction in BN nanosheets, along with their thermal stability, make them ideal for mechanical reinforcement applications

Methods

Results

Conclusion