Ultrafast growth of nanocrystalline graphene films by quenching and grain-size-dependent strength and bandgap opening

Tong Zhao,Shun Feng,Wei Ma,Zhibo Liu,Hui-Ming Cheng,Chuan Xu,Tianya Zhou,Zhen Liu,Ning Kang,Mengjian Zhu,Wencai Ren,Dong-Ming Sun

doi:10.1038/s41467-019-12662-z

Abstract

Nanocrystallization is a well-known strategy to dramatically tune the properties of materials; however, the grain-size effect of graphene at the nanometer scale remains unknown experimentally because of the lack of nanocrystalline samples. Here we report an ultrafast growth of graphene films within a few seconds by quenching a hot metal foil in liquid carbon source. Using Pt foil and ethanol as examples, four kinds of nanocrystalline graphene films with average grain size of ~3.6, 5.8, 8.0, and 10.3 nm are synthesized. It is found that the effect of grain boundary becomes more pronounced at the nanometer scale. In comparison with pristine graphene, the 3.6 nm-grained film retains high strength (101 GPa) and Young’s modulus (576 GPa), whereas the electrical conductivity is declined by over 100 times, showing semiconducting behavior with a bandgap of ~50 meV. This liquid-phase precursor quenching method opens possibilities for ultrafast synthesis of typical graphene materials and other two-dimensional nanocrystalline materials.

Highlights

Nanocrystallization is a well-known strategy to dramatically tune the properties of materials; the grain-size effect of graphene at the nanometer scale remains unknown experimentally because of the lack of nanocrystalline samples
The Pt foil was heated to a high temperature in argon atmosphere and rapidly quenched in liquid ethanol at room temperature
The scaling laws of both mechanical strength and electrical resistance as a function of grain size were derived. These findings resolve the controversies in theoretical predictions on grain-size effect and provide guidelines to tailor the properties of graphene by grain-size engineering

Summary

Introduction

Nanocrystallization is a well-known strategy to dramatically tune the properties of materials; the grain-size effect of graphene at the nanometer scale remains unknown experimentally because of the lack of nanocrystalline samples. In comparison with pristine graphene, the 3.6 nm-grained film retains high strength (101 GPa) and Young’s modulus (576 GPa), whereas the electrical conductivity is declined by over 100 times, showing semiconducting behavior with a bandgap of ~50 meV. This liquid-phase precursor quenching method opens possibilities for ultrafast synthesis of typical graphene materials and other two-dimensional nanocrystalline materials. According to the Arrhenius equation, a very high concentration of active carbon species is required to achieve a high nucleation density[16], the prerequisite to obtain

Methods

Results

Conclusion