**Author details**

Qingbiao Li1,2, Jun Liang1\* and Qing Wang2

\*Address all correspondence to: jliang@licp.cas.cn

1 State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, PR China

2 School of Science, Lanzhou University of Technology, Lanzhou, PR China
