1. State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China.
2. Department of Material Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA.
3. University of Chinese Academy of Sciences, Beijing 100049, China.
4. School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China.