1. Tribology Research Institute, The State Key Laboratory of Rail Vehicle System, School of Mechanical Engineering, Southwest Jiaotong University, Chengdu 610031, China
2. Research Institute of Frontier Science, Southwest Jiaotong University, Chengdu 610031, China
3. State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China