1. State Key Laboratory of Solidification Processing, Center of Advanced Lubrication and Seal Materials, Northwestern Polytechnical University, Xi’an 710072, Shaanxi, P.R. China
2. National Key Laboratory of Special Vehicle Design and Manufacturing Integration Technology, Baotou 014000, Inner Mongolia, P.R. China
3. State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, Gansu, P.R. China