Bo Liao1, Zhenglun Wang1, Wei Li2. 1. Key Laboratory for Advanced Technology of Materials of Ministry of Education, Tribology Research Institute, Southwest Jiaotong University, Chengdu, 610031, China. 2. Key Laboratory for Advanced Technology of Materials of Ministry of Education, Tribology Research Institute, Southwest Jiaotong University, Chengdu, 610031, China. liweijiani@home.swjtu.edu.cn.