1. State Key Laboratory of Solidification Processing Center of Advanced Lubrication and Seal Materials School of Materials Science and Engineering Northwestern Polytechnical University Xi'an Shaanxi 710072 P. R. China
2. Chongqing Technology Innovation Center Northwestern Polytechnical University Chongqing 400000 P. R. China
3. School of Materials Science and Engineering Nanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore