1. State Key Laboratory of Solidification ProcessingCenter of Advanced Lubrication and Seal MaterialsNorthwestern Polytechnical University Xi'an Shaanxi 710072 P. R. China
2. School of Materials Science and EngineeringNanyang Technological University 50 Nanyang Avenue 639798 Singapore Singapore
3. School of Electronics Science and EngineeringUniversity of Electronic Science and Technology of China Chengdu 610054 P. R. China