1. State Key Laboratory of Heavy Oil Processing China University of Petroleum Qingdao 266580 P. R. China
2. Weifang Key Lab of Advanced Light Materials Manufacturing and Forming Weifang University of Science and Technology Weifang 262700 P. R. China
3. Department of Materials Chemistry School of Materials Science and Engineering China University of Petroleum Qingdao 266580 P. R. China
4. Department of Materials Physics School of Materials Science and Engineering China University of Petroleum Qingdao 266580 P. R. China