1. College of Materials and Chemistry & Chemical Engineering Chengdu University of Technology Chengdu 610059 P. R. China
2. The Department of Applied Physics The Hong Kong Polytechnic University Hong Kong 999999 P. R. China
3. College of Materials Science and Engineering Kunming University of Science and Technology Kunming 650093 P. R. China
4. School of Mechanical Engineering Chengdu University Chengdu 610059 P. R. China