1. School of Materials Science and Engineering; North University of China; Taiyuan 030051 China
2. China National Electric Apparatus Research Institute Co, Ltd; Guangzhou 510000 China
3. Department of Chemical and Biomolecular Engineering; University of Tennessee; Knoxville TN 37996 USA
4. College of Chemical and Environmental Engineering; Shandong University of Science and Technology; Qingdao 266590 China