1. School of Materials Science and Engineering, Beijing Institute of Technology 1 , Beijing 100081, People's Republic of China
2. Department of Materials Science and Engineering, University of California 2 , Los Angeles, California 90095, USA
3. Longyuan (Beijing) Wind Power Engineering Technology Co., LTD 3 , Beijing 100034, China
4. Torch High Technology Industry Development Center, Ministry of Science and Technology 4 , Beijing, China