1. Hubei Nuclear Solid Physics Key Laboratory, Department of Physics, Wuhan University, Wuhan 430072, China
2. School of Materials Science and Engineering, Hubei University, Wuhan 430062, China
3. Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, China
4. State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China