1. State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan 430074 P. R. China
2. School of Materials Science and Engineering Huazhong University of Science and Technology Wuhan Hubei 430074 China
3. Engineering Research Center of Power Safety and Efficiency Ministry of Education Wuhan Hubei 430074 China
4. Engineering Research Center of Nano‐Geomaterials of Ministry of Education Faculty of Materials Science and Chemistry China University of Geosciences Wuhan 430078 China