1. Key Laboratory of New Processing Technology for Nonferrous Metal and Materials (Ministry of Education) College of Materials Science and Engineering Guilin University of Technology Guilin 541004 P. R. China
2. Institute of Materials Research and Engineering A*STAR Singapore 138634 Singapore
3. Guangxi Key Laboratory of Electrochemical and Magnetochemical Functional Materials Guilin University of Technology Guilin 541004 P. R. China