1. Department of Materials Science and EngineeringCity University of Hong Kong 83 Tat Chee Avenue Kowloon Hong Kong 999077 P. R. China
2. Institute of Process EngineeringChinese Academy of Sciences Beijing 100190 P. R. China
3. Shenzhen Research InstituteCity University of Hong Kong Nanshan District Shenzhen 518057 P. R. China