1. School of Material Science and Engineering, Lanzhou University of Technology, Lanzhou, 730050 Gansu, P. R. China
2. College of Petrochemical Technology, Lanzhou University of Technology, Lanzhou, 730050 Gansu, P. R. China
3. State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Lanzhou University of Technology, Lanzhou, 730050 Gansu, P. R. China