1. Key Laboratory of Polymer Materials of Gansu Province, Research Center of Gansu Military and Civilian Integration Advanced Structural Materials, College of Chemistry and Chemical Engineering, Northwest Normal University, Anning East Road 967, Lanzhou, Gansu 730070, P. R. China
2. Gansu Natural Energy Research Institute, Renmin
Road 23, Lanzhou, Gansu 730046, P. R. China