1. Key Laboratory for Utility of Environment Friendly Composites and Biomass in Universities of Gansu Province, College of Chemical Engineering, Northwest University for Nationalities, Lanzhou, P. R. China
2. State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, P.R. China
3. University of Chinese Academy of Sciences, Beijing, P.R. China