1. School of Science, Xi'an Polytechnic University, Xi'an 710048, Shaanxi, China
2. Engineering Research Center of Flexible Radiation Protection Technology, University of Shaanxi Province, Xi'an Polytechnic University, Xi'an 710048, Shaanxi, China
3. Xi'an Key Laboratory of Nuclear Protection Textile Equipment Technology, Xi'an Polytechnic University, Xi'an 710048, Shaanxi, China
4. Materials Department, University of California, Santa Barbara, California 93106-5050, USA