Template-Free Synthesis and Mechanistic Study of Porous Three-Dimensional Hierarchical Uranium-Containing and Uranium Oxide Microspheres

• Published in: Chemistry : a European journal Vol. 20; no. 39; pp. 12655 - 12662
• Main Authors: Wang, Lin, Zhao, Ran, Wang, Cong-zhi, Yuan, Li-yong, Gu, Zhan-jun, Xiao, Cheng-liang, Wang, Shu-ao, Wang, Xin-wei, Zhao, Yu-liang, Chai, Zhi-fang, Shi, Wei-qun
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 22.09.2014; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: actinides; Chemistry; Heat treatment; Micrometers; Microspheres; Nanostructure; oxides; phase transitions; Plutonium; porous structures; Reaction time; Synthesis; Three dimensional; Uranium; Uranium oxides; porous structures; actinides; phase transitions; uranium; oxides
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201403724

A novel type of uranium‐containing microspheres with an urchin‐like hierarchical nano/microstructure has been successfully synthesized by a facile template‐free hydrothermal method with uranyl nitrate hexahydrate, urea, and glycerol as the uranium source, precipitating agent, and shape‐controlling agent, respectively. The as‐synthesized microspheres were usually a few micrometers in size and porous inside, and their shells were composed of nanoscale rod‐shaped crystals. The growth mechanism of the hydrothermal reaction was studied, revealing that temperature, ratios of reactants, solution pH, and reaction time were all critical for the growth. The mechanism study also revealed that an intermediate compound of 3 UO3⋅NH3⋅5 H2O was first formed and then gradually converted into the final hydrothermal product. These uranium‐containing microspheres were excellent precursors to synthesize porous uranium oxide microspheres. With a suitable calcination temperature, very uniform microspheres of uranium oxides (UO2+x, U3O8, and UO3) were successfully synthesized. Sea‐urchin‐shaped hierarchical uranium‐containing microspheres are prepared by a facile hydrothermal synthesis. The growth mechanism was systematically investigated. Highly uniform uranium oxide microspheres can be obtained from these hydrothermal microspheres by a thermal treatment process. This is the first example of microscale porous 3D hierarchical materials that involve an actinide element (see figure).