First synthesis of uranyl aluminate nanoparticles.

This paper describes, for the first time, a simple method for the synthesis of uranyl aluminate (URAL) nanoparticles. URAL was prepared by U(VI) hydrolytic precipitation with ammonia at pH = 11 in the presence of mesoporous alumina MSU-X under 20 kHz of sonication followed by annealing of the obtained solids at 800 degrees C. TEM, XAFS, powder XRD, and (27)Al MAS NMR studies revealed that the speciation of uranium in this system strongly depends on uranium concentration. The sample with 5 wt % of uranium yields air-stable nanoparticles ( approximately 5 nm) of URAL. Presumably, UO(2)(2+) cations in this compound are coordinated with bidentate AlO(2)(-) groups. The increase of uranium concentration to 30 wt % causes mostly formation of U(3)O(8) fine particles ( approximately 50 nm) and small amounts of URAL.