Dry synthesis of brannerite (UTi2O6) by mechanochemical treatment

Abstract A powder mixture of UO2 and TiO2 was mechanochemically treated in a planetary ball mill under Ar atmosphere for 1 h using a tungsten carbide vial and balls as the milling medium. Such mechanochemical (MC) treatment reduced the crystallinity of UO2 and TiO2. The mechanochemically treated powder mixture was heated at 700–1,300°C for 6 h under Ar atmosphere and analyzed by X-ray diffraction analysis, scanning electron microscopy-energy-dispersive X-ray spectroscopy, and X-ray absorption fine structure analysis. For comparison, a UO2 and TiO2 mixture without MC treatment was heated and analyzed under the same conditions. UTi2O6 did not form below 1,100°C without MC treatment and only the starting materials were observed. At 1,200 and 1,300°C, a small amount of UTi2O6 and equal amounts of UTi2O6 and UO2 were formed, respectively. The mechanochemically treated sample produced nearly pure UTi2O6 containing small amounts of UO2 impurities when heated above 900°C for 6 h. UTi2O6 was highly crystalline and uniform regardless of the synthesis temperature. It is suggested that the crystallinity of UO2 and TiO2 was reduced and the formation of UTi2O6 was promoted by MC treatment.