八三酸化ウランの反応活性に関する研究, (VI)

Abstract

Using a thermal balance, a X ray diffractometer and its high temperature apparatus, hydration and dehydration were studied for uranium trioxide UO3 I, II and III, which had been prepared from uranyl nitrate, ammonium diuranate and uranium peroxide before decomposing to uranouranic oxide. The crystal system of UO3 I may be monoclinic, UO3 II also may be of a new crystal system (refer to the previous report) and UO3 III is amorphous.These oxides were changed into hydrate by exposing them in air at room temperature for several days or a few months. UO3 I converted into monoclinic UO3·2H2O or orthorhombic UO3·H2O, and UO3 II and III both into monoclinic UO3·2H2O.Dehydration of UO3·2H2O led to monoclinic UO3 through the orthorhombic UO3·H2O and then anhydrous amorphous UO3. Further, high temperature Xray study showed that the Orthorhombic UO3·H2O began to decompose at 320°C, converted into amorphous UO3 at 350°C and then to anhydrous monoclinic UO3 at 415°420°C.