A DTA, TGA, and metallurgical study of the exothermic reactions between aluminum and uranium compounds: The solid state reactions of uranium oxides and uranates with aluminum

Abstract

The exothermic reactions of the type A + BC → AC + B between aluminum and βUO 3, αU 3O 8, αNa 2UO 4, Na 2U 2O 7, Na 6U 7O 24 and MUO 4 (where M = Mg, Ca, Sr, or Ba) were studied using the techniques of differential thermal analysis (DTA), thermogravimetric evolved gas analysis (TGA-EGA), X-ray diffractometry, optical microscopy, and electron microprobe analysis. Two types of exothermic reactions were observed: The first type is a solid-state reaction occurring at the interfaces between particles in the compacted powders, beginning at or near the temperature at which the uranium compound undergoes either a first- or second-order transition. Only U 3O 8, UO 3 and those uranates having pseudo-hexagonal layers of [UO 2(O 1·5)] − groups undergo this first type of reaction. The second type of reaction is the reduction of the solid uranium compounds (all crystal structures) by liquid aluminum beginning at 800–900°C.