Use of a pressurized water treatment to prevent cracking of internal gelation sol-gel microspheres

Structural changes of Nd- and Ce-doped ammonium diuranate microspheres during the conversion to U1−LnO2±

“…composition prepared with Ce IV , the DSC signal indicates at least four exothermic reactions for the second step, occurring at temperatures of 241°C, 259°C, 275°C and 291°C, and result in a more pronounced mass loss during the second major mass loss step. The observations match to the thermal decomposition profile of HMTA/urea mixtures [24,25], which points to residuals of the gelation agents in the particle and an ineffective washing. Similar findings were made for yttria-stabilised zirconia(-ceria) microspheres [24,26].…”

“…Moreover, it was demonstrated that the remaining organics can be removed from the particles by a pressurised water treatment of the gelled spheres [26]. Katalenich [25] applied the latter successfully for ceria microspheres, also prepared with diammonium cerium(IV) nitrate as precursor. TGA of the dried residue from the water treatment showed about 90 wt% mass loss up to 400°C, supporting the assumption of an ineffective washing for the Ce doped batch prepared with the Ce IV dopant precursor.…”