| Popis: |
Structural changes in perovskite and perovskite-like ceramics in the course of thermal treatment were studied by emanation-thermal analysis (ETA) using synthetic calcium metatitanate and aluminotitanate with addition of neodymium and cerium simulating solidified radioactive wastes. The emanation was analyzed as influenced by mechanical (polishing of the surface with diamond paste), radiation (bombardment with helium and krypton ions to certain dozes), and chemical (leaching in aggressive solvents) treatments and by the atmosphere (air, argon, hydrogen) in which the thermal treatment was performed. The ETA curves exhibit characteristic peaks corresponding to regeneration and annealing of both natural structural defects and those appearing after the external treatment of the sample. The model of emanation from material involving structural transformations, which well agrees with experimental data, was proposed. The emanation-thermal analysis under the dynamic conditions allows study of the evolution in the development of the surface relief and solid-state processes proceeding in the fine near-surface layer of material in the course of thermal treatment. It was found that the perovskite-like ceramics, thanks to its high thermal, radiation, mechanical, and chemical stability, can be recommended for solidification and disposal of high-level radioactive wastes. |
