Investigation of ammonium diuranate calcination with high-temperature X-ray diffraction
| Autor: | Thomas Fanghänel, Rachel Eloirdi, D. Ho Mer Lin, Roberto Caciuffo, Klaus Mayer |
|---|---|
| Jazyk: | angličtina |
| Předmět: |
Exothermic reaction
Materials science Mechanical Engineering Thermal decomposition Analytical chemistry Atmospheric temperature range law.invention Thermogravimetry chemistry.chemical_compound Crystallography chemistry Materials Science(all) law Mechanics of Materials Ammonium diuranate Differential thermal analysis X-ray crystallography General Materials Science Calcination |
| Zdroj: | Journal of Materials Science. 49(24):8436-8443 |
| ISSN: | 0022-2461 |
| DOI: | 10.1007/s10853-014-8553-0 |
| Popis: | The thermal decomposition of ammonium diuranate (ADU) in air is investigated using in situ high-temperature X-ray diffraction (HT-XRD), thermogravimetry and differential thermal analysis. Data have been collected in the temperature range from 30 to 1000 °C, allowing the observation of phase transformation and the assessment of the energy changes involved in the calcination of ADU. The starting material 2UO3·NH3·3H2O undergoes a process involving several endothermic and exothermic reactions. In situ HT-XRD shows that amorphous UO3 is obtained after achieving complete dehydration at 300 °C, and denitration at about 450 °C. After cooling from heat treatment at 600 °C, a crystalline UO3 phase appears, as displayed by ex situ XRD. The self-reduction of UO3 into orthorhombic U3O8 takes place at about 600 °C, but a long heat treatment or higher temperature is required to stabilise the structure of U3O8 at room temperature. U3O8 remains stable in air up to 850 °C. Above this temperature, oxygen losses lead to the formation of U3O8−x, as demonstrated by subtle changes in the diffraction pattern and by a mass loss recorded by TGA. |
| Databáze: | OpenAIRE |
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