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Evaluation of the thermal stability under air of the uranyl peroxide nanocluster (NH4)40[(UO2)32(O2)40(OH)24]⋅nH2O

Abstract : The synthesis, characterization and thermal decomposition of the uranyl peroxide nanocluster(NH4)40[(UO2)32(O2)40(OH)24]. nH2O, designated as U32R-NH4, are presented for a series of temperatures ranging from 20 to 800°C. The handlings and annealing were carried out under air and the post-treatment characterizations were managed back to room temperature. The identification of the intermediate compounds was achieved by chemical analysis, infrared spectroscopy and powder X-ray diffraction. The proposed decomposition scheme up to U3O8 comprises three main steps; (i) the low temperature range, from room temperature to 190°C, is characterized by the loss of the molecular species, water molecules, ammonium and peroxo ions, (ii) the intermediate temperature range, from 190 to 590°C, involves mostly structural rearrangements and release of oxygen and nitrogen species, and (iii) the high temperature range, above 590°C, which is associated to the UO3 – U3O8 transition accompanied with O2 release. The thermal treatment up to 800°C does not alter the morphological features of the initial powder suggesting a pseudomorphic decomposition. Upon ageing or heating, the starting compound, (NH4)40[(UO2)32(O2)40(OH)24].nH2O, readily loses its crystallinity.
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Soumis le : mardi 2 mars 2021 - 15:50:18
Dernière modification le : mercredi 23 mars 2022 - 15:50:47

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Paul-Henri Imbert, Olivier Tougait, Philippe Devaux, Natacha Henry, Marine Ellart, et al.. Evaluation of the thermal stability under air of the uranyl peroxide nanocluster (NH4)40[(UO2)32(O2)40(OH)24]⋅nH2O. Progress in Nuclear Science and Technology, 2018, Progress in Nuclear Science and Technology, 5, pp.144-147. ⟨10.15669/pnst.5.144⟩. ⟨hal-03156637⟩



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