Kim B H, Lee Y B, Prelas M A, Ghosh T K
Department of Fast Reactor Technology Development, Korea Atomic Energy Research Institute, 150 Deokjin-dong, Daejeon, 305-353 Korea.
Nuclear Science and Engineering Institute, University of Missouri, Columbia, MO USA.
J Radioanal Nucl Chem. 2012;292(3):1075-1083. doi: 10.1007/s10967-011-1579-8. Epub 2012 Jan 3.
Two types of ammonium uranyl nitrate (NH)UO(NO)·2HO and NHUO(NO), were thermally decomposed and reduced in a TG-DTA unit in nitrogen, air, and hydrogen atmospheres. Various intermediate phases produced by the thermal decomposition and reduction process were investigated by an X-ray diffraction analysis and a TG/DTA analysis. Both (NH)UO(NO)·2HO and NHUO(NO) decomposed to amorphous UO regardless of the atmosphere used. The amorphous UO from (NH)UO(NO)·2HO was crystallized to γ-UO regardless of the atmosphere used without a change in weight. The amorphous UO obtained from decomposition of NHUO(NO) was crystallized to α-UO under a nitrogen and air atmosphere, and to β-UO under a hydrogen atmosphere without a change in weight. Under each atmosphere, the reaction paths of (NH)UO(NO)·2HO and NHUO(NO) were as follows: under a nitrogen atmosphere: (NH)UO(NO)·2HO → (NH)UO(NO)·HO → (NH)UO(NO) → NHUO(NO) → A-UO → γ-UO → UO, NHUO(NO) → A-UO → α-UO → UO; under an air atmosphere: (NH)UO(NO)·2HO → (NH)UO(NO)·HO → (NH)UO(NO) → NHUO(NO) → A-UO → γ-UO → UO, NHUO(NO) → A-UO → α-UO → UO; and under a hydrogen atmosphere: (NH)UO(NO)·2HO → (NH)UO(NO)·HO → (NH)UO(NO) → NHUO(NO) → A-UO → γ-UO → α-UO → UO, NH UO(NO) → A-UO → β-UO → α-UO → UO.
两种硝酸双氧铀铵（NH₄）₂UO₂（NO₃）₂·2H₂O 和 NH₄UO₂（NO₃），在热重-差热分析仪中于氮气、空气和氢气氛围下进行热分解和还原。通过 X 射线衍射分析和热重/差热分析对热分解和还原过程中产生的各种中间相进行了研究。无论使用何种氛围，（NH₄）₂UO₂（NO₃）₂·2H₂O 和 NH₄UO₂（NO₃）都会分解为无定形的 UO₂。由（NH₄）₂UO₂（NO₃）₂·2H₂O 分解得到的无定形 UO₂，无论在何种氛围下都会结晶为γ-UO₂，且重量不变。由 NH₄UO₂（NO₃）分解得到的无定形 UO₂，在氮气和空气氛围下结晶为α-UO₂，在氢气氛围下结晶为β-UO₂，且重量不变。在每种氛围下，（NH₄）₂UO₂（NO₃）₂·2H₂O 和 NH₄UO₂（NO₃）的反应路径如下：在氮气氛围下：（NH₄）₂UO₂（NO₃）₂·2H₂O →（NH₄）₂UO₂（NO₃）·H₂O →（NH₄）₂UO₂（NO₃）→ NH₄UO₂（NO₃）→ A-UO₂ →γ-UO₂ → UO₂，NH₄UO₂（NO₃）→ A-UO₂ →α-UO₂ → UO₂；在空气氛围下：（NH₄）₂UO₂（NO₃）₂·2H₂O →（NH₄）₂UO₂（NO₃）·H₂O →（NH₄）₂UO₂（NO₃）→ NH₄UO₂（NO₃）→ A-UO₂ →γ-UO₂ → UO₂，NH₄UO₂（NO₃）→ A-UO₂ →α-UO₂ → UO₂；在氢气氛围下：（NH₄）₂UO₂（NO₃）₂·2H₂O →（NH₄）₂UO₂（NO₃）·H₂O →（NH₄）₂UO₂（NO₃）→ NH₄UO₂（NO₃）→ A-UO₂ →γ-UO₂ →α-UO₂ → UO₂，NH₄UO₂（NO₃）→ A-UO₂ →β-UO₂ →α-UO₂ → UO₂。
