The ammonium uranyl carbonate, (NH4)4UO2(CO3)3, is an important material used in UO2 and U3O8 ceramics production for the nuclear fuel fabrication. Thermal study and kinetic analysis of ammonium uranyl carbonate conversion under isothermal conditions has been studied in air atmosphere to obtain the tri-uranium octoxide (U3O8), using muffle furnace equipment, UV–visible spectrophotometer, gas adsorption, Hg porosimetry, laser granulometry, and optic spectroscopy. The textural properties (specific surface area, morphology, pore size, grain size, inter-particular porosity, and intra-particular porosity) and characteristics (uranium content and stoichiometry) of the prepared samples were estimated from the physical–chemical characterization. The kinetic parameters were estimated by a fitting of the experimental data. The activation energy Ea , frequency factor A , and reaction rate constants k were calculated from the conventional and iso-conversion kinetic models and were within the range of literature values. The activation energy average values are 36.69 and 30.36 kJ mol−1 by conventional and iso-conversion models, respectively.

中文翻译：

---

(NH4)4UO2(CO3)3等温分解成氧化铀的动力学研究

碳酸铀酰铵 (NH4)4UO2(CO3)3 是一种重要的材料，用于生产用于制造核燃料的 UO2 和 U3O8 陶瓷。使用马弗炉设备、紫外-可见分光光度计、气体吸附、汞孔隙率测定法、激光粒度测定法，在空气气氛中研究了等温条件下碳酸铀酰铵转化的热研究和动力学分析，以获得八氧化三铀 (U3O8)。光学光谱学。制备的样品的结构特性（比表面积、形态、孔径、粒度、颗粒间孔隙率和颗粒内孔隙率）和特征（铀含量和化学计量）通过物理化学表征进行估计。通过拟合实验数据来估计动力学参数。活化能 Ea , 频率因子 A 和反应速率常数 k 由常规和等转化动力学模型计算得出，均在文献值范围内。传统和等转换模型的活化能平均值分别为 36.69 和 30.36 kJ mol-1。