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<p>The thermal decomposition of cerium(III) nitrate hexahydrate into cerium oxide was studied under argon and air atmospheres via simultaneous thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), scanning electron microscopy (SEM), and X-ray diffraction (XRD). XRD and SEM analyses revealed that the synthesized cerium oxide had an average crystallite size of 20&#xa0;nm, although agglomeration resulted in secondary particles up to 1&#xa0;μm in size. The decomposition was monitored under nonisothermal conditions, and the thermal analysis data were evaluated from a kinetics point of view by isoconversional and model-fitting methods. The isoconversional expanded Friedman demonstrated a clear dependence of the activation energy (Eₐ) on the degree of conversion (α), which supports a complex mechanism. Both atmospheres yielded CeO<sub>2</sub> formation, but through rather different mechanisms. Namely, the Ar atmosphere forms CeO<sub>2</sub> through multiple stages, keeping a high concentration of Ce(III) ions, and preventing the oxidation process from Ce(III) to Ce(IV) ions. Decomposition in the air was more energetically favorable compared to the argon atmosphere. The activation energy values were obtained as follows: 156 and 232&#xa0;kJ&#xa0;mol<sup>−1</sup> (expanded Friedman), 190 and 285&#xa0;kJ&#xa0;mol⁻<sup>1</sup> (Discrete model), and 166 and 280&#xa0;kJ&#xa0;mol<sup>−1</sup> (N-th order) for air and Ar atmosphere. Based on these results, a reaction mechanism was proposed for the thermal decomposition of cerium(III) nitrate hexahydrate in both atmospheres.</p>

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Kinetics and mechanism of cerium nitrate thermal decomposition in different atmospheres

  • 期刊论文

  • 发表日期：

    2025年7月1日

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  • Saša Zeljković,
  • Dijana Jelić

摘要

The thermal decomposition of cerium(III) nitrate hexahydrate into cerium oxide was studied under argon and air atmospheres via simultaneous thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), scanning electron microscopy (SEM), and X-ray diffraction (XRD). XRD and SEM analyses revealed that the synthesized cerium oxide had an average crystallite size of 20 nm, although agglomeration resulted in secondary particles up to 1 μm in size. The decomposition was monitored under nonisothermal conditions, and the thermal analysis data were evaluated from a kinetics point of view by isoconversional and model-fitting methods. The isoconversional expanded Friedman demonstrated a clear dependence of the activation energy (Eₐ) on the degree of conversion (α), which supports a complex mechanism. Both atmospheres yielded CeO2 formation, but through rather different mechanisms. Namely, the Ar atmosphere forms CeO2 through multiple stages, keeping a high concentration of Ce(III) ions, and preventing the oxidation process from Ce(III) to Ce(IV) ions. Decomposition in the air was more energetically favorable compared to the argon atmosphere. The activation energy values were obtained as follows: 156 and 232 kJ mol−1 (expanded Friedman), 190 and 285 kJ mol⁻1 (Discrete model), and 166 and 280 kJ mol−1 (N-th order) for air and Ar atmosphere. Based on these results, a reaction mechanism was proposed for the thermal decomposition of cerium(III) nitrate hexahydrate in both atmospheres.