Influence of Crystallization State and Microstructure on the Chemical Durability of Cerium鈥揘eodymium Mixed Oxides

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• 作者：Laurent Claparede ; Nicolas Clavier ; Nicolas Dacheux ; Philippe Moisy ; Renaud Podor ; Johann Ravaux
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：September 19, 2011
• 年：2011
• 卷：50
• 期：18
• 页码：9059-9072
• 全文大小：1327K
• 年卷期：v.50,no.18(September 19, 2011)
• ISSN：1520-510X

文摘

To underline the potential links between the crystallization state and the microstructure of powdered cerium鈥搉eodymium oxides and their chemical durability, several Ce^IV_1鈥?i>xNd^III_xO_2鈥?i>x/2 mixed dioxides were prepared in various operating conditions from oxalate precursors and then leached. The powdered samples were first examined through several physicochemical properties (crystallization state and associated crystallite size, reactive surface area, porosity...). The dependence of the normalized dissolution rates on various parameters (including temperature, nitric acid concentration, crystallization state) was examined for pure CeO₂ and Ce_1鈥?i>xNd_xO_2鈥?i>x/2 solid solutions (with x = 0.09 and 0.16). For CeO₂, either the partial order related to the proton activity (n = 0.63) or the activation energy (E_A = 37 kJ路mol^鈥?) suggested that the dissolution was mainly driven by surface reactions occurring at the solid鈥搇iquid interface. The chemical durability of the cerium鈥搉eodymium oxides was also strongly affected by chemical composition. The initial normalized dissolution rates were also found to slightly depend on the crystallization state of the powders, suggesting the role played by the crystal defects in the dissolution mechanisms. On the contrary, the crystallite size had no important effect on the chemical durability. Finally, the normalized dissolution rates measured near the establishment of saturation conditions were less affected, which may be due to the formation of a gelatinous protective layer at the solid/liquid interface.