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P.?RouraEmail author J.?Farjas J.?Camps S.?Ricart J.?Arbiol T.?Puig X.?Obradors 《Journal of nanoparticle research》2011,13(9):4085-4096
The structural transformations that occur when thermal treatments turn cerium propionate into nanocrystalline ceria have been
analysed with thermoanalytical techniques (TG, DTA and MS) and with structural and magnetic characterization (HRTEM, SQUID
and XRD) of the final and intermediate products. Attention has been paid to what occurs during the decomposition of propionate
and how the process is affected by the furnace atmosphere (oxidizing or inert). In an oxidizing atmosphere, the decomposition
of cerium propionate is triggered by the oxidation of Ce3+ to Ce4+. This reaction entails the loss of large unoxidized propionate fragments of the propionate ligands. As decomposition proceeds,
the carbonaceous residue makes the oxygen transport inside the material more difficult and decomposition becomes diffusion
limited. At this point, extensive oxidation of the residue begins until it is completely removed. Crystallization of CeO2 occurs simultaneously with decomposition. In these conditions, crystalline nanoparticles (diameter of 3–5 nm) can be obtained
at a temperature as low as 300 °C. In an inert atmosphere, decomposition occurs in three steps. During the first step, one
of the three propionate ligands is lost, with little oxidation of Ce3+, and is substituted by a hydroxyl group. The second step entails the loss of the remaining ligands with a substantial oxidation
of Ce3+ to Ce4+. After this step, the intermediate product is, proposed as, a mixture of amorphous Ce(OH)3 and Ce(OH)4. Finally, the third step leads to conversion of the Ce hydroxide into crystalline CeO2. In an inert atmosphere, the process is less reproducible than in air and a carbonaceous residue remains in the product. 相似文献