15750-47-7Relevant articles and documents
STUDY OF THERMAL CO-DECOMPOSITION OF MANGANESE AND CERIUM OXALATES IN AIR AND IN INERT MEDIA
Bulavchenko,Vinokurov,Nikolaeva,Afonasenko,Tsybulya
, p. 467 - 480 (2021/04/26)
Abstract: Controlled thermal decomposition of oxalate salts is a promising method for the preparation of highly dispersed materials. In this work, co-decomposition of Mn and Ce salts is studied upon variations of the cation ratio and the gas atmosphere of the process (air and inert gas). To this aim, a series of Mn and Ce oxalates is prepared by co-precipitation from aqueous solutions of nitrates with Mn:Ce ratios varying from 0:1 to 1:0. It is shown by X-ray powder diffraction and by scanning electron microscopy that cerium Ce(C2O4)3·10H2O and manganese MnC2O4·2H2O oxalates are formed. Also, increasing manganese content increases the amount of the corresponding salts and affects the morphology of the particles. It was shown by a number of physicochemical methods such as thermal analysis, in situ X-ray diffraction, and mass spectrometry shows that the oxalate decomposition proceeds in two stages and depends on the cation ratio and the decomposition atmosphere. The first stage is a weight loss accompanied by removal of structural water; this process is accelerated in a flow of an inert gas. The second stage is the formation of oxides from the anhydrous salt accompanied by CO2 or CO/CO2 release. Due to exothermic oxidation reaction, the decomposition occurs at lower temperatures in air than in an inert gas. The introduction of manganese does not significantly affect the temperature ranges of the first and second stages of salt decomposition. However, the addition of the second cation affects the decomposition product: as the manganese content increases, the size of CeO2 particles decreases and simple manganese oxides Mn3O4 and MnO are formed in air and in the inert atmosphere, respectively. The catalytic properties in the oxidation of CO, Mn and Ce oxides obtained by the decomposition of oxalates in an inert gas and in air are studied. It is shown that the catalysts formed in the oxidizing environment are more active.
Cerium Oxalate Morphotypes: Synthesis and Conversion into Nanocrystalline Oxide
Tyrpekl, Vaclav,Markova, Pavlina,Dopita, Milan,Brázda, Petr,Vacca, Mirko A.
, p. 10111 - 10118 (2019/08/20)
Cerium dioxide is a scientifically and technologically important material with a wide range of potential applications, particularly in solid oxide fuel cells and catalysis. Herein, we report a study focusing on the synthesis of nanocrystalline cerium dioxide via thermal decomposition of the oxalate salt. Simply by changing reaction conditions (temperature, concentration, acidity, strike) during the precipitation of the cerium solution with oxalic acid, we were able to obtain different morphologies. The main reaction parameters were mapped and linked to the morphology of the final products. Additionally, it was proved that oxalate precipitation is a robust reaction proceeding at relatively extreme contitions. Moreover, the conversion of cerium oxalate to nanocrystalline oxide was followed to monitor the progress of the reaction, the texture evolution, and the grain growth. The results showed that, for unvaried heating cycle, the grain size of converted material is linked to morphology. The thinner was the original microcrystal the smaller were the CeO2 nanocrystals after calcination. In addition, the grains were found smaller near the edges of the ex-oxalate microcrystals. In both cases, this behavior results from asymmetrical limitations of diffusion during grain growth.
Ultrasonic-assisted solution-phase synthesis and property studies of hierarchical layer-by-layer mesoporous CeO2
Zhao, Pu Su,Gao, Xiu Mei,Zhu, Feng Xia,Hu, Xin Ming,Zhang, Li Li
, p. 375 - 380 (2018/02/13)
Hierarchical layer-by-layer quadrangle CeO2 was prepared through ultrasonic-assisted solution-phase synthesis strategy using cerium oxalate as the precursor. The as-prepared mesoporous CeO2 displayed a surface area of 98.7 m2 g?1 and pore diameters of 2.0–10.0 nm. The high-resolution TEM image revealed that the layer structures of the CeO2 were made of numerous nanocrystal particles with the crystallite size of about 13–15 nm. High energy and cavitation of ultrasonic wave assists cerium oxalate precursor in building the layer-by-layer quadrangle staking. UV–vis absorption spectrum showed that the direct allowed transition bandgap energy for the as-prepared CeO2 was 2.91 eV. Moreover, the CeO2 exhibited good photocatalytic property for degrading Rhodamine B solution under UV radiation.
Influence of crystallization state and microstructure on the chemical durability of cerium-neodymium mixed oxides
Claparede, Laurent,Clavier, Nicolas,Dacheux, Nicolas,Moisy, Philippe,Podor, Renaud,Ravaux, Johann
, p. 9059 - 9072 (2011/10/17)
To underline the potential links between the crystallization state and the microstructure of powdered cerium-neodymium oxides and their chemical durability, several CeIV1-xNdIII xO2-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 Ce1-xNdxO2-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?mol-1) suggested that the dissolution was mainly driven by surface reactions occurring at the solid-liquid interface. The chemical durability of the cerium-neodymium 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.
Porous lanthanide oxides via a precursor method: Morphology control through competitive interaction of lanthanide cations with oxalate anions and amino acids
Shen, Zhu-Rui,Wang, Jin-Gui,Sun, Ping-Chuan,Ding, Da-Tong,Chen, Tie-Hong
, p. 6112 - 6123 (2010/08/08)
Porous lanthanide oxides were fabricated by a precursor-thermolysis method. The precursors were synthesized by a hydrothermal reaction with lanthanide (La, Ce, Pr and Nd) salts, sodium oxalate and asparagine (or glutamine). Under hydrothermal conditions asparagine and glutamine exhibited greatly different complexation abilities with lanthanide cations. The competitive interactions of lanthanide cations with oxalate anions and asparagine (or glutamine) gave rise to the formation of precursors with different structures and morphologies. ESI-MS detection further confirmed the different complexation abilities of asparagine or glutamine with lanthanide cations at the molecular level. Variation of oxalate anion concentration or the pH value of the reaction solution could tune the morphology of the products. After calcination, porous lanthanide oxides were obtained with the morphologies of their corresponding precursors. Our work suggests that the complexation ability of organic molecules with metal cations could be a crucial factor for morphological control of the precursors. Moreover, considering the diversity of organic additives and metal salts, other metal oxides with complex composition and morphology could be fabricated via this organic molecule-modified precursor method.
Nanocrystalline oxalate/carbonate precursors of Ce and Zr and their decompositions to CeO2 and ZrO2 nanoparticles
Vaidya, Sonalika,Ahmad, Tokeer,Agarwal, Suman,Ganguli, Ashok K.
, p. 863 - 869 (2008/10/09)
The oxalate and carbonate precursors of cerium and zirconium have been prepared using reverse micelles as nanoreactors. Cerium oxalate precursor on thermal decomposition leads to a mixture of nanorods and nanoparticles of cerium oxide (nanoparticles of 10 nm and nanorods with 7 nm diameter and 30 nm length). Cerium oxide with crystallite size of 10 nm was obtained from cerium carbonate precursor. Monodispersed nanoparticles of zirconia with an average size of 3-5 and 12 nm were obtained from the oxalate and carbonate precursor, respectively. Detailed dielectric properties of sintered discs of nanocrystalline ceria and zirconia have been studied with variation of frequency and temperature.
Thermal decomposition of mixed Ce and Gd oxalates and thermal properties of mixed Ce and Gd oxides
Ubaldini,Artini,Costa,Carnasciali,Masini
, p. 207 - 211 (2008/10/09)
The aim of the present work is to study the thermal decomposition of the mixed oxalates (Ce1-xGdx)2(C2O 4)3?nH2O. The mechanisms of decomposition of Ce and Gd oxalate are different, and mixed oxalates behave in an intermediate way. Their dehydration stages are more similar to those of Gd oxalate, as not all the molecules of water are equivalent like the cerium oxalate. The decomposition leads to (Ce1-xGdx)O2-x/2. For x close to 0 or to 1 two solid solutions exist, while for the central composition, the presence of a biphasic region can not be excluded.
On production of cerium dioxide
Lebedev,Rudenko
, p. 1357 - 1359 (2007/10/03)
The possibility of obtaining cerium dioxide by recovery of Ce(IV) phosphate from acid nitrate solutions with subsequent conversion of Ce(IV) phosphate to Ce(III) oxalate was studied.
Magnetic susceptibilities of lanthanide(III)-CMPO complexes and lanthanide(III) oxalate complexes
Nakamura,Yoshimura,Nakatani,Miyake
, p. 303 - 305 (2008/10/08)
Lanthanide(III)-CMPO complexes with nitrate ion as counter-ion and lanthanide(III)-oxalate complexes were synthesized. The former complexes were identified as Ln(NO3)3·3CMPO for La(III), Ce(III), Pr(III) and Nd(III), whereas Ln(NOsu
Thermal decomposition of cerium oxalate and mixed cerium-gadolinium oxalates
El-Houte, S.,El-Sayed, Ali M.
, p. 907 - 914 (2008/10/08)
Cerium oxalate and mixed cerium-gadolinium oxalates containing 20 and 50 mol% gadolinium were subjected to thermal decomposition. Thermal analysis showed that cerous oxalate is transformed to cerium oxide in two steps. The first step involves the endother
