Advanced synthesis of materials for intermediate-temperature solid oxide fuel cells

Synthesis, structural and optical properties of CeO2 nanoparticles synthesized by a simple polyvinyl pyrrolidone (PVP) solution route

Ce1-xZrxO2 (x = 0−0.8) nanoparticulate powders were prepared via a mild urea hydrolysis based hydrothermal method through homogeneous nucleation at 413 K followed by calcination at 773 or 1173 K. X...

Urea-Based Hydrothermally Derived Homogeneous Nanostructured Ce1-xZrxO2 (x = 0−0.8) Solid Solutions: A Strong Correlation between Oxygen Storage Capacity and Lattice Strain

Nanocages with controllable shapes, tunable compositions, and narrow size distributions have been synthesized by using the monodispersed ceria clusters as templates.

Formation of CeO2−ZrO2 Solid Solution Nanocages with Controllable Structures via Kirkendall Effect

This paper reports the synthesis of platelike CeO2 nanoparticles by a simple, cost-effective, and environmentally friendly method using cerium(III) acetate hydrate and freshly extracted egg white (ovalbumin) in an aqueous medium. A platelike structure of CeO2 nanoparticles having the particle size of 6−30 nm was obtained by calcining the precursors in air at 400, 500, and 600 °C, for 2 h. Results from XRD, Raman spectroscopy, and SAED analysis indicated that the synthesized CeO2 nanoparticles have the fluorite structure of the bulk CeO2. All samples show a strong UV−vis absorption below 400 nm (3.10 eV) with a well-defined absorbance peak at around 284 nm (4.37 eV). The estimated direct band gaps are 3.61, 3.59, and 3.57 eV for the samples calcined at 400, 500, and 600 °C, respectively. These band gaps are 0.42, 0.40, and 0.38 eV higher than that of bulk CeO2, indicating the quantum confinement effect of the nanosize particles. The 400 and 500 °C calcined samples exhibited similar emission peaks of room-t...

Egg White Synthesis and Photoluminescence of Platelike Clusters of CeO2 Nanoparticles

CeO2-ZrO2 mixed oxides were synthesized by two mild chemical routes: complexation with citric acid and the sol-gel method. XRD and ESEM investigations revealed the appearance of a solid solution around 400degreesC , depending on the ratio between the two oxides and the preparation method. Solids obtained by the citrate method were more homogeneous on the whole range of composition. Solid-state investigations of the prepared materials did not show segregation of cerium or zirconium oxides, except in the high Ce ranges for samples prepared by the sol-gel method. The thermal stability of both oxides was enhanced by mutual substitution. The most stable solid solutions were obtained in the range 50 < Ce < 90% mol.

Characterization of CeO2-ZrO2 mixed oxides. Comparison of the citrate and sol-gel preparation methods

The distribution of heavy metals in the Sidi Moussa lagoon sediments (Atlantic Moroccan Coast)

The Concept of a Pottery Production Centre. An Archaeometrical Contribution from Ancient Sagalassos

This paper reports a finding, namely a cooperation between separate phases, which may help understand the mechanism of oxidative coupling of methane. The activity of co-precipitated bismuth-manganese oxides in the oxidative coupling of methane, measured in the continuous flow regime, is maximum for Bi:Mn = 1:2. The catalysts have been investigated by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and microanalysis; catalytic pulse experiments were performed. The Bi2Mn4O10 phase is present in these catalysts. But, surprisingly, although it corresponds to the Bi:Mn ratio of 1:2 giving maximum activity, it decomposes to alpha-Bi2O3 and alpha-Mn2O3 in a few hours during the catalytic test. The higher catalytic activity observed at Bi:Mn = 1:2 thus does not seem due to the Bi2Mn4O10 phase. The high activity catalyst is actually composed of Bi2O3 in contact with an other phase. This might be a Bi-depleted Bi2Mn4O10-like phase; it is speculated that this phase could donate oxygen to Bi2O3 and make it more active. This would suggest that oxygen mobility or spill-over between phases. observed to be beneficial in other reactions occurring at 350-450-degrees-C, also promotes the selective oxidative coupling of methane above 700-degrees-C.

Jean Naud

Papers

Characterization of CeO2-ZrO2 mixed oxides. Comparison of the citrate and sol-gel preparation methods

The distribution of heavy metals in the Sidi Moussa lagoon sediments (Atlantic Moroccan Coast)

The Concept of a Pottery Production Centre. An Archaeometrical Contribution from Ancient Sagalassos

Characterization of Bismuth-manganese Oxide Catalysts for Methane Oxidative Coupling

Geochemical evaluation of the Lueshe niobium deposit (Zaire) by Rietveld quantitative X-ray diffraction