Temperature-programmed reduction and dispersive X-ray absorption spectroscopy studies of CeO2-based nanopowders for intermediate-temperature Solid-Oxide Fuel Cell anodes

In this work, we study the influence of the average crystallite size and dopant oxide on the reducibility of CeO2-based nanomaterials. Samples were prepared from commercial Gd2O3-, Sm2O3- and Y2O3-doped CeO2 powders by calcination at different temperatures ranging between 400 and 900C and characterized by X-ray powder diffraction, transmission electron microscopy and BET specific surface area. The reducibility of the samples was analyzed by temperature-programmed reduction and in situ dispersive X-ray absorption spectroscopy techniques. Our results clearly demonstrate that samples treated at lower temperatures, of smallest average crystallite size and highest specific surface areas, exhibit the best performance, while Gd2O3-doped ceria materials display higher reducibility than Sm2O3- and Y2O3-doped CeO2

Conversion of biogas to synthesis gas over NiO/CeO2–Sm2O3 catalysts

The main objective of this work has been to study the catalytic activity in the conversion of biogas to Syngas of a Ni/Ce0.82Sm0.18O1.91 oxide system, which could be used as a component in the anode material of a SOFC directly fed with biogas. The solids were active without need of pretreatment with a stable behaviour during a time on stream of six hours for a carbon dioxide to methane molar ratio of 2.3. This feed composition maximize the production of synthesis gas, with stable catalytic behaviour without formation of carbonaceous compounds and involving CO2 capturing, contributing to the reduction of greenhouse gases. It can be concluded that NiO/CeO2-Sm2O3 catalysts exhibited promising catalytic performance for their use in the composition of anode material of solid oxide fuel cells fed with biogas.Fil: Zimicz, Maria Genoveva. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Reznik, Brian A.. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Química; ArgentinaFil: Larrondo, Susana Adelina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Universidad Nacional de San Martín; Argentin

Effect of Nb5 + content on the high temperature properties of the mixed conductors system La1 − xBaxCo1 − yNbyO3 − δ with 0.6 ≤ x ≤ 1.0 and 0 ≤ y ≤ 0.4

The replacement of Co by Nb in the La1 − xBaxCo1 − yNbyO3 − δ (0.6 ≤ x ≤ 1.0) system and its effects on phase stability and high temperature properties of the cubic perovskite phase were investigated by X-ray diffraction, dilatometry, electrical conductivity, oxygen permeation and electrochemical impedance spectroscopy. The incorporation of Nb in the B site stabilizes the cubic perovskite in the as prepared samples. The Nb solubility increases from y = 0.1, for the sample with Ba content x = 0.6, to y = 0.4 for 0.8 ≤ x ≤ 1.0. However, after a heat treatment at 750 °C during 10 days small amounts of secondary phases were detected for samples with x = 0.9 and 1.0. The linear expansion of the cubic phases decreases with the Nb content as well as with the Ba content. The minimum value, α = 12.9 × 10− 6 K− 1, was obtained for La0.2Ba0.8Co0.6Nb0.4O3 − δ. The behavior of electrical conductivity and oxygen permeation data with Nb content is explained from variations in the oxygen vacancy concentration, which is controlled by Nb5 + and Ba2 + contents. The minimum polarization resistance value, Rp = 0.08 Ω cm2, was obtained at 600 °C for La0.2Ba0.8Co0.9Nb0.1O3 − δ. The low Rp value of this compound and the crystal structure stability of various compositions in the system La1 − xBaxCo1 − yNbyO3 − δ with x ≥ 0.7 and y ≥ 0.1 make these materials of interest as mixed conductors.Fil: Setevich, C. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Sur. Departamento de Física; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Toscani, Lucía María. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; ArgentinaFil: Larrondo, Susana Adelina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Universidad Nacional de San Martín; ArgentinaFil: Prado, F.. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Sur. Departamento de Física; ArgentinaFil: Caneiro, A. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentin

Synthesis and characterization of mesoporous NiO2/ZrO2-CeO2 catalysts for total methane conversion

This work reports the synthesis and characterization of mesoporous NiO/ZrO2-CeO2 composites. These materials are still being developed due to their excellent morphological and structural properties, especially for solid oxide fuel cells (SOFCs) anodes. A soft chemical route using a polymeric template was utilized to synthesize the samples. The structure after two different calcination processes at 400 °C and 540 °C was studied by X-ray diffraction and Rietveld refinement, before and after NiO loading. Nitrogen adsorption, scanning/transmission electron microscopy and small angle X-ray scattering revealed a nanocrystalline bi-phasic porous material. Temperature programmed reduction experiments showed higher Ni and Ce reduction values for samples calcined at 400 °C and 540 °C, respectively. Methane conversion values in the temperature range studied were similar for both calcination temperatures, showing 50% CH4 conversion around 550 °C and 80% around 650 °C. However, a sample calcined at 400 °C exhibited better morphological and textural properties leading to an enhancement in NiO and CeO2 reducibility that might be responsible for an improvement in oxygen surface exchange and gasification of carbon species in catalytic experiments.Fil: Bacani, R.. Universidade de Sao Paulo; BrasilFil: Toscani, Lucía María. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; ArgentinaFil: Martins, T. S.. Universidade Federal de Sao Paulo; BrasilFil: Fantini, M. C. A.. Universidade de Sao Paulo; BrasilFil: Lamas, Diego Germán. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes. Gerencia de Investigación y Aplicaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Larrondo, Susana Adelina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental; Argentin

Structural and morphological properties of Ce(1−x)FexO2−δ synthesized by citrate route

Cerium-based materials were intensively studied in last years because of their high oxygen storage capacity (OSC) associated to the reversible Ce4+ Ce3+ process and their properties closely related to the defect chemistry that could be adjusted by adequate selection of dopant. Fe3+ cation, due to its effective ionic radius smaller than that of Ce4+, is an interesting doping agent. In this work we present the synthesis and characterization of Ce(1-x)FexO2-δ mixed oxides (00.15, not observable in X-ray diffraction experiments. The solidsolutions exhibit high porosity and specific surface area, with nearly 10% of pore volume in the micropore size range, making these materials potentially useful for applications in catalysis.Fil: Mazan, Mariano Osvaldo. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Química; Argentina.Fil: Craievich, Aldo F.. Universidade de Sao Paulo; BrasilFil: Halac, Emilia Beatriz. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; ArgentinaFil: Fantini, Márcia C. A.. Universidade de Sao Paulo; BrasilFil: Lamas, Diego Germán. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; ArgentinaFil: Larrondo, Susana Adelina. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental; Argentin

Effect of swelling agent in the synthesis of porous nanocrystalline nickel-zirconia-ceria composite

Porous ceria-zirconia (Zr0 · 1Ce0 · 9O2 − δδ delete) powders were synthesized by a sol-gel route using inorganic chlorides (ZrCl4 and CeCl3·7H2O) as precursors, block copolymer P123 (PEO20PPO70PEO20) as the template and tri-isopropyl-benzene (TIPB) as the swelling agent. These porous materials show high surface area and gas permeability, important properties for Intermediate Temperature-Solid Oxide Fuel Cell (IT-SOFC) and catalytic applications. The samples were prepared with different P123:TIPB (w/w) % ratios (1:0, 1:1, 1:2 and 1:4), as a strategy to increase porosity. The samples were calcined at 400 °C in air to remove the template. Post-synthesis nickel impregnation was planned to obtain 3 and 10 (w/w) % of NiO after calcination. The structure and morphology of the samples were determined by X-ray diffraction (XRD), small angle X-ray scattering (SAXS), nitrogen adsorption isotherms (NAI) and transmission and scanning electron microscopies (TEM and SEM). The resulting materials have high specific surface area (≈110 m2. g-1) and a wide pore size distribution of mesopores (3–50 nm). They are formed by nanocrystals (≈15 nm) of the predominant (≈90%) Fm3¯m cubic phase and by the P42/nmc tetragonal phase. The micrographs revealed that the nanocrystalline oxides have mesopores with slit shape and a secondary smaller mesoporosity with a narrow size distribution (≈4 nm). An increase of micropore volume (sizes < 2 nm) was observed with the presence of the swelling agent in the synthesis process, ideal for gas diffusion in catalysis and IT-SOFC processes. Temperature programmed reduction (TPR) analysis presented low temperature peaks, a marked increase in the total reduction value and H2 uptake of samples with 3 (w/w)% NiO in contrast to the bare supports. There was no significant further increase in the total reduction value when 10 (w/w)% NiO is incorporated. It is noteworthy that comparing the synthesis methods, all samples presented higher reduction values and H2 uptake.Fil: Cassimiro, V. R. S.. Universidade de Sao Paulo; BrasilFil: Monteiro, R. C.. Universidade de Sao Paulo; BrasilFil: Bacani, R.. Universidade de Sao Paulo; BrasilFil: Toscani, Lucía María. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; ArgentinaFil: Lamas, Diego Germán. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche | Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche; ArgentinaFil: Larrondo, Susana Adelina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; ArgentinaFil: Fantini, M. C. A.. Universidade de Sao Paulo; Brasi

Preliminary Characterization of Erythrocytes Deformability on the Entropy-Complexity Plane

We present an application of wavelet-based Information Theory quantifiers (Normalized Total Shannon Entropy, MPR-Statistical Complexity and Entropy-Complexity plane) on red blood cells membrane viscoelasticity characterization. These quantifiers exhibit important localization advantages provided by the Wavelet Theory. The present approach produces a clear characterization of this dynamical system, finding out an evident manifestation of a random process on the red cell samples of healthy individuals, and its sharp reduction of randomness on analyzing a human haematological disease, such as β-thalassaemia minor