Search

In this work we outline the mechanisms contributing to the oxygen reduction reaction in nanostructured cathodes of La0.8Sr0.2MnO3 (LSM) for Solid Oxide Fuel Cells (SOFC). These cathodes, developed from LSM nanostructured tubes, can be used at lower temperatures compared to microstructured ones, and this is a crucial fact to avoid the degradation of the fuel cell components. This reduction of the operating temperatures stems mainly from two factors: (i) the appearance of significant oxide ion diffusion through the cathode material in which the nanostructure plays a key role and (ii) an optimized gas phase diffusion of oxygen through the porous structure of the cathode, which becomes negligible. A detailed analysis of our Electrochemical Impedance Spectroscopy supported by first-principles calculations point toward an improved overall cathodic performance driven by a fast transport of oxide ions through the cathode surface. (Figure Presented). Fil: Sacanell, Joaquin Gonzalo. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Hernández Sánchez, Joaquín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Rubio Lopez, Adrian Ezequiel. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Martinelli, Hernan. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Siepe, Jimena Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Leyva de Guglielmino, Ana Gabriela. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Ferrari, Valeria Paola. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Juan, Dilson. Universidad Nacional de San Martín; Argentina Fil: Alonso Pruneda, José Miguel. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Mejía Gómez, Augusto Enrique. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Lamas, Diego Germán. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina

Perlite is an abundant mineral that requires minimum processing before use either as raw or expanded perlite, resulting in a low-cost, natural porous material. The application of materials for the removal of radioactive cesium from liquid effluents and contaminated waters is currently of great interest. Perlite has been evaluated in the last years for the sorption of a variety of metals, but it had not been investigated before for removal of Cs+ from contaminated waters. The present work examines the use of perlites from a deposit in Salta, Argentina, for removal of Cs+ from aqueous solutions. The mineral was characterized by means of powder X-ray diffraction, thermal analysis, analysis of specific area, and scanning electron microscopy. The effect of solution pH, presence of concomitant ions, contact time, Cs+ initial concentration, perlite dose, and basic or acidic treatment of the sorbent were studied by batch experiments. Removal increased at high pHs and after treatment with NaOH. Sorption of Cs+ by perlite presented a rapid rise in the first 80 min of contact. The selected material (from Pava mine) yielded removal efficiencies of 84 and 89% before and after treatment with NaOH, respectively, for a dose of 30 g perlite/L and initial cation concentration of 10 mg/L. Our results demonstrate that perlite is a material capable of removing Cs+ from aqueous solutions, even when applied at low doses. These findings are relevant in the context of removal of radioactive Cs isotopes from nuclear effluents and in case of contamination of environmental waters.

In this work we studied the influence of particle size and agglomeration in the performance of solid oxide fuel cell cathodes made with nanoparticles of La0.8Sr0.2MnO3. We followed two synthesis routes based on the Liquid Mix method. In both procedures we introduced additional reagents in order to separated the manganite particles. We evaluated cathodic performance by Electrochemical Impedance Spectroscopy in symmetrical (CATHODE/ELECTROLYTE/CATHODE) cells. Particle size was tuned by the temperature used for cathode sintering. Our results show that deagglomeration of the particles, serves to improve the cathodes performance. However, the dependence of the performance with the size of the particles is not clear, as different trends were obtained for each synthesis route. As a common feature, the cathodes with the lowest area specific resistance are the ones sintered at the largest temperature. This result indicates that an additional factor related with the quality of the cathode/electrolyte sintering, is superimposed with the influence of particle size, however further work is needed to clarify this issue. The enhancement obtained by deagglomeration suggest that the use of this kind of methods deserved to be considered to develop high performance electrodes for solid oxide fuel cells., 20 pages, 17 figures

La0.8Sr0.2MnO3 (LSM) is one of the most commonly used cathodes in Solid Oxide Fuel Cells (SOFC). In spite of the fact that nanostructured cathodes are expected to display improved performance, the high operating temperature (∼ 1000°C) of LSM-based SOFCs hinders their stability. In the present work, we have developed nanostructured cathodes prepared from LSM nanotubes of enhanced performance, allowing its use at lower temperatures (∼ 800°C). We observed that our cathodes have qualitative improvements compared with microstructured materials: firstly, the diffusion in the gas phase is optimized to a negligible level and secondly, evidence of ionic conduction is found, which is extremely rare in LSM cathodes. We propose that this important change in the electrochemical properties is due to the nanostructuration of the cathode and deserves further attention, including the exploration of other materials. Fil: Sacanell, Joaquin Gonzalo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Hernández Sánchez, Joaquin. Comisión Nacional de Energía Atómica; Argentina Fil: Rubio Lopez, Adrian Ezequiel. Comisión Nacional de Energía Atómica; Argentina Fil: Martinelli, Hernan. Comisión Nacional de Energía Atómica; Argentina Fil: Siepe, Jimena. Comisión Nacional de Energía Atómica; Argentina Fil: Leyva de Guglielmino, Ana Gabriela. Comisión Nacional de Energía Atómica; Argentina Fil: Ferrari, Valeria Paola. Comisión Nacional de Energía Atómica; Argentina Fil: Pruneda, Miguel. Institut Català de Nanociència i Nanotecnologia; España Fil: Juan, Dilson. Comisión Nacional de Energía Atómica; Argentina Fil: Lamas, Diego Germán. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

We investigated the electrochemical properties of Co?Fe perovskites, which can be used as cathodes for intermediate-temperaturesolid-oxide fuel cells (IT-SOFCs). We studied the electrochemical properties of nanostructured mixed ionic-electronic conductors for IT-SOFC cathodes with compositions of La0.6Sr0.4Co1-yFeyO3 (y = 0.2, 0.5 and 0.8). We analyzed the performance of two types of nanostructures: nanorods and nanotubes. Our results show that the electrochemical performance is highly influenced by the form of nanostructure, whereas the effect of composition is less significant. Fil: Mejía Gómez, Augusto Enrique. Comision Nacional de Energia Atomica. Gerencia del Area Investicaciones y Aplicaciones No Nucleares; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martin. Escuela de Ciencia y Tecnología. Centro Internacional de Estudios Avanzados.; Argentina Fil: Sacanell, Joaquin Gonzalo. Comision Nacional de Energia Atomica. Gerencia del Area Investicaciones y Aplicaciones No Nucleares; Argentina Fil: Leyva, Ana Gabriela. Comision Nacional de Energia Atomica. Gerencia del Area Investicaciones y Aplicaciones No Nucleares; Argentina Fil: Lamas, Diego German. Universidad Nacional de San Martin. Escuela de Ciencia y Tecnología. Centro Internacional de Estudios Avanzados.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

We investigated the reversible ferromagnetic (FM) behavior of pure and Co doped CeO2 nanopowders. The as-sintered samples displayed an increasing paramagnetic contribution upon Co doping. Room temperature FM is obtained simply by performing thermal treatments in vacuum at temperatures as low as 500^{\circ}C and it can be switched off by performing thermal treatments in oxidizing conditions. The FM contribution is enhanced as we increase the time of the thermal treatment in vacuum. Those systematic experiments establish a direct relation between ferromagnetism and oxygen vacancies and open a path for developing materials with tailored properties., 20 pages, 3 figures; Applied Physics Letters Vol. 100, Issue 17, APR2012