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This paper address the blocking of the electronic conductivity for a BaCe0.8Pr0.2O3-δ (BCP) material due to the addition of a BaCe0.4Zr0.4Y0.2O3-δ (BCZY) thin layer. Barium cerates (BCP and BCZY) show interesting features as electrolytes for Proton Conducting Solid Oxide Fuel Cells (PC-SOFC). BCP perovskite displays good mechanical properties associated to its sintering capability, typically proposed as a possible electrolyte. However, this compound shows poor CO2 tolerance above 500 °C and presents mixed conductivity under wet synthetic air. Protonic transport is the main feature of BCZY perovskite and it presents an excellent CO2 tolerance. However, the drawback of this compound is its high grain boundary resistance. In this work, a BCZY film was grown by Pulsed Laser Deposition (PLD) on BCP in order to block its electronic conductivity and improve CO2 tolerance. From the electrochemical characterization of materials, it is proposed that BCP dominates transport mechanisms on the BCZY/BCP bilayer membranes under wet synthetic air and wet diluted hydrogen. Our measurements confirm that the BCZY film blocks the electronic conductivity of BCP under wet synthetic air and protects it from CO2-containig atmospheres. Due to this set of properties, the BCZY/BCP bilayer membrane represents a possible candidate as electrolyte for PC-SOFC operating between 400 and 600 °C.

N-doped graphene hydrogels were prepared by crosslinking graphene oxide with ethylenediamine. These materials presented 10 at. % nitrogen, as determined by X-ray photoelectron spectroscopy. N-doped graphene was entangled within mesoporous matrices by diffusion of resorcinol-formaldehyde solutions throughout the hydrogels. According to nitrogen desorption isotherms, N-doping graphene slightly reduces the pore size and volume toward values closer to the graphene-free resins. The underlying graphene framework was observed within the amorphous porous carbon by transmission microscopy. These porous materials were impregnated with LiBH4 at 30, 50 and 70 vol %. Differential scanning calorimetry of the nanoconfined hydrides illustrates how N-doped matrix promotes a decrease in LiBH4 decomposition temperature, and this effect was quantified by volumetric studies. Powder diffraction revealed a peak at 12.6° attributed to the interaction of LiBH4 with the N-doped matrix. Owing to Yates analysis, N-doping lowers hydrogen release temperature by 10 °C, while at 325 °C the quantity released is increased by 1 wt %. This effect is more important than the diminution of pore size from 10 to 5 nm and compensates the presence of graphene. The benefit from N-doping is more remarkable for lower size of pores and higher LiBH4 filling, as illustrated by the proposed model.

In this work it is shown a precise way to optimize the heat generation in high viscosity magnetic colloids, by adjusting the Neel relaxation time in core/shell bimagnetic nanoparticles, for Magnetic Fluid Hyperthermia applications. To pursue this goal, Fe3O4/ZnxCo1-xFe2O4 core/shell nanoparticles were synthesized with 8.5 nm mean core diameter, encapsulated in a shell of ~1.1 nm of thickness, where the Zn atomic ratio (Zn/(Zn+Co) at%) changes from 33 at% to 68 at%. The magnetic measurements are consistent with a rigid interface coupling between the core and shell phases, where the effective magnetic anisotropy systematically decreases when the Zn concentration increases, without a significant change of the saturation magnetization. Experiments of magnetic fluid hyperthermia of 0.1 wt% of these particles dispersed in water, DMEM (Dulbecco modified Eagles minimal essential medium) and a high viscosity butter oil, result in a large specific loss power (SLP), up to 150 W/g, when the experiments are performed at 571 kHz and 200 Oe. The SLP was optimized adjusting the shell composition, showing a maximum for intermediate Zn concentration. This study shows a way to maximize the heat generation in viscous media like cytosol, for those biomedical applications that requiere smaller particle sizes .

Zirconia-based ceramics possess a wide range of relevant applications due to its unique mechanical, electrical and optical properties. On the one hand, ZrO2 has a high mechanical and chemical resistance, which is suitable as protective coating. On the other hand, yttria-stabilized zirconia (YSZ) is one of the main electrolyte materials for solid oxide fuel cells (SOFC) devices due to its high ionic conductivity at high temperatures. In this work, ZrO2 and YSZ thin films synthesized by sol-gel method and deposited by dip coating is studied. ZrO2 films are synthesized as coatings for Zircaloy rod spacer grids used for critical heat flux tests, while YSZ films are synthesized for non-electrolyte supported SOFC. Morphological characterization of these films is performed by SEM, while TEM and XRD provide insight on the crystallographic properties. Electrical properties of these materials are measured by conductivity experiments. Highly dense films with good adherence to substrates and thickness above 200 nm are achieved by this method. The nano grain size allows to obtain high symmetry phase stabilization, which enhance the desired properties in both materials for the proposed applications.

In this work, the characterization of ZrO2 thin films synthesized by the sol-gel method, using two different routes, is presented. Thin films were deposited by dip-coating on glass and Zircaloy-4 (Zry-4) substrates, and heat treated at 500 °C under atmospheric air. Characterization was carried out using X-Ray Diffraction (XRD), Grazing Incidence X-Ray Diffraction (GIXRD), High Temperature X-Ray Diffraction (HT-XRD), Raman Spectroscopy (RS), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Electrical properties of films were studied by conductivity measurements. These films present a thickness of 90 and 200 nm on glass, depending on the synthesis route, and consist of nanocrystals with predominantly tetragonal phase. On coated Zry-4, a non-uniform but dense ZrO2 layer without cracks grows, in contrast with the un-coated Zry-4, where a thicker layer was formed with the presence of micro-fissures. A GIXRD study showed that both tetragonal and monoclinic phases are present in the oxide layer. Conductivity measurements indicated that these films have excellent insulating properties, with resistivity values that exceed 0.5 M Ω.cm below 300 °C. These exceptional properties and the retention of high symmetry phases make this method very attractive for growing good electrical insulator and anti-corrosion ZrO2 thin film coatings.

In this work, we studied the cation occupancy of bimagnetic CoO/Co1−xZnxFe2O4 core/shell nanoparticles by means of X-ray absorption and Mossbauer spectroscopies, which provide element-sensitive information at the atomic scale. Our results indicate that, although the spinel ferrite forms a multi-grain shell, the Zn cations occupy solely tetrahedral sites, while the Co cations are mostly in the octahedral site. On the other hand, the Fe cations are distributed in both tetrahedral and octahedral sites for all concentrations. Also the results provide evidence for a Zn-deficient spinel with an excess of Co cations in the shell, whose origin is further rationalized in terms of the two-step synthesis process. In overall, this work gives a description of the cation occupancy in the core/shell nanoparticles and can serve as a guide to the interpretation of the magnetic properties of complex bimagnetic systems for future technological applications.

Oxides with proton conductivity have a great potential for applications in environmental energy technology. Despite the BaCe0.4Zr0.4Y0.2O3−δ (BCZY) perovskites being well-known proton conductors, it is a challenge to determine the optimal operating temperature range where the energy applications benefit most from this unique property. The protonic transport properties strongly depend on crystal structure and local distortions in the participating cation coordination sphere, according to related temperatures and gas feed. The transport and crystallographic properties of BCZY were simultaneously studied by impedance spectroscopy (IS) and synchrotron X-ray diffraction (S-XRD). A strong correlation between conductivity and the lattice parameter, corresponding in principle to a cubic symmetry, was observed, mainly between 400 and 700 °C. The protonic conductivity range was analyzed by the H/D isotopic effect on the impedance spectra, which helped to identify protonic conduction as the governing transport mechanism below 600 °C, while the transport via oxygen vacancies dominates above this temperature. In order to assess the real crystallographic structure, the simultaneous refinement of laboratory XRD and neutron diffraction (ND) patterns was performed. According to this, BCZY changes from rhombohedral symmetry below 400 °C to cubic at 600 °C in a second-order phase transition. Complementary quasielastic neutron scattering (QENS) enables us to determine a protonic jump length of 3.1 Å, which matches the O–O distances in the octahedral oxygen coordination sphere around the cations. These results support the protonic self-diffusion through proton hopping between intraoctahedral O sites as the main transport mechanism up to 600 °C., This work was supported by Agencia Nacional de Promocion de Ciencia y Tecnologia (ANPCyT) PICT-2016-2965 and PICT2014-1849, CONICET PIP-2015-0565, LNLS (Brazil), under proposals 20150099 and 20170278, and ILL (France) under proposal 7-03-168. L. Giebeler is grateful to the German Federal Ministry of Education and Research (BMBF) and the Argentinian Ministry of Science and Technology (MinCyT) for funding in the bilateral project DeFLeST (01DN14002). J. A. Alonso thanks the Spanish Ministry for Science, Innovation and Universities for funding the Project MAT2017-84496-R.

We report the precise control of tunneling magnetoresistance (TMR) in devices of self-assembled core/shell Fe$_3$O$_4$/Co$_{1-x}$Zn$_x$Fe$_2$O$_4$ nanoparticles ($0\leq x\leq 1$). Adjusting the magnetic anisotropy through the content of Co$^{2+}$ in the shell, provides an accurate tool to control the switching field between the bistable states of the TMR. In this way, different combinations of soft/hard and hard/soft core/shell configurations can be envisaged for optimizing devices with the required magnetotransport response., Comment: 25 pages, 7 figures

Mixed ionic and electronic conductor (MIEC) oxides have been proposed as candidates to replace Ni/YSZ composites as anodes for Solid Oxide Fuel Cells (SOFC) due to their good stability under C-based fuels. Some MIECs have also demonstrated a good electro-catalytic activity both for oxygen reduction and hydrogen oxidation, making them suitable for symmetric configurations (S-SOFC). This approach presents remarkable advantages for reducing manufacturing and operational costs, as well as for extending the cell’s lifetime by reversing gas flows and thus partially reversing the negative effects of sulphur poisoning and carbon deposition that may happen during operation. Also, the catalytic activity of MIEC electrodes can be improved by functionalizing the oxide surface with active nanoparticles. In this work, we study the formation of Ni-Fe alloy nanoparticles by exsolution from a Sr0.93(Ti0.3Fe0.63Ni0.07)O3-δ (STFN) perovskite in reducing atmospheres, and also the process of reoxidation when the exsolved material is exposed to an oxidizing atmosphere. The initial Sr-deficient composition was chosen to alleviate the segregation of Sr [1], which typically can occur in these materials. Exsolution has previously been reported to improve the electrochemical performance of STFN anodes [2], but the mechanisms underlying the exsolution process and the solid/gas interface are still not well understood. The possibility of using S-SOFC materials that undergo exsolution also raises the question of whether the material is regenerated during reoxidation. While oxidation-induced redissolution of exsolved nanoparticles has been observed for Fe-Co exsolution on La0.8Sr1.2Fe0.9Co0.1O4−δ perovskites [3], for the Ni-Fe exsolution in Sr2(Fe1.4Ni0.1Mo0.5)O6− δ, nanoparticles remained at the surface even after reoxidation [4]. The first case is a very interesting result to achieve larger cell lifetimes, and the latter case is interesting as it opens an additional route to increase the cathode performance. In fact, in ref. [5] Ni exsolution in SrTi0.1Fe0.85Ni0.05O3− δ is deliberately employed as design strategy, fully exploiting the non-reversibility of the exsolution of nanoparticles. However, it is not clear whether Ni-Fe nanoparticles oxidize to form a (Ni,Fe)Ox phase or if Fe is reincorporated into the lattice leaving only NiO particles at the surface. It is also not clear how Sr segregation is affected by the exsolution/reoxidation treatments, or how the reoxidized STFN perovskite is modified compared to the pristine sample. To address these questions directly, ambient pressure X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopy (AP-XPS and NEXAFS) is used to study the chemical structure of STFN in a complete redox cycle in-situ. Based on the measurements, we can provide insights into the chemical states of Fe and Ni and can differentiate the surface and bulk species for Sr and O in each stage of the cycle. We observe that Ni exsolves readily, but we also note that the amount of surface Fe0 increases with increasing H2 content in the reducing atmosphere; Fe0 also increases with the reduction time following an exponential trend until a plateau value is reached within ~1h. Further, we find a significant Sr segregation in reducing atmospheres, which we presume occurs to compensate for the B-site cation exsolution. The amount of Sr segregation remains constant in the nearest surface after reoxidation, but is partially reversed for larger penetration depths; there is also a rapid reversibility in the Fe oxidation state during reoxidation. These observations were complemented with transmission (TEM) and scanning electron microscopy (SEM) studies, with simultaneous energy dispersive spectroscopy (EDS) analysis. In conclusion, we propose a reoxidation-induced reconstruction which forms a Fe- and Sr-rich STF perovskite in the near-surface region, leaving the Ni segregated from the perovskite. Finally, we link the results to the electrochemical impedance spectroscopy (EIS) response of the STFN electrode, observing that this STFN-reoxidized sample shows a significant improvement in its cathode performance compared to the pristine STFN. [1] Fagg, D. P. et al, J. Eur. Ceram. Soc. 21, 1831–1835 (2001). [2] Zhu, T., Troiani, H. E., Mogni, L. V, Han, M. & Barnett, S. A. Joule 2, 478–496 (2018). [3] Zhou, J. et al. Chem. Mater. 28, 2981–2993 (2016). [4] Liu, T. et al. J. Mater. Chem. A 8, 582–591 (2020). [5] Yang, G., Zhou, W., Liu, M. & Shao, Z. ACS Appl. Mater. Interfaces 8, 35308-35314 (2016). Figure 1

In order to explore an alternative strategy to design exchange-biased magnetic nanostructures, bimagnetic core/shell nanoparticles have been fabricated by a thermal decomposition method and systematically studied as a function of the interface exchange coupling. The nanoparticles are constituted by a ∼3 nm antiferromagnetic (AFM) CoO core encapsulated in a ∼4 nm-thick Co1-xZnxFe2O4 (x = 0-1) ferrimagnetic (FiM) shell. The system presents an enhancement of the coercivity (HC) as compared to its FiM single-phase counterpart and exchange bias fields (HEB). While HC decreases monotonically with the Zn concentration from ∼21.5 kOe for x = 0, to ∼7.1 kOe for x = 1, HEB exhibits a non-monotonous behavior being maximum, HEB ∼ 1.4 kOe, for intermediate concentrations. We found that the relationship between the AFM anisotropy energy and the exchange coupling energy can be tuned by replacing Co2+ with Zn2+ ions in the shell. As a consequence, the magnetization reversal mechanism of the system is changed from an AFM/FiM rigid-coupling regime to an exchange-biased regime, providing a new approach to tune the magnetic properties and to design novel hybrid nanostructures. Fil: Lavorato, Gabriel Carlos. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Lima, Enio Junior. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Zysler, Roberto Daniel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Winkler, Elin Lilian. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

We report the critical current density Jc and the vortex dynamics in phase-separated Tl0.58Rb0.42Fe1.72Se2 crystals by performing magnetization measurements. Structural investigation reveals micro- and nanoscopic phase separation between 122 (superconducting) and 245 (not superconducting) phases. Micrometric phase separation refers to 245 islands with typical diameters of 2 µm embedded in a multiply-connected 122 superconducting network. Nanoscopic phase separation refers to 245 nanoprecipitates embedded in the 122 superconducting paths. The 245 nanoprecipitates with size comparable to the coherence length produce strong vortex pinning. It was observed that the temperature dependence of the flux creep rate presents a peak at intermediate temperatures and magnetic fields lower than 0.5 T. The peak is systematically suppressed as the magnetic field is increased, and it could be related with relaxation generated by double-kink excitations. Double-kinks are low-energy depinning excitations usually associated with strong pinning produced by correlated disorder. Fil: Haberkorn, Nestor Fabian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Condo, Adriana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Wang, Hangdong. Zhejiang University; China. Hangzhou Normal University; China Fil: Mao, Qianhui. Zhejiang University; China Fil: Fang, Minghu. Zhejiang University; China. Collaborative Innovation Center of Advanced Microstructures; China

UO2 nanoparticles doped with 4, 8, 10 and 15 wt% Gd2O3were synthesized by a reverse strike method. Crystal structure and chemical homogeneity were evaluated using a combination of X-ray diffraction and microscopy tools. An exhaustive study of the composition and its homogeneity at the micro and at the nanometer level was carried out in this nuclear fuel material. Field Emission Gun Scanning and Transmission Electron Microscopy images revealed the presence of micrometer scale agglomerates of nanoparticles, with rounded morphology and an average crystallite size of 100 nm. Rietveld refinements of high-statistic X-ray Diffraction data determined the crystal structure and composition. Furthermore, Energy Dispersive Spectroscopy using a 2 nm2 spot on the sample surface determined a Gd concentration variation around the average of ±5% in different spots of a single crystallite and of ±10% between different crystallites. However, when measuring large amounts of nanoparticles the concentration averages, producing a homogeneous composition distribution at the micrometer scale.

In this work, we have studied La0.4Sr0.6Co0.8Fe0.2O3-δ/Ce0.8Gd0.2O2-δ/La0.4Sr0.6Co0.8Fe0.2O3-δ symmetrical cells containing Ce0.8Gd0.2O2-δ electrolytes synthetized with and without the addition of cobalt as sintering aid. Electrochemical impedance spectroscopy results indicate that both electrolyte and cathode impedance response are affected by the addition of Co to the electrolyte, despite using cathodes with similar nano/microstructure according to scanning electron microscopy observations. Transmission electron microscopy characterization revealed the formation of columnar structures at the cathode/electrolyte interface of the cell with Co-doped electrolyte. These columnar structures would negatively affect the cell performance hindering the diffusion of oxide ions from the cathode to the electrolyte.

Transferring CVD graphene using surfactantprotectedAu nanoparticles (Au NPs) avoids the use of PMMAand opens new ways of building heterojunctions for TERS andSERS applications. Thermal treatment removes organics fromthe Au NPs and leads to larger nanoparticles and theformation of networks, dimmers, and nanoplates of variousshapes (circles, hexagons, and triangles). Raman and HRTEMrevealed bilayer graphene and Moirépatterns as determined bythe 2D band and dislocated atomic layers, respectively. TERS performed on the heterojunction exhibits a reversible increase infrequency and sharpening of the characteristic bands in graphene along with the exaltation of bands such as D + D′. A closeexamination into a single triangular-shape nanoplate reveals that the most irregular area of the nanoplate is consistent with thehigher Raman enhancement of Rh6G when compared to other areas of the same feature. This work may shed light onto newways of transferring graphene, fundamental aspects concerning local strains in the heterojunction, and SERS on a single Aunanostructure. Fil: Pérez, Luis Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Dalfovo, Maria Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Soldati, Analía Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Lacconi, Gabriela Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Ibañez, Francisco Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina

New LT-SOFC cathodes with La0.5-xPrxBa0.5CoO3-δ (0 ≤ x ≤ 0.5) compositions were studied. The La-rich compounds exhibit an inter-growing cubic and tetragonal structure whereas the Pr-rich show a tetragonal structure. Cathode polarization resistances, estimated from electrochemical impedance (EIS), take values around 0.15 and 0.04 Ω cm2 in air at 600 and 700 °C, respectively. The O2-reduction mechanism and its kinetic coefficients, O-ion diffusion (Dchem) and O-surface exchange (kchem), were studied by applying the ALS model for macro homogenous porous electrodes to the EIS data, in combination with microstructural parameters obtained from three-dimensional tomography using focused ion beam-scanning electron microscopy (3D FIB-SEM). The diffusion coefficients for samples with mixing of phases take values of Dchem ∼ 10-6 cm2 s-1, at 700 °C in air, whereas the pure tetragonal phases present lower values Dchem ∼ 10-8 cm2 s-1. On the contrary the kchem for all samples takes values ranging between 0.4 and 1 × 10-4 cm s-1 at 700 °C in air. In addition, the origin of time evolution of polarization at 700 °C in air was evaluated by combining the EIS spectra as a function of time and the ex situ sample characterization of fresh and tested samples by 3D FIB-SEM tomography and inductively coupled plasma-optical emission spectrometry (ICP-OES). Little changes of microstructures were detected, whereas an increasing of the amount of a water-soluble Ba surface species in comparison with total cation surface segregation was observed for all samples after the ageing. This may constitute the main reason causing the polarization resistance degradation. However, the analysis of time evolution shows, that contrary to the situations reported for SrO segregation in Sr-based perovskites, the Dchem is the coefficient mainly affected for compositions with inter-grown phases. At the same time, both Dchem and kchem decreases with time when only the tetragonal phase is present. Fil: Garcés, D.. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Wang, H.. Northwestern University; Estados Unidos Fil: Barnett, S.A.. Northwestern University; Estados Unidos Fil: Leyva, Adelma Graciela. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Napolitano, Federico Ricardo. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Fuentes, Rodolfo Oscar. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Mogni, Liliana Verónica. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina

A mixed conducting oxide with a nominal composition Sr(Ti0.3Fe0.7Ru0.07)O3-δ (STFRu) is studied, in comparison with SrTi0.3Fe0.7O3-δ (STF) oxide, as an anode for solid oxide fuel cells. Exposing STFRu to reducing fuel conditions at 800 °C for 4 h results in the exsolution of essentially all of the Ru and a small fraction of the Fe from the oxide, and the formation of Ru1-xFex nanoparticles on the oxide surfaces. Most of the nanoparticles have the hexagonal structure expected for Ru-rich alloys, and thermogravimetric analysis suggests the composition x ∼ 0.2. A small fraction of bcc-structure, presumably Fe-rich, nanoparticles are also detected. Comparison of cells with STFRu and STF anodes shows that the presence of Ru induces a reduced polarization resistance and increases the maximum power density under most cell operating conditions, particularly at lower temperatures and hydrogen partial pressures. For example, at 700 °C and 30% H2 fuel, the maximum power density is 0.1 W cm-2 for STF compared to 0.3 W cm-2 for STFRu. There is also a significant change in the shape of the current-voltage curves and the pH2-dependence of the anode polarization resistances RP,A ∝ (pH2)-m, from m ∼ 0.5-1.0 for STF to m ∼ 0.11-0.29 for STFRu; these suggest that Ru1-xFex nanoparticles improve anode performance by promoting hydrogen adsorption. Fil: Glaser, R.. Northwestern University; Estados Unidos Fil: Zhu, T.. Northwestern University; Estados Unidos Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina Fil: Caneiro, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. YPF - Tecnología; Argentina Fil: Mogni, Liliana Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina Fil: Barnett, S.. Northwestern University; Estados Unidos

Electrically conducting oxides have been proposed as alternatives to Ni-based cermet anodes for solid oxide fuel cells (SOFCs) to overcome issues such as coking and impurity poisoning, but their electrochemical performance is typically inferior to that of Ni-based cermets. Here we show that a new oxide composition, Sr0.95(Ti0.3Fe0.63Ni0.07)O3−δ, yields anode polarization resistance competitive with Ni cermets, and substantially better than that of the corresponding Ni-free compound, SrTi0.3Fe0.7O3−δ. Exposure to fuel results in exsolution and nucleation of Ni0.5Fe0.5 nanoparticles uniformly dispersed on the Ni-substituted perovskite surface, whereas no nanoparticles are observed on SrTi0.3Fe0.7O3−δ. A general thermodynamic model is developed that quantitatively predicts exsolved nanoparticle composition. The reduction in anode polarization resistance by the nanoparticles, by as much as 4 times, is most pronounced at cell operating temperatures below 800°C and low H2 partial pressures, suggesting that the nanoparticles improve performance by promoting H2 adsorption. Mixed conducting perovskite oxides are proposed as alternatives for solid oxide fuel cell anodes, and in situ metallic nanoparticle precipitation/exsolution is considered to improve their performance. However, understanding of exsolution is still lacking, such as the reason why specific cations exsolve from an oxide anode and what determines the exsolved phase composition under various anode conditions. Here we directly compare Sr(Ti,Fe)O3-based anodes with and without exsolved metallic nanoparticles, showing their impact on electrochemical characteristics especially under low anode hydrogen concentrations and low temperatures. Three different methods are used to quantitatively determine the composition of the exsolved (Ni,Fe) nanoparticles, and for the first time demonstrate that this can be achieved through thermogravimetric analysis. This work is the first to propose a detailed thermodynamic theory predicting the exsolved nanoparticle composition with successful experimental verification. Ni-Fe nanoparticles are observed to exsolve from Ni-substituted Sr0.95(Ti0.3Fe0.63Ni0.07)O3−δ anode. The exsolved nanoparticles act to enhance hydrogen dissociative adsorption, yielding much lower anode polarization resistance and higher cell performance, especially under low pH2 and temperatures, which is comparable with the current Ni-based cermets. Fil: Zhu, Tenglong. Northwestern University; Estados Unidos. Nanjing University of Science and Technology; China Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina Fil: Mogni, Liliana Verónica. Comisión Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Han, Minfang. Tsinghua University; China Fil: Barnett, Scott A.. Northwestern University; Estados Unidos

We report a fast method of producing rhodium-decorated platinum nanoparticles (NPs) containing iridium oxides (IrOx) to be used in the glycerol electrooxidation reaction. We synthesize PtIrOx/C electrocatalysts of different atomic compositions dispersed on Carbon Vulcan XC-72R® by using the fast polyol method assisted by microwaves. Afterwards, PtIrOx/C was potentiodynamically decorated by Rh (Rh/PtIrOx/C). The NPs are characterized by energy dispersive X-ray analysis, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. The electrooxidation of glycerol was investigated in acid medium by cyclic voltammetry and chronoamperometry. The electrochemical stability of Rh/PtIrOx/C NPs was evaluated by following a degradation test protocol, which consists in exhaustive cyclic voltammetries. Our results show that the presence of iridium oxides in the architecture of platinum enhances the electrochemical stability of the catalyst by avoiding agglomeration effects. Moreover, the presence of rhodium catalyzes the glycerol electrooxidation reaction. These results help understanding the role of Rh and IrOx in the glycerol electrooxidation and provide new insights for designing nanomaterials with improved stability and activity.

In this study we demonstrate that the effective coupling of the magnetic phases in core/shell nanoparticles can be promoted by an appropriate thermal annealing. In this way, the magnetization thermal stability of the hard ferrimagnetic CoFe2O4 oxide can be increased up to room temperature when coupled to a CoO antiferromagnetic core in an inverse core/shell structure. In addition, the results show that, being encapsulated in a ∼2 nm thick CoFe2O4 shell, the CoO core is successfully protected against oxidation which is crucial for the effectiveness of the magnetic coupling at the interface. Fil: Lavorato, Gabriel Carlos. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Lima, Enio Junior. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Zysler, Roberto Daniel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Winkler, Elin Lilian. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Lithium reactive hydride composite 2LiBH4 + MgH2 (Li-RHC) has been lately investigated owing to its potential as hydrogen storage medium for mobile applications. However, the main problem associated with this material is its sluggish kinetic behavior. Thus, aiming to improve the kinetic properties, in the present work the effect of the addition of Fe to Li-RHC is investigated. The addition of Fe lowers the starting decomposition temperature of Li-RHC about 30 °C and leads to a considerably faster isothermal dehydrogenation rate during the first hydrogen sorption cycle. Upon hydrogenation, MgH2 and LiBH4 are formed whereas Fe appears not to take part in any reaction. Upon the first dehydrogenation, the formation of nanocrystalline, well distributed FeB reduces the overall hydrogen storage capacity of the system. Throughout cycling, the agglomeration of FeB particles causes a kinetic deterioration. An analysis of the hydrogen kinetic mechanism during cycling shows that the hydrogenation and dehydrogenation behavior is influenced by the activity of FeB as heterogeneous nucleation center for MgB2 and its non-homogenous distribution in the Li-RHC matrix. Fil: Puszkiel, Julián Atilio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh; Fil: Gennari, Fabiana Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Centro Atómico Bariloche; Argentina Fil: Arneodo Larochette, Pierre Paul. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Centro Atómico Bariloche; Argentina Fil: Ramallo Lopez, Jose Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Vainio, U.. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh; . Deutsches Elektronen-Synchrotron; Alemania Fil: Karimi, F.. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh; Fil: Pranzas, P. K.. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh; Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Centro Atómico Bariloche; Argentina Fil: Pistidda, C.. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh; Fil: Jepsen, J.. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh; Fil: Tolkiehn, M.. Deutsches Elektronen-Synchrotron; Alemania Fil: Welter, E.. Deutsches Elektronen-Synchrotron; Alemania Fil: Klassen, T.. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh; Fil: Bellosta Von Colbe, J.. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh; Fil: Dornheim, M.. Helmholtz-zentrum Geesthacht - Zentrum Für Material- Und Küstenforschung Gmbh

In this work, we have focused on the size dependence of the magnetic properties and the surface effects of CoFe2O4 nanoparticles synthesized by high-temperature chemical method with diameter d~2, 4.5, and 7 nm, with narrow size distribution. transmission electron microscopy (TEM) images and X-ray diffraction (XRD) profiles indicates that samples with 7 and 4.5 nm present a high crystallinity while the 2 nm sample has a poor one. We have investigated by magnetization measurements and in-field Mössbauer spectroscopy the influence of the surface in the internal magnetic order of the particles. Particles with d=7 nm have almost single domain behavior and the monodomain occupies approximately the whole particle. In the sample with d=4.5 nm the surface anisotropy is large enough to alter the ferrimagnetic order in the particle shell. Then, a surface/volume ratio of ~60% is the crossover between a single domain nanoparticle and a frustrated order in a magnetic core-shell structure, due to the competition between surface anisotropy and exchange interaction+crystalline anisotropy in cobalt ferrite. In the d=2 nm sample the poor crystallinity and the large surface/volume ratio avoid the ferrimagnetic order in the particle down to T=5 K. Fil: Pianciola, Betiana Noelia. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Lima, Enio Junior. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Nagamine, Luiz C.C.M.. Universidade de Sao Paulo; Brasil Fil: Cohen, R.. Universidade de Sao Paulo; Brasil Fil: Zysler, Roberto Daniel. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina

Conjugation of optical and magnetic responses in a unique system at the nanoscale emerges as a powerful tool for several applications. Here, we fabricated bifunctional CoFe2O4-core/ZnO-shell nanoparticles with simultaneous photoluminescence in the visible range and ac magnetic losses suitable for hyperthermia. The structural characterization confirms that the system is formed by a ≈7 nm CoFe2O4 core encapsulated in a ≈1.5-nm-thick semiconducting ZnO shell. As expected from its high anisotropy, the magnetic losses in an ac magnetic field are dominated by the Brown relaxation mechanism. The ac magnetic response of the core/shell system can be accurately predicted by the linear response theory and differs from that one of bare CoFe2O4 nanoparticles as a consequence of changes in the viscous relaxation process due to the effect of the magnetostatic interactions. Concerning the optical properties, by comparing core/shell CoFe2O4/ZnO and single-phase ZnO nanoparticles, we found that the former exhibits a broader optical absorption and photoluminescence, both shifted to the visible range, indicating that the optical properties are closely associated with the shell-morphology of ZnO. Being focused on bifunctional nanoparticles with an optical response in the visible range and a tunable hyperthermia output, our results can help to address current open questions on magnetic fluid hyperthermia. Fil: Lavorato, Gabriel Carlos. Centro Brasileiro de Pesquisas Físicas; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Lima, Enio Junior. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Vasquez Mansilla, Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Zysler, Roberto Daniel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Winkler, Elin Lilian. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina

A scalable, simple, robust and reproducible method is presented for the preparation of chemically homogeneous and ordered nanocrystalline and mesoporous Zr1-xCexO2 thin films. The method utilizes widely available commercial block copolymers as templates. We show how the preparation conditions, film compositions and thermal treatments determine the mesoporous and crystalline structure. Through the scanning of the synthetic process, it was possible to arrive at an optimized and very reproducible method which allows the preparation of high quality, transparent, nanocrystalline and ordered Zr1-xCexO2 mesoporous thin films with different compositions. Fil: Violi, Ianina Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina Fil: Luca, Vittorio. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Soldati, Analía Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia de Área de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina Fil: Soler Illia, Galo Juan de Avila Arturo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área Investigaciones y Aplicaciones no Nucleares; Argentina. Universidad Nacional de San Martin. Instituto de Nanosistemas; Argentina Fil: Zelcer, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina

Anodes and cathodes of fuel cells are usually composed of metallic nanoparticles (NPs) dispersed on carbon, in order to increase their active area. Since the degradation of the catalyst affects the performance of the fuel cells, understanding the stability of its components is pivotal to make these systems more reliable. As such, graphene sheets and carbon nanotubes have been employed as alternative supports to improve the stability of anodes in fuel cells. In this context, we have used polyvinylpyrrolidone (PVP) combined with a one-step chemical reduction induced by ethylene glycol to synthesize Pd NPs dispersed on chemically converted graphene (CCG). We compared the electrochemical stability of Pd NPs supported on carbon black (C), multi-walled carbon nanotubes (MWCNTs) and CCG. MWCNTs and CCG make Pd NPs electrochemically more stable than carbon black. Pd/CCG catalysts are more stable than Pd/MWCNTs during the first potential cycles, while Pd/MWCNTs showed a higher long-term stability. These results allow us to consider a competition between agglomeration of NPs and degradation of the support, where the agglomeration seems to be limited by the available surface area of the support. Fil: Martins, Cauê A.. Universidade Federal do Mato Grosso do Sul; Brasil. Universidade Federal da Grande Dourados; Brasil Fil: Fernández, Pablo Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: De Lima, Fabio. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina Fil: Martins, María Elisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina Fil: Arenillas de la Puente, Ana. Instituto Nacional del Carbón; España. Consejo Superior de Investigaciones Científicas; España Fil: Gilberto, Maia. Universidade Federal do Mato Grosso do Sul; Brasil Fil: Camara, Giuseppe A.. Universidade Federal do Mato Grosso do Sul; Brasil

The Focused Ion Beam (FIB) technique was used to prepare site-specific samples from interfacial regions of different solid oxide fuel cells assemblies. Transmission and Scanning Electron Microscopy on the FIB foils combined with Electrochemical Impedance Spectroscopy (EIS) allowed the characterization of the electrode/electrolyte interphases and the determination of its influence on the cell performance after long-term operation conditions. This work reviews two cases: on one hand, Ln2NiO4+d (Ln= La, Nd) cathodes deposited on both Y0.08Zr0.92O1.96 and Ce0.9Gd0.1O1.95 electrolytes, that react at 900 °C during the adhesion treatment and at temperatures higher than 650 °C during the EIS measurements. These samples present a reaction layer of 10 nm thickness, which contains elements of both phases and was found responsible of the cell performance degradation. On the other hand, La0.4Sr0.6Co0.8Fe0.2O3-δ cathodes showed excelent performance on Ceria electrolytes, even after 1 000 h at operation conditions. In that case, the microscopic analyses of FIB foils showed a semi-coherent interphase growth. Fil: Soldati, Analía Leticia. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Montenegro Hernandez, Alejandra. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Baque, Laura Cecilia. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Mogni, Liliana Verónica. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Schreiber, Anja. Helmholtz-Zentrum Potsdam; Alemania Fil: Serquis, Adriana Cristina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

The Fe-rich corner of the Fe-Al-V system has shown phase separation into disordered A2 and ordered L21 phases. In a former work we model this ordering reaction by using ab-initio thermodynamics. The approach is now employed to suggest the Fe1-2xAlxVx alloys in order to reduce the Al content by increasing the addition of vanadium looking for a better ductility of the solid solution which can be afterwards strengthened by coherent L21 precipitates. Four alloys with compositions in the range 0.08 < X < 0.15 were studied. The phase transition temperatures and microstructures of the alloys were characterized by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM), respectively. The region (A2 + L21) occurs for 0.10 < X < 0.15 up to maximum temperature of 720 C, higher temperatures causes the appearance of (A2 + B2), B2 and (B2 + L21) regions. The microstructure in the (A2 + L21) region consists of nanosized precipitates of L21 phase in A2 matrix which morphology evolutes with temperature and ageing time. The hardness values, measured at room temperature, for the alloys with X < 0.125 and ageing temperature between 650 and 700 C are comparable to those obtained with other Fe-Al based alloys. Fil: Ferreirós, Pedro Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Materiales (CAC); Argentina. Universidad Nacional de San Martín. Instituto Sabato; Argentina Fil: Alonso, Paula Regina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Instituto Sabato; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Materiales (CAC); Argentina Fil: Gargano, Pablo Hugo. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Materiales (CAC); Argentina. Universidad Nacional de San Martín. Instituto Sabato; Argentina Fil: Bozzano, Patricia Beatriz. Universidad Nacional de San Martín. Instituto Sabato; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Materiales (CAC); Argentina Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina Fil: Baruj, Alberto Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina Fil: Rubiolo, Gerardo Hector. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Instituto Sabato; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Unidad de Actividad de Materiales (CAC); Argentina

Multiwall carbon nanotubes (MWCNT) with a diameter of 30e50 nm was added to the negative electrode of a NieMH battery in order to study the effect of its purification treatment on the electrochemical performance. Three different reflux assisted digestion methods were analyzed. MWCNT were structural characterized before and after purifications by means of different techniques such as HRTEM, EDS, SEM, XRD and FTIR. Subsequently they were incorporated into the working electrode to evaluate the electrochemical performance by charge/discharge cycling and rate capability. Fil: Benavides Castillo, Lisbeth Alexandra. Comisión Nacional de Energía Atómica. Gerencia del _rea Investigaciones y Aplicaciones No Nucleares. Gerencia de Física (cab). Grupo de Fisica de Metales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Cuscueta, Diego Javier. Comisión Nacional de Energía Atómica. Gerencia del _rea Investigaciones y Aplicaciones No Nucleares. Gerencia de Física (cab). Grupo de Fisica de Metales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Gerencia del _rea Investigaciones y Aplicaciones No Nucleares. Gerencia de Física (cab). Grupo de Fisica de Metales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Ghilarducci, Ada Albertina. Comisión Nacional de Energía Atómica. Gerencia del _rea Investigaciones y Aplicaciones No Nucleares. Gerencia de Física (cab). Grupo de Fisica de Metales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Salva, Horacio Ramon. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Increasing SOFC electrode's surface area by modification of its microstructure is a well-known technique to reduce electrode polarization resistance. This is because reduced grain size and increased porosity promote diffusion and surface reactions, thus improving the electrode performance. However, a modified microstructure also causes differences in phase stability and in chemical compatibility with other SOFC materials. In this work, we study the effect of particle size in both the electrode performance and the phase stability under different fuel conditions and temperatures. SrTi0.3Fe0.7O3−δ (STF) is both prepared via solid state reaction (STF-SSR) and also by an alternative sol-gel route (STF-SG). The sintering temperature is reduced dramatically with the sol-gel method, hence inducing a higher porosity and a much smaller grain size. As particle size is reduced the stability under fuel conditions is also diminished, so decomposition induced by segregation of metallic Fe and SrO occurs at lower temperatures for the STF-SG sample. The stability under reducing conditions is studied by combined techniques such as TGA, TPR, XRD, SEM and TEM. Performance as anode and cathode is evaluated by Electrochemical Impedance Spectroscopy (EIS) by using electrolyte supported symmetrical cells. Prior to electrochemical experiments, the reactivity between La0.8Sr0.2Ga0.8Mg0.2O3 (LSGM) electrolyte and STF was studied, and also between STF and a Lanthanum Doped Ceria (LDC) buffer layer. It is seen that microstructure also plays a key role in the chemical stability of the STF. The impact of particle size reduction is higher for the anodic polarization resistance, which is reduced twice from STF-SSR to STF-SG.

The exsolution of metal cations from oxides under reducing fuel conditions results in the formation of surface metallic nanoparticles, which can reduce Solid Oxide Fuel Cell anode polarization resistance. However, the loss of the B-site cations shifts the stoichiometry of the perovskite oxide. Depending on the amount exsolved and the initial stoichiometry, the exsolution can presumably shift the oxide away from its single-phase perovskite region. Herein, the direct comparison of initially stoichiometric composition Sr(Ti0.3Fe0.63Ni0.07)O3-δ (STFN0) with initially A-site deficient Sr0.95(Ti0.3Fe0.63Ni0.07)O3-δ (STFN5) is conducted and reported. X-ray diffraction along with scanning and transmission electron microscopy analysis of the oxides, which are both reduced at 850 °C in H2/H2O/Ar, shows a similar size and density of exsolved Fe–Ni alloy nanoparticles, albeit with slightly different alloy compositions. Whereas the oxide phase in reduced STFN5 shows a well-ordered perovskite structure, the greater B-site deficiency in reduced STFN0 results in a highly disordered and strained structure. The electrochemical performance of STFN0 anodes is inferior to that of STFN5 anodes, and even worse than SrTi0.3Fe0.7O3-δ (Ni-free) anodes. It appears that an initial Sr deficiency is important to avoid a too-high B-site deficiency after exsolution, which distorts the perovskite structure and impairs electrochemical processes.

In this research work, DEXTRAN- and polyethyl- ene glycol (PEG)-coated iron-oxide superparamagnetic nano- particles were synthetized and their cytotoxicity and biodistribution assessed. Well-crystalline hydrophobic Fe3O4 SPIONs were formed by a thermal decomposition process with d 5 18 nm and r 5 2 nm; finally, the character of SPIONs was changed to hydrophilic by a post-synthesis pro- cedure with the functionalization of the SPIONs with PEG or DEXTRAN. The nanoparticles present high saturation mag- netization and superparamagnetic behavior at room tempera- ture, and the hydrodynamic diameters of DEXTRAN- and PEG-coated SPIONs were measured as 170 and 120 nm, respectively. PEG- and DEXTRAN-coated SPIONs have a Spe- cific Power Absorption SPA of 320 and 400 W/g, respectively, in an ac magnetic field with amplitude of 13 kA/m and fre- quency of 256 kHz. In vitro studies using VERO and MDCK cell lineages were performed to study the cytotoxicity and cell uptake of the SPIONs. For both cell lineages, PEG- and DEXTRAN-coated nanoparticles presented high cell viability for concentrations as high as 200 lg/mL. In vivo studies were conducted using BALB/c mice inoculating the SPIONs intrave- nously and exposing them to the presence of an external magnet located over the tumour. It was observed that the amount of PEG-coated SPIONs in the tumor increased by up to 160% when using the external permanent magnetic as opposed to those animals that were not exposed to the exter- nal magnetic field. V C

Pure-phase La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM) nanocrystallites have been successfully synthesized by the combustion method, employing glycine as fuel and complexing agent, and ammonium nitrate as combustion trigger. A detailed morphological and structural characterization is performed, by using of X-ray diffraction, N2 physisorption and electron microscopy. The LSCM material consists in interconnected nanocrystallites (∼30 nm) forming a sponge-like structure with meso and macropores, being its specific surface area around 10 m2 g-1. Crystalline structural analyses show that the LSCM nanopowder has trigonal/rhombohedral symmetry in the R-3c space group. By employing the spin coating technique and quick-stuck thermal treatments of the ink-electrolyte, electrodes with different crystallite size (95, 160 and 325 nm) are built onto both sides of the La0.8Sr0.2Ga0.8Mg0.2O3-δ-disk electrolyte. To test the influence of the electrode crystallite size on the electrocatalytic behavior of the symmetrical cells, electrochemical impedance spectroscopy measurements at 800 ºC were performed. When the electrode crystallite size becomes smaller, the area specific resistance decreases from 3.6 to 1.31 Ω cm2 under 0.2O2-0.8Ar atmosphere, possibly due to the enlarging of the triple phase boundary, while this value increases from 7.04 to 13.78 Ω cm2 under 0.17H2-0.03H2O-0.8Ar atmosphere, probably due to thermodynamic instability of the LSCM nanocrystallites. Fil: Chanquia, Corina Mercedes. Comisión Nacional de Energía Atómica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Montenegro Hernandez, Alejandra. Comisión Nacional de Energía Atómica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Troiani, Horacio Esteban. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Física de Metales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Caneiro, Alberto. Comisión Nacional de Energía Atómica. Gerencia de Area de Aplicaciones de la Tecnología Nuclear. Gerencia de Investigación Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Solid oxide fuel cell performance is usually limited by high cathodic area specific resistance (ASR) at intermediate temperatures (500-700°C). ASR can be decreased by reducing particle size to nanometer range. This improvement is usually ascribed to the area/volume ratio increase and a higher concentration of active sites for the oxygen reduction reaction (ORR). Nevertheless, this solely explanation seems not to be enough for explaining the high electrochemical performance of some nanostructured La0.4Sr0.6Co0.8Fe0.2O3-d cathodes previously reported (Baqué et al., Electrochemistry Comm. 10 (2008) 1905-1908). Accordingly, the ORR of these cathodes was studied by electrochemical impedance spectroscopy (EIS) under air and under pure oxygen within the 400-700°C range. The nanostructure was characterized even at atomic level by transmission electron microscopy (TEM), revealing that the cathode is composed of nanocrystals surrounded by zones with some degree of crystalline disorder. These results suggest that this kind of nanostructure facilitate the ORR in this compound. Fil: Baque, Laura Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Technical University Of Denmark; Dinamarca Fil: Soldati, Analía Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina Fil: Schreiber, Anja. Helmholtz Gemeinschaft; Alemania Fil: Caneiro, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina Fil: Serquis, Adriana Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina

Carbon supported Pt nanoparticles (NPs) have been prepared through polyols method using PVP. As observed with a large number of surfactants employed in NPs synthesis, it is very difficult to attain an efficient NPs cleaning, which is a fundamental requirement in catalysis researches. The aim of this paper was to obtain clean NPs, beginning by using “soft” methods, in order to keep unaltered both the NPs size and shape; however, an important surfactant remnant was observed. Consequently, it was performed an electrochemical cleaning through PVP and glycolate electro-oxidation, being accompanied with important perturbations of NPs atoms and dissolution and re-deposition of Pt. Finally, the performance of the catalyst towards the glycerol electro-oxidation reaction (GER), before and after the cleaning process was studied. In addition, we demonstrate how the impurities bring about poor reproducibility in this kind of experiments due to the fact that the cleaning process is occurring at the same time that the GER and because cleaning extent along cycles varies for each independent experiment. Fil: Fernández, Pablo Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; Argentina Fil: Ferreira, Dênis S.. Universidade Federal Do Mato Grosso Do Sul; Brasil Fil: Martins, Cauê A.. Universidade Federal Do Mato Grosso Do Sul; Brasil Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina Fil: Câmara, Giuseppe A.. Universidade Federal Do Mato Grosso Do Sul; Brasil Fil: Martins, María Elisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; Argentina

Gold nanoparticles (NP) were synthesized inside ordered mesoporous TiO2 thin films (MTTF) by stepwise reduction of AuCl4 − with NaBH4. This leads to an optical material (Au@TiO2) of interest for plasmonic applications. The films (pure titania or gold-titania nanocomposites) were thoroughly characterized by UV−visible and ellipsometry spectroscopies. The dielectric function of the MTTF, considered as the dielectric environment in which the NP are embedded, was acquired by ellipsometry and rationalized by the asymmetric Bruggeman model as an effective medium formed by the mixture of dense TiO2 and air. Nanocomposite Au@TiO2 systems present an isotropic dispersion of Au NP in the 5−8 nm range. The UV−visible spectra obtained with a low nanoparticle filling fraction of the pore volume (f NP < 2%) are accurately reproduced by both Maxwell−Garnett (MG) and Mie theories. Accurate and coincident values of f NP and NP size are obtained by this method. The dielectric function of Au NP used in this work was studied in detail; in particular, the interface damping parameter related to the NP/MTTF interface was determined by comparison with TEM microscopy. The potential of the ellipsometry technique to determine the material plasmonic response, and its correspondence with the UV−visible spectra, are discussed. This spectroscopy technique opens the possibility to study the plasmon response of the material to changes in the environment due to the presence of vapors, and other in situ experiments, as well as to provide nanostructural information of metallic nanoparticles (NP size, interparticle distance, number of NP) with well-defined spatial localization in a multilayered system. Fil: Sanchez, Veronica Muriel. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Martínez, Eduardo David. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Martinez Ricci, Maria Luz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Troiani, Horacio Esteban. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Soler Illia, Galo Juan de Avila Arturo. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

This paper presents a project to study the effect of lead factors on the mechanical behaviour of the SA-508 type 3 Reactor Pressure Vessel (RPV) steel used in the reactor under construction Atucha II in Argentina. Charpy-V notch specimens of this steel were irradiated at the RA1 experimental reactor at a temperature of 275 C with two lead factors (186 and 93). The neutron flux was 3.71 1015 n m2 s1 and 1.85 1015 n m2 s1 (E > 1 MeV) respectively. In both cases, the fluence was 6.6 1021 n m2 , which is equivalent to that received by the PHWR Atucha II RPV in 10 years of full power irradiation. The results of Charpy tests revealed significant embrittlement both in the DT = 14 C and DT = 21 C shifts of the ductile–brittle transition temperatures (DBTT) and in the reduction of the maximum energy absorbed. This result shows that the shift of the DBTT with a lead factor of 93 is larger than that obtained with a lead factor of 186. Then, the results of irradiation in experimental reactors (MTR) with high lead factors may not be conservative with respect to the actual RPV embrittlement. Fil: Kempf, Rodolfo. Comision Nacional de Energia Atomica. Gerencia Quimica. CAC; Argentina Fil: Troiani, Horacio Esteban. Comision Nacional de Energia Atomica. Gerencia del Area de Investigaciones y Aplicaciones no Nucleares. Gerencia de Fisica (CAB); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Energía Nuclear. Instituto Balseiro; Argentina Fil: Fortis, Ana María. Universidad Nacional de San Martín; Argentina. Comision Nacional de Energia Atomica. Gerencia Quimica. CAC; Argentina

International audience; In the past decade, the surprising magnetic behavior of gold nanoparticles has been reported. This unexpected property is mainly attributed both to size and surface effects. Mesoporous thin films are ideal matrices for metallic nanoparticles inclusion, because of their highly accessible and tailorable pore systems that lead to completely tunable chemical environments. Exploiting these features, we synthesized Au nanoparticles within mesoporous titania thin films (film thickness of ∼150 nm and pore diameter of ∼5 nm), and we studied their magnetic properties under confinement. Here, we present the results of the magnetization as a function of temperature and magnetic field for this system, which are consistent with the previously reported for free (unconfined) thiol-capped gold nanoparticles. The successful inclusion of stable magnetic Au nanoparticles within transparent mesoporous thin films opens the gates for the application of these nanocomposites in two-dimensional (2D) microdevices technology and magneto-optical devices.

Bimagnetic nanoparticles have been proposed for the design of new materials with controlled properties, which requires a comprehensive investigation of their magnetic behavior due to multiple effects arising from their complex structure. In this work we fabricated bimagnetic core/shell nanoparticles formed by an $\ensuremath{\sim}3$-nm antiferromagnetic (AFM) CoO core encapsulated within an $\ensuremath{\sim}1.5$-nm ferrimagnetic (FiM) ${\mathrm{Co}}_{0.5}{\mathrm{Ni}}_{0.5}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ shell, aiming at studying the enhancement of the magnetic anisotropy and the surface effects of a ferrimagnetic oxide shell. The magnetic properties of as-synthesized and annealed samples were analyzed by ac and dc magnetization measurements. The results indicate that the magnetic response of the as-synthesized particles is governed by the superparamagnetic behavior of the interacting nanoaggregates of spins that constitute the disordered ferrimagnetic shell, whose total moments block at $\ensuremath{\langle}{T}_{B}\ensuremath{\rangle}=49$ K and collectively freeze in a superspin-glass-type state at $\ensuremath{\langle}{T}_{g}\ensuremath{\rangle}=3$ K. On the other hand, annealed nanoparticles are superparamagnetic at room temperature and behave as an exchange-coupled system below the blocking temperature $\ensuremath{\langle}{T}_{B}\ensuremath{\rangle}=70$ K, with enhanced coercivity ${H}_{C}(10\phantom{\rule{4.pt}{0ex}}\text{K})\ensuremath{\sim}14.6$ kOe and exchange bias field ${H}_{EB}(10\phantom{\rule{4.pt}{0ex}}\text{K})\ensuremath{\sim}2.3$ kOe, compared with the as-synthesized system where ${H}_{C}(10\phantom{\rule{4.pt}{0ex}}\text{K})\ensuremath{\sim}5.5$ kOe and ${H}_{EB}(10\phantom{\rule{4.pt}{0ex}}\text{K})\ensuremath{\sim}0.8$ kOe. Our results, interpreted using different models for thermally activated and surface relaxation processes, can help clarify the complex magnetic behavior of many core/shell and hollow nanoparticle systems.

We present a crystallographic, morphologic and redox dynamic study on (60:40) NiO/Ce0.9Gd0.1O1.95 (NiO/GDC) cermets simulating Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC) anodes in situ conditions. We tested micro- and nanometer sized materials at 700ºC in three different atmospheres (5% H2, 5% O2 and 20% CH4). We used Dispersive X-ray Absorption Spectroscopy (DXAS) analysisat the Ce L3-edge and at the Ni K-edge to follow the metal´s oxidation states. A correlation between the catalytic/redox properties and the sample´s characteristics (microstructure, Ni distribution, etc.) was found, indicating that nanometric sized particles showed faster and higher reduction extents than micrometric particles of the same composition. Fil: Fernandez Zuvich, Afra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: 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 de Buenos Aires. Facultad de Ingeniería. Departamento de Ingeniería Química. Laboratorio de Procesos Catalíticos; Argentina Fil: Saleta, Martin. Laboratório Nacional de Luz Síncrotron; Brasil Fil: Napolitano, Federico Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Caneiro, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Lamas, Diego Germán. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Arce, Mauricio Damián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Serquis, Adriana Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Soldati, Analía Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina

One of the remaining challenges for the solid oxide fuel cell (SOFC) technology is decreasing its operation temperature to the 500-800 °C range in a cost-effective way without diminishing the cell performance. In this work, we studied a symmetrical cell composed of Sr0.6La0.4Co0.8Fe0.2O3-δ (LSCFO) cathodes deposited on a Ce0.8Y0.2O2-δ (CYO) substrate by the simple, cost-effective and scalable spin coating technique. The nanostructured cathode is composed of agglomerated ∼100-200 nm particles with ∼50 nm crystallite size. Electrochemical impedance spectroscopy (EIS) analysis indicates that electrolyte grain boundary conductivity strongly depends on the cathode nature. The detailed high resolution transmission electron microscopy (HR-TEM) characterization of the LSCFO/CYO interface reveals that the LSCFO cathode is well adhered to the CYO electrolyte. The improved nano/microstructure of the cathodes and the cathode/electrolyte interface yields to cathode area specific resistance (ASR) values as low as 0.4 Ωcm2 at 550 °C, being these values even lower than those previously reported in literature for cathodes in optimized LSCFO/CYO/YSZ/CYO/LSCFO cells. Fil: Baque, Laura Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Padmasree, K.P.. Centro de Investigación y de Estudios Avanzados; México Fil: Ceniceros Reyes, M.A.. Centro de Investigación en Química Aplicada; México Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Serquis, Adriana Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Soldati, Analía Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina

Uniform polycrystalline SnO2 microtubes formed by sintered nanoparticles (fixed to a surface or in free standing form) were obtained with the infiltration technique using SnCl4 as precursor and a porous polycarbonate (PC) film as template. The advantage of this synthesis method was based on its simplicity, reproducibility, low cost, and the possible applicability to other complex oxides. The morphology and crystal structure of SnO2 tubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The crystalline sizes of the nanoparticles assembled in the tube walls obtained at 600 °C were in the range of 5–7 nm, calculated from both the XRD and the TEM data. The length of the microtubes fixed to a silicon nitride surface ranged between 2 and 7 μm. Sensors fabricated with this material showed unusual sensitivity to ethanol at room temperature and fast reversible response, as compared to those obtained by the deposition of metallic tin film and further oxidation (Rheotaxial Growth and Thermal Oxidation method).

This paper analyses the synergetic effect of the coupled addition of Co particles (Co, 5 wt%) and pure multi-walled carbon nanotubes (MWCNTs, 5 wt%) on hydrogen sorption kinetics of MgH2 (M). Experimental results show that MCo co-milled 50 h plus admixed MWCNTs for 5 h exhibits enhanced absorption/desorption performance, which remains stable after 15 hydrogen sorption cycles. About 6.5 wt% of hydrogen was absorbed after 100 s and desorbed in 85 min at 250 °C, being one of the best conditions reported for Mg-based composites. Furthermore, desorption temperature after cycling was reduced by 55 °C due to the introduction of Co, and 136 °C by the combined Co and MWCNT addition as compared to free MgH2. Activation energy analysis demonstrates that although the MWCNT addition has a slight influence on the energy barrier, the Co particles show a good catalytic effect. Moreover, the coupled effect of Co and MWCNTs reduces the activation energy and it is maintained after cycling. As a consequence of cycling, some nanograins of MgH2 appear covered with a thin external layer of amorphous carbon while some part of the MWCNTs remains intact in the material. An interpretation of the kinetics effect of Co particles and MWCNT coupled addition is proposed.

In this work we successfully applied a FIB/lift-out technique to prepare site-specific thin samples containing the cathode/electrolyte interface between two La0.4Sr0.6Co0.8Fe0.2O3-δ (LSCF) / Ce0.9Gd0.1O2-δ (CGO) half cells. Despite different cathode thickness (15 μm and a 5 μm), both samples presented similar composition and nanostructure. However, an exhaustive microscopic analysis by SEM and TEM at high resolution modes, revealed that: the 15 μm sample presented a perfectly attached interface, while the other showed pores at the interfacial boundary, decreasing the real LSCF/CGO contact. In this way we could explain part of the difference in area specific resistance between measured between them.

This paper presents a study of the mechanical properties of pseudoelastic Cu-Zn-Al foams. Foams of different densities were cycled in compression. The paper shows the retained/dissipated energy by the material, i.e. the area of the compression cycle, as a function of the material density. The frequency and strain amplitude, usual parameters that may influence the damping properties, are studied by evaluating the dissipated energy and the specific damping capacity. Samples cyclically tested under constrained compression conditions show a remarkable mechanical stability and reproducibility. The material does not appreciably degrade after 1000 compression cycles at room temperature. We emphasize the material does not need any thermomechanical processing or training treatment in order to present the mechanical properties detailed in the present paper.

In this work, the mechanical behavior of Fe–28Mn–6Si–5Cr (wt.%) shape memory alloy subjected to a simple thermomechanical treatment consisting in rolling at 600 °C and subsequent aging at 800 °C for 10 min is studied. Martensite can be stress-induced in this material up to 110 °C. No stress-induced martensite was detected at temperatures above 150 °C. Extrapolating the mechanical testing data a yield stress for the austenite at room temperature σ y = 450 MPa was calculated. In addition, a relatively large pseudoelastic behavior was observed at the temperature range between 90 and 110 °C. This effect is discussed on the basis of the formation of stacking faults and the reversible movement of their associated partial dislocations.

Magnetic properties of a single nanotube whose walls are constituted by nanograins of La2/3Sr1/3MnO3 are studied by means of Monte Carlo (MC) simulation. The system is considered as composed by ferromagnetic grains which couple via dipolar interaction. The grain size distribution is obtained from experimental measurements and the inter-grain distance distribution is obtained from a study of distance distribution among magnetic particles distributed in the tube walls. We show the magnetization behavior for a tube of 700 nm of diameter and 3.5 μm length. We discuss the simulation for different temperatures and external fields. As a main result, we show that the distribution of inter-granular distances has a unique behavior for tubular structures of similar diameter/length aspect ratio, independent of their sizes. This scaling relation allows us to perform the simulations using a tube of smaller dimensions. We succeed in explaining the magnetization curves, finding that dipolar interaction is necessary to explain the experimental behavior and that the grains behave as having magnetic dead layers.

This work reports the preparation, characterization and applications of silver nanoparticles synthesized through the chemical reduction of AgNO3 and protected by surface modifier. In order to characterize the formation of nanoparticles and the role of synthesis parameters (time, temperature) several studies were made, such as UV–vis spectroscopy, TEM and AFM. We present the incorporation of Ag nanoparticles in sol–gel obtained matrix, because this technique allows the incorporation of larger concentrations of active optical agents and the obtainment of full-dense films at lower temperature than those possible by other methods. The final goal of this work is the preparation of 80SiO2·20B2O3 films for active optical waveguides doped with Ag nanoparticles and Erbium. We are looking for the reinforcement of the fluorescence intensity due to the effect of the resonant coupling of both optical agents (Er and nanoparticles) to produce optical amplifiers.

In this work, we present a characterization of a hybrid nanocomposite constituted by vanadium oxide (VO x )/ hexadecylamine (Hexa) and the effect of the addition of Ni ions on the magnetic properties. Micrographs of transmission electron microscopy (TEM) show that the nanostructures are multiwall nanotubes. The walls are constituted by the successive intercalation of VO x and Hexa layers. The number of vanadium atoms and the ratio Ni/V were measured by instrumental neutron activation analysis (INAA) and by energy dispersive spectroscopy (EDS), respectively. Measurements of electronic paramagnetic resonance (EPR) and DC magnetic susceptibility, as a function of temperature, reveal that the Ni doping reduces considerably the amount of V 4+ present in the system.

Nanoparticles assembled into nanostructures (NAN) of manganese perovskite oxides for different compositions and diameters have been synthesized following a template-assisted method. We discuss the relationship among geometrical, structural and nanostructural parameters observed when synthesizing LaMnO3, La0.66Sr0.33MnO3, La0.66Ca0.33MnO3 and La0.325Pr0.300Ca0.375MnO3 manganite based complex oxides. For all the studied compounds, the structures are composed of an assembly of small (some few tens of nanometers) grains. They form nanotubes above some threshold diameter of the template, and nanowires below it. Here we focus on the correlation between grain size and the diameter at which the tube to wire crossover occurs. The threshold for this tube to wall crossover seems to depend on the specific compound. We present evidence from TEM observations that allow a rationalization of several phenomena in the synthesis process. Fil: Leyva de Guglielmino, Ana Gabriela. Universidad Nacional de San Martín; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina Fil: Troiani, Horacio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina Fil: Curiale, Carlos Javier. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina Fil: Sanchez, Rodolfo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Levy, Pablo Eduardo. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Advanced Functional Materials Vol. 17 (8), p. 1247 - 1254, Environment-sensitive Bragg reflectors are built using functional mesoporous thin films as building blocks. Tuning of optical properties is achieved by changing the composition or porosity of the slabs or the introduction of planar defects. Sorption or capillary condensation of molecules into the pore system results in a 10-40 nm photonic bandgap (PBG) shift. Organic functions added to the pore surface change the response, permitting tailoring of the selectivity towards small-size molecules.