Microtubular SOFC based on an extruded support

Trabajo presentado al "IV Iberian Symposium on Hydrogen, Fuel Cells and Advanced Batteries" celebrado en Estoril (Portugal) del 26 al 28 de junio de 2013.In this work the processing route for an anode supported microtubular solid oxide fuel cell is adjusted. The fuel cell composition and microstructure design is based on previous work. In this work we have developed microtubular cells based on an extruded support. Firstly, Ni-YSZ anode was manufactured by Powder Extrusion Moulding (PEM). Feedstock composition and extruding parameters were adjusted to obtain tubular green bodies. An YSZ layer was then deposited as the electrolyte and the sintering parameters were optimized to obtain a dense layer. An active area of ~1 cm2 LSMYSZ was deposited as the cathode and its electrochemical performance was measured using pure hydrogen as fuel, yielding a power output at 0.5V of 0.7Wcm-2 at 8500C.Authors would like to thank financial support received from MICINN and Feder program of the European Community (MAT2010-19837-C06 and MAT2012-30763 projects), Madrid regional government (MATERYENER S2009 PPQ-1626 program), and also grant GA-LC-035/2012, financed by the Aragón Government and La Caixa Foundation.Peer Reviewe

High-performance Ni-YSZ thin-walled microtubes for anode-supported solid oxide fuel cells obtained by powder extrusion moulding

Aiming at the fabrication of microtubular anode-supports for Solid Oxide Fuel Cell (SOFC) applications, this contribution deals with the production of Ni-YSZ thin-walled tubes (<1 mm thickness) via Powder Extrusion Moulding (PEM). The overall method has been optimized with an emphasis on the effect of NiO particle size using two commercial NiO powders with mean sizes of 0.7 and 8 μm. A thermoplastic binder system based on polypropylene (PP), paraffin wax (PW) and stearic acid (SA) in volume ratios of 50, 46 and 4, respectively, was used along with corn starch as a pore forming agent. Different feedstocks with solid loadings varying from 45 to 65 vol% were processed and characterized to determine the optimal formulation. Typically, the mixtures exhibited a pseudoplastic behaviour from 100 to 1000 s. Feedstocks with finer NiO particles had the most balanced properties for PEM purposes and an optimal powder volume content of 65 vol% was established. After extrusion and debinding steps, defect-free and constant cross-section tubes with 15 mm of length and 4 mm of nominal diameter were obtained. The final microstructure and DC conductivity were found to be closely linked to the NiO particle size, yielding a higher degree of open porosity and a better performance when using finer NiO powder. Based on this study, the packing mechanism was found to be likely limited by the contribution of steric hindrances when dissimilar and coarse powders are mixed, which may play a decisive role in order to set tailored formulations.Authors would like to thank financial support received from MICINN and Feder program of the European Community (MAT2013-46452-C4-3R and MAT2012-30763 projects), and Madrid regional government (MATERYENER3CM S2013/MIT-2753 Program).Peer Reviewe

High-capacity Li4Ti5O12-C thick ceramic electrodes manufactured by powder injection moulding

Lithium-ion batteries are the most efficient electrochemical energy storage devices. However, there is still room for improvement in terms of safety and energy density, presently limited by conventional tape-casting electrode processing. In this study, a blend of the anodic material Li$_{4}$Ti$_{5}$O$_{12}$ with 2 wt% carbon black has been processed through powder injection moulding (PIM) yielding, after subsequent debinding and sintering processes, to ultra-thick (>500 µm) ceramic binder-free electrodes. The mixture of Li$_{4}$Ti$_{5}$O$_{12}$ with the thermoplastic binder composed of polypropylene, paraffin wax, and stearic acid is investigated to identify a rheologically suitable feedstock for the PIM process. The resulting disk-type green parts contain 50 vol% of ceramic powder. After removing the binder with solvents and subsequent thermal treatment, the parts are sintered at 900 °C, aiming for a relatively high porosity, i.e., 25.7%. The resulting electrodes show very high areal and volumetric capacities up to 26.0 mA·h·cm−2 and 403 mA·h·cm−3 at C/24, respectively, in a half-cell against lithium metal

Microstructure, magnetic and mechanical properties of Ni-Zn ferrites prepared by Powder Injection Moulding

Nowadays, the electronic industry demands small and complex parts as a consequence of the miniaturization of electronic devices. Powder injection moulding (PIM) is an emerging technique for the manufacturing of magnetic ceramics. In this paper, we analyze the sintering process, between 900 °C and 1300 °C, of Ni–Zn ferrites prepared by PIM. In particular, the densification behaviour, microstructure and mechanical properties of samples with toroidal and bar geometry were analyzed at different temperatures. Additionally, the magnetic behaviour (complex permeability and magnetic losses factor) of these compacts was compared with that of samples prepared by conventional powder compaction. Finally, the mechanical behaviour (elastic modulus, flexure strength and fracture toughness) was analyzed as a function of the powder loading of feedstock. The final microstructure of prepared samples was correlated with the macroscopic behaviour. A good agreement was established between the densities and population of defects found in the materials depending on the sintering conditions. In general, the final mechanical and magnetic properties of PIM samples were enhanced relative those obtained by uniaxial compaction

Fabrication of Ni-YSZ tubes by powder extrusion moulding for SOFC anodes

Resumen del trabajo presentado al "IV Iberian Symposium on Hydrogen, Fuel Cells and Advanced Batteries" celebrado en Estoril (Portugal) del 26 al 28 de junio de 2013.Peer Reviewe

Thermal and mechanical characterization of injection moulded high density polyethylene/paraffin wax blends as phase change materials

Thermal and mechanical properties of blends based on high density polyethylene and paraffin wax were investigated. The blends were prepared from 5 to 50vol. % of paraffin wax employing a twin-screw extruder. Thermal behaviour of samples was determined by differential scanning calorimetry, thermogravimetric and dynamic mechanical analyses. A displacement of melting temperature of polyethylene was detected as a consequence of the plasticization effect of wax. These results revealed that melting temperatures and latent heats of samples are suitable for their application as phase change materials. Blends were processed by injection moulding which is an advantageous method to obtain pieces of this kind of materials. The evolution of loss tangent versus temperature of injected samples showed the lack of miscibility between the components of the blend. Tensile tests were carried out to characterize the mechanical strength of blends. Elongation at break decreased as paraffin wax content increased, and Young's modulus decreased with wax content but in the case of blends with a 30vol. % of wax and more, brittle rupture occurred and no yield point was observed.MICINN (MAT2010-19837-CO6 project) and Madrid regional government (MATERYENER S2009 PPQ-1626 program)Scopu

Tratamiento mecanoquímico de la ferrita MgFe₂O₄

Powder of MgFe2O4, previously prepared by solid state reaction, was mechanochemically treated in a centrifugal ball mill in air atmosphere. Different milling conditions has been employed varying ball/powder mass ratio. After low milling time a strong reduction on crystallite size has been detected while the strain lattice increase slowly. The presence of α-Fe2O3 was also observed at different milling time, depending on milling conditions, by means of X-Ray diffraction experiments. Magnetic transition temperatures were evaluated using a thermogravimetric analyser, equipped with a small permanent magnet. An attempt of dependence of magnetic properties with crystallite size has been established.<br><br>La ferrita MgFe2O4, en forma de polvo y previamente preparada por reacción en estado sólido, se ha sometido a un proceso de molienda mecánica en atmósfera de aire usando un molino centrífugo. Se emplearon diferentes condiciones de molienda variando la relación de peso bolas/ferrita. La variación del tamaño de dominio cristalino o de cristalita y lamicrodeformaciones de red a escala de celda unidad se evaluaron mediante difracción de rayos-X de polvo. Para bajos tiempos de molienda se observó una acusada disminución del tamaño de dominio cristalino, mientras que las microdeformaciones de la red experimentaron un ligero aumento. Así mismo, a partir de determinados tiempos de molienda, se detectó la presencia de α-Fe2O3. Las temperaturas de transición magnética fueron evaluadas a partir de un analizador termogravimétrico equipado con un pequeño imán permanente y se estableció un correlación entre la temperatura de Curie y el tamaño de dominio cristalino

Sodium Polymer Electrolytes Based on Sulfonated Polysulfone (SPSU-Na) towards Post Li-Ion Batteries

International audienc

DABCO-functionalized polysulfones as anion-exchange membranes for fuel cell applications: Effect of crosslinking

A series of DABCO-functionalized polysulfones were synthesized and characterized. The effect that crosslinking has on the membrane properties containing different degrees of functionalization was evaluated. These polymers showed good thermal stability below the fuel cell operation temperature, T < 100 °C, reflected by the T, T, and thermal durability. The water uptake increased as the percentage of DABCO groups increased and the crosslinked membranes showed lower capacity to absorb water than the non-crosslinked ones favoring thus the dimensional stability of the first ones. Membranes in the chloride form containing low degree of functionalization exhibited the highest tensile strength values. The ionic conductivity of non-crosslinked membranes varied as a function of the functionalization degree until a value of around 100% achieving a maximum value at 86%. However, the crosslinked ones showed satisfactory ionic conductivities for values higher than 100%. The behavior of these polymeric materials in alkaline solutions revealed a great alkaline stability necessary to be used as solid electrolytes in fuel cells. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1326–1336.We thank Professor Alejandro Varez for fruitful discussion. This work has been supported by the Projects MATERYENER3CM S2013/MIT-2753 of Comunidad de Madrid, MAT2013-46452- C4-3R of MINECO (Spanish Government), and S2013/MAE- 2975 PILCONAER of Comunidad de Madrid and European Social Fund (ESF).Peer Reviewe

A comparison of La0.8Sr0.2MnO3-δ, La0.6Sr0.4Co0.2Fe0.8O3-δ and Pr2NiO4+δ cathodes on the performance of anode supported microtubular cells

Trabajo presentado al: "11th European SOFC & SOE Forum" celebrado en Lucerne (Suiza) del 1 al 4 de julio de 2014.The performance of YSZ-Ni supported microtubular solid oxide fuel cells (mT-SOFCs) with thin YSZ electrolyte and three different cathodes: La0.8Sr0.2MnO3-δ (LSM), La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) and Pr2NiO4+δ (PNO) is compared. The mT-SOFC cells were fabricated using NiO-YSZ support precursors manufactured by Powder Extrusion Moulding (PEM). The YSZ layer was deposited by dip coating. The electrolyte deposition parameters and the sintering parameters were optimized to obtain a dense and thin layer. Three different cathode materials, LSM, LSCF and PNO were then deposited by dip coating. To circumvent reactivity at the sintering temperatures between LSCF and PNO with the YSZ electrolyte, barrier layers were also deposited. Electrochemical characterization under the same fuelling conditions for all the three cells was performed. The results are discussed and compared. As for example, the cell with a LSM-YSZ cathode presented a power density at 0.5V and 850 °C of 0.7 Wcm-2 with an ASR (area specific resistance) at OCV (open circuit voltage) of _0.9 Ωcm2. Similar performance was obtained when using LSCF or PNO cathodes at about 750 ºC, allowing for a significant reduction of the operation temperature of these mT-SOFCs.Authors also acknowledge grant MAT2012-30763 financed by the Spanish Government (Ministerio de Ciencia e Innovación) and Feder program of the European Community, for funding the project.Peer Reviewe