1,354,088 research outputs found
Freeze cast porous membrane catalyst for hydrogen production via oxy-reforming
No full textIn this work, porous catalytic membrane with tailored microstructure has been developed for the production of hydrogen from the oxy-reforming process. Porous catalytic membranes have been produced by freeze-casting of ceria-based powders using camphene as solvent. The process parameters have been optimized in terms of type and amount of dispersant to obtain homogeneous and stable ceramic suspension suitable for the process, while the freezing temperature was chosen on the basis of the microstructure and porosity of the final samples. The obtained freeze cast sample produced showed very high levels of porosity (≈ 80%) and good gas permeability (1.0 × 10−11 m2). The ceria-based porous structure produced was finally evaluated as catalyst in high temperature oxy-reforming reaction for hydrogen production from methane showing high methane conversions (up to 90%) and hydrogen production. The use of a unique catalytic membrane other than pelleted catalysts allowed the obtaining of smooth thermal profiles without the evidence of endothermic or exothermic peaks
Role of different solvents on the purification of as-synthesized nano-Ce1-xGdxO2-d powders
No full textCeria and rare earth-doped ceria powders have important applications in catalysis, gas sensoring, and electronics. Even if many authors report different methods for the synthesis of nano-sized doped-ceria only few of them give information about the necessary washing processes for the powder purification. The organics adsorbed on the as-synthesized particles surface strongly affect, in fact, the properties of the powder. In this work, CeO2 and Ce1-xGdxO2-d (x = 0.10, 0.20, 0.30) solid solutions were produced by polyol microwave assisted method. The amount of synthesis residues adsorbed on the as-synthesized powders was firstly evaluated. The purification ability of different solvents on the as-synthesized Ce0.80Gd0.20O1.90 was, then, accurately studied in order to obtain a clean powder without the need of any thermal treatments. The study shows that water purification allows to reduce the amount of the residues of synthesis leading to the production of nano-particles with a mono-dispersed distribution of dimensions
Alternative production route for supporting La0.8Sr0.2MnO3 -Ce0.8Gd0.2O2 (LSM-GDC)
No full textTape casting is a widely used ceramic process that generally makes use of pore former agents to produce elements with engineered porosity for SOFC applications. In this work, porous La 0.8 Sr 0.2 MnO 3-δ-Ce 0.8 Gd 0.2 O 2-δ (LSM-GDC) supporting cathode of suitable porosity was produced using the reactive sintering approach without using of pore forming agent
Fabrication and electrochemical modelling of 8YSZ and GDC10 freeze tape cast scaffolds for solid oxide cells (SOCs)
No full textThe morphology of electrodes in Solid Oxide Cells (SOCs) has a great impact on their mechanical stability during operation as well as transport properties and kinetics, which in turn affect electrode and cell performance. This study proposes a new experimental procedure based on the freeze tape casting technique for the manufacturing of graded porous electrodes for SOCs. The use of water-based freeze tape casting has enabled the effective fabrication of hierarchical porous ionic backbones featuring the typical porosity of functional and supporting electrodes in a single tape. The porous samples are morphologically characterized and subsequently, for the first time according to the authors knowledge, a Computational Fluid Dynamic (CFD) model has been developed to compare the gas transport properties of conventional spongy-like and graded porous electrodes of planar SOCs. The results presented strongly suggest that hierarchical porous electrodes enable higher performance by decreasing the voltage concentration losses
Development and hydrogen permeation of freeze-cast ceramic membrane
No full textBaCe0.65Zr0.20Y0.15O3-δ - Gd0.2Ce0.8O2-δ (BCZY-GDC) is currently one of the most investigated composites as ceramic membranes for H2 separation and membrane reactors. In this context, we will present for the first time the possibility to exploit the ice-templating method coupled with screen printing to obtain hierarchicallystructured proton-conducting ceramic membranes. All the processing steps to obtain a defect free dense/porous structure were considered and analysed. In particular, the formulation of screen printing ink was optimized in terms of nature/amount of deflocculant and type of starting BCZY powder. An innovative membrane constituted by a 50 %-porous support with well-organized and aligned porosity and a 13 ± 3 μm thick dense layer on the top, was produced. The compressive strength (20.6 ± 5.6 MPa), were considered acceptable for practical applications. Promising H2 fluxes of 0.36 and 0.42 mL min1 cm− 2 at 750 ◦C, using a feed stream with 50 and 80% H2 in He (H2 %vol.) respectively, were obtained
Microwave-assisted synthesis of gadolinia-doped ceria powders for solid oxide fuel cells
No full textGadolinia doped ceria (GDC) is an attractive electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs) for its high ionic conductivity at low temperature (500-700°C). A number of different methods are currently used to prepare nano-sized doped-ceria powder. Among the others, precipitation in solution remains the best method to obtain well-dispersed particles of controlled properties. In this work, nanocrystalline Ce1-xGdxO2-δ (GDC) particles were produced by polyol microwave assisted method in very mild conditions (170°C, 2h, 1 atm). The as-synthesized powder showed good sinterability and ionic conductivity comparable to the ones of the corresponding nanometric commercial GDC
LSGM-based cells for IT-SOFC applications
No full textSolid Oxide Fuel Cells have still many technical problems related
to its high operating temperature (800–1000°C). The most recent
studies deal with reducing the operation temperature increasing at
the same time the durability of the device. The use of
La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) perovskite as electrolyte could be
a very promising solution for IT-SOFC operating at 600°C. In this
work, LSGM bilayers constituted by a thicker porous layer
(namely the anode scaffold) and a dense electrolyte were produced
by tape casting. The critical issues to obtain flexible and crack-free
green tapes suitable for lamination were carefully examined. In
particular, the nature and amount of pore former needed to obtain
an anode scaffold with a porous network suitable for the catalysts
impregnation process were deeply investigated
Indagini scientifiche sui materiali pittorici della cappella del SS. Crocefisso nella chiesa dei Cappuccini a Faenza
No full textRole of carbonate amount and synthesis procedure in the conductivity of SDC-Na2CO3 composite electrolytes for solid oxide cells applications
No full textComposite electrolytes of sodium carbonate and samarium doped ceria (SDC-Na2CO3) provide outstanding proton conductivity between 300 °C and 650 °C, which is extremely sensitive to the synthesis procedure and to the amount and crystallinity of the carbonate phase. Here, the role of sodium carbonate in establishing the composite conductivity is explored in relation to chemical-structural and morphological characterization methods (ICP, XRD, SEM, TEM). A coprecipitation route is properly optimized to prepare composites with <50 nm SDC particles with sodium carbonate in different amounts. The amount of carbonate, carefully quantified via elemental analysis, strongly influences the proton conductivity, while the oxygen ion conductivity is much less affected. The formulation with 27 wt% of carbonate prepared through a single-step synthesis shows the best performance, with 2.27*10^−2 S cm^−1 proton conductivity in dry hydrogen (4 % H2 in N2) at 600 °C, and 1.73*10^−2 S cm^−1 oxygen ion conductivity in air. Interestingly, an SDC-Na2CO3 composite containing the same salt amount but produced via a double-step procedure showed lower conductivity, confirming the pivotal role of the preparation methodology in defining the composite proton conductivity. In addition, humidification is found to depress H+ conductivity, thus indicating that the preferential charge transport mechanism does not involve hydroxides, in contrast to conventional protonic ceramics. Overall, the investigation reveals a strong dependence of the composite proton conductivity on the density of the carbonate/SDC interfaces and the crystallinity of the carbonate
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