Search

Solid Oxide Fuel Cells (SOFCs) are nowadays one of the most promising devices for stationary clean energy production, due to their minimal Green House Gas (GHG) emissions, fuel flexibility (from hydrogen to hydrocarbons and biogas), high efficiency, and power density. They are essentially multilayer structures were a solid dense electrolyte is sandwiched between two porous electrodes. The mechanical resistance of the cell is given by the supporting element, most commonly the thick anode and the electrolyte is an yttria doped zirconia ionic conductor. The single cells are then connected through metallic plates that act as current collectors. Even if this technology is in the verge of commercialization, more work is needed to improve the lifespan and reliability of the single device. In this respect a major role is played by materials. Most of the work is at the moment devoted to reducing the temperature of operation (most commonly 800°C) using most performant materials (such as protonic conductors, ceria-based anionic conductors, etc.), reduce the amount of critical elements and improve the resistance of interconnectors and sealant. The article thoroughly revised the materials considered for the development of the single cell (electrolyte, cathode, and anode) and the cells stack (interconnector, sealant) in light of the more promising actual studied.

L’obiettivo di un Catalogo “open source”, contenente dati di tipo “qualitativo” e “quantitativo” sulle tecnologie energetiche e la loro applicazione nel settore industriale, dei trasporti e nel civile, è quello di fornire al decisore una dettagliata disamina tecnica ed economica delle tecnologie energetiche disponibili, sia di offerta sia di uso finale. Il testo raccoglie informazioni sulle eccellenze italiane, sia pubbliche che private, e sulle migliori pratiche relative alle più importanti tecnologie per la decarbonizzazione. Il lavoro assume un ruolo centrale in vista della elaborazione del prossimo “Piano nazionale Integrato per l’Energia e il Clima”, previsto dall’Unione per l’Energia, nell’ambito del quale dovrà essere fornito anche un quadro conoscitivo di riferimento a livello nazionale sui temi della “Ricerca e dell’innovazione”.

International audience; The present paper refers to an innovative SOFC concept named EVOLVE after a running FP7 project which integrates advanced materials and an inventive anode current collector made from a NiCrAl preoxidized foam impregnated with a conductive perovskite. Even if the concept is the beneficial combination of Metal supported cell (MSC) and Anode supported cell (ASC) technologies, strong improvements in terms of reliability and durability are expected. In order to enhance anode efficiency, the 3D microstructure needs to be precisely described at the microscopic scale. ISTEC has produced LST-GDC active anode layers using screen printing process. Back-scattered electrons (BSE) SEM images that contain relevant microstructure information have been realized by Centre des Matériaux. All the original images have been enhanced by Centre de Morphologie Mathématique using a series of morphological operators to remove artefacts. Finally, a 3D pluri-Gaussian model has been generated from 2D images, and then computed to predict volume fraction of the 3 phases, 3D tortuosity, gas permeation and ionic conductivities.

ZEBRA batteries (Zero Emission Battery Research Activities), are one of the possible solutions to electrical storage for stationary applications due to their high energy and power density. These systems are based on nickel-sodium chloride cells operating at high temperatures (about 270-350°C), and that rely on a ceramic ?"-alumina tube or planar membrane as solid electrolyte. The ceramic process needed to produce the electrolytic compartment has a key role to enhance and adapt the batteries performances to the specific requirements for stationary regime applications. Each minimal composition or process deviation strongly influences the final properties of the device. Aim of this work was the ad-hoc study of the production process, from the powders synthesis to their forming and sintering needed to obtain ?"-alumina membranes with suitable morphological-structural characteristics. The research was deeply focused onto the analysis of the materials sintering behaviour, on the study of reactive sintering processes and on the influence of thermal treatments on the chemical-structural properties of the material. The optimization of the entire ceramic process leaded to the production of a full density material with chemical-microstructural properties suitable for high efficiency batteries.

Among the perovskite structures, lanthanum-doped strontium titanates have attracted a lot of attention as possible candidates for SOFC Ni-free anodes. In particular the composition LaxSr1-(3x/2)TiO3 with x = 0.4 (LST) was recently considered for its tolerance to redox cycles and sufficiently high conductivities values. In this work an extensive study on the synthesis of LST powders with low-cost and easy-scalable methods is reported. The solid state and chemical synthesis as well as a combination of solution-solid state synthesis were considered. The influence of either the nature of the precursors (oxides, carbonates or nitrates) and the calcination temperature (from 500 to 1350°C) onto the perovskite formation was evaluated. The as-synthesized powders were morphologically, structurally and chemically characterized. The Pechini method leads to pure perovskite phase at 700°C for 1h, but it allows the production of only few grams of powder for each batch. On the other hand the solid state synthesis is a more up-scalable method but the phase can be obtained only at 1100°C for 1h. In addition the high reactivity of the lanthanum towards the humidity leads to a difficult control of the system stoichiometry and therefore of the final phase composition. An alternative solution-solid state synthesis was considered to produce batch of 100g of LST powders with good phase purity and in relatively mild conditions. The pure perovskite phase with the correct stoichiometry was obtained starting from the La and Sr nitrate aqueous solutions, highly reactive TiO2 followed by freeze-drying and calcination at 900°C for 1 h.

Preliminary results of a research at CNR are reported about the characterization of various materials for CO2 capture in course of chemical reaction or post-process. A thermo-gravimetric technique as well as a fixed bed reactor were used for characterizing natural and artificial sorbents like limestone, dolomite, Ca oxide, synthetic zeolite, yellow tuff from Campania, and a geopolymer. The limestone proved to be effective and cheap for high temperature absorption, although a decay of its sorption capability was noted along the time. For low temperature sorption, artificial and natural (tuff) zeolites exhibited an appreciable adsorption capability and can be a valid option for post process CO2 removal.

L'obiettivo dello studio è la misura della permeabilità di materiali porosi per applicazioni in sistemi per la produzione di energia. In particolare, l'analisi riguarda la caratterizzazione di supporti ceramici per l'applicazione in dispositivi SOFC (Solid Oxide Fuel Cells) e/o SOEC (Solid Oxide Electrolysis Cells) e in membrane per la separazione di ossigeno ai fini di sostenere reazioni di ossi-combustione. I risultati dello studio riguardano 1) la realizzazione del banco prova per le misure che consente di effettuare le caratterizzazioni in un ampio intervallo di temperature (da temperatura ambiente a 1000°C) e con diversi fluidi (H2, N2, H2O, CO2, CO, O2); 2) la misura della permeabilità in supporti anodici basati su Ni/YSZ e Ni/GDC e in supporti catodici basati su YSZ/LSM; 3) la misura della permeabilità in membrane per la separazione di ossigeno. I risultati consentono di valutare quantitativamente la permeabilità dei materiali in funzione di diverse condizioni operative (es. miscele di gas e temperatura) e micro-struttura dei materiali. La caratterizzazione consente di valutare inoltre l'impatto di fenomeni di degradazione rilevanti, quali la formazione di depositi di carbonio, sul trasporto di massa in anodi SOFC alimentati da idrocarburi.

Tape casting is a widely used shaping technique to produce large area, flat ceramic electrodes with a microstructure suitable for solid oxide fuel cell (SOFC) applications. This cheap and easily scalable ceramic process generally makes use of pore formers to produce elements with the desidered porosity. Thin film electrolyte is generally fabricated on the green electrode substrate by screen-printing; the entire system is finally co-sintered to obtain the electrolyte/electrode bilayer. In this study the possibility to produce a SOFC half-cell constituted of porous La0.8Sr0.2MnO3-Ce0.8Gd0.2O2 (LSM-GDC) supporting cathode and GDC dense electrolyte in a single thermal step was investigated. To avoid the use of pore formers, the reactive sintering approach was considered. The precursor decomposition during a single thermal treatment of calcining-debonding-sintering was exploit to generate at the same time, the suitable porosity and the La0.8Sr0.2MnO3 phase. Different sintering aids were tested for densifying the GDC layer. Carefully studying the effect of the reactive sintering on the sintering profile and the structure integrity of the cathode-supported half-cell allows to successfully obtain bilayers of 5x5cm2. To the author knowledge this is the first time that a dense electrolyte membrane has been obtained in a single step onto a supporting cathode produced by tape casting adopting the reactive sintering approach.

The realization of complete anode supported cells reproducing the IDEAL-Cell concept was approached by standard and inexpensive ceramic processes like tape casting, screen printing and wet powder spraying. Both commercial and custom powders were employed to build-up layers for button cells (1 inch footprint) and larger (5×5 cm2) substrates. This paper reports the details of the slurries formulation as well as the deposition parameters and sintering conditions. Resulting microstructural features are also presented together with an outlook on future steps of the activity

Il progetto IDEAL-Cell propone di sviluppare un nuovo concetto innovativo e concorrenziale di Fuel Cell ad alta temperatura, operante nell'intervallo 600-700°C, sulla base dell'integrazione tra un anodo di una cella a conduzione protonica ed un catodo di una a conduzione anionica. Protoni creati all'anodo migrano verso una membrana centrale per incontrarsi con gli ioni di ossigeno creato al catodo, per formare acqua, la quale è evacuata attraverso una rete di porosità interconessa al sistema

Tape casting is a widely used shaping technique to produce large-area, flat ceramic layers for SOFC applications. This cheap and easily scalable ceramic process generally makes use of pore forming agents in the slurry to produce elements with the desired porosity. In this work, the possibility to obtain porous La0.8Sr0.2MnO3-Ce0.8Gd0.2O2 (LSM-GDC) supporting cathode without the use of pore formers was evaluated. The reactive sintering approach was therefore considered to exploit the porosity induced by the precursor decomposition during a single thermal treatment of calcining-debonding-sintering. A stable tape casting slurry of lanthanum, strontium and manganite precursor salts and GDC powder was therefore used in order to obtain large-area, crack free green tapes where La0.8Sr0.2MnO3 phase was formed directly during the sintering step. This process allowed to obtain 10 x10 cm2 LSM-GDC tapes, 800 ?m thick, with values of porosity and mechanical strength suitable for fuel cells applications without pore former addition and in a single thermal step. To the author knowledge this is the first time that a large area supporting cathode has been produced by tape casting using the reactive sintering approach

Protonic Ceramic Membrane Fuel Cells (PCMFCs) have recently gained considerable interest due to their advantages, as a decreased operating temperature. These devices are based on proton conducting electrolyte perovskite-type oxide like doped BaCeO3 and BaZrO3. One of the major challenges for these materials is to have high values of conductivity assuring at the same time a suitable chemical stability. In this respect, cerate-zirconate solid solutions represents a possible choice exibiting both high proton conductivity and good chemical and thermal stability over a wide range of fuel cells operating conditions. For the purpose of their commercialization, in this work a colloidal spray deposition method, recently developed for the deposition of dense protonic electrolyte films [1], was used to fabricate PCMFCs. In particular, this study deals with the preparation and the characterization of anode-supported planar PCMFCs based on proton conducting BaCe0.65Zr0.20Y0.15O3-delta (BCZ20Y15) electrolyte. A cost effective and facile in situ reaction method for preparing BCZ20Y15 dense electrolyte films on Ni-BCZ20Y15 porous anode substrates is presented. Dense BCZ20Y15 films, having thickness 10-20 um, were fabricated by a suspension spray process starting from metal oxide precursors. Ni-BCZ20Y15 anodic cermet substrates were prepared by die-pressing a suitable mixture of Ni, starch and BCZ20Y15 powders

Solar energy is the most available and deeply used renewable energy. Three different technologies can be used to convert the sun energy into useful power: photovoltaic cells, thermal systems, and concentrated solar power systems. The latter is particularly interesting as can be used to produce electricity also when the sun is not present (during the night or in a cloudy day). The sun rays are in fact concentrated by parabolic mirrors on a defined area. The generated heat warms up a fluid or a reservoir and can be used to generate steam and therefore electricity. The heat produced can however be stored into specific devices that can release it during all the night. The process efficiency takes great advantages by a intimate contact between the collecting tubes and the storage system. For this reason the latter must be of a rather complex shape. Among the possible forming methods for inorganic powder, gel casting was considered the most suitable one. The thermal storage system in fact, besides the shape must have dimensions over 1 meter. Aim of this work was the study and optimization of the gel casting process for the shaping of thermal storage devices. The process wad deeply analyzed from the raw materials (nature and morphology of the inorganic powders, gelling and other organic additives), through the shaping parameters (gelling time and temperature, suspension viscosity etc.) up to the final sintering step. Particular attention was paid on the realization of an experimental set up and standard operation procedures suitable for an industrial scale-up. The optimization of the entire ceramic process leaded to obtain products with density and microstructural properties suitable for thermal storage systems

The present technical report summarizes the activity carried out by ISTEC within the project PON SOLTESS in the period July 2010-July 2011. The main purpose of this activity is the definition of a suitable process to obtain a solar radiation absorbing device for heat storage and transfer. The optimization of the ceramic absorbing device needs the identification of: -suitable materials to achieve good heat exchange (in particular the graphite), -manufacturing processes feasible on an industrial scale,-process conditions sufficiently mild as to be cost effective and less aggressive in the cavity of the containment steel storage media

The increasing use of chemical compounds derived from oil as recently pushed the demand for olefins, especially ethylene and propylene. At the present time, the main sources of olefins are: steam cracking, fluid-catalytic-cracking, and catalytic dehydrogenation. Besides these processes, an intense research activity is taking place to develop catalysts for the oxidative dehydrogenation (ODH) of alkanes. Among the possible materials Perovskite-type mixed oxides have been studied intensively for their good catalytic as well as their mechanical stability. Aim of this activity was the production and characterization of three different compositions of catalytic substrates suitable for the oxidative dehydrogenation. The substrates need to be shaped in form of pellets with the desired level of porosity and a good mechanical strength. To obtain pellets with suitable characteristics, the entire productive process was studied: from the raw materials (catalysts, pore formers, etc.) to the sintering step. The research was particularly focused onto the choice of the suitable shaping method and the optimization of the process parameters. The optimization of the entire ceramic process allowed the production of pellets with dimension and microstructural properties suitable for the catalytic application chosen

The climate change, the decreasing of petroleum supplies and the abrupt increase of the energy demand due to the emerging countries and to an energy-hungry society, has driven the interest towards new energy and more efficient devices of energy production. Only a strong acceleration of alternative devices of energy production and an increase of renewables, can succeed in reducing pollution, improving the climate and at the same time assuring the energetic autonomy and competitiveness. In this scenario, electrochemical cells show several economic and environmental advantages compared to the conventional industrial processes. Fuel cells are an excellent alternative to the conventional systems of energy production in terms of CO2 emissions, low noise and flexibility of fuels and generated power. Solid oxide fuel cells (SOFC) in particular, are one of the most promising energy devices for their high efficiency, modularity, low emissions and the possibility to be directly fuelled with natural gas, GPL and alcohols. Lot of efforts are however necessary to develop commercially available generators and to increase their stability lowering at the same time their costs. These hurdles can be partially overcome lowering the operating temperature but also using more economic and easily scalable manufacturing techniques. These objectives can be reach deepened the knowledge on the relationships between SOFC materials and the main industrial production processes (tape casting and screen printing) necessary to obtain cell of dimensions close to the commercial ones with easily scalable processes. In this work the main issues related to tape casting and screen printing of nanopowders for SOFC ceramic devices is presented. Nano-powders represent the forefront of materials for SOFC. Nano-structured powders exhibit in fact important size-dependant properties such as high catalytic activity, low sintering temperatures and therefore high performances. Aim of this study is to find the correlation that link the process parameters with the nano-materials properties in order to enhance the performances and the durability both of the materials and of the final device. One of the most critical issue is to produce homogeneous and stable ceramic suspensions of nanopowders. The process optimization can be obtained merging the surface and morphological properties of the nanopowders considered (shape, dimensions' distribution, surface area, etc.) to its behavior in suspension (viscosity, zeta potential, etc.) either organic of water-based, in order to obtain a well dispersed and homogenous system. With this kind of control, it is possible to produce large area reliable devices with the necessary reproducibility and reliability