Influence of crystallinity and particle size on the electrochemical properties of spray pyrolyzed Nd2NiO4+δ powders

This paper is dedicated to the study of the relationship between the Nd2NiO4+ı powder micro-structural properties (especially particle size and crystallinity) and electrochemical properties when the oxide is used as SOFC cathode deposited on 8YSZ electrolyte coated with thin doped ceria. Nano-structured particles of Nd2NiO4+ı with controlled crystallinity, size and morphology have been synthesized using ultrasonic spray pyrolysis (USP). The series and polarization resistances measured on symmetrical half cells Nd2NiO4+ı/YDC/8YSZ/YDC/Nd2NiO4+ı are both found to be dependent on the cathode microstructure and present a similar evolution with temperature. The best results are obtained for highly crystalline cathode powders combined with a small particle size

Mise au point d'une cellule de SOFC haute performance alimentée en méthane pur sans dépôt de carbone

La mise au point d'une cellule de SOFC haute performance de configuration anode support pour un fonctionnement sous méthane pur nécessite l'élaboration d'un film mince d'électrolyte et le développement d'une architecture innovante permettant le reformage d'hydrocarbures. La première partie du travail a consisté en l'élaboration de films minces d'électrolyte de zircone stabilisée à l'oxyde d'yttrium par atomisation électrostatique sur un substrat composite poreux NiO-8YSZ. Cette technique originale a permis l'obtention de films minces, denses et étanches à partir d'une suspension, présentant des propriétés électriques comparables à celles d'un échantillon massif de même composition. La seconde partie du travail a porté sur la mise au point d'une cellule de SOFC optimisée dont l'architecture innovante intégrant une membrane anodique catalytique est basée sur le concept associant le reformage interne progressif et le découplage électro-catalytique. Une séquence d'élaboration établie spécifiquement conditionne l'assemblage des éléments optimisés de la cellule. L'adaptation de la cellule dans un banc de mesures a permis la réalisation de tests électrochimiques sous hydrogène et méthane à haute température. Le fonctionnement stable du dispositif pendant plus de 1000 h sous méthane pur avec un taux d'utilisation optimisé, sans apport extérieur d'eau et sans dépôt de carbone a validé le concept étudié.The design of a high performance anode supported SOFC operating under pure methane requires the elaboration of a thin film of electrolyte and the development of an original architecture adapted to the reforming of hydrocarbons. The first part of this work was dedicated to the elaboration of yttria stabilized zirconia thin films of electrolyte by ESD onto a NiO-8YSZ porous substrate. This original technique has allowed the fabrication of thin, dense and gas-tight films starting from a suspension, with good electrical properties comparable to that of a bulk sample of the same nature. The second part of this work concerned the design of an optimized SOFC cell with an original architecture integrating an anodic catalytic membrane based on a concept gathering the gradual internal reforming and the electro-catalytic dissociation. The assembly of the optimized components is conditioned by an elaboration sequence specifically established. The adjustment of the cell in a test bench led to the achievement of electrochemical tests in hydrogen and methane at 800C. The stable operating of the cell fueled by pure and dry methane with optimized faradaic efficiency for more than 1000 h without carbon deposition proved the viability of the studied concept.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Innovative architectured oxygen electrodes for IT-SOFC using electrostatic spray deposition

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Innovative Design of Efficient La2-xPrxNiO4+& based Cathodes for Solid Oxide Fuel Cells

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Innovative architectured oxygen electrodes based on LaPrNiO4+δ for SOCs

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Innovative Design of Efficient La2-xPrxNiO4+& based Cathode for Solid Oxide Fuel Cells

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Microstructural designed S58 bioactive glass/ hydroxyapatite composites for enhancing osteointegration of Ti6Al4V-based implants

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Advanced Nanostructured materials for electrical and biological applications using Electrostatic Spray Deposition

International audienceReplacement of missing or diseased hard tissues has become a common procedure in medicine and dentistry. In this field, coatings are frequently applied onto the surface of metallic implants, such as titanium and titanium alloys in order to improve their biological performance -i.e., to enhance bone contact or bone anchorage, defined as osseointegration-. Because of their similarity to the inorganic component of bones and teeth, calcium phosphate (CaP) ceramics are considered as a suitable material for use as a surface coating.1 Currently, the most frequently applied method to coat titanium implants with CaP films is the plasma spraying technique, which has considerable drawbacks, for instance, unpredictable phase changes, the large thickness needed to completely cover the implant, and possible particle release and delamination.2,3 Among alternative methods of depositing CaP coatings, the Electrostatic Spray Deposition technique (ESD) is investigated as a promising low-temperature deposition technique.ESD is a low-cost method, innovative, based on electrohydrodynamics’ laws, that allows the deposition of films with a large variety of original morphologies and phases including crystalline and amorphous states of CaP. In this study, the microstructural and structural properties of the CaP coatings deposited on Ti alloy are investigated for different precursor solutions containing calcium and triethyl phosphate and for several ESD deposition parameters. The microstructure and composition of the obtained coatings were characterized by scanning electron microscopy (SEM) associated with energy-dispersive X-ray spectroscopy (EDX), and atomic emission spectrometry (ICP-AES). Their structural properties were determined using X-ray diffraction (XRD), Raman spectroscopy and Fourier-transformed infrared spectroscopy (FTIR).This work4 has shown that ESD proved to be a viable and potentially interesting technique to coat pure calcium phosphates such as carbonated hydroxyapatite on metals (Ti alloy) with unique dense, reticular or coral-type microstructures. Moreover, CaP films appear to be adherent and osteoconductive. The biological coating performances in vivo and in vitro studies are in progress.1. Lacefield WR. Hydroxylapatite coatings. In: Hench LL, Wilson J, editors. An introduction to bioceramics. Singapore: World Scientific Publishing Co; 1993. p. 223–38.2. Barrère F. Biomimetic calcium phosphate coatings: physicochemistry and biological activity. Ph.D. Thesis, University of Twente, Enschede, 2002.3. Layrolle P, de Groot K, van Blitterswijk CA. Biomimetic hydroxyapatite coating on Ti6Al4V induced by pre-calcification. Bioceramics; 1998; 11; p. 465– 468.4. Müller V, Djurado E, Tadier S, Pagnier T, Gremillard L, Bioceramics, Acta Biomaterialia, t o be submitte

Structural changes of rare-earth-doped, nanostructured zirconia solid solution

International audienceA systematic study of the influence of the rare-earth (Sc, Yb, Y, Gd, Sm) dopant content and the ionic radius on the structural changes was undertaken on nanocrystalline-doped zirconia ceramics, which present the same microstructure. Tetragonal single-phased ceramics which were prepared by sintering of nano-powders obtained by spray pyrolysis at 1500 °C for 2 h in air, are characterized by an average grain size as low as 60 nm. Their densities are about 96% of the theoretical values. A good homogeneity in composition and in grain size was obtained for all samples. This exceptionally low grain growth during the sintering was related to the high purity of the materials and also to the morphology of the powders. Tetragonal solid solution domains were determined from Differential Thermal Analysis (DTA), X-ray Diffraction (XRD), and Raman spectrometry measurements. The size of the solid solution domain depends on the dopant ionic radius and on the grain size