Reversible melting and equilibrium phase formation of (Bi,Pb)2Sr2Ca2Cu3O10+d

The decomposition and the reformation of the (Bi,Pb)2Sr2Ca2Cu3O10+d (?Bi,Pb(2223)?) phase have been investigated in-situ by means of High-Temperature Neutron Diffraction, both in sintered bulk samples and in Ag-sheathed monofilamentary tapes. Several decomposition experiments were performed at various temperatures and under various annealing atmospheres, under flowing gas as well as in sealed tubes, in order to study the appropriate conditions for Bi,Pb(2223) formation from the melt. The Bi,Pb(2223) phase was found to melt incongruently into (Ca,Sr)2CuO3, (Sr,Ca)14Cu24O41 and a Pb,Bi-rich liquid phase. Phase reformation after melting was successfully obtained both in bulk samples and Ag-sheathed tapes. The possibility of crystallising the Bi,Pb(2223) phase from the melt was found to be extremely sensitive to the temperature and strongly dependent on the Pb losses. The study of the mass losses due to Pb evaporation was complemented by thermogravimetric analysis which proved that Pb losses are responsible for moving away from equilibrium and therefore hinder the reformation of the Bi,Pb(2223) phase from the melt. Thanks to the full pattern profile refinement, a quantitative phase analysis was carried out as a function of time and temperature and the role of the secondary phases was investigated. Lattice distortions and/or transitions were found to occur at high temperature in Bi,Pb(2223), Bi,Pb(2212), (Ca,Sr)2CuO3 and (Sr,Ca)14Cu24O41, due to cation diffusion and stoichiometry changes. The results indicate that it is possible to form the Bi,Pb(2223) phase from a liquid close to equilibrium conditions, like Bi(2212) and Bi(2201), and open new unexplored perspectives for high-quality Ag-sheathed Bi,Pb(2223) tape processing.Comment: 45 pages (including references,figures and captions), 13 figures Submitted to Supercond. Sci. Techno

Fortalecimiento de gestiones a través del Centro de Información de Actividades Porcinas (CIAP) para el desarrollo sustentable de pequeños y medianos productores porcinos familiares de la zona de influencia de la Facultad de Ciencias Agrarias de la Universidad Nacional de Rosario

Fortalecimiento de gestiones a través del Centro de Información de Actividades Porcinas (CIAP) para el desarrollo sustentable de pequeños y medianos productores porcinos familiares de la zona de influencia de la Facultad de Ciencias Agrarias de la Universidad Nacional de RosarioFil: Silva, Patricia. Universidad Nacional de Rosario. Facultad de Ciencias Agrarias; Argentin

Study of nanostructured metal matrix composite material elaborated by additive manufacturing for nuclear components

International audienceThis study focuses on the manufacture of nanostructured metal matrix composite material by an additive manufacturing process. Currently, the reference process induces some difficulties to produce large components with complex geometrical shape for nuclear core reactors. In this framework, the researches consist in studying and comparing microstructural and mechanical properties of materials obtained by standards elaboration methods and additive manufacturing processes.The powders of nanostructured metal matrix composite material are prepared by mechanical alloying and characterized by local (TEM) and global (particle size analysis, SEM) methods. After this characterization step, the powders are used to produce samples by additive manufacturing process (selective laser melting). These samples will be characterized in order to observe the microstructure (chemical composition, precipitate size and distribution) and study mechanical properties (tensile test, Charpy impact tests, creep)

Elaboration of oxide dispersion strengthened Fe-14Cr steel by selective laser melting a new route for new applications

International audienc

Traitements de surface avec et sans apport de matiere pour le nucleaire - Modification de surface par laser, PVD et CVD

International audienceDans le contexte actuel d'optimisation du parc actuel et futur et de l'allongement de la duree de vie des centrales et des installations du cycle, la problematique de duree de vie des materiaux est cruciale. Les problematiques de vieillissement et de reactivite (corrosion) constituent un defi majeur dans l'industrie nucleaire. Pour relever l'ensemble de ces defis, les technologies innovantes dans le domaine des procedes de traitements de surfaces avec ou sans apport de matiere sont des solutions prometteuses d'autant plus que ces dernieres ont connu un developpement significatif ces dernieres annees.Parmi les technologies de traitement de surface etudiees au Service d'Etudes Analytiques et de Reactivite des Surfaces (SEARS) de la DEN (Division de l'Energie Nucleaire), les techniques par laser sont historiquement presentes grace aux competences du LISL (Laboratoire d'Ingenierie des Surfaces et Lasers). Une premiere appartient a la famille des traitements sans apport de matiere. Elle consiste a venir frapper une surface avec un laser dont les proprietes sont judicieusement choisies pour que la matiere presente soit fondue voire ejectee. En pilotant les caracteristiques du faisceau laser incident les proprietes de surface peuvent etre modifiees. Il est par exemple possible de former une couche barriere d'oxydes, d'homogeneiser des phases et d'augmenter la teneur en certains elements chimiques voire de modifier la structure cristallographique ce qui peut conduire a une augmentation de la durete. Les applications de ce procede sont le renforcement de la resistance a la corrosion par piquration d'aciers 304L ou la limitation du relachement de nickel en milieu primaire au niveau des generateurs de vapeur. Enfin, l'ejection de matiere provenant de la surface traitee peut etre maximisee pour utiliser ce traitement comme une technique d'ablation surfacique pour le demantelement ou la maintenance d'installations, son point fort etant la possibilite de decontaminer des composants a distance.Les autres traitements de surface concernent des methodes avec apport de matiere. Parmi les technologies etudiees, certaines passent par un etat gazeux de la matiere. Suivant si la phase gazeuse se condense ou se decompose a la surface du composant a revetir, on parlera de PVD (condensation) ou de CVD (decomposition avec reaction chimique). Ces techniques sous vide sont majoritairement employees pour deposer des revetements protecteurs afin d'augmenter les performances et les durees de vie de composants en milieux extremes (haute temperature, irradiation, oxydation, corrosion ou encore usure abrasive). On peut citer les developpements actuels avec Areva pour les EATFs (Enhanced Accident Tolerant Fuels) concernant les gaines de combustible nucleaire qui, avec un revetement protecteur, resisteraient bien mieux a des hypothetiques conditions accidentelles de perte de refrigerant primaire

Influence of the powder characteristics on the final properties of powder-bed laser additively oxide dispersion strengthened (ODS) Fe-14Cr steel parts

International audienceAdditive manufacturing processes are promising technologies, currently considered as new opportunities to optimize metallic components production routes, especially in aerospace, automotive, medical and energy industries. The development of the application fields of these technologies involves an increase in the number of possible printed materials. In order to become a robust and reliable way of production of metallic functional components, mastering these technologies must still address challenges. In this framework, the study of the defects impact on final properties of designed components is essential.To assess the potentialities of additive manufacturing in nuclear industry, ODS Fe-14Cr steels are produced by selective laser melting (SLM). ODS steels are studied due to their improved resistance under neutron irradiation thanks to a fine dispersion of nanosized Y-Ti-O precipitates. Such materials are produced by a first step mechanical alloying. The resulting powder is characterized by a non-spherical shape and are coarser than powders typically used in SLM equipment. The analyzes such as composition, density, particles size distribution, flowability and morphology are performed on this powder. The milled powder is then used to produce ODS steel parts as raw material or after some modifications such as sieving or annealing.The objective of this work is to study the impact of the powder characteristics on the final material properties. As expected, powder characteristics strongly influence the final density of solidified parts. The choice of the thickness layer is also an important parameter that has to be related with the particle size distribution of the powder. The optimization of processing parameters (scanning speed, scanning strategy, laser power, etc…) and powder characteristics lead to a significant improvement of final material properties. In this context, last results regarding ODS steels additive manufacturing study will be presented and new insights for industrial fabrication will be given

Influence of powder characteristics on final properties of powder-bed laser additively manufactured ods fe-14cr steel

International audienceAdditive manufacturing processes are promising technologies, currently considered as new opportunities to optimize metallic components production routes, especially in aerospace, automotive, medical and energy industries. To assess the potentialities of additive manufacturing in nuclear industry, ODS (Oxide Dispersion Strengthened) Fe-14Cr steels are produced by selective laser melting (SLM). ODS steels are studied due to their improved resistance under neutron irradiation thanks to a fine dispersion of nanosized Y-Ti-O precipitates. Such materials are produced by a first step of mechanical alloying. The resulting powder has a non-spherical shape and is coarser than powders typically used in SLM equipment. The analyzes such as composition, density, particles size distribution, flowability and morphology are performed on this powder. The milled powder is then used to produce ODS steel parts as raw material or after some modifications such as sieving. The objective of this work is to study the impact of the powder characteristics on the final material properties. As expected, powder characteristics strongly influence the final density of solidified parts. The choice of the thickness layer is also an important parameter that has to be related with the particle size distribution of the powder

Catalysis on nanoporous gold-silver systems: Synergistic effects toward oxidation reactions and influence of the surface composition

MATERIAUX:SURFACES+TDR:FMO:JROAu-Ag nanoporous systems were prepared by a recently developed method. Contrary to the electrochemical dealloying, the methodology applied in this work proved that it allowed to prepare bimetallic AuAg NP systems with controlled chemical compositions. Compared with monometallic Au or Ag catalysts, the alloy catalysts exhibited high activity toward CO and/or H-2 oxidation and exceptionally high selectivity at low temperature for CO oxidation in the presence of H-2 showing a synergistic effect between Au and Ag. Among the different characterizations, Low-Energy Ion-Scattering Experiments provided composition data about the topmost atomic layer, i.e., where catalytic reactions occur and allowed us to establish a clear correlation between top layer surface concentration and reactivity. A pronounced dependence of the reaction rate on the silver concentration has been observed only for H-2 oxidation. This strong dependence has been correlated with the number of surface sites constituted of adjacent Ag atoms required for dissociative oxygen adsorption. The high selectivity of the Au-Ag alloys with respect to pure gold has been ascribed to a large segregation of silver, especially on low coordination sites, inhibiting the H-2 adsorption. (C) 2013 Elsevier Inc. All rights reserved