In-situ alloying laser powder bed fusion of Ni-Mn-Ga magnetic shape memory alloy using liquid Ga

Ni-Mn-Ga-based magnetic shape memory alloys can exhibit large magnetic field induced strains (MFIS). Recently, additive manufacturing techniques, especially laser powder bed fusion (L-PBF), have been successfully used to manufacture functional polycrystalline Ni-Mn-Ga with complex geometries, such as ‘bamboo-grained’ lattice structures. However, previous approaches of L-PBF of Ni-Mn-Ga have used pre-alloyed powders, which can limit the compositional freedom of the manufactured devices. This study explores, for the first time, the feasibility of an in-situ L-PBF alloying approach using a powder blend of elemental Ni, Mn, and Ga. Promising results were obtained despite the significant differences between the elemental Ni and Mn powders and the liquid Ga. The microstructure of the as-built sample showed distinct stripe patterns from the 14 M structure confirmed by XRD analysis. Heat-treatment significantly improved chemical homogeneity, dissolved the Ni-rich phase but couldn’t dissolve MnO hindering the shape memory effect

Dynamic modeling of hydrogen desorption from a metal hydride tank using the electrical fluidic analogy

WHEC 2016, World Hydrogen Energy Conference, Saragosse, ESPAGNE, 13-/06/2016 - 16/06/2016International audienceThe current work presents a modeling study of the thermal behavior during discharge of a hydride hydrogen tank. In a thermal coupling between a fuel cell and its associated hydride hydrogen tank, the hydrogen desorption kinetics depends on temperature, nature of the hydride, the tank design, but also on the hydrogen demand from the fuel cell in terms of mass flow and pressure. The objective of the study is to demonstrate the dynamic response of hydrogen discharge from a metal hydride tank by using the fluidic electrica

Cordões de ouro amarelo 18k feitos por Laser Powder Bed Fusion (LPBF): comparação de laser de 1064 nm e 515 nm

International audienceAdditive Manufacturing (AM) allows to manufacture new designs and novel geometries interesting for jewelry and watchmaking items. However, pure gold and gold alloys are challenging materials to manufacture by Laser Powder Bed Fusion (LPBF). Due to the low absorptivity at 1 064 nm Infrared (IR) wavelength combined to high thermal conductivity, it is difficult to manufacture pure gold and gold-based alloys by this process. Recent evolutions in laser technology allowed to build a machine using a 515 nm “green” laser. By changing the wavelength (1 064 nm to 515 nm), absorptivity can be improved from 7 to 37%. This paper will focus on 18 karat gold single tracks analysis produced by both wavelengths on a steel substrate. Different melting states will be detailed and indexed in order to select, correctly, machine parameters for producing gold items. It will be shown that 515 nm laser is more adapted to the material than 1 064 nm laser for manufacturing gold alloys.La Fabricación Aditiva (AM) permite fabricar nuevos diseños y nuevas geometrías interesantes para artículos de joyería y relojería. Sin embargo, el oro puro y las aleaciones de oro son materiales difíciles de fabricar mediante Laser Powder Bed Fusion (LPBF). Debido a la baja capacidad de absorción en una longitud de onda infrarroja (IR) de 1064 nm combinada con una alta conductividad térmica, es difícil fabricar oro puro y aleaciones a base de oro mediante este proceso. Los recientes avances en tecnología láser han hecho posible construir una máquina utilizando un láser "verde" de 515 nm. Al cambiar la longitud de onda (1064 nm a 515 nm), la absortividad se puede mejorar entre un 7% y un 37%. Este artículo se centrará en el análisis de perlas de oro de 18k producidas por ambas longitudes de onda sobre un sustrato de acero. Se detallarán e indexarán diferentes estados de fusión para seleccionar correctamente los parámetros de la máquina para producir artículos de oro. Se demostrará que el láser de 515 nm es más adecuado para el material que el láser de 1064 nm para la fabricación de aleaciones de oro.La Fabrication Additive (FA) permet de fabriquer de nouveaux designs et de nouvelles géométries intéressantes pour les articles de joaillerie et d'horlogerie. Cependant, l’or pur et les alliages d’or sont des matériaux difficiles à fabriquer par Laser Powder Bed Fusion (LPBF). En raison de la faible capacité d’absorption à une longueur d’onde infrarouge (IR) de 1 064 nm combinée à une conductivité thermique élevée, il est difficile de fabriquer de l’or pur et des alliages à base d’or par ce procédé. Les évolutions récentes de la technologie laser ont permis de construire une machine utilisant un laser « vert » de 515 nm. En modifiant la longueur d'onde (1 064 nm à 515 nm), l'absorptivité peut être améliorée de 7 à 37 %. Cet article se concentrera sur l'analyse de traces uniques d'or 18 carats produites par les deux longueurs d'onde sur un substrat en acier. Différents états de fusion seront détaillés et indexés afin de sélectionner correctement les paramètres de la machine pour produire des articles en or. Il sera montré que le laser 515 nm est plus adapté au matériau que le laser 1 064 nm pour la fabrication des alliages d'or.A Manufatura Aditiva (AM) possibilita a fabricação de novos designs e novas geometrias interessantes para itens de joalheria e relojoaria. No entanto, ouro puro e ligas de ouro são materiais difíceis de fabricar por Laser Powder Bed Fusion (LPBF). Devido à baixa capacidade de absorção no comprimento de onda infravermelho (IR) de 1064 nm combinada com alta condutividade térmica, é difícil fabricar ouro puro e ligas à base de ouro por este processo. Desenvolvimentos recentes na tecnologia laser tornaram possível construir uma máquina usando um laser “verde” de 515 nm. Ao alterar o comprimento de onda (1064 nm para 515 nm), a absortividade pode ser melhorada em 7% a 37%. Este artigo se concentrará na análise de esferas de ouro 18k produzidas por ambos os comprimentos de onda em um substrato de aço. Diferentes estados de fusão serão detalhados e indexados para selecionar corretamente os parâmetros da máquina para produzir itens de ouro. Será mostrado que o laser de 515 nm é mais adequado para o material do que o laser de 1064 nm para a fabricação de ligas de ouro

OenVHy, to study hydride storage and Fuel cell system coupling

FDFC 2015 - 6th International Conference on Fundamentals and Development Fuel Cell, TOULOUSE, FRANCE, 03-/02/2015 - 05/02/2015The choice of the hydride material is necessary not only for the hydrogen tank sizing but also for the optimal thermal and electrical energy balance in the overall system including a hydride hydrogen tank coupled to a fuel cell generator. A comprehensive state of the art concerning the coupling between hydride storage and different types of fuel cells (low and high temperature) is proposed. According to the different syntheses, different hydride types can be used for hydrogen storage in order to optimize thermal coupling between hydrogen tanks with various fuel cell system technologies

Morphological, Structural and Hydrogen Storage Properties of LaCrO₃ Perovskite-Type Oxides

Recently, perovskite-type oxides have attracted researchers as new materials for solid hydrogen storage. This paper presents the performances of perovskite-type oxide LaCrO3 dedicated for hydrogen solid storage using both numerical and experimental methods. Ab initio calculations have been used here with the aim to investigate the electronic, mechanical and elastic properties of LaCrO3Hx (x = 0, 6) for hydrogen storage applications. Cell parameters, crystal structures and mechanical properties are determined. Additionally, the cohesive energy indicates the stability of the hydride. Furthermore, the mechanical properties showed that both compounds (before and after hydrogenation) are stable. The microstructure and storage capacity at different temperatures of these compounds have been studied. We have shown that storage capacities are around 4 wt%. The properties obtained from this type of hydride showed that it can be used for future applications. XRD analysis was conducted in order to study the structural properties of the compound. Besides morphological, thermogravimetric analysis was also conducted on the perovskite-type oxide. Finally, a comparison of these materials with other hydrides used for hydrogen storage was carried out

Electrochemical properties of the CaNi 4 . 8 M 0.2 (M=Mg, Zn, and Mn) mechanical milling alloys used as anode materials in nickel‐metal hydride batteries

International audienceAbstract The present research work examines the electrochemical properties of CaNi 4.8 M 0.2 (M=Mg, Zn) type alloy applied as an anode in nickel metal hybrid batteries. Based on an extensive study of the CaNi 4.8 Mn 0.2 compound prepared by mecano‐synthesis; under an argon atmosphere, with a variation of milling time and weigh ratio, using a Retsch PM400 type ball mill. The experimental results show that the excellent electrochemical properties were obtained for a milling time of 40 h and a ball‐to‐powder weight ratio equal to 8:1. Based on this study, we examined electrochemically the CaNi 4.8 M 0.2 (M=Mg, Zn, and Mn) compound according to the optimized parameters. Several methods, such as galvanostatic polarization and potentiodynamic polarization, were applied to characterize these electrodes. CaNi 4.8 M 0.2 (M=Mg, Zn, and Mn) electrodes were activated, respectively, during the first, second, and third cycles. The maximum discharge capacity was about 87, 60, and 96 mAhg −1 at ambient temperature. These electrochemical findings correlate with the kinetic results provided during a long cycle

Energetic modeling, simulation and experimental of hydrogen desorption in a hydride tank

International audienceThis paper presents a zero-dimensional (0D) model of hydride tank. The model aims to study the dynamic heat and mass transfers during desorption process in order to investigate the thermal-fluidic behaviors of this hydride tank. This proposed model has been validated experimentally thanks to a tailor-made developed test bench. This test bench allows the hydride characterization at tank scale and also the energetic characterization. The simulation results of the heat exchanges and mass transfer in and between the coupled reaction bed, show good agreement with the experimental ones. It is shown that the heat produced by a Proton Exchange Membrane Fuel Cell (PEMFC) (estimated starting from an electrical model) is enough to heat the metal alloy (FeTi) and therefore release the hydrogen with a sufficient mass flow rate to supply the PEMFC. Furthermore, the obtained results highlight the importance of the developed model for energy management of the coupling of fuel cell and hydride tank system

Hydride Material for optimal hydrogen storage system of fuel cell electrical vehicles

14 th International Symposium on Metal-Hydrogen Systems, MANCHESTER, ROYAUME-UNI, 20-/07/2014 - 25/07/2014This study proposes the thermal management of the hydrogen 'metal-hydride' storage system. The thermal topic is the main problem of the interaction between this kind of tanks and the fuel cell. A state of the art concerning the coupling between hydride storage and various types of fuel cells (low and high temperature) is given with the perspectives of our study

Fusão seletiva a laser (SLM) de cobre puro usando um laser verde de 515 nm: a partir da análise do cordão à caracterização mecânica e elétrica

International audienceLaser powder bed fusion allows to manufacture new components with optimized geometry and lightweight materials. Many common materials are now available for this process like steel, aluminum, and titanium. Copper is more difficult to produce due to its low absorptivity at 1064-nm wavelength and high thermal conductivity. Recent evolutions in laser technology allowed to build a selective laser melting machine using 515-nm green laser. This wavelength is better absorbed by copper for manufacturing. The absorptivity spectrum shows an absorptivity nearly nine times higher for the green laser by pure copper compared to infrared laser. This paper will focus on the manufacturing of pure copper parts from single-track analysis to electrical and mechanical characterization of the material. Porosity level and roughness will also be studied. Based on these observations, green laser could permit to avoid oxidation or other powder treatments. This new laser technology opens a new way to produce materials with high thermal conductivity.La fusión por láser de lecho de polvo permite fabricar nuevos componentes con geometría optimizada y materiales ligeros. Actualmente se encuentran disponibles muchos materiales comunes para este proceso, como el acero, el aluminio y el titanio. El cobre es más difícil de producir debido a su baja capacidad de absorción en la longitud de onda de 1064 nm y su alta conductividad térmica. Los avances recientes en la tecnología láser han hecho posible construir una máquina de fusión por láser selectiva utilizando un láser verde de 515 nm. Esta longitud de onda la absorbe mejor el cobre para la fabricación. El espectro de absortividad muestra una absortividad casi nueve veces mayor para el láser verde de cobre puro en comparación con el láser infrarrojo. Este artículo se centrará en la fabricación de piezas de cobre puro, desde el análisis de vía única hasta la caracterización eléctrica y mecánica del material. También se estudiará el nivel de porosidad y rugosidad. Según estas observaciones, el láser verde podría ayudar a evitar la oxidación u otros tratamientos con polvo. Esta nueva tecnología láser abre una nueva forma de producir materiales con alta conductividad térmica.La fusion laser sur lit de poudre permet de fabriquer de nouveaux composants avec une géométrie optimisée et des matériaux légers. De nombreux matériaux courants sont désormais disponibles pour ce processus, comme l'acier, l'aluminium et le titane. Le cuivre est plus difficile à produire en raison de sa faible capacité d’absorption à une longueur d’onde de 1 064 nm et de sa conductivité thermique élevée. Les évolutions récentes de la technologie laser ont permis de construire une machine de fusion laser sélective utilisant un laser vert de 515 nm. Cette longueur d'onde est mieux absorbée par le cuivre pour la fabrication. Le spectre d'absorptivité montre une absorptivité près de neuf fois supérieure pour le laser vert au cuivre pur par rapport au laser infrarouge. Cet article se concentrera sur la fabrication de pièces en cuivre pur, depuis l'analyse mono-piste jusqu'à la caractérisation électrique et mécanique du matériau. Le niveau de porosité et la rugosité seront également étudiés. Fort de ces observations, le laser vert pourrait permettre d'éviter l'oxydation ou d'autres traitements des poudres. Cette nouvelle technologie laser ouvre une nouvelle voie pour produire des matériaux à haute conductivité thermique.A fusão do leito de pó a laser possibilita a fabricação de novos componentes com geometria otimizada e materiais leves. Muitos materiais comuns estão agora disponíveis para este processo, como aço, alumínio e titânio. O cobre é mais difícil de produzir devido à sua baixa capacidade de absorção no comprimento de onda de 1064 nm e à sua alta condutividade térmica. Desenvolvimentos recentes na tecnologia laser tornaram possível construir uma máquina seletiva de fusão a laser usando um laser verde de 515 nm. Este comprimento de onda é melhor absorvido pelo cobre para fabricação. O espectro de absortividade mostra uma absortividade quase nove vezes maior para o laser verde de cobre puro em comparação com o laser infravermelho. Este artigo focará na fabricação de peças de cobre puro, desde a análise single-track até a caracterização elétrica e mecânica do material. O nível de porosidade e rugosidade também será estudado. Com base nessas observações, o laser verde poderia ajudar a evitar a oxidação ou outros tratamentos com pó. Esta nova tecnologia laser abre uma nova maneira de produzir materiais com alta condutividade térmica