Lunar regolith as a feedstock for selective laser melting

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Functionalizing surfaces of 3D printed objects with an integrated low-cost atmospheric pressure micro plasma torch

Polymer 3D printing via the Fused Filament Fabrication (FFF) technology is a now well-known process designed to build three-dimensional objects from computer-aided-design (CAD) models in a layer-by-layer method. First dedicated for prototyping, this technology is now widely spread on the additive manufacturing (AM) and production market. With the decreasing costs of the equipment and materials needed as well as the growing simplicity of use and reliability of the technique, one can now have a 3D printer for the same cost and as user-friendly as a regular desktop inkjet printer. Among the commercially distributed thermoplastics, polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) are the two most outspread but one can also find acrylonitrile styrene acrylate (ASA), polyethylene terephthalate (PET) polycarbonate (PA) and much more. When assuming that single material 3D printed objects are obtained from growing layers in the (xy) plane stacked along the z axis, they are known to show really good tensile strength in the x and y direction but much less in the z direction due to insufficient interlayer bounding. Bigger problems arise when trying to print a multi-material object. Indeed, the chemical incompatibility of the different printed materials as well as their different thermal expansion coefficients are from the materials properties that can cause a very weak diffusion bonding at the interface. Authors started recently to focus on this problematic and very few studies can be found on the subject. To overcome the problem, we consider here improving the wettability of the printed polymer at the interface layer as it cause the extruded material to better spread over this layer, hence increasing the diffusion bonding. This work aims to investigate the effect of an atmospheric cold plasma treatment on the wettability and bonding of 3D printed objects. For this task, we designed an atmospheric pressure dielectric barrier discharge (DBD) plasma torch integrated on a commercial 3D printer. Thus, the device can be controlled to apply a plasma treatment while printing an object. As the deposition process will need to be done on complex surfaces and on thermal sensitive materials, a new type of high voltage nano-pulse generator had to be developed for this device. It gives the possibility to generate a homogeneous plasma (with less filament discharge) in a very small volume and a relatively extended plasma plume with a limitation of the gas temperature. Wettability measurements and tensile tests were carried out on 3D printed + plasma treated objects, obtained with our newly designed device. The material bonding is evaluated either within a single-material specimen by applying the treatment at the interlayers or within a multi-material one by treating only the interface layer of the two different materials.

A new ternary compound with the BGa8Ir4 structure type in the Al-Au-Ir system

International audienceFollowing the recent determination of the Al3AuIr structure, a new ternary phase has been identified in the Al-Au-Ir phase diagram. It has a chemical composition Al 9 (Au;Ir)4 with an apparently low gold content. Its crystal structure has been determined with single-crystal X-ray diffraction. The new compound crystallizes in the tetragonal crystal system and has been successfully solved in space group I4 1/acd (Pearson symbol tI104) with lattice parameters a = 8.6339 (2) and c = 21.8874 (7) Å. Atomic environments are described as well as similarities with the BGa8Ir4 compound

Dramatic enhancement of double-walled carbon nanotube quality through a one-pot tunable purification method.

The purification process we propose is a one-pot gas-phase treatment; the CNT powder is simply submitted to a chlorine/oxygen atmosphere at around 1000 °C for 2 h. By varying the oxygen content in an excess of chlorine, the conditions were optimized in order to efficiently remove both metal (catalyst) and carbon impurities from DWCNT samples. Even if a high amount of sample is lost under the oxidative conditions used, a selective elimination of the carbon impurities obviously occurs and a metal impurity removal yield of 99% is obtained from thermogravimetry. Based on a multi-technique approach, we show that the purified DWCNTs are of high structural quality without any surface functionalization. This improvement of the wall quality through the chlorine/oxygen action is seen in particular with a division by 15 of the D over G band intensity of the Raman spectra. Among the existing procedures, the advantages of our purification method are indisputably its simplicity, low time-consuming and high efficiency combined with an enhanced quality of the purified CNTs. Such quasi-pure DWCNTs have high interest since they offer a unique opportunity to study the intrinsic properties and effects of the nanotubes themselves

Le système binaire aluminium-iridium, du diagramme de phases aux surfaces atomiques

A complex metallic alloy (CMA) is an intermetallic compound whose unit cell contains a large number of atoms oftenly forming highly-symmetric clusters. From the complexity of these compounds can arise physical and chemical properties interesting for various fields of application. The aluminium-iridium binary system exhibits numerous intermetallic compounds of which half of them are actually CMAs. Despite this system being extensively studied in the literature, some uncertainies remained unsolved, leading us to reinvestigate the Al-Ir phase diagram. In addition, the "push-pull" systems Al-Au-Ir and Al-Ag-Ir, favorable for the formation of CMA according to the literature, have been explored. Thus, near a hundred of samples have been prepared by arc-melting before being analyzed with different characterizations techniques: X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and differential thermal analysis (DTA). From this study, 4 new intermetallic compounds could be identified: Al2.4Ir, Al72Au2.5Ir29.5, Al3AuIr and Al11SiIr6, the latter being the result of a fortuitous manipulation. The crystallographic structure of each of these compounds has been solved, revealing Al2.4Ir and Al72Au2.5Ir29.5 to be two CMAs with around one hundred of atoms in their unit cell. Calculations based on the density functional theory (DFT) brought further details about the stability of the two other Al3AuIr and Al11SiIr6 compounds. In the Al-Ir binary system, a structural variant of two well-known CMAs has been also unveiled. The crystallographic structures of the Al2.75Ir and Al28Ir9 variant have been approached, revealing 240 and 444 atoms in their respective unit cell. The CMAs oftently exhibit interesting surface properties. In order to study the Al-Ir compound surfaces, iridium adsorption on Al(100) surface followed by annealing has been investigated. The characterizations by lowenergy electrons diffraction (LEED), X-ray photoelectron spectroscopy (XPS) and scanning tunneling miscoscopy (STM) supported by ab initio calculations revealed that, from 320 C, the Al9Ir2 compound is formed at the surface but also in the substrate bulkUn alliage métallique complexe (CMA) est un composé intermétallique dont la maille élémentaire est constituée d’un nombre important d’atomes formant bien souvent des aggrégats de haute symmétrie. De la complexité de ces composés peuvent découler des propriétés physico-chimiques intéressantes pour divers domaines d’application. Le système binaire aluminium-iridium est un système qui présente de nombreux composés intermétalliques dont la moitié sont des CMA. Malgré l’étude approfondie dont ce système a fait l’objet dans la littérature, certaines incertitudes demeuraient irrésolues, nous amenant ainsi à réexaminer le diagramme de phase Al-Ir. Nous avons également exploré les systèmes ternaires dits "push-pull" Al-Au-Ir et Al-Ag-Ir, propices à la formation de phases CMA selon certains auteurs. Au total, une centaine d’échantillons ont été préparés par fusion à l’arc puis analysés par diverses techniques de caractérisations: diffraction des rayons X (XRD), microscopie électronique à balayage (SEM), analyse dispersive en énergie (EDS) et analyse thermique différentielle (DTA). Quatre nouveaux composés intermétalliques ont ainsi été identifiés: Al2.4Ir, Al72Au2.5Ir29.5, Al3AuIr et Al11SiIr6, ce dernier étant issu d’une manipulation accidentelle. La structure cristallographique de chacun de ces composés a été résolue, révélant Al2.4Ir et Al72Au2.5Ir29.5 comme étant des CMA possédant une centaine d’atomes dans la maille. Des calculs basés sur la théorie de la fonctionnelle de la densité (DFT) sont venus apporter des précisions concernant la stabilité des composés Al3AuIr et Al11SiIr6. Pour le système Al-Ir, une variante structurale de deux CMA déjà connus de la littérature a également pu être mise en évidence. Les structures cristallographiques de la variante de Al2.75Ir et de celle de Al28Ir9 ont ainsi été approchées, présentant 240 et 444 atomes dans leur maille respective. Les propriétés de surface comptent parmi les aspects les plus intéressants des CMA, par exemple pour la catalyse hétérogène. En l’absence de monocristaux de taille macroscopique, nous avons étudié la possibilité de former des composés de surface par dépôt de Ir sur une surface Al(100) suivi de recuits. Des caractérisations par diffraction d’électrons lents (LEED), spectroscopie de photoélectrons excités par rayons X (XPS) et microscopie à effet tunnel (STM) supportés par ces calculs ab initio ont révélé qu’à partir de 320°C, le composé Al9Ir2 se formait en surface mais également dans une partie du volume du substra

The Al-Ir binary system, from the phase diagram to atomic surfaces

Un alliage métallique complexe (CMA) est un composé intermétallique dont la maille élémentaire est constituée d’un nombre important d’atomes formant bien souvent des aggrégats de haute symmétrie. De la complexité de ces composés peuvent découler des propriétés physico-chimiques intéressantes pour divers domaines d’application. Le système binaire aluminium-iridium est un système qui présente de nombreux composés intermétalliques dont la moitié sont des CMA. Malgré l’étude approfondie dont ce système a fait l’objet dans la littérature, certaines incertitudes demeuraient irrésolues, nous amenant ainsi à réexaminer le diagramme de phase Al-Ir. Nous avons également exploré les systèmes ternaires dits "push-pull" Al-Au-Ir et Al-Ag-Ir, propices à la formation de phases CMA selon certains auteurs. Au total, une centaine d’échantillons ont été préparés par fusion à l’arc puis analysés par diverses techniques de caractérisations: diffraction des rayons X (XRD), microscopie électronique à balayage (SEM), analyse dispersive en énergie (EDS) et analyse thermique différentielle (DTA). Quatre nouveaux composés intermétalliques ont ainsi été identifiés: Al2.4Ir, Al72Au2.5Ir29.5, Al3AuIr et Al11SiIr6, ce dernier étant issu d’une manipulation accidentelle. La structure cristallographique de chacun de ces composés a été résolue, révélant Al2.4Ir et Al72Au2.5Ir29.5 comme étant des CMA possédant une centaine d’atomes dans la maille. Des calculs basés sur la théorie de la fonctionnelle de la densité (DFT) sont venus apporter des précisions concernant la stabilité des composés Al3AuIr et Al11SiIr6. Pour le système Al-Ir, une variante structurale de deux CMA déjà connus de la littérature a également pu être mise en évidence. Les structures cristallographiques de la variante de Al2.75Ir et de celle de Al28Ir9 ont ainsi été approchées, présentant 240 et 444 atomes dans leur maille respective. Les propriétés de surface comptent parmi les aspects les plus intéressants des CMA, par exemple pour la catalyse hétérogène. En l’absence de monocristaux de taille macroscopique, nous avons étudié la possibilité de former des composés de surface par dépôt de Ir sur une surface Al(100) suivi de recuits. Des caractérisations par diffraction d’électrons lents (LEED), spectroscopie de photoélectrons excités par rayons X (XPS) et microscopie à effet tunnel (STM) supportés par ces calculs ab initio ont révélé qu’à partir de 320°C, le composé Al9Ir2 se formait en surface mais également dans une partie du volume du substratA complex metallic alloy (CMA) is an intermetallic compound whose unit cell contains a large number of atoms oftenly forming highly-symmetric clusters. From the complexity of these compounds can arise physical and chemical properties interesting for various fields of application. The aluminium-iridium binary system exhibits numerous intermetallic compounds of which half of them are actually CMAs. Despite this system being extensively studied in the literature, some uncertainies remained unsolved, leading us to reinvestigate the Al-Ir phase diagram. In addition, the "push-pull" systems Al-Au-Ir and Al-Ag-Ir, favorable for the formation of CMA according to the literature, have been explored. Thus, near a hundred of samples have been prepared by arc-melting before being analyzed with different characterizations techniques: X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and differential thermal analysis (DTA). From this study, 4 new intermetallic compounds could be identified: Al2.4Ir, Al72Au2.5Ir29.5, Al3AuIr and Al11SiIr6, the latter being the result of a fortuitous manipulation. The crystallographic structure of each of these compounds has been solved, revealing Al2.4Ir and Al72Au2.5Ir29.5 to be two CMAs with around one hundred of atoms in their unit cell. Calculations based on the density functional theory (DFT) brought further details about the stability of the two other Al3AuIr and Al11SiIr6 compounds. In the Al-Ir binary system, a structural variant of two well-known CMAs has been also unveiled. The crystallographic structures of the Al2.75Ir and Al28Ir9 variant have been approached, revealing 240 and 444 atoms in their respective unit cell. The CMAs oftently exhibit interesting surface properties. In order to study the Al-Ir compound surfaces, iridium adsorption on Al(100) surface followed by annealing has been investigated. The characterizations by lowenergy electrons diffraction (LEED), X-ray photoelectron spectroscopy (XPS) and scanning tunneling miscoscopy (STM) supported by ab initio calculations revealed that, from 320 C, the Al9Ir2 compound is formed at the surface but also in the substrate bul

Inhibiting the sp2 carbon deposition by adjunction of sulphurous species in refractory ceramics subjected to CO and H2 reducing atmosphere

International audienc