A chemical survey of exoplanets with ARIEL

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10–100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio

Plateforme de spray pyrolyse en flamme pour l’élaboration de nanomatériaux

International audienceDans le cadre de ses activités de recherche dans le domaine de la production et du stockage de l'énergie, le Laboratoire d'Etude des Eléments Légers (LEEL) met en place un dispositif de Spray Pyrolyse en Flamme (SPF) permettant la synthèse à pression atmosphérique, en une seule étape et en continu, de nanoparticules cristallines récoltées en voie sèche sous forme de nanopoudres. La SPF repose sur la décomposition thermique d'un précurseur liquide suivie d'une phase de nucléation et de croissance de nanoparticules produisant un aérosol d'agglomérats [1]. Le précurseur est introduit au sein d'une flamme de combustion pilote sous forme de spray. Le procédé se caractérise par des réactions ayant lieu à haute température mais dans des temps très courts permettant d'obtenir des tailles de particules primaires nanométriques. Ces réactions étant initiées à partir de gouttelettes constituées du mélange de précurseurs initial, les produits obtenus se montrent homogènes en morphologie, composition et phase cristalline. La croissance ayant lieu en phase vapeur, il n'y a pas de contact contaminant avec l'enceinte de synthèse et la pureté des produits n'est limitée que par celle des réactifs utilisés. Comme tout procédé faisant intervenir une étape de combustion, la SPF est toute indiquée pour la synthèse d'oxydes. Toutefois, certains auteurs ont démontré la possibilité d'utiliser la SPF pour synthétiser des particules céramiques non-oxydes [2] ou métalliques [3] en imposant des conditions réductrices dans la flamme pilote produisant des espèces (H2, CO) aptes à capter l'oxygène préférentiellement et éviter ainsi l'oxydation des particules en croissance. Ces nanoparticules de nature variée peuvent être intégrées à différentes préparations (encres, barbotines, matrices organiques ou minérales) afin d'élaborer des matériaux nanostructurés (films minces, revêtements, céramiques massives, composites…) permettant d'étudier et d'utiliser les propriétés spécifiques apparaissant dans ce type de nanomatériaux

Elaboration de revêtements et de massifs à partir de nanoparticules synthétisées opar pyrolyse laser, plasma inductif et PVD: procédés couplés et application à la production et au stockage de l'énergie

International audienc

Advanced nanoparticles synthesis by laser pyrolysis for energy production and storage

International audienceUrging demand for efficient technologies aiming at fossi! fuel replacement dlives the development of innovative materials and motivates abundant research work. ln particular, advanced nanostructured materials, because of their peculiar propelties due to size effects, appear as smalt and efficient solutions to meet this challenge. In this context, novel processes able to synthesize advanced nanopalticJes play a key role in the achievement of innovative devices for alternative energy production and storage. ln this lecture the development of laser pyrolysis process is reported in the fields of photovoltaics and e1ectrochemical storage.Laser pyrolysis is a gas phase flow process enabling the synthesis of various nanopalticJes using a laser beam for precursors thennal decomposition. Because of flow operation and small dimension offocused laser spot, the residence time and growth duration after nucleation is very ShOlt, leading to the collection of very small nanoparticJes. ln the case of silicon quantum dots, palticles as small as 3 mn can be obtained which exhibit quantum confinement with broadened bandgap. Such materials can be doped and deposited in situ, together with the co-deposition of <t;matrix using sputteling, in order to elaborate nanostructured or nanocomposite thin films. ln this process, sources of palticles and mattix are separated and independent, leading toa high versatility in tenns of composites composition. The Si bandgap engineered films prepared with this laser pyrolysis based in situ deposition technique were proven to show interesting electronic and optical propelties for high efficiency solar cells application based on ali-Si tandem cells. For energy stOlllge, Sn0$_2$ or ZnFe$_2$0$_4$. nanopowders can be synthesized from liquid precursors with various morphologies or doping elements. When applied as conversion matelials for batteries, these particles show state of the aIt perfonnances versus Li with very good cyclability. Si@C core-shell structures can also be prepared in a single step thanks to a double stage laser pyrolysis reactor, where Si cores are grown at the first stage before being covered by carbon at the second stage. With this process the nature of the core particle can be chosen independently of the coating nature. Obtained structures can then be used as alloying materials electrodes in Li battelies, showing highly improved cyclability for Si-based batteries

Croissance et propriétés du silicium granulaire en films minces (procédé basse température et rôle critique des radicaux hydrures dans le plasma)

CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF

Synthesis of SiC-ZrC composite powders via a hydrosilylated-polymer-derived ceramic route

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Synthesis of nanoobjects

International audienceTop-down and bottom-up approaches have been developed for the synthesis ofnanoobjects [1]. Top-down ones include, for example, milling and attrition forparticles in the range from 10 nm to several hundred nanometers in diameter.However, these techniques exhibit large size and shape distributions, and significantamounts of impurities from the treatment medium or defects from the process itself.Bottom-up approaches are much more preferred through many different processes asthey generally show more convincing results in terms of uniformity in size, shape andchemical composition distributions. Generally, nanoparticles are synthesized byhomogenous nucleation in the liquid phase or in the gas phase, and nanowires ornanotubes are synthesized by heterogeneous nucleation on a substrate. Fundamentalaspects of nucleation and growth are presented prior to a presentation of differentsynthesis processes

Integration of nanoobjects

International audienceIn this part, we are interested in the different ways of handling nanomaterials aimingultimately at their incorporation into solid-state structures, in general as more orless thick deposits. These different routes are classified according to the processesused, depending on whether they consider handling liquids, solids or gaseous phases.None of these methods appears specific to the implementation of nanoobjects intosolid-state structures. The use of one method rather than another seems essentiallyguided by the“functionality”of the structure, for example, the fact that the depositconstitutes one of the elements of a final structure and/or necessitates a separatecharacterization, or the fact that the deposit brings together several elements whoseproperties are expected to be exploited in synerg

Application of nanoobjects to energy and transportation

International audienc

Laser pyrolyzed SnO2 nanoparticles as anode material in Sodium ion Batteries

International audienc