Tesi sul tema "Gaz rares – Composés"
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Alkaa, Ai͏̈ssa. "Etude des fonctions de distribution des électrons dans les plasmas froids composés de mélanges de gaz rares avec des vapeurs métalliques ou des gaz électronégatifs". Toulouse 3, 1991. http://www.theses.fr/1991TOU30137.
Marrocchi, Yves. "Incorporation des gaz rares dans la matière organique primitive du système solaire". Phd thesis, Institut National Polytechnique de Lorraine - INPL, 2005. http://tel.archives-ouvertes.fr/tel-00258016.
Bakiz, Bahcine. "Etude de systèmes de matériaux évolutifs : interactions solides-gaz, propriétés catalytiques et électriques dans le cas d'hydroxycarbonates, carbonate et oxydes à base de terres rares (La, Ce, Lu)". Toulon, 2010. https://theses.hal.science/tel-00602907/fr/.
The present work deals with the solid gas interactions between lanthanum and cerium based phases (hydroxycarbonates LaOHCO3, CeOHCO3, carbonate La2O2CO3, and oxides La2O3, CeO2), and the gases CH4, CO and CO2. These interactions might be involved in gas sensor or catalytic applications. The main interest of these rare earth based systems resides in the fact that they are evolving materials in environmental conditions. The initial hydroxycarbonate phases are synthesized via specific precipitation sol-gel routes. The phases La2O2CO3, La2O3 and CeO2 are obtained by thermal treatment of the hydroxycarbonates. The various phases are first characterized by X-ray diffraction. Their crystal sizes and morphologies are then determined by scanning and transmission electron microscopy (SEM, TEM). The catalytic interactions of these polycrystalline solids with air-CH4 and air-CO mixtures are studied making use of Fourier Transform Infrared spectroscopy of emitted gases, at various temperatures (100 to 550°C), and as a function of time. The conversions of CH4 and CO into CO2 are observed from air – gas flows crossing through polycrystalline walls of the polycrystalline catalytic materials. The catalytic efficiency is defined as being proportional to the FTIR absorbed intensities due to the CO2 molecules. These intensities depend on time and temperature. The electrical analyses of compacted pellets are performed by electrical impedance spectrometry at various temperatures. For a given temperature, the conversions of CO and CH4 into CO2 reach a stabilized level after an initiation time. This stabilized level increases with temperature and reaches a maximum value depending on material nature and specific area. The conversion of CO is obtained at temperatures lower than the ones observed for CH4. These time dependent catalytic conversions are modeled from an elemental Avrami’s approach. The carbonatation kinetics are determined first by thermal and thermogravimetry analyses, at fixed temperatures, as a function of time. Two steps in carbonatation are evidenced. Using electrical impedance spectrometry as a function of time and temperature the electrical evolutions of lanthanum and cerium based systems subjected to carbonatation and decarbonatation are analyzed. As a first step, the electrical responses associated with the phase modifications of the hydroxycarbonate phases LaOHCO3 and CeOHCO3 during thermal decomposition under air are determined. Then, the electrical signals due to carbonatation and decarbonatation processes are analyzed: the ionic mobility of CO3 2- ions in the carbonate solid is evaluated. The evolving series LaOHCO3-La2O2CO3 - La2O3 might be of a high interest in gas sensor systems, working at variable temperatures and sensitive to CH4, CO or CO2
Comte, Caroline. "Etudes des interactions de gaz rares avec des molécules organiques : inclusion de l'argon, du krypton et du xénon dans des molécules hôtes". Dijon, 1997. http://www.theses.fr/1997DIJOS064.
Almayrac, Matthieu. "Volatile element behaviour in cometary ice analogues under irradiation". Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0320.
Comets represent some of the most pristine and unprocessed bodies in our solar system. As such, their analysis can provide a unique insight into the chemical makeup of the early Solar System. Furthermore, due to their volatile-rich nature, comets may have played an important role in delivering volatile elements (e.g., H, C, N, O) and organic materials to early Earth. Understanding how comets form can therefore provide a wealth of information on how the composition of volatile elements evolved in the solar system, from the pre-solar molecular cloud up until the formation of the terrestrial planets. Decades of cometary studies, and the recent ESA Rosetta mission to comet 67P/Churyumov-Gerasimenko (67P/C-G), have demonstrated that volatile species trapped in comets have a composition that is distinct from any other known reservoir in the Solar System. Cometary nitrogen, in particular, shows strong enrichments in the rare 15N isotope. The origin of these enrichments remains unclear, potentially reflecting the isotopic fractionation of an initial 15N-poor nebular gas, or inheritance from an unknown isotopic reservoir. During this PhD, I have developed an experimental setup to form cometary ices (i.e., water-rich ices formed at very low temperatures and pressures), with the overarching objective of exploring how volatile elements (including N and noble gases) were incorporated into cometary ice during water condensation from the protosolar nebula. Different temperatures of formation (from 28K to 80K) and irradiation conditions have been tested in order to investigate the conditions that best reproduce the actual volatile composition of comet 67P/C-G. It was found that condensing cometary ice analogues at temperatures ~70K is best able to reproduce the nitrogen and noble gas abundances measured in 67P/C-G. Moreover, we discovered that the incorporation of nitrogen and noble gases into, and subsequent release from, cometary ices does not produce significant isotope variations, indicating that isotope signatures in comets were most likely inherited from their environment of formation rather than the result of fractionation during ice formation. Finally, I also investigated the effect that UV irradiation can have on the composition of volatiles trapped within cometary ice. Irradiation during and after ice deposition was found to not have a significant effect on the isotopic composition of the trapped volatile species. However, it was discovered that irradiating the surface of the ice had a major effect on the release pattern of trapped volatiles, with the ice being retentive of trapped volatiles even after the amorphous-to-crystalline ice transition (120-140K), temperatures at which point all trapped volatiles are released from non-irradiated ice. The enhanced retention of volatiles in irradiated cometary ice may have major implications on the potential for comets to deliver volatile elements to the inner solar system
Bekaert, David V. "Isotopic constraints on the origin and nature of primitive material in the Solar System and on early Earth". Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0002.
The Earth formed some 4.5 Ga from the accumulation of dust, rocks and gas. The composition of these primitive materials is today recorded in meteorites. However, the origin of volatile elements within the atmosphere (e.g., H, C, N, O) remains poorly understood. By combining experimental approaches and the analysis of natural samples, I studied the composition of celestial objects comprising the ingredients required for the formation of the terrestrial atmosphere. These mainly correspond to volatile elements trapped in meteoritic organic materials and in the ice of cometary bodies. In order to better understand the timeline of Earth's formation and volatile accretion, I used noble gases (He, Ne, Ar, Kr, Xe) as tracers of the physical processes that occurred in the early Solar System and on primitive Earth. Whilst comets significantly contributed to the heavy noble gas budget of the terrestrial atmosphere (~20%), most of the other terrestrial volatile elements (including water, carbon and nitrogen) would have been supplied to Earth by chondrtitic bodies similar to meteorites. Once formed, the atmosphere evolved over geological periods of time, leading to the establishment of suitable environmental conditions for life to develop. The major processes that affected the mass and composition of the ancient atmosphere can be studied by investigating the isotopic evolution of atmospheric Xe, from 4.5 Ga to ~2 Ga. We investigate the possibility to bring constraints on the age of organic materials isolated from sedimentary ricks older than 2 Ga, using the isotopic signature of the Xe component that was trapped at the time of their formation. This method could have implications regarding the presumed age of the earliest remnants of organic life
Grigoriev, Ivan, e Joël Boissoles. "Etude par spectroscopie infra-rouge a transformee de fourier de l'absorption des composes fluores perturbes par des gaz rares". Rennes 1, 1996. http://www.theses.fr/1996REN10056.
Amarouche, Mohand. "Modelisation des agregats de gaz rares et dynamique d'ar : :(3)**(+)". Toulouse 3, 1988. http://www.theses.fr/1988TOU30135.
Alikhani, Mohammad Esmaïl. "Etude par spectroscopie de diffusion raman du piegeage de trois especes isotopiques de dihydrogene en matrice de gaz rares et d'azote : interpretation theorique des perturbations spectrales observees dans les gaz rares". Paris 6, 1988. http://www.theses.fr/1988PA066015.
Radouani, Abdelhak. "Réaction des atomes métastables de gaz rares (Ar*(3p2,0), Kr*(3p2) et Xe*(3p2)) avec le silane". Grenoble 1, 1986. http://www.theses.fr/1986GRE10143.
Chergui, Majed. "Etude des transitions de Rydberg et de la relaxation intramoléculaire de la molécule NO piégée en matrices de gaz rares". Paris 13, 1986. http://www.theses.fr/1986PA132017.
Ayed, Othman. "Etude des interactions entre atomes alcalins (li, na, k) et monoxyde de carbone en matrices de gaz rares : analyse en spectroscopie vibrationnelle et calcul quantiques de quelques complexes". Paris 6, 1987. http://www.theses.fr/1987PA066117.
Quichaud, Viviane. "Etude des processus elementaires : de synthese de la molecule no, en post-decharge en ecoulement, de collisions titane-gaz rares, titane-molecules, par perturbation laser resolue en temps". Paris 6, 1987. http://www.theses.fr/1987PA066135.
Iftner, Christophe. "Modélisation de complexes et agrégats moléculaires en matrice cryogénique". Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30160/document.
This thesis presents the development and applications of an hybrid quantum-classical formalism in order to describe the electronic structure of an active system in a cryogenic environment (cluster or rare gas matrix). The quantum description of the electronical structure of the active system is based on a a tight-binding approximation of the density functional theory, with self-consistency regarding the charges (SCC-DFTB). The rare gaz environment is described via classical atom-atom potential (FF). The interaction between the active system and the atoms of the cryogenic environment is represented by local anisotropic matricial electron-atom operators, as well as by polarisation and dispersion contributions. Operators and interaction parameters are extracted from post Hartree-Fock \textit{ab initio} calculations (CCSD-T) of active atom/argon atom pairs. The applications involve hydrocarbons, isolated water clusters or hydrocarbon/water complexes in interaction with argon clusters or matrices. The model has been validated on small systems (C6H6 molecule, H2O molecule) in interaction with argon atoms and clusters. We have been able to determine structural and energetic data for (C6H6)Arn (n < 55) clusters which are benchmarked against ab initio results (DFT,CCSD-T) for the smaller sizes, or with respect to FF calculations, available in the literature, for larger sized clusters. The model enables to treat various electronic situations, allows in particular to determine the evolution of the ionization potentials of the active system as a function of the inert cluster size. The SCC-DFTB/FF model has then been applied to water molecules and water nano-clusters (H2O)n (n=2-6) embedded in argon matrices, represented by finite size cristal pieces of the face centered cubic lattice. Structural and energetical data have been obtained. Molecular dynamics studies have enabled the determination of finite temperature infrared (IR) spectra. Comparison between the theoretical and experimental spectra of the water monomer embedded in the matrix validates the SCC-DFTB/FF approach. The case of the water hexamer (H2O)6, the smallest cluster presenting a three-dimensional structure and caracterized by several low-energy isomers, has been investigated exhaustively : the effect of the matrix on the structures of some isomers has been shown as well as differential effects on their respective stabilities. An influence on IR lines positions has also been highlighted. Our theoretical study allows for a satisfactory interpretation of the experimental data for the smallest clusters (n<4). The assignment of the experimental spectra of the hexamer remains in discussion. Finally, preliminary results on structures, energetics and finite temperature IR spectra have been obtained for Polycyclic Aromatic Hydrocarbons (PAH) /water complexes. The results for the complexes are discussed in relation with experimental data obtained in the team of Joëlle Mascetti at the Institute of Molecular Sciences (University of Bordeaux I), in the context of an ANR collaborative project (ANR PARCS no 13-BS08-0005). The thesis has been co-financed by the CNRS Institute of Physics and Conseil Regional of Region Midi-Pyrénées
Cunsolo, Alessandro. "Relaxation phenomena in the THz dynamics of simple fluids probed by inelastic X-ray scattering". Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10166.
Hickel, Probst Sonia Maria. "Propriétés catalytiques et caractérisation de catalyseurs au nickel déposé sur oxydes de terre rare : influence de l'intéraction métal-support". Poitiers, 1989. http://www.theses.fr/1989POIT2296.
Salama, Farid. "Etude de la photoexcitation dans l'ultra-violet lointain des halogènes piégés en matrice de gaz rare à basse température et étude de leur ionisation simple et double par impact protonique en phase gazeuse". Paris 6, 1986. http://www.theses.fr/1986PA066213.
Dahoo, Pierre Richard. "Sur l'intensite et l'elargissement par la pression des raies de vibration-rotation des bandes nu3, nu1 plus nu3 et nu1 plus nu3 moins 2nu2-o de 12c1602 et nu3 de 14n2160 : etude experimentale et interpretation des parametres d'elargissement au moyen". Paris 6, 1988. http://www.theses.fr/1988PA066175.
Hliwa, Mohamed. "Traitement simplifie des interactions moleculaires en chimie quantique". Toulouse 3, 1988. http://www.theses.fr/1988TOU30038.