Rozprawy doktorskie na temat „Composés aromatiques polycycliques – Propriétés optiques”
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Bejaoui, Salma. "Etude spectroscopique des suies et de leurs précurseurs par incandescence et fluorescence induite par laser". Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10145.
In this thesis, we used several techniques of analysis to determine the spectroscopic properties of soots and their precursors (the polycyclic aromatic hydrocarbons: PAH); two types of quite different atmospheric flames were investigated: a premixed flat flame of methane (equivalence ratio: 2.1) and a jet diffusion flame of liquid hydrocarbons (methyl ester of rapeseed oil or diesel fuel). We coupled optical methods in-situ (incandescence and fluorescence induced by laser, extinction, measurement of the thermal radiation by pyrometry) and of soots sampling for analysis by transmission electronic microscopy. Firstly, the premixed flame was characterized in term of soot volume fraction profiles, of temperature of soots before and during the laser excitation and distributions of monomers soot size. Confrontation between the temporal decreases of LII signals experimental and modelled (in the case of a collaboration with NRC, Canada) made it possible to better determine the evolution of the absorption function of soots during their formation. Secondly, by a non-intrusive method, the ratio of the absorption function based on our method using two excitation wavelengths (1064 nm taken as a reference) was obtained directly for 266, 355, 532 and 660nm. To finish, the fluorescence induced by laser was applied to various excitation wavelengths to probe the fluorescence of the PAH along the flames, as well for the intensity and the spectral response. We showed that the HAP absorb and fluoresce from UV to 680 nm. This fluorescence is emitted by various families of PAH (from the smaller to the larger) when the wavelength of excitation increases. With an excitation in UV, we showed that the spectra of fluorescence are shifted towards the red. For an excitation in the visible, the spectra become centered on the laser wavelength at 532 nm and then after comprise a majoritary component “anti-Stokes” when the excitation tends to 680nm
Bouvier, Yoann. "Caractérisation de suies et de précurseurs de suies dans des flammes par incandescence induite par laser". Lille 1, 2006. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2006/50376-2006-Bouvier.pdf.
Cette étude a été effectuée de manière originale en utilisant un profil de faisceau laser gaussien et en comparant la détection "classique" à angle droit à la détection dans le sens contraire à la propagation du faisceau (rétro-LII) Cette comparaison a permis de valider un dispositif de mesure de fraction volumique de suies par rétro-LII à l'échappement des moteurs. Une méthode expérimentale de détermination de révolution de la fonction d'indice de réfraction E(m) avec la longueur d'onde est proposée par comparaison des signaux LII obtenus en utilisant des longueurs d'onde d'excitation dc 532 nm et 1064 nm. Une validation de la méthode est effectuée par comparaison avec des mesures d'extinction obtenues par mesure du temps de déclin d'une cavité optique (CRDS) aux mêmes longueurs d'onde. La structure des flammes "jet" supports a été étudiée par couplage de l'Incandescence Induite par Laser des suies et de la Fluorescence Induite par Laser des HAP à 532 nm (LII / LIF). La calibration des fractions volumiques de suies est effectuée par mesure du temps de vie d'une cavité optique à 1064 nm. Des cartographies suies / HAP sont ainsi obtenues dans une flamme de diffusion de méthane et dans les deux flammes de prémélange. La sensibilité des techniques mises en œuvre permet de détecter de très faibles teneurs en suies (< 1 ppb). Une méthode novatrice de mesure de la vitesse des particules de suie dans les flammes est également proposée
Labarrière, Luc. "Spectroscopic properties of environmental relevant systems : 2’,3-dihydroxyflavone-ion complexes and polycyclic aromatic hydrocarbons : a joint experimental and theoretical study". Electronic Thesis or Diss., Université de Lille (2022-....), 2022. http://www.theses.fr/2022ULILR069.
This manuscript reports the results of an experimental and theoretical study of two molecular systems of environmental interest: 2',3-dihydroxyflavone (2'3HF) and polycyclic aromatic hydrocarbons (PAH). These systems were studied by a combination of electronic spectroscopic techniques (absorption and fluorescence) and quantum chemical calculations (DFT and TD-DFT). In the first part of this thesis, it is shown that 2'3HF has singular acid-base properties compared to other flavonols. The decrease of the pKa by several units is attributed to the presence of a hydrogen-bond network. In the excited state, an intramolecular proton transfer causes a dual fluorescence. An additional emission band, seemingly originating from a tautomeric form perturbed by interaction with the solvent, was revealed. Finally, an exhaustive study of the Ca(II), Mn(II) and Zn(II) complexes showed the formation of chelates with the α-hydroxyketone function. In the second part, three structural hypotheses to explain the experimental observation of visible-range laser-induced fluorescence (LIF) were explored. A study of van der Waals (vdW) dimers of PAHs provided insights into the nature of the monomer interaction and highlighted the difficulty of modelling these systems. However, the calculated electronic transitions suggest that these species cannot be responsible for the LIF signals. Secondly, an identical study of aliphatically bridged PAHs showed very similar results to vdW dimers, ruling out their involvement in the observed fluorescence. Finally, the hypothesis of emission from PAH radicals was explored. The latter is very promising and opens the way for further experimental and theoretical studies
Dontot, Léo. "Propriétés structurales et spectroscopiques des agrégats d'hydrocarbures aromatiques polycycliques". Toulouse 3, 2014. http://thesesups.ups-tlse.fr/4526/.
Modeling of neutral or cationic molecular clusters remains a challenge in ab initio approaches as soon as the molecules involved are large or when their number exceed several units. We develop, in this thesis, a mixed method based on the combination of the DFTB method, an approximation of the Density Functional Theory (DFT), with a Configuration Interaction (CI). This method (DFTB-CI) provides an original and efficient approach to obtain a correct description of the charge resonance within cationic clusters. The application to polycyclic aromatic hydrocarbons clusters is of interest in various fields such as physics and chemistry of the interstellar medium, chemistry of the atmosphere and also combustion processes. This work has enabled the description of structural properties of the ground state of neutral and cationic clusters of pyrene and coronene containing up to ten molecules. A multi-method strategy has been implemented in order to efficient search for the most stable structures with the global exploration algorithm "Parallel Tempering Monte Carlo". In addition to the structural properties, we have determined the quantities characterizing the stability of these clusters (binding and dissociation energies) as well as their electronic properties such as the dependency of the ionization potentials on the size in good agreement with experimental results. Finally, we propose an extension to the DFTB-CI model in order to compute the excited states of molecular clusters. The results on dimers are found in good agreement with ab initio calculations. An application to small cationic clusters of benzene and pyrene presents the determination of their electronic absorption spectra
Dufitumukiza, Jean Pierre. "Développement des techniques optiques pour la caractérisation in-situ de la suie dans des foyers de combustion à haute pression". Electronic Thesis or Diss., Université de Lille (2022-....), 2023. https://pepite-depot.univ-lille.fr/ToutIDP/EDSMRE/2023/2023ULILR010.pdf.
The growth of air traffic urges combustion research to get a detailed understanding of the physical and chemical processes occurring in the aircraft engine; the main objectives are 1) to improve the combustion process and 2) to lower gaseous and particulate emissions. A solution to the first issue lies in the combustion at higher pressure and temperature, but this can impact the second issue, particularly concerning the production of soot and NOx emissions. To find a solution, it is necessary to develop experimental tools applied in representative combustion conditions relative to those encountered in aircraft engines in order to capture complex phenomena occurring inside these engines. To do this, a semi-industrial aeronautical test rig equipped with suitable optical diagnostics implemented/available at ONERA Palaiseau offers a glimpse of information into these combustion processes. As a result, this research aims to develop and implement optical techniques for characterizing soot particles in aeronautical engine-relevant combustors. Laser-Induced Incandescence (LII) is the primary technique on which efforts are directed. This technique is based on Planck's law radiation model. LII technique is used due to its high sensitivity for detecting the soot volume fraction and flexibility for its implementation in various optical configurations. In addition, the coupling of LII with other optical techniques presents a high interest in understanding the mechanisms and parameters leading to soot formation. First, Laser-Induced Fluorescence (LIF) is added as a complementary technique to detect soot precursors known as Polycyclic-Aromatic Hydrocarbons (PAHs). Secondly, light scattering provides information on the distribution of unburnt liquid fuel droplets and possible soot particle localization inside the combustor. Thirdly, OH* chemiluminescence illustrates the reaction zone and heat release. Finally, the PAHs and soot transportation or interactions with the flow field are tackled via particle image velocimetry (PIV)
Michoulier, Eric. "Influence de la glace d’eau sur les propriétés spectroscopiques et énergétiques d’hydrocarbures aromatiques polycycliques". Electronic Thesis or Diss., Lille 1, 2017. http://www.theses.fr/2017LIL10122.
Polycyclic aromatic hydrocarbons (PAH) molecules are thought to be responsible for specific infrared emission bands in the interstellar medium (ISM). The cold and dense areas of the ISM, such as molecular clouds, contain dust particles whose mantle is predominantly composed of water ice. The interaction of PAH with ice tends, on the one hand, to modify its spectroscopic properties and, on the other hand, under UV irradiation, to induce a specific reactivity. Our theoretical work falls within this framework and aims to study the influence of ice on the energetic and spectroscopic properties of PAH, in connection with laboratory experiments. First, we have simulated the adsorption of PAH at the surface of amorphous and crystalline ice by classical molecular dynamics based on a force-field approach. A rigorous methodology has been developed to parameterize the charges of the different PAH. The adsorption energy of a various PAHs could thus be determined and a correlation was established between the adsorption sites and the presence of dangling bonds at the surface. Then, the generated configurations were used for SCC-DFTB calculations: the vibrational, harmonic and anharmonic spectra for the different PAHs and types of ice were determined. The shifts or emergences of bands identified on the calculated spectra were compared with the experimental data. The influence of the local organization of the surrounding water molecules on the vertical ionization potential has been characterized, as this process can impact precursor states to reactivity
Michoulier, Eric. "Influence de la glace d’eau sur les propriétés spectroscopiques et énergétiques d’hydrocarbures aromatiques polycycliques". Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10122/document.
Polycyclic aromatic hydrocarbons (PAH) molecules are thought to be responsible for specific infrared emission bands in the interstellar medium (ISM). The cold and dense areas of the ISM, such as molecular clouds, contain dust particles whose mantle is predominantly composed of water ice. The interaction of PAH with ice tends, on the one hand, to modify its spectroscopic properties and, on the other hand, under UV irradiation, to induce a specific reactivity. Our theoretical work falls within this framework and aims to study the influence of ice on the energetic and spectroscopic properties of PAH, in connection with laboratory experiments. First, we have simulated the adsorption of PAH at the surface of amorphous and crystalline ice by classical molecular dynamics based on a force-field approach. A rigorous methodology has been developed to parameterize the charges of the different PAH. The adsorption energy of a various PAHs could thus be determined and a correlation was established between the adsorption sites and the presence of dangling bonds at the surface. Then, the generated configurations were used for SCC-DFTB calculations: the vibrational, harmonic and anharmonic spectra for the different PAHs and types of ice were determined. The shifts or emergences of bands identified on the calculated spectra were compared with the experimental data. The influence of the local organization of the surrounding water molecules on the vertical ionization potential has been characterized, as this process can impact precursor states to reactivity
Yang, Zhixin. "Préparation et propriétés des polycarbosilanes comportant des groupements acétyléniques et aromatiques dans le squelette". Montpellier 2, 1992. http://www.theses.fr/1992MON20177.
Catanéo, Clément. "Etude des mécanismes de production et de dépôt des composés de la fumée lors du fumage de la chair de poisson : contribution à l'obtention de produits sains possédant de bonnes propriétés organoleptiques". Nantes, 2011. http://www.theses.fr/2011NANT2062.
Quality of smoked fish is altered by several steps during the technological processing. This work aims at bringing out new control points of the final product through a better understanding of smoke production and deposit mechanisms. The studies focused on both volatile phenolic compounds (involved in aroma, colour and shelf life of smoked food) and polycyclic aromatic hydrocarbons (main toxic contaminants of smoke). To directly elucidate smoke composition and indirectly evaluate interactions between gaseous compounds and solid matrices, several analysis techniques were developed and validated. Potential improvement of smoke compounds quantification by means of comprehensive gas chromatography was also investigated. Smoke generation was studied by chemometric characterization of various smokes produced with an industrial friction generator and trapped by means of an electrostatic precipitator. The main importance of wood specie and moisture were confirmed, as well as the complexity of the operating conditions of that type of generator. Deposits and interactions of smoke compounds at the surface of the products were measured with artificial food matrices. Results obtained under both actual industrial smoking and model conditions (static headspaces with controlled composition) highlighted the major role of the oil fraction, particularly concerning phenolic compounds enrichment
Aoulmi, Aïssa. "Contribution à l'étude des propriétés thermodynamiques des hydrocarbures polycycliques, aromatiques et des alcanes à longue chaine". Vandoeuvre-les-Nancy, INPL, 1994. http://www.theses.fr/1994INPL140N.
Thirion, Damien. "Modulation des propriétés d'isomères de diSpirofluorène-indénofluorène pour des applications en diodes électroluminescentes organiques bleues". Rennes 1, 2011. https://hal-univ-rennes1.archives-ouvertes.fr/tel-01217848.
This work is focused on the synthesis and study of 3π-2spiro molecules, DiSpiroFluorene-IndenoFluorene (DSF-IF), having different structures. These compounds are aimed to be used as blue light emitting layer in OLED. The first chapter describes the working principles of OLEDs and their different structures. It focuses then on different approaches of molecular engineering towards ambipolar molecules that can be used in single layer devices. The second chapter is devoted to the study of two different families of DSF-IF isomers that are obtained through one and the same synthetic intermediate. The different structure of the indenofluorene backbone, (1,2-b) or (2,1-a), leads to different properties, mainly because of intramolecular π-π interactions. The third chapter is related to the development of functionalized DSF-IF with electron donor and/or acceptor groups. The impact of the electron donor or acceptor groups substituted on the DSF-IF are discussed, especially the intramolecular charge transfer phenomena. In the last part, some of these new molecules have been tested as emitting layers in OLEDs
Mouaddib, Abderrahim. "Condensations aryniques de cétones cycliques diversement fonctionnalisées : nouvelles voies d'accès à des composés polycycliques". Nancy 1, 1990. http://docnum.univ-lorraine.fr/public/SCD_T_1990_0457_MOUADDIB.pdf.
Leroyer, Léo. "Chromophores carbo-benzéniques quadripolaires : cibles, synthèses, et propriétés". Toulouse 3, 2010. http://thesesups.ups-tlse.fr/902/.
The subject of this study concerns carbo-benzenic chromophores (ring carbo-mers of benzene derivatives) and more particularly the broadening of the variety of targets, synthetic methods and physico-chemical properties. The first chapter is devoted to the synthesis optimization of a [6]pericyclynedione, considered as a key precursor giving a " quick " access to quadrupolar carbo-benzenes by reductive elimination of the corresponding hexaoxy[6]pericyclynes. During the preparation of a representative of this family, the p-dianisyl-carbo-benzene, two unprecedented chromophores have also been isolated: a carbo-cyclohexadiene, resulting from a partial reduction of the pericyclynic precursor, and a dihydro-carbo-benzene, coming from an over-reduction of the same precursor. The spectroscopic, electronic and optical properties of these three chromophores have been studied. The second chapter concerns a new retrosynthesis of carbo-benzenes, involving the sequential ring closing metathesis of three dipropynylbutatriene units (path a). Within this prospect, a series of new dialkynylbutatrienes has been prepared. The third chapter deals with the study of an alternative approach to aromatic carbo-benzenes or carbo-quinoids envisioned here for the first time. The C18 macrocycles are aimed here by sequential coupling of respectively three or two bis-gem-dihalovinylidene units (path b and c). A forth chapter, more conceptual, relates a preliminary study of carbo-enolates reactivity, especially towards palladium catalysts
Mabicka, Iwangou Saint Bickolard. "Impact de la pollution sur les propriétés du bois de palétuviers de mangrove de l’Estuaire du Gabon : cas pratiques de Rhizophora racemosa et d’Avicennia germinans". Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0251.
Mangrove mangroves are plants that grow between land and sea in tropical climates. This interface position gives mangroves an important ecological and socio-economic role. Among other things, they serve to protect biodiversity, protect the coasts against erosion of the littoral, and sequester significant quantities of carbon dioxide. In Gabon, however, mangroves face urban pollution. This pollution includes heavy metals (ETM), polycyclic aromatic hydrocarbons (PAHs) and many other wastes depending on their location. Thanks to its developed root system, especially for the species R. racemosa and A. germinans, these mangroves absorb pollutants and concentrate them in the roots and trunk. The objective of this study was to show the impact of pollution on the properties of mangrove wood. The wood from the PAH-polluted site showed undifferentiated sapwood, reduced extractives content and low durability to fungal attack. The wood from the ETM polluted site had a higher natural durability than the wood collected from the unpolluted sites. These results were compared with samples of beech (Fagus sylvatica) impregnated with ETM at the laboratories which showed the same higher durability to fungi
Delsarte, Isabelle. "Dégradation des dioxines ou du benz[a]pyrène par une approche tripartite : oxydation chimique / oxydation biologique par des champignons telluriques saprotrophes / amidon difonctionnalisé aux propriétés surfactantes". Thesis, Littoral, 2017. http://www.theses.fr/2017DUNK0447/document.
This thesis work deals with the development of bioremediation techniques for contaminated soils by Persistent Organic Pollutants (POPs) such as : Polycyclic Aromatic Hydrocarbons and dioxins (PCDD/F). The degradation of POPs has two main obstacles to efficient biological treatments by fungi : the low bioavailability of POPs and the difficulty of initiating the oxydation of molecules as stable as others. To overcome these technological barriers, we propose to couple a mild chemical oxidation to biological oxidation by saprotrophic telluric fungi and to use starch to improve the spatial proximity between the pollutant and oxidizing reagents. The first part of this study is to functionalize native potato starch by 1,4-butane sultone and 2-octenyl-1-succinic anhydride according to different synthesis conditions. In comparison with native starch, one of the processed products, P9*, has very interesting surfactant properties for our study. Indeed, P9* increases starch apparent aqueous solubility by a factor of 65 (22.60 g.L⁻¹) and stimulates 33-fold benzo[a]pyrene (BaP) aqueous solubilization. For the second part, the use of a simplified study system where the fungus is cultivated in mineral medium under axenic conditions allowed us to determine the best parameters (fungal strainsn type and dose of chemical oxydant) for the development of a POPs degradation method in the laboratory. Comparative studies of BaP degradation are therefore carried out in vitro by different processes of chemical (Fenton's reagent) and/or biologial oxidation. The coupling of the two processes leads to a BaP degradation of 40.0%. Moreover, the BaP encapsulation by starch nanospheres P9* allows a pollutant degradation of 94.6% by the Fenton reagent. Two fungal strains (Penicillium brasilianum and Funsarium solani) are then used for the degradation lab experiment in historically PCDD/F contaminated soil microcosms. the inoculation of the endogene strain P.brasilianum in presence of cardboard chips as a bulking agent led to a decrease in PCDD/F toxicity of 40.5% after only two months of incubation compared to the controm soil. This PhD work draws new perspectives for remediation techniques of contaminated soils by POPs that are cost-effective and environmentally friendly
Laurent, Fabien. "Impact de l'oxydation chimique et de la refonctionnalisation sur des paramètres physico-chimiques et biologiques de terres contaminées au HAP". Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0033/document.
In order to clean up polycyclic aromatic hydrocarbon (PAH) contaminated soils, various techniques have been developed during the last decades, but their impact on soil functions was rarely considered. The objective of this study was to assess the impact of chemical oxidation treatments on different physico-chemical and biological parameters of PAH contaminated soil and to propose solutions to improve the biological functioning of oxidized soil. Various laboratory and field experiments have shown that the efficiency of chemical oxidation reactions (Fenton reaction and activated persulfate) on PAH concentrations depended on pollutant availability and soil physico-chemical properties. Besides, intense acidification processes have been observed on uncarbonated soil with a strong impact on soil physico-chemical and biological parameters. Moreover, this alteration was higher with activated persulfate treatment, leading to the loss of trace metals in water percolation. In the strongly acidified soil, the input of materials, suitable for pH increase, resulted in the restoration of biological activities and soil capacity to support vegetation. The association of chemical oxidation treatment and restoration techniques could present a good mean for soil rehabilitation. Finally, an index, which aimed to represent soil conditions based on the weight given to different parameters, was proposed and was used to evaluate changes induced by oxidation treatments and restoration techniques
Laurent, Fabien. "Impact de l'oxydation chimique et de la refonctionnalisation sur des paramètres physico-chimiques et biologiques de terres contaminées au HAP". Electronic Thesis or Diss., Université de Lorraine, 2012. http://www.theses.fr/2012LORR0033.
In order to clean up polycyclic aromatic hydrocarbon (PAH) contaminated soils, various techniques have been developed during the last decades, but their impact on soil functions was rarely considered. The objective of this study was to assess the impact of chemical oxidation treatments on different physico-chemical and biological parameters of PAH contaminated soil and to propose solutions to improve the biological functioning of oxidized soil. Various laboratory and field experiments have shown that the efficiency of chemical oxidation reactions (Fenton reaction and activated persulfate) on PAH concentrations depended on pollutant availability and soil physico-chemical properties. Besides, intense acidification processes have been observed on uncarbonated soil with a strong impact on soil physico-chemical and biological parameters. Moreover, this alteration was higher with activated persulfate treatment, leading to the loss of trace metals in water percolation. In the strongly acidified soil, the input of materials, suitable for pH increase, resulted in the restoration of biological activities and soil capacity to support vegetation. The association of chemical oxidation treatment and restoration techniques could present a good mean for soil rehabilitation. Finally, an index, which aimed to represent soil conditions based on the weight given to different parameters, was proposed and was used to evaluate changes induced by oxidation treatments and restoration techniques
Dupuy, Nicolas. "Corrélations électroniques des acènes vers la limite de longue taille : étude par Monte Carlo quantique". Electronic Thesis or Diss., Paris 6, 2016. http://www.theses.fr/2016PA066143.
We study the family of acenes by means of quantum Monte Carlo methods (QMC) based on a Jastrow correlated antisymmetrized geminal power (JAGP) wave function. Those methods allows for JAGP optimization in a variational manner (energy minimisation) and for ground state energy evaluations when the wave function nodes are well defined. By tuning the variational freedom of JAGP wave functions we study their electronic properties as a function of the wave function quality. We thus obtain results in favour of a highly resonating character, but smeared on many states, incompatible with a previously supposed open shell character. The study also demonstrates that a too low variational freedom induces high bias in the electronic description. By QMC structural relaxation on wave functions of various quality we demonstrate that the acenes geometry is highly coupled to their electronic structure.We can consider extending this study to general polycyclic aromatic hydrocarbons similar to graphene nanoribbons of growing thickness to investigate possible correlations between Clar sextets et their electronic and spintronic properties
Irimiea, Cornelia. "Characterization of soot particles and their precursors by coupling laser-based techniques". Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10066.
Combustion impacts many important aspects of our life like the air quality, the local and global climate and the use of energy sources. In the last decades, an outstanding progress towards cleaner combustion has been achieved. However, the reaction pathways leading to the formation of some pollutants, especially particulate matter (soot) resulting from incomplete combustion, are still elusive. In this work, we aim to investigate specific aspects of soot and its precursors formation in laboratory flames for a fundamental understanding of the mechanisms leading from the gas phase up to the mature particulate found in the exhausts. This objective is also pursued in field-campaigns to assess the potential impact of soot surface properties on the environment. Following this approach, experimental techniques like in-situ laser induced incandescence and fluorescence, and ex-situ laser desorption and secondary ion mass spectrometry are used to target specific properties of soot and its precursors. Notably, the evolution of the complex refractive index of soot is measured as a function of soot maturity, and the implications on both the flame physico-chemistry and the analytical techniques applicability are discussed. Additionally, a new detection method for soot and precursors based on simultaneous excitation at one wavelength is developed. In parallel, two campaigns are dedicated to the analysis of the surface chemistry of soot sampled from airplane and car exhausts. Statistical methods as multivariate analysis are used to identify patterns and differences within sets of samples by assessing the influence of the combustion parameters or the role of the fuel
Ngo, Thi Linh Dan. "Characterization of soot particles and their precursors produced during the combustion of conventional and alternative fuels : an in-situ laser diagnostics and ex-situ mass spectrometry investigation". Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1R040/document.
Interest in biofuels has increased significantly in recent years as they could reduce dependence on fossil fuels and contribute to carbon-neutral growth. The influence of using biofuels on their exhaust emissions (CO,CO_2,NO_x,HC, etc.) has been studied widely. However, the effects of the nature of these alternative fuels on the physical and chemical properties of the particles and aromatic species produced are not fully understood. As part of this thesis work, we aim to study the emissions of soot particles and polycyclic aromatic hydrocarbons (PAHs) during the combustion of conventional and alternative fuels (biofuels) relevant to the automotive and aerospace sectors, while trying to highlight their influence on the formation of such pollutants. To achieve this goal, two laboratory combustors, a swirled turbulent jet burner and a Combustion Aerosol STandard (CAST), were used as soot generators. In addition, we have combined various complementary in-situ laser techniques, laser-induced incandescence and fluorescence (LII/LIF), and ex-situ two-step laser mass spectrometry (L2MS) and secondary ion mass spectrometry (SIMS). In a swirled turbulent jet flame for five fuels (Diesel, n-butanol, 50/50 Diesel/n-butanol mixture, Jet A1 and Synthetic Paraffinic Kerosene SPK), the LII and LIF profiles and properties of soot particles and their precursors with the height in the flame as well as their chemical composition were studied. Strong correlations between the results obtained with in-situ and ex-situ techniques have been demonstrated which allowed us to characterize these species spectrally and chemically. In addition, a new calibration method has been developed to directly deduce the soot volume fraction from the LII signal using the absolute radiance emitted from a light source having black body behavior. In parallel, experiments using the CAST device were conducted with aeronautical fuels (Jet A1 and SPK). In addition to the influence of the alternative fuel, the effects of a catalytic stripper (CS) on soot particles and volatile species were examined
Dupuy, Nicolas. "Corrélations électroniques des acènes vers la limite de longue taille : étude par Monte Carlo quantique". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066143/document.
We study the family of acenes by means of quantum Monte Carlo methods (QMC) based on a Jastrow correlated antisymmetrized geminal power (JAGP) wave function. Those methods allows for JAGP optimization in a variational manner (energy minimisation) and for ground state energy evaluations when the wave function nodes are well defined. By tuning the variational freedom of JAGP wave functions we study their electronic properties as a function of the wave function quality. We thus obtain results in favour of a highly resonating character, but smeared on many states, incompatible with a previously supposed open shell character. The study also demonstrates that a too low variational freedom induces high bias in the electronic description. By QMC structural relaxation on wave functions of various quality we demonstrate that the acenes geometry is highly coupled to their electronic structure.We can consider extending this study to general polycyclic aromatic hydrocarbons similar to graphene nanoribbons of growing thickness to investigate possible correlations between Clar sextets et their electronic and spintronic properties