The use of femtosecond (fs) laser pulses in laser-induced breakdown spectroscopy (LIBS) and for chemical analysis using mass spectrometry is explored. A comparison of fs-LIBS and remote filament-induced breakdown spectroscopy (R-FIBS) in the analysis of graphite composites yielded more accurate results with filaments due to intensity clamping within the filament. The investigation of fs-LIBS and R-FIBS in the detection of explosives led to the discovery of femtosecond vaporization of intact molecules under ambient conditions. This knowledge was then used in the development of a new ambient laser-based mass analysis technique. The combination of nonresonant femtosecond laser vaporization with electrospray post-ionization called laser electrospray mass spectrometry (LEMS) was investigated as a universal detection method of pharmaceuticals, biological macromolecules and plant tissues. We show the capability of femtosecond lasers to desorb sample without any sample preparation or resonant transition in the sample or substrate. Ambient mass spectral imaging and tissue type classification is also demonstrated. / Chemistry

Electric-arc vaporization of graphite rod/metal (or metal oxide) mixtures in an inert He atmosphere has been the method of choice for the production of endohedral metallofullerenes (Am@C2n). However, yields of endohedral metallofullerenes have been limited to only a few percent of the total fullerene yield, making the production and isolation of macroscopic quantities (grams) difficult. In the present study, fullerene/metal mixtures have been vaporized using a CO₂-laser beam. The sample pellets employed in the laser vaporization were prepared from empty-cage fullerenes (C60, C70, C76, C78, C84, ..• ) and small percentages, by weight, of metal or nletal oxide (La203, SC203, Y 203, Sc, Y, Er). In addition, a sample mixture of a scandium endohedral metallofullerene extract, prepared by electric-arc vaporization, was subjected to the laser. Vaporized samples were analyzed by negative-ion chemical ionization mass spectrometry and by normal phase HPLC. Inert atmospheres of helium, argon, and xenon were compared for optimization of yields of endohedral metallofullerenes, as well as for production of unique endohedral species not observed by production via electric-arc vaporization. Scandium, yttrium, and erbium endohedral metallofullerenes were synthesized by vaporization of fullerene mixtures and the appropriate metal. Optimum conditions were realized with pellet temperatures greater than or equal to 3000°C and inert gas pressures of -100 Torr. This method of CO₂ laser vaporization also served as a valuable tool to analyze the production mechanisms of fullerenes and endohedral metallofullerenes, such as production pathways (Le., C60 -> higher fullerenes -> endohedral metallofullerenes). / Master of Science

Une étude expérimentale de la vaporisation de goutte d'éthanol et de propan-1-ol a été réalisée. Le dispositif expérimental est constitué d’une enceinte chauffée à l’intérieur de laquelle se trouve le support de goutte. Il est formé par deux fibres en quartz croisées. La goutte d'alcool se trouve à l'intersection de ces fibres. Le diamètre initial de la goutte est contrôlé, il varie entre 300 et 600µm. L’étude est faite de 298 à 973K et à pression atmosphérique. La théorie de l’état quasi-stationnaire est utilisée pour comparer et expliquer tous les résultats expérimentaux. L'impact réel de la concentration d'eau sur la vaporisation d'une goutte d'éthanol est également examiné. Deux périodes sont observées sur les courbes en d2. Ceci montre clairement que la vaporisation d'une goutte d'éthanol est accompagnée par la condensation de la vapeur d'eau à la surface de la goutte. L’évolution des taux instantanés de vaporisation du propan-1-ol et de l'éthanol confirme ce phénomène. Les délais d’autoinflammation de l'éthanol, du propan-1-ol et des mélanges d'éthanol et de l'eau ont été mesurés dans une machine de compression rapide. Les conditions de l’étude sont : une pression de compression de 30bar, la gamme de température variant de 750 à 860K, pour des mélanges stoechiométriques carburant/air. Les délais d’autoinflammation enregistrés diminuent lorsque la température augmente. Le propan-1-ol est plus réactif que l'éthanol, ce qui se traduit par des délais d’autoinflammation plus courts. Cependant, l'addition de l'eau à l'éthanol augmente la réactivité du mélange et se traduit par une réduction des délais d’autoinflammation / Detailed investigation of the vaporization of an isolated of ethanol and 1-propanol droplet was carried out in this experimental study. The experimental set-up consists of a heated chamber with a cross quartz fibers configuration as droplet support. An alcohol droplet is located at the intersection of the cross quartz fibre with a controlled initial diameter (300-600µm). Ambient temperature is varied from 298 to 973K at atmospheric pressure. The quasi-steady theory has been used to compare and to explain all experimental results. The real impact of the water concentration on the vaporization rate of an ethanol droplet is also examined, where two ‘quasi-steady’ periods are observed on the d2-curves, clearly showing that the vaporization of an ethanol droplet is accompanied by the simultaneous condensation of water vapour on the droplet surface and thus the temporal evolution of the droplet squared diameter exhibits an unsteady behavior. The histories of the instantaneous vaporization rates of both 1-propanol and ethanol droplets confirm this phenomenon. The autoignition experimental study of ethanol, 1-propanol and blends of ethanol and water have been carried out in a rapid compression machine at a compressed pressure of 30bar over a temperature range of 750-860K for stoichiometric mixture of fuel and air. The ignition delay times recorded show a significant decrease with increasing temperature. 1-propanol is more reactive than ethanol, which results in shorter ignition delay times. However, water addition to ethanol increases the reactivity of the mixture and results in a shorter ignition delay times than 1-propanol

Este trabalho apresenta os resultados de um estudo experimental sobre a ocorrência do atraso de vaporização no escoamento de misturas de fluidos refrigerantes em tubos capilares adiabáticos, com o intuito de aprimorar modelos de simulação do desempenho desse componente do ciclo de refrigeração previamente desenvolvidos. Foi realizada uma série de levantamentos experimentais para o R410A, uma mistura quase azeotrópica composta de 50% de HFC 32 e 50% de HFC 125 em base mássica, utilizando a unidade laboratorial para estudo de tubos capilares do Laboratório de Máquinas Térmicas do PMEEPUSP. Os sensores de temperatura foram posicionados adequadamente ao longo do tubo capilar, com maior concentração na região onde o atraso de vaporização tende a ocorrer, de forma a permitir uma determinação acurada do ponto onde se inicia a mudança de fase para diversas condições operacionais e geométricas. Primeiramente foram realizados estudos para caracterização de alguns parâmetros geométricos, como a medição dos diâmetros dos tubos capilares e a determinação das curvas de fator de atrito em função do n° de Reynolds para cada tubo capilar. A seguir foram realizados 27 ensaios, nos quais se obteve um total de 44 pontos experimentais, caracterizando o efeito de vários parâmetros geométricos e operacionais na diferença de pressão de saturação e no comprimento do trecho metaestável. Os dados obtidos foram correlacionados com os parâmetros experimentais no intuito de obter uma correlação para previsão da diferença de pressão de saturação no escoamento do R 410A em tubos capilares adiabáticos. A correlação obtida prevê 67% dos valores experimentais dentro da faixa de ± 26,4%, com um erro médio de 3,2%, resultado semelhante a outros trabalhos existentes na literatura. / This work presents the results of an experimental study on the occurrence of the delay of vaporization in the flow of refrigerant blends in adiabatic capillary tubes in order to improve previously developed models that simulate this component of refrigeration cycle. Experiments were carried out for R410A, a near azeotropic mixture composed of 50% of HFC 32 and 50% of HFC 125 on mass basis, using the capillary tubes laboratorial unit of the Mechanical Engineering Department of University of São Paulo. The temperature sensors was properly positioned along the capillary tubes, concentrated in the region where the delay of vaporization is expected to happen, to allow an accurate determination of the flashing point inception for a several operational conditions and geometries. Preliminary studies for characterization of some geometric parameters like capillary tubes diameters and determination of friction factor curves as function of the Reynolds number were performed. A total of 44 experimental points, collected from 27 runs, allowed the characterization of the effect of geometric and operational parameters on the underpressure of vaporization and metastable length. A correlation was developed for predicting the underpressure of vaporization as function of operational parameters and capillary tube geometry. The obtained correlation predicts 67% of experimental data within a ± 26,4% range, with an average error of 3,2%. This result is similar to other works in the literature.

O modelo F–SAC (Functional–Segment Activity Coefficient), recentemente introduzido, combina a ideia de contribuição de grupos com a teoria de superfícies de contato COSMO–RS. Este modelo tem uma dependência reduzida dos parâmetros de interação binária quando comparado com as variantes do modelo UNIFAC e precisão melhorada quando comparada com modelos baseados em COSMO. No presente trabalho uma modificação na formulação do modelo F–SAC é proposta para a inclusão de interações dispersivas. Para testar esta modificação, foram considerados os dados experimentais de alcanos, ciclo–alcanos, alcenos, aromáticos e perfluorocarbonetos. O modelo proposto foi capaz de correlacionar entalpias de vaporização de substâncias puras, não consideradas em versões anteriores do modelo. Uma vez que a capacidade calorífica de líquidos está intimamente relacionada com a entalpia de vaporização, o modelo também pode prever a capacidade calorífica de substâncias puras. Em relação ao coeficiente de atividade em diluição infinita e dados de equilíbrio líquido–vapor, o modelo modificado manteve o bom desempenho do modelo original, também semelhante a outros modelos similares, como variantes do modelo UNIFAC. Além disso, o modelo modificado pode agora calcular valores consistentes para a entalpia e entropia de excesso para sistemas onde as interações são principalmente dispersivas. Para estes sistemas, a maioria dos modelos de coeficiente de atividade prevê entalpia de excesso zero, contrabalançando valores de energia de Gibbs de excesso confiáveis com entropias de excesso distorcidas. / The recently introduced F–SAC (Functional–Segment Activity Coefficient) model combines the group contribution idea with a COSMO–RS surface contacting theory. This model has a reduced dependency on binary interaction parameters when compared to classical UNIFAC type models and improved accuracy when compared with COSMO based models. In the present work a modified F–SAC formulation is proposed for including dispersive interactions. For testing the modification, experimental data of alkanes, cycloalkanes, alkenes aromatics and perfluorocarbons were considered. The proposed model was able to correlate pure compound enthalpies of vaporization, not considered in previous versions of the model. Since the heat capacity of liquids is closely related to the enthalpies of vaporization, the model also can predict pure compound heat capacity of liquids. Regarding mixture infinite dilution activity coefficient and vapor–liquid equilibrium data, the modified model maintained the good performance of the original model, also similar to other competing models such as UNIFAC variants. Additionally, the modified model now can compute consistent values for the excess enthalpy and entropy for systems where the interactions are mainly dispersive. For these systems, most activity coefficient models predict zero excess enthalpies, counterbalancing that with distorted excess entropies.

Vapor pressure (Pvap), heat of vaporization (ΔHvap), liquid heat capacity (Cpl), and ideal gas heat capacity (Cpig) are important properties for process design and optimization. This work focuses on improving the thermodynamic consistency and accuracy of the aforementioned properties since these can drastically affect the reliability, safety, and profitability of chemical processes. They can be measured for pure organic compounds from the triple point, through the normal boiling point, and up to the critical point. Additionally, ΔHvap is proportional to the derivative of vapor pressure with respect to temperature through the Clapeyron equation, and the difference between Cpl and Cpig is proportional to the derivative of heat of vaporization with respect to temperature. In order to improve temperature-dependent correlations, all the properties were analyzed simultaneously. First, a temperature-dependent error model was developed using several versions of the Riedel and Wagner Pvap correlations. The ability of each correlation to match Cpl data was determined for 5 well-known compounds. The Riedel equation performed better than the Wagner equation when the best form was used. Second, the Riedel equation form was further modified, and the best correlation form was found for about 50 compounds over 7 families. This led to the development of a new vapor pressure prediction method using different Riedel equation forms to fit Pvap, ΔHvap, and Cpl data simultaneously. Seventy compounds were tested, and the error compared to liquid heat capacity data dropped from 10% with previous methods to 3% with this new prediction method. Additionally a differential scanning calorimeter (DSC) was purchased, and melting points (Tm), enthalpies of fusion (ΔHfus), and liquid heat capacities (Cpl) were measured for over twenty compounds. For many of these compounds, the vapor pressure data and critical constants were re-evaluated, and new vapor pressure correlations were recommended that were thermodynamically consistent with measured liquid heat capacity data. The Design Institute for Physical Properties (DIPPR) recommends best constants and temperature-dependent values for pure compounds. These improvements were added to DIPPR procedures, and over 200 compounds were re-analyzed so that the temperature-dependent correlations for Pvap, ΔHvap, Cpig, and Cpl became more internally consistent. Recommendations were made for the calculation procedures of these properties for the DIPPR database.

L’évaporation du carburant injecté dans une chambre de combustion est un phénomènecrucial dans un foyer aéronautique car elle détermine la quantité de vapeur qui sera ensuite brûléepour fournir de l’énergie au moteur. Cependant, ce phénomène reste mal décrit du fait desdifficultés de mesurer expérimentalement les taux d’évaporation des gouttes appartenant à unbrouillard. D’autre part, les hypothèses des modèles théoriques ne sont toujours pas représentativesdes conditions rencontrées dans les foyers de combustion.La thèse s’inscrit dans une démarche visant à étudier l’évaporation d’un groupe de gouttesdans un écoulement turbulent au moyen de la Simulation Numérique Directe (SND). En effet, lorsde l’évaporation de groupes de gouttes, des effets collectifs peuvent influer sur le taux d’évaporationde chaque goutte ou sur le taux d’évaporation global du nuage de gouttes. L’approche SNDpermet de quantifier précisément ces effets afin d’améliorer les modèles actuels d’évaporation.Dans un premier temps, des algorithmes ont été développés et utilisés dans une configuration1D sphérique pour décrire l’évaporation d’une goutte statique isolée et sans gravité. Puisdans un second temps, l’évaporation d’une goutte a été étudiée dans un écoulement laminaire.Une analyse des échanges de chaleur entre la goutte et le milieu extérieur ainsi que de la force detraînée exercée par l’écoulement laminaire sur la goutte a été effectuée. Dans cette partie, il a étémis en évidence que l’évaporation induit une diminution des échanges thermiques et de la traînée.Il a notamment été observé que dans certains cas de forte évaporation, la traînée de la gouttepeut devenir négative. Cela implique que l’évaporation peut être à l’origine d’un phénomène depropulsion de la goutte. Une analyse théorique permet de lier ce comportement à une asymétriedu débit d’évaporation. Dans un troisième temps, l’influence de la turbulence sur l’évaporationd’une goutte a été étudiée. Pour cela, un générateur de fluctuations turbulentes a été implémentéet des techniques de calculs parallèles ont été introduites pour réduire le temps des calculs. Celaa permis d’analyser les échanges thermiques et le comportement de la traînée d’une goutte eninteraction avec un écoulement turbulent. Il a été montré que ces deux grandeurs ont tendanceà être amplifiées par la turbulence. Enfin, dans un dernier temps, l’évaporation de groupes degouttes a été étudiée. Pour trois groupes de gouttes différents, les déplacements des gouttes ontété analysés avec les échanges de chaleur lorsque ceux-ci sont placés dans un écoulement laminaireou turbulent avec ou sans changement de phase. En présence d’évaporation, il a été mis enévidence que les déplacements sont différents des cas sans évaporation et donc que le changementde phase modifie les effets collectifs. De plus, ces effets de groupes ont aussi été observés sur leséchanges thermiques. / The vaporisation of injected fuel in a combustion chamber is a crucial phenomenon inan aeronautical motor because it determines the vapour quantity which will be burned to bringenergy to the motor. Still, this phenomenon is not well understood due to the difficulties tomeasure on experiments vaporisation rates of injected sprays. Moreover, hypothesis of theoriticalmodels are not representatives of conditions encountered in combustion furnaces.The thesis take place in an effort to analyse the evaporation of droplet groups in a turbulentflow by mean of Direct Numerical Simulation (DNS). Indeed, during droplet group evaporation,collective effects can modify single droplet rates of vaporisation and the group global rate ofvaporisation. The DNS approach should allows to quantify precisely this effect and leads to animprovement of actual models of evaporation.Firstly, algorithms are developped and used in a 1D spherical configuration to describe theevaporation of a single static droplet without gravity. Secondly, the vaporistion of a droplet in alaminar flow has been studied. The analysis focus on heat exchanges between the droplet and theexternal environment as well as the force exerced on the droplet by the laminar flow. In this part,it has been highlighted that the evaporation induced a decrease in thermal exchanges and drag.In some cases of strong evaporation, the drag of the droplet has been observed to be negative.It means that the evaporation can cause a propulsion phenomenon of the droplet. A theoriticalanalysis allows to link this behaviour to an asymetry of the vaporisation rate. Thirdly, a studyof the turbulence influence on the evaporation of a droplet has been carried out. A generator ofturbulent fluctuations has been implemented and parallel approaches have been introduced toreduced computational time. It allowes to analyse thermal exchanges and drag behaviour of adroplet interacting with a turbulent flow. The analysis showed that theses two variables increasewith turbulence. Lastly, the evaporation of groups of droplets has been studied. For three differentgroups of droplets, trajectories of droplets have been analysed with heat exchanges when they areput in a laminar or a turbulent flow with or without phase change. In presence of evaporation,the analysis pointed out that trajectories were different from cases whitout evaporation and sothat phase change modifies collective effects. Moreover, these collective effects have also beenobserved on thermal exchanges.

Polycrystalline CdS/CdTe thin film solar cells are among the leading candidates for low-cost, large scale terrestrial photovoltaic applications. CdTe has a high absorption coefficient and it can absorb the radiant energy within less than 2 µm of thickness. This makes it suitable for thin film applications. CdTe has a band gap of 1.45 eV at room temperature, which is nearly optimum for photovoltaic conversion efficiency under the AM 1.5 solar spectrum. The theoretical maximum efficiency for CdTe solar cells is 29%. However, to-date the experimental value is in the 16 % range. In most cases CdTe cells are subjected to a post-growth heat treatment which involves annealing in the presence of CdCl2. The treatment results in significant increases in conversion efficiency (η) and all three solar cell parameters Voc, FF, and Jsc. In this work, several variations of the CdCl2 treatment were used on more than 100 samples to investigate their effects on the solar cell parameters. A vapor CdCl2 method was applied for the treatment with various source temperatures, substrate temperatures, and treatment times. The cells were characterized by dark and light J-V and spectral response (SR) measurements.

Ultrasonic slurry sampling electrothermal vaporization dynamic reaction cellTM inductively coupled plasma mass spectrometry (USS-ETV-DRC-ICP-MS) has been applied to determine Cr, Cu, Cd, Hg and Pb in several rice samples. The influences of instrument operating conditions and slurry preparation on the ion signals were reported. Ascorbic acid was used as the modifier to enhance the ion signals. The background ions at the chromium masses were reduced in intensity significantly by using 0.4 ml min-1 NH3 as reaction cell gas in the dynamic reaction cell (DRC) while a q value of 0.6 was used. Since the sensitivities of Cr, Cu, Cd, Hg and Pb in rice flour slurry and aqueous solution were quite different, standard addition and isotope dilution methods were used for the determination of Cr, Cu, Cd, Hg and Pb in these rice samples. This method has been applied to the determination of Cr, Cu, Cd, Hg and Pb in NIST SRM 1568a rice flour reference material and two rice samples purchased from the market. The analysis results of the reference material agreed with the certified values. The results for the rice samples for which no reference values were available were also found to be in good agreement between isotope dilution method and standard addition method. The method detection limits estimated from standard addition curves were about 0.44, 1.7, 0.4, 0.53 and 0.69 ng g-1 for Cr, Cu, Cd, Hg and Pb, respectively, in original rice flour.Ultrasonic slurry sampling electrothermal vaporization dynamic reaction cellTM inductively coupled plasma mass spectrometry (USS-ETV-DRC-ICP-MS) has been applied to the determination of Cr, Cd and Pb in several plastic samples. The influences of instrument operating conditions and slurry preparation on the ion signals were investigated. NH4NO3 was used as the modifier to enhance the ion signals. The background ions at the chromium masses were reduced in intensity significantly by using NH3 as reaction cell gas in the DRC. Standard addition method and isotope dilution method were used for the determination of Cr, Cd and Pb in these plastic samples. This method was applied to the determination of Cr, Cd and Pb in two polystyrene and a polyvinyl chloride samples. The analysis results were found to be in good agreement between isotope dilution method and standard addition method. Furthermore, we digested these samples and analyzed the digested sample solutions by ultrasonic nebulization DRC ICP-MS. The analysis results were close to the isotope dilution and standard addition results. The precision between sample replicates was better than 3% with USS-ETV-DRC-ICP-MS method. The method detection limits estimated from standard addition curves were about 6.2-9.2, 1.1-1.6 and 8.4-11 ng g-1 for Cr, Cd and Pb, respectively, in original plastic samples.

Both electrothermal vaporization (ETV) and nebulizer introduction sources offer unique advantages for inductively coupled plasma mass spectrometry (ICP-MS) analyses. A device for coupling the ETV and nebulizer was developed so that a quick switch from the nebulizer to the ETV (termed 'inline-ETV') could help gain additional information. The inline-ETV produced similar limits of detection (LODs) for most elements in both HNO₃ and HCl matrices compared to a conventional nebulizer or ETV. However, in a problematic matrix, isobaric interferences could exist that may not be accounted for in a typical nebulizer analysis. In a 1% HCl matrix, the LODs for ⁵¹V and ⁵³Cr--which are interfered with by ⁵¹ClO⁺ and ⁵³ClO⁺, respectively--improved 65- and 22-fold using the inline-ETV source compared to a typical nebulizer. In recent applications, ICP-MS has gained attention as a way of determining metal-protein associations. A novel broad-based methodology was developed to characterize metal-protein associations. The method utilized native gel electrophoresis for separation followed by electroblotting onto chemically-modified quartz membranes. The membranes were analyzed for metals using laser ablation ICP-MS. Modified membranes were shown to improve sensitivity compared to ablating a dried gel directly or using a commercially-available membrane. The coupling of separation by preparative ultracentrifugation and metal detection by ICP-MS was explored for metal-protein equilibrium determinations. This study characterizes the stoichiometry as well as apparent (K[subscript app]) and intrinsic (K[subscript int]) binding affinities for Cu-BSA, which was used as a model protein. K[subscript app] and K[subscript int] were determined at two different conditions, pH 9.53 and pH 7.93 in 100mM Tris buffer. The pH-independent K[subscript int] value at pH 9.53 agreed closely with literature values, while the value at pH 7.93 was approximately 2.5x larger. BSA undergoes a structural rearrangement between pH 7-9, and the generally accepted pH-dependency of protein tertiary structure may be responsible for the variations in the "intrinsic" binding constant. Overall, this study validates and shows the efficacy of combining preparative ultracentrifugation with ICP-MS detection for interrogating metal-protein associations while causing minimal equilibrium perturbations as a result of the separation and measurement processes. / text