Dissertations / Theses on the topic 'Various pressure and temperature conditions'

京都大学
0048
新制・課程博士
博士(工学)
甲第22420号
工博第4681号
新制||工||1731(附属図書館)
京都大学大学院工学研究科都市社会工学専攻
(主査)教授 岸田 潔, 教授 三村 衛, 准教授 肥後 陽介
学位規則第4条第1項該当
Doctor of Philosophy (Engineering)
Kyoto University
DFAM

Les points triples (jonction entre un gaz, un isolant solide et un conducteur), présents dans de nombreuses applications industrielles, constituent, en raison du renforcement local du champ électrique, une zone critique pour le déclenchement des décharges électriques. De plus, ces points triples peuvent être exposés à des conditions environnementales parfois sévères. Ainsi, l'objectif de cette étude était de parvenir à une meilleure compréhension des phénomènes de décharges partielles (DP) et de claquage du gaz à partir d'un point triple sous différentes conditions de pression et de température. En particulier, ont été examinées les tensions-seuil d'amorçage/d'extinction des DP (Partial Discharge Inception Voltage, PDIV/Partial Discharge Extinction Voltage, PDEV) et la tension de claquage du gaz en surface de l'isolant solide (Flashover Voltage, FOV).Dans ce contexte, un dispositif expérimental a été conçu et exploité dans une atmosphère d'azote dont la pression était comprise entre 50 mbar et pression atmosphérique pour des températures imposées variant de l'ambiante à 400 °C. Une attention particulière a été accordée à l'alumine, matériau isolant solide qui peut être utilisé dans cette plage de température. L'influence de la température sur la PDIV (et PDEV) d'une part, et la FOV d'autre part, a été caractérisée, analysée et interprétée au moyen de mesures diélectriques, d'imagerie rapide et de simulations numériques. Enfin, dans les conditions de température élevée et malgré les précautions prises, une oxydation de l'électrode haute tension a été observée dont l'influence sur la PDIV a été analysée
Triple junctions (between a gas, a solid insulator, and a conductor), which are present in numerous industrial applications, constitute a critical zone for the triggering of electrical discharges due to local reinforcement of the electric field. In addition, these triple points can be exposed to harsh environmental conditions. The aim of this study was therefore to come to a better understanding of the phenomena of partial discharge (PD) and gas breakdown from a triple junction under different pressure and temperature conditions. In particular, the Partial Discharge Inception Voltage (PDIV), the Partial Discharge Extinction Voltage (PDEV), and the Flashover Voltage (FOV) of surface breakdown of the solid insulator were examined.In this context, an experimental set-up was designed and operated in a nitrogen atmosphere ranging from 50 mbar to atmospheric pressure, for imposed temperatures varying from ambient to 400 °C. Particular attention was paid to aluminium oxide, a solid insulator material that can be used in this temperature range. The influence of temperature on PDIV (and PDEV) on the one hand, and FOV on the other, was characterised, analysed and interpreted by means of dielectric measurements, high-speed imagery and numerical simulations. Finally, under high temperature conditions and despite the precautions taken, an oxidation of the high voltage electrode was observed whose influence on the PDIV was analysed

A well is classified as a HPHT (High Pressure High Temperature) well if the static bottomhole temperatures are greater than 350 °C and when the formation pressures exceed 1800 kg/m³ ECD. Mud weights as high as 2400 kg/m³ may be required to maintain a proper well control. The temperature of the drilling fluid when circulating in the well may range from 0 °C to 150 °C and it is important that the drilling fluid maintain acceptable rheological properties within the whole range. The rheological properties of the mud will strongly depend on the temperature and the pressure variations. The problems regarding HPHT wells are mostly due to ECD and cuttings transport.

In order to control and measure the viscosity for deep HPHT wells we have conducted laboratory experiments that deal with aging at different temperatures on a polymer mud, as well as pressure and temperature effects on a field mud. We have also calculated the annular pressure using Landmark Wellplan software. To calibrate the instruments, i.e. the Physica HPHT viscometer and a Fann viscometer, we used ubelohde, known to give an exact value of the viscosity of a fluid. The calibration liquid was a 2-stroke motor oil with different amounts of Exxsol-D60 added.

The aging experiments were conducted in a mixture of water and HEC that were put in three different incubators at 20 °C, 60 °C and 90 °C for 1, 3, 8, 11, 15 and 20 days. The results showed that the viscosity decreased rapidly in the solutions that were aged at the highest temperatures and that most of the decrease took place during the first day of aging.

In the experiments on real (field) mud exposed to high pressures and temperatures the Physica viscometer was used. The results showed that the pressure effects were negligible compared to the temperature effects. During the measurements we experienced that the viscosity decreased as the temperature increased and that the decrease in the viscosity was more significant from 20 to 60 °C than from 60 to 90 °C.

Based on the results obtained in the laboratory and an evaluation of fluid implication on well pressure, we were able to draw the following main conclusions:

• Laboratory experiments are very educational. To learn that reality is not straight forward to measure was enlightening.

• The viscosity is very dependant on the temperature.

• The combined effect of pressure on the viscosity of a field mud is negligible.

• The annular pressure differences calculated in Landmark Wellplan did not show any significant differences for the different well temperatures.

Temperature, pressure and CO₂ and H₂ addition to CH₄ effects on turbulent and laminar burning velocity have been found and discussed. Novel turbulent burning velocity determination methods are presented and uncertainties have been discussed. Turbulent burning velocity correlation with nondimensional numbers have been found and flames structures have been analysed.

Dans cette thèse nous explorons le diagramme de phase des fullerènes intercalées avec des métaux alcalins lourds, Rb6C60 et Cs6C60, à très haute pression (<50 GPa) et à très haute température (de l’ambiante à 1500 K). Ce travail inclue des expériences d’absorption de rayons X, de diffraction de rayons X, de spectroscopie Raman, ainsi que des calculs DFT ab initio à haute pression. Le couplage entre expériences et calculs permet d’observer que la présence de la forte interaction ionique entre chaque molécule et les ions alcalins, empêche la polymérisation des fullerènes sous pression. Dans le cas de Cs6C60, ceci a permis d’étendre le domaine de stabilité en pression des molécules de C60 d’au moins un facteur deux par rapport aux cristaux de C60 non-intercalés. Dans le cas de Rb6C60 une transition réversible est observée à 35 GPa. Nous avons mis en évidence la déformation progressive de la molécule de fullerène sous pression dans les systèmes étudiés. La compressibilité des deux cristaux a été mesurée et calculée
In this thesis, we explore the phase diagram of the heavy alkali metal intercalated fullerenes, Rb6C60 and Cs6C60, under high pressure (<50 GPa) and high temperature conditions (from ambient to 1500 K). The work includes a series of X-ray absorption spectroscopy, X-ray diffraction and Raman spectroscopy measurements as well as ab initio DFT calculations under pressure. By coupling both experiments and calculations, we observed that the presence of strong ionic interactions between each molecule and the alkali metal ions, prevents fullerene polymerization under pressure. In the case of Cs6C60, this allows to extend the pressure stability of the C60 molecules more than twice with respect to pristine solid C60. In the case of Rb6C60 a phase transition, is observed at 35 GPa. A pressure induced enhanced deformation of the fullerene molecule in the studied systems has been evidenced. The compressibility of the both crystals has been measured and calculated

"A series of one dimensional horizontal infiltration experiments were performed to investigate the predictive capabilities of the Kao and Hunt model. By modifying pristine laboratory apparatus, a reasonable range of soil temperatures was achieved. Experiments were run at approximately 5°C, 20°C, and 35°C. Distilled water was used as an infiltrating liquid and silica powder was used as soil. The infiltrating liquid was dispensed into the column at zero pressure head. The results of the experiments show that the model is adaptable to a range of temperature conditions by modifying terms for the liquid effects of the model, viscosity and surface tension. Experimental data and model predictions differed by 30 percent at most. Although the change in the rate of infiltration across the range of temperatures is perceivable, it is small in comparison to the effects caused by heterogeneity encountered in nature. "

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 75-77).
Aluminum fuel has become an attractive form of energy storage in recent years as it is both a highly abundant and extremely energy dense material. Research has discovered methods of treating aluminum with liquid metal, enabling the aluminum to produce large amounts of hydrogen when oxidized by liquid water. When this fuel reacts with water, it produces hydrogen, heat, and aluminum hydroxide (Al(OH) 3 ). Although this aluminum fuel has already been integrated into an effective mobile hydrogen production source for hydrogen fuel cells, the system size and weight is restricted by the amount of water that is required to react the aluminum. The less water that needs to be carried on board, the better, and the only way to decrease the amount of water that is required to produce hydrogen through aluminum-water reactions is to alter the chemistry of the reaction. This thesis investigates the possibility of manipulating the chemistry of these reactions at high pressures and temperatures to produce aluminum oxyhydroxide (AlOOH) or aluminum oxide (Al203 ), both of which are byproducts of aluminum-water reactions which consume less water than the Al(OH) 3 reaction for the amount of hydrogen produced. A MATLAB simulation was constructed to predict the favorability of each byproduct by analyzing the Gibbs free energy of the reactions as a function of pressure and temperature. This simulation revealed that A100H becomes favorable over Al(OH) 3 at 142.38°C and 387kPa and A120 3 becomes favorable over A100H at 174.21°C and 889kPa in a system with a 200ml volume in which 5g of fuel is reacted. Pressurized tests were also carried out and the experiment results showed that A1OOH was produced from these aluminum-water reactions at 181°C and 1035kPa, proving that it is possible to manipulate these reactions to improve the performance of aluminum fuel as a hydrogen source.
by Kelsey Carolyn Seto.
S.M.

Garnet-omphacite gneisses from the island of Otrøy situated in Western Gneiss Region (WGR), Norway, Scandinavian Caledonides, were examined within this study. The WGR is one of the planets most studied ultrahigh-pressure (UHP) terranes. The studied gneisses are hosts for UHP garnet peridotites and eclogites. The presence of the high pressure mineral assemblage including e.g. omphacite and phengite together with assumed remnants of pseudomorphic transition of formerly stable coesite present in omphacite and garnet, suggest formation of the Otrøy gneisses during ultrahigh pressure metamorphism (UHPM). However, geothermobarometry based on the mineral assemblage composed of garnet + clinopyroxene + phengite yielded pressure-temperature conditions of c. 880˚C and 2.2 GPa, characteristic for just high pressure metamorphism.  Nevertheless, it can be concluded that the Otrøy gneisses were formed due to the deep burial of continental crust during the continent-continent collision. This study provides insights into the understanding of the deep subduction of continental crust and expands our knowledge about the complex metamorphic and tectonic evolution of the WGR and the Scandinavian Caledonides.
Granat-omphacitförande gnejser från ön Otrøy i Western Gneiss Region (WGR), Norge, Skandinaviska Kaledoniderna, har undersöks i den här studien. WGR är ett av världens mest studerade område för ultrahögtryckmetamorfa bergarter. I den här typen av gnejser förekommer linser av ultrahögtrycksbergarter så som granat-peridotiter och eklogiter. I den studerade Otrøygnejsen förekommer bland annat phengit och omphacit med inneslutningar av sannolika pseudomorfer efter coesit. Detta visar på att Otrøygnejsen troligen har bildats under metamorfos vid ultrahöga tryck. Geotermobarometriundersökningen, baserat på granat + clinopyroxen + phengitsystemet, visar att tryck- och temperaturförhållandena var ca.880 ˚C och 2.2 GPa. Det innebär att gnejsen metamorfoserats inom intervallet karaktäristiskt för högtrycksmetamorfos. Likväl, kan det fastställas att Otrøygnejsen bildats till följd av en djup subduktion under kontinent-kontinentkollision. Den här studien bidrar till en ökad förståelse av processerna som påverkar den kontinentala skorpan vid djup subduktion och vidgar våra kunskaper om den komplexa metamorfa och tektoniska utvecklingen i WGR och de Skandinaviska Kaledoniderna.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
The unit of sugar and base connected by a N-β-glycosyl linkage is named a nucleoside. In the present work the nucleoside thymidine, whose molecular formula is C10N2O5H14, was studied by Raman spectroscopy, subjecting it extreme conditions of pressure and temperature, as well as X ray diffraction measurements. An auxiliary analysis of normal crystal vibration modes was performed using first principles calculations using the B3LYP functional together with the Gaussian bases 6-31G+(d) and potential energy distribution analysis (PED). These results, together with literature data and Raman spectroscopy measurements in several thymidine scattering geometries, allowed the identification of the various normal modes of crystal vibration. X-ray diffraction experiments were performed in the temperature range between 83 and 413 K. Experiments of Raman spectroscopy under extreme temperature conditions (20 to 380 K) were performed in the spectral range of 20 to 3400 cm-1. From the analysis of the results, it is possible to draw some conclusions. (i) The thymidine crystal remained stable throughout the investigated temperature range, indicating that the temperature effect is not sufficient to modify the hydrogen bonds present between the molecules in such a way as to modify the symmetry of the crystal. (ii) The material studied showed some slight changes in the vibrational spectra in the experiment performed at low temperatures, suggesting, if not a structural phase transition, at least some conformational modification of the thymidine molecules. Raman spectra of thymidine crystal were obtained for pressures up to 5.0 GPa in a diamond anvil cell. The results show the presence of anomaly in the Raman spectrum at pressures close to 3.0 GPa. This anomaly is characterized by disappearance of lattice modes, appearance of some internal modes, splitting of high wavenumbers modes, downshift of modes associated with hydrogen bonds, changes in the intensity of internal modes and discontinuities of the slopes of the wavenumbers versus pressure for several Raman modes. This set of modifications was interpreted as consequence of a phase transition undergone by thymidine close to 3.0 GPa. Further, decompression to atmospheric pressure generates the original Raman spectrum, showing that the pressure-induced phase transition undergone by thymidine crystals is reversible. A comparison with results on other nucleosides submitted to high pressure is also furnished.
Quando a pentose (glicose) e uma base nitrogenada unem-se por meio de uma ligaÃÃo N-β glicosÃdica forma-se uma molÃcula denominada de nucleosÃdeo. No presente trabalho o nucleosÃdeo timidina, cuja fÃrmula molecular à C10N2O5H14, foi estudado atravÃs de espectroscopia Raman, submetendo-o a condiÃÃes extremas de pressÃo e de temperatura, alÃm de medidas de difraÃÃo de raios X. Uma anÃlise auxiliar a respeito dos modos normais de vibraÃÃo do cristal foi realizada atravÃs de cÃlculos de primeiros princÃpios utilizando-se o funcional B3LYP em conjunto com as bases gaussianas 6-31G+(d) e anÃlise de distribuiÃÃo de energia potencial (PED). Esses resultados, juntamente com dados da literatura e medidas de espectrocopia Raman em diversas geometrias de esplalhamento na timidina permitiram uma identificaÃÃo dos vÃrios modos normais de vibraÃÃo do cristal. Os experimentos por difraÃÃo de raios X foram realizados no intervalo de temperatura entre 83 e 413 K. Experimentos de espectroscopia Raman sob condiÃÃes extremas de temperatura (20 a 380 K) foram realizados no intervalo espectral compreendido entre 20 e 3400 cm-1. Da anÃlise dos resultados, à possÃvel tirar algumas conclusÃes. (i) O cristal de timidina manteve-se estÃvel em todo o intervalo de temperatura investigado, indicando que o efeito de temperatura nÃo à suficiente para modificar as ligaÃÃes de hidrogÃnio presentes entre as molÃculas de tal forma que haja modificaÃÃo da simetria do cristal. (ii) O material estudado apresentou algumas leves mudanÃas nos espectros vibracionais no experimento realizado a baixas temperaturas, sugerindo, se nÃo uma transiÃÃo de fase estrutural, pelo menos alguma modificaÃÃo conformacional das molÃculas da timidina. Experimentos submetendo o cristal a pressÃes de atà 5 GPa foram realizados utilizando-se uma cÃlula de pressÃo a extremos de diamantes. Os resultados mostraram anomalias nos espectros Raman por volta de 3.0 GPa. Essas anomalias foram caracterizadas pelo desaparecimento de alguns modos de rede, surgimento de alguns modos internos, deslocamento para menores nÃmeros de onda de modos associados a ligaÃÃes de hidrogÃnio e descontinuidades dos coeficientes lineares de vÃrios modos nos grÃficos de nÃmero de onda em funÃÃo da pressÃo. Essa sÃrie de modificaÃÃes foram interpretadas como consequÃncia de uma transiÃÃo de fase sofrida pela timidina por volta de 3.0 GPa. AlÃm disso, a descompressÃo da amostra atà a pressÃo atmosfÃrica mostrou que a transiÃÃo de fase à reversÃvel. TambÃm fornecemos uma comparaÃÃo com resultados de outros nucleosÃdeos submetidos a altas pressÃes.

Knowledge of thermodynamic fluid properties, such as density and phase behavior, is important for the design, operation, and safety of several processes including drilling, extraction, transportation, and separation that are required in the petroleum. The knowledge is even more critical at extreme temperature and pressure conditions as the search for more crude oil reserves lead to harsher conditions. Currently, there is dearth of experimental data at these conditions and as such, the predictive capability of the existing modeling tools are unproven. The objective of this research is to develop a fundamental understanding of the impact of molecular architecture on fluid phase behavior at temperatures to 523 K (250 °C) and pressures to 275 MPa (40,000 psi). These high-temperature and high-pressure (HTHP) conditions are typical of operating conditions often encountered in petroleum exploration and recovery from ultra-deep wells that are encountered in the Gulf of Mexico. This PhD study focuses on the fluid phase behavior of a low molecular weight compound, two moderately high molecular weight compounds, three asymmetric binary mixtures of a light gas and a heavy hydrocarbon compound with varying molecular size. The compounds are selected to represent the family of saturated compounds found in typical crude oils. Furthermore, this study reports experimental data for two "dead" crude oil samples obtained from the Gulf of Mexico and their mixtures with methane from ambient to HTHP conditions. A variable-volume view cell coupled with a linear variable differential transformer is used to experimentally measure the high-pressure properties of these compounds and mixtures. The reported density data compare well to the limited available data in the literature with deviations that are less than 0.9%, which is the experimental uncertainty of the density data reported in this study. The phase behavior and density data obtained in this study are modeled using the Peng-Robinson (PR), the volume-translated (VT) PR, and the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equations of state (EoS). The EoS pure component parameters, typically obtained from the open literature, are derived from fitting the particular EoS to, critical point, or to vapor pressure and saturated liquid density data, or to HTHP density data. For the density data reported here, the PREoS provided the worst predictions, while the VT-PREoS gives an improved performance as compared to the PREoS. However, the PC-SAFT EoS provided the best HTHP density predictions especially when using HTHP pure component parameters. The situation is however reversed in the modeling performance for the phase behavior data whereby the PC-SAFT EoS with HTHP parameters provided the worst vapor-liquid equilibria predictions. Better predictions are obtained with the PC-SAFT EoS when using parameters obtained from fit of the vapor pressure data and is comparable to the PREoS predictions. This reversal in performance is not surprising since the phase behavior data occur at moderately low pressures. The performance of the PC-SAFT EoS is extended to the experimental density data reported for the dead crude oil samples and their mixtures with methane. The PC-SAFT EoS with either set of pure component parameters yield similar predictions that are within 3% of the reported crude oil density data. However, when using the HTHP parameters, the PC-SAFT gives a good representation of the slope of experimental data, which is crucial in the calculation of second-derivative properties such has isothermal compressibility. The PC-SAFT EoS is also employed to model the crude oil HTHP density data for both the dead crude oils and their mixtures with methane using correlations for both the Low-P parameters and the HTHP parameters. The Low-P parameters are derived from fitting the PC-SAFT EoS to pure compound vapor pressure and saturated liquid density data, while the HTHP parameters are obtained from fitting the PC-SAFT EoS to pure compound HTHP liquid density data. Interestingly, the PC-SAFT EoS with the Low-P parameters provided better HTHP density predictions that are within 1.5% of the experimental data for the dead oils than the HTHP parameters that are within 2 to 4% of the data. Density predictions for the dead oil mixtures with methane are however comparable for both sets of parameters and are within 1% on average. However, the PC-SAFT EoS with HTHP parameters clearly provided better representation of the isothermal property, a derivative property obtained from density data, within 10% while predictions with the Low-P parameters can be as high as 37%. The successful completion of the thesis work expands the current knowledge base of fluid phase behavior at the extreme operating conditions encountered by engineers in the petroleum industries. Furthermore, the reported HTHP experimental data also provide a means to scientists and researchers for the development, improvement, and validation of equations with improved modeling performance.

Dans cette thèse, nous étudions la stabilité et les propriétés des glaces d’eau de haute pression (entre 5 et 300 GPa) et de haute température (entre 300 et 2000 K) comportant ou non des inclusions de NaCl dans leur structure cristalline. Pour attendre ces conditions propres aux intérieurs des exoplanètes océans, nous utilisons une approche théorique basée sur des dynamiques moléculaires ab initio. Nous montrons que l’analyse de la dynamique des liaisons entre hydrogènes et oxygènes permet de distinguer toutes les phases de la glace présentant une structure cubique volume-centrée. En particulier, nous présentons la première description ab initio de la phase plastique, et nous mettons en évidence la présence de multiples transitions dans la phase superionique. Ensuite, nous montrons que jusqu’à 5.9 % en masse de NaCl peuvent être inclus dans la structure de la glace à 1600 K. L’inclusion des ions Na+ et Cl- stimule le désordre orientationel des molécules d’eau par rapport à la glace d’eau pure. À partir de 2.5 % en masse de NaCl, la conduction superionique s’étend à l’ensemble de la gamme de pression étudiée, et la symétrisation des liaisons hydrogènes se produit à plus haute pression. Enfin, nous décrivons les structures de cœur des dislocations vis ayant des vecteurs de Burgers <110> et <111> dans la glace X à 80 GPa, ce qui constitue une étape préliminaire importante à la construction de lois rhéologiques pour les glaces cubiques de haute pression
In this thesis we study the stability and the properties of pure and NaCl-bearing dense water ices at high pressure (between 5 and 300 GPa) and high temperature (between 300 and 2000 K). To reach these conditions that correspond to the interiors of ocean exoplanets, we employ a theoretical approach based on ab initio molecular dynamics simulations. We show that a detailed analysis of the hydrogen bond dynamics allows to distinguish all the different ice phases presenting a body-centered cubic sub-lattice of oxygen atoms. In particular, we present the first ab initio description of the plastic phase of water ice. We also reveal the multiple transitions that occur in the superionic domain. Next, we show that ice VII' can incorporate up to 5.9 wt% NaCl in its structure at 1600 K. The inclusion of Na+ and Cl- ions enhances the orientation disorder of the water molecules in comparison to the pure ice. From 2.5 wt% NaCl, superionic conduction expands over the entire pressure range studied, and the hydrogen symmetrisation is shifted towards higher pressures. Last, we describe the <110> and <111> screw dislocation core structures of ice X at 80 GPa. This constitutes a first step towards the construction rheological laws for high-pressure cubic ices

This thesis project has focussed on the experimental study of simple molecular systems at extreme conditions. High-pressure and high-temperature techniques have been used in combination with Raman spectroscopy and X-ray diffraction diagnostics to characterise three simple molecular systems which are unified by the inclusion of nitrogen as a constituent element. The N2 molecule contains the only triple-bond amongst the elemental diatomics and is considered a model system for exploring the changes in structure and bonding induced by tuning pressure and temperature conditions. As such the nitrogen phase-diagram is a focus-point in current extreme conditions research and nitrogen has been found to exhibit a high-degree of polymorphism not observed in other simple molecular systems such as hydrogen or oxygen. Understanding molecular mixtures of nitrogen with other simple molecules at extreme conditions is significant to many scientific fields varying from chemistry to astronomy. The first system presented is the binary mixture of nitrogen and xenon which was studied as a function of pressure. The study constitutes the first comprehensive study of the xenon-nitrogen system at high-pressures. A new van der Waals compound was observed which underwent a phase transition at 14 GPa and was stable up to at least 180 GPa and 3000 K, conditions where pure nitrogen becomes amorphous. Optical measurements suggested possible metallization of the new compound around 120 GPa. The second system presented is the binary mixture of nitrogen and hydrogen which was studied both as a function of pressure and composition. Two known nitrogen-hydrogen structures were confirmed and a pressure-temperature path-dependent formation of hydrazine or ammonia was discovered. Additionally, one mixture was compressed to 242 GPa, the highest pressure investigated in the nitrogen-hydrogen system. The third system presented is the elemental nitrogen phase known as i-nitrogen, an elusive high-temperature polymorph which has hitherto eluded structure determination and proved challenging to access. i-nitrogen was successfully characterised as having an extraordinarily large unit cell containing 48 N2 molecules, making it the most complex molecular nitrogen structure to be determined unambiguously.

This investigation address the effect that pressure, p, and temperature, T, have on 4f-states of the rare-earth elements in the isostructural YbRh2Si2, EuCo2Ge2, and EuCu2Ge2 compounds. Upon applying pressure, the volume of the unit cell reduces, enforcing either the enhancement of the hybridization of the 4f-localized electrons with the ligand or a change in the valence state of the rare-earth ions. Here, we probe the effect of a pressure-induced lattice contraction on these system by means of electrical resistivity, from room temperature down to 100 mK. At ambient pressure, the electrical resistivity of YbRh2Si2 shows a broad peak at 130 K related to the incoherent scattering on the ground state and the excited crystalline electrical field (CEF) levels. At T_N = 70 mK, YbRh2Si2 undergoes a magnetic phase transition. Upon applying pressure up to p_1 = 4 GPa , T_N increases monotonously while the peak in the electrical resistivity is shifted to lower temperatures. For p &lt; p_1 a different behavior is observed; namely, T_N depends weakly on the applied pressure and a decomposition of the single peak in the electrical resistivity into several shoulders and peaks occurs. Above p_2 = 9 GPa, the electrical resistivity is significantly reduced for T &lt; 50 K and this process is accompanied by a sudden enhancement of T_N. Thus, our results confirm the unexpected behavior of the magnetization as function of pressure reported by Plessel et al. The small value of the magnetic ordering temperature for p &lt; p_2 and the strength of the mechanism that leads to the peaks and shoulders in the electrical resistivity suggest that the f-electrons are still screened by the conduction electrons. Therefore, the observed behavior for pressures lower than p_2 might be a consequence of the competition of two different types of magnetic fluctuations (seemingly AFM and FM). Furthermore, the results suggest that a sudden change of the CEF scheme occurs at pressures higher than p_1, which would have an influence on the ground state. Additionally, a comparison of the pressure dependent features in the electrical resistivity of YbRh2Si2 with similar maxima in other isostructural YbT2X2 (T = transition metal; X = Si or Ge) compounds was performed. For the comparison, a simple relation that considers the Coqblin-Schrieffer model and the hypothesis of Lavagna et al. is proposed. A systematic behavior is observed depending on the transition metal; namely, it seems that the higher the atomic radii of the T-atom the smallest the pressure dependence of the maximum in the electrical resistivity, suggesting a weaker coupling of localized- and conduction-electrons. It is also observed that an increase in the density of conduction electrons reduces the pressure dependence of the characteristic Kondo temperature. The mechanism responsible for the sudden enhancement of T_N in YbRh2Si2 at about p_2 is still unknown. However two plausible scenarios are discussed. The Eu-ions in EuCo2Ge2 and EuCu2Ge2 have a divalent character in the range 100 mK &lt; T &lt; 300 K. Therefore, these systems order magnetically at T_N = 23 K and T_N = 12 K, respectively. The studies performed on EuCo2Ge2 and EuCu2Ge2 as a function of pressure suggest that a change to a non-magnetic trivalent state of the Eu-ions might occur at zero temperature for pressures higher than 3 GPa and 7 GPa, respectively. A common and characteristic feature on EuCo2Ge2 and EuCu2Ge2 is the absence of a clear first order transition from the divalent to the trivalent state of the Eu-ions at finite temperature for p &gt; 3 GPa and for p &gt; 7 GPa, respectively. In other isostructural Eu-based compounds, a discontinuous and abrupt change in the thermodynamic and transport properties associated to the valence transition of the Eu-ions is typically observed at finite temperatures. In contrast, the electrical resistivity of EuCo2Ge2 and EuCu2Ge2 changes smoothly as a function of pressure and temperature. The analysis of the the electrical resistivity of EuCo2Ge2 suggest that a classical critical point might be close to the AFM-ordered phase, being a hallmark of this compound. The overall temperature dependence of the the electrical resistivity of EuCo2Ge2 changes significantly at 3 GPa; therefore, it seems that the system suddenly enters to a T-dependent valence-fluctuating regime. Additionally, the pressure-dependent electrical-resistivity isotherms show a step-like behavior. Thus, it is concluded that discontinuous change of the ground state might occur at 3 GPa. The electrical resistivity of EuCu2Ge2 at high pressure is characterized by a negative logarithmic T-dependence in the pressure range 5 GPa &lt; p &lt; 7 GPa for T &gt; T_N and by a broad peak in the pressure dependent residual resistivity, whose maximum is located at 7.3 GPa. The first behavior resembles the incoherent scattering process typical for an exchange coupling mechanism between the localized electrons and the ligand. This and the peak effect in the local 4f susceptibility observed in NMR measurements are consistent with such a coupling mechanism. Thus, it would be for the first time that a dense Eu-based compound like EuCu2Ge2 show such a behavior. Combining the results of the experiment performed at high pressures on EuCu2Ge2 with the studies performed in the EuCu2(Ge1-xSix)2 series, a crossover from an antiferromagnetically ordered state into a Fermi-liquid state for pressures higher than 7.3 GPa may be inferred from the analysis. Therefore, it may be possible that the sudden depopulation of 4f-level occur mediated by quantum fluctuation of the charge due to a strong Coulomb repulsion between the localized-electrons and the ligand. This phenomenon would explain the broad peak in the residual resistivity. To our knowledge, this would be the first Eu-based compound, isostructural to ThCr2Si2, that show such a transition as function of pressure at very low temperatures.

This work is an attempt to develop a physically realistic model to understand the behavior and failure of rocks, especially under the extreme conditions of High Pressure and High Temperature (HPHT). A platform is laid in the preliminary work where 1D pure and ductile damage models are developed respectively. These models are based on an elasto-plastic model with an additional governing equation incorporated to facilitate the inclusion of damage. This additional governing equation is called the damage evolution equation. In the ductile damage model, it is assumed that the damage is driven and controlled by plasticity. The concepts developed in the preliminary work of 1D modeling are then taken into the study of 3D problems. The main problems studied are: the unconstrained uniaxial compression, the completely constrained uniaxial compression and the dynamic indentation problem. The dynamic indentation problem is the representation of an idealized rock drilling process. The results from the indentation problem are found to be in good qualitative agreement with the experimental results (Abd Al-Jalil, Y.Q 2006).

This investigation address the effect that pressure, p, and temperature, T, have on 4f-states of the rare-earth elements in the isostructural YbRh2Si2, EuCo2Ge2, and EuCu2Ge2 compounds. Upon applying pressure, the volume of the unit cell reduces, enforcing either the enhancement of the hybridization of the 4f-localized electrons with the ligand or a change in the valence state of the rare-earth ions. Here, we probe the effect of a pressure-induced lattice contraction on these system by means of electrical resistivity, from room temperature down to 100 mK. At ambient pressure, the electrical resistivity of YbRh2Si2 shows a broad peak at 130 K related to the incoherent scattering on the ground state and the excited crystalline electrical field (CEF) levels. At T_N = 70 mK, YbRh2Si2 undergoes a magnetic phase transition. Upon applying pressure up to p_1 = 4 GPa , T_N increases monotonously while the peak in the electrical resistivity is shifted to lower temperatures. For p &lt; p_1 a different behavior is observed; namely, T_N depends weakly on the applied pressure and a decomposition of the single peak in the electrical resistivity into several shoulders and peaks occurs. Above p_2 = 9 GPa, the electrical resistivity is significantly reduced for T &lt; 50 K and this process is accompanied by a sudden enhancement of T_N. Thus, our results confirm the unexpected behavior of the magnetization as function of pressure reported by Plessel et al. The small value of the magnetic ordering temperature for p &lt; p_2 and the strength of the mechanism that leads to the peaks and shoulders in the electrical resistivity suggest that the f-electrons are still screened by the conduction electrons. Therefore, the observed behavior for pressures lower than p_2 might be a consequence of the competition of two different types of magnetic fluctuations (seemingly AFM and FM). Furthermore, the results suggest that a sudden change of the CEF scheme occurs at pressures higher than p_1, which would have an influence on the ground state. Additionally, a comparison of the pressure dependent features in the electrical resistivity of YbRh2Si2 with similar maxima in other isostructural YbT2X2 (T = transition metal; X = Si or Ge) compounds was performed. For the comparison, a simple relation that considers the Coqblin-Schrieffer model and the hypothesis of Lavagna et al. is proposed. A systematic behavior is observed depending on the transition metal; namely, it seems that the higher the atomic radii of the T-atom the smallest the pressure dependence of the maximum in the electrical resistivity, suggesting a weaker coupling of localized- and conduction-electrons. It is also observed that an increase in the density of conduction electrons reduces the pressure dependence of the characteristic Kondo temperature. The mechanism responsible for the sudden enhancement of T_N in YbRh2Si2 at about p_2 is still unknown. However two plausible scenarios are discussed. The Eu-ions in EuCo2Ge2 and EuCu2Ge2 have a divalent character in the range 100 mK &lt; T &lt; 300 K. Therefore, these systems order magnetically at T_N = 23 K and T_N = 12 K, respectively. The studies performed on EuCo2Ge2 and EuCu2Ge2 as a function of pressure suggest that a change to a non-magnetic trivalent state of the Eu-ions might occur at zero temperature for pressures higher than 3 GPa and 7 GPa, respectively. A common and characteristic feature on EuCo2Ge2 and EuCu2Ge2 is the absence of a clear first order transition from the divalent to the trivalent state of the Eu-ions at finite temperature for p &gt; 3 GPa and for p &gt; 7 GPa, respectively. In other isostructural Eu-based compounds, a discontinuous and abrupt change in the thermodynamic and transport properties associated to the valence transition of the Eu-ions is typically observed at finite temperatures. In contrast, the electrical resistivity of EuCo2Ge2 and EuCu2Ge2 changes smoothly as a function of pressure and temperature. The analysis of the the electrical resistivity of EuCo2Ge2 suggest that a classical critical point might be close to the AFM-ordered phase, being a hallmark of this compound. The overall temperature dependence of the the electrical resistivity of EuCo2Ge2 changes significantly at 3 GPa; therefore, it seems that the system suddenly enters to a T-dependent valence-fluctuating regime. Additionally, the pressure-dependent electrical-resistivity isotherms show a step-like behavior. Thus, it is concluded that discontinuous change of the ground state might occur at 3 GPa. The electrical resistivity of EuCu2Ge2 at high pressure is characterized by a negative logarithmic T-dependence in the pressure range 5 GPa &lt; p &lt; 7 GPa for T &gt; T_N and by a broad peak in the pressure dependent residual resistivity, whose maximum is located at 7.3 GPa. The first behavior resembles the incoherent scattering process typical for an exchange coupling mechanism between the localized electrons and the ligand. This and the peak effect in the local 4f susceptibility observed in NMR measurements are consistent with such a coupling mechanism. Thus, it would be for the first time that a dense Eu-based compound like EuCu2Ge2 show such a behavior. Combining the results of the experiment performed at high pressures on EuCu2Ge2 with the studies performed in the EuCu2(Ge1-xSix)2 series, a crossover from an antiferromagnetically ordered state into a Fermi-liquid state for pressures higher than 7.3 GPa may be inferred from the analysis. Therefore, it may be possible that the sudden depopulation of 4f-level occur mediated by quantum fluctuation of the charge due to a strong Coulomb repulsion between the localized-electrons and the ligand. This phenomenon would explain the broad peak in the residual resistivity. To our knowledge, this would be the first Eu-based compound, isostructural to ThCr2Si2, that show such a transition as function of pressure at very low temperatures.

The main focus of the present work was the Ge-rich part of the binary Ba – Ge system, in which by inspecting the behavior of the clathrate-I Ba8Ge43 under pressure, several new phases were found. The new phases in this system have the following compositions: BaGe3 (with two modifications), BaGe5, BaGe5.5 and BaGe6, therefore they are quite close in composition range: 75% - ~85% at. Ge. Concerning the conditions required for the synthesis of each phase, several combinations of temperature and pressure were employed in order to find a stability range. It was possible to establish such a formation range for all phases. In some cases two phases were found for a given conditions and in many other cases three or more phases were found to coexist. Thus, the stability range of pressure and temperature for single phase formation turned out to be very narrow. By inspecting of some structural features, for instance the interatomic distances, it is found that the average of the Ge – Ge distances change in line with the composition, i.e. the shorter contacts belong to BaGe6 while the longer distances are present in BaGe3 (both modification). An opposite trend is observed for the calculated density of each phase (neglecting the tI32 form of BaGe3): the lower density is found for BaGe3 and the denser compound is found to be BaGe6. Of course this is not coincidence, since due to the Ge content, BaGe6 has the largest molar mass. Similarly, by examining the density as a function of the interatomic distance. In such case, the denser compound is characterized by shorter Ge – Ge contacts, while the less dense phase holds the longest Ge – Ge contacts. This is in agreement with the building motifs within each crystal structure: columns in BaGe3 (open framework) passing through layers in BaGe5, ending in a three-dimensional network (closed framework) in BaGe6.

The thesis is based on a petrologic and geochemical study of mantle xenoliths from the central Siberian craton and the Baikal-Mongolia region of central Asia. Its goal is to establish the redox regime of the lithospheric mantle in these two domains with distinct tectonic settings and age and relate it to thermal regime and the speciation of C-0-H fluids. Oxygen fugacity is calculated based on Fe2+/Fe3+ ratios in spinel and garnet of mantle peridotites obtained by Mössbauer spectroscopy. The study deals with the following topics: (i) microstructures, chemical and mineralogical composition of the xenoliths; (ii) Fe2+/Fe3+ ratios in minerals by Mössbauer spectroscopy; (iii) equilibration temperatures and pressures using mineral thermo-barometry; (iv) oxygen fugacity from mineral compositions using oxybarometry; (v) proportions of molecular components in C-0-H fluids coexisting with the studied rocks. The three main conclusions of this study are: (1) Oxygen fugacity in the lithospheric mantle in the central Siberian craton decreases from +1 to -4 ΔlogʄO2 (FMQ) at depths from 70 to 220 km and shows significant lateral variations. (2) The lithospheric mantle beneath the Baikal-Mongolia region shows important redox heterogeneities, with a sharp decrease in oxygen fugacity (from +0 to -3 AlogfO2 (FMQ)) during the transition from the spine! to garnet facies peridotites at 50 to 90 km. (3) The speciation of C-O-H fluids changes with depth from essentially H2O-CO2 in the shallow lithospheric mantle to H2O-CH4 at the lithosphere-asthenosphere boundary regardless of the thermal state and the thickness of the lithosphere

Photobacterium profundum SS9 is a γ-proteobacterium which grows optimally at 15°C and 28 MPa (a psychrophilic piezophile) and can grow over a range of temperatures (2-20oC) and pressures (0.1-90 MPa). Previous research had demonstrated that P. profundum SS9 adapts its membrane proteins and phospholipids in response to growth conditions. In this study, methodology was developed for growing P. profundum SS9 under cold temperatures and high pressures in both liquid and solid cultures. The effect of changing growth conditions on cell envelope polysaccharides was then investigated. The lipopolysaccharide (LPS) profile of a rifampicin resistant P. profundum SS9 derivative, SS9R, was shown to change at 0.1 MPa with respect to temperature and at 15°C with respect to pressure. Compositional analysis showed that the LPS was almost entirely composed of glucose. This provides evidence that, under these conditions, the major polysaccharide produced by P. profundum SS9 is a glucan. Two putative polysaccharide mutants, FL26 & FL9, were previously isolated from a screen for cold-sensitive mutants of P. profundum SS9R. Both mutants displayed an increased sensitivity to cold temperatures on solid medium and were unaffected in their growth at high pressure. FL26 was found to exhibit an LPS alteration similar to previously published O-antigen ligase mutants, providing evidence that this mutant is likely to lack O-antigen ligase. Interestingly, FL26 was also shown to have a reduced ability to form biofilms and had increased swimming motility. This suggests that there are a number of changes which occur in FL26 in the absence of O-antigen. FL9 was found to have an altered LPS and capsular polysaccharide (CPS), similar to an E. coli wzc mutant. In E. coli, Wzc is involved in the polymerisation and transport of CPS, disruption of which can also lead to LPS alterations. The LPS and CPS alterations may lead to the cold-sensitivity phenotype, either individually or in combination. In conclusion, alterations in the cell envelope polysaccharides were shown to affect cold temperature sensitivity on solid agar. Cold-sensitivity is most likely directly related to the LPS alterations and stability of the membrane under cold temperatures. Exopolysaccharides (EPS) have previously been shown to affect desiccation and freezethaw resistance, making it is possible that the CPS plays a similar role in this case.

[EN] The potential of diesel engines in terms of robustness, efficiency and energy density has made them widely used as power generators and propulsion systems. Specifically, fuel atomization, vaporization and air-fuel mixing, have a fundamental effect on the combustion process, and consequently, a direct impact on pollutant formation, fuel consumption and noise emission. Since the combustion chamber has a limited space respect to the spray penetration, wall impingement is considered to be a common event in direct injection diesel engines, having a relevant influence in the spray evolution and its interaction with both surrounding air and solid walls. This makes of spray-wall interaction an important factor for the combustion process that is still hardly understood. At cold-start conditions, the low in-chamber pressures and temperatures promote the deposition of fuel in the piston wall, which leads to a boost in the formation of unburned hydrocarbons. Additionally, modern design trends such as the increment of rail pressures in injection systems and the progressive reduction of the engine displacement, favor the emergence of spray collision onto the walls. In spite of the evident relevance of the comprehension of this phenomenon and the efforts of engine researchers to reach it, the transient nature of injection process, its small time scales and the complexity of the physical phenomena that take place in the vicinity of the wall, make challenging the direct observation of this spray-wall interaction. Even though computational tools have proven to be priceless in this field of study, the need for reliable experimental data for the development of those predictive models is present. This thesis is aimed to shed light on the fundamental characteristics of spray-wall interaction (SWI) at diesel-like chamber conditions. A flat wall was set at different impingement distances and angles respect to the spray. In this way, two different kinds of experimental investigations on colliding sprays were carried out: A transparent quartz wall was employed into the chamber to, in isolation, analyze the macroscopic characteristics of the spray at both evaporative inert and reactive conditions, which have been observed laterally and through the wall, thanks to the use of a high-pressure and high-temperature vessel with optical accesses. This same test rig was used in the second kind of experiments, where instead of the quartz plate, a stainless steel wall was used to capture the effect of the operating conditions on the heat flux between the wall and the spray during the injection-combustion events and to determine how spray and flame evolution are affected by realistic heat transfer situations. This wall was instrumented to control its initial in-chamber surface temperature and to measure its variation with time by using high-speed thermocouples. Tests at free-jet conditions were also performed in order to provide a solid comparative base for those experiments.
[ES] El potencial de los motores diesel en términos de robustez, eficiencia y la densidad de energía los ha hecho ser ampliamente usados como generadores de energía y sistemas propulsivos. Específicamente, la atomización de combustible, vaporización y mezcla de aire y combustible tienen un efecto fundamental en el proceso de combustión y, en consecuencia, un impacto directo en la formación de emisiones contaminantes, consumo de combustible y generación de ruido. Dado que la cámara de combustión tiene un espacio limitado con respecto la capacidad de penetración del chorro, el impacto de la pared se considera bastante común en motores de inyección directa diésel, que tienen una influencia relevante en la evolución del chorro y su interacción con el aire circundante y las paredes sólidas. Esto hace de interacción chorro-pared, un factor importante para el proceso de combustión que aún es dificilmente comprendido. En condiciones de arranque en frío, las bajas presiones y temperaturas en la cámara promueven la deposición de combustible en la pared del pistón, lo que conduce a un aumento en los niveles de formación de hidrocarburos no quemados. Además, las tendencias modernas de diseño como el incremento de las presiones de rail en los sistemas de inyección y la progresiva reducción en la cilindrada de los motores, favorecen la aparición de colisiones entre chorro y pared. A pesar de la evidente importancia en la comprensión de este fenómeno y los esfuerzos de los investigadores para alcanzarla, la transitoria naturaleza del proceso de inyección, sus pequeñas escalas de temporales y la complejidad de los fenómenos físicos que tienen lugar en las proximidades de la pared, hacen que la observación directa de esta interacción chorro-pared sea un desafío. Aunque las herramientas computacionales han demostrado ser invaluables en este campo de estudio, la necesidad de datos experimentales confiables para el desarrollo de esos modelos predictivos está muy presente. Esta tesis tiene como objetivo arrojar luz sobre las características fundamentales de la interacción chorro-pared (SWI por sus siglas en inglés) en condiciones de cámara similares a las de un motor diesel. Se colocó una pared plana a diferentes distancias de impacto y ángulos con respecto al jet. De esta manera, dos tipos diferentes de investigaciones experimentales sobre chorros en colisión se llevaron a cabo: se empleó una pared de cuarzo transparente en la cámara para, de forma aislada, analizar las características macroscópicas del chorro en condiciones evaporativas inertes y reactivas, que pueden observarse lateralmente y a través de la pared, gracias al uso de una instalación de alta presión y alta temperatura ópticamente accesible. Esta misma instalación se utilizó en el segundo tipo de experimentos en los que se introdujo una pared de acero inoxidable para capturar adicionalmente el efecto de las condiciones de operación en el flujo de calor entre ésta y el chorro durante los eventos de inyección y combustión y para determinar cómo la evolución del chorro y la llama son afectadas por una situación realista de transferencia de calor. Esta pared fue instrumentada para controlar la temperatura inicial de su superficie expuesta a la cámara y medir su variación con el tiempo, utilizando termopares de alta velocidad. Ensayos en condiciones de chorro libre también se realizaron para proporcionar una base comparativa sólida para esos experimentos.
[CA] El potencial dels motors dièsel en termes de robustesa, eficiència i la densitat d'energia els ha fet ser àmpliament usats com a generadors d'energia i sistemes propulsius. Específicament, l'atomització de combustible, vaporització i barreja d'aire i combustible tenen un efecte fonamental en el procés de combustió i, en conseqüència, un impacte directe en la formació d'emissions contaminants, consum de combustible i generació de soroll. Atès que la cambra de combustió té un espai limitat pel que fa la capacitat de penetració de l'raig, l'impacte de la paret es considera bastant comú en motors d'injecció directa dièsel, que tenen una influència rellevant en l'evolució del doll i la seva interacció amb el aire circumdant i les parets sòlides. Això fa d'interacció doll-paret, un factor important per al procés de combustió que encara és difícilment comprès. En condicions d'arrencada en fred, les baixes pressions i temperatures a la cambra promouen la deposició de combustible a la paret del pistó, el que condueix a un augment en els nivells de formació d'hidrocarburs no cremats. A més, les tendències modernes de disseny com l'increment de les pressions de rail en els sistemes d'injecció i la progressiva reducció en la cilindrada dels motors, afavoreixen l'aparició de col·lisions entre el doll i la paret. Tot i l'evident importància en la comprensió d'aquest fenomen i els esforços dels investigadors per aconseguir-la, la transitòria naturalesa de l'procés d'injecció, les seves petites escales de temporals i la complexitat dels fenòmens físics que tenen lloc en les proximitats de la paret , fan que l'observació directa d'aquesta interacció doll-paret siga un desafiament. Tot i que les eines computacionals han demostrat ser invaluables en aquest camp d'estudi, la necessitat de dades experimentals fiables per al desenvolupament d'aquests models predictius està molt present. Aquesta tesi té com a objectiu donar llum sobre les característiques fonamentals de la interacció doll-paret (SWI per les seues sigles en anglès) en condicions de cambra similars a les d'un motor dièsel. Es va col·locar una paret plana a diferents distàncies d'impacte i angles pel que fa al jet. D'aquesta manera, dos tipus diferents d'investigacions experimentals sobre dolls en col·lisió es van dur a terme: es va emprar una paret de quars transparent a la cambra per, de forma aïllada, analitzar les característiques macroscòpiques del doll en condicions evaporació inerts i reactives, que poden observar lateralment i a través de la paret, gràcies a l'ús d'una instal·lació d'alta pressió i alta temperatura òpticament accessible. Aquesta mateixa instal·lació es va utilitzar en el segon tipus d'experiments en els quals es va introduir una paret d'acer inoxidable per capturar addicionalment l'efecte de les condicions d'operació en el flux de calor entre aquesta i el dull durant els esdeveniments d'injecció i combustió i per determinar com l'evolució del doll i la flama són afectades per una situació realista de transferència de calor. Aquesta paret va ser instrumentada per controlar la temperatura inicial de la seua superfície exposada a la càmera i mesurar la seua variació amb el temps, utilitzant termoparells d'alta velocitat. Assajos en condicions de doll lliure també es van realitzar per proporcionar una base comparativa sòlida per a aquests experiments.
Peraza Ávila, JE. (2020). Experimental study of the diesel spray behavior during the jet-wall interaction at high pressure and high temperature conditions [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/149389
TESIS

Natural soils in work-sites are sometimes detrimental to the construction of engineering projects. Problematic soils such as soft and expansive soils are a real source of concern to the long-term stability of structures if care is not taken. Expansive soils could generate immense distress due to their volume change in response to a slight change in their water content. On the other hand, soft soils are characterised by their low shear strength and poor workability. In earthwork, replacing these soils is sometimes economically and sustainably unjustifiable in particular if they can be stabilised to improve their behaviour. Several techniques have evolved to enable construction on problematic soils such as reinforcement using fibre and planar layers and piled reinforced embankments. Chemical treatment using, e.g. lime and/or cement is an alternative method to seize the volume change of swelling clays. The use of lime as a binding agent is becoming a popular method due to its abundant availability and cost-effectiveness. When mixed with swelling clays, lime enhances the mechanical properties, workability and reduces sensitivity to absorption and release of water. There is a consensus in the literature about the primary mechanisms, namely cation exchange, flocculation and pozzolanic reaction, which cause the changes in the soil characteristics after adding lime in the presence of water. The dispute is about whether these mechanisms occur in a sequential or synchronous manner. More precisely, the controversy concerns the formation of cementitious compounds in the pozzolanic reaction, whether it starts directly or after the cation exchange and flocculation are completed. The current study aims to monitor the signs of the formation of such compounds using a geotechnical approach. In this context, the effect of delayed compaction, lime content, mineralogy composition, curing time and environmental temperature on the properties of lime-treated clays were investigated. The compaction, swelling and permeability, and unconfind compression strength tests were chosen to evaluate such effect. In general, the results of the geotechnical approach have been characterised by their scattering. The sources of this dispersion are numerous and include sampling methods, pulverisation degree, mixing times and delay of compaction process, a pre-test temperature and humidity, differences in dry unit weight values, and testing methods. Therefore, in the current study, several precautions have been set to reduce the scattering in the results of such tests so that they can be used efficiently to monitor the evolution in the properties that are directly related to the formation and development of cementitious compounds. Four clays with different mineralogy compositions, covering a wide range of liquid limits, were chosen. The mechanical and hydraulic behaviour of such clays that had been treated by various concentrations of lime up to 25% at two ambient temperatures of 20 and 40oC were monitored for various curing times. The results indicated that the timing of the onset of changes in mechanical and hydraulic properties that are related to the formation of cementitious compounds depends on the mineralogy composition of treated clay and ambient temperature. Moreover, at a given temperature, the continuity of such changes in the characteristics of a given lime-treated clay depends on the lime availability.

Ce travail de thèse porte sur la synthèse de nouveaux matériaux nanostructurés sous conditions extrêmes de pression et de température (P > 5 GPa et T > 1000 °C). Les matériaux que nous étudions sont basés sur un élément particulier : le bore. Ces matériaux présentent des propriétés uniques. D'une part, les allotropes du bore présentent des duretés élevées et une grande inertie chimique. D'autre part, les alliages du bore (ou borures métalliques) présentent des propriétés variées, de la thermoélectricité (HfB2) à la supraconductivité (MgB2). La synthèse en sels fondus est utilisée afin d'obtenir des systèmes nanostructurés comprenant deux composants : des nanoparticules cristallines d'environ 10 nm de borures métalliques (HfB2 ou CaB6) comprises dans une matrice de bore amorphe.Le traitement sous haute pression et température est le seul permettant de cristalliser la phase amorphe. La conservation de la nanostructure initiale est démontrée. Plusieurs nouveaux matériaux sont ainsi synthétisés : des nanocomposites borure/borate (HfB2/HfB2O5 ou CaB6/CaB2O4) ou borure/bore (HfB2/?-B ou CaB6/?-B), premiers membres de nouvelles familles de nanomatériaux. Un précurseur de bore amorphe nanostructuré synthétisé en sels fondus est ensuite utilisé. Il est cristallisé sous haute pression et haute température. En sus de la première occurrence de bore epsilon nanostructuré, deux nouvelles phases riches en bore sont obtenues, dont la structure est en cours de résolution. En somme, ce travail conduit à une nouvelle méthode de synthèse à la frontière entre la chimie des nanomatériaux et la physique des hautes pressions et températures, à l'origine de nouveaux nanomatériaux et structures
In this PhD work, we develop a way to prepare new nanostructured materials under extreme pressure and temperature conditions (P > 5 GPa et T > 1000 °C). The studied materials are based on a specific element: boron. Indeed, these materials have unique properties. On the one hand, boron allotropes exhibit high hardness and chemical inertness. On the other hand, metal-boron alloys (metal borides) span a wide range of properties, from thermoelectricity (HfB2) to superconductivity (TiB2). We use the synthesis in molten salts to reach nanostructured systems with two components: crystalline boride nanoparticles (ca. 10 nm) embedded in an amorphous boron matrix. High pressure high temperature treatments on these systems enable crystallisation of the amorphous component into unique phases, thus yielding new nanomaterials: boride/borate (HfB2/HfB2O5 or CaB6/CaB2O4) or boride/boron (HfB2/β-B or CaB6/β-B) nanocomposites, representing the first members of new nanomaterials families. In a final step, a specific nanostructured amorphous boron precursor is synthesised in molten salts. It is crystallised under high pressure and temperature. In addition to the first nanostructured occurrence of the epsilon-boron phase, we report two new boron-rich phases, which structure is under resolution. All in all, a new synthetic route is developed at the frontier of nanomaterials chemistry and high pressure and temperature physics, leading to new nanomaterials and structures

This thesis presents the experimental investigation of structure and melting of three important materials under extreme conditions of high pressure and high temperature. The melting points of elements and compounds are of fundamental importance for the study of planetary interiors and for fundamental and applied physics. The high pressure apparatus used in this thesis is the diamond anvil cell, which has been used to reach pressures of up to 137 GPa and temperatures up to 6000-7000 K via laser-heating techniques. The melting point has been determined at high pressure by the first onset of liquid scattering in X-ray diffraction patterns that are collected in situ. At temperatures towards the melting point, important information on the crystalline state of these materials has been extracted. The polymorphism of Sn has been studied into the megabar range (P > 100 GPa) at room temperature. The equation of state of Sn has been determined up to 137 GPa. A previously unreported structural transformation occurs at 32 GPa into a body centered orthorhombic structure (spacegroup Immm). Coexistence of this polymorph with a body centered cubic structure (spacegroup: Im-3m) is observed over a wide pressure range. These new findings for this important element are reported within. The melting relations of Sn have been determined to beyond 1 megabar in pressure and reveal a dip in the melt slope followed by a sudden sharp rise between 40 and 70 GPa. High temperature experiments using resistive-heating and laser-heating in the diamond anvil cell reveal the observation of multiple X-ray diffraction signatures at high temperatures. The results are discussed and overlap with the discoveries from the room temperature investigation of Sn. TaC and MgO are two important refractory materials and have also been investigated using laser-heated diamond anvil cell techniques combined with in situ synchrotron X-ray diffraction. TaC has the highest ambient melting temperature of any binary compound. MgO constitutes approximately 37 % of the Earth’s lower mantle and the melting temperature as a function of pressure can provide us with information on the melting behaviour, phase relations and rheology of the Earth’s lower mantle. The results and their impact on current high pressure research are discussed.

This geothermobarometric investigation of St Persholmen, Utö, in the south central part of Sweden presents an attempt at determining the metamorphic conditions of this important part of the Svecofennian province. Belonging to the geology of the Bergslagen area, Utö historically represent part of Sweden’s vast ore resources with concentrations of iron, copper and sulfides. Rock types from this area are around 1.91-1.89 Ga old (Stephens et al. 2009) and as such Paleoproterozoic in age. The rocks on Utö are considered representative of Bergslagen and record the closing of an ocean starting with subduction followed by volcanic episodes and orogeny (Talbot 2008). The bedrock we observe at Persholmen is thought to represent the remains of the aforementioned orogeny where greywackes from the oceanic stage have been preserved at the base of the mountain range (Stålhös 1982). The two rock types of interest at Persholmen which have been evaluated in this study are 1) normal greywackes and 2) greywackes which have been migmatised either because of the influence of fluids, reworking in an accretionary prism or melted at the base of a mountain range. In this project the area of study has been mapped and samples have been retrieved in order to distinguish the mineralogy and metamorphic history of the bedrock. After petrographic analysis I have determined mineral chemistry by the use of a SEM (Scanning Electron Microscope). These chemical data have then been entered into the computer programs AX and THERMOCALC for determination of temperature and pressure. For the normal/migmatised greywackes a temperature of 538 ±36/756±133°C and a pressure of 3.1±1.3/3.8±3.2 kbars respectively have been estimated. Two generations of muscovite provide evidence of fluid-rock interactions and at the north coast of Persholmen the occurrence of sillimanite indicates a high grade of metamorphism.

La vitesse de flamme laminaire représente une grandeur physique clé à mesurer car elle permet d'obtenir des données fondamentales sur la réactivité, la diffusivité et l'exothermicité du carburant. Elle est également un des paramètres utilisés pour le développement et la validation des mécanismes réactionnels détaillés ainsi que pour la modélisation de la combustion turbulente. Bien que cette grandeur physique ait fait l'objet de nombreuses études expérimentales depuis plusieurs décennies, sa méconnaissance sur des carburants multi-composant dans des conditions haute-pression et haute-température similaires à celles existantes dans les chambres de combustion reste un sujet d'actualité pour les industriels des secteurs automobile et aéronautique. Au cours de cette thèse, un brûleur de configuration bec Bunsen fonctionnant avec un prémélange gazeux combustible/air a été conçu pour produire une flamme laminaire à pression élevée tout en permettant la mesure par voie optique de la vitesse de flamme laminaire de carburants multi-composant (kérosène, biocarburants de seconde génération...). La mesure est basée sur la détection du contour de flamme par diverses diagnostics optiques comme la chimiluminescence OH*, la PLIF-OH et la PLIF-acétone/aromatique. En premier lieu, les mélanges de carburants purs gazeux (CH4) ou liquide (acétone) avec de l'air ont été étudiés pour valider le brûleur expérimental et la méthodologie de mesure de la vitesse de flamme laminaire par voie optique. Les évolutions de la vitesse de flamme laminaire pour des carburants de type kérosène (composants purs, surrogate LUCHE et Jet A-1) en fonction de la pression, température de préchauffage et richesse ont été ensuite étudiées et comparées avec des simulations numériques utilisant un mécanisme réactionnel détaillé. La dernière partie de la thèse est consacrée à l'étude de l'influence des composés oxygénés présents dans un biocarburant de seconde génération de type d'essence sur la vitesse de flamme laminaire. Après avoir mesuré la vitesse de flamme laminaire de différentes molécules oxygénées, les effets d'addition de ces composés oxygénés dans le carburant ont été quantifiés
Laminar flame speed is one of the key parameters for understanding reactivity, diffusivity and exothermicity of fuels. It is also useful to validate both the kinetic chemical mechanisms as well as turbulent models. Although laminar flame speeds of many types of fuels have been investigated over many decades using various combustion methodologies, accurate measurements of laminar flame speeds of multicomponent liquid fuels in high-pressure and high-temperature conditions similar to the operating conditions encountered in aircraft/automobile combustion engines are still required. In this current study, a high-pressure combustion chamber was specifically developed to measure the laminar flame speed of multicomponent liquid fuels such as kerosene and second generation of biofuels. The architecture of the burner is based on a preheated premixed Bunsen flame burner operated in elevated pressure and temperature conditions. The optical diagnostics used to measure the laminar flame speed are based on the detection of the flame contour by using OH* chemiluminescence, OH- and acetone/aromatic- Planar laser induced fluorescence (PLIF). The laminar flame speed of gaseous CH4/air and acetone/air premixed laminar flames were first measured for validating the experimental setup and the measurement methodologies. Then, the laminar flame speeds of kerosene or surrogate fuels (neat kerosene compounds, LUCHE surrogate kerosene and Jet A-1) were investigated and compared with simulation results using detailed kinetic mechanisms over a large range of conditions including pressure, temperature and equivalence ratio. The last part of the thesis was devoted to study the effect of oxygenated compounds contained in the second generation of biofuels on the laminar flame speeds. After measuring the laminar flame speeds of various oxygenated components present in partially hydro-processed lignocellulosic biomass pyrolysis oils, the effect of these oxygenates on the flame speeds of these fuels were quantitatively investigated

Les hautes pressions sont précieuses à plusieurs disciplines scientifiques. Ce sera le cas dans cette thèse avec le développement d'un nouvel appareil permettant des possibilités inédites de tomographie et de déformation sous haute pression et haute température. Il apporte la possibilité de nouvelles études scientifiques dans les différents champs disciplinaires que sont les sciences de la Terre, la chimie mécanique, la physique des matériaux et la physique des liquides
High pressures are essential in several scientific field. This will be the case in this thesis with the development of a new device enabling new possibilities tomography and deformation under high pressure and high temperature. It brings the possibility of further scientific studies in the various disciplines that are Earth science, mechanical chemistry, physics of materials and liquids physics

Cette thèse de physique expérimentale explore le diagramme de phase du monohydrate d'ammoniac (AMH) à haute pression (0
This thesis in experimental physics investigates the phase diagram of ammonia monohydrate (AMH) at high pressure (0

Ce travail de thèse porte sur la synthèse de nouveaux matériaux nanostructurés sous conditions extrêmes de pression et de température (P > 5 GPa et T > 1000 °C). Les matériaux que nous étudions sont basés sur un élément particulier : le bore. Ces matériaux présentent des propriétés uniques. D'une part, les allotropes du bore présentent des duretés élevées et une grande inertie chimique. D'autre part, les alliages du bore (ou borures métalliques) présentent des propriétés variées, de la thermoélectricité (HfB2) à la supraconductivité (MgB2). La synthèse en sels fondus est utilisée afin d'obtenir des systèmes nanostructurés comprenant deux composants : des nanoparticules cristallines d'environ 10 nm de borures métalliques (HfB2 ou CaB6) comprises dans une matrice de bore amorphe.Le traitement sous haute pression et température est le seul permettant de cristalliser la phase amorphe. La conservation de la nanostructure initiale est démontrée. Plusieurs nouveaux matériaux sont ainsi synthétisés : des nanocomposites borure/borate (HfB2/HfB2O5 ou CaB6/CaB2O4) ou borure/bore (HfB2/?-B ou CaB6/?-B), premiers membres de nouvelles familles de nanomatériaux. Un précurseur de bore amorphe nanostructuré synthétisé en sels fondus est ensuite utilisé. Il est cristallisé sous haute pression et haute température. En sus de la première occurrence de bore epsilon nanostructuré, deux nouvelles phases riches en bore sont obtenues, dont la structure est en cours de résolution. En somme, ce travail conduit à une nouvelle méthode de synthèse à la frontière entre la chimie des nanomatériaux et la physique des hautes pressions et températures, à l'origine de nouveaux nanomatériaux et structures
In this PhD work, we develop a way to prepare new nanostructured materials under extreme pressure and temperature conditions (P > 5 GPa et T > 1000 °C). The studied materials are based on a specific element: boron. Indeed, these materials have unique properties. On the one hand, boron allotropes exhibit high hardness and chemical inertness. On the other hand, metal-boron alloys (metal borides) span a wide range of properties, from thermoelectricity (HfB2) to superconductivity (TiB2). We use the synthesis in molten salts to reach nanostructured systems with two components: crystalline boride nanoparticles (ca. 10 nm) embedded in an amorphous boron matrix. High pressure high temperature treatments on these systems enable crystallisation of the amorphous component into unique phases, thus yielding new nanomaterials: boride/borate (HfB2/HfB2O5 or CaB6/CaB2O4) or boride/boron (HfB2/β-B or CaB6/β-B) nanocomposites, representing the first members of new nanomaterials families. In a final step, a specific nanostructured amorphous boron precursor is synthesised in molten salts. It is crystallised under high pressure and temperature. In addition to the first nanostructured occurrence of the epsilon-boron phase, we report two new boron-rich phases, which structure is under resolution. All in all, a new synthetic route is developed at the frontier of nanomaterials chemistry and high pressure and temperature physics, leading to new nanomaterials and structures

An investigation was undertaken to determine the feasibility of increasing the hydrogen production rate by coupling the water gas shift (WGS) process to the hybrid sulphur process (HyS). This investigation also involved the technical and economical analysis of the water gas shift and the H2 separation by means of Pressure swing adsorption (PSA) process. A technical analysis of the water gas shift reaction was determined under the operating conditions selected on the basis of some information available in the literature. The high temperature system (HTS) and low temperature system (LTS) reactors were assumed to be operated at temperatures of 350ºC and 200ºC, respectively. The operating pressure for both reactors was assumed to be 30 atmospheres. The H2 production rate of the partial oxidation (POX) and the WGS processes was 242T/D, which is approximately two times the amount produced by the HyS process alone. The PSA was used for the purification process leading to a hydrogen product with a purity of 99.99%. From the total H2 produced by the POX and the WGS processes only 90 percent of H2 is recovered in the PSA. The unrecovered H2 leaves the PSA as a purge gas together with CO2 and traces of CH4, CO, and saturated H2O. The estimated capital cost of the WGS plant with PSA is about US$50 million. The production cost is highly dependent on the cost of all of the required raw materials and utilities involved. The production cost obtained was US $1.41/kg H2 based on the input cost of synthesis gas as produced by the POX process. In this case the production cost of synthesis gas based on US $6/GJ for natural gas and US $0/Ton for oxygen was estimated to be US $0.154/kg. By increasing the oxygen and natural gas cost, the corresponding increase in synthesis gas has resulted in an increase in H2 production cost of US $1.84/kg.
Thesis (M.Sc. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2006.

This thesis describes investigations into the properties of -phase BEDT-TTF charge transfer salts. Charge transfer salts are mainly studied as they are very useful test beds for fundamental physics due to the tuneability of their proper- ties and ground states. The effects of temperature and pressure on such systems have been studied, as these allow access to a wide range of different states and properties. Transport properties of these systems have been studied to obtain information about the Fermi surface and effective mass, and the effect of deuter- ation and also change of pressure media will be discussed. The interaction of infrared radiation with these systems has also been investigated and simultaneous pressure and temperature measurements will be presented, something not greatly studied due to the large technical challenges. The techniques and approaches for overcoming these are also discussed. Chapter 1 provides an introduction to the organic materials themselves with particular emphasis on the actual compounds studied. Chapter 2 provides the necessary theoretical background for studying organic charge transfer salts using magnetic quantum oscillations and their infrared re- ectivity. Chapter 3 covers the experimental techniques and also discusses some of the challenges encountered and their solutions to aid others working in this area. Chapter 4 describes an investigation into the transport properties of - (ET)2Cu(SCN)2 by studying Shubnikov-de Haas oscillations using both deuter- ated and normal samples and using two different pressure media, and comparing it to work done using a third. Chapter 5 presents an investigation into the pressure dependence of selected phonon modes in -(ET)2Cu(SCN)2 using infrared radiation on a deuterated sam- ple. Chapter 6 presents what is believed to be the first pressure and temperature dependent infrared study of an organic molecular material. In this case the or- ganic molecular material is d8--(ET)2Cu[N(CN)2]Br, but the techniques should be readily transferable to other materials.

La préoccupation de plus en plus importante ces dernières décennies, liée à l’épuisement des ressources pétrolières et au réchauffement climatique par les gaz à effet de serre a accentué l’intérêt du butanol comme carburant alternatif dans le secteur des transports grâce à ses propriétés adaptées pour le moteur à allumage par compression. Cependant, le faible rendement des procédés de production et de séparation empêche encore sa commercialisation en tant que carburant. C’est pourquoi le mélange de fermentation intermédiaire de la production de butanol, Acétone-Butanol-Ethanol(ABE), est de plus en plus considéré comme un carburant alternatif potentiel en raison de ses propriétés similaires au butanol et de ses avantages quant à son cout énergétique pour sa fabrication.Dans ce cadre, ce travail a pour objectif d’étudier l’impact des propriétés de différents mélanges d’ABE et n-dodécane en comparaison avec des mélanges d’alcools (éthanol et butanol) sur le processus de pulvérisation et de combustion et ce,pour différentes proportions en volume allant de 20% à 50%. Pour cela, une nouvelle chambre de combustion appelée"New One Shot Engine ", a été réalisée et utilisée car les conditions haute pression et haute température de "Spray-A" (60bars, 800-900 K et 22,8 kg/m³) définies par le réseau Engine Combustion network (ECN) peuvent être atteintes. Autant les phases liquides et vapeur que de combustion ont été caractérisées grâce à l’utilisation des plusieurs techniques optiques (extinction, Schlieren, chimiluminescence d’OH*) dans des conditions non réactives (Azote pur) et réactives (avec15% d'oxygène). Ces résultats expérimentaux ont non seulement permis d’étudier l’impact en oxygène moléculaire et de fournir une nouvelle base de données fiables, mais aussi d’affirmer la possibilité d’utiliser jusque 20% d’ABE en volume dans des moteurs à allumage par compression, grâce à ses caractéristiques de pulvérisation et de combustion similaires au carburant Diesel conventionnel
The growing concern in recent decades, linked to the depletion of oil resources and global warming by greenhouse gases has increased the interest of butanol as an alternative fuel in the transport sector. However, the low yield of production and separation processes still prevents its commercialization as a fuel. Therefore, the intermediate fermentation mixture of butanol production, Acetone-Butanol-Ethanol (ABE), is increasingly considered as a potential alternative fuel because of its similar properties to butanol and its advantages in terms of the energy and cost in the separation process.The context of this work aims to study the impact of fuel properties on the spray and combustion processes of ABE mixture and alcohol fuels, blended with the diesel surrogate fuel, n-dodecane, in different volume ratio from 20% to 50%. A new combustion chamber called "New One Shot Engine," was designed and developed to reach the high-pressure and high temperatureconditions of "Spray-A" (60 bar, 800-900 K and 22.8 kg/m³) defined by the Engine Combustion Network (ECN).The macroscopic spray and combustion parameters were characterized by using the several optical techniques (extinction,Schlieren, chemiluminescence of OH*) under non-reactive (pure Nitrogen) and reactive (15% of oxygen) conditions. These experimental results not only made it possible to study the molecular oxygen impact and provide a new accurate database,but also to affirm the possibility of using ABE up to 20% by volume in compression-ignition engines, as its spray and combustion characteristics similar to conventional diesel fuel

Les quantités de cendres volantes (CV) produites par la combustion du charbon dans les centrales thermiques sont très importantes, et, même si différentes voies de valorisation existent, leurs applications restent à faible valeur ajoutée. Les CV sont riches en Si et Al et apparaissent alors comme des sources de réactifs potentielles pour la synthèse de zéolithes, matériaux microporeux alumino-siliciques à forte valeur ajoutée. Récemment, de nombreuses études ont été consacrées à la zéolithisation des CV, mais le plus souvent, la transformation se fait par voie hydrothermale à des températures ≥ 100 °C et à pression autogène. L’originalité de cette étude est le développement d’un procédé économique de transformation des CV par voie hydrothermale à basse température (≤ 50 °C) et à pression atmosphérique. Dans un premier temps, les CV ont été caractérisées, l’objectif principal étant la détermination de leur composition minéralogique (quartz, mullite et phase amorphe) ainsi que de leur réactivité. Puis, la synthèse consiste simplement à ajouter une solution de soude aux CV. Les quantités nécessaires de soude et d’eau ont été optimisées dans le but de synthétiser de la faujasite X, le rapport Al2O3/SiO2 (x) du mélange réactionnel étant fixé par la composition des cendres. Avec cette composition (1SiO2 : xAl2O3 : 3,8NaOH : 73,5H2O), la cinétique de transformation des cendres à 30 et à 50 °C a été étudiée par différentes techniques (DRX, adsorption d’azote, RMN du solide, spectrométrie d’absorption atomique et MEB), et un mécanisme de transformation est proposé. Quelles que soient la température et la durée de synthèse, le solide obtenu est un mélange de faujasite et de résidus de quartz, de mullite et de phase amorphe des CV. Il contient également des traces de deux autres zéolithes, la zéolithe NaP1 et la chabazite. L’élévation de température de 30 à 50 °C accélère la transformation, mais finalement, les taux de conversion atteints aux deux températures sont proches : environ 25 à 30 %. D’autres expériences ont été réalisées dans le but d’augmenter le rendement de la réaction : l’ajout de silice au mélange réactionnel, ainsi qu’une méthode de synthèse indirecte consistant à traiter les cendres par une solution acide (HCl) avant leur zéolithisation. Ces essais permettent d’augmenter le taux de conversion qui, dans le cas le plus favorable, dépasse 50 % de faujasite dans le produit final anhydre de la synthèse
The amount of fly ashes (FAs) produced by the coal combustion in thermal power stations is huge, and even if part of these FAs is reused, their applications have a low-added-value. As the FAs are rich in Si and Al, they can be seen as potential sources for the synthesis of zeolites. These aluminosilicate materials are microporous and display a high added value. Recently, many studies have been devoted to the conversion of FAs into various zeolites. Generally, the FA transformation is performed by a hydrothermal synthesis close or above 100 °C and at autogeneous pressure. The originality of this study is the development of a cost-saving process allowing the FA transformation into zeolite by a hydrothermal reaction at low temperature (below 50 °C) and at atmospheric pressure. The FAs were first characterised by different techniques, the most important objective being the determination of their mineralogical composition (quartz, mullite and amorphous phase) but also of their reactivity. Then, the synthesis consists simply in the addition of a NaOH solution to the FAs. The needed NaOH and water amounts were optimised in order to form an X-type faujasite, the Al2O3/SiO2 ratio (x) of the synthesis medium being fixed by the chemical composition of the FAs. Using this composition (1SiO2: xAl2O3: 3,8NaOH: 73,5H2O), the transformation kinetics of the FAs were studied at 30 and 50 °C by different methods (XRD, nitrogen adsorption, solid state NMR, atomic absorption spectroscopy, and SEM), and a transformation mechanism is proposed. Whatever the temperature and the synthesis time, the solid obtained is a mixture of faujasite, and residual quartz, mullite and amorphous phase from the FAs, but it contains also traces of two other zeolites, namely NaP1 zeolite and chabazite. The temperature increase from 30 to 50 °C speeds up the reaction, but finally, the maximal conversion rates reached at both temperatures are close: about 25 to 30 %. Other experiments were performed in order to increase the conversion yield, i. E. The addition of silica to the synthesis medium or an indirect synthesis method consisting in an acid treatment (HCl) of the FAs prior to the classic hydrothermal reaction. These experiments allowed increasing the conversion rate which is, in the most favourable case, above 50 % offaujasite in the final dried product of the synthesis

Transition metals (Ti, Zr, Hf, Mo, W, V, Nb, Ta, Pd, Pt, Cu, Ag, and Au) are essential building units of many materials and have important industrial applications. Therefore, it is important to understand their thermal and physical behavior when they are subjected to extreme conditions of pressure and temperature. This dissertation presents: An improved experimental technique to use lasers for the measurement of thermal conductivity of materials under conditions of very high pressure (P, up to 50 GPa) and temperature (T up to 2500 K). An experimental study of the phase relationship and physical properties of selected transition metals, which revealed new and unexpected physical effects of thermal conductivity in Zr, and Hf under high P-T. New phase diagrams created for Hf, Ti and Zr from experimental data. P-T dependence of the lattice parameters in α-hafnium. Contrary to prior reports, the α-ω phase transition in hafnium has a negative dT/dP slope. New data on thermodynamic and physical properties of several transition metals and their respective high P-T phase diagrams. First complete thermodynamic database for solid phases of 13 common transition metals was created. This database has: All the thermochemical data on these elements in their standard state (mostly available and compiled). All the equations of state (EoS) formulated from pressure-volume-temperature data (measured as a part of this study and from literature). Complete thermodynamic data for selected elements from standard to extreme conditions. The thermodynamic database provided by this study can be used with available thermodynamic software to calculate all thermophysical properties and phase diagrams at high P-T conditions. For readers who do not have access to this software, tabulated values of all thermodynamic and volume data for the 13 metals at high P-T are included in the APPENDIX. In the APPENDIX, a description of several other high-pressure studies of selected oxide systems is also included. Thermophysical properties (Cp, H, S, G) of the high P-T ω-phase of Ti, Zr and Hf were determined during the optimization of the EoS parameters and are presented in this study for the first time. These results should have important implications in understanding hexagonal-close-packed to simple-hexagonal phase transitions in transition metals and other materials.

Return liquor from thermal hydrolysis process (THP) can significantly add to the nitrogen load of a wastewater treatment plant (WWTP) and introduce UV quenching substances to the wastewater stream when recycled. While there are mature technologies in place to handle the inorganic nitrogen produced due to the thermal pretreatment, organic nitrogen remains a parameter of concern for utilities employing THP pretreatment. The impact of operating conditions of the THP on dissolved organic nitrogen (DON) and UV absorbance in return liquor was investigated. Operating conditions studied were (1) operating temperature (2) solids retention time (SRT) in the anaerobic digester (3) THP flash pressure (4) the effect of co-digestion of sewage sludge with food waste and, (5) polymer conditioning. Operating temperature and polymer dose had the most significant impact on DON and UV quenching. It was found that an increase in operating temperature resulted in an increase in DON, which was primarily contributed by the hydrophilic fraction. An increase in temperature also resulted in increased UV254 absorbance. However, this trend was not linear and the increase was more pronounced when the temperature was increased from 150 C to 170 C. Increasing flash pressure from 25 psi to 45 psi did not have a significant impact on the return liquor. However, increasing the flash pressure to 75 psi increased the DON and UV254 absorbing compounds. Co-digesting the sludge with food waste resulted in a slight increase in DON and a decrease in dissolved organic carbon (DOC) and UV quenching compounds. Increasing the SRT from 10 days to 15 days resulted in a slight decrease in DON but did not have any impact on UV254 absorbance. Overall, it can be concluded that optimizing operating conditions of thermal hydrolysis process can result in decreased DON and UV quenching compounds in the recycle stream.
Master of Science

The minerals of the cancrinite group are zeolite-like compounds, sharing the [CAN]-topology of the framework. Their structure shows large 12-ring channels along [0001], bound by columns of cages, the so-called can units. Natural and synthetic compounds exhibit a remarkable chemical variability. Among the natural species, the majority shows an aluminosilicate framework. Two subgroups can be identified according to the extraframework content of the can units: the cancrinite- and the davyne-subgroups, showing Na-H2O and Ca-Cl chains, respectively. The channels are stuffed by cations, anions and molecules. In Nature, cancrinite-group minerals occur in the late/hydrothermal stages of alkaline (SiO2)-undersaturated magmatism and in related effusive or contact rocks. Cancrinite-group compounds have been proposed as stable storage form for alkaline wastes. The characterization of the phase-stability fields, thermo-elastic behavior and structure response to applied (P,T) is needed to evaluate and predict their behavior in natural and industrial processes. The present study aimed to model the thermo-elastic behavior and the mechanisms of (P,T)-induced structure evolution of cancrinite-group minerals, with a special interest on the role played by the extraframework population. The study was restricted to the following (CO3)-rich and (SO4)-rich end-members: cancrinite {[(Na,Ca)6(CO3)1.2-1.7][Na2(H2O)2][Al6Si6O24]}, vishnevite {[(Na,Ca,K)6(SO4)][Na2(H2O)2][Al6Si6O24]}, balliranoite {[(Na,Ca)6(CO3)1.2-1.7][Ca2Cl2][Al6Si6O24]} and davyne {[(Na,Ca,K)6((SO4),Cl)][Ca2Cl2][Al6Si6O24]}. Their high-P and low-T (T < 293 K) behavior was investigated by means of in situ single crystal X-ray diffraction, using diamond-anvil cells and (N2)-cryosystems, respectively. Though sharing a similar volume compressibility and thermal expansivity, these minerals have a different thermo-elastic anisotropy, more pronounced in the cancrinite-subgroup compounds. This behavior is governed by different deformation mechanisms, which reflect the different coordination environments of the cage population between the minerals of the two subgroups. The davyne sample studied at high-P showed a displacive phase transition from the P63/m to the P63 space group after the load of pressure [0.0001 ≤ P (GPa) ≤ 0.38(2)]. In vishnevite, a P-induced re-organization of the extraframework population took place at P > 3.5 GPa, coupled with a significant increase in compressibility, suggesting that the channel-constituents can also play an active role at non-ambient conditions. Besides common features likely ascribable to the [CAN]-topology, the nature of the extraframework population appears to control significantly the (P,T)-induced structure evolution and thermo-elastic behavior of the cancrinite-group compounds.

The theory of the abyssal abiotic petroleum origin considers oil and natural gas to begenerated in the Earth’s upper mantle. Hydrocarbons migrate further through the deep faults into the Earth’s crust, where they can form oil and gas deposits in any kind of rock in any kind of structural position. Until recently one of the main obstacles for further development of this theory has been the lack of the data covering processes of generation and transformations of hydrocarbons. Experimental data, presented in this thesis, confirms the possibility of hydrocarbons formation from mantle inorganic compounds (water, Fe, CaCO3 or graphite) at temperature and pressure of the upper mantle (1500 K and 5 GPa). Experiments were carried out in CONAC high pressure device and multianvil apparatus BARS. Compositions of received gas mixtures were similar to natural gas. Quantity of hydrocarbons depended on the cooling regime of reaction mixture under pressure. Slow cooling favored higher quantity. We found that donor of carbon (CaCO3 or graphite) determines formation of “dry” (methane-rich) gas or “wet” (light hydrocarbons-rich) gas. Experiments in laser-heated diamond anvil cells showed that methane and ethane partially react under upper mantle thermobaric conditions (2-5 GPa, 1000-1500 K) to form mixture of hydrocarbons: methane, ethane, propane and n-butane – main compounds of natural gas. Similarity of final product mixture obtained from methane and ethane means thermodynamic stability of hydrocarbons in the thermobaric conditions of the upper mantle and equilibrium character of the observed processes.
QC 20101203

[ES] Esta tesis doctoral presenta un estudio de compresores scroll con inyección de vapor (SCVI) para bombas de calor que operan en climas fríos o para aplicaciones de calentamiento de agua a alta temperatura. Para ello, se comparó experimentalmente un SCVI con un compresor de dos etapas de pistones (TSRC) trabajando con R-407C en condiciones extremas. La comparación se realizó en términos de eficiencias del compresor, capacidad, COP y rendimientos estacionales tanto para el modo calefacción como para el modo refrigeración. Los resultados proporcionan una idea general sobre el rango de aplicación de los compresores estudiados y sobre las diferencias en los rendimientos de los compresores. Sin embargo, se identificaron varias limitaciones en la caracterización de los compresores y en el análisis del ciclo. Esto motivó a profundizar en el estudio del ciclo de compresión de dos etapas y sus componentes. El siguiente paso fue realizar un análisis teórico de los ciclos de compresión de dos etapas para aplicaciones de calefacción, en donde se identificó a la presión intermedia y a la relación de inyección como los parámetros del sistema más influyentes sobre el COP. La presión intermedia se optimizó para dos configuraciones de inyección (tanque de separación y economizador) utilizando varios refrigerantes. Basándose en los resultados de la optimización, se propuso una correlación que permite obtener la presión intermedia óptima del ciclo, considerando la influencia del subenfriamiento a la salida del condensador. Además, se analizó la influencia del diseño de los componentes del sistema sobre el COP del ciclo. Posteriormente, el estudio se profundizó a nivel de componentes. El factor más crítico en el sistema es el rendimiento del compresor. Por lo tanto, el siguiente paso fue evaluar la influencia de varios sistemas de compresión con inyección de vapor sobre el COP. Se tomaron en cuenta tres tecnologías de compresores, un SCVI, un TSRC y un compresor scroll de dos etapas (TSSC). Estas tecnologías de compresores fueron caracterizadas y modeladas para estudiar su rendimiento. Para ello, se propuso una nueva metodología para caracterizar compresores scroll con inyección de vapor. Esta metodología permite evaluar el rendimiento del compresor independientemente del mecanismo de inyección que se utiliza en el ciclo. Se identificó una correlación lineal entre la relación de inyección de refrigerante y la relación de compresión intermedia. Esta correlación se utiliza para determinar el flujo másico de inyección en función de la presión intermedia. Posteriormente, se propuso un modelo semi-empírico de compresores scroll y una metodología para extender dicho modelo para compresores scroll con inyección de vapor. Los modelos fueron ajustados y validados usando datos experimentales de cuatro compresores scroll trabajando con R-290 y un SCVI trabajando con R-407C. Finalmente, se comparó un SCVI con dos compresores de dos etapas, un TSSC y un TSRC, trabajando en condiciones extremas. Se optimizó la relación de volúmenes de los compresores de dos etapas. Los resultados muestran que, en las condiciones nominales de funcionamiento (Te=-15 °C, Tc=50 °C), la relación de volúmenes óptima del TSSC es 0.58, y del TSRC es 0.57. El TSSC consigue un COP 6% mayor que el SCVI y un COP 11.7% mayor que el TSRC. Bajo un amplio rango de condiciones de operación, el SCVI presenta una mejor eficiencia y COP para relaciones de presión inferiores a 5. Para relaciones de presión más altas, el TSSC presenta mejor rendimiento y consigue una temperatura de descarga más baja. Se concluye que el SCVI es una solución fácil de implementar, desde el punto de vista del mecanizado, y que permite extender el mapa de trabajo de los compresores de una etapa. Sin embargo, los resultados muestran que la compresión en dos etapas consigue mejorar en mayor medida el COP del ciclo y la capacidad, con una mayor redu
[CA] Aquesta tesi doctoral presenta un estudi de compressors scroll amb injecció de vapor (SCVI) per a bombes de calor que operen en climes freds o per a aplicacions d'escalfament d'aigua a alta temperatura. Per a això, es va comparar experimentalment un SCVI amb un compressor de dues etapes de pistons (TSRC) treballant amb R-407C en condicions extremes. La comparació es va realitzar en termes d'eficiències del compressor, capacitat, COP i rendiments estacionals tant per al mode calefacció com per al mode refrigeració. Els resultats proporcionen una idea general sobre el rang d'aplicació dels compressors estudiats i sobre les diferències en els rendiments dels compressors. No obstant això, es van identificar diverses limitacions en la caracterització dels compressors i en l'anàlisi del cicle. Això va motivar a aprofundir en l'estudi del cicle de compressió de dues etapes i els seus components. El següent pas va ser realitzar una anàlisi teòrica dels cicles de compressió de dues etapes per a aplicacions de calefacció, on es va identificar la pressió intermèdia i la relació d'injecció com els paràmetres del sistema més influents sobre el COP. La pressió intermèdia es va optimitzar per a dues configuracions d'injecció (tanc de separació i economitzador) utilitzant diversos refrigerants. Basant-se en els resultats de l'optimització, es va proposar una correlació que permet obtindre la pressió intermèdia òptima del cicle, considerant la influència del subrefredament a l'eixida del condensador. A més, es va analitzar la influència del disseny dels components del sistema sobre el COP del cicle. Posteriorment, l'estudi es va aprofundir a nivell de components. El factor més crític en el sistema és el rendiment del compressor. Per tant, el següent pas va ser avaluar la influència de diversos sistemes de compressió amb injecció de vapor sobre el COP. Es van prendre en compte tres tecnologies de compressors, un SCVI, un TSRC i un compressor scroll de dues etapes (TSSC). Aquestes tecnologies de compressors van ser caracteritzades i modelades per a estudiar el seu rendiment. Per a això, es va proposar una nova metodologia per a caracteritzar compressors scroll amb injecció de vapor. Aquesta metodologia permet avaluar el rendiment del compressor independentment del mecanisme d'injecció que s'utilitza en el cicle. Es va identificar una correlació lineal entre la relació d'injecció de refrigerant i la relació de compressió intermèdia. Aquesta correlació s'utilitza per a determinar el flux màssic d'injecció en funció de la pressió intermèdia. Posteriorment, es va proposar un model semi-empíric de compressors scroll i una metodologia per a estendre aquest model per a compressors scroll amb injecció de vapor. Els models van ser ajustats i validats utilitzant dades experimentals de quatre compressors scroll treballant amb R-290 i un SCVI treballant amb R-407C. Finalment, es va comparar un SCVI amb dos compressors de dues etapes, un TSSC i un TSRC, treballant en condicions extremes. Es va optimitzar la relació de volums dels compressors de dues etapes. Els resultats mostren que, en les condicions nominals de funcionament (Te=-15 °C, Tc=50 °C), la relació de volums òptima del TSSC és 0.58, i del TSRC és 0.57. El TSSC aconsegueix un COP 6% major que el SCVI i un COP 11.7% major que el TSRC. Sota un ampli rang de condicions d'operació, el SCVI presenta una millor eficiència i COP per a relacions de pressió inferiors a 5. Per a relacions de pressió més altes, el TSSC presenta millor rendiment i aconsegueix una temperatura de descàrrega més baixa. Es conclou que el SCVI és una solució fàcil d'implementar, des del punt de vista del mecanitzat, i que permet estendre el mapa de treball dels compressors d'una etapa. No obstant això, els resultats mostren que la compressió en dues etapes aconsegueix millorar en major mesura el COP del cicle i la capacitat, amb una major reducció de la
[EN] This Ph.D. thesis presents a study of scroll compressors with vapor-injection (SCVI) for heat pumps operating in cold climates or in high-temperature water heating applications. To do so, firstly, an SCVI was experimentally compared with a two-stage reciprocating compressor (TSRC) working with R-407C under extreme conditions. The comparison was made in terms of compressor efficiencies, capacity, COP, and seasonal COP, both for heating and cooling modes. The results give a general idea about the application range of the studied compressors and the differences in the compressors' performance. Nevertheless, several restrictions in the compressors' characterization and the cycle analysis were identified. This motivated us to deepen in the study of the two-stage compression cycle and its components. The next step was performing a theoretical analysis of two-stage compression cycles for heating applications, where the intermediate pressure and the injection ratio were identified as the most influential system parameters on the COP. The intermediate pressure was optimized for two vapor-injection configurations (flash tank and economizer) using several refrigerants. Based on the optimization results, a correlation was proposed that allows obtaining the optimal intermediate pressure of the cycle, considering the influence of the subcooling at the condenser outlet. In addition, a theoretical analysis of the influence of the design of the system components on the COP of the cycle was performed. Once the thermodynamic analysis of the two-stage cycle was carried out, the study was deepened at the component level. The most critical factor in the system is the compressor performance. Hence, the next step was evaluating the influence of several compression systems with vapor-injection on the COP. Three compressor technologies were taken into account, an SCVI, a TSRC and a two-stage scroll compressor (TSSC). These compressor technologies were characterized and modeled in order to study their performance. To do so, a new methodology to characterize SCVI was proposed. This methodology allows evaluating the compressor performance independently of the injection mechanism used in the cycle. A linear correlation was identified between the refrigerant injection ratio and the intermediate compression ratio. This correlation is used to determine the injection mass flow as a function of the intermediate pressure. Then, a semi-empirical model of scroll compressors and a methodology to extend the model for scroll compressors with vapor-injection was proposed. The models were adjusted and validated using experimental data from four scroll compressors working with R-290 and an SCVI compressor working with R-407C. Finally, an SCVI was compared with two two-stage compressors, a TSSC, and a TSRC, working in extreme conditions. The displacement ratio of the two-stage compressors was optimized. Results show that, at the nominal operating conditions (Te=-15 °C, Tc=50 °C), the optimal displacement ratio of the TSSC is 0.58, and of the TSRC is 0.57. The TSSC achieves 6% larger COP than the SCVI and 11.7% larger COP than the TSRC. Under a wide range of operating conditions, the SCVI presents a better efficiency and COP for pressure ratios below 5. For higher-pressure ratios, the TSSC presents better performance and achieves lower discharge temperature. It is concluded that the SCVI is an easy solution to implement from the point of view of machining, which allows extending the working map of the single-stage compressors. However, the results show that the two-stage compression technology gets further improve the COP of the cycle and the capacity, with a greater reduction of the discharge temperature operating under extreme conditions.
I thank the financial support provided by the Secretaría de Educación Superior, Ciencia, Tecnología e Innovación (SENESCYT) of Ecuador, through the international scholarship program for postgraduate studies “Convocatoria Abierta 2013 Segunda Fase, Grant No 2015-AR37665”.
Tello Oquendo, FM. (2019). Study of scroll compressors with vapor-injection for heat pumps operating in cold climates or in high-temperature water heating applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/120473
TESIS

L'exploitation des champs de pétrole et de gaz sous haute pression (HP) et haute température (HT) a augmenté ces dernières années, nécessitant de réévaluer les risques de corrosion dans ces milieux de plus en plus sévères. Afin de contribuer à une meilleure évaluation des risques de rupture différée des aciers en présence d'H2S (SSC, Sulfide Stress Cracking) dans ces conditions, trois axes de recherche ont été suivis. Nous avons d'abord identifié un besoin d'amélioration de prédiction des conditions corrosives sous haute pression et haute température, et en particulier pour le calcul du pH in situ. Un modèle a été développé ; il prend en compte le comportement non-idéal des phases en équilibre, et permet un calcul plus précis du pH et de la fugacité des gaz acides à haute pression et haute température. Dans un deuxième temps, nous avons étudié l'effet de la pression partielle de CO2 (PCO2) sur les réactions de surface et sur les risques de SSC. Cette étude, réalisée à l'aide de mesures électrochimiques en l’absence d’un film de sulfure de fer, a permis de montrer que la présence de CO2 augmente sensiblement les cinétiques des réactions cathodiques à la surface de l'acier ainsi que le chargement en hydrogène, en particulier lorsque la pression partielle en H2S (PH2S) est faible. Enfin, des essais SSC ont été mis en œuvre dans des conditions fixes de pH et de PH2S, en faisant varier PCO2 entre zéro et 100 bar. L'objectif était de vérifier que la présence de CO2 sous forte pression augmentait bien les risques de fissuration, comme prévu par les résultats des essais électrochimiques. Les difficultés liées à la mise en œuvre d'essais en autoclave sous pression n'ont pas permis d'apporter une conclusion définitive. Néanmoins, ces travaux montrent qu'il peut exister un risque de sous-estimation de la sévérité des milieux dans les pratiques conventionnelles, lorsque PCO2 est significativement plus élevée que PH2S. Dans ces conditions spécifiques, les résultats de ce travail peuvent servir à améliorer les critères de choix de matériaux pour les milieux HP/HT
The production of high pressure (HP) and high temperature (HT) wells has considerably increased in the last decade. It is therefore needed to reassess the risks of corrosion in always more severe environments. This work was three fold to better assess the risk of Sulfide Stress Cracking (SSC) in these environments. Firstly, there was a need to improve prediction methods for the evaluation of HP/HT environments severity, especially the in situ pH calculation. A model was which taking into account the non-ideal behaviour of gas and liquid phases in equilibrium. The determination of the in situ pH and the acid gas fugacity at high pressure and high temperature is more accurate. In a second part of the work, the impact of CO2 partial pressure (PCO2) on surface reactions and hence on the risk of SSC was examined. Electrochemical and hydrogen permeation measurements in the absence of an iron sulphide film showed that CO2 induces an increase of both cathodic reactions kinetics and hydrogen charging in the steel, especially at low H2S partial pressure (PH2S). In the last part of this work, SSC tests were performed at constant pH and constant PH2S, with various PCO2 from 0 to 100 bar. The objective was to experimentally confirm that increasing PCO2 increases the SSC risk, as inferred from the electrochemical study. Unfortunately, experimental artefacts linked with autoclave test conditions did not lead to clear conclusions on this point. However, this work shows that conventional tools might lead to underestimate SSC risks at high PCO2 and low PH2S. In these specific conditions, the new results presented in this report may contribute to improve materials selection criteria for high pressure and high temperature conditions

L'exploitation des champs de pétrole et de gaz sous haute pression (HP) et haute température (HT) a augmenté ces dernières années, nécessitant de réévaluer les risques de corrosion dans ces milieux de plus en plus sévères. Afin de contribuer à une meilleure évaluation des risques de rupture différée des aciers en présence d'H2S (SSC, Sulfide Stress Cracking) dans ces conditions, trois axes de recherche ont été suivis. Nous avons d'abord identifié un besoin d'amélioration de prédiction des conditions corrosives sous haute pression et haute température, et en particulier pour le calcul du pH in situ. Un modèle a été développé ; il prend en compte le comportement non-idéal des phases en équilibre, et permet un calcul plus précis du pH et de la fugacité des gaz acides à haute pression et haute température. Dans un deuxième temps, nous avons étudié l'effet de la pression partielle de CO2 (PCO2) sur les réactions de surface et sur les risques de SSC. Cette étude, réalisée à l'aide de mesures électrochimiques en l’absence d’un film de sulfure de fer, a permis de montrer que la présence de CO2 augmente sensiblement les cinétiques des réactions cathodiques à la surface de l'acier ainsi que le chargement en hydrogène, en particulier lorsque la pression partielle en H2S (PH2S) est faible. Enfin, des essais SSC ont été mis en œuvre dans des conditions fixes de pH et de PH2S, en faisant varier PCO2 entre zéro et 100 bar. L'objectif était de vérifier que la présence de CO2 sous forte pression augmentait bien les risques de fissuration, comme prévu par les résultats des essais électrochimiques. Les difficultés liées à la mise en œuvre d'essais en autoclave sous pression n'ont pas permis d'apporter une conclusion définitive. Néanmoins, ces travaux montrent qu'il peut exister un risque de sous-estimation de la sévérité des milieux dans les pratiques conventionnelles, lorsque PCO2 est significativement plus élevée que PH2S. Dans ces conditions spécifiques, les résultats de ce travail peuvent servir à améliorer les critères de choix de matériaux pour les milieux HP/HT
The production of high pressure (HP) and high temperature (HT) wells has considerably increased in the last decade. It is therefore needed to reassess the risks of corrosion in always more severe environments. This work was three fold to better assess the risk of Sulfide Stress Cracking (SSC) in these environments. Firstly, there was a need to improve prediction methods for the evaluation of HP/HT environments severity, especially the in situ pH calculation. A model was which taking into account the non-ideal behaviour of gas and liquid phases in equilibrium. The determination of the in situ pH and the acid gas fugacity at high pressure and high temperature is more accurate. In a second part of the work, the impact of CO2 partial pressure (PCO2) on surface reactions and hence on the risk of SSC was examined. Electrochemical and hydrogen permeation measurements in the absence of an iron sulphide film showed that CO2 induces an increase of both cathodic reactions kinetics and hydrogen charging in the steel, especially at low H2S partial pressure (PH2S). In the last part of this work, SSC tests were performed at constant pH and constant PH2S, with various PCO2 from 0 to 100 bar. The objective was to experimentally confirm that increasing PCO2 increases the SSC risk, as inferred from the electrochemical study. Unfortunately, experimental artefacts linked with autoclave test conditions did not lead to clear conclusions on this point. However, this work shows that conventional tools might lead to underestimate SSC risks at high PCO2 and low PH2S. In these specific conditions, the new results presented in this report may contribute to improve materials selection criteria for high pressure and high temperature conditions

碩士
國立成功大學
工程科學系碩博士班
96
The concept of Brownian motors may use for to explain how molecular motors take mechanochemistry coupling of the motion to achieve the directive movement when it subjects to thermal fluctuation. The conformation of molecular motors is changed by the mechanochemistry coupling of the motion with hydrolysis of ATP and the binding of ATP. It means that molecular motors generate the change of potential energy and mechanical motion. In order to Brownian motors produce motion in one direction, and increasing the average velocity effectively. This paper uses the coupling model of Rocking ratchet and Diffusion ratchet to simulate the movement situation of Brownian motors. The Fokker-Planck equation is the governing equation in this paper, it can be used to solve the probability and the probability flux in different temperature conditions and it also used to calculate working model with potential energy switches between an on and an off state by Robust numerical algorithm in the reference[11]. In the algorithm a continuous Markov process is discretized as a jump process and the jump rates are derived from local solution of the continuous systems which contain the property of detailed balance. This paper used MATLAB 7.0 to calculate the equations and the numerical algorithm to analyze what kinds of different temperature conditions influences the average velocities of Brownian motors to achieve the maximum value, and to discuss the average velocities, the effective diffusion coefficients of Brownian motors with increasing the amplitude of potential energy under external force.

碩士
高苑科技大學
化工與生化工程研究所
98
Nano-structured materials have been synthesized by a self-heating detonation process using explosives (TNT, HMX) for providing the need of high temperatures and high shock waves in the presence of metallic-containing catalysts. These results show that catalyzed-blast process is possible for a cheaper process and it is aiso an alternative compared to these high energy and hardware intensive processes to assemble nano-sized carbon nanomaterials. The products of carbon nanoparticles, nanotubes and nanocaosules are characterized by XRD, TEM, HR-TEM, FEG-TEM, EDS and Raman techniques. This research presents the use of this special system to study the catalytic detonation process and the effect of reaction conditions on conditions and the catalytic convevsion of energetic explosives into nano materials. The experimental results show that TNT explosive over the CeO2 and TiO2 metal compounds can be converted into metallic nanoparticles due to the fast decomposition with a reduction reaction after detonation which plays an important role for the growth of different size of carbon nanocapsules. The morphology of carbon nanostructures varied with the reaction conditions such as catalyst type, explosive structure, recipes of reactant composition with the use of different carbon cource. The results carried out using an HMX explosive show no tubular structures but with a lot of disordered amorphous carbon with only little spherical carbon nanoparticles. In the case of Ce-catalyzed detonation, clusters of carbon capsules with some nanocarbon tubes. For Ti-catalyzed system it is interesting that such a detonation process can produce it can be used to feasible operation to synthesis hollow carbon nanocapsules. In this research, a laboratory self-heating process has been successfully designed and a more effective synthesis of carbon nano-materials using TNT and HMX energetic materials in relation to the catalysis-assisted detonation. This approach involving bottom-up nanotechnology is universal and low-cost, and especially it has the potential ability to convert waste energetic explosives to form highly valuable materials, as well as providing the suitable alternatives to reuse the energetic explosive further.