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Liu, Jing. "High temperature and high pressure corrosion of titanium in hydrometallurgical applications." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/52353.
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The corrosion characteristics of titanium (ASTM Grade 2) in copper pressure leaching environments are determined from room temperature and pressure up to high temperatures and pressures (230 °C, 430 psi). Anodic oxidation and controlled chemical oxidation methods are used to improve the corrosion resistance of Ti. Electrochemical and mass loss measurements are performed to evaluate the corrosion resistance of pre-oxidized titanium, compared to that of titanium with no prior oxidation, to generate a best practices guide for the hydrometallurgical industry. The results at low temperature showed that H₂SO₄ solution is very corrosive for Ti with a freshly polished surface. The corrosion rates (CRs) of Ti are obtained using mass loss and electrochemical measurements in H₂SO₄ with Cl-, Cu²⁺ and Fe³⁺ additions up to 175 °C. It is found that the CRs of Ti are unaffected by the presence of Cl− ions in H₂SO₄ solutions. CRs obtained from mass loss and electrochemical measurements confirm that Cu²⁺ and Fe³⁺ ions are good corrosion inhibitors for Ti. Iso-corrosion diagrams, with 0.1, 0.5 and 1 mm yr−1 lines for Ti in 3-50 wt.% H₂SO₄ solutions with Cu²⁺ and Fe³⁺ additions from room temperature to 175 °C are constructed from immersion test data. The effects of temperature (100-230 °C) and SO₄²− concentration (0-0.5 mol L−¹) on the pitting corrosion of Ti are studied in neutral Cl− containing solutions using cyclic potentiodynamic polarization and linear-sweep thermammetry measurements. A metastable pitting temperature threshold (MPTT) is defined for Ti as a function of sulfate to chloride mole ratio using linear-sweep thermammetry measurements.
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Anodic oxide films (AOFs) are potentiostatically formed on Ti in 0.5 M H₂SO₄ solutions at various anodizing voltages (up to 80 V) at 25 °C. A new method is developed to fabricate chemically oxidized films (COFs) with high corrosion resistance by controlled chemical oxidation with H₂O₂ solutions at 90 °C. The corrosion behavior of the as grown AOFs and COFs is investigated in copper sulfide leaching solutions. It is confirmed that chemical oxidation with 2 M H₂O₂/0.1 M HCl solution leads to the best improvement of the corrosion resistance of Ti.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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Leonard, Fabien. "Study of stress corrosion cracking of alloy 600 in high temperature high pressure water." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/study-of-stress-corrosion-cracking-of-alloy-600-in-high-temperature-high-pressure-water(73edf35d-2bf4-42be-9816-b0746620dcf5).html.
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Stress corrosion cracking (SCC) of alloy 600 is regarded as one of the most important challenges to nuclear power plant operation worldwide. This study investigates two heats of alloy 600 (forged control rod drive mechanismnozzle and rolled divider plate) in order to obtain a better understanding of the effects of the material parameter on the SCC phenomenon. The experimental approach was designed to determine the effect of the manufacturing process (forged vs. rolled), the cold-work (as-received vs. cold-worked) and the strain path (monotonic vs. complex) on SCC of alloy 600. Specimens with different strain paths have been produced from two materials representative of plant components and tested in high temperature (360°C) high pressure primary water environment. The manufacturing process has been proven to have a great effect on the stress corrosion cracking behaviour of alloy 600. Indeed, the SCC susceptibility assessment has demonstrated that the rolled materialis resistant to SCC even after cold work, whereas the forged material is susceptible in the as-received state. Microstructural characterisations have been undertaken to explain these differences in SCC behaviour. The carbide distribution is the main microstructural parameter influencing SCC but the misorientation, in synergy with the carbide distribution, has been proven to give a better representation of the materials SCC susceptibilities.
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Ubah, Chinedu Gideon. "Design of high temperature and pressure electrochemical cell and corrosion chemistry of alloy 625 in high temperature and high pressure aqueous media using a two-electrode electrochemical method." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/28201.
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As aqueous processing moves to higher temperatures and pressures to take advantage of
increased kinetics, there is a need to develop and test appropriate reactor materials to ensure that
corrosion is minimized. Corrosion testing often requires an electrochemical approach for a
comprehensive understanding of the range of behaviors exhibited from a corroding metal or
alloy in different environments.
Prior art of designs for electrodes, associated pressure vessels and sealing technology is
presented. The development of an apparatus and methods for high temperature and high
pressure electrochemical corrosion testing are discussed. The final flow-through electrochemical
cell design, the Flow-Through External Pressure-Balanced Reference Electrode (FTEPBRE)
design, working/counter electrode and other components, which were developed for
temperatures and pressures in excess of 500ºC and 5000 PSI is presented.
A two-electrode electrochemical testing method is presented, using Stainless Steel (SS 316) as
both Quasi Reference Electrode (QRE) and Counter Electrode (CE), and Alloy 625 (Ni-062.8%,
Cr-21.8%, Mo-7.35, Fe-3.97%, Nb-2.7%) as the Working Electrode (WE). The effects of
pressure, and its combination with temperature on OCP and corrosion rate of alloy 625 (WE) in
both naturally aerated and de-oxygenated environments in 0.1 M sodium sulphate (Na₂SO₄)
solution with a flow rate of 7 mL/min were investigated and discussed. The effect of pressure
represented as a change in activation volume and reaction volume for the homogenous and
heterogeneous phases is also presented.
The corrosion rate was observed to increase with both temperature and pressure: higher for
naturally aerated conditions than the corresponding de-aerated ones. Results also show that the
instability of the QRE affected the result and direction of the OCP tests. A reduction in the
corrosion current was observed above 207 bar (3000 PSI) in the polarization tests and was
attributed to the increasing stability of the passive film formed on the surface of the alloys.
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Asselin, Edouart. "High temperature and high pressure corrosion of Ni-based alloys and stainless steels in ammoniacal sulphate solution." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/30709.
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The corrosion characteristics of Alloy 625 (UNS 00625, Ni - 22 Cr - 10 Mo) in
oxygenated ammoniacal sulphate environments are determined at room temperature and
pressure and up to high temperatures and pressures (673 K, 250 bar) commensurate with
the process of supercritical water oxidation (SCWO). Electrochemical methods such as
linear polarization, potentiodynamic polarization and impedance spectroscopy are used.
It is found that the electrochemical and morphological response is dictated by the
alloying element Cr and the formation of a Cr(III) oxide. Mo and, to a lesser extent Ni,
are found to dissolve readily. Thermodynamic analysis of the Ni-NH₃-H₂O system,
including new Pourbaix diagrams at temperatures as high as 653 K , has shown that Ni -
ammine formation is possible at moderate temperatures but that the stability of these
complexes decreases substantially with temperature. According to one of the models
investigated, which is based on the only available high temperature equilibrium constant
data, Ni-ammines become unstable above approximately 473 K .
Impedance spectroscopy has shown that transpassive dissolution of the alloy's ptype,
cation conducting, Cr(III) oxide occurs at temperatures as low as 373 K and total
pressure (oxygen saturated) as low as 40 bar. As temperature and pressure are increased
the corrosion process is increasingly diffusion controlled. Transpassive dissolution
results in the thinning and eventual total removal of the alloy's protective semiconductor
barrier layer. Cation ejection from the barrier layer into the solution and porous outer
layer phase results in precipitation of a Cr(III) scale (oxide or hydroxyl-oxide) at the
alloy surface which acts as a diffusion barrier. It is hypothesized that the outer layer is
either physically removed at supercritical conditions due to rapid dissolution and grain boundary attack of the alloy or chemically removed by solution acidification due to the
formation of sulphuric acid at high density supercritical conditions.
Alloys 625, 316 L, Ni - 20 Cr and pure Nb are tested at SCWO conditions and it
is found that the corrosion resistance increases with Cr content and Nb is found to
perform well in sulphate containing SCWO solutions at oxygen concentrations up to 4 m.
It is also confirmed in this work that maximum material loss occurs in the high-density
supercritical region of the reactor.
New Pourbaix diagrams for Nb at elevated temperatures (348 and 368 K) are
calculated and compared to electrochemical and weight loss measurements performed in
concentrated acids. Through electrochemical experiments in concentrated sulphuric and
hydrochloric acids, Nb is found to be an ideal candidate for the high-density supercritical
sections of SCWO reactors.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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Jones, Franziska Anna. "The Effect of a High-Temperature High-Pressure Nitrogen Environment with Carbonaceous Impurities on the Performance of Three Austenitic Alloys." Thesis, University of Canterbury. Mechanical Engineering, 2007. http://hdl.handle.net/10092/3268.
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WhisperGenTM heater head components are currently machined from the austenitic stainless steel Sandvik 253MA. The inner surface of the heater heads is subjected to the working gas of the engine, which is a high-pressure, high-temperature nitrogen-based environment with carbonaceous impurities. As a result of this exposure, a scale forms during operation and eventually spalls. This spalled scale causes abrasive damage to piston seals and guides, which leads to pressure loss and eventual failure of the engine. The aim of the present work was to compare the performance of the austenitic alloy 253MA with two alternative alloys, Incoloy 800H and AISI 310, thereby enabling a material recommendation. A literature review provided information about many general aspects of high temperature corrosion in similar alloys. However, little was found about the application of these alloys in environments similar to those experienced by a WhisperGenTM heater head. Therefore, laboratory experiments were conducted to indicate the relative performance characteristics of the three potential alloys (253MA, Incoloy 800H and AISI 310). To overcome the difficulties with testing at high temperatures and pressures, Thermo-Calc™ was used to calculate gas mixtures at 1 bar that approximated the chemical potentials of carbon and nitrogen in the working gas at 24 bar. Comparisons of the different materials were made via weight loss/gain measurements and metallographic analysis, which included optical microscopy, scanning electron microscopy, X-ray mapping and electron back scatter diffraction (EBSD). The laboratory test sample results were also compared with results from heater heads of the same materials that were run in an actual WhisperGenTM engine. The experimental results taken in total indicate that 253MA is the least suitable alloy for the heater head application because it exhibited poor spalling performance, internal oxidation and formation of a large amount of Cr23C6. AISI 310 was shown in all cases to develop the detrimental sigma phase, although this alloy was the least susceptible to internal oxidation. Incoloy 800H was the most resistant alloy to all forms of degradation and is thus recommended for the heater head application.
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Lasebikan, B. A. "Mechanical behaviour and stress corrosion cracking of super duplex stainless steel pipes in high pressure and high temperature environment." Thesis, University of Aberdeen, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540314.
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The oil and gas industry is constantly looking at ways to keep costs down in high temperature and high pressure (HPHT) well completions. The use of duplex or super duplex stainless steel (DSS or SDSS) for production tubing rather than high alloy (austenitics or nickel based) steels is one way to achieve this. An effective use of DSS or SDSS requires an understanding of the effects of environmental and metallurgical variables on the general and localised corrosion behaviour and resistance to environment assisted cracking (EAC) in HPHT well conditions. This research investigates the behaviour of small scale SDSS pipes subject to combined loads in a chloride and sulphide environment which are commonly found in the non-production annulus of oil and gas well completions. The effects of H2S (which can sometimes leak from the production fluid) on the chloride-based fluid and ammonium bisulphite in the non-production environment is examined. This is used to provide a realistic assessment of the type of fluid that SDSS production tubing may be exposed to in service. Experimental results are presented for the failure envelope under combined internal pressure and axial tension, and mechanical properties of SDSS pipe over a range of temperatures. A standalone autoclave was designed and commissioned to study the initiation of EAC in SDSS pipes in several aqueous solutions under a range of loading conditions: internal pressure, axial load, and a combination of internal pressure and axial load. The work presented in this thesis shows that corrosion tests can be carried out using small scale pipes for better understanding of the effects of stress state on corrosion behaviour. In particular, the safe working envelope of SDSS in terms of load combination, chloride-sulphide environment and temperature is determined in this thesis. This would help the end user understand and gain better in-service performance of SDSS in oil and gas HPHT environment.
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Krishnamoorthy, Vijay. "Effect of gas density on corrosion in horizontal multiphase slug flow at high temperatures and pressures." Ohio : Ohio University, 1997. http://www.ohiolink.edu/etd/view.cgi?ohiou1177096097.
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Parakala, Shilpha R. "EIS Investigation of Carbon Dioxide and Hydrogen Sulfide Corrosion Under Film Forming Conditions." Ohio University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1125871582.
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SALA, BEATRICE. "Contribution a l'etude de la corrosion du titane, de ses alliages et de certains aciers inoxydables en milieu aqueux, a haute temperature et sous pression." Orléans, 1987. http://www.theses.fr/1987ORLE2048.
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Application de l'electrochimie a haute temperature et sous pression illustree par trois cas de corrosion: 1) corrosion du titane et de ses alliages en milieu sulfurique 2) corrosion d'un acier a 13% de chrome en milieu carbonique; 3) corrosion d'aciers austeno-ferritique en milikeu carbonique contenant de l'hydrogene sulfure. Identification de differents facteurs permettant l'amelioration de la resistance a la corrosion de ces differents materiaux
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Plennevaux, Cécile. "Etude des risques de corrosion et de rupture différée des aciers en présence d'H2S dans les conditions d'exploration de pétrole et de gaz à haute pression et haute température." Thesis, Lyon, INSA, 2012. http://www.theses.fr/2012ISAL0101.
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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/HTThe 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
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Beloucif, Bonnet Luisa. "Comportement à températures élevées du cuivre et de l'argent en présence de chlore gazeux sec et de mélanges chlore-vapeur d'eau." Paris 6, 1986. http://www.theses.fr/1986PA066497.
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Etude de la chloruration de l'argent et du cuivre dans une atmosphère statique de chlorure gazeux dans l'intervalle de température 25-900c. Influence de la température et de la pression de chlore sur la corrosion. Démonstration de l'existence de plusieurs domaines régis par des lois cinétiques différentes et d'un domaine d'immunité et de passivité. Influence du taux d'humidité relative dans le cas de la corrosion en présence du mélange chlore, air, vapeur d'eau.
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Giordano, Valentina. "High-pressure high-temperature phases of carbon dioxide." Paris 6, 2006. http://www.theses.fr/2006PA066529.
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Norrby, Niklas. "High pressure and high temperature behavior of TiAlN." Licentiate thesis, Linköpings universitet, Nanostrukturerade material, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-78830.
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This licentiate thesis mainly reports about the behavior of arc evaporated TiAlN at high pressures and high temperatures. The extreme conditions have been obtained in metal cutting, multi anvil presses or diamond anvil cells. Several characterization techniques have been used, including x-ray diffraction and transmission electron microscopy. Results obtained during metal cutting show that the coatings are subjected to a peak normal stress in the GPa region and temperatures around 900 °C. The samples after metal cutting are shown to have a stronger tendency towards the favorable spinodal decomposition compared to heat treatments at comparable temperatures. We have also shown an increased anisotropy of the spinodally decomposed domains which scales with Al composition and results in different microstructure evolutions. Furthermore, multi anvil press and diamond anvil cell at even higher pressures and temperatures (up to 23 GPa and 2200 °C) also show that the unwanted transformation of cubic AlN into hexagonal AlN is suppressed with an increased pressure and/or temperature.
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Xu, Juncheng. "High Temperature High Bandwidth Fiber Optic Pressure Sensors." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/25988.
Full textAbstract:
Pressure measurements are required in various industrial applications, including extremely harsh environments such as turbine engines, power plants and material-processing systems. Conventional sensors are often difficult to apply due to the high temperatures, highly corrosive agents or electromagnetic interference (EMI) noise that may be present in those environments. Fiber optic pressure sensors have been developed for years and proved themselves successfully in such harsh environments. Especially, diaphragm based fiber optic pressure sensors have been shown to possess advantages of high sensitivity, wide bandwidth, high operation temperature, immunity to EMI, lightweight and long life.
Static and dynamic pressure measurements at various locations of a gas turbine engine are highly desirable to improve its operation and reliability. However, the operating environment, in which temperatures may exceed 600 °C and pressures may reach 100 psi (690 kPa) with about 1 psi (6.9kPa) variation, is a great challenge to currently available sensors. To meet these requirements, a novel type of fiber optic engine pressure sensor has been developed. This pressure sensor functions as a diaphragm based extrinsic Fabry-Pérot interferometric sensor. One of the unique features of this sensor is the all silica structure, allowing a much higher operating temperature to be achieved with an extremely low temperature dependence. In addition, the flexible nature of the sensor design such as wide sensitivity selection, and passive or adaptive temperature compensation, makes the sensor suitable for a variety of applications
An automatically controlled CO2 laser-based sensor fabrication system was developed and implemented. Several novel bonding methods were proposed and investigated to improve the sensor mechanical ruggedness and reduce its temperature dependence.
An engine sensor testing system was designed and instrumented. The system generates known static and dynamic pressures in a temperature-controlled environment, which was used to calibrate the sensor.
Several sensor signal demodulation schemes were used for different testing purposes including a white-light interferometry system, a tunable laser based component test system (CTS), and a self-calibrated interferometric-intensity based (SCIIB) system. All of these sensor systems are immune to light source power fluctuations, which offer high reliability and stability.
The fiber optic pressure sensor was tested in a F-109 turbofan engine. The testing results prove the sensor performance and the packaging ruggedization. Preliminary laboratory and field test results have shown great potential to meet not only the needs for reliable and precise pressure measurement of turbine engines but also for any other pressure measurements especially requiring high bandwidth and high temperature capability.Ph. D.
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Vanpeteghem, Carine B. "High-pressure high-temperature structural studies of binary semiconductors." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/11496.
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The last decade has seen a tremendous improvement in high-pressure diffraction techniques. Among other things, this has led to a completely new understanding of the structural systematics of the group IV, III-V and II-VI semiconductors. Many phases have been shown to have more complex, lower-symmetry, high-pressure structures than previously thought. One of the most surprising discoveries has been the non-existence of the diatomic b-tin structure, long believed to be one of the principal high-pressure phases of the III-V and II-VI systems. However, most of the work to date has been performed at room temperature and in fact, very little is yet known about the high-pressure phases of these systems above room temperature. The work presented in this thesis centres on the use of high temperature under pressure to investigate further the absence of the diatomic, site-ordered, b-tin or b-tin-like phases have been found but appear to be site-disordered. Additionally, the P-T phase diagrams of these systems are explored above room temperature. This work has required the development the existing high-pressure facilities on the SRS synchrotron source of Daresbury Laboratory to allow routine high-pressure high-temperature (hp/ht) experiments. These technical developments are described. High-temperature studies of GaSb under pressure reveal a new, previously unknown phase. A detailed study of the structural ordering in the hp/ht phases of GaSb is performed by combining two different experimental techniques. It is shown, by x-ray powder-diffraction, that all the hp and hp/ht phases of GaSb are site-disordered over about two unit cells or less. A complementary high-pressure EXAFS study demonstrates the absence of complete order over nearest-neighbour distances.
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Sphicas, Panagiotis. "High pressure and high temperature measurements on diesel sprays." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/18063.
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Environmental, financial and legal reasons demand the development of cleaner diesel engines. Atomization, evaporation and mixing phenomena observed during injection of Diesel fuel affect the produced emissions. To study these phenomena, under engine-like conditions (50bar, 1000K), a chemically preheated constant volume chamber was built. A system of sensors, driven in real-time by a FPGA (Field Programmable Gate Array) and controlled by a Real Time Controller, was built to monitor and control the operations. A modern common rail fuel injection system (Bosch CP3) was driven by a purpose-modified Hartridge 1100 test stand and controlled by the FPGA (Field Programmable Gate Array). Chemical heating is a technique used widely to simulate the ambient conditions of an industrial combustor in a constant volume vessel. A flammable mixture is ignited in an optically accessible vessel, attempting to produce a post-combustion high pressure and high temperature environment. The flammable mixture usually consists of Hydrogen and a Hydrocarbon. Hydrogen is added, to assist with the ignitability of the pre-ignition mixture and to simulate the water present in industrial combustors as a result of exhaust gas recirculation. To this direction, the mole ratio of Hydrogen to Hydrocarbon and the mixture molecular weight were introduced as independent variables for the first time in the literature of constant volume combustion. An initial computer model, assuming perfect combustion, was used for calculation of adiabatic temperature and pressure. A second computer model investigated the effect of chemical dissociation by solving for the minimization of Gibbs energy and was compared to the former one. To verify the calculations, a dual pressure transducer technique and a High-Speed Schlieren technique were used to validate the combustion conditions inside the vessel To further understand the atomization, evaporation and mixing phenomena in sprays, a Diesel spray was visualized using back-illumination and Schlieren High-Speed cinematography at high pressure and room temperature. To understand the evaporation behaviour of a spray and map the vapour fuel distribution, a tracer Laser Induced Fluorescence was applied on a Dodecane/Methyl-naphthalene spray under evaporating and non-evaporating conditions. To compare the experimental findings to the theoretical models in literature, the evaporation of a single droplet in post-combustion vessel gases was simulated using a purpose-programmed FORTRAN code. A supercritical phase change was suggested to explain the sudden phase change and large differences between the theoretical model and the experimental results.
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Munro, Keith Alistair. "High-pressure high-temperature behaviour of the lanthanide metals." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28881.
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The high-pressure behaviour of the lanthanide series of metals has been the subject of study since the work of Percy Bridgman in the 1940s. Differences in said behaviour between the different lanthanide metals are attributed to the increasing occupation of the 4f electron shell as Z increases. Upon compression, or as Z decreases, the trivalent lanthanides (La to Lu, excluding Eu and Yb) undergo a common phase transformation sequence through various close packed structures: hcp → Sm-type (the structure adopted by samarium at ambient conditions) → dhcp → fcc → distorted fcc (d-fcc). Upon further compression, the lanthanide metals experience a first order transition to a "volume collapsed" phase. Many studies have focused on the low-Z members of the series, since the various phase transitions occur at much lower pressure where it is comparatively easy to collect high quality data. By contrast, the other members of the series have received comparability little attention, and there are even fewer reports of the structural behaviour of the lanthanide metals at high pressure and high temperature. This thesis contains the results of angle-dispersive x-ray powder diffraction experiments at high pressure and high temperature of the various members of the lanthanide metals. Ce has been the subject of many previous studies, but a systematic x-ray diffraction study of the fcc/d-fcc phase boundary has never been attempted. Furthermore, the location in P-T space of the high temperature fcc/bct/d-fcc triple point has only been inferred, due to the lack of data on the fcc/bct phase boundary at high temperature. The high-pressure high-temperature phase diagram of Ce is presented and discussed. La is unique amongst the lanthanide metals due to its empty 4f shell at ambient conditions. Despite this, La undergoes the common lanthanide transformation sequence up to the d-fcc phase, after which it undergoes a re-entrant transition back to the fcc phase at 60 GPa. The diffraction peaks of d-fcc La are shown in this thesis to undergo changes in intensity upon compression, indicating a transformation to the oI 16 structure found in Pr. La is one of the few elements whose behaviour has been unknown above 100 GPa, and results of La's structural behaviour upon compression to 280 GPa are presented and discussed. At 76 GPa, La begins a transition from the fcc phase to a new phase with the bct structure. Finally, the d-fcc→fcc re-entrant phase transition has been determined at various temperatures, and the d-fcc stability region has been mapped out. Finally, x-ray diffraction experiments were performed on Gd up to 100 GPa and ~700 K, to determine the structure of the d-fcc phase and the "volume collapsed" phase. While d-fcc Gd does not undergo pressure-induced changes similar to its low Z brethren, the d-fcc Gd remains stable up to 41 GPa at 700 K, putting a constraint on the d-fcc stability region. The data collected on Gd's "volume collapsed" phase cannot be fitted to the currently accepted mC4 structure. This has implications for our understanding of the lanthanide series as a whole, since most of of the heavier members, and some of the lighter lanthanides, are reported to adopt the mC4 structure.
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Almström, Linda, and Camilla Söderström. "Alternative materials for high-temperature and high-pressure valves." Thesis, Karlstads universitet, Fakulteten för teknik- och naturvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-7393.
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AB SOMAS Ventiler manufactures valves for different applications. A valve of type DN VSSL 400, PN 100, used in high-temperature and high-pressure applications was investigated in this thesis. This type of valve is coated with high cobalt alloys to achieve the tribological properties needed for this severe condition. However there is a request from AB Somas Ventiler to find another solution. This request is based on the fact that demands on higher temperatures, from customers, yields higher requirements on the material. It is also a price issue since cobalt is quite expensive. Materials investigated were high-nitrogen steel, Vanax 75, nickel-based superalloy Inconel 718 and hardened steels, EN 1.4903 and EN 1.4923 presently used as base material in the valve. Calculation of contact pressure that arises when the valve is closed was first approached by using finite element method (FEM). Several models were constructed to show the behavior of the valve during closing in terms of deformation. Hot wear tests, in which a specimen was pressed against a rotating cylinder, were performed to be able to compare the materials to the solution of today and among each other. Data extracted from the tests were compiled in the form of coefficients of friction. Profilometer examinations were used to reveal the volumes of worn and adhered material and together with scanning electron microscopy (SEM) the wear situation for each material couple could be assessed. Wear mechanisms detected in SEM were adhesive and abrasive and the results clearly showed that the steels were not a good solution because of severe adhesive wear due to the similarity of mating materials creating a more efficient bonding between the asperities. Vanax 75 showed much better performance but there was still an obvious difference between the steels and the superalloy in terms of both coefficient of friction and amount of wear. On this basis, Inconel 718 was selected as the most suitable material to replace the high cobalt alloys used in the valves today.AB Somas ventiler är ett företag som tillverkar ventiler för ett brett spann av applikationer. I det här examensarbetet har undersökningar genomförts på en ventil av modell DN VSSL 400, PN 100, som normalt används i applikationer för höga tryck och höga temperaturer. Ventilen beläggs i dagsläget med höghaltiga koboltlegeringar för att uppnå de tribologiska egenskaper som krävs i de påfrestande arbetsförhållanden som råder. AB Somas Ventiler har dock framfört en förfrågan om att hitta en alternativ lösning, en förfrågan som grundar sig i att kundernas ständiga önskemål på att ventilerna ska klara högre arbetstemperaturer också medför högre krav på ventilmaterialen. Det är även en prisfråga, då kobolt är en dyr legering att använda sig av. De material som inkluderades i undersökningen var det kvävelegerade stålet Vanax 75, nickelbaserade superlegeringen Inconel 718 samt de två stålen EN 1.4903 och EN 1.4923 i härdat tillstånd. De två sistnämnda används idag som basmaterial i ventilen. Genom att använda den finita element metoden (FEM) kunde en första beräkning göras av det kontakttryck som uppstår då ventilen stängs. Flera modeller konstruerades för att simulera ventilens deformation vid stängning. Där efter utfördes nötningstester i hög temperatur på de alternativa materialen, genom att låta en provbit pressas mot en roterande cylinder, för att sedan kunna göra en jämförelse mellan materialen och även med den nuvarande lösningen. Från nötningstesterna erhölls data som kunde användas för att ta fram friktionskoefficienter för de olika materialparen. Med hjälp av undersökningar med profilometer och svepelektronmikroskop (SEM) kunde värden på nötta och vidhäfta volymer erhållas tillsammans med information om nötningssituationer för ytorna mellan de olika materialparen. De nötningsmekanismer som påvisades med hjälp av SEM-undersökningen var adhesiv och abrasiv nötning, och resultaten visade tydligt att nötningen av stålen var omfattande, på grund av att lika material i kontakt med varandra skapar starkare band mellan ytorna, och att de därför inte var en intressant lösning. Det kvävelegerade Vanax 75 uppförde sig visserligen bättre men en tydlig skillnad mot superlegeringarna kunde dock fortfarande konstateras, sett till både friktionskoefficient och mängden slitage. Baserat på dessa resultat valdes Inconel 718 som det bäst lämpade materialet att ersätta de höghaltiga koboltlegeringarna som idag används i ventilen.
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Rowane, Aaron J. "High-Temperature, High-Pressure Viscosities and Densities of Toluene." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4188.
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High-temperature, high-pressure (HTHP) conditions are exemplified in ultra-deep petroleum reservoirs and can be exhibited within diesel engines. Accurate pure component hydrocarbon data is essential in understanding the overall behavior of petroleum and diesel fuel at these conditions. The present study focuses on the HTHP properties of toluene since this hydrocarbon is frequently used to increase the octane rating of gasoline and toluene occurs naturally in crude oil. In this thesis experimental densities and viscosity are presented to 535 K and 300 MPa extending the database of toluene viscosity data to higher temperature than previous studies. The data is correlated to a Tait-like equation and a Padѐ approximate in conjunction with a single mapping of the isotherms. Free-volume theory and a superposition of the viscosity in relation to the Leonnard-Jones repulsive force are both used to model the toluene viscosity data. It was found that the data are in good agreement with the available literature data.
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Bloom, Scott Harris. "Superconducting and normal compounds : some high field/high pressure effects /." Thesis, Connect to Dissertations & Theses @ Tufts University, 1989.
Find full textAbstract:
Thesis (Ph.D.)--Tufts University, 1989.Submitted to the Dept. of Physics. Includes bibliographical references (leaves 192-204). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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Larsen, Håvard. "Behaviour of polymer muds under high pressure – high temperature conditions." Thesis, Norwegian University of Science and Technology, Department of Petroleum Engineering and Applied Geophysics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1534.
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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.
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Shiping, Zhu. "Rheology of polymer solutions at high temperature and high pressure." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267965.
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Soignard, Emmanuel. "High pressure - high temperature synthesis and studies of nitride materials." Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407347.
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Kolbus, Lindsay Marie. "Structural variations of feldspars at high pressure and high temperature." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/77063.
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Feldspar minerals are framework aluminosilicates that comprise approximately 60 percent of the Earth's crust. The elastic and thermodynamic properties of this important mineral group are needed for the interpretation of seismic wave velocities, for understanding cation partioning patterns and for the determination of phase boundaries and reactions involving feldspars in the Earth's crust. Until recently, no systematic approach has been applied to describe the structural behavior of feldspars as a function of pressure, temperature and composition. In this thesis, high-pressure and high-temperature X-ray diffraction data were collected for feldspars over a range of compositions which has led to the development a structural model that allows one to predict the structural evolution of feldspars at depth in the Earth's crust. Specifically, the equations of state have been determined for two plagioclase feldspars (An20 and An78) with different states of Al/Si ordering using single-crystal X-ray diffraction. This study has shown that the introduction of Al,Si disorder into plagioclase structures at constant composition softens the structure by 4(1)% for An0, 2.5(9)% for An20 and is essentially zero for An78 compositions. The effect of pressure on the structure of an ordered An20 was also determined up to 9.15 GPa using single-crystal X-ray diffraction and it was found that the dominant compression mechanism involves tilting of the AlO4 and SiO4 tetrahedra. Similarly, high-temperature single-crystal X-ray diffraction data collected from an ordered An26 plagioclase and powder X-ray diffraction collected on a suite of Na-rich plagioclases that were refined using the Rietveld method indicate that the major structural response to increased temperature involves tilting of the tetrahedra. Building on ideas originally proposed by Dr. Helen Megaw, the changes in the conformation of the tetrahedral framework of feldspars can be described in terms of four distinct tilt systems of rigid tetrahedra. This model demonstrates that the fundamental reason for the observed anisotropy and volume change of feldspars lies in the topology of the tetrahedral framework with the greatest contribution attributed to tilt systems 2 and 3.Ph. D.
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Sandford, Richard J. "Lateral buckling of high pressure/high temperature on-bottom pipelines." Thesis, University of Oxford, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.645946.
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On-bottom (or unburied) pipelines) which carry hydrocarbons across the seabed) are typically subjected to compressive axial loading arising from restrained thermal- and pressure-induced expansion. This compressive loading usually causes a nominally straight pipeline to buckle into a mode lying predominantly in the plane of the seabed; this response is widely termed lateral buckling. Predicting the response of an on-bottom pipeline to thermal and pressure-induced axial compressive loading is the primary focus of this thesis. In assessing whether or not the structural integrity of a pipeline is at risk during lateral buckling (and also in the post-buckling regime) finite element analyses are typically carried out. In these analyses) the pipeline is modelled as an assembly of beam elements while the connection between the pipe and the seabed is modelled using a macro-element) which defines the relationship between the loads and displacements of the pipe. In this thesis) the development) calibration and implementation of a macro-element model for use in lateral buckling design is described. The proposed macro-element model accounts for the response during lateral displacement of multiple pipe diameter amplitude (as appropriate to the movement of the crown of a buckle) as well as the reversals in the direction of lateral displacement due to intermittent shut-downs in the operation of the pipe. The model is of the hardening plasticity type and is cast in terms of vertical and horizontal force resultants. Results from numerical analyses (using both finite element limit analysis and the displacement-based incremental finite element method) are used to calibrate the model. Its performance is tested by examining the results of retrospective simulations of experimental tests. Finally) the results of field-representative structural analyses are presented) which demonstrate the suitability of the model for use in design practice.
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Zaheri, Shahram. "High temperature and high pressure cobalt cementation onto zinc dust." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/51855.
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Trace amounts of electrolyte cobalt during zinc electrowinning (EW) significantly decrease the current efficiency of the EW process by accelerating the parasitic hydrogen evolution reaction. The maximum tolerable level of cobalt in zinc EW can be as low as 0.1- 0.3 mg/L. The typical method to remove cobalt from zinc electrolyte, which is based on cementation onto zinc dust at approximately 85°C, is not an efficient process. It suffers from long retention times (2-3 hours) and high consumption of reagents; especially zinc dust.
The aim of the present research was to study cobalt cementation at high temperature and high pressure (HT/HP) to accelerate the rate of cobalt removal and reduce the consumption of the reagents (zinc dust and activators). Experimental variables included temperature (85-150°C), pressure (0-100 psig), zinc dust dosage, zinc dust particle size, and activators (copper and antimony).
Based on this research, the following results were obtained:
1. Increasing temperature had a significant effect on the rate of cobalt removal. The optimum temperature was found to be 125°C - temperature at which the target level of cobalt (0.1 mg/L) could be met in 20 min.
2. At 125°C and in the presence of 2.5 mg/L Sb and 45 mg/L Cu, 3.5 g/L zinc dust was found as the optimum zinc dust addition to lower cobalt concentration from the initial level of 15 mg/L to below 0.1 mg/L.
3. Smaller zinc particles showed better cobalt removal results, but the cement redissolution was also more severe with these particles.
4. The role of Sb in the activation system was more important than Cu. However, the best result in terms of the rate and extent of cobalt removal was achieved when both of the activators were added to the solution together.
5. As expected, increasing the overhead pressure of N₂ (tested at 85°C) did not alter the cobalt removal profile greatly. Also, the effect of increasing the partial pressure of H₂ (tested at 125°C, and above the amount generated in situ by the reaction) on cobalt removal was negligible.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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Balakrishnan, Suresh. "High temperature corrosion of certain nitrogen based ceramics." Thesis, Northumbria University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245259.
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Phongphiphat, Awassada. "High temperature corrosion in waste-to-energy plants." Thesis, University of Sheffield, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489069.
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High temperature corrosion of the heat exchanger materials is the important factor that limits the efficiency of various energy systems. The problem becomes more serious when fuels containing alkali metal, heavy metals, chlorine, and sulphur are used. In combustion systems utilizing biomass and municipal solid waste, the steam temperatures are kept lower than 450"C in order to avoid the corrosion problems. This results in low overall plant efficiencies (e.g. 25 - 30%). Therefore, methods to prevent or control high temperature corrosion in these plants must be investigated.
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Child, Daniel. "Corrosion-fatigue interactions of high-temperature nickel alloys." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/9732.
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Corrosion and fatigue aspects of high temperature turbine components made from Alloy 720Li and RR1000 have been studied with a view to understanding the potential failure mechanisms occurring in these materials. Understanding of such failure mechanisms is important in order to make safety improvements and significant cost savings by reducing engine downtime. Some exservice discs currently exhibit pit-like features at a specific location on the firtree lobes, which potentially may lead to more serious alloy fissuring. Shot peening is currently employed to improve fatigue resistance at the surface of components. This work aims to fully characterise these pits and fissure features in addition to shot peening, and the components in general, using advanced analytical techniques, in order that the failure mechanism(s) can be determined and mitigated against.
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Tveråmo, Camilla. "Pipeline Walking of High Pressure/Temperature Flowlines." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22366.
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The offshore pipeline industry are facing more complex design challenges as the oiland gas industry moves into deeper water in search for hydrocarbons. One of thesechallenges are related to high pressure/high temperature pipelines subjected tofrequent start-up and shut-downs during its? lifetime. One consequence of this kindof load cycles is that the pipeline may move cycle wise and axially towards its? coldend, which may be detrimental for the end connection design. This phenomenonis termed pipeline walking.The SAFEBUCK Joint Industry Project was initiated in 2002 to assess the challengesconnected to pipeline walking, in addition to other related issues. Throughthis project several aspects affecting the walking behaviour have been established.These factors have, in this thesis, been addressed through a sensitivity analysis,where the seabed conditions ? hereby the equivalent friction factor ? the seabedslope, the effect of a global lateral buckle and the effect of a connected SCR havebeen included.The sensitivity study was performed on a pipeline modelled in SIMLA with 900beam elements, each connected with a spring to a seabed beam element. Thisoriginal case have here been labelled the base case. Four cases were analysed, wereone factor were changed throughout each of the cases. The pipeline was subjectedto a transient temperature profile in each case, provided by IKM Ocean Design,to simulate the heat transfer in a pipeline.For the seabed conditions case, the walk per load cycle increased with increasingequivalent friction factor up to a certain point, before the walk per load cycledecreased as the equivalent friction factor continued to increase. The seabed slopecase showed that the relationship between walk per cycle and increasing angle isapproximately linear. In addition it was established that when the seabed slope issteep enough, the pipeline will walk towards its? warm end. In the global lateralbuckle case on could observe that the effective axial friction force was relievedin the buckle, and that the walk per cycle increased as the length of the buckleincreased. When a steel catenary riser tension was introduced, the axial movementof the pipeline appeared to fluctuate around the walk per cycle values for the basecase.An analytical analysis was performed, however, the accordance between the numericaland analytical results was not as good as predicted. For this reason animprovement of the analytical model is suggested for further work. An other topicwhich is relevant for further work is an extension of the seabed conditions case toinclude mobilisation length. Additional sub-cases in the steel catenary riser case, aswell as creating a new case by combining the impact from several walking inducingfactors are other possible topics.
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Abercrombie, Matthew G. "Acoustic microsensor with optical detection for high-temperature, high-pressure environments." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/19467.
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Pinto, Gilberto. "High pressure - high temperature neutral hydrolysis of amorphous poly(ethylene terephthalate)." Thesis, University of York, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310981.
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Pickrell, Gary Robert. "High temperature alkali corrosion kinetics of low expansion ceramics /." This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-163208/.
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Pickrell, Gary R. "High temperature alkali corrosion kinetics of low expansion ceramics." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/38220.
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Littleton, C. J. "Characterisation of high temperature corrosion products using Raman microscopy." Thesis, University of Newcastle upon Tyne, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378937.
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Shittu, Jibril. "Tribo-Corrosion of High Entropy Alloys." Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1752392/.
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In this dissertation, tribo-corrosion behavior of several single-phase and multi-phase high entropy alloys were investigated. Tribo-corrosion of body centered cubic MoNbTaTiZr high entropy alloy in simulated physiological environment showed very low friction coefficient (~ 0.04), low wear rate (~ 10-8 mm3/Nm), body-temperature assisted passivation, and excellent biocompatibility with respect to stem cells and bone forming osteoblast cells. Tribo-corrosion resistance was evaluated for additively manufactured face centered cubic CoCrFeMnNi high entropy alloy in simulated marine environment. The additively manufactured alloy was found to be significantly better than its as-cast counterpart which was attributed to the refined microstructure and homogeneous elemental distribution. Additively manufactured CoCrFeMnNi showed lower wear rate, regenerative passivation, less wear volume loss, and nobler corrosion potential during tribo-corrosion test compared to its as-cast equivalent. Furthermore, in the elevated temperature (100 °C) tribo-corrosion environment, AlCoCrFeNi2.1 eutectic high entropy alloy showed excellent microstructural stability and pitting resistance with an order of magnitude lower wear volume loss compared to duplex stainless steel. The knowledge gained from tribo-corrosion response and stress-corrosion susceptibility of high entropy alloys was used in the development of bio-electrochemical sensors to sense implant degradation. The results obtained herewith support the promise of high entropy alloys in outperforming currently used structural alloys in the harsh tribo-corrosion environment.
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Botteghi, Federico [Verfasser]. "Experimental Investigation of High-Pressure, High-Temperature Solid Fuel Gasification / Federico Botteghi." München : Verlag Dr. Hut, 2016. http://d-nb.info/1094117331/34.
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Wade, Jonathan. "High temperature and high pressure element partitioning between metal and silicate phases." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288307.
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Poloni, Roberta. "Heavy alkali metal-intercalated fullerenes under high pressure and high temperature conditions." Lyon 1, 2007. http://tel.archives-ouvertes.fr/docs/00/19/46/10/PDF/THESIS.pdf.
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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 calculéeIn 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
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Arvanitis, Antonios. "High Temperature High Pressure Water Gas Shift Reaction in Zeolite Membrane Reactors." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563872266361549.
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Jin, Sheng. "Silicon carbide pressure sensors for high temperature applications." Case Western Reserve University School of Graduate Studies / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1296096110.
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Lee, Kyu-Hyun. "Temperature induced pressure differentials in high-rise buildings." Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/4667.
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Jenkins, Delyth Myfanwy. "The characterisation of chemical species in high temperature lamps." Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239677.
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Sultan, Abdelrahman Saleh. "High Temperature Corrosion Of Steels Used In Petroleum Refinery Heaters." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606204/index.pdf.
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The oxidation of three different steels used in the construction of petroleum refineryheaters was investigated by using thermogravimetric analysis technique (TGA). C-5,P-11, and P-22 steel samples were tested in two different oxidizing environmentsair and CO2+N2+H2O (that simulates the combustion products of natural gas) at two different temperatures
450oC and 500oC. In air oxidation P-22 had the best oxidation resistance among the three steels at two temperatures. In CO2+N2+H2O environment,C-5 possessed better oxidation resistance than P-22 and P-11. Analyses of oxidation products by using optical microscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were carried out to correlate TGA results to oxide composition and morphology. Lower oxidation rate of P-22 in air was explained with reference to the formation of Cr-O phase. Analytical rate equations showed that all the steels obeyed parabolic rate equation during oxidation and no transition was observed
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Xie, Wie. "A Study of High Temperature Corrosion in an AFBC System." TopSCHOLAR®, 1998. http://digitalcommons.wku.edu/theses/327.
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The occurrence of furnace wall and superheater corrosion in fluidized bed combustor systems has caused some operational and economic concerns. It is generally accepted that chlorine and sulfur may play roles in this corrosion. In order to predict the performance of high chlorine or high sulfur coals in these combustion systems, it is necessary to have a better understanding of the different corrosion mechanisms in which chlorine and sulfur may be involved. It is also important to evaluate the critical point of coal chlorine content which may cause initial corrosion. The laboratory-sized atmospheric bed combustor (AFBC) at Western Kentucky University was designed to serve as a flexible research and development facility to gain operating experience, evaluate combustion performance, and estimate the effects of flue gas emissions. Fluidized bed combustion systems are particularly suited to waste fuels because of their ability to burn low grade and variable fuels as well as absorb sulfur oxides through the use of limestone. Our study was mainly designed to evaluate the role coal chloride may play in causing corrosion of boiler components Four different metal alloys [carbon steel CI020 (0.18% C and 0.05% Cr), 304 SS (18.39% Cr and 8.11% Ni), 309 SS (23.28% Cr and 13.41% Ni), and 347 SS (18.03% Cr and 9.79% Ni)] were exposed uncooled in the freeboard at the entrance to the convection pass, where the metal temperature was approximately 900 K. The carbon steel samples were essentially destroyed. However, it was expected that CI020 carbon steel samples would not withstand the high temperatures selected for the testing. A small amount of scale spallation was observed on the other three samples in both test runs. Based on the SEM-EDX mapping results, there was no localized chloride distribution observed on the surface of the coupons, neither in the scale spallation area nor on the rest of the metal part. Some trace amount of chloride was found, but evenly distributed on the surface of the coupons. There is no concentration of chloride on the spot of scale spallation. The scale spallation might be due to the effect of erosion. Further study with higher chlorine (> 0.3%) content coals for more conclusive information is needed.
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Du, Hai Liang. "Studies of high temperature corrosion of some MCrAlYX-type alloys." Thesis, University of Newcastle Upon Tyne, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.290941.
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Lamkin, Michael Alan. "The high-temperature oxidation and corrosion of a silicon nitride." Thesis, University of Leeds, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277876.
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Xiang, Shengmei. "High-Temperature Corrosion-Fatigue of Cast Alloys for Exhaust Manifolds." Licentiate thesis, KTH, Materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-235170.
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The introduction of gas-driven Otto engine and the corresponding usage of bio-fuels in heavy-duty engines will render the exhaust atmosphere more corrosive and bring a higher working temperature to exhaust manifolds. The current service material, a ferritic ductile cast iron called SiMo51, will soon meet its upper temperature limit set by the ferrite-austenite transformation at 860ºC. Three alternative materials, as well as SiMo51 serving as reference, are investigated in the present thesis emphasizing on high-temperature corrosion fatigue. The first aim of this study is to obtain material data and give a quantitative ranking of the materials’ performance. Low-cycle fatigue (LCF) tests at 800ºC in a synthetic exhaust gas (5%O2-10%CO2-5%H2O-1ppmSO2-N2 bal.) are conducted to evaluate the materials’ performance in simulated real working scenarios, where high-temperature, corrosive atmosphere and fatigue conditions during testings are similar to the conditions experienced by the exhaust manifolds. To evaluate the individual effect from high-temperature fatigue and isolate the impact from corrosion, the materials are tested under the same settings but in an argon atmosphere. To evaluate the individual effect from high-temperature corrosion and isolate the impact from mechanical deformation, oxidation tests are carried out at 800ºC in the same synthetic exhaust gas. The second aim is to identify and understand different oxidation behavior and failure mechanisms in the materials, realized by considerable characterizations of the tested specimens. From the fatigue tests, it is found that the austenitic stainless steel HK30 has the highest fatigue resistance, followed by the austenitic cast iron Ni-resist D5S, and the ferritic ductile cast irons SiMo1000 and SiMo51, a ranking valid in both atmospheres. In the exhaust atmosphere, for instance, the improvement in fatigue strength at 15,000 cycles relative to SiMo51 are 260%, 194% and 26%, respectively. Different crack initiation and propagation mechanisms are found for the various combinations of materials and atmospheres. In the exhaust atmosphere, for instance, crack initiation is assisted by oxide intrusion in SiMo51 and crack propagation is affected by crack branching in HK30, mechanisms not observed in argon. By comparing the S-N fatigue curves in the two atmospheres, the influence of oxidation on fatigue life is evaluated. The fatigue life of the cast irons are surprisingly found to be higher in the exhaust atmosphere. Several explanations are suggested for this, considering their very different oxidation behaviors. This study provides accurate test data that can be used to help industry avoid over-dimensioned design. The investigation of the failure mechanisms promotes better understanding of the correlation between microstructure and mechanical properties. Moreover, the combination of fatigue tests in argon, fatigue tests in exhaust and oxidation tests in exhaust, shows how corrosion and fatigue individually and synergistically affect the materials’ performance at high temperature.QC 20180917
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Moya, Alice. "High temperature corrosion in exhaust application for heavy-duty trucks." Thesis, KTH, Materialvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-259660.
Full textAbstract:
Increasing awareness of environmental protection has made both governments and the industry aim for lowering carbon dioxide emissions. For the transport industry this means increasing engine efficiency, replacing fossil fuels with bio-based fuels or full electrification. For heavy-duty trucks, the first two options are currently the paths taken as short and mid-term solutions. These alternatives introduce new service conditions to the engines; namely higher combustion temperature and pressure, which will impose increased thermal and mechanical loads on the engine parts. In particular, the exhaust system parts must withstand constant thermal cycles in their normal operation. In heavy-duty trucks, exhaust systems are mostly manufactured from cast iron or cast steel. The usual materials, such as cast iron SiMo51 are reaching their maximum operating temperature, therefore new materials must come forward to fulfill new challenges. These materials oxidize at high temperatures forming different types of scales, which sometimes can act as protective barriers preventing their degradation. However, thermal cycles in the engine can impose new stresses and strains in these newly formed oxide scales, sometimes leading to spallation. A continuous spallation behavior in the exhaust systems is deleterious for the system, and the debris could also affect the downstream engine parts. This investigation focuses on the study of high temperature oxidation behavior of four iron-based candidate materials. Samples of two ductile cast irons and two austenitic stainless steels were exposed to thermal cycling in a simulated exhaust gas atmosphere at 850 °C, and to isothermal experiments at 850 °C and 900 °C in a stagnant air atmosphere. Additionally, the thermodynamics and kinetics were simulated using Thermo-Calc and Dictra software, respectively. The results show that SiMo1000 grows a relatively thick iron-rich oxide layer with evidence of internal oxidation aided by the graphite shape exhibited by the alloy. The other cast iron Ni-Resist behaves better than SiMo1000, forming chromia and silica layers that prevent internal oxidation from occurring, although some spallation did occur in water containing atmospheres. 1.4832 behaved poorly compared to the other materials, entering into breakaway oxidation mode throughout all the exposures; therefore, it is not a material suited for high temperature service. HK30 was susceptible to water aided chromium evaporation but had a comparatively small mass change throughout the experiments; nonetheless, there was evidence of internal oxidation following interdendritic zones. Also casting defects were observed in these areas. Both might affect mechanical properties at high temperature.Ökad miljömedvetenhet har gjort att både industri och politiker har satt upp mål för att sänka koldioxidutsläppen. För transportbranschen innebär detta till exempel ökad motoreffektivitet, att fossila bränslen ersätts med biobaserade bränslen eller full elektrifiering. För tunga lastbilar är de två första alternativen de som är aktuella på kort och medellång sikt. Dessa alternativ innebär nya förhållanden för motorn; nämligen högre förbränningstemperatur och -tryck, vilket kommer att öka termisk och mekanisk last på motorn. Detta är särskilt tydligt för avgassystemet, eftersom det utsätts för termisk cykling vid normal drift. Avgassystemet i en tung lastbil är oftast gjort i gjutjärn och ibland i gjutstål. Gjutjärnen, t ex segjärn SiMo51, börjar nu närma sig sin maximala driftstemperatur och nya material behöver introduceras. Vid höga temperaturer oxiderar dessa metalliska material och bildar olika typer av oxidskal. Beroende på sammansättningen på oxidskalet, kan det fungera som skydd för underliggande material. Termisk cykling kan ge spänningar i oxidskiktet som i sin tur kan ge flagning av skiktet. Om flagningen fortsätter kontinuerligt, förbrukas dels material, men flagorna kan också ge skador nedströms i avgassystemet. I detta arbete undersöks fyra järnbaserade kandidatmaterial avseende högtemperaturkorrosion. Prover av två gjutjärn och två austenitiska rostfria gjutstål exponerades dels isotermt vid 850 °C och 900 °C i stillastående luft, dels i experiment med termisk cykling i en simulerad flödande avgasatmosfär och varm temperatur 850 °C. Dessutom användes termodynamisk programvara (Thermo-Calc/DICTRA) för att simulera termodynamik och kinetik. Resultaten visar att SiMo1000 bildar ett relativt tjockt, järnrikt oxidskikt med viss inre oxidation som verkar följa grafitstråk i materialet. Det andra gjutjärnet, segjärnet Ni-Resist, beter sig bättre än SiMo1000 och bildar krom och kiseldioxidlager som förhindrar intern oxidation. Viss flagning observerades i den cykliska exponeringen. 1.4832 visade ett sämre beteende än de andra materialen och bildade inget skyddande oxidskikt, utan visade kontinuerlig massförlust i samtliga exponeringar. Detta material är därför inte lämpligt för de undersökta högtemperaturmiljöerna. HK30 visade låg massförlust i samtliga undersökningar med oxidation i interdendritiska områden. Även gjutfel som t ex porer observerades idessa områden. Båda kan påverka materialets mekaniska egenskaper vid dessa temperaturer.
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Evin, Harold. "Low Cr alloys with an improved high temperature corrosion resistance." Thesis, Dijon, 2010. http://www.theses.fr/2010DIJOS082/document.
Full textAbstract:
Les aciers ferritiques à faible teneur en chrome tel que le T/P91 sont largement utilisés dans les centrales de productions d’électricité pour leurs bonnes propriétés mécaniques et leur faible coefficient d’expansion thermique. Cependant, la demande croissante en énergie alliée à la nécessité de réduire les émissions de gaz à effet de serre, conduisent à envisager l’augmentation des conditions d’utilisation (température et pression) de ces matériaux. Des études ont montré qu’en modifiant la température de fonctionnement et la pression de vapeur d’eau de 538°C/18.5 MPa à 650°C/30 MPa, le rendement des centrales thermiques progressait d’environ 8%. Se pose alors la question de la tenue à la corrosion à haute température des aciers à 9% de chrome. Au cours de ces travaux, le comportement d’un acier ferritique/ martensitique à 9% de chrome a été étudié à 650°C sous air sec et sous vapeur d’eau de matière isotherme et en conditions de cyclage thermique. La prise de masse des échantillons renseigne sur la cinétique de la réaction d’oxydation et l’adhérence des couches d’oxydes formées. Les produits de corrosion ont été caractérisés par plusieurs techniques d’analyses dans l’optique de clairement identifiés les oxydes en présences et leurs mécanismes de formation. Des oxydes mixtes de fer et de chrome (Cr,Fe)2O3 sont dans un premier temps formés et assurent s’avèrent être temporairement protecteur. Pour des longs temps d’oxydation ou des températures supérieures à 650°C, la magnétite Fe3O4 et l’hématite Fe2O3 sont les principaux oxydes formés, montrant ainsi l’inadéquation des nuances à faible teneur en chrome pour une utilisation dans des conditions aussi drastiques. Dans l’optique d’augmenter la résistance à la corrosion à haute température de cet alliage, diverses solutions ont été envisagées tel que l’aluminisation par cémentation en caisse, les revêtements d’oxydes de terre rare par MOCVD, ou encore l’ajout d’éléments d’addition. Ces solutions ont été également testées à 650°C sous air sec et sous vapeur d’eauThe improvement of high temperature oxidation resistance of low chromium content steels, such as T/P91, is of great interest in regards with their application in thermal power generating plants. Indeed, they possess good creep properties, and low thermal expansion coefficient. Important needs in energy together with environmental issues place power generation plants under constraints which lead to develop high efficiency systems. A usual way to increase the efficiency consists in increasing temperature and pressure parameters of the power generating plant. Studies has shown that the total efficiency of a plant increases by nearly 8 % when changing the steam parameters from 538°C/18.5 MPa to 650°C/30 MPa. Then, the problem of corrosion resistance of 9% chromium steel in those conditions is asked. In this work, the behavior of a ferritic / martensitic 9% chromium steel has been studied at 650°C in dry air and in water vapor containing environment in both isothermal and thermal cyclic conditions. The weight gain of samples provides information on the kinetics of the oxidation reaction and the adhesion of formed oxide scale. Corrosion products were characterized by several analytical techniques in order to identify oxides with accuracy and to understand their formation mechanisms. Mixed iron and chromium oxides (Cr, Fe) 2O3 are initially formed and provide temporary protection to the substrate. For long time exposure or temperatures above 650°C, magnetite, Fe3O4 and hematite Fe2O3 are the main oxides formed, highlighting the fact that low chromium steel are inappropriate for applications in such drastic conditions. In order to increase the high temperature corrosion resistance of this alloy, various solutions have been proposed as aluminizing by pack cementation, reactive element oxides coatings of by MOCVD, or addition of alloying elements in the steel composition. These solutions were then tested at 650 ° C in dry air and in water vapor environments