Dissertations / Theses on the topic 'Mechanical oxidation'
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1
Du, Zhiyou 1959. "Kinetic modeling of carbon oxidation." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/14003.
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Collyer, Matthew. "Catalytic wet air oxidation of thermo-mechanical pulping sludge." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23365.
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Wet air oxidation (WAO) is a waste treatment process which involves the oxidation of organic and inorganic compounds at high temperature and pressure in the aqueous phase. Previous work has shown that WAO is technically feasible for the treatment of sludge from a thermo-mechanical pulping (TMP) mill. In an attempt to improve the degree of oxidation, and consequently reduce the overall cost, the use of different catalysts was investigated. Experiments were carried out in a stainless steel batch reactor using pure oxygen and sludge from the primary clarifier of a TMP mill. Various metal salts were screened in order to determine a suitable catalyst for the process. Further experiments were performed to study the effect of oxygen pressure, temperature, time of reaction, and catalyst concentration.The screening experiments showed that the best catalyst was copper sulfate (CuSO$ sb4).$ When using this catalyst, a 97.6% reduction in the chemical oxygen demand occurred compared to 76.5% reduction without catalyst at the same conditions.
The results indicate that the use of CuSO$ sb4$ significantly improves the treatment of TMP sludge by wet air oxidation.
3
Dabbaghi, Hediyeh. "Oxidation Analysis of Additive Manufacturing Shape Memory Alloys." University of Toledo / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1596450323778946.
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Hasan, Mohammed. "The filtration and oxidation characteristics of a diesel oxidation catalyst and a catalyzed particulate filter : development of a 1-D 2-layer model /." Available online. Click here, 2005. http://sunshine.lib.mtu.edu/ETD/THESIS/hasanm/Thesis.pdf.
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Bruce, Ian A. "The oxidation behaviour of sintered iron." Thesis, Aston University, 1991. http://publications.aston.ac.uk/11909/.
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The oxidation behaviour of porous, sintered iron was studied by thermo-gravimetric analysis (TGA), at temperatures between 300oC and 700oC, in a flowing atmosphere of 20% O2/80% N2. Samples for TGA tests were compacted from pure iron powder, at 150MPa to 550MPa, and vacuum sintered at 1120oC. The mass gain of samples during oxidation was recorded continuously for a period of 24 hours. It was found that the oxidation mass gain of PM samples depended on the permeability of the pore structure and the temperature. At low temperatures, the oxidising gas was able to permeate through the pore structure, causing the oxidation of a large active surface area. At high temperatures the active surface area was smaller, because oxygen diffusing into the pore structure, from the external atmosphere, was adsorbed by pore surfaces close to the external surface of the compact. Although the weight of the external oxide scale on compacts increased with increasing oxidation temperature, the absence of oxide in the core porosity in compacts oxidised at higher temperatures resulted in smaller mass gains than were observed for compacts oxidised at lower temperatures. The heat generated by the oxidation of the large active surface areas of porous samples was studied by thermo-calorimetric analysis (TCA). It was determined that this phenomenon could raise the core temperature of samples significantly above the ambient furnace temperature, and affecting the morphology of the oxide scale formed. The effects (on oxidation behaviour at 500oC) of small, elemental alloy additions of Al, Cu, P and Si to pure iron powder were studied. It was found that elements that promote pore rounding during sintering caused a significant reduction in the mass gain rate of the PM alloys, compared to the PM pure iron. The oxidation resistance due to these elements prevented pore closure by oxide growth, so that the active surface area of these PM alloys remained high. The PM alloys were also studied by thermo-mechanical analysis (TMA, dilatometry), to determine their dimensional stability during sintering and subsequent elevated temperature service. The oxidation experiment was augmented with optical and electron microscopy, and X-ray analysis of alloy and scale compositions.
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Oliveira, Ivan B. (Ivan Borges) 1975. "One-dimensional numerical model for evaporation and oxidation of hydrocarbon fuels." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/32694.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999.Includes bibliographical references (p. 181-182).
In this work, a detailed chemistry, one-dimensional, reactive-diffusive model is implemented to study the basic aspects of evaporation and oxidation of a thin liquid fuel layer exposed to an incoming premixed flame. In particular, the model is applied to predict the total evaporation and ensuing oxidation of a liquid layer under repeated cycles. Methanol was used as a baseline fuel. Simplifications in the flow, geometry, and operating conditions are made to restrict the problem to its fundamental mechanisms. The solution method solves the appropriate governing equations in the liquid and gas phases, observing mass and species conservation with phase-equilibrium at the interface. The resulting eigenvalue problem is solved for pure liquid layers, but the extension of multi-component liquids is possible. Results show that increasing pressures lead to relatively lean regions near the interface due to the inverse dependence of phase-equilibrium concentrations on pressure. As a premixed flame arrives at the interface, large temperature gradients evaporate fuel from the layer as the remaining oxygen diffuses back into core gases. A short-lived diffusion flame results, which greatly enhances the rate of evaporation, serving as both a source of energy and a sink of fuel. Similar results are observed for pressure histories that resemble those of operating spark-ignition engines. Decreasing liquid layer thicknesses, increasing wall temperatures, and decreasing heats of vaporization are all observed to enhance the rate of evaporation mainly due to their impact on the heat transfer characteristics of the problem. Since the liquid layer surface is restricted to temperatures below or equal to the liquid boiling point, however, boundary layer temperatures for all cases are very similar, and thus total survival rate of evaporated fuel, repeatedly found to be roughly 2.9% for methanol, is quite insensitive to these parameters.
by Ivan B. Oliveira.
S.M.
7
Norris, Michael George. "Oxidation of hydrocarbons desorbed from the lubricant oil in spark ignition engines." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/35478.
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Wu, Kuo-chʻun 1968. "Chemical kinetic modeling of oxidation of hydrocarbon emissions in spark ignition engines." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/35377.
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Dehghanghadikolaei, Amir. "Enhance its Corrosion Behavior of Additively Manufactured NiTi by Micro-Arc Oxidation Coating." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1525475381922659.
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Brandstadt, Katrina L. "Thermal oxidation of fine aluminum powders in carbon dioxide gas." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81530.
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The thermal oxidation of fine aluminum (Al) powders in carbon dioxide (CO2) gas was investigated for the purpose of metal-based propulsion fuel development. The thermal behavior and reaction energy was studied using simultaneous thermogravimetric (TG) analysis and differential scanning calorimetry (DSC). The reactivities of Al powders with nanometer and micrometer-scale average particle sizes were compared. The particle morphology was examined at different stages of the process using field emission gun scanning electron microscopy (FEG-SEM) and transmission electron microscopy (TEM). The corresponding chemical changes were analyzed by X-ray diffraction spectrometry (XRD) and energy dispersion X-ray spectrometry (EDS).Nano- and micrometer-scale Al powders exhibited different calorimetric behaviour. The primary oxidation occurred at around 533°C for the nanopowders and at 1045°C for the micropowders. The mechanism of the oxide growth, particle deformations, and hollow oxide shells are discussed. A low-temperature transformation of the amorphous Al2O3 coating to crystalline gamma-Al 2O3 is identified as a trigger to the exothermic reaction in the case of the Al nanopowders. Carbon was also shown to be involved in the reaction.
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Paillard, Julien Michel. "Microstructure and mechanical properties of plasma electrolytic oxidation coatings on titanium substrates." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608619.
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Drobot, Kristine. "Hydrocarbon oxidation in the exhaust port and runner of a spark ignition engine." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/35958.
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Wu, Kuo-Chun 1968. "Modeling of post flame oxidation process of unburned hydrocarbons in spark ignition engines." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43719.
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Alqahtani, Bader. "Examination of Oxidation Sites for Electrolytic In-Process Dressing (ELID) Grinding using SEM." University of Toledo / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1556841748381472.
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Chetty, Aloshan Shaun. "Influence of oxidation treatment on the corrosion behaviour of Ti-6AI-4V alloy." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10219.
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Titanium-6Al-4V is a greatly desired alloy due to its attractive properties and exceptional corrosion resistance. Surface modifications such as thermal oxidation (TO) and oxygen boost diffusion hardening (OBDH) improve the tribological properties and wear resistance of Ti-6Al-4V. However, surface modification influences the corrosion behaviour of the metal. Therefore, the aim of this research project is to characterize how surface modifications influence the electrochemical behaviour of Ti-6Al-4V.
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Rao, Reshma R. "Understanding the active sites and reaction mechanism of water oxidation on metal oxides." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122141.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 184-196).
Solar energy irradiating the Earth's surface exceeds human energy consumption by four orders of magnitude and the key to alleviating the global energy crisis lies in efficiently harnessing it. An ideal means of storing surplus energy from solar is to convert it to hydrogen using proton exchange membrane water electrolyzers, which are amenable to integration with solar devices due to their high performance under fluctuating power input. Water oxidation to molecular oxygen is the most energy intensive part of the water splitting process, limiting the overall efficiency of water splitting devices. Rutile Ruthenium Dioxide (RuO₂) is a gold standard catalyst for water oxidation in acidic solutions. It can also undergo fast surface redox reactions in the electrochemically stable potential window of water, making it an ideal material for electrochemical capacitors that can charge and discharge in a much shorter time scale than batteries.
Understanding the interaction of RuO₂ with water can provide critical insights into the physical origin of its fascinating electrochemical properties and the active site(s) for water oxidation. Herein, we use ambient pressure X-ray photoelectron spectroscopy, in situ surface diffraction, surface enhanced infrared spectroscopy, electrochemical mass spectrometry and ab initio density functional theory calculations on well-defined RuO₂ surfaces to understand the mechanism and kinetics of the water oxidation reaction. We elucidate how different surface terminations can alter the binding energetics of oxygenated intermediates by changing the local environment of surface ruthenium and oxygen atoms.
Going beyond the conventional approach of changing the surface chemistry to tune the energetics of active sites, we also consider how changing the nature of the electrolyte (pH, cations in the supporting electrolyte) can modify the interfacial dynamics and increase electrocatalytic activity. Finally, we consider the use of Li-rich layered ruthenium oxides as a means to access bulk ruthenium redox for electrocatalytic reactions. Thus, through the use of surface-sensitive in operando techniques, this thesis identifies the active sites and reaction mechanism for oxygen electrocatalysis and demonstrates how catalyst surface structure and interfacial water structure can be altered to improve kinetics for next-generation water oxidation catalysts.
by Reshma R. Rao.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering
17
Natelson, Robert Harris Miller David L. Cernansky N. P. "Oxidation of n-butylcyclohexane in the low temperature region /." Philadelphia, Pa. : Drexel University, 2010. http://hdl.handle.net/1860/3259.
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Yao, Koffi Pierre (Koffi Pierre Claver). "Li₂0₂ in Li-0₂ batteries : catalytic enhancement of electrochemical oxidation and thermophysical transformations." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81711.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 95-98).
Electrification of transportation in the United States is of importance in reducing dependence on foreign oil and curtailing global warming. However, optimal market penetration of electric vehicles is confronted with the prohibitive cost and limited energy capacity of current state of the art lithium-ion battery packs, factors which limit range below 300 miles. Lithium-air (Li-air or Li-0 2) batteries could deliver more than three times the gravimetric energy of Li-ion batteries at potentially reduced cost by replacing transition metal oxide cathode with formation of lithium oxides (Li20 2 and Li 20). Being in its infancy, the Li-0 2 technology faces multiple challenges such as inadequate round trip efficiency (below 80%), low power capability, poor cycle life (less than 100 cycles) and thermal safety concerns. This thesis is concerned with the poor oxidation kinetics of the discharge product Li20 2, root cause of poor round trip efficiency, and the thermal stability of the candidate discharge products Li 20 2 and Li20. Catalysis of the Li20 2-oxidation by LaCrO 3, Bao.5Sro.5Coo.8Feo.20 3 (BSCF), LaNiO3, LaMnO3+8, and LaFeO3 was systematically investigated. It was found that LaCrO3, reported with the lowest activity in aqueous OER, shows a threefold higher activity compared to BSCF, reported with two orders of magnitude higher activity in aqueous OER. We postulate that efficient catalysts affect the surface energy landscape of Li20 2 at interfaces to result in larger proportions of low oxidation-overpotential surface orientations and, therefore, enhanced Li2O2-oxidation at lower overpotentials. Regarding the thermal stability of Li20 2 and Li20, X-ray diffraction revealed significant decrease in the c/a ratio of the lattice parameters of Li 20 2 from 280 'C to 700 'C, which are attributed to the transformation of Li 20 2 to Li202-6 . Upon further heating, a lithiumdeficient Li2-6O phase appeared at 300 'C and gradually became stoichiometric upon further heating to ~550 'C. XPS measurements showed growth of Li2CO3 on surfaces of Li20 2 and Li20 at 250 'C attributable to chemical reactions between Li 20 2/Li 2O and carbon-containing species.
by Koffi Pierre Yao.
S.M.
19
Yim, Pyongwon. "The role of surface oxidation in the break-up of laminar liquid metal jets." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10920.
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Yang, Fan. "Oxidation and mechanical damage in unidirectional SiC/Si#N# composite at elevated temperatures." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/19057.
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Chen, Tao. "The mechanical properties and oxidation behavior of nanocrystalline NiAl synthesized via shock consolidation of mechanically alloyed powders of Ni and Al." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/20029.
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Romano, Massimiliano. "Experimental investigation on the sensitization of hydrocarbon-oxygen mixtures to DDT via cool flame oxidation." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33992.
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The effect of cool flame partial oxidation on the detonation sensitivity of a hydrocarbon fuel was investigated experimentally. The detonation sensitivity was quantified by measuring the run-up distance required for a deflagration to transit to a detonation wave (DDT) in a rough tube. Fuel rich pentane-oxygen mixtures at subatmospheric initial pressures were studied. Subsequent to the injection of the mixture into the heated detonation tube, the mixture underwent cool flame oxidation after a well controlled delay time, as it was determined by the temperature of the tube. Typical delays ranged from 0.7 to 2 seconds (depending on temperature) and were reproducible to within one hundred milliseconds. This permitted to spark-ignite the mixture in the detonation tube at various stages of its cool flame process. The results show that increasing mixture temperature from room temperature to values below the cool flame region (below 250°C) resulted in an increase in run-up distance. However, as the mixture begins to undergo cool flame oxidization a significant reduction in the run-up distance was obtained (as large as 50%). The sensitization effect was found to occur only at the initial stage of the cool flame oxidation reaction. If the mixture is ignited at times long after the onset of cool flame, the mixture was found to be desensitized and the run-up distance increased. The sensitizing effect of the cool flame partial oxidation may be attributed to the presence of peroxides and free radicals associated with the initial cool flame process. However these radical species are consumed as the cool flame reaction proceeds and the mixture becomes insensitive again.
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Brooks, Amelia (Amelia Samek). "Modeling of char oxidation in fluidized bed biomass gasifiers : effects of transport and chemical kinetics." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98959.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (page 36).
Technologies for the conversion of biomass to liquid fuels are important to develop because the demand for liquid fuels remains unchanged even with the necessity of limiting dependence on fossil fuels. Fluidized Bed Biomass Gasification (FBBG) is one such technology that can perform the initial step of converting raw biomass into syngas as an intermediate to liquid fuels. The char that is left in the reactor after devolatilization can be oxidized in order to maximize the amount of biomass carbon that is converted to gaseous carbon and generate heat to drive endothermic gasification reactions. This paper examines the rate of each of the three processes that occur during char conversion (external diffusion, chemical reactions, and intraparticle diffusion) to determine which process limits the rate of the reaction under a range of conditions. It was determined that at most FBBG operating points, the rate of char conversion will be limited by the rate of diffusion of oxygen through the particle's boundary layer and through its pores. Only at low reactor temperatures and small particle diameters will the reaction rate be purely kinetically limited. An overall rate expression accounting for all three processes has been formulated which can be implemented in more detailed reactor models.
by Amelia Brooks.
S.B.
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Yao, Koffi Pierre (Koffi Pierre Claver). "Enhancing the oxidation of Li₂O₂ in Li-O₂ batteries : mechanistic and chemical efficacy probing." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104195.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 161-175).
The wide consensus regarding anthropogenic climate change, the positive correlation between economic growth and greenhouse gas emissions, and the humanitarian need for further global growth urges the decoupling of energy usage and emissions. To power portable electronics, enable electrification of transport, level the load on the current fossil-fuel powered grid, and provide storage for clean but intermittent wind and solar, low-cost and high energy density battery chemistries such as lithium-oxygen (Li-O₂) are being vigorously pursued beyond Li-Ion. The present thesis reports on efforts to devise and understand reaction promoters to enhance the kinetics of charging of Li-0₂ cells for the purpose of boosting round-trip efficiency, one of the most severe issues in the system. Investigating trends in electrochemical current output during charge in electrodes containing transition metal nanoparticles and metal oxides, we revealed a strong correlation between the conversion enthalpy of the promoter with Li₂O₂ towards formation of a corresponding lithium-rich metal oxide. Experimental evidence of formation of Li₂CrO₄, and Li₂MoO₄ is provided. Ru nanoparticles showed the formation of a surface phase in contact with Li₂O₂ which is assigned to Li₂RuO₃. We postulate solid-state promoters activate the oxidation of Li₂O₂ by enabling the formation of a lithium-rich metal oxide intermediate which proceeds to delithiate with enhanced kinetics compared to the direct decomposition of Li₂O₂. A microkinetics analysis successfully explains the excellent Li₂O₂ oxidation activity of metal nanoparticles such as Cr, Mo, and Ru as well as the relative inactivity at 3.9 VU of Mn, Co and other derivative oxides. Using differential electrochemical mass spectrometry (DEMS), the same conversion mechanism appears to result in sub-stoichiometric evolution of oxygen on charging as conversion enthalpy increase. In the second and last part of this thesis, cobalt bis(terpyridine) metal complex (Co(Terp)2) is demonstrated as redox mediator of the electron transfer to the insulating Li₂O₂. However, chemical probing using DEMS revealed a parasitic Co II to Co l reduction during discharge using the metal complex while the ideal 2.0 e-/O₂ formation of Li₂O₂ is observed with benchmark mediator tetrathiafulvalene. On charge substoichiometric O₂ regeneration is observed for both mediators; however, improved oxygen regeneration is seen using TTF.
by Koffi Pierre Claver Yao.
Ph. D.
25
Loeffel, Kaspar Andreas. "On the oxidation of high-temperature alloys, and its role in failure of thermal barrier coatings." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79290.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 114-122).
Thermal barrier coating (TBC) systems are applied to superalloy turbine blades to provide thermal insulation and oxidation protection. A TBC system consists of (a) an outer oxide layer that imparts thermal insulation, and (b) a metallic layer that affords oxidation protection for the substrate through the formation of a second, protective oxide layer. This slow oxidation of the metallic layer controls the mechanical integrity of the TBC system since it is accompanied by a large, anisotropic volumetric change on the order of 30 percent. To describe this coupled process at the microscale, in this thesis we formulate a continuum-level, chemo-thermo-mechanically coupled, thermodynamically-consistent theory which integrates (a) diffusion of oxygen, (b) oxidation with accompanying anisotropic volume change, (c) thermo-elasto-viscoplastic deformations that may be locally large, and (d) transient heat conduction. We numerically implement our theory in an implicit finite-element program, and calibrate the material parameters in our theory for an FeCrAlY alloy experimentally studied in the literature. We simulate the high-temperature oxidation of FeCrAlY, and show that our theory is capable of reproducing with reasonable accuracy the oxide thickness evolution with time at different temperatures, the shape distortion of the specimens, as well as the development of large compressive residual stresses in the protective surface oxide which forms. For the consideration of failure of thermal-barrier-coated components at the macroscale, a limitation of this type of model is that numerical simulations become challenging due to the sub-micron resolution of the required mesh. In a second part of this thesis, we therefore present a framework that facilitates macroscopic simulations by noting that the macroscopic effect of oxidation is simply to degrade some mechanical properties in the TBC system. In this framework oxidation is thus not modeled explicitly, but only indirectly manifested by affecting failure-related material parameters. We implement this model in an explicit finite-element program, apply it to a plasma-sprayed TBC system, and calibrate the material parameters. We then show that the model is capable of predicting with reasonable accuracy the load at which crack initiation occurs in a notched four-point bend test experimentally studied in the literature, as well as the overall qualitative load-displacement behavior in this test.
by Kaspar Andreas Loeffel.
Ph.D.
26
Dimitrakopoulos, Georgios T. "Experimental study and modeling analysis of ion transport membranes for methane partial oxidation and oxyfuel combustion." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108949.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 211-223).
The atmospheric concentration of CO 2 has recently exceeded 400 (ppm) (up from 285 (ppm) in 1850), largely because of the burning of fossil fuels. Despite the growth of alternatives, these fuels will continue to play a major role in the energy sector for many decades. In accordance with international agreements, action to curtail C02 emissions is necessary, including carbon capture, reuse and storage. For this purpose, some of the leading technologies are oxy-combustion for power generation and partial oxidation for syngas production. Both require significant quantities of oxygen, whose production can impose considerable energy and economic penalties. Alternative technologies, such as intermediate-temperature ceramic membranes, operating under reactive conditions, promise to ameliorate both. Challenges include the long term stability of the material, reactor design and integration into the overall system. The goal of this thesis is to develop a framework for the thermochemical and electrochemical modeling of oxygen-conducting membranes that can be used in reactor design, based on experimental measurements and detailed surface exchange kinetics and charged species transport. La0. 9Ca0.1Fe03-[delta] (LCF) perovskite membranes have been used because of their long term stability in a reducing environment. Using experimental measurements, we examine the impact of hydrogen, carbon monoxide and methane on oxygen permeation and defect chemistry. While LCF exhibits low flux under non-reactive conditions, in the presence of fuel oxygen permeation increases by more than one order of magnitude. Our experiments confirm that hydrogen surface oxidation is faster compared to carbon monoxide. With methane, syngas production is slow and oxygen permeation is limited by surface exchange on the permeate side. Adding C02 to the fuel stream doubles the oxygen flux and increases syngas production by an order of magnitude. Our modeling analysis shows that different oxidation states of Fe participate in the electron transfer process. To account for this dependency, oxygen transport is modeled using a multi-step (fuel dependent) surface reaction mechanism that preserves thermodynamic consistency and conserves site balance and electroneutrality. Charged species diffusion is modeled using the dilute-limit Poisson-Nernst-Planck formulation that accounts for transport due to concentration gradient as well as electromigration. We use the experimental data to extract kinetic parameters of the model. We couple the aforementioned model with CFD of the gas-phase transport and thermochemistry in an effort to develop a numerical tool that allows the design of membrane reactors that exhibit high oxygen permeation and fuel conversion.
by Georgios T. Dimitrakopoulos.
Ph. D.
27
Chong, Jun Jie. "The application of thermal, catalytic and non-thermal plasma oxidation processes to enhance NO-NO₂ oxidation in the engine exhaust and improve DPF regeneration at lower temperatures." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/3941/.
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Diesel Particulate Filter (DPF) is believed to be one of the most effective methods and provides an efficient system that traps more than 90% of PM. However, the soot accumulated within the filter requires a regeneration process to recover its performance. Thus, the high oxidation ability of NO-NO₂ increases the interest of applying it in the low temperature regeneration process. The intention of this thesis is to investigate several possibilities of on-board NO-NO₂ oxidation methods for increasing the NO₂/NO_x ratio in the exhaust gas. These possible oxidation routes incorporate the in-cylinder to the exhaust gas treatment processes. A wide range of operated temperatures are managed by the application of the non-thermal plasma oxidation (NTP) for low temperatures, catalytic oxidation for moderated temperatures and thermal oxidation for high temperatures studied. The in-cylinder NO oxidation was significantly improved by adding H₂ or the reformed EGR (REGR) to the combustion. The remaining H₂ after the combustion also contributes to the downstream HC-SCR which in turn promotes the NO oxidation. The thermal and NTP methods in the exhaust treatment cannot adequately achieve a satisfactory NO oxidation result under a single occupied condition. The propane (C₃H₈) addition may potentially create useful radicals (HO₂, RO₂) within the system and convert a large portion of NO into NO₂.
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Patterson, Travis. "Effects of Internal Oxidation on Thermo-Mechanical Properties of Atmospheric Plasma Sprayed Conicraly Coatings." Master's thesis, University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2959.
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Thermal barrier coatings (TBC) with MCrAlY (M=Co and/or Ni) bond coats have been widely used in hot sections of gas turbines to protect underlying superalloys from high temperatures, oxidation, and hot corrosion. Deposition of MCrAlY bond coats using atmospheric plasma spray (APS), as oppose to conventionally employed vacuum/low-pressure plasma spray and high velocity oxy-fuel deposition, allows greater flexibility in ability to coat economically and rapidly for parts with complex geometry including internal surfaces. There were three objectives of this study. First, relationships between APS spray parameters and coating microstructure was examined to determine optimum spray parameters to deposit APS CoNiCrAlY bond coats. Second, free-standing APS CoNiCrAlY coatings were isothermally oxidized at 1124ºC for various periods to examine the evolving microstructure of internal oxidation. Third, as a function of time of isothermal oxidation (i.e., internal oxidation), thermal conductivity and coefficient of thermal expansion were measured for free-standing APS CoNiCrAlY bond coats. Thirteen CoNiCrAlY coatings were deposited on steel substrates by APS using the F4-MB plasma torch. APS CoNiCrAlY bond coats were produced by incremental variation in the flow rate of primary (argon) gas from 85 to 165 SCFH and the flow rate of secondary (hydrogen) gas from 9 to 29 SCFH. Optimum coating microstructure was produced by simultaneously increasing the flow rate of both primary and secondary gas, so that the particle temperature is high enough for sufficient melting and the particle velocity is rapid enough for minimum in-flight oxidation. Optimum spray parameters found in this study were employed to deposit free-standing APS CoNiCrAlY coatings that were isothermally oxidized at 1124ºC for 1, 6, 50,100, and 300 hours. Extent of internal oxidation was examined by scanning electron microscopy and image analysis. Internal oxidation occurred by a thickening of oxide scales segregated at the splat boundaries oriented parallel to the coating surfaces. Thermal conductivity and coefficient of thermal expansion (CTE) of the free-standing APS CoNiCrAlY coatings were measured as a function of internal oxidation (i.e., time of oxidation or extent of internal oxidation). Thermal conductivity of free-standing APS CoNiCrAlY was found to decrease with increasing internal oxidation from 28 to 25 W/m-K. This decrease is due to an increase in the amount of internal oxides with lower thermal conductivity (e.g., Al2O3). CTE of free-standing APS CoNiCrAlY, measured in temperature range of 100°~500°C, was also found to decrease with increasing internal oxidation. Internal oxides have lower CTE than metallic CoNiCrAlY coatings. These evolving properties of APS CoNiCrAlY should be beneficial to the overall performance of TBCs in gas turbine applications.M.S.M.S.E.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Materials Science & Engr MSMSE
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Schoeller, Harry E. "Thermodynamics and kinetics of oxidation and temperature dependent mechanical characterization of pure indium solder." Diss., Online access via UMI:, 2007.
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Platt, Philip Michael. "Mechanical degradation in oxides formed on zirconium alloys." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/mechanical-degradation-in-oxides-formed-on-zirconium-alloys(290e5b3b-a07b-404f-9eca-a5301c472dab).html.
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The present work has been produced as part of an on-going collaboration between the University of Manchester and Amec, with the primary aim of furthering mechanistic understanding of corrosion processes in zirconium alloys out-of-reactor. Zirconium alloys are used as cladding material for nuclear fuel pellets, and correct understanding of the corrosion process in autoclave is essential to predicting material behaviour in-reactor. This EngD thesis is composed of five proposed papers that investigate observations and hypotheses under the theme of mechanical degradation in oxides formed on zirconium alloys in autoclave. First investigations concern observed stress relaxation in zirconium oxide. Finite element analysis is used to capture mechanical aspects of the corrosion process and apply this to stress behaviour determined previously using synchrotron x-ray diffraction. The results indicate that a mechanism other than creep or hydrogen induced lattice strain must be present to account for the observed stress relaxation. One such potential mechanism is crack formation; statistical analysis of scanning electron microscopy images has been used to identify a link between the development of roughness at the metal-oxide interface, crack formation in the oxide and transition points or acceleration in the corrosion kinetics. Parameters such as the median radius of curvature and profile slope (Rdq) have been applied, as these parameters do not require the definition of a periodic wavelength or amplitude. These and other parameters are related to information in literature to indicate that for samples of Zircaloy-4 and ZIRLOTM, which go through transition, the interface roughness changes in a way that would increase localised stress concentrations. The third material is an experimental low tin alloy, which under the same oxidation conditions, and during the same time period, does not appear to go through transition and does not develop an interface roughness in the same way. A critical assessment of finite element analysis applied to oxidising non-planar interfaces shows the significant limitations in the existing mechanism for representing oxidation expansion and stress formation. Autoclave oxidation experiments of artificially roughened samples of Zircaloy-4 were carried out to further understand the impact of out-of-plane stress generation. The results indicate a divergence based on surface roughness after ~86 days oxidation. SEM examination of images in cross section highlighted accelerated oxidation above surface roughness peaks, and an increased crack area in rougher samples. Finally, finite element analysis of the tetragonal to monoclinic phase transformation showed that biaxial compressive stress relaxation, or the tri-axial tensile stress associated with an advancing crack tip, could reduce the transformation strain energy and destabilise the tetragonal phase. The volumetric expansion and shear strain associated with the phase transformation produces stress in the surrounding oxide sufficient to generate nano-scale cracks perpendicular to the metal-oxide interface. This would allow fast ingress routes for oxygen containing species, and therefore acceleration in the corrosion kinetics.
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Janda, Daniel [Verfasser], and M. [Akademischer Betreuer] Heilmaier. "Mechanical properties and oxidation behavior of micro-alloyed iron aluminides / Daniel Janda. Betreuer: M. Heilmaier." Karlsruhe : KIT-Bibliothek, 2015. http://d-nb.info/1068263407/34.
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Saeidi, Saman. "Microstructure, oxidation & mechanical properties of as-sprayed and annealed HVOF & VPS CoNiCrAIY coatings." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/11731/.
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Three HVOF and a VPS CoNiCrAlY coating were sprayed using Praxair CO-210-24 and Sulzer Metco Amdry 9951 powders. All coatings were subject to vacuum annealing treatments at different temperatures for different exposure times in order to achieve equilibrium microstructures in all test samples. Both HVOF and VPS, as sprayed and heat treated coatings were oxidised at 850°C and 1100°C for periods of up to 250 hours. Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD) and laser diffraction powder size analyses were used in order to analyse the powder particle size distribution and characterise the microstructure of the as-received powders, as-sprayed coatings and annealed and oxidised coatings. Thermogravimetric analysis (TGA) was carried out on as-sprayed and heat treated HVOF and VPS coatings at 1100°C for 96 hours in order to compare the oxidation rate of HVOF and VPS coatings and investigate the effect of microstructure and heat treatment on the oxidation rate of both types of coatings. Furthermore, micro hardness, nano hardness and dynamic mechanical analysis (DMA) with a 3-point bend clamp were used in order to study the hardness and Young’s modulus of as-sprayed and annealed HVOF and VPS coatings. The Eshelby inclusion model and image analyses were used in order to further investigate the effect of microstructure on the mechanical properties of these coatings. It was observed that heat treatment prior to oxidation will change the dual oxide layer observed for the as-sprayed oxidised coatings to a single alumina layer for the heat treated and oxidised coatings. Furthermore, it was observed that microstructural features such as porosity and oxide stringers have an effect on the oxidation rate of coatings. A model was presented indicating the role of oxide stringers and porosity on the resulting heat treated microstructure and oxidation rate. It was also understood that the beginning stage of oxidation can play an important role on the oxidation behaviour (oxidation rate and different oxides present) of both HVOF and VPS coatings. It was observed that annealing will change the microstructure of the coatings and affect their mechanical properties. It was seen that annealing reduced the hardness of the thermally sprayed coatings while it had increased the Young’s modulus of the coatings. It was also observed that features such as porosity levels and β volume fraction have an effect on the mechanical properties of the coatings.
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Janda, Daniel [Verfasser], and Martin [Akademischer Betreuer] Heilmaier. "Mechanical properties and oxidation behavior of micro-alloyed iron aluminides / Daniel Janda. Betreuer: M. Heilmaier." Karlsruhe : KIT-Bibliothek, 2015. http://nbn-resolving.de/urn:nbn:de:swb:90-461256.
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Mathias, James A. "High-Pressure Oxidation Rates for Large Coal and Char Particles." BYU ScholarsArchive, 1996. https://scholarsarchive.byu.edu/etd/8539.
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The main objective of this study was to investigate the factors that influence the oxidation rate of large (five to eight millimeters in diameter) coal and char particles. To accomplish this, experiments were performed in which the gas temperature, gas velocity, particle size, partial pressure of oxygen, and total pressure were varied. The experiments were performed with the cantilever balance attachment and the high pressure controlled profile reactor.
Approximately 90 combustion experiments were performed with Pittsburgh, Utah Blind Canyon, and Wyodak-Anderson coal. These experiments were performed at atmospheric pressure with air and varied gas temperature, gas velocity, and particle size. Following the experiments performed with coal, approximately 70 experiments were performed with char made from Pittsburgh coal. These experiments varied all the environmental conditions mentioned above as well as partial pressure of oxygen and total pressure.
After the experiments were completed, the data were analyzed and the following conclusions were made. An increase in the partial pressure of oxygen dramatically increased the oxidation rate when the total pressure remained constant. The oxidation rate was only slightly affected when the partial pressure of oxygen was raised by increasing the total pressure. The oxidation rate dramatically decreased when the partial pressure of oxygen was held constant and the total pressure was raised. The oxidation rate noticeably increased when the initial mass of the particle was decreased. The gas temperature and gas velocity did not affect the oxidation rate greatly for the experiments performed with coal. The oxidation rate increased for the experiments performed with char at the high gas temperature and high gas velocity conditions.
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Montalti, Elia. "Mechanical characterisation of thermally aged polymers by bulge test and relation to diffusion-limited-oxidation effect." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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Gli impianti nucleari di terza generazione sono stati progettati in modo da funzionare per un periodo di vita intorno ai quarant’anni, nonostante questo è necessario estendere la loro operatività fino a sessant’anni. Un ruolo importante sarà ricoperto dai cavi elettrici operanti nell’impianto, che vengono solitamente indagati attraverso invecchiamenti artificiali del materiale polimerico, che costituisce il principale composto nello strato isolante, arrivando quindi a definire una valutazione operativa di quello che è il loro tempo di fine vita. Quando i campioni polimerici vengono sottoposti a trattamenti di invecchiamento ad alta temperatura in tempi brevi, essi degradano con effetti che sono imputabili alla diffusion limited oxidation (DLO). Questa tesi tratta il problema della misurazione sperimentale di caratteristiche meccaniche con gradiente spaziale di campioni invecchiati artificialmente in presenza di DLO, utilizzando il polietilene reticolato, principale componente nell’isolante dei cavi elettrici per impianti nucleari. il modulo elastico viene misurato adottando due diverse tecniche. Inizialmente è stato usato un approccio più globale mediante il test di rigonfiamento, al fine di valutare le proprietà di massa; in seguito le proprietà dipendenti dalla profondità sono state indagate mediante nanoindentazione, tecnica che permette di valutare l’andamento del modulo elastico lungo il profilo del campione. I risultati sono poi confrontabili con le analisi chimiche, che sono invece in grado di definire la distribuzione dell’intensità di ossidazione con l’uso di Spettrometria di massa di ioni secondari e a tempo di volo. Questo studio fornisce una solida metodologia per la determinazione sperimentale delle proprietà meccaniche locali di materiali polimerici dopo l’invecchiamento accelerato artificialmente (in condizioni di DLO).
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Stumphy, Brad David. "Mechanical and oxidation properties of some B2 rare earth-magnesium intermetallic compounds (RMg; R = Y, Ce)." [Ames, Iowa : Iowa State University], 2006.
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Papazoglou, Efstratios. "On porcelain bonding, oxidation, mechanical properties and high-temperature distortion of high-palladium dental casting alloys." The Ohio State University, 1999. http://catalog.hathitrust.org/api/volumes/oclc/47770015.html.
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Thesis (Ph. D.)--Ohio State University, 1999.Advisor: William A. Brantley, Oral Biology Program. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
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Wang, Shuo, and 王硕. "Tribological behaviour of anodised alumina nanohoneycombs." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B49618131.
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Anodic alumina nanohoneycombs (AAO) have been widely used because of its convenient fabrication and controllable pores’ geometry. A lot of investigations have been conducted to study its physical and chemical properties. However, the mechanical properties, especially tribological properties, of such a popular nanomaterial still remain almost unknown.
In this project, a series of scratch experiments were conducted on AAO films fabricated by a two-step anodisation method. The testing system is a G200 Nanoindenter provided by Agilent Corporation. A standard diamond Berkovich tip is used as the scratch tip. A scanning electron microscope was used to image the microstructure of the material deformation after scratching. Strengths of AAO domains with different pore regularities were compared by performing the scratch tests at constant normal loads crossing the boundaries separating these domains. Ramping load tests were carried out to show the effects of the normal load on the deformation and friction of the AAO. Scratch cycles and velocities were also varied to see their influence on friction and wear.
The results show that the more ordered AAO structure has higher strength than disordered counterparts under scratch testing. The friction coefficient reduces rapidly on increasing normal load, and an explanation of this unusual behaviour is offered by considering the row-by-row deformation of the AAO structure. In multicycle scratch tests, the friction reaches a maximum at the fourth cycle. A step-like deformation behaviour was observed when the scratch velocity became extremely large, and this is probably due to the dynamic response of the instrument.published_or_final_version
Mechanical Engineering
Master
Master of Philosophy
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Cheng, Chuan, and 程川. "Electro-chemo-mechanics of anodic porous alumina nano-honeycombs: self-ordered growth and actuation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hub.hku.hk/bib/B50899582.
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Self-ordered anodic porous alumina with a nano-honeycomb structure has recently been extensively used as templates for the synthesis of various nanomaterials for diverse applications. However, due to the insufficient knowledge on the combined electro-chemo-mechanical processes, the formation mechanism of self-ordering has been under debate for decades without clear conclusions. Also, fast fabrication of highly self-ordered and mechanically stable anodic porous alumina is still a challenge. Furthermore, the actuation behavior of anodic porous alumina upon external mechanical and electrical triggering in an electrochemical cell has not been exploited.
In this work, firstly, we investigated the self-ordering mechanism by establishing a kinetics model involving the Laplacian electric potential distribution and a continuity equation for current density within the oxide body. Current densities governed by the Cabrera-Mott equation are formed by ion migration within the oxide as well as across the interfaces. The pore channel growth, due to electric-field-assisted reactions, is governed by Faraday’s law. Real-time evolution of pre-patterned pore channel growth was simulated in two-dimensional cases by finite element method. The simulations revealed a parameter domain within which pre-patterned pore channels will continue to grow in a stable manner during the subsequent anodization if the pre-patterns are commensurate with the self-ordered configurations, or these are driven into stable if the pre-patterns do not initially match the self-ordered configurations. This was verified in experimentally observed pore channel growth under the guidance of pre-patterns made by focused-ion-beam milling. Furthermore, the simulations revealed that ionization reaction on (001) oriented Al grain is relatively easier than that on (101) grain, which results in stable and unstable pore channel growth on (001) and (101) Al grains, respectively, both of which were observed from the simulations and experiments.
Secondly, a scheme on quantitative evaluation of self-ordering qualities in anodic porous alumina has been developed, based on which we systematically searched the optimum self-ordering conditions, by varying the key anodization factors, including substrate grain orientation, electrolyte concentration, temperature, voltage, and time. A high acid concentration and high temperature anodization method was found. Compared with conventional methods, the present method can realize fast formation of highly self-ordered, and mechanically stable anodic porous alumina under a continuous range of anodization voltage with tunable interpore distances.
Thirdly, reversible bending was found in anodic porous alumina-Al composites upon cyclic electric actuation, as directly observed by an optical microscope and detected by in situ nanoindentation. The bending is thought to be the result of charge-induced surface stresses in the nanoporous alumina. The results suggest a new type of composite materials for applications as micro-scale actuators to transform electrical energy into mechanical energy. Furthermore, the composite exhibits significant softening during in situ nanoindentation when the estimated maximum stress underneath the indenter is exerted on the metal/oxide interface. Softening was further verified by in situ microindentation. Electron microscopy examination indicated that the softening is due to a combination of high compression stress and electric field acting near the interface, which enhance ionization reaction and cause the interface to move faster into the substrate.published_or_final_version
Mechanical Engineering
Doctoral
Doctor of Philosophy
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Dinan, Benjamin J. "Growth of Titania Nanowires by Thermal Oxidation." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1337650302.
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Chen, Wenhao. "Experimental evaluation of indoor air cleaning technologies and modeling of UV-PCO (photocatalytic oxidation) air cleaners under multiple VOCs conditions." Related electronic resource:, 2007. http://proquest.umi.com/pqdweb?did=1342744161&sid=3&Fmt=2&clientId=3739&RQT=309&VName=PQD.
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Karabela, Alkistis. "An experimental and computational study of damage and crack growth for a nickel-based superalloy under fatigue-oxidation conditions." Thesis, University of Portsmouth, 2011. https://researchportal.port.ac.uk/portal/en/theses/an-experimental-and-computational-study-of-damage-and-crack-growth-for-a-nickelbased-superalloy-under-fatigueoxidation-conditions(5c2951b6-04c4-45db-88ff-0790b2e1a7b8).html.
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Oxidation damage, in conjunction with fatigue, is a concern for nickel-based superalloys utilised as disc rotors in high pressure compressor and turbine of aero-engines. A combined experimental and numerical study has been carried out for alloy RR1000, developed at Rolls-Royce plc through a powder metallurgy route to meet the demands for higher overall pressure ratios, compressor discharge temperatures and rotational speeds for the latest aero-engines. Cyclic experiments have been carried out for waisted specimens at selected temperatures (700°C-800°C), followed by microscopy examination using Focused Ion Beam (FIB). The results suggest that the major mechanism of oxidation damage consists of the formation of surface oxide scales and internal micro-voids and oxide particles beneath the oxide scales, which becomes more severe with the increase of temperature. Applying a cyclic stress does not change the nature of oxidation damage but tends to enhance the extent of oxidation damage for temperatures at 750°C and 800°C. Further energy dispersive X-ray (EDX) analyses show the enrichment of Cr and Ti, together with lower Ni and Co levels, in the surface oxide scales, suggesting the formation of brittle Cr2O3, TiO2, NiO and Co3O4 oxides on the specimen surface. Penetration of oxygen into the material and associated internal oxidation, which leads to further material embrittlement and associated failure, are evidenced from both secondary ion imaging and EDX analyses. Scanning electron microscopy (SEM) studies of fracture surfaces have been performed for dwell crack growth, and the results confirmed the transition from transgranular to predominant intergranular cracking in alloy RR1000 for increased dwell time. This change in fracture mode supports the oxidation-assisted crack growth mechanism via grain boundary embrittlement. Oxidation embrittlement has also been supported by the FIB analyses of fracture surfaces which confirmed the oxidation reaction for alloy RR1000 at high temperatures. A stress-assisted diffusion approach has been used to model oxygen penetration in the waisted specimen based on Fick’s first and second laws. Grain microstructures were considered explicitly in the model using a finite element submodelling technique, and the grain boundary was taken as the primary path for oxygen diffusion. The material constitutive behaviour was described by a crystal plasticity model to consider the effects of heterogeneous deformation at grain level on oxygen diffusion. Two essential diffusion parameters, i.e., oxygen diffusivity and pressure factor, have been obtained from the simulated oxygen penetration as well as the FIB measurements of internal oxidation depth. Using the obtained diffusion parameters, finite element analyses of a compact tension specimen have been carried out to model oxygen diffusion, coupled with viscoplastic deformation, near a fatigue crack tip. A failure curve for crack growth has been constructed based on the consideration of both oxygen concentration and accumulated inelastic strain near the crack tip. The failure curve was then utilized to predict crack growth rates under fatigue-oxidation conditions for selected loading frequencies and dwell periods, with comparison against the experimental results and those predicted from the viscoplastic model alone.
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Johnson, Rodney Miller David L. Cernansky N. P. "A fundamental study of the oxidation behavior of SI primary reference fuels with propionaldehyde and DTBP as an additive /." Philadelphia, Pa. : Drexel University, 2008. http://hdl.handle.net/1860/2834.
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Dehoff, Ryan R. "Microstructure, Oxidation Behavior And Mechanical Behavior Of Lens Deposited Nb-Ti-Si And Nb-Ti-Si Based Alloys." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1221839511.
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Abdulla, Taha. "The effect of pulsed bipolar plasma electrolytic oxidation coatings on the mechanical properties of open cell aluminium foams." Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/3806/.
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Metal foams have attracted wide range of interest from researchers and industries because of their unique combinations of properties. Of particular interest, open cell metallic foams have good weight-specific mechanical properties, and improvements could make these materials highly desirable for lightweight structural and energy absorption applications. These properties could potentially be increased for open cell foams by treatments affecting their large surface areas. The effect could be very significant, especially when the dominant deformation mode is bending of the foam struts, as the coating will be located away from the neutral bending axis of these struts maximizing its effect. This has been previously found after the application of surface treatments, such as electroplating. The technique of Plasma Electrolytic Oxidation (PEO) is another process that shows an even greater effect on foam specific mechanical properties. In this work, Plasma Electrolytic Oxidation (PEO) coating treatment is applied to open celled aluminium foams with different structures, aiming to improve the mechanical and weight-specific properties of the hybrid material. Open cell aluminium foams of different types, both investment cast (Duocel foam) and replicated (produced in the laboratory) have been produced and PEO coated using a range of different processing parameters. Two pore sizes of Duocel aluminium foam (measured as 2.2 mm and 2.5 mm average pore diameter) with porosity of 90–91%, and a single pore size (1.6 mm diameter) of the pure aluminium replicated foam with porosity around 60–64% have been examined. The PEO treatment of foams was carried out in the pulsed bipolar current mode, with a range of processing times (20, 40, 60 and 80 minutes), pulse frequencies (50 to 6250 Hz) and duty cycles (different ON/OFF waveform ratios). These processing parameters were explored in the present work in four different stages of investigation, as will be explained in detail later. The mechanical properties (yield stress, specific strength, Young’s modulus and energy absorption) of the coated foams produced are assessed experimentally, both in tension and compression, and simple models developed to describe the elastic behaviour, based on either the Gibson-Ashby model of foams as a regular cellular array, or the Markaki-Clyne model of randomly intersecting fibres are used to make predictions to compare to these results. Complimentary characterisation was carried out using SEM, EDX, XRD and nanoindentation techniques to understand the nature of PEO coatings on foams (including coating thickness, growth rate, mechanical properties, porosity, elemental and phase compositions), and the effect this has on mechanical properties. Thereby, the process can be optimised to improve the mechanical performance of the foams. It was demonstrated that PEO coatings can be successfully applied to open cell foams (of low and high level of porosity) and the coating penetrates completely into the structure up to several millimetres depth, with thickness diminishing with depth. The presence of this coating is of benefit for uniaxial mechanical properties as well as specific foam properties. PEO pulse frequency influences coating thickness, porosity and the measured mechanical properties. The major effect on coating hardness and elastic modulus as well as on the strength and stiffness of the coated foams is associated with the volume fraction of porosity within the coating. The effect of using different duty cycles (associated with the ON and OFF times in each cycle in the current pulse frequency used) results in different coating morphology, thickness, distribution and deposition rate. Very fast coating growth rate has been shown to be not always beneficial, whereas low coating growth rate may be useful for the formation of good quality coatings (containing fewer microcracks and possibly lower intrinsic stresses), with potential for a very even distribution into the foam internal structure. An assessment based on strength increase (∆σ) and density increase (∆ρ) of the coated foams shows that the benefits of the application of PEO coatings to metal foams are greater than those shown in other metal foams coated by different techniques. The primary reason for this is that the oxide ceramic coatings formed on foams have low density, excellent mechanical properties and good adhesion to the substrate. These properties have been improved for foams by the PEO optimization process carried out in the present work.
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Hernandez-Gonzalez, Sergio Manuel. "Non-Catalytic Production of Hydrogen via Reforming of Diesel, Hexadecane and Bio-Diesel for Nitrogen Oxides Remediation." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1228317376.
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Jones, David C. "NANOMECHANICAL CHARACTERIZATIONS OF HIGH TEMPERATURE POLYMER MATRIX COMPOSITE RESIN: PMR-15 POLYIMIDE." Lexington, Ky. : [University of Kentucky Libraries], 2009. http://hdl.handle.net/10225/1040.
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Thesis (M.S.)--University of Kentucky, 2009.Title from document title page (viewed on August 6, 2009). Document formatted into pages; contains: ix, 65 p. : ill. (some col.). Includes abstract and vita. Includes bibliographical references (p. 59-62).
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Ahmadinejad, Mehrdad. "Modelling soot oxidation in DPF and modelling of PGM loading effect in a DOC." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/7062/.
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The aim of this PhD thesis is to develop a one-dimensional (1D) mathematical model to study in designing and improving emission control systems such as those in Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF). This was achieved by capturing the fundamental reaction kinetics from the microreactor data within the careful choice of concentrations/ temperatures domain; together with good understanding of the physical phenomena’s occurring in these systems. When considering a DOC, it is important to have a good description of the catalyst activity as a function of Platinum Group Metal (PGM) loading, which in this case is Pt, this enables mathematical models to be used in the optimization of the PGM loading. The work presented here looks at the design of a DOC based aftertreatment system through development of kinetics from data obtained from the microreactor for a wide range of PGM loadings (2.5-75g ft-3). The variation in catalyst activity with different PGM loadings for the key reactions was determined. The model developed in this study predicts well all the experimental data for the various loadings. DPF is another important aftertreatment technology that is used for the control of Particulate Matter (PM) emission from diesel engines. Under favourable conditions, the soot collected on the filter can be removed by oxidation with NO2 from temperatures as low as 200°C. The work presented in this thesis shows the fundamental modelling approach to develop kinetics for soot oxidation by NO2. The selectivity to CO was found to differ only marginally with temperature, and is independent of NO2 concentrations. By modelling these data using a 1D model, the rate equations for the soot-NO2 reaction were determined, and experimental data were predicted.
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Gallagher, Michael J. Fridman Alexander A. "Partial oxidation and autothermal reforming of heavy hydrocarbon fuels with non-equilibrium gliding arc plasma for fuel cell applications /." Philadelphia, Pa. : Drexel University, 2010. http://hdl.handle.net/1860/3199.
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Qadeer, Muhammad Irfan. "SmCo for polymer bonded magnets : Corrosion, silanization, rheological, mechanical and magnetic properties." Doctoral thesis, KTH, Keramteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-106809.
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This thesis presents the study of organofunctional alkoxysilane coatings to prevent high temperature oxidation of Sm-Co powders. Sm-Co are important permanent magnetic alloys, owing to their high Curie temperature and large values of magnetocrystalline anisotropy. They possess stable magnetic properties in the temperature range -40 to 120 °C which makes them very attractive candidates for automobile’s electric motors. However, the environmental conditions for such applications are a sum of high temperatures, humidity, fuels and salts which provide perfect breeding ground for corrosion. In this study we report the high temperature oxidation resistance of Sm2Co17 powders coated with four common commercially available organofunctional silanes; (3-aminopropyl)trimethoxysilane (APTMS), (3-aminopropyl)triethoxysilane (APTES), methyltrimethoxysilane (MTMS) and (3-glycidyloxypropyl)trimethoxysilane (GPTMS). The as received powder was a multimodal mixture of many sizes and shapes which represented a typical ball milling product. The thermal analyses of the powders suggested that the powders without surface coatings had profound affinity towards oxidation. The thermal properties of sieved uncoated powders revealed that the small powders were more susceptible to oxidation than the large powders due to their large specific surface area. The isothermal properties of coated powders revealed that the powders coated with silanes had at least 10 times higher resistance to oxidation as compared to uncoated powders heated at 400 °C for 10 h. The non-isothermal tests conducted from room temperature to 500 °C also revealed that the uncoated powders gained 6 times more mass as compared to the powders coated with an ideal (MTMS) silane. The microstructural analysis of the uncoated powders heated from 400 °C to 550 °C revealed diffusion of oxygen, instable intermetallic phases which resulted in a redistribution of alloying elements, precipitation of alloying elements and formation of a featureless shell (approximately 20 µm in thickness) that surrounded the unreacted core. The coated powders on the other hand showed homogenous distribution of alloying elements, stable intermetallic phases and limited the shell thickness (1 µm). The thermo-magnetic properties of Sm-Co powders showed that the thermal instability also affected the magnetic properties adversely. It was found that the magnetic properties were deteriorated with a decrease in powder size. The energy dispersive spectroscopic (EDS) analyses showed that the small powders contained higher oxygen content than the large powders. Moreover XRD analysis also revealed that the small powders contain higher residual strains and smaller crystallite size which can play their role in deteriorating magnetic properties. It was found that surface modification by silanization improve the thermo-magnetic properties by effectively shielding the powder surfaces from surface oxidation. The rheological properties Sm-Co/PA12 composites revealed that the viscosity of the composites was increased with decreasing powder size due to the presence of rough surfaces and sharp corners in small powders. The rheological properties of the melts containing coated powders revealed that the silane layer acted as a lubricant and decreased the melt viscosity. It was found that coating the powders with silanes not only improve the rheological properties but also improve the other physical properties such as glass transition temperature the loss modulus by modifying the interfacial layer between the polymer matrix (PA12) and the powder. It results in a decrease in viscosity, a broadening of the glass transition temperature and a change in the damping properties of the composites. The dynamic mechanical properties of Sm-Co/PA12 composites showed that the storage modulus was increased with decreasing powder size. The results were expected as the rough surfaces act as local welding points between the powder and the polymer matrix. It was found that the surface modification improve the storage modulus. It is assumed that the silanes modify the interfacial properties which not only resulted in increasing the storage modulus but also broadened the glass transition temperature, Tg and damping, tanδ peaks. From the thermogravimetric, microstructural, rheological and magnetic analyses it can be concluded that the silanes are the effective coatings in preventing high temperature oxidation, stabilizing microstructure, enhancing mechanical properties, and improving rheological and magnetic properties.QC 20121205