Дисертації з теми "Microstructural effects"
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Portsmouth, Robert Lynton. "Microstructural effects in adsorptive separations." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260591.
Повний текст джерелаRodriguez, Maria Remedios Carmona. "Small strain effects on microstructural evolution." Thesis, University of Sheffield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392716.
Повний текст джерелаWohlschlögel, Markus Albin. "Microstructural effects on stress in thin films." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-36733.
Повний текст джерелаLi, Ju 1975. "Modeling microstructural effects of deformation resistance and thermal conductivity." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/46283.
Повний текст джерелаIncludes bibliographical references (p. 344-360).
This is a study of the microstructural influences on thermo-mechanical behavior of selected metals and ceramics using computer simulation, with original contributions in both theoretical and applied aspects. There are three major thrusts. First, by constructing a many-body empirical potential for ZrCx and then carrying out MD simulations to calculate its lattice thermal conductivity, I obtain the first quantitative evidence ever that the vibrational contribution is only a small part of the total thermal conductivity of refractory carbides at realistic carbon vacancy concentrations. This is a long-standing problem which even the most recent review article on the subject give what I now believe is the wrong estimate. Second, ideal strengths are calculated for Ar,Cu,SiC crystals using both lattice and molecular dynamics methods. A set of homogeneous instability criteria are derived. Tension tests are performed on amorphous and nanocrystalline SiC at room temperature, based on which a grain size cutoff of ~20 nm is extrapolated for the Hall-Petch effect. Nano-indentation is performed on single-crystal and nanocrystalline Cu, and bursts of dislocation loops is observed at a local stress level consistent with recent experiments on Cu thin films. Third, an invariant loop summation similar to the J-integral is derived for the driving force on defect motion, but with the loop size now down to nanometers, and the summation now expressed in terms of interatomic forces instead of stress, a field concept which is hard to use in atomistic calculations and becomes ill-defined when defect separations approach the nanometer scale. It is shown first that the change in a system's total Helmholtz free energy due to a defect's move can be approximated by a local quantity involving only scores of atoms immediately surrounding the defect. Then, perturbation expansion is used to evaluate this local invariant for defect translation using only the current configuration. This driving force measure is then tested on a) self-interstitial diffusion near free surface in [alpha]-iron, b) crack-tip extension near a void in Si, c) screw dislocation translation in Si, with convincing results down to literally r = 1 nm, at a fraction of the cost of a full relaxation or free energy calculation for the whole system. This means that defect mobility can now be characterized by a universal and invariant standard, computable from a tiny atomistic calculation without relying on elasticity formulas or image summations. The standard is then used to determine the true Peierls-Nabarro stress in Si-like materials.
by Ju Li.
Ph.D.
Rezvanian, Omid. "GRAIN SUBDIVISION AND MICROSTRUCTURAL INTERFACIAL SCALE EFFECTS IN POLYCRYSTALLINE MATERIALS." NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-01052006-204245/.
Повний текст джерелаMorgan, Terence S. "Microstructural effects of neutron irradiation on ferritic/martensitic stainless steels." Thesis, Loughborough University, 1992. https://dspace.lboro.ac.uk/2134/13768.
Повний текст джерелаRohatgi, Aashish. "A microstructural investigation of shock-loading effects in FCC materials /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1999. http://wwwlib.umi.com/cr/ucsd/fullcit?p9944211.
Повний текст джерелаRobinson, Michelle Christina. "Microstructural and geometric effects on the piezoelectric performance of PZT MEMS." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Dissertations/Fall2007/m_robinson_091307.pdf.
Повний текст джерелаBooysen, Theo-Neal. "Microstructural effects on properties of additively manufactured Inconel 625 and 718." Thesis, Cape Peninsula University of Technology, 2019. http://hdl.handle.net/20.500.11838/3043.
Повний текст джерелаThree Dimensional(3D) printing is known as additive manufacturing: it is a method of manufacturing parts or components form sheet, wire or powder in a manufacturing process. This method differs from traditional manufacturing techniques such as casting, moulding or subtracting materials which already exist. The type of material characterization is also very important in the development and improve or manufacturing of new materials for higher strength and various application. Selective Laser Melting(SLM) an additive manufacturing powder-based process has been adopted by automotive and aerospace industries. The reason for this is that it has many potential benefits, such as 3D designs of complex components in a shortened time frame, which offers financial savings. SLM process use metallic powders with different chemical composition to manufacture complex structures, which is an innovative material processing technology. In this research SLM, a typical additive manufacture process method, was used to manufacture additively manufactured Inconel 625 and 718. These sample specimens were investigated to determine their microstructural features and mechanical properties. The microstructural features were characterized using two different experimental surface microscopy methods: scanning electron microscope(SEM) and light optical microscope (LOM). The mechanical properties were determined by studying deformation and hardness characteristics using three-point bending and hardness tests. The relationship between processing, microstructure, grain sizes and mechanical properties was established. The understanding of SLM additive manufacturing of alloys is important as well for the adoption of the technology, and the possibility of replacing commercially produced cast and wrought alloys in the near future.
De, Jesús Aribet M. "Effects of mechanical stimulation on fibroblast-guided microstructural and compositional remodeling." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/3068.
Повний текст джерелаWohlschlögel, Markus Albin [Verfasser]. "Microstructural effects on stress in thin films / vorgelegt von Markus Albin Wohlschlögel." Stuttgart : Max-Planck-Inst. für Metallforschung, 2008. http://d-nb.info/995391246/34.
Повний текст джерелаPratapa, Suminar. "Diffraction-based modelling of microstructural size and strain effects in sintered ceramics." Thesis, Curtin University, 2003. http://hdl.handle.net/20.500.11937/1476.
Повний текст джерелаPratapa, Suminar. "Diffraction-based modelling of microstructural size and strain effects in sintered ceramics." Curtin University of Technology, Department of Applied Physics, 2003. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=14619.
Повний текст джерелаThe size profile component function for the convolution model involves the modal size and the size distribution appropriate for `normal' crystallite growth according to the mean-field theory, as proposed recently in a seminal publication by Dr. Brian York of IBM. A Gaussian strain profile component function was considered in the study on the basis that it has been widely used for specimens which exhibit small microstrain (ca. 10-3 or less). The overall profile describing the diffraction pattern involves convolution of the instrument, size and strain effects. A non-linear least-squares refinement program entitled MOZAIX has been developed for profile fitting with the model. Data simulations were performed with the model, and non-linear least-squares optimisations for fitting the simulated data showed that the calculations were reasonable for low-strain sintered ceramics. The convolution model for size and strain assessments from diffraction line broadening has been evaluated with synchrotron and laboratory x-ray radiation diffraction data (SRD and XRD, respectively). The study made use of MgO ceramics with three different purity levels which had been sintered at a range of temperatures in order to provide diffraction data with a range of microstructural strain and size effects. The cubic symmetry of MgO provided isotropic size and strain effects as had been anticipated. The Voigt function, a convolution of the Gaussian and Lorentzian functions, is widely used to extract crystallite size and strain information from powder diffraction data using (1) Fourier transforms, (2) the Rietveld method and (3) integral breadth methods. Size and strain model evaluation carried out using the Voigt-based Rietveld and integral breadth methods assumes that the size effect contributes only to the Lorentzian component and the strain contributes only to the Gaussian component.
Size and strain assessment using the Voigt integral breadth single-line and Rietveld methods has been examined in this study with diffraction data for MgO ceramics. Two major outcomes from the evaluation confirmed impressions gained from the literature that: 1. the integral-breadth single-line method can be used as a reliable technique for size and strain analysis; 2. analysis using the Voigt function has no physical basis, is inappropriate for profiles with 'super-Lorentzian' character and is inadequate for size-strain analysis since the function does not take into account the size distribution parameter. There has been a strong trend recently towards whole-pattern size and strain evaluations which are progressively replacing single-line methods. However, due to time constraints, this study was confined to single-line analysis with the focus being on the development of the model, and with an expectation that the single-line model would readily be extended in the future to use with whole-powder pattern data. The size-strain analysis results using the convolution model showed that sintering (1) promotes crystallite growth and (2) relieves residual strains in low density sintered ceramics and introduces strains in dense ceramics, presumably due to grain-grain shear interactions. The effect of sintering on the size distribution clearly depends on the crystallite growth behaviour. Comparing the SRD convolution size results with those from scanning electron microscopy (SEM) showed that (1) the "grains" imaged using SEM contain clusters of crystallites and (2) the SEM-derived and convolution size distributions are in a satisfactory agreement.
In general, despite the larger uncertainties due to instrument resolution, the XRD results are in agreement with those from SRD. The size and strain values obtained with the convolution model were compared with those calculated using the Voigt single-line integral-breadth method. The comparison showed that size and strain results for both methods were dependent upon the character of the diffraction peak shapes. The convolution model improves the Voigt model in terms of (1) reliability of models from a physical point of view, (2) the additional size distribution parameter and (3) its applicability to `super-Lorentzian' profiles. Subsequent research is suggested to further improve the model in dealing with large microstrains and developing a whole powder fitting procedure.
Sauter, Linda Xenia. "Microstructural and film thickness effects on the thermomechanical behavior of thin Au films." Stuttgart : Max-Planck-Inst. für Metallforschung, 2007. http://d-nb.info/995370753/34.
Повний текст джерелаAbdeljawad, Fadi Faeq. "Microstructural Modeling of CSL Grain-Boundary Effects and Crack Growth in F.C.C. Polycrystals." NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-01222006-115908/.
Повний текст джерелаGodha, Anshul. "Microstructural effects on fatigue damage evolution in advanced high strength sheet (AHSS) steels." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53510.
Повний текст джерелаMark, Alison Fiona Lockie. "Microstructural effects on the stability of retained austenite in transformation induced plasticity steels." Thesis, Kingston, Ont. : [s.n.], 2007. http://hdl.handle.net/1974/960.
Повний текст джерелаSauter, Linda Xenia. "Microstructural and film thickness effects on the thermomechanical behavior of thin Au films." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-31632.
Повний текст джерелаNelson, Elizabeth A. "Microstructural effects of multiple passes during friction stir processing of nickel aluminum bronze." Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Dec/09Dec%5FNelson.pdf.
Повний текст джерелаThesis Advisor: McNelley, Terry R. Second Reader: Menon, Sarath. "December 2009." Description based on title screen as viewed on January 28, 2010. Author(s) subject terms: friction stir processing, nickel aluminum bronze, propellers, microstructural properties, grain refinement, volume fraction-temperature relationship. Includes bibliographical references (p. 45-46). Also available in print.
Kadri, Shabibahmed Jehangir. "Microstructural breakdown and scale-up effects in equal channel angular extrusion of cast copper." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4341.
Повний текст джерелаShi, Jibin. "Predictive Microstructural Modeling of Grain-boundary Interactions and Their Effects on Overall Crystalline Behavior." NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-02132009-173832/.
Повний текст джерелаDavis, Robin M. (Robin Manes). "Microstructural effects on capacity-rate performance of vanadium oxide cathodes in lithium-ion batteries." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32852.
Повний текст джерелаIncludes bibliographical references (leaf 29).
Vanadium oxide thin film cathodes were analyzed to determine whether smaller average grain size and/or a narrower average grain size distribution affects the capacity-rate performance in lithium-ion batteries. Vanadium oxide thin films were prepared by sputtering onto ITO-coated glass substrates and crystallized in a refined annealing process to generate diverse microstructures. Average grain size and grain size distribution were determined in SEM analysis. No significant difference was observed in capacity rate behavior with changes in microstructure. However, it is speculated that further in situ analysis may show different relative diffusion rates into grains of differing sizes is related to different microstructures.
by Robin M. Davis.
S.B.
Rathore, Shambhu Singh. "Investigation of Microstructural and Carbon Deposition Effects in SOFC Anodes Through Modelling and Experiments." Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/69416.
Повний текст джерелаTakahashi, Keisuke. "Effects of mixing and pumping energy on technological and microstructural properties of cement-based mortars." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2014. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-156776.
Повний текст джерелаWieloch, Marcin Maciej. "The effects of freeze/thaw cycles on the microstructural features of air-entrained cementitious mortars." Thesis, Glasgow Caledonian University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422021.
Повний текст джерелаColman, Charlotte. "Gypsum residues in fine recycled aggregates : effects on mechanical and microstructural properties of cementitious composites." Electronic Thesis or Diss., Ecole nationale supérieure Mines-Télécom Lille Douai, 2020. http://www.theses.fr/2020MTLD0012.
Повний текст джерелаFine recycled aggregates are an important waste steam coming from the demolition of old concrete structures. They are up to now not valorized because of an increased water absorption, lower density and higher fines content compared to natural aggregates. Moreover, they often have a high sulfate concentration. These sulfates could have originated from plaster in a demolished building, or from the residual cement that is commonly present in these materials. The sulfate level of recycled aggregates is recommanded to stay under 0.2 mass% by standard EN206, to limit the risk on sulftate attack: the reaction between cement components, water and sulfates results in the formation of expansive minerals such as ettringite. This expansion can eventually lead to cracking of the material and a general loss in mechanical performances. Fine recycled aggregates from recycling plants did contain 0.15 to 0.80 % of sulfates which is more than allowed, but these amounts did not cause any swelling or degradation when the aggregates were incorporated into mortars. A very elevated sulfate content of 3 % was needed to observe significant expansion, and even this level of contamination could be mitigated by increasing the alkalinity of a mix. Concretes made with varying sulfate levels either expanded or they didn’t: the absolute swelling amount was not proportional to its sulfate content. The actual threshold concentration that started the swelling reaction was dependant on the type of coarse aggregate. The results of this study provide recommandations for the use of fine recycled aggregates contaminated with gypsum residues : a sulfate content of at least 0.3 % could be possible, and even more if certain parameters and mix compositions can be adjusted accordingly. The current limit of 0.2 % seems too strict and hinders the valorization of fine recycled aggregates in high quality construction applications
Zhang, Jinyong. "Mechanical Behavior and Microstructural Evolution in Metastable β Ti-Mo Based Alloys with TRIP and TWIP Effects". Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066313/document.
Повний текст джерелаIn this work, based on combination of the ‘d-electron alloy design method’ and controlling of electron/atom ratio (e/a), a model of binary Ti-12Mo (wt. %) and ternary Ti-Mo based alloys were designed, induced combined TRIP and TWIP effects (TRIP for Transformation Induced Plasticity and TWIP for Twinning Induced Plasticity). The tensile results show that so-designed alloys exhibit true stress-strain values at uniform plastic deformation, of about 1000-1200MPa and between 0.3 and 0.4 of strain, with a large strain-hardening rate. Several characterization techniques, such as conventional X-ray diffraction (XRD), In-situ Synchrotron X-ray diffraction (SXRD), electron backscatter diffraction (EBSD), electrical resistivity measurements (ERM), transmission electron microscopy (TEM) and automatic crystal orientation measurements (ACOM) TEM, were carried out to to investigate the deformation mechanisms and microstructure evolution sequence. Various deformation mechanisms, i.e. {332}<113> mechanical twinning, deformation induced ω phase and stress-induced α’’ martensite, were identified after mechanical testing, resulting in a combination of high strength, large ductility and improved strain-hardening rate. Furthermore, low temperature aging (LTA) treatments were performed on the Ti-12Mo alloy to improve the mechanical property through controlling the ω phase transformation without excessive modification of β matrix chemical composition, keeping the possibility for combined TRIP and TWIP effects to occur. The influence of LTA treatment on the mechanical behavior and microstructural evolution of Ti-12Mo alloy was discussed in detail
Reda, Hilal. "Modeling and computation of the effective static and dynamic properties of network materials accounting for microstructural effects and large deformations." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0007/document.
Повний текст джерелаMicropolar and second gradient effective continua are constructed as two different strategies to account for microstructural effects. The influence of additional degrees of freedom or higher order displacement gradients on the dispersion relations is analyzed in both situations of elastic and viscoelastic behaviors of the material. Generalized effective continua lead to dispersive waves, as observed in experiments. In the second part of the thesis, we analyze the influence of large deformations on the propagation of acoustic waves in repetitive network materials. Both theoretical and numerical methods are developed in order to assess the influence of finite strains developing within the networks on the evolution of their band diagrams. An incremental scheme for the update of frequency and phase velocity of the computed homogenized medium is developed based on a perturbation method for 1D, 2D and 3D structures, considering with a special emphasis auxetic networks. This scheme shows an important effect of the applied finite deformation on the frequency and phase velocity of the propagating waves. A perturbation method for nonlinear periodic structures is developed to extend Bloch’s theorem to cover both geometrical and material nonlinearities. Hyperelastic first and second order gradient constitutive models of different network materials are identified based on dedicated homogenization methods, from which specific wave equations are formulated - Burgers and Boussinesq equations - the dispersion properties of which are analyzed
Ahmed, Mohammad Sharfuddin Aerospace Civil & Mechanical Engineering Australian Defence Force Academy UNSW. "Effects of systematic increase in pozzolanic materials on the mechanical, durability, and microstructural characteristics of concrete." Awarded by:University of New South Wales - Australian Defence Force Academy. School of Aerospace, Civil and Mechanical Engineering, 2007. http://handle.unsw.edu.au/1959.4/38645.
Повний текст джерелаSmith, J. J. "Microstructural characterisation of duplex 316 weld metals : The effects on the mechanical and high temperature properties." Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384218.
Повний текст джерелаYan, Miaolei. "Defect Analysis and Microstructural Effects on the Surface Exchange Properties of La0.7Sr0.3MnO3(LSM) Epitaxial Thin Films." Research Showcase @ CMU, 2015. http://repository.cmu.edu/dissertations/650.
Повний текст джерелаJin, Yan. "THREE-DIMENSIONAL MICROSTRUCTURAL EFFECTS ON MULTI-SITE FATIGUE CRACK NUCLEATION BEHAVIORS OF HIGH STRENGTH ALUMINUM ALLOYS." UKnowledge, 2016. http://uknowledge.uky.edu/cme_etds/63.
Повний текст джерелаNafisi, Shahrooz. "Effects of grain refining and modification on the microstructural evolution of semi-solid 356 alloy = Effets de l'affinage des grains et de la modification sur l'évolution microstructurale de l'alliage 356 semi-solide /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2006. http://theses.uqac.ca.
Повний текст джерелаJamaly, M. A. M. Nasim. "The effects of microstructural features and process parameters on the hottearing in direct chill cast aluminum alloys." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43316.
Повний текст джерелаDing, Yi. "Effects of elevated temperature exposure on the microstructural evolution of Ni(Cr)-Cr3C2 coated 304 stainless steel." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10917/.
Повний текст джерелаBakare, Mayowa Sunday. "The effects of microstructural modifications on corrosion resistance of metallic corrosion resistant materials Inconel 625 and FeCrMoCB." Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546474.
Повний текст джерелаAhmed, Nauman. "Characterisation of different forms of Inconel 625 for determining the effects of microstructural modifications on electrochemical behaviour." Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493327.
Повний текст джерелаNakos, James Spiros. "Effects of crystal growth process parameters on the microstructural optical and electrical properties of CdTe and CdMnTe." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14574.
Повний текст джерелаPontikos, Nicholas Michael. "Laser induced microstructural and morphological alterations and their effects on electron transfer kinetics at glassy carbon electrodes /." The Ohio State University, 1992. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487780865407154.
Повний текст джерелаMcCarthy, John M. "The microstructural effects of metallization and heat treatment on thin gate oxide for use in sub-micron MOSFETs /." Full text open access at:, 1996. http://content.ohsu.edu/u?/etd,13.
Повний текст джерелаKitey, Rajesh Tippur Hareesh V. "Microstructural effects on fracture behavior of particulate composites investigation of toughening mechanisms using optical and boundary element methods /." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Spring/doctoral/KITEY_RAJESH_50.pdf.
Повний текст джерелаSauter, Linda Xenia [Verfasser]. "Microstructural and film thickness effects on the thermomechanical behavior of thin Au films / vorgelegt von Linda Xenia Sauter." Stuttgart : Max-Planck-Inst. für Metallforschung, 2007. http://d-nb.info/995370753/34.
Повний текст джерелаTovee, John-Paul. "Microstructural influence on the effects of forward and reverse mechanical deformation in HSLA X65 and X80 linepipe steels." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5171/.
Повний текст джерелаMeroueh, Laureen. "Effects of doping and microstructural variables on hydrogen generated via aluminum-water reactions enabled by a liquid metal." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/129067.
Повний текст джерелаCataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages [110]-127).
Hydrogen has the potential to replace fossil fuels in numerous industrial sectors, considering its high energy density, ability to be used within our existing power or heating infrastructure, and lack of CO₂ emissions upon conversion of hydrogen's chemical energy into electricity. However, 96% of hydrogen is currently produced through steam methane reformation, which emits ~12 tons of CO₂ for every 1 ton of hydrogen produced. Consequently, hydrogen production accounts for roughly 830 million tons of annual global CO₂ emissions. Additionally, hydrogen storage can be impractical and expensive. The aluminum-water reaction presents itself as a hydrogen storage and generation solution. Without a passive oxide layer, aluminum will react with water to produce emission-free hydrogen, on-demand.
We enable the reaction by harnessing eutectic gallium-indium (eGaIn), an ambient temperature liquid metal that permeates through aluminum grain boundaries, disrupting its passive oxide layer and inhibiting passivation of its grain surfaces. The focus of this work is on the investigation of the underlying aluminum-water reaction mechanism in the presence of eGaIn and on understanding the effects of using scrap aluminum (i.e. doped aluminum) as feedstock. Surprisingly, experiments show that silicon doping has a tremendous accelerating effect on the aluminum-water reaction in the presence of eGaIn. In combination with grain size manipulation, Si-doping can increase hydrogen evolution rates by two orders of magnitude compared to pure aluminum. Doping with magnesium significantly retards the aluminum-water reaction, resulting in relatively steady hydrogen evolution rates. It is also shown that eGaIn permeates through aluminum as a line dislocation front.
These discoveries demonstrate that doping, grain refining and grain coarsening offer latitudes in the engineering of aluminum microstructures to tune hydrogen generation rates across three orders of magnitude and to tune the reaction efficiency. Using the results of this work, I provide a guide to the design/selection of aluminum for controllable hydrogen generation according to application. Lastly, while the corrosion of aluminum and its commercial alloys has been historically studied, results of this work show that the redox behavior of aluminum in the presence of eGaIn strays from what can be understood within the classical corrosion (galvanic theory) framework.
by Laureen Meroueh.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering
Love, Ryan. "A microstructural analysis of the effects of news on order flows and on price discovery in foreign exchange markets." Thesis, London School of Economics and Political Science (University of London), 2005. http://etheses.lse.ac.uk/1788/.
Повний текст джерелаMotaman, S. Amir H. [Verfasser], Wolfgang [Akademischer Betreuer] Bleck, Dierk [Akademischer Betreuer] Raabe, and Ulrich [Akademischer Betreuer] Prahl. "Modeling of the microstructural effects on the mechanical response of polycrystals / Seyedamirhossein Motaman ; Wolfgang Bleck, Dierk Raabe, Ulrich Prahl." Aachen : Universitätsbibliothek der RWTH Aachen, 2021. http://d-nb.info/1229991328/34.
Повний текст джерелаDavidson, Laura Christine. "Microstructural Characterization of LENSTM Ti-6Al-4V: Investigating the Effects of Process Variables Across Multiple Deposit Geometries." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright154505910306871.
Повний текст джерелаHecht, Matthew David. "Effects of Heat Treatments and Compositional Modification on Carbide Network and Matrix Microstructure in Ultrahigh Carbon Steels." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/1023.
Повний текст джерелаDini, Hoda. "As-cast AZ91D magnesium alloy properties : Effects of microstructure and temperature." Doctoral thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Material och tillverkning, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-38148.
Повний текст джерелаNumera finns det ett väsentligt behov av lätta, energieffektiva och miljövänliga tekniksystem. Detta behov är drivkraften för utveckling av ett brett utbud av material för energigenerering, energilagring, framdrivning och transport. Dessa utmaningar motiverade användningen av magnesiumlegeringar för lättviktskonstruktioner. Magnesium har en densitet på 1,74 g/cm3, vilket är ca 30% lägre än för aluminium, en fjärdedel av densiteten för stål och nästan i nivå med många polymerer. Då magnesiumlegeringar dessutom är lätta att återvinna, jämfört med polymerer, gör det dem miljömässigt attraktiva. Låga mekaniska egenskaper är den främsta orsaken till begränsad användning av dessa legeringar för lastbärande tillämpningar. Mg-Al-Zn-legeringen AZ91D uppvisar en utmärkt kombination av styrka, gjutbarhet och korrosionsbeständighet. Dess mekaniska egenskaper vid förhöjd temperatur, som tex kryphållfasthet, är låga. Dessutom är korrelationen mellan mikrostruktur och mekaniska egenskaper oklar. Denna avhandling syftade till att ge ny kunskap om mikrostrukturens roll för magnesiumlegeringars mekaniska egenskaper. Slutligen var materialets egenskaper i förhållande till processparametrar vid tillverkningen av stort intresse. En omfattande karaktärisering av kornstorleks-, sekundära dendritarmavstånds (SDAS)-fördelning och fraktion av Mg17Al12 utfördes med hjälp av optisk mikroskopering och diffraktion av bakåtspridda elektroner (EBSD). Mikrostrukturen korrelerades till sträckgränsen (Rp0.2), brottstyrkan och brottförlängningen. Det föreslogs att den intermetalliska fasen, Mg17Al12, spelar en viktig roll vid bestämning av legeringens mekaniska och fysikaliska egenskaper vid temperaturintervall från rumstemperatur upp till 190°C genom att bilda ett styvt nätverk av intermetaller. Uppkomsten av ett sådant nätverk stöddes genom en studie av den termiska expansionen av legeringen för olika fraktioner av Mg17Al12. En fysikalisk konstitutiv modell med ett brett giltighetsområde användes framgångsrikt för att beskriva det plastiska flytbeteendet hos AZ91D för olika mikrostrukturer. De temperaturberoende variablerna i modellen korrelerade ganska väl med materialets underliggande fysik. Modellen validerades genom att jämföra dislokationstätheten som predikterades av modellen och den med EBSD uppmätta dislokationstätheten. Påverkan av pressgjutningsparametrar på geometrisk tolerans och restspänning hos de gjutna komponenterna studerades. Vidare studerades geometrisk tolerans och restspänning av komponenter efter pening och målning. Intressant nog hade eftermatningsfasen en stor effekt på geometrisk tolerans och restspänningar. Dessutom hade temperaturen på den fasta formhalvan av verktyget även ett visst inflytande på komponentens geometriska tolerans och restspänning.
Mattiello, Adriana. "Visco-plasticity and damage modeling of single crystal superalloys at high temperatures : a tensorial microstructure-sensitive approach." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLN004/document.
Повний текст джерелаA 3D phenomenological model coupling viscoplasticity, microstructural evolutions and damage is proposed for Ni-based single crystal superalloys, which are widely used materials for high pressure turbine blade in helicopter engines. The anisotropy of the gamma'-rafting, the gamma'-coarsening and the dissolution of the hardening gamma' phase are modeled. A tensorial variable and its evolution law allow to describe the variation of the gamma channels. The modeling is based on the Kelvin decomposition of the elasticity tensor. This decomposition leads to a phenomenological multi-criterion description of the cubic visco-plasticity. A formulation based on the single crystal (visco-)plasticity framework is also proposed. A damage law of type dD/dt=… is introduced in order to model the tertiary creep stage and the ductility. A novel rate sensitive damage threshold is introduced in order to account for the rate sensitivity of the damage onset by visco-plasticity. An experimental study has been carried out on the CMSX-4 alloy, which is the material of main interest in this study, in parallel to the modeling work. Dissolution tests have been carried out to measure the gamma'-volume fraction variation with temperature. The deformation mechanisms of the CMSX-4 alloy have been observed by performing tensile creep tests at 1050°C and 850°C. These tests have also constituted a database for the model identification. Three tensile tests have been realized along the <111> crystal direction, two at constant strain rate and the third by varying the strain rate. Non-isothermal creep tests reproducing the 150h-type engine test have been performed on the MAATRE bench. EBSD and TEM analysis have been realized on the specimens oriented along the <011>, <011> and <112> crystal directions and crept at 850° C. These analysis have shown that micro-twinning governs the deformation along these crystal directions during creep at this temperature and at high stresses (> 400 MPa) for deformation in excess of 1-2%. Finally, the model (with and without damage) has been encoded in the ZéBuLoN Finite Element solver and structure computations have been performed