Dissertations / Theses on the topic 'Liquid Metal Alloys'
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Clegg, Richard Edward. "Liquid-metal embrittlement of metals and alloys." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260608.
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Barriga, Salvador A. (Salvador Aguilar). "An electrochemical investigation of the chemical diffusivity in liquid metal alloys." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81058.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 229-239).
The liquid metal battery has been shown to be a viable candidate for grid-scale energy storage, due to its fast kinetics and ability to be constructed from economically feasible materials. Various of the liquid metal couples that form high stable voltages, such as the calcium chemistries, are rate limited because they tend to form solid intermetallic compounds with high melting points. In order to understand and better engineer these batteries, the kinetic properties of these liquid alloys, in particular the chemical diffusivity, must be known accurately so that it can be used as input in computational simulations to avoid the nucleation of any solids. Unfortunately, the dominant experimental methods for measuring diffusion in liquid metals today are unreliable because the measurement timescales are on the order of days, require long capillaries susceptible to buoyancy-driven flow from temperature fluctuations, and composition analysis must be done ex-situ as a solid. To counter all these problems, a new and novel method for measuring the chemical diffusivity of metals in liquid alloys derived from electrochemical principles is presented in this thesis. This new method has the advantage of operating in shorter times scales of minutes rather than days, and requires the use of small capillaries which collectively minimize the effect of convectively-driven flow caused from temperature gadients. This new method was derived by solving the same boundary conditions required by the galvanostatic intermittent titration technique for solid-state electrodes. To verify the validity of the new theoretical derivation, the method was used to measure the chemical diffusivity of calcium in liquid bismuth within the temperature range of 550 - 700 'C using a three-electrode setup with a ternary molten salt electrolyte. Three compositions where studied (5% Ca-Bi, 10% Ca-Bi, and 15% Ca-Bi) for comparison. The chemical diffusion coefficient was found to range between (6.77 ± 0.21)x10- 5 cm 2/s - (10.9 ± 0.21)x10-5 cm 2/s at 5% Ca-Bi, (4.95 ± 0.65)x10- 5 cm2 /s - (7.93 ± 0.37)x10- 5 cm 2 /s at 10% Ca-Bi, and (6.22 ± 1.2)x10- 5 cm 2/s - (10.2 ± 0.26)x10- 5 cm 2 /s at 15% Ca-Bi which, to our knowledge, are the first successful measurements of calcium diffusivity in the liquid state. Arrhenius fits with good correlations revealed the activation energy for diffusion to be (21.4± 1.7) kJ/mol, (23.0± 2.4) kJ/mol, and (17.7 ±5.9) kJ/mol as the calcium concentration increased, which are in excellent agreement with literature published values and lie in the same range of 15-30 kJ/mol that is reported for most liquid metals. The chemical diffusivity value was then used as input in finite element simulations to model how convection affects the overall transport inside a 20-Ah liquid bismuth electrode under the influence of different thermal boundary conditions. Also, a phase field model was created to simulate the motion of the two interfaces inside a liquid metal battery during operation, which to our knowledge, is the first time phase field has been extended beyond two phases. Experimental kinetic values can then be used as input in these numerical models to help characterize and optimize the entire battery.
by Salvador A. Barriga.
Ph.D.
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Silva, M. P. "Oxidation of Aluminium-Magnesium alloys at elevated temperature in the solid, semi-liquid and liquid states." Thesis, Brunel University, 1987. http://bura.brunel.ac.uk/handle/2438/5417.
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Sensitive thermogravimetric equipment was used to monitor the oxidation rates of A1-1 to 9% Mg alloys in 0.21 oxygen/0.79 helium mixtures with and without 0.03 atm water vapour pressure, in the temperature range 500-725°C which include their respective solid, semi-liquid and liquid states. These measurements were supported by structural and topographical studies of oxide films using SEM, X-ray diffraction, and TEM with electron diffraction and EDX techniques. The objective was to provide information in the context of dross formation during melting operations. The only oxidation product observed was MgO. The oxidation rates do not follow simple rate laws. The rate normally increases as the temperature is raised except for a curious inverse relationship for liquid alloys just above the liquidus temperatures due to the formation of undulating surfaces. An amorphous MgO film formed on liquid alloys restricted the initial oxidation but, following an incubation period, crystallisation of the film induced breakaway oxidation. The crystallisation was promoted by high magnesium contents, high temperatures and moist atmospheres. The oxidation rates for alloys in the semi-liquid state were as follows: (i) for < 50% liquid, the rates were faster than those for wholly solid alloys due to preferential oxidation of magnesium-enriched liquid fractions along grain boundaries; (ii) for > 50% liquid, the rates were initially faster than those for wholly liquid alloys due to the presence of solid phase particles which acted both as disruptive stress-raisers and as sources of nuclei for crystallisation of the amorphous oxide film over the liquid phase. For the moist atmosphere: (i) wholly solid alloys and semi-liquid alloys with < 50% liquid oxidised initially faster but eventually slower than in the dry atmosphere. These effects are explained by enhanced initial oxidation but suppressed subsequent nucleation of tertiary MgO particles and by the injection of OH - ions into the oxide; (ii) wholy liquid alloys and semi-liquid alloys with > 50% liquid oxidised faster than in the dry atmosphere because of the injection of OH- ions into the oxide with consequent disruptive effects caused by hydrogen absorption by the alloy. The addition of 0.003% Be to Al-8% Mg alloy decreased the oxidation rate markedly by toughening the MgO films preventing cracking and hence the nucleation of tertiary MgO. Small additions of Mn or Zr offset the effect of Be and probably enhanced the Mg 2+ ion conductivity in the oxide by the 4+ injection of Mn 2+ , Mn 4+ or Zr ions. For alloys with Be, although breakaway eventually occurred it was not initiated by crystallisation of the amorphous film and moisture in the atmosphere increased the oxidation throughout the temperature range, 500-725°C.
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Bozack, Michael J. "Surface phenomena in liquid metal alloys with application to development of a liquid metal ion source of B and As /." Full text open access at:, 1985. http://content.ohsu.edu/u?/etd,76.
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Kart, Hasan Huseyin. "Molecular Dynamics Study Of Random And Ordered Metals And Metal Alloys." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605467/index.pdf.
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The solid, liquid, and solidification properties of Pd, Ag pure metals and especially PdxAg1-x alloys are studied by using the molecular dynamics simulation. The effects of temperature and concentration on the physical properties of Pdx$Ag1-x are analyzed. Sutton-Chen (SC) and Quantum Sutton-Chen (Q-SC) many-body potentials are used as interatomic interactions which enable one to investigate the thermodynamic, static, and dynamical properties of transition metals. The simulation results such as cohesive energy, density, elastic constants, bulk modulus, pair distribution functions, melting points and phonon dispersion curves obtained for Pd, Ag and PdxAg1-x are in good agreement with the available experimental data at various temperatures. The predicted melting points of Pd, Ag and their binary alloys by using Q-SC potential parameters are closer to experimental values than the ones predicted from SC potential parameters.
The liquid properties such as diffusion constants and viscosities computed from Q-SC potentials are also in good agreement with the available experimental data and theoretical calculations. Diffusion coefficients and viscosity results calculated from simulation obey the Arrhenius equation well. The coefficients of the Arrhenius equation are given in order to calculate the self-diffusion coefficient and shear viscosity of Pd-Ag alloys at the desired temperature and concentration.
Using different cooling rates, we investigate glass formation tendency and crystallization of Pd-Ag metal alloys, by analyzing pair distribution function, enthalpy, volume, and diffusion coefficient. Pd-Ag alloys show the glass structure at fast cooling rates while it crystallizes at slow cooling rates. Glass and crystallization temperatures are also obtained from the Wendt-Abraham parameter. The split of the second peak in the pair distribution function is associated with the glass transition. Glass forming ability increases with increasing concentration of Ag in Pd-Ag alloys.
Thermal and mechanical properties of Cu, Au metals and their ordered intermetallic alloys Cu3 Au(L12), CuAu(L10), and CuAu3(L12) are also studied to investigate the effects of temperature and concentration on the physical properties of Cu-Au alloys. The simulation results such as cohesive energy, lattice parameter, density, elastic constants, bulk modulus, heat capacity, thermal expansion, melting points, and phonon dispersion curves are in good agreement with the available experimental and theoretical data at various temperatures.
The Q-SC potential parameters are more reliable in determining physical properties of metals and their random and ordered alloys studied in this work
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Fassler, Andrew L. "Application of Liquid-Metal GaIn Alloys to Soft-matter Capacitance and Related Stretchable Electronics." Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/737.
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Stretchable electronics is an exciting new field of developing technology, allowing devices to undergo large deformations such as, bending, twisting, stretching and compression. As such, they can be easily interfaced with the human body, conforming to its contours and enabling a range of advances in electronic skins. Creating stretchable circuits, however, is not straight forward, as most electrically conductive materials are rigid. Because of this, researchers have developed a number of methods in which conductive materials can support deformation. These include deterministic architectures (e.g. wavy circuits), polymer composites, and electrically conductivid fluids. The focus of this work is the latter technique, utilizing highly conductive gallium-indium (GaIn) metal alloys. Since they are liquid at room temperature, these metals are inherently deformable with no defined shape, and can create highly stretchable electronics when encapsulated within an elastomer. Using these materials, we target stretchable capacitance and related technologies, with capacitive elements playing a vital role in modern electronics and sensors. A family of highly stretchable micro uidic planar capacitors and inductors are introduced, which can be elongated by at least 200% of their initial length. The capacitance-strain response is examined using kinematic modeling and through experiment, and shows that these devices are viable as softmatter strain gauges. Next, new fabrication methods are introduced that incorporate freezing of the GaIn alloys. This enables the creation of tall, 3D circuit features that can be used to tune the capacitance of a given device. Additionally, freezing improves the ease with which the metal can be handled, manipulated, and altered. Conductive materials can be incorporated into polymers, creating composites with improved permittivity, which in turn will improve capacitance. By using GaIn alloys as the conductive inclusion and forming liquid metal embedded elastomers, highly stretchable dielectric materials can be fabricated. These composites can be elongated to as high as 600% strain and with dielectric improvements of over 400%. Continued advances of GaIn based technology can enable inherently compliant electronic skins and soft capacitive sensor arrays that can be incorporated into stretchable bio-compatible devices or bio-mimetic robots.
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Rhamdhani, Muhammad Akbar Brooks Geoffrey. "Reaction kinetics and dynamic interfacial phenomena in liquid metal-slag systems." *McMaster only, 2005.
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Higashino, Shota. "Electrodeposition of reactive metals and alloys from non-aqueous electrolytes and their applications." Kyoto University, 2020. http://hdl.handle.net/2433/259066.
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Ozdemir, Kart Sevgi. "Physical Properties Of Pd, Ni Metals And Their Binary Alloys." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604914/index.pdf.
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The Sutton Chen and quantum Sutton Chen potentials are used in molecular dynamics simulations to describe the structural, thermodynamical, and transport properties of Pd, Ni and their binary alloys in solid, liquid, and glass phases. Static properties including elastic constants, pair distribution function, static structure factor, and dynamical properties consisting of phonon dispersion relation, diffusion coefficient, and viscosity are computed at various temperatures. The melting temperatures for Pd-Ni system are obtained. The transferability of the potentials is tested by simulating the solid and liquid states. The eutectic concentration Pd0.45Ni0.55 is quenched at four different cooling rates. The system goes into glass formation at fast cooling rates, while it evolves to crystal at slow cooling rate. Comparison of calculated structural and dynamical properties with the available experiments and other calculations shows satisfactory consistency.
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Wei, Shuai, Garrett J. Coleman, Pierre Lucas, and C. Austen Angell. "Glass Transitions, Semiconductor-Metal Transitions, and Fragilities in Ge-V-Te (V = As, Sb) Liquid Alloys: The Difference One Element Can Make." AMER PHYSICAL SOC, 2017. http://hdl.handle.net/10150/624356.
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Glass-transition temperatures (T-g) and liquid fragilities are measured along a line of constant Ge content in the system Ge-As-Te, and contrasted with the lack of glass-forming ability in the twin system Ge-Sb-Te at the same Ge content. The one composition established as free of crystal contamination in the latter system shows a behavior opposite to that of a more covalent system. The comparison of T-g vs bond density in the three systems Ge-As-chalcogen differing in chalcogen, i.e., S, Se, or Te, shows that as the chalcogen becomes more metallic, i.e.,in the order S < Se < Te, the bond-density effect on T-g becomes systematically weaker, with a crossover at < r > = 2.3. When the more metallic Sb replaces As at < r > greater than 2.3, incipient metallicity rather than directional bond covalency apparently gains control of the physics. This observation leads us to an examination of the electronic conductivity and then semiconductor-to-metal (SC-M) transitions, with their associated thermodynamic manifestations in relevant liquid alloys. The thermodynamic components, as seen previously, control liquid fragility and cause fragile-to-strong transitions during cooling. We tentatively conclude that liquid-state behavior in phase-change materials is controlled by liquid-liquid (LL) and SC-M transitions that have become submerged below the liquidus surface. In the case of the Ge-Te binary, a crude extrapolation toGeTe stoichiometry indicates that the SC-Mtransition lies about20% belowthe melting point, suggesting a parallel with the intensely researched "hidden liquid-liquid transition" in supercooled water. In the water case, superfast crystallization initiates in the high-fragility domain some 4% above the LL transition temperature (T-LL) which is located at approximately 15% below the (ambient pressure) melting point.
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Antipas, George. "A study of the spray forming of Al-Li alloys." Thesis, University of Surrey, 1995. http://epubs.surrey.ac.uk/843719/.
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The atomization and spray forming of liquid metals was studied. Melt break up algorithms were developed to predict the size distribution of the spray generated as well as secondary aspects of the atomization phenomena. In the model, which is based on the Surface Wave Formation (SWF) theory, the relative velocity between the gas and melt phase was thought to induce a sinusoidal disturbance on the surface of the melt column. Depending on the flow conditions such a disturbance could grow in amplitude and cause certain parts of the surface to be torn off the liquid column. A number of different approaches to the problem of drop disintegration were also considered. Based on experimental observations of the critical Weber number made by other authors, a criterion was formulated, which allowed the secondary break up of drops to be predicted. In addition, an analytical model originally presented by Wolf and Andersen (1965), which was intended to describe the stripping mode of secondary disintegration, was also revised and incorporated into a computer routine. Finally a comparison of the models was made against the predictions of the empirical Lubanska (1970) equation. High Speed Photography studies of a water column atomized by gas revealed that the formation of a surface wave was the prominent mechanism perturbing and finally disintegrating the column into a fine spray of drops. Phase Doppler Anemometry studies of the water/gas jet produced during the atomization of a water column indicated that there was a gradient of particle sizes across the spray. The finer fragments were found in the close proximity of the centre axis of the conical flow, with particles becoming larger in size as the distance from the centre increased. Vaporization of the water drops near the centre due to the high gas velocities should be taken into account when interpreting these results. The break up algorithms were tested against experimental data for a number of different A1 and Fe alloys with various solute elements, obtained using a close coupled atomization facility. Case studies were made for the effects of gas injection pressure, initial melt stream diameter, initial melt stream exit velocity and number of atomizing gas jets on the mean powder particle size produced. The algorithms could predict the distribution of drop sizes in space, a feature that enabled the simulation of spray forming runs and the direct comparison of the numerical predictions to experimental data. The shapes of the Al-1.6wt%Hf and the Al-1.6wt%Hf-3.2wt%Li alloy preforms and the particle distribution along the radial direction of the Al-1.6wt%Hf preform were calculated and compared favourably with experimental data. Microscopic observation of Al-1.6wt%Hf and Al-1.6wt%Hf-3.2wt%Li preforms indicated that there was a variance of particle size as well as grain size along the radial direction of the spray. The grain size was found to decrease with increasing distance from the central axis of the preform, while the radial distribution of drop diameters did not reveal a distinct trend.
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Cao, Xinjin. "Heat treatment of liquid metal : precipitation and sedimentation processing of liquid Al-11.5Si-0.4Mg alloy." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369168.
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Thews, Jonathan Tyler. "Design and Analysis of L-Band Reconfigurable Liquid-Metal Alloy Antennas." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78007.
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Efficient reconfigurable antennas are highly sought after in all communication applications for the ability to reduce space cost while maintaining the ability to control the frequency, gain, and polarization. The ability to control these parameters allows a single antenna to maximize its performance in a wide range of scenarios to satisfy changing operating requirements. This thesis will describe reconfigurable antennas using liquid-metal alloys that give the system this ability by injecting or retracting the liquid metal from various channels. After simulations were performed in an electromagnetic simulation software, proof-of-concept models were built, tested, and compared to the simulations to verify the results.Master of Science
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Krishnardula, Venu Gopal. "Transient liquid phase bonding of ferritic oxide dispersion strengthened alloys." Auburn, Ala., 2005. http://repo.lib.auburn.edu/2005%20Fall/Dissertation/KRISHNARDULA_VENU_19.pdf.
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Forté, Martin. "Modélisation de l'écoulement de l'aluminium semi-solide dans le moulage sous pression /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2006. http://theses.uqac.ca.
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Thèse (M.Eng.) -- Université du Québec à Chicoutimi, 2006.La p. de t. porte en outre: Mémoire présenté à l'Université du Québec à Chicoutimi comme exigence partielle de la maîtrise en génie. CaQCU Bibliogr.: f. [142-145]. Document électronique également accessible en format PDF. CaQCU
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Cherne, Frank Joseph. "Calculation of transport properties of liquid metals and their alloys via molecular dynamics." Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/284305.
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The advanced casting modeler requires accurate viscosity and diffusivity data of liquid metals and their alloys. The present work discusses the use of equilibrium and non-equilibrium molecular dynamics techniques to obtain such data without having to rely on oversimplified phenomenological expressions or difficult and expensive experiments. Utilizing the embedded atom method (EAM), the viscosities and diffusivities for a series of equilibrium and non-equilibrium molecular dynamics simulations of nickel, aluminum, and nickel-aluminum alloys are presented. A critical comparison between the equilibrium and non-equilibrium methods is presented. Besides the transport properties, structural data for the liquids are also evaluated. EAM does a poor job of describing the transport properties of nickel-aluminum alloys, particularly near the equiatomic concentration. It has been suggested that charge transfer between nickel and aluminum atoms is responsible for the discrepancy between numerical calculations and available experimental data. A modified electronic distribution function has been developed to simulate the charge transfer associated with compound formation. The effects of such a "charge transfer" modification to the embedded atom method are evaluated. The results of these simulations indicate that the embedded atom method combined with molecular dynamics may be used as a method to predict reasonably the transport properties.
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Saha, Deepak. "Novel Processing Methods and Mechanisms to Control the Cast Microstructure in Al Based Alloys - 390 and Wrought Alloys." Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-041405-150300/.
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Malra, Gurjinder Kaur. "X-ray photoelectron spectroscopic studies of certain metals and alloys through the solid/liquid transition." Thesis, Brunel University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328949.
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Ponchet, Anne. "Etude des systèmes de fermions lourds UPt3 et CeRu2Si2 à haute pression : régime liquide de Fermi et phase polarisée sous champ magnétique." Grenoble 1, 1987. http://www.theses.fr/1987GRE10014.
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Mesures, sous tres haute pression, de la resistivite et de l'aimantation de deux composes a fermions lourds ceru::(2)si::(2) et upt::(3). Les mesures de transport ont ete realisees de 300 k a 1 k pour upt::(3) et jusqu'a 30 mk pour ceru::(2)si::(2). Mesure de la magnetoresistance de ceru::(2)si::(2) a 4,2 k jusqu'a 19 t et de son aimantation entre 4,2 k et 40 k
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Coruh, Ali. "Molecular-dynamics Investigation Of The Dynamic Properties Of Pd And Al Metals, And Their Alloys." Phd thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/12604716/index.pdf.
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The dynamic properties of Palladium (Pd) and Aluminum (Al) metals and their alloys are investigated by means of Molecular Dynamics using the Quantum Sutton-Chen force field in five different concentrations. Calculations have been carried out for liquid structures. Although this study is done for liquid structures, basic solid state properties are also investigated to prove the validity of potential parameters. Results are compared with each other and with experimental, theoretical and simulated results. Liquid state transferability of Quantum Sutton-Chen parameters have been investigated and discussed. High temperature properties, which are not easy to work experimentally, are simulated and high temperature behavior of Pd-Al alloy is investigated.
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Hans, Stéphane. "Modélisation des transferts couplés de chaleur, de soluté et de quantité de mouvement lors de la refusion à l'arc sous vide (VAR) : application aux alliages de titane." Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL023N.
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L’objectif de ce travail est la modélisation mathématique et numérique du procédé de refusions à l'arc sous vide (VAR), dans le but d'optimiser la refusion d'alliages de titane chargés. En effet, l'intervalle de solidification important de ces alliages les rend sensibles à la formation de défauts de solidification liés à la circulation du liquide interdendritique. Dans le cadre de cette étude, des mesures effectuées par analyse thermique différentielle (ATD) ont permis de quantifier les intervalles de solidification de ces alliages de titane. Le modèle développé décrit les transferts couplés de chaleur, de soluté et de quantité de mouvement en écoulement turbulent, lors de la croissance et de la solidification du lingot VAR. Les transferts au sein de la zone pâteuse sont explicitement pris en compte, celle-ci étant assimilée à un milieu poreux. Le modèle relie directement les paramètres opératoires aux profils de puits liquide, à l'hydrodynamique du bain métallique (convection thermosolutale et forces électromagnétiques) ainsi qu'à l'intensité de la ségrégation dans le lingot. Les simulations effectuées concernent une fusion en four pilote d'un lingotin de titane marqué au cuivre, ainsi que deux fusions industrielles de [Bêta]Cez. Elles ont permis de mettre en évidence l'effet du brassage électromagnétique sur l'écoulement complexe du métal liquide. La prise en compte des transferts au sein de la zone pâteuse permet également de mieux comprendre les phénomènes à l'origine de la macroségrégation. Il apparait que les conditions de brassage des fusions de [Bêta]Cez simulées ont une influence considérable sur l'intensité de la macroségrégation, et donc sur le risque d'apparition de défauts de solidification. Le mécanisme de formation de défauts du type canaux ségrégés, a également été mis en évidence. Dans le cas du [Bêta]Cez, il a été attribué à la convection solutale ascendante de métal liquide fortement appauvri en molybdène. Le modèle peut ainsi être utilisé avec profit afin de choisir les conditions de fusion permettant de minimiser la macroségrégation et donc le risque de formation de défauts
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Holford, W. David (William David). "A measurement technique for refractory erosion/corrosion in molten metals /." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63327.
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Kilian, Rolf. "From cuprates to manganites: spin and orbital liquids." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 1999. http://nbn-resolving.de/urn:nbn:de:swb:14-994411393875-11016.
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Both cuprates and manganites belong to the transition metal oxides. The physics of these compounds is characterized by a dualism of local electron interaction and itinerant charge motion. In the present work, several key issues of metallic cuprates and manganites are addressed on a theoretical level, while close connection to recent experimental work is kept. The work is based on the notion of spin and orbital liquids, representing elegant tools to handle the strongly correlated nature of the metallic state in an efficient and transparent manner. A concise introduction to the physics of cuprates and manganites as well as to the methods employed is presented at the beginning of the work. In a subsequent part, we show that the peculiar magnetic response of metallic cuprates upon impurity doping can be successfully explained within a spin-liquid picture. The remainder of the work is devoted to the metallic state of manganites. Elaborating on the notion of an orbital liquid, the interplay of electron correlations, orbital degeneracy, and double exchange is studied. Thereby, the unconventionally large incoherent optical spectrum of metallic manganites and the pronounced softening of the magnon spectrum observed in experiment can be explained. Finally, a theory of the metal-insulator transition of manganites is presented which is based upon the newly introduced notion of orbital polarons. In general, we believe the close agreement of our results with experiment to strongly support the validity of our approach, giving new insight into the spectacular and sometimes as-tonishing physics of transition metal oxides.
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Shi, Hao [Verfasser], and R. [Akademischer Betreuer] Stieglitz. "Alumina forming alloys (steels, high entropy materials) for the mitigation of compatibility issues with liquid metals and steam in energy related, high-temperature applications / Hao Shi ; Betreuer: R. Stieglitz." Karlsruhe : KIT-Bibliothek, 2020. http://d-nb.info/1205807675/34.
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Christopher, Petersson. "Erosion-Corrosion experiments on Steels in liquid lead and Development of Slow Strain Rate testing rig." Thesis, KTH, Kärnenergiteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-261611.
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CHERRE, JEAN-PIERRE. "Contribution a l'etude de la production de poudres metalliques par atomisation centrifuge de metal ou alliage liquides." Clermont-Ferrand 2, 1989. http://www.theses.fr/1989CLF2D217.
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Etude de la formation de gouttelettes par atomisation centrifuge dans le cas de l'eutectique bismuth-etain. On montre que pour 25% environ de la poudre produite, la taille des particules spheriques peut etre prevue sur la base d'un mecanisme de centrifugation pure. Mise en evidence qualitative de l'effet des chocs entre particules et de l'effet de l'erosion aerodynamique du metal liquide s'ecoulant sur le disque
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Lorrain, Vincent. "Influence des proprietes capillaires sur la corrosion du tungstene par des metaux liquides." Grenoble INPG, 1996. http://www.theses.fr/1996INPG0099.
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Nous etudions les phenomenes de mouillage, d'infiltration capillaire et de penetration intergranulaire de depots de tungstene projetes plasma par l'alliage eutectique u-fe sous vide secondaire. Les principaux parametres explores sont la microstructure du tungstene, la chimie de surface du tungstene et la duree des essais. Des essais de goutte posee realises dans les systemes cu/w et cu-ag/w nous ont permis de qualifier, in situ, la chimie de surface des substrats. Nous montrons que l'infiltration du w projete plasma par le cuivre liquide depend de facon critique de la chimie de surface des parois capillaires (oxyde w#3o herite de l'elaboration) l'alliage u-fe mouille bien le tungstene (=30) et peut de ce fait infiltrer differents types de defauts : les defauts de planeite preexistant sur la surface du tungstene, la porosite ouverte presente dans le tungstene projete plasma et les joints de grains. Des traitements thermiques prealables de grossissement des grains permettent de limiter la penetration intergranulaire du liquide. Ces traitements se sont cependant reveles insuffisants pour proteger le w plasma de la corrosion par l'alliage u-fe qui se traduit par une destruction du squelette solide. Des traitements d'oxydation conduisant a un recouvrement des parois capillaires par des couches d'oxydes wo#n ne nous ont pas permis de proteger le w plasma de la corrosion par l'alliage u-fe car l'oxyde uo#2, forme par reduction de l'oxyde de tungstene, s'est avere non adherent et par consequent non protecteur.
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Chen, Shu. "FePt magnetic nanoparticles : syntheses, functionalisation and characterisation for biomedical applications." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/2151.
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Iron platinum (FePt) has attracted growing interest because of its high Curie temperature, magneto-crystalline anisotropy and chemical stability. Nanoparticles (NPs) made of this alloy are promising candidates for a wide range of biomedical applications including magnetic separation, magnetic targeted drug delivery, hyperthermia for cancer therapy and also as magnetic resonance imaging (MRI) contrast agents. This thesis presents the synthesis, functionalization and characterization of FePt NPs along with a toxicity study and an investigation into their application as MRI contrast agents. Regarding their synthesis, different approaches have been explored including the co-reduction of Fe and Pt precursors in an aqueous media, the thermal decomposition in a conventional high-boiling solvent such as benzyl ether, and in low-melting organic salts (ionic liquids). The data revealed an inhomogeneous composition distribution of Fe and Pt between particles obtained in aqueous media, due to the iron salts hydrolysis, and a mismatch in the co-reduction kinetic of the two metal precursors. While the iron content in the NPs could be increased by using more hydrolytically stable iron precursors or stronger reducing agents, there are remaining limiting parameters which prevent further Fe content increase in NPs. In contrast, by excluding the water from the reaction system and using a Fe²⁻ iron precursor, homogenous 1:1 Fe to Pt ratio NPs can be obtained through a modified thermal decomposition pathway in benzyl ether. Based on the study of synthesis in this conventional chemical, the potential of ionic liquids (ILs) to be used as novel solvents for FePt NPs synthesis was further explored. It was then demonstrated that ionic liquids (ILs) can not only be used as a solvent for synthesis of FePt NPs, but also can provide an exciting alternative pathway to direct synthesis fct-FePt NPs. In the context of the bioapplication of FePt NPs, a family of FePt NPs was specifically designed to enhance their MRI contrast agents properties. In contrast with previous reports, this thesis demonstrates that FePt NPs can be made non-toxic and provides the first data on their cellular uptake mechanisms. A six times increase in the FePt based T₂ contrast properties compared to clinical iron oxide NPs is reported. The relationship between the MRI contrast properties and the NPs architecture is explored and rationalised as the basis for the design of NPs as enhanced MRI contrast agents. Finally, the first observations of cellular and in vivo MR imaging with FePt NPs is also reported. This study opens the way for several applications of FePt NPs such as regenerative medicine and stem cell therapy, thus providing a bio-platform to develop novel diagnostic and therapeutic agents.
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Spinelli, Jose Eduardo. "Influencia da convecção no liquido nas variaveis termicas e estruturais na solidificação descendente de ligas Sn-Pb." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265085.
Full textAbstract:
Orientador : Amauri GarciaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Poucos estudos têm analisado os efeitos da convecção no líquido interdendrítico, bem como a influência da direção de crescimento em relação à gravidade nas variáveis térmicas e estruturais durante a solidificação. Neste trabalho, foi utilizado um dispositivo de solidificação unidirecional vertical descendente, constituído por uma lingoteira de aço inoxidável com diâmetro interno de 60 mm, 157 mm de comprimento e 9 mm de espessura. Na parte superior, foi posicionada uma câmara de refrigeração a água do mesmo material do molde e com espessura útil de 3,0 mm. Após a obtenção dos lingotes e registrados os respectivos perfis térmicos experimentais, foram determinadas as variáveis térmicas de solidificação: coeficiente de transferência de calor metal/molde, velocidades de deslocamento da isoterma liquidus, gradientes térmicos e taxas de resfriamento para a solidificação unidirecional descendente de ligas hipoeutéticas do sistema Sn-Pb (Sn5%Pb, Sn15%Pb e Sn20%Pb). Estas variáveis térmicas são confrontadas com as previsões teóricas de um modelo numérico de solidificação e, em seguida, correlacionadas com os parâmetros estruturais: espaçamentos dendríticos primários, secundários e transição colunar/equiaxial (TCE). Dessa forma, são determinadas equações experimentais de crescimento para a solidificação descendente e verificado um critério de previsão da TCE. Realiza-se também uma análise comparativa dos presentes resultados com aqueles obtidos para solidificação vertical ascendente de ligas de mesma composição. Os resultados comparativos mostram que o efeito convectivo estimula a ocorrência da TCE e ainda é responsável por uma sensível redução dos espaçamentos dendríticos primários. As previsões teóricas de modelos de crescimento dendrítico representativos da literatura são confrontadas com os resultados experimentais
Abstract: Only a few studies have reported influences of interdendritic convection and growth direction on dendrite arm spacings. A downward directional solidification apparatus was used having a stainless steel split mold with an internal diameter of 60 mm, height 157 mm and a 9 mm wall thickness. The upper part of the split mold was closed with a water-cooling chamber made of stainless steel, with a wall thiclmess of 3 mm. A combined theoretical and experimental approach is developed to quantitatively determine the solidification thermal parameters: transient heat transfer coefficients, tip growth rates, thermal gradients and cooling rates during downward unsteady state solidification ofhypoeutectic Sn-Pb alloys. The resulting thermosolutal convection can start in the melt both within the interdendritic region and ahead of the dendrite array. The experimental results have shown that melt convection may be causing pileup of fractioned dendritic arms, which must stimulate the CET occurrence. The results have supported a criterion recently proposed based on a critical tip cooling rate. For upward unidirectional condition this critical value was found to be about 0.014 K/s for hypoeutectic Sn-Pb alloys. In the present study, in conditions of downward solidification, melt convection seems to favor the structural transition, which is anticipated and occurs for a critical cooling rate of about 0.03 K/s, for any of three hypoeutectic alloys experimentally examined. Primary dendritic arm spacings have been affected by the direction of growth, decreasing in conditions of downward vertical solidification when compared with those grown vertically upwards. The main predictive theoretical models for dendritic spacings are compared with the experimental observations
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica
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NASCIMENTO, JAMIL A. do. "Avaliacao neutronica de reator carregado com combustivel metalico e refrigerado por chumbo." reponame:Repositório Institucional do IPEN, 2000. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10789.
Full textAbstract:
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
31
Schwartz, Frédéric. "Etude des parametres d'elaboration de rubans amorphes par la methode du flot planaire : influence d'elements de substitution sur les proprietes d'un alliage amorphe fe::(79)b::(16)si::(5)." Paris 6, 1986. http://www.theses.fr/1986PA066574.
Full textAbstract:
Description de la methode de filage depuis l'etat liquide. Influence des parametres de fabrication sur la qualite micrographique des rubans amorphes de composition donnee. Application de cette methode a l'amorphisation de l'alliage ferromagnetique fe::(79)b::(16)si::(5). Effet de la substitution de differents elements sur les temperatures de cristallisation et de curie de l'alliage ferromagnetique
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Meyer, Nadège. "Simulation numérique de la viscosité de liquides : effets des paramètres d'interaction, de la température et de la pression sous conditions ambiantes et extrêmes." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0293/document.
Full textAbstract:
Ce travail est consacré à l'étude de la viscosité de cisaillement par simulation numérique de dynamique moléculaire classique à l'équilibre avec une attention particulière à l'influence des hautes pressions sur cette propriété. La viscosité est obtenue à partir des trajectoires générées par ces simulations et en appliquant la formule de Green-Kubo. Un large panel de systèmes a été étudié, allant de fluides atomiques purs à un liquide moléculaire, en passant par des mélanges binaires. En premier lieu, nous nous sommes focalisés sur les métaux alcalins. La conclusion majeure de cette étude est que la viscosité des alcalins a un comportement universel sur une large plage du diagramme de phases. Par ailleurs, sur cet intervalle, la relation universelle que nous avons proposée permet de prédire la valeur de la viscosité de n'importe quel élément avec une incertitude inférieure à 10%. La validité de la relation de Stokes-Einstein, reliant le coefficient d'autodiffusion à la viscosité, a également été vérifiée. Une étude systématique a ensuite été menée sur des mélanges modèles de type Lennard-Jones an de tester l'influence des paramètres d'interaction sur le comportement de la viscosité. Une estimation théorique basée sur le modèle de fluide effectif pur a été proposée. D'autre part, la relation de Stokes-Einstein a été étendue aux mélanges avec succès. Ces observations ont été confrontées aux cas de deux alliages réels : K-Cs et Li-Bi. Pour finir, une étude préliminaire a été entreprise sur l'eau en modélisant les interactions par deux potentiels : SPC/E, non polarisable, et BK3, polarisable. L'effet de l'introduction de la polarisabilité sur le calcul de la viscosité a été étudié. La validité des relations de Stokes-Einstein et de Stokes-Einstein-Debye, faisant intervenir la rotation de la molécule, a été évaluée à très haute pressionThis work is devoted to the study of the shear viscosity by numerical simulation of equilibrium classical molecular dynamics with a particular attention to the influence of high pressures on this property. From trajectories generated by these simulations and using the Grenn-Kubo formula, the viscosity is obtained. A broad range of systems has been studied, covering from pure atomic fluids to a molecular liquid, as well as binary mixtures. First, we focused on alkali metals. The main outcome of this study is that the viscosity of these metals has a universal behavior over a wide range of phase diagram. Furthermore, over this interval, the universal relation that we have proposed permits the prediction of the viscosity value of any elements with an uncertainty lower than 10%. The validity of the Stokes-Einstein relation, connecting the self-diffusion coefficient and the viscosity, has also been verified. Then, a systematic study has been carried out on model mixtures of Lennard-Jones fluids to test the influence of interaction parameters on the viscosity behavior. A theoretical estimation based on the effective one-component fluid model has been proposed. Moreover, the Stokes-Einstein relation has been successfully extended to mixtures. These observations have been compared with two real alloys: K-Cs and Li-Bi. Lastly, a preliminary study on water has been undertaken by modeling the interactions with two models: SPC/E, non-polarizable and BK3, polarizable. The effect of the introduction of the polarizability on the viscosity has been studied. The validity of Stokes-Einstein and Stokes-Einstein-Debye, involving the rotation of the molecule, has been evaluated under very high pressure
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Khatim, Othmane. "Contribution à la compréhension et à la maîtrise du procédé d'atomisation de jets métalliques liquides." Phd thesis, Université de Technologie de Belfort-Montbeliard, 2011. http://tel.archives-ouvertes.fr/tel-00703182.
Full textAbstract:
La demande croissante de poudres d‟alliages métalliques aux propriétés spécifiques utilisées en particulier en projection thermique et fabrication rapide pousse les chercheurs à améliorer et à optimiser sans cesse les procédés de production de ces poudres. L‟objectif affiché sur ces procédés est de maîtriser à la fois morphologie/ distribution de taille des particules produites et coût de fabrication. Actuellement, la majorité de ces poudres est produite par des procédés d‟atomisation par fluide et essentiellement par le procédé d‟atomisation gazeuse. Parmi ces procédés, le procédé Nanoval utilisant une buse "De Laval" est l‟un des plus performants en termes de distribution granulométrique et de rendement.L‟objectif principal de ce travail de thèse vise à améliorer la compréhension des phénomènes physiques mis en jeu par le procédé Nanoval afin d‟en optimiser le fonctionnement. Deux approches composent ce travail :- une partie numérique de modélisation sous Fluent. Deux modèles ont été étudiés, un modèle monophasique relatif à l‟écoulement gazeux dans l‟unité d‟atomisation (passage de l‟autoclave à la chambre d‟atomisation) et un modèle diphasique relatif à la constriction du filament de métal liquide en sortie de buse de coulée. Cette étude numérique a permis de mettre en évidence l‟effet des paramètres opératoires tels que la pression d‟atomisation et le diamètre de la buse de coulée sur la dynamique du jet de gaz, sur la striction du filament de métal liquide ainsi que les zones de forte pression et de haute vitesse avant, pendant et après la désintégration du filament métallique.- une partie expérimentale pour laquelle la mise en place d‟outils de diagnostic in-situ a été nécessaire pour la caractérisation du procédé en cours de fonctionnement. Trois analyses ont été conduites. La première renseigne de la dynamique du jet d‟atomisation évaluée à partir de mesures de Vélocimétrie par Images de Particules (PIV) à proximité de la sortie de la buse De Laval. La deuxième concerne les caractéristiques à l‟écrasement des particules sur un substrat placé dans la chambre d‟atomisation. La troisième et dernière analyse porte sur les propriétés des particules produites et la comparaison avec la matière récupérée après refroidissement dans l‟autoclave. Différents paramètres opératoires ont été explorés (pression d‟atomisation, diamètre de la buse de coulée, pression dans la chambre d‟atomisation, nature du métal) et reliés à leur influence sur la vitesse et le diamètre des particules. Des relations directes entre les résultats de ces trois analyses ont pu être démontrées ainsi qu‟une bonne adéquation entre résultats expérimentaux et résultats issus de la modélisation.
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Stiehler, Martin. "Strukturelle und elektronische Eigenschaften binärer amorpher Aluminiumlegierungen mit Übergangsmetallen und Metallen der Seltenen Erden." Doctoral thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-83708.
Full textAbstract:
Der Einfluss der d-Zustände der Übergangsmetalle auf die Strukturbildung in amorphen Legierungen ist bisher nur unzureichend verstanden. Die vorliegende Arbeit hat zum Ziel, zusätzliche Beiträge zum Verständnis am Beispiel binärer amorpher Aluminiumlegierungen mit Übergangsmetallen zu erarbeiten. Speziell standen dabei Legierungen mit einer Untergruppe der Übergangsmetalle, den Metallen der Seltenen Erden, im Vordergrund. Im Rahmen der vorliegenden Arbeit wurden Schichten von Al-Ce im Bereich von 15at%Ce-80at%Ce durch sequentielle Flash-Verdampfung bei 4,2K im Hochvakuum hergestellt und durch Messungen des elektrischen Widerstands und des Hall-Effekts elektronisch, sowie durch Transmissionselektronenbeugung strukturell charakterisiert. Ergänzend wurden Untersuchungen der Plasmaresonanz mittels Elektronenenergieverlustspektroskopie durchgeführt. Im Bereich 25at%Ce-60at%Ce entstanden homogen amorphe Proben. Besonders die Strukturuntersuchungen wurden durch eine Oxidation des Materials erschwert. Der Einfluss der Ce-4f-Elektronen manifestiert sich vor allem im Tieftemperatur- und Magnetowiderstand, die beide vom Kondo-Effekt dominiert werden. Der Hall-Effekt in Al-Ce wird im gesamten untersuchten Temperaturbereich (2K-320K) von anomalen Anteilen dominiert, welche skew-scattering-Effekten, ebenfalls aufgrund der Ce-4f-Elektronen, zugeschrieben werden. Bis hinunter zu 2K trat keine makroskopische magnetische Ordnung auf. Im Bereich 2K-20K wird auf das Vorliegen von Clustern geordneter magnetischer Momente geschlossen. Für T>20K tritt paramagnetisches Verhalten auf. Hinsichtlich der strukturellen und elektronischen Eigenschaften lässt sich a-Al-Ce in eine Gruppe mit a-Al-(Sc,Y,La) einordnen. Im Sinne der Plasmaresonanz ordnet sich a-Al-Ce exzellent in eine von anderen Al-Übergangsmetalllegierungen bekannte Systematik ein. Weiterhin wurde, durch Hinzunahme von Ergebnissen zu binären amorphen Al-Übergangsmetalllegierungen aus der Literatur, gefunden, dass die Strukturbildung in diesen Systemen eng mit einem bekannten, jedoch noch ungeklärtem Strukturbildungseffekt verknüpft ist, der in flüssigen reinen Elementen auftritt. Dieser hat dort zum Ziel, eine Resonanz zwischen der statischen Struktur und dem elektronischen System aufzubauen, die mit einer mittleren Valenz von 1,5 Elektronen pro Atom verknüpft ist. Speziell die Strukturen der untersuchten amorphen Al-Seltenerdlegierungen sind über große Konzentrationsbereiche ebenfalls mit einer mittleren Valenz von 1,5 Elektronen pro Atom korreliert.
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Geldenhuis, Jacobus Marthinus Andreas. "Development of electrochemical sensing techniques for the determination of activity-composition relations in liquid alloys and slags at 1873 K." Thesis, 1991. http://hdl.handle.net/2263/42448.
Full textAbstract:
A plug-type oxygen probe containing a magnesia stabilized solid zirconia electrolyte
rod, was developed. This oxygen sensor was evaluated in the Fe-Cr-0 system at
1873 K by determining the Raoultian chromium and Henrian oxygen activities of an
Fe-Cr alloy which was in equilibrium with pure Cr20 3 and a Cr20rsaturated liquid
slag respectively. However, the slag reacted with the oxygen probe and therefore,
a crucible assembly was developed to prevent direct contact between the slag and the
oxygen sensor. The results obtained with this crucible assembly proved that no
interaction between the oxygen probe and slag occurred and that the smaller
slag/metal interface did not effect equilibrium between the slag and the metal.
The Raoultian chromium activities of the Fe-Cr alloy containing 5 to 25% chromium
determined in this study, deviate negatively from ideal Raoultian behaviour. The
oxygen and chromium activities were used to determine the standard free energy
change for the formation of solid Cr20 3 from the elements at 1873 K, and the value
obtained is in good agreement with existing data. Evidently, the plug-type oxygen
probes and the redesigned crucible assembly can be used to determine the oxygen
activity of an Fe-Cr alloy, in equilibrium with a liquid slag at 1873 K, accurately
and reliably. Therefore, these measurements were extended to the determination of
the activity of MnO in (MgO-Si~-MnO)-slags.
The chemical composition of the equilibrium phases pertaining in (Mg0-Si0Si02-MnO)slags
saturated with (MnO-MgO) solid solutions and in contact with manganese
metal, were determined by microprobe analyses. These results together with the
known activity-composition relations of (MnO-MgO) solid solutions at 1873 K, were
used to determine the activity of MnO in the slag. This method proved to be reliable
and the MnO activities so obtained, could serve as a check for activities determined
with the electrochemical technique. Furthermore, the same method could be used for the determination of the high temperature phase constitution of the slag when the
oxygen potential of the slag/metal system is determined by electrochemical means.
In the course of the determination of the oxygen potential of (MgO-SiOz-MnO)-slags
at 1873 K by means of electrochemical oxygen probes, the magnesia stabilized
zirconia solid electrolytes reacted with manganese metal and vapour which had a
detrimental influence on the accuracy and reliability of the EMF (electromotive
force) measurements. Accordingly, it was illustrated that zirconia solid electrolytes
are not suitable for application in slag/metal systems containing manganese metal at
1873 K. Previous workers have shown that thoria solid electrolytes are not attacked
by manganese metal at these high temperatures and should consequently be used with
the crucible assembly developed in this study, for the determination of activities in
(Mg0-Si02-Mn0)-slags at 1873 K.Thesis (PhD)--University of Pretoria, 1991.
gm2014
Materials Science and Metallurgical Engineering
Unrestricted
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Lee, Pou-Yung. "Thermophysical property measurements at high temperatures for liquid metal alloys and gadolinium oxide-doped uranium dioxide samples." Thesis, 1993. http://hdl.handle.net/1911/13754.
Full textAbstract:
New techniques for obtaining various thermophysical properties, i.e., densities and incremental enthalpies of selected materials at high temperatures have been developed with emphasis on the utilization of levitation technique and drop calorimetry. The density of liquid copper has been evaluated at 1550K. The incremental enthalpies of various Gd$\sb2$O$\sb3$-doped UO$\sb2$ nuclear fuel pellets have been obtained at temperatures between 1700 and 2100K. Determinations of incremental enthalpies, the heat of fusion and specific heats for a liquid Ni-based superalloy have been carried out using levitation drop calorimetry. Contact angle studies between liquid titanium and selected ceramic materials have also been performed.
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"Evidence of amorphous/liquid phase separation in Pd₄₁.₂₅Ni₄₁.₂₅P₁₇.₅ alloy." 2011. http://library.cuhk.edu.hk/record=b5894648.
Full textAbstract:
Yin, Weixin = 非晶液態鈀-鎳-磷合金相位分離的證據 / 殷瑋欣.Thesis (M.Phil.)--Chinese University of Hong Kong, 2011.
Includes bibliographical references.
Abstracts in English and Chinese.
Yin, Weixin = Fei jing ye tai ba-nie-lin he jin xiang wei fen li de zheng ju / Yin Weixin.
Acknowledgement --- p.i
Abstract --- p.ii
Contents --- p.iv
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- A Brief Introduction to Metallic Glass --- p.1
Chapter 1.2 --- Homogeneous Nucleation Frequency --- p.3
Chapter 1.3 --- Heterogeneous Nucleation Frequency --- p.4
Chapter 1.4 --- Spinodal Decomposition --- p.5
Chapter 1.5 --- Conditions for Metallic Glasses Formation --- p.8
Chapter 1.6 --- How to Get Large Undercooling --- p.9
Chapter 1.7 --- Liquid Phase Separation --- p.10
References --- p.12
Figures --- p.13
Chapter Chapter 2 --- Experimental Procedures and Techniques of Transmission Electron Microscopy --- p.18
Chapter 2.1 --- Sample preparation --- p.18
Chapter 2.1.1 --- Ni2P Preparation --- p.18
Chapter 2.1.2 --- Alloying --- p.18
Chapter 2.1.3 --- Fluxing --- p.18
Chapter 2.2 --- Introduction to TEM Specimen Preparation --- p.19
Chapter 2.2.1 --- "Grinding, Polishing and Punching" --- p.19
Chapter 2.2.2 --- Final Thinning by Ion Miller --- p.20
Chapter 2.2.3 --- Final Thinning by Twin Jet --- p.20
Chapter 2.3 --- Introduction to Transmission Electron Microscopy Techniques --- p.21
Chapter 2.3.1 --- Basic Instrumentations of TEM --- p.21
Chapter 2.3.2 --- Elastic Scattering and Inelastic Scattering --- p.21
Chapter 2.3.3 --- Image Contrast --- p.22
Chapter 2.3.4 --- Dark Field Image and Bright Field Image --- p.24
Chapter 2.3.5 --- EDX Mapping --- p.24
Chapter 2.3.6 --- High Resolution Images --- p.25
References --- p.26
Figures --- p.27
Chapter Chapter 3 --- Evidence of amorphous/liquid phase separation in Pd41.25Ni41.25P17.5 alloy --- p.32
Chapter 3.1 --- Introduction --- p.32
Chapter 3.2 --- Experimental --- p.34
Chapter 3.3 --- Discussions --- p.42
References --- p.44
Figures --- p.45
Chapter Chapter 4 --- Conclusions --- p.68
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Chekmarev, Dmitriy S. "Computer simulation studies of the structures of the liquid-vapor interfaces of metals and binary alloys /." 1999. http://wwwlib.umi.com/dissertations/fullcit/9920138.
Full text
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"Formation of bulk nanocrystalline materials." 1999. http://library.cuhk.edu.hk/record=b6073188.
Full textAbstract:
by Guo Wenhua.Thesis (Ph.D.)--Chinese University of Hong Kong, 1999.
Includes bibliographical references.
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Mode of access: World Wide Web.
Abstracts in English and Chinese.
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Huang, Hsin-Yi, and 黃馨儀. "Electrodeposition of electrocatalytic FePt, PdNi alloys and Pd metal from ionic liquids for oxygen reduction reaction, ethanol oxidation reaction and glucose oxidation." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/49289596073069781776.
Full textAbstract:
碩士高雄醫學大學
醫藥暨應用化學研究所
98
In this thesis, the electrochemical behaviors of Pt(II), Fe(II) and the mixtures of Pt(II) and Fe(II) were investigated using platinum, glassy carbon and tungsten electrodes in N-butyl-N-methylpyrrolidinium dicyanamide ionic liquid (BMP-DCA IL), N-butyl-N-methyl pyrrolidinium bis((trifluoromethyl)sulfonyl)imide ionic liquid (BMP-TFSI IL) and a mixture of BMP-DCA and BMP-TFSI. In BMP-DCA, the Pt(II) species were attained by adding PtCl2 and the Fe(II) species were attained by adding FeCl2 or anodic dissolution of Fe wire. In BMP-TFSI, PtCl2 was not soluble; additional two equivalents of BMP-Cl were introduced to assist PtCl2 to dissolve. The Fe(II) ions were introduced into BMP-TFSI by adding FeCl2 and two equivalents of BMP-Cl or by anodic dissolution of Fe electrode. The nucleation process of electrochemical reduction of Fe(II) was investigated by using chronoamperometry (CA) and the 3D instantaneous nucleation was involved in the electrodeposition of Fe. The effect of temperature on the electrochemical behavior was also studied. Electrodeposition of Pt, Fe and FePt alloys was achived by potentiostatic electrolysis and the effect of the applied potentials were carefully studied. The surface morphology and composition of all the electrodeposition samples were characterized by scanning electron microscope (SEM) and energy dispersive spectrometry (EDS), respectively. The electrocatalytic activity towards oxygen reduction reaction (ORR) was studied at the FePt alloy-coated electrodes with various atomic ratios of Pt/Fe. The experimental results revealed that the FePt alloy with an atomic ratio of Pt/Fe ~ 0.5/0.5 had the best catalytic activity to ORR in 0.1 M HClO4 in terms of the reduction overpotential and current density. The FePt alloy electrode also revealed catalytic activity toward ethanol oxidation reaction (EOR). On the other hand, Pd(II), Ni(II) and the mixtures of Pd(II) and Ni(II) were introduced into BMP-DCA IL by adding PdCl2 and NiCl2, respectively. The voltammetric behavior of Pd(II) and Ni(II) were studied and electrodeposition of Pd, Ni, and PdNi alloys was achieved by potentiostatic electrolysis. The PdNi alloy with an atomic ratio of Pd/Ni ~ 80/20 showed the best catalytic activity and stability toward ethanol oxidation compare with other PdNi alloys with different atomic ratios in 1 M NaOH. By using cyclic voltammetry, the dependence of the anodic peak current of ethanol oxidation on the concentration of ethanol was linear from 4.92 μM to 962 μM (R2 = 0.9975). A linearity was observed from 4.92 μM to 988 μM (R2 = 0.998) by using hydrodynamic amperometry. The Pd-electrodeposited electrode prepared from BMP-DCA IL displayed good catalytic activity to glucose oxidation in 0.1 M NaOH. The calibration curve of glucose showed two linear ranges; one occurred at low concentration range and the other one at high concentration range. Therefore, CV, SWV and i-t curve were employed to study the dependence of glucose oxidation current on concentration of glucose in the two concentration ranges.
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"Liquid phase separation in molten Pd-Ni-P alloy =: 熔融鈀-鎳-磷合金的液態相分離." Chinese University of Hong Kong, 1996. http://library.cuhk.edu.hk/record=b5888966.
Full textAbstract:
by Yuen Cheong Wing.Thesis (M.Phil.)--Chinese University of Hong Kong, 1996.
Includes bibliographical references (leaves [138]-[142]).
by Yuen Cheong Wing.
Acknowledgments --- p.ii
Abstract --- p.iii
Table of Contents --- p.v
Chapter Chapter 1: --- Introduction --- p.1-1
Chapter 1.1 --- What is Metallic Glass? --- p.1-1
Chapter 1.2 --- Use of Metallic Glass --- p.1-3
Chapter 1.3 --- A Dilemma --- p.1-4
Chapter 1.4 --- Glass Forming Ability --- p.1-5
Chapter 1.5 --- Role of Liquid State Phase Separation in GFA --- p.1-6
References --- p.1-9
Figure --- p.1-10
Chapter Chapter 2: --- Phase Separation Theory --- p.2-1
Chapter 2.1 --- Free Energy Curve --- p.2-1
Chapter 2.2 --- Nucleation and Growth --- p.2-2
Chapter 2.2.1 --- Liquid state nucleation and growth --- p.2-2
Chapter 2.2.2 --- Nucleation and growth during solidification --- p.2-4
Chapter 2.3 --- Spinodal Decomposition --- p.2-5
Chapter 2.3.1 --- Cahn-Hilliard linearized equation --- p.2-6
Chapter 2.3.2 --- Temporal evolution --- p.2-9
References --- p.2-12
Figures --- p.2-15
Chapter Chapter 3 ： --- Experimental Setup and Techniques --- p.3-1
Chapter 3.1 --- Technique in Achieving High Undercooling --- p.3 -1
Chapter 3.1.1 --- Effects and limitation of B203 --- p.3-1
Chapter 3.1.2 --- Preparation of B203 --- p.3-3
Chapter 3.1.3 --- Cleansing of apparatus --- p.3-4
Chapter 3.2 --- Experimental --- p.3-5
Chapter 3.2.1 --- Sample preparation --- p.3-6
Chapter 3.2.2 --- Experimental setup --- p.3-7
Chapter 3.2.3 --- Procedures --- p.3-8
Chapter 3.3 --- Observing the Microstructure --- p.3-9
Chapter 3.3.1 --- Cutting --- p.3-10
Chapter 3.3.2 --- Molding --- p.3-10
Chapter 3.3.3 --- Polishing --- p.3-11
Chapter 3.3.4 --- Etching --- p.3-12
Chapter 3.3.5 --- Observation --- p.3-12
References --- p.3-14
Table --- p.3-15
Figures --- p.3-16
Chapter Chapter 4: --- Metastable liquid phase separationin undercooled molten PD40. 5]\l40.5P19 --- p.4-1
Abstract --- p.4-1
References --- p.4-9
Figures --- p.4-10
Chapter Chapter 5 ： --- Transformation in undercooled molten PD40.5NI40.5P19 --- p.5-1
Chapter 5.1 --- Abstract --- p.5-1
Chapter 5.1 --- Introduction --- p.5-2
Chapter 5.3 --- Experimental --- p.5-4
Chapter 5.4 --- Results --- p.5-6
Chapter 5.5 --- Discussions --- p.5-13
References --- p.5-20
Figures --- p.5-22
Chapter Chapter 6 ： --- Solidification of liquid spinodal in undercooled PD40.5NI40.5P19 --- p.6-1
Chapter 6.1 --- Abstract --- p.6-1
Chapter 6.2 --- Introduction --- p.6-2
Chapter 6.3 --- Experimental --- p.6-3
Chapter 6.4 --- Results --- p.6-5
Chapter 6.5 --- Discussions --- p.6-10
References --- p.6-17
Figures --- p.6-18
Chapter Chapter 7: --- Conclusion --- p.7-1
References --- p.7-4
Bibliography --- p.B-1
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(11196129), Ruiji Sun. "RHEOLOGICAL CHARACTERIZATION DURING METALLURGICAL SOLID-LIQUID PHASE CHANGES IN RESISTANCE SPOT WELDING AND BINDER JET PRINTING." Thesis, 2021.
Find full textAbstract:
The dissertation offers a Multiphysics perspective in analyzing emerging metallurgical techniques. Heat transfer, structural deformation, and fluid flow associate with one another in phase-changing materials processing methods. To comprehensively analyze these aspects for an optimized final product, the authors have proposed a numerical mathematical model describing the thermal and geometric progression of the binary alloy casting process. The model is further executed in COMSOL Multiphysics, adapted in two metal manufacturing applications, resistance spot welding (RSW) and binder jet printing (BJP).
Resistance spot welding is a well-adapted metal sheeting joining technique with comparably limited modeling and simulating research. The heat transfer module and geometric deformation module are applied to the simulation of RSW to discuss the thermal gradient development of the welding zone. The model was further calculated and verified through a case study with Python.
BJP is a rapidly developing additive manufacturing method. The novel 3D printing technique brings challenges in post-processing geometric control and material selection limitations. Multiphysics simulation serves as an excellent tool in process parameters analysis and quality control. This dissertation focuses on the sintering process of BJP of binary alloy powders. Melting and solidification mathematical models were implemented in COMSOL, where the sintering shrinkage rate could be calculated. The shrinkage rate was further verified through experimental analysis of binder jet printed samples.
Microstructural analysis on sintered binder jet printed parts was performed to assess the validity of BJP to substitute the die casting method for manufacturing of valvebody. Sintering shrinkage and metallurgical analysis have been performed on the green and sintered BJP samples. After sintering, the final part achieved 98% density, and the integrity of the designed channels was preserved. The shrinkage analysis has indicated the effect of printing orientation and sintering orientation on the geometry and metallurgy of the final products. Microstructure analysis on the cross-sections of the sintered products also indicates the various defects induced from biner jet 3D printing.
The research aims to provide a systematic rheology analysis of the phase transformation process of binary alloys. The dissertation has connected the physical, mathematical modeling with 15
simulative modeling through the rheological evaluation of phase-changing manufacturing techniques. The connections were conclusively verified through empirical studies, including case assessment and experimentation. The research aims to offer universally applicable models that can be applied to phase-changing metal processing techniques.
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Khodja, Abdellah. "Investigations of transport phenomena and dynamical relaxation in closed quantum systems." Doctoral thesis, 2015. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2015031713128.
Full textAbstract:
The first part of the present Phd thesis is devoted to transport investigations in disordered quantum systems. We aim at quantitatively determining transport parameters like conductivity, mean
free path, etc., for simple models of spatially disordered and/or percolated quantum systems in the limit of
high temperatures and low fillings using linear response theory. We find the transport behavior for some models to be in accord with a Boltzmann equation, i.e., long mean free paths, exponentially decaying currents although there are no band-structures to start from, while this does not apply to other models even though they are also almost completely delocalized. The second part of the present PhD thesis addresses the issue of initial state independence (ISI) in closed quantum system. The relevance of the eigenstate thermalization hypothesis (ETH) for the emergence of ISI equilibration is to some extent addressed. To this end, we investigate the Heisenberg spin-ladder and check the validity of the ETH for the energy difference operator by examining the scaling behavior of the corresponding ETH-fluctuations, which we compute using an innovative numerical method based on typicality related arguments. While, the ETH turns out to hold for the generic non-integrable models and may therefore serve as the key mechanism for ISI for this cases, it does not hold for the integrable Heisenberg-chain. However, close analysis on the dynamic of substantially out-of-equilibrium initial states indicates the occurrence of ISI equillibration in the thermodynamic limit regardless of whether the ETH is violated. Thus, we introduce a new parameter $v$, which we propose as an alternative of the ETH to indicate ISI equillibration in cases, in which the ETH does not strictly apply.
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Stiehler, Martin. "Strukturelle und elektronische Eigenschaften binärer amorpher Aluminiumlegierungen mit Übergangsmetallen und Metallen der Seltenen Erden." Doctoral thesis, 2011. https://monarch.qucosa.de/id/qucosa%3A19668.
Full textAbstract:
Der Einfluss der d-Zustände der Übergangsmetalle auf die Strukturbildung in amorphen Legierungen ist bisher nur unzureichend verstanden. Die vorliegende Arbeit hat zum Ziel, zusätzliche Beiträge zum Verständnis am Beispiel binärer amorpher Aluminiumlegierungen mit Übergangsmetallen zu erarbeiten. Speziell standen dabei Legierungen mit einer Untergruppe der Übergangsmetalle, den Metallen der Seltenen Erden, im Vordergrund. Im Rahmen der vorliegenden Arbeit wurden Schichten von Al-Ce im Bereich von 15at%Ce-80at%Ce durch sequentielle Flash-Verdampfung bei 4,2K im Hochvakuum hergestellt und durch Messungen des elektrischen Widerstands und des Hall-Effekts elektronisch, sowie durch Transmissionselektronenbeugung strukturell charakterisiert. Ergänzend wurden Untersuchungen der Plasmaresonanz mittels Elektronenenergieverlustspektroskopie durchgeführt. Im Bereich 25at%Ce-60at%Ce entstanden homogen amorphe Proben. Besonders die Strukturuntersuchungen wurden durch eine Oxidation des Materials erschwert. Der Einfluss der Ce-4f-Elektronen manifestiert sich vor allem im Tieftemperatur- und Magnetowiderstand, die beide vom Kondo-Effekt dominiert werden. Der Hall-Effekt in Al-Ce wird im gesamten untersuchten Temperaturbereich (2K-320K) von anomalen Anteilen dominiert, welche skew-scattering-Effekten, ebenfalls aufgrund der Ce-4f-Elektronen, zugeschrieben werden. Bis hinunter zu 2K trat keine makroskopische magnetische Ordnung auf. Im Bereich 2K-20K wird auf das Vorliegen von Clustern geordneter magnetischer Momente geschlossen. Für T>20K tritt paramagnetisches Verhalten auf. Hinsichtlich der strukturellen und elektronischen Eigenschaften lässt sich a-Al-Ce in eine Gruppe mit a-Al-(Sc,Y,La) einordnen. Im Sinne der Plasmaresonanz ordnet sich a-Al-Ce exzellent in eine von anderen Al-Übergangsmetalllegierungen bekannte Systematik ein. Weiterhin wurde, durch Hinzunahme von Ergebnissen zu binären amorphen Al-Übergangsmetalllegierungen aus der Literatur, gefunden, dass die Strukturbildung in diesen Systemen eng mit einem bekannten, jedoch noch ungeklärtem Strukturbildungseffekt verknüpft ist, der in flüssigen reinen Elementen auftritt. Dieser hat dort zum Ziel, eine Resonanz zwischen der statischen Struktur und dem elektronischen System aufzubauen, die mit einer mittleren Valenz von 1,5 Elektronen pro Atom verknüpft ist. Speziell die Strukturen der untersuchten amorphen Al-Seltenerdlegierungen sind über große Konzentrationsbereiche ebenfalls mit einer mittleren Valenz von 1,5 Elektronen pro Atom korreliert.