Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. Description based on print version record. Includes bibliographical references.

M.Sc. (Physics) / Please refer to full text to view abstract

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. On t.p. "x̲" is subscript. Document formatted into pages; contains viii, 34 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 30-31).

Ab initio plane wave based density functional calculations within the generalised gradient approximation (GGA) have been carried out on a wide range of phases and stoichiometries for the platinum-titanium (Pt-Ti) and iridium-titanium (Ir-Ti) alloy systems, using the Vienna Ab Initio Simulation Package (VASP) with projector augmented wave (PAW) potentials. For all of the phases in this work, the equilibrium structures were found by performing a full relaxation of the atoms. There were 20 di erent phases considered for varying atomic percentage compositions for each alloy system. Energy-volume calculations and heats of formations were used to determined the equilibrium structures at each atomice percentage composition and to determine if there were high temperature phases at that composition. The elastic constants and elastic moduli are calculated and the electronic structure and density of states (DOS) were considered to understand the hardness and stability properties of the alloys. For the Pt-Ti system, the low and high temperature phases at di erent compositions agreed with previously published results in the literature. Intermediate phases at 50% were also determined, in agreement with previous results. Alloying Pt with Ti resulted in a decrease in the bulk modulus, i.e. not adding strength to the metal. However, the shear modulus increased for most of the alloys compared to bulk Pt and it was found that in general, alloying may increase the resistance to shear. PtTi alloys were found to be ductile in nature, as with both constituent metals in their bulk form. In the Ir-Ti system, bulk Ir was found to have the highest bulk, shear and Young's modulus with each of these values decreasing with increasing percentage Ti in the alloy. IrTi alloys with 66.7% Ir composition or higher were found to be brittle in nature, similar in behaviour to bulk Ir; alloys with a higher percentage concentration of Ti were found to be ductile. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Thesis (Ph. D.)--Lehigh University, 1998. / Includes vita. Includes bibliographical references (leaves 168-180).

Thesis (M.Sc.(Metallurgical Engineering))--University of Pretoria, 2003. / Includes bibliographical references (leaves 127-128).

No abstract available. / Dissertation (MSc (Metallurgy))--University of Pretoria, 2006. / Materials Science and Metallurgical Engineering / unrestricted

Indiana University-Purdue University Indianapolis (IUPUI) / In this thesis two research objectives have been accomplished using computational simulation techniques. (1) The surface segregation phenomena in the surfaces of (111), unreconstructed (110) and reconstructed (1x2) missing row (110) surfaces of Pt-Ni and Pt-Co disordered alloys have been accurately predicted using Monte Carlo (MC) simulation method, and (2) the configuration and energy of the adsorption of O, O2, OH, and H2O molecules which are presented in oxygen reduction reaction (ORR) on the surface of pure Pt and surface-segregated Pt-binary alloys (i.e., Pt-Ni, Pt-Co and Pt-Fe) have been determined using density functional theory (DFT) calculations. This thesis yields some guiding principles for designing novel catalysts for proton exchange membrane fuel cells. The Pt concentration profiles of the surfaces of Pt-Ni and Pt-Co alloys were attained from the MC simulations in which the system energy was evaluated through the developed modified embedded atom method (MEAM) for Pt-Ni and Pt-Co alloys. It was found from our simulations that the Pt atoms strongly segregate to the outermost layer and the Ni atoms segregate to the second sub-layer in the (111) surface of both Pt-Ni and Pt-Co alloys. When Pt concentration is higher than 75 at.%, pure Pt top layer could be formed in the outermost layer (111) surface of both alloys. Moreover, segregation reversal phenomenon (Ni atoms segregating to the outermost layer while Pt atoms to the second sub-layer) was observed in our MC simulations of unreconstructed (110) surface of Pt-Ni alloys. In contrast, a Pt enriched outermost surface layer was found in a Pt-Ni reconstructed (1x2) missing row (110) surface. Our MC simulation results agree well with published experimental observations. In addition, adsorption of atomic and molecular oxygen, water and hydroxyl on the (111) and (100) surfaces of pure Pt and Pt-based alloys (Pt-Ni, Pt-Co and Pt-Fe) were studied using spin DFT method and assuming a coverage of 0.25 monolayer. Both the optimized configurations and the corresponding adsorption energies for each species were obtained in this study. In particular, we elucidated the influence of the adsorption energies of atomic oxygen and OH on the activity for ORR on Pt binary alloy catalysts in acidic environment. The calculated adsorption energies of atomic oxygen on the (111) surfaces of pure Pt, Pt-Ni, Pt-Co and Pt-Fe are -3.967 eV, -3.502 eV, -3.378 eV and -3.191 eV, respectively. The calculated adsorption energies of hydroxyl on the (111) surfaces of pure Pt, Pt-Ni, Pt-Co and Pt-Fe are -2.384 eV, -2.153 eV, -2.217 eV and -2.098 eV, respectively. The interaction between the adsorbed atomic and hydroxyl and the corresponding (111) surface becomes weaker for the surface-segregated alloys compared to pure Pt catalyst. The same results were obtained for the (100) surfaces.

In the present work, the thermodynamic activites of ironoxide, denoted as "FeO" in the slag systems Al2O3-"FeO", CaO-"FeO", "FeO"-SiO2, Al2O3-"FeO"-SiO2, CaO-"FeO"-SiO2and "FeO"-MgO-SiO2were investigated by employing the gasequilibration technique at steelmaking temperatures. Thestrategy was to expose the molten slag mixtures kept inplatinum crucibles for an oxygen potential, determined by aCO/CO2-ratio. A part of the iron reduced from the "FeO"in the slag phase was dissolved into the Pt crucible. In order to obtain the activites of "FeO", chemical analysisof the quenched slag samples together with thermodynamicinformation of the binary metallic system Fe-Pt is required.Careful experimental work was carried out by employing asolid-state galvanic cell technique as well as calorimetricmeasurements in the temperature ranges of 1073-1273 K and300-1988 K respectively. The outcome of these experiments wasincorporated along with previous studies into a CALPHAD-type ofthermodynamic assessment performed with the Thermo-Calc™software. The proposed equilibrium diagram enabledextrapolation to higher temperatures. The experimentally obtained activites of "FeO" in thepresent work, along with earlier investigations were assessedwith the KTH slag model, THERMOSLAG©. New binaryparameters were evolved and incorporated in THERMOSLAG©.The present model calculations are compared with othercommercially available software such as F*A*C*T™andThermo-Calc™. The validity of the modified model wasinvestigated by measurements carried out in case of Al2O3-"FeO"-SiO2, CaO-"FeO"-SiO2and "FeO"-MgO-SiO2ternary slags. The potential of the model tocompute the activities in the case of multicomponent slags wasdemonstrated. A correlation between the activity of a metallic oxide in aternary slag system and the sulphide capacity of the slag wasinvestigated by using the solubility of sulphur in the binarysystems CaO-SiO2and Al2O3-CaO along with the sulphide capacity of the Al2O3-CaO-SiO2system. The estimated values of the activitieswere found to be in good agreement with the measured values.This correlation also gives the possibility to elucidate theapplicability of Henry's law to the activity of a metallicsulphide and to determine the order in the affinity of a cationto sulphur between two metallic oxides in a slag. Model calculations were performed with THERMOSLAG©, by using plant data from the ladle refiningprocess at OVAKO Steel, Hofors, Sweden. It was found thatoxygen estimations in the metal from the "FeO" analyses ofslags, obtained by conventional sampling and analysis methodwere less reliable. Reliable estimation of the oxygen levelsutilising the sulphur partition between the slag and the metalwere carried out using THERMOSLAG© software. <b>Keywords:</b>Thermodynamics, Activity, Galvanic cell,Calorimetry, Gas equilibration technique, Iron-platinum alloys,FeO, Slags, Modelling, Ladle

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