Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 224-239). Also available via the Internet.

No description available.

Due to the aluminum industry demands, a large effort has recently been devoted to the development of special alloys to be used as inert anodes for a newly designed aluminum reduction cell. The implementation of this new technology aims at the replacement of the graphite anodes that have been used for over 100 years in aluminum smelting, which would reduce fossil carbon consumption, and eliminate the emission of carbon dioxide and of perfluorocarbons. Ternary alloys containing copper, nickel, and iron have been the subject of the research activities. The present research focused on the stability of the Cu-Ni-Fe alloys at high temperatures in oxidizing and fluoridating environments. The experimental methods included thermodynamic calculations of the phase diagram ('Thermocalc'), optical microscopy and microprobe microstructural and chemical investigations (EMIPA-WDS), small-angle neutron scattering (SANS), differential thermal analysis (DTA), and air-oxidation studies. The results have led to the optimization of the Cu-Ni-Fe ternary phase diagram and to an extensive study of the thermodynamics and kinetics of the spinodal decomposition and discontinuous reactions occurring during ageing as a function of alloy composition. The oxidizing reactions occurring in air at high temperatures at the surface of the alloys have been also discussed in terms of thermodynamic and kinetic laws. The phase formation in a fluorine containing environment as encountered in an aluminum electrolytic cell is predicted using principles of physical chemistry. / Graduation date: 2004 / Best scan available. Figures in original document are very dark and have a moray pattern.

Graduation date: 1997

In the present study, dilute alloys in the Mg-rich corner of the Mg-Ce-In ternary system in the composition range 0 to 3% In and 0 to 1.5% Ce were synthesized. Cooling curve analysis was used to determine the liquidus points in order to construct the liquidus surface of the ternary phase diagram in the Mg corner. Energy dispersive spectroscopy (EDS), wavelength dispersive spectroscopy (WDS), and x-ray diffraction (XRD) techniques were used to examine phases present at the compositions studied. A thermal arrest presumed to represent a eutectic transformation was discovered at 580°C. Two new intermetallic compounds, designated tau and theta, were found. Trace silicon present in the alloys was found to concentrate in one of the intermetallic compounds. / To further investigate these compounds, an induction furnace was used to synthesize alloys containing the concentrations of Ce and In seen in electron probe micro-analysis (EPMA) examinations of these compounds. The alloys were examined using the cooling curve technique and XRD, and proved to contain the compounds already observed with some variation in dissolved indium content. In addition, differential scanning calorimetry (DSC) was used to confirm the liquidus and solidus values determined using cooling curve analysis. / A diffusion couple with terminal compositions of pure Ce and a Mg-In alloy was prepared in order to determine the equilibrium phases present in the system between these two compositions at 390°C. EPMA was used to identify the zones obtained, and confirmed the presence of several Mg-Ce compounds with 1 at% dissolved indium, as well as a ternary compound corresponding to the theta compound found in the dilute alloys. / Finally, literature values and experimental data were used to calculate a preliminary ternary phase diagram using FACTSage, in collaboration with the CTRC at Ecole Polytechnique, in order to affirm the validity of the experimentally determined values as well as to project the diagram beyond the studied composition range.

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

No description available.

The thermodynamic and kinetic phenomena involved in the formation of sub-micron polyimide particles from polyimide/solvent/nonsolvent ternary systems were studied. A quantitative equilibrium approach was considered in the B-bonding studies of these ternary systems. The effect of H-bonding on the physical properties and phase behavior of the ternary systems was investigated. The critical requirements for the control of polymer particle size and size distribution during particle formation by precipitation from solution are discussed. It was found that the equilibrium constants, enthalpies and entropies of H-bonding in the ternary systems containing water can be obtained by analysis of the ^lH_NMR data. Using the calculated equilibrium constants, the determination of the concentration of H-bonds between N-methylpyrrolidinone (NHP) and water is possible. We found a very good correlation between the B-bond concentrations and the deviations of the specific volume and viscosity from ideal mixing in the NHP/water mixtures. / Ph. D.