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Thesis (M.S.)--Cleveland State University, 2008. / Abstract. Title from PDF t.p. (viewed on May 8, 2008). Includes bibliographical references (p. 72-76). Available online via the OhioLINK ETD Center. Also available in print.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references. Also available in electronic version. Access restricted to campus users.

A dissertation submitted in fulfilment of the requirements of the degree of Master of Science. Department of Chemistry. University of the Witwatersrand. Johannesburg 2016. / The lattice parameters and thermal expansion coefficients for La2Hf2O7, Eu2Hf2O7, Gd2Hf2O7, Y2Hf2O7, Gd2Zr2O7, Y2Zr2O7, Eu2Ti2O7, Gd2Ti2O7, and Y2Ti2O7 were determined relative to temperature over the range of 30°C to 850°C. All materials were determined to be of the pyrochlore phase expect for Y2Hf2O7, which crystallised in the defect fluorite phase. All materials were shown to have positive thermal expansion, which was not consistent over the experimental temperature range. The change in the thermal expansion coefficient was positive for La2Hf2O7, Y2Zr2O7, Eu2Ti2O7 and Y2Ti2O7, of which the largest change was experienced by Y2Zr2O7. The remaining materials experienced a negative change in their thermal expansion coefficients. The largest negative change was experienced by Gd2Ti2O7. It was shown that the x parameter of the 48f oxygen atom increased with increasing temperature. This had the effect of distorting the transition metal octahedral, and creating a more perfect rare-earth cube as the parameter increased. / TG2016

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering, July 2015 / ABSTRACT Solid titanium (Ti) and Ti-6Al-4V (wt.%) materials were fabricated from powders using spark plasma sintering (SPS), cold isostatic press (CIP) and sinter, layered (rapid) manufacturing, centrifugal and vacuum casing. ASTM Grade 4 Ti, Al and V, 60Al-40V (wt.%) and the pre-alloyed Ti-6Al-4V powders were used as starting materials. The solid Ti and Ti-6Al-4V materials produced by the SPS were compared to the CIP and sinter method on the basis of density, microstructure and chemistry. The materials produced by the CIP and sinter method were also compared to those produced by vacuum casting method on the basis of microstructure, oxygen pick-up, chemistry and room temperature tensile properties. Centrifugal casting was compared to the vacuum casting technique on the basis of microstructural homogeneity. Rapid manufacturing was compared to SPS and CIP and sinter on the basis of microstructural homogeneity, density and tensile properties. The tensile properties of all materials were also compared to their commercial counterparts to investigate the effect of interstitial oxygen. The technology resulting in materials with superior properties was finally identified as most promising for commercial production of Ti-based materials. On the basis of densification, the SPS method appears superior compared to the CIP and sinter and rapid manufacturing method due to the benefit of pressure aided sintering, while the rapid manufacturing method is superior to the CIP and sinter method due to the use of a high power laser resulting in high densification rates. In cases where microstructural homogeneity is the key requirement, the CIP and sinter and rapid manufacturing methods appear superior compared to the SPS method due to longer isothermal holding time and higher sintering temperature and the use of pre-alloyed Ti-6Al-4V powder, respectively. On the basis of oxygen pick-up and additional contamination, the vacuum casting route is inferior due to the tendency of melt-crucible interaction, resulting in the dissociation of ZrO2 and subsequent pick-up of O and Zr. Based on the homogeneity of the microstructure, centrifugal casting is better than vacuum casting. The ductility of vacuum cast Ti was better than that of CIP and sintered Ti, possibly due to limited diffusion of oxygen from the crucible compared to oxygen absorbed from the controlled atmosphere during CIP and sinter. The vacuum casting of the Ti-6Al-4V alloy resulted in dissolution of oxygen and Zr due to melt-crucible interaction. Hence the ductility was worse compared to the alloy produced by CIP and sinter. The rapidly manufactured Ti-6Al-4V specimens exhibited superior ductility and strength compared to all alloys produced by other methods due to the use of high purity starting powder. The tensile properties of these specimens were also comparable to standard requirements. The similarity of the tensile properties of wrought Ti-6Al-4V alloy reported in the literature was an indication of limited oxygen pick-up during rapid manufacturing. Therefore based on low oxygen pick-up, microstructural homogeneity, high density and superior tensile properties, the rapid manufacturing route appears to be the most promising approach for commercial processing of titanium based materials.

Dwell time low cycle fatigue (DLCF), low cycle fatigue (LCF), and creep tests were performed at ambient temperature on Ti-6Al-2Sn-4Zr-2Mo-0.1Si (Ti-6242Si). Test specimens were solution annealed at various temperatures below the beta transus to control the volume fraction of primary alpha. The influence of the changes in primary alpha phase on low cycle dwell time fatigue life were determined and compared to the conventional low cycle fatigue properties of the alloy. A dwell period significantly decreased the number of cycles to failure, but by a decreasing factor with decreasing stress. The increased primary alpha phase present associated with lower solution anneal temperatures significantly increased susceptibility to low cycle dwell time fatigue. It is believed that dwell fatigue sensitivity may be associated with cyclic, ambient temperature, time-dependent plasticity (creep). / Graduation date: 1999

Thesis (M.S.)--University of Akron, Dept. of Mechanical Engineering, 2008. / "August, 2008." Title from electronic thesis title page (viewed 01/13/2010) Advisor, T. S. Srivatsan; Faculty Readers, C. Menzemer, Anil Patnaik, Amit Prakash; Department Chair, Celal Batur; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

Thesis (Ph. D.)--School of Materials Science and Engineering, Georgia Institute of Technology, 2004. Directed by W. Steven Johnson. / Includes bibliographical references (leaves 261-271).

Thesis (Ph. D.)--School of Mechanical Engineering, Georgia Institute of Technology, 2004. Directed by Richard W. Neu. / Vita. Includes bibliographical references (leaves 269-278).

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy