Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Physics

Language

English (en)

Date of Award

January 2009

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Kenneth Kelton

Abstract

Since the discovery of quasicrystals in 1985 and the development of commercially viable bulk metallic glasses: BMGs) in the mid 1990's a great deal of attention has been given to the characterization of new alloys with desirable properties, such as larger amorphous casting thickness, higher mechanical strength, or hydrogen storage capacity. Here, the results of a number of investigations into the structures and properties of some noncrystalline solid alloys will be presented and analyzed. Beamline electrostatic levitation: BESL), a method for determining supercooled liquid structure and phase formation insitu, was used. Using BESL, the development of structural and chemical inhomogeneity was observed in supercooled liquid Cu46Zr54: a BMG when cast) with an onset at 845 ┬▒ 5┬░C, providing experimental support for structural changes determined from molecular dynamics: MD) simulations of these liquids. Differing segregation of Hf and Zr atoms was observed in solidified Ti45Zr(38-x)HfxNi17 using scanning electron microscopy: SEM), and correlated to a previously observed, sharp boundary in phase formation near x = 19 that was further investigated using BESL. In addition to the BESL studies, results will be presented and discussed on changes in microstructure and devitrification mechanisms with the addition of Ag in Mg65Cu(25-x)AgxGd10 BMGs, interesting for their light weight and resistance to oxygen during casting, using transmission electron microscopy: TEM), SEM, and differential scanning calorimetry: DSC). Previous, preliminary results on the hydrogen storage capacity of icosahedral quasicrystal Ti45Zr38Ni17 were re-examined, using an improved apparatus and analysis method developed as part of this work, and the previous results found to be in error.

Comments

Permanent URL: http://dx.doi.org/10.7936/K76D5R24

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