ORCID

http://orcid.org/0000-0002-4743-7993

Date of Award

Spring 5-15-2020

Author's School

Graduate School of Arts and Sciences

Author's Department

Physics

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

The first quantitative measurements of the electrical resistivity in binary metallic liquids, used to probe local order in the liquid, are reported in this dissertation. The electrical resistivity is very sensitive to short and medium range ordering because the electron mean free path is approximately the same length scale as the atomic spacing. Particular attention is given to the resistivity value at a crossover temperature that, based on molecular dynamics (MD) simulations, is the onset of cooperative motion in liquid alloys. Experimental evidence for the crossover is found in measurements of the shear viscosity, a dynamical property. An indication of the crossover temperature in the electrical resistivity would support the MD prediction of a direct connection between liquid dynamics and structure. Thermophysical properties of supercooled metallic liquids are difficult to measure due to crystallization induced by heterogeneous nucleation and reactions with container walls that occur with many reactive metals. Electrostatic and electromagnetic containerless processing techniques are used to minimize heterogeneous nucleation and to allow for measurements of the electrical resistivity and the shear viscosity in the equilibrium and supercooled liquid. This dissertation reports the results of electrical resistivity measurements of two binary liquids, made on the International Space Station (ISS) using an electromagnetic levitator. The shear viscosity is measured using the ground-based Beamline Electrostatic Levitation facility located at Washington University in St. Louis. It is found that the electrical resistivity as a function of temperature saturates above the onset of cooperative motion in the liquid, likely due to the ineffectiveness of electron-phonon scattering at high temperatures. These measurements give clear evidence that the liquid structure and the dynamics are strongly related. In a different project, BaO_2SiO2 and 5BaO_8SiO2 glasses are numerically modeled using the classical nucleation theory and the diffuse interface theory. Fortran computer code is developed to numerically solve the rate equations of the classical theory to probe the transient and steady-state nucleation and crystal growth in these glasses. A differential thermal analysis technique is simulated to determine the temperature range of significant nucleation. It is found that the numerical technique reproduces the experimental results when the diffusion coefficient is calculated from the measured induction time and the measured growth velocity. It is also shown that changing the scanning rate during the simulations does not obscure the measured region of significant nucleation, indicating that the differential thermal analysis technique is robust. This dissertation also includes measurements of the specific heat of NASA ISS batch 1, 2, and 3 equilibrium and supercooled metallic liquid alloys. The specific heat is measured with the electromagnetic levitator aboard the ISS using the modulation calorimetry technique. It is also measured with the ground-based electrostatic levitator at Washington University in St. Louis, in which the external heat transport time constant is determined and combined with emissivity data. The dissertation concludes with calculations of the X-ray absorption and multiple scattering corrections for a cylindrical geometry, where the beam is in general off-center from the axis of the cylinder. These precise corrections are needed to search for subtle changes in scattering during the nucleation processes in glasses.

Language

English (en)

Chair and Committee

Kenneth F. Kelton

Committee Members

Kenneth F. Kelton, Katharine Flores, Erik Henriksen, Zohar Nussinov,

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