High Temperature Thermal and Optical Properties of Oxide Ceramics
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To: All Interested Faculty, Students and Research Scientists
Announcing: Ph.D. Dissertation Proposal by William T. Riffe
Date: Wednesday, April 23, 2025
Time: 3pm to 5pm
Location: MECH 346
Committee:
Prof. Elizabeth Opila, Chair
Prof. Patrick E. Hopkins, Advisor
Prof. Prasanna Balachandran
Prof. Bi-Cheng Zhou
Prof. Ethan Scott
Title: High Temperature Thermal and Optical Properties of Oxide Ceramics
Abstract
The primary objective of this proposed body of work is to investigate the thermal and optical transport of oxide ceramics at intermediate to high temperatures. Technologies such as leading edges of hypersonic vehicles, gas turbine engines of modern jets, or plasma-facing walls of nuclear reactors face a bottleneck to improved performance—that is, finding materials that can withstand harsh, degenerative environments. For example, convective fluxes, high temperatures, molten salts, and ion irradiation incident on outer components represent are problems engineers must address when designing turbine blades and other hot components in turbine engines. Thermal and/or environmental barrier coatings with optimized thermomechanical and thermochemical properties are commonly employed on structural components to mitigate their degeneration. Turbine engines produce more thrust operating at higher temperatures because of the amount of work that can be extracted from the combusted gas. This necessitates the characterization of materials that improve upon the conductive and radiative resistance of concurrent coatings. Industry-standard yttria-stabilized zirconia has been shown to be less thermally insulative at high temperatures than its pyrochlore phase counterpart, notably when certain rare earth lanthanides are incorporated into the lattice. Also, radiative fluxes emitted by the hot gas scale with temperature quadratically which demands a rethinking of the optical performance of coatings. Incorporating rare earth lanthanides offer a solution to improve opaqueness in the pertinent wavelengths range because of innate excited electronic states acting as spectral absorbers.
This research seeks to answer fundamental questions regarding the thermal/electronic transport, thermomechanical behavior, and optical properties of rare earth sesquioxides and rare earth pyrochlore zirconates, two potential systems for thermal barrier coatings, from room temperature up to melting temperature. To measure the temperature-dependent properties of these ceramics, I employ laser- and spectroscopy-based techniques such as transient thermoreflectance, spectroscopic ellipsometry, and spectroscopic radiometry. Through transient methods, I will temporally elucidate the thermal transport and excited electronic state dynamics to gain understanding of the ultrafast nonequilibrium physics in these materials. Additionally, through spectroscopic methods, I will investigate the high temperature emittance, thermal conductivity, melting temperature, and dielectric function in these systems. The aim of this proposal is to investigate the thermal and optical performance in emergent classes of barrier coatings and understand the underlying mechanisms governing the transport dynamics.
All interested persons are invited to attend. Please contact William T. Riffe for Zoom information.