Sean Li

Advisors: Prof. Preet M. Singh, Prof. Chaitanya S. Deo

will propose a doctoral thesis entitled:
High-Temperature Oxidation Behavior of Zr-Nb Binary Alloys in Air and Steam-Containing Environments.

On

Wednesday, April 8th at 02:00 p.m.
Love 295

and 

 Virtually via https://teams.microsoft.com/meet/2556594914946?p=beXUDwR6sVW7XbpZwd

Committee
             Prof. Preet Singh – School of Materials Science and Engineering (advisor)
             Prof. Chaitanya Deo– School of Mechanical Engineering (advisor)
             Prof. Hamid Garmestani – School of Materials Science and Engineering 

Prof. Rick Neu – School of Mechanical Engineering
             Prof. Yifeng Che – School of Mechanical Engineering

Dr. Remi Dingreville – Sandia National Laboratories

Abstract
 Zirconium-based alloys are widely utilized in nuclear and high-temperature industrial applications due to their excellent corrosion resistance and mechanical strength. However, their long-term performance in oxidizing environments is strongly influenced by the type of oxide scale formed at the surface. While it is known that the addition of niobium (Nb) significantly affects the oxidation kinetics and oxide morphology of Zr alloys, the influence of Nb concentrations above 5 at.% on these mechanisms remains poorly understood. The transition in oxide chemistry—from highly protective Zr-rich oxides (such as ZrO₂) to potentially rapid-oxidizing Nb-rich oxides (such as Nb₂O₅)—creates complex kinetic behaviors depending on the environment. The problem presented here is to systematically determine how varying Nb concentrations dictate the oxidation kinetics and scale protectiveness of Zr-Nb binary alloys when exposed to both air and steam-containing environments.

       This study aims to quantitatively compare and elucidate the oxidation mechanisms of Zr-Nb alloys across a full compositional range at elevated temperatures (300–500 °C). To accomplish this goal, several objectives must be met. First, characterizing the initial microstructure and phases of the as-formed, arc-melted alloys. Next, determining the oxidation kinetics, rate constants, and activation energies through long-term thermogravimetric analysis (TGA) in both air and steam-containing environments. Then, characterizing the resulting oxide scale structure, phase composition, and elemental distribution using post-oxidation analytical techniques such as XRD and SEM/EDS. Finally, correlating these experimental findings with thermodynamic predictions to propose a comprehensive oxidation mechanism for the entire range of Zr-Nb binary alloys. These goals, if met, will bridge the knowledge gap between fundamental reaction kinetics and applied material performance, providing mechanistic insights applicable to the design of advanced nuclear cladding and oxidation-resistant materials.