Oxidation Behavior Of Silicon Carbide, Matrix Graphite, And Refractory Multi-Principal Element Alloy

Author

Visharad Jalan, Missouri University of Science and Technology

Keywords and Phrases

electron microscopy; matrix graphite; oxidation; refractory multi-principal element alloy; silicon carbide; water vapor oxidation

Abstract

"The present study focuses on the investigation of the oxidation behavior of silicon carbide, matrix graphite in a water vapor environment. It also examines the oxidation behavior of refractory multi-principal element alloys when exposed to air. The oxidation behavior of silicon carbide and matrix graphite were investigated in conditions pertaining to off-normal incidents in high-temperature gas-cooled nuclear reactors. Understanding this is crucial for the prediction of their performance in such accidents and ensuring that the nuclear reactor is accident tolerant. Upon exposure to water vapor, the two A3-based matrix graphite exhibited different behaviors. The A3-27 type showed oxidation in all three regimes of graphite oxidation over the temperature range (700 – 1200 °C), while the A3-3 type oxidized in the in-pore diffusion-controlled regime. The SiC layer in a tristructural isotropic (TRISO) fuel particle exhibited similar oxidation behavior at 5, and 10 kPa pH₂O, which varied from the response at 20 kPa H2O. Crystalline oxide was observed at all temperatures (1000 – 1300 °C) for particles oxidized at 5 and 10 kPa H₂O while the oxide was amorphous when particles were oxidized in 20 kPa H₂O at lower temperatures (<1200 >°C). A change in oxidation mechanism was observed around 1200 °C for particles oxidized in 20 kPa H₂O. The activation energy for the oxidation of SiC in 5 and 10 kPa H₂O (1000 – 1300 °C) was similar to those observed at higher temperatures in 20 kPa H₂O, prompting similar oxidation mechanisms were at play. Oxidation behavior for three refractory multi-principal element alloys was compared as a function of composition and synthesis route (arc melting and arc melting + laser remelting). The addition of Al and Cr led to an improved oxidation resistance"-- Abstract, p. iv

Advisor(s)

Wen, Haiming

Committee Member(s)

Lipke, David W.
Hilmas, Greg
Graham, Joseph T.
Liang, Xinhua

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Materials Science and Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Spring 2025

Pagination

xiv, 142 pages

Note about bibliography

Includes_bibliographical_references_(pages 44, 67, 95, 123 and 133-141)

Rights

©2024 Visharad Jalan , All Rights Reserved

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 12460

Recommended Citation

Jalan, Visharad, "Oxidation Behavior Of Silicon Carbide, Matrix Graphite, And Refractory Multi-Principal Element Alloy" (2025). Doctoral Dissertations. 3369.
https://scholarsmine.mst.edu/doctoral_dissertations/3369