Tuesday, November 12, 2024 12:30pm to 2:30pm
About this Event
1400 N. Bishop, Rolla, MO 65409-0330
Visharad Jalan, a doctoral candidate in materials science and engineering, will defend their dissertation titled “Oxidation Behavior of Silicon Carbide, Matrix Graphite, And Refractory Multi-Principal Element Alloy.” Their advisor, Dr. Haiming Wen, is an associate professor in the materials science and engineering department. The dissertation abstract is provided below.
The 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.
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