Analyzing the Effects of Light Ion Irradiation on Dispersion Strengthened Tungsten
Open Access
- Author:
- Higgins, Levko
- Graduate Program:
- Nuclear Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 18, 2024
- Committee Members:
- Xing Wang, Thesis Advisor/Co-Advisor
Mia Jin, Committee Member
Dipanjan Pan, Professor in Charge/Director of Graduate Studies - Keywords:
- Fusion
Tokamak
nuclear engineering
SEM
APT
Tungsten
DSW
Helium
Interface - Abstract:
- The ability to harness nuclear fusion for energy has been considered the “holy grail” of energy generation for much of the past century. The tokamak is a promising type of fusion reactor for achieving this goal. Within the tokamak, the divertor region is subject to extreme working conditions, including erosive plasma, high thermal load, and intense radiation damage. Therefore, there is a significant need for research to design materials that can withstand these harsh operating conditions. Tungsten alloys strengthened with second phase dispersoids stand out as promising candidates because of their exceptional thermomechanical properties. However, their resilience under irradiations requires further investigation. In this work, tungsten containing titanium carbide and tantalum carbide dispersoids were both irradiated with helium and hydrogen ions and put under microstructural analysis for the defects caused by those light ions. Specifically, atom probe tomography (APT) was applied to characterize the chemistry of the dispersoids and the dispersoid-tungsten interfaces and scanning electron microscopy (SEM) analysis was utilized to examine the stability of surface dispersoids after extended helium ion irradiation. Our APT analysis uncovered that due to their high affinity for oxygen, the transition metal carbides were fully oxidized into TiO and Ta_2 O_5. In addition, there was minimum element intermixing at the dispersoid-tungsten interfaces. These findings lay the groundwork for understanding the excellent resistance of dispersion strengthened tungsten interfaces to helium irradiation. Meanwhile, our SEM analyses rule out the possibility that dispersoid fallout from the sample surfaces was solely due to high-energy He irradiation, underscoring the need for future investigations into the underlying mechanisms for the fallout phenomenon in the complex working conditions in tokamaks.