Timothy Lach
- Name
- Dr. Timothy Lach
- Institution
- Oak Ridge National Laboratory
- Position
- R&D Staff Member
- Affiliation
- TMS, ANS
- h-Index
- 22
- ORCID
- 0000-0002-4745-4179
- Biography
- Tim is a research scientist in the Applied Microanalysis and Thermophysics group. He joined Oak Ridge National Laboratory as an associate research scientist in the Materials Science and Technology Division in February 2020. Previously, he was a research scientist in the Reactor Materials and Mechanical Design group in the Nuclear Sciences Division at Pacific Northwest National Laboratory. His research interests focus on the characterization and testing of advanced nuclear materials for fission/fusion energy and spallation neutron applications. In particular, he uses analytical electron microscopy (SEM and TEM) and atom probe tomography (APT) in conjunction with properties testing to elucidate processing-microstructure-property-performance relationships in materials exposed to extreme environments. He is the custodian of the focused ion beam (FIB)/SEMs in the Low Activation Materials Development and Analysis (LAMDA) lab and the Cameca LEAP 4000XHR APT in the Materials Characterization Core at ORNL. Ph.D. 2016, Materials Science and Engineering, University of Illinois at Urbana-Champaign B.S. 2010, Materials Science and Engineering, The Ohio State University.
- Expertise
- APT, Electron Microscopy, Nuclear Structural Materials, Precipitation, Radiation, STEM
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"Characterization of the microstructure of yttrium hydride under proton irradiation"
Stephen Taller, Fabian Naab, Takaaki Koyanagi, Timothy Lach,
Journal of Nuclear Materials
Vol. 606
2025
Link
High moderation per unit volume solid moderator materials like yttrium hydride (YHx) are necessary for compact nuclear microreactors. However, the phase stability and hydrogen transport processes of YHx under high-temperature irradiation are largely unknown. Proton irradiation was conducted on YHx at 300 °C and 580 °C to 0.2 dpa using 1 MeV or 2 MeV protons in a high-vacuum environment. The hydrogen concentration was determined before and after irradiation using elastic recoil detection analysis, and microstructural evolution was examined via post-irradiation scanning transmission electron microscopy and Raman spectroscopy. Dislocation loops and cavities were observed in all conditions; their distribution was correlated with the bombarding proton energy and ion irradiation temperature. This work revealed that hydrogen retention is proportional to the formation of traps for hydrogen gas atoms and identified pathways for hydrogen release. The relative contributions of bulk or fast diffusion paths, such as grain boundaries, delamination boundaries, and stacking faults are discussed; the primary mechanisms of hydrogen loss are likely based on diffusion, ruling out artefacts of the experimental design. The study suggests proton irradiation may be a strong surrogate to study hydrogen transport in hydride moderator materials under irradiation. |
Irradiation-Assisted Stress Corrosion Cracking Susceptibility of Service-Exposed Baffle Former Bolt Stainless Steel Following Post-Irradiation Annealing - FY 2026 Super RTE Call, #26-5842
IASCC Characterization of 316 and 347 SS Baffle Bolts in the Context of Internal Oxidation - FY 2026 Super RTE Call, #26-5853
Understanding the Synergistic Effects of Hydrogen, Helium and Radiation Damage in FCC and BCC Nuclear Structural Materials - FY 2026 Super RTE Call, #26-5856
In-Situ Synchrotron X-Ray Diffraction Study of Neutron Irradiated AM 316L Stainless Steel Under Uniaxial Tension - FY 2026 RTE 1st Call, #26-5618
In-Situ Synchrotron X-Ray Diffraction Study of In-Service Baffle Former Bolt Material Under Uniaxial Tension at the Advanced Photon Source - FY 2026 RTE 1st Call, #26-5734
The Role of Helium on Microstructure Evolution in A709 - FY 2024 Super RTE Call, #24-5012
Impact of re-irradiation on strain-induced structure in heavy irradiated austenitic steel - FY 2024 RTE 2nd Call, #24-4965
Characterization of Irradiation-Assisted Stress Corrosion Cracking in 316 Stainless Steel Baffle-Former Bolts Harvested from Commercial Pressurized Water Reactor - FY 2024 CINR, #24-31412
Advanced hydride moderator irradiations for microreactor and space nuclear reactor deployment - FY 2024 CINR, #24-31397
The effect of radiation temperature on H/He core-shell structures in nuclear structural materials - FY 2024 RTE 1st Call, #24-4880
Evolution of Heterogeneous 316LSS Microstructures Under Neutron Irradiation - FY 2024 RTE 1st Call, #24-4862