Steven Zinkle
Governors Chair Professor
Steve Zinkle joined the University of Tennessee as a Governor’s Chair Professor in October, 2013. He previously worked at Oak Ridge National Laboratory in a variety of research and technical management positions. His research interests are centered on the design and advanced manufacturing of structural materials, microstructural evolution and radiation effects in metallic and ceramic materials for fusion and fission energy systems, deformation mechanisms in structural materials, space nuclear reactor materials, and plasma-materials interactions in fusion energy systems. His hobbies include jogging and basketball.
Postdoctoral Research Associates
Siwei Chen
Siwei Chen joined the University of Tennessee as a Post-Doctoral Research Associate in September, 2022. She previously worked at Central Research Institute of Electric Power Industry as a Visiting Researcher. She received a Ph.D. in the field of materials science and engineering from Hokkaido University in 2014. Her research interests include irradiation damage of structural materials in fission and fusion energy systems, advanced electron microscopy techniques, and atom probe tomography techniques. Outside of working, she likes spending time outdoor with family and friends.
Yajie Zhao
Yajie Zhao joined Dr. Zinkle’s group at the University of Tennessee as a Post-Doctoral Research Associate in May 2024. She received her Ph.D degree with a major in materials science and engineering (MSE) from the University of Tennessee in spring 2023, after which she worked as a Postdoc research associate at the Oak Ridge National Laboratory for one year. Her research interests include radiation effects in a variety of structural materials including Fe-based alloys and advanced characterization techniques. Outside of working, she likes hiking, reading novels, and staying with her family and cats.
Yao Li
Yao Li was born and raised in one of the oldest continuously inhabited cities, Xi’an, China. He graduated from Prof. Zinkle’s group in 2023 and returned to the group in April 2025 after one-year period at Los Alamos National Laboratory. His research focuses on the effects of concurrent stress and irradiation on microstructural evolution. Outside of his research journey, he enjoys photography as a personal hobby.
Graduate Researchers
Kacie Breeding
Kacie is from a small town in rural Middle Tennessee. She graduated with her bachelor’s degree in Nuclear Engineering from the University of Tennessee in 2017. She is currently working towards her Ph.D in Nuclear Engineering/Material Science at University of Tennessee in Dr. Zinkle’s research group. Her research focuses on hydrogen isotope permeability in materials for potential use in tritium extraction devices for fusion reactors. Outside of academics, she loves music and concerts, videogames, and her pet cats and reptiles.
Zehui Qi
Zehui Qi is from Shanghai, the most populous city in China. She got her Bachelor’s degree in nuclear science and technology from Fudan University. She is interested in radiation effects in metals and ceramics such as microstructural evolution in irradiated SiC/SiC composites. In her spare time, she enjoys hiking and music
Emily Proehl
A Wisconsin native, Emily obtained a Bachelor’s degree in Materials Science and Engineering (MSE) from the University of Wisconsin-Madison in 2019. Emily joined Dr. Zinkle’s group to pursue a Ph.D. in MSE and explore the intersection of materials with nuclear power. Her primary research interests are radiation damage and mechanical properties, and her research is associated with advanced electron microscopy characterization of ferritic/martensitic steels. In her free time, Emily enjoys baking, knitting, and the great outdoors.
Ryan Thier
Ryan Thier is a PhD student from the Chicago area. After graduating from the University of Illinois with a B.S. in Materials Science and Engineering in 2016, he worked as a metallurgist in the aerospace industry before joining Nuclear Engineering at Tennessee. He is interested in structural alloy development for both fission and fusion applications. He enjoys hiking and reading, and is a member of Citizen’s Climate Lobby
Mediha Merve Karatas
Mediha Merve Karatas is a PhD student in the Nuclear Engineering Department at the University of Tennessee, Knoxville. Before joining Prof. Zinkle’s group, she received her Bachelor’s of Science in Physics from Middle East Technical University (METU), Turkey. She received Master of Science Degree in Metallurgical and Materials Engineering from METU. She also received Master of Science Degree in Nuclear Engineering and Engineering Physics from University of Wisconsin, Madison. She was interested in physical metallurgy and studied in Novel Alloys Design and Development Laboratory (NOVALAB) in METU. Her thesis title is ”Synthesis and Characterization of Bulk Amorphous/Nanocrystalline Soft Magnetic Materials”. In UW, Madison, her graduate research focused on characterization capabilities using XRD/EDS/SEM tools to explore the many compositions of High Entropy Alloys for nuclear reactors, especially the ones being generated by high-throughput synthesis.
Sydney Copp
While Sydney was born and raised in Vancouver, Canada, her family now resides just outside of Washington DC. Sydney recently graduated from the University of Tennessee with a B.S. in nuclear engineering in May 2021, and is joining Dr. Zinkle’s research group to pursue her Ph.D. in the same. Sydney is most interested in radiation effects in materials for advanced reactors. When she is not working, she enjoys reading, baking, and indoor cycling.
July Reyes Zacarias
July was born and raised in the Dominican Republic, where she earned her bachelor’s degree in physics from the Autonomous University of Santo Domingo (UASD). Before joining Dr. Zinkle’s research group, she worked in the education and nuclear sector. Now, she is pursuing a Ph.D. in Nuclear Engineering and a Master’s degree in Materials Science and Engineering at the University of Tennessee. Her current research is on additive manufacturing techniques for extreme environmental conditions such as nuclear power. Outside of work, July enjoys spending time with her loved ones and traveling. She also knows three languages and is learning the fourth one.
Alex Nadermann
Alex Nadermann grew up in Redmond, Oregon, a small town in Central Oregon. He received a B.S. in Engineering and B.S. in Physics at Northwest Nazarene University in Nampa, Idaho, while competing in the NCAA Division II Men’s Soccer program. He joins Dr. Steven Zinkle‘s group in the Fall of 2022 as a Ph.D. student. His interests include fuel materials for nuclear thermal propulsion and small modular reactor technologies. His hobbies include hiking, fishing, and spending time outdoors with his wife and their golden retriever.
Thomas Siggillino
Thomas is a PhD student from Pennington, New Jersey. He received his BS and MS in Materials Science & Engineering from Lehigh University before joining Dr. Zinkle’s group in the Fall of 2022. He is interested in materials tolerant of intense radiation and other extreme environments relevant to advanced fission reactors, particularly those that can be additively manufactured. Outside of work he enjoys learning languages, baking, rock climbing, and choral singing.
Luke Hansen
Luke Hansen graduated from Louisiana Tech University with a B.S in Mechanical Engineering. He worked as a Mechanical Design Engineer testing subsea equipment with Schlumberger for 3 years before joining Dr. Zinkle’s group in the Fall of 2023. Luke’s research interests lie in creating nuclear materials for extreme environments such as Nuclear Thermal Propulsion, and he is pursuing a Ph.D. in Nuclear Engineering with a Master’s in Material Science. Some of Luke’s hobbies include triathlons, hiking, learning music, reading biographies, writing, and game nights with friends.
Ethan Payne
Ethan Payne graduated from Wake Forest University with a B.S. in Physics, and joined Dr. Zinkle’s group in the fall of 2023 to pursue a PhD in Nuclear Engineering and a Master’s Degree in Materials Science and Engineering after gaining interest in the fields while researching radiation and spaceflight effects on biological tissue in undergrad. He is interested in nuclear fuels and materials for application in nuclear thermal propulsion. Outside research and classes, he enjoys exploring the outdoors, reading, and finding a good coffee shop.
Josina “Wilna” Geringer
Josina Geringer, or “Wilna” as everyone knows her, is a PhD student in the Nuclear Engineering Department at the University of Tennessee. She grew up in South Africa, where she obtained a Bachelor’s degree in Industrial Engineering at the University of Pretoria as well as a Master’s degree in Nuclear Engineering at North-West University in Potchefstroom. As a junior engineer she started her career working on South Africa’s Pebble Bed Modular Reactor (PBMR), a high temperature reactor concept. This triggered her research interest in advanced reactors. Her more recent experience involves managing HFIR irradiations programs, where she is involved with fusion reactor and materials research. Her current interest and focus is on advanced nuclear materials under extremes. Besides travelling and spending time with loved ones, she enjoys the outdoors and quiet time in nature.
Maxx Jackson
Maxx Jackson is an R&D Scientist with a background focused on researching and developing manufacturing solutions for nuclear and nuclear related materials. He spent six years exploring various processing and fabrication methods of refractory ceramics and metals for pilot and demonstration scale applications in the nuclear security enterprise at the Y-12 National Security Complex and two years working with TRISO-X, LLC to help improve their fuel element fabrication capabilities. He holds a B.S. in Biochemistry from Claflin University, and an M.S. in Physics, concentrating in Materials Science from Alabama Agricultural and Mechanical University. His pastimes include spending time with his wife and their children, listening to formal debates, playing the violin, producing music, star gazing, and learning about anything dealing with space. His favorite quotes are “To whom much is given, much will be required.” (Luke 12:48) and “You can’t solve a problem you’re not willing to have” – Dave Evans. Maxx is currently interested in the irradiation effects of radiation resistant materials and developing advanced materials that can be used under extreme conditions.
Darnell Lambert
Darnell Lambert is a PhD nuclear engineering student from Aiken, South Carolina. He graduated from the University of South Carolina with a B.S. in Mechanical Engineering in the spring of 2024. He is a GEM Fellow joining Dr. Zinkle’s group in the fall of 2024. Darnell’s interest in materials stemmed from his time spent at the Oak Ridge National Laboratory. He is interested in finding and creating better materials intended for use in nuclear thermal propulsion. His hobbies include photography, fashion, and playing music, especially his saxophone.
Katie Baker
Katie is a PhD student that grew up just outside Philadelphia, PA. While pursuing her B.S. in Nuclear Engineering at Penn State University, she was a Reactor Operator at the Breazeale Nuclear Reactor. Her interests include radiation damage in materials for both Generation IV fission and fusion reactors. In her free time, you will find Katie playing with her bunnies and cat or FaceTiming her mom to show her the family dogs.
Ashley Lee
Ashley is a Nuclear Engineering PhD student studying vanadium alloys for fusion structural applications and is also pursuing a M.S. in Materials Science and Engineering. She is from Ventura County, California and graduated from the University of California, Berkeley with a B.S. in Nuclear Engineering and Mechanical Engineering. Her interests include radiation damage in structural materials and radiation effects on the magnetic properties of materials. In her free time, Ashley pilots a Cessna-150, skydives, snowboards, bakes, and loves walking her beagle-dachshund mix, Winnebago.
Michael Fuller
Michael is a PhD student in the Nuclear Engineering Department at the University of Tennessee. A Kansas native, he joined the U.S. Navy’s submarine force and served on nuclear powered submarines as a certified naval nuclear engineer, and finally as the Director of Nuclear Engineering and Training at Submarine Learning Facility, Norfolk, VA. After leaving the U.S. Navy, Michael served as a NRC Licensed Senior Reactor Operator on a four loop Westinghouse pressurized water reactor. He is currently a member of the Experiments Group at ORNL’s HFIR, where he evaluates the nuclear safety analysis for materials research and isotope production projects. He holds graduate degrees in Mechanical and Nuclear Engineering from the Naval Post Graduate School and Kansas State University, respectively. He also holds an MBA from the University of New Haven, a doctorate in education from the University of Southern California and has PhD work in Material Science Engineering at Norfolk State University. His research will focus on high temperature materials applications in GEN IV/advanced reactor designs. He enjoys jazz, sports, learning and family.
Alicia Raftery
Alicia Raftery is a PhD student in Nuclear Engineering at the University of Tennessee, focusing on advanced nuclear fuel fabrication and characterization. Her research interests include high-temperature processing, thermal property measurements, the development of advanced characterization methods, and the fabrication of ceramic, CERMET, and TRISO fuel forms. Prior to beginning her doctoral studies, Alicia worked in both the national laboratory and private nuclear sectors, where she gained experience optimizing fuel production methods and performing high-precision material characterization in support of industry and government programs. She holds dual master’s degrees in Nuclear Engineering from KTH Royal Institute of Technology and Grenoble INP, as well as a bachelor’s degree in Nuclear Engineering from Texas A&M University. She is currently a member of Oak Ridge National Laboratory’s Advanced Fuel Fabrication Group.
Charles Søren Thompson
Søren is from Nashville, TN. He graduated with a B.S. in Physics and Applied Mathematics from Lipscomb University. His research interests include plasmas and materials for fusion applications. Outside of his studies, he enjoys music, linguistics, history, and gaming.
Tim Stack
Tim is a PhD student from Saginaw, Michigan. He graduated from the Illinois Institute of Technology in Chicago, Illinois with a B.S. in Physics and a B.S. in Astrophysics in 2023. He worked as an Operator at the Facility for Rare Isotope Beams at Michigan State University for a little over a year before joining Dr. Zinkle’s group in the Fall of 2025. Tim is interested in advanced nuclear materials for application in fission reactors. Outside of classes and research Tim enjoys traveling, exploring the outdoors, watching a movie, and spending time with friends and family.
Keaton McNulty
Keaton McNulty joined Dr. Zinkle’s group in Fall 2025 after graduating from Stony Brook University with a B.E. in Engineering Science. Through his thermal spray research at Stony Brook University, he gained an interest in the materials developed to withstand extreme environments. He is now working towards a PhD in Nuclear Engineering and Master’s in Materials Science. Particularly, he is drawn to the materials research for nuclear-based space exploration, such as nuclear thermal propulsion. Outside of research and classes, he likes to enjoy nature, weightlift, rock climb, and read fantasy.
Kaden Bleck
Kaden Bleck graduated from Texas Tech University with a B.S. in Chemical Engineering before joining Dr. Zinkle’s group in the Fall of 2025. He is pursuing a PhD in Nuclear Engineering and Master’s Degree in Materials Science. Kaden’s interest in nuclear engineering comes from his time as a research intern at Abilene Christian University’s NEXT Lab. There, he performed research related to the analysis of molten salt and gases within a molten salt reactor. In his free time, Kaden enjoys staying active with his dog, listening to country music, and keeping up with the Packers and Brewers.