Collaborative Research: Decoding Grain Boundary Complexion Dynamics in Irradiated Compositionally Complex Carbides

NON-TECHNICAL SUMMARY Modern technologies, from nuclear energy to spacecraft and advanced electronics, depend on materials that can survive extreme conditions, including intense radiation environments. Developing materials that remain safe, reliable, and durable in these environments is essential for the nation’s energy security, technological leadership, and future space exploration. This project focuses on a promising new class of ceramic materials made by combining multiple metals with carbon. These materials have shown an unusual ability to resist radiation damage, making them attractive candidates for next-generation energy and aerospace systems. However, scientists still do not fully understand how radiation affects the internal interfaces, known as grain boundaries. These interfaces often control how materials degrade and ultimately fail. This research project is investigating how radiation changes the chemistry and structure of grain boundaries in this new class of ceramics, and tests whether their behavior under radiation can be controlled by adjusting which metals are combined and how much carbon is present. This project is integrating material synthesis, irradiation experiments, advanced microscopy, machine learning, and multiscale modeling to uncover the underlying mechanisms that control radiation-driven changes at grain boundaries. The findings of this research are anticipated to help advance the design of more reliable ceramics for small modular reactors, fusion energy systems, spacecrafts, and high-power electronics that must operate reliably in radiation-rich environments. In this way, the project is promoting the progress of science and supporting national priorities in energy security, space technology, and technological resilience. This project is also establishing a collaborative training pipeline across two universities, providing graduate and undergraduate students with hands-on experience across materials synthesis, nuclear science, data science, and computational modeling. Outreach activities are introducing middle school students to the science of nuclear radiation effects and materials design through hands-on demonstrations, thereby helping inspire the next generation of scientists and engineers. TECHNICAL SUMMARY This research project examines how radiation changes the chemical and structural states of grain boundaries in compositionally complex carbides, a class of refractory ceramics formed by combining multiple transition metal elements with carbon in a rock-salt crystal structure. Although these materials are known for their strong resistance to bulk radiation damage, the mechanisms governing radiation-induced changes at grain boundaries, known as complexion transitions, remain largely unexplored. The project is testing the hypothesis that transition metal chemistry and carbon stoichiometry jointly govern defect generation, transport, and reaction pathways, thereby controlling the radiation-induced complexion transitions at grain boundaries. This research is integrating compositionally controlled synthesis of carbide ceramics with varying transition metal combinations and carbon contents, conducting ion beam irradiation, and performing high-resolution electron microscopy characterization. These experimental observations are being interpreted using a physics-informed graph neural network trained on first-principles calculations to predict defect formation and migration energetics across compositional space, coupled with a multiscale rate-theory model that links atomic-scale defect kinetics to long-term interfacial evolution. By systematically comparing simple monocarbides with compositionally complex carbides and varying carbon vacancy concentrations, the project is establishing predictive relationships between chemical composition and grain boundary stability under irradiation. The resulting framework is expected to inform the design and evaluation of radiation-tolerant ceramics for advanced nuclear energy systems, aerospace components, and high-temperature electronics. This grant is also providing integrated training for graduate and undergraduate students across two institutions in synthesis, irradiation science, advanced characterization, and computational modeling, while also engaging K-12 students through hands-on outreach activities introducing concepts of radiation effects and materials design. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.