Heterogeneous 3D Morphological Evolution of Ni Microparticles in Molten Salts

February 1, 2023

The Science 

Materials in molten salt nuclear systems undergo complex structural evolution that is difficult to observe directly during operation. Researchers used in situ synchrotron X-ray nano-tomography to track the three-dimensional evolution of nickel microparticles in molten KCl–MgCl₂ at high temperature. They observed highly heterogeneous behavior, including rapid particle coarsening, local dissolution, and formation of smaller particles within the same system. These results show that multiple competing transport and reaction mechanisms govern particle evolution in molten salt environments. 

The Impact 

Understanding how metals evolve in molten salts is important for predicting corrosion, deposition, and particulate behavior in reactor systems. This work provides direct visualization of dynamic morphological evolution under realistic conditions. The findings improve understanding of how local chemical and transport conditions influence particle stability and structural evolution in molten salts. 

Summary 

This study used in situ synchrotron X-ray nano-tomography to investigate the time-dependent evolution of nickel microparticles in molten KCl–MgCl₂. 

Particles immersed in molten salt underwent rapid aggregation and coarsening compared with particles heated in inert environments. Rather than evolving through classical sintering, particles merged through liquid-mediated transport processes enabled by the molten salt environment. 

At the same time, strong heterogeneity was observed across the system. Some regions exhibited rapid coarsening into large structures, while others showed local dissolution or formation of smaller particles. These competing behaviors indicate that multiple mechanisms—including dissolution, diffusion, and radiolytic reduction—operate simultaneously. 

The study further suggests that local variations in temperature, salt chemistry, and radiation conditions strongly influence particle evolution pathways. Small particles may form through fragmentation, re-precipitation, or reduction of dissolved metal ions. 

Overall, the results demonstrate that morphological evolution in molten salts is controlled by coupled growth, dissolution, and transport processes that vary spatially throughout the system. 

Contact 

Yu-chen Karen Chen-Wiegart, Stony Brook University / Brookhaven National Laboratory, Karen.Chen-Wiegart@stonybrook.edu 

Funding 

This work was supported by the Molten Salts in Extreme Environments Energy Frontier Research Center, funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. This research used resources of the National Synchrotron Light Source II at Brookhaven National Laboratory. 

Citation 

Liu, X., A. Ronne, L.-C. Yu, P. Halstenberg, X. Xiao, W.-K. Lee, S. Dai, M. Ge, and Y.-c. K. Chen-Wiegart. “Heterogeneous 3D Morphological Evolution of Ni Microparticles in Molten Salts: Visualized by Operando Synchrotron X-ray Nano-tomography.” JOM 75 (2023). https://doi.org/10.1007/s11837-023-05715-8 

2023-23154  |  INT/EXT  |  Newsroom