Visualizing the Invisible: Confined Crystallization in Porous Media from Pilot to Pore Scale

Abstract:

Gas hydrates are ice-like crystalline compounds formed when gas molecules are trapped within hydrogen-bonded water cages under high-pressure, low-temperature conditions. In porous sediments, hydrate formation and dissociation involve a complex interplay of phase transitions, multiphase flow, and mechanical deformation, a classic problem of confined crystallization in deformable porous media. However, the fundamental questions of where, how, and why crystals nucleate and grow in pore spaces remain poorly understood.

In this seminar, Dr. Kou will present a journey to make confined crystallization visible across scales. Beginning at the pilot scale, where traditional pressure/temperature monitoring revealed little about internal evolution, she turned to X-ray computed tomography to map the phase distribution and to observe how phase transitions alter pore architecture. Recognizing the temporal resolution limits of CT, she further developed high-pressure silicon-tube micromodels that enable real-time visualization of dynamic crystal growth and porous structure change. These observations have clarified the “where” and “how” of hydrate crystallization but have also exposed the limits of experimental resolution in answering “why”. Why crystals select certain nucleation sites, adopt specific growth habits, and interact with pore walls in particular ways? The seminar will conclude by outlining the next step in this scaling-down journey, integrating pore-scale visualization with classical molecular simulations and poromechanics to build a multiscale physics of confined crystallization.

Short bio:

Dr. Xuan Kou is an Associate Professor at the CAS Key Laboratory of Gas Hydrate, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences. She received her Ph.D. in Chemical Engineering from the University of Chinese Academy of Sciences in 2022. Her research focuses on confined phase transitions and multiphase transport in porous media, with emphasis on in situ visualization of hydrate crystallization from pore to pilot scales using X-ray CT and high-pressure micromodels. She has published 33 SCI journal papers with an H-index of 15. She currently leads a Young Scientists Fund project from NSFC on wetting effects during hydrate dissociation in porous media, and serves as an editorial board member of Frontiers in Energy Research and reviewer for Chemical Engineering Journal, Applied Energy, and Energy.