Probing interface processes with high-resolution x-ray reflectivity

We have developed a technique for studying oxide-and-water interfaces under hydrothermal conditions up to 350 °C and 20 MPa. In-situ high-resolution x-ray reflectivity (HRXR) under such condition can provide unique information of interfacial hydration, ion adsorption, and dissolution/growth/alteration processes on the metal-oxide surfaces with molecular scale resolution (typically less than 0.1 nm) which are crucial to understanding the fundamentals related to materials integrity in the nuclear power plant conditions. The prototype cell has been designed and pilot tested. This is the first of this kind, and gives us a unique position leading the in-situ hydrothermal study of solid-water interface processes. The next step is to extend the application of the developed hydrothermal HRXR cell to various scientific subjects including electrical double layer phenomena under hydrothermal conditions, mineral dissolution, hydrophobic surface (e.g., diamond) interacting with hydrothermal water, etc. Meanwhile, further development includes the cell designs and experimental procedures for higher temperature-pressure conditions. (Key personnel: Changyong Park)