Intrusion-extrusion of water into-from hydrophobic nanopores at high temperature: unexpected dependence of dewetting pressure above 200°C

Wetting of a porous solid by a fluid is of significant interest to many industrial processes. However, at the nanoscale, this process is complex, and little is known about its temperature dependance. In this work, we explored the intrusion-extrusion of water for a heterogeneous lyophobic system composed of a hydrophobic mesoporous silica gel and water over a wide 25–250 °C temperature range. The intrusion pressure was found to have a classical negative temperature dependance in the whole 25–250 °C temperature range. However, an unexpected non-monotonic temperature dependance was observed for the extrusion pressure. In particular, it became temperature independent above 200 °C. This observation suggests that dewetting of nanopores at high temperature is more complex than previously thought of and serves as experimental grounds for further theoretical exploration.