Heat Capacity Studies of Nano-Confined Argon

The effect of confinement on the thermodynamic properties and phase transitions of liquids and solids in confinement has been of long-standing interest and recent interest has focused on the effects of dimensionality. Hydrogen has been of interest due to the importance of quantum effects, in particular zero-point motion, and has been studied extensively in a variety of porous media. Argon is a good model for hydrogen as it will exhibit similar behaviors, in general, to hydrogen. Furthermore, it is important to understand the behavior of noble gasses in confinement as it may be useful for understanding gasses like hydrogen. Templated porous materials, such as MCM-41, provide an attractive model system for studying the effects of confinement due to their highly uniform one-dimensional pores with variable pore size. Unfortunately, the minimum pore diameter is typically limited to a few nanometers which limits our ability to approach the one-dimensional limit. We will present measurements of the heat capacity of argon confined in MCM-41.