Dielectric studies of freezing behavior in porous materials: Water and methanol in activated carbon fibres

Abstract

We report both experimental measurements and molecular simulations of the melting and freezing behavior of two dipolar fluids, water and methanol, in activated carbon fibres. Differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DS) were used to determine the melting point in these porous materials. The melting point was found to be very sensitive to the relative strength of the fluid–wall interaction compared to the fluid–fluid interaction. Monte Carlo simulations and the Landau free energy formalism were used to determine the shift in the melting point, T_m, for simple fluids in pores having weakly attractive and strongly attractive walls. The strength of the interaction of the fluid with the pore wall is shown to have a large effect on the shift in T_m, with T_m being reduced for weakly attracting walls and elevated for strongly attracting walls.