Phase Transitions of Water in Zeolite Pores

Abstract

Phase transition temperatures of water are experimentally determined for the case in which ice melts in the pores of zeolite (natural mineral) with a pore size of 0.2–2 nm. Three temperatures with a sharp change in the heat capacity and extremes of low-frequency electrical fluctuations are found when moistened material is heated from –150 to 100°C, the values of which are –20, 43, and 86°C. These values are associated with the melting of polygonal structures containing from five to seven water molecules.