Melting Behavior of Nanosize Crystals : Part 1. Thermodynamic Description of Melting Point and Melting Point of Ice

Melting of nanosize crystals of ice and polymer measured with differential scanning calorimeter (DSC) has been reviewed on the research work by the present authors. The whole article was divided into the two parts due to limitations of space. In part 1, melting of nanosize ice has been treated.Firstly the thermodynamic aspect of melting point depression of nanosize crystals was treated briefly. The inversely proportional increase of specific surface area due to the decrease of crystal size was explained to be the origin of the melting point lowering from the equilibrium value.Secondly the melting point of ice formed in water-saturated microporous materials such as silica gels for HPLC use and polymer hydrogel membranes for artificial kidneys revealed the depression from 0°C inherent to its crystal size. This encouraged us to establish a new technique called “Thermoporosimetry” which can measure the pore size distribution (PSD) curve of porous materials thermally. The most advantage of this technique is that it can measure the PSD curve of polymer hydrogel for which the already existing techniques such as gas adsorption method and mercuryporosimetry cannot apply because the prior freeze-drying of the hydrogel samples destroys their nanosize pores.