MELTING AND FREEZING BEHAVIOR OF INDIUM METAL IN POROUS GLASSES

The size-dependent melting and freezing behavior of In metal in porous silica glasses with mean pore diameters between 6 and 141 nm has been studied by differential scanning calorimetry. The melting and freezing temperatures of the pore In were always less than the corresponding bulk values, and varied in inverse proportion to the diameter of the confining silica pores. In the smallest pores the latent heat of fusion was also determined, and found to be about one-third of its bulk value. The observed size dependence of the melting temperature was in good agreement with the predictions of thermodynamic treatments of melting in finite systems, and allowed the solid-liquid interfacial free energy to be estimated for several different geometrical models. The measured latent heat, however, was smaller than expected based on thermodynamic considerations. No evidence for an energy barrier separating the solid from the liquid was found.