PORE-SIZE DISTRIBUTION (PSD) MEASUREMENTS OF SILICA-GELS BY MEANS OF DIFFERENTIAL SCANNING CALORIMETRY .1. OPTIMIZATION FOR DETERMINATION OF PSD

A new method for the determining of the pore size distribution (PSD) i n porous materials by applying dynamic and thermodynamic relationships for the freezing and melting curves of water in silica gels filled wi th water has been investigated. The thickness beta of the layer of non freezable pore water and the inverse proportional coefficients a betwe en the pore radius and the depression Delta T of the melting or freezi ng temperature of freezable pore water have been determined by simulta neous iterative optimization of both the peak radius of the PSD and th e entire pore volume. Assuming a cylindrical pore, the alpha values du ring melting and freezing were estimated to be 33.30 +/- 0.32 Delta T and 56.36 +/- 0.90 Delta T (in nm K), respectively. The pore shape dep endence of a was negligible. The ice-water interfacial tension was als o estimated to be 20.4 x 10(-3) (1 - 15.9 x 10(-3) Delta T) in N m(-1) from the temperature dependence of ct during melting. (C) 1995 Academ ic Press, Inc.