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) in porous materials by applying dynamic and thermodynamic relationships for the freezing and melting curves of water in silica gels filled with water has been investigated. The thickness beta of the layer of nonfreezable pore water and the inverse proportional coefficients a between the pore radius and the depression Delta T of the melting or freezing temperature of freezable pore water have been determined by simultaneous iterative optimization of both the peak radius of the PSD and the entire pore volume. Assuming a cylindrical pore, the alpha values during 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 dependence of a was negligible. The ice-water interfacial tension was also 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 Academic Press, Inc.