A NEW APPROACH TO THE DETERMINATION OF THE SURFACE FRACTAL DIMENSION OF POROUS SOLIDS

A new approach to the determination of surface fractal dimension is proposed. It is based on the approximation of a given surface by a set of inscribed equicurvature surfaces. The surface fractal dimension, d(fs), is determined from the relationship between the area, S(c), and the mean radius of curvature, a(c), of these surfaces, S(c) approximately a(c)2-dfs. It is the common relationship for the area of a fractal surface measured by a yardstick of varying size, whose role here is played by a(c). The equicurvature surfaces can be realized in practice as the interfaces between fluids at the conditions of capillary equilibrium in the vicinity of a given surface. The area and the mean radius of curvature of equilibrium interfaces can be calculated on the basis of experimental data by using general thermodynamic relationships. Corresponding thermodynamic methods for calculating the surface fractal dimension are developed for capillary condensation and intrusion of a nonwetting fluid.