Fractality of porous silicas: A comparison of adsorption and porosimetry data

The fractal dimensions of seven porous silicas were determined by means of gas adsorption, chemisorption of chlorosilanes, and mercury porosimetry. The silicas under investigation are shown to be surface fractals in the range of cross-sectional areas from 0.162 (N-2) to 1,450 sq. mn ((C6H13)(3)SiCl). The surface fractal dimensions obtained range from 2.05 to 2.90. On the other hand, mercury porosimetry data show that the silicas studied can be hardly considered as pore fractals within the range of a pore radius from 3.5 to 1000 nm. The apparent contradiction is discussed in the text. (C) 1996 Academic Press, Inc.