N

The surface fractal dimension enters Equation (6.24) through the pore size distribution [50]. Equation (6.24) holds for any surface with 2 < Ds < 3. Despite the quite different form of the isotherms in Equations (6.17) and (6.24), the numerical values of adsorption that are calculated from these equations agree well, up to x « 0.7.

The asymptotic behavior of Equation (6.24) can be described as follows: for a geometrically flat surface, Ds = 2 and Equation (6.24) yields the classical BET isotherm [3]. For x ^ 1, the growth of the adsorbed film scales as

N , „ ^ N ln[1/(1 - x)] — a- for 2 < Ds < 3 and — a- for Ds = 3

0 0

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