THE APPLICATION OF SAXS TO DETERMINE THE FRACTAL PROPERTIES OF POROUS CARBON-BASED MATERIALS

A simple derivation of Bale and Schmidt's equation for the intensity of X-rays scattered through small angles (SAXS) by a porous solid with a fractal surface is given. This expression is then used in conjunction with experimental SAXS data to estimate the surface fractal dimension, D, of a wide range of porous, carbon-based solids. The measured values of D vary over virtually the whole theoretically allowable range. Further, we show that for a black coal sample both the fractal dimension and the extent of the surface are a function of the degree of oxidation of the coal sample. Thus, this method may be used to follow processes in porous solids and, given appropriate apparatus, the technique could be adapted to follow such processes in situ. © 1990.