Small angle x-ray and ultra small angle x-ray scattering from some fractal porous solids - theory and experiment

摘要

Small angle scattering from a range of porous solids including coal, processed coal, glassy carbon, charcoal and porous catalyst supports indicates that the surfaces of the pore walls in these solids are not smooth i.e. that Porod's law is not obeyed. However, the small angle scattering curves for both X-rays and neutrons for many systems still obeys a simple power law dependence with scattering angle, as in Porod's law, but with a power law index alpha not equal to 4. Depending on the value of alpha this scattering behaviour may be interpreted as arising from different effects. Some porous solids have walls whose surfaces are fractaly rough i.e. exhibit self-similar surface structures, whilst some exhibit behaviour characteristic of mass fractals. Other systems, however, have been described as having pore walls which are not sharp i.e. possess fuzzy interfaces.