Interprétation de la diffusion centrale des rayons X par les systèmes poreux. I

A porous system may be characterized by using two statistical distributions of chord lengths: (l) (particle chords) and f(m) (pore chords). Calculations are presented giving a general relationship between the shape of small angle scattering and the distribution of segment lengths limited by particle and pore boundaries. This development represents a generalization of Porod's method. By means of an approximation, this general expression is simplified and can be applied in many cases. The properties of distributions (l) [or f(m)] are analysed and it is shown that the condition (0) = 0 (or f(0) = 0] means that particles (or pores) do not possess any sharp edges. The presence or absence of sharp edges allows the separation of small angle scattering curves into two characteristic forms. The functions (l) and f(m) corresponding to several simple geometrical forms are analysed.