Small-angle X-ray scattering analysis of porous powders of CaCO₃

The results of small-angle and ultra-small-angle X-ray scattering on porous CaCO₃ microparticles of pulverulent vaterite made by a conventional chemical route and by using supercritical CO₂ are presented. The scattering curves are analysed in the framework of the Guinier-Porod model, which gives the radii of gyration of the scattering objects and their fractal dimension. In addition, the porosity and the specific surface area are determined by using the Porod invariant, which is modified to take into account the effective thickness of the pellet. The results of this analysis are compared with those obtained by nitrogen adsorption.