COATED SILICAS AND SMALL-ANGLE X-RAY-INTENSITY BEHAVIOR

Porod plots of the small-angle X-ray intensities scattered by porous silicas that have undergone different coating processes show deviations from the predicted constant asymptotic behaviour. The deviations are ascribed to the effect of the coating film. We propose a constant-electron-density model for these films. The theoretical scattering function calculated from the model permits an estimate of the film thickness, electron density and average number of coating molecules per unit area of the support.