Determination of average pore diameter of SiO2 xerogels by small angle X-ray scattering

Small angle X-ray scattering (SAXS) with synchrotron radiation as X-ray sou rce has been used to study the structure of Sig xerogels prepared by sol-ge l process. All SAXS profiles in this paper deviate from Porod's law and sho w negative or positive deviation. In order to obtain the information of por e in SiO2 xerogels, we have proposed the corresponding methods to correct t he negative and positive deviations from Pored's law. Then, the average por e diameter of SiO2 xerogels is determined with Debye's method and Guinier's method, separately, and the results are found to be close to each other. T he average diameters fall in the rang1 3-25 nm for samples prepared under v arious conditions. The results of SAXS are also close to that determined by N-2 adsorption method at 77 K with ASAP2000.