Chinese Acad Sci, Inst Coal Chem, State Key Lab Coal Convers, Taiyuan 030001, Peoples R China
; Chinese Acad Sci, Inst High Energy Phys, Natl Synchrotron Radiat Lab, Beijing 100039, Peoples R China
SiO2 and ZrO2 sols were prepared by base-catalyzed hydrolysis and condensation of alkoxides In alcohol. PEG and diglycol were used as organic modifiers of SiO2 and ZrO2 sols respectively. The structure evolution during the sol-gel process was investigated by small angle X-ray scattering (SAXS) with synchrotron radiation as X-ray source. SAXS results show that the silica and zirconic sols are polydispersed, i.e., with proper size distribution. SAXS results also show that silica and zirconic aggregates are mass fractals, fractal dimensions span the regime 0.23-2.56 corresponding to very sparse and more branched and compact structures. The formation of a mass fractal is a kind of nonlinear process. Both RLCA and Eden models dominate the kinetic growth under base-catalyzed condition. it is also shown that the SAXS profiles do not agree with Pored's law and have negative or positive slopes, suggesting that the dispersive interfacial layer exists between sol particle and dispersing agent. The thickness of the interfacial layer falls between approximately 1.00 and 22.00 MI for samples prepared under various conditions. Both agreement with and deviation from Pored's law in SAXS are summarized, especially proposing the analysis method upon positive deviation with slit-smeared SAXS data.