Porous silica gel has been prepared by acdification of water glass. To study aggregation, gelation andaging use has been made of 29Si-NMR to investigate silica transformations on molecular scale. Qn ratios were used to define distribution of silica in particles and gels. On colloidal scale both 1H relaxation of water and small angle scattering (SAXS, SANS) was very informative, especially because changes in fractal dimension could be used to describe silica transformations during aggregation and aging.
Interpretation of fractal dimension in terms of aging mechanisms is performed by computersimulations of both aggregation/aging processes and calculation of the corresponding scattering spectra. Comparison of simulated spectra of aged silica, based on hypothetical aging mechanisms, with experimental spectra emphasized the important role of formation of rings on local scale.
In freeze-dried silicas pore distributions were investigated with both neutron scattering (SANS) and physisorption (BET), revealing different pore structures, both in growth and form, after aging at 80°C and aging catalyzed by fluorine.
|Naam||Studies in Surface Science and Catalysis|
|ISSN van geprinte versie||0167-2991|
|Congres||conference; International Symposium on the Scientific Bases for the Preparation of Heterogeneous Catalysts ; 6 (Louvain-La-Neuve) : 1994.09.05-08; 1995-09-05; 1995-09-08|
|Periode||5/09/95 → 8/09/95|
|Ander||International Symposium on the Scientific Bases for the Preparation of Heterogeneous Catalysts ; 6 (Louvain-La-Neuve) : 1994.09.05-08|