A small-angle X-ray scattering study of aggregation and gelation of colloidal silica

Schantz Zackrisson, Anna,1973Gothenburg University,Göteborgs universitet,Institutionen för kemi,Department of Chemistry (author)

Aggregation and gelation in colloidal silica dispersions have been studied by time-resolved, small-angle X-ray scattering. Two different ways of raising the ionic strength, leading to destabilization of the dispersions, have been examined. In situ destabilization by urease-catalyzed hydrolysis of urea has been used as well as an approach with simple mixing of sols with salt solutions. For concentrated dispersions different structures result from the two destabilization methods. Structures differ also in the gelled state, with essentially no fractal scattering from the directly mixed samples whereas fractal scattering on intermediate length scales is observed for the in situ destabilized samples. In contrast, for more dilute particle concentrations, similar structures are generated in both cases and at gelation structures are in close agreement. However, gel times differ drastically in some cases for the two methods, as do the conditions for gelation. These differences are tentatively rationalized by some degree of irreversible aggregation occurring in the mixing stage that, given sufficient time, leads to gelation.

NATURVETENSKAP Kemi hsv//swe
NATURAL SCIENCES Chemical Sciences hsv//eng
Colloidal dispersions; Silica particles; Aggregation; Sol–gel transition; SAXS; Small-angle X-ray scattering

Pedersen, Jan Skov (author)
Bergenholtz, Johan,1964Gothenburg University,Göteborgs universitet,Institutionen för kemi,Department of Chemistry(Swepub:gu)xbjohq (author)
Göteborgs universitetInstitutionen för kemi (creator_code:org_t)

In:Colloids and surfaces. A, Physicochemical and engineering aspects: Elsevier BV315:1-3, s. 23-300927-7757

By the author/editor: Schantz Zackriss ...; Pedersen, Jan Sk ...; Bergenholtz, Joh ...

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