Concentration effects on irreversible colloid cluster aggregation and gelation of silica dispersions.
Journal article, 2006

Effects of particle concentration on the irreversible aggregation of colloidal silica are studied using in situ destabilization via the ionic strength increase derived from the enzymatic hydrolysis of urea by urease. Aggregation is monitored by time-resolved optical density and dynamic light scattering measurements. It terminates at a gel boundary, signaled by a prominent increase of the optical density and incipient non-ergodicity. Raman scattering is used to demonstrate that the enzymatic reaction continues, well beyond gelation for the compositions studied here, until the urea is consumed. Calibration of the ionic conductivity permits for constructing stability diagrams in terms of particle and salt concentration. As with reversible gelation, the process exhibits a collective character in that lower ionic strengths are required for gelation of concentrated dispersions and vice versa. However, light scattering demonstrates that the gel boundary is preceded here by a line marking the transition from reversible to irreversible cluster formation, with the two transition boundaries tracking each other. Comparisons are made with dispersions destabilized by direct addition of salt solutions, which gel under very different conditions.

Author

Anna Schantz Zackrisson

University of Gothenburg

Anna Martinelli

Chalmers, Applied Physics, Condensed Matter Physics

Aleksandar Matic

Chalmers, Applied Physics, Condensed Matter Physics

Johan Bergenholtz

University of Gothenburg

Journal of Colloid and Interface Science

0021-9797 (ISSN) 1095-7103 (eISSN)

Vol. 301 1 137-44

Subject Categories

Physical Chemistry

DOI

10.1016/j.jcis.2006.04.066

PubMed

16723134

More information

Created

10/7/2017