Evolution of the viscoelastic properties of SnO2 colloidal suspensions during the sol–gel transition

This paper describes the effect of the concentration of electrolyte and pH on the kinetics of aggregation and gelation processes of SnO2 colloidal suspensions. Creep, creep-recovery, and oscillatory rheological experiments have been done in situ during aggregation and gelation. A phenomenological description of the structure of the colloidal system is given from the time evolution of rheological parameters. The dependence of the equilibrium steady-state shear compliance on the terminal region of clusters or aggregates seems to be a way to determine the beginning of interconnection of aggregates and the gel point. We propose that at this point the equilibrium steady-state compliance is a minimum. The steady-state viscosity determined from creep experiment can be fit with a power law with the extent of the transformation, giving critical exponent s=0.7±0.1. The value of the critical exponent Δ=0.78±0.05 was determined from oscillatory experiment. These results indicate that gelation of SnO2 colloidal suspension exhibits the typical scale expected from the scalar percolation theory.