Diffusing-wave spectroscopy of concentrated alumina suspensions during gelation

Using diffusing-wave spectroscopy, we followed the aggregation and gelation of concentrated (30 vol%) alumina suspensions. The suspensions were destab ilized by either shifting the pH to the isoelectric point or by increasing the ionic strength. Both effects can be achieved continuously and homogeneo usly by using an enzyme-catalyzed internal chemical reaction. Based on the light-scattering data, we could derive quantitative information about the s ol-gel transition and the viscoelastic properties of the gels, as well as a characterization of changes in the microstructure. The elastic moduli dete rmined from light scattering are found to be in good agreement with rheolog ical measurements. (C) 2001 Academic Press.