title: Relation between microstructure and mechanical behavior of concentrated silica gels.
abstract: We produce concentrated (40 vol%) gels of uniformly sized silica particles by an in situ process, based on the enzyme-catalyzed hydrolysis of urea in the liquid phase of electrostatically stabilized suspensions. Two different methods are used: Either the pH of the suspensions is shifted toward the isoelectric point of the particles (delta pH method), or the ionic strength is continuously increased at constant pH (deltaI method). We compare the two kinds of gels in terms of elastic and yield behavior as well as microstructure by using rheological measurements in oscillation and high-pressure freezing in combination with cryo-SEM, respectively. Results suggest a strong increase of elastic and yield properties in concentrated particle gels with decreasing homogeneity of their microstructures.
authors.affiliation: Nonmetallic Materials, Department of Materials, ETH Zurich, Zurich, CH-8092, Switzerland.
authors.forename: Hans M
authors.initials: HM
authors.lastname: Wyss
authors.forename: Elena
authors.initials: E
authors.lastname: Tervoort
authors.forename: Lorenz P
authors.initials: LP
authors.lastname: Meier
authors.forename: Martin
authors.initials: M
authors.lastname: Müller
authors.forename: Ludwig J
authors.initials: LJ
authors.lastname: Gauckler