The Role of Water in Densification of Gels

Abstract

ABSTRACTThe densification behavior of a gel-derived borosilicate glass was studied. Surface area, thermal gravimetric and infrared measurements were used to calculate the surface hydroxyl coverage as a function of time at several temperatures. Application of a viscous sintering model to the isothermal shrinkage data showed viscosity to increase isothermally by almost two orders of magnitude at the lowest investigated temperature. Although most of this increase is attributable to increased crosslinking accompanying dehydroxylation, structural relaxation was also shown to significantly affect the densification kinetics.