Published online by Cambridge University Press: 21 February 2011
The beam-bending method was used to measure the effect of partial drying on the viscoelastic relaxation behavior and permeability of a two-step acid-base catalyzed silica gel. Both the elastic modulus (E) and the permeability (D) showed a power-law dependence on density (ρ): E ~ ρm, m ≈ 3.0; D ~ ρ-n, n ≈ 2.5. The viscosity of the network rose from ~1011 to ~1013 Pa·s, and was strongly dependent on age as well as density of the gel. The viscoelastic relaxation function was well described by the stretched exponential function with an exponent of 0.3–0.5.