Mechanical Properties of Gels; Stress from Confined Fluids

Abstract

Unexpended funds: NoneThis program began under the title of "Mechanical Properties of Gels", with the goal of understanding how the elastic modulus of a gel is controlled by its structure. Our early focus was on characterization of the elastic properties of the network, including the elastic efficiency (or, load-bearing fraction) of the network [1,2]. We also studied methods for characterization of the network, including development of a new model for adsorption on networks [3,4,5] that was used to follow the evolution of microstructure during sintering [6,7]. We proved that aerogels contract severely during nitrogen condensation in a standard adsorption experiment [8,9,10] and showed how the (erroneous) measured size distribution could be corrected [11]. The phenomenon of shrinkage during adsorption has recently attracted considerable interest, as indicated by the dedication of an entire session to it at a recent conference [12]. We also developed a novel method for measuring the gas permeability of aerogels over a wide range of pressure [13].The next few years were devoted to an extremely fruitful program of computer simulation in which we developed a new algorithm for simulating growth of clusters, allowing for flexibility in the branches [14]. This model, developed by Hang-Shing Ma in collaboration