Deformation of silica aerogel during fluid adsorption

Aerogels are very compliant materials---even small stresses can lead to large deformations. In this paper we present measurements of the linear deformation of high porosity aerogels during adsorption of low surface tension fluids, performed using a linear variable differential transformer. We show that significant deformation can occur under conditions common in studies of helium in aerogel, and that the degree of deformation of the aerogel during capillary condensation scales with the surface tension. This scaling may then be used to suggest limits on safe temperatures for filling and emptying low density aerogels with helium.