Ultraporous materials with low permeability

Physical and chemical properties of silica aerogels are influenced by their texture. Silica aerogels exhibit both high porosity and low permeability. This low permeability results from the small size of the pores. The behaviour of gels subjected to a stress is linked to permeability and low rigidity. It is shown that the interaction of the solid network with the fluid within the pores is responsible for stress development which in turn gives rise to easily measured strains. Interactions between the solid and a liquid, a supercritical fluid and finally a gas are investigated. Experiments are reported to demonstrate the solid-fluid interaction.