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 perm eability. This low permeability results from the small size of the por es. The behaviour of gels subjected to a stress is linked to permeabil ity and low rigidity. It is shown that the interaction of the solid ne twork with the fluid within the pores is responsible for stress develo pment which in turn gives rise to easily measured strains. Interaction s between the solid and a liquid, a supercritical fluid and finally a gas are investigated, Experiments are reported to demonstrate the soli d-fluid interaction.