Effect of re-wetting on silica aerogel structure: a SANS study

Small angle neutron scattering (SANS) has been used to study (1) the ability to refill the pores of a silica aerogel (rho = 0.3 g/cm(3)) with water and (2) and effect of the water and the re-wetting process on the aerosol structure on the 1 nm to 100 nm scale. A sample filled with a D2O:H2O solution which was chosen tu match the scattering properties of silica shows no scattering at length scales < 40 nm down to the detection limit (similar to 2 nm) of the experiment. This lack of scattering demonstrates that the mesopores of the silica aerogel were successfully filled with the contrast-matching fluid. SANS spectra for samples filled with air or D2O are similar, indicating that the aerogel structure as detected by this technique is not affected by the reintroduction of water into the pores. Results suggest that some aerogels may be suited for applications in aqueous environments such as catalysis or chemical sensing. (C) 1998 Elsevier Science B.V.