Textural properties of ambient pressure dried water-glass based silica aerogel beads: One day synthesis

Abstract

The tedious surface modification and solvent exchange steps (∼six days) involved in the conventional ambient pressure drying of silica hydrogels (bead or bulk type) prohibit the commercial production of silica aerogels despite the low cost of water-glass precursor. The present studies were intended to reduce the processing time of the ambient pressure dried silica aerogel beads using the co-precursor method for the surface modification in the hydrogels. The textural properties of such aerogel beads have been reported and discussed. The experimental results revealed that the aerogel beads (1–2 mm in diameter) are mesoporous solids with average pore diameter ranging from 32 to 49 Å. The specific surface area and pore size distribution of the aerogel beads could be tailored over a wide range by varying the content of surface modifying agents such as trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDS) in the sol. The aerogel beads with specific surface area as high as 591 m 2/g and the corresponding cumulative pore volume of 0.5 cc/g have been synthesized in one day using the new route for the rapid surface modification in hydrogels. The aerogel beads retain their hydrophobic property up to a temperature of 773 K.