Facile Preparation of Nanoporous Silica Aerogel Granules

Hydrophobic silica aerogel beads with low thermal conductivity and high porosity were prepared using a cost-effective sodium silicate as a silica source via an ambient-pressure drying process. Monolithic wet gels were first prepared by adjusting pH ~5) of a diluted sodium silicate solution. The silica aerogel beads (0.5~20 mm) were manufactured by breaking the wet gel monoliths under a simultaneous solvent exchange/surface modification process and an ambient-pressure drying process without using co-precursors or templates. Dried silica aerogel beads exhibit a comparable porosity (593 of surface area, 34.9 nm of pore size, and 4.4 of pore volume) to that of the aerogel powder prepared in the same conditions. Thermal conductivity of the silica aerogel beads (19.8 mW/mK at 20 ) is also identical to the aerogel powder.