Surface modification of silica aerogels with trimethylchlorosilane in the ambient pressure drying

Silica aerogels were made by sol-gel techniques using tetraethoxysilane, followed by drying under ambient pressure. BET and XRD results show that the silica aerogels have a high inner surface area and are amorphous. Laser granularity analysis shows that the average particle size of silica aerogels is less than 20 mu m and that they have mesoporous structure. The surface chemical modification was confirmed by FTIR spectroscopy. The thermal stability of the hydrophobic aerogels was studied from 25 to 1200 degrees C. The hydrophobic nature of the aerogels could be maintained up to around 500 degrees C. Above this temperature, the aerogels become hydrophilic.