Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5370191 | Applied Surface Science | 2006 | 7 Pages |
The experimental results on the synthesis and characterization of tetraethoxysilane (TEOS) based hydrophobic silica aerogels using hexadecyltrimethoxysilane (HDTMS) as a hydrophobic reagent by two step sol-gel process, are described. The molar ratio of tetraethoxysilane (TEOS), methanol (MeOH), acidic water (0.001 M, oxalic acid) and basic water (10 M, NH4OH) was kept constant at 1:55:3.25:1.25 and the molar ratio of HDTMS/TEOS (M) was varied from 0 to 28.5 Ã 10â2. The organic modification was confirmed by infrared spectroscopic studies, and the hydrophobicity of the aerogels was tested by the contact angle measurements. The maximum contact angle of 152° was obtained for M = 22.8 Ã 10â2. The aerogels retained the hydrophobicity up to a temperature of 240 °C and above this temperature the aerogels became hydrophilic. The aerogels were characterized by the thermal conductivity, density, contact angle measurements, optical transmission and scanning electron micrographs.