Effect of different chemical additives and heat-treatment on ambient pressure dried silica aerogels

The experimental results on the physical and super-hydrophobic properties of the ambient pressure-dried silica aerogels doped with different chemical additives (CAs) and heat-treated at 350°C for 2 h in air are reported. N,N-dimethylformamide (DMF), glycerol (GLY) and ethylene glycol (EG) were doped as CAs to the tetraethyoxysiliane (TEOS) precursor prepared aerogels. The molar ratio of CAs/TEOS (G) was varied from 0 to 1.2. DMF-doped aerogel at G = 0.8 possessed minimum shrinkage (≈6%) and low bulk density (≈0.2 g cm−3). The contact angle (θ) at G = 0.8 DMF-doped aerogel was ∼178°, which decreased a little (θ ≈ 162°) when heat-treated at 350°C in air, but the super-hydrophobic property was retained. The small angle X-ray scattering testing results showed that DMF-doped aerogel had the most uniform and smallest particles and particle size distributions compared with GLY- and EG-doped aerogels. But the CAs doping had a little influence on the degree of surface roughness of the particles.