Facile preparation of superhydrophobic silica nanoparticles by hydrothermal-assisted sol-gel process and effects of hydrothermal time on surface modification

Superhydrophobic silica nanoparticles were prepared by hydrothermal-assisted sol-gel process using a two-step synthesis route. Silica nanoparticles were obtained by hydrolysis and condensation of tetraethyl orthosilicate (TEOS). Hexadecyltrimethoxysilane (HDTMS) was added to allow the condensation reaction between HDTMS hydroxyl group and silica hydroxyl group, rendering silica particles hydrophobic. Silica nanoparticles had a HDTMS/TEOS molar ratio of 2:40 and exhibited good hydrophobic property with a high water contact angle of 156.1A degrees. Water droplet rolled off the surface of silica powder owing to a low sliding angle of 3.6A degrees. When hydrothermal time of TEOS decreased from 120 to 60 min, all silica powders gave rise to high water contact angles (ae154.8A degrees) and low sliding angles (ae5.5A degrees). However, silica powder became hydrophilic when HDTMS and TEOS were added to the precursor together. This facile preparation of superhydrophobic silica nanoparticles with short reaction time provided the advantages for potential application in industrial production. [GRAPHICS] Silica nanoparticles were synthesized by hydrothermal-assisted sol-gel process and hydrophobized using small amount of hexadecyltrimethoxysilane. Short reaction time facilitates the efficient production of superhydrophobic silica powders. Effects of hydrothermal time on surface modification of silica have been analyzed.