Hydrophobicity Silica Aerogels Synthesized At Ambient Pressure

Silica aerogels are the solid materials which possess the lightest density and highestporosity, providing with high thermalinsulation and low sound velocity, they are a class ofporous materials with a wide range of potential applications.The influences experiment was designed for each factor on their different properties,inthis work. The as-prepared aerogels have been characterized by bulk density, porosity, N₂adsorption desorption （BET）, Scanning electron microscopy （SEM） The result is thatprocess yields silica aerogels exhibiting very low bulk density and the highest specificsurface area1213m²/g, respectively,The average pore diameter from14nm to30nm.The experiment using methyltrimethoxysilane （MTMS） and tetraethoxysilane（TEOS）as the co-precursor and C₂H₅OH as solvent、C₆MimBF₄as the catalyze by aone-step Sol-Gel process followed by the solvent replacement and Ambient Pressure dryingsynthesis of superhydrophobic silica aerogels.The experiment using methyltrimethoxysilane （MTMS） and tetraethoxysilane （TEOS）asthe co-precursor and H₂O as solvent, C6MimBr or C₁₂MimBr as co-solvents by a two-step（acid-base catalyze） Sol-Gel process followed by the solvent replacement and AmbientPressure drying synthesis of hydrophobic silica aerogels. The two-step （acid-base catalyze）sol-gel process C6MimBr or C₁₂MimBr ionic liquids have been shown to act as structuredirecting agents and cosolvents.The key of disadvantage was shrinkage and crack when drying the preparation of hydrophobicsilica aerogels at ambient pressure． Hydrophobic modification bad been studied byco-precursor methods, In order to obtain hydrophobic silica aerogels with different degree ofhydrophobicity, the molar ratio MTMS/TMOS （M） was varied from0.5to3, silica networkstructure were determined by²⁹Si nuclear magnetic resonance （NMR） and the infraredtransmission spectra （IR）. From these data, the mixed hydrophilic–hydrophobic nature of thesurface of these materials is proposed. the proportional of hydrophilic–hydrophobic groups is related to the M, when the M achieve to3there is no hydrophilic groups（Si-OH） appearance.