Synthesis and characterization of silica aerogels by a novel fast ambient pressure drying process

摘要

Using cheap waterglass as silica source, silica aerogels were synthesized via a novel fast ambient drying by using an ethanol/ trimethylchlorosilane (TMCS)/Heptane solution for modification of the wet gel. One-step solvent exchange and surface modification were simultaneously progressed by immersing the hydrogel in EtOH/TMCS/Heptane solution, in which TMCS reacting with pore water and Si-OH group on the surface of the gel, with ethanol and heptane helping to decrease the rate of TMCS reacting with pore water and extrude water from gel pores. The synthesized silica aerogel was a light and crack-free solid, with the density of 0.128-0.136 g/cm~3 and 93.8-94.2 percent porosity. The microstructure, morphology and properties of the aerogels were studied by FTIR, SEM, TEM and BET measurement. The results indicate that silica aerogels exhibit a sponge structure with uniform nano-particle and pores size distribution. The specific surface areas of silica aerogels are 559-618 m~2/g. And there is an obvious Si-CH_3 group on the surface of the silica aerogel.