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The paper has investigated that the crack-free silica aerogels was prepared with TEOS as silica source by sol-gel method and ambient pressure drying. The process of mixture surface mo-dification, solvent mixture exchange have been systematically researched. The surface group, thermal stability, morphology and microstructure of silica aerogels have been investigated by FT-IR, DSC-TG, XRD, SEM, TEM and BET adsorption method.The results indicate that the density of silica aerogel modified by TMCS/HMDSO is0.1213g·cm-3under the best conditions, the contact angle is155°, the surface area is899.8m2·g-1, and the pore volume is2.856cm3·g-1; the density of silica aerogel modified by HMDZ/HMDSO is0.2752g·cm-3, the contact angle is129°, the surface area is812.8m2·g-1, and the pore volume is2.338cm3·g-1; The properties of aerogels modified by TMCS/HMDSO is better than that of HMDZ/HMDSO. Appropriate low-temperature heat treatment can improve the pore structure of airgel and the pore size distribution uniform. The heat-resistant temperature of hydrophobic silica aerogel is about450℃.Compared with other mixture solvents, aerogels using hexane/toluol have the best properties. Under the best conditions, the density of silica aerogel by Hexane/toluol is0.103g·cm-3, the contact angle is156°, the specific surface area is928.4m2·g-1, and the pore volume is3.295cm3·g-1; the density of silica aerogel by heptane/benzene is0.122g·cm-3, the contact angle is143°, the surface area is891.5m2·g-1, and the pore volume is2.881cm3·g-1; the density of silica aerogel by heptane/toluol is0.116g·cm-3, the contact angle is160°, the surface area is912.1m2·g-1, and the pore volume is3.353cm3·g-1The dropping of CaO or MgO will lead to the decrease of SiO2aerogel surface area and pore volume; part of the mixed material graft to the network framework, partially filled in the hole. Surface area of9.7%MgO/SiO2aerogel is824m2·g-1, and pore volume is2.168cm3·g-1; Surface area of12.6%CaO/SiO2aerogel is812.8m2·g-1, pore volume is2.338cm3·g-1. Aerogels and composite aerogels have fine adsorption capability for acidic gas, and their adsorption efficiency on the acid gases is NO>SO2>H2S. Mainly physical adsorption, hydrophobic pure SiO2aerogel has a good recycling ability. There are two kinds of forms of Composite aerogel, physical adsorption and chemical adsorption, which has the characteristics of high absorbance and stable adsorption, But it requires the activation energy of adsorption, and the capacity of the repetition adsorption is not high.
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