水玻璃常压制备块状SiO_2气凝胶及特性的研究

Preparation of Nubbly Silica Aerogels and Their Properties in Sodium Silicate at Ambient Pressure

以廉价水玻璃为硅源,常压干燥制备出了低密度、高性能的块状SiO_2气凝胶,结果表明:所制备的SiO_2气凝胶平均密度在0.11~0.15 g/cm3,比表面积在450~650 m^2/g,孔隙率为90%~98%,具有高疏水性,对甲基红的吸附率可达80%;最佳制备方案为:向20%硅酸钠溶液中加入乙二醇和乙酰胺,硅酸钠与乙二醇和乙酰胺的摩尔比为1∶1∶2,无水乙醇为置换剂,1∶5的三甲基氯硅烷/无水乙醇混合液为表面改性剂,置换和改性时间分别为72 h和24 h;酸的种类、浓度和量,疏水改性剂的种类和比例,干燥工艺,乙二醇和乙酰胺的添加对SiO_2气凝胶的制备都存在影响;所制备的SiO_2气凝胶的疏水性能和吸附性能均非常良好。

Monolithic silica aerogels was prepared with low density and high performance under ambient pressures drying.The experiment results demonstrated that when the average density and specific surface area of preparedsilica aerogels are0.11~0.15 g/cm^3 and 450~650 m^2/g,respectively,and the porosity is 90%~98%. It has higher hydrophobicity and the rate of adsorption of methyl red can reach up to 80%. The best preparation scheme is that ethylene glycol and acetamide adding into sodium silicate solution at 20%,the molar ratio of sodium silicate to ethylene glycol and acetamide was 1 ∶1∶2,ethanol as a displacer,trimethyl chlorosilane/1 ∶5 ethanol mixture as surface modification agent,replacement and modification time were72 h and 24 h. The preparation of silica aerogels are affected by concentration and quantity of acid,hydrophobic modification type and proportion of the agent,drying process,adding ethylene glycol and acetamid. The hydrophobic properties and adsorption properties of the prepared silica aerogels is very well.