关键词: SiO₂气凝胶, 化学干燥剂, 水洗工艺, 复合材料

Abstract: In this experiment, sodium silicate was used as the silicon source to prepare SiO₂ aerogel by drying under normal pressure. The influence of different sodium silicate mass fraction and chemical desiccant content on the vibrating density, specific surface area, pore volume and pore diameter, microstructure and other indicators of SiO₂ aerogel was mainly explored. The best washing efficiency was determined and the effect of Na⁺on the performance of aerogels was analyzed. The results show that when the mass fraction of sodium silicate is 7wt%, the prepared aerogel has excellent performance, specifically, the gel time is 3 min; the compaction density can be as low as 0.209 g/cm³; the higher porosity is 90.5%. When n(DCCA)∶n(Si)=2∶1, the aerogel has a larger specific surface area of 531.69 m²/g and a higher total pore volume of 2.51 ml/g, and the pore structure is the most uniform. When removing Na⁺ through water washing, the washing temperature should be controlled at around 50 ℃, and the water consumption should be controlled at around 15 times the amount of accumulated water. Four washes can remove 97.24% of the original Na⁺. Finally, it is found that the residual Na⁺ will have a negative impact on the density and thermal conductivity of SiO₂ aerogels, so the process of removing Na⁺ is very important.

Key words: SiO₂ aerogel, chemical desiccant, water washing process, composites