常压制备SiO_2气凝胶的温度控制研究

Preparation and Temperature Control of Silica Aerogels at Ambient Pressure

以正硅酸乙酯(TEOS)为先驱体,乙醇(EtOH)为溶剂,盐酸和氨水为酸碱催化剂,N,N-二甲基甲酰胺(DMF)为干燥控制化学添加剂,通过溶胶-凝胶法制备SiO_2醇凝胶,经异丙醇(IPA)/正己烷(Hexane)溶剂置换,三甲基氯硅烷(TMCS)/正己烷表面改性等工艺,最后经常压干燥制备完整,低密度,高比表面积,超疏水的SiO_2气凝胶块体。研究了各工艺阶段温度变化对气凝胶性能的影响。研究发现:水解温度为35℃,凝胶温度为室温,老化温度为50℃,分步溶剂置换中前4步为50℃,第5步为35℃,改性温度为35℃,清洗温度为50℃,制备的SiO_2气凝胶块体,比表面积高达892.33 m^2/g,密度0.142 g/cm^3,疏水角140°。

Based on the sol-gel method,complete block silica aerogels with high specific surface area,low density and super-hydrophobic property were prepared by using tetraethoxysilane（ TEOS） as precursor,ethanol（ EtOH） as solvent,hydrochloric acid and ammonia as acid-base catalyst,N,N-dimethylformamide（ DMF） as drying control chemical additives,isopropanol（ IPA） / normal hexane（ Hexane） as exchanging solvent and trimethylchlorosilane（ TMCS） as hydrophobic surface modification at ambient pressure. In this paper,the influences of the temperature variation on silica aerogels properties were studied. The result reveals that block silica aerogels have good hydrophobic property whose contact angel is 140°,surface area is 892. 33 m^2/ g and density is only 0. 142 g / cm^3 when hydrolysis temperature is 35 ℃,gelation temperature is room temperature,aging temperature is 50 ℃,exchange temperature of the first four steps is 50 ℃,exchange temperature of step 5 is 35 ℃,surface modifying temperature is 35 ℃ and clearing temperature is 50 ℃.