摘要
研究了用溶胶凝胶和常压干燥的方法制备SiO2气凝胶粉体时,硫酸-水玻璃体系的成胶规律,发现凝胶时间与体系的pH值有较大的关系;在反应物浓度一定的条件下,凝胶时间t-pH曲线成“W”型,随反应物浓度的降低,逐渐向“U”型曲线转变;体系凝胶时间最快点的pH值,在碱性环境中随反应物浓度的减小而降低,在酸性环境中随反应物浓度的减小而增大;这与在碱性和酸性环境中所存在的两种成胶机理有直接的关系。甲酰胺的引入不会明显改变硫酸-水玻璃体系的成胶特点,但明显改善了SiO2气凝胶的物理性能。
The preparation of silica aerogelat ambient pressure from waterglass is a promising method. The gelation process of H2SO4-waterglass system was investigated, and was used to prepare SiO2 aerogel powders. The results indicate that the pH value had a strong impact on the gelation time of H2SO4- waterglass system. For the system with constant reactant concentrations, the relationship between gelation time and pH value showed a ＂W＂ shape curve, which changed gradually to ＂U＂ shape when the reactant concentration decreased continuously. The pH value of the sol system with the shortest gelation time decreased in basic condition （pH≥7） and increased in acidic condition （pH〈7） with decreasing reactant concentrations. The two different gelation mechanisms of H2SO4-waterglass system in acidic and basic conditions should be responsible for this variation. Addition of formamide did not change obviously the gelation characteristic of H2SO4-waterglass system, but improved remarkably the physical properties of resultant silica aerogel.
出处
《化工学报》
EI
CAS
CSCD
北大核心
2007年第2期501-506,共6页
CIESC Journal
