Abstract: To maintain their excellent hydrophobic properties after high temperature service,fiber reinforced SiO₂ aerogel composites were prepared with tetraethyl silicate and mullite fiber needled felt as the main raw materials.Then,trimethoxy (1H,1H,2H,2H-heptafluorodecyl) silane (HDFTES) was used as the hydrophobic modifier to modify their hydrophobic properties by vapor deposition (reaction time of 5-22 h).The microstructure,pore diameter and hydrophobic property of the composites were studied.The results show that the vapor deposition enables aerogels to attain highly stable hydrophobic properties while preserving their original structure.With the increase of the hydrophobic reaction time,the water contact angle of the sample first increases gradually and then remains basically.When the reaction time is 18 h,the water contact angle reaches the maximum of 147°;after hydrophobic modification,the sample can maintain a good hydrophobic state in acid and alkali corrosive solutions;after the heat treatment at 600 ℃ for 3 h,the water contact angle of the sample is maintained at 132°,after the heat treatment at 750 ℃ for 36 min,the water contact angle is maintained at 123°,and its microstructure shows no significant changes,demonstrating excellent thermal stability.

Key words: silica aerogel, hydrophobic modification, high thermal stability

摘要： 为使纤维增强SiO₂气凝胶经高温使用后仍保持优异的疏水性能,首先以硅酸四乙酯、莫来石纤维针刺毡为主要原料制备了纤维增强SiO₂气凝胶复合材料,再采用三甲氧基(1H,1H,2H,2H-十七氟癸基)硅烷作为疏水改性剂,利用气相沉积(反应时间为5~22 h)对其进行疏水改性,并研究了其显微结构、孔径、疏水性能等。结果表明:气相沉积法能在保持气凝胶原有结构的同时使其具有高稳定疏水性能,随着疏水反应时间的增加,试样的水接触角先逐渐增大后基本不变,当反应时间为18 h时,水接触角达到最大值147°;经疏水改性后的试样在酸、碱腐蚀液作用下都可保持良好的疏水状态;经600 ℃热处理3 h后,试样的水接触角仍可保持在132°,经 750 ℃ 处理36 min后水接触角仍可保持在123°,且其显微结构无明显变化,表现出优异的热稳定性。

关键词: SiO₂气凝胶, 疏水改性, 高热稳定性