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复合增强型SiO2气凝胶的一步法快速制备与性能表征
作者:刘光武1 2 周斌2 倪星元2 刘燕刚1 
单位:1. 上海交通大学药学院 上海 200040 2. 同济大学 上海市特殊人工微结构材料与技术重点实验室 上海 200092 
关键词:复合二氧化硅气凝胶 纤维增强 一步法 超疏水 保温隔热 
分类号:TQ174
出版年,卷(期):页码:2015,43(4):934-940
DOI:10.14062/j.issn.0454-5648.2015.07.13
摘要:

 以水玻璃为前驱体,去离子水为溶剂,经溶胶−凝胶反应形成陶瓷纤维(含15%)增强的SiO2湿凝胶,采用乙醇/三甲基氯硅烷/正己烷的混合液进行一步溶剂替换和表面基团改性后,经常压干燥制备出复合SiO2气凝胶块体。该复合气凝胶密度低(0.216 g/cm3)、成形性好,经高温处理后仍维持未开裂块状。样品与纤维复合后,纤维与SiO2气凝胶网络结合较好,复合材料的孔洞保持完整,骨架未发生断裂,基本保持较明显的海绵状网络结构和球形骨架结构。通过对气凝胶样品进行微观结构和比表面积分析、热重和疏水性测试、弹性模量及热导率表征,测得复合SiO2气凝胶的比表面积为743 m2/g,疏水接触角为146°,弹性模量为5.1 MPa。当温度升至400 ℃时,该气凝胶的热导率从0.026 3 W/(m·K)增加到0.051 2 W/(m·K),疏水接触角为138°。此外,对一步法涉及的溶剂替换及表面修饰机理也进行了分析。

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 A composite of silica hydrogel with ceramic fibers (15% in mass fraction) was synthesized with sodium silicate as a precursor and deionized water as a solvent by a sol−gel method, and the composite was subsequently modified with a solution of ethanol/trimethylchlorosilane/n-hexane via one-step solvent exchange and surface modification, thus obtaining the crack-free and high hydrophobic composite aerogel monoliths. The composite aerogel has a low density of 0.216 g/cm3 and a superior formability. The ceramic fibers can be dispensed into the sample and combined with the silica aerogel network. There is a spongy meshwork structure on the surface of the aerogel. The aerogel samples were characterized by microstructure, analysis, specific surface area measurement, thermogravimetric analysis, hydrophobicity, elastic modulus and thermal conductivities test, respectively. The results show that the specific surface area of the composite aerogel is 743 m2/g, the contact angle with water is 146°, and the elastic modulus is 5.1 MPa. After a thermal process in the temperature range from room temperature to 400 ℃, the hydrophobicity remains unchanged (~138°), and the thermal conductivity of composite aerogel monoliths changes from 0.026 3 W/(m·K) to 0.051 2 W/(m·K). In addition, the mechanisms of solvent exchange and surface modification were also discussed.

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基金项目:
国家自然科学基金(21172145, 21372152, 21402117)项目。
作者简介:
刘光武(1985—),男,博士,讲师。
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