Preparation of Al2O3-SiO2 composite aerogel and the influence of modifier on its structure and thermal insulation properties
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摘要: 以AlCl3·6H2O为前驱体,采用离子交换工艺和溶胶-凝胶法,在正硅酸四乙酯(TEOS)乙醇溶液中浸泡实现Al2O3和SiO2的复合,经表面改性和常温常压干燥制备出低成本、无杂质离子、低热导率的Al2O3-SiO2复合气凝胶。探索了不同有机硅烷改性剂对Al2O3-SiO2复合气凝胶结构和隔热性能的影响。结果表明,在改性剂为三甲氧基甲基硅烷(MTMS),改性环境为中性(pH为7)时,Al2O3-SiO2复合气凝胶表现出最均匀的微观结构,SiO2和Al2O3主要以无定形形式存在。MTMS可有效减少Al2O3-SiO2湿凝胶表面的-OH基团,形成Si-O-Si和Al-O-Si基团。Al2O3-SiO2气凝胶比表面积和孔体积分别达到574 m2/g和2.3 cm3/g,热导率低至0.029 W(m·K)-1。以上研究为促进气凝胶材料在隔热领域的应用提供了支持。Abstract: Low cost, impurity-free and low thermal conductivity Al2O3-SiO2 composite aerogel were prepared from AlCl3·6H2O derived gel through ion exchange technology and sol-gel method by dipping silicon in tetraethyl orthosilicate (TEOS), subsequently surface modification and ambient pressure drying were employed. The effects of different organosilane modifiers on the structure and thermal insulation properties of the Al2O3-SiO2 composite aerogels were explored. The results show that Al2O3-SiO2 composite aerogel shows the most uniform microstructure in the neutral (pH=7) modified environment of trimethoxy methylsilane (MTMS). The SiO2 and Al2O3 phases mainly exist in amorphous form. MTMS is more effective in reducing the -OH group on the surface of Al2O3-SiO2 wet gel to form Si-O-Si and Al-O-Si groups. The specific surface area and pore volume of Al2O3-SiO2 aerogels are as high as 574 m2/g and 2.3 cm3/g, respectively, and the thermal conductivity is as low as 0.029 W(m·K)-1. The above research provides support for the application of aerogel materials in the field of thermal insulation.
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Key words:
- Al2O3-SiO2 /
- composite aerogel /
- ion exchange /
- heat insulation /
- surface modification /
- ambient pressure drying
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