Al2O3-SiO2复合气凝胶的制备及改性剂对其结构与隔热性能的影响

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。 

Preparation of Al2O3-SiO2 composite aerogel and the influence of modifier on its structure and thermal insulation properties

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.