硅铝纤维复合气凝胶的制备及热学稳定性

Preparation and Thermal Stablity of Silica- alumina-fibers Composite Aerogels

以正硅酸四乙酯(TEOS)和仲丁醇铝(ASB)为前驱体,硝酸为催化剂,复合莫来石纤维为增强支撑骨架,在不使用螯合剂情况下,采用溶胶-凝胶技术,超临界干燥制备了块体硅-铝纤维复合气凝胶。制备的样品分别进行600,800和1000℃热处理。利用扫描电镜、红外分光光度计、X射线衍射仪、Hotdesk热导率分析仪等仪器对复合气凝胶的微观形貌、结构及热性能进行表征。硅铝复合气凝胶在室温下热导率为0.035W/m·K,复合气凝胶的热导率随着温度的升高而升高。硅铝纤维复合气凝胶室温下的热导率为0.046W/m·K,高温处理后的收缩率相比硅铝复合气凝胶有所降低。

The silica-alumina-fibers composite aerogels were prepared by a sol-gel method combined with the ethanol supercritical drying technique using aluminum tri-sec butoxide(ASB) and tetraethylorthosilicate(TEOS) as the precursor and nitric acid as catalyzer without the chelating agent. The mullite fibers were distributed inside the composite aerogels to act as a supporting skeleton material, which could increase the mechanical property. Si to Al molar ratio is 3:1 according to the composition of mullite. The effects of the catalyst and water's amount on the gelation time of aerogels were studied. The aerogels samples were heat-treated at different temperatures of 600, 800 and 1000 oC. The structure and thermal capability of the composite aerogels were characterizated by SEM, IR, XRD and Hotdisk etc. The silica-aluminaa-fibers composite aerogels exhibit excellent thermal insulating properties. The thermal conductivity of silicon-aluminum composite aerogel at room temperature is 0.035 W/m·K, which increases as temperature rises. The thermal conductivity of silica-alumina-fibers composite aerogel is 0.046 W/m·K at normal temperature. The shrinkage rate of the silica-alumina-fiber composite aerogel after high temperature treatment decreases compared to that of silica-aluminum composite aerogel.