块状石英纤维/Al_2O_3气凝胶复合材料的非超临界干燥法制备及表征

采用溶胶-凝胶法和常压干燥法以N,N′-二甲基甲酰胺(DMF)作为干燥控制化学添加剂制备了低密度石英纤维增强Al2O3气凝胶复合材料.通过氮气吸附-脱附实验比较研究了石英纤维对氧化铝气凝胶孔结构参数的影响;采用X射线衍射技术表征了在升温过程中石英纤维/Al2O3气凝胶复合材料的相结构变化;利用扫描电子显微镜和透射电子显微镜观察了Al2O3气凝胶基体及其石英纤维复合材料的微观形貌;初步探讨了DMF对Al2O3气凝胶形貌和密度的影响.研究结果表明石英纤维/Al2O3气凝胶复合材料成块性好,纤维与气凝胶基体结合紧密,石英纤维提高了Al2O3相转变温度,适量的DMF有利于形成均匀凝胶网络结构,减小干燥收缩压力.

Preparation and Characterization of Monolithic Silica Fiber/ Al2O3 Aerogel Composites by Non-Supercritical Drying

Low-density alumina aerogel/silica fiber composites were prepared by sol-gel technology and an atmospheric pressure drying method with N,N'-dimethylformamide (DMF) as a drying control chemical additive. The variation of pore structure and specific surface area were compared with alumina aerogel without adding silica fiber based on the nitrogen adsorption-desorption method. The changes in phase structure during the heating process were characterized by X-ray diffraction. The micro-morphology of the alumina aerogel and its composites were studied in detail by scanning electron microscopy and transmission electron microscopy. The influence of DMF on the aerogel matrix is discussed. We found that the fabricated bulk composites are a close combination between alumina aerogel and silica fiber. The silica fiber improves the phase transition temperature of the alumina aerogel. An appropriate amount of DMF is helpful for the formation of a uniformgel network, thus decreasing the drying shrinkage pressure.