中文摘要：

以仲丁醇铝为前驱体,盐酸为催化剂,采用溶胶-凝胶法再经过超临界修饰和干燥,制备出块体Al_2O_3气凝胶。将莫来石纤维跟Al_2O_3溶胶混合,用同样的方法制备出纤维复合Al_2O_3气凝胶。用场发射扫描电子显微镜（FESEM）、热分析仪、孔径分布仪和X线衍射仪（XRD）表征Al_2O_3气凝胶及复合样品的结构和热学性能。结果表明：经过超临界修饰的Al_2O_3气凝胶具有更高的结晶度和耐温性能,并通过与莫来石纤维复合,其力学强度得到了有效的提高。

英文摘要：

monolithic alumina aerogels were prepared by a sol-gel method combined with the ethanol supercritical drying and modification technique using alumina tri-sec butoxide and hydrochloric acid as the precursor and the catalyst respectively. Fiber composite alumina aerogels were prepared with the same method. The micro-structure and thermal properties of the alumina-based aerogels were characterized by field emission scanning electron microscope（ FESEM）,thermal analyzer,pore size distribution analyzer,and X-ray diffraction（ XRD）. Results showed that the alumina aerogels prepared by the supercritical modification had higher crystallinity and thermal stability,thus their mechanical strength was effectively improved by compositing with fiber.