Preparation and Characterization of Mullite Fiber-Reinforced Al_2O_3-SiO_2 Aerogel Composites

摘要

Mullite fiber-reinforced Al_2O_3-SiO_2 aerogel composite was prepared through hybrid sol-gel process, vacuum pressure impregnation technology and ethanol supercritical drying technology using aluminum chloride hexahydrate (AlCl_3-6H_2O), tetraethoxysilane (TEOS) and mullite fiber as raw materials. The samples were characterized by XRD, SEM, BET, Hot Disk and Universal Testing Machine. The results showed that mullite fiber-reinforced Al_2O_3-SiO_2 aerogel composite possessed excellent heat-insulation performance, high-temperature stability and mechanical property. The thermal conductivities of composite increased from 0.0186W/mK at 150°C to 0.1198W/mK at 1200°C. The surface area of Al_2O_3-SiO_2 aerogel increased from 589m~2/g at ambient temperature to 667m~2/g at 600°C, and correspondingly the pore diameter increased from 21.47nm to 27.82nm. The phase of Al_2O_3-SiO_2 aerogel was from boemite at ambient temperature to γ-Al_2O_3 at 600°C, and to mullite at 1200°C. The compressive strength was 1.8MPa, when the shape variables reached 10%, the tensile strength was 0.69MPa, the bending strength was 6.4MPa.