Preparation and Characterization of Mullite Fiber-Reinforced Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub> Aerogel Composites

Abstract

Mullite fiber-reinforced Al2O3-SiO2 aerogel composite was prepared through hybrid sol-gel process, vacuum pressure impregnation technology and ethanol supercritical drying technology using aluminum chloride hexahydrate (AlCl3·6H2O), 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 Al2O3-SiO2 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 Al2O3-SiO2 aerogel increased from 589m2/g at ambient temperature to 667m2/g at 600°C, and correspondingly the pore diameter increased from 21.47nm to 27.82nm. The phase of Al2O3-SiO2 aerogel was from boemite at ambient temperature to γ-Al2O3 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.