Preparation and characterization of monolithic Al2O3–SiO2 aerogel

摘要

Al₂O₃–SiO₂ aerogel was prepared through mixed sol–gel process and ethanol supercritical drying technology using aluminum chloride hexahydrate (AlCl₃·6H₂O) and tetraethoxysilane (TEOS) as precursors. Under the condition of the propylene oxide used as gelation initiators, during the process, a kind of Al₂O₃–SiO₂ aerogel with porous and large specific surface area were achieved in our experiments. Structures and properties of Al₂O₃–SiO₂ aerogel are investigated by means of X-ray Diffraction, Nitrogen adsorption/desorption analysis, Scanning Electron Microscopy, Fourier Transform Infrared Spectroscope, and Thermogravimetry-Differential Thermal analysis. The results showed that the Al₂O₃–SiO₂ aerogel with the mole ratio of Al/Si = 3/1 possessed better heat-insulation performance and high-temperature stability. And it possessed a porous network structure made up of leaf shape particles. At the same time, Al₂O₃–SiO₂ aerogel showed a low density of 0.071 g/cm3 at room temperature, specific surface areas of 708 m2/g at 600°C, as well as 255 m2/g at 1200°C. The Al₂O₃–SiO₂ aerogel is the polycrystalline boehmite (γ-AlOOH) phase at room temperature. As the temperature growing, it transferred to γ-Al₂O₃ at 600°C, and mullite phase at 1200°C.