China's Refractories

Abstract: ：To optimize the preparation of alumina aerogels, the sol-gel method was combined with supercritical drying, using aluminum isopropoxide (AIP) as the precursor, ethanol (EtOH) as the solvent, and acetic acid (HAc) as the catalyst. The effects of the ethanol addition [n(AIP) : n(EtOH) : n(H₂O) : n(HAc)=1 : 8 : 0.8 : 2, 1 : 12 : 0.8 : 2, 1 : 16 : 0.8 : 2, and 1 : 20 : 0.8 : 2] and acetic acid addition [n(AIP) : n(EtOH) : n(H₂O) : n(HAc)=1 : 16 : 0.8 : 1, 1 : 16 : 0.8 : 2, 1 : 16 : 0.8 : 3, and 1 : 16 : 0.8 : 4] on the pore structure and specific surface area of Al₂O₃ aerogels were studied. The results show that ethanol affects the pore structure of Al₂O₃ aerogels by affecting the condensation probability of Al—OH troups, and acetic acid affects the pore structure of Al₂O₃ aerogels by affecting the reaction rate; when n(AIP) : n(EtOH) : n(H₂O) : n(HAc)= 1 : 16 : 0.8 : 2, the Al₂O₃ aerogel has a porous microstructure, and its internal pore diameters is generally smaller than the average free path of air molecules, showing excellent thermal insulation characteristics, low density of 0.20 g·cm^-3, and the specific surface areas of 458, 102, and 51 m²·g^-1 at 25, 1 000, and 1 200 °C, respectively.

Key words: Al₂O₃ aerogel, thermal insulation material, specific surface area, pore size distribution