Abstract: Al₂O₃-SiO₂ composite membrane was prepared by sol-gel process using aluminium isopropoxide and
tetraethoxysilane as raw materials. The phase constitution, thermal stability, and the pore structure were characterized by means of XRD, DTA-TGA, IR, BET
etc. The results show that the phase constitution of the composite membrane was SiO₂ and γ-Al₂O₃ after calcined at 550℃ for 10h,
and the particle size range from 2nm to 4nm. The XRD results of the composite membrane (Al₂O₃/SiO₂=3:2) calcined at different temperatures show that
the membrane is constituted of γ-AlOOH and γ-Al₂O₃ at 400℃, γ-Al₂O₃ at 550℃ to 1150℃, γ-Al₂O₃ and α-Al₂O₃ at 1220℃, mullite
and α-Al₂O₃ at 1300℃. Al₂O₃-SiO_₂ composite membrane is constituted of Al--O and Si--O networks, and no Al--O--Si network
found membrane. The composite membrane has high thermal stability, and the pore structure of the membrane can influence on its constitution and
the thermal treatment temperatures.

Key words: aluminium isopropoxide, tetraethoxysilane, sol-gel, Al₂O₃-SiO₂ composite membrane