Silicon dioxide inorganic membranes on Al2O3 matrix were prepared by Sol -Gel method using tetraethox ysilane (TEOS)as precursor and ethanol as the solvent .The effects of pH , chemical additives, heat treatment rate of temperature increase and the mole ratio of TEOS to ethanol on the quality of inorganic membranes were investigated .The results show that pH can affect the polymerization rate of TEOS , accordingly relate the quality of film directly .The gelation time is the long est w hen pH is 1 .8.Adding chemical additive N , N -dimethylformamide can prevent the film to chap.The rate of temperature increase during the heat treatment process is the main factor of film quality .Controlling the rate of temperature increase should be divide into two stages.It is controlled a t 0 .5 ℃/min before 210 ℃, and 1 ℃/ min from 210 ℃ to 600 ℃.When the mole ratio of TEOS to ethanol is 1∶6 .08,the film coating period is shorter than that of 1∶13 .64.

The silica sol is a kind of colloid solution, silica drop dispersing in water or solvents.Silica sol was prepared by sol-gel method from tetraethoxy silane (TEOS)with the ethanol as solvent and dilute hydrochloric as catalyst .Orthogonal test was used to study the effects on silica sol stability such as the mole ratio of water and TEOS , the mole ratio of EtOH and TEOS, pH , the mole ratio of DMF and TEOS and the temperature .The effects of the above factors can be used to control the silica sol stability .The results show that the mole ratio of EtOH and TEOS exhibits significant effect on the silica sol stability , the silica sol stability increases with the increasing mole ratio of EtOH and TEOS .The next is the mole ratio of DMF and TEOS .DFM makes gelation time become long .The other effects are least .The effect of temperature is the least, sol stability decreases with the increasing temperature .