Method for synthesizing SiO2Al2O3 containing sol solution and method for forming porous alumina film

A method for synthesizing SiO2Al2O3 containing sol solution for forming a porous alumina to which silica is added, the method including:

• preparing an alkoxysilane solution comprising an alkoxysilane, water, an alcohol, and an inorganic acid;
• preparing an aluminum solution comprising an aluminum compound and water, the aluminum compound being selected from among aluminum nitrate, sodium aluminate, aluminum chloride, and aluminum sulfate;
• precipitating a precipitate of aluminum hydroxide in the aluminum solution;
• filtering the precipitate from the aluminum solution, and washing the filtered precipitate with water to prepare a precipitate cake;
• preparing Al2O3 containing sol solution, in which boehmite particles are dispersively present as sol particles, by preparing a slurry solution with adding water to the precipitate cake, performing a pH adjusting treatment on the slurry solution, and thereafter performing an autoclave treatment on the slurry solution;
• and
• preparing the SiO2Al2O3 containing sol solution, in which sol particles with silica bonded to boehmite particles are dispersively present, by adding the alkoxysilane solution to the Al2O3 containing sol solution,
• wherein the pH adjusting treatment on the slurry solution controls pH value of the slurry solution within a specific pH range so that a solution state of the Al2O3 containing sol solution after the autoclave treatment is a sol state.