Microstructure control of porous alumina film using aqueous sol containing poly(ethylene glycol)

To fabricate a porous and thick alumina film with large surface area on a substrate by a dip-coating technique, we prepared an aqueous sol containing poly(ethylene glycol) (PEG). The sol was prepared by hydrolysis of aluminum (III) isopropoxide with large amount of water and following peptization to colloidal particle from precipitate. The films were coated on the glass substrate by the dip-coating and then calcined at 500 °C. The maximum thickness of the film prepared by one-run dip-coating was ca. 1,000 nm. The film was an aggregate of alumina particles with a diameter of 30–50 nm and pores were interstices between the particles. The porosity of alumina film can be controlled in the range of 40–59% by changing PEG concentration in the dip-coating solution.