Improvement of Thermal Stability of Porous Titania Films Prepared by Electrostatic Sol-Spray Deposition (ESSD)

Abstract

A porous titania film with uniform pores of micrometer size was obtained on a dense stainless steel substrate by the electrostatic sol-spray deposition (ESSD) method. A porous film without cracks was obtained from the parent titania sol after more than 5 h of aging. This porous structure comprised an aggregation of fibrous titania. The pore size and the surface morphology were controlled by changing the aging period of the parent sol. The as-deposited films were shown to be amorphous titania by XRD analysis. They were calcined in order to obtain anatase or rutile titania. The structures of the porous films were damaged during the calcination at 873 K in air. Improved thermal stability of the porous titania films was obtained from a parent sol made by mixing fresh reactive titania sol and aged sol. Additionally, small particle structures were observed intergrown with the fibrous structures. The surface morphology of these films was not damaged by calcination at 873 and 1273 K in air. After calcination at 873 K, only the anatase phase was observed by the XRD measurement, whereas only the rutile phase was found after calcination at 1273 K. Porous anatase or rutile films can be produced using ESSD and proper calcination.