Alternative modification methods for sol-gel coatings of silica, titania and silica-titania using ultraviolet irradiation and water vapor

We investigated relatively new techniques for densification and crystallization of sol-gel silica, titania and silica-titania coatings at relatively low temperatures. irradiation of ultraviolet photons above the hand-gap energy was found to lead shrinkage of the sol-gel films through electronic excitations. Crystallization of sol-gel titania coatings was achieved by irradiation of ultraviolet laser (4.7 eV) beam. Exposure to water vapor was shown to he effective in rearrangement of sol-gel films causing densification of silica, crystallization of titania and phase separation of silica-titania around 100 degrees C. These techniques are useful for preparation of hard silica coatings and crystalline titania films on low-heat-resistant substrates, such as polymer prates.