Textural characterization of porous silica films prepared by the sol–gel process

Abstract

Porous thin silica films were prepared on glass plates using the dip-coating process from colloidal solutions of silicon alkoxide dissolved in ethyl alcohol. The influence of solution parameters such as viscosity, pH, dipping velocity and thermal treatment temperature on the film formation was determined. The films were adherent, transparent and free of cracks. The porosity was estimated by the Lorentz–Lorenz equation using the refractive index measured by UV–vis spectroscopy and compared with values obtained by the nitrogen adsorption method. For a certain thickness and porosity, it was possible to prepare antireflective layers, which were identified by the transmission spectra in the visible region.

Acknowledgements: The authors thank and Flávio Plentz for the thickness measurements. This work was supported by CNPq and FAPEMIG.