Dense silica-based coatings prepared from colloidal silica

Two sets of silica-based coatings have been prepared using two different wet methods. Set A was obtained using the conventional sol–gel method from thetraethyl-orthosilicate (TEOS) as the main precursor. Set B was produced from commercial colloidal silica added with two structural modifiers, KOH and sodium metasilicate (Na2SiO35H2O). The structure of both sets of coatings was characterized using infrared absorption, X-ray diffraction and nitrogen adsorption isotherms measurements. The results show a much lower surface area and a slower oxygen diffusion rate for coatings of set B, indicating that these coatings have a denser structure and therefore are more effective as oxygen barriers.