Wettability of anatase ceramic glazes
Coatings with catalytic properties, i.e., activated by UV radiation, can form surfaces with a number of special features, based on the ability of such coatings to interact with UV radiation. Also, they change the surface wettability and, therefore, the water that is deposited naturally or artificially on these surfaces can easily runoff. Some coatings can exhibit the hydrophilic effect, where droplets of water deposited on them decrease their contact angle with the photocatalytic surface after exposure to UV radiation, forming a highly uniform thin film of water, which behaves optically like a clear sheet of glass, avoiding the fogging of the surfaces and, therefore, making self-cleaning surfaces. The aim of this work was the study of the wettability of anatase ceramic glazes for self-cleaning tiles developed by the addition of TiO2 in commercial frits. Glazes were developed by adding anatase in commercial ceramic frits as an agent of photocatalysis. The glazes were coated on ceramic tiles, which were fired between 800 and 1000°C. The formulations were characterized (SEM), and the wettability was determined by measuring the water contact angle. The microstructural analysis (SEM) showed that the anatase particles can disperse properly in the glaze matrix. The determination of the contact angle shows the clear influence of the glaze type and sintering temperature on the wettability characteristics of the obtained layer.
The photocatalytic semiconductors have attracted much attention because they are a low cost and non-toxic alternative to develop photoactive surfaces that could destroy organic compounds by oxidation reactions. In addition, the semiconductor particles can be immobilized in a thin layer on any surface, and can maintain their activity after repeated catalytic cycles (1). Among the various semiconductor available, such as metal oxides (e.g. TiO2, ZnO and CeO2) and metal sulfides (e.g. ZnS or CdS), the titania (TiO2) has been the most suitable for photocatalysis and photovoltaic activity because of its relatively high quantum yield (2).
Titanium dioxide has two main catalytically active crystalline phases, anatas