Printing nano TiO2 on large-sized building materials: Technologies, surface modifications and functional behaviour.

The industrial feasibility of large-sized, photocatalytic building materials was assessed by the adoption of suitable, fast and environmental friendly technological solutions. Nanostructured TiO2 coatings can be realized by ink-jet or roller printing of nano-anatase suspensions by modifying, in one single step, the chemistry and microstructural features of products. Functional coatings must be consolidated through additional thermal steps, which necessarily entail modifications of the current production cycles of ceramic tiles. This is due to the fact that the direct functionalization of unfired ceramics is detrimental to the photocatalytic performance. The microstructure of coatings depends on deposition technologies and processing conditions. However, photoactive materials that also display superhydrophilic behaviour can be obtained by employing much lower amounts of TiO2 than 1.0 g m-2, and by annealing at temperature as low as 400-500 °C. A limited increase of the cost of products is involved, especially in the case of large-sized elements.