Slot-Die Process of a Sol–Gel Photocatalytic Porous Coating for Large-Area Fabrication of Functional Architectural Glass

The slot-die process is an appealing technology for the fabrication of coatings on large-area substrates. However, its application on the production of photocatalytic coatings based on sol–gel formulations remains virtually unexplored. Thus, assessing the suitable formulation of the sol and operational parameters that allow one to yield high-efficacy photocatalyst coatings is a current challenge. This work aims to analyze the transferability of titania sol formulation optimized for dip-coating processes to slot-die technology. In this sense, firstly, the sol formulation is optimized by analyzing the influence of several types of surfactants on the microstructural features and photoactivity of TiO2 coatings’ growth on glass substrates. All formulations rendered a meaningful porosity and nanoscopic anatase crystallites (11–15 nm) with optical band gap values close to the expectation (3.25–3.31 eV). Accordingly, the performance of the photocatalytic dye degradation was closely related to the porosity and crystallite size led by each titania sol, and no meaningful differences were found between the results provided by the coatings developed by dip-coating and the slot-die method, which demonstrates the capability of the latter for its application on a large-scale fabrication of photocatalytic coatings.

Development of Adhesive, Bioactive and Antibacterial Titania Sol-Gel Coating on Titanium Substrate by Dip-Coating Technique

The sol-gel method provides a wide variety of applications in the medical field. One of these applications is the formation of coatings on the metal implants. The coatings containing specific additive can enhance or improve the existing surface properties of the substrate. In this work, titania sol-gel coatings were doped with two forms of silver (AgNO3, Ag3PO4) and synthetic hydroxyapatite and applied on the titanium samples by dip-coating technique. After drying and slow firing, all coatings were characterized with scanning electron microscopy. Thin coatings were successfully prepared with excellent adhesion to the substrate (measured by ASTM D 3359-2), despite cracks. Coatings containing silver and hydroxyapatite demonstrated a 100% antibacterial effect against Escherichia coli after 24 h. The bioactivity of the coatings containing hydroxyapatite tested in modified simulated body fluid under static-dynamic conditions was confirmed by bone-like hydroxyapatite precipitation. To better understand the interaction of the coatings with simulated body fluid (SBF), changes of Ca2+ and (PO4)3− ions concentrations and pH values were studied.

Photocatalytic Degradation Study of Titania Sol-Gel Coated on Commercial Unglazed Ceramic Tiles

In this research photocatalytic degradation of nanotitania synthesized via sol-gel method and coated on commercial unglazed ceramic tiles was investigated. The starting precursors were titanium (IV) tetraisopropoxide (Ti [OCH(CH3)2]4; TIP), ethanol, hydrochloric acid and distilled water. Unglazed ceramic tiles were sintered at 900°C and 1100°C. The nanotitania based sols were applied on the tile surface using air-brush and calcined at 500°C for 3 h. The particle size of the synthesized TiO2 varied in the range 8-20 nm. The photocatalysis of nanotitania was studied through the photodegradation of methylene blue solution under UVC irradiation using UV-Vis Spectrophotometer. The presence of nanotitania on unglazed ceramic tiles was confirmed by a scanning electron microscope equipped with energy dispersive X-ray spectrometer (EDS). Ceramic tiles sintered at 900°C gave higher % open porosity and hence higher amount of nanotitania embedded on the ceramic surface. The results showed that all unglazed ceramic tiles coated with nanotitania were able to show photodegradation of methylene blue.