Experimental Study of Thermal Stability of TiO2 in Presence of Dopants and Silica as a Catalyst Support at High Temperatures

One method to prevent contamination of glazed building tiles by volatile organic materials is coating their surfaces with nanophotocatalyst titanium dioxide, preferably at temperatures above 1000 °C. However, at such high temperatures titanium is subjected to phase change and cannot maintain its photocatalytic properties. In other words, the conventional coating methods encounter phase change problem. The main purpose of this experimental research is to resolve the aforementioned problem to maintain the thermal stability of titanium dioxide at temperatures more than 1000C. In order to achieve this purpose, silica and duPont two-component were used. Silica-based titanium dioxide nanostructure was doped with N and Ni ions. Then the coating materials were calcined at 1250 °C. FTIR, SEM, XRD, EDX and TGA technics were used for nanostructure analysis which indicated thermal stability of the nanostructure up to 1250 °C. The main advantage of the utilized coating method is its simplicity and economically reasonability.  Titanium has a catalytic effect only in the UV region. In order to enjoy the benefits of the visible light, the nanostructure was modified with different ions. Note that, the titanium dioxide has three phases, namely anatase, rutile and brookite, among which photocatalytic properties of anatase have received more attentions. DuPont and silica together cause a delayed phase change from anatase to rutile at high temperatures. The delay is very essential for some industrial applications such as preserving self-cleaning properties of surfaces after they have been coated. The resulting environmental impact is less consumption of chemical detergents. Results indicate that for titanium dioxide the presence of the anatase phase at 700 °C is 83%, but at 800 °C anatase completely converts to rutile phase. Furthermore, catalyst modifications by duPont two-component using silica along with calcination at higher temperatures makes anatase phase to grow. So that at 1250 °C it comprises 86% of the nanostructure.