Synthesis of Nanoparticles of Mixed Oxides Containing Titanium Cerium Silver and Silicon: Phase Transformation

Abstract

Problem statement: Titanium dioxide is a well known material using with self-cleaning application. This is due to its properties after exposed to UV light: Superhydrophilicity and photocatalysis. The addition of other oxides could prolong these properties without continuing exposed to UV. However, titanium dioxide phase is essential. In order to obtain these properties, titanium dioxide needs to be in anatase phase. Approach: In this Research, phase transformation temperatures of mixed oxide of titanium dioxide and other oxides were determined. Samples of different mixed oxides were prepared by sol gel method. The first sample contained 30%TiO₂ and 70%SiO₂. The second sample contained 30%TiO₂, 15%CeO₂ and 55%SiO₂. The last sample contained 30%TiO₂, 15%CeO₂ and 55%SiO₂. Each sample was separately calcined at various temperatures from 350-850°C stepping by 50°C and followed by grinding and sieving to obtain in the form of powders. Then, each powder was characterized for its microstructure and phases of titanium dioxide, crystallite size by X-Ray diffraction. Results: The results from XRD showed that for a 30%TiO₂/SiO₂, an increase in calcined temperatures from 350-850°C (increasing by 50°C) increased average crystallite sizes of titanium dioxide (from 5.1-11.8 nm). Also, titanium dioxide phase found in the samples was only anatase. For a 30%TiO₂/15%CeO₂/SiO₂, an increase in calcined temperatures was not affect to the structure of the samples and XRD patterns seemed to be in an amorphous structure. Finally, for a 30%TiO₂/15%AgO/SiO₂, titanium dioxide was found in an anatase phase at 350°C until 650°C. Then, at calcined temperatures greater than 700°C, rutile phase started appearing in the structure while anatase phase peaks slowly declined with an increasing in calcined temperatures. This result showed that using these mixed oxides to coat over glass slides or mirrors for self-cleaning purposes, the films should be treated at certain temperatures to obtain an anatase phase. Conclusion: Phase transformation of titanium dioxide depends on calcined temperatures. The addition of other oxides such as silica, cerium or silver can effectively suppress the anatase-rutile phase transformation and resulted in an increase of anatase-rutile phase transformation temperatures.