"The phase content and grain size of titanium dioxide often have a strong influence on properties for a variety of applications. In many cases it would be desirable to produce the stable rutile phase with an ultra-fine particle size (<10nm), but most low temperature synthesis methods produce predominantly the metastable anatase phase. The anatase-rutile transformation in TiO2 is known to be affected by dopant type and concentration, as well as the titanium precursor used in solution chemical synthesis. Recently, use of cavitation in the synthesis process has been shown to yield smaller grain size for a variety of oxides. However, the relative importance of these synthesis variables on the grain size and phase content of TiO2 is not well understood. In this study, Taguchi analysis was used to determine the relative effects of dopants (Sn), titanium precursor (butoxide, sulfate, chloride), and cavitation power on grain size and phase content. Precursor residuals were also measured by analytical chemistry. Grain size and phase content results were analyzed statistically to determine whether there is a size dependence of the anatase-rutile transformation. Results show that grain size is strongly dependent on the concentration of chlorine. Absent chlorine, a definite grain size-phase content correlation exists; rutile content increases as grain size decreases. An L-4 orthogonal Taguchi analysis shows chlorine content and tin content as the major influences on the final product. With minimum grain size and maximum rutile content being considered optimal, our best result was 100% rutile and an average grain size of 5nm, which was achieved by acoustic synthesis with 3% tin dopant and low residual chlorine. "
Worcester Polytechnic Institute
Materials Science & Engineering
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Farrell, Kimberly A., "Synthesis Effects on Grain Size and Phase Content in the Anatase-Rutile TiO2 System" (1999). Masters Theses (All Theses, All Years). 937.
grain size, rutile, titania, Titanium dioxide, Powder metallurgy, Nanostructured materials