Ultrafine crystalline TiO2 powders were prepared by just heating and stirring
aqueous TiOCl2 solution with a Ti+4 concentration of 0.5 mol/l at room
temperature to 100°C under one atmosphere. The crystallinity, the phase
transformation and the particle shape of ultrafine TiO2 powders obtained by
this simple precipitation method were analyzed using an X-ray diffractometer
(XRD), transmission electron microscopy (TEM), differential thermal analyzer
(DTA), and scanning electron microscopy (SEM). TiO2 crystalline precipitates
with a pure rutile phase were formed below 65°C, then TiO2 crystalline
precipitates with an anatase phase started forming at temperatures higher than
65°C, which ends with the pure anatase phase at 100°C. The direct formation
of TiO2 crystalline precipitates from an aqueous TiOCl2 solution is due to the
existence of the OH- ions in distilled water which cause the crystallization of
TiOCl2 to TiO2 without hydrolyzation to Ti(OH)4. Conventionally, rutile-phase
TiO2 is obtained at much higher temperatures. However, in this study a stable
rutile-phase TiO2 was obtained by a simple method at close to room
temperature.
To investigate color properties by inclusion of hematite in the iron zircon pigments, different samples were prepared by the sol-gel method without mineralizer. The starting amount of the ferric salt in the sol-gel reacting mixture was varied in order to obtain Fe2O3/Zr molar ratio in the range of 5-30%. Fe-ZrSiO4 pigments of the sol-gel reaction were calcined the range 600-1300°C. The crystalline phases were determined by using X-ray diffraction(XRD). The process of inclusion of hematite in iron zircon pink color were studied by UV-Vis-NIR spectroscopy and FT-IR spectroscopy. It was found that the coral pink and reddish color in the iron zircon pigments is due to α-Fe2O3 particles incorporated in the zircon matrix.
In high temperature ceramic glazes, a stable range of pink-red colors that produced Cr 2 O 3 -SnO 2 -CaO-SiO 2 pigments were factored by Cassiterite(SnO 2
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