Reverse micelles directed synthesis of TiO2-CeO2 mixed oxides and investigation of their crystal structure and morphology
Abstract
The synthesis of TiO2-CeO2 mixed oxides based on the sol-gel process controlled within reverse micelles of non-ionic surfactant Triton X-114 in cyclohexane is reported. The crystallization, phase composition, trends in nanoparticles growth and porous structure properties are studied as a function of Ti:Ce molar composition and annealing temperature by in-situ X-ray diffraction, Raman spectroscopy and physisorption.
The brannerite-type CeTi2O6 crystallizes as a single crystalline phase at Ti:Ce molar composition of 70:30 and in the mixture with cubic CeO2 and anatase TiO2 for composition 50:50. At Ti:Ce molar ratios 90:10 and 30:70 the mixtures of TiO2 anatase, rutile and cubic CeO2 appear.
In these mixtures TiO2 rutile is formed at higher temperatures than conventionally. Additionally, the amount of a present amorphous phase in individual mixtures was estimated from diffraction data.
The porous structure morphology depends both on molar composition and annealing temperature. This is correlated with the presence of carbon impurities of different character.