Abstract
In the sulfate process for the production of TiO2 white pigments, amorphous metatitanic acid is calcined to microcrystals of the rutile polymorph by experiencing the dehydration, desulfurization, crystallization into anatase and the phase transformation from anatase to rutile (ART). Surface structure and thermal stability of metatitanic acid was characterized by Simultaneous Thermal Analyzer (STA) and FTIR Spectrometer. Powder X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) were used to describe the changes of phase composition and granule morphology. It was found that Free SO42- ions and S=O asymmetric structure existed on the surface of metatitanic acid as well as H2O with various adsorption state. The calcination intensity has a much stronger impact on crystallinity’s increase than dehydration, desulfurization. The temperature region of phase transform was 900∼1000°C. Rutile would not appear until amorphous metatitanic acid has crystallized into anatase completely and the anatase grain was in a slow growth before that. It was also found that particles were mutually merged by means of fusion of grain boundaries.
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