Tio2 powder is earned after sulfate process by solving illmanite in the sulfuric acid and a purity of up 95% of TiO2 is gained . why the color of Tio2 turns yellow after 2h annealing in 900 oC temperature ?
as shown in the picture the white is before annealing and yellow is after annealing .
thank you
your friend from iran.
Dear Arman,
I think there are traces of iron hydroxides left in your TiO2 concentrate during your chemical and annealing process. These iron hydroxides may turn the colorless TiO2 yellowish. The most common natural Fe-hydroxide is the mineral goethite, chemical formula FeOOH. It generally colors ocher-yellow.
Kind regards,
Guenter Grundmann
1) can be resudes from the synthesis. To avoit this, try secuential washes with diffent solvents/pH, like water/NaOH pH 8, after deionized water, after ethanol anhydric.
2) change of phase, can be TiO2 in phase anathasa that change to rutile, is less probable due to the temperature. Depend of the envirioment of the anniling.
Regards.
Since you used natural ilmenite, FeTiO3, as the starting material for your synthesis, it is likely to be an iron phase that is causing the color is suggested by Guenter. You said you obtained 95% purity. Did you analyse what the remaining 5% is?
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