Sciencemadness Discussion Board - titanium dioxide turns yellow when heated.

titanium dioxide turns yellow when heated.

rockyit98 - 1-4-2021 at 01:12

store bought titanium dioxide turns yellow and back to white when cooled like ZnO do.so try to dissolve in H2SO4 to see if indeed ZnO but no such luck. I also extracted TiO2 from old dried up white paint (not that old so Lead safe)by burning it in a kiln. they also did that .
the reason for ZnO do that is Oxygen vacancies in it when heated. maybe TiO2 have ZnO impurity. can any one repeat this experiment with pure TiO2 ?
thanks.

itsallgoodjames - 1-4-2021 at 05:13

I found a paper on this with 2 seconds of research

Quote:

However, the TiO2 decomposes to other titanium oxides, which are TiO, Ti2O3 , and Ti3O5 , above 180°C. The titanium oxides re- main on the surface between 200 and 330 °C. Between 330 and 400 °C, TiO is a stable oxide in comparison with Ti3O5 and TiO2

Fulmen - 1-4-2021 at 09:32

James: That's surface oxidation of metallic Ti, not TiO2. According to Wikipedia TiO2 is reduced to TiO by metallic Ti @ 1500°C.

Johnny Cappone - 1-4-2021 at 09:43

Quote: Originally posted by rockyit98

store bought titanium dioxide turns yellow and back to white when cooled like ZnO do.so try to dissolve in H2SO4 to see if indeed ZnO but no such luck. I also extracted TiO2 from old dried up white paint (not that old so Lead safe)by burning it in a kiln. they also did that .
the reason for ZnO do that is Oxygen vacancies in it when heated. maybe TiO2 have ZnO impurity. can any one repeat this experiment with pure TiO2 ?
thanks.

https://en.m.wikipedia.org/wiki/Thermochromism

itsallgoodjames - 1-4-2021 at 10:31

Quote: Originally posted by Fulmen

James: That's surface oxidation of metallic Ti, not TiO2. According to Wikipedia TiO2 is reduced to TiO by metallic Ti @ 1500°C.

Oh. I didn't read the whole paper, as sci-hub is blocked by my school, so there was really only the title and the abstract to go on. I interpreted the Ti metal layer to be a substrate (in the materials science sense of the word, not the chemistry sense of the word), and it wasn't actually doing anything besides holding the titanium oxides.

Fantasma4500 - 21-5-2021 at 04:37

i believe i saw this while TIG welding titanium without shielding gas, i cant remember if it turned back to white once it cooled down, but of course were looking at a change in structure that reports a different spectrum of light back to you when you shine white light at it, im almost sure that the yellow remained once it was cooled down.

Morgan - 21-5-2021 at 08:28

I noticed some galvanized pipe I used for an intake/exhaust would change to a yellow after running for a bit like around the 6:50 mark. I recall buffing the snorkel to remove corrosion in the past which may have removed some zinc coating, but as the yellow seems to have formed only on one side it momentarily caused me to wonder if some sort of dual flow was occurring during part of the phase, one side favoring a cooler intake or two columns of air flowing past each other. In a typical pulsejet (in part of the cycle) using schlieren photography inflow at the exhaust occurs at the perimeter while simultaneously rarified air is still exiting at the center of the tube.
Anyway I guess zinc oxide could be used for a crude thermometer.
https://youtu.be/KUYgTN1erJc

[Edited on 21-5-2021 by Morgan]

unionised - 21-5-2021 at 08:32

The TiO2 used in paint is often coated with a thin layer of SiO2 to prevent photochemical damage to the organic materials in the paint.
That can lead to some unexpected results (and slows down dissolution in acid)

[Edited on 21-5-21 by unionised]