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Formation of manganese oxides




I'm doing research on thin films. I aimed at preparing MnO2 thin films by spray pyrolysis using a precursor of manganese acetate+100%ethanol at a spraying temp. of 400 degrees. But I ended up in getting Mn3O4 films which were confirmed by XRD. I want to know the reason for that?

Sally Fletcher
student - Tamilnadu, India
April 10, 2008



Essentially, too much oxygen in the reaction environment, so you get the more highly oxidised trimanganic tetroxide instead of the manganese dioxide you are seeking.

Find a way of lowering the oxidising activity of the reaction environment.

Bill Reynolds
Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.

April 12, 2008



Mn3O4 is a mixture of MnO2 and MnO; that is, the manganese in in two oxidation states, 2 and 4. What you want is MnO2, which is pure Mn(IV).
MnO2 is a powerful oxidising agent and is unstable at high temperatures. When heated, it will liberate oxygen to give Mn(II).
Whilst I am not familiar with your reaction, I suspect the manganese dioxide (if it is indeed formed by your reaction) is reacting with the ethanol to oxidise it to acetaldehyde (CH3CHO) and even acetic acid (CH3COOH).

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
April 18, 2008


You're right, Trevor, and I was wrong - I had my oxidation numbers around the wrong way. Note to self - stick to metallurgy and leave chemistry to chemists, and be very careful in areas where the two disciplines overlap!

My apology to the OP - I hope she wasn't inconvenienced by my mistake.

Bill Reynolds
Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.

April 21, 2008


Bill, I am a chemist that specialised in industrial metallurgy. However, I consider myself a better chemist than metallurgist (it is also easier to spell!). Have a good one.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
April 23, 2008




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