alizter
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Manganese Dioxide Thermite
Hi All,
I was preparing some Manganese dioxide thermite with some Manganese dioxide I had laying around that was salvaged from some old zinc batteries. There
were small pieces of zinc and the powder was very clumpy (possibly due to some sort of binder). Anyway I mixed it with some aluminium powder in a 3
aluminium to 4 manganese dioxide ratio. I mixed with a metal spoon to break up any clumps and mixed it as thoroughly as I could.
I then left it whilst going to get some magnesium and a blow torch. I set up outside and was going to bring the glass container I used to mix it
outside. The glass was really hot to the touch and I burnt my hand. Worrying that there would be a spontaneous thermite reaction in my kitchen I took
some oven gloves and quickly brought it outside.
I continued to watch it however it did not react and further and it looked roughly the same. There appeared to be some fuming (which I assume was the
binder) but it was getting hot.
The image attached shows the appearance of the powder.
I am assuming that when mixing I scratched off some of the oxide layer of the aluminium powder and caused it to react spontaneously. I am unsure
whether or not the zinc had anything to do with it.
I tried to ignite it with magnesium however there was no visible reaction. I proceeded to heat it directly with a blow torch until it was glowing
orange in order to encourage a reaction. There was no visible thermite like outburst.
However after heating I did notice some orange flakes as attached. I want to say I oxidised the manganese however I am unsure about this.
The remaining powder proceeded to react spontaneously with HCl and NaOH (seperately). I am just assuming this is to do with the aluminium. I then
covered the whole thing in vinegar to wash away.
Has anybody else noticed spontaneous reactions with aluminium and manganese dioxide? Is there something else going on here that I haven't stated?
 
[Edited on 10-6-2016 by alizter]
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Daffodile
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I'd bet it was because of water in the Manganese Dioxide. Copper Oxide thermite does the same thing when dampened.
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crystal grower
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Just to make sure, u meant manganese dioxide instead of MAGNESIUM dioxide, right?
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elementcollector1
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I've had this exact problem before with the manganese dioxide from batteries. You may need to strongly dry the MnO2 before use in thermite,
as it's quite 'sticky' compared to the pottery-grade stuff I bought, which when mixed with aluminum powder and a small amount of magnesium powder in
the center ignited readily upon heating with a blowtorch.
Elements Collected:52/87
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Next in Line: Nd
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phlogiston
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Is it possible that your manganese dioxide was contaminated with some of the potassium hydroxide present in batteries? Did you purify it in any way?
I believe that can cause the symptoms you describe. Ammonium salts (also used in some batteries) can also react with aluminium powder exothermically,
enough to ignite certain pyrotechnic mixtures.
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"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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blogfast25
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'manganese dioxide from batteries' contains at least 30 % graphite (for cell conductivity), not to mention a whole host of other impurities at lower
levels.
It's TOTALLY useless for thermite reactions.
Extraction procedures for MnO2 from battery filler you can find on this board in spades. Just UTSF.
Proper MnO2 thermites can be quite violent, so take care and read up!
[Edited on 9-6-2016 by blogfast25]
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Dan Vizine
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The most violent I ever did. Far outstripped copper thermite. Much of the contents of the 1" diameter x 6 " long graphite crucible was ejected
straight up to rain down on the surrounding apartment building parking lot. Interestingly, a cloud of manganese metal coalesced as tiny beads all
around the crucible. Not really a good idea to do.
"All Your Children Are Poor Unfortunate Victims of Lies You Believe, a Plague Upon Your Ignorance that Keeps the Youth from the Truth They
Deserve"...F. Zappa
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blogfast25
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Quote: Originally posted by Dan Vizine  |
The most violent I ever did. Far outstripped copper thermite. Much of the contents of the 1" diameter x 6 " long graphite crucible was ejected
straight up to rain down on the surrounding apartment building parking lot. Interestingly, a cloud of manganese metal coalesced as tiny beads all
around the crucible. Not really a good idea to do. |
But it works better if you tame it with some heat sink like CaF2. Coarser ingredients also make it more manageable.
You'll always lose quite a bit of the metal to evaporation, as discussed several times here and as you stated.
As regards copper thermite, that works much better with Cu2O than with CuO.
[Edited on 10-6-2016 by blogfast25]
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careysub
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There is also the option of heating MnO2 to 500-600 C and lowering its oxidation state to Mn2O3.
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blogfast25
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In my experience that doesn't make a lot of difference as to how the thermite runs. The big problem is that the MP of alumina and the BP of Mn are too
close together. Using another oxide doesn't fix that. I even tried MnO, prepared from pyrolysis of MnCO3 under CO2.
[Edited on 10-6-2016 by blogfast25]
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