Forest Innovations
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Pyrophoric Iron
Hello.
Could anyone tell me at what particle size iron powder becomes pyrophoric and also at what temperature?
I'm making good progress refining iron powder in my wife's old blender, to then use in some sintering experiments.
Currently the powder is approximately 25um particle size and is reaching a temperature of about 40 deg C as the blender works its magic.
What I don't want to do is set fire to my workshop accidentally.
Thank you very much for your help with this.
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blogfast25
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You're achieving 25 micron with a blender? What's your secret? 
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HgDinis25
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"The Pyrophoric Iron particles, when viewed under a microscope, are determined to be from approximately 100 nm to 1 micron in size."
Quote from the following video: http://www.youtube.com/watch?v=vinu8ZzNvRw
25um should already be pyrophoric. Are you sure it's 25um? How are you measuring it?
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Little_Ghost_again
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Quote: Originally posted by Forest Innovations  | Hello.
Could anyone tell me at what particle size iron powder becomes pyrophoric and also at what temperature?
I'm making good progress refining iron powder in my wife's old blender, to then use in some sintering experiments.
Currently the powder is approximately 25um particle size and is reaching a temperature of about 40 deg C as the blender works its magic.
What I don't want to do is set fire to my workshop accidentally.
Thank you very much for your help with this. |
Thank you. I have shown this to my mum to prove that it is perfectly normal practice to use the kitchen blender for chemistry. It's still a no though
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bbartlog
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To my understanding, 25µm is still too large to be pyrophoric. That's still far larger (by about 100x) than the '100 nm to 1 micron in size' quoted
above. Here's a link to some investigations of a 'pyrophoric' iron system, with particle sizes in the 1-10µm range - but notice that their particles
are not spontaneously pyrophoric, they need some additional heat to ignite them: http://download.springer.com/static/pdf/947/art%253A10.1007%...
I expect that to see spontaneous ignition in air you would need to get particle sizes well under a micron.
The less you bet, the more you lose when you win.
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aga
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No, it isn't.
Food and Chemistry should never cross paths, apart from Analysis of what shit it is that someone not observing this Rule put in the food you just
bought.
The Big Secret is the existence of Used Blender #2 bought off ebay for a fiver that lives in your Lab.
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Little_Ghost_again
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| Quote: Originally posted by bbartlog |
To my understanding, 25µm is still too large to be pyrophoric. That's still far larger (by about 100x) than the '100 nm to 1 micron in size' quoted
above. Here's a link to some investigations of a 'pyrophoric' iron system, with particle sizes in the 1-10µm range - but notice that their particles
are not spontaneously pyrophoric, they need some additional heat to ignite them: http://download.springer.com/static/pdf/947/art%253A10.1007%...
I expect that to see spontaneous ignition in air you would need to get particle sizes well under a micron.
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Wouldnt it also be a biological hazard under 10 micron?
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Artemus Gordon
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I am surprised blender blades are hard enough to pulverize iron, but if it is working for you, that is interesting to know.
You say it is reaching temps of 40c, but I assume that is the bulk temperature of the iron powder. What you have to watch out for is just a few
particles being heated to ignition temp and then igniting the rest of the powder. When grinding steel, sparks are generated that have individual temps
hot enough to melt pits in a <a href="http://forum.atomiczombie.com/archive/index.php/t-4526.html">car windshield</a> while the mass of
the steel is cool enough to hold with bare hands.
If I were trying this, I would work with very small batches, keeping the rest of my powder in a closed container, and I would try to keep iron dust
from settling on my work surface.
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HeYBrO
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| Quote: Originally posted by Forest Innovations | Hello.
Could anyone tell me at what particle size iron powder becomes pyrophoric and also at what temperature?
I'm making good progress refining iron powder in my wife's old blender, to then use in some sintering experiments.
Currently the powder is approximately 25um particle size and is reaching a temperature of about 40 deg C as the blender works its magic.
What I don't want to do is set fire to my workshop accidentally.
Thank you very much for your help with this. |
Perhaps you should look into iron oxalate, which when heated creates pyrophoric iron. But beware as it also creates carbon monoxide which is very
dangerous.
[Edited on 24-9-2014 by HeYBrO]
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Ozone
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To the best of my knowledge, the oxalate decomposes to (mostly) CO2. This is nice because it blankets (heat the oxalate in an ampoule) your pyrophoric
iron keeping it safe long enough to seal for later use (like starting a campfire or somesuch).
If your batches are small, say a gram or two, I wouldn't worry myself to death about the CO.
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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bbartlog
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According to Hurd, pyrolysis of ferrous oxalate yields roughly equal quantities of the oxide and the metal, which would imply roughly equal amounts of
CO and CO2 are released. It's always possible that different temperature regimes would yield different results, though.
The less you bet, the more you lose when you win.
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Ozone
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Interesting. I always got a fine grey (didn't look much like either ferrous or ferric oxide) powder. There was no evidence of flammable gas exiting
the ampoule, but maybe CO just won't burn if there is a bunch of CO2 with it. In any case, the blanket was always successful, and the material (so
long as you didn't overheat it and blob the particles) would always catch fire.
If the quantities are small, and the experiment performed with adequate ventilation (if larger), the only risks I see are fire (I used a MAPP gas
torch), hot glass, and the product itself.
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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