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Cappy
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Aluminum powder synthesis
There was enough interest in this that I thought I'd put it here. (for convenience, I am not showing aqueous compounds as ions):
2Al (s foil) + 3H2SO4 (aq) --> Al2(SO4)3 (aq) + 3H2 (g)
Al2(SO4)3 (aq) + 3Mg (s) --> 3MgSO4 (aq)+ 2Al (s powder)
You say the following reaction will occur:
Al (s powder) + H2O (l) --> Al(OH)3 (s)
If I added excess Mg, the following would occur:
Mg (s) + Al(OH)3 (s) --> Mg(OH)2 (s) + Al (s powder)
I have enough Mg to pull this off, but I'm not sure non aqueous reactants will undergo single replacement easily.
Is there a possiblity that Al(OH)3 would never form in the first place if enough Mg(OH)2 formed first and used up all of the water?
[Edited on 4/3/2003 by Cappy]
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BASF
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I don´t think aqueous media is the way to go because the finely dispersed aluminum could not be prevented from reacting with the water to form
aluminum oxides.
What about making the oxalate, then heating to the decomposition temp. in inert gas?
Eventually you get pyrophoric aluminum...
HLR
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rikkitikkitavi
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you can never make pure Al from an Al-compound that contains oxygen by just heating it without a stronger reductant that than Al...
/rickard
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BASF
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Yeah, you may be right.....it was just thinking out of the stomage....i had the methods involving Fe- and Pb-oxalates for pyrophoric iron and lead in
mind, but forgot considering they are more or less heavy metals.....
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BASF
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This thread is discussing all about making aluminum powder, especially atomized aluminum.
It seems that pyrophoric, atomized aluminum powder or weapons-grade aluminum is fairly hard to do.
Maybe there is a chance to make flake aluminum, which is also very reactive....
http://yarchive.net/explosives/aluminum_powder.html
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Organikum
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good link BASF!
cost me a few hours I would have had to spend with urgent work.
ORG 
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Theoretic
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Al powder
If you need Al powder for thermite mixtures or burning, you could just file it from a Coke can (and use a sieve to separate the finer component if you
want to, since Al powder made with that method comes in all sizes. Grainy powder would do for thermite mixtures).
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vulture
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That's going to take ALOT of time.
Electric grinding isn't an option because you would have lots of dust floating around while getting a red hot coke can due to friction.
Not my idea of being safe...
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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DDTea
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If you want to have Aluminum powder by means of a single-replacement reaction, why not have the byproduct be solube in water, thus facilitating the
extraction of the Aluminum? Unfortunately, I can't think of any ion that would make this possible .
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vulture
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2AlCl3 + 3Mg ----> 3MgCl2 + 2Al?
However, this can not be done in water, as the AlCl3 would hydrolize. Hmm, pure liquid (it's a liquid at room temp IIRC) AlCl3 and simply adding
Mg? MgCl2 solidifies and shifts the equilibrium to the right?
I can't say why, but my intuition says this wont work...
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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madscientist
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I think AlCl<sub>3</sub> melts just below 200C. 
Replacement reactions will typically yield metal crystals that are far larger than the particles found in a powder.
I weep at the sight of flaming acetic anhydride.
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Iv4
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IMHO the best way of making fine AL powder is taking some foil and adding liquid nitrogen(or something to that extent)and using a mortat and pestle on
it.Though that's probably not very convenient(though a cryo cooler could be made from the materials in extremely condducitve thread and that
might be able to pull it).
I've heard of water and foil in blenders.Suposedly the water in it keeps the heat acceptable.Paranoid as it may seem I'm worried it might
liberate hydrogen and oxygen.
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Twed The Terrible
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Go get some metallic paint. The sort that dries with the shiny metal in it, like that on some cars. Guess what the shiny metal is....Al! Wehey!
Now, add a generous amount of solvent (I use acetone) to the paint to thin it down to a watery thickness. Filter the mixture to remove the Al
particles. Wash them, dry them, and do what you want with them. Simple.
[Edited on 1-7-2003 by Twed The Terrible]
Pain is only weakness leaving the body
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blip
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I read a great article on making magnallium powder where you alloy aluminum and magesium in a 1:1 ratio. It's brittle even at room temperature,
so you can just use a hammer to break it up.
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GZAust
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Where are you thinking of getting the 3 mol of Mg? Sharpeners?
50 or so grams of Al isnt a lot for two steps and all that Mg, but I'm all for the chemically atomised product! very cool
Doesnt most foil have a chrome coating on one side? In aus they do.
Iv4 have you tried lateral thinking puzzles? - You'd be great at them
I wonder if CO2 would do it? But I don't know how to freeze CO2, placing the compressed gas in the freezer?
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Organikum
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How to freeze CO2
open the valve
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Marvin
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Under optimum conditions making solid CO2 by expanding from a room temp cylinder wastes about 75% of the CO2. Putting the cyclinder in the freezer
would probably help a bit but buying dry ice directly from icecream sellers is probably the way to go here.
I'm unsure if it would be cold enough to make the aluminium brittle, but it shouldnt be used anyway. CO2 is not inert to aluminium powder and a
mix of aluminium dust and CO2 gas is flammable/explosion hazard.
Ballmilling paint grade aluminium or aluminium foil is supposed to work quite well at room temp dispite mallability. Inert gas of some sort would be
a must there I think, and the result could be pyrophoric. Not tried this yet, the paint grade Al Ive been able to buy here is rather course.
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Mongo Blongo
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You can buy Al powder from Fibreglass suppliers. Does anyone know how fine /mesh the powder is? (I have yet to get some)
You can also get Brass,Bronze,Copper and Nickel powders.
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Organikum
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Marvin: Yes it´s a waste but dryice isn´t easily available where I live but CO2 bottles are and they are asscheap here. Get a bottle with two
adaptors where one is for taking out liquid CO2. Filling the liquid CO2 in a thermoinsulated bucket makes it freeze instantly by the cooling
invovlved in the expansion and phasechange on the surface and the special properties of CO2 which goes from solid to gaseous state directly. The
liquid state in the bottle resembles a kind of denaturated solid phase. The losses are not so big this way.
Very important and right on the point is that CO2 cannot be regarded as inert gas for chemistry. Argon is most favorable (pure no welding mixture) and
nitrogen as cheaper substitute in most cases sufficices.
Mongo Blongo, might you hint me to the fibreglasssupplier carrying the metal-dust. Mine doesn´t.
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Mongo Blongo
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Cheak your email.
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AngelEyes
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I have tried the fibreglass (cold-casting) metal powder additive. It's definitely Al, but it seems very difficult to get it to any usable state.
Rinsing with acetone seemed to do nothing - in it's present state it can be ground up with NaNO3 and it still won't ignite. You'll get
the occasional spark coming off it...but that's all. No good for flash.
I have heard it said that you can put in the oven for a few hours at 200 Celsius (or thereabouts) to remove the coating on the Al, but I have not
tried this. Anyone confirm if it works or not? Anyone confirm if there even is a coating, and it's not just mixed with an inert
'filler' to pad it out?
If you're looking for this stuff just do a search for fibreglass, resin, metal powder and the metal of your choice - you can get copper, bronze,
brass, aluminium etc. No Mg though :-(
I have a few pots of various metal powders but no way to turn it into a really useful product.
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BASF
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Another weird idea...
Melt aluminum with an inorganic salt(or a combination of different ones) having the same specific density and melting point.
The hope is this would then mix thoroughly and the inorganic salts could then lateron be washed out by means of a suitable organic solvent.
(It is understood that the number of inorganic salts soluble in organic solvents is quite small.)
I know this would afford a LOT of experimenting and recherche, but who knows...
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vulture
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I have heard it said that you can put in the oven for a few hours at 200 Celsius
Even if it did work in removing the coating, you'll be reinforcing the oxide layer on the particles. You'll be left with 80% Al and 20%
Al2O3 layer on the outside which makes the particles very unreactive.
Any means to remove the oxide layer attack the aluminium as well.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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chemoleo
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Aluminium powder grades
although it's slightly off topic, does anyone have information on the different grades of Al powder?
For instance, there are the 'mesh' grades, which come in 200, 400, 600 etc. What does this stand for? 200 micrometer particles?
Also, then there are varietes like dark German Al powder (dendritic?) , or American etc - what are those? Especially the dendritic version, sounds to
me like some nano-crystallised form - how the hell is that made??
PS I am sure a number of people have been wondering the same... so hail to my bravery for askign this... or flaming me for asking something as
seemingly trivial?
[Edited on 16-10-2003 by chemoleo]
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blip
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This is the closest thing I could find, I think this page was mentioned here: http://www.fisher.co.uk/techzone/tables/chemicals1.htm#Sieve...
I've gotten into the habit of collecting useful links and saving them into text files for future reference, sometimes it really helps.
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