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Author: Subject: Aluminum powder synthesis
Wolfram
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Would you please stop call powdering metal for "synthesis". Synthesis suggest at least that you make something more complicated from less complicated, the compunds you use should be organic.
tom haggen
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Preventing aluminum oxide

i'm somewhat new to the chemistry field but i have been studying metal for 3 years now, i have been expirementing with aluminum powder as a fuel because that seems to be the most widely used fuel in flash powder and its easier to work with than magnesium. anyway, I went to the camping store and bought one of those fire starter strips that came with a strip of magnesium glued to a bar of cast type aluminum. i filed this stuff down and the grade was very fine. however i flashed up somewhat. so i mixed this with an oxidizer and when i burn't it i kept leaving chunks of unburnt oxidizer. then i read a synthesis about using a binder like water or something,and mixing your composition wet is this what i need to do to get better results. and if i do need to use a binder will water create aluminum oxide in my compostion.

P.S. i filed down some 6061 common aluminum and this stuff didn't burn for crap. leading me to believe that you need a special series of aluminum to create the pyrophoric aluminum powder.

-Tom
Hermes_Trismegistus
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GUYS

pretty much all aluminum you are going to get is going to be an alloy!!!

pop cans and aluminum foils are NOT pure ALuminum How did you think that pop cans are so strong or that aluminum foil has a shiny side anyway????

if you do find some aluminum (smelting with flux is cheap and easy)just look at my BALL MILL post in apparatus

it will (slowly) give you all the aluminum you need

however you can't really use aluminum alloys because they are specifically formulated to avoid stress fracturing which is what allows the powdering of fairly pure aluminum in a ball mill

also aluminum oxide powders much more easily in a ball mill that Al metal, since it forms the oxide almost instantly on contact with air (and thats what you get when you buy al powder) (for the most part)..........

[Edited on 30-11-2003 by Hermes_Trismegistus]

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unionised
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If the aluminium powder was mainly oxide;
1 It wouldn't work and
2 It wouldn't look like aluminium.
Of course, it will have the annoying oxide layer, but that is thin, even the layer on anodised Al is only about 10 or 20 microns.
Wolfram,
What's wrong with inorganic synthesis?

[Edited on 30-11-2003 by unionised]
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Aluminum powder

Ball milling is the easy part. The mill is doing the work for you.
The problem is filtering to the desired mesh. An old shirt or tightly
woven fabric should do the trick. If the powder is dusty through
the filter, it's fine enough for making a good flash.

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BromicAcid
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Ran across an interesting article on nickel powder production. Although not economical it called for making a sodium dispersion in mineral oil and heating it to 200C with constant stirring then adding NiCl2 (anhydrous of course) with constant stirring. Pyrophoric nickel powder is the result after adding alcohol to decompose remaining sodium and filtering.

So possibly anhydrous aluminum chloride could be reacted with dispersed sodium but maybe something stronger like potassium would be needed to produce your aluminum powder. Again, not practical but interesting.

(Yes, I could do the thermodynamic calcultions like I'm wanting to but it's getting too late, maybe I'll edit this tomorrow.)

Edit: Even though it's late I compared the delta H of the two reactions, the one for nickel chloride reacting with sodium releases 517 kJ and the theoretical one with aluminum chloride releases 592 kJ therefore the reaction is comparatively exothermic.

[Edited on 8/2/2004 by BromicAcid]

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Theoretic
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Sodium will reduce AlCl3 just fine, anyway your calculations show it.
I read somewhere in this forum that at a high temperature, Al is brittle. Maybe it could be ground down into a powder with a mortar and pestle, under a blanket of N2 gas to prevent oxidation (some AlN will form, but much less aluminium will be wasted and the powder will be more reactive that with an oxide layer. The mortar would be heated with a flame (if one uses electric heating then an added bonus is that H2 can be used for shielding the metal, no stuff will form on the surface), you have to admit that (ceramic) mortars make damn good crucibles.

vulture
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Nuclear fusion is pretty damn exothermic. Does it therefore happen spontaneously? No.

You need to calculate the gibbs energy to be sure.

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Organikum
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Actually the literature states that Al reduces NaCl to the metal. It is mentioned IIRC in the sodium article in the SCM library whic was provided by Bromic_Acid.

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 Quote: Originally posted by vulture Nuclear fusion is pretty damn exothermic. Does it therefore happen spontaneously? No. You need to calculate the gibbs energy to be sure.

Gibb's Energy does decrease in nuclear fusion (at least in the reactions proposed for energy production). It doesn't happen spontaneously for kinetic, not thermodynamic reasons. Energy is released by the nuclei attracting each other, due to the strong nuclear force. However, this has an extremely short range, and so energy must first be expended in overcoming the mutual electrostatic repulsion of the nuclei.

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neutrino
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Gibbs free energy doesn't tell you whether a reaction will occur in a reasonable amount of time. Some things that should be spontaneous at room temp have to be heated considerably to work at a noticeable rate.

Now, a thought on cleaning the oxide layer off: adding concentrated nitric acid. The following two reactions (or something close to them) should occur:

Al<sub>2</sub>O<sub>3</sub> + 6HNO<sub>3</sub> -> Al(NO<sub>3</sub><sub>3</sub> + 3H<sub>2</sub>O

2Al + 6HNO<sub>3</sub> -> Al<sub>2</sub>O<sub>3</sub> + 3H<sub>2</sub>O + 3NO<sub>2</sub> + 3NO

There should be en equilibrium between how fast the oxide layer is taken off and how fast a new one if made. This final thickness might be very thin or very thick. Does anyone have any experience with this?
Blackout
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you could put Al foil in a blender with NaCl until you have a powder.
you could have a more finnest powder by oxidize the Al powder you've made before and grind it in a coffee-grinder to get a finnest powder an the heat it (with a gaz burner; blue flame) with charcoal powder and bubbuled the CO2 in water. Decant the C, you will get a very fine Al powder.

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Blackout
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oh, you can stop to heat when no more CO2 is given off.

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BromicAcid
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I wasn't really saying that the delta H was justification. Just that they were comparatively exothermic and therefore could probably be carried out in the same medium, there was the chance that the reduction of aluminum chloride with sodium may have been considerably more exothermic and affected the solvent adversely. However they release about the same amount of energy.

I knew the reaction itself, that between sodium and aluminum chloride would work because that is the way that aluminum was originally 'mass' produced. Quite expensive that way but workable. That is until the invention of the Hall process displaced it.

Of course I fogot to take melting/subliming points of AlCl3 into play.

[Edited on 12/4/2004 by BromicAcid]

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Marvin
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Blackout,

You cannot reduce alumina with carbon.
kclo4
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is there was a way to get Al powder from Al2S3
evilgecko
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I by some aluminium window frames and then attack them with my angle grinder with a very large disc on it. A cardoard box is put around the vice so it catches most of the particles. Then I ball mill them with iron rods for a day.
nodrog19
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mesh size is hole/sq in (6.55 sq cm)
its crimminaly american.
try shredded foil in coffee grinder.
Tinton
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If you are going to obtain particles as small as you're theorizing, you might need an alternative to filtering. Many filters available to the home chemist quite frankly, suck.
I haven't seen any filters that can separate good mesh metal powders efficiently on any of the supplier's websites.
Correct me if I'm wrong, I haven't been equipment-searching in a while.

evil_lurker
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Easiest way I have found to do it is to use what is known as a "step bit" in a drill press on sheet metal, followed by grinding the turnings in a coffee grinder, and then ball milling to size.

PITA, yes, but it works.

Luckily I have access to 1100 series aluminum, which cuts very easily. The coffee grinder is where most of the work gets done very quickly, and the milling can take several days for "black" or "dark" aluminum.

I have found that a standard Harbor Freight single barrel rock tumbler is most acceptable for powdering. Harbor freight also sells a dual barrel model, but they just don't seem capable of handling two fully loaded drums worth a crap. Under such conditions the motors produce a lot of heat and the cheap drive belts break quite easily... in my experience one can expect to break a belt every 1-3 days, sometimes they go in only a few hours.

It also helps to increase the gear ratio slightly. The easiest way to do it is to first is to slice a section of correct sized ID PVC tubing down one side and then affix it around the main drive shaft. This causes the shaft to get bigger and as such the drums turn faster giving more of a pounding action.

The best media IMO would be chrome steel bearings, and if they are too expensive for one's taste case hardened steel bearings second. All bearings can be purchased from the Ebay seller "toolsupply" pretty cheap IIRC. Alumina is just too light (bout half the weight of steel) to give a decent grind and of course lead is just too soft.

Sizing is somewhat up in the air, but my first choice for a harbor freight mill would probably be 9/16" first, 1/2" second, and 5/8" third. I'm guessing that one cup in volume would equal in the neighborhood of 120 1/2" ball bearings.

Appropriate charge I'm guessing is somewhere a little over a cup, and around 125g of aluminum. Again its just a guess. I'm sure some pyro expert would be much more knowlegable of proper ball mill loading than me.

[Edited on 10-6-2008 by evil_lurker]

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nodrog19
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add some rock salt to the mix.
if i can get a blender, i might start selling
it. reynolds alum foil is 97% Al, 1%Fe, 2% Sn
w/ a polymer coating. if you want to get really pure,
wash w/ a solvent and the digest in HNO3
not_important
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Use cheaper generic foil and avoid the polymer, or just do not use the Reynolds "non-stick" varieties .

Cooking foil is usually a 1xxx alloy, 99+ percent Al with fractions of a percent of iron and silicon unintentionally picked up in production of the metal. I'd like to see a reference for that alloy you gave, especially as tin is not a common alloy additive for Al.
Diablo735
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Referring to the blender idea of making Aluminum powder: I have read in other threads here and on other websites that one can use other materials to keep the Aluminum on the bottom near the blades. One of the most interesting ideas I found was using water... but my friend brought up a good point that wouldn't that cause oxidation to the "powdering" Aluminum? (significant enough that the result will be more oxidized than not...)
(Sorry if that is an elementary question.... I am about start Gr 12. )
bigbigbeaker
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Many decades ago, when I got the "After Dinner Science" book for my birthday, the first experiment I tried was mixing iodine crystals and powdered aluminum with a drop of water. The druggist who sold me the iodine sent me to the art store to buy a one ounce bottle of aluminum dust pigment. It's so fine it seems to float. If you just need a very fine, highly reactive aluminum, then take shredded Al foil, a bunch of 50 caliber lead balls and ball mill it for 3 days. If you want to try the paint route go to Richard Nakka's rocketry website. There's is alot of good rocketry info there and he gives detailed instructions for harvesting Al from paint. Here's the link - www.nakka-rocketry.net/igniter.html#Aluminum. If you are planning to make flash powder, learn what you're doing first. An unenclosed 30 gram pile of it "detonates" with amazing force. Make sure the humidity is 40% or higher and ground yourself with a wrist strap. Better safe than sorry. An accident with an energetic can be life changing or ending.
LSD25
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2 seconds on google found this

http://www.pyrobin.com/files/manufacturing%20of%20flake%20al...

They utilise scrap Al foil to prepare fine Al Flake/Powder using a ball mill and inert atmosphere.

Next, design ideas - any thoughts?

Whhhoooppps, that sure didn't work
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 Sciencemadness Discussion Board » Fundamentals » Chemistry in General » Aluminum powder synthesis Select A Forum Fundamentals   » Chemistry in General   » Organic Chemistry   » Reagents and Apparatus Acquisition   » Beginnings   » Responsible Practices   » Miscellaneous   » The Wiki Special topics   » Technochemistry   » Energetic Materials   » Biochemistry   » Radiochemistry   » Computational Models and Techniques   » Prepublication Non-chemistry   » Forum Matters   » Legal and Societal Issues