Atomizing Aluminum

[jeffchem2000]

Because powdered alluminium is too expensive for me to buy in the quantities I would like to, I have been trying to make my own.

The first way that I tried was using a file. But for the effort put in I ended up with such a small amount of product that passed through a fine sieve.

Then I looked on the internet and it mentioned on a site (can't remember which one) that the way atomised alluminium and all other "high" melting metals are made was by making a stream of it pour to the ground and a jet of water or air blasts the flow and atomises it.

What I would like to know really is has anyone had any experience with making powders in that way and where there any problems with water and hot metals making steam. And if air was used how far would the metal have to be blasted to make sure it was solid by the time it lands on something.

[Mumble]

First of all powdered and atomized are two different things. In industry I believe they use fine nozzles with an ultrasonic crystal at the tip to break up the spray even more I believe. It might not be an ultrasonic crystal, but a different name is escaping me at the moment. I don't know how well blasting liquid metal being poured with water or air would atomize it. I would think that the molten metal would have too stong of an affinity towards itself to break up to the particle size you desire. I would think that using swater or air any particles that did infact form would be heavily oxidised. Ballmilling aluminum foil can yield quite a fine powder if I'm not mistaken as well.

Perhaps if you told us what your intentions were we could help you better. Without knowing the project it is hard to recomend an applicable solution.

[yt2095]

IF your capable of making such a machine, I`de stick with perfectly dry air or inert gas! Al being pyrophoric would ignite spontaniously on contact with water ruining your efforts and making quite a mess I should imagine! :(

the Ultrasonic transducer idea is infact utilised in many such procedures though.

can`t you just buy some from a paint shop? save alot of hassle :)

[GibboNet]

I think atomised aluminum is going a bit too far for home manufacture. It would require very precise parts, contolled atmosphere and the like. At such small particle sizes, Al is supposedly pyrohoric, which means you're going to have to be very careful.

Aside from that, if you have the means to make such a machine / apparatus, you would more then likely be able to construct a ball mill, which means you have the means to produce very fine Al with an appropriate time anyway. Or a chemical method, I can't remember if it was decided this was suitable or not, you'll have to look it up.

Whatever method, I think you've chosen the most difficult unnecasarily.

[jeffchem2000]

the accurate parts bit isn't a problem because a friend of mine has a metal working lathe and a milling machine which run off 3-phase. What I was thinking was that once the machine was built the only cost to me would be the alluminium and the power to run the machine and alluminium pipe is readily availible for free.

the way that i understand it works is like the spray guns and compressors for painting cars. the paint is forced out of the nozzle by the air ompressor and as it does it makes a very fine mist.

I have the air compressor and have built a test version. I have tested it what I would call successfully with water pouring over the jet of air. The problem i have had is that the hopper isn't hot enough when i do the alluminium test and so it solidifies in the hole. what I'm going to do is make the hopper out of something thinner than 3mm steel maybe a baked bean can and heat it up in a furnace.

thanks for all the input.

[Imperial]

Here is my idea: Get an aluminium salt solution (for example AlCl₃) and then add some metal which is higher in the reactivity series (for example Mg) to it. The Mg will replace the Al³⁺ in the solution, and you will get little bits of aluminium powder forming on the bottom. Then simply filter out the aluminium and wash with water! This is a slow process, but requires very little effort on your part apart from getting the reaction started, and later filtering out the aluminium.

One thing I am not sure about, though, is whether or not the aluminium will form "chunks" which it may. I don't think it will, but I haven't tried this yet except with silver powder in chemistry at school.

[jeffchem2000]

I've tried this with a solution of Alluminium chloride, It works for a bit, but the magnesium reacts with water slowly forming magnesium hydroxide. This made the alluminium very impure and it had very little use.

[Imperial]

Ah good point....damnit there is nothing in between the two metals in the series. Calcium is too reactive, as are sodium and potassium.
I guess you could try electrolysis, but that wouldn't give you a powder. It would give you a thin coating.

I think you will have to stick to the filing or milling to get your aluminium :(.

[yt2095]

AFAIK, Al will not be produced under any electrolysis reaction or displacement reaction at all.
Al is produced by electrolysis at molten metal tempratures only.

[Anthony]

Why would you use an expensive useful metal like Mg to make a less useful, less valuable one like Al?:confused:

JeffChem2000, if you've got it working except for a clogging nozzle, I'd persevere, the results will be interesting if nothing else. Like you say, simply keeping the nozzle hot should cure it. One problem might be the oxidation of the molten Al if the you're running the sprayer off of compressed air.

[jeffchem2000]

What I think I'll do if the alluminium is too oxidised by the compressed air I'll buy a tank of CO2 from the pub. or would the alluminium react with the CO2 and make lots of CO?

[yt2095]

it may, but then that might not be a bad thing if you could find a way to recirculate this CO again via your air compressor intake :)
it would mean you`de only lose the initial amount of Al but the rest would be perfect :)

[yt2095]

sorry if this is seen as post whoring :(

Jeff (or anyone else for that matter) I`ve just had a new idea that almost anyone could do :)
take a look;

http://www.yt2095.net/tests/AluGen.jpg

it`s almost simplicty in itself. the box would have to be airtight almost so you didn`t lose any alu dust.

the angle grinder motor outside (heat and sparks) obviously.

I saw it like this... imagine an upside down lighter for cigarettes the flint type.
imagine it being gravity fed instead of spring and the roller being a fine grain (finer the better) angle grinder disc.
yes, I realise your already commited now with your new machine and don`t wish to waste any of the effort you`ve put in so far, but treat this as a backup plan :) better to have and not need etc... :)

all the best :)

[zaibatsu]

Aha! You've suffered from what I have had to endure many a time. I call it "Reverse idea theft". You think up an idea, then realise some stinking, cheating thief has stolen your idea, gone back in time, and presented YOUR idea.

This link has been posted before - http://members.shaw.ca/justin.le/grinder.html which orignally had what you describe, but the flow of Al powder directed into water.

[Tuatara]

The trouble with grinding Al is that it tends to be rather sticky, and will rapidly clog the grinder. The solution is to run the grinder fairly slow, and submerge the bottom into a tank of kerosene so that the grinding surface is constantly lubricated.

There is another way of atomising metal. The molten metal is poured in a thin stream onto a metal disk spinning at high speed. The molten metal gets flung off the disk and atomises in the process. Still need an inert atmosphere for reactive metals though

[ALENGOSVIG1]

LOL yt2095 your keyboard looks like a fucking bioharzard!

[GibboNet]

That is a filthy keyboard. Zaibatsu, I got a page not found error on that one, but I've seen it before anyway, I think I know.

You may not want to waste Mg on the chemical reaction method, but I'm sure galvanised metals like zinc plated nails areeasy to come by, and zinc is more reactive that Al. in fact, I wanted to try (never got round to it) Al, dissolved in HCL, react with Mg to get the Al powder, then add zinc to get the Mg powder.

I think I have the metal reactivities around the wrong way, but it may be worth a try.

[Anthony]

Potassium
Sodium
Lithium
Calcium
Magnesium
Aluminium
Zinc
Iron
Tin
Lead
Copper
Silver
Gold
Platinum


Zinc is a bit too far down for your idea to work :)

[yt2095]

yeah whatever, it`s not 100% sterile sure, but it`s my `Dispaly Model` and I only bring it out on special occasions or photo sessions.

you should see my DIRTY one... 1 bolt of lightening and I`de have the beginings of life all over again :P

[jeffchem2000]

ahh, if it was in kerosene the aluminium would be completely free from any oxides. Ideal :)

[Skean Dhu]

if you have the resources to melt AL why not make magnalium?(Mg+Al if you didn't know)
it can be used in flashpowder and for the most part anywhere Al is used.

PGI Magnalium flash
Potassium perchlorate 50
Magnalium, -325 mesh 50

[metal dragon]

I have always made al with a fine file, a bench press drill and an al bar. put the bar in the press turn it on, place a file to the rotating bar and presto instant al.

[GibboNet]

Thanks anthony. I couldn't find a reactivity table.

Still, If you have Zinc, Al, and Mg, you could get zinc powder, then aluminium powder, at a cost of the Mg. Get your hands on one of those Mg engine blocks and that wouldn't be a problem. There's a VW service centre closing down nearby, I might go and see how much they've discounted parts which could be useful. :)

metal dragon, I like your idea, only you've got to stand and hold the file, which would get clogged fairly quickly wouldn't it ? I might try it if I can get my hands on a drill.

[metal dragon]

The file may get clogged but the spinning motion usually gets it the little bits out and if it doesn’t just clean it every minute or so. It doesn’t give high-grade stuff but useful for generally chem., explosives and pyrotechnics. It work reasonable in flash but it best satiated to fountains, etc.

[josef]

An alternative way of atomizing is centrifugal disc atomizer.

A thin stream of molten aluminum is poured onto a rotating disc (10,000+ rpms). This flings the aluminum outward creating very small oblong spheres of aluminum.

An actual home made device was attempted here: http://members.shaw.ca/justin.le/metal_powders.html - not perfect, but could work if designed more appropriately.


This method is much easier concerning home use.

[Sonny Jim]

The problems with the angle grinding I've noticed:

Bits of the grinder stick to the Al which flakes off rather than atomises. So you get a vast amount of too big flakes and the fine powder is contaminated by equally fine bits of grinding wheel.

[tmp]

This is what works for me:


1 ball mill(a rock tumbler made by Lortone)

1 pound 3/8" steel slingshot ammo

AND the thinnest aluminum foil I can find


Cut the foil into thin strips, place in the rock

tumbler with the slingshot ammo.


Run the tumbler until you get the grade of

powder you want. This is time consuming

but it works well.


My Al powder is so fine it easily makes

its own dust cloud just by letting fall a

couple of inches.

[Kid Orgo]

TMP: What about the aluminum oxides that coat aluminum foil? Won't that remain a problem for your ball-milled stuff?

EDIT:
Kingspaz: I could have sworn I read somewhere that a dilute solution of NaOH will take off the oxides leaving the aluminum. It was probably in a drug synthesis anyway. I could look it up, but I'm kinda busy right now.

[kingspaz]

the Al will also dissolve in lye.

[EP]

I tried the "chemistry method" of making some metal powders recently based on this info copied from a thread on rec.pyrotechnics:

zinc dust - pennies 1983 and newer...are 98% zinc... take a bunch of them and place them on concrete... then scrape them with your foot to expose some fresh zinc. then place these pennies in a solution of hydrochloric acid, put an excess of pennies to most of the HCl reacts to the zinc... precision isnt necessary, but just as long as there isnt a large excess of HCL in solution. Filter it so you get a solution of Zinc Chloride. put a lot of aluminum foil in, allow this to react, and atomized zinc powder will fall out of soln. once no more AL will react, filter out the powdered zinc, and rinse with distilled water. then, rinse with Isopropyl alcohol anhydride (the 99% stuff, not the 70%). this is necessary as the zinc will react with water to make zinc oxide. which is a good source of zinc oxide if you wanna make smoke comps, just omit the step with alcohol. dried you will have some of the best zinc powder possible (waaay better than the ground stuff you buy from the suppliers) as it is a much smaller particle size and often "flakes" off in the reaction.

Aluminum dust- same procedure except instead of the pennies, react the HCl with aluminum foil, and use magnesium to get the al out of soln... makes a powder simmilar to german black.

Aluminum Powder - "West Systems 420 Aluminum Powder" can be found in boating supply shops. simmilar to "Firefly Aluminum" some flake and some sperical...

It didn't work for me. :(

I dissolved a ton of pennies (probably at least 100) in a beaker of HCl until the Zn stopped reacting. Then I filtered to get the zinc solution alone and added balls of Al foil. Let it sit for 2 days and got....pretty much nothing. The Al seems to have a whitish coating in places and there is a tiny bit of stuff at the bottom of the beaker that may be Zn but it doesn't seem that fine and there is hardly any of it. Maybe I just need to add more Al but it doesn't seem to be a very good way of doing things...

If nothing else, I did create lots of hollow pennies, it's pretty cool to have just the copper shell with all the Zn hollowed out by acid. :)

[Chemical_burn]

LOL if all else fails Ep you now have some near pure copper hehe
SC's anyone now just melt that copper down and cast some nice little SC cones or EFP platters.


I would think that it woudl be easier and/or cheaper to just grind your Al down to the smallest mesh you can get it. Then just ball mill it. It may take longer but think about it you have to construct this thing and also then melt down the Al then while its still molten spray it into an inert atmosphere. Hmm this sounds like its a lot harder than ball milling it.

[metal dragon]

I have been doing a lot of research on the preparation of powdered metals from means of perception out of solution. I am going to try precept Fe from AlCl3 By the following process

Fe + HCl à H2 + Fe2Cl3
Fe2Cl3 + Al à AlCl3 + Fe

It could easily be filtered now. It does however have two problems your Fe could form in clumps but this is countered by stirring and the evolution of Cl gas could be a possibility but the amount would be extremely small.

I would do this with Zn but I don’t have any, does anybody know where a source of Zn is in Australia?
With Zn the formation of heat is a problem because the HCl most people use is 30% there is a lot of water diluted in it so the water could react with Zn and for a lot of heat. Look at Frogfots page under Zn flash powder he states that Zn powder with water gets hot. This could also produce a problem with formations of oxides.

I hope this helps

[Sparky]

So you want to make fine iron powder eh? :D Supposedly you can make pyrophoric iron powder by heating iron oxalate. There is a post on the science madness forum about this in this thread:
http://www.sciencemadness.org/talk/viewthread.php?tid=253&page=1#pid3581

BTW if I couldn't get solid zinc from pennies and I wanted some to experiment with then I would use the zinc sheet that forms the casing for a zinc carbon cell. A 6 volt lantern battery for example has some zinc sheet in it.

[tmp]

Aluminum oxide does form a protective layer on foil and powder.

The tumber barrel has a limited amount of air inside it so

oxidation isn't a major concern.

Anyway the oxidation doesn't interfere with the performance

of my flash.


BTW, NaOH attacks aluminum.


Hope this helps.

[tmp]

Hi gang ! Just purchased some 600 mesh German Dark Aluminum Powder.

Will compare this to my homemade stuff.

I will compare such things as density, particle size,

staining, reactivitiy, dustiness.


Staining: German - Dark but easily washed stain.
HomeBrew - Silver but tough stain.
This may relate to particle size.

Dustiness: German - Produces little dust when dropped
HomeBrew - Produces alot of dust when dropped
Again, this may relate to particle size


I'll follow up when I'm done testing.



BTW, I'm looking for a good filter to produce

sub-micron powder. Any suggestions ?

++++++++++++++++

Here's a suggestion...STOP using the return on every line

so your

posts don't

look like

this, eh? :mad:




-----------------------------------------------------------------
Saw this on a bumper sticker:

OF ALL THE THINGS I'VE LOST,
I MISS MY MIND THE MOST !

[jeffchem2000]

The reason that I am interested in the "blasting with nitrogen" method is that although the equipment is harder to obtain or make there is a huge advantage to it. huge amounts of powdered metal can be made in really short times. I mean it would only take the time of the metal passing through the nozzle. The setup I am building will hold about a kilo of aluminium. When it is working I will make the metal container bigger so it could hold about 10Kg of metal.

I think the extra hassle at the start will be worth it in the end.

[grandyOse]

If you are going the HCl precipitation route, start out with rusty tools. This will clean your tools and put iron and iron oxides in the solution. zinc will then go into solution, precipitating your iron and iron oxides for use in thermite. Then your aluminum will precipate the zinc. May as well get all you can out of the process.

[anthracis]

tmp that quote is from Ozzy Osbourne :D
On topic: a method for getting finely powdered metals (SOME metals…with Al it won’t work) is by reducing the oxide (or other salts such as chloride – e.g. copper chloride) with H2. Fe can be obtained in particles so small that they ignite when spreaded in open air. Zn can be obtained from ZnO, sold as a white pigment in hardware stores. The idea is that if you already have finely powdered oxide, then the particles of resulting metal will be even smaller.

The best way for doing this is by using a big glass pipette filled with metal oxide. This will also allow you to see when the heating should be stopped (Zn may melt if heated too much, Fe is easier to obtain in this way). You have to connect a hidrogen generator (see a simple one here http://www.physchem.co.za/Inorganic/Hydrogen.htm ; you can also use HCl/Al or NaOH/Al in order to generate H2) to one end of the pipette, run some H2 through it until the air is out and ONLY after that you should ignite the H2 at the other end of the pipette. After doing this you can proceed with carefully heating the pipette in the areas where the metal oxide is. Other powdered metals that can be obtained in this way: Cu (see here http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/MAIN/REDOXCU/PAGE1.HTM ), Cr, W, Ti,V, Ni (see here http://www.yu.edu/faculty/afrenkel/NiO%20reduction.htm ) etc.

Hope it helps somehow.

[tmp]

The flash(w/KClO4) tests between my "homemade" aluminum powder and the German Dark haven't impressed me so far. I won't be buying anymore commercially made powder. I don't see a difference in burning, at least not unconfined. The next test will involve confinement of very small amounts. I'll report back with the results when I'm done. Also, I may have found a way to get the powder filtered down to 1 micron or less. I'm using a HEPA filter rated for .5 to 1 micron with denatured alcohol to push the smallest aluminum particles through. The alcohol is andydrous to avoid oxidation of the aluminum. I'll post again when I have more results.

[tmp]

Sorry I didn't get back sooner. The experiment with the HEPA filter
worked out great. Problem with my experiments is that I have many
going on simultaneously and trying to work 2 jobs. I will adapt a vaccum
and filtration flask setup because normal gravity filtering is slower than
molasses in winter. A problem I have encountered with this stuff is that
when I open the jar a cloud of aluminum dust escapes and settles on
everything and is a pain in the ass to cleanup ! Vulture has commented
on this problem with powdered aluminum in another post. The stuff does
react quickly when mixed with KClO4 or KMnO4 and ignited.

I'll be working on powdering magnesium as soon as my "block" of it
arrives.

[chillardbee]

what I've been doing to obtian Al powder is gathering the shavings from a machine shop where they have an Aluminum recycling bin. These shavings are real fine but have a little bit of oil on them that they used in the machining proccess so I spread it out on a clean metal surface and heat it with a blow torch careful not to melt it. It smokes from the heated oil and once it doesn't smoke anymore I through it into the coffee grinder grind it up to near powder. after ever 1 minute of grinding I screen it with a coffee filter screen and continue to grind the remaining with a little more grounds added from the coffee grinder. The shit that you get from the screening from the coffee filter (you know, those reusable ones) can be used as is but if you really want to take that extra step then into the ball mill with it and the ammount of time you leave it there is depends on the size of mill, how much powder, type of media, ect, so take a flying guess at it. It takes my 3 pound mill five days to get it to the way I like it and I know others might say thats to long or a waste of time but thats my preference so there. The end result is a near liquid type of powder thats so very,very fine. I do this to magnesium as well and when added the aluminum 50/50, it makes a freakin' awsome powder when used in flash. actually, even with out an oxidizer this stuf will burn with a little 'whoosh'. Anyway, I find this a reliable way of getting my metal powders since where i live i can not find a source for powdered Al or Mg. PS: for the magnesium I get the firestarter bars sold in the camping section of most dept stores and drill holes into it and save the shavings to grind up.

[Alexires]

chillardbee - Maybe you could atomize some paragraph breaks through your block of text hmm?

Makes things much easier on those of us who have been reading the forum for a couple of hours straight.


You'd probably be better off just buying aluminium, or pulling out the off cuts from the bin and then turning it into shavings on a wire brush wheel (credit goes to someone else for that gem).

Much easier than picking out each individual piece.

But still, good one on getting the free Al. Another good source of Al/Mg (Magnalium) is old Mini engine blocks. Rip parts off of them and run 'em through the brush wheel.

[10fingers]

A ball mill and aluminum foil is the way to go. Maybe you could use a rock tumbler also. Go get some steel ballbearings, 1/2 to 3/4 inch. Put a piece of plastic or metal strip running lengthwise in the tumbler so it lifts the ball bearings and drops them onto each other. All this work with a grinder and blender, etc., is a lot of work and you won't get a fine aluminum. For the effort you put into it you could have built a ballmill. If you are into pyrotechnics they are indispensable. There is a site that tells you how to make one, do a search. It's very easy.
You have to add a little bit of oil to the mill when you start to keep the aluminum from oxidizing. One time I forgot to do this and when I took the lid off the tumbler the aluminum started to burn from the rapid oxidation. That's how fine it was.

[nbk2000]

Normal motor oil or cooking oil?

Also, regarding oxidation, perhaps throwing some dry ice into the mill would help things along, by both shielding the powder from oxygen when it's opened, and by embrittling the foil from the cold, making it easier to pulverize. :)

[10fingers]

I tried different types of oil, motor oil, cooking oil, kerosene, to see if it would effect the milling time. I can't remember which worked best since it's been a couple of years. I think that norwegian pyro site that gives info on the ball mill might know what to use. I did find out the hard way that you have to use something, got a melted ball mill.

It ususally took 2 or 3 days to get the aluminum very fine, it did start to turn grey like the type of German dark you can buy, not quite as dark. The time it takes depends on a lot of things, ball mill speed, type of bearings, how much foil you put in and how fine it is to begin with.

Hmmm, I don't know about the dry ice idea, might work. If you had something to prevent oxidation other than oil, it might mill faster.

[c.Tech]

Maybe burning something like a match or Mg ribbon inside the milling jar before you start milling to 'suck up' the oxygen.

Better still is to pump an unreactive gas into the jar to blast out the oxygen, nitrogen should work well.

EDIT: Sorry if this has been mentioned before.

[jetz]

Maybe burning something like a match or Mg ribbon inside the milling jar before you start milling to 'suck up' the oxygen.

Better still is to pump an unreactive gas into the jar to blast out the oxygen, nitrogen should work well.

When metals are milled they absorbs the oxygen in the milling jar to get an oxide layer, then its broken off again by the milling and is reformed until the is no oxygen left in the jar so that solves the problem with the oxygen.

The problem with milling metals isn’t the oxidation while the metal is being milled its when you open the milling jar, the rapid oxidization causes heat which ignites the metal. A common thing to do is open the milling jar every two hours or so to let the metal oxidize.

The placing of oils in the milling jar is a good idea and will stop the metal form oxidizing as 10fingers has found out. I don’t think that burning the oxygen in the jar will help or the inert gas, it just seen to me that it will increase the chance of the metal igniting when you open the milling jar.

[nbk2000]

If the metal can be kept from being oxidized, and handled in an inert atmosphere while mixing with the intended explosive, that may help increase it's power release since there'd be no inert oxide layer to burn through first. :)

[DONMAN]

I tried making zinc powder in the way described above using hydrochloric acid and scratched pennies. When I added the Al to the Zinc Chloride nothing happed. Then, it occurred to me that maybe be there was some activation energy required for this reaction to take place. So I got a hot water bath and placed the beaker in it; Nothing happened. Should I try boiling the mix?

[c.Tech]

In the water your zinc and Al could be getting oxidised, rendering them useless. Making powdered metals chemically isn’t worth it IMO, most of the time it doesn’t work and when it does the yield is crappy.

[NitroKaBooM]

I tried too... but got no good result... I think it's better if we keep on experimenting mechanical methods improving our home made metal powders...

[DONMAN]

I didn't even get zinc oxide to form. :(

[ultma]

A word of caution in the first post some one mentioned pouring molten Aluminum through a jet of fine water or air

DO NOT mix MOLTEN ALUMINIUM with WATER it can EXPLODE

I only know this because I used to work in an Al smelter in my holidays while I was at uni.

On the first day they showed a video of Al being poured into water and it exploded fiercely the video said they also didn’t know if the effect was physical from super heated steam or chemical form some sort of reaction. As a result at the smelter you can not take in any cans of drink or liquid as if chucked into a pot they could explode.

[in_flames]

NBK - Wouldn't the oxidized layer on the outside of powdered aluminium be the only thing stopping it from spontaneously reacting with any oxidiser you mixed with it?

[hydra]

the pressurized spray method should work fine for you; if you do it right.

First, you have to eliminate oxygen. Both in the pressurization, and in the receiver.

Second, you don't want to spray gases -with- the liquid metal; you want to just pressurize the container the metal is in; and spray only metal.

You control the droplet/particle size via adjusting the process parameters; i.e. the orifice size and the discharge pressure. With orifice-size held constant, higher pressure produces smaller particles. Each orifice-size gives you a range of sizes commensurate with the pressure and mass-rate capability of the rest of your machine.

Also, virtually all orifices act non-linearly...i.e., below a certain critical pressure, they will not atomize properly at all.

Use the smallest orifice you can find/make; and build your apparatus to withstand a fairly healthy pressure; e.g. 200psi...then use 100-125 psi gas on it.

Get a tank of Argon from the welding house, put a regulator on it, and set it to 100-125psi. Flood the receiver with argon until all air is displaced. Heat your nozzle/container to temp, and when the aluminum is melted, apply the pressure. Away ya go...

Note that many metals are applied to plastics etc. via plasma-spray directly from wire. I.e., the wire is melted within the plasma-torch handpiece and blasted out by inert gas.

That is probably what I would try first, if I was doing it. I.e., modify a plasma-torch to replace the tungsten center-electrode with a wire-feeder.

Replace the usual compressed-air feed with Argon; and have the torch mounted on an argon-flooded receiver. A suitable receiver would probably be a 20' long piece of pipe with a pressure-bleed at the far end.

Note that you might be able to do the same thing with a TIG torch if you fed it with 125 psi argon; instead of the usual 1 psi....but you might want to verify capability of the stock hose first... :D

In either case, TIG or Plasma torch, you're going to have to insure good current conduction to the moving wire....i.e. arrange for the feed rolls to carry the current. However, if you use thin wire...like .035 aluminum MIG wire or similar, I do not think you will need that high a current...

Please keep us posted on results. I do think that atomization is an entirely practical way to go about it; and only needs some process development to work out a usable and pretty cheap setup...


Edit: by the way, you might check into replacement oil-furnace nozzle/orifice at the hardware store. Some of them have quite small orifices, and all the ones I've seen are made of steel, not brass...and I think you want steel for this job.

Also, you could try nitrogen in the above processes; but I think it likely you'd get a fair percentage of aluminum nitride in the output...which I don't think you want...which is why I said Argon in the above. Nitrogen's worth a try though; as it's a lot cheaper...

[asilentbob]

If you have Mg and Al making 50/50 brittle MgAl alloy then breaking it up and ball milling it is ideal.

Having a simple method for spherical/atomized powder production like the above proposed method, which I think is fantastic, would be excellent. As is I have to get my spherical Al for glitter stars online.

+++++++++++

The letter I is always capitalized when used in reference to oneself. NBK

[Charles Owlen Picket]

At a PGII event several years back this issue was discussed at length. The conclusion to the concept of making one's own Al powder at home was reached in-so-far as work input & time vs. amount of material collected.

In a nutshell here is what was agreed upon......
The use of an angle grinder (4" 8-amp was fine) and a garbage bag set up to be opened via a wire coat-hanger frame. The garbage bag was taped to the coat-hanger opened up in a wide "mouth" to collect the grindings. This was very efficient. There were techniques to make stable both the collection bag and the grinder, thus making the operation easy on the individual. The grindings were then ball-milled with tractor or tank ball bearings (1-2"). [These are nice balls, albeit steel and will produce the needed size of powder dependent upon time of milling.] The problem of "caking" aluminum on the grinding surface was addressed by a product from Norton Abrasives.

A Hell of a lot of other techniques had been tried. But all seemed to suffer from either too much initial expenditure of money to produce a small amount of powder or difficult to control conditions for consistent results.

TIG/MIG/Plasma techniques may prove viable. I would be VERY interested in the results. But initially I believe someone DID test techniques with welding apparatus and the problem was that the powder was limited regarding alloy & the time / money / yield issue. With simple techniques like grinding, the alloy can be most anything available or desired.

[hydra]

Charles; I quite agree....ball-milling is an excellent method.

I was thinking more along the lines of high mass-rate processes; although if a person has a LARGE ball-mill... :D

The grinding method can also be high-production, if the right wheels are used...so many cubic-inches per horsepower per hour.

I think I have to admit that I favor the plasma-arc method only because I really like very high-energy things. :D

In any case, the atomization-from-melt method (conceptually at least) is really pretty low complexity (heat and pressure is about it); and potentially very high mass-rate and low cost.

[Charles Owlen Picket]

I also enjoy high energy goods! - What collection method would be proposed with a plasma-arc technique?

The reason for my query is this: With a grinder (and I'm not cheering for that technique mind you) a collection bag can be set up and the material "focused" into the ringed collection bag. But with the plasma-arc would we not have the issue of heat and wide dispersal to contend with? Hot material melting a plastic bag and possibly burning a cloth one would make collection a problem......

I can see high yield from several methods, however the bother of sweeping a floor is a complication as it would add impurities and extra steps to the process. I'm with you 100% on this as I would love to find a suitable high yield method.

I actually have collected floor sweepings as have a few friends and collected dozens of pounds. it's (IMO) only at the 10 lbs+ level that it begins to get worth the effort. Cleaning took a seriously long time. I have spoken to a few people who did this at machine shops and one guy took home about 50 lbs of fair quality Al ! The total time in cleaning and milling (he had a seriously nice mill as well) was quite a bit.

I did a search for "tank" & "tractor" ball bearings, surplus, imperfect. And I found some good sources. Some as low a $4 for 1.25".

[hydra]

yeah....anything that runs at 10,000++ degrees...ya just gotta love it, huh? :D

Grinding: there are wheels specifically designed to grind aluminum with minimal loading. They don't cost that much either. Check the MSC catalog.

I believe that the high-rate grinding should be run with 'coolant'....of which, probably regular #2 diesel fuel (or home heating-oil) would work well. Run a continuous stream of it onto the wheel right above/at the intersection of wheel and work.

Build a pan under the grinder to collect the take. Build a motorized bar feeder using an old C-band sat-dish jackscrew. A lot of those used 12v or 24vdc motors; so can be easily speed-controlled. Load a 1/2" or 1" bar in, and go have a brew. :D

Alloys: someone up above said something about making a 50-50 alloy with Mg; so that it'd be brittle, and would break up better/finer. I don't have the exp. knowledge that you guys do....will alloys work for your purpose?

If so, then aluminum-foil is about the worst thing to use; because it's softer than shit...essentially pure aluminum (1100 alloy). Just about ANY alloy is much harder than 1100. Common finned heatsink extrusions are kinda gummy...they're 6053. But compared to 1100, even they are 'harder'.

6061 is the 'standard' machine-part alloy...it's a little harder than 6053, but still what I'd call a 'gummy' material to machine (compared to steel or brass anyway). Both of the above use magnesium as the main alloying element (6000 series are Mg/Si based).

If you can get any 2024 series alloy scrap, that's a nice hard alloy. It uses copper as the alloying element. 7075 is quite hard, but not as common as 6061 or 2024.

But if alloys do work for ya in general, and silicon in particular doesn't bother the reactions, then by all means forget all the above, and use CASTING alloys !!

They are MUCH harder than any of the 'wrought' alloys. Not only that, but in almost any practical quantity, they're almost always FREE! :D

Every piston on the planet is made out of a hard/brittle aluminum casting alloy...usually 356, if my memory is working right. Something like 5-10% silicon in it, I think.

Scrap an old broken Briggs lawn-mower engine and grind the piston...see how that powder burns. Heck, for that matter, grind the whole freaking -case-. :D

The entire Briggs engine-case is nothing but a big aluminum casting. It's likely a slightly different alloy than the piston, but still much harder than the wrought alloys.

And brittle too. Hit a Briggs case hard with a ball-peen hammer; and you'll shatter a hole in the side. You can't do that with extruded or sheet aluminum....too soft/ductile.

Need big-time production? Go for car-scrap then. Virtually every automatic-transmission has a case made out of the same basic thing. About 25 lbs worth in every typical 'detroit' auto trans...like a TH350 GM trans.


Atomization: on the FTP, there is a book about investment-casting...i.e. lost-wax method (thanks tmp!). The entire book is about building your own investment-casting setup from scratch; including a -pressure- injector for the molds. I.e., to inject the molten metal into the mold under something like 40psi pressure. Note: this is SIMPLE stuff. No precision machine-shop work required. If you've got a hand-drill and a hacksaw, you can make most everything in that book; including the kiln.

Since the audience was jewelers, the whole setup was designed for casting gold, etc.; which takes a fair bit higher temp than aluminum. So anything in that book should work for aluminum.

Now, 40psi is unlikely to be enough pressure to 'atomize' a metal. But if all it did was produce pounds of pretty small balls or flakes, and did it in just minutes; that'd be a big step forward all by itself, yes?

I.e., no more hours of noisy grinding!

Because of the viscosity and surface-tension of molten metal, no 'valve' was required at the bottom of the pressure-injector crucible. There was simply a 'capillary' tube. I.e, the tube ID was small enough that the metal would just sit there in the crucible without running out, at 1-atm pressure. But push the lever down, and it'd squirt out into the mold that quick.

OK, picture this thing beefed up a little...to take the 125psi of a typical home-shop air compressor. And the capillary tube ID made as small as will still let the metal spray out under 100+ psi. This ought to make quite a good shower of pretty small aluminum droplets. Even a small coffee-cup size crucible holds several pounds of aluminum.

So....about 30 mins to melt it, a single minute to squirt it; and you've got perhaps 5 pounds of aluminum ready for the ball-mill...with very little effort.


Charles, you asked about collecting the output of a plasma-spray setup...

For that, or for the above liquid-squirt method, I'd just use a piece of steel pipe; and if that works OK, call it good. From the liquid-squirter above, with droplets much larger than a plasma-spray, it's going to take some time for them to solidify. If they hit the walls first, then you're likely to get little splat-flakes instead of spheres. Does that hurt in ball-milling? Probably not.

But if it does, then stand up a 20' piece of 6-12" pipe vertically, and squirt down into it outta your 2nd-floor window... :D

[209]

I found a very usful link just a few minutes ago while cruising google for aluminum powder, I have access to 650 mesh, it's so damn expensive (50+ dollars per pound :eek: :eek: !!) I was looking for an effective method of obtaining large amounts cheeply.

I have heard of grinding, the thread of sodium hydroxide reaction, files, grinders and everything else under the sun, however I think this method doesn't require any physical labor while grinding increadably fine amounts quickly :http://gamekeeper.deds.nl/metal_grinding_machine.html - take a look, tell me if you've seen it already.

[Charles Owlen Picket]

Grinding, sanding or what have you, if it is not processed with an appropriate abrasive, you wind up with a lot of extraneous material in with the metal powder. In the sited link those issues are met via a water wash. but Norton Abrasives actually manufactures a few of the needed abrasive surfaces designed to tear down Al -fast- and still maintain it's purity.

That's one of the biggest reasons for the consideration of plasma, etc.......no intermediate wash step. A 4" "NO-Clog" scaler & ripper wheel will never clog up with Al and will grind down well over a pound in less than 15 minutes. Which is pretty damn fast. You also need a strong (at least 8 amp) little grinder....using something weak will take much longer.

[Gumby]

I have access to 650 mesh, it's so damn expensive (50+ dollars per pound :eek: :eek: !!)

You don’t want to know what nanopowders cost then or how deadly it can be.

I'm curious as to why no one has suggested the explosive wire technique for making submicron powders? In theory it is actually much simpler than something like the centrifugal set up. Building a chamber for this to happen would be easy, displace the air with argon, and run a large enough current through a wire and boom, now you have powder. Capacitors could be used to generate the required amps and voltage.

I’ve been toying with building such a device as well as an arc furnace. Both are relatively simple in design and operation and I could manufacture the parts for them myself so it isn’t like I’d be out a huge sum of money; though I’d want to be able to make Kg sized amounts of powder at a time.

[nbk2000]

Imagine you had a vertical tube, through which a continuous wire feed of your desired metal was fed in through the top through roller conductors.

As soon as a length of wire touched the bottom of the tube, it completed the circuit and fired the capacitors, vaporizing the length of wire between the two contacts.

A blast of argon or nitrogen would then sweep the tube clean of most of the powder as the wire continued to feed into the chamber, in a continuous process, as the caps recharged.

[Gumby]

Imagine you had a vertical tube...as the caps recharged.

That is very similar to what I was thinking. I think it would be a very do-able set up and not as expensive as you'd think. Once built you'd then have the tools for a small business selling powders.