Powdered Aluminum

[FrenchFries]

Hello every one, haven't posted here before but hope this goes well.
SWIM is considering making powdered aluminum (sure this topic has been beaten to death) the search engine has yielded a lot of results, of things that involve manual work or sending someone money to get something in the mail. Any way, SWIM is considering a reaction that goes something like this.

SWIM wants to use a double displacement reaction to obtain finely powdered aluminum

A stoichiometric amount of Aluminum is added to an equal molar amount of 25% NaOH solution, producing aluminum hydroxide, after reaction goes to completion, next a stoichiometric amount of magnesium shavings are added to the aluminum hydroxide solution. Which, if this chemistry is right, will then result in the aluminum hydroxide reacting with the magnesium to produce a solution of magnesium hydroxide and precipitated aluminum.

Alternate double displacement reaction being considered is dissolving aluminum foil in a stoichiometric amount of Hydrochloric acid, and adding to the resulting aluminum chloride solution, a stoichiometric amount of magnesium shaving which will hopefully result in reaction between the magnsium and aluminum chloride(which is supposedly a strong lewis acid) resulting in a solution of magnesium chloride with precipitated aluminum.

Do any SWIY's have an opinion about these proposed procedures. Or more specifically if either of them would work?

Thanks for the help, the forum is great, SWIM did try using the search engine to find some elusive procedure for powdering aluminum, where in legend has it that the aluminum could be done powdered with table salt and a blender?

Any how, any help is more than what SWIM is getting right now.

Be safe, wear goggles.

[The_Duke]

Just one suggestion, UTFSE and look harder ;)

We don't usually like n00bs posting new topics and you could have posted this in a few other threads without starting a new topic. But since I can't merge threads and I guess your post was better than alot of the stuff we see here I have unlocked the thread as per your request, even if the route you propose will not work...

But do try and lay off the SWIM and SWIY crap, it doesn't fool anyone nor will it save you from being convicted if the jackboots really want you...

[Yafmot]

Why bother with all that caustic slop? Harbor freight has a six pound ball mill/rock tumbler for fifty bucks ($34.95 for the next week or so), aluminum foil is shit cheap, and there's zippo paper trail.

Use

Just in case you're unfamiliar with the procedure, here you go: First, youre going to need some grinding media. If you really want to go first class, CoorsTek Has various diameters of ceramic (Alumina) balls that work great. They're non-static (muy importante when dealing with flammable powders), and very hard, which speeds up the process. They're a little light, however, so the trick for that is to add a small percentage of brass balls to the media.

Paragraph

Then go and get a couple of rolls of the cheapest Aluminum foil you can find, like that 98c store crap you can hold up to the light and see through. Cut into little strips and stick 'em in a blender. It'll zap it all into little shards, which are then thrown into the tumbler, along with a fistful of marbles, brass balls, dedicated media or, really, just some small river rocks. Run the booger for about a month. Any longer and you'll have to open the barrel in an inert glove box.

breaks

By the way, adding Al to that strength NaOH solution will generate shitloads of Hydrogen. When I was a kid, we used to take a glass quart Pepsi bottle, put in a few spoonsful of lye, some elongated wads of aluminum foil, and a cup or two of water, and then quickly pull a balloon over the neck of the bottle and fill it with H. This had to be done in an ice bath, of course, both to keep a runaway from breaking the bottle and to avoid boiling off too much water, which would condense on the walls of the balloon and weigh it down. Then we'd tie about a three foot strand of linearly-wadded toilet paper to the neck of the balloon, light the end of it, and let it go. If the thing didn't go out at launch, it could get up a couple hundred feet (once it's moving with the air, there's no relative wind). Then, the satifying thump. (And you should have seen my idiot friend's expression when one went off in his face!)

[Killy]

Were talking here about chemical procedure of obtaining powdered aluminium, so dont spam the thread with ideas with ball mill and some shitty hydrogen in balloon collection.

Duke said it right, cut that SWIM crap, its your first post, and youre getting on my nerves with that already.

Ive seen that method of producing Al, in some pyro/ex manual, its interesting, but one setback is that you must use powdered mg, which is hard to obtain just like powdered Al, so does anybody know some other metal which could be used in reaction instead of Mg ?

[hatal]

Using the described procedure would cost you more time and money than just simply using a 2 or 3 different blenders (to further refine the obtained powder. Ofcourse the chemical procedure would get you the "finest" aluminium powder but the expenses would leave a bitter taste in your mouth for such a small price...

[Man Down Under]

Magnesium rods for water heaters are quite large and very cheap.

[hatal]

Is there any simple and cheap way to "extract" aluminium from mercury out of the Al-Hg amalgam form? I remember seeing a patent for, but I can't recall it. Not to mention if it fits the cheap and easy criteria.

[megalomania]

Don't quote me, but I think strongly heating the amalgam will cause the mercury to vaporize, which can be distilled. This strikes me as an odd way to get aluminum when mercury is so much harder to come by...

[Man Down Under]

Mercury is readily available from gold panning suppliers. They also sell mercury stills to recover the mercury from amalgamations, so you can recycle the mercury many times.

If aluminum was amalgamated with mercury, would it be left as a useably fine powder after distilling off the mercury?

[Bert]

Allthough the production of Al powder throught chemical or other non mechanical means is intellectually interesting... If you want some in a reasonable ammount of time and at a minimum cost and risk from toxic processes, you'd be better off with a cheap blender and/or a ball mill.

If you've got enough metalic mercury to be seriously thinking about this, there are more entertaining uses for it!

[Killy]

Hm, man can never be satisfied,
since with ball-mill you get atomized powdered aluminum, which is not so good as industry made flake pow. aluminium.

Whats the chemical basis of reaction with magnesium and aluminum ? Could it be somehow swapped with some other metal, not Mg, maybe by valence numbers?

[Lewis]

Much effort by various forum members seems to have been put toward this task, and it's beginning to look like a ball mill is always the way to go.

Hm, man can never be satisfied,
since with ball-mill you get atomized powdered aluminum

Since when?
Atomized Al is not made with a ball mill, as far as I know.

[Bert]

Killy, "atomized" means the Aluminum has been blown through a spray nozzle while molten, forming more or less round drop shaped particles. It has less surface area than the stamped or milled powders, but in fine enough size is still useable for flash- I have seen commercial atomized Al offered in 2 micron size. We have used it in other sizes from 10 to 36 microns in stars and other pyrotechnic mixes.

Home made ball milled flake can be made quite fine and reactive enough for flash if it is done properly.

[megalomania]

I have been considering dedicating some effort into manufacturing aluminum for the serious amateur user. I don't exactly concern myself with the making of pyrotechnics, but fedgov crackdowns on chemicals really inspire me to circumvent their pathetic legislation by taking the power out of the hands of the elected terrorists, and giving control of chemical production directly the people.

The de facto criminalization of powdered aluminum via closing down pyro suppliers amounts to an abuse of power by the fedgov terrorists. All of human endeavor is motivated by scarcity and necessity, and now it seems necessary for any common man to make as much powdered aluminum as they need.

It is not an easy task, but it is not impossible. No idea to make the home manufacture of powdered metals is too outlandish or far fetched at this point because there is still much innovation left to be done.

I fondly hope we can look back some years from now and think, why did I ever buy this stuff when I could have made my own by the ton so easy?

Unfortunately, the plan as it stands now it still stick at the first stage...

1) Collect underpants

2) ???

3) Profit!

Industry can do it, industry can do lots of things, but that means it is possible, not that it is only possible in industry. Industry is good at doing things on a humongous scale, not necessarily using the most efficient process (for those of you who work in factories, do you honestly believe the powers that be know their ass from a hole in the ground when it comes to doing things the best way?). Every chemical reaction and manufacturing process starts out in the lab, on a small scale. Then the engineers figure out how to do it big.

[Charles Owlen Picket]

I did actually have that motivation awhile back and wrote somewhere within about collecting floor sweepings of a variety of metals. My attempts came down to a rather moderate ball mill with media ranging from steel "tractor ball bearings" to billiard balls.

I had dozens of pounds of Al and Mg in very, very usable mesh sizes when finished. Frankly, even though I attempted various techniques, the ball mill was the real winner. With no exaggeration I ended up with about 10 lbs of dark Al that is certainly as reactive as the material from pyro suppliers.

As with most things, I put some under a microscope to compare with a commercial sample and was damn pleased. If a starting point is developed (mine was several machine shops in town) then the question is generally the scale one operates on. The whole thing gets very attractive at the 10-30lbs level. That's not too much to work with at home but enough so that when completed, you have a real supply.

~-=I also found actual gov't surplus metal powders! Admittedly a rare find but it's out there. I got some tin, nickel, zinc, tungsten, molybdenum, & copper that way. They were a real find. PM me if you want to know about it in depth.=-~

[Roy Paci]

Do you know Dremel minidrill? Using that device I obtained i nice zinc dust that reacted with sulfur (50:50) when ignited. Do you think this is a road that deserves further esploration?
I will try to grind an aluminum bar with the finest miller they sel for this microcutter.
And...
What were you guys doing on new years eve? Posting on the forum? Not drinking or at least blowing something up? (just joke)

[totenkov]

New years eve?!

A bit late or a bit early..........

[Aristocles]

New years eve?!

A bit late or a bit early..........

Check the dates of the two posts immediately prior to his

;)

[Charles Owlen Picket]

I am attempting an experiment with the manufacture of aluminum powder from foil. This was presented in two articles (found in the FTP) from alternative sources. And yes, frankly, it was Mega who got me thinking about this as well as the various pdf's that (as re-prints from journal articles) provided some background...

The purpose of this post is an ongoing method of producing Aluminum powder for the hobbyist with minimum cost. Presently cost factor is at less than one dollar per pound.
The concept is simple; foil is introduced into a ball mill and through a annealing proves it is hammered into flake aluminum. This appears simple enough and I have worked with Al powder from a variety of sources including surplus, ink and paint suppliers (Ekhart is an ink mfg.) floor sweepings, chemical breakdown, etc. I have samples of over two dozen products and unfortunately don’t have any camera for my microscopes so words will have to do for now.

Conceptually what I want is always a single micron size (2-9um) flake Al. I believe this to be optimum and a fair goal. Ekhart provides the best product thus far on the market with a consistent size material that is unusually expensive due to it’s consistency and it’s origin. ALCAN/AlCOA is generally considered to be the source of the material used in much energetic materials as Ekhart is an ink mfg. & does not sell it’s product for uses in bulk (it would cost too much).
I began with common foil that had no coating. This is available as the cheapest house brand foil product and if available, purchased from a restaurant supply will provide for pounds at a very low cost. Two pounds were cut in a specific manner. It needs to be separate and it’s not as simple as one may think. Tin snips are needed to begin the process or it will be an all day affair. One inch squares or close are needed and placed in a blender. This is then used to bring the foil down to a rounded, individuated appearance about 1mm in size. It’s non-injurious to the blender but makes a bit of noise. These pieces are then the starting material for ball milling. Starting with this technique will improve the speed and most importantly the annealing process for the ball mill to break down the material into true flake Al. The material is introduced into the ball mill for a ten hour period, at which time it is examined and “aired”. This is very important, so as to cool it down. The Al needs to be beaten and then it will heat, - cooled and then re-beaten. At the ten hour mark the material will be flat and one half the size of starting size. This is an important time. Approx. 15% will be starting to powder. The powder will be granular and VERY hard. The annealing process is starting to work.
Selection of milling media is very important. Lead produced a product similar to steel balls but steel is faster. Lead is safer. Gases can build in the mill. Albeit the risk of explosion is slight, it’s still there with the use of steel. However, from doing this several times, I can assure you that steel is about 33% faster. What is needed is at least 50% weight in media (use one pound of Al; use ½ lb of media for efficiency and to maintain consistency with the testing). Safety issues arise if moisture is in contact with the material. I am going to make the leap that most people know about that and that the stearic acid is used to not only lube the Al but to deal with some oxidation issues.

At 24 hours the Al is now totally granular and at 20-40 mesh size. there are some very large pieces and they are VERY hard. At the lowest portion of the mill, some Al is starting to flake and is 325 mesh at it finest. At 48 hours most all is 325 mesh and mostly granular, very hard, very brittle. At 72 hours the material is starting to look like dark Al. It is air float and must be seen under a microscope to actually see what’s going on. It is starting to be a mix of granular and true flake. The product is a highly mixed bag of Al some of it being truly single micron sized: some being fairly large (325 mesh). This method can be used to make energetic Al with ease and some volume. Using a mill that will support 5 lbs at once is actually a fairly small mill. I believe the hobbyist can produce as much as needed using Aluminum foil as a starting source, the final product is mostly flake. However, it has some granular product and is NOT consistent sized. For energetic materials it is excellent. For use within paint, ink, etc……it is too non-uniform. It is VERY reactive and responds to flame in a manner similar to any high-end single micron particulate Al.

Granular and flake powder are very different. Granular powder is very dense as the size gets smaller. It compacts and feels almost solid in a bag when very small. Flake is more “fluffy” in feel. This Al is pure. It has no stearic acid or lubricants. It is unique in that and is elemental aluminum. The "lubrication element" places a new dimension of the use of a ball mill for this effort and will be dealt with separately from this first effort

This post will be an on-going effort to produce Al powder. This product has been tested with a variety of materials and can certainly be appropriate for flash. It’s works quite well and in direct comparison with commercial dark Al is similar in size. However it does maintain inconsistency in size due to speed of production.
Observations:

The preparation of Al Foil is a must. No damage to a home use blender was observed. The blender cleaned up very well.

The product is pure. It does have granular particulate in it. However that does not appear to diminish it’s reactivity and if more time than 72 hours was allotted that may have not been an issue.

The finest particulate appears through microscopic examination to be sub micron. There does not appear to be an average size however at 72 hours. Some material is still above 40 mesh in size.

All of the material is hardened. This is due to the annealing process. In addition, there is need for “airing” of the material. This allows for cooling and increases the annealing. After the material is taken from the mill it will decrease FURTHER in size due to shaving.
This process can be scaled into the ten pound level with sourcing for the milling media to be the highest priority. “Tractor” or “Tank” steel ball bearings can be used but the buildup of gasses is an issue. The need for lubricant in the form of stearic acid would decrease the need for lead composition media.

You will see the Al Powder go through “stages’ while in this process. During the initial process the foil is stripped from the roll by the use of “tin-snips” as this is really the only way to break down the roll of foil into manageable size. it will be .5” by 1” sectionals of the roll and those pads of foil introduced into the blender. At this starting point it will be torn into one millimeter balls and formed into smaller sections. The blender should be allowed to run for at least three full minutes and the materials will be ready for effective ball-milling. The milling will flatten the foil and the air held within. Note that the simple use of this process of tin-snips and a blender will yield tiny aluminum micro-balloons that are very valuable in themselves. From here they are flattened and annealed for the first time. This stage will take approximately 10 hours and the result will be fine granular aluminum. Note that the first stage will always be to produce a granular product as the material will be annealed first then broken down. It is very important to cut small sections and then use a blender prior to ball-milling. This ensures effective use of time. To place the foil into the mill without using the blender will have limited effect as the foil will flex and line the container of the ball-mill for quite some time.
Next the granular and flattened aluminum will start to break down. The smallest pieces will start to rip into the existing foil “balloons” that escaped being torn initially and the whole of the product will begin to become granular aluminum; varying in size from 10 mesh to fairly fine. This will be roughly at the 24 hour mark. This granular condition will continue and the material will start to become quite fine. Some material will become flattened and remain so. These chunks will actually tear into other sections of granular powder and will start to chip apart. At the 48 hour mark the aluminum will start to become flake. Some of it will still be granular at about the 50/50 point. The material will start to have some of it’s reflections return and some will start to “air-float”. Remember, this material has NO lubricants (stearic acid) in it. It is pure elemental alumij8um. If it did have some lubricants, it may take less of a period of time for these stages to progress. At the seventy two hour mark the material appears to be about 325 mesh with some of it still larger. But it will never be a consistent size with this process. It also will not “feel” the greasy way that flake aluminum feels, in part due to the percentage of granular material that appears to exist even after a lengthy period. At this point it is almost all flakes but compacts very tightly and seems to be almost a solid when formed into a container. It may have this quality due to the lack of lubricants; it’s elemental fineness, or both issues. At the ninety six hour mark it appears to be as fine as would be needed. Most of it is all air float and seems under microscopic examination to be flake 80% granular 20% and about 2-9um (some notable larger material on top).
Samples were tested for reactivity and the results we astounding. The finest flakes when compared side by side with Alcan 808, 813, Reynolds 400, were close to identical. The same compared with Reynolds 400 was also virtually indistinguishable. When a sample of flash powder was made the results were the same as any American Dark at the 600 mesh level. From one pound of foil, approximately four grams were waste as they bulked up and needed to be processed in with other batches.

In summation, can an individual take some Al foil, throw it in a blender then put it in a ball mill and have a quality product? Yes. Provided that the introductory aluminum is not coated, cut to small size to begin with and the ball mill is a well prepared one with media that is either lead spheres and numerous, brass and large or steel (and one remembers that there is a serious safety issue with steel). This is a "do-able" technique and outlined in a few journal articles. Patience is a must. It won't break down over night. The media is a very import issue as is the preparation of the material. However, it WILL provide a seriously high quality product.

Average cost to hobbyist:

Ball mills are essentially, rock tumblers. They are so important in a variety of applications that such a thing is an investment. But generally they are available from as low as $9.98 / $19.98 to as high as one would want to spend. Media can be free if you have a source for ball bearings, if you want lead, 50 caliber round balls are available & work quite well. Tin snips and tools are not included nor is the cost of the foil…..Generally consider spending $25 and having the utility to make as much as you would want.
Availability of aluminum powder that has no coating, no mechanism for oxidation prevention can be a boon to the manufacture of certain materials. Many sources for pure powdered particulate excepting government surplus has become difficult to obtain in small qualitative. Slight oxidation can make powders even more reactive than reducing their particulate size; all things being equal.

So basically we are talking about the cost of a one pound roll of foil as the cost of a pound of Al powder!

Implications for Ignition of Aluminum Powders (PE&P 2005: this was the basis for the first experiment...)
The oxidation mechanism described above can qualitatively explain why aluminum particle ignition may occur over a wide temperature range. For the simplest analysis of a metal particle ignition in a practical combustion system, one should compare the rate of particle heating by external sources as it enters the combustion system against the rate of particle self-heating due to oxidation. When the rate of particle self-heating becomes dominant, particles would be observed to ignite. Physically, upon ignition the rate of the particle self-heating increases dramatically because of the changing mechanism of oxidation. For example, the vapor phase reaction and respective heat release could rapidly become the dominant source of the heat generation. Therefore, the ignition model discussed here can only be considered up to the moment when the selected ignition criterion is satisfied, for example, the external heating rate becomes equal to the internal heating rate produced by the heterogeneous oxidation.
Description of the ensuing processes leading to the full-fledged particle combustion should be considered separately. For most of the practical applications, heating of the particle by the external sources is only a weak function of the particle size, and is defined by the specific configuration of the combustion system. Thus, for a very simplified, qualitative analysis, the external heating rate could be considered as a constant, determined by the experimental configuration.

I have also concluded testing with magnesium. The Mg was substantially different in it's size reduction and shape (it does not flake, for the most part). My cost on single micron size Mg is related to the use of floor sweepings. Basically what would have cost $28+ a lb. from Skylighter when they were allowed to sell it is equal cost-level to Al. The Mg was extremely reactive and some different issues arose from it's sensitivity to oxidation. More on that in a separate piece.

There are techniques within techniques here. There is also the ability to produce both size and shape differentiation. This is a work in progress; more will be added to this as time goes on.

[Lewis]

Great post. Makes me want to break out my old mill!

It's strange, I've heard from several sources that lead media won't effectively mill aluminum, but this is clearly not the case. Perhaps experimenters haven't payed close enough attention to the source of their foil. Is there an easy way to tell if the foil is coated?

Also, what is an effective drum material for milling Al?

[totenkov]

Excellent post Charles! I was going to add to your rep but I noticed that its gone, forgot that Mega disabled that feature. I have never made flake Al using this method but it looks quite appealing for the near future, where Al powder of this mesh will most certainly be outlawed :(

[Charles Owlen Picket]

Thank you both. I can only say that the look and feel of coated vs. uncoated is something that you can't forget once you check it out....but you could always light it and see if you have a smoky flame. The cheap shit is almost always a good bet.

Lead media will work but not as fast.....I choose .50 cal muzzle loader balls as that was laying around (If I was really going to make some serious pounds I would invest in brass one inch media, I believe). I used a rock tumbler for this as I really wanted to keep cost at a minimum so that someone could copy it. The containers were rubber as you know and that aids the "tearing" of material with lead.

[tmp]

The butane lighter test is one way I test my powdered Al. If it's fine enough
it'll burn without oxidizer. It's not scientific but I compare it to some German
Dark kept on hand. One thing's for sure - if it burns in the open as easily as
the German Dark, you'll get a hell of BOOM in flash. Again, not scientific, but
it works for me ! :D I agree with anybody who states that the blender
chopping is an excellent way to prep for the ball mill. I've also used a hand
cranked flour mill with excellent results. With proper "filtering", the blender or
flour mill by themselves, without a ball mill, can produce good results even if it
is more tedious. Determination is everything !

Given the high cost of flash grade Al and the CPSC's efforts to discourage our
hobbies, no avenue to produce powdered Al should be left unexplored !
The government bastards will never stop pyros as long as forums like this one
are available to determined DIY types such as ourselves ! Happy pyro ! :D

[Zer4tul]

I don't remember where i saw it, but an individual posted a way to get aluminum powder that was quite simple. It went something like this:

1. Obtain piece of aluminum
2. Place piece of aluminum in a plastic bag
3. Get a rotary sander, place in the bag and somehow contain the sander/bag assembly
4. Sand piece of aluminum while in the bag
5. Collect the residual aluminum dust that remains in the bag

This idea does seem a bit K3wlish, but it strikes me as alot easier than messing with NAOH and other messy/expensive procedures.

[Bert]

I believe the proper term for the hardening and accompanying embrittlement of the Al during milling is "work hardening". Annealing is the process of heating a (work hardened) piece of metal and allowing it to cool slowly, thereby softening it-

[Charles Owlen Picket]

I believe the proper term for the hardening and accompanying embrittlement of the Al
I actually paused at that before I wrote it. One article uses that expression and I wondered why - at first. I agree (work,heat=anneal). Well I also found that if that mill runs for a 20+ hour period that material gets quite warm. Warm enough to comprise the true annealing process? I'm not quite sure, but I believe it appeared in the Journal of Materials Processing Technology article.

[Bert]

Annealing would require a furnace. Your jar would be melted long before you reached a temperature that would anneal metal.

Typically, annealing is used during cold mechanical processing such as deep drawing, to allow the metal to be further processed without cracking due to hardening.

It seems from your description of your process that you wish to work harden and render brittle the Aluminum, causing it to fracture under the blows of your milling media. Is this correct?

It's good to hear your method produces useable material, understanding the mechanism may help you refine or speed the process.

[flippy]

It seems from your description of your process that you wish to work harden and render brittle the Aluminum, causing it to fracture under the blows of your milling media. Is this correct?

Obviously annealing would be counterproductive given this as a goal. But, what of the "flake" type product? Would an anneal at a fine size contribute to "flake" being formed?

[Charles Owlen Picket]

Yes, that is exactly what occurred TTBoMK. It fractured, broke down to granular material and at a certain stage started to appear as flake. This was monitored at various times through out the course of several days. Undeniably, this produced a quite useful material.

I was eager to compare it to commercial samples. I had many available to me and a microscope with measurement-metered slide assembly. I found that although it was inconsistent, in that it had several sizes within the finished product, it was damn finely composed! [I considered the term "finished" after so many days, it no longer reduced appreciably] The reactivity of this material was wonderfully powerful. I tested, as many do, with and without an oxidizer, to flame and the result was a profoundly reactive Al power. Without question, on the same level as any American Dark. The question that one journal article posed was: "with stearic acid as a lubricant, would the material pass the stage of granular-to-flake? And would it still be as reactive"? These are still unknowns to me.

What I saw was at smallest, it was beyond the micron measurement scale. Largest was about 60 mesh with some unfinished blobs taking perhaps 3 grams of unusable material.

[Bert]

An acquaintance has this method for looking at samples of Al powder under the microscope. This method disperses the particles, so you don't have to look at "clumps"-

Take a slide and put a drop of acetone on it. Dip just the point of a pencil or similar pointed object into the metal powder to be tested. Withdraw, and tap the pencil gently against a solid object to knock the majority of the powder off. Touch the end of the pencil with the residual powder clinging to it to the drop of solvent, washing some of it off. Allow the solvent to evaporate, and take a look at what you've got.

A method of separating sub mesh sized powders is to set up a long tunnel or tube with an air flow through it. Disperse the powder into the air flow, and the various sizes will distribute themselves down the tunnel, smallest sizes settling out furthest from the inlet-

Have you tried your powder at any stage of milling in any star formulations, most particularly in a nitrate based glitter star?

[Charles Owlen Picket]

I know just what your talking about there! I do something very similar: clumps will make my slide tool useless. I have become very fond of using a microscope and I am hoping to locate a low cost digital camera for use on a microscope, precisely for discussions like these and my own little notes & so forth.

I have not yet tested in a "formal" composition. All I did was try a wee bit in a few "lady-finger" flash crackers made as super small as I could wind (to test reactivity). When I do, there are two stars I really want to try as that will seal the deal for performance. A slow burn and tail and a "puff" type bright star.
I am finishing the last of some magnesium, which has been provided free via floor sweepings.
For a total of just over two weeks of milling I have close to five pounds of both materials. I can only underline that the results were much better than expected. I thought I would get something that was usable.....what I got - was really worth continuing!

Some time back I bought some metal powders that were actually gov't surplus directly from a dealer. I got some really unique stuff (nickel, tin, manganese, molybdenum, copper, tungsten, zirconium, and silicon). I only wish that this would work with other metals to the degree it does with Al & Mg.

[tmp]

Charles, great to hear that everything is working out for you ! Just curious -
have you made any flash using the Mg powder ? Talk about reactive ! :eek:
The flash I've made with Mg powder is more reactive and certainly more
blinding than powdered Al.

[Bert]

Commercial Mg powders have yielded perchlorate flash with a "critical mass" equivalent to an amount that would fit in a .22 LR case in my experience. Other people I have known who attempted to mill their own Mg and 50:50 Mg/Al have accidentally reached a pyrophoric grade, which they realized when the jars were opened and dumped out- Making one's own metal powders has its own special dangers, as well as rewards. Opening the Al at least daily to let the fresh surfaces oxidize is a good idea. Opening Mg and Mg/Al mill jars away from your house or other flammables when reaching fine powder stages is also a good idea.

[Charles Owlen Picket]

Indeed if the above point had not been broached I would have done so & I also would like to underline it as it may be the most important thing about this issue. In the various Journal articles, they speak of opening the container with some regularity for various reasons, not the least of which is safety.

Mg is seriously more reactive. There was a time when I had a great interest in flash-type compositions from burst-report-visual effects. When I was experimenting I kept the amounts seriously small. I always felt that experimenting on a very small scale reviles a lot while saving me from learning new typing skills.

Depending on where one lives static may or may not be a serious issue. If it is, you may not know it until it reveilles itself. This is actually WHY there are almost hysterical warnings and commentary about some materials that others have felt to be "tame". From a personal perspective, I am very conservative about how I go about experimenting... With that said, I have worked with visual oriented flash comps that utilized Mg and the results were stunning (no pun intended). From a report perspective I can't comment as I don't have access to a sound meter or even a quasi professional bit of equipment to answer that. but it's loud enough to make an impression that care sound be used with it.... :-]

[JouMasep]

Charles Owlen Picket,
It goes without saying that this is outstanding work and very well presented.

Conceptually what I want is always a single micron size (2-9um) flake Al

A few observations:

-Most metals, including Al will work-harden on mechanical stresses; this process continues till it will “go no further” at which stage it will be very hard and also brittle indeed. (Aluminium -when alloyed with other metals- in particular will also undergo a process of age hardening; but as aluminium needs to be quite pure in order to be milled to foil, this should be less of a factor in the process at hand)
-Hence when very much work hardened, particles can be fractured into smaller particles, but will resist flattening into flakes.
-Statistically some particles will be repeatedly fragmented sooner before they are much work hardened than others, thus allowing for a relatively easier flattening into flakes; conversely others will get hard quite soon, thus allowing more for further fracturing into non-flat particles, but not into flakes.
-Aluminium, like most other metals will undergo annealing when subjected to a specific temperature, fur a specific duration; for Al this temperature lies between 300 to 400 degrees and takes from less than one hour to several hours –depending on the article's size and type of alloying metals.
-Some metals need to be brought to their annealing temperature and then cooled down at a certain minimal rate of speed –this is not the case for aluminium (or copper) it can be virtually quenched in water and still be “annealed”. This is different as for e.g. carbon steels as there one deals with the solution –and dissolution- of carbon and an carbon/iron compounds (cementite) into the metal itself. -The case with plain un-alloyed aluminium is less complicated in this regard as now we only deal with (re-) crystallisation and grain formation within the metal.

-We do have another phenomenon to consider in order to fully explain what may happen; this is called “recovery annealing”. Recovery occurs below well below the annealing temperature and also works against work hardening. It can be either “Static Recovery”-, and occurs at higher temperatures (seems to overlap “plain annealing” then), or it can be Dynamic Recovery. (I presume this happens at lower temperatures). In the latter case the grain and crystallization originally created by the work hardening, is now modified and reduced by the relief thereof, as induced by the internal flow that results from the moving of the material at elevated temperatures.

The latter explanation seems almost self-contradictory, but it occurs to me that this is what also could take place. This concept is new to me, and frankly I have no idea at which temperatures this process will commence in the case of foiled Aluminium compositions.

I am convinced that annealing will strongly aid in the procurement of very fine, very flaked product.

A few recommendations:

-To interrupt the milling process intermittently at the final stages and to then subject the product for at least one hour to a temperature between 300 and 400 degrees Celsius. After this the milling is continued. The annealing and cooling down should happen under an inert atmosphere. A control batch is milled as normally –sans annealing. Comparisons should indicate the optimal stage(s) at which the annealing should be done in future.

-To construct a ball mill that is heated to –say- temperatures between 150 and 225 degrees in the final stages of milling. Comparisons with the unheated process should indicate any advantages and optimal times and temperatures. It will have to be established if more frequent intermittent exposure to air is sufficiently safe practice in order to prevent sudden combustion. Alternatively a weak stream of pressurised air could be introduced. CO2 would be nice of course, but then the handling hazard is postponed to the end of the milling.

[Bert]

I believe hot Al without oxide coating would be able to reduce CO2. Mg certainly can-

[JouMasep]

Hmm, to be frank I felt like you, when I wrote it. It went against my instincts.
Argon gas is what I have standing here in a bottle: a far more obvious choice then!

So you are quite right, I made an error by trying to be too clever.

Thanks.

In my defense, when I wrote "inert atmosphere" I thought of N2 or Ar, by no means do I considder CO2 "inert"

[Charles Owlen Picket]

Thank you, frankly I am going to do another "run" pretty soon here. I have a whole list of things I am going to try and document. I really want to do my runs with larger amounts so that it really pays off. - I am thinking of running up a much larger, more professional ball mill that will hold well over 5lbs. - I also believe that differing volumetric levels may have an effect on the product...

What I want to do is set up a microscope and camera to document (in a little PDF) all the nuances for people to see 1st hand.

[Lewis]

I recently started an Al ball milling project out in the shop.

My mill is homebuilt, and quite large. It has a wooden frame, and is powered by an AC motor I picked up for next to nothing at a scrap yard. (I think it's a dryer motor) I used the first thing I could find for a drum, which happened to be one of those big plastic weight lifting supplement containers, maybe 6-7" diameter. Media is 150 .50 caliber lead balls.

For my first trial run, I'm milling a very small amount of foil Al, about 100g. After running for a day and a night, the ball mill had turned the blended foil balls into thin, large flakes a couple millimeters long. The flakes were extremely smooth, and bright silver. I then ran them through a coffee grinder again, at which point they turned into dark, granular material.

On a side note, there is a little charcoal in this batch, as that's what the media was last used for. I figured a light dusting of carbon on the lead balls wouldn't affect much.

Pictures to come in the future.

Note: I should also add that I've got the drum spinning at about 120 rpm. Not sure if this is too fast, but the belt ratio was sort of non-negotiable.

[Charles Owlen Picket]

I used .50 cal lead balls. They were fine. Just remember that the volume of the container vs. the amount of material to be milled (in ratio & proportion) has a great impact on time, level of milling, & overall effectiveness. There seems to be an "optimum" for each container; that will preform best in terms of both speed & effectiveness.

On occasion you may have to run the mill longer than other times you've used it due to volume issues. The thing I noticed about lead media is that it needs to run for some time to get hardened itself. Therein lies an issue.

[Lewis]

Indeed, it seems the process is speeding up now. I wasn't sure if it was due to the fact that the lead balls have a very hard coating of aluminum on them that cannot be scraped off. They look like they're made of aluminum through and through.

Will the tendency for aluminum to be fused to the media be a problem? I could see some sort of "snowballing" effect happening, where all the finest powder just forms around the media, similar to how stars are made.

[Charles Owlen Picket]

Only my opinion based on much different proportions than you are dealings with, but...no, it shouldn't. They should shake off after a time. But then you may want to deal with [as long as] 7 days of milling (that's why I always try to go as large as possible in my amounts: so that there is a larger reward for the time expended).

[Bert]

Note: I should also add that I've got the drum spinning at about 120 rpm. Not sure if this is too fast, but the belt ratio was sort of non-negotiable.

If you change the drive pulley size you will have a different ratio and hence a different final RPM. Pulleys in many sizes are available for wood working machinery and such, why can't you vary the speed this way?

[Lewis]

It's not like I can't change the hardware for a slower ratio, but the thing was built out of materials at hand. Is it too fast to be efficient?

[Bert]

As long as the media rolls over the charge rather than being centrifuged out to the walls, the speed is not too high. The Lloyd Sponenburgh book gives a formula for computing the optimum RPM vs. jar diameter. There's a link to it somewhere on this site, haven't found it yet.

[Charles Owlen Picket]

I'm not sure of the spelling of Lloyd's last name (Spoonburgh?) but if you Google a close one & "Ball Mill" you'll come up with his stuff from rec.pyrotechnics also. Those issues had been discussed quite in depth. And damn cheap pulleys, etc can be gotten from swamp coolers at the hardware store local to you.

The idea of getting the bucket down slow is to use gravity as well as the rotational shift to crush to the limit of the thing's ability. But just as you can go too fast, you could (in theory) go too slow so the material isn't climbing the walls.

[Bert]

Too slow is merely... Too slow. It just makes the process take longer than it needs to. Too fast stops it from grinding at all.

If the charge isn't climbing the walls and allowing the media to roll back over the slopeing pile of charge, you need lifter bars on the inside of the drum. When I made PVC drums I needed to do that, at least untill the inside of the drums got scratched up. Rubber lined drums have not had that problem, neither did hexagonal or octagonal drums.

[Yafmot]

Right now, at the time of this post, Harbor Freight Tools has a 1 1/4 cubic ft. cement mixer for $99 (regular $139). You could make one hell of a mill out of that. If you wanted to coat the drum's interior with some sort of polymeric material, spray-on truck bed liner is a good bet. Hell, one of those Bhino Liner shops would probably do it for free, since they throw away that much just cleaning out the equipment at the end of the day. You'd probably want to do some sort of surface preparation first. I'm thinking maybe sandblasting the paint out, then a treatment in an epoxy/chromate based primer/bonding agent, and then shoot the liner on.

The stuff is urethane based, and it's just tough as a two dollar steak. If you try to cut it with a knife, it tends to sort of displace, rather than shear, so chunking or fragmenting shouldn't be a problem.

There's another product that's rather more DIY oriented. I've forgotten who makes it (somebody big), but it's called "Herculon." It's primarily for lining truck beds, and it can be applied with a brush, or thinned and shot from an air gun or even an airless rig. I know some midwesterners who swear by it for undercoating their vehicles. (If you've been there, you may have noticed 4 and 5 year old cars with rust holes big enough to stick your head through, due to the salt they scatter on the roads.) A quart can should be enough for several cement mixers.

Obviously, you'd need to cover the opening with something, and a music store may be the place to look. A drum head with a marmon band would probably do it. Or, for that matter, maybe just a sheet of rubber and a large hose clamp, similar to what they use for flexible, temporary ductwork. Lots of options here.

Cleaning would be fairly straightforward. Just toss in a bucket of BBs, a squirt of detergent, some hot water, and run it for a while (how long would depend on what you've got caked in there). A follow up with a pressure washer would be a good idea. When you're processing on this scale, cross contamination is out of the question; there are no "little" mistakes. Since these things have some fairly substantial lifter bars, consisting of secondary weldments, the urethane coating is pretty much a matter of course, keeping the product from collecting in little gaps and spaces.

Media? Economies of scale, in this case, favor ceramic. Theres enough room in there that you can use large diameter ceramic balls such as those supplied by Coors Tek. A lot of people don't know this, but the brewing company also owns what is probably the world's largest technical ceramics supplier. Labware, armor, catalyst supports, you name it. What their grinding media lacks in weight, it makes up for in hardness. I use 5/8 in. in my 2x3 lb. tumbler, but I have to add about 30% brass or steel balls along with it, just to add enough mass to the impact and grinding action. On a big scale, you can use much bigger spheres (1 1/2 to 2") to increase the forces, and toss in some 1/2 to 5/8 stuff to fit in between, increasing the surface area at work and still having enough interstitial volume for lots of product.

When I upgrade from my little $35, rubber-drummed tumbler, this is the direction I plan to go.

[Alexires]

After a little searching, I believe I found that equation that everyone seems to be looking for. Not too sure if it is the right one, but it seems to give reasonable results.

The critical speed (the speed at which the centripetal acceleration overcomes gravity, hence your media just sticks to the inside wall) is equal to 42/sqrt(diameter in metres).

Hence, for a 6-7" container the critical speed is about 100RPM.

Basically, that means at 120RPM, your media is sticking to the inside walls of the container like a centrifuge. You need to drop it back a little if you can, by about 45-30RPM (to about 75-90% of the critical).

This is assuming that the equation is correct.

Edit: I just double checked it using conventional physics, and 100RPM seems correct for the critical speed.

[Lewis]

I wish physics were as simple as that. My media very obviously isn't being centrifuged to the walls, as the whole drum sits on rollers, pressed by its own weight. If that weight was all on one side, spinning that quickly, the thing would not make contact with the rollers on account of it being thrown around, no contact with rollers = slowing down. You get the idea.

The drum does not slip on the rollers, and furthermore I can hear the media rolling and bumping on the bottom. There are way too many factors to determine the best speed. I'm putting those pictures up just as soon as humanely possible. Probably tomorrow.

[justme]

Here is the link to the book on ball mills again.

http://rapidshare.com/files/107703431/ballmill.pdf.html

[megalomania]

I would think the mass and surface area of the media would play a role in determining the max RPM. For example, a light dusting of material may stick to the walls of the container at 100 RPM, but a larger quantity of material piled on top of itself would effectively make the container smaller, and thus it would experience less force. The balls being round have the majority of their mass in the center, some distance from the wall of the container, which only has a small portion of the sphere touching it. The spheres are also spinning downwards which makes them still able to grind.

I suppose experimentation is in order. Measure out the same quantity of material and do several trial runs at different speeds, but identical times. You should be able to judge for yourself what speed is best based on the quality of your powder. Just keep notes about each of your millings and you should make some effective observations.

Every ball mill will likely have its own optimum speed, add to this the quantity of material, the balls used, etc. and an equation will only give you a ball park figure.

[Lewis]

In case anyone was holding their breath, well, you're probably dead by now.

For everyone else, here's the pictures, as promised.


Prepping the foil
http://i282.photobucket.com/albums/kk278/orbital_Saucer/DSCN1154.jpg?t=1208405543




The Mill
http://i282.photobucket.com/albums/kk278/orbital_Saucer/DSCN1150.jpg?t=1208405610
http://i282.photobucket.com/albums/kk278/orbital_Saucer/DSCN1152.jpg?t=1208405648



The Product
http://i282.photobucket.com/albums/kk278/orbital_Saucer/DSCN1147.jpg?t=1208405695



Phenomenon involving the lead media forming strange tumor like protrusions:
http://i282.photobucket.com/albums/kk278/orbital_Saucer/DSCN1157.jpg?t=1208405746

I apologize for the apparent hugeness, but this was the smallest my camera would take the photos!

[Charles Owlen Picket]

Nice mill Lewis: perhaps one of the more professional I've seen! Product looks sweet and pure like a virgin bride. Well done!

[Bacon46]

Agreed; Excellent results and damn nice ball mill. What did you use for the ball mill drum? I can’t tell by looking at the images

[Alexires]

Lewis and Mega - Fair point. Consider this. As there is effectively a force pushing outwards at 90º to the container, this would push the balls into the sides of the container. If the balls were sitting on top of one another, they would be pushing down on the balls at the bottom, hence would spread themselves evenly (assuming there is just enough balls to cover to container).

I didn't say that I was right, only that conventional physics agrees with the equation given.

You do seem to be getting a fine product, on a fantastic looking ball mill. All I'm suggesting is that perhaps 120RPM is a little fast and that you would benefit from trying to reduce the RPM to about 90 to maximise effectiveness. Then again, if it ain't broke, don't fix it.

How long did you run it for to get that product?

[Killy]

Just one advice, use photoshop or similar program to resize pictures.

[Lewis]

It took 3 or four days to get to the last stage. Probably closer to three days of continuous run time.

Next on my agenda is probably finding a cheaper source than foil. The best way would be finding an aluminum-only metalworking place, and ask for floor sweepings. Perhaps recycling centers would offer shredded cans with the paint/plastic burned off?

Only inquiry will tell.