29 replies to this topic

[Phoenix]

As I mentioned in another topic, I have successfully made Al powder in a ball mill. Here are the details of how it was made:

Ball Mill
- 4" I.D. jar (pvc pipe)
- 100-120 rpm operating speed (depending on weight, jar contents etc.)
- Flint Pebble grinding media (NOT for BP. I just use my flint media for single chems, and it lends itself very well to Al as it is very hard)

Materials
- The starting material is Al kitchen foil. This needs to be reduced to small pieces. This can be done by ripping it up by hand, but a much better and more effective way is to put crumpled balls (fist sized) into a blender.
- I always add 2% stearin to the aluminium to coat it with a less reactive layer, as there is a risk that the Al will become pyrophoric and ignite on contact with air. I have never experienced this, but have only made two small batches of Al.
- The addition of lifting bars in the mill would no doubt have reduce the milling time, but my mill got the job done without them.

Procedure
- The mill jar is loaded with media and then filled to the top with the shredded Al. The stearin is also added. The jar is sealed and left to run for about 10 minutes. After this time, the Al will have reduced in volume considerably, and the jar can be topped up again. This is repeated until you either run out of Al (as was the case with me) or you judge that your mill jar appears to have the right amount in (my 1 litre jar held about 50g. This was not 1/4 of its volume, but I think it would have taken a lot longer with much more)
- The mill is then allowed to run until you have achieved the grade of powder you want. of course, the longer it runs the finer the product will be. I ran mine for about 36 hours and the result was very fine silver powder.

Safety
- The addition of stearin should give the Al a protective coating. However, the mill should still be opened very cautiously. It is probably a good idea to briefly open it every few hours to admit fresh air and allow the Al to slowly develop and oxide coating. (If you're like me, you will want to open it regularly anyway to see how it's getting on)
- The Al powder has a habit of floating about if disturbed. Therefore when opening the mill, handling the powder and certainly when sieving it a dust mask should be worn. It has been suggested that aluminium could cause Alzheimer?s disease. I don't know if this theory is still valid, but even if not, inhaling fine metal particles is not good for you.
- Airborne Al dust can be an explosion hazard, like flour.

Notes

- The result was 50g of very fine powder that worked well in small hummers and stars, poorly in a 1/2" fountain (it seemed too fine - the sparks only went about 1m before burning out. An Fe fountain using the same construction shot sparks 2.5m) and I tried some nitrate based flash powder with it too (KNO3:50, Al:20 S:30). It was difficult to light, and burned about the same speed as meal powder, but much brighter.
- I made a previous batch in my old ball mill (slower, bigger, uglier, noisier, leaked) using lead media. This took days, was quite coarse and was horribly blackened by the lead. Don't bother trying this with lead media.
- Finally, the reason I did this was because I hadn't heard of Tiranti. I don't know how this powder compares to theirs, but now that I have seen their prices I suspect that making it isn't worth the trouble.

Edited by Phoenix, 03 January 2004 - 09:08 PM.

[Pyromaster2003]

Yes Tiranti's Al powder is quite fine at 250 mesh but is also only spherical. Maybe you could buy a tub of Tiranti's spherical Al then mill it for 12 hours or so to turn it into a much finer but maybe more importantly, flake Al powder?

Im sure using your method for making Al would be great for making what ever Al flitter mesh you want for fountains, waterfalls, stars...?

[Phoenix]

I want Al powder for spark effects really, and I find bright flashes just hurt my eyes. I am considering getting some metal powders from Tiranti. I have searched and found that people have said their 250 mesh Al is good in small fountains, so I'll probably get some and use if for fountains and stars and sparklers.

Is their iron powder suitable for spark effects, and if it is has anyone used it larger fountains (1/2" - 3/4") or only small devices. The only iron I have used has been a by-product of sawing or filing metal, and I have seen a lot of variation in brightness, ignitability and "branchiness" between different irons/steels. Is their alloy a good one? I seem to remember the website said it was around 325 mesh, although now it is only "fine powder". Skylighter stocks -325 mesh iron powder, and say it is good for stars and comets, but no mention of its suitability for fountains. Sorry if this question has already been answered, but I did search and found nothing definite (although I did find questions about the aluminium's suitability in flash powder).

Edited by Phoenix, 02 January 2004 - 05:19 PM.

[alany]

I've got some -100 mesh iron and it isn't really that good for fountians. It makes long lasting dull orange sparks, better than charcoal, but not as good as the Skylighter sparkler steel.

The sparkler steel is much larger, needle like filings with a lot of carbon giving fracturing sparks. I'd imagine -325 mesh iron would burn quite quickly leaving a fairly short effect. It might be just fine for stars, but in gerbs, nah.

Be sure to coat the iron if you intend to store the composition for more than a few hours. It will rapidly react with BP varient mixtures and ruin the batch. It is especially important when making stars. I made a batch of golden rain #2 once believing my iron was coated. It wasn't and it generated enough heat to start the composition steaming.

If you can afford it buy Titanium and Ferrotitanium, they are fantastic in gerbs, saxons, rockets, stars, etc. Pricy compared to Aluminium or Iron/Steel, but a little goes a long way and the white crackling sparks of spherical Titanium are something nothing else really gives.

Aluminium doesn't burn well in BP mixtures in my experence. With excess charcoal and large flakes you get the firefly effect, finer flake and spherical can burn well too, but you still get mostly orange in the flame. It has to hit the oxygen before it starts getting hot enough to burn blue-white. Barium Nitrate can help you there, it is often used to burn Aluminium silver rather than bright orange, but then you have a much more poisonous and expensive composition.

A little Antimony metal or the Trisulfide, or some Sodium Oxalate makes for a nice gerb effect too. Some Sodium Bicarbonate makes a good cheap glitter with any old Aluminium (drossy though, I've blown up several gerbs this way by nozzle slagging), so does table salt or a metal carbonate, like Strontium or Barium Carbonates, washing soda is too hygroscopic so I avoid it. Anyway, this has drifted into something better put in another thread.

[DrDerekDoctors]

I just picked up a packet of "sintered metal powder (aluminium)" from the local Fred Aldous (over-paid but convenient), and I understand sintered just refers to the process of making it by heating but without melting. D'you think this stuff will be alright (and if so, what for?).

It's appearance is of a light grey powder (which makes me a bit concerned considering that pyro aluminium seems to be referred to as "dark").

Edited by DrDerekDoctors, 03 January 2004 - 12:17 PM.

[alany]

It is probably spherical or granular. Should be OK in glitter.

Try some in a little nitrate flash, it will likely be very hard to ignite and burn slowly but very bright.

[BigG]

I was curious about posts in this forum. I managed to ball mill titanium with lead media and was curious that people had problems with aluminium. This weekend I took an atomized 200 mesh aluminium and try to pass it through a 400 mesh screen (which failed). Then I put about 50 grams in a lead media jar and run the ball mill for 4 hours – stopping every hour to open the jar for five minutes. By the end of the run, about 15% of the aluminium passed 400#.

It’s very important to note that grinding any metal is dangerous. If you wish to try it, work with small batches, wear thick gloves when opening the jar and direct the opening away from you as you take off the lid. Very fine aluminium can create an explosive cloud after ball milling and you don’t want this to have enough powder to send the lead balls toward you.

When milling aluminium you need to stop every hour or so, let the jar cool and open it for five minutes. It allow the aluminium to renew its protective film and become more stable.

[alany]

I find it very hard to believe lead media made any dint in Titanium. Titanium is hard, fantastically so. Just look at the base of my stinger tooling, it is full of little pits where some spilt spherical Titanium has migrated under it and been forced into the Aluminium by ramming.

I guess it could be brittle fracturing, especially if it was sponge or perhaps flake to start with.

When I tried ball milling spherical Al with lead all I got was sliver coloured lead that was very hard to clean. Honestly, it is probably the lead passing the 400 mesh!

[BigG]

I find it very hard to believe lead media made any dint in Titanium.  Titanium is hard, fantastically so.  Just look at the base of my stinger tooling, it is full of little pits where some spilt spherical Titanium has migrated under it and been forced into the Aluminium by ramming.

I guess it could be brittle fracturing, especially if it was sponge or perhaps flake to start with.

When I tried ball milling spherical Al with lead all I got was sliver coloured lead that was very hard to clean.  Honestly, it is probably the lead passing the 400 mesh!

Alany, I'm surprised by your post. Surely if I tell you I done so, it's not just me fantasizing?

The titanium I started with was scrap titanium, a wool material that comes off machines that process it. This is not a space alloy but the generally used Ti-Vn-Al alloy that contain a very high percent of TI (I think it's 96% but I can check). These springs of titanium could actually be broken by bending in your hands. They also left me with a few nasty cuts, but they are not impossible to mill down. After a good cleaning in acetone – and washing up, they were loaded into the jar. There is no doubt that the finished mill material was the titanium, simply because the wool was gone, completely, and replaces by the large quantity of dull silver dust of different mesh.

As for the aluminium. The answer is no. The material that pass the 400# was not the lead, but aluminium. How do I know? Well, I just heat it above a lab burner for a few minutes to get the cubical surface to 400c. At this temp lead melts, but aluminium not. There was not melting of the metal inside the cubical - hence it was aluminium.

The lead ball sdid become silver coloured. This aluminium adhere itself into any surface.

BigG

[alany]

I am just relating my experence of the extreme hardness of Titanium. If your lead balls broke up your turnings with little wear and contamination then I am amazed but will take your word for it.

For discussion's sake the Moh's hardness for Lead is 1.5, Antimony hardened Lead is about 2, Aluminium is about 3, T6-6063 Aluminium gets up to about 4.5, Iron is 4, Steel 4-7 depending on the alloy, mild steel is about 5 only tool steels and cast irons approach the higher numbers, Titanium is about 6.5 unless exceptionally pure where it approaches 6, aerospace Titanium (Ti/Al/V alloys) are about 7.

In BP terms, Sulfur and Potassium Nitrate are about 2, Charcoal varies greatly, graphite is 0.5, some charcoals get up 2.5. No BP ingredient is ductile to any appreciable degree so they break up quickly compared to most metals.

Steel or ceramic media is more common for milling metal powders. Using media softer than the material to be milled is just asking to wear it down. The only thing I can see lead had going for it is its density (ie smashing powder). It was likely scratched up to all hell before the rough stuff was reduced to a powder.

I've had absoutely no luck milling spherical Aluminium with lead. I've tried it, and let it run for hours and hours. All I got was silver media and basically no improvement. Steel ball bearings on the other hand seemed to make a bit of an impact, but it looked like it would take weeks to get flash capable Aluminium that way so I gave up.

[BigG]

I am just relating my experence of the extreme hardness of Titanium.  If your lead balls broke up your turnings with little wear and contamination then I am amazed but will take your word for it.

For discussion's sake the Moh's hardness for Lead is 1.5, Antimony hardened Lead is about 2, Aluminium is about 3, T6-6063 Aluminium gets up to about 4.5, Iron is 4, Steel 4-7 depending on the alloy, mild steel is about 5 only tool steels and cast irons approach the higher numbers, Titanium is about 6.5 unless exceptionally pure where it approaches 6, aerospace Titanium (Ti/Al/V alloys) are about 7.

In BP terms, Sulfur and Potassium Nitrate are about 2, Charcoal varies greatly, graphite is 0.5, some charcoals get up 2.5.  No BP ingredient is ductile to any appreciable degree so they break up quickly compared to most metals.

Steel or ceramic media is more common for milling metal powders.  Using media softer than the material to be milled is just asking to wear it down.  The only thing I can see lead had going for it is its density (ie smashing powder).  It was likely scratched up to all hell before the rough stuff was reduced to a powder. 

I've had absoutely no luck milling spherical Aluminium with lead.  I've tried it, and let it run for hours and hours.  All I got was silver media and basically no improvement.  Steel ball bearings on the other hand seemed to make a bit of an impact, but it looked like it would take weeks to get flash capable Aluminium that way so I gave up.

I guess we will have to leave it at that. Both of us don't have the facilities to make a research of it. I can just say I kept ball milling one titanium batch after the other for about a week or so, with no notible tear on the lead balls. The verity of flake received was very large and ranged from about 20 to 150.

[Matt]

Wouldnt milling spherical powder only make it wider?
Think about those new ball toys, you press them and they turn into a frisbee. I figure the same thing would be applicable to milling spherical powders.

Ive always thought to myself if i was to mill Al i would check to see if it "sparkles" when a pinch is dropped into air, spherical just makes a grey cloud however if anyone has seen flake they will know it "sparkles"

Just my 2 cents

[BigG]

No, Milling the aluminium actually grind bits and pieces of it as well as flatten it. In the industry, powder is made by milling, stamping or other methods, so we are not inventing the wheel here. The main conversation between alany and me is what materials need to be employed and whether it’s visible on home scale.

[Phoenix]

Matt said;

Wouldnt milling spherical powder only make it wider?

I think that it does at first, but as the metal gets thinner and wider it is also getting bent about as it is hit by the media. Eventually, due to metal fatigue and it becoming very thin it breaks into pieces.

Edited by Phoenix, 13 January 2004 - 07:11 PM.

[Rip Rap]

[QUOTE]- The addition of lifting bars in the mill would no doubt have reduce the milling time, but my mill got the job done without them.

Lifting bars really do make a difference when milling aluminium.
I have milled aluminium turnings (using a 7" diameter jar with steel ball bearings ranging in diameter from 0.25" to 1", at about 90 - 100 rpm).
Without the lifting bars, after a total of about 12 hours milling, only about 2 or 3 % of the powder passed a 100 mesh screen.
After installing the lifting bars & 12 hours milling (using a fresh batch of aluminium) that figure had gone up to about 10 %. Unfortunately, the noise level goes up considerably too.
The action of the steel balls dropping & pounding the aluminium is what is needed.