Pyropow3r Posted April 22, 2011 Posted April 22, 2011 Here is what i have done loaded my ball mill with steel media and shredded aluminium foil milled it for 4 days opening every 12 hours to build up an oxide protective coating on the aluminium.....After 3 days of milling i had a grey powder.... 4th day was dark grey when left exposed to oxygen it went up in flames!!! my milling jar was destroyed. It appears the aluminium underwent rapid oxidation with the vast surface area that came with dark al resulting in excessive heat and then combustion.... After researching some more.... i found out i should of added steratic acid to the mill jar contents and dont open the mill jar at all then open when the milling process is complete ... and extract the dark al as if it were a store brought product UNREACTIVE WITH AIR... correct ? So here is what i need to do now do a mill run with steratic acid and i shouldnt incurr any problems? If so what about the potential of an air fuel explosion with the milling jar becasue steel media can spark ...my theory is this shouldnt happen because some of the aluminium will turn into oxide thus there will be no oxygen in the milling jar meaning a fuel air explosion cant happen because no oxygen is this correct as well im still not sure ???
dan999ification Posted April 22, 2011 Posted April 22, 2011 ive heard that the jar should be opened more frequently to oxidize it in stages and avoid over oxidation not sure about the stearic acid part though. never done it ive always been put off by examples of your experience.dan
superstring Posted April 22, 2011 Posted April 22, 2011 (edited) Sounds like your Al went pyrophoric Edited April 22, 2011 by superstring
Ralph Posted April 22, 2011 Posted April 22, 2011 steric acid will help also as was said by dan you should open it more frequently as well be careful this could end very badly when you mix it with something and you have a bunch of flash go off in your face
Pyropow3r Posted April 22, 2011 Author Posted April 22, 2011 Overall my primary consern is the possibility of a fuel air explosion due to super fine aluminium in the jar in the air and steel milling media.... but is a fuel air explosion in the confines of a milling jar even possible ? say if there was a spark from milling media would or could the milling jar possibly explode?
dagabu Posted April 22, 2011 Posted April 22, 2011 A fuel-air explosion is actually very difficult to make and liquids are definitely better then solids. Don't confuse a metal dust explosion with flash either, they are very different in nature and power. Stearin is your only hope to grinding and coating the aluminum but just so we understand each other, dark Al is not milled or stamped, dark Al is made by a specific process, you are just making aluminum powder, the color is inconsequential.
dan999ification Posted April 22, 2011 Posted April 22, 2011 Overall my primary consern is the possibility of a fuel air explosion due to super fine aluminium in the jar in the air and steel milling media.... but is a fuel air explosion in the confines of a milling jar even possible ? say if there was a spark from milling media would or could the milling jar possibly explode? change your media.as far as an explosion i dont know, from how i see it if the air fuel ratio isn't correct it can't explode [you may be able to achieve it with atmospheric air pressure]but if it caught light the smoke/gasses building up would probably open the jar at very least its all dependant on how fast it burns and if confined in the jar and turning its probably going to burn fast given the particle size and the fact that its available in the air above the media it could well support fast combustion.this is what put me off .dan
MadMax Posted April 22, 2011 Posted April 22, 2011 Dan has a point on the media. I would seriously look into Alumina media. No harm in contaminating Al with it's own oxide. Also, I'd be opening that thing every 3 hours or so - give it a few minutes to settle and if possible let just some air in at a time. I wouldn't completely flood it with fresh air. Stearic acid will probably help. Another possibility - if you intend to make a lot of Al with this milling canister then it might be of value to drill a couple of 1/32 inch holes at each end to let in just a little air at a time. Experts please give your opinion on this. This is not something that I know of that's used in practice so it may not be safe - but technically neither is attempting to ball mill aluminum for that matter.
oldguy Posted April 22, 2011 Posted April 22, 2011 (edited) NO EXPERT HERE, as a matter of fact a beginner of sorts.If you have a commercial grade blender? You can buy the thin cheap Al foil rolls from the dollar store. Cut it into thin confetti strips. Fill the blender ½ full of water. Add +/- an ounce of Al confetti at a time & pulse blend it down to around 50 or 60 mesh. Then strain off the water through a paper coffee filter & air dry it. This is hard on blenders, so you need a commercial grade one. Otherwise the motor will get hot & burn out. I made about a pound of Al this way. I then milled it down further, using steric acid & Zirconia M ceramic media. I opened the mill about every 30 or 45 minutes, for a minute or 2. Not sure how fine I got it down to, as I don't have screens beyond 100 mesh. But, I got it down so it would shake right through my smallest screen. This Al was not near as good or reactive as 325 mesh Al powder I bought. It is nowhere near dark pyro Al. I would not take the time or trouble & PITA to do it again. It is not cost effective. Edited April 22, 2011 by oldguy
NightHawkInLight Posted April 22, 2011 Posted April 22, 2011 There's no problem using steel media, so long as it's not rusty (possible thermite reaction). You also do not have significant risk of a fuel/air explosion while in the mill. By the time the aluminum is fine enough to create such an explosion all the oxygen in the mill will have been consumed. By the time you opened your lid and it ignited on you there was effectively 0% oxygen remaining in the barrel. To prevent that, as others have said open your barrel more frequently. There is a slim chance for ignition between when you open your mill to allow in more oxygen and the point where the O2 has been consumed and brought down to concentrations not capable of sustaining a fuel/air reaction. Overall it's very little to worry about, and the slim chance of ignition in the barrel is only for short periods when the Al is nearly in the finest form achievable. Milling in an area suited to safely mill BP is more than adequate to safely mill Al. The trouble comes when opening the lid if it has not been done frequently enough, as you have seen.
Pyropow3r Posted April 22, 2011 Author Posted April 22, 2011 when you get to the small partical sizes ive been makeing with aluminium like the 3 micron range building and oxide coating on the aluminium is not desirable becasue the al is so fine there will be more oxide than aluminium.... the finer the particale size the more oxide and the less aluminium..... so the main idea with the steratic acid or another animal fat or simmilar is to completey stop oxide build up thus leaveing pure aluminium which is most desireable. As far as i know commercial dark aluminium contains little oxide coating the steratic acid seems to completey inhibit oxidation the same like if you coated a piece of steel with oil to stop it rusting... Dagabu.... you mentioned dark al is not produced by ball milling during the 1950s Indian black head was produced by ball milling and still is the only real way to get super fine aluminium is ball milling there is no other way to produce dark flake aluminium other than ball milling.
Ralph Posted April 23, 2011 Posted April 23, 2011 Dagabu.... you mentioned dark al is not produced by ball milling during the 1950s Indian black head was produced by ball milling and still is the only real way to get super fine aluminium is ball milling there is no other way to produce dark flake aluminium other than ball milling. Hammer milling soon took over and is a much suppiroror method to ball milling and according to starmolecule hammer milling is becoming obsolete now too
dagabu Posted April 23, 2011 Posted April 23, 2011 when you get to the small partical sizes ive been makeing with aluminium like the 3 micron range building and oxide coating on the aluminium is not desirable becasue the al is so fine there will be more oxide than aluminium.... the finer the particale size the more oxide and the less aluminium..... so the main idea with the steratic acid or another animal fat or simmilar is to completey stop oxide build up thus leaveing pure aluminium which is most desireable. As far as i know commercial dark aluminium contains little oxide coating the steratic acid seems to completey inhibit oxidation the same like if you coated a piece of steel with oil to stop it rusting... Dagabu.... you mentioned dark al is not produced by ball milling during the 1950s Indian black head was produced by ball milling and still is the only real way to get super fine aluminium is ball milling there is no other way to produce dark flake aluminium other than ball milling. Sorry man, I only knew about hammer milling with stearin, I wasnt around in the 50's
Algenco Posted April 23, 2011 Posted April 23, 2011 Sorry man, I only knew about hammer milling with stearin, I wasnt around in the 50's youngster
Mumbles Posted April 23, 2011 Posted April 23, 2011 I think you're confusing hammer milling with stamp milling. Hammer milling would never work. It is only effective on friable particles, which metals are not. A hammer mill is like a lawnmower on steroids. If you think you can even approach 3 micron in a hobbyist sized mill, you're out of your mind. Best case scenario, you're getting a poor quality 30-60 micron flake. That is if you're REALLY good. Try a slow oxidation over a period of several hours. It will prevent flare ups and be lower risk. Commercial dark aluminum contains more aluminum oxide than it does stearic acid. There is a fairly sizable amount. I really suggest you look at some of the real literature on these methods, patents, etc. There is a lot of misinformation in this thread. I'm not going to bother correcting it all, because I don't think you need to be using any dark Al. It has marginally more than one use, and it's one you probably don't need to be investigating.
dagabu Posted April 23, 2011 Posted April 23, 2011 (edited) Sorry, that was careless, its stamp milling as you said, "is supposedly made by stamp milling foil to which a quantity of carbon black is added" per Mike Swisher. I was thinking about atomized aluminums and got all confuselated. Edited April 23, 2011 by dagabu
Pyropow3r Posted April 23, 2011 Author Posted April 23, 2011 Whats with all the talk about stamp milling and hammer milling..... In my setup i am useing a BALL MILL any info on stamp milling is useless. On A small scale setup ball milling is the only way to go to reach the sub micron range...The main issue is what to coat the aluminium with ? oxide would be least desireable in the sub micron range there is so much surface area which mean lots of oxide meaning there will be more oxide than aluminium that is what i think.....so for my next run i will add 5% parrafin wax to the ball mill run and observe what happens....
Mumbles Posted April 23, 2011 Posted April 23, 2011 Let me say this again. You will never, EVER, reach single micron or sub-micron flakes with a hobbyist sized ball mill, or the methods you are using. It's naive to think otherwise. As for the stamp milling, it was being discussed as it is one of the more efficient ways to make these products. Don't get so upset if the conversation diverges from what you want to hear.
Ralph Posted April 23, 2011 Posted April 23, 2011 Let me say this again. You will never, EVER, reach single micron or sub-micron flakes with a hobbyist sized ball mill, or the methods you are using. It's naive to think otherwise. As for the stamp milling, it was being discussed as it is one of the more efficient ways to make these products. Don't get so upset if the conversation diverges from what you want to hear. yeah my bad I meant stamp milling but couldnt think of the word (4am is no time to be browsing the forum)
Pyropow3r Posted April 24, 2011 Author Posted April 24, 2011 You guys seem to think i have the harbour freight 40 dollar special for my ball mill or something ???? I made my mill useing 4 pillow block bearings and a 1/2 hp motor its no toy... It turned the aluminium into a fine grey colured powder after just 3 days milling before it went pyrophoric You will see i will prove you wrong......
Algenco Posted April 24, 2011 Posted April 24, 2011 who are you proving wrong?It's time consuming, dangerous and not cost effective. You've proven all the above
Ralph Posted April 24, 2011 Posted April 24, 2011 You guys seem to think i have the harbour freight 40 dollar special for my ball mill or something ???? I made my mill useing 4 pillow block bearings and a 1/2 hp motor its no toy... It turned the aluminium into a fine grey colured powder after just 3 days milling before it went pyrophoric You will see i will prove you wrong...... I dont see why you think its safe to mix something thats borderline pyrophoric with an oxidiser oxidisers give up their oxygen easily something thats dying to get oxygen will just take it and well the equates to the salute your halfway through pasting taking off your hands or the shell your boosting permanently destroying your fingers because of your supper dangerous home made booster
dagabu Posted April 24, 2011 Posted April 24, 2011 ...your supper dangerous home made booster Ralph, could you flesh that though out a little more? -dag 1
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