Sciencemadness Discussion Board - Powdering aluminum - any "tricks" like quenching in liquid N2 or flash freezing?

Powdering aluminum - any "tricks" like quenching in liquid N2 or flash freezing?

RogueRose - 24-7-2016 at 18:52

I put some Al slices (about .5" x .5") from a soda can (the side, not thicker bottom or top) into a blender and it did nothing. It wouldn't chop anything up as it just twisted the pieces. The batch was run until the motor got so hot I was afraid it would burn up, so a good try was made.

I was wondering if there are any ways to make Al more brittle or other ways to make Al powder (not using a grinder) & a ball mill is available but I don't think starting with that will work.

I was thinking that dropping the temp may work by doing the dry ice & alcohol or liquid N2 if available - then putting in the blender. Another idea is get it really hot and then put in the sub zero liquid(s). I know that this works for iron/steel to weaken it but I've heard Al is much different and is very cold resistant (her is an article some might find interesting - http://www.totalmateria.com/Article23.htm

When dissolving in acids, which acids leave a pure Al powder vs leaving a salt?

careysub - 24-7-2016 at 21:10

Quote: Originally posted by RogueRose

I put some Al slices (about .5" x .5") from a soda can (the side, not thicker bottom or top) into a blender and it did nothing. It wouldn't chop anything up as it just twisted the pieces. The batch was run until the motor got so hot I was afraid it would burn up, so a good try was made.

I was wondering if there are any ways to make Al more brittle or other ways to make Al powder (not using a grinder) & a ball mill is available but I don't think starting with that will work.

I was thinking that dropping the temp may work by doing the dry ice & alcohol or liquid N2 if available - then putting in the blender. Another idea is get it really hot and then put in the sub zero liquid(s). I know that this works for iron/steel to weaken it but I've heard Al is much different and is very cold resistant (her is an article some might find interesting - http://www.totalmateria.com/Article23.htm

When dissolving in acids, which acids leave a pure Al powder vs leaving a salt?

Here is an informative video about converting scrap aluminum to powder.

It involves some pretty scary shredders, high temperature processing and a ball mill.

Commercially very fine aluminum powders (atomized) are made by melting the aluminum and spraying it in a vacuum (gas is dissolved in the aluminum melt) or into an argon or other inert gas jet.

Aluminum flake can be produced by ball milling foil scraps.

Here is a survey metal powder forming:
http://www.energy.ca.gov/process/pubs/sic33991.pdf

No acid can dissolve metallic aluminum without turning it into a compound.

[Edited on 25-7-2016 by careysub]

elementcollector1 - 24-7-2016 at 21:33

Coffee grinders are much better in my opinion. Use foil, preferably not Reynolds-brand, and ball mill as desired.

PHILOU Zrealone - 25-7-2016 at 03:42

Sand paper or sander Wheel does wonders then coffee grinding.

For ultrafine Al powder...electric blast of Al wire into inert atmosphere, then cooling and slow introduction of cold air into the reactor to get the minimum thickness oxyd layer (and more reactive Al per weight...usually when lowering the particle size, the oxyde layer "dead weight" becomes significative vs the active metal)...at a certain particle size, because the oxyd layer remains inevitable constant (owing to Al reactivity), the native metal may become inferior to the amount of oxyde (*) and in certain cases may even dissapear --> only Al2O3 and no more Al! (**)

(*) This happens when particle size < 4*oxyd layer thickness.
(**) This happens when particle size < 2*oxyd layer thickness.

[Edited on 25-7-2016 by PHILOU Zrealone]

ficolas - 25-7-2016 at 04:42

This may be stupid but, when galium amalgamates with aluminium, it maked it brittle, would letting galium amalgamate with aluminium and then using something to crush/ball mill or whatever make it easier to get galium contamined aluminium powder?
However you woulf probably want to recover the galium, wich woulf make this (if it even works) not really useful

Praxichys - 25-7-2016 at 05:20

Taking an orbital sander to a wet block of aluminum yields powder that I have found suitable for flash compositions. Use a coarse sandpaper or it will clog. For chemistry, it is far from ideal since a lot of sandpaper grit ends up in it. For chem purposes, I have found dollar-store foil to be suitable.

Cans are a bad choice because they are laquer coated on the inside and inked on the outside. The alloy used is typically in the 3xxx series so is almost 5% magnesium and 2% manganese. Aluminum foil is typically Alloy 8011 which is 97-99% aluminum with the substantial remainder being iron and silicon.

Aluminum is very reactive so there aren't any practical reactions that precipitate aluminum. Usually aluminum is used to reduce other metals from their solutions.

wg48 - 25-7-2016 at 05:22

Quote: Originally posted by RogueRose

I tried a blender with approximately similar sized scrap aluminium (heat sink fins of a MO magnetron) with some graphite powder to stop the aluminum from cold welding together as recommended for ball milling (this may be an important trick).

Initial it was very noisy with the larger pieces making dents in the aluminum cover. After about half an hour of intermittent shredding it reduced the Al to half powder (by volume) and half balls of twisted Al with a range of diameters of a few millimeters. The limitation was the attrition of the plastic housing and the temperature raise.

There was a significant fraction of the powder that was so fine it floated on air currents when the cover was removed for inspection. I intend to try again with the housing replaced with a stainless steel one and the blades welded to their shaft as they are no loose. There are protruding baffles on the housing and judging from their wear they may significantly contribute to the shredding by bouncing the Al back in to the blades. I will add some to the new housing

I also need to research the safety issues ie can the powder ignite, should it be done remotely in a hole in the ground.

RogueRose - 25-7-2016 at 19:17

Has anyone ever experienced strong static discharge while grinding the Al in a coffee grinder? I would suspect that there would be a buildup of some static charge similar to a capacitor (can be felt through the grinder lid) since the aluminum electrolytic use foil. The grinder doesn't have a grounding pin which I would suspect would take care of this problem.

Bert - 25-7-2016 at 19:43

Quote: Originally posted by ficolas

This may be stupid but, when galium amalgamates with aluminium, it maked it brittle, would letting galium amalgamate with aluminium and then using something to crush/ball mill or whatever make it easier to get galium contamined aluminium powder?
However you woulf probably want to recover the galium, wich woulf make this (if it even works) not really useful

A 50:50 by weight alloy of Mg and Al is about as brittle as ice, cracks easily with a hammer, ball mills quickly compared to pure Al- And you had best be careful about opening the mill jar and leting the extremely fine and unoxidized powder contact atmospheric O2 if you let the ball mill run too long.

symboom - 6-4-2017 at 15:20

brittle aluminum copper alloy could melting aluminum with copper which makes a brittle alloy then dissolving away the copper from the aluminum copper alloy with nitric acid form aluminum powder? Although aluminum forms a passivating layer that protects the aluminum metal underneath ah nevermind then aluminum reacts with copper nitrate forming alluminum nitrate

Maybe zinc aluminum alloy because zinc nitrate cant be reduced by zinc

PHILOU Zrealone - 6-4-2017 at 15:38

Quote: Originally posted by symboom

brittle aluminum copper alloy could melting aluminum with copper which makes a brittle alloy then dissolving away the copper from the aluminum copper alloy with nitric acid form aluminum powder? Although aluminum forms a passivating layer that protects the aluminum metal underneath ah nevermind then aluminum reacts with copper nitrate forming alluminum nitrate

Maybe zinc aluminum alloy because zinc nitrate cant be reduced by zinc

Just like for the copper case since Cu is more oxydant than Al (or Al more reductor than Cu)
Then invariably:
Cu(2+) + Al(s) --> Cu(s) + Al(3+)

Same applies to Zn...
the redox potential tables give the order Cu> Zn > Al
So here also battery in shortcut...
Zn(2+) + Al(s) --> Zn(s) + Al(3+)

Beating Electrochemistry will be though

phlogiston - 7-4-2017 at 00:23

An alloy with magnesium known as "magnalium"" would probably be preferable since the properties of magnesium are not dissimilar to those of aluminium.

A 50:50 Mg:Al alloy is very brittle and can be crushed into a powder with a simple hammer. I don't know what purpose you have in mind for the Al powder, but you could try if MgAl works as a substitute.

symboom - 27-4-2017 at 00:06

I think I might have figured out a trick to make it brittle enough to make powdered aluminum the answer dry ice and molten aluminum the co2 forming bubbes in the molten aluminum along with the sudden temperature change.

Praxichys - 27-4-2017 at 04:22

Be careful with that method. Both magnesium and aluminum can burn in CO2. Intimately mixed dry ice and aluminum powder with molten aluminum poured in sounds like a recipe for explosion.

curiosity_cat - 27-7-2017 at 19:24

Grinding wheel in an environment of inert gas I guess argon helium ect.

Powerful motor to spin your grind wheel and springs or some method to press your aluminum against that a grinding wheel.

I remember the grist mill corn grinding museum by the lake up and running water had about a 10 foot drop belts and gears whole building shook must have produced 100's of horsepower.

physics inclination - 27-7-2017 at 20:52

I like curiosity_cat's idea of a grist-mill-like thing, I've thought about something like that for grinding aluminum too instead of a ball mill. Specifically, maybe the wheels could be two plates of stainless steel, parallel to the ground, and have one be stationary while the other rotates, and the top plate have a hole in the middle to feed in aluminum flakes/chunks. I think, maybe if you scratched a pattern of lines into one or both plates, then perhaps the rotation itself would both push the particles centrifugally outwards and grind them at the same time.
Stainless steel grinding worked for Dornier335 to make really fine aluminum powder as shown below, so maybe making a grinding mill machine to automate his process could work.
https://www.youtube.com/watch?v=JeMeRhgKFsk

PHILOU Zrealone - 28-7-2017 at 09:35

The only drawback I see with grinding way of production is the contamination from the balls, the walls of the ball mill or the plate and pestle you use (into Dornier335 the iron/steel).
Because the Al oxydizes to Al2O3 what is hard like corundum/saphire (harness 9 on Morh's scale); so just below diamond...any metal will be eroded/abrased by Al oxides...at least partially and "pollute" the Al with exogen metal oxides.

Exploding wire has nothing but the original Aluminium.

Sonication into an inert solvent must also be interesting way to get relatively pure nano-Al.

[Edited on 28-7-2017 by PHILOU Zrealone]

curiosity_cat - 28-7-2017 at 21:35

Quote: Originally posted by RogueRose

It wouldn't chop anything up as it just twisted the pieces. The batch was run until the motor got so hot I was afraid it would burn up, so a good try was made.

I did the blender meltdown trying to make Al powder too. Got so hot the top warped and lost its seal so much of the fine stuff escaped. $3 yard sale blender let it run.

It made Al dust from torn up strips of aluminum foil but it was time consuming tearing the foil into bits to feed into the blender so my next thought was a paper shredder should be able to make little bits of a restaurant supply store size roll in no time unless it jams up for some reason cause foil and paper have different ways about them.

The sifting out of the fine stuff should be easy enough.

I have never seen the thermite reaction in real life https://www.youtube.com/watch?v=a8XSmSdvEK4

The lava flows on you-tube and TV science shows were one thing in real life in Hawaii completely different .

[Edited on 29-7-2017 by curiosity_cat]

PHILOU Zrealone - 29-7-2017 at 00:52

Quote: Originally posted by curiosity_cat

Quote: Originally posted by RogueRose

It wouldn't chop anything up as it just twisted the pieces. The batch was run until the motor got so hot I was afraid it would burn up, so a good try was made.

Electric Coffee grinder and aluminium foils cutted with scisors end up into tiny wrapped foil balls....the grinding takes ages...and the yield is low.

Would be better to use SiC sand or or emeri sand (corundum/Al2O3) into a Al tumble with the Al foil shredds.

Also a big Al foil ball pressed against a spinning abrasion disc should deliver quite fast a good quantity of finer material to start with.

The document paper shredder will work but the blades will very soon be less efficient...just like scisors because of the Al2O3 oxid layer that abrases all cutting metals...

Dornier's method with a hard plate and an hard ruler may be good if it is made out of Aluminium so no pollution from external metals and only Al and Al2O3 will be present.

symboom - 13-8-2017 at 04:54

Heating aluminum on an exposed flame causes it to crumble due to oxidation :-(
An idea would be to mix molten aluminum with graphite powder may cause porosity in the aluminum and make it brittle

[Edited on 13-8-2017 by symboom]