Chemgineer
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Aluminium powder creation
I read a Youtube comment that suggested using a food blender on aluminium foil and adding a cup of water to allow an efficient blend rather than
clumping you get when trying dry.
It seemed like a bad idea due to aluminium reaction with water and I think I have proven it so.
After 1 hour of blending, allowing to cool and then a second hour of blending what I have actually ended up with once cool and dry is a white powder
which I assume is aluminium oxide.
I can get good aluminium powder by gas torching the foil to make it brittle and then ball milling it for days but this is very slow.
Anyone got any faster ways to produce aluminium powder finely?
[Edited on 17-11-2025 by Chemgineer]
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fx-991ex
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i tryed this blender method but with mineral oil instead and it didnt make particle fines enough.
Using a sanding drum on a solid block of aluminium worked much better.
[Edited on 17-11-2025 by fx-991ex]
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j_sum1
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Mood: Just got through yet another "take this job and shove it" moment.
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I have destroyed a food processor by dry-blending aluminium foil. The blade died surprisingly quickly, and the motor got very hot.
Passing the product through some sieves gave me different grades of powder. Nothing extremely fine, but some that has been good enough for thermites.
This is not something that I am keen to revisit, but, depending on your requirements, you may get something useful.
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currawong
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I can second the destruction-of-blender issue with foil. If this is to make thermite, aluminium turnings that can be purchased from a scrapyard or
machinists shop very cheaply are usually good enough. You do need either a small amount of fine thermite or some other way to get it started though,
it's a bit harder to ignite than fine thermite. The other benefit is it's also much slower and more controlled than when you use very fine thermite, a
5kg batch I did a few months back with turnings and iron oxide pigment took several minutes to fully react.
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MrDoctor
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for thermite 100% of the aluminum doesnt have to be ultra fine powder. Theres a bit of an art to it but you can let a proportion of it get quite
coarse. for your purposes it might only be neccesary to half ball mill foil, then thoroughly mixed and packed nice and dense it should have a
comparable effect. i did this once, supplementing fine powder with half milled foil that was still rather large and flakey. I intended to next try
adding turnings to see how those would fare but the place clsoed down and noone else kept their scrap seperate for recycling.
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bariumbromate
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here's some good aluminium powder that you can get in australia, i have not tested it in thermite yet though
[Edited on 18-11-2025 by bariumbromate]
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clearly_not_atara
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Lol I'm glad nobody set their blender on fire. Aluminum is very malleable and aluminum oxide is very hard and the heat of oxidation is very large.
Overall that's a bad situation for blending.
Blending in mineral oil might work. What I would be more inclined to do is to get a high-silicon aluminum alloy (silumin) which can actually be quite
brittle and then just pulverize it. I think in most applications the silicon will be essentially inert or it will be oxidized with little effect on
the rest of the process.
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MrDoctor
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It seems that one industrial method of producing aluminum powder involved using a wire or bar feedstock, and the resulting arc is blasted with an
inert gas at high pressure, however i could see something working on the small scale along the lines of, using a peristaltic pump to recirculate inert
gas, blown through a jet nozzle that ideally blows hard on both electrode surfaces, or just the arc, while you maintain positive pressure with argon
for example, without relying on the gas cylinder for the energy for dispersing the metal.
You have a couple choices, using pulsed, lets call it DC, such as that you get from a flyback or car ignition coil that is fed square wave DC pulses,
because no ionization path is sustained, theres a delay/buildup of energy until breakdown is achieved, resulting in a chain of explosive releases.
adding HV capacitors to the mix would amplify this.
the mechanism would pretty much be etching the metal away in a series of explosions focused to a single tiny point, since the arc is limited only to
the channel it strikes through, though to you it will still look like a regular-ish arc.
Next option is to use a higher voltage low current AC source, like a flyback transformer again but ZVS controlled, and i dont know the efficiency but
a microwave transformer might be good too if those struggle like i remember to sustain arcs at high power, only pushing a couple hundred watts
through. the difference between low power AC vs pulses is that the arc/plasma is kept ionized between cycles so it doesnt have to re-strike each time
and theres no buildup. as a result the heat is more spread out as the ionization path is wider. Instead of exploding you would more likely be blowing
vapor fumes out of the arc sites, and having gas blow through is going to be important. depending on your power supply it might struggle to initiate
however, and can even self extinguish, like a jacobs ladder that is held too far apart in effort to get wider arcing. the distance the arc initiates
at wont neccesarily be the best one to get good vaporization at. the shorter the gap the higher the current, wheras a longer arc gap has a higher
voltage and probably has hotspots that will eject vapor more easily since the arc voltage will fluctuate more wildly as it changes shape.
Lastly, you could have a high power source, basically a welder, like a stick welder. unlike the previous option, wether AC or not (like transformer
welder or DC inverter), but this has to be managed carefully, the voltage/current ratio is problematic since it doesnt allow you to easily build up
the temperature locally in a way that makes it easy to disperse with a pumpable/filterable amount of gas. the upside is if you can make this work, it
will produce dozens of grams a minute, but without a certain known method its not the best setup to experiment with.
in short welders are good for liquifying aluminum easily, but liquid alone requires a fair bit of effort and specialty hardware to disperse at the
rate it forms.
There exists something called electro metal sprayers, i think, its essentially a mig wire fed plasma torch that sprays out metal to apply metal
coatings to things. if you can source the nozzle from one of those, it would make this incredibly easy.
to capture/quench the alu a high temp boiling oil like silicone oil might be good, as long as the particulates stay fine, a peri pump will have no
problem sucking it out constantly, but i dont know how well filtering that will go continuously. its important the oil doesnt volatize much and
decompose in the arc because that will probably end up forming carbon that is difficult to wash out.
I was going to try something along these lines anyway for another project, while im at it i suppose ill come back when i have some characterizations
of how high voltage arcs break up aluminum with/without flow, but also importantly, under vacuum or not. i have a suspicion that there is a certain
power density where a proportion of the mass of something relatively thick like rod or tube, can be boiled off quicker than it can melt and drip away,
with basic cooling, but it might need a vacuum to accomplish unless i wanted to feed in really thin wire.
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ManyInterests
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For me, personally, I used a rock tumbler and used glass marbles as the medium, I then added a little charcoal (powdered willow charcoal) and added
finely shredded aluminum foil to it. Tumbling it for 7-10 days usually did the trick.
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