Sciencemadness Discussion Board

powdering aluminium

skullandfeather - 12-9-2006 at 21:31

the idea is to get a stainless blender (vita-mix)
or similar (or make one as i now have to do)
and fill with salt, and while the blender is running
pour molten Al in.... <please wear protective clothing!!!>

i tried the direct route to thermite using Fe2o3 insted of salt
it did work, unfortunatly the "Al" i used was scrap and from a bike
and contained a sizeable amount of Mg. the sparks suprised me
but was enough of a warning to stop looking at the contents of the blender
(which had perfectly ground the thermite mix to a fine black powder:(
which then ignited and lept out of the blender as i ran to unplug it.
i wish i had a digital camera to show the current (or for that matter the white hot) state of my beautiful blender

Bert - 13-9-2006 at 06:33

Why in the name of God would you want to handle molten Aluminum. Unless you have the knowledge and industrial equipment used to make blown spheroidal Aluminum powder, you're going to hurt yourself to no good end.

Mechanical methods will produce enough fine Aluminum flake type powders for experimental purposes.

skullandfeather - 14-9-2006 at 19:56

molten aluminium isnt so bad, treat it with respect, welding gloves
apron, face sheild etc.
thermite is a very interesting casting method
i was under the impression that such a mixture would not ignite at such a low temperature, even at the temperature of molten Al.
do you think increased surface area would have such an effect with pure Al?

i didnt think blenders alone would do a decent job:)
thanks for the link

franklyn - 14-9-2006 at 22:57

Originally posted by skullandfeather
molten aluminium isnt so bad, treat it with respect,
thermite is a very interesting casting method

In years gone by vocational and technical high school trade shops included
well equipped foundries where aluminum was smelted and molds poured.

I'm repeating myself here,
Aluminothermy chemistry is a very useful method for the reduction of metals
such as Molybdenum, Tungsten and Titanium from their oxides to cast metal
parts without the need for an expensive foundry furnace. The welding and
repair of large broken structural and mechanical parts in the field makes this
an invaluable application.

A very useful excerpt on these techniques first published in 1910 is here
in pdf ->

A related thread post _

Additionally a mention of the reduction of Plutonium metal using Calcium
described in The Curve of Binding Energy ->


nitro-genes - 15-9-2006 at 04:20

I can't imagine that the molten aluminium plus iron oxide would ignite in a blender. The temperature of molten aluminium is nowhere near the decomposition temperature of Fe2O3 or even combustion of the aluminium with air. The sprayed spheroidal aluminium powder Bert was talking about can be safely produced in oxygen containing environment because of this...

The blender method does produce a coarse powder, suitable for thermite, or for addition to high explosive, but for things like flash it sucks. A blender doesn't flatten te aluminium foil, like ballmilling or stamping does. This means the particles will not become smaller than the thickness of the aluminium foil, which is 40 um or thicker.

An airtight ballmill with some steel ball bearings from ebay will produce a far more consistent and finer powder. I run batches of 200 grams a time, and the result doesn't have to be screened as it has a very consistent particle size already.

One time I decided to run the mill for 2 weeks after reading about nano aluminium on this forum. I turned of the ball mill and waited a whole week before opening the drum, because of the feared pyrophoricity. The result was the darkest of grey coloured powder with a slight blueish shine, almost black. Mixing it with ironoxide produced something that couldn't be named thermite anymore, as its behaviour was more like 7/3 perc flash...:D

[Edited on 15-9-2006 by nitro-genes]

Zinc - 23-12-2007 at 14:41

Al powder can be easily made with an angle grinder with a sanding disc. Just sand some Al and collect the powder. But you must use old sanding disc that are mostly spent. Using new ones introduces granule from the disc in the Al powder. And wear a dust mask when grinding the Al. Al powder made that way is grey in color and not shiny. It is a mixture of very fine and coarse particles. It works very good in KMnO4 flash powder.

skullandfeather - 24-12-2007 at 02:21

i had always thought that the heat and air would form excessive al2o3 on the surface of the powder, plus its time consuming to get a sizeable amount.
sure is a good way to get fe3o4 though!

i still like the molten al+blender method, as soon as i find another vita-mix.......
maybe one of those restaraunt dough mixers... quantity is important to me, and fine
particles are not, as i have to moderate the reaction with steel anyway.

slightly OT; many of the castings decomposed to iron power/fe304
i assume its excessive sulfur (from the reek)
is there a convienient way to purify it? i heard something about filtering aqueous ammonia
through it? any confirmation?

Alan - 25-12-2007 at 08:34

To make my AL powder I take a blender and some petrol and some Al foil (water will allow it to oxidize) and i turn it on. The foil is suspended in the petrol which runs though the blades many times thus you have very fine Al powder. Then evap or filter which ever you want.

evil_lurker - 25-12-2007 at 08:58

Actually, the best way that I have found it is to use a drill to make "curls", then put them into a cheapo $12 coffee grinder from wal-mart.

I've used melted alminum from engine blocks and scrap tooling with equal success.

Yeah you wouldn't think it'd work, but damn it sure does, and it takes waay less time than a ball mill... and those little coffe grinders will go 30-45 seconds at a time before they start to get hot, maybe more.

The trick is to grind till it gets hot, let sit for 10-15 minutes to cool, then repeat another 30-45 second grinding run.

Once it gets so fine though, you have to run it in a ball mill.

All in all if only powdered/flake is necessary its quite cost effective as most places want freaking $12-17 per pound for aluminum, plus there is shipping.

If a coffee grinder can last for 2-3 pounds and your using scrap, you've saved enough money to pay for another one.


MadHatter - 25-12-2007 at 12:10

Nitro-genes, Al powder that fine produces super-thermite, a faster reaction due to the
finer materials involved. Ball mills, blenders, and flour mills can make the Al very fine.
I've used all 3, sometimes using them in steps. The blender chops up the Al foil nicely
before putting it into the ball mill. In the past, my hand-cranked little flour mill did
the job.

A filtering flask, hydroaspirator, denatured alcohol, 1-micron filters(vacuum cleaner HEPA),
produces the blackest Al powder I've ever made. Vacuum is needed because gravity is
just too slow. The powder resembles airfloat charcoal and is extremely reactive ! It will
burn on its own without oxidzer.