Fleaker - 20-7-2005 at 13:30
http://www.artstuf.com/atomized-metal-powders.html
This seems to be a good source for aluminum powder at least in terms of price. No questions asked either since it is commonly used in the
'cold casting' process.
I have no idea as to the purity of it or the actual mesh but the company claims it's atomized. I hope to report back on its quality in a few
days.
Please note that atomized metal powders are usually round in shape rather than angular (or flake). Flake powders consequently have more surface area
(making them more useful in pyrotechnics) since they are not spherical.
uber luminal - 20-7-2005 at 20:49
Commercial atomized aluminum powder, is intentionally oxidized in the process. (where compressed gasses sprayed(or many other methods) at the liquid
metal, in order to create the little droplets as they fall. (like a rain drop)) Anyway, they use an oxygen base, to coat every particle, such that
the product does not become rocket fuel, or start a fire when the chamber is opened.
In this sense, Atomized does not mean a small uniform size either. it means it was done with a proccess that could yield small particles. The yield,
is pretty cheap and gets you particles anywhere from 2-800 microns. For hot applications, it works OK... not as good as research atomization
though...
12AX7 - 20-7-2005 at 21:05
If nothing else, it would make good feedstock for your ball mill. A'course if you've got one, you might as well load turnings from the
local machine shop for free, so, eh...
Tim
Fleaker - 21-7-2005 at 14:01
Depending on the process, either compressed inert gas or high pressure water is used to atomize the metal. I don't know how likely a fire is in
inert or high moisture environment but intentional oxidation is correct depending on the use of the powder.
I do agree that it is a cheap process and yields a product of varying quality in respect to the actual size of the grains.
Regardless, I merely suggested the link as a source of "feedstock" for a ball mill since it is already small in size and would go quickly.
Nothing wrong with using it for reductions or general chemistry.
Unfortunately, turnings from the local machine shop are often mingled with other metals and covered in lubricants. Depending on the cleanliness of
the turnings, you can get a good product which doesn't clump or one that is entirely useless. I've had good and bad results from ball
milling those shavings.
In regards to research grade powders, they are far superior but also far more expensive (mainly the hazmat shipping). I doubt most home chemists have
ready access to supply houses such as Fisher, Sigma, or Alfa (to name a few) so obtaining these nice, consistent, quality powders might be a bit
difficult. Again, it all depends on the situation.
Caution with fine aluminium powder and water !
Lambda - 21-7-2005 at 15:22
Fine Aluminium powder and water are detonatable, with more explosive power than TNT (reff. Bretherick). If you try and extinguish an Aluminium fire
with water or CO2, then the fire will intensify, and in the case of water, even explode. Water is reduced, and forms Aluminium oxide and Hydrogen gas,
which in turn ignites. The heat of the aluminium fire cases water to instantly turn into steam, and therefore cases a blast wave, throughing molten
Aluminium through the air.
Fleaker - 21-7-2005 at 18:13
Even worse with magnesium powder
as that does burn in CO2/N2.
Yet good point Lambda, the finer the powder, the more dangerous, some are even pyrophoric
(i.e. certain grades of Raney nickel).
neutrino - 21-7-2005 at 18:59
Very true. In fact, even untrafine Pt powder is pyrophoric.
12AX7 - 21-7-2005 at 21:06
Must be nano-sized? Is that making PtO2 or catalyzing something in the air (O3?)? If the former, that would suggest Pt is normally covered in a
layer of PtO2, which I thought it was inert??
Oh well, lots of interesting things happen with colloids.
Tim
bio2 - 21-7-2005 at 23:03
Just now reading this thread got me thinking about some .012 inch granular aluminum, RA grade, that I recently aquired.
The particle size distribution is actually about 100-500 microns (quessing) ranging from rough spherical to jagged irregular with some flakes also as
seen thru a strong magnifying glass.
I have succesfully performed an organic reduction on a small scale after running amalgamation tests.
This is what is puzzling me and I thought perhaps one of you pyromaniacs might shed some light on this.
The assumption I had due to the surface area was that the reaction rate would be much accelerated compared to foil or .2-.3mm sheet. This is not the
case and a larger amount of HgCl2 is needed to amalgamate (3g/L versus 1g/L used with foil). Could this stuff have the intentionally higher oxide
coating as was mentioned for the powder? It amalgamates in 10-30min yet takes 16-18 hours to all dissolve without using excess. Heat is added at about
30 min to get it to reflux wheras foil will reflux for about an hour on the exotherm alone. Under the same circumstances (refluxing MeOH) foil is gone
in 1-2 hours and .2mm sheet in 12-14 hours.
Also I see in one of my catalogs for fine chems that some non-sheet or wire Al (99% +)is annealed. Could this change the reaction rate.
If it was annealed it would surely be done prior to grinding?I don't think it needs any cleaning as it dissolves very quickly (<30min) in 5%
NaOH and begins to generate hydrogen in dry MeOH with HgCl2 in only 5 min
12AX7 - 22-7-2005 at 10:04
I doubt they'd add fire to a powder for any reason. To make the powder in the first place it has to be worked somehow, if it was atomized then
it might be annealed but any other way involves tearing for the very reason that it's under stress, such as in a ball mill where particles are
repeatedly bashed to pieces.
I'd think it would tend to amalgamate slower in general because there's more Al2O3 surface available.
Tim
tina_craig - 22-7-2005 at 11:35
What about the atomized zinc found on the same page, good for experiments?
Fleaker - 22-7-2005 at 11:41
I have a better source for zinc. This is used in the cementation process for precious metals refining. This source is cheaper, and yes, it is high
surface area. This company also sells other things, sodium cyanide, gallon quantities of nitric, sulfuric, and hydrochloric acids. litharge/red lead
oxide, very high purity bismuth, zinc, lead foil, and silver used in cupellation and inquartation processes are available too.
http://www.lmine.com/minesupply/m68.htm
bio2 - 22-7-2005 at 13:12
.........I'd think it would tend to amalgamate slower in general because there's more Al2O3 surface available..........
Yes, this only ocurred to me after the amalgamation experiments indicated that the 1g HgCl2 per liter used with thick foil was not enough. I settled
on 3g/L which is about 45mg per gram Al in the amount of MeOH that it's amalgamated in.
As the slow dissolving is what I actually want in the reduction the excess Al should probably be increased from the 1.2:1mole used in the experiment
to maybe around 2-3m Al to 1m substrate. Foil takes about 5:1 and sheet 2-3:1 in my experience with all eventually dissolving.
So now I'm thinking that the oxide is not all being removed and perhaps more HgCl2 is needed to speed it up a little to say a 12 hour reaction.
When the HgCl2 reacts with the oxide it is deposited as the liquid metal in the bottom of the flask.
Does this elemental mercury continue to have any further effect in oxide removal or can it be considered spent?
In this reaction which is stirred it still remains on the bottom and essentially is unable to contact the Al. I did experiment with periodic stirring
as the small granuals float from clinging hydrogen and then sink when the bubbles break as they surface. The natural (unstirred) circulation is quite
vigorous with a small amount trapped underneath where it could contact elemental Hg if that does any good.
When stirring only a few seconds every 10 minutes was tried this seemed to be enough to keep most of the Al grains in the soup and redistributing the
particles on the bottom which were trapped. A flat bottom flask works well in this regard and a larger one will be tried next experiment.
[Edited on 23-7-2005 by bio2]
Zinc powder
MadHatter - 19-8-2005 at 23:29
A couple of years ago, I found powdered zinc on eBay for pretty cheap - $75 for 50 LBS, IIRC.
Where mesh size is concerned, I recently ordered some 635 mesh stainless steel screen.
Definitely not cheap, but it will serve as an excellent filter for my ball-milled aluminum.
neutrino - 20-8-2005 at 06:50
How much did you shell out for it?
Lambda - 20-8-2005 at 12:38
Neutrino, based on a stainless steal price of ~ 10 Euro per kg, it is rather expensive. But what realy sucks when I order it from a non-ferro
supplier, is the minimum take-off. But still, a lot cheaper than certain art suppliers would ask for the same. On the average, they do not have a
minimum take-off. An other way to obtain this mesh-wire cheaply, is to buy a kitchen sieve, which can also be obtained in stainless steal. This
mesh-wire is also sold in Brass, copper, aluminium, steal and variouse types of plastic .
German ALUMINUM
((Blasta)) - 20-8-2005 at 19:57
I just bought 2 kg from a plastic supply place without any hassle. Pretty fine too...made great photoflash mix with KNO3...even better with KCLO4!!
$20 USD...
[Edited on 21-8-2005 by ((Blasta))]