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Author: Subject: Thermite using 'blender grade' Al powder, is it possible ?
Pyro_cat
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[*] posted on 26-7-2019 at 19:40




Quote: Originally posted by James Ikanov  
steel case ammo


You got me thinking, steal case ammo made me think of "tin" cans and that took me to go big and fill a trash can with water and load it up with empty food cans from a restaurant or recycle day. Might have to hit them with the torch or some sand paper to get past any coatings that may be applied to speed things up. Find enough may have to crush them a bit too.

How did farmers make all that rust to paint barns red back in the day ?

What about a fish tank pump to oxygenate the water ? I believe its the oxygen dissolved in the water not the 2 Os stuck to the H that does the oxidation.



[Edited on 27-7-2019 by Pyro_cat]
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[*] posted on 27-7-2019 at 06:30


The antiquated forum software here on sciencemadness ate my account, along with all my posts. Apparently this happens sometimes.

In any case, rather than re-typing my post on chlorates I'll give you a reference. It's a bit of a recipe, but it discusses electrode materials: Preparing chlorates - PyroGuide

Long story short, no, you didn't make sodium chlorate, you were using the wrong anode type. In the video you referenced you'll note he was using a titanium cathode and a MMO (mixed metal oxide) anode. While the cathode isn't as important, production of chlorates requires an anode that selects for chlorates over oxygen. I don't fully understand the details, electrolysis reaction mechanisms tend toward the byzantine, but that's what the literature says. Selectivity between Oxygen and Chlorine Evolution in the Chlor-Alkali and Chlorate Processes




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[*] posted on 17-11-2019 at 20:15


I couldn't light blender grade Al + my rust and lost interest in the project for a wile but I just got some containers of iron oxide pigment powder a masonry contractor was throwing out.

All these different colors, very interesting stuff https://en.wikipedia.org/wiki/Iron_oxide

Trying to learn whats unique that makes each color, there is even green, I thought maybe it was a copper compound but its https://en.wikipedia.org/wiki/Green_rust

The tan has a black layer on top that I guess was from what ever it started as further oxidizing.

So I got to grab some balls and start milling some Al. One container is the classic rust color so I will try that first with some milled Al and if that works and no reason it shouldn't, use some of that to see if it will get a mixture using blender grade Al going.

Finally going to see the legendary thermite reaction in real life.
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[*] posted on 17-11-2019 at 23:22


If you want to use coarse grades of Al for thermite, you just need to get the reactants molten by way of a "booster" made from finer materials. Coarse thermite is actually better in several regards, since a slower reaction means less scattering of the molten products, and more time for the heat to be transferred to whatever you want to heat (and also more opportunity for the molten iron to settle to bottom of the slag).
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[*] posted on 18-11-2019 at 17:07


You might be able to use a low-grade pyrotechnic mixture to get the thermite to ignite. I remember using black powder (KNO3, C, and S mixture) to ignite my thermite test mixes. Just ignite the pyrotechnic mixture with a torch, and it should ignite the thermite. You could also potentially use a a potassium chlorate and sugar mixture and a drop of concentrated sulfuric acid as the ignition source.
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[*] posted on 18-11-2019 at 22:58


During WWII, some thermite based charges were ignited using a small charge of KMnO4 and iron powder placed in the main charge.
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[*] posted on 19-11-2019 at 21:51


Maybe I should try the powder inside the little red firecrackers, it burns very bright and left that green stain in my vision when I lit a little pile worse then I expected but bright makes me think its very hot. Or maybe a road flare. Now after thinking that I have to search road flares and see what makes them work, always learning !

We will see. I have KNO3 to mess with too but no KMnO4, can I get that OTC ?

Milling sure takes a wile using small marbles, but the blender bits are now flakes. Started with heavy duty foil, ooops.

[Edited on 20-11-2019 by Pyro_cat]
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[*] posted on 21-11-2019 at 12:34


One might try adding a bit of Sulfur to the top increment. Or using a bit of mixed (finely powdered) Al:S.

https://youtu.be/XfwpYH_qd2I




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[*] posted on 11-12-2019 at 21:20


That was very interesting, white hot burn followed by a puddle of molten iron left behind just like in the videos. The videos don't really show that white hot burn.

First small batch total of 16 grams the usual ratio using 'airfloat' Al powder lit right up with a sparkler.

2nd batch same amount but using courser Al powder that I added carbon to wile milling wouldn't light.

Then I mixed up another 16g using the fine Al powder without any carbon put it on top of the batch that wouldn't light but only the top batch completely burned.

Is it possible to light blender grade Al thermite ? Don't know yet.

And I just learned thermite can be made with sand https://www.amazingrust.com/Experiments/how_to/Thermite.html
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[*] posted on 11-12-2019 at 23:42


It absolutely is possible, I have done it myself many times. It does require a certain minimal amount though. The starter mix should be enough to melt a significant amount of the main charge, and I would place it inside the main charge rather than on top of it.
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[*] posted on 11-12-2019 at 23:51


Just reading through this thread real quick and I figured I would mention aluminum foil is specifically created to be flexible, It might be worth it for you guys to heat then quench the foil before attempting to blend it to make it more brittle, hell I know after hitting it with a blow torch you can turn it into powder pretty much in your fingers. It will likely prevent the balling issue you all seem to be having.




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[*] posted on 12-12-2019 at 05:45


Quote: Originally posted by Sedit  
Just reading through this thread real quick and I figured I would mention aluminum foil is specifically created to be flexible, It might be worth it for you guys to heat then quench the foil before attempting to blend it to make it more brittle, hell I know after hitting it with a blow torch you can turn it into powder pretty much in your fingers. It will likely prevent the balling issue you all seem to be having.


I thought that the reason aluminium foil became brittle after heating to redness was due to it being oxidised, meaning it is so thin that after heating, it is mostly the oxide. It can even become translucent. Though that may be due to lots of small pin holes.







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[*] posted on 12-12-2019 at 21:14


Quote: Originally posted by wg48temp9  

I thought that the reason aluminium foil became brittle after heating to redness was due to it being oxidised, meaning it is so thin that after heating, it is mostly the oxide. It can even become translucent. Though that may be due to lots of small pin holes.


My next search is "tempered aluminum"

Last time I tempered metal was around Halloween a few years ago carving pumpkins with that little blade that comes the kit.
We are all cutting with the little cutters but it kept bending so I stopped and I heated it red hot and quenched it in a cup of water.

People giving me a hard time what are you doing... Bla bla bla

It worked hardened the metal and it didn't bend see easy anymore and worked much better, now they want to borrow my lighter.

Story time over, lets search temper aluminum ... Leads to heat treatment of aluminum alloys

"HEAT TREATING
7075 may be solution annealed at 900°F for 2 hours at temperature, followed by a water quench.... Also, a maximum in strength was found to correlate with a minimum in fracture toughness.

So I guess heating the foil does brittle it but it seems thinner after you heat foil, does some evaporate ?

I was recently making thermite and now I don't have any foil to heat some with a torch to investigate this.

[Edited on 13-12-2019 by Pyro_cat]
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[*] posted on 12-12-2019 at 23:16


Heating aluminum in air will oxidize the surface layer. With foil that means most of it, which is indeed why it becomes brittle. Heating it in an inert gas will anneal it (make it softer and more ductile). The hardening happens when you quench the hot metal by dunking it in a suitable liquid. Another way that is more applicable to aluminum is to work harden the metal by deforming it while cold. You can do this by hammering it, but it will likely also happen during any grinding process such as in a blender or ball mill.

At any rate, the question is if you can use coarse aluminum in a thermite blend, and my claim is that you indeed can. However, you need a hot starter mix that is large enough to melt some of the main charge. This starter mix should be embedded in the main charge (I prefer a little packet of Al-foil with starter mix). I have done this with foil, and also very large Al particles from milling operations. These are at least 3 times thicker than Al foil, and work just fine.
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[*] posted on 12-12-2019 at 23:32


You cannot harden aluminum by quenching. It can only be work hardened or (depending on the alloy) precipitation hardened by "aging" at slightly elevated temperatures (2-300°C).



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[*] posted on 14-12-2019 at 02:38


Hmm, according to this paper, the alloy series 2xxx, 6xxx and 7xxx are "quench hardenable wrought alloys". I'm not a metalurgist though so I don't have any first hand knowledge. Whether it is true or false, I think it is also academic; I believe we agree that work hardening is the way to go with Al, but even that is really beside the point.
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[*] posted on 14-12-2019 at 03:59


The page you're linking to gives a good description of the process, but there's no references to any quench hardening. Besides, those alloys are the ones that are precipitation hardenable. So I expect it to be a misunderstanding of sorts, after all the precipitation process starts with a solution treatment that does involve a quench.

Precipitation hardening utilizes the reduced solubility of allying elements at low temperature. The first step is to heat the alloy to around 500°C, increasing both the solubility and the mobility of the alloying elements. The quench "freeze" the alloy into a supersaturated state. Subsequent aging causes the alloying elements to precipitate out, causing strain in the crystal structure that increases strength.

Quench hardening is pretty specific to carbon steel.




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[*] posted on 15-12-2019 at 15:05


I was using Al foil in the kitchen today. So I got my butane torch fired up.

By carefully holding the edges of the foil was was able to heat an area to about its melting point as judge by a flat area forming. As the foil is so thin it cools very quickly even from red heat in less than a second

It was difficult to determine if there was any differences in stiffness between heated area and unheated area by bending it or folding it. It was cheap thin foil and very flexible.

With care it is also possible to heat an areas of the foil to a bright redness for tens of seconds. The foil heated to bright redness does not melt if heated again. It retains some ductility as it bends with out cracking and if anything is slightly stiffer than new foil but its difficult to tell by bending it by hand As it does not crack or crumble I assume it is not completely oxide. It also allows some light thru. When examined with a magnifying glass the light appears to get though lots of small holes that are small compared to the separation between the holes. The area between the small holes looks no different in colour than unheated foil and appears to be total opaque just like unheated foil.

My conclusion is that the foil heated to bright redness for about 10 to 20 seconds is probably still aluminium but with a thicker coating of oxide. I do not know what causes the small pinholes. The diameter of the holes are about the thickness of the foil.

Previously I had only examined the remains of foil from trash fires that had been heated for much longer periods.


[Edited on 12/15/2019 by wg48temp9]




i am wg48 but not on my usual pc hence the temp handle.

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[*] posted on 20-12-2019 at 22:08


I just got some cheap foil at a discount store, real thin like the inside wrapper on a fancy chocolate candy. Doesn't say on the box how thin.

Tried it too with a little torch and was thinking maybe when the foil melts the surface tension of the liquid Al attempts to pull it into spheres and creates those holes, looked that way but then when I touch it it just flakes away. I need a little microscope, be interesting to use it look at powdered stuff and crystals too.

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