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Author: Subject: Exotic thermites & analogs
Fenir
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[*] posted on 24-10-2013 at 16:29


By adding a drop of water to a potassium permangenate and glycerin slurry, one can speed up the reaction time immensely. This is quite helpful when igniting thermite mixes.
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[*] posted on 24-10-2013 at 16:32


Quote: Originally posted by A Fresh Lunatic  
SO, how can we determine if Mercuric Oxide would have a thermic reaction with copper metal , other than trying it? presum,ably, the end products woudl be mercury metal and cupric oxide ?

How about looking up the reactivity series?




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[*] posted on 24-10-2013 at 16:45


Quote: Originally posted by elementcollector1  
Quote: Originally posted by A Fresh Lunatic  
SO, how can we determine if Mercuric Oxide would have a thermic reaction with copper metal , other than trying it? presum,ably, the end products woudl be mercury metal and cupric oxide ?

How about looking up the reactivity series?

Better yet, calculate the enthalpy of reaction. If you're lazy, you can get WolframAlpha to do it for you.




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[*] posted on 24-10-2013 at 17:49


Quote: Originally posted by DraconicAcid  

Better yet, calculate the enthalpy of reaction. If you're lazy, you can get WolframAlpha to do it for you.


Even better yet, calculate the enthalpy and entropy. That way, you can determine what the temperature needs to be for the reaction to be spontaneous.

A word of caution: If the reaction is spontaneous and exothermic, it may produce highly toxic mercury vapor.

[Edited on 25-10-2013 by Cheddite Cheese]




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[*] posted on 1-2-2014 at 15:36
Yttrium Thermite


After a semi-failure with zinc thermite (the entire pile of thermite did not burn), I tried using 5 grams of Y2O3 and 2 grams of powdered Al. The mixture was placed on a piece of tile flooring outside with an air temp of 40 degrees F.

The results were very gratifying. The mixture burned much quicker than conventional iron thermite. The temperature was high because the slab of tile cracked and all that was left were chunks of fused Yttrium metal and Al2O3.
I have no way of measuring the actual temperature of the reaction but the melting point of Y2O3 is 2,410C, Yttrium metal melts at 1,522 and boils at 3,338.

The 99.99% pure Y2O3 was purchased on Ebay and, for a "rare earth" metal oxide, was relatively cheap.
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[*] posted on 7-2-2014 at 10:26


Here, halogen wondered if 3NaCl + Al --> AlCl3 + 3Na would work because it works with NaOH and Al.
Why wouldn't it work? The enthalpy of formation of AlCl3 is −704 kJ·mol, while NaCl's is only −411.12 kJ mol.
Is it because there is more atoms in AlCl3 than in NaCl? And thus higher molar mass, so it releases more energy because it contains more matter?

[Edit] Sorry if this question is stupid, I just did a little research on the subject.

[Edited on 7-2-2014 by Zyklonb]




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[*] posted on 7-2-2014 at 11:52


Quote: Originally posted by Zyklonb  
The enthalpy of formation of AlCl3 is −704 kJ·mol, while NaCl's is only −411.12 kJ mol.


Yes, but it's 3 moles of NaCl, so net enthalpy change is +529.36 kJ/mol.




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[*] posted on 7-2-2014 at 12:11


OK, that's kind of what I was thinking.



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[*] posted on 22-2-2014 at 22:38


Ag2SO4 thermite

I gave this a whirl about three years ago. I used 300MESH magnalium powder as the fuel and diapered the mixture together. The mixture was ignited with a piece of visco-fuse.

vlcsnap-2010-11-11-19h12m36s190.png - 139kB


The composition would self-confine easily and it was a very vigorous reaction. Due to no presence of nitrogen in the reagents, one could only deduce that it would decompose the nitrogen in the air into various oxides, as evident from the orange fumes in this still image.

Compared to silver nitrate, silver sulfate has a low solubility in water with a quick glance at Wiki quoting its solubility at 0.79g/100mL at 20 degrees Celsius. I actually never experimented whether or not it would be water sensitive, but having no interest in its practical uses it wasn't an interest at the time.

I also experimented with silver oxide, but the results weren't nearly as exciting. Perhaps my ratio calculations were off. To this day, I still have 300g of both these silver salts, as well as acetate...
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[*] posted on 28-3-2014 at 11:42


I just tried the CuO-Al thermite, it was much slower than I expected.
The walls of my crucible where coated in a red-orange copper color, but no nuggets of copper where recovered.
I am dissolving the mess in dil. HCl (aq) as I type. Large volumes of a flammable gas (hydrogen I assume) where given off.
My question is, why would H2 evolve?
The reaction of the thermite would be: 3 CuO + 2 Al → 3 Cu + Al2O3.
None of the reactants react with HCl to produce H2.
The purity of my CuO is unknown, I made it by dissolving a Cu anode in water with electricity. The resulting CuOH was heated to make CuO. My Al is quite pure. One possibility is unreacted Al, but my stoichiometry was correct, perhaps my scale is inaccurate?




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[*] posted on 28-3-2014 at 13:43


CuO/Al thermite is rather unpredictable in my experience. I've made nano-CuO/MgAl which did not burn completely, although it exploded violently on heating. If you want higher burn speeds, some confinement or preheating is necessary as small amounts unconfined with different particle sizes will burn almost identical speeds.

Your "mess" probably contains quite a bit of aluminium. That would at least explain the evolution of hydrogen gas.
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[*] posted on 28-3-2014 at 15:34


Ok, I might try it again, there was no practical reason for the experiment.
I did find a lot of tiny grains of Cu after the HCl treatment was complete, but some gray powder was also present.
I just through it out, because I didn't want to try to separate it.




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[*] posted on 30-3-2014 at 18:27


Quote: Originally posted by Zyklonb  
I just tried the CuO-Al thermite, it was much slower than I expected.


That is a very vague conclusion. I know for a fact that copper (II) oxide from a ceramic supplier and any fine aluminum powder (eg. 325 mesh) will deflagrate almost as fast as conventional 7:3 flash powder. It is dangerous stuff.

The reason it may have been a slow reaction for you could be the purity of your reactants (from your post), their particle size, how homogenous the mixture was prepared and/or the ratio.

Someone could read your one-off comment and interpret that it is safe to ignite a large quantity with a gas-torch because it will burn slow, when in actuality it would practically explode.

Specifics matter! You never know who may read your findings and reproduce the experiment with the same expectations.
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[*] posted on 30-3-2014 at 19:02


Like I said, I assumed that it would be faster, if someone tries this, thinking it would be slow, just because of my account, without reading anything else, it would be his/her fault.
Al was ~350 mesh, I'm pretty sure the copper II oxide was impure, it was mixed very well.
I shall make some more, and try again.
BTW, can you light Al/CuO thermite with a torch?
I do have Mg ribbons, but instead of waiting them, I light all my thermites with a visco fuse coated in KClO3, it's never failed, but I haven't really tried any hard to light thermites yet.
[EDIT] Typo.

[Edited on 31-3-2014 by Zyklonb]




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[*] posted on 10-4-2014 at 13:41


Are you asking a question?



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[*] posted on 1-6-2014 at 11:44


http://www.popularmechanics.com/technology/military/research...

Copper Oxide + Al or Mg cutting torch.
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[*] posted on 5-10-2014 at 21:17


Quote: Originally posted by j_sum1  
Forgive me if this has been covered. I'm new here and have only read about 20% of this thread.

I had questions about the Al-S method for ignition of thermites.
My standard method is KMnO4/glycerine with a strip or two of Mg ribbon. Several people here are extolling the virtues of Al S.

I mixed up some 400 mesh Al powder and garden quality sulfur in a 1:2 ratio and hit it with a butane burner. I got the two to react under the flame but it was not self-sustaining. I also got a brownish gas coming off which I was not expecting.

So, my questions
1. What am I missing here?
2. What set up are others using to get this to act as an igniter?
3. What the cow was the brown gas? It looked like N2O but that seems really unlikely. Do I have sulfur that is that full of impurities?


This stuff usually burns quite well and pretty quickly as well for me. My first issue is your sulfur being "garden variety", though, which often contains 10%, sometimes more, of bentonite clay. I don't know that this would matter a ton though. It could also be that your aluminum is too oxidized on the surface, this happens with older samples. Your brownish gas might've just been some dust kicked up by the reaction; sulfur dioxide fumes also look kind of misty and dirty to me also.

If you have the materials available, I often use a mixture of 2:1 potassium chlorate to powdered bituminous coal(most coal you encounter is this) as a thermite lighter; it's very reliable, and burns with a nice consistent rate, plus no sulfur dioxide/hydrogen sulfide smell. I've also been able to light thermite with coarse black powder. With both of these, you can just stick a visco fuse into the mixture, light it with time to spare, and walk away.




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[*] posted on 5-10-2014 at 21:30


Oh, and for anyone wondering about the explosive properties of bismuth trioxide thermite, look no further: https://www.youtube.com/watch?v=lg8NLzUngr8

I believe this is SM user Tdep's channel; the video shows some pretty good examples of the explosive nature of this thermite.




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[*] posted on 14-10-2014 at 06:35


Quote: Originally posted by siegfried  
After a semi-failure with zinc thermite (the entire pile of thermite did not burn), I tried using 5 grams of Y2O3 and 2 grams of powdered Al. The mixture was placed on a piece of tile flooring outside with an air temp of 40 degrees F.

The results were very gratifying. The mixture burned much quicker than conventional iron thermite. The temperature was high because the slab of tile cracked and all that was left were chunks of fused Yttrium metal and Al2O3.
I have no way of measuring the actual temperature of the reaction but the melting point of Y2O3 is 2,410C, Yttrium metal melts at 1,522 and boils at 3,338.

The 99.99% pure Y2O3 was purchased on Ebay and, for a "rare earth" metal oxide, was relatively cheap.


You're lying.

The RE oxides cannot be reduced with Al, their heat of formation is too high.

Y is not strictly speaking a lanthanide but Wolfram Alpha gives a value for Standard Heat of Formation of Y2O3 of - 1905 kJ/mol. Al2O3 is only - 1676 kJ/mol, so that reaction simply CANNOT proceed!

Trust me, if aluminothermy could yield RE metals, we'd all be doing it!

[Edited on 14-10-2014 by blogfast25]




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[*] posted on 14-10-2014 at 06:38


Quote: Originally posted by blogfast25  
Quote: Originally posted by siegfried  
After a semi-failure with zinc thermite (the entire pile of thermite did not burn), I tried using 5 grams of Y2O3 and 2 grams of powdered Al. The mixture was placed on a piece of tile flooring outside with an air temp of 40 degrees F.

The results were very gratifying. The mixture burned much quicker than conventional iron thermite. The temperature was high because the slab of tile cracked and all that was left were chunks of fused Yttrium metal and Al2O3.
I have no way of measuring the actual temperature of the reaction but the melting point of Y2O3 is 2,410C, Yttrium metal melts at 1,522 and boils at 3,338.

The 99.99% pure Y2O3 was purchased on Ebay and, for a "rare earth" metal oxide, was relatively cheap.


You're lying.

The RE oxides cannot be reduced with Al, their heat of formation is too high.

Y is not strictly speaking a lanthanide but Wolfram Alpha gives a value for Standard Heat of Formation of Y2O3 of - 1905 kJ/mol. Al2O3 is only - 1676 kJ/mol, so that reaction simply CANNOT proceed!

Trust me, if aluminothermy could yield RE metals, we'd all be doing it!

[Edited on 14-10-2014 by blogfast25]



Quote: Originally posted by siegfried  
The 99.99% pure Y2O3 was purchased on Ebay and, for a "rare earth" metal oxide, was relatively cheap.



Is it possible it wasn't Y2O3? Just kind of quick to call someone a liar.

[Edited on 14-10-2014 by Loptr]
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[*] posted on 14-10-2014 at 07:59


I recently found a way to do the thermite demonstration in class, without the tedious mixing of powders and setting up of a tray of sand and other safety measures. Take two large rusty ball bearings, wrap one in aluminum foil, and smack them together. I just need to find a manganese ball bearing....



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[*] posted on 14-10-2014 at 08:27


I'm surprised that the impact is enough to start the reaction. Thermite generally needs a lot of heat to start.



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[*] posted on 14-10-2014 at 09:05


Quote: Originally posted by Cheddite Cheese  
I'm surprised that the impact is enough to start the reaction. Thermite generally needs a lot of heat to start.


The kinetic energy from the moving spheres* gets converted to thermal energy at a very small point. The physics instructor here does a similar demo with stainless steel ball bearings and a piece of paper (which gets a hole burned through it). I gave up regular thermite demos because of the safety issues and the hassle of igniting the stuff, but this works like a charm.

I tried folding some MnO2 inside some aluminum foil, and smacking that between the spheres, but I don't know if it was reacting with the rust or the MnO2. I may have to try again with the stainless steel ones.

*Yes, I've heard enough comments about "playing with my balls" that I will refer to them as spheres for the rest of my life.




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[*] posted on 14-10-2014 at 09:28


Quote: Originally posted by Loptr  

Is it possible it wasn't Y2O3? Just kind of quick to call someone a liar.



Call it what you want. It's serious disinformation that could lead other members and Googlers to waste precious Y2O3 on something that can not possibly work, not even remotely.

Tar and feathers, please.




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[*] posted on 14-10-2014 at 13:23


Quote: Originally posted by No Tears Only Dreams Now  

I believe this is SM user Tdep's channel; the video shows some pretty good examples of the explosive nature of this thermite.


And yet, what is proved by this kind of idiocy? You only need to do the thermochemistry calculation to know what will happen!

Of course with their kind of guesswork sooner or later someone will get hurt. It won't be so funny then...




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