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Author: Subject: Exotic thermites & analogs
Mardec
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[*] posted on 5-2-2008 at 06:22


xD

I fucking hate thermite. It is sort of a urban myth, must be.

I specially got new Fe2O3 and half a kg of german dark to make good thermite.

Make 200 grams, lit perfectly and burned pretty fast. But then I went to look.. It even didn't go trough a coocky can.. pathethic..

What am I doing wrong?!
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[*] posted on 5-2-2008 at 08:22


For a start, you should use coarser Aluminum to slow the reaction enough so it doesn't just blow the molten Iron around the area, rather letting it settle to the bottom of the reaction. You also need to surround the mix with a sand dam or clay flower pot or some other refractory to channel the molten Iron to where you wish to perform your work- Be it welding or melting a hole.

Thermite works for some purposes. It's nothing like the movies, however.

http://www.youtube.com/watch?v=nR6K90cR8Lg

http://www.youtube.com/watch?v=FEmHJORTlqk

[Edited on by Bert]
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Neil
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[*] posted on 19-3-2008 at 16:40


Quote:
Originally posted by Mardec
xD

:mad:

I hate when something doesn't work...

I made TH-3 thermite today, the same shit the military uses. I lit perfectly like it should. Burned very intense. Left a big pile of molten metal (Iron probably).

But it didn't get through a small (empty) gas container for my bunsen burner.. The iron stayed on top...

I don't get it, why didn't it go through it? Everything in the facinaty was charred.

I used this comp:

-12 g Fe2O3
-4 g Al
-6 g Ba(NO3)2
-0,2 g sulpher.

I lit it with 50/50 kno3/mg and the whole charge was packed in a 1,5 cm ID carbboard tube with the burning side directly aimed against the bottom of the gas container.

And it didn't even made a small hole.

The container was emty yes, I am not a noob/stupid.

It was one like this: http://content.answers.com/main/content/wp/en-commons/thumb/...

What are these things?! there was an aluminum can holding the tube in place, that completly vanished.

[Edited on 19-9-2007 by Mardec]



The idea of barium and sulfur is to cool the slag/metal and produce flame damage in military thermate. straight thermite produces a hotter slag/metal and confined, directed thermite produces the most effective cut.

if you had a refractory and pressure resistant container themate can be packed in and vented out of a single hole in a jet so that it produces a cutting jet which has moderate penetrating powers.

the card board tube would've sucked out alotta heat too...


Try CaSO4 or better MgSO4... both need to be dehydrated... MgSO4 puts any thermite I've run across to shame.
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Neil
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[*] posted on 26-3-2008 at 04:32


I'm wondering, has anyone here ever tried to use thermite to reduce zirconium silicate ?

3ZrSiO4 + 8Al + Boost ---> 3SiZr + 4Al2O3 + Crude from boost
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[*] posted on 26-3-2008 at 19:23
Thermite issues


Nothing like a good physics class on sat. lol.

I offered to show my physics teacher what thermite can do this up coming sat. I was looking through this book that i bought about all sorts of chemicals and how to make them. Now i have Al And FeO2 but they are both 300 mesh, and the book says that i need 2 g of Iron oxide for every 1 g of aluminum powder that are 400 mesh? will that change the density enough to make it so that i will have a different reachtion???

and how much should i make?? enought to scare the CRAP! out of him?!?!?! lol :D




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[*] posted on 26-3-2008 at 19:43


300 mesh will work fine just mix them well. You will also need something to light them like Mg ribbon or potassium permanganate and glycerine.


About how much to make its up to you I would stay around 10-15g or less




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[*] posted on 26-3-2008 at 19:50


1g of 400 mesh is the same as 1g of 200 mesh. The only difference will be the burn rate, and volume of the mixture.
Small mesh metal powders sometimes do not give the classic thermite display as they burn too fast leaving no slag.

Also it is Fe2O3




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[*] posted on 24-5-2008 at 12:27


I just want to make sure I understand everything correctly. I bought a couple oxides which I hoped would work, but didn't. I wasn't surprised by MgO not working, but CaO didn't, and neither did La2O3 or CeO2. What is the reason they didn't work? What are the calculations needed to determine if a thermite reaction will proceed?
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Jor
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[*] posted on 28-5-2008 at 16:05
HgO..


So whos gonna try a HgO thermite? :D:cool:
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[*] posted on 29-5-2008 at 01:30


I tried it around 2 years ago. It was a small amount of red HgO mixed with Mg. It burned quite fas. All the Hg was vaporised.

[Edited on 29-5-2008 by Zinc]




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[*] posted on 9-6-2008 at 18:18


No one's gonna help me out here?
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[*] posted on 10-6-2008 at 08:24


egloskerry, aren't all of those metals whose oxides you've tried more reactive than aluminum? I'm pretty sure the oxide has to be an oxide of a metal that's less reactive than aluminum.



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[*] posted on 11-6-2008 at 07:25


Imho all the oxides listed above will not react at room temperature (with Al, no matter how high the activation energy).
An Ellingham diagram can quickly tell you if the oxide involved will be reduced at room temperature (by Al or any other metal) / what temperatures are required in order to make the reaction occur. 2 Mg + O2 --> 2 MgO generally lies above 4 Al + 3 O2 --> 2 Al2O3, however they cross somewhere around 1500K (not too sure about that one, the point is: very hot).
But careful, don't confuse that with the activation energy! The above would mean that Al is capable of reducing MgO at temperatures above 1500 K. Aside from that, a certain activation energy is needed.

[Edited on 11-6-2008 by natriumperoxid]




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[*] posted on 11-6-2008 at 20:05


Where would the activation energy be found? Is that what determines if the reaction will proceed? I'm assuming what needs to be found is the temperature at which the reaction will occur.
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natriumperoxid
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[*] posted on 12-6-2008 at 03:22


My post should give you exactly this information,
for example an Ellingham diagram of the involved compounds will tell you that the following reaction: 3 MgO + 2 Al --> Al2O3 + 3 Mg will only occur at temperatures of roughly 2000 K and above. On top of that, a certain activation energy is needed in order to initiate the reaction.

Ellingham diagram for dummies: if the line of the oxide involved (e.g. 2 Cu + O2 --> CuO) lies ABOVE the line of the reducing metal involved (e.g. 4 Al + 3 O2 --> 2 Al2O3), a reation will occur! This is the case for the above, therefore it is a suitable thermite reaction. However, a certain activation energy is needed, this is the ignition mix such as a sparkler or permanganate + glycerin.




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[*] posted on 12-6-2008 at 04:53


Alright, I think I can figure it out. I'll return if I need more help.

That's odd, though. The diagram says ZnO should react, but I've never been able to get it to do anything.

[Edited on 12-6-2008 by egloskerry]
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[*] posted on 12-6-2008 at 10:29


ZnO should work without a problem, you probably did not provide the necessary activation energy. Some thermites are very hard to ignite and may even stop reacting again (e.g. SiO2 - thermite).

What ignition method did you use? It's probobably worth trying a more "brutal" one.

It is important to note that the distance between the lines does not indicate how exothermic the reaction will be or how rapidly it will progress.




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[*] posted on 13-6-2008 at 11:33


I remember using a sparkler as well as KMnO4/Glycerin. I'll try it again, using some Fe3O4 thermite to initiate it.
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[*] posted on 16-6-2008 at 15:22
Useful thermodynamic data on thermites and intermetallics


It's a 'must' resource, and it answers several questions above.

This has been posted before, but I think these posts were deleted.

Attachment: A survey of combustible metals, thermites, and intermetallic.pdf (1.2MB)
This file has been downloaded 960 times





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[*] posted on 19-6-2008 at 00:14


That is a great reference chemoleo!

The only thing i think it is lacking is information on the speed of the thermite reactions, m/s or something.

I have to say I like the Mg + B2O3, at 2134 cal/g that is pretty amazing. I wonder how fast it would be? I like how easy it is to make though, borax + acid + alot of heat should do it.

Also I wonder how useful some of these might be for producing metals from oxides, like B, Ti, Si, Mn, etc.
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[*] posted on 19-6-2008 at 00:40


Quote:
Originally posted by 497
...
I have to say I like the Mg + B2O3, at 2134 cal/g that is pretty amazing. I wonder how fast it would be? I like how easy it is to make though, borax + acid + alot of heat should do it.

Also I wonder how useful some of these might be for producing metals from oxides, like B, Ti, Si, Mn, etc.


I posted this a few dats ago on the MW NaOAc thread
Quote:
In Inorganic Synthesis V2 is a procedure for producing porous boron oxide. The normal method is to fuse boric acid, at the tepid temperature of 600 to 1000 C; then chilling it to a hard, difficult to powder glass. The alternative method in I.S.v2 is to pull a vacuum on the boric acid, then slowly raise the temperature to 200 C; this results in a lightly sintered porous product that rather energetically rehydrates. On a large scale a multi-stage fluid bed dryer can be used.

Note that powdered B2O3 picks up water from the air fairly readily.

As for other metals, search for "Goldschmidt process" or "Goldschmidt reaction".
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[*] posted on 20-6-2008 at 15:27


You are right, the high powered hygroscopicity(?) of B2O3 would pose a major problem for the practical use of a thermite that contains it. Its almost as strong as concentrated sulfuric IIRC. Still I think it would be worth the trouble for a whole 2134 calories per gram! Some of the I2O5 compositions looked pretty amazing too, but I'm not sure I'd want to mess with clouds of iodine and such...
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[*] posted on 20-6-2008 at 16:19


NOt to mention iodine pentoxide is a REAL oxidizer compared to the other oxides so I would shy away from this too. Unless it made up less than 20% of a composition and you increase reaction rate and get a purple cloud as a bonus!:P:D



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[*] posted on 30-6-2008 at 05:14


The most powerful thermite I could think of would involve a noble metal oxide or fluoride...Gold(III) oxide would certainly be nasty. Expensive, but explosive.
Au(3+) is an extremely powerful oxidizer. Standard reduction potential (to Au metal) is about +1.6 V, if I remember correctly.
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thumbup.gif posted on 23-7-2008 at 08:01
Manganese thermite using Mn2O3/MnO blends


Making manganese metal by thermite reduction of manganese oxides is one of the more frustrating oxide reductions I've ever carried out.

To get a better understanding of what the issues are I'd firstly recommended reading my blog post on this subject.

The issue with manganese thermite, especially from the higher oxides MnO2 and Mn3O4, is that these reactions generate so much heat that in adiabatic conditions the temperature of the reaction products will exceed the boiling point (BP) of Mn (2,061 C, 2,334 K). It's this characteristic that causes MnO2 thermites to deflagrate often violently, almost 'explosively'. The end-temperature of a thermite reaction (in adiabatic conditions) can be estimated quite accurately from the molar reaction heat (ΔH, reaction enthalpy), and the molar heat capacities and molar heats of fusion of the reaction products, basically by applying [url=http://en.wikipedia.org/wiki/Hess's_Law]Hess's Law[/url]. If of interest to readers I can give an example of such a calculation (on request).

The obvious solution to the problem would be to create conditions in which the reaction enthalpy is either lower or partly dissipates away (non-adiabatic conditions) but there's another problem complicating this approach.

For a thermite reaction to yield liquid metal, separated from the liquid slag (both solidify on cooling of course), the melting point (MP) of both (whichever is highest) the produced metal and the by-product alumina (Al2O3) has to be reached at the end of the reaction. For alumina the MP is 2,327 K (2,054 C), for Mn, 1519 K. But as stated before, the BP of Mn is also only 2,061 C, perilously close to the MP of alumina.

This creates a real lose-lose situation: to achieve metal-slag separation of Mn/Al2O3 this mixture has to reach a temperature that's really close to the BP of manganese metal. Even higher temperatures will cause much of the Mn metal to simply boil off. At temperatures somewhat below the MP of alumina, the vapour pressure of the Mn will be less but metal/slag separation will not be able to occur, resulting in powdered, sintered metal frozen in the slag.

Accurate control of the end-temperature in near-adiabatic conditions is therefore essential to obtain any lump metal from such a reduction.

I therefore started out on a series of experiments designed to cool the MnO2 thermite by co-reducing MnO2 and MnO. The reaction enthalpies per mol of oxide for both reductions are respectively - 597 kJ per mol of MnO2 and - 173 kJ per mol of MnO. Initial results with a blend of 1 mol MnO and 0.4 mol MnO2 and a high level of CaF2 (calcium fluoride, fluorite, fluorspar) as a heat sink and slag fluidiser, showed that this kind of mix with a stoichiometric amount of Al powder is capable of making nice blobs of clean Mn metal, albeit at low yields.

In the mean time I've switched from MnO2 to Mn2O3 because thermochemical calculations show that an Mn2O3 runs a little cooler than the corresponding MnO2 reaction, mainly because the Mn2O3 reaction generates more moles of reaction products (per mol of Mn2O3, 2 mol of Mn and 1 mol Al2O3, against 1 mol Mn and 2/3 mol Al2O3 for MnO2).

I've run several small (20 g and 50 g batches) thermites using blends of Mn2O3 and MnO, always using a high level of CaF2. I set the level of CaF2 as a constant molar ratio of CaF2/Al = 0.225, the alumina slag therefore contains always the same molar fraction of CaF2.

On the whole the results indicate that obtaining yields (recovered metal/metal present in the oxide x 100 %) is hard to push much beyond 35 % or so. The last two batches, both with 50 g stoichiometric (and CaF2 = 0.225 molar ratio) mixes, gave the following yields:


...........................mol....................mol

Mn2O3................1.........................1
MnO....................1.........................0

Yield....................37 %...................19 %

The 1/0.5 blend gave the highest yield of Mn metal I've ever achieved (out of probably over 20 or so reactions) and the metal is clean skinned and solid. The largest regulus was 7.3 g. Both reactions ran well-contained, leaving a molten slag/metal puddle at the bottom of the crucible. The 1/0 batch yielded metal that was significantly more oxidised, yet on the whole of passable quality.

It's clear though although these results constitute a great improvement to the usual 'explosive' MnO2 thermite, there is only so much cooling the Mn2O3 thermite by blending it with the much cooler MnO can actually achieve in terms of yield improvement.

The only real solution to reducing Mn oxides (or halides) with higher yields is by using a reductant with a much lower melting oxide (or halide).

One such reaction that springs to mind is the reduction of anhydrous MnCl2 with Mg. The reaction enthalpy of MnCl2 + Mg ---> Mn + MgCl2 is unfortunately only a measly - 161 kJ/mol of MnCl2, about a 100 kJ short of success. Thermocalcs show that in adiabatic conditions the reaction products would be heated to about 1,200 K, well above the MP of MgCl2 (987 K) but about 300 K short of the MP of Mn (1,519 K). Pre-heating the mixture by about 300 K or simply heating it to spontaneous ignition could work to obtain liquid Mn and liquid MgCl2.

As regards using a reductant with an oxide of lower MP, that excludes both Mg and Ca, as both have oxides with insanely high MPs. That then really only leaves the alkali metals, in particular Li and Na.

Thermochemical calculation for the reaction Mn2O3 + 6 Li ---> 2 Mn + 3 Li2O (ΔH = - 838 kJ per mol Mn2O3) shows that in adiabatic conditions the estimated end-temperature would be 2,320 K which is still too high and too close to the BP of Mn.

But here we could blend with MnO again. Setting a target end-temperature of 2,000 K (well above the MP of Mn, yet well below its BP as well), the blend composition of a stoichiometric mix has been estimated to be about 1 mol Mn2O3 + 2.6 mol MnO.

One small problem: I haven't got any Li... :(

Sodium, with a ΔH = - 295 kJ per mol Mn2O3 for Mn2O3 + 6 Na ---> 2 Mn + 3 Na2O could also be a good candidate... Haven't got any Na either...:mad:

[Edited on 23-7-2008 by blogfast25]

[Edited on 23-7-2008 by blogfast25]

[Edited on 24-7-2008 by blogfast25]
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