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Offline Weldmann

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Thermite
« Reply #75 on: 14/08/2007 06:56:42 »
Well, I managed to find and purchase some atomized Al powder and I mixed it thoroughly with black iron oxide in the amounts --> 5 grams Al powder (grey) and 16.1 grams black iron oxide.  I found myself an old Aluminum forklift propane tank that was cut in half and placed a healthy pile of KMnO4 underneath the thermite and on top of it.  Then I poured another healthy dose of glycerine on top of it all and quickly moved wayyyy back.  Sure the permanganate went off at about fifteen seconds after contact with the glycerine but ultimately, nothing even remotely began to melt the aluminum tank the mix was in.  I have been trying to get this right for months and was so sure today was the day!  Possible reasons for failure:
1.  the black iron oxide is too damp to be ignitable without being heated in an oven for a while to dehydrate it fully.
2.  the aluminum powder came as fiberglass filler powder and was too old perhaps and had already turned into Aluminum Oxide.
3.  the KMnO4 is just not hot enough to light this particular mixture even though ingredients checkout to be genuine.
4.  I need to add some Aluminum chips or filings or turnings of a larger nature along with the powder.

Anyhow though, thank you for your help and I am all ears as to anymore  suggestions or comments pointing me in the right direction. I won't give up till I succeed! ;D
 

Offline lightarrow

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« Reply #76 on: 14/08/2007 11:00:19 »
Well, I managed to find and purchase some atomized Al powder and I mixed it thoroughly with black iron oxide in the amounts --> 5 grams Al powder (grey) and 16.1 grams black iron oxide.  I found myself an old Aluminum forklift propane tank that was cut in half and placed a healthy pile of KMnO4 underneath the thermite and on top of it.  Then I poured another healthy dose of glycerine on top of it all and quickly moved wayyyy back.  Sure the permanganate went off at about fifteen seconds after contact with the glycerine but ultimately, nothing even remotely began to melt the aluminum tank the mix was in.  I have been trying to get this right for months and was so sure today was the day!  Possible reasons for failure:
1.  the black iron oxide is too damp to be ignitable without being heated in an oven for a while to dehydrate it fully.
2.  the aluminum powder came as fiberglass filler powder and was too old perhaps and had already turned into Aluminum Oxide.
3.  the KMnO4 is just not hot enough to light this particular mixture even though ingredients checkout to be genuine.
4.  I need to add some Aluminum chips or filings or turnings of a larger nature along with the powder.

Anyhow though, thank you for your help and I am all ears as to anymore  suggestions or comments pointing me in the right direction. I won't give up till I succeed! ;D
Why 5 grams Al and 16.1g black iron oxide? It should be ~ 4 times so 5*4 = 20g FeO.
However, if the powders are good, I think you should have had a reaction (even if slower) the same.

You don't have to put any other substance under the termite, and if you ignite it with KMnO4 or other powders, don't put much of it comparing to the thermite mix, or this last powder will be spread off by the first reaction. However, if the Al and iron oxide powders are good and well dry, there is no very much need of extremely hot igniting reactions: you could use little amounts of simple black powder or KNO3/sugar or a good flame-torch. Be sure to really have FeO and not something like FeOOH*xH2O. How did you get the iron oxide?
Better is Fe2O3 however (I have experimented almost always with this one).

Remember that you can't fuse an Al container even as little as what you used, with such amounts of thermite. The reason is that the melted iron formed in the centre of the reaction is just a tiny volume, comparing to the mix, also considering that much of it remains attached to the slag. With a big glass full of pressed thermite mix I could obtain ~ a ball 1cm in diametre of melted iron.
 
The reaction is not very fast: it proceeds in several seconds, and you recognize it well from the high luminosity of it: a Very bright and growing light-yellow/white spot; if you keep looking at it, you could have serious problems to your eyes!
 

Offline Weldmann

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« Reply #77 on: 23/08/2007 00:43:09 »
Ahh, thankyou lightarrow, your guidance has finally helped me achieve success!  In using just a small amount of the potassium permanganate with the glycerine I was able to finally ignite the (adjusted 4:1  <-> FeO:Al) thermite!  I found another way to ignite it as well.  I used a small piece of kanthal wire, (similar to nichrome) and attached some long leads to a car battery and feathered the connection causing the wire to heat up like it does in your toaster.  Right when the wire was so hot it was about to melt, the thermite ignited!  I was surprised to learn and now see first hand that most of the literature on the net about thermite is exaggerated as to its strength.  I have read time and again how a couple of table spoons can melt through the hood of a car and through the engine block into the pavement below... ya right, not even close!  In using a few cups of thermite I couldn't even burn through quarter inch plate steel.  I was thinking back to something I had read though, about how coarser pieces of aluminum and iron oxide were used to slow down the reaction rate (combustion) of the thermite.  Is it possible then to use the fine powdered thermite to begin the reaction and have some coarse stuff mixed in to propagate a stronger yet slower result?  In other words, could I burn through thicker steel if I was able to successfully ignite coarser thermite?  One other question, I see that there are many oxides of metals one can use to mix with the aluminum dust, is iron oxide going to give you the strongest and hottest reaction where burning through steel is concerned, or is there another combination or mixture of combinations that would burn hotter and stronger?
 

Offline lightarrow

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« Reply #78 on: 23/08/2007 14:01:04 »
Ahh, thankyou lightarrow, your guidance has finally helped me achieve success!  In using just a small amount of the potassium permanganate with the glycerine I was able to finally ignite the (adjusted 4:1  <-> FeO:Al) thermite!  I found another way to ignite it as well.  I used a small piece of kanthal wire, (similar to nichrome) and attached some long leads to a car battery and feathered the connection causing the wire to heat up like it does in your toaster.  Right when the wire was so hot it was about to melt, the thermite ignited! 
That's the best way.
Quote
I was thinking back to something I had read though, about how coarser pieces of aluminum and iron oxide were used to slow down the reaction rate (combustion) of the thermite.  Is it possible then to use the fine powdered thermite to begin the reaction and have some coarse stuff mixed in to propagate a stronger yet slower result?
Yes, you have to use enough fine powder thermite (let's say ~ 50 - 100 grams) put inside a cavity of the coarser one and on it, and you'll ignite it. I could use aluminum shavings for the coarser one. Of course it burns slower, but the heat is the same.
If you want to melt a metal plate under the thermite (I haven't experimented it, however), you should put a thin-metal layer at the bottom of the container (brass, copper, aluminum ecc), before the thermite, to allow the melted iron to collect a little at the bottom of the container before escaping from it; then it melts the thin-metal layer and drops down to the metal plate you want to burn through.
Quote
One other question, I see that there are many oxides of metals one can use to mix with the aluminum dust, is iron oxide going to give you the strongest and hottest reaction where burning through steel is concerned, or is there another combination or mixture of combinations that would burn hotter and stronger?
Ah, that's the 1-million dollars question! I believe they have made a lot of experiments on this subject. I have personally experimented with:
1.MnO2
2.TiO2
3.Cr2O3
4.CuO
5.BaO2
6.CaSO4

With 1. I had problems of stability; with 2.  the reaction is extremely slow and not much hot (TiO2 has a high ΔΗformation in absolute value); with 3. the reaction is slower and less hot in comparison to Fe2O3 but, at the end, you have a bulk of pure chromium! With 4. and 5. it goes off almost like flash powder, so you can't use it (at least with fine powders); the same I think should happen with SnO, SnO2, PbO, PbO2, Pb3O4, CdO, HgO (these last two, especially the last, will release toxic metals, so I don't advise to you!); with 6. it's very good, I think it's hotter than with Fe2O3.

Sometimes, with the standard thermite, to increase the amount of melted iron formed, I used to add iron powder to the thermite (fine) powder. Of course the reaction is less hot (the more the iron, the less hot) but still hot to go over 1500C and melt the iron. I don't remember the percent, you could try with 25% (in weight) at the beginning and then increase it.

Make me know if you succedeed to melt the steel plate!
« Last Edit: 23/08/2007 14:03:44 by lightarrow »
 

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