| Pages:
1
..
11
12
13
14
15
..
25 |
Mardec
Harmless
Posts: 33
Registered: 29-5-2007
Location: In a Lab
Member Is Offline
Mood: No Mood
|
|
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?!
|
|
|
Bert
Super Administrator
Posts: 2821
Registered: 12-3-2004
Member Is Offline
Mood: " I think we are all going to die. I think that love is an illusion. We are flawed, my darling".
|
|
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]
|
|
|
Neil
National Hazard
Posts: 556
Registered: 19-3-2008
Member Is Offline
Mood: No Mood
|
|
| Quote: | Originally posted by Mardec
xD
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.
|
|
|
Neil
National Hazard
Posts: 556
Registered: 19-3-2008
Member Is Offline
Mood: No Mood
|
|
I'm wondering, has anyone here ever tried to use thermite to reduce zirconium silicate ?
3ZrSiO4 + 8Al + Boost ---> 3SiZr + 4Al2O3 + Crude from boost
|
|
|
Epew23
Harmless
Posts: 1
Registered: 26-3-2008
Location: Philly!
Member Is Offline
Mood: Oxidized
|
|
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 
FeO + Al = FUN!
|
|
|
crazyboy
Hazard to Others
Posts: 436
Registered: 31-1-2008
Member Is Offline
Mood: Marginally insane
|
|
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
|
|
|
The_Davster
A pnictogen
Posts: 2861
Registered: 18-11-2003
Member Is Offline
Mood: .
|
|
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
|
|
|
egloskerry
Hazard to Self
Posts: 63
Registered: 7-2-2007
Member Is Offline
Mood: No Mood
|
|
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?
|
|
|
Jor
National Hazard
Posts: 950
Registered: 21-11-2007
Member Is Offline
Mood: No Mood
|
|
HgO..
So whos gonna try a HgO thermite? 
|
|
|
Zinc
Hazard to Others
Posts: 472
Registered: 10-5-2006
Member Is Offline
Mood: No Mood
|
|
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]
|
|
|
egloskerry
Hazard to Self
Posts: 63
Registered: 7-2-2007
Member Is Offline
Mood: No Mood
|
|
No one's gonna help me out here?
|
|
|
indigofuzzy
Hazard to Others
Posts: 145
Registered: 1-10-2006
Location: DarkCity, Bay of Rainbows, Moon
Member Is Offline
Mood: Distilled
|
|
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.
|
|
|
natriumperoxid
Harmless
Posts: 5
Registered: 11-6-2008
Location: germany
Member Is Offline
Mood: No Mood
|
|
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]
Scientia non habet inimicum nisp ignorantem.
|
|
|
egloskerry
Hazard to Self
Posts: 63
Registered: 7-2-2007
Member Is Offline
Mood: No Mood
|
|
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.
|
|
|
natriumperoxid
Harmless
Posts: 5
Registered: 11-6-2008
Location: germany
Member Is Offline
Mood: No Mood
|
|
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.
Scientia non habet inimicum nisp ignorantem.
|
|
|
egloskerry
Hazard to Self
Posts: 63
Registered: 7-2-2007
Member Is Offline
Mood: No Mood
|
|
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]
|
|
|
natriumperoxid
Harmless
Posts: 5
Registered: 11-6-2008
Location: germany
Member Is Offline
Mood: No Mood
|
|
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.
Scientia non habet inimicum nisp ignorantem.
|
|
|
egloskerry
Hazard to Self
Posts: 63
Registered: 7-2-2007
Member Is Offline
Mood: No Mood
|
|
I remember using a sparkler as well as KMnO4/Glycerin. I'll try it again, using some Fe3O4 thermite to initiate it.
|
|
|
chemoleo
Biochemicus Energeticus
Posts: 3005
Registered: 23-7-2003
Location: England Germany
Member Is Offline
Mood: crystalline
|
|
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 1237 times
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
|
|
|
497
National Hazard
Posts: 778
Registered: 6-10-2007
Member Is Offline
Mood: HSbF6
|
|
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.
|
|
|
not_important
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
| 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".
|
|
|
497
National Hazard
Posts: 778
Registered: 6-10-2007
Member Is Offline
Mood: HSbF6
|
|
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...
|
|
|
chloric1
International Hazard
Posts: 1140
Registered: 8-10-2003
Location: GroupVII of the periodic table
Member Is Offline
Mood: Stoichiometrically Balanced
|
|
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!
Fellow molecular manipulator
|
|
|
ducksan
Harmless
Posts: 2
Registered: 30-6-2008
Member Is Offline
Mood: No Mood
|
|
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.
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
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...
[Edited on 23-7-2008 by blogfast25]
[Edited on 23-7-2008 by blogfast25]
[Edited on 24-7-2008 by blogfast25]
|
|
|
| Pages:
1
..
11
12
13
14
15
..
25 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
