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adam.braley
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Let me first start by saying that I'm approaching this from the perspective of a chemistry student, not a welder.
Magnesium may burn at high temp, but the heat is quite localized and may be recorded as much lower if you were, say, to take at thermometer to it.
Also, powdered and thin strips of magnesium burn readily, but good luck igniting a solid block; i would expect the see different temps listed for
different forms. Also, magnesium will also burn in water. The only way to put it out is to remove it from a reactive atmosphere, which usually means
smothering it in dry sand. I imagine that if you bury it in the thermite mix, it may go out before you reach ignition.
The easiest way to ignite thermite is, shocker, with thermite. Get a tiny bit ignited and it will set off the rest.
If your aluminum has formed an aluminum oxide layer, it will increase the temp needed for ignition since you'll need to melt through to the aluminum
(mp is over 3x that of elemental aluminum) Note that aluminum oxide is a product, and therefore it will slow the reaction.
There are ways to make this reaction occur more easily, depending on the intended use. Sulfur is a good additive because it lowers the melting point
of surrounding Fe and leads to superior welds. Oh, yeah. Don't forget that the molten Fe you make is well past the melting point. It will melt into
and through a lot. I personally love the scene in Burn Notice where Michael bores through the engine block of a car using a coffee can of a thermite
mixture.
Thermate is a mixture of iron thermite (yes, you can have copper, chromium, ect thermites; thermite is actually any mixture of reactants that undergo
a thermite reaction) and several other additives like sulfur, barium nitrate, and a binder (which allows you to shape it and avoid losing reactants to
the slightest breeze). Red gum should work. It's often used in fireworks and the like, though I've heard that synthetic polymer resins like PBAN are
used by the military in thermate anti-material grenades.
Thermate is nice because it's easier to ignite and interacts more with the surrounding metal. Now, before you point and say, "Hey, I want to weld, not
melt through heavy artillery", I will point out that thermite is also used for welding (didn't mean to get you excited by all that "anti-material"
stuff).
@4s2: This is pure conjecture, but I would assume that thermate is the thing you heard about the marines using for quick welds.
I'd promote unitednuclear.com as a decent place to buy all these things. They sell lots of fun science stuff, including reagents like aluminum powder,
barium nitrate, sulfur, red gum, magnesium (ribbon and powder), not to mention a standard thermite (premixed) and "thermite ignition mix" which I
cannot comment on. They say it overcomes the difficulty in using magnesium, but I've never tried it and I don't know what's in it.
Oh, one final note. Sparklers are often cited as a good tool for igniting thermite because they are a cheap, readily available source of magnesium,
though they do contain a mix of metals. You can smother them just as easily as magnesium. "Burning" is simply an exothermic redox reaction. If you
remove the reactants, you terminate the reaction.
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hissingnoise
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| Quote: | | "Burning" is simply an exothermic redox reaction. |
Good opening post, but pointing out the bleedin' obvious is a bit superfluous!
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condennnsa
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sparklers can not be 'smothered' like magnesium, it is a pyrotechnic composition, with an oxidiser and fuel.
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hissingnoise
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It isn't smothering - it's disrupting and it happens because Fe3O4 requires very high heat for its decomposition!
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blogfast25
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Thermite welding is still used for welding together tram rails. You just need a little ‘mould’ around where the joint is to be made and use
approximately the right amount of thermite mix to form enough iron to fill the cavity. Alloys can also be produced by means of mixed oxide thermites.
Thermites are also used in unstoppable incendiary bombs, see e.g. the London 'Blitz'.
‘Drop-moulding’ (as it’s also known as) is also used for producing crude niobium from Nb2O5 + 10/3 Al === > 2 Nb + 5/3 Al2O3. The hot, newly
formed liquid metal (T > 2,500 C!) flows straight into a mould below the reaction crucible.
Glycerine is a sweetener (among many other things) that you can find on the shelves of supermarkets (in the UK).
I prefer a stoiciometric mix of Al powder and KClO3 as ignition mix, lit with Mg ribbon or festive sparkler.
All intensive white light causes skin to bronze: argon welder's hands for instance tend to go brown due to exposure to UV in the very hot white light.
[Edited on 13-2-2011 by blogfast25]
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peach
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Thermite is still used to weld train tracks together, where it needs to be done quickly and there is a big gap to fill.
There are even companies who produce the special crucibles that sit over the rails and they come with bags of premixed thermite to pour in and set
off. Mixing some magnesium powder in can help the entire thing go. The thermite is set off and allowed to fully melt before the gate is opened and the
molten iron is poured into the mould around the track. Once it's cooled enough, a grinder smooths the crud off to give a bump free finish.
I once looked at the prices for producing iron for casting by thermite, and it is a lot more expensive than using a gas flame.
In terms of producing high quality, precise welds, you would be far better off using an arc welder. The same for cutting. Thermite just gets hot.
Making something hot alone is not a great way to cut it. Oxy/acetylene torches, plasma cutters and laser tables all use a jet of gas to blow the
molten material out of the way. The goal is usually to melt the smallest amount as possible and blow as much of it out of the cut as can be done, to
save energy and produce a thin kerf, slag free cut. You'll notice they are using a gas torch in the video about welding the track with thermite.
There was a mythbusters episode in which they set off half a ton of thermite.
<iframe sandbox title="YouTube video player" width="853" height="510" src="http://www.youtube.com/embed/vCqG3rWtNbc" frameborder="0"
allowfullscreen></iframe>
<iframe sandbox title="YouTube video player" width="640" height="510" src="http://www.youtube.com/embed/PPAYZMzGMwQ" frameborder="0"
allowfullscreen></iframe>
<iframe sandbox title="YouTube video player" width="853" height="510" src="http://www.youtube.com/embed/BnHR4cMXiyM" frameborder="0"
allowfullscreen></iframe>
[Edited on 13-2-2011 by peach]
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blogfast25
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The ‘thermite a car’ video was pretty lame: these freaks don’t know the first thing about thermites. They must have been using a slow burning
mix and those just don’t reach the same temperatures because a lot of the heat is lost to the environment and can’t heat up the reaction products.
A ‘fast and hot’ ferric thermite would at least have burned through the roof like melting butter in a pan, like the one that ‘burned’ through
four plates… ‘Mythbusters busted’!
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peach
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I was going to say the same thing, but didn't want to cloud the thread up with too much negativity.
The car was not impressive. 
Even the constant explosions begin to get a little boring. It's more amusing watching Adam go down a hillside slide and into a lake, or them trying to
saw their way out of a prison with dental floss.
With regards to the exploding ice, I suspect Jamie is correct. I have seen lead blow it's self all over the place when even slightly damp solid bits
are added to a molten pool. It is common practice among the at home casters to warm bits of metal up on top of the furnace prior to dunking extra in,
to boil off the water first.
Since they have the money to buy half a ton of it, they could have put 11lbs into a tank of water. I expect it wouldn't produce the same effect.
[Edited on 14-2-2011 by peach]
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The WiZard is In
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Thermite incendiaries
A lot of info on thermite has been posted here, to put it politely —
a lot of what has been posted is not three-sigma.
Let me start with thermite’s use as an incendiary, it was not much
used (“The production of magnesium bombs had no sooner been
fairly launched when it became apparent that there was not going
to be sufficient magnesium available to the Service for the great
quantity of incendiaries required. To circumvent this shortage the
Service devised another type of metallic incendiary, a steel-cased
bomb containing thermite with a standard flare mixture of barium
nitrate and aluminium. The design of this bomb, the 4-pound M54
incendiary, was completed in October 1941, and the following April
it was tested by General Doolittle in his historic raid on Japan. By
the summer of 1942 the CWS had produced several millions of
these bombs for the Army Air Forces. Their production was cut
down shortly thereafter, however, when supplies of magnesium,
which was produced a superior incendiary, again began to flow into
factories producing incendiaries for the service.” Anon. The
Chemical Warfare Service in World War II : A Report of
Accomplishments. Rienhold Publishing for The Chemical Corps
Association. 1948) .
Themite use in air dropped munitions has two problems. 1-
Mechanical. It is a powder and thus difficult to contain, therefore a
strong case in required – dead weight. 2- Chemical. Perhaps one of
the chemists here will save me the time and explain thermite’s
obvious chemical problem when used in air delivered munitions.
Attempts were made to consolidate it. AMCP 706-185 Engineering
Design Handbook, Military Pyrotechnic Series – Part One – Theory
and Application. (Free DL from DTIC.mil). “During World War I,
binders such as sodium silicate, sulfur or celluloid were added in
order to reduce segregation of the thermite during loading;
however, these techniques were only partially successful. Thermite
has not been used since World War I for incendiary applications.”
Thermite is used on a local basis, thermite grenades and
Cryptographic Equipment Destroyers, TH4 , M1A2 and TH4, M2A1
[MIL-C-12469K] (28-pounds of thermite) come to mind.
Mention has been made of incendiary’s that could not be
extinguished. In WW II the Germans found a method – “It was
German technicians who first though of combining a high explosive
charge with an incendiary bomb in order to discourage fire fighters
from extinguishing it. Scores of fire wardens in England were killed
in the first raid in which these bombs were uses, for the explosive
charge did not go off until some time after the bomb had began to
burn. We retaliated immediately by incorporating into the M50
bomb 35 grams of tetryl whit a delay detonator.” Chemical Warfare
Service in WWII.
I don’t have the time to expend this into a treatise on incendiary
warfare so I will just not in passing I shelve:—
George J.B. Fisher
Incendiary Warfare
McGraw-Hill, 1946
Incendiary Warfare
A SIPRI Monograph
The MIT Press/Almqvist & Wiksell, Sweden.,
1975
E. Bartlett Kerr
Flames Over Tokyo : The U.S. Army Air Forces’ Incendiary
Campaign Against Japan 1944-1945
Donald I. Fine, Inc. 1991
And two others I cannot at the moment put hands on.
Noted in passing—
The US Army built typical Japanese and German buildings at
Dugway Proving Ground [UT] and dropped incendiary bombs on
them "to learn what happened when bombs of certain types struck
enemy structures." "They also dropped phosgene, cyanogen
chloride, and hydrogen cyanide bombs ranging in size from 100 to
4,000 pounds....."
LP Brophy, & et al
United States Army in World War II
The Technical Services
The Chemical Warfare Service : From Laboratory to Field
Department of the Army, 1959.
The US army set a hanger and a generals car a fire with incendiary
(phosphorus) carried by bats!
Jack Couffer
Bat Bomb : World War II's Other Secret Weapon
U of Texas Press, 1992
There is a phrase in Latin by Virgil that best describes this book –
Apparent rari nantes in gurgite vasco. I translate it as — This book
is Long on Chit-chat and BS.
Before I forget - Myth Busters Thermite.... Well dem MB's
occasional are in well over their heads technically speaking.
I remember their Guncotton/cellulose nitrate expert nitrating a pair
of blue jeans... red fumes pouring out of the glass vessel... if I
was standing there I would A- Dump it into cold water, B- Run. Red
fumes are a clear indication that the HNO3/H2SO4 it tooo hot, the
red fumes are often followed by the cotton bursting into flame.
MB's thermite ... they used aluminium and iron oxide which was
much too fine. I don't know why they used red iron oxide (ferric
oxide Fe2O3 ) military thermite uses "iron oxide scale"
(Ferrosoferric oxide, Magnetic iron oxide, Fe3O4).
Extra credit - what is the oxidation number for the iron in Fe3O4?
Next up - thermite welding, except I have to go down to the shop
and pick up a few books.
djh
----
To the meaningless French idealism's,
Liberty, Equality, and Fraternity, we
oppose the German realities, Infantry,
Cavalry, and Artillery.
Prince Bernhard von Bulow
[Edited on 14-2-2011 by The WiZard is In]
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The WiZard is In
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Quote: Originally posted by The WiZard is In  |
I don’t have the time to expend this into a treatise on incendiary
warfare so I will just not in passing I shelve:—
And two others I cannot at the moment put hands on. |
Found one book —
Sir Donald Banks, K.C.B., D.S.O., M.C., T.D.
Flame Over Britain : A Personal Narrative of Petroleum Warfare
Sampson Low, Marston, & Co. London, ND
More than you ever wanted to know 'bout British plans to use
Fougasse &c. in WW II.
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The WiZard is In
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| Quote: Originally posted by 4s2 | Sure everyone asks about how to make thermite etc, but has anyone done any in depth reaction testing?
I have heard that railroad rails used to be welded together with a simple thermite proccess. I want to try and work it with .25 inch plate steel on
some general joints. I also want to use it for cutting. |
I am going to take the easy-way out time wise. I recommend —
[I own hard copies of these.]
Ethan Viall
Gas Torch and Thermit Welding
McGraw Hill 1921
Free DL from Google.com/books
http://tinyurl.com/67xaa7g
Richard N Hart
Welding Theory Practice, Apparatus and Tests
McGraw Hill 1910
Chapter IV has been reprinted by Lindsay Publications.
You can DL the entire book from Google.com/books
http://tinyurl.com/4o6r3xo
Welding Handbook
Volume 3
Resistance and Solid-State Welding and Other Joining Processes
American Welding Society
7th ed 1980 [There may be a litter ed I own this ed.]
NB - Note that whatever is themite welded is first heated to red
heat. If you do not ... the molten metal flowing down will rapidly
cool-solidify and block the flow. Heating is covered in la books.
An aside ... I remember years back standing on the station
platform watching track being stick welded. The power source
was the 3rd rail through a box of metal coil - current limiting
resistors. Then even more years back my father and I built
an carbon arc using one of the 500 W wire coil wrapped around
a ceramic cone heater elements for current control with D cell
carbon electrodes.
AWS Handbook
Table 13.1 Examples of Thermit weld dimensions and mold
requirements.
Size of opening 16" Gap. 1 - 5/8" Thermit required lb. 3 125.
Eat you hearts out Myth Busters!!
----
RR Track Welding 101
http://www.youtube.com/watch?v=hsigudZdWMY
Sorry to say they cut off the last 30-seconds or so, catch it when its
is on TV again. Or buy the video.
djh
----
WALL STREET JOURNAL
REVIEW & OUTLOOK
JANUARY 27, 2011
Land of Milk and Regulation
Preventing the next dairy farm oil slick.
President Obama says he wants to purge regulations that are "just plain dumb," like
his humorous State of the Union bit about salmon. So perhaps he should review a
new rule that is supposed to prevent oil spills akin to the Gulf Coast disaster-at the
nation's dairy farms.
Two weeks ago, the Environmental Protection Agency finalized a rule that subjects
dairy producers to the Spill Prevention, Control and Countermeasure program,
which was created in 1970 to prevent oil discharges in navigable waters or near
shorelines. Naturally, it usually applies to oil and natural gas outfits. But the EPA
has discovered that milk contains "a percentage of animal fat, which is a non-
petroleum oil," as the agency put it in the Federal Register.
In other words, the EPA thinks the next blowout may happen in rural Vermont or
Wisconsin. Other dangerous pollution risks that somehow haven't made it onto the
EPA docket include leaks from maple sugar taps and the vapors at Badger State
breweries.
The EPA rule requires farms-as well as places that make cheese, butter, yogurt, ice
cream and the like-to prepare and implement an emergency management plan in
the event of a milk catastrophe. Among dozens of requirements, farmers must train
first responders in cleanup protocol and build "containment facilities" such as dikes
or berms to mitigate offshore dairy slicks.
These plans must be in place by November, and the U.S. Department of Agriculture
is even running a $3 million program "to help farmers and ranchers comply with on-
farm oil spill regulations." You cannot make this stuff up.
The final rule is actually more lenient than the one the EPA originally proposed. The
agency tried to claim jurisdiction over the design specifications of "milk containers
and associated piping and appurtenances," until the industry pointed out that such
equipment was already overseen by the Food and Drug Administration, the USDA
and state inspectors. The EPA conceded, "While these measures are not specifically
intended for oil spill prevention, we believe they may prevent discharges of oil in
quantities that are harmful."
We appreciate Mr. Obama's call for more regulatory reason, but it would be more
credible if one of his key agencies wasn't literally crying over unspilled milk.
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peach
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| Quote: Originally posted by blogfast25 |
All intensive white light causes skin to bronze: argon welder's hands for instance tend to go brown due to exposure to UV in the very hot white light.
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Oh yes, I forgot someone mentioned that. You certainly can get a suntan from the UV of intensely hot objects and particularly welding torches.
I used to have a summer job welding custom iron gates and railings. We only had one one automatic visor. One afternoon we had a big 12ft+ high and
wide automatic set to do, so I was holding the bars still and closing my eyes whilst the other guy welded them into place.
2 or so hours of intensive welding later, I came out looking like Dale Winton. Which began many days of funny remarks from just about everyone we had
to visit. I knew the torch was giving out a lot, because it was a three phase industrial set. But, as with going on holiday and getting sunburnt
outdoors, it's easy to misjudge what's happening at the time.
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The WiZard is In
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| Quote: Originally posted by The WiZard is In | A lot of info on thermite has been posted here, to put it politely —
a lot of what has been posted is not three-sigma.
I don’t have the time to expend this into a treatise on incendiary
warfare so I will just not in passing I shelve:—
And two others [books] I cannot at the moment put hands on. |
Found the second book.
Major J.W. Mountcastle
The Holocaust : American Incendiary Bombs of World War II
Master of Military Art and Science (MMAS) Thesis.
US Army Command and General Staff College
10 Jun 1977
AD A042872
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Neil
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| Quote: Originally posted by Hermes_Trismegistus |
P.S. You REALLY don't have to worry about any danger from mixed thermite.
Anything hot enough to get that burning would have........
Well, lets put this in perspective, a propane torch can't ignite thermite, a campfire.... can't ignite thermite, a fifty caliber bullet at close
range.....can't ignite thermite........ a blazing inferno of a housefire......can't ignite thermite.....
Okey Dokey Smokey. |
A propane torch will ignite thermite, a campfire can ignite thermite, a 50cal bullet can ignite some thermites. I've also ignited very fine thermites
with a candle flame.
I haven't shot any thermites but i do recall seeing videos of CuO/Al being set off by a .308 IIRC.
(Really going out a limb, I think the videos may have been produced by an Aussie member of this forum?)
| Quote: Originally posted by adam.braley | Let me first start by saying that I'm approaching this from the perspective of a chemistry student, not a welder.
Magnesium may burn at high temp, but the heat is quite localized and may be recorded as much lower if you were, say, to take at thermometer to it.
Also, powdered and thin strips of magnesium burn readily, but good luck igniting a solid block; i would expect the see different temps listed for
different forms. Also, magnesium will also burn in water. The only way to put it out is to remove it from a reactive atmosphere, which usually means
smothering it in dry sand. I imagine that if you bury it in the thermite mix, it may go out before you reach ignition.
The easiest way to ignite thermite is, shocker, with thermite. Get a tiny bit ignited and it will set off the rest.
If your aluminum has formed an aluminum oxide layer, it will increase the temp needed for ignition since you'll need to melt through to the aluminum
(mp is over 3x that of elemental aluminum) Note that aluminum oxide is a product, and therefore it will slow the reaction.
There are ways to make this reaction occur more easily, depending on the intended use. Sulfur is a good additive because it lowers the melting point
of surrounding Fe and leads to superior welds. Oh, yeah. Don't forget that the molten Fe you make is well past the melting point. It will melt into
and through a lot. I personally love the scene in Burn Notice where Michael bores through the engine block of a car using a coffee can of a thermite
mixture.
Thermate is a mixture of iron thermite (yes, you can have copper, chromium, ect thermites; thermite is actually any mixture of reactants that undergo
a thermite reaction) and several other additives like sulfur, barium nitrate, and a binder (which allows you to shape it and avoid losing reactants to
the slightest breeze). Red gum should work. It's often used in fireworks and the like, though I've heard that synthetic polymer resins like PBAN are
used by the military in thermate anti-material grenades.
Thermate is nice because it's easier to ignite and interacts more with the surrounding metal. Now, before you point and say, "Hey, I want to weld, not
melt through heavy artillery", I will point out that thermite is also used for welding (didn't mean to get you excited by all that "anti-material"
stuff).
@4s2: This is pure conjecture, but I would assume that thermate is the thing you heard about the marines using for quick welds.
I
Oh, one final note. Sparklers are often cited as a good tool for igniting thermite because they are a cheap, readily available source of magnesium,
though they do contain a mix of metals. You can smother them just as easily as magnesium. "Burning" is simply an exothermic redox reaction. If you
remove the reactants, you terminate the reaction. |
The easiest way to put out magnesium ribbon is to look at it funny.
Sulfur + weld = super brittle metal
Thermate was created with intention of producing a high heat incendiary which would be able to produce widespread damage. while Thermite throws some
heat and some fumes(none in a perfect world) it's damage is so localized that it is not effective as a weapon. Thermate was an attempt to use sulfur
and barium nitrate to diffuse the heat allowing for a wider area of damage. The temperatures of it's molten products are at lower temperatures then
plain Fe3O4 thermite made from scale.
Curiously, the last batches of sparklers I purchased explicitly stated "Magnesium free" on the packaging. That being said I can wrap them tightly in
paper or Al foil, bury them in sand or even something horrific like flour and still have them burn contentedly. They work very well for igniting
thermite; far better in my experience then Mg ribbon. They can be very dangerous in that the sparks are more then capable of igniting some of the
more spirited thermites and care must be taken to prevent pre-ignition.
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Neil
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| Quote: Originally posted by blogfast25 | | The ‘thermite a car’ video was pretty lame: these freaks don’t know the first thing about thermites. They must have been using a slow burning
mix and those just don’t reach the same temperatures because a lot of the heat is lost to the environment and can’t heat up the reaction products.
A ‘fast and hot’ ferric thermite would at least have burned through the roof like melting butter in a pan, like the one that ‘burned’ through
four plates… ‘Mythbusters busted’! |
 Going off the color of the iron oxide and the way it burned... I'd put my money
on them having used a hydrated oxide.
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symboom
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thermite paint
Ive dissolved Styrofoam in acetone with forms a plastic and using ratios
of sulfur potassium nitrate aluminum and iron oxide ive just have had problems with the ratios
i know i have to add a lot more oxidizer since the Styrofoam burns sooty
2 KNO3 + 4 Al + S → K2S + N2 + 2 Al2O3 but this is the formulation for flash powder add iron oxide and Styrofoam so anyone guess how this is
going to work or whats the best ratios
Of>
Al
S
KNO3
C(Styrofoam dissolved in acetone as the binder)
<the acetone makes it more of a paint once the acetone leaves its plastic material with the compounds embedded in it
Fe2O3
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Neil
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http://spot.colorado.edu/~dziadeck/zf/LZ129fire2005jan12.pdf
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AJKOER
Radically Dubious
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I would add that don't just ignite the thermite with an arc, use the arc in a stream of Hydrogen gas. This is the so called Atomic Hydrogen torch.
Why? Because it operates in the range of Thermal plasma torches with a temperature of 3,700 C!
More details:
http://www.lateralscience.co.uk/AtomicH/atomicH.html
EXTRACT:
"Invented by Langmuir in 1926 , this device produces a temperature of 3700 degrees centigrade. Tungsten can be melted, diamond vapourised.
A jet of hydrogen gas is dissociated as it passes through an electric arc. H2 > H + H - 422 kJ. An endothermic reaction, with the intensely hot
plasma core of the arc providing the dissociation energy. The atomic hydrogen produced soon recombines; and this recombination is the source of such
high temperatures (easily outperforming oxy-hydrogen: 2800oC and oxy-acetylene: 3315oC)."
I wonder if replacing H2/O2 mixture with H2/Cl2 in an arc would actually produce a hotter flame? I know that a so called "Hydrogen Chlorine Controlled
Explosion" torch is much hotter than H2/O2 mixture.
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