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Author: Subject: Detonation of erythritol tetranitrate (ETN) with heated aluminum
Melgar
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[*] posted on 13-3-2010 at 01:41
Detonation of erythritol tetranitrate (ETN) with heated aluminum


I'm not sure if this is normal, but ETN seems to have a special reaction with aluminum, in that it detonates when in contact with it and heated to boiling. I tried heating tiny pieces of ETN on various materials steel, aluminum, and glass) and the stuff actually detonated when in contact with aluminum, though not the other two. So far this has been a very reliable way to detonate it, although the timing would not be nearly as accurate as with a blasting cap. ETN can even be detonated by wrapping it in aluminum foil and putting a chunk of black powder underneath it to provide the heat. This would also explain why reports have indicated ETN can be detonated with flash powder, since flash powder tends to have a lot of aluminum in it. Of course, flash powder isn't all that stable, but I'm willing to bet thermite would detonate it, especially if a little extra aluminum was used. Anyone have any experience with this?
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[*] posted on 13-3-2010 at 02:25


Quite interesting.
Did you notice any different behaviour between rapid heating e.g. with BP, or by slow heating on a burner or hotplate?




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Melgar
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[*] posted on 13-3-2010 at 04:20


Ah right. Yes, when heating ETN with aluminum, there was a rapid bubbling and a change in color (to orange) immediately preceding the detonation. I'm quite certain this orange color was from nitrogen oxides, although I did not repeat the experiment due to the extremely loud noise generated by said detonation coupled with the fact that I have neighbors. It was a very small amount though, perhaps the size of the head of a pin. It turned the aluminum foil it was being heated on to a large number of tiny flakes, so I couldn't examine the surface of the aluminum.

When heated on non-aluminum materials, ETN first melted, then boiled, then went "poof", shooting a noiseless jet of flame up as it combusted all at once.

My current working theory is that there is a highly exothermic reaction between ETN and aluminum at high temperatures, which releases enough energy quickly enough to create detonation conditions.
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[*] posted on 13-3-2010 at 04:55


Quote:
It was a very small amount though, perhaps the size of the head of a pin.

Surely that small quantity going off wouldn't disturb neighbours if you have any kind of walls between you.
But since you've discovered this interesting principle, the next logical step would be to devise a detonator which uses Al flakes dispersed in ETN without recourse to a primary.
A small quantity of BP could be pressed onto the mixture to ensure ignition.

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[*] posted on 13-3-2010 at 05:36


That indeed is what i thought.
Would you mind performing some test with Al powder.
I have some erythritol somewhere what better to do with it than eat it, oh wait.. I could also toss it in a nitrating bath.

This would indeed, if made reliable be better than working with primary's.




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[*] posted on 13-3-2010 at 06:06


Why not discharge a capacitor through an Al-wire (which is in contact with the stuff) ...
==> That way no timing-problem any more ... (if it works)

If done right and functioning the capacitor could be throwaway, near the charge,
==> so no thick wires etc. necesary

The discharge-contact could be made via eg. a reed-relais (50 ct. a piece) ... remotely controlled by some thin wire and a 9V-Battery ...

Only: Would it be safe to have the Al over long periods in the ETN ? Maybe it would have to get a thin layer of paint or paraffine to prevent any cold reactions ...
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[*] posted on 13-3-2010 at 07:40


Quote: Originally posted by hissingnoise  
the next logical step would be to devise a detonator which uses Al flakes dispersed in ETN without recourse to a primary.




The next step is to make sure the detonation does not occur between ETN and Al when stored for a while....

Perhaps also dissolve some ETN in acetone and leave in contact with Al, and separately, copper.

Perhaps repeat the experiment on Mg, see if the electropositivity of the metal has an effect.

Are you sure your ETN is acid free? Synthesis method?




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[*] posted on 13-3-2010 at 10:16


Maybe it is just that Al is a better conductor of heat
so the ETN heats more rapidly (or the foil is thinner etc).

Was the heating done under controlled conditions?
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[*] posted on 13-3-2010 at 10:28


Process for making ETN:

mix half and half fuming nitric acid and H2SO4 in a beaker in an ice bath
add erythritol bit by bit (slowly) while stirring until the liquid starts to thicken
add a little bit more nitric acid (like 10% of original volume) and see if the temperature goes up indicating incomplete nitration
if not (it didn't) let it sit for a half hour or so, then dump whole beaker into about 5X its volume of water
neutralize with ammonia, carefully, in ice bath
when pH is basic, filter crystals out of solution (crystals smelled strongly of ammonia)
rinse with distilled water, then let dry

I made two batches, one which was crystallized from ethanol, and one that wasn't. Both had the same reaction with aluminum. The uncrystallized ones are very pale yellow chunks and the the crystallized ones are white crystals.

The piece I detonated was maybe a little bigger than a pinhead, but it was as loud as a gunshot... not sure i want that noise to be coming from my house on a regular basis.

However, I have detonated ETN three times by wrapping in aluminum foil and heating it with some sort of fire. (One with black powder, one with alcohol flame, and another I just threw in some coals from a campfire, carefully of course!) I also detonated it once by just putting a bit on top of some foil and heating it over a flame.

My thought for reliable detonation was to put a little bit of aluminum-rich thermite on top, then detonate it by igniting the thermite. Another thought was to bend aluminum wire in a U-shape, then notch the base so that part gets the hottest when you run current through it. Then pack ETN powder around it. Theoretically, it would also be possible to melt ETN and pour it around the wire, but I don't plan on trying that any time soon unless I have a death wish. Still, I could heat a tiny bit of ETN in a water bath and see if that heat is enough to detonate it, which it almost certainly isn't. Maybe use a higher-BP solvent bath and try that, just to see what my factor of safety is.
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[*] posted on 13-3-2010 at 12:39


The materials compatability for such a mixture is a huge unknown, but it seems possible that something like a crackling microstar (dragons eggs) type of mixture
is a definite possibility here.....resulting in an increased output from what is a fulminating mixture undergoing a rapid DDT in small quantities unconfined.
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[*] posted on 13-3-2010 at 13:18




Quote:
The next step is to make sure the detonation does not occur between ETN and Al when stored for a while....

If prolonged contact with the common metals could cause detonation of ETN wouldn't we have known about it long ago?

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[*] posted on 13-3-2010 at 13:21


I have cast ETN a fair bit. I have found I can add spherical Al to the Molten ETN, without reaction. It is a rather fun mix :)

I have had such a mix, in a small charge, for well over a year now. It was 50:50 ETN:Al, the idea was to try make 'thermobaric mix'.

However, with Al flake... ETN can make the DDT, Perhaps the Al particles cause local heating at the points, have a reaction with the ETN causing heat, then DDT?

I know a fuse through ETN, loose, in Al foil can go DDT. Not reliable though.

I much prefer the Azo Clathrate, Nitrotetrazoles, or DPNA primaries :)

My DPNA dets PETN... With ~3mg... There is 2mg Lead Styphinate used to 'Fire' it.




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[*] posted on 13-3-2010 at 15:00


I have read whatever I could find on ETN, which were not only the original patents but some background studies from the USBoM & European material printed close to the time of the patents, encluding studies of ETN from DuPont and Nobel (who apparently struggled for the patent rights). Some of the material were comparisons of the various nitrated solid alcohols & their stability. I have never heard of a acid-free nitrated polyol or for that matter nitric ester in general having a sensitivity to a metal [in that there would be a formation of higher sensitivities].
Did you employ a stabilizer when recrystallizing your ETN? Did you check with more than one means, the ph of the product to satisfy yourself that the material is truly acid free? There are similarities between MHN and ETN in that they demand a ph neutral synthesis to stay stable. They both are quite stable when neutral and can be exposed to many environmental variables but heat is not one of them.

In the course of reading a particular comparison of impact & heat sensitivity, both nitrated polyols are similar to NG. This can be raised dramatically with a sample that is not acid free (USBoM 1913). A "rolling boil" can vary in temp due to container but comes close to the level of heat necessary for detonation. TTBoMK ETN has no sensitivity to aluminum. However if your sample is not acid free you could be playing with fire especially if you have not employed a stabilizer. ETN was not employed commercially due to the raw material (at the time) being much too expensive to be practical for profit. MHN was used to a limited degree but the demands for a powdered nitric ester was outweighed by the production cost of #1 Gehr dynamite.

From a standpoint of concern for safety, I suggest that you check the ph in a manner that satisfies you totally that the product is neutral. The power of ETN is very close to NG - as is it's demands for an acid-free condition. I have not heard of a common energetic material except Hg Fulminate that has a sensitivity to Al. However an acidic batch of most nitric esters eventually become "hyper sensitive" to most stimuli (heat, friction, impact, static discharge). Generally solid alcohols benefit from re-crystallization in that there is an opportunity to remove acid levels from within the particulate. Employing a stabilizer is generally a standard (Naoum -- US Railway Commission) in that they can deal with extra Nx should that be necessary (product may be neutral upon synthesis but contaminated in storage, etc.) Nitric esters were frequently re-washed due to the havoc acidic conditions can render.
Stabilizers do not HAVE to be diphenyalamine. You may use Urea, Betain ( a vitamin B), or the physical presence of an antacid (not truly a stabilizer but serves).
Be safe. If you notice higher levels of sensitivity than in the past - check until you are satisfied! However, if you are not very familiar with nitrated solids, ETN (or MHN in particular) note that they are VERY sensitive & should be treated with the same caution one would NG, Flash, or any material that demands elimination of ignition stimuli.



[Edited on 13-3-2010 by quicksilver]
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[*] posted on 13-3-2010 at 18:18


Another thought is that ETN is an oxidizer of sorts, in that when it decomposes, oxygen is one of the decomposition products. Now, if enough heat was generated from the reaction of this oxygen with aluminum, isn't it feasible that the reaction rate could increase fast enough to cause detonation? This would be especially true for ETN that was already near its decomposition temperature, as much of it would be.

Now, for both batches of ETN, the crystals were made basic with ammonia, then allowed to evaporate, then rinsed, then allowed to evaporate for a really long time (like a week). Now, I doubt there would be a significant amount of acid remaining because of the excess of ammonia, and any extra ammonia would have evaporated a long time ago, plus it tested neutral with test strips, so I really don't think acid is what's doing it, unless it's formed in-situ from the decomposition of the ETN.

I don't suppose anyone has a small amount of ETN to verify this reaction with? It would be at most an easier way to detonate ETN and at least a huge warning to anyone who plans to use the stuff.
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[*] posted on 13-3-2010 at 21:09


While the molecule does carry oxygen ETN is not an oxidizer; it's actions when heated would most likely yield nitrogen first prior to anything. It's good to hear that you washed the yield with a basic material and did a test. However, there are exposure phenomenon such as placement in a container wherein an acid existed, etc, etc. I am only re-iterating this for surety's sake and the description of what may have been "a reaction". Principally because the last damn thing I want is for anyone to get hurt. One thing that would certainly help is a re-crystallization. ETN is interesting in that acetone is actually a bit too strong a solvent and ethanol or methanol is generally used (or a mix ). The re-crystallization opens the material to antacids and is a solid way to make sure a bit isn't creeping around in there & is the most opportune time to test for acidity.

Decomposition in nitric esters is accompanied by the release of Nx and the smell generally alerts one to that issue. Smokeless powder has been known to decompose to the point of seeing the "brown fumes" when a container is opened. Nitric esters have some similarities in that respect. Getting in the habit of using a stabilizer is always a good move. And the best opportunity to use it is during a re-crystallization. One of the difficulties when reading written descriptions is that the reader does not see the phenomenon. The material IS seriously sensitive & packs a punch: that's a fact! Likelihood is that as long as you check on it periodically & respect it like you would NG everything will be fine.
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[*] posted on 14-3-2010 at 00:50


Quote: Originally posted by Melgar  

I made two batches, one which was crystallized from ethanol, and one that wasn't. Both had the same reaction with aluminum. The uncrystallized ones are very pale yellow chunks and the the crystallized ones are white crystals.


This is what I was wanting to know. While in solution during recrystalization did you do any neutralization?

As quicksilver says, base rinsing while solid can leave small traces of acid trapped within the crystal.
I am trying to eliminate the possibility of acid traces having a reaction with the metal. This would release nitrous gasses greatly accelerating decomposition.

When you said it turned orange, was it just a small layer at the bottom where it was in contact with Al, or was the pile completely orange?




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[*] posted on 14-3-2010 at 08:47


Quote: Originally posted by The_Davster  
This is what I was wanting to know. While in solution during recrystalization did you do any neutralization?

As quicksilver says, base rinsing while solid can leave small traces of acid trapped within the crystal.
I am trying to eliminate the possibility of acid traces having a reaction with the metal. This would release nitrous gasses greatly accelerating decomposition.

When you said it turned orange, was it just a small layer at the bottom where it was in contact with Al, or was the pile completely orange?

I checked the pH of the dissolved ETN, and it was neutral. When I put it over the flame, it first melted to a clear liquid, then the orange color started to appear from the bottom once it started to boil. But the amount was very small and the detonation followed this phase almost immediately, so I wasn't able to observe it that closely. However, I can state for certain that I didn't see the orange color when I did the same thing on steel and glass. Although, thinking about it, the steel was really dark and the glass didn't provide any contrast, so I'll have to try that again with closer observation.
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[*] posted on 14-3-2010 at 10:05


What you're seeing is decomposition....This is pretty common nitric ester phenomenon. Imagine what happens with a so-called "run-a-way"......What do you see? Those red-brown fumes, right? So when you expose the material to decomposition stimuli like heat, you get a change in color. The decomposition continues....to a point; & then the material breaks down. And when it breaks down, you have an energetic reaction.
.....Sounds like all is cool & and well. The original phrasing of the 2nd post made it seem like the stuff was "going orange on you" for no apparent reason. - Thus the concern. Think of color changes that occur as a rattle from a snake; unless there is voluntary input on your part (heat, etc).
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[*] posted on 14-3-2010 at 11:17


Anyhow there was a thread on roguesci where they detonated stuff with exploding wires,
==> i.a. capacitor-discharges through thin wires ...

A larger Capacitor will have at 1 kV an amout of energy expressable in terms of "grams of TNT", and the release is just as quick as the circuit permits ...
==> So it's no big deal to create a shockwave around a thin wire ...

Has anyone tried that ? Probably much safer than handling primary-explosives ...

[Edited on 14-3-2010 by chief]
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[*] posted on 14-3-2010 at 11:28


Nitromannite is close to being a primary as it can detonate from the heat of the flame of a match.
It's a good candidate for this kind of experimentation. . .


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[*] posted on 14-3-2010 at 13:55


If this turns out to be a real and reliable way to induce detonation, I think you just missed out on a possible business opportunity. I can certainly think of quite a large number of uses for such a phenomenon.
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[*] posted on 14-3-2010 at 19:12



Quote:

Anyhow there was a thread on roguesci where they detonated stuff with exploding wires,
==> i.a. capacitor-discharges through thin wires ...

A larger Capacitor will have at 1 kV an amout of energy expressable in terms of "grams of TNT", and the release is just as quick as the circuit permits ...
==> So it's no big deal to create a shockwave around a thin wire ...

Has anyone tried that ? Probably much safer than handling primary-explosives ...


I assume you are familiar with the term "EBW" and its complications for assembling a decent system, not saying it is impossible.
Or do you mean incorporating such a system into the Al+ETN idea, e.g. pumping a lot of power into a Al wire so that it super heats(burning or evaporating) very sudden thus detonating the ETN?


The last case I described would seem plausible.
It would be a very controllable method.


[Edited on 15-3-2010 by User]




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[*] posted on 15-3-2010 at 01:15


I tried a setup like that a few years ago. It wasn't a true EBW, but a piece of cardboard with a strip of Al foil glued on. The foil covered both sides, crossing a single edge. I then cut out triangular sections of the foil where it crossed the edge so only a ca. 1 mm bridge connected the two sides. Leads were then connected to the sides and two capacitors from disposable cameras were discharged through the setup.
The narrow bridge of Al foil exploded with a very sharp crack, so I tested an identical setup in a 3 mm ID brass tube with loosely packed MHN.
This produced an explosion that ruptured the brass tube, but didn't produce a large number of fragments.
So I just concluded that either it was a low order detonation or a deflagration.
Either way, with sufficient tweaking it could definately be employed in a detonating train, but the question is how much reliability you would sacrifice for a little safety.
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[*] posted on 15-3-2010 at 10:48


Of course I talk about detonating the Al-wire ...; not sure what you mean with EBW, probably "exploding bridge wire" ?

The circuit has to be quick enough, that means: Thick enough wires to conduct the energy to the point, resistivity only in the detonating wire, high enough voltage ...
==> Double the voltage at the same capacitance gives 4 times the energy, double the speed and 8 times the peak-wattage ... (linear assumptions ...), so much more meaningful to use 5 kV than 500 V ... ;

I would first try thin copper-wires: Standard-quality obtainable; can be very thin: The discharge will go through the plasma as well ...

Maybe another way is possible: Discharge through a thin layer of insulating explosive ... ; maybe with some graphite-content ...
==> Could be much quicker superheated ... (shocked ...)
==> A good insulator will need anything between 5 and 50 kV per mm, so use 5 kV at 0.1 mm ; the plasma will have pressure and extremely high temperatures, beyond that of any combustion ...

[Edited on 15-3-2010 by chief]

[Edited on 15-3-2010 by chief]
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[*] posted on 16-3-2010 at 06:31


To my feeling there are two factors that might explain the ease of D2DT of ETN in contact with heated Al foil.

Aluminium and Iron belongs to a class of metals that react weird upon exposure to concentrated HNO3...they get passivated...Aluminium displays a stonger passivation hability than Iron because it forms a protective unsoluble oxyd layer so HNO3 doesn't need to be as concentrated to lead to passivation.
The passivity is weird in that it can be deactivated for Iron by a simple contact with a metallic copper piece. The passivity of Aluminium is dependant on the nature of other dissolved components like ammonium cation, chloride anion...

1°)So it can be that during your neutralisation process with ammonia you make some NH4NO3 and that this allows the Al to be unpassived and unprotected by an oxyd layer and therefore very much more reactive (strong reducer).
Upon contact with NH4NO3, Al foil is rapidly chewed through and this oxydation process evolves heat!

I find strange that you use strong ammonia base to affect neutralisation while mild neutralisation by carbonate/bicarbonate is the favoured way to conserve the polyesterification level; strong base inducing the reverse reaction to the esterfification (nitratation); thus the hydrolysis.

2°)It can be that during the heating some ETN decomposes leading to HNO3, HNO2, NOx and carboxylic acid moeties (from the oxydation of the alcoholic functions)...then HNO2 and carboxylic acids corrodes the Al leading to unpassivation and naked unprotected Al. Aluminium salts are very prone to hydrolyse and so their pH in water is very acidic! I suppose that during the unpassivation process locally you have high acidity spots.




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