Sciencemadness Discussion Board

Urea, NH4NO3, Ba(NO3)2, CuO ::castable

niertap - 1-8-2012 at 15:49

I'm interested in the explosives made by melting urea and ammonium nitrate together. The 1:1 euchetic mixture is apparently nearly impossible to detonate and has a poor OX balance. it helped to have excess H4NO3 and not melt the entire mixture. Alkyl amines are apparently good sensitizers. The paper I read said it compared with TNT.

Yesterday I Dreamed the following::::

--90g urea, 122g NHNO3, 60g Ba(NO3)2, and 10g CuO were blended in a coffee grinder until fairly uniform. It is worth noting that it would be better to blend everything except the urea, which can be left in prills. They can melt some and shit it up.

--The mixture was then added to a mason jar and heated carefully over a sterno can. (I tested it a little and it seemed pretty safe) The urea started to melt and it became pasty, then a thick liquid with ammonium nitrate prills in it. lastly it started to get really thin as most of the ammonium nitrate melted.

--I then let the black liquid cool, occasionally swirling over an hour. It was still slightly warm and still liquid, so It had a stay in the freezer. The freezer solidified it. I think It's hard to solidify because the urea/ammonium nitrate release heat upon crystalizing/ solidifying.

I'm considering adding Al powder, but it might just lead to a lot of nitrate to ammonia reduction.

Pro: it melts at a fairly low temp

con: very hygroscopic

I might have another dream later and will try to see how it performs.

Ral123 - 1-8-2012 at 19:39

Maybe you haven't tried to melt AN/UN and that's why you're so enthusiastic. Ba(NO3)2 is totally stupid for the mixture and for zero ob you need like AN/UN 1:2. I'd recommend UN with a little egdn. Unlike AN mixtures, this one can be blown up at 1.5 density.

AndersHoveland - 19-8-2012 at 09:40

I have read of urea nitrate mixed with a lesser portion of ammonium nitrate for complete oxygen balance.
Urea by itself is nearly impossible to get to burn or detonate. It is a very stable molecule. Not only that, but when exposed to flame it first melts, making burning difficult. This is the reason, for example, that polyethylene burns relatively easily while wax does not. They are both essentially hydrocarbons, and both do melt under heat, but the polyethylene has a higher melting point and is more viscous, so when exposed to flame the heated portion mostly stays where it is, being heated enough to ignite. By contrast, wax easily melts. When exposed to flame it just quickly flows away from the flame as fast as it is heated. This matters much more if the wax is used in a deflagrating composition than in a detonating composition. Of course, the melting point does not make any difference if the substance vaporizes easily, such as kerosene, in which case it is extremely flammable. But again, in a detonation kerosene would not be any better than wax. Indeed, there are a few reasons why wax would be better (density, holding the oxidizer in place, uniformity of the mixture).

When just looking from the oxygen balance perspective, it is not difficult to see why many people would think urea would be a good fuel. Urea only needs 3 oxygen atoms to be fully oxidized, and then it would release all gas that would contribute to the explosion, especially since the molecule contains two atoms of nitrogen. So how is this not ideal? Unfortunately, urea is a very stable substance. The two amino groups are electron donating to the oxygen atom, and all the bonds in the molecule are fairly strong already. There are also intermolecular hydrogen bonds, and urea is a very polar molecule, so just separating the urea molecules from eachother consumes a fair ammount of energy, at least initially.

Ral123 - 19-8-2012 at 12:33

Oh soo stable. That's why UN even with much less energy content then anfo explodes well with only AP in plastic medicine bottle at near maximum density. And yeah, adding Al to UN gives dramatic effect.

AndersHoveland - 19-8-2012 at 14:39

Quote: Originally posted by Ral123  
Oh soo stable.

Just saying that urea is a poor fuel. Ammonia is not a particularly good fuel either, and it becomes worse when in ionic form.

Obviously the reason UN is more powerful than plain AN is better oxygen balance. Despite acting as a poor fuel, an advantage of UN over ANFO is that the fuel and oxidizer are more intimately mixed together, with the urea ions sitting right next to nitrate ions in the crystal structure. In contrast, if one looks at an ANFO composition through a microscope, one sees that that the crystals of AN and the fuel still exist in separate phases, no matter how seemingly well mixed physically.

We can see that the fuel performance outweighs the oxygen balance here. For example, methylamine nitrate is more powerful than urea nitrate, yet it has a worse oxygen balance.
(cannot find a reference now, feel free to prove me wrong)
Those C-H bonds are much weaker, so more energy is released.

[Edited on 19-8-2012 by AndersHoveland]

Ral123 - 19-8-2012 at 20:43

Sorry for trying to be sarcastic. Your concept is fine. Interestingly for UN, nearly half the weight of the molecule is fuel. With AN, the same HNO3 group oxidizes lighter and more reactive hydrocarbon, surely AN/fuel is quite more energetic for weight basis. The concept of oxygen balance rarely give objective picture, tnt is more brisant then almost everything AN based.