Official pyrotechnics thread!

[jdurg]

I believe that octanitrocubane is considered the most powerful explosive at the moment due to the fact that the entire decomposition array is only CO2 and N2. (There aren't very many H atoms in there to form H2O). Though I could be wrong so I will have to look that up.

 

Also, woelen brought up a very good point. Any time you hear something go 'bang' an explosion happened. The 'bang' is the result of rapidly expanding gases. If you look at unconfined gunpowder, it simply hisses and fizzes a lot, so that's a good sign that it's not an explosive.

[RyanJ]

I believe that octanitrocubane is considered the most powerful explosive at the moment due to the fact that the entire decomposition array is only CO2 and N2. (There aren't very many H atoms in there to form H2O). Though I could be wrong so I will have to look that up.

 

Also' date=' woelen brought up a very good point. Any time you hear something go 'bang' an explosion happened. The 'bang' is the result of rapidly expanding gases. If you look at unconfined gunpowder, it simply hisses and fizzes a lot, so that's a good sign that it's not an explosive.[/quote']

 

Hmm, I have never heared of octanitrocubane...

 

I see, thanks jdurg and woelen for all your information!

 

Cheers,

 

Ryan Jones

[YT2095]

a High VOD isn`t an indication of "Power" either, only Brissance. take ANFO for example, it has a comparitively Low DV but is extremely "Powerfull" as a "Heaving" Charge.

[woelen]

Hmm' date=' I have never heared of octanitrocubane...

[/quote']

Cubane is a hydrocarbon with formula C8H8. All C-atoms are arranged at the eight vertices of a cube. This takes three bonds for each C-atom and one bond per C-atom is left for the hydrogen atom.

 

What Jdurg refers to is cubane, with all its hydrogen atoms replaced by -NO2 groups, so this compound has formula C8(NO2)8.

 

@Jdurg: Has this compound octanitrocubane actually been synthesized, or does it only exist in the memory of computers in molecular simulation programs?

[jdurg]

I do believe it has been synthesized. I'll have to find the link to the article that mentions it, but when I do I'll post it here. (I know it had been thought of for a good long while, but I think it was within the past year or so that it was actually made).

 

 

EDIT: With a quick search on google, one can quickly find a source on chemsoc.org which mentions that the once thought to be 'unmakeable' octanitrocubane has in fact been synthesized. (I would post a direct link here, but some synthesis is mentioned there and that's a no-no). Basically, they tack on more and more nitro groups to the nitrocubanes they've made until all 8 groups are nitrated. One may also believe, therefore, that something like a tetraoctotetraazocubane may be even more powerful, but I would like to see if that's even possible to make.

[YT2095]

I`m familiar with cubane, it`s actualy claimed to be the most powerfull (non nuclear) explosive and very difficult to make, it`s similar to hexanitrobenzene.

 

And to think,once upon a time Astrolite was claimed to be the most powerfull

[RyanJ]

Thanks guys so tetraoctotetraazocubane is probably the most powerful explosive then?

 

Now onto one of my favourite areas - thermite!

 

Why does thermite work? What "types" of thermite are there? Does the ignition temperature vary according to the reactivity of the netals involved?

 

Cheers,

 

Ryan Jones

[pyromaster22]

well there are lots of different thermit reactions out there Fe2o3/al CuO/Al caso4/al to name a few. caso4/al is the hardest to light but the difference between reactivity is the least.. so perhaps theres a link there?. i dont make many thermites really.. theres not much you can do with them and they get boring very quickly.

[jdurg]

Barium metal is produced industrially via a BaO/Al thermite reaction. Pretty much ANY metal oxide and a more reactive 'pure and powdered' metal will react with each other.

[RyanJ]

Barium metal is produced industrially via a BaO/Al thermite reaction. Pretty much ANY metal oxide and a more reactive 'pure and powdered' metal will react with each other.

 

Thats true, its the subject of my Fact Of The Week In my signature

 

I've heared Copper Oxide thermite is pretty powerful too, apparently its more like flash powder!

 

I've also been doing some more research and it seems the difference in the reactivity of the metals involved has a huge effect onn it, if the product of the two metals reactivities is high then it wil get hotter and burn safter and the opposite if true for a lower product!

 

Cheers,

 

Ryan Jones

[YT2095]

Hmmm.. Unless I`m missing something, there seems to be a bit of a puzzel with Flash powder, the reactants are solids, the products are all solids too, unlike Gunpowder where there are solid and gaseous products.

so how come Flash Powder goes off with such a bang?

where does this Gas come from?

surely the net product would be of the same volume and mass of the starting reactants?

 

or has my brain slipped a gear today?

[RyanJ]

Maybe its the air expanding fast in the extreme heat?

 

Cheers,

 

Ryan Jones

[rthmjohn]

Does the powder itself go off with a loud report? I believe that in order to produce a report, the powder has to be confined to a closed container (preferably a tiny plastic bottle). The reaction of the powder itself releases LOTS of heat. This rapid change in heat in such a small container creates a tremendous rise in pressure that's almost instantaneous. Like RyanJ said, it is the air in the container that creates the blast.

[YT2095]

ok, but given that the air in the container is quite a small volume, the sound seems to be disproportionately loud, how much Can air expand to upon heating anyway, it`s already a gas?

 

for instance, If I have a Suitable pressure vessel and ignite 1 gram of flash inside this, there will be expansion and pressure built up, now I then wait for the vessel to cool and open the valve, would any gas come out? I don`t think any should, unlike with Gunpowder where some of the product is a gas and so the pressure would remain until opened.

[rthmjohn]

ok, but given that the air in the container is quite a small volume, the sound seems to be disproportionately loud, how much Can air expand to upon heating anyway, it`s already a gas?

 

Well, air in a container can expand quite a bit. Using PV=nRT, which I'm sure you already know, I can give an example. So let's say you had a closed plastic bottle of capacity 20 mL and a fuse protruding from the top. You fill only 15 mL with flash powder so that the other 5 is just air (and close the container obviously). Let's say the initial T is around 24 degreesC (297 K) and the moles all the gasses in the container is about .05 mol. After we light the powder, the T almost instantaneously rises to, say, 260 degrees C (533 K, or 500 F, wich is about as hot as a household kitchen oven gets). Using PV=nRT (and using atm as the unit of P) we get P=[(.05 mol)(.082052)(533 K)]/.005L which means that P would equal 437 atm (437 times standard atmospheric pressure)! This very sharp rise to such an incredibly high pressure (combined with the high heat of reaction) creates a structural failure of the bottle which suddenly releases air (regardless of the small volume) molecules of very high KE creating pressure waves that translate into the loud report that you hear.

 

for instance, If I have a Suitable pressure vessel and ignite 1 gram of flash inside this, there will be expansion and pressure built up, now I then wait for the vessel to cool and open the valve, would any gas come out? I don`t think any should, unlike with Gunpowder where some of the product is a gas and so the pressure would remain until opened.

 

Well, obviously, if you let the air in the vessel cool to thermal equilibrium, the pressure will also be the same as the pressure outside the vessel, thus, the air in the container won't want to rush out of the vessel

[YT2095]

Hmmm.. that Might explain then, why some flash powder can be "dead pressed" and will merely just burn.

 

thnx for that

[bob000555]

Flash powder does not need confinement as demonstrated in this video that I found. It demonstrates a few of the most common pyrotechnic mixtures. One of my favorite things to do is fill a bottle with negative X poke a tiny hole in it an throw it in a lake http://video.google.com/videoplay?docid=5705524740871409535&q=flash+powder+whistle+mix&hl=en

[RyanJ]

Flash powder does not need confinement as demonstrated in this video that I found. It demonstrates a few of the most common pyrotechnic mixtures. One of my favorite things to do is fill a bottle with negative X poke a tiny hole in it an throw it in a lake http://video.google.com/videoplay?docid=5705524740871409535&q=flash+powder+whistle+mix&hl=en

 

Just be careful not to loose any fingers, flash powder is really touchy stuff in my limited experience. I've seen the stuff ignore without contact which is pretty scary to think about if your packing the stuff and it goes off while your holding it... the best advice is don't

[bob000555]

oh im not stupid enough to mess with flash powder its just a vid i found on google.

[RyanJ]

Its a pretty cool video and it shows just how severe the stuff can be I've made milligram quantities of certain flash powders (no instructions will be posted here by me) to study the effects of varying quantities of the components on the rate of reaction.

 

It was an interesting set of experiments I must say but anything more than milligram quantities is bad news if you ask me

[Gilded]

Hmm apparently I've been missing out on a great thread. Speaking of flash powder "unconfined", you shouldn't count on it not making a loud report if the surface is on is something that can be broken by the blast (duh). I had probably around a 10g pile on a plastic cover of an ice cream container or something, and when it went off and shattered the cover to pieces... well, it was loud.

 

Here's something related I did in the summer but only because I hate foreign apples with all my heart:

(Notice the kewl in the comment section.)

[bob000555]

They all get odd replys "hey pyro has it got nitroglycerine" any way im suprised you didnt get a dust explosion with that flour one.

[Gilded]

The flour ones shown beneath that one are not from me but from a user named PyroTechnix. He seems to know what he's doing, if that can even be said when dealing with over an ounce of flash powder.

[woelen]

To my opinion it is quite insane to use more than a few grams of flash powder. I do not advice against making such powders, but I really urge anyone who intends to do so to carefully study the chemistry and the risks of it. You would not be the first one to loose limbs (or more).

 

Another very nasty risk is the risk of self-ignition on storage. Some powders (most notably sulphur-based) can ignite after weeks of storage. Also certain metal-compositions (most notably with Mg) can ignite spontaneously, especially if they become a little humid.

[Gilded]

Storing any flammable powders in great amounts is generally a bad idea. The only one I've had for a longer period of time was a small batch of very crappy BP meal.

 

Anyhow, reading through the past posts I'm shocked to see that pyrotechnics is forbidden in Netherlands considering their other policies concerning drugs, prostitution etc. are quite liberal.