Metal additives in dynamites

[Bert]

Typical industrial active base dynamites were often compounded with ammonium nitrate and various cheap organic fuels/absorbents such as wood meal. The ammonium nitrate was said to lower the temperature of explosion compared to the alkali nitrates used in the same fashion, and particularly compared to chlorates or perchlorates. (this information based on Naoum's NG & NG explosives). This lower flame temperature was desirable for many applications, particularly for mining where the lower temperatures were less likely to ignite methane and clouds of flammable dust. ("permissible" explosives)

I am interested in conjecturing how to produce the OPPOSITE effect to these permissible explosives- A "dynamite" with a large hot flame, perhaps even capable of giving a visual effect similar to Al/perchlorate flash powders. I theorize that the replacement of part or all of the organic fuel/absorbent used in conventional dynamite mixes with Aluminum flake might produce this effect. Further, I suspect that Ammonium nitrate might be unsuitable as the active base oxidizer for such a formulation due to the lower flame heat attributed to ammonium nitrate active base dynamites... If these won't ignite methane air mixes or coal dust clouds, they might not ignite Aluminum powders effectively either.

To produce such an effect, I hypothesize a mix such as this:

Nitroglycerine----------------50 %

Nitrocellulose------------------3

Potassium perchlorate---------35

Fine flake Al-------------------12


(As the perchlorate and Aluminum would have less ability to hold liquid NG without exudation, it seems it might be desirable to use NG gelatinized with NC)

Has anyone experience with such a mix, or any background on NG based HE's with metal fuel additives? Can anyone think of any stablity issues with such a mix?

[vulture]

If these won't ignite methane air mixes or coal dust clouds, they might not ignite Aluminum powders effectively either.

Yes, but methane air mixes and coal dust clouds have a small explosion range and they have pretty high ignition temperatures. The aluminium powder would be mixed with the AN itself and actually sensitize the AN. Like I pointed out in another post, extreme caution is required, because AN is an acidic salt. Basic stabilizers will make matters only worse because they'll decompose the AN to NH3, which might than react with the Al, but I'm not sure about that.

I believe Brainfever has done a bit of testing on this subject here (http://ci.cambridge.md.us/brainfever/NG5NC5Al-small.jpg).

[Boomer]

I once read about blasting gelatine with aluminium added for higher energy. It decreased Vod slightly but increased gas pressure and lead block expansion considerably (>700ml IIRC).

Another thing I head was that tritonal (TNT/alu) gives a considerable flash at detonation in the night. I doubt that alu with AN is flashless, but better look in the exploding target threat, it was discussed there. Anyway, alu with a metal oxidisers will be brighter - but is K/Na-NO3 not enough, does it have to be perchlorate?

[Mr Cool]

Heavily aluminised explosives do not generally give reliable results in lead block expansions due to increased errosion at the higher temperatures...

I wonder if you could just make up a normal flash powder and only slightly moisten it with NG in order to make it cap sensitive?

[Bert]

I once read about blasting gelatine with aluminium added for higher energy.
Could you dig out the source? I assume this would be a blasting gelatine with ONLY some additional Al added, the Al reacting with the water vapor from the gelatine's detonation as it does in TORPEX?

As far as needing perchlorate rather than an alkali nitrate, I have no idea. But the higher density of the perchlorate is attractive, and the issue of reactivity of nitrates with fine Al should the mixture become damp would also be avoided.

The brainfever site shows a BURN test of an Al/NG mix. No detonation is described? The site had exceeded it's bandwidth allotment shortly after I accessed it.

As far as simply adding NG to standard flash, the information I have on detonating mixes similar to flash usually call for a much lower ratio of metal fuel to oxidizer than flash- around 90:10 rather 70:30. The addition of NG would change the Oxygen balance in this direction of course.

As a separate issue, fumed silica (cab-o-sil, Cabot M-5) can be used to "gel" liquids. It is a very fine fumed silicon dioxide- I have seen the mix of silica and Al claimed to function as a thermite if the reactants are finely enough powdered. This leads me to speculate that if NC in excess of the amount that could be held by a flash type mix without exudation were used, an addition of cab-o-sil might result in a non-exuding mixture while actually contributing something to the Oxygen balance, rather than taking away from it as does wood pulp or other hydrocarbon absorbents. Any comments on the feasibility of this idea? Has anyone ever TRIED to gel NG with fumed silica? Cab-o-sil could be more efficient than diatomaceous earth for the purpose.

[Marvin]

Bert, I'm not sure what you are trying to achieve, you want it to look like flash and not be flash, I'm not following. I suspect the way the altered oxygen balence texts were going, would be to use the explosive to distribute the metal powder into the air, and have it burn in that asa sort of fuel air explosion. I think wrench was thinking along similar lines recently. As for fumed silica, this sounds chemically more like a step backwards to kieselguhr. I cant help but think the impurities are going to ruin the det wave properties of the jelly, not that I think this matters to you, but I still dont see why you need a 'classic' det wave before the flash as opposed to what Al/Perc flash would get you anyway. If you wanted to go slightly less orthodox idea, you could ditch NG/NC alltogether, mix fine Al and a heavily chlorinated solvent like carbon tet and detonate that.

vulture, my understanding is that Al mixes are not stabilised by making them basic or adding a base, they are usually stabilised by adding something like boric acid, Al being less sensitive to mild acid than to mild base and that formation of base is usually the big threat. My main objection would be the way metal powder mixes with AN tend to ignite on contact with water, and that under normal humidity levels outside AN is deliquescent. My secondary objection would be the way metal powders tend to reduce nitrates to ammonia (more of a problem with AN than alkali nitrates I would think), though the boric acid should stop this being a problem on longer term storage. On balence staying away from AN/metal is a better general rule IMHO.

[vulture]

vulture, my understanding is that Al mixes are not stabilised by making them basic or adding a base, they are usually stabilised by adding something like boric acid, Al being less sensitive to mild acid than to mild base and that formation of base is usually the big threat.

Yup, but AN being more acidic and hygroscopic than boric acid, you always have a problem. Either you add nothing and have acid reacting with Al, or add basic stabilizers and you have other nasty side reactions.

I agree that AN/metal powders should be avoided unless absolutely dried and sealed from moisture.

If you're using it in a mix with a large NG content, that would probably prevent side reactions, although degrading NG which produces NOx and/or HNO3 could ofcourse make matters worse.