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Dany
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A rare but interesting method for enhancing detonation performance
Dr Vitally PEPEKIN from the N. Semenov Institute of Chemical Physics, Moscow, Russia published and interesting paper dealing with detonation
performance of composite explosive. In his paper, PEPEKIN tried to prove both experimentally and theoretically that using dense organic oxidizer with
dense organic/inorganic fuel can enhance the detonation performance of an explosive system. The oxidizer used by him is
Bis(2,2,2-trinitroethyl)nitramine (BTEN) and Bis(2-difluoroamino-2,2-dinitroethyl)nitramine. Also, Various fuel are used like HMX, Benzotifuroxan
(BTF), aluminium powder, carbon and ultra-fine diamond. Although, some of the "fuel" cited above are true powerful high explosive (e.g., HMْX
& BTF), but their oxygen balance is negative (OB= -21.6% and -38.1% for HMX and BTF, respectively), and consequently they are considered as fuel
with respect to BTEN which has positive oxygen balance (OB=+16.5%). both BTEN and it's fluorine analogue were mixed with different proportion of the
fuel and were used to measure detonation velocity and metal acceleration ability. Both theoretical and experimental work confirm that detonation
properties are enhanced which is not surprising. We all know that mixing the proper material so as to make an explosive with nearly zero oxygen
balance enhance the detonation performance. Amatol is an example where TNT (negative oxygen balance) is mixed with ammonium nitrate (positive oxygen
balance) so to produce a mixture where the excess non-oxidized detonation product of TNT can react with excess oxidizing product of ammonium nitrate,
the net effect is enhancing detonation performance. What is really important and new in this study is the effect of adding carbon and ultra-fine
diamond. BTEN is mixed with only 7% by mass carbon or ultra-fine diamond but the heat of detonation is increased by 250 kcal/kg relative to pure BTEN.
what is more important is that the mixture of BTEN/carbon increase the velocity of a steal plate by 100 m/s while BTEN/diamonds by 140 m/s. the author
explained the enhancing acceleration ability by the reaction of carbonaceous material with excess oxidizing product of BTEN. also, he pointed out that
diamond can enhance acceleration ability by undergoing exothermic phase transition in the detonation wave. This method of adding energy to
detonation wave is rare and interesting because one can search different material that can undergo exothermic phase transition and enhancing
detonation energy without the need to added the energy to the pure explosive molecule because it will probably increase the sensitivity.
i'd love to know If any one of the member can propose such solid that can undergo exothermic phase transition . The energy added by such
transition should be fast, because if it were slow, this energy will be added downstream of the detonation wave (behind the chapman-jouguet plane).
According to detonation theory, any energy added behind chapman-jouguet plane (in the rarefaction wave) do not contribute to the energy of the
detonation wave.
For more information on this study read:
"DEVELOPMENT OF HIGH EFFICIENCY ENERGETIC EXPLOSIVES", Vitally PEPKIN, 27th International Annual Conference of ICT, June 25 - June 28, 1996,
Karlsruhe, Federal Republic of Germany.
Dany.
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Microtek
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But what, if any, is the correlation between plate acceleration and brisance with these methods? In my opinion, the most useful aspect of high
performance HEs is their ability to shatter, and I suspect that this strategy would give high blast, but low brisance.
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Dany
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From what i understand from the study, is that the calculated detonation velocity is higher for BTEN/C/diamond than that of pure BTEN which prove that
the energy is added in the detonation wave and hence you have an increase in detonation performance in term of detonation velocity and brisance
(Pcj). The formation of more gaseous product (from the oxidation of carbon with oxidizing product of BTEN) enhance the acceleration
ability. I believe that the exothermic phase transition energy is given off in the detonation wave and not in the late gaseous expansion of detonation
products (like aluminized explosive).
Dany.
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hossam6006
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| Quote: | | I believe that the exothermic phase transition energy is given off in the detonation wave and not in the late gaseous expansion of detonation products
(like aluminized explosive). |
I belive that too.
Dr_Pind noticed similar effect when mixing AN:UN at 25:75 ratio.
http://parazite.nn.fi/roguesci/index.php/t-131-p-7.html
this is also the case when burning H2 + O2, when zero balance is achieved much better better performance was noticed
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Motherload
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Combustion is an entirely different thing.
Better O.B. doesn't necessarily mean better performance.
Eg. PETN vs. ETN
Also if the O.B. is negative ..... (O2 being the limiting factor)
1 mole O2 will net 1 mole of (gas) CO2 @ a higher temp in a balanced condition.
vs.
1 mole O2 will net 2 mole of (gas) CO @ a lower temp in a negative O.B
Scenario one probably has higher energy output but scenario two probably has higher detonation pressure.
I wonder if the gain in 40m/s form carbon to diamond is just purely based on higher density and not phase transition.
40m/s just doesn't seem significant enough to merit an exotic phenomenon 
[Edited on 29-8-2013 by Motherload]
"Chance favours the prepared mind"
"Fuck It !! We'll do it live !!"
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Dany
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In general composite explosive having near oxygen balance have better performance than the pure separate component. yes of course, performance is not
only a factor of oxygen balance, but also density, heat of detonation, heat of formation etc...
Although 40 m/s is not a huge, but it give us idea so as to search other inert solids capable of exothermic phase transition , so any idea?
Dany.
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Marvin
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Energy from phase transition sounds a bit woolly. Diamond will not support a detonation wave on it's own, so it seems fair to say that it contributes
less energy to the det wave than the explosive it is displacing. To me this suggests the effect depends on local hot spots, the same mechanism as
microbaloons and the reason mercury fulminate dead presses. They may also act to different degrees as opacifiers but I'm not seeing the magic.
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phlogiston
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Any such material capable of exothermic phase transition will be in a metastable phase.
How about the explosive allotrope of antimony? Granted, it is very sensitive and therefore impractical/dangerous, but for experimental purposes, i.e.
to gather additional evidence for this concept, it might be possible to test it.
-----
"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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Dany
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Hello Marvin,
first nobody said that diamond will support a detonation wave. It is well known that shock/detonation wave can induce phase transition when
interacting with solids and especially metals, and diamond is not an exception. What is clear from the publication is that diamond "reacted" during
the reaction. this is evident from experimental calorimetric data, which show an increase in detonation energy. also, what is impressive that
according to PEPEKIN, adding diamond to the explosive charge does not increase sensitivity despite the abrasive properties of diamond.
Dany.
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Dany
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Nice idea phlogiston, try to post references to these metastable allotrope of antimony, so we can discuss more deeply in this subject.
Dany.
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Ral123
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I rely only on liquids for good mixing that would allow high velocity of two non explosive components. I mixed NA/DNT once and it was similar to EGDN.
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Dany
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Unfortunately, it turned out that the metastable antimony although interesting, but the heat produce when the sample undergoes the exothermic phase
transition is very small (20 cal/g). 20 cal/g is one order of magnitude smaller than the smallest heat of detonation of virtually any chemical
explosive. So if the energy added is fast enough to be coupled to the detonation wave no appreciable effect will be noticed on the detonation
performance.
video on the exothermic phase transition induced by friction with a knife:
http://www.youtube.com/watch?v=k4IABmgd968
also an attachment of a study on the properties of explosive antimony (heat of phase transition, density...)
Dany.
Attachment: On the Explosive Semiconductor-Semimetal Transition antimony.pdf (382kB)
This file has been downloaded 902 times
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Motherload
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That seems like the "explosive" Allotrope of Sb in the video.
The most stable allotrope ..... "metallic" Sb doesn't do that..
Diamond is the most stable allotrope of C.
What is the proposed phase it transitions to ?
"Chance favours the prepared mind"
"Fuck It !! We'll do it live !!"
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Dany
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Diamond crystals may contain strain energy that can be liberated by shear forces. We know that the soviet union has performed studies on nano-diamond
based high energy density materials. The same materials is being investigated by Dr Betsy RICE from the U.S army research lab. watch this conference
for Dr. RICE where she talks about nano-diamond.
http://www.youtube.com/watch?v=GftyIvDvqpw
Dany.
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Ral123
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Lol, so much about some fancy diamond fuel. I'm sure some cheap ass aluminium will beat it's performance.
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Fantasma4500
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by brisance what i know (understand) is that the more perfect OB, the higher the brisance
i have seen it mentioned that this is the reason that EGDN is so brisant, because it has chemically OB 0
i would understand that adding Al to ETN (94.6 - 5.4 IIRC) would increase its performance, but surely if there was a solvent for Al that might be used
instead, as it would get more throughly mixed up
one could try making decent golden powder with KNO3 and ascorbic acid, without mixing them both wet, this is very weak compared to pretty much any HE
similar is seen with armstrongs mix when mixed wet, the performance increases
the ultimate in armstrongs mix would be to dissolve red p in NaClO then recrystallize both NaClO and red p from that, but that would give alot of
impurities
i think its useful to perspectivate to slower and easier to observe reactions, such as combustion difference with golden powder, compared to high
explosives, as you cant get very visual differences from it, its more simple to understand..
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Dany
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Antiswat, 2 important thing must be corrected in your comment:
1-the brisance of an explosive materials do not depend only on OB. Density is another more important factor. remember that detonation pressure (which
represent brisance) is proportional to density squared, so increasing little the density increase considerably the detonation pressure. so brisance as
well as other explosive characteristic depend on many factors not only one.
2-the addition of aluminium don't increase performance of explosive. What we understand by performance is detonation pressure and velocity.
experimental findings shows that aluminium decreases little Dcj and Pcj but increase the blast effect of an explosive charge and
this by what we call afterburning (oxidation of aluminium with ambient oxygen). The reason why aluminium decreases the detonation performance is that
aluminium don't have time to react in the detonation wave, so it will behave as an inert solid. the detonation wave will compress the aluminium and
thus looses energy. The enhancing blast effect is seen at relatively large expansion of gaseous products. at relatively small expansion volume (up to
7 time the volume of the original charge volume) there is a decrease in the acceleration ability of aluminized explosive compared to non-aluminized
explosive, for example the Gurney velocity of tritonal (80/20 TNT/Al powder) is 2.32 km/s while gurney energy of TNT is between 2.38-2.44 km/s. this
Gurney energy is a measure of the ability of an explosive to accelerate metals and it is obtained by the cylinder expansion test (for experimental
value of Gurney energy see "LLNL Explosives Handbook: Properties of Chemical Explosives and Explosive Simulates" revision 2 (1985).
some studies mention a small increase in detonation speed when nanometric aluminium is added to TNT while other report mention the contrary effect.
Although one can think that the nano-aluminium is much more reactive in the detonation wave than the micron size aluminium this effect is not seen
which is due to thicker aluminium oxide on nano-aluminium than the micron-size analogue.
Dany.
[Edited on 31-8-2013 by Dany]
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papaya
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What about addition of endothermic compounds (non-explosive), is there any chance they will "atomize" contributing in energy instead of exploiting
the heat of phase transition?
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Dany
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Quote: Originally posted by papaya  | | What about addition of endothermic compounds (non-explosive), is there any chance they will "atomize" contributing in energy instead of exploiting
the heat of phase transition? |
Papaya, if you can give us some examples with references before any discussion.
Dany.
[Edited on 1-9-2013 by Dany]
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papaya
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Not that I'm familiar with this topic and can provide references, rather the idea came into my mind that many compounds exist with positive enthalpy
of formation, like stable naphthalene (ΔfH°solid =77. ± 10 kJ/mol, http://webbook.nist.gov/cgi/cbook.cgi?ID=C91203&Mask=2) and unstable acetylene(+226.73 kJ/mol)/-lides (that being the cause of their
explosibility), so why this energy cannot be exploited? Of course they need to decompose into elements for this and the condition of detonation may or
may not be appropriate for that.
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Dany
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As you said papaya the condition of detonation is not appropriate for these carbonaceous endothermic compounds. Cuban itself has one of the highest
known heat of formation for a hydrocarbon which is approx. +542 kj/mol (Kybett, Carroll, et al., 1966) however cubane can not be added to explosive to
enhance detonation because simply it will not react in the time scale of detonation. Weak bond are needed for releasing energy stored in molecule
which we calle it a trigger linkage (e.g., N-NO2 bond in nitramine). Carbon-carbon bond are strong and cannot be easily broken. Nitrogen-nitrogen
single and double bond are easily broken, this why azides for example derive all their explosiveness from their positive heat of formation
(endothermicity). So purely carbonaceous compounds are not useful for enhancing the detonation performance in the reaction zone, but they can be used
to enhance blast effect by afterburning mechanism with ambient oxygen.
Under shock wave, benzene and can be transformed to other aromatic polycyclic hydrocarbon. check this study:
http://ir.nul.nagoya-u.ac.jp/jspui/bitstream/2237/15855/32/o...
Dany.
[Edited on 1-9-2013 by Dany]
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papaya
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Thanks Dany, now I see what I omitted - small activation energy is needed in addition to endothermicity, and in this case compound becomes explosive
itself! What an unfortunate conclusion for me. Cool bullet synthesis is described in that paper btw.
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Fantasma4500
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sorry @Dany for late reply, i forget many times too often to search my own name and find mentionings of me in threads ive been around..
but yes i did forget to mention density, it means alot in brisance, surely does.. (:
actually, i think ive heard something around aluminium and explosive material before, i did also read that it will increase the heat, ANAl - Ammonal
was used as examble about this, and by the very simple logic of how gasses behave heat equals expansion of gasses, but if the detonations wave is
faster than the combustion of aluminium, well then i guess it wouldnt matter much if anything at all
it would actually decrease the brisance, if its acting as filler..
i guess where it pays off is as the total gas expansion and perhaps as thermobaric effect (i guess for any serious thermobaric effect you would need
to drown it in aluminium)
i just wonder what the density of NI3 is, as i see it its relatively brisant, something that has gone unseen before, as its density is quite unknown
it brings me to think: how the hell do you measure the density of a contact explosive??
offtopic i know, but im quite glad about the thought of having permission soon to make as much NI3 'as i can keep control of'
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Dany
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Antiswat,
This what Jimmie OXLEY (http://www.chm.uri.edu/index.php?dest=display_abstract&b...) tell you about NI3:
Nitrogen Triiodide NI3, due to its low brisance and high sensitivity, has
no practical use in the energetic materials community.1 However, it has remained
a favorite of teenagers due to its ready synthesis. This is probably the reason
its synthesis is also included in the do-it-at-home explosive literature.6 Iodine
crystals are added slowly to concentrated ammonium hydroxide. A brownish-red
precipitate forms. The precipitate is filtered and washed with alcohol and ether.
This material can be handled only when wet because when dry, the slightest touch,
such as a fly, can set it off.
synthesis: I2 + NH3OH --> NI3
decomposition: 8 NH3.NI3 --> 5 N2 + 6 NH4I + 9 I2
A recent incident during a Hollywood talk show points upthe ease with which NI3 can be prepared and transported. One can envision a cotton sweater
saturated with the wet nitrogen triiodide acting as a wireless, metal-less initiator to some more brisant energetic material.
Read also the file attached, it is about non traditional explosives
For the density of NI3, i didn't make any search for experimental crystal density but the density of this small molecule can be
theoretically calculated using for example DFT methods.
Dany.
Attachment: UKTERROR-1.pdf (90kB)
This file has been downloaded 667 times
[Edited on 20-9-2013 by Dany]
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caterpillar
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Well, in that case one may try C2H2- liquid, solid or dissolved in something. And what about mixture of N2O and C2H2? Both are endothermic compounds.
Women are more perilous sometimes, than any hi explosive.
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