ni3rtap
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anyone know power difference between Pb and Ag azide?
The lead salt likely has more "power" from the higher nitrogen content, however the silver salt likely has more self confining abilities. Didn't know
if anyone had experience with both?
As for the silver salt, I've never been able to light a small enough amount that didn't "crack" and dent the side of a soda can.
Also, It's very cool to look at the can after putting ~2mm dot on it and lighting it. Punches a clean hole and send bits of shrapnel through the
other side.
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Microtek
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The silver salt has slightly greater initiating ability, if that is what you mean by "power". It is also more sensitive, and darkens rapidly from
exposure to sunlight.
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Rosco Bodine
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The silver salt is regarded as being superior because of its chemical stability and initiating ability being comparable and actually superior. The
expense of the silver is the drawback for commercial uses, but for many military applications where the expense is a secondary concern to long term
storage stability, the silver azide is already used as a drop in replacement. The difference in costs for a per unit basis is not that significant
until really huge quantities come into consideration as would make the silver raw material more precious and costly for the demand. If you think
about it in terms of utility, the contacts on CPU's and memory modules and other critical electronics is 24 carat gold because functionality is more
important concern than is the expense. Silver is used as a material in electronics also because of the high electrical conductivity. And the resource
there for electrical applications is recoverable and recyclable, but with the silver used in an explosive it is a lost raw material which has been
available only as a finite resource in the first place. So the use decision would depend on the scenario and the munition, whether it is cost
effective to use the superior material or defer to the more economical, for both strategic as well as monetary reasons.
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Dany
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Quoted from [1]:
"Silver azide is sensitive to light, insoluble in water, and soluble in ammonia, from which it can be recrystallized. It is prepared from sodium
azide and solutions of silver salts (depending on the working conditions) as a cheesy, amorphous precipitate. It gives a very satisfactory
initiating effect which is superior to that of lead azide. Nevertheless, its practical use is limited, because of its high sensitivity to
friction, and because its particular texture makes the dosing difficult"
the superior explosive power of AgN3compared to Pb(N3)2 is also demonstrated in [2] by comparing the measured maximum
absolute acoustic level of silver and lead azide on a special drophammer test:
"Figure 2 shows the max. abs. acoustic level diagrams of silver and lead azide. The average value for silver azide is higher than the one for lead
azide, although the amount is lower. This indicate that AgN3 is a more powerful substance under the test condition applied in this
study than is Pb(N3)2..."
References
[1] Meyer, Rudolf; Köhler, Josef; Homburg, Axel, Explosives, 6th edition, WILEY-VCH, 2007.
[2] Klapotke T.M; Rienaker, M.C, Drophammer test investigation on some inorganic and organic azides, Propellants Explos. Pyrotech. , 26,
43-47, 2001.
Dany.
[Edited on 17-10-2013 by Dany]
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Ral123
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Why is the silver azide "more powerful" is this weight or volume basis? Is the compressibility taken into consideration?
Why is the silver salt more stable, what storage stability issues LA has?
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Rosco Bodine
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Weight basis is always the convention for comparison unless it is otherwise specified. The bulk density of the uncompressed material is an important
consideration along with the particle size and the ability of a compressed pellet to remain intact without crumbling and reverting to a less dense
condition of indefinite density. These physical considerations must be within acceptable parameters in addition to the chemical and temperature
stabiulity of any candidate material being considered for use as an initiator which includes silver azide along with all the other compounds which are
possibly useful. Having one property just right while the other properties are wrong will rule out the use of that material because of practical
considerations.
The silver salt is stable in storage without reacting and decomposing in the presence of atmospheric carbon dioxide and moisture and without reacting
chemically with brass and copper. There are forms of silver azide which have an assigned Mil-spec designation number and are made by very exacting
methods.
I have the data on some of the silver azide related material and will be posting it in the dedicated azide thread when my time allows for me to get to
it.
In early work with silver azide it was reported by some as being equally treacherous as silver fulminate, but continued study of the material
evidently found ways to tame the beast that it is and brought it into practical use, even though the semi-precious metal aspect would necessarily be
scale limiting with regards to the extent of its deployment and implementation. Silver Azide does definitely have niche applications and specialty use
where the cost is no deciding issue.
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Ral123
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So the Pb(N3)2 has almost infinite stability at STP, and the limiting factors for it's predictable behaviour are acids from the basecharge, in the
air, other metals etc? It's interesting that LA would react with copper and SA wont. But copper is ok for pressed TNP boosters right? Do you know what
is that turns silver azide from "treacherous" to predictable material?
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Rosco Bodine
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It would be my guess that the particle size and crystalline form is what would make the distinction about sensitivity for silver azide.
Precipitations can be accompanied by a generation of a static charge that remains as a "squeaky gremlin" residing in the dried colloidal material on a
filter. Breaking apart a clump of the dried material is like ripping adhesive tape from a roll and the static charge is sufficient potential
difference to initiate the material, from little more or only being gently touched. Likely at a certain state of subdivision and moisture content,
the newborn silver azide cries out with a bang when mama touches the baby. But that would be my best guess about its early bad reputation is static
sensitivity that is inherent to the material and not just external influences.
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