Sciencemadness Discussion Board

Metallic Low Melting Alloys and High Explosives

Sickman - 10-7-2006 at 00:27

Ther are several metallic, low melting alloys available that
have a melting point below 100°C. Some are eutectic others are not.

Some include:

Cerrobend®, made by Cerro Metal Products, is also known as Wood's metal, Bend alloy, or pewtalloy. Or even Lipowitz Metal in Europe.

It is a eutectic fusible alloy of bismuth, lead, tin, and cadmium, known for its low melting point of 70 °C (158 ºF). Molten Cerrobend can be held in an unprotected hand (though not without considerable discomfort).

It is named for its primary use as a filler when bending thin-walled metal tubes. For this use the tubing is filled with molten Cerrobend. Once the Cerrobend hardens the tubing is bent, the filler preventing collapse of the tubing. The Cerrobend is then removed by heating, often by simply boiling in water.

Cerrobend also has uses for making custom-shaped apertures for medical radiation treatment, and making metal inlays in wood.

A similar alloy is called Cerrosafe®. This non-eutectic alloy melts at 165 ºF (74 °C). Its main use is measuring gun chambers. When it solidifies it first shrinks, allowing its easy removal from the chamber. When it cools it expands back to the exact size of the chamber.

Alloys with even lower melting temperatures are Cerrolow® 136 and Cerrolow 117 that melt at 136 ºF (58 °C) and 117 ºF (47 °C) respectively. The Cerrolow alloys are eutectic alloys.

Their compositions are as follows:

Cerrobend Tin 13.3%, Bismuth 50%, Lead 26.7% Cadmium 10%

Cerrosafe Tin 11.3%, Bismuth 42.5% Lead 37.7% Cadmium 8.5%

Cerrolow 136 Tin 12% Bismuth 49% Lead 18% Indium 21%

Cerrolow 117 Tin 8% Bismuth 4.7% Lead 22.6% Cadmium 5.3% Indium 19.1% (source Birchon's Dictionary of Metallurgy London 1965)

Considering the various melting points of many high explosives and their sundry densities perhaps advantage may be taken in the use of metallic, low melting alloys; their tremendous density, and closeknit crystalline structure when solidified.

These alloys come with various properties depending on the alloy, some shrink when they solidify others expand and still others remain constant and true to their mold.

Other advantages of these alloys include the low boiling points of their constituents.

The following is a list of some high explosives along with
their melting points:

RDX 202°C
PETN 140-141°C (when pure)
Tetry 129.4°C
ETN 61°C
TNT 80°C (some souces give other figures)
TNP (Picric Acid) 122.5°C

The melting points of these or any other explosive may be errelevant from other than a safety or mechanical point of view.

Let us suppose we have a molten bath of say 1 gram of cerrobend, melting point 158°F or 70°C and we maintain a temperature just high enough to keep the alloy a liquid and to this we add PETN till we have a homogenous saturated "solution" of PETN and the low melting alloy.
And suppose we can overcome any mechanical problems stemming from the obvious differences in density of the two materials. And suppose this "solution" were solidified in this condition having PETN thoroughly, and homogenously distributed thoughout the mass of the alloy. And suppose this "high explosive/metallic, low melting alloy" ingot were capable of communicating a shock wave through itself to cause the complete detonation of the PETN there contained, when a sufficient detonater is used.

I know I'm doing allot of "supposing" in this thread, but the idea has intrigued me and I may very well investigate this line of thought with experimentation.

One thought I've had is that if this idea worked and the high explosive were completly high order detonated within the confinement of the alloy's compact crystalline structure, that the heat produced by the detonation very likely would be sufficient to flash boil the constituents of the alloy with their very low boiling points into a gaseous state, contributing greatly to the overall gas volume of the detonation. Not only that but these metals in their gaseous form would react with atmospheric oxygen or available oxygen in oxygen positive explosives releasing heat and further contributing to the expansion of gases.

Obviously, adding acidic explosives such as picric acid and styphnic acid to a low melting alloy(lead is present and so on) would be undesirable, unless for some reason the corresponding picrates didn't form. But with the explosives that don't react with the metals used in the alloy, such problems would be overcome.

Of course their are several factors to consider, even supposing that the mechanical trouble of difference in density of the explosive and metallic alloy were overcome and the materials may be mixed.

Some things to consider are what will the effects be if the explosive used is in a crystalline or molten form when being mixed with the alloy, which is basically more mechanical problems to think about.

That aside, I must also consider the effect of the alloy on the explosive upon solidification. Will the alloys crystalline structure crush the explosive within it, perhaps causing detonation? Or supposing that wasn't a problem, how would the explosive be distributed throughout the structure of the alloy?

There are several questions to be answered. Would this "high explosive/metallic, low melting alloy" ingot be capable of detonation, or would the structure of the alloy interfere with this process? Perhaps the dense structure and extreme confinement of the alloy would enhance the detonation. What about detonation velocity? What about shock sensitivity; if the ingot were dropped on concrete and so on. Just several things to think through and of course some things may be assumed, but others cannot be understood without careful and observant experimentation.

Any thoughts on this topic are welcome.:D

[Edited on 10-7-2006 by Sickman]

[Edited on 10-7-2006 by Sickman]

YT2095 - 10-7-2006 at 01:12

let me see if I have this clear, you`re considering using low MP metal as a Plastisizer for HE?

I think you`ve already identified the main problems with that, 1) the density is Real issue 2) metals contract on cooling, and so if it didn`t detonate right away, it would be very unstable to fracture.

JohnWW - 10-7-2006 at 02:59

Where can I find Birchon's Dictionary of Metallurgy London 1965? Is it available as an ebook?

Marvin - 10-7-2006 at 04:44

Well, 3 more problems off the bat.

1, Assuming the explosive will dissolve in the molten metal.

2, Assuming an alloy with a low melting point will be easily vapourised.

3, Assuming that adding an inert that will suck energy from the explosion and turn to vapour will increase the effect.

YT2095 - 10-7-2006 at 04:54

I notice most of these materials in the alloys you mentioned are also very Heavy, Cd,Pb,Sn,Bi etc...
that would make your density problem quite profound.
if you Don`t mind a little extra cost, you could go the Galium Alloy route, It`s Much lighter and you can more or set your own MP for it, right down to -20c !
it also works as a good wetting agent, so mixing maynot be all that much of a problem.

Just a thought;)

froot - 10-7-2006 at 07:14

I enjoy reading ideas from people that 'think out the box', even if they don't work. Not often, but somtimes they hit and it's usually a major discovery.

What comes to mind when reading this is when they coat subjects for observation under an electron microscope with an extremely thin layer of gold. "If" (yes yes I know) one could divide the HE into the finest crystals possible and then coat them in one of those alloys much the same way they do with gold for EM's, then the HE could be 'compacted' together at a malleable temperature for that alloy to form the 'metallic/HE' composition.
Problem would be making sure it's uniform without air in it.
I think it's worth a try if the 'IF' part is possible.

neutrino - 10-7-2006 at 07:29

I'm confused about this idea. Are you trying to make a true solution or just a mechanical mix?

>Assuming the explosive will dissolve in the molten metal.

If you're going for a true solution, this sounds like the biggest problem. The only things I’ve ever seen that can dissolve in metals are elements. A metallic element can dissolve in a metal to make an ordinary alloy. A nonmetallic element can dissolve in a metal to form an alloy (e.g. C in Fe makes steel). But I’ve never seen a compound dissolve in a metal.

If you only want a mixture, froot's idea is worth a try. Or you could try mixing powdered alloy and powdered explosive, adding some heat and pressure, maybe squeezing out any extra molten metal from in between the explosive grains...Sounds like it would be worth a try.

[Edited on 10-7-2006 by neutrino]

Sickman - 10-7-2006 at 11:18

Quote:
Originally posted by neutrino
I'm confused about this idea. Are you trying to make a true solution or just a mechanical mix?

>Assuming the explosive will dissolve in the molten metal.

If you're going for a true solution, this sounds like the biggest problem. The only things I’ve ever seen that can dissolve in metals are elements. A metallic element can dissolve in a metal to make an ordinary alloy. A nonmetallic element can dissolve in a metal to form an alloy (e.g. C in Fe makes steel). But I’ve never seen a compound dissolve in a metal.

If you only want a mixture, froot's idea is worth a try. Or you could try mixing powdered alloy and powdered explosive, adding some heat and pressure, maybe squeezing out any extra molten metal from in between the explosive grains...Sounds like it would be worth a try.

[Edited on 10-7-2006 by neutrino]



In reply to if the HE would form a true solution with molten alloy, I don't know.

The problem here as far as information goes is that there seems to be absolutly nothing in the literature about such mixtures. Prabably because the concept itself is hard to come by as most people when they think about the melting point of the common metals being so high that any high explosive would likely decompose on contact with molten metal. However because the melting point of these alloys is so very low that particular aspect is overcome.

Anyway today I have conducted an experiment that gives me further encouragement on this topic:

Into a molten bath of cerrobend was added finely powdered corn starch. I decided to use corn starch as it is organic and has a similar molecular composition of some high explosives with the obvious exception of having no nitro groups. A metal spoon was used to stir and immediatly it was realised that even though the starch was insoluble in the metal alloy (which is what I expected) the starch is easily wetted by the alloy. So to assist this process a lid was put on the bath along with a large amount of starch and the mixture was shaken vigourously for 60 seconds and allowed to cool and solidify.

The best of what I hoped for has been realized, the starch upon cutting the ingot in half was very thoroughly integrated into the crystalline structure of the alloy.

The new composition has new characteristics. Including relatively less density, a duller yet light colored apperance that could be described as ashy. Small flakes of the composition are brittle. When a large chunk of it is dropped on concrete from a hieght of six feet the chunk is not broken or dented in any way. When washed with water it takes on the appereance of wet concrete and dries very quickly. But is however insoluble in water. The composition can be scratched with a knife, but is still much much harder than Lead. When reheated the composition melts at the same temp as the pure alloy does, so it would seem. And the starch does'nt rise to the surface but stays wetted and dispersed.

So anyway the first step has been taken, the next may very well include a low explosive then moving on eventually to a high explosive.

Besides mixing powders with the alloy I have also considered making chunks of compressed or cast explosive and then mixing the chunks into the alloy, to distribute them here and there throughout.

There is much research that can be done in this area I believe!

Also I would like to point out that the density of this material is tremendous in every way.

neutrino - 10-7-2006 at 13:31

Can you post a picture or two of the cross-section? I would be interested to see that.

Sickman - 10-7-2006 at 21:40

Quote:
Originally posted by neutrino
Can you post a picture or two of the cross-section? I would be interested to see that.


Unfortunately, I don't own a digital camera, nor have I ever.
Last time I looked at them at the store a good one cost 300 to 400 USD. Although I do see the convienience of owning one. So I guess I will put it on my Christmas wish list.

However I do own a scanner and I will see what I can do with that.

Will someone please tell me what picture format is exceptable for this forum as I have never posted pictures on the internet before.

Also tonight I am planning on doing a few more experiments
with the cerrobend alloy, as I have a few pounds in my stewardship. I plan on being more scientific this time and posting exact weights of materials used so there is no confusion and others may wish to reproduce some of the experiments.

I will do the cerrobend alloy + finely powdered corn starch again, this time paying attention to the ratios.

Also I plan on doing a cerrobend alloy + parrafin wax as I am thinking this may give me an idea of how the alloy behaves in presence of another molten component. Hopefully from this experiment I will get an idea of how a molten explosive such as TNT or ETN would blend and behave with the alloy.

My feeling so far from what I have seen in my first "unscientific" experiment was that the more powdered corn starch that is added to the alloy the more brittle it becomes. However this alloy seems to be slighlty brittle any way because of it's high bismuth content. Allthough like I said when it is dropped on concrete in a chunk it has no problems(the alloy +corn starch).

This brittleness may not show itself in the case of the parrafin wax experiment, but at this point that is just speculation.

I have come to believe that the great differences in density is a problem that can be overcome with a little effort. I also believe that any problems with brittleness may also be over come by adding materials and explosives that are not finely powdered but more granular to give the alloy a greater wall thickness between components. I guess you could say by adding explosive "nuggets" to the alloy and thoroughly dispersing them.

I liked the idea of Nuetrino to use a powdered form of the alloy and mix it thoroughly with what ever form of explosive may be desired. I think this would have about the same results as my shaking method to get the material completly wetted by the alloy.

I believe the next step towards eventually using a high explosive after these initial experiments to get the mechanics figured out, would be to add a low explosive to the alloy.

A couple that come to mind would be a black powder substitute in grain form and also basic lead picrate.

From these two (and the black powder would be first) I would get an idea if the solidification process causes ignition/detonation etc.

As the alloy has such a low melting point and it is a liquid I feel that thermal decomposition and friction should not be a problem for the materials I named, when being mixed.

Some may wonder where am I going with these experiments?
What makes me think these will be useful in any way even if they work as I may have hoped?
Well I can say now that they may not end up with much of a military use because of the relative costs of the low melting alloys (around 10 USD per kilo). However, because I don't work for the government and I'm more interested in the science and grandeur of explosives rather than necessarily their applications in war. I guess I can focus my energies on whatever the hell I won't!:P

The truth is I don't know what will happen yet, maybe these compositions will have outstanding properties and explosive power, or maybe they won't work at all, but one things for sure 10 USD per kilo won't put us amatuers out of business any time soon!;)

I will post pictures if I can get my scanner to work for that purpose!

neutrino - 10-7-2006 at 22:00

As long as it can be viewed from a standard PC and doesn't take up too much space, it's fine. In other words no bitmaps. Jpeg, gif, png, etc. are fine.

Could you borrow a camera from someone? Many people have them these days.

Sickman - 11-7-2006 at 01:34

Upon further experimentation, I have made some observations and come to some conclusions.

First off the experiment of reacting equal amounts by weight of cerrobend alloy and parrafin wax resulted in a most undesirable result. The two of course did not mix with each other. Unlike the unscientific mixture of starch and alloy that was based on the alloys ability to wet the starch. It would seem at least in this case that a liquid doesn't wet a liquid, which of couse can be expected unless they are miscible,but we are talking about a metal alloy and wax, it just doesn't work.

It is a conclusion of mine, based on the established facts of experimentation that most likely a molten high explosive would likewise not mix with said alloy.

Secondly, more information has revealed itself about the nature of mixtures of cerrobend alloy and powdered corn starch. Which can give an idea of how a high explosive powder may behave with the alloy, at least from a mechanical point of view.

I must say I'm a bit disappointed in some of the results of the experiments. However the newly dicovered information has given me some new ideas along side the old.

Upon further testing it is now believed that my original unscientific experiment, mixing cerrobend alloy with corn starch was likely in a low ratio of 3-5% corn starch by weight,
which results in a hard, only slightly brittle composition.

The rate at which this hard, only slightly brittle material becomes much much more brittle upon further addition of starch is 5-15% by weight until finely at 25% by wieght the material is an extremely heavy grey powder not a hard metallic ingot at all.

I'ts amazing to me how you can go from such a hard, only slighlty brittle alloy to a fine soft powder in just a few percents?

That is the facts though!

I would very much like to know if an explosive composition only containing 3-5% by weight of explosive is capable of detonation at all?

However, inspite of these facts this heavy grey powder has given me a few new thoughts.

Supposing around 80% explosive, wetted with 20% cerrobend alloy were pressed and detonated! Would the alloy be instantly flash boiled into a gas contributing greatly to the explosive effect, likely an adavantage over aluminized explosives?

I think that it is very likely that the alloy would flash boil considering the boiling point of each metal and the common temps at which most high explosives detonate.

Perhaps my experiments will turn towards this effect alone, if a 3-5% can not be detonated at least when it comes to finely powdered explosives.

If a 3-5% could be detonated and it produced enough heat to gasify all the 95-97% alloy this would be a very interesting effect. Of course this is just wishful thinking if it cannot be detonated.

HOWEVER I FULLY INTEND TO DO TESTING ON THIS GREY POWDER, WHICH WOULD SEEM AT LEAST TO BE DESIRABLE WHEN A HIGH EXPLOSIVE IS USED IN PLACE OF CORN STARCH.

Like FROOT said it is some times enjoyable to think about someones idea that is "thinking outside the box" which perhaps I too often do.

Some times it pays off, lots of times it does'nt, but still if my grey powder is an improvement over aluminized explosives I'll still be happy! If not oh well; back too the drawing board!:D

Swany - 11-7-2006 at 11:21

Most commom high explosives detonate at 3000C+, but they only retain a flame for milliseconds, if even. Granted, the low specific heat capacity and melting point of your metal addition may allow vaporization, but they are taking energy away from the decomposition that is used to heat gasses thus adding to the explosive effect.

I doubt a 5% mixture can be detonated, however I encourage you to try. To illustrate my point, you can place organic peroxides in blenders if and only if you have a suitable amount of water, which acts as an inert filler.

Like dissolves like prevents metals from being alloyed with organic compounds. Perhaps some organometallic explosive compounds would dissolve better. I can think of a salt where copper is chelated by an aminoguanidine deriv., which I belive is explosive.

Chris The Great - 11-7-2006 at 19:44

The thing that gives Al explosives their boost in blast is the massive energy release and corresponding extreme temperatures. Then, the Al oxides will condense out as the gas expands and cools, prolonging the already increased pressure effect by reheating the gas. The only real way to improve them is to use something like boron or beryllium instead of Al, because of the even greater energy release.

Now, what you are doing is potentially adding more gas to the mixture, but at the same time flashboiling the metal will consume a massive amount of energy. End result is you'll end up with less gas volume, since the resulting gas mixture might have more moles of gas but is at a much lower temperature than if it was just the straight explosive.
If your idea would work, wet explosives would have increased blast because the water would flashboil- it does, but the explosion is much weaker and not just because the explosive is diluted, but because a lot of it's energy is used up just to boil all the water.
Basically, if you're trying to have better blast performance from an explosive, this idea is not going to work at all (for that).

However, I think it more likely the heavy alloy will just get accelerated in the expanding gas, and so cause greater local damage by impacting surrounding material (very close to the blast effect, as it will slow down very quickly). The same effect is known with tungsten, it being mixed into an explosive in a 50/50 ratio. Since the alloys you are using would appear to be fairly dense, they might realize the same effect.


Now, that isn't to say such cerrobend compositions using are useless. They may in fact detonate if an explosive such as RDX or PETN is used in the formulation (since you will need a very easily detonated explosive in order to have a chance of detonating such a diluted mixture), and the fact that they act like a solid piece of metal gives the mixture some extremely interesting mechanical properties, which I find much more promising than the explosive properties might be.

franklyn - 13-7-2006 at 10:18

Quote:
Originally posted by Sickman
maybe these compositions will have outstanding properties and explosive power, or maybe they won't , if my grey powder is an improvement over aluminized explosives I'll still be happy! If not oh well; back too the drawing board!


The blending of explosive compounds with inert materials is usually intended
to facilitate the fabrication of ordinance or attribute other properties not
present in the base explosive. Flex-X is a Dupont product that resembles
sheets of the rubber from which shoe soles are made , mild detonating cordeau
resembles the flexible curve used for technical drawing See "Davis" page 11 .
Compounding in this way always dilutes the content of actual explosive
thereby reducing its principle effects. The metals of low melting solder as
oxides , are reduced by other more reactive metals , the reason why Aluminum
is used to enhance blast in explosives not the ones in these alloys. Overall the
explosives effect will be lessened and the velocity of detonation certainly will
be less. This is not to say that there might not be an application for this ,
what do you envision ?


Quote:
Originally posted by Chris The Great
likely the heavy alloy will just get accelerated in the expanding gas, and so cause greater local damage by impacting surrounding material (very close to the blast effect, as it will slow down very quickly). The same effect is known with tungsten, it being mixed into an explosive in a 50/50 ratio. Since the alloys you are using would appear to be fairly dense, they might realize the same effect.


Low grade explosives containing Silicon Carbide were used by the Japanese
during the war to endow these for perforating metals. This was an expedience
due to wartime shortage rather than a technical improvement. I quote a U.S.
army text "Military Explosives" _
" The number of markedly different compositions used for a single purpose
indicates the necessity under which the Japanese labored to utilize everything
available having explosive value. Technical investigation after World War II
indicated that the Japanese explosives industry made no significant advances
during the war period. "
I recall from somewhere having read of a composition of TNT and Lead oxide
called Plumbatol. Although this increases the density , it is intended to serve
as an extender rather than to enhance explosive properties , allowing for a greater
amount of explosive to be made of the available TNT but reducing its performance
comparable to that of Ammonium Nitrate. Think of it as hamburger helper.

.

[Edited on 13-7-2006 by franklyn]

Sickman - 13-7-2006 at 21:20

Quote:
Originally posted by franklyn

This is not to say that there might not be an application for this ,
what do you envision ?


Well based on my findings so far that 3-5% finely powdered explosive may be added to a cerrobend alloy, the result being a hard, heavy continous mass, but not being sure if it is capable of detonation in this condition, I'm not sure.

However, I believe if a more granular form of explosive such as prills is used the explosive content may be increased significantly possibly up to 35%+, the trick being to create larger, thicker, and fewer bridges between the prills as opposed to many, many microbridges when a powder is used, which results in increasing fragality the more small diameter bridges are formed.

I hope you can understand what I mean by these bridges. It's like basically you use the same amount of alloy binder, but because the explosive takes the form of chunks throughout the alloy, it creates stronger thicker "bridges" which is the word I use to descibe the alloy content between one explosive particle and another.

Think of it this way if you were to add powdered starch to molten wax and supposing it is not soluble in the wax, but at the same time is mechanically dispersed evenly through the mass of the wax and solidified. Now suppose you did the same thing, but this time you add peanuts to the wax. In both cases you will have a mixture upon solidification of the wax, but they would have different mechanical properties, while at the same time using the exact same amount of wax.

Wax may be a very bad comparison to the characteristics of cerrobend alloy which is much harder and stronger than Lead(Pb).

Because this material is very dense like Lead, imagine forming it into a projectile shape that can be fired from artillary or even a firearm. This projectile on it's own would probably have good ballistic properties to it. based on it's density, and hardness, while being only very slightly brittle.

If you were to take the same projectile and add explosive prills to it say up to 25-35% and propelled it at normal firing velocity at something like an armor plate and suppossing that as each section of the projectile hit the taget that the explosive material in each section of the projectile denonated. I would predict that it would have a sort of digging effect on the armor plate. I would also predict that the projectile with the explosive content, even though being around 1/4 less dense than the same projectile without any explosive content would be more effective aggainst the target than a completly inert projectile composed completly of the cerrobend alloy.

Now this is all just speculation! if the explosive prills didn't high order detonate in the confinement of the alloy it would obviously be an idea that is lacking practicality.