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D4RR3N
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[*] posted on 23-1-2020 at 07:54
A true implosive


Is there such thing as a true implosive?

An explosive is defined as a rapid increase in temperature and pressure which generates an expanding pressure wave.

A true implosive would be the exact opposite, a rapid decrease in both temperature and pressure. I know that there are endothermic reactions but I have never seen one that occurs fast enough to justify calling it an implosive.

I have heard about these implosive reactions going off in tankers and airships but mystery surrounds the mechanics of it.
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[*] posted on 23-1-2020 at 09:31


Quote: Originally posted by D4RR3N  
Is there such thing as a true implosive?

An explosive is defined as a rapid increase in temperature and pressure which generates an expanding pressure wave.

A true implosive would be the exact opposite, a rapid decrease in both temperature and pressure. I know that there are endothermic reactions but I have never seen one that occurs fast enough to justify calling it an implosive.

I have heard about these implosive reactions going off in tankers and airships but mystery surrounds the mechanics of it.


I don't think we have true implosions on planets environment and scale. What we call implosions is rapid loss of low pressures, (filling of the vacuum).

If you wanted a piece of matter implode, some weird physics should act on it.




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D4RR3N
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[*] posted on 23-1-2020 at 13:12


In an explosive you have a liquid or solid suddenly turning into a gas.

An implosive would require the reverse a gas suddenly turning into a liquid or solid.
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[*] posted on 23-1-2020 at 13:23


There is this one example of a trainload of, I believe it was dimethyl ether, suddenly turning the train into some sort of trashed can: https://www.youtube.com/watch?v=Zz95_VvTxZM
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[*] posted on 23-1-2020 at 13:32


That is a truck being pulled vacuum. The only thing qualifing as an implosion is this, or a submarine sinking too deep. There is no chemical energy changing state here, it is just mechanical. A "normal" explosion has chemical energy changing state, unless it is a pressure vessel rupture.
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[*] posted on 23-1-2020 at 13:44


Years ago I read about eyewitness who seen a hydrogen airship suddenly implode into water without flames, nobody could explain it.
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[*] posted on 23-1-2020 at 14:52


maybe not exactly what you're looking for, but the self-crushing soda can is a classic demo:

https://www.aps.org/programs/outreach/guide/demos/cancrush.c...

https://www.youtube.com/watch?v=TrluA_tcjVE




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[*] posted on 23-1-2020 at 16:14


It's unlikely because gases have a lot of energy which gets released when they're converted to solids:

http://en.wikipedia.org/wiki/Heat_of_vaporization

That energy release tends to make up for any loss in pressure caused by gases reacting to produce a solid.

However, I think if you reacted e.g. trimethylamine and hydrogen bromide gases in a sealed vessel (somehow) you might get a large pressure drop.

A more common case of sudden pressure drop is hydrogen chloride gas passing over a liquid such as water or acetic acid, where the gas is rapidly "sucked into" the liquid. This can cause a dangerous "suckback" situation when working with a multi-vessel reaction apparatus.




[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 23-1-2020 at 16:45


yes ?kinda but. under water.it is perfect mix of H2 and O2 under deep sea. for example a balloon filled with only those gases ignite in deep water would make a explosion first but the water pressure is so high not much expands .but after while the steam made from the reaction rapidly cools(because the mix can't expand as much it get hotter than normal temperature for the reaction in the air, which lead to higher black body radiation, so cools fast.) and make liquid water so and implode



a lot less people died from radioactivity related illness before the discovery of radioactivity.
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[*] posted on 23-1-2020 at 18:23


Quote: Originally posted by rockyit98  
yes ?kinda but. under water.it is perfect mix of H2 and O2 under deep sea. for example a balloon filled with only those gases ignite in deep water would make a explosion first but the water pressure is so high not much expands .but after while the steam made from the reaction rapidly cools(because the mix can't expand as much it get hotter than normal temperature for the reaction in the air, which lead to higher black body radiation, so cools fast.) and make liquid water so and implode


The trouble with that, is whatever the initial pressure might be, the pressure increase due to heating will be some multiple of that initial pressure, even after it has increased the volume by several times. The implosion, on the other hand, would go from that peak volume to near zero volume while being forced in by a pressure equal to the initial pressure. The expansion will probably always involve a bigger change in volume, under greater pressure, than the collapse, regardless of whether the mixture is under 100 millibar or 100 kilobar initial pressure.

On the other hand, it is possible to see an implosive effect by putting the mixture in a container which can contain pressure but is unable to resist external pressure.

here is a stoichiometric hydrogen-oxygen mixture ignited in a container that withstood the initial pressure increase and didn't get much thermal damage because it was cooled by the water.

here is one in which the heat and force overcame the strength of the container.

I guess you might be able to call the absorption of HCl by water a chemical reaction, since the compounds partially dissociate in solution. Same for NH3, to a lesser degree.

One more thing: the demonstration with an aluminum can filled with steam is worth doing at least once. It's louder and more violent than common sense would suggest, probably because the first few ml of icewater to be drawn in get splashed around inside and cool the steam almost instantly.




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[*] posted on 24-1-2020 at 04:59


Quote: Originally posted by clearly_not_atara  


A more common case of sudden pressure drop is hydrogen chloride gas passing over a liquid such as water or acetic acid, where the gas is rapidly "sucked into" the liquid. This can cause a dangerous "suckback" situation when working with a multi-vessel reaction apparatus.


A similar experiment can be done with a bottle half filled with cold water and filling the rest with carbon dioxide gas. When you seal and shake it the carbon dioxide is rapidly absorbed by the cold water to form carbonic acid. The container then implodes.
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[*] posted on 24-1-2020 at 05:10


I was thinking a true implosive would have to rapidly react with atmospheric gases otherwise you will need two or more containers with the reactants and one of those containers is going to be large because it will be containing gas. You could put one container inside the other both separated until activated but still its a closed system in a container.

Nitrogen gas is the bulk of the atmospheric air so a substance that would rapidly react with nitrogen and bind it into a solid or liquid would result in a huge drop in pressure thus an implosion.

What I need is a reaction that is hungry for nitrogen.

[Edited on 24-1-2020 by D4RR3N]
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[*] posted on 24-1-2020 at 09:57


Imploding glassware is a hazard in laboratories.
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[*] posted on 24-1-2020 at 15:56


The ignition of hydrogen in air definitely produces an implosion!

The volume instantly decreases from a gas to a liquid.







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[*] posted on 24-1-2020 at 15:59


Quote: Originally posted by Simoski  
The ignition of hydrogen in air definitely produces an implosion!

The volume instantly decreases from a gas to a liquid.



Not really because the product is hot water vapour...
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[*] posted on 24-1-2020 at 16:01


Quote: Originally posted by DavidJR  
Quote: Originally posted by Simoski  
The ignition of hydrogen in air definitely produces an implosion!

The volume instantly decreases from a gas to a liquid.



Not really because the product is hot water vapour...


Do it yourself and you will see a drop of liquid water form when a football sized balloon of hydrogen is ignited

[Edited on 25-1-2020 by Simoski]




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[*] posted on 24-1-2020 at 23:33


Do it in a football sized baloon and you will see a beach ball sized blinding flash of incandescent steam and carbon from the balloon rubber, at a temperature somewhere between 2500 and 3500 C. Assuming it's burning with oxygen, and no nitrogen is involved.

Edit: no fair talking anout a diffusion flame in air, since a huge plume of warm (expanded) nitrogen also gets emitted. Seriously, even if you had a reaction that bound all the molecules in a volume of air into a dense solid, the effect would still be very localized. The biggest pressure change it could create would be limited by the ambient pressure. That means you can't have a small very high intensity reaction region that sends a shockwave and does significant damage at a distance.

[Edited on 25-1-2020 by Vomaturge]




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[*] posted on 25-1-2020 at 01:15


With explosives (excluding nuclear) the upper limit as far as I know is a RE factor of 2.38 with octanitrocubane.

But with "implosives" the driving force is the external atmospheric pressure. - There are many ways to do something but imo you may as well fill a barrel with steam and cool it to room temp to create a vacuum. Then open it with a small amount of det cord.

The comparison is apples to oranges but I think anyone/everyone would rather stand next to the barrel of vacuum over the barrel of HE.

As for reacting nitrogen, anything with enough energy to break the triple bond rapidly would not give "solid" results. (Boom)
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[*] posted on 25-1-2020 at 03:23


In my opinion the most useful definition of an implosive is a material that suddenly decreases it's pressure causing a shockwave. An explosive should then be a material that causes a sudden increase in pressure causing a shockwave, foregoing the temperature. Of course a sudden increase in temperature will often result in a sudden increase in pressure. With this definition i think there are two ways to categorize implosives:

1. Implosive device. For example a bottle of hydrogen and oxygen gas which contracts if the contents are ignited while the bottle is cold enough.

2. True implosive or an implosive substance. This would be some mixture that contracts on ignition without the need for external cooling from the walls of the container it is inside.

For the case of two gases forming one it is fairly easy to give an estimation by solving the following equation system:

na A + nb B ---> nc C

P0 = 101000 Pa
P0⋅V = (na + nb)⋅N⋅R⋅T0
P1⋅V = nc⋅N⋅R⋅T1
T1 = T0 + ΔE⋅Cm-1

For hydrogen and oxygen ΔP is +1.354⋅106 Pa , very far from an implosive.

This calculation is obviously dependant on heat of vaporization and in better cases heat of fusion too. For calculating metal-gas implosive properties it is hard to find the data and even then neither R, the heat capacity nor the energy released are likely to be canstant over the wide temperature range when considering all kinds of equilibriums that are liekly to be formed. Thinking of what would make a good implsosive it should have some of the following properties:

1: It should consist of at least one gas to maximize initial volume.

2: The products formed should have a small enthalphy of formation. Ideally the reaction should be driven only by entropy (another reason to use diatomic elemental gases). This is to not vaporize the products with excessive heat. Still some is required due to kinetics, especially since unlike an explosive an implosive would work against the rate enchancing effect of increasing pressure.

3: Since the only thing that matters for the initial pressure is the moles of gas the gas should ideally be monoatomic. This is obviously impossible or at the very least impractical so instead diatomic gases should always be used to maximize volatility and bond strength.

4: Nonvolatile products are ideal. To get a nonvolatile product i think it is best to go for gases that contain small atoms for maximum charge density and volatility to maximize nonvolatility of the products and initial volume respectively.

5: The two components should be chosen to form as large a molecule as possible. To do this the difference in valency should be as large as possible and ideally in a pair of even/uneven most stable charge. For example Phosphorous pentoxide forms larger less volatile molecules than, say, Carbon Dioxide.

With this considered i think oxygen is the ideal gas to use for the oxidizer and low valency element. It has enough charge to form covalent bonds while having fairly low valency and it is a strong enough oxidizer to force metals into very high valencies. Which is why i think a metal aerosol in oxygen would be a true implosive. There are of course a lot of metals to choose from but an obvious candidate is titanium. Its oxide is very nonvolatile, it does not ignite in oxygen at room temperature and it as a decent valency of four. There is probably some better metal i have'nt thought of though.

EDIT: Tantalum is probably better

A simpler implosive may be anhydrous ammonia and hydrogen chloride which can be initiated with a small amount of water per the Wikipedia article on ammonia: "Perfectly dry ammonia will not combine with perfectly dry hydrogen chloride; moisture is necessary to bring about the reaction"

[Edited on 25-1-2020 by Σldritch]
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[*] posted on 25-1-2020 at 05:53


Quote: Originally posted by Simoski  
Quote: Originally posted by DavidJR  
Quote: Originally posted by Simoski  
The ignition of hydrogen in air definitely produces an implosion!

The volume instantly decreases from a gas to a liquid.



Not really because the product is hot water vapour...


Do it yourself and you will see a drop of liquid water form when a football sized balloon of hydrogen is ignited

[Edited on 25-1-2020 by Simoski]


It produces an explosion followed by an implosion. You can prove this by igniting hydrogen in a tube with a rubber stopper in the end, it will blow the stopper out when ignited.
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[*] posted on 25-1-2020 at 06:40


Quote: Originally posted by Σldritch  



1: It should consist of at least one gas to maximize initial volume.


In a closed system yes but you could use the atmospheric gases to replace that container. Anything that would rapidly bind an atmospheric gas will result in an implosion. Since Nitrogen gas makes up 78% of our atmosphere it would produce the best results but it might be impossible to find a reaction that can rapidly bind nitrogen. Binding atmospheric Oxygen would be simpler but less effective.

Quote: Originally posted by Σldritch  

With this considered i think oxygen is the ideal gas to use for the oxidizer and low valency element. It has enough charge to form covalent bonds while having fairly low valency and it is a strong enough oxidizer to force metals into very high valencies. Which is why i think a metal aerosol in oxygen would be a true implosive. There are of course a lot of metals to choose from but an obvious candidate is titanium. Its oxide is very nonvolatile, it does not ignite in oxygen at room temperature and it as a decent valency of four. There is probably some better metal i have'nt thought of though.

EDIT: Tantalum is probably better

A simpler implosive may be anhydrous ammonia and hydrogen chloride which can be initiated with a small amount of water per the Wikipedia article on ammonia: "Perfectly dry ammonia will not combine with perfectly dry hydrogen chloride; moisture is necessary to bring about the reaction"

[Edited on 25-1-2020 by Σldritch]


You could have a fine metal powder in a capsule under high pressure argon gas. The container could be designed to rupture when activated and the pressurised argon would propel the fine metallic powder outwards producing a cloud that would then react with oxygen to form a metal oxide.

I am not sure about Titanium, Something that oxidises more rapidly in atmospheric oxygen would be better? The more electropositive the faster it will loose electrons and oxidise. A metal selected from the bottom left of the periodic table.

[Edited on 25-1-2020 by D4RR3N]
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[*] posted on 25-1-2020 at 07:23


The topic brought to mind Tubes Rendered Harmonious by Hydrogen Gas where I think the products of combustion come into play, as "spirits of wine or ether" are said not to work. With other fuels perhaps it is the portion of CO2 which might dilute the collapse of the products of combustion as the gases cool.. The higher temperature of hydrogen was also thought to be a factor. So as the hot gases come in contact with cooler air it seems both a higher contrast in temperature and greater collapse of hydrogen over other fuels favors the effect.
https://books.google.com/books?id=IU_waKO_J1QC&pg=PA24&a...
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[*] posted on 25-1-2020 at 09:20


D4RR3N i imagine it as a balloon filled with metal aerosol in pure oxygen gas. What is outside the ballon should not matter as long as it keeps a reasonable pressure on it such as one athmosphere. If it did matter then the outside would be a part of what makes the mixture implode and it would not make any sense to call it an implosive substance anymore because its ability to implode is not derived from the substance itself. Similarly we dont call ethanol explosive because it burns, the ethanol air mixture is explosive.

An alkali metal would not work because as an aerosol it would instantly ignite. Also their oxides are volatile and very energetically favored so it is likely it creates a higher pressure when it burns in isolation (if you can find heat of fusion and vaporization for them it should be possible to calulate it). Perhaps you could inject liquid metal into a chamber of gas with an atomizer but i wonder if this would be quick enough to cause a shockwave.

Something that would be really interesting is a solid implosive. Perhaps one could be made by filling a metal foam with a stochiometric amount of oxygen gas. Though how one would get the oxygen there in the first place i have no idea. I guess in this case using the athmosphere would be the easiest way to do it. Perhaps magnesium foam would work since it should react with the nitrogen in the athmosphere too. Problem is it would be very energetic.

EDIT: If someone is crazy enough this may be within the amateurs grasp: http://www.aerogel.org/?p=932 Im going to add this to the long list of things i want to do.

[Edited on 25-1-2020 by Σldritch]
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[*] posted on 25-1-2020 at 20:29


Quote:
I still think that the very high temperatures created by oxygen reacting with any reducing agent (metals especially) will cause an increase in pressure and/or volume. Any residual oxygen, or any volatile impurities, will expand vigorously. Seemingly solid, dense, inert combustion products can do strange things at elevated temperature. For instance:

[Quote]The heat released from burning one gram of aluminium power is at least 6 times more than the energy released from exploding one gram of TNT. The flame temperature of an aluminium dust explosion is limited mainly by the vapourisation temperature of the oxide.
http://explosionconsultancy.co.uk/curiosities/

A mixture of aluminum and cupric oxide will increase in temperature as it burns, until it gets to a point where the temperature is so high that there is an equilibrium between Al2O3 and the pure elements. For the last bit of aluminum to burn up and release its energy, some of the heat has to be lost to the outside: https://www.google.com/url?q=https://www.archives-ouvertes.f...

Here is a video of what the 3CuO+2Al reaction looks like. Note that the free oxygen increases involume rapidly and exits out the top of the reaction vessel, taking some aerosolized copper with it.

The reaction between dispersed metallic fuels and elemental oxygen should release more high-pressure oxygen per gram of reactants, but less per unit volume. here is a study of aluminum burning in nearly pure oxygen, and propagating a shockwave with a peak pressure of 31 atmospheres.

First oxyhydrogen, next oxygen-metal combustion. What next, supernovas, antimatter?

If you want a true implosive, you'll want something less exothermic. A small amount of icewater dispersed rapidly into a container of steam or ammonia might collapse that container.

Likewise, i've noticed that if you have say, a 1 inch plastic pipe, and plug one end, and push a semi sealed piston (a wood dowel wrapped in tape will do nicely) into it, you can gradually push it in over a few seconds while the air leaks out around your badly made piston. Now pull it out (fast, so no air can leak back in around it) and you will make a pretty loud pop, followed by the air that has entered the tube resonating. I don't know which contributes to the sound more, the air rushing in, or the pressure when it rebounds back out of the tube. If a solid object goes into the tube before the air, it will accelerate rapidly toward the plugged end.

None of these experiments give the spectacular results of even a gas phase deflagration, for three simple reasons. Firstly, the maximum pressure change you can get is inherently limited by atmospheric pressure.
Secondly, there are few truly rapid chemical reactions which are not exothermic enough to somehow mess up the implosion.
And finally, when the effect of a pressure drop hits, water, or sand, or brick, or air, or anything else, if it does move it or break it or expand it it also reduces it's ability to transfer force to whatever is the next object behind it. A pressure peak has the opposite effect. It boosts the density and viscosity of air, and can drive broken glass bottles and thin sheet metal through a block of steel even after they are fractured in a hundred places. Almost any material will transmit a push when held together by inertia or hydrostatic pressure, but no material can transmit a pull after its tensile strength has been broken.

TLDR; Can you make a chemical reaction that reduces atmospheric pressure? Sure. Will it ever be more spectacular, or more dangerous, or more energetic than opening an equal sized container holding a non reactive gas at twice ambient pressure? Never. Can you make an analog to a dense solid EM that causes proportional implosive effects? Not a chance. Would it be cool if you could? Not as cool as a flashlight that shoots out darkness.

[Edited on 26-1-2020 by Vomaturge]




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[*] posted on 26-1-2020 at 01:18


Vomaturge i do not think there is anything stopping a reaction mixture from imploding. There is no reason an implosive could not contain an internal heatsink since any solid added would result in a negligible volume increase. As for copper thermite, that is about as good of a equivalent for a theoretical implosive as thermite is for an explosive.

However i think you are correct about force transfer. It should not be possible to get the equivalent of a shockwave because the negative pressure can only travel at the speed of sound of the material. It is really a question about what you would call an explosive and implosive. I think what i am describing, assuming it works, is at least as close you can come physically without something like a cloud of hot gas to an implosive.
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