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Defect-free crystals can endure tensile strains which are just
below those needed to break all the interatomic bonds in
the
material. (Most materials have defects which act as stress
concentrators, meaning the material will break well below
this
level of strain.) As a result, when such
crystals break in
tension, they often disintegrate into microscopic particles,
since the stored strain energy was almost enough to break
every [longitudinal] bond in the crystal.
As a result of this, the strain energy in a highly-strained
crystal
can be roughly equivalent to its chemical energy.
It follows, then, that a highly-strained crystal of an
explosive
will release significantly more energy when detonated than
an
unstrained crystal. In other words, its explosive yield will be
significantly (maybe 10-30% higher) if it is pre-stressed.
(As an aside, many explosives are already stressed at the
molecular level, since they contain rings of atoms that can't
adopt their preferred bond angles.)
How, though, to make pre-stressed explosives that can be
easily handled? Well, one way would be to make long-chain
polymeric explosives and encapsulate them in very fine glass
capillaries. In fact, the ideal would be to have an explosive
that can survive glass-melting temperatures (which can be
quite low, with the right sort of glass), and to draw out
fibres
consisting of a thin glass skin with an explosive core. If the
explosive polymer melts at a different temperature to the
glass, then a lot of strain will be built into it as the fibre
cools,
due to differential contraction of the glass and the
explosive.
Once cooled, the fibres could be compacted, woven or
otherwise formed into suitable shapes.
Octanitrocubane
https://en.wikipedi...iki/Octanitrocubane
Should be #3, but not yet made to pack densely enough [notexactly, Feb 26 2019]
Heptanitrocubane
https://en.wikipedi...ki/Heptanitrocubane
#3 currently because it packs better [notexactly, Feb 26 2019]
Octaazacubane
https://en.wikipedi.../wiki/Octaazacubane
#2 [notexactly, Feb 26 2019]
Cubic gauche nitrogen
https://en.wikipedi...trogen#Cubic_gauche
#1 [notexactly, Feb 26 2019]
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Annotation:
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How do you expect the yield to be 10–30% higher? I don't see
you putting that much energy in just by stretching it. |
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I added links to the four best chemical explosives yet
developed or predicted (IIRC), which are good examples of
// already stressed at the molecular level, since they
contain rings of atoms that can't adopt their preferred bond
angles //. |
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//I don't see you putting that much energy in just by
stretching it.// For materials you're likely to encounter day
to day, that's true - most materials fail at a tiny fraction of
the strain (and stress) predicted solely from bond strengths
and numbers. But a defect-free crystal can be strained
(and stressed) much further. |
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If it helps, look at it this way. A material is held together
only by interatomic bonds. If it burns or detonates, all
those bonds are broken (and usually new ones are formed -
the energy you get out is the difference). If you strain the
material, and don't allow it to fail at a stress concentration
(or to undergo slip, like ductile metals do), then you
eventually reach the breaking point dictated by the bond
strengths. At that point, all of the longitudinal bonds are
storing as much energy as you'd get from breaking them
chemically. In other words, in energetic terms, it doesn't
make much difference whether you break the material
chemically or by stressing it to its limit. |
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//encapsulate them in very fine glass capillaries// |
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Even if you had 100% extra energy from stored
mechanical energy, you have to add a whole lot of
capillaries. These are dead weight. You also put yourself
at risk of accidental detonation, breakage of a single
capillary might release enough energy to detonate the
content. Wouldn't it be simpler to just add extra
explosive? All that glass flying around might get someone
hurt. |
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I like the principle though. Maybe there are explosives
that can be grown as large single crystals and pre-
stressed in a casing, or internal stress could be added by
tempering processes. |
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//Wouldn't it be simpler to just add extra explosive?// Hello,
[bs0], and welcome to the Halfbakery. |
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If you designed it right, the glass capillary could be stressed
to its limit in compression whilst the explosive was stressed in
tension, or vice versa. In that way, the capillary becomes
part of the explosive. |
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So it's only just NOT an explosion. How about other
mechanical means, O2 really likes to be a gas, but if you
really force it, you can make it a liquid. Maybe you could
get a good ratio of say, methane to dissolve in it. Keep them
in a container that ONLY JUST doesn't explode, and you
have extra energy stored right there. Only you can keep it
cold/drop the pressure a bit when you need to
move/breathe near it. |
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I've often wondered if you could make little micrometre-sized
plastic bubbles containing liquid oxygen under intense
pressure. A slurry of those in oil would make a great rocket
fuel. |
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// All that glass flying around might get someone hurt. //
[+] |
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hmmmm, could you contain an explosive within a Prince Rupert Drop? |
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//I've often wondered if you could make little micrometre-
sized plastic bubbles containing liquid oxygen under intense
// |
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It can be done, I just calculated it, not in a particularly
sophisticated manner, just spherical approximation from the
thick-walled hoop stress formulae. A 1um sphere of O2
would need about 50 GPa to keep it liquid, that gives you a
wall thickness of about 1.5mm. The rocket would run a
touch rich. |
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//contain an explosive within a Prince Rupert Drop// A P.R.D
is an excellent example of a highly-stressed solid, thanks,
[2fries]. The strain energy it stores is enough to turn all of it
into powder. Even higher energy density is possible with
small, perfect crystals. |
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//It can be done, I just calculated it// Many thanks; I knew
that smaller bubbles can sustain higher pressures. What
happens if you make the central void slightly bigger - is there
a size that gives a higher ratio of contents to wall? |
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I'm seeing large single-use crystal chandeliers. |
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And what about those toasts which are followed by dashing the
glass into the fireplace? This idea could certainly add
something there. |
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There are many very good (and one truly excellent) reasons why this has never, and will never, be done - even though it is technically possible. |
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In fact, although large (multi-kilogramme) single crystals of HMX have been around for decades, after manufacture they are carefully annealed to avoid this very effect. |
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// I've often wondered if you could make little micrometre-
sized plastic bubbles containing liquid oxygen under intense
pressure. A slurry of those in oil would make a great rocket
fuel. // |
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I feel like I just read about that very idea (or its inverse,
maybe) yesterday. There was math and everything. |
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//There are many very good (and one truly excellent)
reasons// I am leaving the following space blank so that
you can write down those reasons. |
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In typical usage, one of the strengths of an explosive is its insensitivity to minor knocks.
This is why dynamite was widely used, instead of straight nitroglycerin. |
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So I'm not sure the market for your proposed product range would be large. |
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It might be large but transient. |
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No, no, don't let me stop you - feel free to go ahead with
the experiment. |
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Maybe you'll be able to sweep up both the Ig Nobel prize and
Darwin awards in one fell swoop. That would certainly get
you into the Halfbakery hall of fame. |
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Wigner energy springs to mind, too. |
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Having made your crystal of stressed explosive, irradiate it
with neutrons until it almost but not quite goes bang. |
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Then work out how to store it. |
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^ How are you going to collapse the Prince Rupert Drop? |
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A variable of stress that isn't in the working environment would be good. High magnetic field? |
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[Wrongfellow], you may take this Platinum star and affix it next to your name on the class achievement chart. Wigner energy is absolutely spot on. |
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//many explosives are already stressed at the molecular level// I'm currently able to stop just short of throttling the near-terminally stupid...oh dear, I may be the personification of this idea. |
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//if you had 100% extra energy from stored mechanical energy, you have to add a whole lot of capillaries// This idea explains the growing network of spider veins (not possibly due to the Collingwood Select), and the throbbing vein appearing intermittently just over my right orbital socket at times of maximum stress. |
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//little micrometre-sized plastic bubbles containing liquid oxygen under intense pressure// News reports say that every living thing on Earth--even the unnamed citizens at the bottom of Mariana Trench--now contains plastic. So, every time I breathe, I pressurize these plastic bubble beads. |
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