Sciencemadness Discussion Board - PTFE Magnesium thermite fun

PTFE Magnesium thermite fun

IndependentBoffin - 20-6-2011 at 12:29

So I was fooling around with my 99.7% 180 micron Mg powder that just arrived...

Tried lighting small piles of the powder by itself (no oxidiser) and it was disappointingly quiescent to a butane pen torch

With a bit of PTFE sealing tape however...different story as you can see

I coated the tape in non-stoichiometric amounts of Mg powder by tearing off a strip and pushing it around in a beaker filled with Mg powder. The powder stuck to the PTFE tape very easily (it seems to stick to everything!)

I then put the coated tape in a safe place

and brought a butane pen torch to it, wearing thick leather electrician's gloves in case burning metal bits fly. And of course UV protection polarised sunglasses

In the movie you can actually see the tape melt a bit from the heat of the butane torch. Then everything goes blindingly incandescent

Movie link:
www.noveldefence.com/downloads/ptfe_mg_thermite.mp4

IndependentBoffin - 20-6-2011 at 13:07

My thermochemistry is a bit rusty (last did the sums more than a decade ago) but here are the reaction calculations. Please feel free to correct me if you spot a mistake.

Overall equation: 2Mg + (C2F4

n -> 2MgF2 + 2C

Mg + F2 -> MgF2 ................................ ΔHf = -1124 kJ/mole

2C + 2F2 -> -(C2F4

n- ................................ ΔHf = -832.6kJ/mole

Heat of reaction = 832.6 - 2×1124 = -1416 kJ for 2 moles of Mg and 1 mole of (C2F4

n.

Because I am an engineer and tend to think in terms of specific energy this gives 1416/(2×12 + 4×19 + 2×24.31)kJ/g or 9.526 kJ/g of reactants.

By contrast TNT has an energy density of 4.61 kJ/g and diesel 46.2 kJ/g.

The most energetic known Al - oxygen thermite reaction is the reaction with iodine pentoxide I2O5 with a reaction heat of 6.217 kJ/g. Other notable ones: 2Al + 3CuO (-4.076kJ/g), 2Al + Fe2O3 (-3.956kJ/g), 4Al + 3MnO2 (-4.849kJ/g).

The most energetic known Mg - oxygen thermite reaction is the reaction with 3Mg and B2O3, with a reaction heat of 8.929 kJ/g. Other notable ones: Mg + CuO (-4.611kJ/g), 3Mg + Fe2O3 (-4.644kJ/g), 2Mg + MnO2 (-5.531kJ/g).

See citation below for further details:

http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefi...

Quote:

Accession Number : ADA419762

Title : A Survey of Combustible Metals Thermites and Intermetallics for Pyrotechnic Applications

Corporate Author : SANDIA NATIONAL LABS ALBUQUERQUE NM

Personal Author(s) : Fischer, S. H. ; Grubelich, M. C.

Handle / proxy Url : http://handle.dtic.mil/100.2/ADA419762

Report Date : JUL 1996

Pagination or Media Count : 15

Abstract : Thermite mixtures, intermetallic reactants, and metal fields have long been used in pyrotechnic applications. Advantage of these systems typically include high energy density, impact insensitivity, high combustion temperature, and a wide range of gas production. They generally exhibit high temperature stability, and possess insensitive ignition properties. In this paper, we review the applications, benefits, and characteristics of thermite mixtures, intermetallic reactants, and metal fuels.

Descriptors : *EXOTHERMIC REACTIONS, *PYROTECHNICS, METALS, THERMAL STABILITY, COMBUSTION, FUELS, IGNITION, THERMITE.

Subject Categories : PYROTECHNICS
COMBUSTION AND IGNITION

Distribution Statement : APPROVED FOR PUBLIC RELEASE

[Edited on 20-6-2011 by IndependentBoffin]

The WiZard is In - 20-6-2011 at 13:33

Quote: Originally posted by IndependentBoffin

My thermochemistry is a bit rusty (last did the sums more than a decade ago) but here are the reaction calculations. Please feel free to correct me if you spot a mistake.

Overall equation: 2Mg + (C2F4

n -> 2MgF2 + 2C

Mg + F2 -> MgF2 ................................ ΔHf = -1124.24kJ/mole

2C + 2F2 -> -(C2F4

n- ................................ ΔHf = -832.616kJ/mole

Heat of reaction = 832.616 - 2×1124.24 = -1415.9kJ/mole

Take good notes there will be a test.

A Theoretical Study of the Combustion of Magnesium/Teflon ...
... OF MAGNESIUM / TEFLON / VITON PYROTECHNIC COMPOSITIONS ...
Combustion of Magnesium/Teflon!Viton Pyrotechnic Compositions .
www.dtic.mil/dtic/tr/fulltext/u2/a243244.pdf - 1991-08-01 - Text Version - [Citation]

[PDF] Thermochemistry and Kinetics Models for Magnesium/Teflon
www.dtic.mil/dtic/tr/fulltext/u2/a377423.pdf - 1999-12-01 - Text Version - [Citation]

------
TASK NUMBER: 08-F-66
TITLE: Mag Teflon Counterambush Weapon (MTCAW)
AUTHORIZED FUNDING: $209,737
TASK DURATION: 14 March 1966 to 24 July 1968
DESCRIPTION AND RESULTS: The purpose of this task was to determine a suitable
method of employing Magnesium Teflon (Mag Teflon) in conjunction with a vehicle
mounted counter ambush kinetic energy weapon in order to enhance its output and
effectiveness.
Mag Teflon pellets, ignited inside the gun barrel, were fired from a
gun tube. The initial combination, although primitive in terms of a developed
round, demonstrated the feasibility of propelling burning fragments capable of
producing a burn over a predetermined range and with a predictable area coverage.
Several minor design problems became apparent during the Engineering
Design Tests (EDT) conducted 4th Qtr FY68. Review of the total Counter Ambush
Weapon Program resulted in the decision to cease any further development of this particular system

TASK NUMBER: 02-B-65
TITLE: Investigation of New Incendiary Agent
AUTHORIZED FUNDING: $86,348
TASK DURATION: 3 August 1964 to 13 April 1967
CONTRACTOR: University of Cincinnati , Kettering Laboratory
DESCRIPTION AND RESULTS: The purpose of this task was to assess the anti-personnel
and anti-materiel effectiveness of magnesium teflon formulations. The physical
properties of various formulations were correlated with their physiological effects
in tests with animals.
The contract was completed and the contractor's final report received
during the 3rd quarter FY66. The results reported by the contractor show that
aspirin tablet-shaped pellets of magnesium-teflon 3/8" x 1/4" produce 3rd degree
burns in the abdominal skin of rabbits and pigs.
Dynamic tests indicated that pellets of a given size when fired from
an air gun at an average velocity of 65 f/s at pigs and rabbits produced 3rd
degree burns in 70% of the rabbits whether the pellet adhered or not and in 501
of the pigs under similar circumstances. The remaining burns were 2nd or 1st
degree burns.
The results were of sufficient interest to stimulate additional work
to determine the effects of directional explosive dissemination of various sizes
and shapes of mag-teflon pellets. Preliminary tests indicated that a 47 grain
mag-teflon pellet might be useful in a counterambush weapon. A prototype
weapon was fabricated consisting of 6, 14 inch aluminum tubes, ID of 3", each
containing 200, ',7 gr mag-teflon pellets with 300 grains of black powder

TASK NUMBER: 09-B-69
TITLE: Prototype LACI System
AUTI1ORIZED FUNDING: $287,016
TASK DURATION: 2 October 1968 to 8 May 1970
CONTRACTOR: AAI Corporation
DFSCRIPTION AND RESULTS: The LACI (Large Area Coverage Incendiary) is a prototype air-droppable incendiary munition that utilizes magnesium teflon pel lets
as the incendiary fill. A single prototype munition weighs approximately 30 lbs
of which 25 lbs is incendiary payload. The LACI is designed to be released from
a specially designed dispenser that attaches to standard bomb shackles on the
AH-IG or UH-l aircraft. Two dispensers, each carrying three LACI's, can be
mounted on the outboard stores stations; the inboard stations can be utilized
for conventional weapons. An extensive program of field test/evaluation was
completed in CONUS and OCONUS (Hawaii) and two prototype dispensers and forty
LACIs were delivered to LWL

TASK NUMER: 06-B-71
TTILE: Evaluation of the Mag..Teflon Perimeter Defense Weapon
AUTHORIZED FUNDING: $140,524
TASK DURATION: 25 August 1970 to 28 February 1974
CONTPACTORS: AAI Corporation; Antenna Research Associates, Inc.
DESCRIPTION AND RESULTS: A one-shot, throw-away, flame fougasse utilizing
mag-teflon as the ;ncendiary fill was developed. Firing data, including area
coverage and allet distribution, were acquired and were used to estimate provisional inrapacitating effectiveness.
Each unit consists of a modified LAW tube, 22 inches long, with a
diameter of 2.75 inches, factory-filled w.ith 625 magnesium-teflon pellets.
Firing tests of prototype units showed that the weapon has a maximum effective
range of 50 meters with a fan-shaped dispersion angle of 45'.
The concept of use for this weapon is that it can he emplaced in a
perimetor as a defensive weapon, or in other appropriate tactical situations,
where it can be command- i,-ed or fired by trip-wire. Because it is cheap,
small, and would come to ýh• 'ield completely assembled, reddy to emplace and
fire jl•tiple emplacements are practicable. In a multiple emplacement,
indiv-'io,•.. weapons can be ripple-fired or fired simultaneously.
Two hundred and, twenty mao-teflon perimeter defense weapons were
procured in FY 73 for t-ser field ev3!uation. Twenty of these units were subjected to environmental hazard tests, including impact (drop), shake and
vibration, in accordance' with LWL safety procedures, Twenty units were shipped
Lo Thailand for user evaluation

&c., &c,

[PDF] US Army Land Warfare Laboratory. Volume II Appendix B. ...
... B-45 09-E-69 Ambush Light B-46 ... [0-80 01-F-54 Light weight Truclk Armor
B-81 ... B-101 08-F-66 Mag Teflon Counterambush Weapon (MTCAW) ...
www.dtic.mil/dtic/tr/fulltext/u2/a002573.pdf - 1974-06-01 - Text Version - [Citation]

djh
---
The FBI has just added the
American EcoNut Terrorist
Daniel Andreas to its top
terrorist list.

Maliciously Damaging and Destroying,
and Attempting to Destroy and Damage, by
Means of Explosives, Buildings and Other
Property; Possession of a Destructive Device
During, in Relation to, and in Furtherance of
a Crime of Violence

http://www.fbi.gov/wanted/wanted_terrorists/daniel-andreas-s...

[Edited on 20-6-2011 by The WiZard is In]

IndependentBoffin - 20-6-2011 at 13:56

Thank you for the delightful references, The WiZard is In

Quote:

Dynamic tests indicated that pellets of a given size when fired from
an air gun at an average velocity of 65 f/s at pigs and rabbits produced 3rd
degree burns in 70% of the rabbits whether the pellet adhered or not and in 501
of the pigs under similar circumstances. The remaining burns were 2nd or 1st
degree burns.

Are magnesium teflon pellets sufficiently shock sensitive to spontaneously combust upon impact at those velocities? Presumably it must be affected by Mg/PTFE particle size, compaction, porosity and additives.

I have not yet tested the shock sensitivity of the stuff and forewarned is forearmed

Mg/PTFE/Viton...

albqbrian - 20-6-2011 at 15:11

Are commonly used for igniters in solid fueled rockets. They're normally cast in pellets.

IndependentBoffin - 20-6-2011 at 15:22

Quote: Originally posted by albqbrian

Are commonly used for igniters in solid fueled rockets. They're normally cast in pellets.

Presumably there is a compaction stage to get a dense slug with no porosity and consistent mechanical properties. Do they just mix everything together and compact + heat or is the casting done at lower temperatures under vacuum to get rid of porosity?

Do they have sufficient electrical conductivity to facilitate ignition by direct application of an electric voltage to them, or are they ignited by a nearby resistance wire?

I'm also curious what the burn characteristics of a fully densified Mg/Teflon/Viton slug would be. Are there any charts of porosity vs. linear burn rate available for this composition?

ZHANGNIUBI - 20-6-2011 at 18:25

Chinese people did some research on that((but they mix AL powder and (CF2)n), and I got that paper, but I can not imagine how it works...
it is wonderful and really powerful !!!(I believe it is much better than black powder) thank you for sharing the video..!!!

IndependentBoffin - 20-6-2011 at 23:37

Quote: Originally posted by ZHANGNIUBI

Chinese people did some research on that((but they mix AL powder and (CF2)n), and I got that paper, but I can not imagine how it works...
it is wonderful and really powerful !!!(I believe it is much better than black powder) thank you for sharing the video..!!!

Greetings, Zhangniubi

It is amazing I can meet people from across the world here on Sciencemadness and exchange thoughts/share our interests

Yes I have been doing sums on the energy evolved from PTFE + Al and PTFE + Mg mixtures.

I found this great website that has a huge database of data:
http://webbook.nist.gov/chemistry/form-ser.html

Anyway,

Mg + F2 -> MgF2............ΔHf = -1124 kJ/mole

2Al + 3F2 -> 2AlF3............ΔHf = -1510 kJ/mole

2nC + 2nF2 -> -(C2F4

-n............ΔHf = -833 kJ/mole

Balanced aluminum-PTFE reaction:
4Al + 3-(C2F4

- -> 4AlF3 + 6C

ΔH = 833×3 - 4×1510 = -3544 kJ (when 3 moles of -(C2F4

- react with 4 moles of Al)

Mass of reactants = 4×27 + 3×(12×2 + 4×19) = 408g
ΔH per gram of reactants = -3544/408 = -8.686 kJ/g

Still a respectable yield

If you guys spot any mistakes in my calculations please feel free to peer review them

. Always eager to learn....

Jimbo Jones - 21-6-2011 at 03:22

http://www.sciencemadness.org/talk/viewthread.php?tid=15187#...

IndependentBoffin - 21-6-2011 at 03:59

Quote: Originally posted by Jimbo Jones

http://www.sciencemadness.org/talk/viewthread.php?tid=15187#...

Thanks.

Quote:

In the past I have tried to initiate some ETN based caps with fast thermite, but they all fail to detonate, even in bigger diameters. The thermite was based on “painted” with acetone & NC & flake aluminum powder Teflon tape. This thing is extremely fast, almost as flash powder, so in confined spaces….how knows. It’s somewhat difficult for ignition, but even a Visco will do the trick if the tape thermite is rolled around the fuse. After 3 tests, I just abandoned the idea.

I tried igniting a PTFE/Al powder (unfortunately I bought the Al powder off Ebay so I can't tell you the mesh size) and after significant heating the PTFE tape melted but no visible reaction happened between the PTFE/Al.

What about a PTFE/Al mixture with trace quantities of KOH, K2CO3 or KClO to attack the oxide layer?

According to compatibility datasheets alumina has severely poor compatibility with all of these. Can any of the above (or other) additives attack the oxide layer without needing a troublesome aqueous medium? What about gaseous HCl from thermally decomposing NH4Cl?

Jimbo Jones - 21-6-2011 at 04:19

The methanol will do the trick to some degree, but my advice is just to use the finest aluminum powder you can get.

IndependentBoffin - 21-6-2011 at 05:42

Quote: Originally posted by Jimbo Jones

The methanol will do the trick to some degree, but my advice is just to use the finest aluminum powder you can get.

There are obvious economic and ease-of-acquisition reasons to pursue PTFE/Al thermites instead of PTFE/Mg thermites.

My ability to experiment has been severely hampered by my upcoming house move in just over a week but next up I will be trying thermite mixtures.

CuO/Al or MnO2/Al to kindle the flame and the main bulk being PTFE/Al (due to the large ΔH). CuO/Al in particular has been known to be very easy to initiate.

Just think of the detonation train for explosives, but this time for thermites

The WiZard is In - 21-6-2011 at 08:15

Quote: Originally posted by IndependentBoffin

Thank you for the delightful references, The WiZard is In

Quote:

I'll give you an educated WAG ... la Pellets were ignited before
being fired. I be having a hard time believing they are sensitive
enough to ignite on impact with a rabbit.

Morgan - 21-6-2011 at 08:25

I wonder how the waxy version would work if mixed intimately with magnesium powder? Or are they using the word waxy loosely?

"PTFE was accidentally invented by Roy Plunkett of Kinetic Chemicals in New Jersey in 1938. While Plunkett was attempting to make a new CFC refrigerant, the tetrafluoroethylene gas in its pressure bottle stopped flowing before the bottle's weight had dropped to the point signaling "empty." Since Plunkett was measuring the amount of gas used by weighing the bottle, he became curious as to the source of the weight, and finally resorted to sawing the bottle apart. Inside, he found it coated with a waxy white material which was oddly slippery. Analysis of the material showed that it was polymerized perfluoroethylene, with the iron from the inside of the container having acted as a catalyst at high pressure. Kinetic Chemicals patented the new fluorinated plastic (analogous to known polyethylene) in 1941[1] and registered the Teflon trademark in 1945.[2][3]"
http://en.wikipedia.org/wiki/Polytetrafluoroethylene

Chemistry
Structurally, there are different types of Teflon:
- Teflon PTFE resin is a polymer consisting of recurring tetrafluoroethylene monomer units with the formula: (CF2-CF2)n
http://www.lenntech.com/teflon.htm

I would suggest being cautious with breathing any of the fumes from burning any of these substances. If it isn't air, I don't want to breathe it. ha

[Edited on 21-6-2011 by Morgan]

IndependentBoffin - 21-6-2011 at 14:13

For further experimental delight I am currently trying to source some 10-20 micron PTFE powder

. I was thinking about nanometric PTFE powder but such a fine powder would require further safety measures during handling and manufacture.

Trust me guys this is going into my next invention I just enjoy my work too much I can appear like a kid in a candy shop

PTFE/FEP health risks

argyrium - 22-6-2011 at 10:04

From what I've read - you do NOT want to be downwind of any of these experiments.
I have no references at hand but recall that the decomposition products were potentially quite toxic - at least giving one exposed to them "flue-like symptoms".

Should have read: "flu-like symptoms" :-0

[Edited on 22-6-2011 by argyrium]

IndependentBoffin - 22-6-2011 at 10:21

Quote: Originally posted by argyrium

From what I've read - you do NOT want to be downwind of any of these experiments.
I have no references at hand but recall that the decomposition products were potentially quite toxic - at least giving one exposed to them "flue-like symptoms".

*Cough cough* I'm fine...really...

But alright, thanks, point noted better safe than sorry.

If you come across the references please let me know.

From what I can tell the complete combustion products should just be MgF2 and C, but of course since we are talking about fast reaction rates and self-dispersal by the expanding gas the probability of absolutely everything reacting to completion is small.

Morgan - 22-6-2011 at 11:42

I've read that teflon coated irons, waffle makers, pans, even some ovens, are all hazarous to birds becaue they/some have a teflon coating. I remember one pan I bought came with a warning that it could cause headaches if overheated.

I don't know how scientific this paper is but it's some food for thought.
"At 680°F Teflon pans release at least six toxic gases, including two carcinogens, two global pollutants, and MFA, a chemical lethal to humans at low doses. At temperatures that DuPont scientists claim are reached on stovetop drip pans (1000°F), non-stick coatings break down to a chemical warfare agent known as PFIB, and a chemical analog of the WWII nerve gas phosgene."
http://www.ewg.org/reports/toxicteflon

IndependentBoffin - 22-6-2011 at 12:05

OK thanks. I did do the tests outside in the garden but I will use delayed or remote electric ignition from now onwards

Didn't imagine anything majorly toxic could come about from -(CF2

- compounds but we learn something new every day

Hopefully I wasn't exposed to too much toxic fumes. When you overheat a Teflon pan with no strong reducing agent for the carbon there is nothing that can happen to the PTFE except vaporise and/or decompose. In the presence of a strong reducing agent like Mg or Al it would hopefully sieze and bind to (most of) the fluorine and leave behind carbon soot.

[Edited on 22-6-2011 by IndependentBoffin]

argyrium - 22-6-2011 at 13:10

Quote: Originally posted by IndependentBoffin

Quote: Originally posted by argyrium

*Cough cough* I'm fine...really...

Here is one.
http://www.fluoridealert.org/pesticides/teflon.effects.lung....

IndependentBoffin - 22-6-2011 at 14:08

Thanks folks. I look embarrassingly uninformed about the dangers of burning Teflon. The combustion byproducts look quite serious even despite my macabre sense of humour.

I hope I wasn't exposed to too serious byproducts by the sequestration of the F- ions by the Mg.

That said I am moving to the countryside soon so finding a quiet, open, well ventilated place to test this thermite shouldn't be difficult.

And thanks again. I learnt a lesson here. I wasn't expecting toxic byproducts because I assumed all that would be left was MgF2 and C. I forgot about secondary byproducts. Next time I will do a thorough risk assessment and discuss the issues with you guys for peer review.

[Edited on 22-6-2011 by IndependentBoffin]

pjig - 24-6-2011 at 16:41

Is finely powdered PFTE even available to the Gen. public?
I guess micro powders are used in molding parts.

DHT420 - 24-6-2011 at 16:51

Quote: Originally posted by pjig

Is finely powdered PFTE even available to the Gen. public?
I guess micro powders are used in molding parts.

Www.google.com

Specifically...

http://www.google.com/search?q=ptfe%20powder

Specifically...

http://www.spurlocktools.com/id39.htm

So nope, only super scientists can buy it.

pjig - 24-6-2011 at 18:30

I did find that last site as well...., its just to dang expensive .

It is a very interesting mix though. Having a greater energy output by flame initiation v.s. a #8 det. Most would assume that the reaction would behave like copper thermite and or the standard Flash powder. These increase in VOD , while the while flame ignitionof the PFTE/mag seems to create a longer duration of a shock wave....creating much more damage than being detonated by a cap.

IndependentBoffin - 25-6-2011 at 00:25

Quote: Originally posted by pjig

I did find that last site as well...., its just to dang expensive .

It is a very interesting mix though. Having a greater energy output by flame initiation v.s. a #8 det. Most would assume that the reaction would behave like copper thermite and or the standard Flash powder. These increase in VOD , while the while flame ignitionof the PFTE/mag seems to create a longer duration of a shock wave....creating much more damage than being detonated by a cap.

PTFE powder in itself is not a controlled substance so individuals can buy it. If you wish to buy nanometric PTFE powder I would invest in proper handling equipment for it. Nanometric PTFE powder can probably be suspended for long durations in air and would stick to most surfaces. Once inhaled, given its inert nature, it would persist in your lungs.

Also the powders would also have a size distribution. So in nominal 10 micron powders, expect to find a small percentage at the nm size. This is why I decided to go for 20 - 30 micron powders.

Mixed sufficiently intimately and shocked, PTFE/Mg may be capable of detonation. PTFE/Al apparently is: "Detonation-like energy release from high speed impacts of polytetrafluoroethylene-aluminum projectiles", R.G. Ames, R.K. Gerrett and L. Brown (2002). Presentation at 5th Joint Classified Bombs/Warheads and Ballistics Symposium, Colorado Springs, June.

According to an article I downloaded from here ("Advanced Energetic Materials") research is currently ongoing into thermite-gas generator mixes.

Stoichiometric PTFE + Mg doesn't generate gas on its own (unless some reactants/products vaporise or the carbon sublimates), but produces tremendous amounts of heat, c.f. PTFE/Al (-8.7kJ/g) or PTFE/Mg (-9.5kJ/g).

Explosives (esp. primaries) have relatively feeble reaction enthalpies per gram; TNT -4.6kJ/g and HMX -5.7kJ/g.

So a really powerful thermite-gas generator explosive would have the thermite producing the heat (thereby increasing pressures) and a gas generator producing the gas. Quote from the reference below:

Quote:

A second major area of effort is being pursued at LLNL, where the incorporation of metal oxides (e.g., ferric oxide) with nanoscale aluminum into polymer support is being sought using sol-gel technology to produce a xerogel. The reaction of aluminum with ferric oxide produces a thermite reaction. The polymer binder and/or added gas-generating materials are able to produce a working fluid when this is desired. The incorporation of nanodimensional organic energetic materials (e.g., RDX and pentaerythritol tetranitrate) and inorganic oxidizers (e.g., ammonium perchlorate) into silicate gels or resorcinol-formaldehyde (RF) gels by the use of sol-gel methods was initially pursued at LLNL, with tantalizing results. Recently this direction has also become a thrust area in the DURINT program, where an attempt is being made to desensitize impact-sensitive materials such as CL-20 by incorporating them on the nanoscale into RF and nitrocellulose gels.

If you have an ultrafine thermite, you can try mixing that with an explosive and making an assessment of its enhancement*. I'd recommend starting with PTFE/Al because of its stability, low sensitivity and the well documented passivation properties of Al2O3....and low initial costs of investigating.

Until I read more on the topic, I do not know how stable the MgO passivation layer is in the presence of various primary or secondary explosives. We already do know that some metal and metal oxides catalyse the decomposition of organic peroxides, a very common primary available to home experimenters. So proceed with caution.

*Enhancement mechanisms:
1) Better shock coupling to targets due to higher density of the shockwave by metal/metal oxide particles.
2) Hotter reactions leading to higher overpressures and/or blast enhancement. Note that even in military aluminised explosives (100 - 150 micron powders), the aluminum additive does not react in time with the detonation products over the explosion timescales, yet is still capable of increasing damage when it does react within about 10ms of initiation.

Attachment: Advanced Energetic Materials.pdf (828kB)
This file has been downloaded 1371 times

[Edited on 25-6-2011 by IndependentBoffin]

malford - 7-11-2013 at 06:50

Quote: Originally posted by IndependentBoffin

n -> 2MgF2 + 2C

Mg + F2 -> MgF2 ................................ ΔHf = -1124 kJ/mole

2C + 2F2 -> -(C2F4

n- ................................ ΔHf = -832.6kJ/mole

Heat of reaction = 832.6 - 2×1124 = -1416 kJ for 2 moles of Mg and 1 mole of (C2F4

n.

Because I am an engineer and tend to think in terms of specific energy this gives 1416/(2×12 + 4×19 + 2×24.31)kJ/g or 9.526 kJ/g of reactants.

http://www.sciencemadness.org/talk/viewthread.php?tid=24980

As you can see in the chart, regular flash powder ranks high with -10.59 kJ/g, but more importantly for munitions -27.38 kJ/cm³. To slow the reaction of flash powder, one can use dissolved nitrocellulose as a binder. This makes for a spectacular igniter.

Zyklon-A - 26-2-2014 at 12:52

I know this has been dead for a while, but I here is a good read on the subject:

Attachment: (MTV-1) Magnesium-Teflon-Viton Pyrotechnic Compositions.pdf (1.8MB)
This file has been downloaded 765 times