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Turner
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Al/KNO3 -- No reaction
With intense heat from a propane torch, I tried to ignite roughly half and half KNO3 and Aluminum powder (supposedly 425 Mesh) and got no reaction,
the aluminum melted into a solid piece. I am wondering if this is even 425 mesh? It looks very fine, but I bought on Ebay a while ago. I figured, it
is rated at 3 for flamability, but no chance of igniting it with a lighter, and impossible to ignite with KNO3/Al and a lot of heat?
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Bot0nist
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Not a good mix, try perchlorates instead. The potassium nitrate probably melted before the activation temp of the Al (and oxide layer) where reached.
Also, for flash like compositions, you will want to go for the finest mesh, non spherical Al available, like some german black or similar micron sized
material. Your Al may work well in ferroaluminum thermite reactions though. Maybe even a nice "thermate" if you add some small amount of
chlorate/perchlorate. Remember that chlorate containing mixes are inherently dangerous and prone to detonation in some instances...
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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WGTR
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Edit: added extra details.
http://www.youtube.com/watch?v=C0HzR_9USHg
has an interesting comparison test. A KNO3 and Al powder mix is relatively weak, even when well-mixed.
I would guess your problem is either:
1. This may sound dumb, but did you dry the KNO3 and grind it to a powder? Solid granules won't work in this situation.
2. The components were not well-mixed. Just for safety, I diaper the powders well on a piece of paper, wearing a face shield and leather
gloves. In other words, don't impact it by grinding the mixture between a mortar and pestle. In fact, never grind metal powders into a
pyrotechnic mix. It's a really bad idea. In addition, experiment with less than a gram or two until you have some experience, or are working
with someone who does.
3. The aluminum has been oxidized by over-exposure to air.
An aluminum and KNO3 mix is not very stable in storage, especially in the presence of moisture, as the mixture slowly reacts. About 1% boric
acid is sometimes added as a stabilizer.
Even if the aluminum is spherical, if it is really that fine (and fresh), the mix should at least do something. See the above video, using
spherical aluminum.
[Edited on 19-12-2013 by WGTR]
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Turner
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I tried the aluminum powder alone (which at this mesh, should have no problem burning so I thought) and got nothing but a cast chunk of aluminum. This
Aluminum is spherical, I don't intend to use it for any flash compositions. I'll try grinding up the KNO3 and then mixing.
[Edited on 19-12-2013 by Turner]
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Bot0nist
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Spherical is best for making a "shooting spark" effect in some pyrotectics. This is also.why you are having trouble getting it to burn. The surface
area. Go for flakes next round. Good luck.
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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elementcollector1
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The aluminum melted from the propane torch? Can't get mine to do that.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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Turner
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The number one use I had in mind was an Ammonium Perchlorate Composite cast rocket fuel w/ this aluminum later on.
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DubaiAmateurRocketry
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This is normal,
Aluminum dont go with nitrates, thats all. Aluminum have a much higher activation energy nitrate salts can give.
For nitrates, magnesium works.
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Turner
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Good to know thanks.
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DubaiAmateurRocketry
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Thats weird, A flame temperature of a normal cigarette lighter can do that, just apply the hottest part of the flame(end part) to aluminum, and it
will melt.
If it dosnt, it might be because its too big of a piece, aluminum have a very high heat conductivity and transfer the heat to other parts as it cools.
Therefore, if you heat a small rock of aluminum, it will melt, propane tourch will do it in seconds.
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Zyklon-A
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I don't think a cigarette lighter can melt Al, maybe a verrrrrry small chunk, a propane torch however.....
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Bot0nist
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I can also confirm what Dubaiamateurrocketry claims. 300 mesh will melt and glow, even if spherical from the butane flame of a bic lighter.
Small amounts in foil, in my experiamce. Through a little dry red rust in with it for some effect.
[Edited on 20-12-2013 by Bot0nist]
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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IrC
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From: http://www.engineeringtoolbox.com/melting-temperature-metals...
Aluminum melts: 660 C 1220 F
From: http://en.wikipedia.org/wiki/Propane_torch
The maximum adiabatic flame temperature a propane torch can achieve with air is 1,995 °C (3,623 °F).
Some propane torches are also used with a tank of pure oxygen to achieve a flame temperature nearing 2,820 °C (5,110 °F).
I don't see why not.
Quote: Originally posted by Turner  | | The number one use I had in mind was an Ammonium Perchlorate Composite cast rocket fuel w/ this aluminum later on. |
Not a very safe way to go:
http://www.youtube.com/watch?v=oc_nnnBmMbM
Ammonium Perchlorate production facility catches fire and detonates 3 times with shock waves racing across the desert floor in Henderson, Nevada.
Pay attention to the words in the video mentioning combination with any contamination, and especially when combined with any type of fuel.
"Science is the belief in the ignorance of the experts" Richard Feynman
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DubaiAmateurRocketry
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| Quote: Originally posted by IrC |
Ammonium Perchlorate production facility catches fire and detonates 3 times with shock waves racing across the desert floor in Henderson, Nevada.
Pay attention to the words in the video mentioning combination with any contamination, and especially when combined with any type of fuel.
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Well, not too bad, when you have binder.
One bad thing about it is its fast burn rate, where amateurs often end up over pressuring their combustion chamber and explode.
Happened to me once, I added a burn rate modifier and its safe.
http://www.sciencemadness.org/talk/viewthread.php?tid=28001
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Zyklon-A
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My propane torch can get maybe 1400C.
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Turner
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How does AP compare to some materials that are usually used for thei detonations (ETN, RDX, HDN, AN etc.) Not sure Id ever use ETN as a propellant but
RDX seems to be fairly sensitive to flame and the burn looks quiet energetic, although lighting larger amounts the flame looks quiet poor Asa. Rocket
fuel.
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DubaiAmateurRocketry
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| Quote: Originally posted by Turner | How does AP compare to some materials that are usually used for thei detonations (ETN, RDX, HDN, AN etc.) Not sure Id ever use ETN as a propellant but
RDX seems to be fairly sensitive to flame and the burn looks quiet energetic, although lighting larger amounts the flame looks quiet poor Asa. Rocket
fuel.
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RDX in the above list is often used as propellant in binders because it produces a large amount of gas with low molecular weight, N2, CO, H2O. However
it does not contribute to the OB of the system. AP is less energetic than RDX alone, however have an OB of +34%. AP's OB is debatable due to its
chlorine atom and its unbalanced decomposition. In many calculations people take chlorine as 0.5 oxygen, however the OB +34% seems higher than its
reality, I often get some traces un-burned char from fuels when I use AP as +34%, I find it for closer to +29-31% with my own calculations :p
[Edited on 21-12-2013 by DubaiAmateurRocketry]
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Turner
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And RDX is roughly -21% by weight, so would trying a propellant that is about half RDX and half Ammonium perchlorate (30%) plus binder be a good
energetic propellant?
I'd like to sometime build my own motor with far greater thrust and burn time and try this in a stock model rocket.
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Zyklon-A
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There are a few Al + KNO3 recipes that work well. Check this out.
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Zyklon-A
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Does anyone Know the equation for Al + KNO3? I have not seen it anywhere.
I think it might be 2KNO3 + 2 Al --> Al2O3 + K2O + N2 + O2. Is this correct?
[Edited on 10-1-2014 by Zyklonb]
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Dornier 335A
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Yes, that sounds plausible.
Balanced it would be 6 KNO3 + 10 Al → 3 K2O + 5 Al2O3 + 3 N2
That's 69.2% KNO3 and 30.8% Al by mass.
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smithdotyu
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Actual， the KNO3 with Al Recat slowly.because your Al is thick , the firework Al is too thin to light，you can use Mg instead。
here is my test video：
KNO3 + Al
http://youtu.be/Lt3XAUmD1ps
KNO3 + Mg
http://youtu.be/crkuTDuqK44
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Zyklon-A
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My aluminum always burns well with potassium nitrate. It's coated in a de-duster and is less oxidized.
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blogfast25
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I've used KNO3 + Al powder as a heat booster in some thermite mixtures and found it almost perfectly equivalent to the better known KClO3 + Al powder
system.
Less well known is the CaSO4 (anh.) + Al powder system which also burns very, very hot (> 2500 C).
[Edited on 26-2-2015 by blogfast25]
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Bert
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The OP had a fairly coarse spherical Aluminum, more suited to fireworks stars than flash powder- And his mixture was too low on oxidizer as well.
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