Sciencemadness Discussion Board - Ammonium nitrate as propellant

Ammonium nitrate as propellant

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ecos - 18-3-2015 at 02:27

Can I make a propellant using AN+Polystyrene?I know it is used in BLU - 82 with Al but that an explosive not a propellant.

I would give you my point of view but it might not be correct.

the molcular formula for Polystyrene (C8H8)n , the ratio of H/C is not high also it would still need oxygen for its burning , this would mean extra oxidizer.

Fulmen - 18-3-2015 at 02:39

In theory: Sure. In reality? Probably not. Formulating a working propellant involves much more than simply combining an oxidizer with a fuel. For the novice the only realistic approach is to follow the work of others.

PHILOU Zrealone - 18-3-2015 at 07:42

Quote: Originally posted by kecskesajt

Can I make a propellant using AN+Polystyrene?I know it is used in BLU - 82 with Al but that an explosive not a propellant.

NH4NO3 (= AN)
MM= 80.04
d= 1.72

(-CH2-CH(-C6H5)-)n (=(C8H8)n = PS)
MM/unit= 104.15
d= 1.06

NH4NO3 --> N2 + 2 H2O + 1/2 O2
So each mole of NH4NO3 gives 1/2 mole O2 (or 1 mole O).

You would need 20 moles of O to burn completely C8H8 into CO2 and H2O, and 12 moles O to burn it uncompletely to CO and H2O.

Partial combustion case
So 12*80.04g of NH4NO3 are needed for the of 104.15g of PS.
Weight ratio: 960.48/104.15
or 9.783% PS and 90.217% AN
Density of the mix = 1.65543

Complete combustion case
So 20*80.04g of NH4NO3 are needed for the of 104.15g of PS.
Weight ratio: 1600.8/104.15
or 6.109% PS and 93.891% AN
Density of the mix = 1.67968

From my experience with PS and NaClO3 (MM=106.44) what is a much better oxydant (3 O / mole) than NH4NO3 (so you need less oxydizer material% and it allows to increase the PS binder%); NaClO3 is also denser (so the volume to coat by the binder is also less):
The stoechiometric mix with PS is very brittle and doesn't burn well (while NaClO3/fuel is usually easily set in fire and burns fiercely).
There are big chances AN/PS will be even more brittle and doesn't hold well together...also the flamability might be low and the burn propagation might be ineffective (especially if AN not wel anhydrous).

To help a bit one may find interest in investigating polynitrostyrene ((C8H7NO2)n MM/U= 149.16) and polydinitrostyrene ((C8H6N2O4)n MM/U= 194.17)!
PNS needs 9.5 mole O for uncomplete combustion and 17.5 for complete burning.
PDNS needs 7 mole O for uncomplete combustion and 15 for complete burning.

The increase of the Oxygen balance will increase the % of binder:
AN/PNS (uncompl) weight%: 16.400% PNS / 83.600% AN
AN/PNS (compl) weight%: 9.624% PNS / 90.376% AN

AN/PDNS (uncompl) weight%: 25.737% PDNS / 74.263% AN
AN/PDNS (compl) weight%: 13.921% PDNS / 86.079% AN

The use of polytrinitrostyrene (expected density in the vicinity of 1.83 vs 1.54 for the monomer (TNS)) is unadvisable for propellant applications because of the risk of detonation.
But as a brisant explosive,the stoechiometric mix AN/PTNS would display a good density and VOD.

Note that the nitrogroups can be set on the aromatic ring but also on the alkanic chain...so nothing prevent the study of poly-trinitrophenyl-nitroethylenes and poly-trinitrophenyl-dinitroethylenes. The later two would have very high density because polymers have always (a few rare exceptions exists) much higher densities than the monomeric material.
Typical examples:
Ar-CH=O + CH3-NO2 --> Ar-CH=CH-NO2 + H2O
Ar-CH2-NO2 + CH2=O --> Ar-C(NO2)=CH2 + H2O
Ar-CH=O + CH2(NO2)2 --> Ar-CH=C(NO2)2 + H2O
First and last conformation are less prone to easy polymerisation because the aromatic ring is not on the same side as the nitro group(s) and there is thus a competition for the polarization of the double linkage...a polymerization inducer might then be needed!

If you start from mononitro-, dinitro- or trinitroaromatic reactants...you get the desired monomers with high densities!

In the case of TNP-C(NO2)=CH2 it should display a density arround the 1.79g/ccm, polymerization will boost the density up to a density arround 2.0573g/ccm!

[Edited on 18-3-2015 by PHILOU Zrealone]

ecos - 20-3-2015 at 06:41

I am sorry but I don't understand what is the benefit of Polystyrene for BLU-82 ? is it used as binder ?

ecos - 25-3-2015 at 01:24

I am in the last steps of building my ball mill.

The problem now is to find a 1/2 HP motor that rotates at 80 RPM ! , most of motors in the market starts with 1000 RPM.

This means I need to have a control circuit for speed.

Any suggestions ?

Fulmen - 25-3-2015 at 02:23

What you need is a pair of pulleys to reduce the speed.
The classic design uses a jar driven by a roller, in that case the diameter of the roller and the jar also works as gearing.
Let's say you have a 1" roller and a 4" jar, this gives a gearing-ratio of 4, meaning the roller must rotate at 320rpm. So if your motor runs at 1000rpm you need a 1000/320=3,1-ratio for the pulleys.

In theory you could use a VFD to drop the motor speed, but they are not cheap. A DC-motor should not be used as they spark continuously from the brushes.

[Edited on 25-3-15 by Fulmen]

ecos - 27-3-2015 at 00:54

Hi Fulmen, this idea is great and easy

. I will try to use pulleys.

regarding the media in the jar , I found this balls.

weight = 21 grams
diameter = 1 "
It seems it is strong glass.

I think if it was iron balls it would be 60 grams but I still couldn't find them.

I understood from the ball mill document that, the media density should be higher than the charge.

Aluminum 2.7 (103 kg/m3)
Glass 2.4 - 2.8 (103 kg/m3)

I don't know why we have the rule of density here ?! would the glass balls work ?

Fulmen - 27-3-2015 at 03:28

I don't recall anything about the media density being higher than the charge, but as a general rule the density should be as high as possible. This is related to the energy of each impact, smaller, high density media will provide more impacts per time unit. For any charge and jar size there will be an optimal ball weight (it should decrease with increasing jar diameter IIRC), lighter balls won't have the energy to grind efficiently while heavier balls will simply waste energy causing increased media wear. Determining this will require experimentation, looking at others results should provide some guidelines.
The media must also be harder than the charge, that is certainly the case with glass. However, glass does come with some drawbacks. It can produce fine glass powder which is known to increase friction sensitivity of powders. I would recommend steel media if you can get it, ceramics are probably also safer. Just don't grind black powder with hard media, lead or copper alloys are the safest alternatives.

ecos - 27-3-2015 at 06:15

Quote: Originally posted by Fulmen

I don't recall anything about the media density being higher than the charge, but as a general rule the density should be as high as possible. This is related to the energy of each impact, smaller, high density media will provide more impacts per time unit. For any charge and jar size there will be an optimal ball weight (it should decrease with increasing jar diameter IIRC), lighter balls won't have the energy to grind efficiently while heavier balls will simply waste energy causing increased media wear. Determining this will require experimentation, looking at others results should provide some guidelines.
The media must also be harder than the charge, that is certainly the case with glass. However, glass does come with some drawbacks. It can produce fine glass powder which is known to increase friction sensitivity of powders. I would recommend steel media if you can get it, ceramics are probably also safer. Just don't grind black powder with hard media, lead or copper alloys are the safest alternatives.

I remember I read the sentence regarding the densities in "pyrotechnics_ball_mill_theory_sponenburgh" but I don't recall the page

Anyway your statements are very logical.

regarding the Jar, the document stated this design , I don't know what is the aim of the reducer and the smaller pipe?

I think the author uses rubber cap to avoid any friction for the media , is my understanding correct ?

hissingnoise - 27-3-2015 at 06:39

Quote:

I think the author uses rubber cap to avoid any friction for the media , is my understanding correct ?

In a case of accidental ignition, a rubber cap easily pops off ─ could make a difference between a deflagration and an explosion . . . ?

Fulmen - 27-3-2015 at 06:53

The reducer is there to provide clearance for the rubber cap and hose clamp, remember that the jar will rest on rollers. The rubber cap is probably the most convenient end cap available, it also reduces friction that in theory could ignite the powder when opening the jar. If the powder ignites during milling no cap is going to save the mill, it will explode.

[Edited on 27-3-15 by Fulmen]

kecskesajt - 27-3-2015 at 09:21

Ok,thanks.I might give it a try with KNO3

hissingnoise - 27-3-2015 at 09:52

Quote:

If the powder ignites during milling no cap is going to save the mill, it will explode.

I was referring to ordinary BP ─ you're talking about something other than BP, apparently!

Fulmen - 27-3-2015 at 12:01

An explosion doesn't automatically mean detonation if that's where you're going, the powder would still only deflagrate. The word "explode" can simply mean "to increase rapidly", for instance a "population explosion" does not mean that people are exploding (although that happens sometimes as well)

If a BP mill ignites it will explode, shattering the jar into fragments and propel the media at potentially dangerous speeds pretty much regardlessly of any rubber cap.

hissingnoise - 27-3-2015 at 12:27

Quote:

An explosion doesn't automatically mean detonation.

Since you don't appear to know what a detonation actually entails; a detonation is a reaction which proceeds through a mass of material at a speed which corresponds to the speed of sound in the material!

BP cannot be made to detonate and its deflagration proceeds at the speed of heat conductance in BP.

BP when confined can deflagrate at a high speed but which is below supersonic!

A detonation is generally taken to mean any reaction which proceeds at supersonic speed!

When you can mill your own powders you'll find yourself on a learning curve . . .

Bert - 27-3-2015 at 13:44

From the viewpoint of actually seeing the results of various amateur pyrotechnists and rocketey experimenters who DID manage to explode a ball mill- Milling such things as black powder and perchlorate based rocket fuels:

Nope, they didn't detonate.

Damn the difference anyhow, the explosions were substantial and easily would have killed someone who was close by. A couple of them partially destroyed buildings the mills were being run inside of.

Rather than worry about the semantics, worry about locating your mill where it will do no harm to people and minimum damage to property.

Oh, and one other thing: After somehow avoiding arrest, even after explaining truthfully to police and fire department how your garage exploded? Do NOT call your insurance company and file a claim. The provision of insurance policies that you not be covered in case of losses caused by illegal acts WILL spur the insurer to make sure that you get properly arrested!

Fulmen - 27-3-2015 at 16:11

Quote: Originally posted by hissingnoise

Since you don't appear to know what a detonation actually entails

I know the difference between detonation and deflagration. I was only correcting you on this part:

Quote:

rubber cap easily pops off ─ could make a difference between a deflagration and an explosion

Deflagration is a mode of combustion, nothing else. It can cause a slow burn or a violent explosion depending on the conditions, they're not exclusive. So what you meant to say was "difference between a *poof* or a BOOOM" or something to that effect.

Now I could be wrong, as I've never tried to blow up a mill before, but my gut feeling tells me it probably won't do much difference if the lid is made from rubber or solid PVC. Mill powder will burn extremely rapid if confined, a reasonable sturdy jar should provide ample confinement for an explosion.

hissingnoise - 28-3-2015 at 03:21

Quote:

I was only correcting you on this part.

(sigh!)Son, I've forgotten more on the subject than you'll ever know!

But seriously, in the unlikely event of ignition within a jar containing moist BP, a flexible cap which pops off at the initial increase in pressure within the jar will be a few magnitudes safer than otherwise!

That said, I've dry-milled BP using AH lead many times without problems ─ not something I recommend, obviously ─ but lead shot is non-sparking and when properly earthed the mill is relatively safe to run!

Fulmen - 28-3-2015 at 05:22

Quote: Originally posted by hissingnoise

(sigh!)Son, I've forgotten more on the subject than you'll ever know!

Do I look impressed? Rather than telling me how much you've forgotten, could you educate me on exactly where I am wrong?

As for your claim that a rubber lid will reduce the blast, can you document this? From what I've read over the years a BP mill will explode violently if ignited. Perhaps a rubber lid will reduce the blast somewhat, but I seriously doubt if it will prevent it from exploding. Remember that much of the powder will be in between the media, this alone should provide a significant amount of confinement.
If you think a rubber cap fixed with a hose clamp will simply slip off at the first sign of pressure you're flat out wrong. You need a fair amount of clamping force to guarantee that the lid will stay on during the milling process, more than enough to provide a fair amount of confinement during an explosion.
And while my memory is somewhat rusty after 20 years, I cannot for the life of me recall that Lloyd ever claimed that these rubber lids would prevent an explosion. IIRC it was chosen as a cheap, readily available lid that provided perfect seal with a minimum of friction during assembly/disassembly.

hissingnoise - 28-3-2015 at 09:54

Quote:

From what I've read over the years a BP mill will explode violently if ignited.

Jeeez! Anyone can parrott the various texts they've read but it's a poor substitute for hands-on experience . . .

Go make your own powder, FFS ─ then perhaps you'll have more idea of what it may or may not do?

Fulmen - 28-3-2015 at 14:07

Who said I haven't? I actually have a mill (6" mill jar) built after Lloyds design, complete with the rubber lid in question. What I haven't done (for obvious reasons) is to blow it up, therefore I have to rely on the experience of others. Is that so unreasonable? As Bert also confirms, these mills are known to blow up violently if they ignite. The risk is slim, I've never tried to claim otherwise, but believing that a rubber lid will reduce the severity of the blast can be a dangerous assumption.
Now if you have first hand experience with blowing up mills, both with a hard and a rubber lid, that's another story and I would very much like to hear of your experience.

Bert - 28-3-2015 at 19:39

Everyone calm down and discuss either engineering concepts, which suggests some theory be provided and math to back it up quoted-

Or relevant personal experiences, ideally a precise and dispassionate description, with photographic evidence if available.

[Edited on 29-3-2015 by Bert]

ecos - 28-3-2015 at 23:05

Hi all ,
I am not experienced like most of you but i read a lot of articles that state that milling BP is dangerous operations. Some add alchol to BP to decrease its sensitivity.

The last chapter of the ball mill that Bert shared has a real accident of the author while milling magnesium powder. Just have a look.

PHILOU Zrealone - 29-3-2015 at 10:06

I always use an electric coffee ginder, and grind separately oxydizers and fuels.

I think that in a ball milling you may do the same to get extra security. Eventually with a highly unbalanced ratio oxydizer/fuel.
That way even if something happens, the powder will not explode.

Afterwards you may mix two powders (fuel(s) and oxydizer(s) (or unbalanced Fuel (+) Oxydizer (-) and unbalanced Oxydizer (+) and Fuel (-)) by the Rolling paper method.

[Edited on 29-3-2015 by PHILOU Zrealone]

hissingnoise - 30-3-2015 at 01:32

Quote:

Afterwards you may mix two powders (fuel(s) and oxydizer(s) (or unbalanced Fuel (+) Oxydizer (-) and unbalanced Oxydizer (+) and Fuel (-)) by the Rolling paper method.

Diapering PHILOU? Jeez, it's a propellant ─ not a fucking primary?

Bert - 30-3-2015 at 04:25

It is not a bad thing to suggest an inexperienced amateur choose a lower friction method from the spectrum of those possible.

Someone just starting out and mixing a few grams of a (new to them) EM might use a natural bristle paint brush to stir and a paper to diaper. Probably won't have a friction issue, can judge degree of mixing by color-

If you have some experience and a feel for the sensitivity of a mixture, you might choose to use ingredients previously screened separately through 40 mesh, briefly diaper mix them on a large sheet of paper and then run the full mix through a 20 mesh screen into a receiver three times.

If you were REALLY experienced, and had the barrier space and equipment- You could dump the chemicals into a "Y" mixer and run that remotely for however long your manufacturing experience had shown to be adequate.

ecos - 30-3-2015 at 06:24

Hmm , most of the caps i found were made of rubber and as i read here it still won't help a lot if spark happens !

I think plastic bags would work ? I think it is more weaker than rubber and would cause deflagration instead of explosion

PHILOU Zrealone - 30-3-2015 at 07:00

Quote: Originally posted by hissingnoise

Quote:

Afterwards you may mix two powders (fuel(s) and oxydizer(s) (or unbalanced Fuel (+) Oxydizer (-) and unbalanced Oxydizer (+) and Fuel (-)) by the Rolling paper method.

Diapering PHILOU? Jeez, it's a propellant ─ not a fucking primary?

Some mixes are very prone to initiation...
1°)I had the case with a big spark-flash in my electric coffee grinder (11000 rpm) by grinding dry NH4NO3 prills...due to the friction some of the inox had intimately mixed with the NH4NO3...resulting in a bright flash and spark inside the grinder. Hopefully it was just NH4NO3 and only a very tiny % of metalic dust...thus highly unbalanced.
2°)In the beginning I used coffee grinding of my black powder (KNO3/S/C) but once I did it on a small quantity to test for ultrafine BP and it took fire in less than 3 seconds...propelling the top of the grinder away in a big fire ball...the quantity was low like one coffee spoon and the mixing was not 100% acheived.
3°)Afterwards I was working with much more powerfull mixes involving chlorates...so from now on with a new coffee grinder I remain on the safe side even if the mix does seem safe...I don't want to take the 1 on 1000 chances for the mishaps.

Coffee Grinder

MineMan - 31-3-2015 at 18:28

I second that. I was once grinding magnesium in a coffee grinder and saw about a 1 inch diameter flash. Decided to stop right there.

ecos - 1-4-2015 at 00:23

I found a nut in the same size of the glass pall i presented before , The Nut is 3.2 times heavier than the glass ball and almost the same volume.

I put the glass ball over the nut to present the idea :

the nut is 69 grams. would that size fit well or I need a smaller nut ?

I found a smaller one but it was 21 grams weight. the larger nut is 121 gram but really big !

any suggestions ?

hissingnoise - 1-4-2015 at 01:57

You need non-sparking antimony-hardened lead balls if you're intent on grinding ingitible mixtures!
Steel and ceramic media will spark and are dangerous ─ glass is essentially useless . . .

ecos - 1-4-2015 at 04:31

Quote: Originally posted by hissingnoise

You need non-sparking antimony-hardened lead balls if you're intent on grinding ingitible mixtures!
Steel and ceramic media will spark and are dangerous ─ glass is essentially useless . . .

Thx for the link and the info.

I plan to grind Al only in the current time. I would use 6" X 8 " jar. I need to fill 50% of it with media "milling balls". Therefore I would need large amount of balls.

the webiste offers 2.5lb of Hardened Lead for $25. of course I would need more, I still need to pay for shipping cost !

I think metal will not spark till it become so hot or hit with a strong force.

I found some videos on youtube that use similar nuts as media :
https://youtu.be/nA94uHqUQvg?

picture for the media :

[Edited on 1-4-2015 by ecos]

hissingnoise - 1-4-2015 at 06:23

Quote:

I plan to grind Al only in the current time. I would use 6" X 8 " jar. I need to fill 50% of it with media "milling balls". Therefore I would need large amount of balls.

A good Al flake can be produced from light Al foil using lead media, given time!

Steel balls are too prone to sparking in combination with Al and steel nuts that might contain traces of Fe₃O₄ on their threads even more so!

In an air-tight mill-jar freshly exposed Al will use up the contained oxygen as milling progresses so that when the run is complete you have Al which is potentially pyrophoric.

If the jar-cap is removed suddenly the inrush of fresh oxygen can cause ignition of the Al which will result in a quick, very hot and long flare ─ and for this reason the cap should be removed slowly so that air may be allowed seep in, rather than rush in!

ecos - 1-4-2015 at 09:51

Quote: Originally posted by hissingnoise

Quote:

I plan to grind Al only in the current time. I would use 6" X 8 " jar. I need to fill 50% of it with media "milling balls". Therefore I would need large amount of balls.

wouldnt the 5% carbon i added to Al prevent the oxidation?

hissingnoise - 2-4-2015 at 05:31

When Al is first exposed to oxygen, oxidation occurs and the oxide forms a thin surface-layer!

It's worth bearing in mind, and no, it isn't preventable by ordinary means . . .

Hennig Brand - 2-4-2015 at 18:18

Not to interrupt the ball mill talk, but I found a couple of igniter compositions that I thought might be interesting. The following is a copy/paste from, "A MANUAL FOR PYROTECHNIC DESIGN, DEVELOPMENT AND QUALIFICATION", which is a NASA Memorandum report from 1995.

TABLE V.- Properties of Boron/Potassium Nitrate (B/KN03)
- Gas generating material
- Burn rate minimally affected by ambient pressure
- High-temperature combustion, hot particles
- Thermally stable
- Vacuum stable
- Long shelf life
- Application as rocket motor igniter and gas generator

References 11 and 12

TABLE V1.- Properties of NASA Standard Initiator (NSI) Mix Zirconium/potassium perchlorate (Zr/KCl04)
- Burn rate of hundreds of feet per second
- Rapid pressure rise Output = hot particles, little gas
- Electrostatically sensitive Good hotwire initiation interface
- Thermally and vacuum stable
- Long shelf life
- Application as an initiator and as an energy source

Edit:
I see where Bert has already mentioned the Boron/Nitrate igniter mix in another thread.

Quote: Originally posted by Bert

Use something that makes a hot flame, and/or something that leaves hot molten dross. Not something normally used to provide shock!

Elemental Boron and Potassium nitrate is a good high temperature gas/flame igniter.

Elemental Silicon and Potassium nitrate will also burn hot, and leave white hot glass slag stuck to the surrounding areas, which will continue to transfer heat to a pyrotechnic fuel for a good long time-

Black Copper oxide/Aluminum thermite is a popular igniter for high power rocketry amateurs as well-

[Edited on 3-4-2015 by Hennig Brand]

Bert - 6-4-2015 at 07:21

I have made & used the Boron/Potassium nitrate mix, it's a reasonably well mannered and effective ignition mixture from personal experience. And can even be ordered ready made from Firefox, shipped as a flammable solid. True enough shipping description, if a bit understated.

image.jpg - 17kB

I have learned to respect the sensitivity of mixtures containing fine Zr powder, they are NOT overstating the sensitivity to ESD in use with typical pyrotechnic oxidizers. Best reserved for applications requiring this, Ti is a bit more forgiving in handling from my personal experience- Also cheaper & more available. Finely powdered Zr metal by itself is not to be trifled with either.

Opening a jar of very fine Zr, supposedly packed safely with sufficient water, using a stainless steel lab scoop to dig out a few grams... And discovering it settled to the point of excluding sufficient water from the lower layer. By having the stuff ignite in your face from steel/Zr friction on scooping it out.

Ah memories... We will enjoy them.

Hennig Brand - 6-4-2015 at 11:14

Boron is something that I have seen many times sitting on drugstore shelves as well as agricultural and garden supply outlets IIRC. Bert, can the B/KNO3 mix be bound with a bit of NC lacquer and easily ignited by low voltage bridge wire?

Bert - 6-4-2015 at 13:19

It would not be the fastest /most sensitive first fire coating, but will work if the bridge wire is robust enough. Crude igniters made by taking a piece of multi strand 18ga insulated copper hook up wire, stripping approx. 3/16" and cutting away all but one strand (the high resistance element!) and bending double at the stripped part, then dipping in pyrogen have worked with the composition. It is not the kind of device that is reliable in series shots, or lights off in 10 micro seconds- But it's easy to make.

(Edit) You have probably seen BORIC ACID and/or BORAX in the places you mention. Elemental Boron is not a common OTC chemical-

[Edited on 6-4-2015 by Bert]

Hennig Brand - 6-4-2015 at 13:33

Ah yes, now that you mention it that is what I think I have seen, not boron. I have a good memory, it's just awful short.

Here are a couple of YouTube videos that show how elemental boron can be made starting with boric acid or borax, producing B2O3 which is reduced in a thermite type reaction to produce elemental boron the same way silicon dioxide can be reduced to produce silicon. There are many more videos also.

https://www.youtube.com/watch?v=0QBCyOrjR2o

https://www.youtube.com/watch?v=niTY6ImAFyk

From Wiki:

"Boron trioxide is produced by treating borax with sulfuric acid in a fusion furnace. At temperatures above 750 °C, the molten boron oxide layer separates out from sodium sulfate. It is then decanted, cooled and obtained in 96–97% purity.[2]

Another method is heating boric acid above ~300 °C. Boric acid will initially decompose into water steam and metaboric acid (HBO2) at around 170 °C, and further heating above 300 °C will produce more steam and boron trioxide. The reactions are:

H3BO3 → HBO2 + H2O2

HBO2 → B2O3 + H2O

Boric acid goes to anhydrous microcrystalline B2O3 in a heated fluidized bed.[8] Carefully controlled heating rate avoids gumming as water evolves. Molten boron oxide attacks silicates. Internally graphitized tubes via acetylene thermal decomposition are passivated."

"The earliest routes to elemental boron involved reduction of boric oxide with metals such as magnesium or aluminium. However the product is almost always contaminated with metal borides. Pure boron can be prepared by reducing volatile boron halides with hydrogen at high temperatures. Ultrapure boron for use in the semiconductor industry is produced by the decomposition of diborane at high temperatures and then further purified with the zone melting or Czochralski processes.[22]"

[Edited on 7-4-2015 by Hennig Brand]

Bert - 6-4-2015 at 17:44

Goldschmidt reaction product should be serviceable for a pyrotechnic hot prime composition in display fireworks, probably not advised for critical applications such as gas less delay elements though.

The grades of Boron and Silicon used in pyrotechnic igniters are NOT semiconductor grade- Way too expensive. I recall buying powdered Silicon from Skylighter claimed at 80% purity, years ago. No idea what the Boron used in the ignition granules is, but really pure Boron would be far too expensive to sell in this mixture at the product's advertised price.

PHILOU Zrealone - 7-4-2015 at 11:07

Boron nitride (BN) might also be a good fuel...with regard to its high positive heat of formation.
Apprently it can be done from B2O3 and NH3 or NH2-CO-NH2 and despite its positive H°f it is quite stable up to 1000°C and above

ecos - 13-4-2015 at 12:21

For the ball mill, I have to run it for 7-11 days to have a very fine AL powder

it is a time/power consuming process !

I think the motor would burn due to the long run-time!, wouldn't it?

hissingnoise - 14-4-2015 at 01:57

Quote:

I think the motor would burn due to the long run-time!, wouldn't it?

Heat sink ─ cooling fan ─ thermal cut-out . . .

A thermal cut-out is the most reliable!

Bert - 14-4-2015 at 05:30

I have a couple of ball mills. They were made to be rock polishing tumblers- This process usually runs for weeks, the motors were specified to take that kind of use. I have had belts wear out, bearings wear out or become corroded, but not burned out a motor yet.

If you make your own mill, pick a motor suitable for the load- A thermal cutout is a good safety feature too.

ecos - 6-5-2015 at 01:07

Ok , I am planning to use pulleys to get the desired RPM.

it should be something like that (just skip the ratios on the figure):

pulley A is driver pulley. pulley D is the mill jar.

This mean the motor would not have any electronic speed control. it will run with maximum speed and the pulleys will take care of speed control due to the diameter ratios.

any advice before I start ?

[Edited on 6-5-2015 by ecos]

[Edited on 6-5-2015 by ecos]

ecos - 3-6-2015 at 05:13

Hi All,

I am in the last state of finishing my ball mill.I couldn't find any steal/lead balls nearby. I decided to use the 1" steal Nuts. I think Nuts have more vacuum in its volume compared to balls.

I need to calculate my material charge percentage according to this statement :

do i need to add excess amount of Al to compensate the full empty space inside the Nuts or just a certain ratio ?

[Edited on 3-6-2015 by ecos]

ecos - 3-9-2015 at 06:01

The nuts are jumping inside the milling jar in a funny way, i think it doesn't work well!!

I prefer now to buy the milling media from the internet ! , any suggestions for good price source and acceptable material?

I made some search on amazon and ebay :
These are lead balls , the amount is nice but the size is not mentioned
http://www.ebay.com/itm/Lead-Balls-Milling-Media-5-lbs-12-an...
sounds good but price is an issue for 6" X 8" milling jar :
http://www.ebay.com/itm/Ball-Mill-Grinding-Media-Yittrium-St...
also
http://www.ebay.com/itm/Ceramic-Balls-Cylpebs-White-Milling-...

[Edited on 3-9-2015 by ecos]

Bert - 3-9-2015 at 07:37

I have used Coors ceramic milling media for grinding pyrotechnic chemicals, particularly oxidizers such as Barium nitrate that like to cake up rock hard (never a fuel/oxidizer mixture).

http://m.ebay.com/sch/i.html?_nkw=Ball+mill+media&isNewK...

400 series stainless would be a good choice for milling Aluminum to powder.

The Tungsten carbide balls certainly look pretty- At 35.00 US$ EACH for a 20mm ball, I don't think I will be finding out how well they work!

greenlight - 3-9-2015 at 07:41

I've never got around to buying any actual media from the internet.
What are you going to be using your mill to make?
I only mill black powder in mine and have found that round fishing sinkers do fine for this purpose. Plus they are 99% non-sparking.
I have made a fair few batches with them and haven't had any trouble.

Bert - 3-9-2015 at 08:20

As a teen, I used several rolls of the USA 5 cent pieces- "Nickels". They are made of a 75:25 Cu:Ni alloy, since 1946. Non sparking and very slow to wear away with mill charges of Potassium nitrate, charcoal & Sulfur-

They worked quite well, and you can always rinse them off and take them back to the bank for a full refund in "folding money" if you get some better media later!

Or just keep them, they're worth more as metal than the face value lately. US is considering replacing the material with stainless steel soon, or just doing away with one and five cent coins. Isn't inflation grand?

greenlight - 3-9-2015 at 08:39

Coins? I never thought of using them.
Coins here have the same composition; 75:25 Cu/Ni alloy.
I might throw some in with my lead sinkers next time and see how they go.

ecos - 4-9-2015 at 05:54

Thanks all ,

I plan to grind Aluminium to fine powder. maybe chlorate in the future.

I tried to order the 400 series but it the shipping would cost me a lot since I am located in Europe , shipping = $135 !

I found some balls made of lead and others from SS but none from ceramic !

would the lead be better or the SS balls ? i have difference sizes 15 mm and 12 mm diameters.
I was searching for 20 mm diameter but it would take time in the order

Bert - 4-9-2015 at 06:09

One man's opinion (And I have lived over 40 years doing this).

If you wish to grind Aluminum, SS is first choice, ceramic second, do not use Lead.

If you wish to grind chlorates or perchlorates, or Sr/Ba nitrates, or just about any other organic/inorganic chemical for colored stars, use ceramic.

HARD Lead alloys, such as water quenched 92Pb:6Sb:2Sn or brass will work for black powder- DO NOT use brass or a Copper alloy with ammonium nitrate or ammonium perchlorate, Cu catalyzes decomposition.

hissingnoise - 4-9-2015 at 08:03

Quote:

If you wish to grind Aluminum, SS is first choice, ceramic second, do not use Lead.

I have ground thin, aluminium foil using AH lead Bert, and it worked out fine (pardon?)?

Bert - 4-9-2015 at 19:06

Aluminum foil gets work hardened during ball milling, the comminution has much to do with work hardening/embrittlement. Yes, Lead media may work- But substantial Lead will end up in your milled powder. Maybe acceptable for your process, maybe not for some others.

Lead, and most of the commonly available quench hardening Lead alloys such as wheel weight metal, Linotype & etc. work SOFTEN. That is, as you're smacking that Aluminum with your lead chunks, the Aluminum grows HARDER. And the Lead surface grows SOFTER. Call me a perfectionist, but this seems like something to avoid?

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