Milling Titanium

[Miech]

MOD EDIT: The following was split from another topic, and moved here for further discussion. Thank you!

 

 

Heheh, I can't wait to see you using that titanium. I've put mine through a #300 sieve, and put the fine powder in my ball mill. I'm gonna let it run for a week or so, that should produce something like -12 micron titanium which is really nice for *very* bright and loud flash reports. Before you get concerned, I took the proper precautions for milling the stuff, and I certainly will take precautions when making flash with the milled stuff. I just like my fingers too much to risk them.

 

To get back on topic, the 14 mm rammer I received was just a very tiny bit too thick. Freakydutchman will send me an new, slightly thinner for free, so I think they have very good service too. The other stuff is just great.

Edited October 21, 2008 by TheSidewinder
split from another post

[tentacles]

Miech: Milling Ti is very dangerous, probably as dangerous as Mg when the particle size gets very small. Ti also has a VERY strong tendency to spark from friction/impact - be excessively careful emptying the jar. Do it remotely somehow. Fine metal powders + heavy (likely steel?) milling media = big UV fireball of pyro death.

 

Ti in very fine particle sizes also has a tendency to spontaneously ignite in compositions, although I think the particle size for that is around 4 microns? All I can say is, BE CAREFUL. Milling Mg/Al is one thing, milling Ti or Mg is just a bad idea unless you're just breaking up some coarse sponge a little.

[Miech]

I know. I'm using ceramic media, and use water as emusifier to reduce the risk of ignition in the mill. I will store it under water too, and do not even think about making amounts of composition being enough to serious injure me. I did some research before I put it in the mill, and milling in an emulsion with water should not cause any problems, since it is occasionally done in industry. The only other way to make very fine flake titanium is by hammering it for days and days using a special apparatus. This seemed not too practical for home production. Titanium is inert enough to not react with water during processing.

Maybe a week milling time and -12 microns were somewhat exaggerated though, but I just want it to be very fine stuff.

 

It's getting a bit off topic, but thanks for the warning.

[Mumbles]

On the contrary. Very fine samples of Ti, Zr, and Hf are shipped and stored in water due to air reaction concerns.

[tentacles]

I think Mumbles would agree, Safety is NEVER off topic when there's valid concerns. Good to hear you've got a plan of action. You could also try milling it with mineral spirits + stearic acid to make a sort of "bright" Ti flake, similar to how the bright aluminum is milled. Probably not necessary with Ti, though it may reduce the air/spontaneous reaction tendency if it gets super fine.

[Miech]

I took it out of the mill already. It formed some kind of foam filling the whole bucket, so milling any longer wouldn't work anyway. Adding a very small amount of alcohol next time (if any) would probably break down surface tension enough to prevent it from foaming. It's a grey powder now, slightly darker in color than 5413 aluminium, so I think it is quite reactive now. You can actually see some particles reflecting light like a mirror. It has been milled for about 14 hours, so not even close to a week. I'm going to look at it under a microscope, to compare it to its original particle size and shape. I'll see if I can manage to make a picture of it, that would be interesting I think.

 

Maybe it would be an idea to split of the last few post of this topic to a new topic?

[TheSidewinder]

This is a good bit of info for everyone to have so, as requested, it was split from a Review thread. Please continue!

[Swede]

I know you are referring to ball milling Ti, but I've noticed some interesting effects just machining and grinding it. I had some Ti sheet, and was using a belt sander to clean up the edges a bit, and the shower of brilliant white sparks was impressive. Some of the dust accumulated a bit, and I could see clusters of Ti dust at the base of the sander go POOF a bit. Ti is definitely touchy when finely divided.

[GraafVaag]

@Miech, I made 1g of flash with my 250+mesh Ti, and it was so bright and fast that I don't even WANT it finer. I'd better stick to GD for it's much safer to use.

[Miech]

I draw the same conclusion when observing a 0,2 gram test batch burn. It's for sure not something to actually apply in a device. It surprised me a little it was somewhat hard to get it going, but when it finally lit it impressed me.

[asilentbob]

http://www.itponline.com/index_files/ArmProcess.htm

I have a few pounds of strange titanium that was made by this process. I posted about it in the PRRT a few pages back here:

http://www.apcforum.net/forums/index.php?s...ost&p=41089

Its strange that its in somewhat tough lumps and not free flowing powder... BUT it is still VERY flammable. I haven't measured particle size range, but was told 1000mesh by Danny Creagan. Hopefully Theo will look at the sample I sent him under microscope and email me back.

 

One of the PGI guys ball milled a few grams by itself and his mill blew up, don't know for certain who. I know your milling in water... but still... that titanium can very easily become pyrophoric. Remember that one of the reasons that titanium is so expensive... is that it is so tricky to make since you need an inert atmosphere and something like liquid sodium metal.

 

TiCl4(g) + 4Na(l) ---> Ti(s) + 4NaCl(l)

 

I wonder if you could have your titanium powder in water... and add an extremely dilute metal salt solution... like .005g total or something... to plate out a less reactive metal onto your titanium... not much, just enough to make it slightly more safe, a extremely thin layer. Would this actually happen? I dunno, with redox chemistry sometimes they tend to plate out onto each other, sometimes the solution tends to just dissolve the metal and precipitate the other on the bottom of the container...

 

Hmm... then you could possibly also be in the realm of funky intermetallic reactions and alloys and shit... hmm no telling what that would do for reactivity. Maybe?

[optimus]

These 'super flash' notes from passfire make for interesting reading:

 

"WARNING:

Be very careful with this mixture, as it is very sensitive to static, friction and impact. Never mix more than 5g at a time.

The critical mass is about 300mg when very fine (<3µ) Titanium is used.

NOTES:

Produces an enormous flash and report, much superior to the usual mixtures containing Aluminium.

Use flake Titanium powder with less than 3 micron particle size. Larger particle sizes will not work properly."

 

I have some very fine Ti sponge and some 'dark' Ti flake. Not totally sure of the exact meshes though... Might do a few little tests...

 

Scary stuff...

[Miech]

I think coating it with stearin or something similar would be better I think. That could even be done in the process of milling, although I very dislike the idea of having organic (combustible) materials in my mill with a potential source of sparks. My titanium isn't free flowing as well, it seems the particles stick together somehow. I dried a 2 gram sample of it lately, and it caked if it were some kind of hygroscopic nitrate salt.

 

Edit:

I made some pictures through a crappy microscope to compare the unmilled stuff to the milled stuff. The differences are quite more visible than I expected them to be. The exact magnification factor is unknown by me, but it should be somewhere in the 300-400x range.

 

Before milling:

 

After milling:

 

Someone sent me that flash composition Optimus is refering to. It might be worth an experiment, I'd like to compare it to the fastest flash I have made yet. That was potassium perchlorate with dark magnalium in a 50:50 ratio. An amount of 0,02 grams of this stuff already 'pops' when lit.

Edited October 22, 2008 by Miech

[Boomer]

Never worked with flash, but seeing "critical mass" values from 20mg to 50g is strange.

 

Of course it depends on reactivity, and when people say "my best flash pops at ... milligrams" I assume a popping noise.

 

While when Bill Ofca states "A good quality flash has a critical mass of about 50 grams. This means it will detonate with concussion in open air ... Compare this with black powder which has a critical mass of about 500 pounds!" I assume a shock wave. (Let's ignore the D-word for now, and the fact you can name any high enough amount for BP which only burns, but will level buildings if enough burns next to them, just like fuel/air clouds will).

 

What I don't understand is how this self-confinement happens - like a constantly rising burn speed, until it gets too fast for the unbunrt material to move away, or a sharp transition with a jump in destructive power of several magnitudes? As a HE guy I only know the latter (called DDT): You keep lighting off gram samples of acetone peroxide, they all goo whoommpp. Next day a 200mg sample detonates and leaves you with ringing ears.

 

I used TATP as a simple + well known example, not a good one since it already burns very fast. But take a test tube full of nitro that gets ignited at the surface. It starts burning at 1-2mm/s, heats up and reaches maybe 1-2cm/s, then suddenly jumps to KILOMETERS per second, which means over 100000x increase. Using less and less, you reach a point where some samples will detonate, some will just burn out.

 

Now if flash behaved that way, you could light ten batches of 50g on ten tables, five would be just scorched, the other five would be in splinters.

 

???

[Mumbles]

I don't like detonate either, as it doesn't actually do so. Self-confine would be a better term. Using your TATP example it's similar to how you can burn 1g piles generally without issue and get a poof, some fire, and light smoke. If you placed that same 1g into a confined container it would almost surely result in a loud crack. If you placed, say 10g on a table, and lit it unconfined you may get it to DDT. A similar type of situation happens with flash powder. Certain amounts will flash, but confine them and they would make a very loud noise. Sometimes this is purely from the destruction of the casing and sudden release of pressure.

 

Pressure increases the burn rate of many materials, flash and black powder both. The theory I've always heard is that the powder burns and produces gas faster than the surrounding air can expand. After a certain point the pressure is high enough that it does it's thing and burns nearly instantly sending off a shockwave.

 

There is also something to be said about geometry. If you spread 10g over a table, it surely wont go off with a crack. If you placed it into a pile, it very well could. I've heard other things where if the fire can get to the center of the pile, the surrounding unburned mass can serve as enough confinement to burn instantly.

 

Popping is certainly different than self confining. Even my BP pops when I burn small samples of it. I really don't give that test much weight. Every flash powder I've ever made also pops, so I don't see it as something special.

[Boomer]

"After a certain point the pressure is high enough that it does it's thing and burns nearly instantly sending off a shockwave"

 

That's about what I assumed. It's not a DDT phenomenon with a sudden 100000x increase of speed + pressure, but a gradual increase of both (while pressure increases burn rate, which gives more pressure and so on), until the rest of the pile and the air around it cannot move away fast enough.

 

This will create a blast wave, *without* any need for hypersonic velocities. The hot compressed gas has a much higher sound velocity, it does not need to come from a hypersonic detonation to shock up the surrounding air.

 

And to be fair, flash is at least legally a HE by ATF definition, and it *has* been shown (by the ATF?) to detonate under some special circumstances, read blasting cap, several pounds in a steel pipe..... but not in fireworks. Does anybody know the VoD they measured in that experiment?

[FrKoNaLeaSh1010]

For some reason 3200m/s comes to mind but I dont have anything to back that up. I remember them saying that at the appropriate amounts black powder was around 350m/s and the flash they used was 3200m/s but that seems a little high

[Boomer]

Not at all if you consider Cheddites. With the much higher energy of burning Al, and the fact that Al is a sensitizer while vaseline is a *de*sensitizer, it's not surprising.

 

What is surprising is that it does not make the jump from 1200m/s deflagration to 3200m/s detonation on its own if confined but loosely packed.

 

The 1200m/s are often called detonation even by professionals, because it *is* faster that the sound speed in the unreacted material, which is the definition. As I pointed out before, this is a moot point since the calculated CJ-pressure is below the static pressure of the reaction gases.

Plus, the definition does not apply here IMO, since the sound speed is only <1200m/s because of the loose nature, i.e. there is no uniform sound speed with all that air. Al has a sound speed around 6 km/s and homogeneous crystals of perc should also be above 1200m/s.

If you compressed flash to 99% TMD it would *not* burn at 1200m/s, it would either burn from the surface down like rammed BP in a rocket (but much faster), or detonate at over 3,2km/s (unless it gets deadpressed, who knows). The latter would definitely need cap initiation, and probably a heavy booster at that density. It's just not worth it, with AN and diesel both much cheaper than perc and Al, at the same performance.

 

BTW I have read 400m/s for BP, and in one book even 600m/s for very good BP in very fine granulation.

Whatever, it's way too slow to create a CJ-shock that's over the static pressure after the burn.

Any BP device will explode via container failure, creating only that burst pressure. Read 10-100 bar for cardboard, 100-1000 bar for metal pipes. The max it generates is 2800 bar IIRC, make the walls *too* thick and it won't even explode. Hard to do but I once managed to get thin pipes (25mm ID) with thick walls (4mm) to only develop a big crack to vent the gas - no fragments formed.

[Miech]

A detonation is when a combustion reaction is propagated by a shock wave faster than the speed of sound, rather than by the combustion itself. This can be proved by making a diagram, where a detonation will show an increase in pressure from 1 bar to hundreds of bars in less than a millisecond. A deflagration would show a less extreme increase in pressure, and usually a way lower peak pressure. Nor flash neither BP will detonate under normal conditions in normal amounts, even when confined, although I have to admit they do react seriously fast.

 

This is quite a lot off topic though.

[popi1955]

im going to get a few kilogram of titanium flakes

when i mean a few i mean more then 5 on sure, this is a huge amount!

how the hell i am going to mill so much titanium?!?, well ill be satisfied even from 100 - 200 mesh

anyone having idea how to mill so much??, how much time dose it takes to get to 100 mesh??, is it ok to use steel media if im not going to get more then 200 or 300 mesh??, and what are the rates of spontanius ignition when the particals arent so small like what im planing to do

 

thx for those who helps

sorry for the english

[tentacles]

I'm not sure why you would want your titanium so fine - very few comps use it finer than 100 mesh. Rockets and stuff want it 20-80 mesh. Is there some specific reason you want it so fine? Titanium is a big time friction sensitizer. Most times when it's machining chips/curls, you can just run it through a blender with some water and laundry detergent. Curls and chips end up as flake so you want them a bit bigger than you would atomized or sponge. For salutes I just stuff a wad of curls in the shell, there's no actual need to break it up, the flash can do that quite nicely for you. Use blended in stars and rockets, but NEVER EVER press it around a spindle. EVER. --> .

[swervedriver]

I have some +20 mesh Ti sponge I want to reduce to 40-80 mesh. Will the blender do the trick on sponge too? The stuff is hard and sharp granules.

[popi1955]

100 mesh will work fine? it wold give a good white flame without any interaptions

sorry for english

[tentacles]

I've never heard of using Ti for a white star - it's used for white sparks exclusively, as far as I've ever seen or heard. And it does make very good white sparks! It could probably be used for a white star, but I don't see the point - you can make nice whites with aluminum or magnesium, or Mg/Al - all of which are typically cheaper. In the case of MgAl, maybe not cheaper, unless you make it yourself.

[popi1955]

luckly too me, titanium is cheaper, ill get from there more than a kilogram on sure, and it costs me nothing

and if u will have a short look on my messages u will see that iv allready posted a link to a white star formula that i made, i attend to work on other white formulas, and i wont to find some using titanium and aluminum so there woldent be any waste of aluminum (in my formula 40 grams of aluminum powder is needed to make 120 grams of white mixture, i dont work, and aluminum price is too high right now)

Edited April 19, 2009 by popi1955