Sciencemadness Discussion Board - Sintering Fe3O4 powder?

Sintering Fe3O4 powder?

axehandle - 1-2-2005 at 02:17

I've given some thought on sintering Fe3O4 powder using induction heating to obtain a solid chunk/rod/weird shape of magnetite to use as a chlorate anode. The idea struck me when seeing this: http://www.powerlabs.org/indheating.htm

Does anyone have any spontaneous ideas?

Microwave Responsive

chloric1 - 1-2-2005 at 10:04

If you maybe put a beaker of 1000 ml of water in a microwave to protect the magnetron and then simply put your magnetite in the microwave it should get quite hot. Actually, I have a few microwave chemistry articles. One actually depicts a mold cavity with silicon carbide coating inside as heating element. An ideal setup like this should reach 1500 C.

What could be used as a binder for magnetite. It is an oxidizer easily reduced by carbon compounds.

Twospoons - 1-2-2005 at 13:17

What size particles? How big a chunk do you want?

My gut feeling is that microwave is too high a frequency to get the penetration you'll want. You'll plenty of heating in the first centimetre or so, but very little in the centre.

Energy penetration will improve as the frequency drops, but absorption drops too ( to zero at DC, obviously).

Gut feel again - I'd go for something in the 500kHz to 1MHz region. Building a high power FET bridge for those frequencies shouldn't be impossible - neither will it be easy, since you're going to want 500 - 1000 W output.

Maybe a resonant bridge?

Cyrus - 1-2-2005 at 17:18

How about using ye big furnace?

I haven't researched much about the melting point of Fe3O4, but I have gotten some to fuse onto clay in my furnace and make a glaze. (Of course some parts turned red - Fe2O3 becuase the furnace atmosphere isn't controlled)

And this works for chlorate? In place of lead dioxide? That would just be way too simple! Next time I fire my furnace I might throw in a bit of Fe3O4 in a clay crucible and see how it goes.

Needs a binder or high pressure for shapes

chloric1 - 1-2-2005 at 18:01

Since most binders would reduce magnetite at high temps then a hydraulic press capable of 2000 or 300 psi would work follwoing by an oxidizing atmosphere. A few centimeters would work for small rods. The problem is the magnetite would have to be pretty dense for effective conductivity.

Two spoons, what references would you recoomend concerning 500W or 1000W resonant bridges? It could be interesting and I would surely like to learn more. I do have basic electronic knowledge.

rift valley - 1-2-2005 at 18:04

My Merck Index is tells me that magnetite has a melting point of 1538C. It also says that it oxidizes to Iron (III) oxide when heated in the presence of air.

Twospoons - 1-2-2005 at 19:21

chloric1: I don't have specific refs, but browsing the Application Notes from the major semiconductor manufacturers can be very rewarding. For power electronics look at comps like International Rectifier, National Semiconductor, OnSemi, TI, IXYS, Harris, Infineon, Fairchild, Philips Semiconductor, SGS Thompson ... There's a wealth of info out there - just got to hunt for it!

These Ferrite electrodes from TDK might be useful.

[Edited on 2-2-2005 by Twospoons]

Chris The Great - 1-2-2005 at 21:10

I dunno, I'd just slap it into the microwave without any water and turn it on, and stop when it's done. I'd be more concerned about the stuff spilling onto the microwave, or the electronics getting to hot from the amount of heat present.

Also, if you do use a microwave, get and old 1500W one. Not only will you get enough power to actually DO stuff, you won't be able to kill it. Trust me on that one

And I've put some weird things in microwaves, including, but not limited to: Boiling down battery acid, 60W light bulbs (mini lighthouse), 40 gauge wire (plasma!), computers, etc.

Just make sure that the heat radiated by it as it heats up to 1500C doesn't get onto the sides of the microwave, as it may overheat the electronics and melt the plastic parts.

You might also be able to turn an u-wave into an arc furnace.....just though of that. Hmm, planning needs to be done. An arc furnace with a u-wave field. Now that's my kinda project! Would take a fair amount of work though.

chloric1 - 2-2-2005 at 10:04

Quote:

Originally posted by Twospoons
chloric1: I don't have specific refs, but browsing the Application Notes from the major semiconductor manufacturers can be very rewarding. For power electronics look at comps like International Rectifier, National Semiconductor, OnSemi, TI, IXYS, Harris, Infineon, Fairchild, Philips Semiconductor, SGS Thompson ... There's a wealth of info out there - just got to hunt for it!

Oh yes! I forgot about the spec sheets!

If I got desperate I am sure I could call for engineering support or send email. This relatively moderate frequency would also be good for speeding up dissolution of difficultly soluble ingredients or making more homegenous slurries.

These Ferrite electrodes from TDK might be useful.
P.S Thnak for the link, I will have to contact TDK and ask for minimum orders and such. I just tell them I have a 40000 gallon pool I need to chlorinate :cool:

[Edited on 2-2-2005 by Twospoons]

[Edited on 2/2/2005 by chloric1]

Twospoons - 2-2-2005 at 13:45

Do I detect a hint of sarcasm over the TDK link? Seems you have yet to explore the wonderful world of FREE SAMPLES. Its a totally brilliant scam I've often used to obtain parts - cook up a project, pretend to be a company and request some samples. Usually you'll get them couried to you gratis. Occaisionally you'll get a "no", or need to pay for the samples( but its still better than 10,000 pc MOQ !). From the suppliers point of view the few bogus requests are not worth worrying about - its small potatoes compared the the business they can acquire by sending samples to genuine customers. I'm currently building a home theatre amp from free parts from TI and Nat Semi.

Hey Chris_the_Great: uWave arc has been done! Google search will turn up lots of ideas to play with. Generally requires a tapered waveguide, shorted at the ends. The arc forms ~1/4 wave from the short, at the narrow end. Its also useful to have some tuning stubs somewhere in the waveguide, and a circulator feeding a dummy load so any residual power doesn't wind up back in the magnetron.

[Edited on 2-2-2005 by Twospoons]

Cyrus - 2-2-2005 at 16:29

Ok, if the mp is 1538 deg. C, then I think I can get temperatures good enough to sinter it at least, but that's just my guess.

Yeah, it would oxidize in air, but with a working oil burner and charcoal, I think I, or others, can pretty near a neutral atmosphere.

Chris, you could also use the transformer in the microwave and another transformer as an inductor, and make a more standard arc furnace, which I hope to do. (got the transformers) That'll need some crazy refractories, but I have a crazy idea- bake a cake and burn it on purpose- this cake would have zircon, or magnesia in it, and now we have a magnesia carbon bonded refractory. I've gotta try it.
Yes, I'm still working on refractories, and BromicAcid, I will have a paper on refractories that I'll post here by the end of April.

Twospoons - 2-2-2005 at 17:58

Maybe its a silly idea, but maybe the magnetite powder could be fed into an oxy/propane torch, like the way ruby laser rods were made by feeding doped alumina into an H2 /02 torch. The molten particles exiting the flame are aimed at a rotating substrate, and as the torch is slowly withdrawn the fused material builds into a long rod.

Mumbles - 2-2-2005 at 17:59

Instead of sintering preexisting Mangenite, why not try to make the mangenite which would fuse into a mass?

I'm thinking 1 molar part Ferrous sulfate, and 1 molar part Ferric sulfate mixed in excess with NaOH. Heat to probably 5-600C and it will convert to mangenite. Washings with water will remove unreacted Iron Sulfates and Sodium sulfates. It may actually form a porus block that has a decent surface area.

What about just pressing the mangenite using some sort of non-polar binder?

Chris The Great - 2-2-2005 at 19:34

Hmm, some time ago I started building a Mega Microwave, which would have a water cooled magnetron running at over 10,000 watts AC input. I didn't finish as I didn't have anything I could make the hose connect to the magnetron in a watertight manner. But it might be something I may take up again.
I only need to make the water cooling part, and fix my busted 240V circuit to power it.

Actually, maybe I'll just forget the cooling, and turn it off when the magnetron glows red

HEHHE

chloric1 - 3-2-2005 at 13:43

THats right Chris the great! Live dangerously!

[Edited on 2/3/2005 by chloric1]

Cyrus - 3-2-2005 at 19:41

I can use a 2 ton tile press at the local ceramic place for like $4 an hour, so that might be an option to make electrodes.

I'll do some tests.

chloric1 - 4-2-2005 at 09:05

Quote:

Originally posted by Twospoons
Do I detect a hint of sarcasm over the TDK link?
[Edited on 2-2-2005 by Twospoons]

I did not mean anything by it. The free sample route may be some aproach I could take. I could stick with my 40000 gal pool story or maybe I am a motorcycle customizer and I need them for chrome plating. I definately wont be buying 10000 electrodes anytime soon. My car is in the shop and my daughter is do to be born this month!!

I need to hoard my cash!

Sintering Fe3O4

Cyrus - 4-2-2005 at 22:00

Well I heated black iron oxide from the pottery store (I'm pretty sure it's magnetite) in a crucible in the furnace, and it sintered/melted quite nicely into a solid mass at the bottom. No problems there. It did of course oxidize a bit- it is now greyish and in some places red. I'm confident that the oxidation itself is no big deal- a covered crucible would help, and so would a covering of flux (NaCl and CaCl2 or something else with a reasonably low melting point) The starting iron oxide and the end product were both magnetic, though the sintered powder was much less magnetic.

The problem is that none of the iron oxide (fired or not fired) is electrically conductive!

(as far as I can tell with my pathetic analog meter) How conductive ought these electrodes to be?

Maybe I should do some tests to make sure I really do have magnetite.

In conclusion, I don't think binders are really nescessary, but if ya want them maybe something like a low melting temperature glass (high fluxes) or sodium silicate would be suitable.

Cyrus - 20-3-2005 at 22:41

Sorry to double post and all, but did we ever find out if Fe3O4 is electrically conductive? This might be an important consideration if it is to be used as an electrode. Otherwise I like this process a lot. I can sinter my "black iron oxide" which is magnetic pretty easily in my furnace. The m.p. of Fe3O4 is 1420 deg. C. though, and I didn't think my furnace got that hot on that run.

12AX7 - 20-3-2005 at 22:44

Sintering works a lot lower than the melting point, although best results (without hot pressing) do come just below.

You might try another metal oxide, say litharge, to liquid phase sinter it. Well, maybe something a little more/less reactive, since the ultimate goal is what, perchlorate cell?

Tim

Cyrus - 21-3-2005 at 18:37

Yeah, perchlorate cell, why not?

I don't know about litharge, but PbO2 decomposes, right? So that won't work as far as sintering goes...

The iron oxide really looked kind of melted- it shrunk to about 1/3 of its original size... would sintering do that?

12AX7 - 21-3-2005 at 20:06

Yeah- but 1/3? Is that 33 or 66% shrinkage?

Even for a coarse grain, that's an awful lot of shrinkage.

Tim