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Homemade Ferrofluid

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LAN_403

Part Scavenger

Thu Mar 02 2006, 04:10AM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

Mine's clear. That's all I've ever seen my mom buy.

About the filter paper, I wonder what that guy was using. I had similar problems (although I didn't have any "filter paper") but he says it "flowed right through." I hope to try all this stuff out on friday. I will by Sunday or it's gonna kill me.

Omicron

Fri Mar 03 2006, 02:05AM

Registered Member #131 Joined: Fri Feb 10 2006, 09:25PM
Location:
Posts: 185

$40 CND thatâ€™s about $50 USD and for a gal thatâ€™s cheap, United Nuclear wants $15 for 30 ml. Where did you get yours? What was the quality like?

Michael W.

Fri Mar 03 2006, 02:40AM

Registered Member #50 Joined: Thu Feb 09 2006, 04:07AM
Location: Vernon, B.C, Canada
Posts: 324

I do believe there talking about oleic acid, not ferrofluid....

Chris

Fri Mar 03 2006, 08:28PM

Registered Member #8 Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214

Has anyone tried forming magnetite from the FeCl2/FeCl3 solution with sodium hydroxide? It should work with any base, and a faster reaction with stronger solution should yield smaller (better) particles. The ammonia is not important until it comes time to coat the magnetite with oleic acid, so forming the magnetite first with sodium hydroxide and then adding ammonia should be a far better method.

Part Scavenger

Sun Mar 05 2006, 01:55AM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

Cool. I'll try that. I didn't get a chance to work on anything today or yesterday. But Sunday I have time. Yeah! I'll see what that does. I have noticed that the olive oil/HCL combo I left sitting on my desk the last several days has changed. The "big yellow layer" has almost completely turned into the "little layer above the yellow" I guess this is what Bored Chemist meant by "It would take forever." My chem friend also pointed out that too much HCl could mess up the resulting oleic acid if done this way, so I'll just pitch the stuff sitting on my desk and go for BC's method.

Carbon_Rod

Sun Mar 05 2006, 03:05AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

Suspension of material in water needs a surfactant no matter what:
2FeCl3 + FeCl2 + 8NH3 + 4H2O -> Fe3O4 + 8NH4CL

Oleic acid C17H33COOH is somewhat easily confused with linoleic acid C17H31COOH. However, tetramethylammonium hydroxide N(CH3)4OH is known to work well as a surfactant for this process. IIRC it is pretty toxic so look at the MSDS.

Have fun,

Chris

Sun Mar 05 2006, 03:54AM

Registered Member #8 Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214

Suspension of material in water needs a surfactant no matter what:
2FeCl3 + FeCl2 + 8NH3 + 4H2O -> Fe3O4 + 8NH4CL

What do you mean here? That reaction doesn't have anything to do with the surfactant, which is oleic acid.

Anyway, the Fe3O4 can be added from any source to the surfactant, which uses ammonia to break it down and bond it to the magnetite. I quote from Andrew's website:

THE OLEIC ACID REACTS WITH THE AMMONIA TO FORM AMMONIUM OLEATE, A SLIGHTLY SOLUBLE SOAP. THE HEAT CAUSES THE AMMONIUM OLEATE TO BREAK DOWN, AND THE OLEATE ION ENTERS SOLUTION WHILE THE AMMONIA ESCAPES AS A GAS. THE OLEATE ION ATTACHES TO A MAGNETITE PARTICLE, AND IS RECONVERTED TO OLEIC ACID.

I simply propose the magnetite be formed first using this reaction below, since no one seems to be able to get the reaction above to work at all, and they get poor results when it does (probably because a fast reaction will form smaller particles before larger crystals can form, which is necessary to get spiking, and household ammonia is only 5%-10% NH4OH, plus other additives).

2FeCl3 + FeCl2 + 8NaOH => Fe3O4 + 8NaCl + 4H2O

Once the magnetite is formed here, ammonia and oleic acid would be added in to coat the particles as described above.

It's a rather common idea that "homemade ferrofluid will not spike" or "homemade ferrofluid is not as good as 'real' ferrofluid" but is there some real reason for this? If people who have been attempting to make it at home are getting poor results, obviously we have been doing it wrong. Surely there is nothing magical about making "real" ferrofluid and it's a process that can be replicated. Trying to get the magnetite to precipitate out quickly and uniformly with a small particle size is the first step in trying to produce a quality fluid - commercial ferrofluids are actually available with a variety of particle sizes, where all the home attempts so far seem to have trouble even getting particles to precipitate, much less out of a clear solution.

It might we worth looking into other carrier solvents as well, with different viscosities and surface tension than kerosene. Also has anyone started with anhydrous or a better grade of FeCl3? The PCB etchant you buy could contain additives that interfere. Steel wool is a rather dirty source of iron for the FeCl2 as well, how about washed scrap iron turnings (yes probably a little slow to react) or pure iron powder?

I think I will try the NaOH magnetite sythesis when I go home next weekend for spring break if no one else has tried it by then, just to see how well it works (but I won't be able to get any farther than that because I don't have any oleic acid now

Part Scavenger

Sun Mar 05 2006, 06:06PM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

Here's another useful link I found:

Chris

Sun Mar 05 2006, 06:36PM

Registered Member #8 Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214

Cool.

That's an aqueous based ferrofluid rather than a non-polar solvent, but the idea remains similar. Look at it spike beautifully too! Again the Fe3O4 synthesis itself should work with about any hydroxide, but I see an acidic solution must be what everyone has been missing, and why iron hydroxide was formed. But, umm, what keeps a side reaction between ammonia and HCl from occurring? They can react to form NH4Cl if it doesn't react with the iron chlorides first.

Carbon_Rod

Mon Mar 06 2006, 01:14AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

Chris, I think you know what I meant. ;op

Here is some low yield crud holding a magnet showing creep. I would say about 2/3 of the probable yield was lost because it was made a little differently.

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