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encipher
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Ferrofluid
Hi,
I have been trying, for quite some time, to successfully synthesize a ferrofluid that exhibits 'spiking' when exposed to a magnetic feild.
Unfortunately, I haven't been able to, and I don't really know what I am doing wrong.
I began with a mixture of FeCl2 and FeCl3 in stoichiometric quantities (two to one ratio) and, using a buret, slowly dripped in Ammonia (aq).
Magnetite was successfully precipitated (very fine particles). This step works fine.
However, I run into trouble when I try to surfact. Most well documented papers avaliable use TMAOH, and the result is an ionic water based ferrofluid
(which spikes very well). I however do not have any TMAOH and am using oleic acid as a surfactant.
I performed two different prodecures using oleic acid:
1. decant the solution after the magnetite settles, wash several times. I did this to reduce the PH of the solution, since the addition of oleic acid
directly to a very alkaline precipitate (at a pH of 12 to 13) will create an unstable colloid in the solvent I will use (I tried both hexane and
kerosene). After the washing, I added in around 5 mL of oleic acid and heated for approx. 15 mins. I then added in the hexane (after cooling).
2. I did not decant the solution. I added in the oleic acid directly to the solution, and heated. This is what most websites say should be done
(although the sources aren't reliable. Sci-spot.com and some random google results). Apparently, the Ammonium Oleate is formed, and upon heating for a
decent amount of time, the ammonia will escape as NH3 and the oleic acid will surfact to the magnetite, then add in the solvent (kerosene).
In both cases, my result was non-spiking. However, i should be noted that there was no agglomeration of magnetite particles. They were, as far as I
can tell, collodially suspended and when a magnet was brought near the solution, the ferrofluid did follow the magnet.
Does anyone have any experience with ferrofluid and might be able to shed some light on what could be going on. Perhaps I am overlooking something. I
am pretty sure it is not my particle size( at least not the magnetite). Any ideas?
Thanks
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Lambda
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@encipher, I have used Ferrofluid in Tweeters and other Loudspeakers, and bought it from VISATON. Maxwell wants introduced a new type of Ferromagnetic
Grain in there VHS-tapes, that had a Rod-Shaped conjuncture with higher than normal magnetizing properties. They must have Patented this Grain, as for
many other Chrome-based ones. Maybe it's your Grain-Shape and/or size, that's lacking the desired properties. There aught to be many Patents relating
to all types of Grain-Shapes and sizes, as to the dispersion media used. Magnetic Tapes have after all been around for more than half a century, so
there must be tons of useful info on this subject.
Regards,
Lambda.
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matei
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encipher,
I happened to work some time ago in a laboratory where a colleague was making ferrofluids. From what I can remember (although I dind't pay attention
to what he was doing, so I may be wrong), precipitated magnetite was washed well with water and than was treated with an aqueous solution of sodium
oleate. Than the particles were dried (this took very long because they dried them at room temperature in a dessicator) and finally they were
suspended in a solvent.
Hope this might help somehow.
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matei
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And another thing I've just remembered. After coating the magnetite with surfactants, they used to grind it in a thing called "planetary ball mill". I
think this is how they obtained nanoparticles of magnetite suitable for ferrofluids.
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encipher
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@Lambda
I do not believe it was the particle shape, or size for that matter. Since I sucessfully used the same process for making the magnetite, and at the
lab I used TMAOH to surfact, and I got spiking. It seems that the water based ionic ferrofluids seem to work. (I tried both cationic and anionic
ferrofluid)
@matei
I don't believe its the particle size, I know that when nasa first synthesized a ferrofluid, they used a ballmill and kept the magnetite running in it
for quite some time. Buy precipitating the magnetite out using FeCl3/FeCl2 and ammonia yeilds particles within the desired range (IIRC, the max is
around 20nm). In fact, one could use sodium hydroxide to precipitate the magnetite, but that yeilds much larger particles (around 18 nm, ammonia gives
around 6nm).
I really don't know what it could be. That sci-spot.com article claims successfully making spiking oleic acid surfacted ferrofluid. I also saw a few
posts on some random forums who also succeeded using the oleic acid method. I think it has to do with how I am adding the oleic acid, or the actual
procedure that is going on there. I might try making some sodium oleate and doing what matei said. Over this weekend possibly, and then report my
findings.
Any other ideas are also welcome.
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UnintentionalChaos
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How have you been adding the oleate? This may be a bit weird sounding, but what came to my mind was candy making. I'd ball mill the powder together
with bits of dry sodium oleate (soap) kinda like the rotating drums for making candy shells on gumballs and the like, except the size and shape of the
particles will limit them from rolling over each other correctly, hence adding the grinding media. Perhaps you could use a saturated fatty acid,
actually the saturated form of oleic, stearic acid, sold as stearate for making candles. It is quite hard at room temp (like hard wax), and I would
imagine would give a smooth coat without clumping. Having not worked with pure oleic acid, I'm not sure what its texture is like. Best of luck.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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Twospoons
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Perhaps this is a silly question, but how strong a magnet did you use?
Helicopter: "helico" -> spiral, "pter" -> with wings
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Lambda
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@encipher, I am interested to know how you measured the spiking.
Did you put your sample in a test tube, surrounded by a coil, and then multi-pulse the coil with fixed intervals while taking Oscilloscope snapshots
of the induction waveform ?
If the particle size and shape are not the cause of the problem, then it may be the particle attachment to the Oleic acid. You need a Wetting Agent,
and I therefore think that what @matei said about adding Sodium Oleate, as being a very feasible way to do it. Maybe by adding one or two drops of
dishwasher liquid (Detergent) to water, and then mixing this with your Magnetite, and then evaporating the water, may have similar effects upon the
intermit contact of the thus obtained particle with Oleic acid.
I am very interested in your research, and would like to conduct similar experiments myself. Maybe you can supply us with a few useful links
concerning this matter. Furthermore, I am eagerly awaiting the results of your experiments.
Regards,
Lambda.
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encipher
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@UnintentionalChaos
I had already mentioned in a previous post here how I added in the oleic acid. Both methods I tried involve oleic acid and not sodium oleate.
@Twospoons
I used a 2" x 2" x .5" NdFeB magnet (magnetized through thickness, N40) and a 1" x 3" rod SmCo magnet. Both are pretty strong magnets
@Lambda
No, I only inspected my ferrofluid visually. There were no visible spikes, as opposed to using TMAOH which gave very beatuful spiked. However, I do
plan on plotting magnetization curves once I get this to work with oleic acid as a surfactant.
I used some online and offline sources. Below are links to some of the online sources I used. The procedures outlining the use of oleic acid as a
surfactant are very 'unscientific' however:
http://sci-spot.com/Chemistry/liqimag.htm
http://www.phy.hr/~npoljak/files/Ferrofluid.pdf
http://mrsec.wisc.edu/Edetc/nanolab/ffexp/index.html
http://www.instructables.com/id/EWMSJWI1BWEP2878DV/
http://voh.chem.ucla.edu/classes/Magnetic_fluids/pdf/Chemica...
The ones using oleic acid all seem to come from the same source, with a couple different words here and there =\
Also, I was looking at topics here on SMDB like a couple of minutes ago, and went into this thread about cool experiments and followed one of hte
links a user posted. It led to a website that had used oleic acid as a surfactant for ferrofluid. And it too, did not spike, but didnt agglomerate
either (similar to my result):
http://www.cci.ethz.ch/en/exlist.html?ismovie=-1&exchap=...
Its near the very bottom of the page.
Anyways, right now its about 7pm here. So I guess there is some time for me to experiment with my newly gathered information from you guys. I will
post my results if I am able to finish anything and get conclusive results. I will also (if successful) be writing up a procedure for this, since
there is little, well documented, articles out there (at least from what I could find.
Regards,
encipher
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Ozone
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I know this seems like a mundane question, but are you using oleic acid or oleic acid Na salt? There is a big difference, as in a whole charge...
Just a thought,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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encipher
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Ok,
Results are in. I have for the first time using oleic acid as a surfactant, made a ferrofluid that spikes!
I'm quite happy. Well, not anymore. First of all my yeild was crap, and the procedure could use a little refining. Plus, after I took photos, I
accidentally spilled some on the carpet. Anyone know what I can use to get it out? It looks Horrrrible.
The key was the concentration of the ammonia and how long I heated. That's what solved it. there is still a problem though, but im exhuasted right
now, so I will post tomorrow.
Here are two photos of the stuff:
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12AX7
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Nice.
I think the best method to remove it from carpet is going to be cutting the carpet and gluing in a new section.
I suppose ~10% HCl would do it, if the surfactant isn't too much trouble eh?
Tim
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Lambda
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@encipher, excellent !, very nice results indeed. I am impressed !
Magnetite dissolves in Phosphoric acid. You need diluted Phosphoric acid in order to prevent Carpet damage. Some people would refer to this as being
COCA COLA (Not a joke, it really contains Phosphoric acid).
I am dead tired, and will now lye down an die, which is a very suthing comfort to me at this moment.
You will without any doubt dream spikes tonight, which is more than I can possibly think of now.
Regards,
Lambda.
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12AX7
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Inhale some zinc fumes or somethin there, λ?
Tim
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Ozone
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Awesome!
I have been dying to make some myself! H2PO4 is definitely worth a shot (and it likely will not eat your carpet). Or... you could try vacuuming it up
with a nic Nd magnet, then cleaning the residue more conventionally, viz. soap, water, and a scrub-brush. Good luck getting 20nm particles off of your
magnet, though.
Excellent pictures too!
Would you give us a more detailed account?
I too must now retire for work comes early.
Excellent work, encipher!
O3
[Edited on 12-1-2007 by Ozone]
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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woelen
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Wow, that really looks good! Good work!
Encipher, that thing with the carpet is a bad thing, but true science has its price, isn't it? 
I would try the dechalcing solution with 4% H3PO4, which can be purchased at hardware stores for dissolving the iron oxide, together with some
acid-resistant soap. To my opinion coca-cola is a little too weak solution.
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encipher
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Hi,
I'm at work right now, (working of course =D ). Anyways, I already started working on a write up which I will post in the prepublication section. A
few problems though.
If you look carefully at the second image I posted. ( Here is the same image with the important part circled).
If you notice what I circled. The whole ferrofluid doesnt have the same consistency. The actual 'fluid' that spikes has a mud-like consistency (what
I have circled, is what some of the ferrofluid looks like when the magnet is removed.) The rest of the flowing liquid doesn't 'mix'. although it all
gathers together when i stick the magnet to the bottom of the petri dish. It's kind of difficult to explain.
After I surfacted the magnetite, I added in the Kerosene and mixed. when I brought the magnet to the bottom of the beaker and stuck it there, it
attracted all the magnetite there. I poured off the excess kerosene. Now, what I had left was that mud-like stuff. What you see in the petridish is
after I took the mud-like ferrofluid and added a little more kerosene to it. Basically, what I am trying to say is, The kerosene isnt mixing well
with the ferrofluid and the ferrofluid doesnt have the right consistency.
If photos are needed for a better explanation, when I'm back home from work I can take a couple more.
I will also be working on another batch, from which I will take pictures for the publication.
cheers,
encipher
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Lambda
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| Quote: | Originally posted by 12AX7
Inhale some zinc fumes or somethin there, λ?
Tim |
Have I become such a Nail in your Coffin @12AX7 ?, or do you just want me downright Dead and Gone ? 
You are right @woelen, Coca-Cola would be a too weak Phosphoric acid solution.
Phosphoric acid will also have a hard time getting to the Magnetite grains through the Oleic acid coating. Cleaning the Carpet section with Detergent
and soaking it up in paper towels may be a first step. By then applying a 4% Phosphoric acid mix with Detergent, and letting it sit for a while may
then have better results as to dissolving the Magnetite grains. A last step may be by only using Detergent, and if available, sucking it up with a
water resistant vacuum cleaner.
Regards,
Lambda.
[Edited on 12-1-2007 by Lambda]
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12AX7
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Mmm? A question of curiosity. I'm not Quince
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mericad193724
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Very cool OTC project. What is the easiest way to get Oleic acid?
I read olive oil has 55-80% oleic acid, so this is one source, although not pure.
Is purity a concern with this project, or not so much?
thanks
Mericad
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UnintentionalChaos
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Olive oil has it's issues.
The problem with isolating the oleic acid from olive oil is that an oil isnt just a heap of fatty acids. You have fat molecules with the fatty acids
bonded to glycerols. In order to recover the oleic acid, you'd need to 1: saponify the cheapest, most chemically extracted olive oil you can find (It
won't have much in the way of contaminants) with a water soluble hydroxide which is a pain in the ass unless you are trying to make soap
intentionally. 2: treat the soaps with an acid to form a metal salt and free up the fatty acids. 3: seperate the salt and glycerin from the free fatty
acids (although oleic and similar acids would be insoluble in water and the salt would be soluble) 4: You still end up with 55-80% oleic acid. The
soap making will take a lot of vigorous stirring (whisking or blending is better) on your part to get it intimately mixed enough to react (Stirbar is
good for jack squat here), followed by several hours of refluxing to allow it to fully saponify. I would be quite interested if someone was able to
make a spiking ferrofluid using easily available stearic acid Look at craft supply places for "stearate" or just stearic acid as a candle or soap
hardener...I'm fairly sure that it is the free fatty acid, but a bit of HCl or H2SO4 could resolve that uncertainty real fast.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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encipher
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I doubt Stearic acid will work. Oleic acid has a double bond at the 9th carbon atom. The bend is important for creating a non dense surfacted layer.
However, Stearic acid has no double bond. The kinetic motion of the tail is what prevents the merging of the surfacted molecules with each other. So
it probably wouldnt provide effective surfaction.
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H2O?!
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@ encipher. We also tried to make a ferrofluid that exhibits spiking for a school experiment. Also used oleic acid and it didn't work. We used a
prescription from the Utrecht university in Holland. We thougt it was a good one, but it doesn't work until now. We have follewed the experiment
correctly, but no spikes. We didn't use a very concentrated oleic aced (think it was around 50%), is this why our ferrofluid don't show spikes? We
have also got some ferrofluid from the university, but that ferrofluid also don't show spikes.
Another strange thing with our ferrofluid is that when we hold a magnite close to it the ferrofluid dont react but only the (iron?)particles. We hope
that we can compare our prescripton with yours.
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UnintentionalChaos
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Ah, I see what you're saying encipher.
H2O?! If only the particles are being attracted and are visibly seperating from the fluid, then your particles are either way too large, or not
surfacted properly.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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uzaymaymunu
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could you please tell me the concentrations (ammonia and FeCl3/FeCl2 mixture)?
i think i should use diluted solutions. isn't it?
// İm new so i want you to say hello 
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