magnetic liquid/solid

FlyingFishFinger

Hello,
this is probably way out of place here, but I was going to do a Science Fair project starting from this weird stuff I saw somewhere. It was this: Either it was a liquid that turned solid under influence of magnetism or it turned liquid from a solid, I can't remember exactly. Does anyone know the name of this stuff and if it is available to the public?
Rafael

Tim-M

Hi Rafael,

It's called Ferrofluid and it's quite easily available to all of us. Just do a quick Google search for more information, and a Froogle search for where to buy it.

Tim

Paul Baker

Im familiar with ferrofluid (pretty neat stuff), but it doesn't change phase (liquid <-> solid), its just ferrous material in liquid suspension (btw keep it in a sealed container, or evaporation will turn it into a mess, a very cool experiment with it is to remove a coil from a speaker and play "bass-y" music through it and watch it dance). I did a pretty extensive search for phase transformation in the presence of magnetic fields, but I could find nothing which does this at room temperature (all references to such properties occur at high temperatures (>1000C)), so its quite possible Rafael is misrecollecting the phase issue, and was thinking of ferrofluid.

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Post Edited (Paul Baker) : 10/6/2005 11:13:17 PM GMT

FlyingFishFinger

Possibly you're right. I saw it about a year ago in a double syringe. With a magnet on them one couldn't push it from one to the other, but without it you could (or vice versa, as I said, can't remember)

Wait- I read several of the google results and it seems that the stuff just gets a little thicker. But does it get so thick I wouldn't be able to move the two syringes any more???

What I'm trying to do is to use electric currents instead of magnets to get the stuff take shape

Anyway Thanks
Rafael

Post Edited By Moderator (Chris Savage (Parallax)) : 10/7/2005 12:21:00 AM GMT

Paul Baker

Using hand made inductors, and a little experimentation, you can get it to do quite a few things using electrical currents. Dan's data does a write up on the stuff here.·A friend left his out in an uncovered·petri dish for about half a year and it did something like·this



up the petri dish, and across several research papers of his (not an actual photo, but looks alot like it). At the time we though evaporation caused it, but reading Dan's data I think maybe the fact it was·on a filing cabinet caused it somehow (he did have his stereo system next to it, placed there from the speaker experiment, then left there, maybe the close proximity of the speakers to the cabinet slightly magnetised it). So I guess my warning about evaporation may be overstated.


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Post Edited (Paul Baker) : 10/7/2005 12:22:06 PM GMT

Tim-M

Rafael,

Yes, I've had the double syringe demonstration in my hands and I can tell you that when the magnet is applied to the narrow area where the nozzles come together, the flow is completely stopped between the two. I could not move either syringe, even the slightest, with all the strength I had -- it's that dramatic! The automative industry, among others, is starting to use ferrofluid in suspension systems so that they can be electronicly controlled and variable.

Tim

Dave Paton

Tim, just an aside, I believe the correct term for these fluids is magnetorheological fluids.

An interesting use...:
http://science.nasa.gov/headlines/y2002/23aug_MRfluids.htm

-dave

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This is not a sig. This is a duck. Quack.

FlyingFishFinger

So how does the syringe get immobilized?

And if i remember correctly, the syringe I played with was gray, not black as I see on google all over(???)

Rafael

FlyingFishFinger

I found the syringe (borrowed it from someone). So I searched for specs on it and found the following: the syringe doesn't use ferrofluid, it uses a paste just called MR fluid. Its viscosity depends on its composition, but it's mainly oil and the gray color comes from a normally white additive to slow down the seperationof particles ond oil b/c they are too large to be chemically bound. Also it differs from ferrofuid in that the iron particles are about 5 microns large (ideally) compared with the 10 nm particles in ferrofluid.
Anyway thanks for starting me off on the right track, everyone.
Rafael

Beau Schwabe

Thought I would chime in... Years ago when I worked at a prosthetic R&D facility, we
looked into making our own ferrofluid with iron filings suspended in oil for use in
a "smart" hydraulic knee application.

You can buy iron filings for cheap, or I know of two ways to make your own.

http://www.physlink.com/estore/cart/IronFilings.cfm

Method #1) Sand off a piece of iron with a magnet in the "spark" path.

Method #2) Set some fine steel wool on fire until it burns completely out. Iron filing
"dust" will readily fall out when steel wool is roughly handled

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Post Edited (Beau Schwabe (Parallax)) : 10/9/2005 3:37:08 AM GMT

FlyingFishFinger

Hello, thanks Beau.
I just realized that my approach to this project won't work for my teacher's criteria. It turned out to be more a physics project than a chemistry one. And since it's a chemistry class I can't do it. I'm looking into endothermic and exothermic reactions now, that might be better project. We have to write 2 ten-page papers about it (one general one and one for an experiment we're supposed to do). I think this one is already well established so it will be easier to write the papers.
Rafael

quick question

You can also look at Electrorheoligical fluids (sp?) - ER fluids for short. High voltage is needed, but the hardward is pretty easy. Actually corn starch in silicon oil will work. (if you can keep it in suspension)

A good place to find how things work is at the United States Patent and Trademark Search page.

If you follow the life of·ANY techology throught the patents, you can·quickly see how the technology developed.

I·was once in the public search room years ago - before the computer -·and decided to·learn how infrared cameras worked. ·In about 1/2 hour, I was able to·see the technology grow to its current status- through tubes into ccd chips.

This method works for EVERY technology.· (I suspect this is why the classification system at the USPTO is set up the way it is)



kritz