Ferrofluid as Core Material

It should work fine. The permeability isn't going to be all that high

- few sources report it, and 2.5 seems to be a representative figure, though

found one ferrofluid that got up to a relative permeability of ten.

-- Bill Sloman, Nijmegen

I got a sample of ferrofluid years ago in a sealed glass tube and the material in solution congealed. I'm not sure it is very stable.

I would think it to be too lossy..

They should make ferromayo, that stuff lasts forever :-)

Tim

-- Deep Friar: a very philos>> >>> Can anyone predict how ferrofluid would function as an electromagnetic

I would think it's an emulsion or suspension more than a solution. they are colloids, and colloids are not stable for long.

-- Les Cargill

Isn't that what jap screws are made of?

Nah. Thye use old flattened out beer cans, found in the trunks of junked Hondas. ;-)

The wiki goes into stability of the fluid. I hadn't realized they use the fluid in disk drives.I know it is used in high fidelity speakers.

I expect ferropeanutbutter *would* last forever!

-- Les Cargill

You could always make up your own eg grind up ferrite and mix it into molten wax or somesuch before casting it.

Some colloids can last forever. It depends on particle size and double layer charges ...

-- Bill Sloman, Nijmegen

Aren't some inductors already using ferrous epoxy? I seem to recall cracking open some surface mount chokes and seeing no gaps around the wires.

Ferrofluid would be erratic because the particles can move around by gravity and low frequency fields, at a speed that would be temperature dependent.

Ferrofluids are colloidal suspensions. The particles move around due to Brownian motion, and there will be way too many involved for their mobility to create any detectable flucuations in gross permeablity or inductance.

-- Bill Sloman, Nijmegen

I believe the Internet wisdom for making your own ferrofluid is to precipitate iron oxide from FeCl3 solution, in stearic acid. You get nice small particles that way...

But do you want small particles?

Depends on the application. For typical transformers, it might cause problems. In this case, you want as much flux as possible to pass through both windings. Providing a low reluctance path between the turns could cause more flux to link only the one turn and increase the transformer leakage reactance.