I am wanting to make a reasonable quantity (10-100g) of iron powder that I can use to visualise magnetic fields (by putting the powder in a thin layer between two transparent materials). The finer the powder and more consistent the size the better. Ideally I would like a particle size 1 micron or smaller.

I've used a very fine grit sandpaper of about 2000 grit and this had a great result but took an eternity to produce.

I also made iron powder via electrolysis with an iron anode/cathode, in an aqueous solution of iron sulphate. I used an old repurposed PC PSU to supply 3V and however many amps the PSU could output for the electrolysis.

This produced some iron flakes which seemed a bit too large for what I wanted but it made a lot of iron particles quickly and with little effort.

Main question: Do you know of any good processes I could use to make fine iron particles using electrolysis or another chemical process?

Related side questions: What's a good liquid medium for suspending iron particles?

Is iron the best material to use for a viewing magnetic fields? How does it compare to other materials like Cobalt,Nickel,magnetite,Tungsten (Paramagnetic), NdFeB dust, etc?

A magnetic field viewer with silvery white particles (as opposed to black particles) could look nice. What might be a good way to turn the magnetic powder more silvery instead of black?

Is there a way to produce a good quantity of very fine, needle-like rods of iron? This could also work well for visualising magnetic fields as I believe the 'needles' would want to align to the magnetic fields.

I appreciate any help you can offer me!

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    $\begingroup$ One can buy iron powder of various diameters from standard chemical suppliers. One supplier has 250g of 10 micron powder for about $65. $\endgroup$ – Jon Custer Sep 20 at 18:50

A less laborious path to very fine iron dust (in fact, likely pyrophoric iron) perhaps follows from first purchasing or preparing iron(II) oxalate (a path is detailed in a reference provided below). Next, thermally decompose the salt and finally, stabilize the nano-iron product with say mineral oil.

The details on the thermal decomposition in an atmosphere of hydrogen is discussed in this paper: Pyrophoric Nanoparticles and Nanoporous Foils for Defense Applications. See also this discussion which includes a suggested preparation for Iron(II) oxalate together with a video here.

Lastly, follow a similar process as is outlined in this US Patent 3,520,676 which claims, to quote:

Pyrophoric powder of metals (such as iron, cobalt, nickel and alloys thereof) is stabilized to prevent its spontaneous ignition. Such stabilization is achieved by Wetting the metal particles with a high-boiling organic liquid (such as an ester of carboxylic acid, mineral oil, silicone oil or fatty acid) and holding the wetted particles in the presence of oxygen until a thin oxide layer is formed on the surfaces thereof.

in order to stabilize the very fine iron product for your intended use.

A particular advantage to this approach is the low cost, and actually, not a great need for a large amount of the nano-particles for your demonstration purposes.

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Fast and easy , maybe not cheap. Look up Non Destructive Testing such as Magneflux Corp. They supply iron oxide and iron powders to perform magnetic flaw inspection . Also fluorescent liquid. The expense may be caused by minimum quantity. If you are in an oil/gas producing area there are likely pipe ( OCTG ) inspection companies that will sell/give you a small amount ( such as Tuboscope ). And, more sophisticated auto garages and machine shops may have mag particle inspection equipment and supplies they would be willing to sell. You are sort of reinventing the wheel.

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