In my third Instructable I am going to describe a way to make ferrite powder from scrap ferrite cores.
I am posting this because I am always looking for alternatives to the alternative. Synthesising magnetite from vinegar and metal sponges may be simple but grinding down ferrite cores may even be simpler to some people.
The end product will be a black powder similar to magnetite but not exactly the same by chemical composition. There are different types of ferrite and you can learn more about them on the respective Wikipedia page.
The important technical issue of this method is finding a suitable mortar and a good pestle. Ferrite is a ceramic and thus quite hard. Large forces are needed to crush it, though it is brittle.
Step 1: Finding Ferrite Cores
I got my ferrite E-cores from broken CFLs and phone chargers. They are small and easy to work with. One half of an E-core is actually large enough to provide hours of fun while playing with the ferrite powder obtained from it.
Beads from cables are also a good source because the raw material is cleaner than the one from CFLs and chargers. On the other hand beads can be reused in more rational ways.
In any case, don't take components from devices that are in working order and/or owned and used by someone else.
Step 2: Dismantling the Cores
Use a knife to pry open the cores.
The wire from the coils can be used elsewhere so I suggest you store it.
Some of the cores may break upon dismantling but that is not much of a problem because we'll be breaking them anyway.
Step 3: Clean the Cores
Clean the cores of all the contaminating material.
A knife can be used here but sanding paper may also be useful.
Step 4: Initial Cracking
Before using the pestle, I broke the cores into smaller pieces with pliers.
Step 5: The Pestle
I used an M14 cap nut.
My variety was galvanized but it isn't the best one. The best would be stainless because it is harder and doesn't have any coatings that can come off like the zinc in my case. On the second picture you may see the subtle difference of the nut on the left which I used and the one on the right that is less worn down.
The handle of the pestle I used was quite arbitrary. The parts had been used in another project and seemed to suit my needs during this one.
I'm sure you'll come up with a suitable contraption.
Step 6: The Mortar
Yes, it's a ladle.
I bought it from a thrift shop for a €. It had the right curvature and was made of stainless steel.
You can also use a large spoon.
The stainless steel is not magnetic and thus the ferrite can be kept in one place with a magnet on the outer side of the ladle. This helps in many ways, one of which is that pieces of ferrite don't fly away.
Step 7: Grinding
There isn't much to say about the grinding process itself. You have to apply enough force and also position the magnets correctly to keep the material in the ladle. Everything else is in the wrist.
Step 8: The Product
Grab some neodymium magnets and play around. You'll be surprised at the different shapes that can be produced with this stuff. Be sure not to contaminate your magnets with the material, it's hard to get it off afterwards.
Thanks for reading.