Ferrofluid
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Ferrofluid is a colloidal liquid that is attracted to the poles of a magnet and can change shape as a result.
Contents
General
It is a colloidal liquid made of nanoscale ferromagnetic or ferrimagnetic particles suspended in a carrier fluid (usually an organic solvent or water). Each magnetic particle is thoroughly coated with a surfactant to inhibit clumping. Large ferromagnetic particles can be ripped out of the homogeneous colloidal mixture, forming a separate clump of magnetic dust when exposed to strong magnetic fields. The magnetic attraction of tiny nanoparticles is weak enough that the surfactant's Van der Waals force is sufficient to prevent magnetic clumping or agglomeration. Ferrofluids usually do not retain magnetization in the absence of an externally applied field and thus are often classified as "superparamagnets" rather than ferromagnets.
Ferrofluids are composed of very small nanoscale particles (diameter usually 10 nanometers or less) of magnetite, hematite or some other compound containing iron, and a liquid (usually oil). This is small enough for thermal agitation to disperse them evenly within a carrier fluid, and for them to contribute to the overall magnetic response of the fluid. This is similar to the way that the ions in an aqueous paramagnetic salt solution (such as an aqueous solution of copper(II) sulfate or manganese(II) chloride) make the solution paramagnetic. The composition of a typical ferrofluid is about 5% magnetic solids, 10% surfactant and 85% carrier, by volume.
Availability
Ferrofluids can be bought online.
Preparation
Ferrofluids can be prepared from ferric chloride, which is converted into magnetite nanoparticles. These are coated with a surfactant and mixed with a solvent/liquid of choice.[1]
Projects
- Demonstration of magnetism
- Cool science tricks
Handling
Safety
Ferrofluid itself is not harmful, but it will stain.
Storage
In closed bottles.
Disposal
No special disposal is required.
