Ferrofluid

An Introduction to Ferrofluid

Ferrofluid consists of sub-domain magnetic particles of ferromagnetic magnetite (10nm average size) as a stable colloidal suspension in a liquid carrier (hydrocarbon). The particles do not conglomerate together as they are coated with an oil soluble surfactant (a stabilizing dispersing agent) which disperses the particles (preventing van der Waal’s forces and magnetic forces from causing conglomeration). A typical ferrofluid may contain by volume 5% magnetic solid, 10% surfactant/dispersant and 85% carrier.

When no external magnetic fields are applied to the ferrofluid, the magnetic moments within the ferrofluid particles are randomly distributed resulting in no net measureable magnetization. But when an external magnetic field is applied, the magnetic moments of the particles orient along the field lines of the externally applied field. The ferrofluid will move to regions of highest magnetic field strength. When the external magnetic field is removed, the moments return to a random alignment again.

Because the ferrofluids have high permeabilities and offer high magnetisation, they offer design efficiencies in magnetic circuits. They can be used to fill air gaps to produce higher field in the air gaps (advantageous in loudspeaker designs). They can also reduce magnetic field fringing effects. They also allow a reduction in the total magnetic circuit “resistance” (a reduction in magnetic reluctance) allowing the magnetic field strengths within the total magnetic circuit to be increased.

Ferrofluid has many applications. The application affects the choice of type of ferrofluid. Applications include seals, loudspeakers, liquid seals in hard drive shafts, motors, sensors, bearings, dampers, suspension systems and sound reduction. Ferrofluids can be used as friction reducers (e.g. put ferrofluid onto a NdFeB disc and place it onto a stainless steel plate and it can glide over the surface).

The ferrofluid we offer is EFH1. The user should wear protective gloves and safety goggles/glasses for their own safety. Please be aware that ferrofluid stains the skin and textiles, will fill skin pores and will derogate in the eye. It is also recommended that the users check that the ferrofluids are compatible with the materials they are to come in contact with (to avoid chemical reactions).

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Part No.	Size	Grade	Pull (kg)
FF25	25ml Bottle	Ferrofluid	N/A

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