Ferrofluid - magnet liquid Ferrotec USA
Ferrofluids contain tiny particles of ferrous material that are suspended in a viscous liquid such as oil. The oil keeps the particles separated while also allowing them to align and congregate magnetically. Ferrofluid displays liquid properties at rest and semi-solid, malleable properties in the presence of a permanent magnet. When a magnetic field is introduced to the liquid the fluid is attracted and moves toward the source of the field which, in the case of a Loudspeaker diaphragm, is the permanent Ring magnet or the electromagnetic voice coil. Ferrofluids are used to improve audio quality and to dissipate heat in speaker cones and voice coils and to create a frictionless semi-liquid seal for rotating shafts in computer hard drives.