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Audio Ferrofluids
Technical Information
Designing With Ferrofluids
Audio Fluids
Audio Ferrofluids

A ferrofluid is a stable colloidal suspension of sub-domain magnetic particles in a liquid carrier. The particles, which have an average size of about 100Å (10 nm), are coated with a stabilizing dispersing agent (surfactant) which prevents particle agglomeration even when a strong magnetic field gradient is applied to the ferrofluid. In the absence of a magnetic field, the magnetic moments of the particles are randomly distributed and the fluid has no net magnetization.



When a magnetic field is applied to a ferrofluid, the magnetic moments of the particles orient along the field lines almost instantly. The magnetization of the ferrofluid responds immediately to the changes in the applied magnetic field and when the applied field is removed, the moments randomize quickly.

In a gradient field the whole fluid responds as a homogeneous magnetic liquid which moves to the region of highest flux. This means that ferro-fluids can be precisely positioned and controlled by an external magnetic field. The forces holding the magnetic fluid in place are proportional to the gradient of the external field and the magnetization value of the fluid. This means that the retention force of a ferrofluid in a gap can be adjusted by changing either the magnetization of the fluid or the magnetic field in the gap.

Audio ferrofluids are based on two classes of carrier liquid: synthetic hydrocarbons and esters. Both oils possess very low volatility and high thermal stability. The choice of fluid is dictated by the environmental considerations of the application (e.g. humidity, adhesives, contact with water, solvent vapors and reactive gases) combined with the best balance of magnetization and viscosity values to optimize the acoustical performance.

By varying the quantity of magnetic material in a ferrofluid, and by using different carrier liquids, it can be tailored to meet a variety of needs. The saturation magnetization (the maximum value of the magnetic moment per unit volume when all the domains are aligned) is determined by the nature of the suspended magnetic material and by the volumetric loading of the material. The physical and chemical properties such as density and viscosity correspond closely to those of the carrier liquid.

Ferrofluidics' highly refined manufacturing process, combined with a long term quality assurance program is the key to its repeatable, reproducible product quality.


Ferrofluid | Vacuum Feedthroughs | Thermoelectric Modules
Contract Manufacturing | Literature Rack | Specialty Seals
Inertia Dampers | Electron Beam Evaporation



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